JP2018167517A - Thermal transfer printing method - Google Patents

Abstract

To provide a thermal transfer method which can suppress a curl amount of a printed matter.SOLUTION: This thermal transfer print method comprises: a process for heating an ink ribbon 5, transferring an ink on a print sheet 7 from the ink ribbon, and printing an image; and a process for heating the ribbon including a protection layer, and transferring the protection layer on the image. The method sets a print speed at the transfer of the ink to 2.5 times or higher and 5 times or lower of the print speed of the protect layer, and brings a protection layer surface after the transfer into a matte state. The matte state exhibits a surface such as a raster and a silky pattern which are called in silver halide photography.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal transfer printing method for suppressing a curl amount of a printed material.

  There is known a thermal transfer printer in which an ink ribbon and a printing sheet are sandwiched between a thermal head and a platen roll, heat is applied from the thermal head to the ink ribbon, and ink on the ink ribbon is transferred to the printing sheet.

  In a thermal transfer printer, in order to form an image on a printing sheet, it is essential to heat the printing sheet with a thermal head. However, due to heating and pressurization during printing, the resin layer applied and pasted on the front or back side of the printing sheet, the pulp layer of the core paper, etc. may shrink or be deformed due to changes in moisture content. However, there is a problem that curling (warping) occurs in a printed material produced by a thermal transfer printer.

  Thermal transfer printers are known in which a curled path is formed by passing a bent path when a printed product is discharged to reduce curling. However, this method complicates the structure of the thermal transfer printer.

JP 2011-5700 A JP-A-2015-147336

  An object of the present invention is to provide a thermal transfer printing method that suppresses the curl amount of a printed material.

As a result of earnest research to solve the above-mentioned problems, the inventor appropriately sets the surface speed of the transferred protective layer by appropriately setting the printing speed and applied energy at the time of transferring the protective layer. The present inventors have found that curling can be suppressed.
The present invention has been achieved based on such findings, and the gist thereof is as follows.

  The thermal transfer printing method according to the present invention includes a step of heating an ink ribbon, transferring an ink from the ink ribbon onto a printing sheet to print an image, and heating a ribbon including a protective layer to form the protective layer on the image. And a printing speed when transferring the ink is set to 2.5 to 5 times the printing speed of the protective layer, and the surface of the protective layer after transfer is matted. is there.

  The thermal transfer printing method according to the present invention includes a step of heating an ink ribbon, transferring an ink from the ink ribbon onto a printing sheet, and printing an image, and heating the ribbon including a protective layer using a thermal head. A step of transferring the protective layer thereon, and changing the amount of heat energy per screen applied by the thermal head when the protective layer is transferred in accordance with the printing speed of the protective layer. The subsequent protective layer surface is matted.

  In one aspect of the present invention, when the amount of heat energy per screen applied by the thermal head when the printing speed when the protective layer is printed in the mat state is V is E, the printing speed of the protective layer is The amount of thermal energy E ′ per screen applied by the thermal head when V / n (n is an integer of 2 or more) is E <E ′ <n × E.

  According to the present invention, the curl amount of a printed product can be suppressed.

1 is a schematic configuration diagram of a thermal transfer printing apparatus according to an embodiment of the present invention. It is a top view of an ink ribbon. It is sectional drawing of a printing sheet.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a thermal transfer printing apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view of an ink ribbon used in the thermal transfer printing apparatus. The thermal transfer printing apparatus prints an image by sublimation transfer of yellow, magenta, and cyan onto a printing sheet (printing paper, image receiving paper). The image to be printed is, for example, a human image such as a face image, or characters such as an address or name.

  In the thermal transfer printing apparatus, a Y layer 51 containing a yellow dye (Y), an M layer 52 containing a magenta dye (M), a C layer 53 containing a cyan dye (C), and a protective (OP) layer 54 are provided in the surface order. A thermal head 1 is provided which uses the ink ribbon 5 thus formed to print Y, M, and C by sublimation transfer onto a printing sheet 7 to print an image and form a protective layer on the image.

  The thermal head 1 has a plurality of heating elements. Heat is generated by passing a current through the heating element. Each heating element is connected to a switching element that switches on / off of the current.

  An ink ribbon supply unit 3 formed by winding an ink ribbon 5 is provided on the downstream side of the thermal head 1, and an ink ribbon collection unit 4 is provided on the upstream side of the thermal head 1. The ink ribbon 5 fed out from the ink ribbon supply unit 3 passes through the thermal head 1 and is collected by the ink ribbon collection unit 4.

  A rotatable platen roll 2 is provided below the thermal head 1. The printing unit 10 including the thermal head 1 and the platen roll 2 sandwiches the printing sheet 7 and the ink ribbon 5 and heats the ink ribbon 5 to thermally transfer ink onto the printing sheet 7 to form an image.

  In the ink ribbon 5, a Y layer 51, an M layer 52, a C layer 53, and an OP layer 54 are sequentially formed on one surface of the base material layer from the ink ribbon collection unit 4 side. In other words, a plurality of sets of the ink layer 50 including the Y layer 51, the M layer 52, the C layer 53, and the OP layer 54 are continuously provided. For the Y layer 51, the M layer 52, and the C layer 53, it is preferable to use a material obtained by melting or dispersing a sublimable dye in a binder resin.

  The OP layer 54 is preferably made of a transparent material having adhesiveness, light resistance, and the like. By reducing the energy applied to the thermal head 1 when the OP layer 54 is transferred onto the image, the surface of the protective layer can be brought into a glossy state with high glossiness, and by increasing the energy applied, The surface of the protective layer can be in a matte state with a low glossiness. For example, a state where the glossiness is about 70% or more is called a glossy state, and a state where the glossiness is 40% or less is called a matte state. The glossiness is a value measured at an incident angle of 45 ° during measurement using a gloss meter.

  Further, when the OP layer 54 is transferred, thermal energy is applied in a random pattern by the thermal head 1 (the high energy application portion and the low energy application portion are made random), and the raster or silk pattern in silver salt photography is used. By imitating a rough surface, it is possible to perform a matte finish that adds value to the printed matter. When the applied thermal energy is appropriate, the mat finish is such that a portion having at least two gradations of a generally glossy portion and a non-glossy portion can be visually discriminated in a fine pattern.

  The base material layer of the ink ribbon 5 is a layer for supporting the ink layer 50, and a conventionally known material having a certain degree of heat resistance and strength can be used. For example, a polyethylene terephthalate (PET) film, a polyethylene naphthalate film, a polystyrene film, a polypropylene (PP) film, a polycarbonate film, etc. are mentioned.

  A back layer is provided on the other surface of the base material layer, that is, the surface opposite to the surface on which the ink layer 50 is provided. The thermal head 1 heats the ink ribbon 5 from the back layer side. The back layer has a function of improving heat resistance so that the ink ribbon 5 is not deformed by heat at the time of thermal transfer, and also improving the running performance of the thermal head 1 at the time of thermal transfer to suppress sticking and the like. The back layer can be generally formed by applying and drying a binder resin to which a lubricant, a surfactant, inorganic particles, organic particles, a pigment, and the like are added.

  In addition to the OP layer 54, the ink ribbon 5 includes a melt layer containing a binder resin and a coloring material such as pigment or carbon black, a Y layer 51, a M layer 52, and a C layer 53, which are dye layers for sublimation transfer. They may be provided in the surface order.

  On the upstream side of the thermal head 1, there are provided a capstan roller 9 a that can be rotated and driven to convey the printing sheet 7, and a pinch roller 9 b that presses the printing sheet 7 against the capstan roller 9 a.

  The photographic sheet 7 is wound around the photographic paper roll 6 and is fed out from the photographic paper roll 6. The printing sheet roll 6 (capstan roller 9a, pinch roller 9b, etc.) feeds the printing sheet 7 (forward conveyance) and winds (rear conveyance).

As the printing sheet 7, a known sheet used in this type of thermal transfer printing apparatus can be used. For example, as shown in FIG. 3, a resin coat layer 71, paper 72, an adhesive layer 73, and a void-containing film 74 are used. , And a receiving layer 75 laminated in this order can be used. As the void-containing film 74, various films can be used as long as voids are formed in the film. For example, it is possible to use a film in which a void is formed in a film by adding a void developing agent in PET, forming a film, and stretching. As the base material, in addition to PET, polyolefin resins such as PP and PE (polyethylene) can be used.

  The control device 14 controls the driving of each unit of the thermal transfer printing apparatus and performs printing processing. In the printing process, first, the printing sheet 7 and the Y layer 51 are aligned, and the thermal head 1 contacts the platen roll 2 via the printing sheet 7 and the ink ribbon 5. Next, the capstan roller 9a and the ink ribbon collection unit 4 are driven to rotate, and the printing sheet 7 and the ink ribbon 5 are sent to the rear side. During this time, the area of the Y layer 51 is selectively and sequentially heated by the thermal head 1 based on the image data, and Y is sublimated and transferred from the ink ribbon 5 onto the printing sheet 7. The switch element of the thermal head 1 is repeatedly turned on the number of times corresponding to each pixel value of the image data, and a current flows through the heating element.

  After the sublimation transfer of Y, the thermal head 1 rises and leaves the platen roll 2. Next, the printing sheet 7 and the M layer 52 are aligned. In this case, the printing sheet 7 is fed forward by a distance corresponding to the print size, and the ink ribbon 5 is fed backward by a distance corresponding to a margin between the Y layer 51 and the M layer 52.

  In the same manner as the method for sublimation transfer of Y, M and C are successively sublimated and transferred onto the printing sheet 7 to form a screen having an image on the printing sheet 7. Next, the OP layer 54 is transferred onto the screen by the thermal head 1 to form a protective layer.

  After that, the printing sheet 7 having the protective layer formed on the screen is cut by the cutter 8 provided on the downstream side to cut the rear edge of the screen to produce a printed sheet (printed material) 7a on which the screen is formed. Is done. The printed sheet 7a is discharged from a discharge port (not shown).

  When thermal energy is applied to the printing sheet 7 from the thermal head 1 or when it is sandwiched between the thermal head 1 and the platen roll 2 and pressed, the resin layer and the paper pulp layer of the printing sheet 7 contract. The printed sheet 7 may be curled (warped) by being deformed due to a change in moisture content.

  By increasing the energy at the time of printing, curling occurring on the printed sheet 7 can be reduced. For example, between a printed sheet 7 on which a high-density image is printed and a printed sheet 7 on which a low-density image is printed, the printed sheet 7 on which a high-density image is printed has a smaller curl. . However, since the energy at the time of image printing affects the image quality of the printed image, it is not preferable to change the energy at the time of image printing for the purpose of curling suppression.

  It is conceivable to reduce curl by increasing the energy when transferring the OP layer 54. However, for example, if the printing parameters and printing speed at the time of transferring the OP layer 54 are kept as they are, the energy is simply increased and the OP layer 54 is transferred with an energy out of the energy range suitable for mat finishing, thereby reducing the curl. However, the mat finish is not appropriate.

  Therefore, in the present embodiment, the time required for the transfer of the OP layer 54 (transfer time) is set to be 2.5 times or more and 5 times or less of the time for thermal transfer of the Y layer 51, the M layer 52, and the C layer 53, respectively. In other words, the printing speed of the Y layer 51, the M layer 52, and the C layer 53 is set to 2.5 times or more and 5 times or less of the printing speed of the OP layer 54. For example, the printing speed of the Y layer 51, the M layer 52, and the C layer 53 is 1 msec. / Line, the printing speed of the OP layer 54 is 2.5 msec. / Line or more 5 msec. / Line or less.

  In the present embodiment, the “printing speed” of the OP layer 54 is expressed in accordance with the “printing speed” of the Y layer 51, the M layer 52, and the C layer 53, but the OP layer 54 performs color printing. Since it is not a thing, it can be paraphrased as “transfer speed”.

  Usually, the application of energy by the thermal head 1 is performed in a pulse manner. In the printing of the Y layer 51, the M layer 52, and the C layer 53, the gradation of the image is expressed by changing the pulse amount. For this reason, the accuracy of the applied pulse is ensured so that 64 to 256 gradations can be expressed per line of printing. Therefore, when the OP layer 54 is thermally transferred over 2.5 times the transfer time of each of the Y layer 51, the M layer 52, and the C layer 53, it is sufficient for supplying heat energy when forming the protective layer. As a result, an energy non-application time, that is, a cooling time can be obtained.

  Specifically, when energy equivalent to 128/255 gradations is applied when forming the protective layer, the required time per line is 1, the energy application time per line is 0.5, and the energy non-application time is 0. If the transfer time is 2.5 times with the applied energy amount per screen being equal, the energy application time is 0.5 and the energy non-application time is 2.0. It can be considered that the application time is approximately quadrupled.

  A longer energy non-application time is synonymous with a longer cooling time during printing, so the total applied energy per screen is reduced while maintaining the same matte finish before and after changing the printing speed. It can be increased. In that case, the effect of suppressing the occurrence of curling can be simultaneously obtained by increasing the applied energy.

  Since the printing speed affects the printing time, it is preferable that the printing speed is fast in this respect. In the present embodiment, only the transfer time of the OP layer 54 is set to five times or less of the transfer times of the Y layer 51, the M layer 52, and the C layer 53, so that the Y layer 51, the M layer 52, and the C layer 53 are reduced. Compared with the case where all the transfer times are equal to the transfer time of the OP layer 54, it is possible to suppress an increase in the time required for producing the printed sheet 7a.

  The thermal transfer printing apparatus stores a table (not shown) that stores a table that defines the relationship between the printing speed of the OP layer 54 and the amount of energy per screen applied by the thermal head 1 in order to put the surface of the protective layer in a mat state. (May be omitted).

  In this table, a larger amount of energy is specified as the printing speed is slower. When the printing speed becomes 1 / n times (transfer time n times), the amount of energy becomes a value larger than 1 and smaller than n times (n is an integer of 2 or more). For example, when the energy amount at the printing speed V is E, the energy amount E ′ at the printing speed V / n is E <E ′ <n × E. In other words, assuming that the energy amount in the transfer time T is E, the energy amount E ′ in the transfer time n × T is E <E ′ <n × E.

  When the control device 14 receives an instruction to change the setting of the production time of the printed sheet 7a from the user, the control device 14 calculates the printing speed (transfer time) of the OP layer 54 and refers to the table to calculate the calculated OP layer 54 printing. Determine the amount of energy corresponding to the speed. Then, the control device 14 controls the thermal head 1 so as to apply the determined amount of heat during the transfer of the OP layer 54. As a result, the printed sheet 7a with curl suppressed can be manufactured regardless of the manufacturing time of the printed sheet 7a.

  In the above embodiment, the configuration using the ink ribbon 5 in which the Y layer 51, the M layer 52, the C layer 53, and the OP layer 54 are sequentially formed has been described. However, the Y layer 51, the M layer 52, and the C layer 53 are formed. The ribbon on which the OP layer 54 is formed may be a separate body. Further, instead of an ink ribbon for transferring a plurality of colors, a single color ribbon may be used.

Using the thermal transfer printing apparatus shown in FIG. 1, under the following printing conditions, the printing speed of the OP layer 54 and the applied energy (energy input amount) per screen during the transfer of the OP layer 54 are changed, and the printing sheet 7 A protective layer having a matte surface was formed on the substrate, a printed sheet 7a was produced, and the curl amount of the printed sheet 7a was measured. As the printing sheet 7, a thermal transfer image receiving sheet dedicated to the sublimation printer DS680 (Dai Nippon Printing Co., Ltd.) was used.
Heating element average resistance: 3000Ω
Main scanning direction printing density: 300 dpi
Sub-scanning direction printing density: 300 dpi
Printing voltage: 27.5V

  The size of the printed sheet 7a is 6 inches × 8 inches, and the average amount of lifting at the four corners when the printed sheet 7a is placed on a flat surface is defined as the curl amount. The results are shown in Table 1 below. Moreover, the surface of the protective layer was visually confirmed. Those in which the mat state is good are surrounded by broken lines in Table 1.

  The thermal transfer printing apparatus used has the same form as a commercially available thermal transfer printer, and the ink of the Y layer 51, M layer 52, and C layer 53 is 1 msec. The image could be transferred at a printing speed of about / line. Only the printing speed of the OP layer 54 is ½ times the printing speed of the Y layer 51, M layer 52, and C layer 53, that is, 2 msec. Each energy input amount shown in Table 1 is shown as an energy input amount ratio when the energy amount per screen in which an appropriate mat state is set to 1 is set to 1 / line.

  The printing speed of the OP layer 54 is 2 msec. / Line twice, that is, 4 msec. / Line, when the applied energy per screen is larger than 1 time and slightly smaller than 2 times, the printing speed is 2 msec. / Line, it was confirmed that a good mat state was obtained while curling amount was suppressed as compared with the case of energy input amount 1.

  The printing speed of the OP layer 54 is 2 msec. / Line times 1/3, that is, 6 msec. / Line, the applied energy per screen is made larger than 1 and smaller than 3 times, so that the printing speed is 2 msec. / Line, it was confirmed that a good mat state was obtained while curling amount was suppressed as compared with the case of energy input amount 1.

DESCRIPTION OF SYMBOLS 1 Thermal head 2 Platen roll 3 Ink ribbon supply part 4 Ink ribbon collection | recovery part 5 Ink ribbon 6 Printing paper roll 7 Printing sheet 10 Printing part 14 Control apparatus

Claims (3)

Heating the ink ribbon, transferring ink from the ink ribbon onto a printing sheet, and printing an image;
Heating the ribbon including the protective layer to transfer the protective layer onto the image;
With
A thermal transfer printing method, wherein a printing speed at the time of transferring the ink is set to 2.5 times or more and 5 times or less of a printing speed of the protective layer, and the surface of the protective layer after transfer is put into a mat state. Heating the ink ribbon, transferring ink from the ink ribbon onto a printing sheet, and printing an image;
Heating the ribbon including the protective layer using a thermal head to transfer the protective layer onto the image;
With
According to the printing speed of the protective layer, the amount of heat energy per screen applied by the thermal head when the protective layer is transferred is changed so that the surface of the protective layer after transfer is matted. Thermal transfer printing method. When the amount of heat energy per screen applied by the thermal head when the printing speed when the protective layer is printed in the mat state is V is E, the printing speed of the protective layer is V / n (n is 2). 3. The thermal transfer printing method according to claim 2, wherein an amount of heat energy E ′ per screen applied by the thermal head at the time of the above integer is set to E <E ′ <n × E.

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