JP2005242127A - Liquid crystal display device and fabrication method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can sufficiently stabilize alignment of liquid crystal with relatively simple constitution and can be fabricated through simpler processes than heretofore, and a fabrication method therefor. <P>SOLUTION: The liquid crystal display device has a plurality of pixels each including a first electrode 1111 formed on a first substrate 110a, an inter-layer insulating film 115a provided between the 1st substrate 110a and 1st electrode 111, a second electrode 131 formed on a second substrate 110b, and a liquid crystal layer interposed between the first electrode 111 and the second electrode 131. The inter-layer insulating film 115a has at least one recessed part 117 formed at a specified position and the liquid crystal layer has at least one liquid crystal domain containing liquid crystal molecules slanted in an azimuth prescribed by at least one recessed part 117 when at least a specified voltage is applied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device suitably used for a personal digital assistant (for example, PDA), a mobile phone, an in-vehicle liquid crystal display, a digital camera, a personal computer, an amusement device, a television, and the like.

  In recent years, liquid crystal display devices have been widely used for information devices such as notebook personal computers, mobile phones, electronic notebooks, or camera-integrated VTRs equipped with a liquid crystal monitor, taking advantage of their thinness and low power consumption. ing.

  As a display mode capable of realizing a high contrast and a wide viewing angle, a vertical alignment mode using a vertical alignment type liquid crystal layer has attracted attention. The vertical alignment type liquid crystal layer is generally formed using a vertical alignment film and a liquid crystal material having negative dielectric anisotropy.

  For example, Patent Document 1 discloses that an oblique electric field is generated around an opening provided in a counter electrode facing a pixel electrode via a liquid crystal layer, and liquid crystal around the liquid crystal molecules in a vertically aligned state in the opening. A liquid crystal display device in which viewing angle characteristics are improved by tilting molecules is disclosed.

  However, in the configuration described in Patent Document 1, it is difficult to form an oblique electric field in the entire region in the pixel. As a result, a region in which the response of the liquid crystal molecules to the voltage is delayed occurs in the pixel, and an afterimage phenomenon occurs. The problem of appearing arises.

  In order to solve this problem, Patent Document 2 discloses a liquid crystal display device having a plurality of liquid crystal domains exhibiting a radially inclined alignment in a pixel by providing openings regularly arranged in the pixel electrode or the counter electrode. doing.

  Furthermore, Patent Document 3 discloses a technique for stabilizing the alignment state of a liquid crystal domain having an inclined radial alignment that appears around a convex portion by providing a plurality of convex portions regularly in a pixel. . Further, this document discloses that the display characteristics can be improved by regulating the alignment of liquid crystal molecules using an oblique electric field by an opening provided in the electrode, together with the alignment regulating force by the convex part.

  On the other hand, in recent years, liquid crystal display devices capable of high-quality display both outdoors and indoors have been proposed (for example, Patent Document 4 and Patent Document 5). This liquid crystal display device is referred to as a transflective liquid crystal display device, and has a reflective region in a pixel for displaying in a reflective mode and a transmissive region for displaying in a transmissive mode.

  The transflective liquid crystal display devices currently on the market use the ECB mode, the TN mode, and the like. However, in Patent Document 3, the vertical alignment mode is not limited to the transmissive liquid crystal display device but also the transflective liquid crystal. A configuration applied to a display device is also disclosed. Further, in Patent Document 6, in a semi-transmissive liquid crystal display device having a vertical alignment type liquid crystal layer, an insulating layer provided to make the thickness of the liquid crystal layer in the transmissive region twice the thickness of the liquid crystal layer in the reflective region. A technique for controlling the alignment (multiaxial alignment) of liquid crystals by the formed recesses is disclosed. A configuration is disclosed in which the recess is formed in, for example, a regular octagon, and a projection (projection) or a slit (electrode opening) is formed at a position facing the recess via the liquid crystal layer (for example, FIG. 4 and FIG. 16).

Further, in order to improve display quality in the reflection mode, a technique for forming a diffuse reflection layer having excellent diffuse reflection characteristics has been studied. For example, Patent Document 7 discloses a technique for obtaining good diffuse reflection characteristics by forming fine uneven shapes randomly arranged on the surface of the reflective electrode through a photolithography process using a two-layer photosensitive resin film. Is disclosed. Further, in Patent Document 8, for the purpose of simplifying the manufacturing process, a single layer of photosensitive resin is used to expose and develop a contact hole and a photomask for forming fine irregularities. Thus, a technique for forming a reflective electrode having a fine uneven shape is disclosed.
JP-A-6-301036 JP 2000-47217 A JP 2003-167253 A Japanese Patent No. 29555277 US Pat. No. 6,195,140 JP 2002-350853 A JP-A-6-75238 Japanese Patent Laid-Open No. 9-90426

  In the technique disclosed in Patent Document 2 or Patent Document 3, a plurality of liquid crystal domains are formed by providing convex portions or openings in a pixel (that is, divided into pixels), and the alignment regulation force on liquid crystal molecules is strengthened. However, according to the study of the present inventors, in order to obtain a sufficient alignment regulating force, alignment regulating structures such as convex portions and openings are formed on both sides of the liquid crystal layer (the liquid crystal layer side of a pair of substrates facing each other). There is a problem that the manufacturing process becomes complicated. In addition, the contrast ratio may be lowered due to light leakage from the periphery of the convex portion in the pixel. Further, in the case where the alignment regulating structure is provided on both substrates, since it is affected by the alignment margin of the substrates, the effective aperture ratio and / or the contrast ratio are further reduced.

  Further, in the technique disclosed in Patent Document 6, it is necessary to arrange a convex part or an electrode opening on the side opposite to the concave part provided in order to control the multiaxial orientation. Occur.

  In addition, for example, when the reflective electrode is formed using the method described in Patent Document 7 or 8 in order to improve the display quality of the reflective mode of the transflective liquid crystal display device, the manufacturing process becomes complicated. There is. That is, it is necessary to form not only convex portions for regulating the orientation but also fine irregularities for improving the diffuse reflection characteristics, leading to an increase in the cost of the liquid crystal display device.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a liquid crystal display device that can sufficiently stabilize the alignment of liquid crystals with a relatively simple configuration and can be manufactured by a simpler process than before. It is in providing the manufacturing method.

  The liquid crystal display device of the present invention includes a first substrate, a second substrate provided so as to face the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate. Each of which includes a first electrode formed on the first substrate, an interlayer insulating film provided between the first substrate and the first electrode, and a second electrode formed on the second substrate. A plurality of pixels including an electrode and the liquid crystal layer provided between the first electrode and the second electrode, and the interlayer insulating film has at least one recess provided at a predetermined position. The liquid crystal layer is characterized by forming at least one liquid crystal domain including liquid crystal molecules inclined in an orientation defined by the at least one recess when at least a predetermined voltage is applied.

  In one embodiment, the first electrode has at least one opening, and the at least one opening includes an opening formed at a position corresponding to the at least one recess.

In one embodiment, when the plurality of pixels are arranged in a matrix and the shorter pitch is P _S , the maximum inner diameter width D _C of the at least one recess is D _C <0.35 · P _S. Satisfy the relationship.

  In one embodiment, the relationship between the thickness Id of the interlayer insulating film and the depth h of the at least one recess satisfies a relationship of h <0.8 · Id.

  In one embodiment, the first electrode further has at least one notch.

  In one embodiment, the image forming apparatus further includes a wall structure formed integrally with the interlayer insulating film, and the wall structure is regularly arranged around each of the plurality of pixels.

  In one embodiment, a light shielding region is provided around each of the plurality of pixels, and the wall structure is regularly arranged in the light shielding region.

  In one embodiment, the liquid crystal layer is a vertical alignment type liquid crystal layer, and the at least one liquid crystal domain formed when at least a predetermined voltage is applied to the liquid crystal layer includes a liquid crystal domain exhibiting axial symmetry alignment. The central axis of the axially symmetric orientation is formed in or near the at least one recess.

  In one embodiment, the second electrode has at least one further opening formed at a predetermined position in a pixel, and the liquid crystal layer is a vertical alignment type liquid crystal layer, and the liquid crystal layer is at least in the liquid crystal layer. The at least one liquid crystal domain formed when a predetermined voltage is applied includes a liquid crystal domain exhibiting an axially symmetric orientation, and a central axis of the axially symmetric orientation is formed in or near the at least one further recess.

  In one embodiment, a switching element electrically connected to the first electrode is further provided on the first substrate, and at least a part of the switching element is covered with the interlayer insulating film.

  In one embodiment, the first electrode includes a transparent electrode that defines a transmissive region and a reflective electrode that defines a reflective region.

  In one embodiment, the at least one liquid crystal domain includes a liquid crystal domain formed in the transmissive region and exhibiting axially symmetric alignment, and a central axis of the axially symmetric alignment is formed in or near the at least one recess. .

  In one embodiment, the interlayer insulating film has a first region having a substantially flat surface and a second region having a concavo-convex shape on the surface, and the transparent electrode is formed on the first region. The reflective electrode is formed on the second region.

  In one embodiment, the first substrate and / or the second substrate and the pair of polarizing plates have a pair of polarizing plates disposed so as to face each other with the first substrate and the second substrate interposed therebetween. And at least one biaxial optically anisotropic medium layer.

  In one embodiment, the liquid crystal display device further includes a pair of polarizing plates disposed so as to face each other with the first substrate and the second substrate interposed therebetween, and the first substrate and / or the second substrate and the pair of polarizations It further has at least one uniaxial optically anisotropic medium layer between the plates.

  The method of manufacturing a liquid crystal display device according to the present invention includes a first substrate, a second substrate provided to face the first substrate, and a liquid crystal provided between the first substrate and the second substrate. A first electrode formed on the first substrate, a circuit element electrically connected to the first electrode, and between the first substrate and the first electrode A liquid crystal display device comprising a plurality of pixels, comprising: an interlayer insulating film provided; a second electrode formed on the second substrate; and the liquid crystal layer provided between the first electrode and the second electrode. And a step of forming a circuit element on a first substrate, a step of forming a positive photosensitive resin film covering the circuit element, and a step of exposing the photosensitive resin film. A step of forming predetermined regions having different exposure amounts, and developing the exposed photosensitive resin film A step of forming a contact hole exposing a part of the circuit element, an interlayer insulating film having at least one recess, and a step of forming a first electrode on the interlayer insulating film. It is characterized by.

  In one embodiment, the step of forming the interlayer insulating layer includes a step of forming a first region having a substantially flat surface and a second region having a concavo-convex shape, and forming the first electrode. The step of forming includes a step of forming a transparent electrode on the interlayer insulating film in the first region and a step of forming a reflective electrode on the interlayer insulating film in the second region.

  In one embodiment, the exposure step uses a first photomask to form a region that becomes the second region and other regions, and a second photomask is used for the other regions. And a second exposure step of forming a region to be the contact hole and a region to be the at least one recess.

  In one embodiment, the liquid crystal display device further includes a wall structure regularly arranged around each of the plurality of pixels and integrally formed with the interlayer insulating film, and the first exposure step includes: Forming a region to be the second region and a region to be a wall structure;

  In one embodiment, the step of forming the first electrode and / or the second electrode includes a step of forming a conductive film and a step of patterning the conductive film. The step of patterning includes the step of forming the first electrode. Including a step of forming a plurality of openings or notches at predetermined positions of one electrode and / or the second electrode.

  In the liquid crystal display device of the present invention, an interlayer insulating film provided between a first electrode (for example, a pixel electrode) and a first substrate has a recess in a predetermined region. A recess formed on the surface on the liquid crystal layer side corresponding to the recess acts as an alignment regulating structure, and defines an orientation in which the liquid crystal molecules are tilted when at least a predetermined voltage (voltage equal to or higher than a threshold value) is applied. The interlayer insulating film is typically formed so as to cover circuit elements (wiring, switching elements (TFTs, etc.)) electrically connected to the first electrode, and the recess forms a contact hole in the interlayer insulating film. Since it can be formed using a process, the manufacturing process is not complicated. In addition, when the opening is provided at a position corresponding to the concave portion of the first electrode, the direction (direction) in which the liquid crystal molecules are tilted can be regulated by an oblique electric field generated in the vicinity of the opening when a voltage is applied.

  Furthermore, when the notch is provided in the first electrode, the direction in which the liquid crystal molecules are tilted can be defined by the oblique electric field generated in the vicinity of the notch. In addition, by providing a wall structure regularly arranged around the pixel, the direction in which the liquid crystal molecules tilt can be defined. The wall structure defines the direction in which the liquid crystal molecules are tilted by the electric field by the anchoring action (alignment regulating force) of the inclined side surface, and the liquid crystal molecules having different alignment directions are substantially surrounded by the wall structure. This exhibits an effect that at least one liquid crystal domain containing is stably formed. By forming the wall structure integrally with the interlayer insulating film, the manufacturing process can be prevented from becoming complicated. Further, since the periphery of the pixel is a light shielding region, light leakage due to the wall structure is suppressed / prevented.

  The recesses formed in the interlayer insulating film, the openings formed in the first electrode (typically, the pixel electrode), and the orientation regulating structure such as the wall structure are all formed on the first substrate side, and the second substrate Even if an orientation regulating structure is not provided on the side, a sufficient orientation regulating force can be obtained.

  For example, when a vertical alignment type liquid crystal layer is used as the liquid crystal layer, an axially symmetric alignment domain in which the central axis is fixed and stabilized can be formed in or near the recess. By providing the opening at a position corresponding to the recess, the central axis is more reliably fixed and stabilized. Further, the axially symmetric orientation itself can be stabilized by utilizing the orientation regulating force of the notch and / or the wall structure. In particular, when a plurality of axially symmetric alignment domains are formed in a pixel, the axially symmetric alignment domains can be effectively stabilized by providing notches at their boundaries.

  In order to fix and stabilize the central axis of the axially symmetric orientation, an opening may be provided in the second electrode facing the first electrode, and a notch may be provided as necessary.

  As described above, according to the present invention, for example, the axially symmetric orientation can be stabilized and the central axis can be fixed and stabilized, so that the position of the central axis is non-uniform in the display area (varies from pixel to pixel). In particular, it is possible to improve the afterglow phenomenon caused by the generation of a rough feeling of display caused by the delay or the slow relaxation response time seen at the transition between halftone voltages. Note that at least one liquid crystal domain may be formed in each pixel, but two or more liquid crystal domains may be formed depending on the size and shape of the pixel. For a typical rectangular pixel, It is preferable to form two or more liquid crystal domains.

  A liquid crystal display device according to an embodiment of the present invention includes a first substrate (for example, a TFT side glass substrate), a second substrate (for example, a color filter side glass substrate) provided to face the first substrate, and these substrates. A liquid crystal layer (for example, a vertical alignment type liquid crystal layer) provided between the first substrate, a first electrode (for example, a pixel electrode) formed on the first substrate, and a second electrode (for example, a counter electrode) formed on the second substrate. And an interlayer insulating film provided between the first electrode and the first substrate. The interlayer insulating film has at least one concave portion regularly arranged, and the concave portion formed on the surface on the liquid crystal layer side defines the direction in which the liquid crystal molecules are inclined by the electric field. Depending on the shape and arrangement of the recesses, a plurality of regions having different orientations in which liquid crystal molecules are inclined by an electric field can be formed in one pixel. Hereinafter, a configuration in which each liquid crystal domain forms an axially symmetric alignment domain including liquid crystal molecules inclined in different directions depending on an electric field is exemplified, but the present invention is not limited thereto. For example, the liquid crystal molecules in each liquid crystal domain are inclined. The recesses may be arranged so as to form a plurality of domains (preferably four domains that differ by 90 °) having the same direction and different directions.

  The present invention can realize a liquid crystal display device capable of displaying with a wide viewing angle and a high contrast ratio, particularly when a vertical alignment type liquid crystal layer is used and a plurality of axially symmetric alignment domains are formed in each pixel. Therefore, in the following, an embodiment of the present invention will be described taking a liquid crystal display device using a vertical alignment type liquid crystal layer (so-called VA mode liquid crystal display device) as an example. However, the present invention is not limited to this, and at least a predetermined voltage is described. Can be applied to a liquid crystal display device in which at least one liquid crystal domain including liquid crystal molecules aligned in different directions is formed in a pixel. From the viewpoint of viewing angle characteristics, the liquid crystal molecules preferably have liquid crystal domains having four or more alignment directions, and an axially symmetric alignment domain is exemplified below.

  In the following embodiments, transmissive and transflective liquid crystal display devices are exemplified, but the present invention can also be applied to reflective display devices.

  The configuration of the liquid crystal display device according to the embodiment of the present invention will be specifically described below with reference to the drawings.

(Transmission type liquid crystal display)
First, a configuration of a transmissive liquid crystal display device 100 as an example of an embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically showing the configuration of one pixel of the transmissive liquid crystal display device 100, (a) is a plan view, and (b) is 1B-1B ′ in FIG. 1 (a). It is sectional drawing along a line.

  Here, an example in which one pixel is divided into two (N = 2) is shown, but the number of divisions (= N) can be set to 3 or more according to the pixel pitch. Note that as the number of divisions (= N) increases, the effective aperture ratio tends to decrease. Therefore, when applied to a high-definition display panel, it is preferable to reduce the number of divisions (= N). Also, the present invention can be applied to a case where the pixel is not divided (may be expressed as N = 1). The divided area is sometimes referred to as “sub-pixel”. In a preferred embodiment of the present invention, one axisymmetric alignment domain is formed in the subpixel.

  The liquid crystal display device 100 includes a transparent substrate (for example, a glass substrate) 110a, a transparent substrate 110b provided to face the transparent substrate 110a, and a vertical alignment type liquid crystal layer provided between the transparent substrates 110a and 110b. 120. A vertical alignment film (not shown) is provided on the surfaces of the substrates 110a and 110b in contact with the liquid crystal layer 120. When no voltage is applied, the liquid crystal molecules of the liquid crystal layer 120 are substantially perpendicular to the surface of the vertical alignment film. Oriented. The liquid crystal layer 120 includes a nematic liquid crystal material having negative dielectric anisotropy, and further includes a chiral agent as necessary.

  The liquid crystal display device 100 includes a pixel electrode 111 formed on the transparent substrate 110a, an interlayer insulating film 115a provided between the transparent substrate 110a and the pixel electrode 111, and a counter electrode 131 formed on the transparent substrate 110b. The liquid crystal layer 120 provided between the pixel electrode 111 and the counter electrode 131 defines a pixel. Here, both the pixel electrode 111 and the counter electrode 131 are formed of a transparent conductive layer (for example, an ITO layer). Typically, on the liquid crystal layer 120 side of the transparent substrate 110b, a color filter 130 provided corresponding to the pixel (a plurality of color filters may be collectively referred to as the color filter layer 130), and A black matrix (light-shielding layer) 132 provided between adjacent color filters 130 is formed, and a counter electrode 131 is formed thereon. The color filter layer 130 is formed on the counter electrode 131 (the liquid crystal layer 120 side). Alternatively, the black matrix 132 may be formed.

  The interlayer insulating film 115a has a concave portion 117 provided at a predetermined position in the pixel. The concave portion 117 forms a concave portion on the surface on the liquid crystal layer side, and due to the shape effect thereof, the liquid crystal molecules have an axially symmetric orientation. It works to fix and stabilize the central axis. Here, the pixel electrode 111 has an opening 114 at a position corresponding to the recess 117, and the recess 117 is formed in the opening 114. The opening 114 of the pixel electrode 111 generates an oblique electric field around it when a voltage is applied, and acts to fix and stabilize the central axis of the axially symmetric orientation along with the shape effect by the recess 114, but the opening 114 is omitted. Even so, a recess corresponding to the recess 117 is formed on the surface of the pixel electrode 111 on the liquid crystal layer side (and the surface of the alignment film formed thereon).

  Furthermore, the liquid crystal display device 100 has a light shielding region around each pixel, and has a wall structure 115b on the transparent substrate 110a in the light shielding region. The wall structure 115b includes an interlayer insulating film 115a formed on the transparent substrate 110a so as to cover circuit elements (including not only active elements such as switching elements but also wires and electrodes: not shown here). It is integrally formed. For example, as will be described later, when an interlayer insulating film is provided in a transmissive liquid crystal display device having a TFT as a circuit element, the pixel electrode 111 can be partially overlapped with the gate signal wiring and / or the source signal wiring. Thus, the aperture ratio can be improved.

  Here, the light shielding region is shielded by, for example, a TFT, a gate signal wiring, a source signal wiring, or a black matrix formed on the transparent substrate 110b, which is formed in the peripheral region of the pixel electrode 111 on the transparent substrate 110a. This area does not contribute to display. Therefore, the wall structure 115b formed in the light shielding region does not adversely affect the display.

  The illustrated wall structure 115b is provided as a continuous wall so as to surround the pixel. However, the wall structure 115b is not limited thereto, and may be divided into a plurality of walls. Since the wall structure 115b acts to define a boundary formed in the vicinity of the extension of the pixels in the liquid crystal domain, it is preferable that the wall structure 115b has a certain length. For example, when the wall structure 115b is composed of a plurality of walls, the length of each wall is preferably longer than the length between adjacent walls.

  The pixel electrode 111 illustrated here has two openings 114 and four notches 113 formed at positions corresponding to the recesses 117. When a predetermined voltage is applied to the liquid crystal layer, two liquid crystal domains each having an axially symmetric alignment are formed, and the central axis of each of the liquid crystal domains is an indentation 117 formed in the interlayer insulating film 115a. It is formed in or in the vicinity thereof. As will be described in detail later, the recess 117 (and the opening 114 of the pixel electrode 111) acts to fix the position of the central axis of the axially symmetric orientation. The notch 113 is provided in the vicinity of the boundary of the axially symmetric alignment domain, and defines the direction in which the liquid crystal molecules are tilted by the electric field, and acts to form the axially symmetric alignment domain. An oblique electric field is formed around the notch 113 by the voltage applied between the pixel electrode 111 and the counter electrode 113, and the direction in which the liquid crystal molecules are inclined is defined by the oblique electric field. Acts as follows. Further, here, the notch 113 is point-symmetric about a recess (here, the recess on the right side in FIG. 1) 117 corresponding to the central axis of the liquid crystal domain formed in the pixel (here, the entire transmission region). The four notches 113 are arranged in the.

  By providing such a notch 113, the direction in which the liquid crystal molecules fall when a voltage is applied is defined, and two liquid crystal domains are formed. In FIG. 1, the reason why the notch is not provided on the left side of the pixel electrode 111 is that the notch provided at the right end of the pixel electrode (not shown) located on the left side of the illustrated pixel electrode 111 has the same effect. Therefore, a notch that reduces the effective aperture ratio of the pixel is omitted at the left end of the pixel electrode 111. Here, since the alignment regulating force by the wall structure 115b described above can also be obtained, a stable liquid crystal domain can be formed as in the case where the notch portion is provided without providing the notch portion on the left end of the pixel electrode 111. In addition, the effect of improving the effective aperture ratio can be obtained. Here, four cutout portions 113 are formed, but at least one cutout portion may be provided between adjacent liquid crystal domains. For example, here, a long and thin cutout portion is provided at the center of the pixel. Others may be omitted.

  The shape of the concave portion 117 provided in the approximate center of the sub-pixel (liquid crystal domain) in order to fix the central axis of the axially symmetric alignment domain is preferably circular as illustrated, but is not limited thereto. However, in order to exert substantially the same orientation regulating force in all directions, the polygon is preferably a quadrilateral or more, and is preferably a regular polygon. When the opening 114 corresponding to the recess 117 is provided in the pixel electrode 111, the shape of the opening 114 is preferably designed in the same manner as the recess 117, and preferably the same shape. Here, the shapes of the opening 114 and the recess 117 are both circular.

  Since the wall structure 115b is formed integrally with the interlayer insulating film 115a having the recess 117, for example, the wall structure 115b can be manufactured by a series of steps of forming, exposing, and developing the photosensitive resin film 115. For example, a photosensitive resin film (preferably a positive photosensitive resin) is provided so as to cover circuit elements such as switching elements (for example, TFTs), and contact holes (pixel electrodes and circuit elements (for example, TFTs) are provided in the photosensitive resin film. In an exposure / development process for forming a contact hole for connecting an electrode connected to the drain electrode (sometimes referred to as a connection electrode)), the exposure amount is changed for each predetermined region (when not selectively exposed) Can be formed. For example, when a positive photosensitive resin film is used, a non-exposed region can be the wall structure 115b, a contact hole can be formed in the completely exposed region, and a recess 117 can be formed in the intermediate exposure amount region. . Here, the pixel electrode 111 is formed on a region where the exposure amount is smaller than the region to be the concave portion 117, and the concave portion 117 is exposed in the opening 114 of the pixel electrode 111.

  In addition, the shape of the notch 113 that acts so as to define the direction in which the liquid crystal molecules in the axially symmetric alignment domain are tilted by the electric field is set so as to exhibit substantially the same alignment regulating force with respect to the adjacent axially symmetric alignment. For example, a quadrangle is preferable. The notch 113 is formed simultaneously with the opening 114 in the process of patterning the pixel electrode 111.

  If the support 133 for defining the thickness (also referred to as a cell gap) of the liquid crystal layer 120 is formed in the light shielding region (here, the region defined by the black matrix 132), the display quality is not deteriorated. preferable. The support 133 may be formed on either of the transparent substrates 110a and 110b, and is not limited to being provided on the wall structure 115b provided in the light shielding region as illustrated. When the support 133 is formed on the wall structure 115b, the sum of the height of the wall structure 115b and the height of the support 133 is set to be the thickness of the liquid crystal layer 120. When the support body 133 is provided in a region where the wall structure 115 b is not formed, the height of the support body 133 is set to be the thickness of the liquid crystal layer 120. The support 133 can be formed by a photolithography process using a photosensitive resin, for example.

  In this liquid crystal display device 100, when a predetermined voltage (a voltage equal to or higher than the threshold voltage) is applied to the pixel electrode 111 and the counter electrode 131, the concave portion 117 (and the opening formed in the approximate center of the sub-pixel (axisymmetric alignment domain)). Two axially symmetric alignment domains each having a stabilized central axis are formed in or near the portion 114), and two adjacent notch portions 113 provided at the center in the longitudinal direction of the pixel electrode 111 are adjacent to each other. The direction in which the liquid crystal molecules in the liquid crystal domain are tilted by the electric field is defined, and the notch 113 provided in the corner portion of the wall structure 115b and the pixel electrode 111 is the direction in which the liquid crystal molecules in the vicinity of the extension of the pixels in the liquid crystal domain are tilted by the electric field. Is specified. It is considered that the alignment regulating force by the wall structure 115b, the recess 117 (and the opening 114), and the notch 113 acts cooperatively to stabilize the alignment of the liquid crystal domain.

  Note that, on the liquid crystal layer 120 side of the transparent substrate 110a, for example, an active element such as a TFT and circuit elements (not shown) such as a gate signal wiring and a source signal wiring connected to the TFT are provided. Further, the transparent substrate 110a, the circuit elements formed on the transparent substrate 110a, and the pixel electrode 111, the wall structure 115b, the support 133, the alignment film, and the like described above may be collectively referred to as an active matrix substrate. On the other hand, the transparent substrate 110b and the color filter layer 130, the black matrix 132, the counter electrode 131, the alignment film, and the like formed on the transparent substrate 110b may be collectively referred to as a counter substrate or a color filter substrate.

  Further, although omitted in the above description, the liquid crystal display device 100 further includes a pair of polarizing plates arranged so as to face each other through the transparent substrates 110a and 110b. The pair of polarizing plates are typically arranged so that the transmission axes are orthogonal to each other. Furthermore, as described later, a biaxial optically anisotropic medium layer and / or a uniaxial optically anisotropic medium layer may be provided.

  Next, an example of the structure of an active matrix substrate that is preferably used in the transmissive liquid crystal display device 100 will be described with reference to FIGS. 2A and 2B. 2A is a partially enlarged view of the active matrix substrate, and FIG. 2B is a cross-sectional view taken along line X-X ′ in FIG. 2A. The active matrix substrate shown in FIGS. 2A and 2B is different from the active matrix substrate shown in FIG. 1 in that the number of notches 113 is small, but other configurations may be the same.

  The active matrix substrate shown in FIGS. 2A and 2B has a transparent substrate 110a made of, for example, a glass substrate, and the gate signal lines 2 and the source signal lines 3 are provided on the transparent substrate 110a so as to be orthogonal to each other. . A TFT 4 is provided in the vicinity of the intersection of these signal wires 2 and 3, and the drain electrode 5 of the TFT 4 is connected to the pixel electrode 111.

  The active matrix substrate has an interlayer insulating film 115a that covers the gate signal line 2, the source signal line 3, and the TFT 4, and a recess 117 is formed in the interlayer insulating film 115a. The concave portion 117 is formed so as to be positioned substantially at the center of the axially symmetric alignment domain formed in the pixel. The wall structure 115b provided in the periphery of the pixel is formed integrally with the interlayer insulating film 115a. As described above, the wall structure 115b can be formed from the single photosensitive resin film 115 through a series of processes. It is possible and can be manufactured by a simple process.

  The pixel electrode 111 is a transparent electrode formed of a transparent conductive layer such as ITO, and is formed on the interlayer insulating film 115a. The drain electrode 5 is connected to a contact portion 111a formed in the contact hole of the interlayer insulating film 115a. In the predetermined region of the pixel electrode 111, as described above, the notch 113 and the opening 114 are provided in order to control the orientation of the axially symmetric orientation domain. The opening 114 is formed so that the recess 117 is exposed inside.

The pixel electrode 111 is superimposed on the gate signal line of the next stage through the gate insulating film 9. The TFT 4 has a structure in which a gate insulating film 9, a semiconductor layer 12, a channel protective layer 13, and an n ⁺ -Si layer 11 (source / drain electrodes) are stacked on the gate electrode 10 branched from the gate signal line 2. doing.

  Note that although a configuration example of a bottom-gate TFT is shown here, the present invention is not limited to this, and a top-gate TFT can also be used. In addition, a switching element (for example, MIM) other than the TFT can be used.

  In the liquid crystal display device 100, the recess 117 is formed in the interlayer insulating film 115a on the transparent substrate 110a, and the wall structure 115a is provided integrally with the interlayer insulating film 115a. Further, an opening 114a and a notch 113 are formed in the pixel electrode 111 formed on the interlayer insulating film 115a. That is, all of the alignment control structures for forming the axially symmetric alignment domains are formed on the transparent substrate 110a side, and no alignment regulating structure is provided on the counter substrate 110b side. According to the present embodiment, there is an advantage that a stable axially symmetric alignment domain can be formed with such a simple configuration. However, the present invention is not limited to this. For example, an alignment regulating structure may be provided on the counter substrate 110b side as in the liquid crystal display device 100 'shown in FIG. By adopting such a configuration, the alignment of liquid crystal molecules can be further stabilized.

  The liquid crystal display device 100 ′ has substantially the same configuration as the liquid crystal display device 100 except that the counter electrode 131 has an opening 114 ′. Common reference numerals are used and description thereof is omitted here.

  The opening 114 ′ formed in the counter substrate 131 of the liquid crystal display device 100 ′ is provided at a position that substantially overlaps the recess 117 and the opening 114 formed in the pixel electrode 111 when viewed from the normal direction of the substrate. The plan view of the liquid crystal display device 100 ′ is substantially the same as FIG. The opening 114 ′ arranged in this way acts to fix and stabilize the central axis of the axially symmetric orientation together with the recess 117 and the opening 114 formed in the pixel electrode 111. As a result, the orientation of the axially symmetric orientation domain is further stabilized.

  Note that it is preferable not to provide a structural orientation regulating structure such as a wall structure on the counter substrate 110b side. In order to form a wall structure or the like, unlike the openings and notches formed in the electrodes, the number of manufacturing steps increases, which is a factor in increasing costs, which is not preferable. In addition, unlike the recess having the function of fixing the central axis, the notch 113 is provided so as to define the direction in which the liquid crystal molecules are tilted by the electric field in cooperation with the anchoring action of the side surface of the wall structure 115. It is preferably provided only on the same substrate 110 a as the wall structure 115.

(Transflective liquid crystal display device)
Next, the configuration of the transflective liquid crystal display device 200 according to the embodiment of the present invention will be described with reference to FIG.

  FIG. 4 is a diagram schematically showing a configuration of one pixel of the transflective liquid crystal display device 200 according to the embodiment of the present invention, FIG. 4A is a plan view, and FIG. 4B is a diagram. It is sectional drawing which followed the 2B-2B 'line in 4 (a).

  The liquid crystal display device 200 includes a transparent substrate (for example, a glass substrate) 210a, a transparent substrate 210b provided to face the transparent substrate 210a, and a vertical alignment type liquid crystal layer provided between the transparent substrates 210a and 210b. 220. A vertical alignment film (not shown) is provided on the surfaces of both the substrates 210a and 210b in contact with the liquid crystal layer 220. When no voltage is applied, the liquid crystal molecules of the liquid crystal layer 220 are in contact with the surface of the vertical alignment film. Oriented substantially vertically. The liquid crystal layer 220 includes a nematic liquid crystal material having a negative dielectric anisotropy, and further includes a chiral agent as necessary.

  The liquid crystal display device 200 includes a pixel electrode 211 formed on the transparent substrate 210a and a counter electrode 231 formed on the transparent substrate 210b, and a liquid crystal provided between the pixel electrode 211 and the counter electrode 231. Layer 220 defines the pixel. Circuit elements such as TFTs are formed on the transparent substrate 210a as will be described later. The transparent substrate 210a and the components formed thereon may be collectively referred to as an active matrix substrate 210a.

  Further, typically, a color filter 230 (corresponding to a plurality of color filters may be collectively referred to as the color filter layer 230) provided corresponding to the pixel on the liquid crystal layer 220 side of the transparent substrate 210b. A black matrix (light shielding layer) 232 provided between adjacent color filters 230 is formed, and a counter electrode 231 is formed thereon, and the color filter layer 230 is formed on the counter electrode 131 (the liquid crystal layer 120 side). Alternatively, a black matrix 232 may be formed. The transparent substrate 210b and the components formed thereon may be collectively referred to as a counter substrate (color filter substrate) substrate 210b.

  The pixel electrode 211 is formed of a transparent electrode 211a formed from a transparent conductive layer (for example, an ITO layer) and a metal layer (for example, an Al layer, an alloy layer including Al, and a laminated film including any of these). A reflective electrode 211b. As a result, the pixel includes a transparent area A defined by the transparent electrode 211a and a reflective area B defined by the reflective electrode 211b. The transparent area A displays in the transmissive mode, and the reflective area B displays in the reflective mode.

  The liquid crystal display device 200 has a light shielding region around each pixel, and has a wall structure 215b on the transparent substrate 210a in the light shielding region. In addition, the active matrix substrate 210a has a recess 117 at the approximate center of the sub-pixel (liquid crystal domain) of the interlayer insulating film 215a. Furthermore, it has a wall structure 115b regularly arranged around the pixel, and this wall structure 215b is not only a circuit element (an active element such as a switching element) formed on the transparent substrate 210a but also a wiring or It is formed integrally with an interlayer insulating film 215a formed so as to cover an electrode (not shown here). For example, when an interlayer insulating film is provided in a transmissive liquid crystal display device having a TFT as a circuit element, a pixel electrode can be partially overlapped with a gate signal wiring and / or a source signal wiring, thereby improving an aperture ratio. There is an advantage that you can.

  Further, since the light shielding area does not contribute to the display, the wall structure 215b formed in the light shielding area does not adversely affect the display. The wall structure 215b illustrated here is provided as a continuous wall so as to surround the pixel, but is not limited thereto, and may be divided into a plurality of walls. Since the wall structure 215b acts so as to define the boundary formed in the vicinity of the outer extension of the pixels in the liquid crystal domain, it preferably has a certain length. For example, when the wall structure 215b is composed of a plurality of walls, the length of each wall is preferably longer than the length between adjacent walls.

  The pixel electrode 211 illustrated here has an opening 214 provided in the transmissive electrode 211 a so as to correspond to the recess 217, and four notches 213. In addition, the reflective electrode 211 b has one opening 214. When a predetermined voltage is applied to the liquid crystal layer, three liquid crystal domains each having an axially symmetric alignment are formed, and the central axes of the respective liquid crystal domains are in or near the recess 217 and the opening 214. Formed. As will be described later, a concave portion 217 provided substantially at the center of the sub-pixel acts to fix the position of the central axis of the axially symmetric alignment, and the notch 213 causes the liquid crystal molecules in the axially symmetric alignment domain to fall by an electric field. Acts to define the direction. An oblique electric field is formed around the opening 214 and the notch 213 by a voltage applied between the pixel electrode 211 and the counter electrode 213, and a direction in which liquid crystal molecules are inclined is defined by the oblique electric field. As a result, it operates as described above. The recess 217 defines the direction in which the liquid crystal molecules are tilted due to the shape effect.

  Here, the notch 213 is arranged in a point-symmetric manner with respect to a recess 217 (here, the recess on the right side in FIG. 1) corresponding to the central axis of the liquid crystal domain formed in the transmission region A of the pixel. Two notches 213 are included. By providing such a notch 213, the direction in which the liquid crystal molecules fall when a voltage is applied is defined, and three liquid crystal domains are formed. The arrangement of the recesses 217, the openings 214 and the notches 213, and preferred shapes thereof are the same as those of the transmissive liquid crystal display device 100 described above. Although FIG. 4 shows an example in which two liquid crystal domains are formed in the transmissive region A and one liquid crystal domain is formed in the reflective region B, the present invention is not limited to this. In addition, it is preferable that each liquid crystal domain has a substantially square shape from the viewpoint of viewing angle characteristics and alignment stability.

  If the support 233 for defining the thickness (also referred to as a cell gap) of the liquid crystal layer 220 is formed in the light-shielding region (here, the region defined by the black matrix 232), the display quality is not deteriorated. preferable. The support 233 may be formed on either of the transparent substrates 210a and 210b, and is not limited to the case where the support 233 is provided on the wall structure 215b provided in the light shielding region as illustrated. When the support 233 is formed on the wall structure 215 b, the sum of the height of the wall structure 215 b and the height of the support 233 is set to be the thickness of the liquid crystal layer 220. In the case where the support 233 is provided in the region where the wall structure 215 b is not formed, the height of the support 233 is set to be the thickness of the liquid crystal layer 220.

  In this liquid crystal display device 200, when a predetermined voltage (a voltage equal to or higher than the threshold voltage) is applied to the pixel electrode 211 and the counter electrode 231, the respective central axes are stabilized in or near the three openings 214 and the recess 217. Three axially symmetric orientations are formed, and the four notches 213 provided in the pixel electrode 211 define the direction in which the liquid crystal molecules in the three adjacent liquid crystal domains are tilted by an electric field, and the wall structure 215b is the liquid crystal domain The boundary formed in the vicinity of the outer extension of the pixel is stabilized.

  Next, a preferable configuration unique to the transflective liquid crystal display device 200 capable of performing both transmission mode display and reflection mode display will be described.

  In the transmission mode display, the light used for display passes through the liquid crystal layer 220 only once, whereas in the reflection mode display, the light used for display passes through the liquid crystal layer 220 twice. Therefore, as schematically shown in FIG. 4B, it is preferable to set the thickness dt of the liquid crystal layer 220 in the transmissive region A to about twice the thickness dr of the liquid crystal layer 220 in the reflective region B. By setting in this way, the retardation that the liquid crystal layer 220 gives to the light in both display modes can be made substantially equal. Although dt = 0.5dr is most preferable, good display can be realized in both display modes as long as it is within the range of 0.3dt <dr <0.7dt. Of course, dt = dr may be used depending on the application.

  In the liquid crystal display device 200, in order to make the thickness of the liquid crystal layer 220 in the reflective region B smaller than the thickness of the liquid crystal layer in the transmissive region A, the transparent dielectric layer 234 is provided only in the reflective region B of the glass substrate 210b. Yes. By adopting such a configuration, there is no need to provide a step using an insulating film or the like under the reflective electrode 211b, so that there is an advantage that the manufacturing of the active matrix substrate 210a can be simplified. Further, when the reflective electrode 211b is provided over the insulating film for providing a step for adjusting the thickness of the liquid crystal layer 220, light used for transmissive display is blocked by the reflective electrode that covers the inclined surface (tapered portion) of the insulating film. However, since the light reflected by the reflective electrode formed on the slope of the insulating film repeats internal reflection, there is a problem that it is not effectively used for reflective display. Is suppressed, and the light utilization efficiency can be improved.

  Furthermore, if the transparent dielectric layer 234 having a function of scattering light (diffuse reflection function) is used, a good white display close to paper white can be realized without providing the reflection electrode 211b with a diffuse reflection function. it can. Even if the transparent dielectric layer 234 is not provided with a light scattering ability, a white display close to paper white can be realized by providing an uneven shape on the surface of the reflective electrode 211b. The position of the central axis of the symmetric orientation may not be stable. On the other hand, if the transparent dielectric layer 234 having light scattering ability and the reflective electrode 211b having a flat surface are used, the position of the central axis can be more reliably stabilized by the opening 214 formed in the reflective electrode 211b. Benefits are gained. In addition, in order to provide a diffuse reflection function to the reflective electrode 211b, when forming unevenness on the surface, the uneven shape is preferably a continuous wave shape so that no interference color is generated, and the central axis of the axially symmetric orientation is It is preferable to set so that it can be stabilized.

  In the transmissive mode, light used for display passes through the color filter layer 230 only once, whereas in reflective mode display, light used for display passes through the color filter layer 230 twice. Therefore, when a color filter layer having the same optical density is used for the transmission region A and the reflection region B as the color filter layer 230, color purity and / or luminance in the reflection mode may be lowered. In order to suppress the occurrence of this problem, it is preferable to make the optical density of the color filter layer in the reflective region smaller than that in the transmissive region. The optical density here is a characteristic value characterizing the color filter layer, and the optical density can be reduced by reducing the thickness of the color filter layer. Alternatively, the optical density can be reduced by reducing the concentration of the added dye, for example, while maintaining the thickness of the color filter layer.

  Next, an example of the structure of an active matrix substrate that is preferably used in a transflective liquid crystal display device will be described with reference to FIGS. FIG. 5 is a partially enlarged view of the active matrix substrate, and FIG. 6 is a cross-sectional view of the liquid crystal display device, which corresponds to a cross-sectional view along the line X-X ′ in FIG. 5. The active matrix substrate shown in FIGS. 5 and 6 has a configuration in which one liquid crystal domain is formed in the transmissive region A (that is, the opening 214, the recess 217 (only the transmissive region), and the notch 213. 4 is different from the active matrix substrate shown in FIG. 4 in that the other components may be the same, and common components are denoted by common reference numerals.

  The active matrix substrate shown in FIGS. 5 and 6 includes a transparent substrate 210a made of, for example, a glass substrate, and the gate signal lines 2 and the source signal lines 3 are provided on the transparent substrate 210a so as to be orthogonal to each other. . A TFT 4 is provided in the vicinity of the intersection of these signal lines 2 and 3, and the drain electrode 5 of the TFT 4 is connected to the pixel electrode 211.

  The pixel electrode 211 includes a transparent electrode 211a formed from a transparent conductive layer such as ITO, and a reflective electrode 211b formed from Al or the like. The transparent electrode 211a defines the transmission region A, and the reflective electrode 211b reflects. Region B is defined. Note that a transparent conductive layer may be formed over the reflective electrode 211b as necessary.

  The pixel electrode 211 is formed on the interlayer insulating film 215a, and the pixel electrode 211 (transparent electrode 211a) is connected to the drain electrode 5 at a contact portion 211a formed in the contact hole of the interlayer insulating film 215a. The connection electrode 25 is connected. The reflective electrode 211b is connected to the transparent electrode 211a.

  The pixel electrode 211 may extend to the slope of the wall structure 215b formed integrally with the interlayer insulating film 215a. By adopting such a configuration, it is possible to obtain an effect that the direction in which the liquid crystal molecules of the liquid crystal layer are inclined when a voltage is applied can be efficiently regulated. The pixel electrode 211 has an opening 214 for fixing and stabilizing the central axis of the axially symmetric orientation and a notch 213 for controlling the orientation of the axially symmetric orientation domain in a predetermined region. The connection electrode 25 forms an auxiliary capacitance with an auxiliary capacitance wiring (auxiliary capacitance electrode) provided so as to face each other with the gate insulating film 9 interposed therebetween. For example, the auxiliary capacitance line is provided in parallel with the gate signal line 2 below the reflective electrode 211b. For example, the auxiliary capacitor wiring is supplied with the same signal (common signal) as that of the counter electrode provided on the color filter side substrate.

  The reflective electrode 211b of the transflective liquid crystal display device of this embodiment has an uneven surface, and has excellent diffuse reflection characteristics. The uneven shape on the surface of the reflective electrode 211 b reflects the uneven shape formed on the surface of the interlayer insulating film 215.

  The interlayer insulating film 215a has a concave portion 217 regularly arranged at substantially the center of the sub-pixel (liquid crystal domain), and is formed integrally with the wall structure 215b. Further, the interlayer insulating film 215a includes a region having a substantially flat surface (sometimes referred to as a “first region”) and a region having an uneven surface (sometimes referred to as a “second region”). doing. A transparent electrode 211a is formed on the first region having a flat surface, and a reflective electrode 211b is formed on the second region having irregularities.

  The interlayer insulating film 215a that is formed integrally with the on-wall structure 215b, has the recess 217, and includes a region 215c having an uneven shape on the surface is formed from a single photosensitive resin film, as will be described later. Therefore, it can be manufactured by a simpler process than before.

The pixel electrode 211 is superimposed on the gate signal line 2 in the next stage via the gate insulating film 9. The TFT 4 has a structure in which a gate insulating film 9, a semiconductor layer 12, a channel protective layer 13, and an n ⁺ -Si layer 11 (source / drain electrodes) are stacked on the gate electrode 10 branched from the gate signal line 2. doing.

  Note that although a configuration example of a bottom-gate TFT is shown here, the present invention is not limited to this, and a top-gate TFT can also be used. In addition, a switching element (for example, MIM) other than the TFT can be used.

  As described above, the liquid crystal display device 200 having the configuration shown in FIG. 4 is similar to the liquid crystal display device 100 in that the alignment regulation structure (the concave portion 217 formed in the interlayer insulating film and the recess 217 formed on the interlayer insulating film) is formed only on one substrate. With a relatively simple configuration in which the wall structure 215b and the notch 213 and the opening 214) formed in the pixel electrode 211 are provided, the liquid crystal alignment can be sufficiently stabilized. Note that, in the transflective liquid crystal display device 200 as in the transmissive liquid crystal display device 100 ′ illustrated in FIG. 3, the alignment can be further stabilized by providing the alignment regulating structure on the counter substrate side. However, for the reasons described above, it is preferable that the orientation regulating structure provided on the counter substrate is only an opening for fixing the central axis of the axially symmetric orientation.

  Furthermore, the liquid crystal display device 200 can improve the brightness and color purity of display in the transmissive mode and the reflective mode by configuring the transparent attractant layer 234 and / or the color filter layer 230 as described above.

  Next, a method for forming the interlayer insulating layer 215a having the recess 217 and the wall structure 215b will be described in detail with reference to FIGS. 7 (a) to (f). 6 and 7, the transparent substrate 210a and circuit elements such as TFTs and signal wirings formed thereon are collectively referred to as “circuit board 210A”.

  First, as shown in FIG. 7A, a circuit board 210A on which predetermined circuit elements such as TFTs are formed is prepared, and a positive photosensitive resin film (for example, Tokyo Ohka Co., Ltd.) is provided so as to cover the circuit elements. Manufactured, OFPR-800) 215. The thickness of the photosensitive resin film 215 is 4.5 μm, for example.

  Next, as shown in FIG. 7B, the photosensitive resin film 215 is exposed. At this time, predetermined regions having different exposure amounts are formed. That is, a region that becomes the wall structure 215b (a region shielded by the source signal wiring, the gate signal wiring, and the like) and a region that forms unevenness on the surface (a region where the reflective electrode is formed) are hardly exposed (exposure amount is almost equal). Zero) and other areas are exposed by a predetermined amount (intermediate exposure without complete exposure).

Specifically, a light shielding part 52a is provided at a position corresponding to the convex part (the convex part of the concave / convex surface) formed in the reflective region and the wall structure, and the other is provided through a photomask 52 which is a light transmitting part 52b. Then, the photosensitive resin film 215 is exposed. The shape of the light-shielding part 52a corresponding to the convex part formed in the reflection region is, for example, a circular shape or a polygonal shape, and is randomly arranged with a predetermined center interval (5 to 30 μm) and a predetermined density. The arrangement of the convex portions may be random as long as the interference color is suppressed. As the light source, for example, an ultrahigh pressure mercury lamp (for example, illuminance of i-line: 20 to 50 mW) is used, and exposure is performed uniformly (irradiation time: 1 to 4 seconds). For example, the exposure amount is preferably about ²⁰ to 100 mJ / cm ² .

Next, as shown in FIG. 7C, the light-transmitting portion 62b corresponding to the contact hole portion and the light-transmitting portion 62c for providing the concave portion 217 at a predetermined position in the pixel are provided, and the other is the light-shielding portion 62a. The photomask 62 is used for uniform exposure (irradiation time: 10 to 15 seconds). The amount of exposure is preferably about 200 to 500 mJ / cm ² , for example. The region where the contact hole and the recess are formed is in the other region in the previous exposure process.

  At this time, in particular, the irradiation length of the light transmitting portion 62c that forms the concave portion is set to be smaller than the irradiation diameter of the light transmitting portion 62b of the normal contact hole portion (for example, less than or equal to ½ of the mask diameter of the contact hole portion). (Design), even in the one-step contact hole formation exposure process, the interlayer insulating film does not penetrate to the lower connection electrode, and the predetermined depth of the recess can be satisfied. It is preferable that the thickness Id of the interlayer insulating film and the depth h of the recess satisfy the relationship of h <0.8 · Id. This will be described later.

  However, the present invention is not limited to this, and a separate exposure process is provided before the contact hole forming process, and the exposure process is continuously performed by adding the exposure process for forming the recesses, thereby forming a multi-stage shape of the interlayer insulating film. It is also possible to do.

  Next, as shown in FIG. 7D, for example, development processing is performed under predetermined conditions using a TMAH (tetramethylammonium hydroxide) developer. For example, the resin film in the high-exposure region is completely removed (contact hole 229 is formed), and about 90% of the resin film in the unexposed region is left (wall structure and protrusions are formed), and low About 40% of the resin film in the exposed region remains (recesses 217 are formed).

  Further, as shown in FIG. 7E, drying and baking are performed as necessary. Firing is performed at 200 ° C., for example. By performing the baking, a smooth uneven shape 215c is obtained due to a thermal sag phenomenon or the like of the resin in the reflective region 215c 'formed with a plurality of fine protrusions. By making the surface of the reflective electrode 211b smooth and uneven, it is possible to obtain good diffuse reflection characteristics in which the generation of interference colors is suppressed.

  In this way, by performing a continuous batch exposure process on the photosensitive resin film 215 and then performing a subsequent development process, the region 215c formed in the wall structure 215b and having a fine uneven shape and the inside of the pixel are formed. Thus, an interlayer insulating film 215a having a recess 217 and a contact hole 229 regularly arranged in the approximate center of the liquid crystal domain is obtained.

  In the above exposure process, the method of forming regions with different exposure amounts by adjusting the irradiation time for each region using a photomask having a light transmitting portion and a light shielding portion has been described. An interlayer insulating film having a surface whose shape continuously changes can also be formed by performing exposure using a grayscale mask having a changing shading pattern.

  Further, in the exposure process, an exposure step in a separate process is performed before the exposure process for forming the contact hole by using a photomask in a separate process in which only the region and the concave portion in which the wall structure is formed is independently used as the light shielding portion. Can also be performed continuously.

  Next, as shown in FIG. 7F, the pixel electrode 211 is formed on the interlayer insulating film 215a and the wall structure 215b obtained through the above-described steps. For example, the transparent electrode 211a is obtained by depositing and patterning a transparent conductive film (for example, an ITO film) to a predetermined film thickness (for example, 100 nm) by a sputtering method. The reflective electrode 211b is formed by depositing a reflective electrode film (for example, an Al thin film) to a predetermined thickness (for example, 180 nm) by sputtering and patterning. When forming the respective electrodes 211a and 211b, the opening 214 and the notch 213 are formed.

  According to the present embodiment, the wall structure 215b and the fine uneven shape of the reflective electrode portion are formed in the same layer as the interlayer insulating film 215a having the recess 217 in the pixel, and the pixel electrode is formed thereon. . The pixel electrode 211 can be arranged also on the inclined side surface of the wall structure 215b, particularly on the pixel side. By extending the pixel electrode 211 on the inclined side surface of the wall structure 215b, the electric field (electric lines of force) around the side surface of the wall structure 215b is distorted, so that it is combined with the structural orientation regulating force by the wall structure 215b. Thus, the effect of efficiently regulating the tilt direction of the liquid crystal molecules is brought about.

  In addition, you may form a transparent electrode film on the reflective electrode 211b as needed. By forming a transparent conductive film over the reflective electrode 211b, it is possible to reduce a difference in potential difference (electrode potential difference) between the reflective region and the transmissive region. The material of the transparent electrode film formed on the reflective electrode 211b is preferably the same material as the transparent electrode 211a.

  As described above, according to the manufacturing method of the present embodiment, by simply performing a photolithography process on a single photosensitive resin film, it can be applied to irregularities for expressing diffuse reflection characteristics and pixels as an alignment control structure. It is possible to form the concave portions arranged regularly and the wall structure arranged outside the pixels, and cost can be reduced effectively.

  Hereinafter, after forming a vertical alignment film on a counter substrate (CF substrate) facing the active matrix substrate obtained as described above under a predetermined condition, these are bonded to each other through a seal resin, and the gap is formed in the gap. By enclosing a liquid crystal material having a negative dielectric anisotropy, the liquid crystal display device of this embodiment can be obtained. Since these steps are performed by a known method, description thereof is omitted.

  Although an example of a method of manufacturing a transflective liquid crystal display device has been described here, a wall structure that is a liquid crystal domain alignment regulating structure, a concave portion and a contact hole disposed in the center of the liquid crystal domain when forming an interlayer insulating film The technology for manufacturing a batch process in a continuous process can of course be applied to a transmissive liquid crystal display device and a reflective liquid crystal display device, and it is a simpler process than before, reducing costs and shortening the tact time during production. There are effects such as.

  Next, in the embodiment of the present invention, a preferable configuration of the concave portion regularly arranged at the approximate center of the liquid crystal domain in the pixel will be described with reference to FIGS.

As schematically shown in FIG. 8, the relationship between the shorter pitch P _S (μm) of pixels arranged in a matrix and the maximum inner diameter width D _C (μm) of the recesses is D _C <0.35 · P _S It is preferable to satisfy this relationship. The maximum inner diameter width D _C, if the recess is circular in diameter, in the case of other shapes is defined as the length of the longest straight line that can be written on the inside of the recess.

Here, FIG. 9 is a graph showing the relationship between the maximum internal diameter width D _C and the effective numerical aperture of the recess. The effective aperture ratio tends to decrease monotonously by providing the concave portion. However, when the aperture ratio decreases within 10%, the optical design of the liquid crystal layer is optimized to reduce the luminance decrease as a liquid crystal display device. Therefore, the lower limit value of the set aperture ratio when the concave portion is provided is set to 90%. In order to satisfy this condition, it can be seen from FIG. 9 that the maximum inner diameter width D _C (μm) of the recess must satisfy the relationship of D _C <0.35 · P _S. That is, for example, in the case of a pixel having a short side pitch of 50 μm, the maximum inner diameter of the recess is preferably 17 μm or less. More preferably, it is 10 μm or less (D _C ≦ 0.2 _{P S} ). When the specified value of the maximum inner diameter width is exceeded, the effective aperture ratio is reduced by more than 10%, the panel brightness is significantly lowered, and the display quality is deteriorated.

  Furthermore, the relationship between the depth h (μm) of the recess and the thickness Id (μm) of the interlayer insulating film satisfies the relationship of h <0.8 · Id, as will be described later with an experimental example. It is preferable. When the depth of the recess is increased and becomes larger than this specified value, the tendency of the liquid crystal molecules to be inclined and aligned along the step surface in the liquid crystal domain increases and has birefringence. Since the light leakage becomes remarkable, the contrast ratio is lowered. Further, when the depth h of the concave portion is increased, the liquid crystal layer thickness is locally increased, so that the writing characteristic (charging characteristic) to the liquid crystal layer is changed, which causes the display characteristic to vary. A more preferable recess depth h is in the range of h <0.6Id.

  Next, with reference to FIGS. 10A and 10B, preferred shapes of the wall structure 215b and the interlayer insulating film 215a will be described in more detail. 10A and 10B are cross-sectional views taken along the line 10A-10A 'in FIG. 4, and FIG. 10B is an enlarged view of a portion surrounded by a broken line in FIG. 10A. .

  According to the embodiment of the present invention, as described above, the interlayer insulating film 215a as the upper layer of the switching element, the recess 217, and the wall structure 215b are integrally formed through a batch exposure process. Therefore, as schematically shown in FIGS. 10A and 10B, the cross-sectional shape of the wall structure 215b and the interlayer insulating film 215a in the plane perpendicular to the first substrate 210a is the center of the axially symmetric alignment of the liquid crystal domain. The region where the shaft is formed can be a continuous shape with the bottom 215B. Here, since the pixel electrode 211a has the concave portion 217 for fixing and stabilizing the position of the central axis of the axially symmetric alignment domain, the bottom portion 215B of the cross-sectional shape of the interlayer insulating film 215a is at a position corresponding to the concave portion 217. Is formed.

  As described above, when the inclined side surface 215S of the wall structure 215b and the upper surface of the interlayer insulating film 215a have a continuous mortar shape, the pixel electrode 211 and the vertical alignment film formed on the mortar-shaped surface allow the axially symmetric alignment. The domain orientation can be further stabilized. As a result, it is possible to obtain the effect of improving the response characteristics in the halftone, the effect of reducing the rough feeling of the display in the halftone, and the effect of recovering in a short time even if the alignment disorder occurs when the liquid crystal panel is pressed. it can. Note that the effect of stabilizing the alignment by forming a mortar shape is obtained because the surfaces of the pixel electrode and the vertical alignment film are formed in a mortar shape. That is, the pixel electrode having a mortar-shaped surface generates an electric field inclined about the bottom of the mortar with respect to the liquid crystal layer, and the vertical alignment film having the mortar-shaped surface allows liquid crystal molecules to center on the bottom of the mortar. Demonstrate the ability to regulate orientation so that it tilts. As described above, since the alignment regulating force due to the mortar-like shape is additionally obtained, the axially symmetric alignment domain is further stabilized. This effect can be expected to be effectively exhibited by arranging the concave portions regularly at substantially the center of the liquid crystal domain in the pixel, and the stabilization of the axially symmetric orientation and the center axis fixing work more effectively. The mortar shape can be controlled by, for example, patterning the photosensitive resin film that forms the interlayer insulating film 215a, the recess 217, and the wall structure 215b, and then adjusting the temperature and time of the heat treatment step. it can.

  As schematically shown in FIG. 10B, the inclination angle α of the side surface 215S of the wall structure 215b with respect to the surface of the substrate 210a is preferably 45 ° or less, and preferably 25 ° or less. .

  The vertical alignment film (not shown) formed on the side surface 215S of the wall structure 215b has a regulating force so that the liquid crystal molecules are aligned perpendicular to the surface thereof, so that the liquid crystal molecules on the side surface 215 are the substrate 210a. Oriented in a direction inclined with respect to the surface. The degree of inclination of the liquid crystal molecules increases as the inclination angle α of the side surface 215S increases. Since the alignment regulating force by the vertical alignment film acts regardless of the presence or absence of voltage, light leakage due to tilted liquid crystal molecules in the vicinity of the side surface 215S occurs in the black display state. Therefore, when the inclination angle α of the side surface 215S of the wall structure 215b is too large, the contrast ratio is lowered. In order to suppress the decrease in the contrast ratio, the inclination angle α is preferably 45 ° or less, and more preferably 25 ° or less. On the other hand, when the inclination angle α exceeds 45 °, the vertical alignment of the liquid crystal molecules is lowered, and the alignment may become unstable. However, in order to obtain the effect of stabilizing the alignment, the inclination angle α is preferably 3 ° or more, and more preferably 5 ° or more.

  Here, design parameters such as the recess 217 formed integrally with the interlayer insulating film 215a are described in the example of the transflective liquid crystal display device. However, this parameter is the same as that in the transmissive liquid crystal display device and the reflective liquid crystal display device. It is applicable to.

〔Operating principle〕
The reason why the liquid crystal display device according to the embodiment of the present invention having the vertical alignment type liquid crystal layer has excellent wide viewing angle characteristics will be described with reference to FIG.

  FIG. 11 is a diagram for explaining the action of the alignment regulating force by the recess 16c formed in the interlayer insulating film 16a, the wall structure 16b formed integrally with the interlayer insulating film 16a, and the opening 6a provided in the pixel electrode 6. 4A and 4B schematically show the alignment state of liquid crystal molecules when no voltage is applied, and FIG. The state shown in FIG. 11B is a state where a halftone is displayed.

  The liquid crystal display device shown in FIG. 11 has an interlayer insulating film 16a, a pixel electrode 6 having an opening 6a, and an alignment film 22 in this order on a transparent substrate 1. Further, a wall structure 16b formed integrally with the interlayer insulating film 16a is provided outside the pixel. A recess is formed on the surface (alignment film 12) on the liquid crystal layer 20 side corresponding to the recess 16c. On the other transparent substrate 17, the color filter layer 18, the counter electrode 19, and the alignment film 32 are formed in this order. The liquid crystal layer 20 provided between the two substrates includes liquid crystal molecules 21 having negative dielectric anisotropy.

  As shown in FIG. 11A, when no voltage is applied, the liquid crystal molecules 21 are aligned substantially perpendicular to the substrate surface by the alignment regulating force of the vertical alignment films 12 and 32. However, since the liquid crystal molecules in the wall structure 16b (typically forming a vertical alignment film so as to cover the wall structure) and the recess 16c are aligned substantially perpendicular to the respective inclined surfaces, Inclines against. That is, the wall structure 16b and the recess 16c define the direction in which the liquid crystal molecules are inclined.

  When a voltage is applied, as shown in FIG. 11B, the liquid crystal molecules 21 having negative dielectric anisotropy are formed around the opening 6a because the molecular long axis tends to be perpendicular to the lines of electric force. The direction in which the liquid crystal molecules 21 are tilted is defined by the oblique electric field. Therefore, for example, it is oriented in an axially symmetrical manner around the opening 6a. In this axially symmetric alignment domain, the liquid crystal directors are aligned in all directions (directions in the substrate plane), so that viewing angle characteristics are excellent. Note that the tilting direction of the liquid crystal molecules due to the oblique electric field or the wall structure is strong in the periphery of the pixel, and the tilted orientation of the liquid crystal molecules affected by the influence tends to proceed to the inside of the pixel. The central axis is easily stabilized in the vicinity of the central recess of the pixel.

  Here, the action of the oblique electric field formed around the opening 6a has been described. However, an oblique electric field is similarly formed in the vicinity of the notch formed at the edge of the pixel electrode 6, and the liquid crystal molecules 21 are formed. The direction in which is tilted by the electric field is defined. It is shown that the center axis is stably fixed by the central portion of the liquid crystal domain when a voltage is applied, by the combined action of the alignment regulating force by the oblique electric field and the alignment regulating force by the concave portion 16c and the wall structure 16b described above. It is.

  Next, a more specific configuration example of the liquid crystal display device according to the embodiment of the present invention will be described with reference to FIG.

  The liquid crystal display device shown in FIG. 12 includes a backlight, a transflective liquid crystal panel 50, a pair of polarizing plates 40 and 43 provided so as to face each other through the transflective liquid crystal panel 50, and the polarizing plate 40. Quarter wave plates 41 and 44 provided between the liquid crystal panel 50 and the liquid crystal panel 50, and the optical anisotropy provided between the quarter wave plates 41 and 44 and the liquid crystal panel 50 is negative. The phase difference plates 42 and 45 are included. The liquid crystal panel 50 includes a vertical alignment type liquid crystal layer 20 between a transparent substrate (active matrix substrate) 1 and a transparent substrate (counter substrate) 17. Here, a liquid crystal panel 50 having the same configuration as that of the liquid crystal display device 200 shown in FIG. 4 is used.

  The display operation of the liquid crystal display device shown in FIG. 12 will be briefly described below.

  For the reflection mode display, incident light from above passes through the polarizing plate 43 and becomes linearly polarized light. This linearly polarized light becomes circularly polarized light when it enters the quarter wavelength plate 44 so that the transmission axis of the polarizing plate 43 and the slow axis of the quarter wavelength plate 44 are 45 °, and is formed on the substrate 17. It passes through a color filter layer (not shown). Here, a phase difference plate 45 that does not give a phase difference to light incident from the normal direction is used.

  When no voltage is applied, since the liquid crystal molecules in the liquid crystal layer 20 are aligned substantially perpendicular to the substrate surface, the incident light is transmitted with a phase difference of approximately 0 and is reflected by the reflective electrode formed on the lower substrate 1. The The reflected circularly polarized light passes through the liquid crystal layer 20 again, passes through the color filter layer, passes again through the retardation plate 45 having negative optical anisotropy as circularly polarized light, passes through the quarter-wave plate 44, and then first. The light is converted into linearly polarized light having a polarization direction orthogonal to the polarization direction when passing through the polarizing plate 43 and reaches the polarizing plate 43, so that light cannot pass through the polarizing plate 43 and is displayed in black.

  On the other hand, when a voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are inclined in the horizontal direction from the direction perpendicular to the substrate surface, so that the incident circularly polarized light becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20 and is formed on the lower substrate 1. Reflected by the reflected electrode. The reflected light is further broken in the polarization state by the liquid crystal layer 20, passes through the liquid crystal layer 20 again, passes through the color filter layer, passes through the retardation plate 45 having negative optical anisotropy again, and becomes 1/4. Since the light is incident on the wave plate 44 as elliptically polarized light, all the light does not become linearly polarized light orthogonal to the polarization direction at the time of incidence when reaching the polarizing plate 43, and part of the light is transmitted through the polarizing plate 43. In particular, by adjusting the applied voltage, the direction in which the liquid crystal molecules are tilted can be controlled, and the amount of light that can be reflected by the polarizing plate 43 is modulated, thereby enabling gradation display.

  Regarding the display of the transmission mode, the two upper and lower polarizing plates 43 and 40 are arranged so that their transmission axes are orthogonal to each other, and the light emitted from the light source becomes linearly polarized light by the polarizing plate 40, This linearly polarized light becomes circularly polarized light and has a negative optical anisotropy when incident on the ¼ wavelength plate 41 so that the slow axis between the transmission axis of the polarizing plate 40 and the ¼ wavelength plate 41 is 45 °. The light enters the transmission region A of the lower substrate 1 through the phase difference plate 42. Here, a phase difference plate 42 that does not give a phase difference to light incident from the normal direction is used.

  When no voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are aligned substantially perpendicular to the substrate surface, so that incident light is transmitted with a phase difference of approximately 0 and is incident on the lower substrate 1 in a circularly polarized state. In the state of circular polarization, the light passes through the liquid crystal layer 20 and the upper substrate 17 and passes through the retardation plate 45 having the negative optical anisotropy to reach the quarter-wave plate 44. Here, the slow axis of the lower ¼ wavelength plate 41 and the upper ¼ wavelength plate 44 intersect each other by 90 °, so that the upper ¼ wavelength plate 44 is separated by the polarizing plate 40. The linearly polarized light is orthogonal to the linearly polarized light, and is absorbed by the polarizing plate 43 to display black.

  On the other hand, when a voltage is applied, since the liquid crystal molecules 21 in the liquid crystal layer 20 are inclined in the horizontal direction from the direction perpendicular to the substrate surface, the circularly polarized light incident on the liquid crystal display device becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20, and the upper side. Since the CF substrate 16 and the retardation plate 45 and the quarter wavelength plate 44 having negative optical anisotropy on the upper side reach the polarizing plate 43 as elliptically polarized light, the linearly polarized light orthogonal to the polarization component at the time of incidence is not obtained. Instead, light passes through the polarizing plate 43. In particular, by adjusting the applied voltage, the direction in which the liquid crystal molecules are tilted can be controlled, and the amount of light that can be reflected by the polarizing plate 43 is modulated, thereby enabling gradation display.

  A retardation plate having a negative optical anisotropy minimizes the amount of change in retardation when the viewing angle is changed in a vertically aligned state of liquid crystal molecules, and suppresses black floating on the wide viewing angle side. Further, a biaxial retardation plate in which a retardation plate having negative optical anisotropy and a quarter wavelength plate are integrated may be used.

  When a normally black mode in which black display is performed when no voltage is applied and white display is performed when a voltage is applied as in the present invention is performed in an axially symmetric alignment domain, a pair of quarter wavelengths are formed above and below the liquid crystal display device (panel). By providing the plate, it is possible to improve the brightness by eliminating the extinction pattern caused by the polarizing plate. In addition, when the normally black mode is performed in the axially symmetric alignment domain by arranging the transmission axes of the upper and lower polarizing plates orthogonally to each other, in principle, the same degree as that of a pair of polarizing plates arranged in crossed Nicols. Since a black display can be realized, an extremely high contrast ratio can be realized, and a wide viewing angle characteristic led to an omnidirectional orientation can be achieved.

  Below, the specific example regarding this invention is described and demonstrated.

(Example 1)
A liquid crystal display device was configured by arranging an active matrix substrate having the configuration shown in FIG. 6 and a color filter substrate in which a color filter layer, a transparent dielectric layer 234 layer, and a counter electrode were laminated on the opposite side.

  In the active matrix substrate of this example, the interlayer insulating film and the wall structure were formed by the above-described process under the following exposure conditions.

The first exposure step for forming the concavo-convex shape and the wall structure on the positive photosensitive resin film is performed using the first photomask 52 under the low exposure amount condition (60 mJ / cm ² ), and the pixel The second exposure step for forming a recess, a contact hole, and the like, which are regularly arranged at substantially the center of the liquid crystal domain in the inside to control the axial position, includes the second photomask 62 (the inner diameter width of the recess). Was carried out under high exposure conditions (300 mJ / cm ² ) using a contact hole diameter of 5 μm.

  Then, the active matrix substrate of the present example was obtained by executing the series of steps described above. The baking process after development was performed at 200 ° C. for 1 hour. As a result, the inclination angle α of the side surface of the wall structure was about 10 °, and a mortar-like cross-sectional shape was obtained. As for the recess, the finished inner diameter was 2 μm, the depth was 1.8 μm, and the thickness of the flat portion of the interlayer insulating film in the pixel was 2.5 μm.

  On the other hand, in the color filter substrate, a step of the transparent dielectric layer is arranged in the reflection region, and a support (dielectric) provided to define the liquid crystal layer thickness in the light shielding layer portion outside the display pixel is formed.

  After forming a vertical alignment film on the active matrix substrate and the color filter substrate under predetermined conditions (no rubbing treatment), the substrates are bonded together with a seal resin, and a liquid crystal material having a negative dielectric anisotropy ( Refractive index anisotropy Δn; 0.1 and dielectric anisotropy Δε; −4.5) were injected and sealed to prepare a liquid crystal display panel. In this example, the liquid crystal layer thickness dt in the transmissive region was 4 μm, and the liquid crystal layer thickness dr in the reflective region was 2.1 μm.

  Subsequently, an optical film was disposed on both sides of the liquid crystal display panel for the following, to obtain a liquid crystal display device.

  The configuration of the liquid crystal display device of the present embodiment includes a polarizing plate (observation side), a quarter-wave plate (retardation plate 1), and a retardation plate with negative optical anisotropy (retardation plate 2) in this order from the viewer side. (NR plate)), liquid crystal layer (upper side: color filter substrate, lower side: active matrix substrate), retardation plate with negative optical anisotropy (retardation plate 3 (NR plate)), quarter wavelength plate ( The phase difference plate 4) and the polarizing plate (backlight side) were laminated. In addition, in the upper and lower quarter-wave plates (the phase difference plate 1 and the phase difference plate 4) of the liquid crystal layer, their slow axes were orthogonal to each other, and each phase difference was set to 140 nm. Retardation plates having negative optical anisotropy (retardation plate 2 and retardation plate 3) each have a retardation of 135 nm. The two polarizing plates (observation side and backlight side) were arranged with their absorption axes orthogonal to each other.

  A drive signal was applied to the obtained liquid crystal display device (4 V was applied to the liquid crystal layer) to evaluate display characteristics.

  A viewing angle-contrast characteristic result in the transmissive display is shown in FIG. The viewing angle characteristics in the transmissive display are almost omnidirectional and symmetric, the CR> 10 region is as good as ± 80 °, and the transmissive contrast is as high as 300: 1 or more in the front.

  On the other hand, the characteristics of the reflective display are evaluated by a spectrocolorimeter (CM 2002 manufactured by Minolta Co., Ltd.). Therefore, the contrast was high as compared with the conventional liquid crystal display device.

  In addition, it was confirmed that the rough feeling in the halftone (gradation level 2 at the time of eight gradation division) was also improved. Furthermore, the halftone response time (time required for the change from gradation level 3 to gradation level 5 when divided into 8 gradations; m seconds) is 30 msec, and a conventional liquid crystal with positive dielectric anisotropy is used. Compared to the ECB mode, the characteristics were equivalent or better.

  In addition, the alignment disturbance generated when the display panel was pressed with the fingertip when the voltage of 4 V was applied (white display) was recovered immediately after the pressing was stopped. As described above, the on-wall structure formed so that the central axis is effectively fixed to the concave portion regularly formed substantially in the center of the liquid crystal domain in the pixel and substantially surrounds the pixel, and the periphery of the pixel The alignment stability of the axially symmetric alignment domain is improved by the pixel electrode and the vertical alignment film formed on the mortar-shaped surface that continuously changes from the side surface of the structure on the wall to the center of the pixel. .

  In addition, when the cross-sectional shape is not a mortar shape, when the inclination angle of the side surface of the wall-shaped structure exceeds 45 °, the contrast ratio does not reach 300: 1, or the alignment disorder due to pressing occurs. Something was seen.

(Example 2)
A semi-transmission type liquid crystal display device having the structure shown in FIG. 9 was manufactured in the same process as in Example 1 (Prototype Examples 1 to 6). Table 1 below shows the shape factor of the recess and the panel characteristics in each prototype.

Here, the pixel short side pitch P _S maximum inner diameter width to (μm) D _C (μm) ratio; D _C / P _S and the interlayer insulating film (the pixel flat portion) Id ([mu] m) of the recess to the depth h ( μm) ratio; preferred conditions for the value of h / Id were studied.

In addition, as the characteristics of the liquid crystal panel, the transmittance when applying a voltage of 4 V to the reference backlight light (2000 cd / m ² ), the front contrast ratio when applying the voltage of 4 V, and the results of evaluating the impact resistance are also described. did.

The design value of the transmittance was 4.0%, and the lower limit allowable value was 3.6%. For the front contrast ratio, the design value was 300, and the lower limit allowable value was 270. In the impact resistance evaluation, the time until the orientation was restored (returned to the original orientation state) after pressing the panel with a pressure of 1 kgf / cm ² was evaluated. The case where the orientation was restored from the defective orientation to the normal orientation within 1 minute was marked as ◯, the case where the orientation was restored from the defective orientation within 5 minutes over 1 minute, and the case where the alignment disorder remained after 10 minutes.

As can be seen from the results in Table 1, decrease or recess in transmittance with decreasing maximum extent the inner diameter width D _C and depth h is increased effective aperture ratio of recesses regularly arranged in a substantially center of the liquid crystal domains in the pixel Since the liquid crystal molecules on the side surfaces of the liquid crystal molecules are inclined, light leakage tends to occur, and the front CR tends to decrease. On the other hand, since the impact resistance is restored within 5 minutes even in the case where alignment failure occurs due to pressing in the prototype example shown in Table 1, it was confirmed that the effect of the arrangement of the recesses in the present invention is large. . A significant improvement effect was also observed in the feeling of roughness.

(Comparative example)
An ECB mode homogeneous alignment liquid crystal display panel was manufactured using a liquid crystal panel having the same configuration as the liquid crystal panel of the example. The liquid crystal panel of the comparative example is not formed with a wall structure or an opening or notch of the pixel electrode. In addition, the liquid crystal panel of the comparative example uses a horizontal alignment film instead of the vertical alignment film of the liquid crystal panel of the embodiment, and the liquid crystal layer has a liquid crystal material (Δn; 0.07, Δε having positive dielectric anisotropy). 8.5) was injected to form a homogeneously oriented liquid crystal layer. The liquid crystal layer thickness dt in the transmissive region was 4.3 μm, and the liquid crystal layer thickness dr in the reflective region was 2.3 μm.

  A liquid crystal display device of a comparative example was obtained by arranging optical films formed of a plurality of optical layers including retardation plates such as polarizing plates and quarter-wave plates on both surfaces of the liquid crystal display panel.

  A drive signal was applied to the liquid crystal display device of this comparative example (4 V was applied to the liquid crystal layer), and display characteristics were evaluated according to the same evaluation method as in the example.

  The viewing angle characteristics in transmissive display were ± 30 ° in the region of CR> 10, and the gradation inversion was significant. The transmission contrast was 140: 1. On the other hand, the characteristics of the reflective display are about 9.3% (value converted to 100% aperture ratio) with respect to the standard diffusion plate, the contrast value of the reflective display is 8, and the display image is compared with the embodiment in the vertical mode. White contrast was low and blurred.

  As described above, the liquid crystal display device according to the embodiment of the present invention has a transmissive and reflective display by applying the vertical alignment mode to the transmissive display and the reflective display as compared with the conventional homogeneous liquid crystal display device and the conventionally known technology. A good contrast ratio can be obtained in both reflection displays.

  Furthermore, in the embodiment of the present invention, the regulation structure (wall structure and opening or notch) of the liquid crystal domain alignment is disposed only on one side substrate (illustratively, active matrix substrate), and the wall structure is disposed between the layers. The manufacturing process can be simplified because it can be formed integrally with the insulating film and continuously with the formation of the fine irregularities of the reflecting portion and the contact hole forming step. In addition, it is possible to regulate the direction in which the liquid crystal molecules fall when a voltage is applied in the rubbing-less process by the alignment regulating force of the wall structure, the opening, or the notch. In addition, as exemplified in the embodiment of the present invention, by providing a liquid crystal domain alignment regulating structure, a plurality of liquid crystal domains that exhibit axial symmetry when a voltage is applied are formed for each pixel. Angular characteristics can be realized.

  In the above embodiment, the configuration in which the axially symmetric alignment domain is formed in the liquid crystal display device including the vertical alignment type liquid crystal layer is exemplified. However, by modifying the shape and arrangement of the recesses provided in the interlayer insulating film, for example, The present invention can also be applied to an MVA liquid crystal display device as described in JP-A-11-242225.

  As described above, the liquid crystal display device according to the present invention can realize a liquid crystal display device with excellent display quality with a relatively simple configuration. The present invention is suitably applied to a transmissive liquid crystal display device and a transflective (transmission / reflection) liquid crystal display device. In particular, the transflective liquid crystal display device is suitably used as a display device for mobile devices such as mobile phones.

It is a figure which shows typically the structure of one pixel of the transmissive liquid crystal display device 100 of embodiment by this invention, (a) is a top view, (b) is 1B- in FIG. 1 (a). It is sectional drawing along a 1B 'line. It is a top view which shows typically the structure of the active matrix substrate of the other transmissive liquid crystal display device of embodiment by this invention. It is sectional drawing which shows typically the structure of the active matrix substrate shown to FIG. 2A. It is sectional drawing which shows typically the structure of the other transmissive liquid crystal display device 100 'of embodiment by this invention. It is a figure which shows typically the structure of one pixel of the transflective liquid crystal display device 200 of embodiment by this invention, (a) is a top view, (b) is 4B in Fig.4 (a). It is sectional drawing along the -4B 'line. It is a top view which shows typically the structure of the active matrix substrate of the transflective liquid crystal display device of embodiment by this invention. It is sectional drawing which shows typically the structure of a liquid crystal display device provided with the active matrix substrate shown in FIG. (A) to (f) are schematic views for explaining a method of manufacturing the active matrix substrate shown in FIG. It is a schematic diagram showing the relationship between the short pitch P _S of the inner diameter width D _C and the pixel of the recess. Is a graph showing the relationship between the maximum internal diameter width D _C and the effective numerical aperture of the recess. (A) And (b) is sectional drawing along the 10A-10A 'line of FIG. 4, (b) is an enlarged view of the part enclosed with the broken line of (a). It is the schematic explaining the operation | movement principle of the liquid crystal display device of embodiment by this invention, (a) shows the time at the time of no voltage application, and (b) at the time of voltage application, respectively. It is a schematic diagram which shows an example of a structure of the liquid crystal display device of embodiment by this invention. It is a figure which shows the viewing angle-contrast ratio characteristic of the liquid crystal display device of the Example by this invention.

Explanation of symbols

1 TFT (active matrix) substrate 2 Gate signal line 3 Source signal line 4 TFT
5 Drain electrode 6 Pixel electrode 6a Opening 7 Transparent electrode 8 Reflective electrode 9 Gate insulating film 10 Gate electrode 11 Source / drain electrode (n + -Si layer)
12 Semiconductor Layer 13 Channel Protection Layer 14 Opening 16a Interlayer Insulating Film 16b Wall Structure 16c Recess 17 Transparent Substrate (Counter (CF) Substrate)
18 Color filter layer 19 Counter electrode 20 Liquid crystal layer 21 Liquid crystal molecule 22, 32 Alignment film 50 Liquid crystal panel 40, 43 Polarizing plate 41, 44 1/4 wavelength plate 42, 45 Retardation plate (NR plate) with negative optical anisotropy )
100, 100 'Transmission type liquid crystal display device 110a Active matrix substrate 110b Counter substrate (color filter substrate)
DESCRIPTION OF SYMBOLS 111 Pixel electrode 113 Notch 114 Opening 115a Interlayer insulation film 115b Wall structure 117 Recess 130 Color filter layer 131 Counter electrode 133 Support body 200, 300 Transflective liquid crystal display device 210a Active matrix substrate 210b Counter substrate (color filter substrate) )
211 Pixel electrode 213 Notch 214 Opening 215a Interlayer insulating film 215b Wall structure 217 Recess 230 Color filter layer 231 Counter electrode 232 Transparent dielectric layer (reflection part step)
233 Support

Claims (20)

A first substrate, a second substrate provided to face the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate,
A first electrode formed on the first substrate; an interlayer insulating film provided between the first substrate and the first electrode; a second electrode formed on the second substrate; A plurality of pixels including the liquid crystal layer provided between the first electrode and the second electrode;
The interlayer insulating film has at least one recess provided at a predetermined position, and the liquid crystal layer tilts in a direction defined by the at least one recess when a predetermined voltage is applied. A liquid crystal display device forming at least one liquid crystal domain containing   The liquid crystal display device according to claim 1, wherein the first electrode has at least one opening, and the at least one opening includes an opening formed at a position corresponding to the at least one recess. The plurality of pixels are arranged in a matrix, and when the shorter pitch is P _S , the maximum inner diameter width D _C of the at least one recess satisfies the relationship of D _C <0.35 · P _S. The liquid crystal display device according to claim 1.   4. The liquid crystal display device according to claim 1, wherein a relationship between a thickness Id of the interlayer insulating film and a depth h of the at least one recess satisfies a relationship of h <0.8 · Id. .   The liquid crystal display device according to claim 1, wherein the first electrode further includes at least one notch.   6. The apparatus according to claim 1, further comprising a wall structure integrally formed with the interlayer insulating film, wherein the wall structure is regularly arranged around each of the plurality of pixels. The liquid crystal display device described.   The liquid crystal display device according to claim 6, further comprising a light shielding region around each of the plurality of pixels, wherein the wall structure is regularly arranged in the light shielding region.   The liquid crystal layer is a vertical alignment type liquid crystal layer, and the at least one liquid crystal domain formed when at least a predetermined voltage is applied to the liquid crystal layer includes a liquid crystal domain exhibiting an axially symmetric alignment. The liquid crystal display device according to claim 1, wherein a central axis is formed in or near the at least one recess. The second electrode has at least one further opening formed at a predetermined position in the pixel,
The liquid crystal layer is a vertical alignment type liquid crystal layer, and the at least one liquid crystal domain formed when at least a predetermined voltage is applied to the liquid crystal layer includes a liquid crystal domain exhibiting an axially symmetric alignment. The liquid crystal display device according to claim 1, wherein a central axis is formed in or near the at least one further recess.   The switching element electrically connected to the first electrode is further provided on the first substrate, and at least a part of the switching element is covered with the interlayer insulating film. A liquid crystal display device according to 1.   The liquid crystal display device according to claim 1, wherein the first electrode includes a transparent electrode that defines a transmissive region and a reflective electrode that defines a reflective region.   The at least one liquid crystal domain includes a liquid crystal domain that is formed in the transmission region and exhibits an axially symmetric orientation, and a central axis of the axially symmetric orientation is formed in or near the at least one recess. The liquid crystal display device described.   The interlayer insulating film includes a first region having a substantially flat surface and a second region having a concavo-convex shape on the surface, the transparent electrode is formed on the first region, and the reflective electrode includes The liquid crystal display device according to claim 11, wherein the liquid crystal display device is formed on the second region.   A pair of polarizing plates arranged to face each other with the first substrate and the second substrate interposed therebetween, and at least between the first substrate and / or the second substrate and the pair of polarizing plates The liquid crystal display device according to claim 1, further comprising one biaxial optically anisotropic medium layer.   It further has a pair of polarizing plates arranged so as to face each other with the first substrate and the second substrate interposed therebetween, and between the first substrate and / or the second substrate and the pair of polarizing plates. The liquid crystal display device according to claim 1, further comprising at least one uniaxial optically anisotropic medium layer. A first substrate; a second substrate provided to face the first substrate; and a liquid crystal layer provided between the first substrate and the second substrate, each of which A first electrode formed on one substrate; a circuit element electrically connected to the first electrode; an interlayer insulating film provided between the first substrate and the first electrode; and the second electrode A method of manufacturing a liquid crystal display device including a plurality of pixels including a second electrode formed on a substrate and the liquid crystal layer provided between the first electrode and the second electrode,
Forming a circuit element on the first substrate;
Forming a positive photosensitive resin film covering the circuit element;
A step of exposing the photosensitive resin film, the step of forming predetermined regions having different exposure amounts;
Developing the exposed photosensitive resin film to form a contact hole exposing a part of the circuit element and an interlayer insulating film having at least one recess;
Forming a first electrode on the interlayer insulating film;
A method for manufacturing a liquid crystal display device. The step of forming the interlayer insulating layer includes a step of forming a first region having a substantially flat surface and a second region having a concavo-convex shape on the surface,
The step of forming the first electrode includes a step of forming a transparent electrode on the interlayer insulating film in the first region and a step of forming a reflective electrode on the interlayer insulating film in the second region. A method for manufacturing a liquid crystal display device according to claim 16. The exposure step includes
A first exposure step of forming a region to be the second region and other regions using a first photomask;
A second exposure step of forming a region to be the contact hole and a region to be the at least one recess by using a second photomask in the other region.
The manufacturing method of the liquid crystal display device of Claim 17. The liquid crystal display device further includes a wall structure regularly arranged around each of the plurality of pixels and integrally formed with the interlayer insulating film,
19. The method for manufacturing a liquid crystal display device according to claim 18, wherein the first exposure step is a step of forming a region to be the second region and a region to be a wall structure.   The step of forming the first electrode and / or the second electrode includes a step of forming a conductive film and a step of patterning the conductive film. The step of patterning includes the first electrode and / or The method for manufacturing a liquid crystal display device according to claim 16, comprising a step of forming a plurality of openings or notches at predetermined positions of the second electrode.