JP5358150B2 - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display excellent in display quality in both transmissive display and reflective display while maintaining wide visual field characteristics. <P>SOLUTION: The liquid crystal display in which each of pixels includes a reflective display part PR and a transmissive display part PT includes: an array substrate AR in which a pixel electrode EP is formed on the reflective display part and the transmissive display part of each pixel; a counter substrate CT provided with a counter electrode ET common to a plurality of pixels; a liquid crystal layer LQ which is held between the array substrate AR and the counter substrate CT and contains liquid crystal molecules 40 of which the dielectric constant anisotropy aligned approximately vertically to the main surface of the substrate is negative when an electric field is not formed between the pixel electrodes and the counter electrode; and an alignment control means ALC extended along boundaries B between the reflective display parts and the transmissive display parts of the pixels to control the alignment of the liquid crystal molecules 40 while an electric field is formed between the pixel electrodes and the counter electrode. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using a vertical alignment (VA) mode.

  Liquid crystal display devices are utilized in various fields as display devices for OA equipment such as personal computers and televisions, taking advantage of features such as light weight, thinness, and low power consumption. In recent years, liquid crystal display devices are also used as mobile terminal devices such as mobile phones, display devices such as car navigation devices and game machines.

  Such a liquid crystal display device is required to improve display quality such as an increase in viewing angle and an improvement in contrast ratio. In a multi-domain vertical alignment (MVA) mode liquid crystal display device having a plurality of domains having different alignment directions in one pixel, the viewing angle is compensated for by the plurality of domains, and vertical alignment processing is adopted. The liquid crystal molecules in the vicinity of the surface of the alignment film are aligned substantially perpendicular to the main surface of the substrate, and the birefringence of the liquid crystal layer is almost zero, so that sufficient black can be displayed and a high contrast ratio can be obtained Yes.

As an MVA mode liquid crystal display device, for example, according to Patent Document 1, instead of providing electrode slits or protrusions in a dot, an oblique electric field generated at the edge of the dot is actively used to control the alignment direction of the liquid crystal. A transflective liquid crystal display device is disclosed. According to this, since an oblique electric field is generated at the edge of the entire circumference of the dot, the transmissive display areas or the reflective display areas of two adjacent dot areas are configured to be inclined and oriented in opposite directions when a voltage is applied. .
JP 2004-341486 A

  An object of the present invention is to provide a transflective liquid crystal display device having a wide viewing angle characteristic and excellent in display quality for both transmissive display and reflective display.

A liquid crystal display device according to an aspect of the present invention includes:
A liquid crystal display device comprising an active area composed of a plurality of pixels arranged in a matrix, each having a reflective display portion and a transmissive display portion,
An array substrate provided with pixel electrodes in the reflective display portion and transmissive display portion of each pixel;
A counter substrate disposed opposite to the array substrate and provided with a common counter electrode for a plurality of pixels;
A dielectric anisotropy that is held between the array substrate and the counter substrate and is oriented substantially perpendicular to the main surface of the substrate when no electric field is formed between the pixel electrode and the counter electrode. A liquid crystal layer containing negative liquid crystal molecules;
An alignment control means for controlling the alignment of the liquid crystal molecules in a state where an electric field is formed between the pixel electrode and the counter electrode, extending along the boundary between the reflective display portion and the transmissive display portion of each pixel;
It is provided with.

  According to the present invention, it is possible to provide a transflective liquid crystal display device having a wide viewing angle characteristic and excellent in display quality for both transmissive display and reflective display.

  A liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings. Here, as a liquid crystal display device, a reflective display unit that displays an image by selectively reflecting external light within one pixel and a transmissive display unit that displays an image by selectively transmitting backlight light. An example of a transflective liquid crystal display device having

  As shown in FIGS. 1 and 2, the liquid crystal display device is an active matrix type liquid crystal display device and includes a transflective liquid crystal display panel LPN. The liquid crystal display panel LPN includes a pair of substrates, that is, an array substrate (first substrate) AR, and a counter substrate (second substrate) CT disposed to face the array substrate AR. The liquid crystal display panel LPN includes a liquid crystal layer LQ held between the array substrate AR and the counter substrate CT.

  Such a liquid crystal display panel LPN includes an active area (display area) DSP for displaying an image. The active area DSP is composed of a plurality of pixels PX arranged in an m × n matrix (m and n are positive integers). Each pixel PX includes a reflective display part PR and a transmissive display part PT.

  In addition, the liquid crystal display device includes a first optical element OD1 provided on one outer surface of the liquid crystal display panel LPN (that is, a surface opposite to the surface in contact with the liquid crystal layer LQ of the array substrate AR), and the liquid crystal A second optical element OD2 provided on the other outer surface of the display panel LPN (that is, the surface opposite to the surface in contact with the liquid crystal layer LQ of the counter substrate CT) is provided. Further, the liquid crystal display device includes a backlight unit BL that illuminates the liquid crystal display panel LPN from the first optical element OD1 side.

  The array substrate AR is formed using an insulating substrate 10 having optical transparency such as a glass plate or a quartz plate. In other words, the array substrate AR has m × n pixel electrodes EP arranged in each pixel PX on one main surface of the insulating substrate 10 (that is, the surface facing the liquid crystal layer LQ) in the active area DSP. N scanning lines Y (Y1 to Yn) respectively arranged so as to extend along the row direction of each pixel PX and m lines arranged so as to extend along the column direction of each pixel PX. Signal lines X (X1 to Xm), mxn switching elements W arranged in a region including the intersection of the scanning line Y and the signal line X in each pixel PX, similarly to the scanning line Y, in the row direction Auxiliary capacitance lines AY and the like that are arranged so as to extend along the liquid crystal capacitance CLC and that are capacitively coupled to the pixel electrode EP are provided in parallel with the liquid crystal capacitance CLC.

  The scanning lines Y and the auxiliary capacitance lines AY are arranged substantially in parallel on the insulating substrate 10 and can be formed of the same material. The auxiliary capacitance line AY is disposed so as to face the pixel electrode EP through an insulating film such as the interlayer insulating film 16 and to cross the plurality of pixel electrodes EP. The signal line X is disposed so as to be substantially orthogonal to the scanning line Y and the auxiliary capacitance line AY via the interlayer insulating film 16. These signal lines X, scanning lines Y, and auxiliary capacitance lines AY are made of a conductive material such as aluminum, molybdenum, tungsten, or titanium.

  Each switching element W is configured by, for example, an n-channel thin film transistor. The switching element W includes a semiconductor layer 12 disposed on the insulating substrate 10. The semiconductor layer 12 can be formed of, for example, polysilicon or amorphous silicon, and is formed of polysilicon here. The semiconductor layer 12 has a source region 12S and a drain region 12D on both sides of the channel region 12C. The semiconductor layer 12 is covered with a gate insulating film 14.

  The gate electrode WG of the switching element W is opposed to the channel region 12C of the semiconductor layer 12 with the gate insulating film 14 interposed therebetween. The gate electrode WG is connected to the scanning line Y (or formed integrally with the scanning line Y), and is disposed on the gate insulating film 14 together with the scanning line Y and the auxiliary capacitance line AY.

  The gate electrode WG, the scanning line Y, and the auxiliary capacitance line AY can be formed in the same process using the same material, for example, and are covered with the interlayer insulating film 16. The gate insulating film 14 and the interlayer insulating film 16 are made of an inorganic material such as a silicon oxide film and a silicon nitride film, for example.

  The source electrode WS and the drain electrode WD of the switching element W are disposed on both sides of the gate electrode WG on the interlayer insulating film 16. That is, the source electrode WS is connected to the signal line X (or formed integrally with the signal line X), and the semiconductor layer 12 is connected to the source electrode WS through a contact hole that penetrates the gate insulating film 14 and the interlayer insulating film 16. The source region 12S is contacted. The drain electrode WD is connected to the pixel electrode EP (or formed integrally with the pixel electrode EP), and the drain region 12D of the semiconductor layer 12 through a contact hole that penetrates the gate insulating film 14 and the interlayer insulating film 16. Is in contact. The source electrode WS, the drain electrode WD, and the signal line X can be formed in the same process using the same material, for example, and are covered with the insulating film 18.

  The insulating film 18 is made of, for example, an organic material. On the surface of the insulating film 18, a concavo-convex pattern 18 </ b> P is formed in the reflective display portion PR for the purpose of improving display quality in reflective display.

  The pixel electrode EP includes a reflective electrode EPR disposed in the reflective display portion PR and a transmissive electrode EPT disposed in the transmissive display portion PT. In each pixel PX, the reflective electrode EPR and the transmissive electrode EPT are electrically connected. Such a pixel electrode EP is disposed on the insulating film 18.

  The reflective electrode EPR covers the surface of the concavo-convex pattern 18P of the insulating film 18. The reflective electrode EPR is made of a light reflective conductive material such as aluminum. The transmissive electrode EPT covers a substantially flat surface of the insulating film 18. The transmissive electrode EPT is formed of a light-transmitting conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

  Such a pixel electrode EP is electrically connected to the switching element W. Here, the switching element W is disposed, for example, in the reflective display portion PR, and an insulating film 18 is interposed as an insulating layer between the reflective electrode EPR of the pixel electrode EP. The reflective electrode EPR is in contact with the drain electrode WD of the switching element W through a contact hole formed in the insulating film 18.

  The surface in contact with the liquid crystal layer LQ of the array substrate AR is covered with the first alignment film AL1.

  On the other hand, the counter substrate CT is formed using an insulating substrate 20 having optical transparency such as a glass plate or a quartz plate. That is, the counter substrate CT includes the counter electrode ET, the resin layer 23, and the like on one main surface of the insulating substrate 20 (that is, the surface facing the liquid crystal layer LQ) in the active area DSP.

  The counter electrode ET covers the resin layer 23 and is disposed so as to face the pixel electrodes EP corresponding to the plurality of pixels PX. The counter electrode ET is formed of a light-transmitting conductive material such as ITO similarly to the transmissive electrode EPT.

  The resin layer 23 forms a gap difference between the liquid crystal layer LQ in the reflective display part PR and the transmissive display part PT. That is, in the transflective liquid crystal display panel LPN, the gap between the array substrate AR and the counter substrate CT is formed to be different between the reflective display portion PR and the transmissive display portion PT. The reflective display portion PR and the transmissive display portion PT are formed in appropriate gaps so that the substantial optical path lengths (or retardations) are substantially equal. In many cases, the gap in the reflective display part PR is set to approximately half of the transmissive display part PT.

  Such a gap difference is formed by the resin layer 23. The resin layer 23 is disposed mainly corresponding to the reflective display portion PR. Therefore, a gap difference substantially corresponding to the thickness of the resin layer 23 is formed between the reflective display part PR and the transmissive display part PT (the thickness of the liquid crystal layer LQ in the reflective display part PR is equal to the transmissive display part PT). Smaller than the thickness of the liquid crystal layer LQ). For example, the resin layer 23 is formed of a resin material having optical transparency. The structure that forms such a gap difference may be provided on the array substrate AR side.

  The color display type liquid crystal display device includes a color filter layer CF provided on the inner surface of the liquid crystal display panel LPN corresponding to each pixel PX. In the example shown in FIG. 2, the color filter layer CF is provided on the counter substrate CT. The color filter layer CF is formed of colored resins that are colored in a plurality of different colors, for example, three primary colors such as red, blue, and green. The red colored resin, the blue colored resin, and the green colored resin are disposed corresponding to the red pixel, the blue pixel, and the green pixel, respectively.

  In the example of the color display type liquid crystal display device shown in FIG. 2, the color filter layer CF is disposed on the counter substrate CT side, but may be disposed on the array substrate AR side. In this case, it is possible to replace the insulating film 18 in the array substrate AR with the color filter layer CF.

  Each pixel PX is partitioned by a black matrix (light shielding layer) BM. The black matrix BM is formed of a black colored resin or the like, and is disposed so as to face wiring portions such as the scanning lines Y, the signal lines X, and the switching elements W provided on the array substrate AR. Further, the black matrix BM is arranged along the boundary between the transmissive display part PT and the reflective display part PR.

  In the counter substrate CT, an overcoat layer may be disposed between the color filter layer CF and the counter electrode ET in order to reduce the influence of the unevenness on the surface of the color filter layer CF.

  The surface in contact with the liquid crystal layer LQ of the counter substrate CT is covered with the second alignment film AL2.

  The array substrate AR and the counter substrate CT as described above are arranged so that the first alignment film AL1 and the second alignment film AL2 face each other. At this time, a spacer (not shown) (for example, a columnar spacer formed integrally with one substrate by a resin material) is disposed between the array substrate AR and the counter substrate CT, thereby forming a predetermined gap. Is done. The array substrate AR and the counter substrate CT are bonded together with a sealing material in a state where a predetermined gap is formed.

  The liquid crystal layer LQ is composed of a liquid crystal composition including liquid crystal molecules 40 enclosed in a gap formed between the first alignment film AL1 of the array substrate AR and the second alignment film AL2 of the counter substrate CT. Yes. The liquid crystal molecules 40 have, for example, negative dielectric anisotropy.

  The first alignment film AL1 and the second alignment film AL2 are in a state where no potential difference is formed between the pixel electrode EP and the counter electrode ET, that is, no electric field is formed between the pixel electrode EP and the counter electrode. When there is no electric field, the liquid crystal molecules 40 have a characteristic of being aligned substantially perpendicularly to the main surface of the insulating substrate 10 (or array substrate AR) and the main surface of the insulating substrate 20 (or counter substrate CT). . A material for forming the first alignment film AL1 and the second alignment film AL2 is not particularly limited as long as it is a light-transmitting thin film that basically exhibits vertical alignment.

  The liquid crystal display device also includes at least a part of the scanning line driver YD connected to the n scanning lines Y and at least a part of the signal line driver XD connected to the m signal lines X. May be provided. In particular, when a configuration in which the switching element W includes the semiconductor layer 12 made of polysilicon is applied, at least a part of the scanning line driver YD and the signal line driver XD can be integrally formed on the array substrate AR, and switching is performed. Like the element W, it can be configured to include a thin film transistor including a polysilicon semiconductor layer.

  The scanning line driver YD sequentially supplies scanning signals (driving signals) to the n scanning lines Y based on control by the controller CNT. Further, the signal line driver XD supplies video signals (drive signals) to the m signal lines X at the timing when the switching elements W in each row are turned on by the scanning signal based on the control by the controller CNT. Thereby, the pixel electrode EP of each row is set to a pixel potential corresponding to the video signal supplied via the corresponding switching element W.

  For the transflective liquid crystal display panel LPN as described above, reflection display and transmission display are performed using circularly polarized light or elliptically polarized light. For this reason, each of the first optical element OD1 and the second optical element OD2 includes at least a polarizing plate and a retardation plate, and is configured as a circularly polarizing element or an elliptically polarizing element.

  In this embodiment, the liquid crystal molecules 40 included in the liquid crystal layer LQ have their major axes substantially perpendicular to the main surface of the substrate by the alignment control by the first alignment film AL1 and the second alignment film AL2 when there is no electric field. It is aligned substantially parallel to the direction (or the normal direction of the liquid crystal display panel LPN). In such a state, in the transmissive display unit PT, the backlight light transmitted through the first optical element OD1 is absorbed by the second optical element OD2 after passing through the liquid crystal layer LQ having a substantially zero retardation. . Further, in the reflective display part PR, the external light transmitted through the second optical element OD2 is reflected by the reflective electrode EPR after passing through the liquid crystal layer LQ in which the retardation is substantially zero, and again through the liquid crystal layer LQ. Absorbed by the second optical element OD2. Therefore, the transmittance of the liquid crystal display panel LPN is the lowest (that is, a black screen is displayed).

  On the other hand, in a state where an electric field is formed between the pixel electrode EP and the counter electrode ET, the liquid crystal molecules 40 having negative dielectric anisotropy are aligned in a direction substantially perpendicular to the electric field. With respect to the electric field inclined with respect to the normal line of the substrate main surface, the liquid crystal molecules 40 are aligned in the direction in which the major axis is substantially parallel to or inclined with respect to the substrate main surface. For this reason, the liquid crystal layer LQ has a predetermined retardation.

  In such a state, in the transmissive display portion PT, the backlight light transmitted through the first optical element OD1 is given retardation when transmitted through the liquid crystal layer LQ, and at least a part of the backlight light is transmitted through the second optical element OD2. It becomes possible. In the reflective display section PR, the external light transmitted through the second optical element OD2 is reflected by the reflective electrode EPR after being given retardation when transmitted through the liquid crystal layer LQ, and is again transmitted through the liquid crystal layer LQ. Retardation is imparted, and at least a part of the retardation can pass through the second optical element OD2. Therefore, a white screen is displayed.

  In this way, a normally black mode vertical alignment mode is realized. By adopting such a normally black mode, the contrast ratio can be improved, and an image with good display quality can be displayed.

  By the way, in this embodiment, the liquid crystal display panel LPN has a multi-domain structure capable of viewing angle compensation. More specifically, the liquid crystal display device includes alignment control means for controlling the alignment of liquid crystal molecules in a state where an electric field is formed between the pixel electrode EP and the counter electrode ET.

  This orientation control means will be specifically described with reference to FIGS. 3 and 4, only the configuration necessary for the description is shown.

  In the example shown in FIG. 3, the alignment control means ALC is provided by a slit SL provided on the counter substrate CT side and formed in the counter electrode ET. The slit SL faces the pixel electrode EP of each pixel PX, and is formed in a straight line, for example, so as to cross almost the center of the pixel PX.

  In the example shown in FIG. 4, the orientation control means ALC is configured by a projection CP disposed on the surface of the counter substrate CT facing the array substrate AR, more specifically, on the counter electrode ET. The protrusion CP is formed in a straight line so as to face the pixel electrode EP and cross, for example, substantially the center of the pixel PX.

  Thus, when the slit SL is applied as the orientation control means ALC, the slit SL can be formed at the same time in the electrode patterning process, and a separate process is required as in the case of forming a structure such as the protrusion CP. This is unnecessary, and the number of manufacturing steps and the manufacturing cost can be reduced.

On the other hand, when the protrusion CP is applied as the orientation control means ALC, the protrusion CP is formed of an insulating film. As the insulating film, for example, inorganic materials such as SiO ₂ , SiN _x , and Al ₂ O ₃ , organic materials such as polyimide, photoresist resin, and polymer liquid crystal can be used. When the protrusion CP is an inorganic material, it can be formed by vapor deposition, sputtering, CVD (Chemical Vapor Deposition), or solution coating. Further, when the protrusion CP is an organic material, it is applied by a spinner coating method, a screen printing coating method, a roll coating method, or the like using a solution in which an organic substance is dissolved or a precursor solution thereof, and a predetermined curing condition ( It can be formed by a method of curing by heating, light irradiation, or the like, or a vapor deposition method, a sputtering method, a CVD method, an LB (Langumura-Blodgett) method, or the like.

  In the configuration provided with such an alignment control means ALC, the electric field between the pixel electrode EP and the counter electrode ET is formed so as to avoid these alignment control means ALC. Therefore, an electric field inclined with respect to the normal line of the substrate main surface PL can be formed between the pixel electrode EP and the counter electrode ET around the alignment control means ALC. Therefore, the liquid crystal molecules 40 around the alignment control means ALC are aligned in a predetermined direction by such a gradient electric field.

  That is, as shown in FIG. 5, in the regions R1 and R2 adjacent to each other with the alignment control unit ALC interposed therebetween, electric fields inclined in opposite directions are formed with respect to the alignment control unit ALC. The molecules 40 are also oriented in opposite directions. That is, in the main surface of the substrate, the respective liquid crystal molecules 40 in the regions R1 and R2 adjacent to each other with the alignment control means ALC are aligned in directions that are line-symmetric with each other as indicated by arrows in the drawing.

  In particular, in this embodiment, the alignment control means ALC extends along the boundary between the reflective display portion PR and the transmissive display portion PT of each pixel PX. That is, in the example shown in FIG. 5, the regions R1 and R2 correspond to the reflective display portion PR and the transmissive display portion PT, respectively. That is, each pixel PX is configured by a single reflective display part PR and a single transmissive display part PT.

  In such a pixel structure, the alignment control means ALC extends in a direction orthogonal to the arrangement direction of the reflective display portion PR and the transmissive display portion PT. In other words, one alignment control means ALC is arranged in one pixel PX, and extends so as to be substantially divided into the reflective display part PR and the transmissive display part PT. For a rectangular pixel PX having a long side in a direction parallel to the arrangement direction of the reflective display part PR and the transmissive display part PT, the orientation control means ALC extends in parallel to the short side of the pixel PX.

  At this time, the orientation control means ALC may extend so as to overlap the boundary B between the reflective display part PR and the transmissive display part PT, or the boundary in the reflective display part PR or the transmissive display part PT without overlapping the boundary B. It may extend parallel to B.

  With such a configuration, in the reflective display portion PR and the transmissive display portion PT of each pixel PX, electric fields inclined in opposite directions are formed, and the liquid crystal molecules 40 in the respective regions are aligned in opposite directions.

  On the other hand, since the portion corresponding to the alignment control means ALC does not contribute to the display, it is desirable that the area where the alignment control means ALC overlaps the pixel PX is as small as possible in a pixel configuration that requires a high aperture ratio. That is, in the active area DSP, when the pixel pitch is 45 μm or less, for the rectangular pixel PX, if the orientation control means ALC is arranged parallel to the long side of the pixel PX, the transmittance and the reflectance are reduced. Since it becomes a problem, it is desirable to arrange in parallel with the short side of pixel PX.

  In this case, the side surface of the resin layer 23 for forming a gap difference between the transmissive display portion PT and the reflective display portion PR is located at the boundary B between the transmissive display portion PT and the reflective display portion PR. Since they are arranged substantially perpendicular to the side surfaces and are inclined with respect to the substrate, light is transmitted during black display (light leakage), and the contrast ratio of the transmissive display is greatly reduced.

  In contrast, in this embodiment, the black matrix BM is arranged so as to overlap the boundary B. In a pixel configuration in which one reflective display part PR and one transmissive display part PT are arranged in one pixel, there is one boundary B between them, and a BM that shields the boundary B may be arranged. This does not lead to a large aperture ratio loss, but rather contributes to an improvement in contrast ratio.

  According to such a configuration, it is possible to obtain excellent display quality for both the reflective display mainly using the reflective display part PR and the transmissive display mainly using the transmissive display part PT.

  The specific pixel structure according to the embodiment of the present invention will be described below.

<< First configuration example >>
In the first configuration example shown in FIGS. 6 and 7, each pixel PX of the active area DSP has a configuration in which the transmissive display unit PT and the reflective display unit PR are arranged in this order along the column direction V. That is, all the pixels PX have the transmissive display portion PT and the reflective display portion PR that are arranged in the same manner. The transmissive display portion PT and the reflective display portion PR are formed with substantially the same aperture ratio.

  More specifically, the first pixel PX1 has a transmissive display part PT1 and a reflective display part PR1 arranged along the column direction V. The second pixel PX2 adjacent to the first pixel PX1 in the row direction H has the transmissive display part PT2 adjacent to the transmissive display part PT1 of the first pixel PX1, and the reflective display part PR1 of the first pixel PX1. The reflective display part PR2 is provided adjacently. The third pixel PX3 adjacent in the column direction V of the first pixel PX1 and the fourth pixel PX4 adjacent in the column direction V of the second pixel PX2 have the same configuration. The active area DSP is constituted by a repeating pattern of these four pixels.

  In the array substrate AR of each pixel PX, the transmissive electrode EPT is disposed over, for example, the transmissive display portion PT and the reflective display portion PR, and the reflective electrode EPR is formed on the transmissive electrode EPT corresponding to only the reflective display portion PR. Has been placed.

  In the counter substrate CT of each pixel PX, the resin layer 23 is disposed corresponding to only the reflective display portion PR. The black matrix BM extends along the row direction H so as to overlap the boundary B between the transmissive display part PT and the reflective display part PR (more specifically, to shield the misalignment region near the side surface of the resin layer 23). Has been placed. The counter electrode ET is disposed over the entire active area DSP so as to cover the resin layer 23 and the like.

  In the first configuration example, the protrusion CP is applied as the orientation control means. The protrusion CP is disposed in the vicinity of the boundary B of the reflective display portion PR. More specifically, the protrusion CP is disposed along the row direction H on the counter electrode ET that passes through the approximate center of the pixel PX and covers the resin layer 23 corresponding to the reflective display portion PR.

  Both the protrusion CP and the black matrix BM do not contribute to display, but extend substantially parallel to each other, and at least a part of both overlap. For this reason, the aperture ratio loss in the reflective display part PR and the transmissive display part PT can be suppressed extremely small. That is, a decrease in contrast due to light leakage in the vicinity of the boundary B can be suppressed, and a decrease in reflectance and transmittance can be suppressed, so that a liquid crystal display device with high display quality can be provided.

<< Second configuration example >>
In the second configuration example shown in FIGS. 8 to 10, each pixel PX of the active area DSP has a configuration in which the transmissive display unit PT and the reflective display unit PR are arranged along the column direction V. Between the pixels adjacent in the column direction V, the transmissive display part PT and the reflective display part PR are reversely arranged. Note that the transmissive display portion PT and the reflective display portion PR of each pixel PX are formed with substantially the same aperture ratio.

  More specifically, the first pixel PX1 has a transmissive display part PT1 and a reflective display part PR1 arranged along the column direction V. The second pixel PX2 adjacent to the first pixel PX1 in the row direction H includes the reflective display part PR2 adjacent to the transmissive display part PT1 of the first pixel PX1, and the reflective display part PR1 of the first pixel PX1. A transmissive display part PT2 is provided adjacently.

  In the second configuration example, the protrusion CP is applied as the orientation control means. The protrusion CP is disposed in the vicinity of the boundary B of the reflective display portion PR. More specifically, the protrusion CP is disposed along the row direction H on the counter electrode ET that passes through the approximate center of the pixel PX and covers the resin layer 23 corresponding to the reflective display portion PR.

  Both the protrusion CP and the black matrix BM do not contribute to display, but extend substantially parallel to each other, and at least a part of both overlap.

  In such a second configuration example, during the formation of the electric field, the alignment directions of the liquid crystal molecules 40 in the transmissive display portions and the reflective display portions are opposite to each other between adjacent pixels. That is, in the transmissive display portion PT1 of the first pixel PX1 and the transmissive display portion PT2 of the second pixel PX2, electric fields inclined in opposite directions with respect to the protrusion CP are formed. As shown by the arrows in the figure, they are oriented in mutually opposite directions (or directions that are line-symmetric with respect to the protrusion CP).

  According to such a second configuration example, in addition to the effects obtained in the first configuration example, viewing angle compensation is performed, and the viewing angle can be increased.

  In the second configuration example shown in FIG. 8, the third pixel PX3 adjacent to the first pixel PX1 in the column direction V includes the reflective display portion PR3 and the transmissive display portion PT3 having the same arrangement as the second pixel PX2. doing. Further, the fourth pixel PX4 adjacent to the second pixel PX2 in the column direction V includes the reflective display part PR4 and the transmissive display part PT4 that are arranged in the same arrangement as the first pixel PX1. The active area DSP is constituted by a repeating pattern of these four pixels.

  In this way, in the two adjacent pixels PX or the two pixels PX adjacent in the row direction and the column direction in the active area DSP, the transmissive display portion PT and the reflective display portion PR are arranged in a point-symmetric manner, thereby transmissive display. The orientation directions of the liquid crystal molecules 40 when voltages are applied between the portions and between the reflective display portions are opposite to each other.

  For this reason, a decrease in transmission contrast ratio and a collapse in symmetry of the viewing angle are small, and the transmittance and reflectance are improved, so that a liquid crystal display device with excellent display quality can be provided.

<< Third configuration example >>
In the third configuration example shown in FIGS. 11 to 13, each pixel PX of the active area DSP has a configuration in which the transmissive display unit PT and the reflective display unit PR are arranged along the column direction V, as in the second configuration example. However, between the pixels adjacent in the row direction H and the column direction V, the transmissive display part PT and the reflective display part PR are reversely arranged. Note that the transmissive display portion PT and the reflective display portion PR of each pixel PX are formed with substantially the same aperture ratio.

  In the third configuration example, the protrusion CP is applied as the orientation control means. In particular, the protrusion CP is disposed so as to overlap the boundary B between the reflective display portion PR and the transmissive display portion PT. More specifically, the protrusion CP is disposed along the row direction H on the counter electrode ET so as to pass through the approximate center of the pixel PX and straddle the reflective display portion PR and the transmissive display portion PT.

  At this time, the entire protrusion CP overlaps the black matrix BM.

  In such a third configuration example, in addition to the effects obtained in the second configuration example, the alignment stability can be improved. That is, since the protrusion CP is disposed so as to overlap the boundary B, the directions of the electric fields are easily aligned in the reflective display portion PR and the transmissive display portion PT. Thereby, in each of the reflective display part PR and the transmissive display part PT, the alignment is not disturbed, so that the response speed can be improved.

<< Fourth configuration example >>
The fourth configuration example shown in FIGS. 14 to 16 is the same as the third configuration example except that the slit SL formed in the counter electrode ET is applied as the orientation control means.

  That is, the slit SL is disposed so as to overlap the boundary B between the reflective display part PR and the transmissive display part PT. More specifically, the slit SL is formed along the row direction H in the counter electrode ET so as to pass through the approximate center of the pixel PX and straddle the reflective display portion PR and the transmissive display portion PT.

  At this time, the entire slit SL overlaps the black matrix BM.

  In such a fourth configuration example, the same effect as in the third configuration example is obtained.

  Next, examples will be described.

(Example 1; corresponding to the first configuration example)
A circular polarization mode with a diagonal screen size of 2.4 type, a pixel number of 640 × 480 RGB, a pixel size of 75 μm × 25 μm, a cell gap of the transmissive display portion of 3.8 μm, and a pixel pitch of 25 μm (332 ppi). In the transflective device used, as shown in FIGS. 6 and 7, the transmissive display portion PT and the reflective display portion PR have the same aperture ratio, and the pixel configuration is divided into two along the column direction within one pixel. The array substrate AR and the counter substrate CT were formed so that

  Here, the width a along the column direction of the reflective electrode EPR of the array substrate AR is 25 μm, and the width b along the column direction of the resin layer 23 formed on the counter substrate CT is longer than the reflective electrode, 30 μm. Further, the protrusion CP for controlling the alignment direction of the liquid crystal molecules 40 when a voltage is applied is formed on the counter substrate CT with a width of 10 μm so as to be parallel to the short side of the pixel and not to reach the transmissive display portion PT.

  Further, in two pixels adjacent in the row direction, the transmissive display portions and the reflective display portions are arranged so as to be adjacent to each other, and the alignment directions of the liquid crystal molecules when the voltage is applied between the transmissive display portions and the reflective display portions are the same. The pixel arrangement was oriented.

  On the surfaces of the array substrate AR and the counter substrate CT, alignment films AL1 and AL2 each exhibiting vertical alignment are applied with a thickness of 100 nm, and the thickness of the liquid crystal layer LQ of the transmissive display portion PT is 3. Two substrates were bonded so as to be 8 μm. A cell was filled with a liquid crystal material having negative dielectric anisotropy manufactured by Merck and assembled into a module.

(Example 2; corresponding to the second configuration example)
As shown in FIGS. 8 to 10, when the transmissive display unit and the reflective display unit are arranged adjacent to each other in two pixels adjacent in the row direction, and a voltage is applied between the transmissive display units and the reflective display units. A liquid crystal module was produced in the same manner as in Example 1 except that the pixel arrangement was such that the orientation directions of the liquid crystal molecules were opposite to each other.

(Example 3; corresponding to the third configuration example)
As shown in FIGS. 11 to 13, except that the position of the protrusion CP for regulating the alignment direction of the liquid crystal molecules is arranged at a position covering both the resin layer 23 and the transmissive display part PT of the reflective display part PR. In the same manner as in Example 2, a liquid crystal module was produced.

(Example 4; corresponding to the fourth configuration example)
As shown in FIGS. 14 to 16, a liquid crystal module was produced in the same manner as in Example 3 except that the slit SL was applied as an alignment control means for regulating the alignment direction of the liquid crystal molecules.

(Comparative example)
In a device having a pixel pitch of 30 μm, a pixel configuration in which two transmissive display units sandwich a reflective display unit at the center of the pixel, and the transmissive display unit and the reflective display unit have the same aperture ratio. A liquid crystal module was produced by the same process as in Example 1 except that.

  About this comparative example, when the optical characteristic in transmissive display and reflective display was measured, it turned out that the transmittance | permeability and reflectance are comparatively low. This is because the reflective display portion is located at the center of the pixel, so that the boundary between the reflective display portion and the transmissive display portion is on two sides, and the substantial aperture ratio is reduced by shielding both with a black matrix. Because. Further, since the resin layer is located at the center of the pixel, it was confirmed that the electric field is distorted on the side surface of the resin layer, and the alignment stability of the liquid crystal molecules is not significantly affected.

  When the contrast ratio and transmittance in the transmissive display in this comparative example were set to 100% and the contrast ratio and reflectance in the reflective display were set to 100%, the following results were obtained.

  That is, for each example, when observed from the front direction of the screen, both the optical characteristics of the transmissive display (transmittance and contrast ratio) and the optical characteristics of the reflective display (reflectance and contrast ratio) are generally comparative examples. Better results were obtained.

For Example 1, the transmittance was 125% and the contrast ratio was 100% during transmissive display, and the reflectance was 125% and the contrast ratio was 225% during reflective display. In addition, the orientation stability was confirmed to be relatively good by returning immediately after a moment when a load (1 kg / cm ³ ) was applied in subjective evaluation.

In Example 2, the transmittance was 125% and the contrast ratio was 100% during transmissive display, and the reflectance was 125% and the contrast ratio was 225% during reflective display. In addition, the orientation stability was subjectively evaluated, and when a load (1 kg / cm ³ ) was applied, a momentary trace remained, but it returned immediately and it was confirmed that it was relatively good. Furthermore, when the viewing angle was subjectively evaluated, it was confirmed that the screen was generally symmetric in the vertical and horizontal directions of the screen, and that gradation inversion did not occur in any direction.

For Example 3, the transmittance was 119% and the contrast ratio was 94% during transmissive display, and the reflectance was 130% and the contrast ratio was 200% during reflective display. In addition, the orientation stability was confirmed to be very good with no change even when a load (1 kg / cm ³ ) was applied in the subjective evaluation. Furthermore, when the viewing angle was subjectively evaluated, it was confirmed that the screen was generally symmetric in the vertical and horizontal directions of the screen, and that gradation inversion did not occur in any direction.

  For Example 4, the transmittance was 125% and the contrast ratio was 100% during transmissive display, and the reflectance was 125% and the contrast ratio was 225% during reflective display. Further, it was confirmed that the alignment stability and viewing angle were very good as in Example 3.

  As described above, according to this embodiment, in the transflective liquid crystal display device in the vertical alignment mode, the structure (resin layer) and the liquid crystal molecules for forming the gap difference between the reflective display part and the transmissive display part Providing a liquid crystal display device that does not impair the optical characteristics of both transmissive display and reflective display, and further, the display quality by optimizing the arrangement of orientation control means (projections or slits) that control the orientation of the display Can do.

  In addition, this invention is not limited to the said embodiment itself, In the stage of implementation, it can change and implement a component within the range which does not deviate from the summary. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

FIG. 1 is a diagram schematically showing the configuration of an MVA mode liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of the array substrate and the counter substrate applied to the liquid crystal display device shown in FIG. FIG. 3 is a cross-sectional view schematically showing a configuration example of the orientation control means in the present embodiment. FIG. 4 is a sectional view schematically showing another configuration example of the orientation control means in the present embodiment. FIG. 5 is a plan view showing an average orientation direction of the liquid crystal molecules when a voltage is applied by the orientation control means. FIG. 6 is a diagram for explaining a first configuration example of the present embodiment, and is a diagram illustrating a reflective display portion and a transmissive display portion between adjacent pixels, and their orientation directions. FIG. 7 is a diagram schematically showing a cross-sectional structure of a pixel when cut along line AA shown in FIG. FIG. 8 is a diagram for explaining a second configuration example of the present embodiment, and is a diagram illustrating a reflective display portion and a transmissive display portion between adjacent pixels, and their orientation directions. FIG. 9 is a diagram schematically showing a cross-sectional structure of the pixel when cut along line AA shown in FIG. FIG. 10 is a diagram schematically showing a cross-sectional structure of a pixel when cut along the line BB shown in FIG. FIG. 11 is a diagram for explaining a third configuration example of the present embodiment, and is a diagram illustrating a reflective display portion and a transmissive display portion between adjacent pixels, and their orientation directions. FIG. 12 is a diagram schematically showing a cross-sectional structure of the pixel when cut along the line AA shown in FIG. FIG. 13 is a diagram schematically showing a cross-sectional structure of a pixel when cut along the line BB shown in FIG. FIG. 14 is a diagram for explaining a third configuration example of the present embodiment, and is a diagram showing a reflective display portion and a transmissive display portion between adjacent pixels, and their orientation directions. FIG. 15 is a diagram schematically showing a cross-sectional structure of a pixel when cut along line AA shown in FIG. FIG. 16 is a diagram schematically showing a cross-sectional structure of a pixel when cut along the line BB shown in FIG.

Explanation of symbols

LPN ... Liquid crystal display panel DSP ... Active area PX ... Pixel PR ... Reflection display part PT ... Transmission display part B ... Boundary AR ... Array substrate CT ... Counter substrate LQ ... Liquid crystal layer EP ... Pixel electrode EPR ... Reflection electrode EPT ... Transmission electrode ET ... Counter electrode BM ... Black matrix ALC ... Orientation control means SL ... Slit CP ... Protrusion

Claims (6)

A liquid crystal display device comprising an active area composed of a plurality of pixels arranged in a matrix, each having a reflective display portion and a transmissive display portion,
An array substrate provided with pixel electrodes in the reflective display portion and transmissive display portion of each pixel;
A counter substrate disposed opposite to the array substrate and provided with a common counter electrode for a plurality of pixels;
A dielectric anisotropy that is held between the array substrate and the counter substrate and is oriented substantially perpendicular to the main surface of the substrate when no electric field is formed between the pixel electrode and the counter electrode. A liquid crystal layer containing negative liquid crystal molecules;
The reflective display portion and the transmissive display portion of each pixel are substantially divided into two and extend parallel to the short side of the pixel so as to overlap the boundary between the reflective display portion and the transmissive display portion, and between the pixel electrode and the counter electrode An alignment control means for controlling the alignment of the liquid crystal molecules with an electric field formed between them, a slit formed in the counter electrode or a protrusion disposed on a surface of the counter substrate facing the array substrate An orientation control means ;
A resin layer disposed on the reflective display unit, forming a gap difference between the liquid crystal layer in the reflective display unit and the transmissive display unit, and having a side surface located at the boundary between the reflective display unit and the transmissive display unit;
Equipped with a,
The liquid crystal display device , wherein the counter substrate includes a light shielding layer that extends in parallel with the alignment control unit and overlaps at least a part of the alignment control unit in the active area . The active area is
A first pixel;
A second pixel adjacent to the first pixel, having a reflective display portion adjacent to the reflective display portion of the first pixel and having a transmissive display portion adjacent to the transmissive display portion of the first pixel;
The liquid crystal display device according to claim 1, comprising: The active area is
A first pixel;
A second pixel adjacent to the first pixel, having a transmissive display portion adjacent to the reflective display portion of the first pixel and having a reflective display portion adjacent to the transmissive display portion of the first pixel;
The liquid crystal display device according to claim 1, comprising: The active area is
A first pixel having a transmissive display portion and a reflective display portion arranged in a column direction;
A second pixel adjacent in the row direction of the first pixel, having a transmissive display portion adjacent to the reflective display portion of the first pixel, and having a reflective display portion adjacent to the transmissive display portion of the first pixel; ,
A third pixel adjacent to the first pixel in the column direction and having a reflective display portion and a transmissive display portion in the same arrangement as the second pixel;
The liquid crystal display device according to claim 1, comprising: The counter substrate is provided with the resin layer,
The liquid crystal display device according to claim 1, wherein a thickness of the liquid crystal layer in the reflective display unit is smaller than a thickness of the liquid crystal layer in the transmissive display unit.   The liquid crystal display device according to claim 1, wherein a pixel pitch in the active area is 45 μm or less.

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