JP2005316330A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of obtaining excellent contrast characteristics and contrast visual angle characteristics as optical characteristics in an AVAN (Advanced Vertical Alignment) mode. <P>SOLUTION: The liquid crystal display device is provided with an array substrate 4 having pixel electrodes 6, a counter substrate 3 having a common electrode 5 disposed opposite to the pixel electrodes 6, a liquid crystal layer 8 interposed between the array substrate 4 and the counter substrate 3 and first and second regions 1 and 2 having intensities of electric fields when voltage is applied between the pixel electrodes 6 and common electrode 5 or thicknesses of the liquid crystal layer 8 different from each other in a pixel region being a part of the liquid crystal layer 8 interposed between the pixel electrodes 6 and the counter electrode 5. The first and the second regions are arranged by an irregular layer B, refractive indices of a member for the first region and a member for the second region disposed between an upper and lower surface positions of the irregular layer B form a periodical pattern in an in-plane and the refractive indices, thicknesses and shapes of the members for the first and the second regions are determined so that incident light is not diffracted and not scattered by the irregular layer B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device in which a pixel region is divided into a plurality of domains having different tilt directions of liquid crystal molecules.

  A liquid crystal display device has various features such as thinness, light weight, and low power consumption, and is applied to various uses such as OA equipment, information terminals, watches, and televisions. In particular, a liquid crystal display device having a thin film transistor (hereinafter referred to as TFT) is used as a monitor for displaying a large amount of information, such as a portable television or a computer, because of its high responsiveness.

  In recent years, with an increase in the amount of information, there is an increasing demand for higher definition of images and higher display speed. Of these requirements, high definition of an image is realized, for example, by miniaturizing an array structure formed by the TFT described above. On the other hand, regarding the increase in display speed, instead of the conventional display mode, OCB mode, VAN mode, HAN mode, and π alignment mode using nematic liquid crystal, and interface stable ferroelectric liquid crystal using smectic liquid crystal are used. (Surface Stabilized Ferroelectric Liquid Crystal) mode and antiferroelectric liquid crystal mode are being studied.

  Among these display modes, the VAN mode can obtain a faster response speed than the conventional TN (Twisted Nematic) mode, and does not require a rubbing process that causes defects such as electrostatic breakdown due to vertical alignment. In particular, the multi-domain VAN mode (hereinafter referred to as the MVA mode) is particularly attracting attention because the viewing angle compensation design is relatively easy.

  However, in the conventional liquid crystal display device adopting the MVA mode, it is necessary to form a hook-like protrusion structure not only on the array substrate but also on the counter substrate, or to provide a slit or the like on the common electrode on the counter substrate. is there. Therefore, the alignment between the array substrate and the counter substrate must be performed with extremely high accuracy, resulting in an increase in cost and a decrease in reliability.

  In recent years, a technique for forming a color filter layer on an array substrate has been put into practical use in the manufacture of a TN mode liquid crystal display device. According to this technology, when the cell is formed by bonding the array substrate and the counter substrate, it is not necessary to align each color region constituting the color filter layer and the pixel electrode. Therefore, it is desirable to apply such a technique to the manufacture of an MVA mode liquid crystal display device. In the conventional MVA mode liquid crystal display device, a cell is formed by bonding an array substrate and a counter substrate. In addition, it is necessary to align the hook-like protrusion structure and the slit between them. Therefore, in the conventional MVA mode liquid crystal display device, even if the color filter layer is formed on the array substrate, it is not possible to enjoy the benefits obtained by the TN mode liquid crystal display device.

As means for solving such a problem, the following liquid crystal display device is known (for example, see Patent Document 1). This liquid crystal display device has an array substrate having a pixel electrode disposed on one main surface and covered with an alignment film, a counter substrate having a common electrode disposed facing the pixel electrode and covered with an alignment film, and facing the array substrate A liquid crystal layer sandwiched between the substrate and the substrate. Further, in this liquid crystal display device, the electric field strength or the liquid crystal layer when a voltage is applied between the pixel electrode and the common electrode in the pixel region which is a part of the liquid crystal layer sandwiched between the pixel electrode and the common electrode. There are provided first and second regions having different thicknesses. The first and second regions are parallel to the substantially flat interface composed of the liquid crystal layer and one of the alignment films, and are on the upper surface at the position where the liquid crystal layer is thinnest in the thickness direction of the liquid crystal layer, and the substantially flat interface. The concavo-convex layer having the lower surface at the position where the liquid crystal layer is thickest in the thickness direction of the liquid crystal layer is parallel to the shape and extends in one direction within the plane including the liquid crystal layer and intersects with one direction in the plane. Arranged to repeat alternately in the direction. The uneven layer can be selectively provided on the array substrate with respect to the counter substrate. Therefore, it is not necessary to perform highly accurate alignment when the array substrate and the counter substrate are bonded together. That is, even when the MVA mode is adopted, it is possible to manufacture the array substrate and the counter substrate without aligning with high accuracy. Such a liquid crystal display mode is referred to as an AVAN mode (Advanced Vertical Alignment mode).
JP 2003-161947 A

  In the AVAN mode liquid crystal display device, pixels are configured by first and second regions that are arranged in a stripe shape when seen in a plan view. The first region and the second region are obtained by, for example, the presence / absence of a pixel electrode, the presence / absence of a structure on the pixel electrode, the presence / absence of a pixel electrode and a structure, the presence / absence of a structure below the pixel electrode, and the like. With such a pixel structure, when a voltage is applied to the pixel, an electric field distribution is generated in the pixel, or a volume exclusion effect is generated by the distribution of the liquid crystal layer thickness, so that the liquid crystal molecules are arranged in the above-described stripe direction. . The first and second regions are arranged in stripes, and either one of the first region and the second region is formed as a continuous pattern, and two orientations in which the stripe orientations are orthogonal or four orientations every 90 ° are used. The alignment is divided by dividing the liquid crystal molecular arrangement into the azimuth or the four azimuths. Furthermore, if the polarizing plate is arranged so as to form an angle of 45 ° with the liquid crystal molecular arrangement, it is possible to efficiently control the transmission of incident light.

  However, these AVAN mode liquid crystal display devices are parallel to a substantially flat interface composed of a liquid crystal layer and one alignment film, and an upper surface at the position where the liquid crystal layer is thinnest in the thickness direction of the liquid crystal layer and the substantially flat surface. The light incident on the liquid crystal layer is scattered by changing its traveling direction in the uneven layer that is uneven with the bottom surface at the position where the liquid crystal layer is thickest in the thickness direction of the liquid crystal layer in parallel with the smooth interface. Has occurred. As a result, the optical characteristics originally in the oblique visual field affect the front visual field. When a compensation plate that compensates for the viewing angle characteristics of the phase difference of the liquid crystal layer is used, the light entering or exiting the compensation plate is not compensated for the phase difference by the compensation plate, and the contrast viewing angle deteriorates. End up.

  An object of the present invention is to provide a liquid crystal display device capable of obtaining excellent optical characteristics in the AVAN mode.

  According to the present invention, an array substrate having a pixel electrode disposed on one main surface and covered with an alignment film, a counter substrate having a common electrode disposed opposite to the pixel electrode and covered with an alignment film, and the array substrate, In the pixel region that is part of the liquid crystal layer sandwiched between the liquid crystal layer sandwiched between the counter substrate and the pixel electrode and the common electrode, the electric field when the voltage is applied between the pixel electrode and the common electrode First and second regions having different strengths or thicknesses of the liquid crystal layer, and the first and second regions are parallel to a substantially flat interface comprising the liquid crystal layer and one alignment film, and the liquid crystal layer Each of the liquid crystals is formed by a concavo-convex layer having a top surface at a position where the liquid crystal layer is thinnest in the thickness direction and a bottom surface which is parallel to the substantially flat interface and is at a position where the liquid crystal layer is thickest in the thickness direction One direction in the plane containing the layer Refraction of the first region member and the second region member arranged in an extended shape and alternately repeated in a direction intersecting with one direction in the surface and disposed between the upper surface position and the lower surface position of the uneven layer. The refractive index forms a periodic pattern in the plane, and the refractive index, thickness, and shape of the members for the first region and the second region are determined so that incident light is not diffracted and scattered by the uneven layer. A liquid crystal display device is provided.

  In this liquid crystal display device, it is possible to improve the light scattering in the concavo-convex layer, the decrease in contrast ratio due to refraction, and the deterioration in the contrast viewing angle characteristics. That is, even when the AVAN mode is adopted, excellent contrast characteristics and contrast viewing angle characteristics can be obtained as optical characteristics.

  Hereinafter, an AVAN mode liquid crystal display device according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a planar pattern of each pixel in this liquid crystal display device, and FIG. 2 shows a pixel structure in a cross section taken along the line A-A 'shown in FIG. This liquid crystal display device has a structure in which a liquid crystal layer 8 is sandwiched between an active matrix substrate (or array substrate) 4 and a counter substrate 3. The distance between the active matrix substrate 4 and the counter substrate 3 is kept constant by a spacer (not shown). Further, a pair of polarizing plates PL1 and PL2 having absorption axes in the directions 10 and 11 shown in FIG. The active matrix substrate 4 includes a transparent substrate 4A such as a glass substrate. Wiring and switching elements are formed on one main surface of the transparent substrate 4A. Further, a color filter layer CF, a pixel electrode 6, and an alignment film AL1 are sequentially formed thereon. Wirings formed on the transparent substrate 4A are scanning lines and signal lines made of aluminum, molybdenum, copper, or the like. The switching element is a TFT having amorphous silicon or polysilicon as a semiconductor layer and aluminum, molybdenum, chromium, copper, tantalum or the like as a metal layer, for example, wiring such as scanning lines and signal lines, and pixel electrodes 6. Connected with. The active matrix substrate 4 can selectively apply a voltage to a desired pixel electrode 6 with such a configuration.

  The color filter layer CF interposed between the transparent substrate 4A and the pixel electrode 6 is composed of colored layers of blue, green, and red. The pixel electrode 6 is made of a transparent conductive material such as ITO, and is connected to the switching element through a contact hole provided in the color filter layer CF. The pixel electrode 6 can be formed by, for example, forming a thin film by sputtering or the like and then patterning the thin film using a photolithography technique and an etching technique. The alignment film AL1 is formed of a thin film made of a transparent resin such as polyimide. In this embodiment, the alignment film AL1 is given a vertical alignment without being subjected to a rubbing process.

  The counter substrate 3 has a structure in which a common electrode 5 and an alignment film AL2 are sequentially formed on a transparent substrate 3A such as a glass substrate. The common electrode 5 and the alignment film AL2 can be formed of the same material as the alignment film AL1 formed on the pixel electrode 6 and the active matrix substrate 4. Here, the common electrode 5 is formed as a flat continuous film.

  The liquid crystal display device shown in FIGS. 1 and 2 includes a first region 1 and a second region 2 in which pixels are arranged in a stripe shape when seen in a plan view. The first region 1 is obtained by the pixel electrode 6, and the second region 2 is obtained by a slit in the pixel electrode 6.

  When no voltage is applied between the pixel electrode 6 and the common electrode 5, the alignment films AL1 and AL2 are liquid crystal molecules 7 constituting the liquid crystal layer 8, specifically, liquid crystal molecules having a negative dielectric anisotropy. Acts to be vertically aligned. Therefore, the liquid crystal molecules 7 are aligned so that their long axes are substantially perpendicular to the film surfaces of the alignment films AL1 and AL2 (FIG. 2 shows a state in which a voltage is applied).

  An electric field generated by applying a voltage between the pixel electrode 6 and the common electrode 5 acts to align the liquid crystal molecules 7 in a direction perpendicular to the lines of electric force thereof. Therefore, the liquid crystal molecules 7 try to align as shown in FIGS. 1 and 2 by the action of the alignment films AL1 and AL2 and the electric field. That is, with only the structure provided on the active matrix substrate 4, four domains having different tilt directions of the liquid crystal molecules 25 can be formed in one pixel region. In the present embodiment, the tilt angle can be changed while maintaining the average tilt direction of the liquid crystal molecules 7 in a plane perpendicular to the arrangement direction of the second regions (slits) 2, so that a faster response speed is achieved. In addition, it is difficult to cause orientation failure and good orientation division is possible. In the present embodiment, the pixel electrode 6 has a thickness of 15 nm and a refractive index at a wavelength of 550 nm of 2.00. The liquid crystal layer 8 uses nematic liquid crystal MLC-2038 having a negative dielectric anisotropy manufactured by Merck Co., Ltd. The ordinary refractive index at 550 nm of MLC-2038 is 1.47. In the range of the concave / convex layer B, the pixel electrodes 6 and the liquid crystal layer 8 are periodically arranged in a plane as shown in FIGS. 1 and 2 in the in-plane direction. When the refractive index of the pixel electrode 6 disposed in the first region 1 and the refractive index of the liquid crystal layer 8 disposed in the second region 2 are different, the uneven layer B functions as a diffraction grating. Therefore, the incident light is diffracted according to the refractive index difference and the layer thickness.

The first region 1 and the second region 2 are not limited to the presence / absence of the pixel electrode as described above, for example, the presence / absence of the structure 9 on the pixel electrode 6 as shown in FIG. 3, as shown in FIG. It can also be obtained by the presence / absence of the pixel electrode 6 and the structure 9, the presence / absence of the structure 9 below the pixel electrode 6 as shown in FIGS. 3 to 6, the same parts as those in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted.

FIG. 7 and Formula 1 show the diffraction intensity of light in such a structure having a periodic refractive index distribution. Im is the intensity of the diffracted light with respect to the first and higher orders, Iq is the intensity of the incident light, m is the order of diffraction, and l is in the periodic arrangement direction in the plane of the regions 1 and 2 with the higher refractive index. The width, p is the pitch in the periodic arrangement direction in the plane of the regions 1 and 2, δn is the difference between the average refractive index of the first region 1 and the average refractive index of the second region 2 in the concavo-convex layer B, and t is the concavo-convex layer B , Λ is the wavelength of the incident light, and I0 is the intensity of the diffracted light with respect to the 0th order. In Equation 1, 10 = Iq is a state where there is no scattering due to diffraction, and 10 = 0 indicates a state where all incident light is scattered.

  FIG. 7 and Formula 2 show the diffraction direction of light in the structure having such a periodic refractive index distribution. θm is the angle of the diffracted light with respect to the m-th order, and the pixel normal direction is 0 °. θq is an angle indicating the direction of incident light, and the pixel normal direction is 0 °. θ0 is the angle of 0th-order diffracted light, that is, light traveling straight, and θ0 = θq.

Here, the contrast ratio in a certain visual field will be described. FIG. 8 schematically shows a path of light that is emitted from the concavo-convex layer B and is incident on the liquid crystal layer 8 positioned thereon from a direction inclined by θr from the pixel normal direction. In the figure, LC indicates the refractive index ellipse of the liquid crystal layer 8, and OC schematically indicates the refractive index ellipse of the compensation layer for compensating for the phase difference occurring in the oblique orientation of the liquid crystal layer 8. It is a thing.

Equation 3 shows the sum of the light emitted from the concavo-convex layer B and incident on the liquid crystal layer 8 positioned thereon in the direction inclined by θr from the pixel normal direction, and Iθr is the light intensity of the sum of the light. , Δnd is a value obtained by multiplying the refractive index anisotropy Δn of the liquid crystal layer 8 by the thickness d of the liquid crystal layer 8.

  Equation 4 emits the concavo-convex layer B when it is assumed that the contrast ratio of the pixel without the concavo-convex layer B is infinite and the compensation layer completely compensates the viewing angle dependency of the phase difference of the liquid crystal layer 8. The liquid crystal layer 8 positioned thereon has contrast characteristics in a direction inclined by θr from the pixel normal direction, and CRθr is a contrast ratio in a direction inclined by θr from the element normal direction. As apparent from Equation 2, when the pitch p ′ in the periodic arrangement direction in the plane of the region 1 and the region 2 is not sufficiently large with respect to the visible light wavelength, specifically, the first order or more unless it is about 100 times or more. The diffracted light becomes 90 ° or less. Further, as apparent from Equation 1, the value obtained by multiplying the difference δn between the average refractive index of the first region 1 and the average refractive index of the second region 2 in the concavo-convex layer B and the thickness t of the concavo-convex layer B is the incident light wavelength. If it does not match the integer multiple, first-order ≧ diffracted light is generated. In such a case, the light incident on the liquid crystal layer 8 from the angle θr is the sum of the light emitted from the concavo-convex layer B from the direction parallel to θr and from θr to θ1, θ2,. Assuming that the compensation layer completely compensates the viewing angle dependence of the phase difference of the liquid crystal layer 8, as shown in the drawing, the light emitted from the concavo-convex layer B from the direction parallel to θr, that is, the 0th-order diffracted light in the concavo-convex layer B Although the absolute value of the phase difference R (LC) of the liquid crystal layer 8 and the phase difference R (OC) of the compensation layer are equal, the respective phase differences are compensated, but the concave-convex layer B is applied from the direction inclined from θr to θ1, θ2,. For the emitted light, the absolute values of the phase difference R (LC) of the liquid crystal layer 8 and the phase difference R (OC) of the compensation layer are not equal, so that each phase difference is not compensated, and as a result, in the field of view of θr. A phase difference occurs. Since such a phenomenon occurs regardless of the value of θr, as a result, a phase difference occurs in all fields of view including the front surface (pixel normal direction). When there is no concavo-convex layer B, and when the compensation layer completely compensates for the viewing angle dependence of the phase difference of the liquid crystal layer 8, the phase difference is zero in all fields of view, and black display is performed with no phase difference. Although excellent contrast characteristics are obtained in all fields of view, the contrast characteristics are degraded in all fields of view under the conditions described above. In recent years, as the viewing angle of liquid crystal display devices has been increasing, in viewing fields such as liquid crystal monitors and liquid crystal TVs, the viewing angle with a contrast (CR) viewing angle characteristic of CR> 10 is 170 ° in all directions (85 ° from the normal direction). It is desired that this is the case.

9 to 12 show a liquid crystal display device that controls the phase difference of the liquid crystal layer 8 between 0 and 1/2, that is, the refractive index anisotropy Δn of the liquid crystal material of the liquid crystal layer 8 and the thickness d of the liquid crystal layer 8. The multiplied value Δnd is ½ or more of the central wavelength 550 nm of visible light, and the contrast ratio of the pixel when the uneven layer B is not present is infinite, and the compensation layer has a phase difference of the liquid crystal layer 8. Assuming that the viewing angle dependency is completely compensated, the condition that the viewing angle with CR viewing angle characteristics CR> 10 is 170 ° (85 ° from the normal direction) or more is calculated based on Equations 1 to 4. It is shown. FIG. 9 shows the structure of the structure 9 constituting the uneven layer B and the step of the uneven layer B having the characteristic of CR> 10 in the pitch of the uneven layer B of 10 μm in the AVAN mode shown in FIGS. 2 and 4 to 6. FIG. 10 is a diagram showing a relationship between a lower limit value of a difference between an average refractive index at a wavelength of 550 nm and an ordinary refractive index light at a wavelength of 550 nm of the liquid crystal layer 8, and FIG. 10 shows a pitch of the uneven layer B of 10 μm in the AVAN mode shown in FIG. Yes, the relationship between the step of the concavo-convex layer B that obtains the characteristic of CR> 10 and the lower limit value of the difference between the average refractive index at the wavelength 550 nm of the structure 9 constituting the concavo-convex layer B and the ordinary refractive index light at the wavelength 550 nm of the liquid crystal layer 8 FIG. 11 shows the steps of the concavo-convex layer B and the concavo-convex layer B with the pitch of the concavo-convex layer B of 20 μm and obtaining the characteristic of CR> 10 in the AVAN mode shown in FIGS. 2 and 4 to 6. Structure to configure FIG. 12 is a diagram showing the relationship between the lower limit of the difference between the average refractive index of the body 9 at a wavelength of 550 nm and the ordinary refractive index light of the liquid crystal layer 8 at a wavelength of 550 nm, and FIG. 12 shows the pitch of the uneven layer B in the AVAN mode shown in FIG. Is the lower limit of the difference between the step of the concavo-convex layer B and the average refractive index at the wavelength 550 nm of the structure 9 constituting the concavo-convex layer B and the ordinary refractive index light at the wavelength 550 nm of the liquid crystal layer 8. It is a figure which shows the relationship of a value. As shown in these drawings, and as can be seen from Equation 1 and FIG. 2, the thickness of the concavo-convex layer B that achieves the target CR viewing angle characteristics (denoted as steps in FIGS. 9 to 12), region 1 and region The refractive index difference of 2 depends on the pitch of the concavo-convex layer B, the structure of the concavo-convex layer B, the structure 9 constituting the concavo-convex layer B, and the taper angle (φ) of the electrode. (n1-n2) t where t is the average refractive index at a wavelength of 550 nm of the members for the first region 1 and the second region 2 made of an electrode, an alignment film, a liquid crystal material, an insulating layer, and the like. Is 539m-11 <(
n1-n2) t <561m + 11 [nm], where m = 0, ± 1, ± 2,... unless the above-mentioned diffraction results in a decrease in CR characteristics and CR viewing angle characteristics, and there is no uneven layer B Even when the contrast characteristic is infinite in the entire field of view, the viewing angle of CR> 10 does not become 170 ° (85 ° from the normal direction) or more in all directions.

  In this embodiment, the thickness of the pixel electrode 6 (refractive index 2.00 at a wavelength of 550 nm) is set to 15 nm, and | (n1-n2) t | = (2.00-1.47) × 15 nm = 7.95 nm. <11 nm.

  Hereinafter, a manufacturing example of the liquid crystal display device of the present embodiment will be described.

(Production Example 1)
In this manufacturing example, the liquid crystal display device having the pixel structure shown in FIGS. 1 and 2 was manufactured. The liquid crystal layer 8 is MLC-2038 manufactured by Merck Co., Ltd., which exhibits negative dielectric anisotropy, and the ordinary refractive index at 550 nm is 1.47. The pixel electrode 6 is made of ITO and has a refractive index of 2.00 at a thickness of 15 nm and 550 nm, and the aforementioned (n1-n2) t is | (n1-n2) t | = (2.00-1. 47) × 15 nm = 7.95 nm. A value Δnd obtained by multiplying the refractive index anisotropy Δn of the liquid crystal material by the thickness d of the liquid crystal layer 8 is set to 300 nm. In addition, a biaxial arton resin phase difference plate (manufactured by Nitto Denko Corporation) is adjacent to the upper and lower sides of the liquid crystal layer 8 as means for compensating for the phase difference of the liquid crystal layer 8 when no voltage is applied. It arrange | positions so that it may orthogonally cross with the absorption axis of a polarizing plate. The retardation value of the retardation plate described above has an in-plane orientation of 120 nm and a normal orientation of 50 nm (value obtained by multiplying (nx−ny) by thickness), and the refractive index anisotropy of the liquid crystal material described above. And a value Δnd = 300 nm obtained by multiplying the thickness of the liquid crystal layer 8 by this condition. Further, SEG1224DU manufactured by Nitto Denko Corporation was used for the polarizing plate.

  When a voltage of 4 V was applied between the pixel electrode 6 and the common electrode (counter electrode) 5 of the liquid crystal display device thus obtained, and a contrast viewing angle was measured between the state where no voltage was applied, a CR> 10 was obtained.

(Comparative example)
In Production Example 1, a liquid crystal display device similar to that in Production Example 1 was produced with the pixel electrode 6 having a thickness of 50 nm, and a voltage of 4 V was applied between the pixel electrode 6 and the common electrode (counter electrode) 5 of the liquid crystal display device. When the contrast viewing angle was measured between the voltage applied and no voltage applied, the viewing angle for obtaining CR> 10 was only 15 ° cone.

(Production Example 2)
In this manufacturing example, the liquid crystal display device having the pixel structure shown in FIGS. 1 and 3 was manufactured. The liquid crystal layer 8 is MLC-2038 manufactured by Merck Co., Ltd., which exhibits negative dielectric anisotropy, and the ordinary refractive index at 550 nm is 1.47. The structure 9 formed on the pixel electrode 6 is made of a fluorine-based transparent resist manufactured by JSR Co., Ltd., and has a thickness of 150 nm and a refractive index of 1.48 at 550 nm, and the aforementioned (n1-n2) t is | (N1-n2) t | = (1.48-1.47) × 150 nm = 1.5 nm. The liquid crystal layer 8, the polarizing plate, and the compensation plate for the liquid crystal layer 8 are the same as those in Production Example 1. When a voltage of 4 V was applied between the pixel electrode 6 and the common electrode (counter electrode) 5 of the liquid crystal display device thus obtained, and the contrast viewing angle was measured between the state where no voltage was applied, the CR> 10 was obtained.

It is a figure which shows the plane pattern of each pixel in the liquid crystal display device of the AVAN mode which concerns on one Embodiment of this invention. It is a figure which shows the pixel structure in the cross section along the A-A 'line shown in FIG. 1 with the liquid crystal molecule arrangement | sequence at the time of voltage application. It is a figure which shows the 1st modification of the pixel structure in the cross section along the A-A 'line shown in FIG. 1 with the liquid crystal molecule arrangement | sequence at the time of voltage application. It is a figure which shows the 2nd modification of the pixel structure in the cross section along the A-A 'line shown in FIG. 1 with the liquid crystal molecule arrangement | sequence at the time of voltage application. It is a figure which shows the 3rd modification of the pixel structure in the cross section along the A-A 'line shown in FIG. 1 with the liquid crystal molecule arrangement | sequence at the time of voltage application. It is a figure which shows the 4th modification of the pixel structure in the cross section along the A-A 'line shown in FIG. 1 with the liquid crystal molecule arrangement | sequence at the time of voltage application. It is a figure explaining the diffraction phenomenon of the light in the uneven | corrugated layer shown in FIGS. It is a figure explaining the principle of the contrast fall of the element by the diffraction phenomenon of the light produced by the uneven | corrugated layer shown in FIGS. The pitch of the concavo-convex layer shown in FIGS. 2 and 4 to 6 is 10 μm, the step of the concavo-convex layer that obtains the characteristic of CR> 10 and the average refractive index at the wavelength of 550 nm of the structure forming the concavo-convex layer and the wavelength of the liquid crystal layer It is a figure which shows the relationship of the lower limit of the difference of the ordinary-light refractive-index light in 550 nm. The pitch of the concavo-convex layer shown in FIG. 3 is 10 μm, the step of the concavo-convex layer obtaining the characteristic of CR> 10, the average refractive index at the wavelength 550 nm of the structure forming the concavo-convex layer, and the ordinary refractive index light at the wavelength 550 nm of the liquid crystal layer It is a figure which shows the relationship of the lower limit of the difference of. The pitch of the concavo-convex layer shown in FIGS. 2 and 4 to 6 is 20 μm, the step of the concavo-convex layer that obtains the characteristic of CR> 10 and the average refractive index at the wavelength of 550 nm of the structure forming the concavo-convex layer and the wavelength of the liquid crystal layer It is a figure which shows the relationship of the lower limit of the difference of the ordinary-light refractive-index light in 550 nm. The pitch of the concavo-convex layer shown in FIG. 3 is 20 μm, the step of the concavo-convex layer that obtains the characteristic of CR> 10, the average refractive index at the wavelength 550 nm of the structure forming the concavo-convex layer, and the ordinary refractive index light at the wavelength 550 nm of the liquid crystal layer It is a figure which shows the relationship of the lower limit of the difference of.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st area | region, 2 ... 2nd area | region, 3 ... Counter substrate, 4 ... Array substrate, 5 ... Common electrode, 6 ... Pixel electrode, 7 ... Liquid crystal molecule, 8 ... Liquid crystal layer, 9 ... Structure, 10 ... Front Side polarizing plate absorption axis direction, 11... Rear side polarizing plate absorption axis direction, AL1, AL2... Alignment film, PL1, PL2.

Claims (4)

An array substrate having a pixel electrode disposed on one main surface and covered with an alignment film, a counter substrate having a common electrode disposed opposite to the pixel electrode and covered with an alignment film, the array substrate and the counter substrate, A voltage applied between the pixel electrode and the common electrode in a pixel region that is part of the liquid crystal layer sandwiched between the pixel electrode and the common electrode. First and second regions having different electric field strengths or liquid crystal layer thicknesses, wherein the first and second regions are substantially flat with respect to the liquid crystal layer and one alignment film. A top surface parallel to the thickness direction of the liquid crystal layer and the thinnest liquid crystal layer, and a position parallel to the substantially flat interface and thickest in the liquid crystal layer thickness direction. Having a lower surface Each of the convex layers has a shape extending in one direction within the plane including the liquid crystal layer and is arranged so as to be alternately repeated in a direction intersecting the one direction within the plane, and the upper surface position and the lower surface position of the concave-convex layer Refractive indexes of the first region member and the second region member disposed between the first region member and the second region member form a periodic pattern in a plane, and the refractive index, thickness, and thickness of the first region member and the second region member, and The liquid crystal display device is characterized in that the shape is determined so that incident light is not diffracted and scattered by the uneven layer. When the thickness of the concavo-convex layer is t, and the average refractive index of the first region member and the average refractive index of the second region member with respect to incident light having a wavelength of 550 nm are n1 and n2, respectively (n1-n2 2. The liquid crystal display according to claim 1, wherein t satisfies a relationship of 539m-11 <(n1-n2) t <561m + 11 [nm] with respect to m = 0, ± 1, ± 2,. apparatus. The liquid crystal display device according to claim 1, wherein the liquid crystal layer contains a liquid crystal material having a negative dielectric anisotropy. 4. The liquid crystal display device according to claim 1, wherein the alignment film has a vertical alignment property.

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