JP5315852B2 - Method for manufacturing retardation substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology suitable for optical compensation of a liquid crystal display device for displaying a multi-color image. <P>SOLUTION: A retardation substrate 20 includes: a substrate 210; a solidification liquid crystal layer 230 as a continuous film including regions 230a to 230c; and a birefringence layer 240 which faces the substrate 210 by holding the solidification liquid crystal layer 230 in between. Each of the regions 230a to 230c has an optical axis in a thickness direction vertical to a main face of the substrate 210, and a refractive index in the thickness direction is larger than that in a direction parallel to the main face, and the refractive index in the thickness direction is different from each other. The birefringence layer 240 has an optical axis which is parallel to the main face, and the refractive index in a first face direction which is parallel to the optical axis is larger than the refractive index in a second face direction, which is parallel to the main face, and vertical to the first face direction, and the refractive index in the thickness direction. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical technique applicable to a display device such as a liquid crystal display device.

  The liquid crystal display device has features such as thinness, light weight, and low power consumption. Therefore, in recent years, the use in fixed devices such as portable devices and television receivers has been rapidly increasing.

  When displaying a multicolor image on a liquid crystal display device, a color filter is used. For example, a transmissive or reflective liquid crystal display device capable of displaying a multicolor image generally uses a color filter including red, green, and blue colored regions. Further, a transflective liquid crystal display device capable of displaying a multicolor image generally includes a color filter including red, green and blue colored regions for transmissive display and red, green and blue colored regions for reflective display. I use it.

  In-plane switching (IPS) system and fringe field switching (FFS) system are attracting attention as display systems for liquid crystal display devices capable of displaying these multicolor images, particularly for liquid crystal display devices used in large-screen television receivers. ing. In the liquid crystal display device adopting the IPS mode and the FFS mode, all electrodes for changing the alignment state of liquid crystal molecules are formed only on one of the two substrates constituting the liquid crystal display panel. The liquid crystal molecules exhibit homogeneous alignment when no voltage is applied.

  According to the IPS system or the FFS system, a wider viewing angle can be achieved as compared with other display systems. In recent years, use of an optical element for optical compensation has been studied in order to further expand the viewing angle of a liquid crystal display device employing an IPS mode or an FFS mode.

  For example, Patent Document 1 describes a liquid crystal display panel including a liquid crystal cell, a first optical element, and a second optical element interposed therebetween. The liquid crystal molecules contained in the liquid crystal cell exhibit homogeneous alignment in a state where no voltage is applied to the liquid crystal layer. Each of the first and second optical elements has a main refractive index nz in the thickness direction. In the first optical element, the main refractive indexes nx and ny in the in-plane direction and the main refractive index nz in the thickness direction satisfy the relationship represented by the formula: nz> nx = ny. In the second optical element, the main refractive indexes nx and ny in the in-plane direction and the main refractive index nz in the thickness direction satisfy the relationship represented by the formula: nx> ny = nz.

Patent Document 2 describes that a retardation film including an optically anisotropic film and a retardation layer formed thereon is used in an IPS liquid crystal display device. The optically anisotropic film has a slow axis and a fast axis in the in-plane direction. In the retardation layer, the refractive indexes nx and ny in two directions orthogonal to each other in the plane and the refractive index nz in the thickness direction satisfy the relationship represented by the formula: nx ≦ ny <nz.
JP 2007-206605 A JP 2008-122885 A

The above-described technique is effective for optical compensation of a liquid crystal display device that displays a monochromatic image, but does not show high effectiveness for optical compensation of a liquid crystal display device that displays a multicolor image.
An object of the present invention is to provide a technique suitable for optical compensation of a liquid crystal display device that displays a multicolor image.

According to one aspect of the present invention, a solidified liquid crystal layer is formed on one main surface of a light-transmitting substrate, and an optical axis parallel to the main surface is provided, and a first surface parallel to the optical axis The refractive index in the inward direction is greater than the refractive index in the second in-plane direction that is parallel to the main surface and perpendicular to the first in-plane direction and the refractive index in the thickness direction perpendicular to the main surface. Providing a birefringent layer on the solidified liquid crystal layer, the formation of the solidified liquid crystal layer includes a photopolymerizable or photocrosslinkable thermotropic liquid crystal compound supported by the main surface, At least three regions of the liquid crystal material layer in which the mesogen of the thermotropic liquid crystal compound has a homeotropic structure are exposed with different exposure amounts, and a polymerized or crosslinked product of the thermotropic liquid crystal compound is formed in the liquid crystal material layer. Including the first region and the polymerization or rack A second region containing a product and the thermotropic liquid crystal compound as an unreacted compound, wherein the content of the polymerized or crosslinked product is lower than that of the first region, and the polymerized or crosslinked product and an unreacted product. An exposure process comprising forming a third region having a lower content of the polymerized or crosslinked product compared to the second region, and the thermotropic liquid crystal compound as a reactive compound; The liquid crystal material layer is heated to a temperature equal to or higher than a phase transition temperature at which the thermotropic liquid crystal compound changes from a liquid crystal phase to an isotropic phase to reduce the degree of orientation of the mesogen at least in the second and third regions. And a development process including a fixing process for polymerizing and / or crosslinking the unreacted compound while reducing the degree of orientation. Method for producing ® emission substrate.

  According to the present invention, a technique suitable for optical compensation of a liquid crystal display device that displays a multicolor image is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same referential mark is attached | subjected to the component which exhibits the same or similar function through all drawings, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a cross-sectional view schematically illustrating a liquid crystal display device according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a retardation substrate included in the liquid crystal display device shown in FIG.

  1 and 2, the X direction and the Y direction are parallel to the display surface and intersect each other, and the Z direction is a direction perpendicular to the X direction and the Y direction. Here, as an example, it is assumed that the X direction and the Y direction are orthogonal to each other.

The liquid crystal display device shown in FIG. 1 is an active matrix liquid crystal display device employing an IPS method.
This liquid crystal display device includes a liquid crystal display panel and a backlight (not shown). The liquid crystal display panel includes an array substrate 10, a counter substrate 20, a liquid crystal layer 30, and a pair of polarizing plates 40.

  The array substrate 10 includes a substrate 110. The substrate 110 is a light transmissive substrate such as a glass plate or a resin plate.

On one main surface of the substrate 110, the scanning lines and the common electrode 120b are arranged.
Each scanning line extends in the X direction, and is arranged in the Y direction corresponding to a row of pixels to be described later. Each scanning line includes a plurality of projecting portions each projecting in the Y direction corresponding to the pixel column. These protrusions constitute a gate 120a.

The common electrode 120b includes an electrode body and a wiring part.
For example, the electrode bodies are arranged in the X direction and the Y direction corresponding to the pixels. At least a part of each electrode body includes, for example, a portion extending in an oblique direction with respect to the Y direction. Here, as an example, each electrode body has a portion in which the length direction forms an angle of + 45 ° with respect to the Y direction and a portion that forms an angle of −45 ° are alternately connected in the Y direction. And a triangular wave shape.

  Each of the wiring portions extends in the X direction, and is arranged in the Y direction corresponding to the pixel row. Each wiring part electrically connects electrode bodies arranged in the X direction to each other.

  The scan line and the common electrode 120 b are covered with an insulating layer 130. A portion of the insulating layer 130 covering the gate 120a is used as a gate insulating film. The insulating layer 130 is typically transparent when covering the substrate 110.

  On the insulating layer 130, the semiconductor layers 140 are arranged in the X direction and the Y direction corresponding to the pixels. Each semiconductor layer 140 is formed so as to straddle the gate 120a. The semiconductor layer 140 includes a channel region that faces the gate 120a and is used as a channel, and an impurity diffusion region that is arranged in the X direction and is used as a source and a drain. The gate 120a, the gate insulating film, and the semiconductor layer 140 constitute a thin film transistor that is a switching element.

On the insulating layer 130, signal lines 150a and pixel electrodes 150b1 and 150b2 are further arranged.
Each of the signal lines 150a extends in the Y direction, and is arranged in the X direction corresponding to the pixel column.

  Pixel electrodes 150b1 and 150b2 form a pair. Pairs of the pixel electrode 150b1 and the pixel electrode 150b2 are arranged in the X direction and the Y direction corresponding to the pixels. The pixel electrode 150b1 and the pixel electrode 150b2 forming a pair have an electrode body of the common electrode 120b interposed therebetween. The end surfaces of the pixel electrode 150b1 and the electrode body facing each other are substantially parallel. Similarly, the end surfaces of the pixel electrode 150b2 and the electrode body facing each other are substantially parallel. The pixel electrodes 150b1 and 150b2 may have light transmittance or may not have light transmittance.

  Each pixel electrode 150b1 covers one impurity diffusion region of the semiconductor layer 140. Thereby, each pixel electrode 150b1 is connected to the signal line 150a via the switching element. Each pixel electrode 150b1 and the pixel electrode 150b2 paired therewith are electrically connected to each other. Each pixel is a portion of the liquid crystal display panel corresponding to the paired pixel electrodes 150a and 150b and a region sandwiched between them.

  The insulating layer 130, the switching element, the signal line 150a, and the pixel electrodes 150b1 and 150b2 are covered with an alignment film 160. The alignment film 160 aligns the liquid crystal molecules included in the liquid crystal layer 30 so that, for example, the azimuth angle in the length direction of the mesogen is substantially parallel to the Y direction in the state where no voltage is applied. The alignment film 160 is, for example, a transparent resin layer such as a polyimide film subjected to an alignment process such as a rubbing process or an optical alignment process.

  The counter substrate 20 includes a substrate 210. The substrate 210 faces the alignment film 160. The substrate 210 is a light transmissive substrate such as a glass plate or a resin plate.

  A color filter layer 220, a solidified liquid crystal layer 230, a birefringent layer 240, and an alignment film 260 are formed in this order on the surface of the substrate 210 facing the alignment film 160. The color filter layer 220 may be interposed between the solidified liquid crystal layer 230 and the birefringent layer 240, or may be interposed between the birefringent layer 240 and the alignment film 260. Alternatively, the color filter layer 220 may be provided on the array substrate 10 instead of being provided on the counter substrate 20.

  The color filter layer 220 includes colored regions 220 a to 220 c arranged on one main surface of the substrate 210.

  The colored regions 220a to 220c have different absorption spectra. That is, the colored regions 220a to 220c transmit light having different spectra when the color filter layer 220 is irradiated with white light. For example, the colored region 220a mainly transmits light having a longer wavelength compared to the colored region 220b, and the colored region 220c mainly transmits light having a shorter wavelength than the colored region 220b. Here, as an example, when white light is irradiated, the colored region 220a transmits red light, the colored region 220b transmits green light, and the colored region 220c transmits blue light.

  The colored regions 220a to 220c are arranged corresponding to the pixel columns. Each of the colored regions 220a extends in the Y direction and forms a plurality of strip patterns arranged in the X direction. The colored region 220b extends in the Y direction, and forms a plurality of strip patterns arranged so as to be adjacent to the colored region 220a in the X direction. The colored region 220c extends in the Y direction, and forms a plurality of strip patterns arranged so as to be adjacent to the colored regions 220a and 220b in the X direction. That is, the colored regions 220a to 220c form a stripe arrangement.

  The colored regions 220a to 220c may form other arrangements. For example, the colored regions 220a to 220c may form a square array or a delta array.

  The solidified liquid crystal layer 230 is a retardation layer. The solidified liquid crystal layer 230 is formed by polymerizing and / or crosslinking a thermotropic liquid crystal compound or composition.

  The solidified liquid crystal layer 230 faces the substrate 210 with the color filter layer 220 interposed therebetween.

  An alignment film may be interposed between the solidified liquid crystal layer 230 and the color filter layer 220. As this alignment film, for example, a vertical alignment film can be used.

  The solidified liquid crystal layer 230 may be interposed between the substrate 210 and the color filter layer 220. However, when a structure in which the color filter layer 220 is interposed between the substrate 210 and the solidified liquid crystal layer 230 is employed, the color filter layer 220 can be formed on a substantially flat surface. In this case, the solidified liquid crystal layer 230 is not exposed to the heat treatment necessary for manufacturing the color filter layer 220.

  The solidified liquid crystal layer 230 includes regions 230a to 230c arranged perpendicular to the Z direction. The regions 230a to 230c face the colored regions 220a to 220c, respectively.

  In each of the regions 230a to 230c, the mesogen forms an alignment structure. That is, each of the regions 230a to 230c has refractive index anisotropy.

  Each of the regions 230a to 230c is a positive C plate corresponding to a homeotropic alignment in which the length direction of the mesogen is aligned in a direction substantially parallel to the Z direction. That is, each of the regions 230a to 230c has an optical axis in the Z direction, and the refractive index in the Z direction is larger than the refractive index in the direction perpendicular thereto.

  The regions 230a to 230c have different refractive indexes in the Z direction. Here, as an example, the region 230a has a higher refractive index in the Z direction than the region 230b, and the region 230c has a lower refractive index in the Z direction than the region 230b.

  For example, in each of the regions 230a to 230c, the degree of mesogen orientation is substantially uniform. The region 230a has a higher degree of mesogen orientation than the region 230b, and the region 230c has a lower mesogen orientation than the region 230b.

  The “degree of mesogen orientation” in a certain region means the degree of mesogen orientation in that region. The degree of orientation of the mesogen may be constant throughout the region or may vary along the Z direction. For example, in a certain region, the degree of orientation may be higher near the lower surface and the degree of orientation may be lower near the upper surface. In this case, “degree of orientation of mesogen” indicates an average of the degree of orientation of mesogen in the thickness direction. It can be confirmed by comparing the refractive index anisotropy of a certain region that the degree of orientation is larger than that of the other region.

  The regions 230a to 230c have different thickness direction retardations Rth. For example, the ratio of the thickness direction retardation Rth of the region 230a to the thickness direction retardation Rth of the region 230b is in the range of 1.15 to 1.45, and the thickness direction retardation Rth of the region 230b is relative to the thickness direction retardation Rth. The ratio of the thickness direction retardation Rth of the region 230c is in the range of 0.70 to 0.90.

  Here, the “thickness direction retardation Rth” of each of the regions 230a to 230c is calculated from the in-plane refractive indexes nx and ny and the thickness direction refractive index nz and the thickness d at a specific wavelength. Can do. Specifically, the thickness direction retardation Rth of the region 230a is obtained by subtracting the refractive index nz from the average of the refractive indexes nx and ny of the region 230a at a specific wavelength, here 535 nm, and the thickness d. The product of [(nx + ny) / 2−nz] × d. The thickness direction retardation Rth of the region 230b is the product of the value obtained by subtracting the refractive index nz from the average of the refractive indexes nx and ny of the region 230b at the specific wavelength and the thickness d [(nx + ny) / 2-nz] × d. The thickness direction retardation Rth of the region 230c is the product of the value obtained by subtracting the refractive index nz from the average of the refractive indexes nx and ny of the region 230c at the above specific wavelength and the thickness d [(nx + ny) / 2-nz] × d. Typically, the refractive indexes nx and ny are substantially equal in each of the regions 230a to 230c.

  The solidified liquid crystal layer 230 may have a non-uniform thickness, but typically has a uniform thickness throughout. In this case, it is easy to control the optical characteristics of the solidified liquid crystal layer 230.

  The solidified liquid crystal layer 230 may be patterned, but is typically a continuous film. When the solidified liquid crystal layer 230 is a continuous film, it is not necessary to perform development for removing unpolymerized and uncrosslinked thermotropic liquid crystal compounds or compositions in the manufacturing process.

  The birefringent layer 240 covers the solidified liquid crystal layer 230. The birefringent layer 240 has an optical axis perpendicular to the Z direction. In the birefringent layer 240, the refractive index in the first in-plane direction parallel to the optical axis is perpendicular to the Z direction and the refractive index in the second in-plane direction perpendicular to the first in-plane direction and Z Greater than the refractive index in the direction. Here, as an example, it is assumed that the first in-plane direction is parallel to the Y direction.

  The birefringent layer 240 may be a stretched film, but is typically formed by polymerizing and / or crosslinking a liquid crystal compound or composition. That is, the birefringent layer 240 is typically a positive A plate corresponding to a homogeneous orientation in which the length direction of the mesogen is aligned in one direction substantially perpendicular to the Z direction.

  When the birefringent layer 240 is formed by polymerizing and / or crosslinking a liquid crystal compound or composition, an alignment film may be interposed between the birefringent layer 240 and the solidified liquid crystal layer 230. As this alignment film, for example, a transparent resin layer subjected to an alignment process such as a rubbing process or an optical alignment process can be used.

  The birefringent layer 240 may be patterned, but is typically a continuous film. The birefringent layer 240 typically has uniform optical characteristics over the entire surface. The birefringent layer 240 typically has a uniform thickness over the entire surface.

  The alignment film 260 covers the birefringent layer 240. The alignment film 260 aligns the liquid crystal molecules included in the liquid crystal layer 30 so that, for example, the azimuth angle of the length direction of the mesogen is substantially parallel to the Y direction when no voltage is applied. The alignment film 260 is, for example, a transparent resin layer such as a polyimide film subjected to an alignment process such as a rubbing process or an optical alignment process.

  The substrate 210, the color filter layer 220, the solidified liquid crystal layer 230, and the birefringent layer 240 constitute a retardation substrate. The retardation substrate may further include other components. For example, the retardation substrate may further include a black matrix. Alternatively, the color filter layer 220 may be omitted from the retardation substrate.

  The array substrate 10 and the counter substrate 20 are bonded together via a frame-shaped adhesive layer (not shown). The array substrate 10, the counter substrate 20, and the adhesive layer form a hollow structure.

  The liquid crystal layer 30 is made of a liquid crystal compound or a liquid crystal composition. This liquid crystal compound or liquid crystal composition has fluidity and fills a space surrounded by the array substrate 10, the counter substrate 20, and the adhesive layer. The array substrate 10, the counter substrate 20, the adhesive layer, and the liquid crystal layer 30 form a liquid crystal cell.

  Here, as an example, the liquid crystal compound included in the liquid crystal layer 30 is a liquid crystal molecule having a positive dielectric anisotropy including a rod-shaped mesogen, and the mesogen of the liquid crystal molecule is substantially parallel to the X direction when no voltage is applied. Is oriented. When a voltage is applied, the mesogens of the liquid crystal molecules are substantially perpendicular to the Z direction and inclined with respect to the X direction, for example, an angle of + 45 ° or −45 ° with respect to the X direction. It shall be oriented in the direction where it is. Then, the retardation of the liquid crystal cell at the time of voltage application is set to ½ of the wavelength of visible light. Specifically, the retardation of the liquid crystal cell when a voltage is applied is, for example, ½ of 535 nm. Alternatively, the retardation of the liquid crystal cell at the time of voltage application is ½ of the wavelength of light transmitted through the region 220a in the portion corresponding to the region 220a, and the wavelength of light transmitted through the region 220b in the portion corresponding to the region 220b. Of the light that is transmitted through the region 220c in the portion corresponding to the region 220c.

  The polarizing plate 40 is attached to both main surfaces of the liquid crystal cell. These polarizing plates 40 are linearly polarizing plates, and are typically arranged so that their transmission axes are orthogonal to each other. Here, as an example, the polarizing plate 40 attached to the array substrate 10 is a linear polarizing plate having a transmission axis parallel to the X direction, and the polarizing plate 40 attached to the counter substrate 20 is the Y direction. It is assumed that the linear polarizing plate has a transmission axis parallel to.

  The backlight faces the liquid crystal cell with the polarizing plate 40 attached to the array substrate 10 interposed therebetween. For example, the backlight irradiates white light toward the liquid crystal cell.

  The above-described configuration shows high effectiveness in optical compensation of a liquid crystal display device that displays a multicolor image. A simulation result indicating this will be described below. In the following description, the results of a simulation performed on a liquid crystal display device that is substantially the same as that described with reference to FIGS. 1 and 2 are illustrated, but the present invention is not limited to these.

First, conditions set in common in this simulation will be described.
(Common condition 1-Polarizing plate)
The polarizing plate 40 has a single transmittance of 40.24%, 43.52%, and 43.95% at wavelengths of 450 nm, 535 nm, and 630 nm, respectively, and the two are arranged so that the transmission axes are parallel to each other. Transmittance at wavelengths of 450 nm, 535 nm, and 630 nm are 32.19%, 37.57%, and 38.28%, respectively, and when the two pieces are arranged so that the transmission axes are orthogonal to each other, The transmission was assumed to have polarizers of 0.015%, 0.004%, and 0.001%, respectively. On both sides of the polarizer, the light transmittance is 100%, the in-plane refractive index is 1.5005 regardless of the wavelength, and the refractive index in the thickness direction is 1.5000 regardless of the wavelength, It was assumed that a protective layer having a thickness of 80 μm was bonded. The spectral transmission characteristics of these polarizing plates 40 are shown in FIGS.

  FIG. 3 is a graph showing the spectral transmission characteristics of each polarizing plate assumed in the simulation. FIG. 4 is a graph showing the spectral transmission characteristics of a laminate in which two polarizing plates each having the spectral transmission characteristics shown in FIG. 3 are stacked so that the transmission axes are parallel to each other. FIG. 5 is a graph showing the spectral transmission characteristics of a laminate in which two polarizing plates each having the spectral transmission characteristics shown in FIG. 3 are overlapped so that the transmission axis is vertical. In the figure, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance.

(Common condition 2-Glass substrate)
Glass substrates 110 and 210 were assumed to have a refractive index and transmittance of 1.5 and 100%, respectively, regardless of wavelength. The thickness of the glass substrates 110 and 210 was 0.7 mm.

(Common condition 3-color filter)
The colored region 220a has transmittances of 0.4%, 0.1%, and 94.3% at wavelengths of 450 nm, 535 nm, and 630 nm, respectively, and the chromaticity coordinates x and y are 0. 650 and 0.335, and the red color region where the tristimulus value Y is 20.1.

  The colored region 220b has transmittances of 0.2%, 82.3%, and 0.7% at wavelengths of 450 nm, 535 nm, and 630 nm, respectively, and the chromaticity coordinates x and y are each 0. 275 and 0.600, and the green color region where the tristimulus value Y is 53.7.

  The colored region 220c has transmittances of 82.4%, 8.6%, and 0.1% at wavelengths of 450 nm, 535 nm, and 630 nm, respectively, and the chromaticity coordinates x and y are 0. 135 and 0.102, and the blue color region where Y of the tristimulus value is 11.6.

  The refractive index of the colored regions 220a to 220c is assumed to be 1.7 regardless of the wavelength, and the thickness is assumed to be 1.8 μm.

Table 1 summarizes the color characteristics of the colored regions 220a to 220c. The spectral transmission characteristics of the colored regions 220a to 220c are shown in FIGS.

  FIG. 6 is a graph showing the spectral transmission characteristics of the red colored region assumed in the simulation. FIG. 7 is a graph showing the spectral transmission characteristics of the green colored region assumed in the simulation. FIG. 8 is a graph showing the spectral transmission characteristics of the blue colored region assumed in the simulation. In the figure, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance.

(Common condition 4-Liquid crystal layer)
The liquid crystal layer 30 has refractive indexes of 1.5508, 1.5559, and 1.5593 in the major axis direction at wavelengths of 450 nm, 535 nm, and 630 nm, that is, the length direction of mesogen, respectively, and a minor axis at wavelengths of 450 nm, 535 nm, and 630 nm. The refractive index in the direction, that is, the direction orthogonal to the major axis direction is assumed to be 1.4604, 1.4702, and 1.4768, respectively. The thickness of the liquid crystal layer 30 was 3.6 μm. The azimuth angle of the length direction of the mesogen with respect to the X direction is 0 ° in the black display state (no voltage applied state), and 0 in the region from the both interfaces to 0.2 μm in the white display state (voltage applied state). It was 45 ° in other regions. The pretilt angle was 1 ° in both the black display state and the white display state. The transmittance was assumed to be 100% regardless of the wavelength.

  FIG. 9 shows the refractive index of the liquid crystal layer assumed in the simulation. In FIG. 9, the horizontal axis indicates the wavelength, and the vertical axis indicates the refractive index. In the drawing, “major axis” and “minor axis” indicate the refractive indexes in the major axis direction and the minor axis direction, respectively.

(Common condition 5-Positive C plate)
Each of the regions 230a to 230c is a uniaxial optically anisotropic element having a slow axis in the thickness direction. The average refractive indexes of the regions 230a to 230c at wavelengths of 450 nm, 535 nm, and 630 nm are 1.6045, 1.5932, and 1.5831, respectively, and the birefringence at the wavelength of 535 nm is 1, and the double refractive index is 450 nm and 630 nm. The relative values of the refractive index were 1.0916 and 0.9525, respectively. The transmittance of each of the regions 230a to 230c is assumed to be 100% regardless of the wavelength.

  Here, the “average refractive index” is an average of the refractive index nz in the direction parallel to the optical axis and the refractive indexes nx and ny in two directions perpendicular to the optical axis and orthogonal to each other (nx + ny + nz) / 3. The “birefringence” is a difference nz−nx between the refractive index nz and the refractive index nx. The refractive index ny is equal to the refractive index nx.

  FIG. 10 shows the refractive index of each region of the solidified liquid crystal layer assumed in the simulation. FIG. 11 shows the birefringence ratio of each region of the solidified liquid crystal layer assumed in the simulation. In FIG. 10, the horizontal axis indicates the wavelength, and the vertical axis indicates the refractive index. In FIG. 11, the horizontal axis represents the wavelength, and the vertical axis represents the birefringence ratio, that is, the relative value of the birefringence when the birefringence at the wavelength of 535 nm is 1.

(Common condition 6-Positive A plate)
The birefringent layer 240 is assumed to be a uniaxial optically anisotropic element having a slow axis in the plane. The optical characteristics of the birefringent layer 240 are the same as those of the solidified liquid crystal layer 230 except that the direction of the optical axis is different.

(Common condition 7—Configuration of display device)
In the liquid crystal display device described with reference to FIGS. 1 and 2, the polarizing plate 40 attached to the array substrate 10 is a linear polarizing plate having a transmission axis parallel to the X direction. The attached polarizing plate 40 is a linear polarizing plate having a transmission axis parallel to the Y direction. The birefringent layer 240 is assumed to have a slow axis parallel to the Y direction. For the constituent elements other than those for which the optical characteristics are defined in the common conditions 1 to 6, the optical characteristics do not affect the display characteristics of the liquid crystal display device.

  In addition, the thickness direction retardation Rth of the region 230b for light having a wavelength of 535 nm was −210 nm, and the in-plane retardation Re of the birefringent layer 240 for light having a wavelength of 535 nm was 130 nm. The in-plane retardation Re of the birefringent layer 240 is the difference nx−ny between the refractive index nx in the direction parallel to the slow axis and the refractive index ny in the direction parallel to the fast axis and the thickness d. (Nx−ny) × d.

<Simulation 1>
The solidified liquid crystal layer 230 was assumed to have a thickness of 2.20 μm throughout. Regarding the region 230a, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.667. Regarding the region 230b, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.657. Regarding the region 230c, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.650.

  Simulation was performed under these conditions. As a result, the contrast ratio when the polar angle with respect to the Z direction is 45 ° is 540, 750, respectively when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °. 780 and 550. The contrast ratio when the polar angle with respect to the Z direction is 60 ° is 200, 200, and 220 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. And 200.

Table 2 summarizes the optical characteristics set for the solidified liquid crystal layer 230. Table 3 and FIG. 12 show the contrast ratio and viewing angle characteristics obtained by the simulation.

  FIG. 12 is a graph showing the viewing angle dependence of the contrast ratio obtained by the simulation 1. In the figure, the angle described on the outer periphery of the circle drawn with a solid line represents the azimuth angle, and the distance from the center of the circle represents the polar angle. The polar angle at the center of the circle is 0 °, and the polar angle at the position of the circle drawn by a solid line is 80 °. The curves in the circle are obtained by connecting coordinates having the same contrast ratio, and the numerical values attached to these curves represent the contrast ratio.

<Simulation 2>
The solidified liquid crystal layer 230 has a thickness of 2.45 μm throughout. Regarding the region 230a, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.667. Regarding the region 230b, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.650. Regarding the region 230c, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.639.

  Simulation was performed under these conditions. As a result, the contrast ratio when the polar angle with respect to the Z direction is 45 ° is 780, 900, when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. 940 and 790. The contrast ratio when the polar angle with respect to the Z direction is 60 ° is 300, 240, 260 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. And 300.

Table 4 summarizes the optical characteristics set for the solidified liquid crystal layer 230. Table 5 and FIG. 13 show the contrast ratio and viewing angle characteristics obtained by the simulation. The graph shown in FIG. 13 depicts the viewing angle dependence of the contrast ratio in the same manner as described with reference to FIG.

<Simulation 3>
The solidified liquid crystal layer 230 was assumed to have a thickness of 2.67 μm throughout. Regarding the region 230c, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.667. Regarding the region 230b, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.646. Regarding the region 230a, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.633.

  Simulation was performed under these conditions. As a result, the contrast ratio when the polar angle with respect to the Z direction is 45 ° is 790, 750, respectively when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °. 780 and 790. The contrast ratio when the polar angle with respect to the Z direction is 60 ° is 310, 210, 230 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. And 310.

Table 6 summarizes the optical characteristics set for the solidified liquid crystal layer 230. Table 7 and FIG. 14 show the contrast ratio and viewing angle characteristics obtained by the simulation. The graph shown in FIG. 14 depicts the viewing angle dependence of the contrast ratio in the same manner as described with reference to FIG.

<Simulation 4>
The solidified liquid crystal layer 230 has a thickness of 2.77 μm throughout. Regarding the region 230c, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.667. Regarding the region 230b, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.644. Regarding the region 230a, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.629.

  Simulation was performed under these conditions. As a result, the contrast ratio when the polar angle with respect to the Z direction is 45 ° is 670, 570 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. 600 and 670. The contrast ratio when the polar angle with respect to the Z direction is 60 ° is 260, 170, 180 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. And 260.

Table 8 summarizes the optical characteristics set for the solidified liquid crystal layer 230. Further, Table 9 and FIG. 15 show the contrast ratio and viewing angle characteristics obtained by the simulation. The graph shown in FIG. 15 depicts the viewing angle dependence of the contrast ratio in the same manner as described with reference to FIG.

<Simulation 5>
For comparison, the following simulation was performed. That is, the solidified liquid crystal layer 230 is assumed to have a thickness of 1.91 μm throughout. The regions 230a, 230b, and 230c have the same optical characteristics. Specifically, the refractive index in the Z direction at a wavelength of 535 nm is assumed to be 1.667 for all of the regions 230a, 230b, and 230c.

  Simulation was performed under these conditions. As a result, the contrast ratio when the polar angle with respect to the Z direction is 45 ° is 440, 580 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. 590 and 450. The contrast ratio when the polar angle with respect to the Z direction is 60 ° is 160, 200, and 210 when the azimuth angles with respect to the X direction are 45 °, 135 °, 225 °, and 315 °, respectively. And 160.

Table 10 summarizes the optical characteristics set for the solidified liquid crystal layer 230. Further, Table 11 and FIG. 16 show the contrast ratio and viewing angle characteristics obtained by the simulation. Note that the graph shown in FIG. 16 depicts the viewing angle dependence of the contrast ratio in the same manner as described with reference to FIG.

<Evaluation>
Table 12 summarizes the thickness direction retardation ratios set in simulations 1 to 5 and the average contrast ratio values obtained by these simulations. In Table 12, “230a / 230b” represents the ratio of the thickness direction retardation Rth of the region 230a to the thickness direction retardation Rth of the region 230b, and “230c / 230b” represents the thickness of the region 230b. The ratio of the thickness direction retardation Rth of the region 230c to the thickness direction retardation Rth is shown.

  As shown in Table 12, the thickness direction retardation Rth of the region 230a is set to about 0.70 to 0.90 times the thickness direction retardation Rth of the region 230b, and the thickness direction retardation Rth of the region 230c is set. Is about 1.15 to 1.45 times the thickness direction retardation Rth of the region 230b, compared with the case where the optical properties of the regions 230a, 230b and 230c are the same, excellent viewing angle characteristics are obtained. Can be achieved. That is, it can be seen from the results of simulations 1 to 5 that the configuration described with reference to FIGS. 1 and 2 is highly effective for optical compensation of a liquid crystal display device that displays a multicolor image.

  Although not shown here, the simulation is performed under substantially the same conditions as described for simulations 1 to 4 except that the stacking order of the solidified liquid crystal layer 230 and the birefringent layer 240 is reversed. Went. As a result, it was found that if the stacking order of the solidified liquid crystal layer 230 and the birefringent layer 240 is reversed, the optical compensation effect is reduced.

  Although not shown here, the simulation was performed under substantially the same conditions as described for simulations 1 to 4 except that the optical axis of the birefringent layer 240 was parallel to the X direction. It was. As a result, it was found that when the direction of the optical axis of the birefringent layer 240 is changed, the effect of optical compensation is reduced.

  Next, a method for manufacturing a retardation substrate included in the liquid crystal display device described with reference to FIGS. 1 and 2 will be described.

  17 to 19 are cross-sectional views schematically showing an example of a method for manufacturing a retardation substrate.

  In this method, first, a light transmissive substrate 210 is prepared. The light transmissive substrate 210 is, for example, a glass plate or a resin plate. The substrate 210 may be hard and may have flexibility.

  The substrate 210 may have a single layer structure or a multilayer structure. For example, a glass plate having a silicon oxide layer and / or a silicon nitride layer formed on the surface may be used as the substrate 210.

  Next, the colored regions 220 a to 220 c of the color filter layer 220 are formed on the light transmissive substrate 210.

  Each of the colored regions 220a to 220c is a colored layer containing a transparent resin and a pigment dispersed therein. Each of these colored layers can be obtained, for example, by forming a thin film pattern of a colored composition containing a pigment carrier and a pigment dispersed in the pigment carrier and curing the thin film pattern. This thin film pattern can be formed using, for example, a printing method, a photolithography method, an ink jet method, an electrodeposition method, or a transfer method.

  As this pigment, an organic pigment and / or an inorganic pigment can be used. Each of the colored regions 220a to 220c may include one type of organic or inorganic pigment, or may include a plurality of types of organic pigments and / or inorganic pigments.

  The transparent resin is a resin having a high transmittance over the entire wavelength range of visible light, for example, the entire wavelength range of 400 to 700 nm, such as an acrylic resin and a methacrylic resin. As a material of the transparent resin, for example, a photosensitive resin can be used.

  Next, the solidified liquid crystal layer 230 is formed on the color filter layer 220 by, for example, the following method.

  First, as shown in FIG. 17, a liquid crystal material layer 230 ′ containing a photopolymerizable or photocrosslinkable thermotropic liquid crystal material is formed on a substrate 210. For example, a liquid crystal material layer in which mesogen MS is aligned in one direction perpendicular to the main surface of substrate 210, that is, a liquid crystal material layer in which mesogen MS is homeotropically aligned is formed. Then, the liquid crystal material layer 230 ′ is subjected to an exposure process, a development process, and a fixing process to obtain a solidified liquid crystal layer 230.

  The liquid crystal material layer 230 ′ is obtained, for example, by applying a coating liquid containing a thermotropic liquid crystal compound on the substrate 210 and drying the coating film as necessary. In the liquid crystal material layer 230 ′, the mesogen MS of the thermotropic liquid crystal compound forms an alignment structure.

  In addition to the thermotropic liquid crystal compound, the coating liquid is, for example, a solvent, a chiral agent, a photopolymerization initiator, a thermal polymerization initiator, a sensitizer, a chain transfer agent, a polyfunctional monomer and / or oligomer, a resin, a surfactant, Components such as a polymerization inhibitor, a storage stabilizer, and an adhesion improver can be added as long as the composition containing the liquid crystal compound does not lose liquid crystallinity.

  Examples of the thermotropic liquid crystal compounds include alkylcyanobiphenyl, alkoxybiphenyl, alkylterphenyl, phenylcyclohexane, biphenylcyclohexane, phenylbicyclohexane, pyrimidine, cyclohexanecarboxylic acid ester, halogenated cyanophenol ester, alkylbenzoic acid ester, alkylcyano. Tolane, dialkoxytolane, alkylalkoxytolane, alkylcyclohexyltolane, alkylbicyclohexane, cyclohexylphenylethylene, alkylcyclohexylcyclohexene, alkylbenzaldehyde azine, alkenylbenzaldehyde azine, phenylnaphthalene, phenyltetrahydronaphthalene, phenyldecahydronaphthalene, derivatives thereof, Or those It may be used acrylate compound.

  Examples of the solvent include cyclohexanone, ethyl cellosolve acetate, butyl cellosolve acetate, 1-methoxy-2-propyl acetate, diethylene glycol dimethyl ether, ethylbenzene, ethylene glycol diethyl ether, xylene, ethyl cellosolve, methyl-n amyl ketone, propylene glycol monomethyl ether, toluene , Methyl ethyl ketone, ethyl acetate, methanol, ethanol, isopropyl alcohol, butanol, isobutyl ketone, petroleum solvent, or a mixture containing two or more thereof can be used.

  Examples of the photopolymerization initiator include 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)- Acetophenone photopolymerization initiators such as butan-1-one; benzoin photopolymerization initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzyldimethyl ketal; benzophenone, benzoylbenzoic acid, benzoylbenzoate Benzophenone photopolymerization initiators such as methyl acid, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone and 4-benzoyl-4′-methyldiphenyl sulfide; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone and 2 Thioxanthone photopolymerization initiators such as 2,4-diisopropylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis (trichloromethyl) -s-triazine, 2- (p-methoxy) Phenyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (p-tolyl) -4,6-bis (trichloromethyl) -s-triazine, 2-piperonyl-4,6-bis (trichloro) Methyl) -s-triazi 2,4-bis (trichloromethyl) -6-styryl-s-triazine, 2- (naphth-1-yl) -4,6-bis (trichloromethyl) -s-triazine, 2- (4-methoxy- Naphth-1-yl) -4,6-bis (trichloromethyl) -s-triazine, 2,4-trichloromethyl- (piperonyl) -6-triazine and 2,4-trichloromethyl (4'-methoxystyryl)- A triazine photopolymerization initiator such as 6-triazine; a borate photopolymerization initiator; a carbazole photopolymerization initiator; an imidazole photopolymerization initiator; or a mixture containing two or more thereof can be used.

  A sensitizer can be used with a photoinitiator, for example. As sensitizers, α-acyloxy ester, acylphosphine oxide, methylphenylglyoxylate, benzyl, 9,10-phenanthrenequinone, camphorquinone, ethylanthraquinone, 4,4′-diethylisophthalophenone 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone and 4,4′-diethylaminobenzophenone can be used.

  As the chain transfer agent, for example, a polyfunctional thiol can be used. A polyfunctional thiol is a compound having two or more thiol groups. Examples of the polyfunctional thiol include hexanedithiol, decanedithiol, 1,4-butanediol bisthiopropionate, 1,4-butanediol bisthioglycolate, ethylene glycol bisthioglycolate, and ethylene glycol bisthiopropioate. , Trimethylolpropane tristhioglycolate, trimethylolpropane tristhiopropionate, trimethylolpropane tris (3-mercaptobutyrate), pentaerythritol tetrakisthioglycolate, pentaerythritol tetrakisthiopropionate, trimercaptopropionic acid Tris (2-hydroxyethyl) isocyanurate, 1,4-dimethylmercaptobenzene, 2,4,6-trimercapto-s-triazine, 2- (N, N-dibu Arylamino) -4,6-dimercapto -s- triazine, or a mixture containing two or more of them may be used.

  Examples of the polyfunctional monomer and / or oligomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, polyethylene glycol diacrylate, and polyethylene glycol diester. Methacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, tricyclodecanyl acrylate, tricyclodecanyl methacrylate, melamine acrylate , Acrylic and methacrylic esters such as lamin methacrylate, epoxy acrylate and epoxy methacrylate; acrylic acid, methacrylic acid, styrene, vinyl acetate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, acrylonitrile, or Mixtures containing two or more of them can be used.

  As the resin, for example, a thermoplastic resin, a thermosetting resin, or a photosensitive resin can be used.

  Examples of the thermoplastic resin include butyral resin, styrene-maleic acid copolymer, chlorinated polyethylene, chlorinated polypropylene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyurethane resin, and polyester resin. Acrylic resins, alkyd resins, polystyrene resins, polyamide resins, rubber resins, cyclized rubber resins, celluloses, polybutadiene, polyethylene, polypropylene, or polyimide resins can be used.

  As the thermosetting resin, for example, epoxy resin, benzoguanamine resin, rosin-modified maleic acid resin, rosin-modified fumaric acid resin, melamine resin, urea resin or phenol resin can be used.

  Examples of the photosensitive resin include an acrylic compound having a reactive substituent such as an isocyanate group, an aldehyde group, and an epoxy group on a linear polymer having a reactive substituent such as a hydroxyl group, a carboxyl group, and an amino group. A resin in which a photocrosslinkable group such as an acryloyl group, a methacryloyl group and a styryl group is introduced into a linear polymer by reacting a compound or cinnamic acid can be used. Further, a linear polymer containing an acid anhydride such as a styrene-maleic anhydride copolymer and an α-olefin-maleic anhydride copolymer is used as an acrylic compound or methacrylic compound having a hydroxyl group such as hydroxyalkyl acrylate and hydroxyalkyl methacrylate. A resin half-esterified with a compound can also be used.

  Examples of the surfactant include polyoxyethylene alkyl ether sulfate, sodium dodecylbenzenesulfonate, alkali salt of styrene-acrylic acid copolymer, sodium alkylnaphthalenesulfonate, sodium alkyldiphenyletherdisulfonate, monoethanolamine lauryl sulfate. , Anionic surface activity such as triethanolamine lauryl sulfate, ammonium lauryl sulfate, monoethanolamine stearate, sodium stearate, sodium lauryl sulfate, monoethanolamine of styrene-acrylic acid copolymer and polyoxyethylene alkyl ether phosphate Agents: polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, polio Nonionic surfactants such as ciethylene alkyl ether phosphates, polyoxyethylene sorbitan monostearate and polyethylene glycol monolaurate; chaotic surfactants such as alkyl quaternary ammonium salts and their ethylene oxide adducts; alkyl Amphoteric surfactants such as alkylbetaines such as dimethylaminoacetic acid betaine and alkylimidazolines; or a mixture comprising two or more thereof can be used.

  Examples of the polymerization inhibitor include 2,6-di-t-butyl-p-cresol, 3-t-butyl-4-hydroxyanisole, 2-t-butyl-4-hydroxyanisole, and 2,2′-methylenebis. (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4, 4′-thiobis (3-methyl-6-tert-butylphenol), styrenated phenol, styrenated p-cresol, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane Tetrakis [methylene-3- (3 ′, 5′-di-1-butyl-4′-hydroxyphenyl) propionate] methane, octadecyl 3- (3,5- Di-t-butyl-4-hydroxyphenylpropionate), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 2,2 '-Dihydroxy-3,3'-di (α-methylcyclohexyl) -5,5'-dimethyldiphenylmethane, 4,4'-methylenebis (2,6-di-t-butylphenol), tris (3,5-di -T-butyl-4-hydroxyphenyl) isocyanurate, 1,3,5-tris (3 ', 5'-di-t-butyl-4-hydroxybenzoyl) isocyanurate, bis [2-methyl-4- ( 3-n-alkylthiopropionyloxy) -5-tert-butylphenyl] sulfide, 1-oxy-3-methyl-isopropylbenzene, 2,5-di-tert-butylhydroxy 2,2'-methylenebis (4-methyl-6-nonylphenol), alkylated bisphenol, 2,5-di-t-amylhydroquinone, polybutylated bisphenol A, bisphenol A, 2,6-di-t-butyl -P-ethylphenol, 2,6-bis (2'-hydroxy-3-t-butyl-5'-methyl-benzyl) -4-methylphenol, 1,3,5-tris (4-t-butyl- 3-hydroxy-2,6-dimethylbenzyl) isocyanurate, terephthaloyl broth (2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl sulfide), 2,6-di-tert-butylphenol, 2, 6-di-t-butyl-α-dimethylamino-p-cresol, 2,2′-methylene-bis (4-methyl-6-cyclohexylphenol) Toluethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], hexamethylene glycol-bis (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 3,5-di-t-butyl-4-hydroxytoluene, 6- (4-hydroxy-3,5-di-t-butylaniline) -2,4-bis (octylthio) -1,3,5-triazine N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamide), 3,5-di-t-butyl-4-hydroxybenzyl-phosphoric acid diethyl ester, 2,4 -Dimethyl-6-t-butylphenol, 4,4'-methylenebis (2,6-di-t-butylphenol), 4,4'-thiobis (2-methyl-6-t- Tilphenol), tris [β- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl-oxyethyl] isocyanurate, 2,4,6-tributylphenol, bis [3,3-bis (4 ′ -Hydroxy-3'-tert-butylphenyl) -butyric acid] glycol ester, 4-hydroxymethyl-2,6-di-tert-butylphenol and bis (3-methyl-4-hydroxy-5-tert-butylbenzyl) ) Phenol inhibitors such as sulfide; N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine, N, N′-diphenyl -P-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer and diaryl- -Amine inhibitors such as phenylenediamine; sulfur inhibitors such as dilauryl thiodipropionate, distearyl thiodipropionate and 2-mercaptobenzimidanol; phosphorus such as distearyl pentaerythritol diphosphite Inhibitors; or mixtures containing two or more thereof can be used.

  Examples of storage stabilizers include benzyltrimethyl chloride; quaternary ammonium chlorides such as diethylhydroxyamine; organic acids such as lactic acid and oxalic acid; methyl ethers thereof; t-butylpyrocatechol; tetraethylphosphine and tetraphenylphosphine. Organic phosphines; phosphites; or mixtures containing two or more thereof can be used.

  As the adhesion improver, for example, a silane coupling agent can be used. Examples of the silane coupling agent include vinyl silanes such as vinyl tris (β-methoxyethoxy) silane, vinyl ethoxy silane, and vinyl trimethoxy silane; acrylic silanes such as γ-methacryloxypropyl trimethoxy silane, and methacryl silanes; β -(3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) methyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, β- (3,4 -Epoxycyclohexyl) epoxysilanes such as methyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane; N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N β (aminoethyl) γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl- Aminosilanes such as γ-aminopropyltrimethoxysilane and N-phenyl-γ-aminopropyltriethoxysilane; γ-mercaptopropyltrimethoxysilane; γ-mercaptopropyltriethoxysilane; or a mixture containing two or more thereof Can be used.

  Application of the coating liquid includes, for example, a spin coating method; a slit coating method; a printing method such as letterpress printing, screen printing, planographic printing, reversal printing, and gravure printing; a method combining these printing methods with an offset method; an ink jet Method; or the bar coat method can be used.

  The liquid crystal material layer 230 ′ is formed as a continuous film having a uniform thickness, for example. According to the method described above, the liquid crystal material layer 230 ′ can be formed as a continuous film having a uniform thickness as long as the coated surface is sufficiently flat.

  Prior to the application of the coating liquid, an alignment film that regulates the alignment of the liquid crystal compound, specifically, a vertical alignment film may be formed on the color filter layer 220. This alignment film is obtained, for example, by forming a transparent resin layer such as polyimide on the color filter layer 220.

  Next, an exposure process is performed. That is, as shown in FIG. 17, the light L is irradiated to a plurality of regions of the liquid crystal material layer 230 ′ with different exposure amounts. For example, the region 230a 'corresponding to the region 230a in the liquid crystal material layer 230' is irradiated with light with the maximum exposure amount. Of the liquid crystal material layer 230 ′, the region 230 b ′ corresponding to the region 230 b is irradiated with the light L with a smaller exposure amount than the region 230 a ′. The region 230c 'corresponding to the region 230c in the liquid crystal material layer 230' is irradiated with the light L with a smaller exposure amount than the region 230b '. This causes polymerization or crosslinking of the thermotropic liquid crystal compound while maintaining the alignment structure formed by the mesogen MS at the portion irradiated with the light L of the liquid crystal material layer 230 ′.

  In the polymerized or crosslinked product of the thermotropic liquid crystal compound, the mesogen MS is immobilized. In the region where the exposure amount is maximum, the content of the thermotropic liquid crystal compound is the highest in the content of the polymerized or crosslinked product, and the content of the unpolymerized and uncrosslinked thermotropic liquid crystal compound is the lowest. And the content rate of superposition | polymerization or a crosslinked product becomes lower, and the content rate of the unpolymerized and uncrosslinked thermotropic liquid crystal compound becomes higher, so that exposure amount becomes small.

  Therefore, the mesogen MS is immobilized at a higher rate in the region where the exposure amount is larger, and the mesogen MS is immobilized at the lower rate in the region where the exposure amount is smaller.

  The light L used in the exposure process is electromagnetic waves such as ultraviolet rays, visible rays, and infrared rays. An electron beam may be used instead of the electromagnetic wave. Only one of them may be used, or two or more of them may be used.

  The exposure process may be performed by any method as long as the above-described non-uniform polymerization or crosslinking can be caused. For example, in this exposure process, exposure using a photomask may be performed a plurality of times. Alternatively, in this exposure process, exposure using a halftone mask, a gray tone mask, or a wavelength limiting mask may be performed. Alternatively, instead of using a photomask, a radiation or light beam such as an electron beam may be scanned on the liquid crystal material layer 230 ′. Alternatively, these may be combined.

  After completing the exposure process, a development process is performed. That is, the liquid crystal material layer 230 ′ is heated to a temperature equal to or higher than the phase transition temperature at which the thermotropic liquid crystal compound changes from the liquid crystal phase to the isotropic phase. The mesogenic MS of the thermotropic liquid crystal compound which is an unreacted compound is not immobilized. Therefore, when the liquid crystal material layer 230 ′ is heated to a temperature higher than the phase transition temperature, the degree of alignment of the unreacted mesogen MS decreases as shown in FIG. For example, the mesogen MS of the unreacted compound changes from a liquid crystal phase to an isotropic phase. On the other hand, the mesogen MS is immobilized in the polymerized or crosslinked product of the thermotropic liquid crystal compound.

  Therefore, in the region where the exposure amount in the exposure process is smaller, the degree of orientation of the mesogen MS is lower than in the region where the exposure amount in the exposure process is larger.

  Thereafter, the fixing process described below is performed while the degree of orientation of the unreacted compound mesogen MS is lowered. That is, the unreacted compound is polymerized and / or crosslinked while reducing the degree of orientation of the unreacted compound mesogen MS.

  For example, the liquid crystal compound layer 130 ′ is exposed while reducing the degree of alignment of the unreacted compound mesogen MS. That is, the entire liquid crystal compound layer 130 ′ is irradiated with light while maintaining the liquid crystal compound layer 130 ′ at a temperature higher than the phase transition temperature at which the thermotropic liquid crystal compound changes from the isotropic phase to the liquid crystal phase. Inducing polymerization and / or cross-linking of the reaction compound. For example, the liquid crystal compound layer 130 ′ is irradiated with light with an exposure amount sufficient to cause almost all of the unreacted compound to undergo polymerization and / or crosslinking reaction. As a result, polymerization or cross-linking of the unreacted compound is caused, and the mesogen having a reduced degree of orientation is immobilized. The solidified liquid crystal layer 230 is obtained as described above.

  A certain liquid crystal compound has a lower first phase transition temperature that changes from an isotropic phase to a liquid crystal phase than a second phase transition temperature that changes from a liquid crystal phase to an isotropic phase. Therefore, in certain cases, the temperature of the liquid crystal compound layer 130 ′ in the fixing process may be lower than the heating temperature in the development process. However, normally, from the viewpoint of simplicity, the temperature of the liquid crystal compound layer 130 ′ in the fixing process is set to be equal to or higher than the first phase transition temperature.

  As the light used in the fixing process, the same light as described for the light L can be used. These lights may be the same or different.

  In the fixing process, the exposure amount may be equal over the entire liquid crystal compound layer 130 ′. In this case, it is not necessary to use a photomask provided with a fine pattern. Therefore, in this case, the process can be simplified.

  Alternatively, the fixing process may be performed such that the total exposure amount, which is the sum of the exposure amount in the exposure process and the exposure amount in the fixing process, is equal between the regions 130a 'to 130c'. For example, when the total exposure amount of the region 130a 'is significantly larger than the total exposure amount of the region 130c', the region 130a 'and / or the colored layer 120a may be undesirably damaged. Such damage can be prevented by making the total exposure amount equal between the regions 130a 'to 130c'.

The polymerization and / or cross-linking of the unreacted compound may be performed by other methods.
For example, if the unreacted compound, ie the thermotropic liquid crystal compound, is a material that polymerizes and / or crosslinks by heating to a polymerization and / or crosslinking temperature higher than the first phase transition temperature, in the fixing process, instead of exposure A heat treatment may be performed. Specifically, instead of exposure, the liquid crystal material layer 230 ′ is heated to a polymerization and / or crosslinking temperature or higher to polymerize and / or crosslink unreacted compounds. Thereby, the solidified liquid crystal layer 230 is obtained. The heating temperature in the development process is, for example, not lower than the first phase transition temperature and lower than the polymerization and / or crosslinking temperature.

  Alternatively, heat treatment and exposure may be sequentially performed after the development process. Alternatively, exposure and heat treatment may be sequentially performed after the development process. Alternatively, a heat treatment process, exposure, and heat treatment may be sequentially performed after the development process. As described above, when exposure and heat treatment are combined in the fixing process, polymerization and / or cross-linking of the unreacted compound can proceed more reliably. Therefore, a stronger solidified liquid crystal layer 230 can be obtained.

  If the unreacted compound is a material that polymerizes and / or crosslinks by heating to a certain temperature, the heating temperature in the development process may be above the temperature at which it polymerizes and / or crosslinks. However, in this case, a decrease in the degree of orientation and polymerization and / or crosslinking proceed simultaneously. Therefore, the influence of the manufacturing conditions on the optical characteristics of the solidified liquid crystal layer 230 is relatively large.

  Next, as shown in FIG. 19, a birefringent layer 240 is formed on the solidified liquid crystal layer 230. The birefringent layer 240 can be formed by, for example, the following method.

  First, a liquid crystal material layer containing a polymerizable or crosslinkable liquid crystal material is formed. For example, a liquid crystal material layer in which mesogens are aligned in one direction parallel to the main surface of the substrate 210 is formed. In order to align the mesogens in a predetermined direction, the solidified liquid crystal layer 230 may be subjected to an alignment process such as a rubbing process. It may be formed on top. As the liquid crystal material, for example, the thermotropic liquid crystal material exemplified for the liquid crystal material layer 230 ′ can be used. Further, other polymerizable or crosslinkable liquid crystal materials may be used as the liquid crystal material.

  Next, the birefringent layer 240 is obtained by polymerizing or crosslinking the liquid crystal material. The liquid crystal material can be polymerized or crosslinked, for example, by the methods exemplified for the fixing process.

  By the way, in this method, a development process using a heat treatment is performed without performing a development process using a developer. That is, in this method, the liquid crystal material layer 230 'is not patterned. Therefore, it is possible to easily obtain the solidified liquid crystal layer 230 having a uniform thickness throughout.

  Further, it is difficult to strictly control the conditions of the wet process, particularly the conditions of the development process using the developer, and the influence of these conditions on the optical characteristics of the final product is extremely large. Therefore, according to the method including the wet process, the optical characteristic is likely to deviate from the target value.

  On the other hand, according to the previous method, the wet process is not performed after the exposure process. Therefore, according to this method, it is possible to prevent the optical characteristic from deviating from the target value due to the wet process.

Although the IPS liquid crystal display device has been described here, the above-described technique can also be applied to other display liquid crystal display devices. For example, the above technique may be applied to an FFS liquid crystal display device.
The invention described in the original claims is appended below.
[1]
A light transmissive substrate;
A solidified liquid crystal layer as a continuous film facing one main surface of the light transmissive substrate, including first to third regions arranged in parallel to the main surface, the first to third The region has an optical axis in a thickness direction perpendicular to the main surface, and a refractive index in the thickness direction is larger than a refractive index in a direction parallel to the main surface, and the first region is A solidified liquid crystal layer having a higher refractive index in the thickness direction compared to the second region, the third region having a lower refractive index in the thickness direction than the second region;
The solid-state liquid crystal layer is sandwiched between and faces the light-transmitting substrate, and has an optical axis parallel to the main surface. A refractive index in a first in-plane direction parallel to the optical axis is parallel to the main surface. A birefringent layer that is larger than the refractive index in the second in-plane direction perpendicular to the first in-plane direction and the refractive index in the thickness direction.
A retardation substrate comprising:
[2]
The retardation according to claim 1, wherein the first region has a higher degree of mesogen orientation than the second region, and the third region has a lower degree of mesogen orientation than the second region. Circuit board.
[3]
Item 3. The retardation substrate according to Item 2, wherein the solidified liquid crystal layer has a uniform thickness throughout.
[4]
A ratio of the thickness direction retardation of the first region to the thickness direction retardation of the second region is in a range of 1.15 to 1.45, and the thickness direction retardation of the second region is Item 4. The retardation substrate according to any one of Items 1 to 3, wherein a ratio of retardation in the thickness direction of the third region to 0.73 is in a range of 0.70 to 0.90.
[5]
Item 5. The retardation substrate according to any one of Items 1 to 4, wherein the birefringent layer is a continuous film.
[6]
Item 6. The retardation substrate according to any one of Items 1 to 5, wherein the birefringent layer has uniform optical characteristics over the entire surface.
[7]
Item 7. The retardation substrate according to any one of Items 1 to 6, further comprising a color filter layer including first to third colored regions that face the first to third regions and have different absorption spectra.
[8]
The retardation substrate according to item 7, wherein the first colored region is a red colored region, the second colored region is a green colored region, and the third colored region is a blue colored region.
[9]
First and second light transmissive substrates facing each other;
A liquid crystal layer interposed between the first and second light-transmitting substrates;
A first polarizing plate facing the liquid crystal layer with the first light transmissive substrate interposed therebetween;
A second polarizing plate facing the liquid crystal layer with the second light-transmitting substrate in between and having a transmission axis orthogonal to the transmission axis of the first polarizing plate;
A solidified liquid crystal layer as a continuous film supported on a main surface of the first light-transmitting substrate facing the second light-transmitting substrate, the first to the second being arranged in parallel to the main surface. The first to third regions have an optical axis in the thickness direction perpendicular to the main surface, and the refractive index in the thickness direction is compared with the refractive index in the direction parallel to the main surface. The first region has a larger refractive index in the thickness direction than the second region, and the third region has a refractive index in the thickness direction compared to the second region. A smaller solidified liquid crystal layer,
The solid-state liquid crystal layer is sandwiched between and supported by the main surface, and has an optical axis parallel to the main surface. A refractive index in a first in-plane direction parallel to the optical axis is parallel to the main surface. A birefringent layer that is larger than the refractive index in the second in-plane direction perpendicular to the first in-plane direction and the refractive index in the thickness direction;
A color filter layer including first to third colored regions facing each of the first to third regions and having different absorption spectra from each other;
A liquid crystal display device comprising:
[10]
The liquid crystal layer further includes a plurality of electrodes that change the alignment state of the liquid crystal molecules included in the liquid crystal layer by applying a voltage, and the plurality of electrodes are one of the first and second light transmissive substrates. Item 10. The liquid crystal display device according to item 9, wherein the liquid crystal molecules are supported only on the liquid crystal layer and have a homogeneous alignment in a state where no voltage is applied to the liquid crystal layer, and are aligned in a direction parallel to the transmission axis of the second polarizing plate. .
[11]
Item 11. The liquid crystal display device according to Item 9 or 10, wherein a slow axis of the birefringent layer is perpendicular to the transmission axis of the second polarizing plate.
[12]
Item 12. The liquid crystal display device according to any one of Items 9 to 11, wherein the first colored region is a red colored region, the second colored region is a green colored region, and the third colored region is a blue colored region. .
[13]
Forming a solidified liquid crystal layer on one main surface of the light-transmitting substrate; and having an optical axis parallel to the main surface, and a refractive index in a first in-plane direction parallel to the optical axis being the main surface. Solidifying a birefringent layer that is parallel to the surface and larger than the refractive index in the second in-plane direction perpendicular to the first in-plane direction and the refractive index in the thickness direction perpendicular to the main surface Providing on the liquid crystal layer,
The formation of the solidified liquid crystal layer is as follows:
The photothermographic or photocrosslinkable thermotropic liquid crystal compound is supported on the main surface, and at least three regions of the liquid crystal material layer in which the mesogen of the thermotropic liquid crystal compound has a homeotropic structure are formed with different exposure amounts. A first region containing a polymerized or crosslinked product of the thermotropic liquid crystal compound and the thermotropic liquid crystal compound as an unreacted compound in the liquid crystal material layer upon exposure; A second region where the content of the polymerized or crosslinked product is lower than that of the first region, and the thermotropic liquid crystal compound as an unreacted compound and the polymerized or crosslinked product, An exposure process comprising forming a third region having a lower cross-linked product content compared to the second region;
Thereafter, the liquid crystal material layer is heated to a temperature equal to or higher than a phase transition temperature at which the thermotropic liquid crystal compound changes from a liquid crystal phase to an isotropic phase, and at least the degree of orientation of the mesogens in the second and third regions. Developing process including reducing
A fixing process in which the unreacted compound is polymerized and / or crosslinked while reducing the degree of orientation;
A method for manufacturing a retardation substrate including
[14]
Item 14. The manufacturing method according to Item 13, wherein in the fixing process, polymerization and / or crosslinking of the unreacted compound is induced by light irradiation.
[15]
Item 15. The manufacturing method according to Item 14, wherein the light irradiation is performed by exposing the entire liquid crystal material layer.
[16]
The thermotropic liquid crystal compound is a material that polymerizes and / or crosslinks by heating to a polymerization and / or crosslinking temperature that is higher than the phase transition temperature. In the development process, the liquid crystal material layer is polymerized and / or crosslinked. The degree of orientation of the mesogenic groups is reduced by heating to a temperature below the temperature, and in the fixing process, the liquid crystal material layer is heated to a temperature equal to or higher than the polymerization and / or cross-linking temperature. Item 16. The production method according to any one of Items 13 to 15, wherein the thermotropic liquid crystal compound is crosslinked and / or crosslinked.
[17]
Item 17. The method according to any one of Items 13 to 16, wherein the liquid crystal material layer is formed as a continuous film having a uniform thickness.
[18]
Item 18. The method according to any one of Items 13 to 17, further comprising forming a color filter layer on the main surface, the solidified liquid crystal layer, or the birefringent layer.

1 is a cross-sectional view schematically illustrating a liquid crystal display device according to one embodiment of the present invention. Sectional drawing which shows the retardation board | substrate which the liquid crystal display device shown in FIG. 1 contains. The graph which shows the spectral transmission characteristic of each polarizing plate assumed in simulation. The graph which shows the spectral transmission characteristic of the laminated body which piles up two polarizing plates which each have the spectral transmission characteristic shown in FIG. 3 so that a transmission axis may become parallel. The graph which shows the spectral transmission characteristic of the laminated body which piles up two polarizing plates which each have the spectral transmission characteristic shown in FIG. 3 so that a transmission axis may become perpendicular | vertical. The graph which shows the spectral transmission characteristic of the red coloring area | region assumed in simulation. The graph which shows the spectral transmission characteristic of the green coloring area | region assumed in simulation. The graph which shows the spectral transmission characteristic of the blue coloring area | region assumed in simulation. The graph which shows the refractive index of the liquid-crystal layer assumed in simulation. The graph which shows the refractive index of each area | region of the solidified liquid crystal layer assumed in simulation. The graph which shows the birefringence ratio of each area | region of the solidified liquid crystal layer assumed in simulation. The graph which shows the viewing angle dependence of the contrast ratio obtained by the simulation 1. FIG. The graph which shows the viewing angle dependence of the contrast ratio obtained by the simulation 1. FIG. The graph which shows the viewing angle dependence of the contrast ratio obtained by the simulation 1. FIG. The graph which shows the viewing angle dependence of the contrast ratio obtained by the simulation 1. FIG. The graph which shows the viewing angle dependence of the contrast ratio obtained by the simulation 1. FIG. Sectional drawing which shows schematically an example of the manufacturing method of a retardation substrate. Sectional drawing which shows schematically an example of the manufacturing method of a retardation substrate. Sectional drawing which shows schematically an example of the manufacturing method of a retardation substrate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Array substrate, 20 ... Counter substrate, 30 ... Liquid crystal layer, 40 ... Polarizing plate, 110 ... Substrate, 120a ... Gate, 120b ... Common electrode, 130 ... Insulating layer, 140 ... Semiconductor layer, 150a ... Signal line, 150b1 ... Pixel electrode, 150b2 ... Pixel electrode, 160 ... Alignment film, 210 ... Substrate, 220 ... Color filter layer, 230 ... Solidified liquid crystal layer, 220a ... Colored region, 220b ... Colored region, 220c ... Colored region, 230 ... Liquid crystal material layer , 230a ... region, 230a '... region, 230b ... region, 230b' ... region, 230c ... region, 230c '... region, 240 ... birefringent layer, 260 ... alignment film.

Claims (6)

Forming a solidified liquid crystal layer on one main surface of the light-transmitting substrate; and having an optical axis parallel to the main surface, and a refractive index in a first in-plane direction parallel to the optical axis being the main surface. Solidifying a birefringent layer that is parallel to the surface and larger than the refractive index in the second in-plane direction perpendicular to the first in-plane direction and the refractive index in the thickness direction perpendicular to the main surface Providing on the liquid crystal layer,
The formation of the solidified liquid crystal layer is as follows:
The photothermographic or photocrosslinkable thermotropic liquid crystal compound is supported on the main surface, and at least three regions of the liquid crystal material layer in which the mesogen of the thermotropic liquid crystal compound has a homeotropic structure are formed with different exposure amounts. A first region containing a polymerized or crosslinked product of the thermotropic liquid crystal compound and the thermotropic liquid crystal compound as an unreacted compound in the liquid crystal material layer upon exposure; A second region where the content of the polymerized or crosslinked product is lower than that of the first region, and the thermotropic liquid crystal compound as an unreacted compound and the polymerized or crosslinked product, An exposure process comprising forming a third region having a lower cross-linked product content compared to the second region;
Thereafter, the liquid crystal material layer is heated to a temperature equal to or higher than a phase transition temperature at which the thermotropic liquid crystal compound changes from a liquid crystal phase to an isotropic phase, and at least the degree of orientation of the mesogens in the second and third regions. Developing process including reducing
And a fixing process for polymerizing and / or cross-linking the unreacted compound while reducing the degree of orientation. The production method according to claim 1 , wherein in the fixing process, polymerization and / or crosslinking of the unreacted compound is induced by light irradiation. The manufacturing method according to claim 2 , wherein the light irradiation is performed by exposing the entire liquid crystal material layer. The thermotropic liquid crystal compound is a material that polymerizes and / or crosslinks by heating to a polymerization and / or crosslinking temperature that is higher than the phase transition temperature. In the development process, the liquid crystal material layer is polymerized and / or crosslinked. The degree of orientation of the mesogenic groups is reduced by heating to a temperature below the temperature, and in the fixing process, the liquid crystal material layer is heated to a temperature equal to or higher than the polymerization and / or cross-linking temperature. The production method according to any one of claims 1 to 3 , wherein a crosslinked thermotropic liquid crystal compound is polymerized and / or crosslinked. The method according to any one of claims 1 to 4, formed as a continuous film having the liquid crystal material layer a uniform thickness. The main surface, the method according to any one of further inclusive claims 1 to 5 to form a color filter layer on the solidified liquid crystal layer or the birefringent layer.

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