JP2009086161A - Liquid crystal display, manufacturing method for liquid crystal display, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display capable of preventing a phase difference from being shifted in a tapered area, and allowing a high contrast, and bright display. <P>SOLUTION: This liquid crystal display 100 is provided with: a pair of substrates 10A, 25A; a liquid crystal layer 50 held between the paired substrates; and a phase difference layer 29 provided in a liquid crystal layer side of the one substrate 25A out of the paired substrates. The tapered area TP is formed on an end face of the phase difference layer 29, and the phase difference per unit layer thickness of the phase difference layer 29 in the tapered area TP is larger than the phase difference per unit layer thickness of the phase difference layer 29 in an area (flat area FL) other than the tapered area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a retardation layer built-in type liquid crystal display device having a retardation layer on the inner surface side of a liquid crystal panel, a method for manufacturing the liquid crystal display device, and an electronic apparatus.

In a transflective liquid crystal display device, it is necessary to adjust a phase difference between display modes in order to realize reflective display and transmissive display using a single liquid crystal layer. In recent years, a technique for installing a retardation layer inside a liquid crystal panel has been developed. The material used in this technology is a material based on a liquid crystal that is polymerized by ultraviolet rays, and is applied by spin coating or the like on an alignment film that has been subjected to an alignment treatment, and is polymerized by ultraviolet rays to maintain the alignment state. Curing is a common production method (see Patent Document 1).
JP 2005-338256 A

  In general, when the liquid crystal material is polymerized with ultraviolet rays, the end face of the retardation layer is tapered by diffracted light that wraps around the back side of the exposure mask. The size of the taper region is represented by dtan θ, where θ is the incident angle of diffracted light and d is the thickness of the retardation layer. The incident angle θ of the diffracted light increases as the exposure mask pattern pitch decreases. Therefore, when the size of the sub-pixel is reduced, the tapered region of the retardation layer is also increased. Since the optical characteristics of the tapered region are different from those of the flat region, the light is usually shielded by a black matrix or the like.However, if the tapered region is shielded from light, the aperture ratio decreases accordingly. The luminance is lowered, which is disadvantageous in display characteristics.

  The present invention has been made in view of such circumstances. A liquid crystal display device capable of preventing a phase difference shift in a tapered region, having a high contrast, and capable of bright display, a method for manufacturing the liquid crystal display device, and an electronic apparatus. The purpose is to provide.

  In order to solve the above problems, a liquid crystal display device of the present invention is provided on a liquid crystal layer side of a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and one of the pair of substrates. A retardation region formed on the end surface of the retardation layer, and the retardation per unit layer thickness of the retardation layer in the tapered region is the taper region. The retardation is larger than the retardation per unit layer thickness of the retardation layer in a region other than the region. According to this configuration, the phase shift between the tapered region and the region other than the tapered region (flat region) is reduced. Therefore, when considering the net phase difference formed by the phase difference layer and the liquid crystal layer (the sum of the phase difference of the phase difference layer and the phase difference of the liquid crystal layer), the magnitude of the phase difference in the tapered region is set in the flat region. It can approach the magnitude of the phase difference. As a result, light leakage (polarization deviation) that occurs in the tapered region of the retardation layer is eliminated, and high-contrast image display can be realized.

In the present specification, “retardation per unit layer thickness” means an average retardation in the layer thickness direction of the retardation layer. When the magnitude of the phase difference has a distribution in the plane area of the phase difference layer, the “phase difference per unit layer thickness” is calculated for each portion in the plane area. Specifically, the layer thickness of the retardation layer in a specific portion in the plane region is d ₀ , and the birefringence magnitude of the retardation layer in the layer thickness direction is Δn (t) (the birefringence magnitude is the layer thickness). (Represented by a function of the position t in the direction), the phase difference Δn _av per unit layer thickness is represented by the following equation (1).

  In the present invention, in the tapered region, the retardation per unit layer thickness of the retardation layer continuously changes from a region where the retardation layer is thick to a region where the retardation layer is thin. It is desirable that According to this configuration, variation in phase within the tapered region is eliminated, and an image display with high contrast becomes possible.

  In the present invention, the retardation layer is formed of a liquid crystal material, and the alignment state of the liquid crystal material in the tapered region is different from the alignment state of the liquid crystal material in a region other than the tapered region. it can. For example, the liquid crystal material may be homogeneously aligned in the tapered region, and the liquid crystal material may be bend aligned in a region other than the tapered region.

  The liquid crystal display device of the present invention includes a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and a retardation layer provided on the liquid crystal layer side of one of the pair of substrates. The retardation layer is formed of a liquid crystal material, a tapered region is formed on an end surface of the retardation layer, and the unit thickness of the retardation layer in the tapered region per unit layer thickness. An average tilt angle of the liquid crystal material is smaller than an average tilt angle of the liquid crystal material per unit layer thickness of the retardation layer in a region other than the tapered region. According to this configuration, the phase shift between the tapered region and the region other than the tapered region (flat region) is reduced. Therefore, when considering the net phase difference formed by the phase difference layer and the liquid crystal layer (the sum of the phase difference of the phase difference layer and the phase difference of the liquid crystal layer), the magnitude of the phase difference in the tapered region is set in the flat region. It can approach the magnitude of the phase difference. As a result, light leakage (polarization deviation) that occurs in the tapered region of the retardation layer is eliminated, and high-contrast image display can be realized.

In the present specification, the “average tilt angle of the liquid crystal material per unit layer thickness” refers to the average tilt angle of the liquid crystal material in the layer thickness direction of the retardation layer. When the tilt angle has a distribution in the plane region of the retardation layer, the “average tilt angle of the liquid crystal material per unit layer thickness” is calculated for each portion in the plane region. Specifically, the layer thickness of the phase difference layer in a specific portion in the plane region is d ₀ , and the tilt angle of the liquid crystal material in the layer thickness direction is T (t) (the tilt angle is in the layer thickness direction). The average tilt angle T _av of the liquid crystal material per unit layer thickness is expressed by the following equation (2).

  The method for manufacturing a liquid crystal display device of the present invention includes a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and a retardation layer provided on the liquid crystal layer side of one of the pair of substrates. A method of manufacturing a liquid crystal display device comprising: a step of forming the retardation layer, the step of forming a first control electrode on the one substrate; and the first control electrode of the one substrate. A step of forming a first alignment film for horizontally aligning the liquid crystal material on the substrate, and a control in which a second control electrode having a smaller area than the first control electrode of the one substrate is formed. Preparing a substrate and forming a second alignment film on the surface of the control substrate on which the second control electrode is formed to align a liquid crystal material horizontally with the substrate; and the first control electrode and the second control The first alignment film of the one substrate was formed facing the electrode Disposing a liquid crystal material having positive dielectric anisotropy, which is a material for forming the retardation layer, between the control substrate and the surface on which the second alignment film is formed, and the first control electrode; Applying a voltage between the second control electrode and aligning the liquid crystal material by an electric field formed between the first control electrode and the second control electrode; and the same as the second control electrode An exposure mask having a light-transmitting portion having a planar shape is prepared, the light-transmitting portion of the exposure mask is opposed to the second control electrode of the control substrate, and ultraviolet rays are emitted from the control substrate side through the exposure mask. Irradiating and curing the liquid crystal material.

  According to this method, the alignment of the liquid crystal material, which is a material for forming the retardation layer, is controlled by both the alignment regulating force by the alignment film and the alignment regulating force by the electric field. Here, since the second control electrode formed on the control substrate is smaller than the first control electrode formed on one substrate, an electric force inclined obliquely with respect to the control substrate is formed on the outer periphery of the second control electrode. A line is generated, and the electric field strength decreases as the distance from the outer periphery of the second control electrode increases. Therefore, when the retardation layer is formed using a liquid crystal material having positive dielectric anisotropy (positive type), the tilt angle of the liquid crystal material increases in the region facing the second control electrode, and the end of the tapered region (outer peripheral portion) ), The tilt angle becomes smaller. As a result, the phase difference per unit layer thickness is increased in the tapered region where the thickness of the retardation layer is small, and the phase shift between the tapered region and a region other than the tapered region (flat region) is reduced. Then, when considering the net phase difference formed by the phase difference layer and the liquid crystal layer (the sum of the phase difference of the phase difference layer and the phase difference of the liquid crystal layer), the magnitude of the phase difference in the tapered region is determined in the flat region. It can approach the magnitude of the phase difference. As a result, light leakage (polarization deviation) that occurs in the tapered region of the retardation layer is eliminated, and high-contrast image display can be realized. In the present invention, since the orientation of the liquid crystal material constituting the retardation layer is controlled by the first alignment film disposed on the lower surface portion of the retardation layer and the second alignment film disposed on the upper surface portion of the retardation layer. Compared to a normal retardation layer in which the orientation is controlled only by the orientation film on the lower surface portion of the layer, a desired orientation can be easily realized.

  In the present invention, it is desirable to include a step of forming a release layer on the surface of the second control electrode before forming the second alignment film on the control substrate. According to this method, it is possible to prevent the retardation layer from being peeled from one of the substrates when the control substrate is peeled from the retardation layer.

  In the present invention, it is desirable that the resistance of the central portion of the second control electrode is smaller than the resistance of the outer peripheral portion of the second control electrode. According to this method, compared with the case where the resistance of the second control electrode is formed uniformly over the entire electrode, the strength of the electric field can be precisely controlled, and the phase of the retardation layer can be easily controlled.

  In the present invention, it is preferable that the first control electrode functions as an electrode for driving the liquid crystal layer after the retardation layer is formed. According to this method, it is not necessary to form an electrode for driving the liquid crystal separately from the first control electrode, so that the manufacturing process is simplified.

  An electronic apparatus according to the present invention includes the above-described liquid crystal display device according to the present invention. According to this configuration, it is possible to provide an electronic device with high contrast and capable of bright display.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, number, and the like of each structure are different.

  In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. At this time, the predetermined direction in the horizontal plane is the X-axis direction, the direction orthogonal to the X-axis direction in the horizontal plane is the Y-axis direction, and the direction orthogonal to each of the X-axis direction and the Y-axis direction (that is, the vertical direction) is the Z-axis direction. And For example, in this embodiment, the X-axis direction is the data line extending direction, the Y-axis direction is the scanning line extending direction, and the Z-axis direction is the viewing direction of the liquid crystal panel by the observer.

[Configuration of liquid crystal display device]
FIG. 1 is a plan view of one pixel of a liquid crystal display device 100 according to an embodiment of the present invention. The liquid crystal display device 100 is a transflective liquid crystal display device including a thin film transistor (hereinafter referred to as “TFT”) as a pixel switching element.

  As shown in FIG. 1, in one pixel region of the liquid crystal display device 100, three sub-pixels D corresponding to red, green, and blue are provided. A color layer (color filter) of one of the three primary colors is formed corresponding to one subpixel D, and a pixel region including the three color layers 22R, 22G, and 22B is formed by the three subpixels D1 to D3. Has been. The colored layers 22R, 22G, and 22B are each formed in a stripe shape extending in the X-axis direction, are formed across the plurality of sub-pixels D in the extending direction, and are periodically arranged in the Y-axis direction. Has been.

  In the planar area of the sub-pixel D, a pixel electrode 9 having a substantially rectangular shape in plan view is provided. In the display area of the liquid crystal display device 100, a plurality of data lines 6 a extending in the X-axis direction and a plurality of scanning lines 3 a extending in the Y-axis direction are provided along the boundary portion of the pixel electrode 9. . Each region surrounded by the data line 6a and the scanning line 3a is a sub-pixel D, and a TFT element 30 for driving the sub-pixel D is provided near the intersection of the data line 6a and the scanning line 3a. . The sub-pixels D are arranged in a matrix along the scanning lines 3a and the data lines 6a, and a plurality of sub-pixels D arranged in a matrix form a display area as a whole.

  The subpixel D is divided into two regions in the X-axis direction. The left area in the figure is a reflective display area R having a reflective display pixel electrode 9r, and the right area in the figure is a transmissive display area T having a transmissive display pixel electrode 9t. In this embodiment, the reflective display pixel electrode 9r is a rectangular reflective electrode made of a light-reflective conductive film such as aluminum or silver, and the transmissive display pixel electrode 9t is made of ITO (indium tin oxide). ) And the like, and a transparent electrode having a rectangular shape in plan view. The reflective display pixel electrode 9r and the transmissive display pixel electrode 9t have substantially the same shape and size in plan view, and are connected to each other at the center of the sub-pixel region.

  In the vicinity of the intersection between the scanning line 3a and the data line 6a, a TFT element 30 for connecting the reflective display pixel electrode 9r to the scanning line 3a and the data line 6a is provided. The TFT element 30 includes a semiconductor layer 35, a gate electrode portion 32 provided on the lower layer side of the semiconductor layer 35, and a source electrode portion 33 and a drain electrode portion 34 provided on the upper layer side of the semiconductor layer 35. Yes. A channel region is formed in a region facing the gate electrode portion 32 of the semiconductor layer 35, and a source region and a drain region are formed on both sides of the channel region. The gate electrode portion 32 is formed by extending a part of the scanning line 3a in the extending direction (X-axis direction) of the data line 6a. Opposite through the membrane. The source electrode portion 33 is formed by extending a part of the data line 6 a in the extending direction (Y-axis direction) of the scanning line 3 a and is electrically connected to the source region of the semiconductor layer 35. The drain electrode 34 is electrically connected to the drain region of the semiconductor layer 35 on one end side, and is electrically connected to the reflective display pixel electrode 9r on the other end side.

  FIG. 2 is a cross-sectional view taken along line AA in FIG. The liquid crystal display device 100 includes an element substrate (first substrate) 10 and a counter substrate (second substrate) 25 arranged to face the element substrate 10. A liquid crystal layer 50 is sandwiched between the element substrate 10 and the counter substrate 25. A polarizing plate 19 is provided on the outer surface side of the element substrate 10, and a polarizing plate 17 is provided on the outer surface side of the counter substrate 25. Further, a backlight 15 that is an illumination device for transmissive display is disposed on the outer surface side of the polarizing plate 19.

  The element substrate 10 has a translucent substrate 10A such as quartz or glass as a base. A TFT element (only the scanning line 3a is shown in FIG. 2) is formed on the inner surface side of the base 10A. A first insulating film 40 made of a light-transmitting insulating material such as acrylic resin is formed so as to cover the base 10A and the TFT element. A second insulating film 24 made of a translucent insulating material such as acrylic resin is formed so as to cover the first insulating film 40. On the surface of the second insulating film 24, a reflective display pixel electrode 9r made of a light-reflective metal film such as aluminum or silver, or a laminated film of these metal films and a light-transmitting conductive film such as ITO, A transmissive display pixel electrode 9t made of a translucent conductive film such as ITO is formed. An alignment film (not shown) made of polyimide or the like is formed on the surface of the second insulating film 24 so as to cover the reflective display pixel electrode 9r and the transmissive display pixel electrode 9t.

  The region corresponding to the reflective display region T of the second insulating film 24 is provided with an uneven shape 24a. An uneven surface following the uneven shape 24a is formed on the surface of the reflective display pixel electrode 9r. The reflective display pixel electrode 9r also serves as a scattering reflective film for reflective display that reflects external light. The region where the reflective display pixel electrode 9r is formed is the reflective display region T, and the transmissive display pixel electrode 9t. A region where is formed is a transmissive display region T. The reflective display pixel electrode 9r is provided with light scattering properties by the concavo-convex surface provided by the concavo-convex shape 24a, and prevents reflection from the outside and enlarges the viewing angle. On the other hand, the region other than the reflective display region R in the second insulating film 24 is a flat surface. The transmissive display pixel electrode 9t is formed on the flat surface.

  The counter substrate 25 has a translucent substrate 25A such as quartz or glass as a base. A color filter layer including a colored layer 22R, an overcoat film 23 made of an acrylic resin, etc., and a flat solid first control electrode 39 made of a transparent conductive film such as ITO are laminated on the inner surface side of the base 25A. ing. A phase difference layer 29 is formed on the first control electrode 39 in a region corresponding to the reflective display region R, and a plane made of a transparent conductive film such as ITO covering the phase difference layer 29 and the first control electrode 39. A solid common electrode 31 is formed, and an alignment film (not shown) made of polyimide or the like is formed so as to cover the common electrode 31. The phase difference layer 29 is formed of a liquid crystal material, and is prepared, for example, by applying a liquid crystal monomer or a liquid crystal oligomer on a substrate and polymerizing and curing in a state of being aligned in a predetermined alignment state.

  A tapered region TP is formed on the end face of the retardation layer 29. The tapered region TP has a forward tapered shape in which the cross-sectional area decreases as the distance from the base body 25A increases. The region other than the taper region TP is a flat region FL having a flat surface. The tapered region TP is formed on the outer peripheral portion of the retardation layer 2, and the position of the outer peripheral portion of the tapered region TP matches the position of the outer peripheral portion of the reflective display region R.

  FIG. 3 is a schematic diagram showing the alignment state of the liquid crystal material L in the vicinity of the end face of the retardation layer 29. In the present embodiment, the alignment state of the liquid crystal material (liquid crystal molecules) L constituting the retardation layer 29 is different between the tapered region TP and the flat region FL. The alignment of the liquid crystal material L in the taper region TP is homogeneous alignment, and the alignment of the liquid crystal material L in the flat region FL is bend alignment. Thereby, the average tilt angle (phase difference) per unit layer thickness of the retardation layer 29 in the tapered region TP is greater than the average tilt angle (phase difference) per unit layer thickness of the retardation layer 29 in the flat region FL. Is also getting smaller. When attention is paid to the sum of the phase differences with the phase difference layer 29 and the liquid crystal layer 50, the sum of the phase differences in the taper region TP and the sum of the phase differences in the flat region FL are substantially equal.

[Method for manufacturing liquid crystal display device]
FIG. 4 is a cross-sectional process diagram for explaining the manufacturing method of the liquid crystal display device 100 with a focus on the process of forming the retardation layer 29. FIG. 4 shows only the configuration necessary for the step of forming the retardation layer 29, and other configurations, for example, a color filter layer and an overcoat film disposed on the base 25A are omitted.

  In the step of forming the retardation layer 29, first, as shown in FIG. 4A, the first control electrode 39 having a solid shape in plan view is formed on the entire surface of the base 25A, and the first control electrode 39 of the base 25A is formed. A first alignment film 75 made of polyimide or the like is formed on the surface. The first alignment film 75 is a horizontal alignment film that horizontally aligns a liquid crystal material, which is a material for forming a retardation layer, on a substrate.

  Next, as shown in FIG. 4B, a control substrate 60 on which the second control electrode 61 is formed is prepared, and a second substrate made of polyimide or the like is formed on the surface of the control substrate 60 on which the second control electrode 61 is formed. An alignment film 76 is formed. The second alignment film 76 is a horizontal alignment film that horizontally aligns a liquid crystal material, which is a material for forming a retardation layer, on the substrate. As shown in the plan view of FIG. 5, the second control electrode 61 is formed in a region corresponding to the reflective display region R of the base body 25A. In the case of the present embodiment, the retardation layer is formed in a stripe shape across the plurality of subpixels D1 to D3, and therefore the second control electrode 61 is also formed in a stripe shape across the plurality of subpixels D1 to D3. Yes. The shape and size of the second control electrode 61 match the shape and size of the flat region of the retardation layer. The second control electrode 61 is made of a light-transmitting conductive film that can transmit ultraviolet light such as ITO, and the base of the control substrate on which the second control electrode 61 is formed is made of ultraviolet light such as glass. Therefore, the entire control substrate is a light-transmitting substrate that can transmit ultraviolet rays.

  Returning to FIG. 4B, when the second alignment film 76 is formed on the control substrate 60, the first control electrode 39 of the base body 25 </ b> A and the second control electrode 61 of the control substrate 60 are opposed to each other, and the second control electrode is formed. 61 is positioned in the area | region which forms the phase difference layer on 25 A of base | substrates. The dielectric anisotropy that is a material for forming the retardation layer is positive between the surface of the base body 25A on which the first alignment film 75 is formed and the surface of the control substrate 60 on which the second alignment film 76 is formed ( A material layer 29A made of a positive-type liquid crystal material is disposed. As the liquid crystal material 29A, for example, an ultraviolet curable liquid crystal monomer or liquid crystal oligomer is used.

  Next, as shown in FIG. 4C, a voltage is applied between the first control electrode 39 of the base body 25 </ b> A and the second control electrode 61 of the control substrate 60 to form the electrodes 31 and 61. The liquid crystal material in the material layer 29A is aligned by an electric field. Then, ultraviolet rays UV are irradiated from the control substrate 60 side through the exposure mask 70, and the liquid crystal material in the region corresponding to the light transmitting portion 71H of the exposure mask 70 is polymerized (cured).

  Here, the exposure mask 70 is provided with a light shielding portion 71 and a light transmitting portion 71H where the light shielding portion 71 is not disposed. The shape and size of the translucent part 71 </ b> H coincide with the shape and size of the second control electrode 61. The exposure mask 70 is disposed on the upper portion of the control substrate 70 (on the side opposite to the base body 25A) in a state where the light transmitting portion 71H and the second control electrode 61 are aligned. When the ultraviolet ray UV is irradiated from the upper part of the exposure mask 70, the ultraviolet ray UV that wraps around from the translucent part 71H of the exposure mask 70 to the back side of the exposure mask 70 is obliquely incident on the material layer 29A, and has a trapezoidal area. Is polymerized. The hypotenuse of the trapezoidal region becomes the tapered region of the retardation layer.

  Next, as shown in FIG. 4D, the control substrate 60 is peeled off, and the uncured portion of the material layer 29A is removed with an organic solvent. At this time, it is desirable to form a release layer in advance on the surface of the second control electrode 61 because the retardation layer 29 does not peel from the base body 25A when the control substrate 60 is peeled from the retardation layer 29. As described above, the retardation layer 29 including the tapered region TP and the flat region FL is formed in the region corresponding to the reflective display region of the base 25A.

  FIG. 6 is an explanatory diagram of the alignment state of the liquid crystal material L when a voltage is applied between the second control electrode 61 and the first control electrode 39. When the material layer 29A is sandwiched between the base 25A and the control substrate 60, the liquid crystal material L in the material layer 29A is caused by the alignment regulating force by the alignment films 75 and 76 and the alignment regulating force by the electric field between the electrodes 31 and 61. Orientation is controlled.

  Here, the first control electrode 39 is a solid electrode formed on the entire surface of the display area, and the second control electrode 61 is a stripe electrode formed corresponding to the reflective display area. Therefore, the second control electrode 61 is formed with an area smaller than that of the first control electrode 39, and electric lines of force E obliquely inclined with respect to the control substrate 60 are generated on the outer periphery of the second control electrode 61. . As a result, the influence of the electric field decreases as the distance from the outer periphery of the second control electrode 61 increases, the tilt angle of the liquid crystal material L increases in the region facing the second control electrode 61, and the end of the tapered region TP (the outer peripheral portion). ), The tilt angle becomes smaller.

  Further, since the material layer 29A is sandwiched between the first alignment film 75 and the second alignment film 76, in the flat region FL, the upper surface (surface on the control substrate 60 side) and the lower surface (surface on the base body 25A side) of the retardation layer. The alignment of the liquid crystal material L is horizontal alignment, and the central portion is vertical alignment perpendicular to the substrate. This alignment is similar to the bend alignment, and the liquid crystal material L at the center standing perpendicular to the substrate hardly contributes to a change in the polarization state of light (giving a phase difference). Therefore, the magnitude of the retardation of the flat region FL is determined by the liquid crystal material L of the portion horizontally aligned on the substrate near the upper surface and the lower surface of the retardation layer.

  On the other hand, since the influence of the electric field is small at the end portion (outermost peripheral portion) of the tapered region TP, the liquid crystal material L is horizontally aligned (homogeneous alignment) on the substrate by the alignment regulating force of the alignment film 75. Therefore, the magnitude of the phase is determined approximately by the product of the layer thickness of the retardation layer and the phase of the liquid crystal material L per unit layer thickness.

  This will be described in detail with reference to FIG. In general, when the liquid crystal material is polymerized with ultraviolet rays, the end face of the retardation layer becomes tapered as shown in FIG. In the conventional retardation layer, the region A (flat region) with a large layer thickness and the region B (taper region) with a small layer thickness have the same orientation as shown in FIG. The difference in layer thickness directly becomes the phase difference. That is, if the phase differences in the regions A and B are Γa and Γb, respectively, Γa> Γb.

  On the other hand, in this embodiment, the liquid crystal material L in the region A rises slightly as compared with the liquid crystal material L in the region B as shown in FIG. When attention is paid to the phase difference per thickness, the phase difference per unit layer thickness in the region A is smaller than the phase difference per unit layer thickness in the region B. As a result, the phase difference between the region A and the region B is smaller than that in the case of FIG. 7B (Γa≈Γb), and the entire phase difference including the liquid crystal layer is considered. The phase differences are approximately equal.

  In FIG. 7, the region B is set at the central portion of the tapered region, but this situation is the same in other portions of the tapered region. For example, the portion near the flat region (region A) in the taper region has a large layer thickness, but the influence of the electric field is strong, so that the alignment state is the same as in region A. Therefore, an intermediate phase difference between the region A and the region B is realized. On the other hand, in the portion far from the flat region (the outermost peripheral portion of the tapered region), the layer thickness is small, but the influence of the electric field is small, and the orientation parallel to the substrate is realized. It becomes larger than B. Therefore, when considering the sum of the phase differences between the phase difference layer and the liquid crystal layer, there is not much difference between the region B and the outermost periphery of the tapered region.

  Therefore, in the taper region, the area per unit layer thickness of the retardation layer from the region where the retardation layer is thick (region close to region A) to the region where the retardation layer is thin (region far from region A). Although the phase difference changes continuously, the magnitude of the change is smaller than that of the conventional phase difference layer for the reason described above. Considering the sum of the retardation of the retardation layer and the liquid crystal layer, the thickness of the liquid crystal layer is large in the tapered region, and the thickness of the liquid crystal layer is small in the flat region. The entire retardation layer including the flat region becomes substantially uniform, and an image display with high contrast is realized.

  As described above, according to the liquid crystal display device 100 of the present embodiment, the phase shift between the tapered region TP and the region other than the tapered region (flat region FL) of the retardation layer 29 is reduced. Therefore, when considering the net phase difference formed by the phase difference layer 29 and the liquid crystal layer 50 (the sum of the phase difference of the phase difference layer 29 and the phase difference of the liquid crystal layer 50), the magnitude of the phase difference in the tapered region TP is large. The height can be made close to the magnitude of the phase difference in the flat region FL. As a result, light leakage (polarization deviation) generated in the tapered region TP of the retardation layer 29 is eliminated, and an image display with high contrast can be realized. In this embodiment, the orientation of the liquid crystal material L constituting the retardation layer 29 is controlled by the first alignment film 75 disposed on the lower surface portion of the retardation layer and the second alignment film 76 disposed on the upper surface portion of the retardation layer. Therefore, it is easy to realize a desired orientation as compared with a normal retardation layer in which the orientation is controlled only by the orientation film on the lower surface portion of the retardation layer.

  In the present embodiment, the retardation layer 29 is formed on the first control electrode 39 of the counter substrate 25, but the retardation layer 29 may be formed on the pixel electrode 9 of the element substrate 10. In this case, since the pixel electrode 9 is formed for each sub-pixel, the second control electrode 61 is also formed for each sub-pixel. The second control electrode is preferably formed to have the same size as or slightly smaller than the reflective display pixel electrode 9r. This is because the tapered region of the retardation layer is formed outside the second control electrode by the diffracted light that wraps around the back side of the exposure mask.

  In this embodiment, the alignment state of the liquid crystal material L in the flat region FL of the retardation layer 29 is bend alignment. However, the alignment state of the liquid crystal material L in the flat region FL is not limited to this, and the retardation layer is designed. Can be changed based on request. For example, the second alignment film formed on the control substrate 60 side may be a vertical alignment film, and the alignment of the liquid crystal material L in the flat region FL may be hybrid aligned. Also in this case, the phase shift between the flat region FL and the taper region TP can be reduced for the same reason as in the above embodiment.

  In the present embodiment, the first control electrode 39 is formed separately from the common electrode 31 for driving the liquid crystal. However, the first control electrode 39 may also be used as the common electrode for driving the liquid crystal, and the common electrode 31 may be omitted. it can. That is, in the liquid crystal display device 100 of this embodiment, the first control electrode 39 is formed only for forming the retardation layer 29, and after the retardation layer 29 is formed, the first control electrode 39 is used for driving the liquid crystal. The structure does not function as an electrode. However, the step of forming the common electrode 31 can be omitted by causing the first control electrode 39 to function not only as an electrode for forming the retardation layer but also as a common electrode.

  In this embodiment, the striped electrode shown in FIG. 5 is used as the second control electrode 61. The second control electrode 61 in FIG. 5 has a uniform resistance throughout the electrode. In the present invention, the second control electrode 65 of FIG. 8 can be used instead of the second control electrode 61 of FIG. In the second control electrode 65, the resistance of the central portion 62 is smaller than the resistance of the outer peripheral portion 63. The magnitude of the resistance can be controlled, for example, by making the film thickness of the electrode in the central portion 62 different from the film thickness of the electrode in the outer peripheral portion 63. According to the second control electrode 65 in FIG. 8, the electric field strength can be controlled more precisely than in the case where the second control electrode 61 in FIG. 5 is used, and the phase of the retardation layer 29 can be easily controlled.

  Further, in the present embodiment, the liquid crystal display device 100 has been described as a vertical electric field type liquid crystal display device in which liquid crystal is driven by an electric field (vertical electric field) perpendicular to the substrate. However, the present invention is not limited to such a liquid crystal display device, and the present invention can also be applied to a horizontal electric field mode liquid crystal display device such as an IPS mode or an FFS mode. In this case, no electrode for driving the liquid crystal is formed on the counter substrate side. Therefore, the first control electrode formed on the counter substrate is also used only for forming the retardation layer, and does not function as an electrode for driving the liquid crystal.

[Electronics]
FIG. 9 is a schematic perspective view of a mobile phone 1300 which is an example of the electronic apparatus of the present invention. A cellular phone 1300 includes the liquid crystal display device of the present invention as a small-sized display portion 1301, and includes a plurality of operation buttons 1302, an earpiece 1303, and a mouthpiece 1304. The liquid crystal display device of the above embodiment is not limited to a mobile phone, but is an electronic book, a personal computer, a digital still camera, a liquid crystal television, a viewfinder type or a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator. , Word processors, workstations, videophones, POS terminals, devices equipped with a touch panel, etc., and can be suitably used as image display means. In any electronic device, both high-brightness and high-contrast are provided for both reflective display and transmissive display. Image display can be realized.

It is a top view of 1 pixel of a liquid crystal display device. It is sectional drawing of the liquid crystal display device. It is a schematic diagram which shows the orientation state of the liquid-crystal material of the end surface vicinity of a phase difference layer. It is explanatory drawing explaining the manufacturing method of a liquid crystal display device centering on the formation process of retardation layer. It is a top view of the control board used with the manufacturing method. It is explanatory drawing of the orientation state of the liquid-crystal material at the time of a voltage application. It is explanatory drawing explaining the effect of this invention. It is a top view of the other structural example of the control board used with the manufacturing method of a liquid crystal display device. It is a schematic perspective view of the mobile telephone which is an example of an electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 ... Pixel electrode, 10 ... Element substrate, 10A ... Base | substrate (translucent substrate), 25 ... Opposite substrate, 25A ... Base | substrate (translucent substrate), 29 ... Retardation layer, 31 ... Common electrode, 39 ... 1st Control electrode, 40 ... retardation layer, 50 ... liquid crystal layer, 60 ... control substrate, 61 ... second control electrode, 65 ... second control electrode, 70 ... exposure mask, 71H ... translucent part, 75 ... first alignment film 76 ... second alignment film, 100 ... liquid crystal display device, 1300 ... mobile phone (electronic device), L ... liquid crystal material, FL ... flat region, TP ... tapered region, UV ... ultraviolet light

Claims (10)

A liquid crystal display device comprising: a pair of substrates; a liquid crystal layer sandwiched between the pair of substrates; and a retardation layer provided on a liquid crystal layer side of one of the pair of substrates. ,
A tapered region is formed on the end face of the retardation layer, and the retardation per unit layer thickness of the retardation layer in the tapered region is a retardation per unit layer thickness of the retardation layer in a region other than the tapered region. A liquid crystal display device characterized by being larger.   In the tapered region, the retardation per unit layer thickness of the retardation layer continuously changes from a region where the retardation layer is thick to a region where the retardation layer is thin. The liquid crystal display device according to claim 1.   The phase difference layer is formed of a liquid crystal material, and the alignment state of the liquid crystal material in the tapered region is different from the alignment state of the liquid crystal material in a region other than the tapered region. Liquid crystal display device.   4. The liquid crystal display device according to claim 3, wherein the liquid crystal material is homogeneously aligned at an end of the tapered region, and the liquid crystal material is bend aligned in a region other than the tapered region. A liquid crystal display device comprising: a pair of substrates; a liquid crystal layer sandwiched between the pair of substrates; and a retardation layer provided on a liquid crystal layer side of one of the pair of substrates. ,
The retardation layer is formed of a liquid crystal material, a tapered region is formed on an end surface of the retardation layer, and an average tilt angle of the liquid crystal material per unit layer thickness of the retardation layer in the tapered region is A liquid crystal display device, wherein an average tilt angle of the liquid crystal material per unit layer thickness of the retardation layer in a region other than the tapered region is smaller. A method for manufacturing a liquid crystal display device, comprising: a pair of substrates; a liquid crystal layer sandwiched between the pair of substrates; and a retardation layer provided on a liquid crystal layer side of one of the pair of substrates. Because
The step of forming the retardation layer comprises
Forming a first control electrode on the one substrate;
Forming a first alignment film on the surface of the one substrate on which the first control electrode is formed to align the liquid crystal material horizontally with the substrate;
A control substrate having a second control electrode having a smaller area than the first control electrode of the one substrate is prepared, and a liquid crystal material is applied to the surface of the control substrate on which the second control electrode is formed. Forming a second alignment film to be horizontally aligned;
The first control electrode and the second control electrode are opposed to each other, and between the surface of the one substrate on which the first alignment film is formed and the surface of the control substrate on which the second alignment film is formed. Arranging a liquid crystal material having a positive dielectric anisotropy, which is a material for forming the retardation layer,
Applying a voltage between the first control electrode and the second control electrode, and orienting the liquid crystal material by an electric field formed between the first control electrode and the second control electrode;
An exposure mask having a translucent portion having the same planar shape as the second control electrode is prepared, the translucent portion of the exposure mask and the second control electrode of the control substrate are opposed, and the control substrate side And a step of curing the liquid crystal material by irradiating ultraviolet rays through an exposure mask.   The method for manufacturing a liquid crystal display device according to claim 6, further comprising a step of forming a release layer on a surface of the second control electrode before forming the second alignment film on the control substrate.   The method of manufacturing a liquid crystal display device according to claim 6, wherein a resistance of a central portion of the second control electrode is smaller than a resistance of an outer peripheral portion of the second control electrode.   The method of manufacturing a liquid crystal display device according to claim 6, wherein the first control electrode functions as an electrode for driving the liquid crystal layer after the retardation layer is formed.   An electronic apparatus comprising the liquid crystal display device according to claim 1.

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