JP2007206634A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display that effectively performs four-color display that uses a VA liquid crystal. <P>SOLUTION: A pixel 10 is constituted with four-color display dots 12R, 12G, 12B, 12C. Each display dot 12 is long in the vertical direction. A longitudinal alignment control part 14 is disposed at the center part of each display dot that is long in the vertical direction. Furthermore, a polarizing plate is made to be a linearly polarizing plate, having a polarization axis of 45° with respect to the alignment control part 14 on the center part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device composed of a plurality of pixels arranged in a matrix, and more particularly to one in which one pixel is formed by display dots of four colors.

  Conventionally, various display devices are known, and liquid crystal display devices are widely used as thin and light display devices. In particular, an active matrix type device in which a switching transistor is provided for each pixel (display dot) and the display is controlled for each display dot enables high-definition display. In addition, there is a vertical alignment type VA liquid crystal in the liquid crystal, and this liquid crystal can easily display black, and the alignment film can be used without rubbing, and an alignment control protrusion, an alignment control window, etc. are provided. By providing, there is an advantage that it is easy to control the orientation of the liquid crystal and to widen the viewing angle.

  Here, in the case of performing full color display, each display dot is provided with one of R (red), G (green), and B (blue) color filters to form one pixel with three display dots. On the other hand, when a displayed image is printed on a personal computer or the like, the colors are different. This is because the color area that can be displayed on the display device is different from the color display area that can be printed on the printer.

  Therefore, it has been proposed to add C (cyan) display dots in addition to RGB in the display device (see Patent Document 1). This makes it possible to bring the display image on the display device closer to the color of the printed image.

JP 2001-306003 A

  Here, when the viewing angle is widened by the VA liquid crystal, the initial alignment direction of the liquid crystal is set to various directions. For this reason, when a linearly polarizing plate is used, the transmittance cannot be increased so much, and a circularly polarizing plate is usually used. Since circularly polarizing plates are expensive, there is a demand for cost reduction.

  Further, in order to obtain four colors for one pixel, one pixel must be composed of four display dots. Therefore, four pixel circuits are required for one pixel, and the aperture ratio is lowered as a whole. For this reason, there is a demand for further increasing the transmittance.

  The present invention is a liquid crystal display device comprising a plurality of pixels arranged in a matrix, wherein each pixel is formed of four display dots, and four color filters are respectively provided corresponding to the four display dots. Provided separately, each display dot is provided with an alignment control unit for controlling the alignment of the liquid crystal, each display dot is formed in a narrow rectangular shape, and the alignment control unit has a linear portion extending in the central portion in the longitudinal direction. In addition, the liquid crystal is a VA liquid crystal.

  Further, the alignment control unit is preferably a protrusion provided on an alignment control film in contact with the liquid crystal.

  The alignment control unit is preferably a slit provided in an electrode for applying a voltage to the liquid crystal.

  In addition, it is preferable to dispose a linear polarizing plate having a polarization axis in a direction of 45 degrees with respect to the linear portion of the alignment control unit on both sides of the liquid crystal.

  According to the present invention, in the four-color long and narrow display dots, the orientation control unit is arranged at the center in the longitudinal direction. Thereby, the orientation direction of the liquid crystal can be controlled, and particularly the viewing angle dependency in the left-right direction of the display device can be reduced, and suitable display can be performed. In addition, by using a VA liquid crystal and adopting a linear polarizing plate having a polarizing axis in the direction of 45 degrees with respect to the central alignment control unit as polarizing plates disposed above and below the liquid crystal, a low-cost polarizing plate is used, and White display with sufficient transparency can be performed.

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

  FIG. 1 is a diagram illustrating a schematic plan configuration of one pixel in the liquid crystal display device according to the embodiment. The pixel 10 includes four display dots 12R, 12G, 12B, and 12C. The display dot 12R is red (R), the display dot 12G is green (G), the display dot 12B is blue (B), the display dot 12C is a cyan (C) display dot, and has a color filter of the corresponding color. Yes.

  The pixel 10 has a substantially square shape (slightly horizontally long), and the four display dots 12R, 12G, 12B, and 12C are arranged in the horizontal direction. ing.

  Each display dot 12R, 12G, 12B, and 12C is provided with an upper and lower Y-shaped orientation control unit 14 that combines Y and reverse Y.

  Here, FIG. 2 shows a schematic cross-sectional configuration for one display dot. The liquid crystal display device includes a backlight 20, a TFT substrate 100 and a counter substrate 102 provided above the backlight 20, and a liquid crystal 104 is sealed between the TFT substrate 100 and the counter substrate 102. The liquid crystal 104 is a VA (vertical alignment) liquid crystal.

  The TFT substrate 100 has a glass substrate 24, and a linear polarizing plate 22 is provided on the lower surface of the glass substrate 24.

  A TFT layer 26 is provided on the glass substrate 24. The TFT layer 26 is a layer provided with a circuit for controlling the voltage applied to the liquid crystal for each display dot in accordance with an image signal. For example, a switching TFT having an active layer of polysilicon or the like is provided for each display dot. Liquid crystal display is performed by controlling on / off of the switching TFT for each display dot.

  A pixel electrode 28 is provided on the TFT layer 26. The pixel electrode 28 is provided independently for each display dot, and a voltage based on the image signal of the display dot is applied. An alignment film 30 is provided on the pixel electrode 28. The pixel circuit in the TFT layer 26 is a separate circuit for each display dot.

  The counter substrate 102 includes a glass substrate 40, and a color filter 38, a counter electrode 36, and an alignment film 34 are provided in this order on the lower surface thereof. Accordingly, the liquid crystal 104 is located between the alignment films 30 and 34. The color filter 38 is basically provided for each display dot, but may be provided continuously as long as display dots of the same color are arranged. A linear polarizing plate 42 is provided on the glass substrate 40. On the counter substrate 102 side, all the pixels other than the color filter 38 are provided in common.

  The alignment films 30 and 34 are rubbing-less, and the liquid crystal is aligned in a direction perpendicular to the alignment films 30 and 34 when no electric field is applied.

  Although not shown in FIG. 2, the alignment control unit 14 is provided on the counter substrate 102 on the liquid crystal 104 side. FIG. 3 shows a cross section of an example of the alignment control unit 14, and an alignment control protrusion 50 having a triangular cross section is provided on the counter electrode 36. The planar shape of the alignment control protrusion 50 is the same as that of the vertical Y-shaped alignment control unit 14 in FIG. 1, and is formed of a resin or the like.

  An alignment film 34 is formed to cover the counter electrode 36 and the alignment control protrusion 50, and the surface of the alignment film 34 has a shape in which the alignment control section 14 protrudes in a bowl shape according to the shape of the alignment control protrusion 50. ing. Since the VA liquid crystal is aligned in a direction perpendicular to the surface of the alignment film 34, the liquid crystal molecules are aligned in the opposite direction with the top of the alignment control unit 14 as a boundary. When a voltage is applied to the pixel electrode 28, the liquid crystal molecules are tilted in a direction parallel to the electrode based on the orientation direction.

  In the present embodiment, as shown in FIG. 1, one display dot 12 is formed in an elongated rectangle in its planar shape, and the orientation control unit 14 is mostly located in the center in the longitudinal direction. ing. Therefore, the alignment direction of the liquid crystal is mostly the direction corresponding to the alignment control unit 14 in the longitudinal direction.

  FIG. 4 shows a configuration in which an alignment control window 52 in which no electrode exists is provided in the counter electrode 36. When the orientation control window 52 is provided as described above, the lines of electric force concentrate on the edge portion that forms the end of the orientation control window 52 when a voltage is applied. Therefore, the orientation of the liquid crystal molecules is determined by the electric field from this edge in the initial stage of applying a voltage to the pixel electrode 28, and then the liquid crystal molecules are tilted based on the direction initially determined by the electric field between the electrodes.

  In the present embodiment, the polarization axes of the two linear polarizing plates 22 and 42 are 45 degrees with respect to the direction of the central portion of the orientation control unit 14 (the two polarizing plates 22 and 42 are polarized The directions of the axes are different from each other by 90 degrees. When no electric field is applied to the liquid crystal 104, the light passes through the liquid crystal 104 as it is. Therefore, light does not pass through the action of the linearly polarizing plates 22 and 42 having polarization axes different from each other by 90 degrees, and black display is obtained. On the other hand, when an electric field is applied to the liquid crystal, the liquid crystal molecules lie in a direction parallel to the alignment films 30 and 32, and the phase difference between ordinary light and extraordinary light changes due to the change in the refractive index of the liquid crystal. By giving a phase difference of 180 degrees, linearly polarized light whose polarization axis is rotated by 90 degrees is obtained and white display is obtained. In addition, by controlling the voltage application to the liquid crystal, the angle at which the liquid crystal molecules lie is controlled to become elliptically polarized light and circularly polarized light, thereby displaying a gray scale.

  Further, as described above, the orientation of the liquid crystal is controlled by the alignment control unit 14. In the present embodiment, most of the liquid crystals are oriented in a direction perpendicular to the central alignment control unit 14. The transmittance of the liquid crystal is high in the direction along the liquid crystal molecules, and thus the viewing angle from the left and right direction when the display device is viewed from the front is improved.

  Furthermore, as shown in FIG. 1, in the present embodiment, the orientation control unit 14 has a vertical Y shape. Accordingly, some liquid crystal molecules are oriented in the direction parallel to the central alignment control unit 14 at the upper and lower ends, and the viewing angle in the vertical direction in the display device can be maintained to some extent.

  Thus, according to the present embodiment, the orientation control unit 14 is arranged at the center in the longitudinal direction of the elongated display dot. Thereby, the orientation direction of the liquid crystal can be controlled, and particularly the viewing angle dependency in the left-right direction of the display device can be reduced, and suitable display can be performed. In particular, VA liquid crystal is used, and polarizing plates disposed above and below the liquid crystal are linear polarizing plates 22 and 42 having a polarization axis in a direction of 45 degrees with respect to the central alignment control unit 14, so that a low-cost polarizing plate can be obtained. White display with sufficient transparency can be used.

  Further, the display color of each display dot is determined by the color filter. Therefore, the color region of the color filter constitutes one pixel by the four color regions.

  The four colored areas are the blue hue colored area, the red hue colored area, and the hue from blue to yellow in the visible light area (380 to 780 nm) whose hue changes according to the wavelength. It consists of colored areas of two types of hues selected from among them. Although it is used here as a system, for example, if it is a blue system, it is not limited to a pure blue hue, but includes a bluish purple or a bluish green. If it is a red hue, it is not limited to red but includes orange. These colored regions may be composed of a single colored layer, or may be composed of a plurality of colored layers having different hues. In addition, although these colored regions are described in terms of hue, the hue can be set by changing the saturation and lightness as appropriate.

Specific hue ranges are, for example, as follows.
-The colored region of the blue hue is blue-purple to blue-green, more preferably indigo to blue.
・ The colored area of red hue is orange to red,
-One colored region selected with a hue from blue to yellow is blue to green, more preferably blue green to green,
-The other coloring area | region selected by the hue from blue to yellow is green to orange, More preferably, it is green to yellow. Or it is green to yellowish green.

  Here, the same hue is not used for each colored region. For example, when a green hue is used in two colored regions selected from hues of blue to yellow, the other uses a blue or yellowish green hue for one green.

  Thereby, a wider range of color reproducibility than the conventional RGB colored region can be realized.

In addition, a wide range of color reproducibility has been described in terms of hue.
The blue colored region is a colored region having a wavelength peak at 415 to 500 nm, preferably a colored region at 435 to 485 nm.
The red colored region is a colored region having a wavelength peak of 600 nm or more, preferably a colored region of 605 nm or more.
-One colored region selected with a hue from blue to yellow is a colored region having a wavelength peak at 485-535 nm, preferably a colored region at 495-520 nm,
The other colored region selected with a hue from blue to yellow is a colored region having a wavelength peak in the range of 500 to 590 nm, preferably a colored region in the range of 510 to 585 nm, or a colored region in the range of 530 to 565 nm.

Next, it is expressed by an x, y chromaticity diagram.
The blue colored region is a colored region where x ≦ 0.151 and y ≦ 0.056, and preferably 0.134 ≦ x ≦ 0.151 and 0.034 ≦ y ≦ 0.056 The red colored region is a colored region in which 0.643 ≦ x, y ≦ 0.333, and preferably 0.643 ≦ x ≦ 0.690, 0.299 ≦ y ≦. The colored region at 0.333 is one colored region selected from hues from blue to yellow, and is a colored region at x ≦ 0.164, 0.453 ≦ y, preferably 0. It is a colored region in 098 ≦ x ≦ 0.164, 0.453 ≦ y ≦ 0.759,
The other colored region selected with a hue from blue to yellow is a colored region in which 0.257 ≦ x and 0.606 ≦ y, and preferably 0.257 ≦ x ≦ 0.357,. 606 ≦ y ≦ 0
. 670 is a colored region.

  These four colored areas can be applied within the above-described range when the sub-pixel includes a transmission area and a reflection area.

  As a backlight, an LED, a fluorescent tube, or an organic EL may be used as an RGB light source. Alternatively, a white light source may be used. The white light source may be a white light source generated by a blue light emitter and a YAG phosphor.

As the RGB light source, the following are preferable.
・ B has a wavelength peak between 435 nm and 485 nm ・ G has a wavelength peak between 520 nm and 545 nm ・ R has a wavelength peak between 610 nm and 650 nm

  A wider range of color reproducibility can be obtained by appropriately selecting the CF depending on the wavelength of the RGB light source.

  In addition, a light source having a plurality of peaks, for example, having peaks at wavelengths of 450 nm and 565 nm may be used.

Examples of the configuration of the four colored regions include the following.
・ Colored areas of red, blue, green, cyan (blue green) ・ Colored areas of red, blue, green, and yellow ・ Colored areas of red, blue, dark green, and yellow ・ Hue Red, blue, emerald, yellow colored areas / hues are red, blue, dark green, yellow green colored areas / hues are red, blue green, dark green, yellow green colored areas

It is a figure which shows the plane schematic structure for 1 pixel in the liquid crystal display device which concerns on embodiment. It is a schematic sectional drawing for 1 display dot. 3 is a diagram illustrating an example of an orientation control unit 14. FIG. It is a figure which shows the other example of the orientation control part.

Explanation of symbols

  10 pixels, 12R, 12G, 12B, 12C display dots, 14 orientation control unit, 20 backlight, 22, 42 linear polarizing plate, 24, 40 glass substrate, 26 TFT layer, 28 pixel electrodes, 30, 34 alignment film, 34 Counter electrode, 36 Counter electrode, 38 Color filter, 50 Alignment control protrusion, 52 Alignment control window, 100 substrate, 102 Counter substrate, 104 Liquid crystal.

Claims (4)

A liquid crystal display device comprising a plurality of pixels arranged in a matrix,
One pixel is formed with four display dots,
Four color filters are provided separately corresponding to the four display dots,
Each display dot is provided with an alignment control unit for controlling the alignment of the liquid crystal,
Each display dot has an elongated rectangular shape, and the orientation control unit includes a linear part extending in the center part in the longitudinal direction,
A liquid crystal display device, wherein the liquid crystal is a VA liquid crystal. The liquid crystal display device according to claim 1.
The liquid crystal display device, wherein the alignment control unit is a protrusion provided on an alignment control film in contact with the liquid crystal. The liquid crystal display device according to claim 1.
The liquid crystal display device, wherein the alignment control unit is a slit provided in an electrode for applying a voltage to the liquid crystal. The liquid crystal display device according to claim 1,
A liquid crystal display device comprising: a linearly polarizing plate having a polarization axis in a direction of 45 degrees with respect to a linear portion of the alignment controller on both sides of the liquid crystal.

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