JP2010115845A - Printer and printing method - Google Patents

Abstract

Printing with improved ink aggregation and bleeding while increasing the weight of ink per unit area discharged onto a medium.
(A) a head that forms an image by ejecting ink onto a medium; and (B) a control unit that controls the head, and (b1) does not eject the ink to edge pixels of the image. And (b2) the amount of ink ejected when forming a portion excluding the edge pixels of the image on the medium is smaller than that in the first mode, And a control unit that controls the head so as to select the second mode in which the head is controlled so as to form the image by ejecting the ink to the edge pixels of the image.
[Selection] Figure 7

Description

  The present invention relates to a printing apparatus and a printing method.

  2. Related Art Inkjet printers that discharge images of a plurality of colors onto a medium and form an image on the medium are known. In such an ink jet printer, the ink that has been used so far causes a phenomenon of agglomeration when the total weight (discharge duty) per unit area discharged onto the medium is increased. Could not be used. For these reasons, since ink is not ejected at a high ejection duty, there was little ink bleeding on the medium.

Patent Document 1 discloses that pixel etching is performed as one method for reducing bleeding between colors.
Japanese Patent Laid-Open No. 10-100453

In order to perform high color printing, it is necessary to increase the weight of ink per unit area discharged onto the medium. However, when the ink weight per unit area is increased, ink bleeding and agglomeration may occur, and it is difficult to perform beautiful printing. That is, there is a problem that it is difficult to perform printing without aggregation and bleeding while increasing the liquid weight per unit area in order to perform high color printing.
The present invention has been made in view of such circumstances, and an object of the present invention is to perform printing with improved ink aggregation and bleeding while increasing the weight of ink per unit area discharged onto a medium.

The main invention for achieving the above object is:
(A) a head that forms an image by ejecting ink onto a medium;
(B) a control unit for controlling the head,
(B1) a first mode for controlling the head so as not to eject the ink to the edge pixels of the image;
(B2) The ink is also ejected to the edge pixels of the image while the amount of ink ejected when the portion excluding the edge pixels of the image is formed on the medium is smaller than that in the first mode. A second mode for controlling the head to form the image;
A control unit for controlling the head so as to be selectable,
Is a printing apparatus.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

(A) a head that forms an image by ejecting ink onto a medium;
(B) a control unit for controlling the head,
(B1) a first mode for controlling the head so as not to eject the ink to the edge pixels of the image;
(B2) The ink is also ejected to the edge pixels of the image while the amount of ink ejected when the portion excluding the edge pixels of the image is formed on the medium is smaller than that in the first mode. A second mode for controlling the head to form the image;
A control unit for controlling the head so as to be selectable,
A printing apparatus comprising:
In this way, it is possible to perform printing with improved ink aggregation and bleeding while increasing the weight of ink per unit area discharged onto the medium.

  In this printing apparatus, the ink is an ink including at least a colorant, water, an alcohol solvent, and a surfactant, and includes an ink including a slightly water-soluble alkanediol in at least one of the alcohol solvents. It is desirable. Further, the alcohol solvent comprises a slightly water-soluble alkanediol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol. It is desirable to include. The control unit obtains a filtered image obtained by applying an edge filter to the image when controlling the head in the first mode, performs binarization processing on the filtered image, and performs edge pixel processing. It is desirable to control the head so that the ink is not ejected to the edge pixel by using data in which the pixel of the image to be processed corresponding to the edge pixel is set to colorless. Further, it is preferable that the control unit has a plurality of tables for obtaining a dot size generated from a gradation value, and the tables used in the first mode and the second mode are different.

In addition, it is desirable that the ink ejected from the head in the first mode is different from the ink ejected from the head in the second mode. Moreover, it is desirable that the medium is a synthetic paper or a printing paper whose main raw material is a synthetic resin.
In this way, it is possible to perform printing with improved ink aggregation and bleeding while increasing the weight of ink per unit area discharged onto the medium.

A first mode in which the head is controlled so as not to eject ink to the edge pixels of the image; and a second mode in which the head is controlled so that the ink weight per unit area on the medium is smaller than in the first mode. Selecting at least one of
Controlling the head in a mode selected from the first mode and the second mode, and ejecting ink onto the medium to form an image;
Including printing method.
In this way, it is possible to perform printing with improved ink aggregation and bleeding while increasing the weight of ink per unit area discharged onto the medium.

=== Embodiment ===
FIG. 1 is a block diagram of the overall configuration of the printing system. The printing system 100 includes a printer 1, a computer 110, a display device 120, and an input device 130. In the first embodiment, the printer 1 is an ink ejection type line printer that prints an image on a medium such as paper, cloth, or film.

The computer 110 includes a CPU 113, a memory 114, an interface 112, and a recording / reproducing device 140. The CPU 113 executes various programs such as a printer driver and performs image processing on an image to be printed by the printer 1 described later, for example. The memory 114 stores programs such as a printer driver and data. The interface 112 is an interface for connecting to the printer 1 such as a USB or parallel interface. The recording / reproducing device 140 is a CD-ROM drive or hard disk drive, and is a device for storing programs and data.
The computer 110 is communicably connected to the printer 1 via the interface 112, and outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image.
A printer driver is installed in the computer 110. The printer driver is a program for causing the display device 120 to display a user interface and converting image data output from the application program into print data.

<About printer configuration>
FIG. 2A is a cross-sectional view of the printer 1. FIG. 2B is a perspective view for explaining the paper S transporting process of the printer 1. Hereinafter, a basic configuration of the line printer will be described with reference to FIG.

The printer 1 includes a paper transport mechanism 20, a head unit 40, a detector group 50, an ASIC 60, and a drive signal generation circuit 70. The printer 1 receives print data from the computer 110. Based on the received data, the ASIC 60 of the printer 1 controls each unit (the paper transport mechanism 20, the head unit 40, and the drive signal generation circuit 70) of the printer 1 and prints an image on the paper S.
The situation inside the printer 1 is monitored by a detector group 50. The detector group 50 outputs the detection result to the ASIC 60. And ASIC60 controls each part based on this detection result.

  The paper transport mechanism 20 is for transporting a medium (for example, the paper S) in a predetermined direction (hereinafter referred to as a transport direction). The paper transport mechanism 20 includes a paper feed roller 21, a transport motor (not shown), an upstream transport roller 23 A, a downstream transport roller 23 B, and a belt 24. The paper feed roller 21 is a roller for feeding the paper S inserted into the paper insertion opening into the printer. A conveyance motor (not shown) is connected to the conveyance roller 23B on the downstream side. When the transport motor rotates, the downstream transport roller 23B rotates. If it does so, the belt 24 will rotate according to this, and the upstream conveyance roller 23A will also rotate. The rotation of a conveyance motor (not shown) is controlled by the ASIC 60. A spring 29 is attached to the upstream conveying roller 23A. The upstream conveying roller 23A can be displaced slightly in the horizontal direction so that the belt 24 is not bent.

  The paper S fed by the paper feed roller 21 is conveyed by the belt 24 to a printable area (area facing the head). As the belt 24 transports the paper S, the paper S moves in the transport direction with respect to the head unit 40. The paper S that has passed through the printable area is discharged to the outside by the belt 24. The sheet S being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

  The head unit 40 is for ejecting ink droplets onto the paper S. The head unit 40 forms dots on the paper S by ejecting ink droplets onto the paper S being conveyed, and prints an image on the paper S. The printer 1 is a line printer, and the head unit 40 has four heads, a first head 410 to a fourth head 440, as will be described later. The configuration of the head unit 40 will be described in detail later.

  The detector group 50 includes a rotary encoder (not shown) and the like. The rotary encoder detects the rotation amount of the upstream side conveyance roller 23A and the downstream side conveyance roller 23B. The ASIC 60 can detect the transport amount of the paper S based on the detection result of the rotary encoder. The conveyance of a predetermined amount of the paper S can be controlled.

  The ASIC 60 is a control unit for controlling the printer 1. The ASIC 60 is connected to the interface unit 61 in the printer 1 and can communicate with the computer 110. The ASIC 60 has a function of performing arithmetic processing for controlling the entire printer. A memory for storing programs and data is also included. Then, each mechanism is controlled according to a program stored in the memory.

  The drive signal generation circuit 70 is a circuit that generates a drive signal applied to the piezo element 417 in the head in order to eject ink droplets from the nozzles. The drive signal generation circuit 70 outputs a drive signal to the head unit 40 based on the waveform data output from the ASIC 60. The drive signal is a signal including a plurality of drive pulses during a predetermined period T. The driving pulse is a pulse that is selectively applied to the piezo element 417 and ejects ink droplets. The drive signal is repeatedly generated from the drive signal generation circuit 70 and output.

<About the configuration of the head unit>
Referring to FIG. 1 again, the head unit 40 includes a head controller HC. A drive pulse applied to the piezo element 417 of each nozzle is selected under the control of the head controller HC. Then, when a driving pulse is applied to the piezo element 417, ink droplets are ejected from individual nozzles. Specifically, the head controller HC can control the ejection of ink droplets from each nozzle so as to form a dot of any size of small dots, medium dots, and large dots according to dot identification data described later. It has become. The head controller HC is controlled based on data sent from the ASIC 60. That is, the head controller HC is controlled by the ASIC 60.

  FIG. 3 is a diagram for explaining the detailed arrangement of the four heads of the head unit 40. In the figure, the first head 410 to the fourth head 440 are viewed from the top of the printer 1. When viewed from the top of the printer 1, these nozzles are blocked by other elements and cannot be seen. However, here, the positions of the nozzles are drawn with solid lines so that the relationship between the nozzles of the first head 410 to the fourth head 440 can be easily understood.

  The head unit 40 includes four heads, a first head 410 to a fourth head 440. These heads are arranged so that the direction perpendicular to the nozzle row direction is the paper transport direction. Each head includes four nozzle rows so that ink droplets of four colors can be ejected. The distance (nozzle pitch P) between the nozzles in each nozzle row is 1/720 inch. Further, 720 nozzles for each color and a piezo element 417 for ejecting ink droplets from the nozzles are included. Piezo elements 417 are individually attached to the nozzles one by one. Note that a head having a smaller nozzle pitch may be employed in order to further increase the printing resolution. Further, by disposing a similar head unit on the downstream side of the head unit 40 by shifting it by P / 2 in the nozzle row direction, printing with higher resolution may be performed.

Further, the nozzle # 720 of the first head 410 and the nozzle # 1 of the second head 420 are arranged so as to have a nozzle pitch P (1/720 inch). Each of the second head 420 to the fourth head 440 is also arranged at the same interval.
In addition, each head is provided with a nozzle row for discharging ink droplets of yellow Y, magenta M, cyan C, and black K so that color printing can be performed.

<About aggregation>
FIG. 4 is a diagram for explaining aggregation. Aggregation is density spots of similar colors that occur locally when printing is performed by ejecting ink. When aggregation occurs, the printing becomes a rough feeling, that is, a grainy feeling due to density unevenness. Therefore, in order to perform high quality printing, it is necessary to reduce such aggregation.
Such agglomeration of ink is considered to occur when the printing book paper repels ink because the surface tension of the ink dots is high and the contact angle between the printing paper surface and the ink droplets is high. Therefore, it is considered that the aggregation of the ink is reduced when the surface tension of the ink attached to the surface of the printing paper is reduced as described later.
Further, such ink aggregation tends to occur particularly in a portion where the ink discharge amount is large. Further, since the above-described aggregation occurs in the conventional ink, there is a problem in that the discharge amount per unit area cannot be increased and high color printing cannot be performed. Therefore, in the present embodiment, by using an ink having a composition described later, printing is performed in which aggregation is reduced while increasing the ink weight per unit area.

  By the way, when the total ink amount per unit area is increased to perform printing with high color using such an ink that hardly causes aggregation, bleeding occurs in which different colors are blurred.

  FIG. 5 is a diagram illustrating ink in the medium when bleeding does not occur. In the figure, ink droplets of magenta ink M and cyan ink C are shown. Here, for ease of explanation, ink droplets of a single color are shown. Of course, when the dot size is small as shown in the drawing, even when the dot size is large, both inks are separated from each other, so that they do not mix and cause bleeding. Also here, for simplicity of explanation, the ink droplets of a single ink color are shown and described, but when one ink droplet shown in the figure is a composite color composed of a plurality of ink colors Even so, bleeding is not caused if the ink droplets are separated from each other. Further, as shown in the drawing, even when ink droplets have permeated into the paper S, the inks are separated from each other inside the paper S, so that they do not mix.

  FIG. 6 is a diagram illustrating ink in the medium when bleeding occurs. As shown in the figure, even when the dot size is large or the dot size is small, when the total amount of ink per unit area is large, the ink landed on the paper S overlaps on the paper. Become. That is, both are mixed on the paper and bleeding occurs.

  Even if one ink droplet shown in the figure is a composite color composed of a plurality of ink colors, bleeding occurs if different composite colors are mixed on the paper. A color different from the color of is formed. When the synthesized color is generated by synthesizing desired ink colors, an image formed thereby is also desired. However, when ink that is not originally planned is mixed to cause bleeding, the image quality deteriorates.

  By the way, it is considered that bleeding that occurs in gradation in which the color gradually changes among bleedings does not have a large visual effect. On the other hand, if bleeding of different colors occurs in a place where the color changes rapidly, the edge portion of the image becomes indistinct and the deterioration of the image quality becomes conspicuous.

  Therefore, in the present embodiment, these problems are solved by the printer 1 having the following two print modes. That is, the printer 1 according to the present embodiment includes a high color development mode (corresponding to the first mode) with a large ink discharge amount per unit area and a normal mode (corresponding to the second mode) with a small ink discharge amount per unit area. There are two printing modes.

  In the high color development mode, the ink discharge amount per unit area is set to be larger than that in the normal mode described later in the halftone process described later. Further, in the high color development mode, the edge pixel whose color changes abruptly is intentionally set to be colorless (hereinafter referred to as pixel etching). In the subsequent ink ejection, ink is not ejected to a location corresponding to the edge pixel. By doing in this way, the bleeding which the color which changes rapidly in an edge pixel mixes can be prevented, and a favorable image can be obtained. Further, in the high color development mode, aggregation is less likely to occur by using the ink described below. In this way, printing is performed with improved ink aggregation and bleeding while increasing the weight of ink per unit area discharged onto the medium.

  On the other hand, in the normal mode, the ink discharge amount per unit area is set to the same amount as when normal printing is performed in halftone processing described later. Then, printing in the normal mode is performed with less ink weight per unit area in the high color development mode to be described later. By doing so, it is possible to perform printing while reducing the ink discharge amount per unit area to such an extent that the problem of aggregation and bleeding does not occur.

<About print data generation processing>
FIG. 7 is a flowchart for explaining print data generation processing. Hereinafter, the print data generation process will be described with reference to this flowchart. The print data generation process is performed in the printer driver of the computer 110. When the print data generation process is performed in the computer 110, the ASIC 60 that controls the operation of the computer 110 and the printer 1 corresponds to the control unit of the printing apparatus. However, these processes may be performed in the ASIC 60 of the printer 1. In this case, the ASIC 60 corresponds to the control unit of the printing apparatus.

First, a print mode is selected (S101). In the selection of the print mode, the computer 110 displays an image prompting the user to select whether to perform printing in the “high color development mode” or “normal mode”. Then, any mode is selected by the user via the input device 130. When any mode is selected, which print mode is used for printing is stored in the memory 114 of the computer 110. The printing mode can be stored by providing a printing mode flag, setting the flag when the high color development mode is selected, and resetting the flag when the normal mode is selected. .
Here, the print mode is input via the computer 110. However, the printer 1 may be provided with a print mode changeover switch so that the high color mode or the normal mode can be selected via the printer 1. Good.

  Next, a size conversion process (S102) is performed. The size conversion process is a process for converting the image data into a resolution for printing an image on the paper S. Here, in order to distinguish from the resolution conversion process performed in the pixel etching process mentioned later, it will call a size conversion process.

  Next, color conversion processing (S103) is performed. The color conversion process is a process of converting each RGB pixel data of the RGB image data into data having multi-stage gradation values represented by the YMCK color space. This color conversion processing is performed by referring to a table (color conversion lookup table) in which RGB luminance values and YMCK gradation values are associated with each other.

  Next, the print mode is determined (S105). The print mode can be determined by referring to the print mode flag in the memory 114 of the computer 110. When the high color development mode is selected, a pixel etching process (S106) is performed. Although the detailed method of the pixel etching process will be described in detail later, the edge pixel in the portion where the color changes abruptly can be set to be colorless by performing the pixel etching.

  When the pixel etching process (S106) is completed, the halftone process (S107) in the high color development mode is performed next. Although the halftone process in the high color development mode will be described in detail later, since the generation ratio table for the high color development mode is used and the halftone process is performed, printing with an increased ink weight per unit area is performed. Will be able to.

  By the way, if it is determined in step S105 that the normal mode has been selected in the print mode determination, halftone processing (S108) in the normal mode is performed. The halftone processing method in the normal mode is almost the same as the halftone processing in the high color development mode, but the halftone processing is performed using the normal mode generation rate table as will be described later. In addition, the ink weight per unit area is reduced so that printing with less aggregation and bleeding can be performed.

  When the halftone process in the high color mode or the halftone process in the normal mode is completed, the YMCK pixel data having multi-stage gradation values is converted into small-stage gradation data that can be expressed by the printer. Become. By these halftone processes, for example, 2-bit dot identification data indicating four-step gradation values is obtained from YMCK pixel data indicating 256-step gradation values. That is, any one of 2-bit dot identification data of [00] indicating no dot formation, [01] indicating small dot formation, [10] indicating medium dot formation, and [11] indicating large dot formation is set for each pixel. Will be set to.

  In the halftone process in the present embodiment, for example, a dither method is used as described later. In the halftone process according to the present embodiment, a method that causes a dot to be generated at a position where no dot originally exists, such as an error diffusion method, is not used. This is because, when the high color development mode is selected, dots are formed at positions corresponding to the edge pixels by using the error diffusion method even though the edge pixels are set to be colorless by the pixel etching process. This is because the pixel etching process becomes useless.

  When the high color development mode is selected, the pixel etching process (S106) is performed before the halftone process (S107) in the high color development mode. However, the pixel etching process (S106) is performed after the halftone process in the high color development mode. Also good.

  Next, rasterization processing (S110) is performed. The rasterizing process is a process for changing the dot identification data obtained by the halftone process in the order of data to be transferred to the printer. The rasterized dot identification data is sent to the printer 1 as print data together with command data and the like. The printer 1 receives the print data and sends the dot identification data after the rasterizing process to the head controller HC. The head controller HC prints on the paper S according to the dot identification data in each pixel.

  By doing so, even when the ink weight per unit area is large in printing in the high color development mode, it is possible to perform printing without causing bleeding by performing pixel etching. In addition, since the ink having the composition described later is used in the high color development mode, printing with less aggregation can be performed. On the other hand, in printing in the normal mode, since the ink weight per unit area is not so large as to cause bleeding, printing without causing bleeding can be performed. The ink used in the normal mode may be a conventional ink instead of the ink described below. This is because the ink weight per unit area is not large, and aggregation is unlikely to occur even when conventional ink is used. In this way, the ink used in the normal mode and the high color development mode can be made different.

  By the way, in the above-described print data generation process, either the high color development mode or the normal mode is selected by the user. This is automatically performed based on the data indicating the gradation value of the image. It may be required for In this case, the print mode selection in step S101 described above is not performed, and the “print mode automatic selection process” in step S104 described below is performed between step S103 and step S105.

  In step S104, YMCK tone value data after color conversion processing is added for each predetermined area. Here, the “predetermined area” is described as a 3 × 3 pixel area.

  FIG. 8 is a diagram illustrating an example of the gradation value of each pixel. In the figure, gradation values for each pixel in the black K plane are shown. First, the sum of gradation values in a predetermined area is obtained. For example, the sum of the gradation values of 3 × 3 pixels shown in FIG. Similarly, the sum of the gradation values of the yellow plane, magenta plane, and cyan plane C in the same region is also obtained. Then, all these sums are added to obtain a total gradation value which is the sum. When the total gradation value exceeds the predetermined value, the high color development mode is selected. On the other hand, when the total gradation value is equal to or less than the predetermined value, the normal mode is selected. The print mode can be selected by setting or resetting the print mode flag as described above. Here, for ease of explanation, the predetermined area is described as 3 × 3 pixels, but an area corresponding to one sheet may be set as the predetermined area.

  By doing so, when the amount of ink exceeds a predetermined amount in a predetermined region, it is possible to perform printing with less aggregation and bleeding by performing printing in the high color development mode in which pixel etching is performed. Further, when the amount of ink in the predetermined region is equal to or smaller than the predetermined amount, although pixel etching is not performed, printing can be performed with the ink weight per unit area equivalent to the amount during normal printing.

<About pixel etching process>
FIG. 9 is a flowchart for explaining the pixel etching process. Here, a method of performing pixel etching for one pixel at a color boundary will be described. In the following description, it is assumed that image data is given as the gradation value of each pixel in the YMCK color space.
The printer 1 is controlled so as not to eject ink onto the edge pixels of the image so that the image after the pixel etching process is printed. When the pixel etching process is performed by the printer driver in the computer 110, the computer 110 and the AIC 60 of the printer 1 correspond to the control unit of the printing apparatus. However, when the pixel etching process is performed in the ASIC 60 of the printer 1, the ASIC 60 corresponds to the control unit of the printing apparatus.
First, an image to be subjected to pixel etching processing is input (S202). For convenience of explanation, the image to be subjected to the pixel etching process input here is referred to as “original image P”.

FIG. 10 is a diagram for explaining each pixel in the original image P. In the figure, some pixels in the original image P are shown. And the gradation value p of each pixel is shown as an array.
When the original image P is input, a first resolution conversion process (S204) is performed. The first resolution conversion process is a process for reducing the image resolution in advance by reducing the resolution of the image in advance because the resolution of the image is converted to an integral multiple in the subsequent process.

  In the present embodiment, the resolution of the original image P is lowered to 1/3 by the bicubic method. For example, when the resolution of the original image P is 720 dpi, the resolution is lowered to 240 dpi. For convenience of explanation, the image after the first resolution conversion process is referred to as “first resolution converted image P ′”. Such processing is performed for each plane of the YMCK plane.

FIG. 11 is a diagram for explaining each pixel in the first resolution-converted image P ′. In the figure, some pixels in the first resolution-converted image P ′ are shown. The gradation value p ′ of each pixel of the first resolution-converted image P ′ is shown as an array.
Here, the resolution is converted so that the resolution becomes 1/3. Therefore, a plurality of pixels surrounded by thick lines in FIG. 10 are converted to correspond to one pixel in FIG. For example, a pixel in a region surrounded by a thick line including p (1,1) to p (3,3) is converted so as to correspond to the pixel p ′ (1,1) in FIG.

Next, a second resolution conversion process is performed (S206). In the second resolution conversion process, the resolution of the first resolution-converted image P ′ is converted at a magnification equal to or greater than the number of matrices of edge detection filters (edge filters) to be applied later. In this embodiment, since the number of matrixes of the edge detection filter is 3, a value of 3 or more (3, 4, 5,...) Can be used as the resolution conversion magnification in the second resolution conversion process. Here, the image conversion is performed so that the resolution of the image P ′ after the first resolution conversion is multiplied by six. Here, for convenience of explanation, the image after converting the resolution of the first resolution-converted image P ′ is referred to as “second resolution-converted image P ″”.
In this way, the resolution of the second resolution-converted image P ″ is 1440 dpi. That is, compared with the original image P, the resolution of the image P ″ after resolution conversion is doubled.

The conversion method used in the second resolution conversion process is performed by a technique that does not include interpolation, such as the nearest neighbor method (nearest neighbor method). Here, the method that does not include interpolation is applied in order to avoid occurrence of a gradation that does not exist in the original image P in the image P ″ after resolution conversion.
In the second resolution conversion process, the image is converted so as to have a value corresponding to the size of the edge detection filter matrix (eg, an integer of 3 or more for a 3 × 3 edge detection filter). This is because, in order to obtain at least edge pixels when the 3 × 3 edge detection filter is applied, it is necessary to arrange at least three pixels of the same color in a row.

FIG. 12 is a diagram for explaining each pixel in the second resolution-converted image P ″. In the figure, some pixels in the second resolution-converted image P ″ are shown. The converted gradation values p ″ of each pixel are shown as an array.
Here, the image conversion process is performed so that the resolution is 6 times. Therefore, one pixel surrounded by a thick line in FIG. 11 is converted so as to correspond to a 6 × 6 pixel surrounded by a thick line in FIG. For example, the pixel of p ′ (1,1) in FIG. 11 is converted so as to correspond to the pixels p ″ (1,1) to p ″ (6,6) in FIG. Such processing is performed for each plane of the YMCK plane.
Next, edge detection processing is performed (S208). In the edge detection process, an edge detection filter is applied to the second resolution converted image P ″.

FIG. 13 shows an edge detection filter applied in this embodiment. In this embodiment, a 3 × 3 edge detection filter is used as shown in the figure. When an edge filter is applied to an image, a large value is obtained in a pixel having a strong edge. On the other hand, a small value is obtained in a pixel whose edge is not strong. That is, a large value is set when the color change is large, and a small value is set when the color change is small. Note that the edge detection filter applied here is not limited to that shown in FIG.
The edge detection filter is applied to each plane of YMCK. Then, a post-filter application image F in which the edge detection filter is applied to each plane is obtained.

Next, a process of synthesizing the filtered image of each plane is performed (S210).
FIG. 14 is a diagram for explaining the synthesis of the filtered image F for each plane. The synthesis of the filtered image of each plane is performed by obtaining the average value of the values set in the pixels at the same position of the filtered image F in each plane. That is, it is performed by obtaining the average value of the values set for the pixels having the same array number in the post-filter application image F in each plane. In the figure, the image after applying the filter for each plane is shown (one of the characters YMCK is attached to the subscript of the image F after applying the filter as indicating each plane). In this way, the planes of the four post-filter application images are converted into one post-combination filter application image F.

  Next, edge binarization processing (S212) is performed. In the edge binarization process, the value of each pixel in the post-synthesis filter applied image is converted into one of two numerical values with a predetermined threshold as a reference. In the present embodiment, the predetermined threshold is 128, and the two numerical values are 0 or 255. Then, 0 is set to pixels having a threshold value of 128 or more in the post-synthesis filter applied image. That is, a value of 0 is set for pixels with strong edges. On the other hand, 255 is set to a pixel having a value less than 128. That is, a value of 255 is set for a pixel with a weak edge. The image thus obtained is referred to as a binarized image E for convenience of explanation.

FIG. 15 is a diagram for explaining each pixel in the image E after binarization application. In the figure, some pixels in the image E after binarization application are shown. And the value e of each pixel is shown as an array.
At this time, the resolution of the binarized image E is 1440 dpi, but here, the process of reducing the resolution is performed again. In this embodiment, the resolution of the binarized image E is converted to 720 dpi, which is ½ resolution, using the nearest neighbor method. Then, the binarized image E after resolution conversion is set as a new binarized image E ′.

  FIG. 16 is a diagram for explaining each pixel of the binarized image E ′. In the figure, some pixels in the binarized image E ′ are shown. The value e ′ of each pixel is shown as an array. As described above, here, conversion processing is performed to reduce the resolution to ½. Therefore, 2 × 2 pixels surrounded by a thick line in FIG. 15 are converted so as to correspond to one pixel in FIG. For example, the pixels e (1,1) to e (2,2) surrounded by a thick line in FIG. 15 are converted so as to correspond to the pixel e ′ (1,1) in FIG.

  Next, a binarized image overlay process (S214) is performed. In the binarized image superimposing process, the pixel value at the same position is compared with the pixel value of the binarized image E ′ and the gradation value of the pixel of the original image P, and the smaller numerical value is obtained. Is used as the gradation value of the pixel, and an image C after pixel etching is obtained.

FIG. 17 is a diagram for explaining each pixel in the image C after the pixel etching process. In the drawing, some pixels in the image C after pixel etching are shown. And the value c of each pixel is shown as an array. Assuming that the function min is a function for selecting one of the smaller values, an image after pixel etching processing is performed using the pixel p (x, y) of the original image P and the pixel e ′ of the binarized image E ′. The gradation value of each pixel c (x, y) of C is
c (x, y) = min (p (x, y), e ′ (x, y))
It becomes. This process is applied to each plane of the YMCK plane of the original image P.

  A value of 0 or 255 is set for each pixel of the binarized image E ′. Then, 0 is set for pixels with strong edges, and 255 is set for pixels with weak edges. In addition, any value of 0 to 255 is set as a gradation value for each pixel of the original image P. Here, the YMCK color space is used, and the subtractive color mixture is adopted in the YMCK color space. Therefore, the closer the gradation value is to 0, the brighter the color, and the closer the gradation value is to 255, the darker the color. When one of the smaller values is selected according to the above equation, 0 is set as the gradation value for the pixels for which 0 is set in the binarized image E ′. On the other hand, for a pixel for which 255 is set in the binarized image E ′, the gradation value in the pixel of the original image P is set as the gradation value.

  In this way, the post-pixel etching image C is set to a gradation value such that the pixel having a strong edge of the original image P is white. Later, when printing is performed based on the pixel data in which the gradation value is set in this way, ink is not ejected from the white pixels. That is, it is possible to set so that ink is not ejected to a portion where the edge is strong and the color changes drastically. By doing in this way, the image which can prevent the bleeding of the ink in the location can be obtained.

  FIG. 18 is a diagram for explaining a pixel before pixel etching. The figure shows how two different colors are set for each pixel. Here, for ease of explanation, only two types of colors are shown. Here, for convenience of explanation, a circle painted with diagonal lines is a first color, and a circle painted with white is a second color.

  FIG. 19 is a diagram for explaining pixels of an image after pixel etching processing. In the figure, in the image after the pixel etching process, the state where the color of any one of the pixels where the first color pixel and the second color pixel are adjacent to each other is set to be colorless is shown. It is shown.

  By performing the pixel etching described above, as shown in the figure, the color of the pixel at the boundary between two different colors can be easily set to be colorless. Thereafter, print data for ejecting ink droplets is generated based on the data of the pixels having the gradation values set in this way. When printing is performed based on the print data, ink droplets are not ejected to colorless pixels, so that ink droplets are not ejected to different color boundaries. In this way, since a region where ink droplets are not ejected is set at the boundary between different colors, bleeding due to different colors can be prevented.

  It should be noted that if the reduction ratio in the first resolution conversion process (S204) is increased, the amount of missing information may increase. Therefore, when the number of edge filter matrices is 3, as described above, the first resolution conversion process (S204) performs conversion to halve the resolution, and the second resolution conversion process (S206) sets the resolution to 4 times. Conversion that doubles may be performed, and in edge binarization processing, conversion that doubles the resolution may be performed. In this way, the pixel etching process can be performed while minimizing the amount of information missing from the original image.

  The setting of the magnification at the time of each resolution conversion at times other than the above-described embodiment can also be performed based on a generalized method as follows. For example, when the number of matrixes of the edge filter is i, the resolution conversion magnification j in the second resolution conversion process (S206) is i or more (for example, when i = 3, j = 3, 4, 5,... ). In accordance with this, the magnification at the time of resolution conversion in the edge binarization process (S212) can be set to (1 / (j-1)) times. In order to make the resolution of the finally obtained image the same as the resolution of the original image P, the resolution conversion magnification in the first resolution conversion process (S204) is ((j−1) / j) times. Can be set to be

<About halftone processing>
FIG. 20 is a flowchart for explaining halftone processing in the present embodiment. Hereinafter, halftone processing will be described with reference to this flowchart.

First, in step S302, YMCK image data is acquired. The YMCK image data acquired here is data of an image after pixel etching after the pixel etching process described above. The YMCK image data includes Y image data relating to yellow (Y), M image data relating to magenta (M), C image data relating to cyan (C), and K image data relating to black (K). Each of these Y, M, C, and K image data is composed of pixel data indicating the gradation value of each ink color.
The following description applies to any of Y, M, C, and K image data, and therefore K image data will be described as a representative of these.

Next, for all K pixel data in the K image data, the process from step S304 to step S326 is executed while sequentially changing the K pixel data to be processed. The data is converted into 2-bit data indicating any one of “None”, “Small dot formation”, “Medium dot formation”, and “Large dot formation”. In this embodiment, this data is referred to as dot identification data for convenience.
The dot identification data is assigned [00] when “no dot formation”, “01” is assigned when “small dot formation”, and [10] is assigned when “medium dot formation”. In the case of “large dot formation”, [11] is assigned.

  FIG. 21 is a diagram illustrating a generation rate table in the normal mode. Here, first, halftone processing in the normal mode will be described. In the figure, the horizontal axis is the gradation value (0 to 255), the left vertical axis is the dot generation rate (%), and the right vertical axis is the level data (0 to 255). Here, the “dot generation rate” means a ratio of pixels in which dots are formed among pixels in the region when a uniform region is reproduced according to a certain gradation value. In both figures, the profile SD indicated by the thin solid line in the figure indicates the generation rate of small dots, the profile MD indicated by the thick solid line indicates the generation rate of medium dots, and the profile LD indicated by the dotted line indicates that the large dots are large dots. The production rate is shown respectively. The level data refers to data obtained by converting the dot generation rate into values 0 to 255 in 256 levels. In the figure, a profile Total indicating the total generation rate of small dots, medium dots, and large dots is shown.

  In step S304, the level data LVL corresponding to the gradation value is read from the large dot profile LD. For example, as shown in FIG. 21, if the gradation value of the K pixel data to be processed is gr, the level data LVL is obtained as 1d using the profile LD. Actually, this profile LD is stored in a memory in the computer 110 in the form of a one-dimensional table, and the printer driver obtains level data by referring to this table.

  Next, in step S306, it is determined whether or not the level data LVL set as described above is larger than the threshold value THL. Here, dot on / off determination is performed by the dither method. As the threshold value THL, a matrix in which a value of 0 to 254 appears in each pixel block of the dither matrix is used.

  FIG. 23 is a diagram showing a state of dot on / off determination by the dither method. For the sake of illustration, FIG. 23 shows only some K pixel data. First, as shown in the figure, the level data LVL of each K pixel data is compared with the threshold value THL of the pixel block on the dither matrix corresponding to the pixel data. When the level data LVL method is larger than the threshold value THL, the dot is turned on, and when the level data LVL is smaller, the dot is turned off. In the figure, shaded pixel data is K pixel data for turning on a dot. That is, in step S306, when the level data LVL is larger than the threshold value THL, the process proceeds to step S322, and otherwise, the process proceeds to step S308. If the process proceeds to step S322, the printer driver records dot identification data [11] indicating a large dot in association with the K pixel data to be processed, and the process proceeds to step S324. In step S324, it is determined whether or not the process has been completed for all K pixel data. If the process has been completed, the halftone process is terminated. If the process has not been completed, the process target is determined. The process proceeds to unprocessed K pixel data, and the process returns to step S304.

  On the other hand, when the process proceeds to step S308, the printer driver sets the medium dot level data LVM. The medium dot level data LVM is set by the above-described generation rate table based on the gradation value. The setting method is the same as that for setting the large dot level data LVL. That is, in the example shown in FIG. 21, the level data LVM is obtained as 2d.

  In step S310, the medium dot level data LVM and the threshold value THM are compared to determine whether the medium dot is on or off. The on / off determination method is the same as that for large dots, but the threshold THM used for determination is different from the threshold THL for large dots as shown below.

  FIG. 24A is a diagram showing a dither matrix used for determination of large dots. FIG. 24B is a diagram showing a dither matrix used for medium dot determination. In this embodiment, the first dither matrix TM in FIG. 24A is used for large dots, and the second dither matrix UM in FIG. 24B in which each threshold value is moved around the center in the transport direction for medium dots. Is used. In the present embodiment, as described above, a 16 × 16 matrix is used, but for convenience of illustration, FIG. 24B shows a 4 × 4 matrix. Note that dither matrices that are completely different for large dots and medium dots may be used.

In step S308, if the medium dot level data LVM is greater than the medium dot threshold value THM, it is determined that the medium dot should be turned on, and the process proceeds to step 320; The process proceeds to S312. If the process proceeds to step S320, the printer driver records dot identification data [10] indicating a medium dot in association with the K pixel data to be processed, and the process proceeds to step S324. In step S324, it is determined whether or not the process has been completed for all K pixel data. If the process has been completed, the halftone process is terminated. If the process has not been completed, the process target is determined. The process proceeds to unprocessed K pixel data, and the process returns to step S304.
On the other hand, when the process proceeds to step S312, the small dot level data LVS is set in the same manner as the setting of the level data for large dots and medium dots.

  In step S314, if the level data LVS is larger than the small dot threshold THS, the printer driver proceeds to step S318, and otherwise proceeds to step S316. If the process proceeds to step S318, dot identification data [01] indicating a small dot is recorded in association with the K pixel data to be processed, and the process proceeds to step S324. In step S324, it is determined whether or not the processing has been completed for all the K pixel data. If not, the processing target is moved to unprocessed K pixel data, and the process returns to step S304. . On the other hand, if it has been completed, the halftone process for the K pixel data is terminated, and the halftone process is similarly performed for the image data of other colors.

On the other hand, if the process proceeds to step S316, the printer driver records dot identification data [00] indicating that there is no dot in association with the K pixel data to be processed, and the process proceeds to step S324. In step S324, it is determined whether or not the processing has been completed for all the K pixel data. If the processing has not been completed, the processing target is moved to unprocessed K pixel data, and the process returns to step S304. On the other hand, if it has been completed, the halftone process for the K image data is terminated, and the halftone process is similarly performed for the image data of other colors.
By performing halftone processing in this way, ink can be ejected in an amount corresponding to the gradation value.

  FIG. 22 is a diagram showing a generation rate table in the high color development mode. In the present embodiment, when performing such halftone processing, the generation rate table in the normal mode and the generation rate table in the high color development mode are different as described above. That is, in the case of halftone processing in the high color development mode, the same processing as described above is performed, but the dot generation rate table used is that shown in FIG. As can be seen from the figure, the dot generation rate in the high color development mode is set to be higher than the generation rate in the normal mode. By doing so, it is possible to print with good color by increasing the ink discharge amount per unit area in the high color development mode than in the normal mode.

  Note that the method of varying the ink discharge amount per unit area is not limited to the method of varying the dot generation rate table. For example, the ink weight per unit area may be made different by making the dither matrix in the dither method different from that used in the normal mode and that used in the high color development mode. .

<About ink>
The ink composition for ink jet recording according to the present embodiment is an ink composition for ink jet recording comprising at least a colorant, water, an alcohol solvent, and a surfactant, and the alcohol solvent is hardly water-soluble. An alkanediol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol. Hereinafter, each component will be described.

<Definition>
In the present specification, the alkanediol, dialkylene glycol, and alkanetriol may be either linear or branched.
Water-soluble means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is 10.0 g or more, and poorly water-soluble means the solubility in water (100 g of water). It means that the amount of solute relative to 1.0 g is less than 1.0 g.

<Alcohol solvent>
The alcohol solvent used in the ink composition for ink jet recording according to the present embodiment includes a slightly water-soluble alkanediol, a water-soluble 1,2-alkanediol, and an alkane having a side chain on any one carbon having a hydroxyl group. It contains at least four kinds of organic solvents of diol and water-soluble alkanetriol. By including these four kinds of alcohol solvents as essential components, printing paper, especially art paper, POD application paper (for example, Ricoh Business Coat Gloss 100 manufactured by Ricoh Co., Ltd.), laser printer, etc., which have a relatively high ink absorption capacity With special paper (for example, Seiko Epson Corporation, LPCCTA4), ink aggregation is suppressed, and even when printed at low resolution, a high-quality image without white streaks or roughness can be realized, and ejection stability In addition, an excellent ink composition can be realized. In this specification, “aggregation” means local density variation of similar colors that occurs when printed as a surface (for example, when printed in a single color (not the number of ink colors) on a 6-inch square). This does not mean that a portion of the surface of the recording medium that is not covered with ink remains. White streaks mean that when printed as a surface (for example, when printed in a single color on a 6-inch square), there is no local color density unevenness, and the surface of the recording medium moves in the drive direction of the recording head. It means a phenomenon in which a portion not covered with ink remains on the streaks. Further, the rough feeling or poor filling means that, when printed as a surface in the same manner as described above, there is no local color density unevenness and the surface of the recording medium is not covered with ink. This means a phenomenon in which the surface of the material has a grainy texture.

Further, in the present embodiment, in the recording medium as described above, even when a thin printing paper having a basis weight of 73.3 to 104.7 g / m ² is used, the printing surface warps inward, so-called. Curling can be suppressed.

  As described above, in addition to poorly water-soluble alkanediol and water-soluble 1,2-alkanediol, alkanediol having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriol are essential. The reason why a high-quality image without white streaks or roughness can be realized by adding it as a component is not clear, but is considered as follows.

  The agglomeration of ink that occurs when recording on printing paper is due to the fact that the printing paper repels ink because of the high surface tension of the ink dots and the high contact angle between the printing paper surface and the ink droplets. it is conceivable that. Even when white streaks or filling defects occur when recording at low resolution, aggregation of ink is suppressed by reducing the surface tension of the ink adhering to the surface of printing paper.

  Also, white streaks and poor filling in low-resolution recording are caused by ink dots adhering to the surface of printing paper coming into contact with adjacent ink dots, spreading each other, and causing undried ink to flow with each other. Conceivable. This mutual ink flow is considered to be due to the difference in the drying time of the ink dots depending on the difference in the adhesion time between adjacent ink dots and the size of the droplets at the time of adhesion. Therefore, in order to realize a high-quality image without white streak or roughness even when printing at low resolution, ink aggregation is suppressed, and ink with low surface tension and low fluidity is printed. It is considered preferable to adhere to the paper.

  However, if a permeable wetting agent is not used to reduce the fluidity of the ink, the ink dots adhering to the surface of the printing paper will dry faster and the ink will be absorbed faster, so that the adhering ink dots will get wet. It is considered that the spreading time is lost, and as a result, white streaks and poor filling occur in low resolution recording.

  The alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol used in the present embodiment are substances exhibiting viscosity such as glycerin. Further, alkanediol having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriol are penetrating wetting agents having a lower surface tension than glycerin. For example, the surface tension of 3-methyl-1,3,5-pentanetriol in a 10% aqueous solution is 47.5 mN / m, and 3-methyl-1,3-in a 10% aqueous solution. The surface tension of butanediol is 52.6 mN / m.

  An alkanediol having a side chain on any one carbon having a hydroxyl group having such properties and a water-soluble alkanetriol are combined with the above-mentioned poorly water-soluble alkanediol and water-soluble 1,2-alkanediol. By using it, discharge stability is also improved. The discharge stability is better as the alkyl chain length of the alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol is shorter.

  In addition to poorly water-soluble alkanediols and water-soluble 1,2-alkanediols, alkanediols and alkanetriols having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriols as essential components The reason why curling can be suppressed when it is added onto thin printing paper is not clear, but is considered as follows.

  Water-soluble 1,2-alkanediol is a polar solvent and a resin film-forming aid. By inhibiting this effect, it is considered that film shrinkage of the resin is prevented. In order to inhibit this effect, a weakly polar solvent is preferable. It is considered that the nonpolar solvent has a weak affinity with the resin, and an inhibitory effect cannot be obtained. As a weakly polar solvent, it is considered preferable to simultaneously have a + I effect alkyl group and a −I effect hydroxyl group on the same carbon. Alkanediol having a side chain on one of the carbons having a hydroxyl group inhibits the film-forming shrinkage of water-soluble 1,2-alkanediol, and under these conditions, the curling effect of water-soluble alkanetriol causes curling. It is thought that the occurrence of is suppressed.

  In the present embodiment, the slightly water-soluble alkanediol is preferably an alkanediol having 7 or more carbon atoms, more preferably an alkanediol having 7 to 10 carbon atoms, such as 1,2-heptanediol, 1, Examples include 2-octanediol, 5-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, 4,4-dimethyl-1,2-pentanediol, and the like. Among these, 1,2-octanediol is more preferable.

  The water-soluble 1,2-alkanediol is preferably an alkanediol having 6 or less carbon atoms, such as 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, 4-methyl- 1,2-pentanediol, 3,3-dimethyl-1,2-butanediol and the like. Among these, a water-soluble alkanediol having a surface tension of 28 mN / m or less when a 15% aqueous solution is used is more preferable. 1,2-hexanediol (surface tension: 26.7 mN / m), 4-methyl 1,2 -Pentanediol (surface tension: 25.4 mN / m), 3,3-dimethyl-1,2-butanediol (surface tension: 26.1 mN / m) are particularly preferred. From the viewpoint of odor during printing, 1,2-hexanediol is preferred.

Moreover, as for the alkanediol which has a side chain in any one carbon which has a hydroxyl group used in this embodiment, 3-methyl- 1, 3- butanediol is mentioned.
Further, in the present embodiment, examples of the water-soluble alkanetriol include 1,2,6-hexanetriol and 3-methyl-1,3,5-pentanetriol.
Further, as a solubilizing aid for the slightly water-soluble alkanediol, an alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol can be used in combination.

  In the four types of alcohol solvents described above, the content ratio of the slightly water-soluble alkanediol to the water-soluble 1,2-alkanediol is preferably 6: 1 to 1: 3, more preferably 6: 1. ~ 1: 1. By setting it within this range, the slightly water-soluble alkanediol can be stably dissolved in the ink, and the ejection stability is improved. On the other hand, when the ratio of the water-soluble 1,2-alkanediol is larger than the above range, it is difficult to achieve both reduction of the initial ink viscosity and reduction of aggregation spots. In addition, when the ratio of the water-soluble 1,2-alkanediol is less than the above range, it becomes difficult to stably dissolve the poorly water-soluble alkanediol in the ink, and the viscosity change at the time can be suppressed or stored. It becomes difficult to maintain stability.

  The content ratio of the slightly water-soluble alkanediol to the total amount of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is 1: 1 to 1:18. Preferably, it is 1: 1 to 1: 6. By setting it within this range, the initial viscosity of the ink can be lowered and good clogging recovery can be realized. On the other hand, when the ratio of the total amount of alkanediol having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriol is larger than the above range, the ink initial viscosity is increased and drying property is lowered. In addition, if the ratio of the total amount of alkanediol having a side chain on one of the carbons having a hydroxyl group and the water-soluble alkanetriol is less than the above range, the clogging recovery property is deteriorated and the drying property is increased. As a result, it becomes impossible to secure the time for spreading the ink, so that the recording medium cannot be covered with ink, and white streaks are likely to occur.

  The content ratio of the water-soluble 1,2-alkanediol to the total amount of the alkanediol having a side chain on one of the carbons having a hydroxyl group and the water-soluble alkanetriol is 1: 1 to 1:36. It is preferable that the ratio is 1: 1 to 1:18. By setting it within this range, white streaks and roughness can be further suppressed when printing is performed on the printing paper at a low resolution. On the other hand, when the proportion of the water-soluble 1,2-alkanediol is larger than the above range, the ink initial viscosity is increased and the drying property is lowered. In addition, if the ratio of the total amount of alkanediol having a side chain on one of the carbons having a hydroxyl group and the water-soluble alkanetriol is less than the above range, the clogging recovery property is deteriorated and the drying property is increased. As a result, it becomes impossible to secure the time for spreading the ink, so that the recording medium cannot be covered with ink, and white streaks are likely to occur.

  Furthermore, the content ratio of the alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol is preferably 3: 1 to 1: 3, and 2: 1 to 1: 2 is more preferable. By setting this range, the occurrence of curling can be further suppressed. When the proportion of alkanediol having a side chain on any one of the carbons having a hydroxyl group is larger than the above range, the initial viscosity becomes lower, so that the flying speed of the ink is increased, so that the droplet deposition accuracy is improved, More preferred. Moreover, it is more preferable from the viewpoint that the slightly water-soluble 1.2-alkanediol can be stably dissolved. On the other hand, if the proportion of the alkanediol having a side chain on any one of the carbons having a hydroxyl group is less than the above range, the effect of inhibiting the film-forming shrinkage of the water-soluble 1,2-alkanediol becomes poor. It is difficult to obtain the effect of suppressing the occurrence of

  The content ratio of the water-soluble 1,2-alkanediol and the alkanediol having a side chain on any one carbon having a hydroxyl group is preferably 1: 1 to 1:12, and preferably 1: 1. More preferably, it is 1: 6. By setting it within this range, white streaks and roughness can be further suppressed when printing is performed on the printing paper at a low resolution. On the other hand, when the proportion of the water-soluble 1,2-alkanediol is larger than the above range, the ink initial viscosity is increased and the drying property is lowered. Also, if the proportion of alkanediol having a side chain on any one of the carbons having a hydroxyl group is less than the above range, clogging recoverability deteriorates and drying properties increase, so that it becomes impossible to secure time for ink to spread. The recording medium cannot be covered with ink, and white streaks are likely to occur.

  Furthermore, in this embodiment, the sum of the contents of the slightly water-soluble alkanediol and the water-soluble 1,2-alkanediol is preferably 6% by weight or less with respect to the ink composition. By setting it within this range, a recording medium having a low ink absorbency such as printing paper does not cause aggregation spots and is excellent in ejection stability.

  In this embodiment, the sum of the contents of the slightly water-soluble alkanediol, the alkanediol having a side chain on any one of the carbons having a hydroxyl group, and the water-soluble alkanetriol is an ink composition. The content is preferably 21% by weight or less. By setting it within this range, there is no occurrence of agglomeration in a recording medium having low ink absorbency such as printing paper, and ejection stability and curl suppression are good.

  The slightly water-soluble alkanediol is preferably contained in an amount of 1 to 3% by weight, more preferably 1.5 to 2.5% by weight, based on the entire ink composition. If it is less than 1% by weight, printing spots may occur on a recording medium having low ink absorbability such as printing paper. On the other hand, if it exceeds 3% by weight, it may not completely dissolve in the ink.

  The water-soluble 1,2-alkanediol is preferably contained in an amount of 0.5 to 6% by weight, more preferably 0.5 to 3.0% by weight. If it is less than 0.5% by weight, the slightly water-soluble alkanediol may not be dissolved in the ink. On the other hand, if it exceeds 6% by weight, the initial viscosity of the ink may increase, which is not preferable.

  The sum of the contents of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is preferably 3 to 18% by weight with respect to the entire ink composition. More preferably, it is 4 to 8% by weight. If the amount is less than 3% by weight, white stripes or roughness may occur when printing on a printing paper at a low resolution. On the other hand, if it exceeds 18% by weight, the dryness of the printed material immediately after printing may be inferior.

The alkanediol having a side chain on any one carbon having a hydroxyl group is preferably contained in an amount of 2 to 12% by weight, more preferably 3 to 6% by weight, based on the entire ink composition.
The water-soluble alkanetriol is preferably contained in an amount of 2 to 12% by weight, more preferably 3 to 6% by weight, based on the entire ink composition.

<Colorant>
As the colorant used in the ink composition for ink jet recording according to the present embodiment, both dyes and pigments can be used, but pigments can be preferably used from the viewpoint of light resistance and water resistance.

  As the pigment, inorganic pigments and organic pigments can be used, and each can be used alone or in combination. As the inorganic pigment, for example, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye-type chelates, acidic dye-type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used.

  Specific examples of the pigment are appropriately given according to the type (color) of the ink composition to be obtained. For example, as a pigment for a yellow ink composition, C.I. I. Pigment Yellow 1, 2, 3, 12, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185 and the like, and one or more of these are used. Of these, C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Yellow 74, 110, 128, and 147. Examples of the pigment for the magenta ink composition include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. Pigment violet 19 and the like, and one or more of these may be used. Of these, C.I. I. Pigment red 122, 202, 209, and C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Violet 19. Examples of the pigment for the cyan ink composition include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60; I. Bat Blue 4, 60 etc. are mentioned, and one or more of these are used. Of these, C.I. I. Pigment Blue 15: 3 and / or 15: 4 are preferably used, especially C.I. I. Pigment Blue 15: 3 is preferably used.

  Examples of the pigment for the black ink composition include lamp black (CI pigment black 6), acetylene black, furnace black (CI pigment black 7), and channel black (CI pigment black). 7), carbon blacks such as carbon black (CI Pigment Black 7), inorganic pigments such as iron oxide pigments, and organic pigments such as aniline black (CI Pigment Black 1). In the form, carbon black is preferably used. Specifically, as carbon black, # 2650, # 2600, # 2300, # 2200, # 1000, # 980, # 970, # 966, # 960, # 950, # 900, # 850, MCF-88, # 55, # 52, # 47, # 45, # 45L, # 44, # 33, # 32, # 30 (above, manufactured by Mitsubishi Chemical Corporation), SpecialBlaek4A, 550, Printex95, 90, 85, 80, 75 , 45, 40 (above, manufactured by Degussa), Regal660, RmogulL, monarch1400, 1300, 1100, 800, 900 (above, manufactured by Cabot), Raven7000, 5750, 5250, 3500, 3500, 2500 ULTRA, 2000, 1500, 1255 , 1200, 1190 ULTRA, 1170, 1100 ULTRA, Raven5000UIII (above, manufactured by Columbian) and the like.

  The concentration of the pigment is not particularly limited because it may be adjusted to an appropriate pigment concentration (content) when the ink composition is prepared, but in this embodiment, the solid content concentration of the pigment is 6% by weight or more. It is preferable to make it 12% by weight or more. When ink droplets adhere to the recording medium, the ink spreads wet on the surface of the recording medium. However, by increasing the pigment solid concentration to 6% by weight or more, the fluidity of the ink after the wet spreading stays early. Since the ink is lost, bleeding can be further suppressed when printing is performed on a recording medium such as printing paper at a low resolution. That is, by using a combination of the above four specific alcohol solvents, the ink spreads even on a recording medium with low ink absorbency, and at the same time, by increasing the solid content concentration of the ink, It is considered that bleeding of ink can be suppressed by reducing the fluidity of ink. In particular, the effect of suppressing bleeding is remarkable at the boundary between a portion with a small amount of ink adhesion and a portion with a large amount of ink in the recording medium.

  The pigment is a pigment that has been kneaded with a dispersant, which will be described later, to achieve both the glossiness of the image, the prevention of bronzing, and the storage stability of the ink composition, and to form a color image that is further excellent in glossiness. From the viewpoint of being able to.

<Dispersant>
The ink composition according to the present embodiment includes at least one resin selected from a styrene-acrylic acid copolymer resin, a urethane resin, and a fluorene resin as a dispersant for dispersing the colorant. Is preferred. These copolymer resins are adsorbed on the pigment to improve dispersibility.

  Specific examples of the hydrophobic monomer in the copolymer resin include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso- Octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl meta Relate, decyl acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate Relate, nonylphenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1, 4-butanediol diacrylate, 1,4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate Acrylate, tetraethylene glycol dimethacrylate, poly Tylene glycol diacrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane tri Examples thereof include acrylate, trimethylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methylstyrene, vinyltoluene and the like. You may use these individually or in mixture of 2 or more types.

Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.
From the viewpoint that the copolymer resin of the hydrophobic monomer and the hydrophilic monomer can form a color image having both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. , Styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic ester copolymer resin Or at least one of styrene- (meth) acrylic acid- (meth) acrylic ester copolymer resins.

The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, a salt such as sodium, potassium, or ammonium may be used.
The content of these copolymer resins is 100 parts by weight of the pigment from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image with further excellent glossiness. The amount is preferably 20 to 50 parts by weight, and more preferably 20 to 40 parts by weight.

  In this embodiment, by using a urethane resin as a pigment dispersant, a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness can be obtained. Can be formed. The urethane resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound. In this embodiment, the urethane resin is a resin having a urethane bond and / or an amide bond and an acidic group. It is preferable.

Examples of the diisocyanate compound include aromatic aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products thereof. .
Examples of the diol compound include polyethers such as polyethylene glycol and polypropylene glycol, polyesters such as polyethylene abido and polybutylene abates, and polycarbonates.

The urethane resin preferably has a carboxyl group.
In the present embodiment, a fluorene-based resin can also be used as the pigment dispersant.

The weight ratio (the former / the latter) of the copolymer resin and the urethane resin is preferably 1/2 to 2/1. However, the gloss of the color image, the prevention of bronzing, and the storage stability of the ink composition are compatible. From the viewpoint of forming a color image having further excellent glossiness, the ratio is more preferably from 1 / 1.5 to 1.5 / 1.
The weight ratio of the solid content of the pigment to the solid content other than the pigment (the former / the latter) is compatible with the glossiness of the color image, the prevention of bronzing, and the storage stability of the ink composition, and is further excellent in the glossiness. From the viewpoint of forming a color image, it is preferably 100/20 to 100/80.

The content of the copolymer resin is 100 parts by weight of the pigment from the viewpoint of achieving both color image glossiness, bronzing prevention, and storage stability of the ink composition and at the same time forming a more glossy color image. The amount is preferably 20 to 50 parts by weight, and more preferably 20 to 40 parts by weight.
The content of the urethane resin is 100 parts by weight of the pigment from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition, and forming a color image with further excellent glossiness. On the other hand, it is preferably 10 to 40 parts by weight, and more preferably 10 to 35 parts by weight.
The content of the fluorene-based resin is 100 parts by weight of the pigment from the viewpoint of achieving color image glossiness, prevention of bronze, and storage stability of the ink composition and forming a color image having further excellent glossiness. The amount is preferably 20 to 100 parts by weight, and more preferably 20 to 80 parts by weight.

  The total amount of the copolymer resin and the urethane resin is used so as to be 90 parts by weight or less (more preferably 70 parts by weight or less) with respect to 100 parts by weight of the pigment. This is preferable in that it is possible to form a color image having both excellent prevention of bronzing and storage stability of the ink composition and further excellent glossiness.

The acid value of the copolymer resin is preferably from 50 to 320 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image having further excellent glossiness. More preferably, it is 100-250.
The acid value of the urethane resin is preferably 10 to 300 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image having further excellent glossiness. Yes, more preferably 20-100. The acid value is the mg amount of KOH required to neutralize 1 g of resin.

The weight-average molecular weight (Mw) of the copolymer resin is preferable from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is from 2,000 to 30,000, more preferably from 2,000 to 20,000.
The weight-average molecular weight (Mw) before crosslinking of the urethane resin is compatible from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and at the same time forming a more glossy color image. , Preferably it is 100-200,000, More preferably, it is 1000-50,000. Mw is measured by GPC (gel permeation chromatography), for example.

The glass transition temperature (Tg; measured in accordance with JISK6900) of the copolymer resin is a viewpoint capable of forming a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is preferably 30 ° C. or higher, and more preferably 50 to 130 ° C.
The urethane resin has a glass transition temperature (Tg; measured in accordance with JISK6900) from the viewpoint of achieving a color image having excellent glossiness while maintaining the glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. Is preferably −50 to 200 ° C., and more preferably −50 to 100 ° C.

  The copolymer resin has a case where it is adsorbed to the pigment in the pigment dispersion and a case where it is liberated, and achieves both glossiness of color images, prevention of bronzing, and storage stability of the ink composition. In addition, from the viewpoint of forming a color image having further excellent gloss, the copolymer resin preferably has a maximum particle size of 0.3 μm or less, and an average particle size of 0.2 μm or less (more preferably 0.1 μm). The following is more preferable. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

The fluorene resin is not limited as long as it has a fluorene skeleton, and can be obtained, for example, by copolymerizing the following monomer units.
Cyclohexane, 5-isocyanate-1- (isocyanatomethyl) -1,3,3-trimethyl (CAS No. 4098-71-9)
Ethanol, 2,2 ′-[9H-fluorene-9-ylidenebis (4,1-phenyleneoxy)] bis (CAS No. 117344-32-8)
Propionic acid, 3-hydroxy-2- (hydroxymethyl) -2-methyl (CAS No. 4767-03-7)
Ethanamine, N, N-diethyl- (CAS No. 121-44-8)

  A surfactant may be used as the dispersant. Such surfactants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate esters, naphthenates, liquid fats. Anionic surfactants such as oil sulfate esters and alkyl allyl sulfonates; Cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene alkyl ethers and polyoxyethylene alkyls Nonionic surfactants such as esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters and the like can be mentioned. It goes without saying that the surfactant also functions as a surfactant when added to the ink composition.

<Surfactant>
The ink composition for ink jet recording according to the present embodiment contains a surfactant as an essential component. Glossy recording media such as photographic paper, where glossiness is more important by using a surfactant, compared to a recording medium coated with a resin for receiving ink on the surface. Can be realized. In particular, even when a recording medium having a coating layer for receiving oil-based ink is provided on the surface receiving layer, such as printing paper, bleeding between colors (bleeding) can be prevented. At the same time, it is possible to prevent whitening due to reflected light of light generated with an increase in the amount of ink attached.

  As the surfactant used in the present embodiment, an organopolysiloxane-based surfactant can be suitably used, and when forming a recorded image, the wettability to the surface of the recording medium is increased to increase the ink permeability. Can do. When an organopolysiloxane-based surfactant is used, it contains three types of alcohol solvent as described above, so that the solubility of the surfactant in the ink is improved and the generation of insoluble matter can be suppressed. An ink composition having better ejection stability can be realized.

  Commercially available surfactants such as those described above may be used, such as Olfine PD-501, Olfine PD-502, Olfine PD-570 (all manufactured by Nissin Chemical Industry Co., Ltd.) and the like. be able to.

Further, as the organopolysiloxane surfactant, the following formula (I):

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 11, m represents an integer of 2 to 50, and n represents an integer of 1 to 5.)
Or a compound represented by the above formula (I), wherein R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, and m is More preferably, it is an integer of 2 to 50, and n comprises one or more compounds that are integers of 1 to 5. In the compound of the above formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 8. More preferably, it comprises one or more compounds. Or in the compound of the said formula (I), R is a methyl group, a is an integer of 6-18, m is 0, n is 1 or 1 type, or 2 or more types of compounds are included. More preferably. By using such a specific organopolysiloxane surfactant, unevenness of ink aggregation is further improved even when printing on a printing paper as a recording medium.

  In the compound of the above formula (I), a is an integer of 2 to 5, m is an integer of 20 to 40, n is an integer of 2 to 4, and a is an integer of 7 to 11. , M is an integer of 30 to 50, n is an integer of 3 to 5, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 It is more preferable to use a certain compound or a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, the unevenness of ink aggregation can be further improved.

  In the compound of the above formula (I), R is a hydrogen atom, a is an integer of 2 to 5, m is an integer of 20 to 40, and n is an integer of 2 to 4, Alternatively, it is more preferable to use a compound in which a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (I), R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2, Alternatively, it is more preferable to use a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the compound of the above formula (I), it is more preferable to use a compound in which R is a methyl group, a is an integer of 6 to 12, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (I), R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5; R is a methyl group, a is an integer of 9-13, m is an integer of 2-4, n is an integer of 1-2, R is a methyl group, and a is 6 It is most preferable to use a mixture of a compound having an integer of -10, m is an integer of 10-20, and n is an integer of 4-8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

The surfactant is preferably contained in the ink composition according to the present embodiment in an amount of 0.01 to 1.0% by weight, more preferably 0.05 to 0.50% by weight. In addition, it is more preferable to use the surfactant in which R is a methyl group in combination with the surfactant in which R is a hydrogen atom because small font characters are not crushed. In particular, in the case of using the surfactant in which R is a methyl group, the content may be larger than in the case of using the surfactant in which R is H, from the viewpoint of ink aggregation spots. preferable.
Furthermore, it is more preferable that the content of the surfactant in which R is H is increased with respect to the surfactant in which R is a methyl group. By doing in this way, ink aggregation spots and bleeding can be improved even in printing main paper such as cast-coated paper, which is easy to repel ink and has a low permeation rate.

The ink composition according to the present embodiment may further contain other surfactants, specifically, acetylene glycol surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like. .
Among these, acetylene glycol surfactants include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Diol, or 3,5-dimethyl-1-hexyne-3-ol, 2,4-dimethyl-5-hexyn-3-ol, and the like can be mentioned. Commercially available acetylene glycol surfactants can also be used. For example, Olphine E1010, STG, Y (trade name, manufactured by Nissin Chemical Co., Ltd.), Surfynol 61, 104, 82, 465, 485 or TG (Trade name, manufactured by Air Products and Chemicals Inc.).

<Water, other ingredients>
The ink composition for inkjet recording according to the present embodiment contains the above-described specific alcohol solvent, surfactant, and other various additives, and water as a solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria is prevented for a long period of time.
The ink composition according to the present embodiment preferably contains a penetrant in addition to the above components.

As the penetrant, glycol ethers can be preferably used.
Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert. -Butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-iso-propyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene Glycolmo Non-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether , Dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol-iso-propyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-tert-butyl ether 1-methyl-1-methoxybutanol, and the like. It can be used as a mixture of two or more.

  Among the above glycol ethers, alkyl ethers of polyhydric alcohols are preferable, and ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, propylene glycol are particularly preferable. Monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether or triethylene glycol mono-n-butyl ether are preferred. More preferred is triethylene glycol mono-n-butyl ether.

The addition amount of the penetrant may be appropriately determined, but is preferably about 0.1 to 30% by weight, more preferably about 1 to 20% by weight.
In addition, the ink composition according to the present embodiment preferably contains a recording medium solubilizer in addition to the above components.
As the recording medium solubilizer, pyrrolidones such as N-methyl-2-pyrrolidone can be preferably used. The addition amount of the recording medium solubilizer may be appropriately determined, but is preferably about 0.1 to 30% by weight, more preferably about 1 to 20% by weight.

In addition, the ink composition for ink jet recording according to the present embodiment preferably does not substantially contain a wetting agent. A wetting agent has a function of preventing ink from drying and solidifying in an ink jet nozzle or the like. Therefore, when ink is dropped on synthetic paper having particularly low ink absorption performance, the ink does not dry and high-speed printing is possible. Can be problematic. In addition, when ink containing a wetting agent is used, the next ink adheres to the recording medium in a state where unabsorbed ink exists on the surface of the recording medium, so that aggregation spots may occur.
For this reason, in the present embodiment, it is preferable that the wetting agent is not substantially contained when such a recording medium having particularly low ink absorption performance is used. Even when the ink is dried and solidified in the inkjet nozzle, the solidified ink can be redissolved by applying a solution containing a wetting agent.

In particular, in this embodiment, it is preferable that a wetting agent having a vapor pressure of 2 mPa or less at 25 ° C. is not substantially contained. “Substantially free” means that the amount of the wetting agent added is less than 1% by weight based on the ink composition.
When the content of the wetting agent having a vapor pressure at 25 ° C. of 2 mPa or less is less than 1% by weight with respect to the ink, not only the recording medium having low ink absorbability such as printing paper, but also the ink absorbing ability is completely eliminated. Even for metals and plastics that are not present, printing can be performed by the ink jet recording method. In addition, although it is clear for those skilled in the art that a part of the above-described penetrating solvent also acts as a wetting agent, in the present specification, the above-described penetrating solvent is not included in the wetting agent. . In the present specification, the above alcohol solvent is not included in the wetting agent.

In the present specification, the wetting agent means a wetting agent used in ordinary ink jet recording inks. Specifically, glycerin, ethylene glycol, 1,3-propanediol, 3-methyl-1,3. -Water-soluble alkane diols having 3 to 5 carbon atoms such as butanediol, 1,3-butanediol, 1,2-pentanediol, trimethylolpropane, trimethylolmethane, trimethylolethane and the like. When the recording medium is a printing paper having a low ink absorbency, these wetting agents can be appropriately added.
The ink composition according to the present embodiment further includes an anti-clogging agent for nozzles, an antiseptic, an antioxidant, a conductivity adjusting agent, a pH adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen absorber, and the like. Can do.

  Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, 2-pyridinethiol-1-oxide sodium, sodium sorbate, sodium dehydroacetate, 1,2-dibenzthiazoline-3-one ( ICI's Proxel CRL, Proxel BND, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  Furthermore, as examples of pH adjusters, other solubilizers or antioxidants, amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, hydroxide Inorganic salts such as lithium, ammonium hydroxide, quaternary ammonium hydroxide (such as tetramethylammonium), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate, and other phosphates, or N-methyl-2-pyrrolidone, urea And L-ascorbic acid and salts thereof, such as ureas such as thiourea and tetramethylurea, allophanates such as allophanate and methylallohanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret.

  In addition, the ink composition according to the present embodiment may contain an antioxidant and an ultraviolet absorber, and examples thereof include Tinuvin 328, 900, 1130, 384, 292, 123, Ciba Specialty Chemicals, Inc. 144, 622, 770, 292, Irgacor 252 153, Irganox 1010, 1076, 1035, MD1024, lanthanide oxide, and the like.

  The ink composition according to the present embodiment can be produced by dispersing and mixing the above-described components by an appropriate method. Preferably, the pigment, polymer dispersant, and water are first used in a suitable dispersing machine (for example, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ang mill, etc.). Mix to prepare a uniform pigment dispersion, then add separately prepared resin (resin emulsion), water, water-soluble organic solvent, sugar, pH adjuster, preservative, fungicide, etc. An ink solution is prepared. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove the coarse particle diameter and foreign matters that cause clogging.

Inkjet Recording Method The inkjet recording method according to the present embodiment performs printing by ejecting droplets of the ink composition and attaching the droplets to a recording medium. In the recording method according to the present embodiment, it is preferable to use synthetic paper or main printing paper as a recording medium. In particular, art paper, high-quality paper used for POD (print on demand) and dedicated paper for laser printers, Even when printed at a low resolution, a high-quality image without white streaks or roughness can be realized. Examples of the high-quality paper for POD use include Ricoh Business Coat Gloss 100 (manufactured by Ricoh Co., Ltd.). Moreover, as an exclusive paper for laser printers, LPCCTA4 (made by Seiko Epson Corporation) is mentioned, for example.
Hereinafter, this embodiment will be described in more detail.

<Preparation of ink composition>
Each ink was prepared by mixing each component according to the composition of the following Tables 1-5, and filtering with a 10 micrometer membrane filter. The styrene-acrylic acid resin in the table is a copolymer having a molecular weight of 1600 and an acid value of 150. The urethane resin is a copolymer having a molecular weight of 6000 and an acid value of 50. In addition, fluorene-based resin is CAS No. This resin has a molecular weight of 3300 and contains a monomer having a fluorene skeleton represented by 117344-32-8 and a monomer composition ratio of approximately 50% by weight. Further, the surfactant used is an organopolysiloxane surfactant, and in the above formula (I), R is a methyl group, a is an integer of 9 to 13, and m is 2 to 4. An integer, a compound in which n is an integer of 1 to 2, R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5 Is a surfactant mixed with a compound.

Tables 1 to 5 are shown below.

(Examples 17 to 32 and Comparative Examples 5 to 8)
In addition, the ink sets 17 to 32 of the examples and the ink sets of Examples 1 to 16 and the ink sets of Comparative Examples 1 to 4 were similarly replaced with the following surfactants. Comparative ink sets 5 to 8 were prepared.
The surfactants used in Examples 17 to 32 and Comparative Examples 5 to 8 are, in the above formula (I), R is a methyl group, a is an integer of 6 to 10, and m is 10 to 20. It is a surfactant composed of a compound which is an integer and n is an integer of 4 to 8.

(Examples 33 to 48 and Comparative Examples 9 to 12)
In addition, the ink sets 33 to 48 of the examples and the ink sets of Examples 1 to 16 and the ink sets of Comparative Examples 1 to 4 were changed in the same manner except that the surfactants were changed to the following surfactants. Comparative ink sets 9 to 12 were prepared.
The surfactants used in Examples 33 to 48 and Comparative Examples 9 to 12 are those represented by the formula (I) in which R is a hydrogen atom, a is an integer of 7 to 11, and m is 30 to 50. A compound in which n is an integer of 3 to 5, R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 And a compound in which R is a methyl group, a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. is there.

(Examples 49 to 64 and Comparative Examples 13 to 16)
Further, the ink sets 49 to 64 of the examples and the ink sets of Examples 1 to 16 and the ink sets of Comparative Examples 1 to 4 were changed in the same manner except that the surfactants were changed to the following surfactants. Comparative ink sets 13 to 16 were prepared.
The surfactants used in Examples 49 to 64 and Comparative Examples 13 to 16 are the above formula (I), wherein R is a methyl group, a is an integer of 6 to 18, m is 0, A surfactant comprising a compound in which n is 1.

<Evaluation>
Evaluation of initial viscosity of ink The ink viscosity of each ink obtained as described above was evaluated. Using a vibration viscometer (MV100 model, manufactured by Yamaichi Electronics Co., Ltd.), the viscosity of the ink after 1 hour from the preparation of the ink was measured and evaluated according to the following criteria. The measurement temperature was 20 ° C.
S: The viscosity is 4 mPa · s or less.
AA: The viscosity is more than 4 mPa · s and not more than 5 mPa · s.
A: The viscosity exceeds 5 mPa · s and is 6 mPa · s or less.
B: Viscosity exceeds 6 mPa · s and is 7 mPa · s or less.
C: Viscosity exceeds 7 mPa · s and is 8 mPa · s or less.
D: The viscosity exceeds 8 mPa · s.
The evaluation results were as shown in Table 6 below.

Evaluation of Ink Viscosity of Ink After the ink prepared as described above was allowed to stand for 3 days in an environment of 70 ° C., the viscosity of the ink was measured in the same manner as described above and evaluated according to the following criteria.
A: The difference from the initial viscosity is 0.5 mPa · s or less.
B: The difference from the initial viscosity is more than 0.5 mPa · s and 1.0 mPa · s or less.
C: The difference from the initial viscosity is more than 1.0 mPa · s and not more than 2.0 mPa · s.
D: The difference from the initial viscosity exceeds 2.0 mPa · s.
The evaluation results were as shown in Table 6 below.

Evaluation of ink agglomeration spots and embedding properties Each ink of Y, M, C, and K obtained above is set as an ink set on an ink cartridge of an ink jet printer (PX-G920, manufactured by Seiko Epson Corporation), and main scanning is performed. Recording was possible at 720 dpi in the (head drive) direction and 360 dpi in the sub-scanning (recording medium conveyance) direction. Next, the voltage of the printer is adjusted so that the dot size upon landing is approximately 7 ng. One drive is 720 × 360 dpi, OKT + (made by Oji Paper Co., Ltd.) of about 128 g / square meter, 720 × 720 dpi solid Images were recorded. Recording was performed in a room temperature and normal humidity environment. The ink adhesion amount was approximately 3.6 mg / inch square meters.

The obtained image was evaluated according to the following criteria.
A: There are no white stripes due to aggregated spots and poor filling.
B: There are no aggregated spots, but there are white streaks due to poor filling.
C: There are white spots due to aggregation spots and poor filling.
D: The ink flow is intense and cannot be determined.
The evaluation results were as shown in Table 6 below.

Curl Evaluation Printing was performed in the same manner as above except that 104.7 g / square meter of OKT + (manufactured by Oji Paper Co., Ltd.) was used as the recording medium. With the printed surface of the obtained printed matter facing upward, it was allowed to stand for 24 hours in a 40% RH environment at 25 ° C. on a flat desk. After that, the distance between the desk and the four corners of the printed material warped was measured and averaged.
A: Height is less than 5 mm A: Height is 5 mm or more and less than 10 mm B: Height is 10 mm or more and less than 20 mm C: Height is 20 mm or more The evaluation results are as shown in Table 6 below.

Evaluation of Initial Fixability The OKT + printed material was rubbed with a finger after 3 minutes.
A: There is no peeling of the coloring material.
B: Coloring material is peeled off.
The evaluation results were as shown in Table 6 below.

Evaluation of solubility of poorly water-soluble alkanediol 1,2-octanediol was used as the poorly water-soluble alkanediol, and an aqueous solution containing 10% by weight of 1,2-octanediol was prepared. In this aqueous solution, 1,2-octanediol was not completely dissolved and was in a cloudy state.
To 10 g of the prepared aqueous solution, 1,2-hexanediol (hereinafter abbreviated as HED), 3-methyl-1,3-butanediol (hereinafter abbreviated as 3MBUD), 1,3-butanediol (hereinafter abbreviated as HED) 1,3-BUD), 1,2,6-hexanetriol (hereinafter abbreviated as HET), and 3-methyl-1,3,5-pentanetriol (hereinafter abbreviated as 3MPET). Five types of alcohol solvents were added, respectively, until the aqueous solution became transparent.
Further, instead of the above aqueous solution, an aqueous solution containing 10% by weight of 1,2-octanediol as the hardly water-soluble alkanediol and 10% by weight of 1,2-hexanediol as the water-soluble 1,2-alkanediol was prepared. In the same manner as above, each alcohol solvent was added until the aqueous solution became transparent.
The addition amount (g) of each alcohol solvent in which the aqueous solution became transparent, that is, the slightly water-soluble alkanediol was completely dissolved was as shown in FIG.

  As is clear from FIG. 25, 3MBUD which is an alkanediol having a side chain on any one carbon having a hydroxyl group in a two-component alcohol aqueous solution containing 1,2-octanediol and 1,2-hexanediol. Is higher in the ability to dissolve 1,2-octanediol than 1,3-BUD, which is an alkanediol having no side chain on any one carbon having a hydroxyl group. It can also be seen that the ability to dissolve 1,2-octanediol is higher than when only HED is added.

  On the other hand, as is clear from FIG. 25, in the aqueous solution containing 1,2-octanediol, HET and 3MPET, which are water-soluble alkanetriols, are compared with the case where only HED is added. It can be seen that the ability to dissolve octanediol is low. Therefore, in an ink composition containing 1,2-octanediol, 3MBUD, which is an alkanediol having a side chain on any one carbon having a hydroxyl group, or 1,2-, which is a water-soluble 1,2-alkanediol. It turns out that it is preferable to contain hexanediol simultaneously.

Evaluation of Clogging Recoverability Using the ink cartridge and the ink jet printer described above, the ink replacement button was pushed, and then the outlet was removed. Thus, after the head cap was removed, the printer was left in an environment of 40 ° C. and 15% RH for 1 day. After leaving, the cleaning operation was repeated until all nozzles ejected at the same level as the initial stage, and the ease of recovery was evaluated according to the following criteria.
A: The clogging is recovered by repeating the cleaning operation three times.
B: The clogging is recovered by repeating the cleaning operation six times.
C: The clogging is recovered by repeating the cleaning operation 12 times.
D: The clogging does not recover even if the cleaning operation is repeated 12 times.

The evaluation results were as shown in Table 6 below.

Moreover, when evaluation similar to the above was performed also about Examples 17-32 and Comparative Examples 5-8, it was the same evaluation result as Examples 1-16 and Comparative Examples 1-4.
Furthermore, when Examples 33 to 48 and Comparative Examples 9 to 12 were evaluated in the same manner as described above, the evaluation results were the same as those of Examples 1 to 16 and Comparative Examples 1 to 4.
Moreover, when evaluation similar to the above was performed also about Examples 49-64 and Comparative Examples 13-16, it was the same evaluation result as Examples 1-16 and Comparative Examples 1-4.
Further, in Examples 1 to 64 and Comparative Examples 1 to 16, the examples were exactly the same except that 3-methyl-1,3,5-pentanetriol was used instead of 1,2,6-hexanetriol. 65-128 were created. When evaluation similar to the above was performed, Examples 1 to 64 and Comparative Examples 1 to 16 were the same evaluation results except for the evaluation results of curl. The evaluation result of curl was improved by one level. It can be seen that the alkanetriol having a side chain on any one of the carbons having a hydroxyl group has a higher curl suppressing effect.

=== Other Embodiments ===
In the above-described embodiment, the printer 1 has been described as a printing apparatus. However, the printer 1 is not limited to this, and is not limited to this. Other fluids other than ink (such as liquids and liquids in which functional material particles are dispersed, gels, and the like) It is also possible to embody the present invention in a liquid ejecting apparatus that ejects or ejects a fluid. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, gas vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to the above-mentioned embodiment to the various apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

  The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

1 is a block diagram of an overall configuration of a printing system. 2A is a cross-sectional view of the printer 1, and FIG. 2B is a perspective view for explaining the paper S conveyance process of the printer 1. 4 is a diagram for explaining a detailed arrangement of four heads of a head unit 40. FIG. It is a figure for demonstrating aggregation. It is a figure which shows the ink in a medium when bleeding does not arise. It is a figure which shows the ink in a medium when bleeding occurs. 6 is a flowchart for explaining print data generation processing; It is a figure which shows an example of the gradation value of each pixel. It is a flowchart for demonstrating a pixel etching process. 4 is a diagram for explaining each pixel in an original image P. FIG. It is a figure for demonstrating each pixel in the image P 'after 1st resolution conversion. It is a figure for demonstrating each pixel in the image P '' after 2nd resolution conversion. It is an edge detection filter applied in this embodiment. It is a figure for demonstrating the synthesis | combination of the image F after the filter application of each plane. It is a figure for demonstrating each pixel in the image E after binarization application. It is a figure for demonstrating each pixel of the image E 'after binarization application. It is a figure for demonstrating each pixel in the image C after a pixel etching process. It is a figure for demonstrating the pixel before pixel etching. It is a figure for demonstrating the pixel of the image after a pixel etching process. It is a flowchart for demonstrating the halftone process in this embodiment. It is a figure which shows the production | generation rate table at the time of normal mode. It is a figure which shows the production | generation rate table in the time of high coloring mode. It is a figure which shows the mode of the dot ON / OFF determination by a dither method. 24A is a diagram showing a dither matrix used for determination of large dots, and FIG. 24B is a diagram showing a dither matrix used for determination of medium dots. It is the graph which showed the solubility of 1,2-octanediol at the time of adding each alcohol solvent to 1,2-octanediol aqueous solution.

Explanation of symbols

1 printer, 20 paper transport mechanism,
21 Paper feeding roller, 23A Upstream conveying roller, 23B Downstream conveying roller,
24 belts, 29 springs, 40 head units, 50 detector groups,
60 ASIC, 61 interface, 70 drive signal generation circuit,
100 computer, 112 interface, 113 CPU, 114 memory,
120 display device, 130 input device, 140 recording / reproducing device,
417 Piezo element, HC head controller, S paper

Claims (8)

(A) a head that forms an image by ejecting ink onto a medium;
(B) a control unit for controlling the head,
(B1) a first mode for controlling the head so as not to eject the ink to the edge pixels of the image;
(B2) The ink is also ejected to the edge pixels of the image while the amount of ink ejected when the portion excluding the edge pixels of the image is formed on the medium is smaller than that in the first mode. A second mode for controlling the head to form the image;
A control unit for controlling the head so as to be selectable,
A printing apparatus comprising:   2. The ink according to claim 1, wherein the ink is an ink including at least a colorant, water, an alcohol solvent, and a surfactant, and the ink includes a sparingly water-soluble alkanediol in at least one of the alcohol solvents. Printing device.   The alcohol solvent includes a slightly water-soluble alkanediol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol. The printing apparatus according to claim 1 or 2. When the control unit controls the head in the first mode,
An image after applying a filter obtained by applying an edge filter to the image is obtained, binarization processing is performed on the image after the filter application to obtain an edge pixel, and a pixel of the image to be processed corresponding to the edge pixel is set to be colorless The printing apparatus according to claim 1, wherein the head is controlled so that the ink is not ejected to the edge pixels by using the obtained data.   5. The control unit according to claim 1, wherein the control unit includes a plurality of tables for obtaining a dot size generated from a gradation value, and the tables used in the first mode and the second mode are different. A printing apparatus according to 1.   The printing apparatus according to claim 1, wherein the ink ejected from the head in the first mode is different from the ink ejected from the head in the second mode.   The printing apparatus according to any one of claims 1 to 6, wherein the medium is synthetic paper or printing paper whose main raw material is synthetic resin. A first mode in which the head is controlled so as not to eject ink to the edge pixels of the image; and a second mode in which the head is controlled so that the ink weight per unit area on the medium is smaller than in the first mode. Selecting at least one of
Controlling the head in a mode selected from the first mode and the second mode, and ejecting ink onto the medium to form an image;
Including printing method.