CN115298604A

CN115298604A - Liquid crystal display element

Info

Publication number: CN115298604A
Application number: CN202180022331.3A
Authority: CN
Inventors: 宫地弘一; 黑田美彦
Original assignee: JSR Corp
Current assignee: JSR Corp
Priority date: 2020-04-02
Filing date: 2021-04-01
Publication date: 2022-11-04
Anticipated expiration: 2041-04-01
Also published as: CN115298604B; WO2021201257A1

Abstract

The liquid crystal display element 10 includes: a first substrate 11; a second substrate 12 disposed to face the first substrate 11; and a liquid crystal layer 13 disposed between the first substrate 11 and the second substrate 12 and including liquid crystal molecules having negative dielectric anisotropy. The liquid crystal display element 10 has a plurality of pixels 30. The liquid crystal display element 10 has a photo-alignment film or a polymer layer. Each pixel 30 has a plurality of alignment regions in which the alignment directions of the liquid crystal molecules are different. The liquid crystal layer 13 contains a chiral agent, liquid crystal molecules are twist-aligned between the first substrate 11 and the second substrate 12 in a state where a voltage is applied, and twist directions of the liquid crystal molecules in the plurality of alignment regions are the same.

Description

Liquid crystal display element

Cross reference to related applications

This application is based on japanese patent application No. 2020-67028 filed on 2/4/2020, and the contents of the description thereof are incorporated herein by reference.

Technical Field

The present disclosure relates to a liquid crystal display element.

Background

In a liquid crystal display panel, one pixel is divided into a plurality of alignment regions, and the alignment orientations of liquid crystal molecules are made different in the plurality of alignment regions, thereby improving the viewing angle. On the other hand, at the boundary between alignment regions where the alignment orientations of the liquid crystal molecules are different, or at the peripheral edge of each side of the pixel, a dark line may be generated due to the alignment disorder of the liquid crystal molecules. Dark lines generated in the pixels cause a decrease in panel transmittance.

Therefore, various techniques for suppressing the occurrence of dark lines in pixels in an alignment-divided liquid crystal display panel have been proposed (see, for example, patent documents 1 and 2). Patent document 1 discloses a liquid crystal display panel: in one pixel, four alignment regions in which the tilt azimuths of the liquid crystal molecules are different from each other are arranged along the longitudinal direction of the pixel, and the twist angle of the liquid crystal molecules is substantially 0 degree in each of the four alignment regions when the liquid crystal display panel is viewed in plan. Further, patent document 2 discloses a liquid crystal display panel: in each of the four alignment regions arranged along the longitudinal direction of the pixel, the twist angle of the liquid crystal molecules is substantially 45 degrees or less.

Documents of the prior art

Patent literature

Patent document 1: international publication No. 2017/057210

Patent document 2: international publication No. 2017/073496

Disclosure of Invention

Problems to be solved by the invention

In recent years, higher definition (1920 × 1080 pixels) of 4K (3840 × 2160 pixels) or 8K (7680 × 4320 pixels) has been achieved from the past. However, in the 4K or 8K liquid crystal display panel, the panel transmittance tends to decrease due to an increase in the number of wirings, switching elements, or the like. If the panel transmittance decreases, the light utilization efficiency of the backlight decreases, which leads to an increase in power consumption. Therefore, it is desirable to suppress the occurrence of dark lines in the pixels, which is a factor of the decrease in transmittance, as much as possible.

The present disclosure has been made in view of the above problems, and an object thereof is to provide a liquid crystal display element with high transmittance, in which generation of dark lines in pixels can be suppressed.

Means for solving the problems

According to the present disclosure, the following means are provided.

[1] A liquid crystal display element comprising: a first substrate; a second substrate disposed to face the first substrate; and a liquid crystal layer which is disposed between the first substrate and the second substrate and includes liquid crystal molecules having negative dielectric anisotropy, wherein the liquid crystal display element includes a plurality of pixels, a photo-alignment film is formed on at least one of the first substrate and the second substrate, or a polymer layer formed by polymerization of a photo-polymerizable monomer is provided at a boundary portion between the first substrate and the liquid crystal layer and a boundary portion between the second substrate and the liquid crystal layer, each of the plurality of pixels has a plurality of alignment regions in which alignment directions of the liquid crystal molecules are different, the liquid crystal layer includes a chiral agent, the liquid crystal molecules are twist-aligned between the first substrate and the second substrate in a state where a voltage is applied, and twist directions of the liquid crystal molecules in the plurality of alignment regions are the same.

[2] The liquid crystal display element according to [1], wherein d · Δ n is 405nm or more, where d is a thickness of the liquid crystal layer and Δ n is a refractive index anisotropy of the liquid crystal.

[3] The liquid crystal display element according to [1] or [2], wherein the following expression (1) is satisfied where d is a thickness of the liquid crystal layer, Δ n is a refractive index anisotropy of the liquid crystal, p is a chiral pitch of the liquid crystal, x is 1/(p/d), and y is d · Δ n.

y≥4661.2x ² -2431.5x+723.0…(1)

[4] The liquid crystal display element according to any one of [1] to [3], wherein an optical alignment film is formed on each of the first substrate and the second substrate, a pretilt angle defined by the optical alignment film formed on the first substrate and a pretilt angle defined by the optical alignment film formed on the second substrate are each less than 90 degrees, a twist angle of the liquid crystal molecules in a state where a voltage is applied to the liquid crystal layer is 60 degrees to 120 degrees, and an azimuth of projecting a major axis direction of the liquid crystal molecules existing in a vicinity of a center in a thickness direction of the liquid crystal layer onto the first substrate in each of the plurality of pixels is ± 15 degrees with respect to a horizontal direction of a display surface of the liquid crystal display element or ± 15 degrees with respect to a vertical direction of the display surface.

[5] The liquid crystal display element according to any one of [1] to [4], wherein an optical alignment film is formed on at least one of the first substrate and the second substrate, one of a pretilt angle defined by the liquid crystal alignment film formed on the first substrate and a pretilt angle defined by the liquid crystal alignment film formed on the second substrate is smaller than 90 degrees and the other is substantially 90 degrees, and an alignment azimuth of liquid crystal molecules present in the vicinity of the alignment film having a pretilt angle smaller than 90 degrees is 30 to 60 degrees with respect to a horizontal direction of a display surface of the liquid crystal display element.

[6] The liquid crystal display element according to [5], wherein in each of the plurality of pixels, an orientation in which a long axis direction of liquid crystal molecules existing in the vicinity of a center in a thickness direction of the liquid crystal layer is projected onto the first substrate is ± 15 degrees with respect to a horizontal direction of the display surface, or ± 15 degrees with respect to a vertical direction of the display surface.

[7] The liquid crystal display element according to any one of [1] to [6], wherein a photo alignment film is formed on at least one of the first substrate and the second substrate, and the plurality of alignment regions are aligned in a line along a predetermined direction.

[8] The liquid crystal display element according to the above [1], wherein a photo-alignment film is formed on each of the first substrate and the second substrate,

among the plurality of alignment regions, a pretilt angle defined by the optical alignment film formed on the first substrate is less than 90 degrees and a pretilt angle defined by the optical alignment film formed on the second substrate is substantially 90 degrees in some of the alignment regions, and a pretilt angle defined by the optical alignment film formed on the first substrate is substantially 90 degrees and a pretilt angle defined by the optical alignment film formed on the second substrate is less than 90 degrees in the remaining alignment regions.

[9] The liquid crystal display element according to [8], wherein an alignment azimuth of liquid crystal molecules present in the vicinity of the alignment film having a pretilt angle of less than 90 degrees is ± 50 degrees with respect to a horizontal direction of a display surface of the liquid crystal display element.

[10] The liquid crystal display element according to any one of [8] and [9], wherein when a thickness of the liquid crystal layer is d and refractive index anisotropy of the liquid crystal is Δ n, d · Δ n is 370nm or more.

[11] The liquid crystal display element according to any one of [8] to [10], wherein when a shift angle of an alignment azimuth with respect to a horizontal direction of a display surface of the liquid crystal display element of liquid crystal molecules present in the vicinity of an alignment film having a pretilt angle of less than 90 degrees is represented by v (wherein a shift angle in a predetermined rotation direction is represented by a positive value with respect to the first substrate side, and a shift angle in a direction opposite to the predetermined rotation direction is represented by a positive value with respect to the second substrate side), a thickness of the liquid crystal layer is represented by d, a chiral pitch of the liquid crystal is represented by p, and 360/(p/d) is represented by w, expression (7) below is satisfied.

0.0263w ² -4.2945w+151.89≤v≤-0.0337w ² +4.8753w-123.82…(7)

[12] The liquid crystal display element according to any one of [8] to [11], wherein the plurality of alignment regions are arranged in a line along a prescribed direction.

[13] The liquid crystal display element according to any one of [1] to [12], wherein the plurality of pixels are arranged in a matrix shape including a plurality of rows and a plurality of columns, each of the plurality of pixels displays a color corresponding to the pixel, and the pixels of the same color are arranged in a stripe shape extending in a row direction or a column direction.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the liquid crystal display element of the present disclosure, generation of a dark line in a pixel can be suppressed by providing a structure including a liquid crystal layer including liquid crystal molecules having negative dielectric constant anisotropy, and each of a plurality of pixels has a plurality of alignment regions in which alignment azimuths of the liquid crystal molecules are different, in which the liquid crystal layer includes liquid crystal molecules having negative dielectric constant anisotropy and a chiral agent, the liquid crystal molecules are twist-aligned between a first substrate and a second substrate in a state where a voltage is applied, and twist directions of the liquid crystal molecules in the plurality of alignment regions are the same. This can improve the transmittance of the liquid crystal display element.

Drawings

Fig. 1 is a schematic diagram showing a schematic configuration of a liquid crystal display element according to a first embodiment.

Fig. 2 is a schematic diagram showing the arrangement of pixels and the electrode structure.

FIG. 3 is a schematic view showing the arrangement of pixels and the exposure orientation.

Fig. 4 is a diagram showing the results of analyzing the state of occurrence of dark lines by simulation.

FIG. 5 is a graph showing the relationship between d.DELTA.n and 1/(p/d).

Fig. 6 is a view showing a schematic configuration of a liquid crystal display element according to a fifth embodiment.

Fig. 7 is a schematic diagram showing the arrangement and electrode structure of a pixel according to a sixth embodiment.

Fig. 8 is a schematic diagram showing the arrangement and exposure orientation of pixels according to a sixth embodiment.

Fig. 9 is a diagram showing a result of analyzing the generation state of the dark line in the sixth embodiment by simulation.

Fig. 10 is a diagram showing the relationship between d · Δ n and transmittance in the sixth embodiment.

Fig. 11 is a diagram illustrating a liquid crystal azimuth offset angle according to a sixth embodiment.

FIG. 12 is a diagram showing the relationship between 360/(p/d) and the liquid crystal azimuth offset angle and transmittance characteristics in the sixth embodiment.

FIG. 13 is a view showing the relationship between 360/(p/d) and the liquid crystal azimuth shift angle and the transmittance characteristic in the sixth embodiment.

Detailed Description

(first embodiment)

Hereinafter, a first embodiment will be described with reference to the drawings. In the following embodiments, the same or equivalent portions are denoted by the same reference numerals in the drawings, and the same portions will be referred to by the same reference numerals. In the following description, for convenience, the top, bottom, left, and right are shown with reference to the direction when the display region of the liquid crystal display element is viewed from the front.

In this specification, the term "pixel" refers to a minimum unit expressing the shade (gray scale) of each color in display, and corresponds to a unit expressing each gray scale such as red (R), green (G), and blue (B) in a color filter type display element, for example. Therefore, when the expression "pixel" is used, it refers to each of the R pixel, the G pixel, and the B pixel, and not to a color display pixel (dot) in which the R pixel, the G pixel, and the B pixel are combined. That is, in the case of a color liquid crystal display element, one pixel corresponds to any one color of the color filters. The "pretilt angle" refers to an angle formed between the surface of the alignment film and the longitudinal axis direction of the liquid crystal molecules in the vicinity of the alignment film in a state where no voltage is applied to the liquid crystal layer.

The "orientation" refers to the orientation on the substrate surface or a plane parallel to the substrate surface. The orientation does not take into account the inclination angle of the substrate surface with respect to the normal direction. When the reference is not particularly described, the azimuth represented by 0 to 360 degrees is set to the reference azimuth (0 degree) with the azimuth angle of the x-axis direction in the horizontal direction of the display surface (i.e., the left-right direction of the display surface, also referred to as the "pixel horizontal direction") as the reference azimuth, and the counterclockwise direction is set to a positive angle. The "orientation azimuth of the liquid crystal layer" refers to a direction starting from the long axis end on the substrate (first substrate) side where the pixel electrode is arranged among the liquid crystal molecules present in the vicinity of the center in the thickness direction of the liquid crystal layer (more specifically, the liquid crystal molecules present in the vicinity of the center in the layer surface in the liquid crystal layer of each pixel and in the vicinity of the center in the thickness direction of the liquid crystal layer) and ending with the long axis end on the other substrate (second substrate) side. Therefore, the "orientation in which the long axis direction of the liquid crystal molecules present in the vicinity of the center in the thickness direction of the liquid crystal layer is projected onto the first substrate" refers to a direction in which the long axis end on the first substrate side and the long axis end on the second substrate side of the liquid crystal molecules present in the vicinity of the center in the thickness direction of the liquid crystal layer are projected onto the first substrate from a starting point in the direction. The "orientation direction of liquid crystal molecules" refers to the direction of liquid crystal molecules controlled by the liquid crystal orientation film, and refers to the direction starting from the long axis end of the liquid crystal molecules existing in the vicinity of the orientation film on the orientation film side and ending at the long axis end on the opposite side of the orientation film in a state where no voltage is applied. In the present specification, the display state in front view (that is, when viewed from the normal direction of the display surface) is shown without particularly showing the visual direction.

(liquid Crystal display element)

The liquid crystal display element 10 is a Thin Film Transistor (TFT) type liquid crystal display device, and a plurality of pixels 30 are arranged in a matrix in a display region 29 where an image is displayed. As shown in fig. 1, the liquid crystal display element 10 includes: a pair of substrates including a first substrate 11 and a second substrate 12; and a liquid crystal layer 13 disposed between the first substrate 11 and the second substrate 12. In addition, although the present embodiment has been described with respect to the case of applying the present disclosure to a TFT-type liquid crystal display device, the present disclosure may be applied to other driving methods (for example, a passive matrix (passive matrix) method, a plasma address (plasma address) method, and the like).

The first substrate 11 is a TFT substrate: on the surface of the transparent substrate 14 made of glass, resin, or the like on the liquid crystal layer 13 side, pixel electrodes 15 made of a transparent conductor such as Indium Tin Oxide (ITO), and various kinds of wiring such as TFTs, scanning lines, and signal lines serving as switching elements are arranged. The second substrate 12 is a counter substrate (Color Filter (CF) substrate) as follows: a black matrix 17, a color filter 18, and an opposed electrode 19 including a transparent conductor are provided on a surface of a transparent substrate 16 including glass, resin, or the like on the liquid crystal layer 13 side. The pixel electrode 15 and the counter electrode 19 are planar electrodes (entire electrodes) without slits (see fig. 2 (i)). The counter electrode 19 is a common electrode common to all the pixel electrodes 15.

The first substrate 11 and the second substrate 12 are respectively provided with a liquid crystal alignment film for aligning liquid crystal molecules in the vicinity of the substrate surface in a predetermined orientation with respect to the substrate surface (i.e., the electrode arrangement surface). The liquid crystal alignment film is a vertical alignment film that aligns liquid crystal molecules such that the long axis direction of the liquid crystal molecules is substantially perpendicular to the substrate surface when no voltage is applied. The liquid crystal display element 10 includes, as liquid crystal alignment films, a first alignment film 22 formed on the electrode arrangement surface of the first substrate 11, and a second alignment film 23 formed on the electrode arrangement surface of the second substrate 12.

In the present embodiment, the first alignment film 22 and the second alignment film 23 are photo-alignment films. The photo-alignment film is formed by photo-aligning a coating film formed on a substrate using a polymer composition (liquid crystal aligning agent) containing a polymer having photo-alignment groups. The polymer having a photo-alignment group is not particularly limited, and conventional polymers can be used, and examples thereof include polymers having a cinnamic acid structure, an azobenzene structure, a coumarin structure, a chalcone structure, and a cyclobutane structure (for example, polyamic acid, polyimide, polyorganosiloxane, a maleimide polymer, a styrene-maleimide polymer, and the like).

The first substrate 11 and the second substrate 12 are arranged with a predetermined gap (cell gap) provided between the spacers 24 so that the electrode arrangement surface of the first substrate 11 faces the electrode arrangement surface of the second substrate 12. In fig. 1, the spacers 24 are shown as columnar spacers, but may be spacers for other liquid crystal devices such as bead spacers. The first substrate 11 and the second substrate 12, which are disposed to face each other, are bonded to each other at their peripheral edges via a sealing member 25. The space surrounded by the first substrate 11, the second substrate 12, and the sealing member 25 is filled with a liquid crystal composition. Thereby, the liquid crystal layer 13 is formed between the first substrate 11 and the second substrate 12. The liquid crystal layer 13 is filled with a liquid crystal composition containing a liquid crystal having negative dielectric anisotropy and a chiral agent.

As the liquid crystal, a conventional liquid crystal material having negative dielectric anisotropy can be used. The refractive index anisotropy Δ n of the liquid crystal can be appropriately set so that the retardation (d · Δ) expressed by the product of the refractive index anisotropy Δ n of the liquid crystal and the thickness d of the liquid crystal layer 13 becomes a desired value. The chiral agent is not particularly limited, and conventional chiral agents can be used. Examples of the chiral reagent to be used include S-811, R-811 and CB-15 (manufactured by Merck). The amount of the chiral agent added is, for example, 0.1 to 10% by mass based on the total amount of the liquid crystal having negative dielectric anisotropy.

Polarizing plates are disposed outside the first substrate 11 and the second substrate 12, respectively. The polarizing plates include a first polarizing plate 27 disposed on the first substrate 11 side, and a second polarizing plate 28 disposed on the second substrate 12 side. In the liquid crystal display element 10, the first polarizing plate 27 and the second polarizing plate 28 are arranged so that transmission axes thereof are orthogonal to each other. In the present embodiment, the first polarizing plate 27 and the second polarizing plate 28 are arranged such that the transmission axis of the first polarizing plate 27 extends in the horizontal direction and the transmission axis of the second polarizing plate 28 extends in the vertical direction. A terminal region is provided at the outer edge portion of the first substrate 11. The liquid crystal display element 10 is driven by connecting a driver Integrated Circuit (IC) or the like for driving liquid crystal to the terminal region.

The plurality of pixels 30 are arranged in a matrix including a plurality of rows and a plurality of columns. In the present embodiment, the plurality of pixels 30 are arranged such that the short side direction (pixel horizontal direction) of the pixel 30 is parallel to the axial direction of the transmission axis of the first polarizing plate 27, and the long side direction (pixel vertical direction) of the pixel 30 is parallel to the axial direction of the transmission axis of the second polarizing plate 28. The liquid crystal display element 10 employs a stripe arrangement as an arrangement pattern of the color filters 18. Therefore, the plurality of pixels 30 are arranged in a stripe shape such that the same color pixels extend in one of the row direction and the column direction, and are arranged such that different color pixels are adjacent to each other along the other direction. For example, the color filters 18 are arranged in the order of red (R), green (G), and blue (B) for each column.

(Pixel Structure)

Next, a pixel structure of the liquid crystal display element 10 will be described with reference to fig. 2 and 3. In addition, the arrows in fig. 3 indicate the exposure azimuth of the photo-alignment treatment (i.e., the alignment azimuth of the liquid crystal molecules). The first substrate 11 (TFT substrate) is shown in an exposure orientation when the first substrate 11 is viewed from the front side of the side where the photo-alignment film is formed, and the second substrate 12 (counter substrate) is shown in an exposure orientation when the second substrate 12 is viewed from the front side of the side opposite to the side where the photo-alignment film is formed.

As shown in fig. 2 and 3, the pixel 30 has a plurality of alignment regions (hereinafter also referred to as "liquid crystal regions") in which the alignment azimuths of the liquid crystal molecules are different. Thereby, the viewing angle characteristic of the liquid crystal display element 10 is compensated. In the present embodiment, in each pixel 30, four liquid crystal domains are formed in half of the pixel by alignment division based on photo-alignment.

Specifically, the pixel 30 includes a half pixel having four liquid crystal domains, i.e., the first domain 31 to the fourth domain 34, and the plurality of liquid crystal domains are arranged in a line in the vertical direction of the pixel region (see (i) of fig. 3). In each domain, the first alignment film 22 and the second alignment film 23 define the alignment orientation of the liquid crystal molecules in the vicinity of the alignment films. The orientation direction of the liquid crystal molecules in the vicinity of the orientation film is preferably 30 degrees to 60 degrees with respect to the horizontal direction of the display surface. When the orientation direction of the liquid crystal molecules is expressed as an angle relative to the horizontal direction of the display surface, that is, an angle formed by the orientation direction of the liquid crystal molecules and the horizontal direction of the display surface, the angle is an acute angle.

When the counterclockwise direction with respect to the horizontal direction of the display surface is expressed as a positive value, the exposure direction of each domain in the alignment film on the first substrate 11 side and the alignment film on the second substrate 12 side is preferably 45 degrees ± 15 degrees with respect to the horizontal direction of the display surface (i.e., the axial direction of the transmission axis of the first polarizing plate 27), or 45 degrees ± 15 degrees with respect to the vertical direction of the display surface (i.e., the axial direction of the transmission axis of the second polarizing plate 28). In the present embodiment, as shown in fig. 3 (i), the exposure orientation of each field is an orientation at substantially 45 degrees with respect to the respective axial directions of the transmission axis of the first polarizing plate 27 and the transmission axis of the second polarizing plate 28. Specifically, the angle of the exposure azimuth of each field with respect to the reference azimuth (0 degree) is approximately-45 degrees (= approximately 315 degrees) in the first field 31, approximately 45 degrees in the second field 32, approximately 225 degrees in the third field 33, and approximately 135 degrees in the fourth field 34. The exposure azimuth on the first substrate 11 side and the exposure azimuth on the second substrate 12 side are different from each other by substantially 90 degrees (see fig. 2 (i)). In the figure, reference numeral 39 denotes a signal line.

By controlling the alignment orientations of the liquid crystal molecules in the vicinity of the alignment films by the first alignment film 22 and the second alignment film 23, the alignment orientation of the liquid crystal layer 13 differs by an integral multiple of 90 degrees between any two liquid crystal domains. The orientation of the liquid crystal layer 13 in each liquid crystal domain is preferably ± 15 degrees with respect to the horizontal direction of the display surface, or ± 15 degrees with respect to the vertical direction of the display surface, and more preferably ± 5 degrees with respect to the horizontal direction of the display surface, or ± 5 degrees with respect to the vertical direction of the display surface. In the present embodiment, the angle of the orientation azimuth of the liquid crystal layer 13 with respect to the reference azimuth (0 degree) is substantially 0 degree in the first domain 31, substantially 90 degrees in the second domain 32, substantially 270 degrees in the third domain 33, and substantially 180 degrees in the fourth domain 34.

The pretilt angle defined by the first alignment film 22 (hereinafter, also referred to as "first tilt angle θ 1") and the pretilt angle defined by the second alignment film 23 (hereinafter, also referred to as "second tilt angle θ 2") are each less than 90 degrees. From the viewpoint of suppressing the response retardation of the liquid crystal molecules, the first tilt angle θ 1 and the second tilt angle θ 2 are preferably 89.9 degrees or less, more preferably 89.5 degrees or less, and even more preferably 89.0 degrees or less. In addition, from the viewpoint of suppressing the decrease in contrast of the liquid crystal display element 10, the first inclination angle θ 1 and the second inclination angle θ 2 are preferably 81.0 degrees or more, more preferably 83.0 degrees or more, and still more preferably 84.0 degrees or more. The first inclination angle θ 1 and the second inclination angle θ 2 may be the same or different.

The first alignment film 22 and the second alignment film 23 are subjected to photo-alignment treatment so that the exposure directions intersect at a predetermined angle (preferably, are orthogonal) with each other in a state where the first substrate 11 and the second substrate 12 are disposed facing each other. In addition, the liquid crystal layer 13 contains a chiral agent. Thereby, the liquid crystal molecules in the liquid crystal layer 13 are twisted and aligned between the first substrate 11 and the second substrate 12 in a state where a voltage is applied. At this time, the exposure azimuth of each liquid crystal domain is set so that the twist direction of the liquid crystal molecules becomes the same direction among the plurality of liquid crystal domains. The twist angle of the liquid crystal molecules in a state where a voltage is applied to the liquid crystal layer 13 is preferably set to be in a range of 60 degrees to 120 degrees. In this embodiment, the twist angle of the liquid crystal molecules is set to approximately 90 degrees. The term "orthogonal" in the present specification means that the two are substantially orthogonal to each other, specifically, an angle of 80 to 100 degrees, preferably 85 to 95 degrees.

In consideration of the influence of the optical rotation in the twisted state of the liquid crystal expressed by the chiral agent, the retardation (d · Δ n) expressed by the product of the refractive index anisotropy Δ n of the liquid crystal and the thickness d of the liquid crystal layer 13 is preferably high. Specifically, from the viewpoint of obtaining a liquid crystal display element having sufficiently high transmittance, it is preferably 405nm or more, and more preferably 415nm or more. Therefore, it is preferable to select the liquid crystal so that the retardation is within the above range according to the thickness d of the liquid crystal layer 13. In the present specification, the measurement wavelength of the refractive index anisotropy Δ n is in the vicinity of 546nm (more specifically, a wavelength in the range of 546nm to 550 nm). The "chiral pitch of liquid crystal" is a distance at which liquid crystal molecules are twisted by one period (360 degrees) in the thickness direction of the liquid crystal layer 13. The chiral pitch p can be adjusted to a desired value by adjusting the amount of chiral agent added to the liquid crystal.

(function of liquid Crystal display element)

Next, the operation of the liquid crystal display element 10 will be described. In the liquid crystal layer 13 of the liquid crystal display element 10, a chiral agent is added to a liquid crystal having negative dielectric anisotropy. By adding the chiral agent, generation of dark lines in the pixel can be suppressed, and a liquid crystal display element having excellent transmittance characteristics can be obtained.

Fig. 4 shows the results of analyzing the generation of dark lines within the pixel by simulation in the case where the liquid crystal layer 13 is formed using a liquid crystal composition in which a chiral agent is added to a liquid crystal having negative dielectric anisotropy, and in the case where the liquid crystal layer 13 is formed using a liquid crystal composition in which a chiral agent is not added to a liquid crystal having negative dielectric anisotropy. Fig. 4 (i) shows simulation results corresponding to the pixel structure of the liquid crystal display element 10 according to the present embodiment (see fig. 2 (i) and 3 (i)).

In the pixel structures of fig. 2 (i) and 3 (i), when no chiral agent is added to the liquid crystal having negative dielectric anisotropy, a dark line DL1 (more specifically, a dark line DLl extending in the a direction in a portion adjacent to each domain) extending along the boundary portion is generated at the boundary portion of the alignment division as shown in the lower stage (comparative example) of fig. 4, and a dark line DL2 (more specifically, a dark line DL2 extending in the b direction in one of both end portions in the a direction in each domain) extending in a direction orthogonal to the boundary portion is generated at one end portion of each domain. On the other hand, when a chiral agent is added to the liquid crystal having negative dielectric anisotropy, the dark lines DL1 and DL2 disappear as shown in the upper stage (example) of fig. 4, and the area of the white display portion in the pixel region increases. This improves the transmittance of light for each pixel, and as a result, the liquid crystal display element 10 having excellent transmittance characteristics can be obtained.

Fig. 5 shows a relationship between retardation (d · Δ n) obtained by simulation analysis and 1/(p/d) represented by the reciprocal of the value of the chiral pitch (p) relative to the thickness (d) of the liquid crystal layer 13 in the liquid crystal display element 10. In fig. 5, curve a is a function of the increase rate of the transmittance with respect to the reference transmittance of about 3.0% in the case where the transmittance of a liquid crystal display element in which the liquid crystal layer 13 is formed using a liquid crystal composition in which no chiral agent is added to a liquid crystal having negative dielectric anisotropy is used as the reference transmittance, and is represented by the following equation (3). Curve B is a function of the increase rate of the transmittance with respect to the reference transmittance of about 6.0%, and is represented by the following expression (4). Further, the retardation of the liquid crystal display element for which the reference transmittance is calculated has been optimized so as to maximize the transmittance. The increase rate Δ Q (%) of the transmittance is calculated by the following numerical formula (5). In the following expressions (3) to (5), d · Δ n is in nm, and p and d in 1/(p/d) are in μm.

y＝4661.2x ² -2431.5x+723.0…(3)

y＝5140.4x ² -2758.3x+787.1…(4)

(in the numerical formulas (3) and (4), x represents 1/(p/d) and y represents d.DELTA.n)

ΔQ＝((Q2-Q1)/Q1)×100…(5)

(in the formula (5), Q1 represents a reference transmittance, and Q2 represents a transmittance of a liquid crystal display element in which a liquid crystal layer 13 is formed using a liquid crystal composition in which a chiral agent is added to a liquid crystal having negative dielectric anisotropy.)

From fig. 5, it can be said that the transmittance can be further improved by blending a chiral agent in a liquid crystal having negative dielectric anisotropy and setting d, Δ n, and p of the liquid crystal display element 10 to d · Δ n so as to satisfy the following expression (1). From the viewpoint of further improving the transmittance, it is more preferable to set d, Δ n, and p so as to satisfy the following expression (2). In the following numerical expressions (1) and (2), d · Δ n is in nm, and p and d are in μm, 1/(p/d).

y≥4661.2x ² -2431.5x+723.0…(1)

y≥5140.4x ² -2758.3x+787.1…(2)

(in the numerical formulae (1) and (2), x represents 1/(p/d), y represents d.DELTA.n)

The liquid crystal display element 10 thus obtained can be effectively applied to various uses. The liquid crystal display element 10 can be used as various display devices such as a clock, a portable game machine, a word processor, a notebook Personal computer (note type Personal computer), a car navigation system, a camcorder (camcorder), a Personal Digital Assistant (PDA), a Digital camera (Digital camera), a mobile phone, a smartphone (smartphone), various monitors, a liquid crystal television, and an information display.

(second embodiment)

Next, the second embodiment will be described focusing on differences from the first embodiment. In the first embodiment, the entire surface electrodes are used as the pixel electrode 15 and the counter electrode 19. In contrast, the present embodiment is different from the first embodiment in that a slit electrode formed with a plurality of linear slits is used as the pixel electrode 15 and the entire surface electrode is used as the counter electrode 19.

An example of a pixel structure when the pixel electrode is a slit electrode is shown in fig. 2 (ii) and 3 (ii). In the pixel 30 shown in fig. 2 (ii), eight liquid crystal domains (specifically, two half pixels each having four liquid crystal domains) having different slit extending directions between two adjacent domains are arranged along the vertical direction (b direction in fig. 2) of the display surface. In the slit electrode, an angle formed by the horizontal direction of the display surface (a direction in fig. 2) and the direction in which the slits extend is preferably 30 degrees to 60 degrees, and more preferably 40 degrees to 50 degrees. In the present embodiment, an angle formed between the horizontal direction of the display surface and the direction in which the slits extend is set to approximately 45 degrees.

(third embodiment)

Next, the third embodiment will be described focusing on differences from the first embodiment. The liquid crystal display element of the present embodiment is different from the first embodiment in that one of the pretilt angle (first inclination angle θ 1) defined by the first alignment film 22 and the pretilt angle (second inclination angle θ 2) defined by the second alignment film 23 is smaller than 90 degrees and the other is substantially 90 degrees.

Fig. 3 (iii) shows the exposure orientations of the first alignment film 22 and the second alignment film 23 in each pixel 30 of the liquid crystal display element 10 according to the present embodiment. As shown in fig. 3 (iii), the liquid crystal alignment film (first alignment film 22) on the first substrate 11 side is a photo-alignment film that is split into individual pieces by photo-alignment treatment, and the first tilt angle θ 1 is smaller than 90 degrees. On the other hand, the liquid crystal alignment film (second alignment film 23) on the second substrate 12 side is not subjected to the divisional exposure. In the present embodiment, the same coating film formed using the polymer composition as the first alignment film 22 is used as the second alignment film 23 without being irradiated with light. The second inclination angle θ 2 is substantially 90 degrees.

Instead of the structure in which the second alignment film 23 is not irradiated with light, the entire surface of the second alignment film 23 may be exposed to unpolarized light from the substrate normal direction without using a photomask. In this case, the exposure to the second substrate 12 may be parallel light or diffused light. In the present specification, the term "substantially 90 degrees" refers to a range of 90 degrees ± 0.5 degrees. The pretilt angle θ 2 defined by the second alignment film 23 is preferably 90 degrees ± 0.2 degrees, and more preferably 90 degrees ± 0.1 degrees.

From the viewpoint of suppressing the response retardation of the liquid crystal molecules, the first tilt angle θ 1 is preferably 89.0 degrees or less, and more preferably 88.5 degrees or less. In addition, from the viewpoint of suppressing the decrease in contrast of the liquid crystal display element 10, the first inclination angle θ 1 is preferably 81.0 degrees or more, more preferably 83.0 degrees or more, and still more preferably 84.0 degrees or more.

The angle of the orientation azimuth of the liquid crystal molecules present in the vicinity of the first orientation film 22 with respect to the horizontal direction of the display surface (i.e., the angle formed by the orientation azimuth of the liquid crystal molecules present in the vicinity of the first orientation film 22 with respect to the horizontal direction of the display surface) is preferably 30 to 60 degrees. When the counterclockwise direction with respect to the horizontal direction of the display surface is represented as a positive value, the orientation direction of the liquid crystal molecules present in the vicinity of the first alignment film 22 is preferably 45 degrees ± 15 degrees with respect to the horizontal direction of the display surface or 45 degrees ± 15 degrees with respect to the vertical direction of the display surface, and more preferably 45 degrees ± 5 degrees with respect to the horizontal direction of the display surface or 45 degrees ± 5 degrees with respect to the vertical direction of the display surface. In the present embodiment, as shown in fig. 3 (iii), the exposure orientation of each field is an orientation at substantially 45 degrees with respect to the respective axial directions of the transmission axis of the first polarizing plate 27 and the transmission axis of the second polarizing plate 28. Specifically, the angle of the exposure azimuth of each field with respect to the reference azimuth (0 degree) is approximately-45 degrees (= approximately 315 degrees) in the first field 31, approximately 45 degrees in the second field 32, approximately 225 degrees in the third field 33, and approximately 135 degrees in the fourth field 34. The alignment orientation of the liquid crystal layer 13 differs by an integral multiple of 90 degrees between any two liquid crystal domains of the first to fourth domains. In this case, the angle formed by the orientation direction of the liquid crystal molecules present in the vicinity of the first alignment film 22 and the horizontal direction of the display surface is 45 degrees.

In each pixel 30, the orientation of the long axis direction of the liquid crystal molecules present in the vicinity of the center in the thickness direction of the liquid crystal layer 13 projected onto the first substrate 11 (that is, the orientation of the liquid crystal layer 13) is preferably ± 15 degrees with respect to the horizontal direction of the display surface, or ± 15 degrees with respect to the vertical direction of the display surface.

In the liquid crystal display element 10 of the present embodiment, only one substrate may be used for alignment division, and therefore, the number of times of alignment treatment can be reduced in manufacturing the liquid crystal display element 10. Therefore, it is possible to obtain a liquid crystal display element in which generation of a dark line in a pixel region is suppressed while efficiency of a manufacturing process is improved.

(fourth embodiment)

Next, the fourth embodiment will be described focusing on differences from the third embodiment. In the third embodiment, the entire surface electrodes are used as the pixel electrode 15 and the counter electrode 19. In contrast, the present embodiment differs from the third embodiment in that a slit electrode having a plurality of slits formed therein is used as the pixel electrode 15.

An example of the pixel structure when the pixel electrode is a slit electrode is shown in fig. 2 (iv) and 3 (iv). The pixel 30 shown in (iv) of fig. 2 uses a slit electrode having the same structure as that of the second embodiment as a pixel electrode. The opposed electrode 19 is a full-surface electrode. In the liquid crystal display device 10 of the above embodiment, only one substrate may be used for alignment division, and therefore, the number of alignment processes can be reduced even when the liquid crystal display device 10 is manufactured. Therefore, it is possible to obtain a liquid crystal display element in which generation of a dark line in a pixel region is suppressed while efficiency of a manufacturing process is improved.

(fifth embodiment)

Next, the fifth embodiment will be described focusing on differences from the first embodiment. In the first embodiment, a vertical alignment liquid crystal display element 10 having a photo alignment film will be described. In contrast, the liquid crystal display element 10 of the present embodiment is different from the first embodiment in that it is a vertical Alignment type liquid crystal display element obtained by using a Polymer Stabilized Alignment (PSA) technique.

Fig. 6 shows a schematic configuration of the liquid crystal display element 10 of the present embodiment. In fig. 6, the liquid crystal display element 10 includes a polymer layer 21 formed by polymerization of a photopolymerizable monomer at a boundary portion between the first substrate 11 and the liquid crystal layer 13 and a boundary portion between the second substrate 12 and the liquid crystal layer 13. The polymer layer 21 is formed together with the liquid crystal layer 13 by disposing a layer containing a liquid crystal composition using a liquid crystal composition containing a liquid crystal having negative dielectric anisotropy, a chiral agent, and a photopolymerizable monomer, and by performing photopolymerization in a state in which liquid crystal molecules are aligned in a pre-tilt manner after the liquid crystal cell is constructed. Initial alignment of liquid crystal molecules in the liquid crystal layer 13 is controlled by the polymer layer 21. The first alignment film 22 and the second alignment film 23 are used as they are without alignment treatment of a coating film formed using a liquid crystal alignment agent.

The pixel structure of the liquid crystal display element 10 in fig. 6 is shown in fig. 2 (v) and fig. 3 (v). As shown in fig. 2 (v), the pixel electrode 15 is a slit electrode, and the counter electrode 19 is a full-surface substrate. The pixel electrode 15 is configured to divide a half pixel into 2 rows, 2 columns, and 4 alignment regions, and the direction in which the slits extend has 8 regions different between the adjacent 2 regions. In the slit electrode, an angle formed by the horizontal direction of the display surface (a direction in fig. 2) and the direction in which the slits extend is preferably 30 degrees to 60 degrees, and more preferably 40 degrees to 50 degrees. In the present embodiment, an angle formed between the horizontal direction of the display surface and the direction in which the slits extend is set to substantially 45 degrees.

In the PSA liquid crystal display device 10 of fig. 6, the occurrence of dark lines in the pixel can be suppressed by adding a chiral agent to the liquid crystal having negative dielectric anisotropy. This point will be explained based on the analysis result obtained by the simulation according to fig. 4. Fig. 4 (v) shows the simulation result of the liquid crystal display element 10 according to the present embodiment.

In the pixel structures of fig. 2 (v) and 3 (v), when no chiral agent is added to the liquid crystal having negative dielectric anisotropy, a dark line DL3 extending along the boundary portion (more specifically, a dark line DL3 extending along the b direction) and a dark line DL4 extending in a direction from each side of the pixel 30 toward the inner side of the pixel 30 (more specifically, a dark line DL4 extending along the four sides constituting the pixel 30 and extending in an oblique direction from each side toward the center of a half pixel) are generated at the boundary portion of the alignment division as shown in the lower stage (comparative example) of fig. 4 (v) in white display of the liquid crystal display element 10. On the other hand, when the chiral agent is added to the liquid crystal having negative dielectric anisotropy, the dark lines DL3 and DL4 disappear and the area of the white display portion increases as shown in the upper stage (example) of fig. 4 (v). This improves the light transmittance per pixel, and the liquid crystal display element 10 having excellent transmittance characteristics can be obtained.

(sixth embodiment)

Next, the sixth embodiment will be described focusing on differences from the first embodiment. In the liquid crystal display element of the present embodiment, both the first alignment film 22 and the second alignment film 23 are photo-alignment films. The pixel 30 differs from the first embodiment in that a pretilt angle defined by the optical alignment film formed on the first substrate 11 (TFT substrate) is smaller than 90 degrees in a part of the plurality of alignment regions (first to fourth regions 31 to 34), and is substantially 90 degrees in the pretilt angle defined by the optical alignment film formed on the second substrate 12 (counter substrate), and a pretilt angle defined by the optical alignment film formed on the first substrate 11 (TFT substrate) is substantially 90 degrees in the remaining alignment regions, and is smaller than 90 degrees in the pretilt angle defined by the optical alignment film formed on the second substrate 12 (counter substrate).

Fig. 7 shows an electrode structure of the liquid crystal display element 10 according to the present embodiment, and fig. 8 shows exposure orientations of the first alignment film 22 and the second alignment film 23 in each pixel 30 of the liquid crystal display element 10 according to the present embodiment. In fig. 7 and 8, (i) is a case where the exposure azimuth is set to the pixel horizontal direction, and (ii) is a case where the exposure azimuth is set to a predetermined angle α with respect to the pixel horizontal direction. As shown in fig. 7, the pixel electrode 15 and the counter electrode 19 of the pixel 30 are planar electrodes (entire electrodes) without slits. The counter electrode 19 is a common electrode common to all the pixel electrodes 15.

As shown in fig. 8, the liquid crystal alignment film (first alignment film 22) on the first substrate 11 side is a photo-alignment film subjected to alignment division by photo-alignment treatment. Specifically, of the first to fourth domains 31 to 34, the second domain 32 and the fourth domain 34 are subjected to the photo-alignment treatment, and the first domain 31 and the third domain 33 are not subjected to the photo-alignment treatment. Accordingly, the tilt angle of the liquid crystal molecules existing in the vicinity of the first alignment films of the second domain 32 and the fourth domain 34 is smaller than 90 degrees on the first substrate 11 side, and the tilt angle of the liquid crystal molecules existing in the vicinity of the first alignment films of the first domain 31 and the third domain 33 is substantially 90 degrees.

The liquid crystal alignment film (second alignment film 23) on the second substrate 12 side is also a photo-alignment film subjected to alignment division by photo-alignment treatment, similarly to the first alignment film 22. The first alignment film 22 and the second alignment film 23 have different alignment domains subjected to photo-alignment treatment. Specifically, on the second substrate 12 side, the first domain 31 and the third domain 33 are subjected to the photo-alignment treatment, and the second domain 32 and the fourth domain 34 are not subjected to the photo-alignment treatment, among the first domain 31 to the fourth domain 34. Accordingly, on the second substrate 12 side, the tilt angle of the liquid crystal molecules present in the vicinity of the second alignment films of the first domain 31 and the third domain 33 is smaller than 90 degrees, and the tilt angle of the liquid crystal molecules present in the vicinity of the second alignment films of the second domain 32 and the fourth domain 34 is substantially 90 degrees.

In the alignment domains subjected to the photo-alignment treatment, the pretilt angle (first tilt angle θ 1) defined by the first alignment film 22 and the pretilt angle (second tilt angle θ 2) defined by the second alignment film 23 are preferably 89.0 degrees or less, and more preferably 88.5 degrees or less, from the viewpoint of suppressing the response retardation of the liquid crystal molecules. In addition, from the viewpoint of suppressing a decrease in contrast of the liquid crystal display element 10, the first inclination angle θ 1 is preferably 81.0 degrees or more, more preferably 83.0 degrees or more, and even more preferably 84.0 degrees or more.

In the first alignment film 22 and the second alignment film 23, the angle of the alignment azimuth of the liquid crystal molecules present in the vicinity of the alignment region having a pretilt angle of less than 90 degrees with respect to the horizontal direction of the display surface (i.e., the angle formed by the alignment azimuth of the liquid crystal molecules in the vicinity of the alignment films and the horizontal direction of the display surface) is preferably 0 degree or more and 50 degrees or less. When the counterclockwise direction with respect to the horizontal direction of the display surface is a positive value, the alignment azimuth of the liquid crystal molecules present in the vicinity of the alignment region having a pretilt angle of less than 90 degrees is preferably ± 50 degrees with respect to the horizontal direction of the display surface.

In the liquid crystal display element having the pixel structure shown in fig. 8 (i), the exposure azimuth of each domain is an azimuth parallel to the axial direction of either the transmission axis of the first polarizing plate 27 or the transmission axis of the second polarizing plate 28. Specifically, the angle of the exposure azimuth of each field with respect to the reference azimuth (0 degree) is substantially 180 degrees in the second field 32, substantially 0 degrees in the fourth field 34, substantially 0 degrees in the first field 31, and substantially 180 degrees in the third field 33 of the first substrate 11. In this case, the angle formed by the orientation direction of the liquid crystal molecules present in the vicinity of the first alignment film 22 and the horizontal direction of the display surface is 0 degrees.

In the liquid crystal display element having the pixel structure shown in fig. 8 (ii), the exposure orientation of each domain is 15 degrees with respect to the axial direction of either the transmission axis of the first polarizing plate 27 or the transmission axis of the second polarizing plate 28. Specifically, the angle of the exposure azimuth of each field with respect to the reference azimuth (0 degree) is approximately 195 degrees in the second field 32, approximately 15 degrees in the fourth field 34, approximately-15 degrees (= approximately 345 degrees) in the first field 31, and approximately 165 degrees in the third field 33 of the first substrate 11. In this case, the angle formed by the orientation direction of the liquid crystal molecules present in the vicinity of the first alignment film 22 and the horizontal direction of the display surface is 15 degrees.

In terms of further improving the transmittance characteristics, in the first alignment film 22 and the second alignment film 23, the angle formed by the alignment azimuth of the liquid crystal molecules present in the vicinity of the alignment region having a pretilt angle of less than 90 degrees and the horizontal direction of the display surface is more preferably 0 degree or more and 40 degrees or less, and still more preferably 0 degree or more and 30 degrees or less.

From the viewpoint of obtaining a liquid crystal display element having sufficiently high transmittance, the retardation (d · Δ n) represented by the product of the refractive index anisotropy Δ n of the liquid crystal and the thickness d of the liquid crystal layer 13 is preferably 370nm or more, and more preferably 400nm or more.

In the liquid crystal layer 13 of the liquid crystal display element 10, a chiral agent is added to liquid crystal having negative dielectric constant anisotropy. By adding the chiral agent, generation of dark lines in pixels can be suppressed, and a liquid crystal display element having excellent transmittance characteristics can be obtained. In particular, in the liquid crystal display element 10 of the present embodiment, the orientation direction of the liquid crystal molecules present near the center in the thickness direction of the liquid crystal layer 13 (i.e., the orientation direction of the liquid crystal layer 13) can be set to be near 45 degrees with respect to the transmission axis of the first polarizing plate 27 and the transmission axis of the second polarizing plate 28. This makes it possible to achieve liquid crystal alignment with respect to the transmission axis of the polarizing plate having the highest transmittance in the optical rotation mode.

In order to obtain a plurality of alignment regions in which the alignment direction of the liquid crystal molecules present in the vicinity of the center in the thickness direction of the liquid crystal layer 13 is about 45 degrees with respect to the transmission axis of the first polarizing plate 27 and the transmission axis of the second polarizing plate 28 by exposure processing of one of the TFT substrate and the counter substrate, it is necessary to make the direction in which the liquid crystal molecules are to be aligned (exposure direction) orthogonal to the scanning direction during exposure (moving direction of the substrate). Therefore, a novel exposure machine is developed, resulting in an increase in manufacturing cost. In contrast, in the present embodiment, by performing exposure processing on a part of the alignment regions of the TFT substrate and the counter substrate, a plurality of alignment regions can be formed when the direction in which the liquid crystal molecules are to be aligned (exposure direction) is not orthogonal to the scanning direction during exposure (moving direction of the substrate). As a result, the transmittance can be improved without increasing the manufacturing cost.

In addition, in this embodiment, dark lines extending along the boundary portions of the alignment division and dark lines extending from each side of the pixel toward the inside of the pixel can be eliminated, and the transmittance of the white display portion can be improved as compared with embodiments 1 to 5 having the same d · Δ n.

(other embodiments)

The present disclosure is not limited to the above-described embodiments, and may be implemented in the following embodiments, for example.

In the third and fourth embodiments, the pretilt angle defined by the first alignment film 22 is set to be smaller than 90 degrees and the pretilt angle defined by the second alignment film 23 is substantially 90 degrees, but the pretilt angle defined by the second alignment film 23 may be set to be smaller than 90 degrees and the pretilt angle defined by the first alignment film 22 may be substantially 90 degrees.

In the second, fourth, and fifth embodiments, the case where the slit electrode having the slit formed on the entire surface of the pixel region is used as the pixel electrode is described, but the slit electrode having the slit formed only on a part of the pixel region (for example, a boundary portion between two adjacent regions, or an outer edge portion in any one of the vertical direction and the horizontal direction of the pixel 30) may be used as the pixel electrode.

The number of orientation divisions of the pixel or the shape of the pixel is not limited to the configuration of the above embodiment. For example, the present disclosure may be applied to a liquid crystal display element in which one pixel orientation is divided into two regions, or a liquid crystal display element in which one pixel orientation is divided into four regions. In addition, the present disclosure can be applied to a liquid crystal display element including the following pixels: each side of the pixel includes a short side portion extending in the vertical direction and a long side portion extending in the horizontal direction, and the plurality of alignment regions are arranged in a line in the short side direction.

In the above embodiment, the color filter is provided on the second substrate 12, but the color filter may be provided on the first substrate 11.

Examples

The embodiments are described below based on examples, but the present disclosure is not to be construed as being limited by the following examples.

< preparation of liquid Crystal alignment agent >

1. Synthesis of polymers

[ Synthesis example 1]

5.00g (8.6 mmol) of the compound represented by the following (MI-1), 0.64g (4.3 mmol) of 4-vinylbenzoic acid, 2.82g (13.0 mmol) of 4- (2, 5-dioxo-3-pyrrolin-1-yl) benzoic acid, 3.29g (17.2 mmol) of 4- (glycidoxymethyl) styrene, 0.31g (1.3 mmol) of 2,2' -azobis (2, 4-dimethylvaleronitrile) as a radical polymerization initiator, 0.52g (2.2 mmol) of 2, 4-diphenyl-4-methyl-1-pentene as a chain transfer agent, and 25mL of tetrahydrofuran as a solvent were charged in a 100mL two-necked flask under nitrogen, and polymerized at 70 ℃ for 5 hours. After reprecipitation in n-hexane, the precipitate was filtered and dried under vacuum at room temperature for 8 hours, thereby obtaining a styrene-maleimide polymer (referred to as "polymer (PM-1)"). The weight average molecular weight Mw as measured by Gel Permeation Chromatography (GPC) in terms of polystyrene was 30000 and the molecular weight distribution Mw/Mn was 2.0.

[ solution 1]

The weight average molecular weight Mw and the number average molecular weight Mn of the polymer are polystyrene converted values measured by GPC under the following conditions.

Pipe column: TSKgelGRCXLII manufactured by Tosoh (Strand, tosoh)

Solvent: tetrahydrofuran (THF)

Temperature: 40 deg.C

Pressure: 68kgf/cm ²

[ Synthesis example 2]

13.8g (70.0 mmol) of 1,2,3, 4-cyclobutanetetracarboxylic dianhydride and 16.3g (76.9 mmol) of 2,2 '-dimethyl-4, 4' -diaminobiphenyl were dissolved in 170g of N-Methyl-2-Pyrrolidone (N-Methyl-2-pyrollidone, NMP) and reacted at 25 ℃ for 3 hours, thereby obtaining a solution containing 10 mass% of polyamic acid. Then, the polyamic acid solution was poured into a large excess of methanol to precipitate a reaction product. The obtained precipitate was washed with methanol and dried at 40 ℃ for 15 hours under reduced pressure, thereby obtaining a polyamic acid (which was referred to as "polymer (PAA-1)").

2. Preparation of liquid crystal aligning agent

To 10 parts by mass of the polymer (PM-1) and 100 parts by mass of the polymer (PAA-1), N-methyl-2-pyrrolidone (NMP) and Butyl Cellosolve (BC) were added to prepare a solution having a solvent composition of NMP/BC =50/50 (mass ratio) and a solid content concentration of 4.0 mass%. The solution was filtered using a filter having a pore size of 1 μm, thereby preparing a liquid crystal aligning agent (AL-1).

< Effect of adding chiral agent >

[ example 1]

1. Manufacture of liquid crystal display element

A liquid crystal display element is manufactured using a TFT substrate and a counter substrate. As the pixel electrode of the TFT substrate and the electrode of the counter substrate, a full-surface electrode without a slit is used (see fig. 2 (i)). First, a liquid crystal aligning agent (AL-1) was applied to the electrode arrangement surfaces of the TFT substrate and the counter substrate by spin-casting. The film was prebaked at 80 ℃ for 1 minute, and then, after 40 minutes at 230 ℃, the film was postbaked to form a coating film having a film thickness of 120 nm.

Next, the coating film formed on the TFT substrate is subjected to scanning exposure. As shown in (i) of FIG. 3, the scanning exposure is performed at 20mJ/cm ² The exposure direction of each of the domains is 45 degrees with respect to the short side direction (the a direction of fig. 3) of one pixel, and the exposure direction of each of the domains is arranged along the long side direction (the b direction of fig. 3) of one pixel by 8 domains different by an integral multiple of 90 degrees between the adjacent 2 domains. In addition, the coating film formed on the opposing substrate was also subjected to scanning exposure in the same manner as the TFT substrate, thereby forming a photo-alignment film.

Next, a liquid crystal composition is dropped on the surface of the TFT substrate on which the photo alignment film is formed. The liquid crystal composition is prepared by adding a chiral agent (product name "S-811", manufactured by Merck) to a nematic liquid crystal having negative dielectric anisotropy. In the preparation of the liquid crystal composition, the amount of the chiral agent to be added was adjusted so that the chiral pitch was 18 μm. The refractive index anisotropy (Δ n) of the liquid crystal used was 0.127.

Next, a thermosetting epoxy resin was placed as a sealant on the outer edge portion of the counter substrate, and the TFT substrate and the alignment film surface of the counter substrate were bonded to each other so as to be positioned inside each other, and then the epoxy resin was cured by heating at 130 ℃ for 1 hour, thereby obtaining a liquid crystal cell having a liquid crystal layer thickness (cell thickness d) of 4.5 μm. Further, in order to remove the flow alignment at the time of liquid crystal injection, the liquid crystal cell was heated at 150 ℃ and then gradually cooled to room temperature. Then, polarizing plates are bonded to both outer surfaces of the substrate of the liquid crystal cell so that transmission axes thereof are parallel to and orthogonal to each other in the longitudinal direction and the short-side direction of the pixel, respectively, to obtain a liquid crystal display element. The pretilt angle of the obtained liquid crystal display element was 88.0 degrees on both the TFT substrate side and the counter substrate side. The pretilt angle is a value measured using the OPTI-Pro manufactured by Shintech corporation (hereinafter the same).

2. Evaluation of transmittance characteristics

(1) Calculation of transmittance

The transmittance of the Liquid Crystal Display element 1 was calculated by simulation using an Liquid Crystal Display (LCD) of the type known as the Expert (Expert) manufactured by linkgglobal 21. As calculation conditions, liquid crystal physical properties: Δ ∈ =3.0, Δ n =0.127, cell gap: 4.5 μm, pretilt angle: measured value (in example 1, both TFT substrate side and opposing substrate side are 88.0 °), applied voltage: 6V. In the embodiment, the light transmittance is 0.296.

(2) Evaluation of dark line suppression based on pixel transmission map

For the liquid crystal display element of 1, an ipart (Expert) LCD manufactured by linkgglobal 21 company was used and a generation state of a dark line within a pixel was analyzed by simulation. The transmission of one pixel is illustrated in (i) of fig. 4. As shown in (i) of fig. 4, in the embodiment, a dark line is hardly recognized within the pixel.

[ example 2]

A liquid crystal display element was manufactured in the same manner as in example 1, except that the slit electrode shown in (ii) of fig. 2 was used as the pixel electrode. The Line and Space (L/S) of the slit electrode were set to L/S =3.5 μm/2.5 μm (the same applies hereinafter). The photo-alignment process is performed according to the exposure orientation shown in (ii) of fig. 3. In addition, the transmittance characteristics of the manufactured liquid crystal display element were evaluated by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was 0.292. In addition, almost no dark line was observed in the pixel (see (ii) of fig. 4).

[ example 3]

A liquid crystal display element was produced in the same manner as in example 1, except that the liquid crystal alignment film on the counter substrate side was not subjected to photo-alignment treatment (see fig. 2 (iii) and 3 (iii)). In addition, the transmittance characteristics of the manufactured liquid crystal display element were evaluated by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was 0.296. In addition, almost no dark line was observed in the pixel (see (iii) of fig. 4).

[ example 4]

A liquid crystal display element was produced in the same manner as in example 2, except that the liquid crystal alignment film on the counter substrate side was not subjected to photo-alignment treatment (see fig. 2 (iv) and 3 (iv)). In addition, the transmittance characteristics of the manufactured liquid crystal display element were evaluated by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was 0.287. In addition, almost no dark line was observed in the pixel (see (iv) of fig. 4).

[ example 5]

The transmittance characteristics of the PSA liquid crystal display device of fig. 6 were analyzed by simulation in the same manner as in example 1. The pixel electrode of the TFT substrate is an 8-segment slit electrode shown in fig. 2 (v), and the electrode of the counter substrate is a full-surface electrode. The pixel structure of example 5 is a structure in which the electrode structure is divided into 4 rows and 2 columns in a matrix manner. In the above embodiment, the alignment film on the TFT substrate side and the alignment film on the counter substrate side were not subjected to alignment treatment. As the liquid crystal composition, one obtained by adding a chiral agent (product name "S-811", manufactured by Merck) and a photopolymerizable monomer to a nematic liquid crystal having negative dielectric anisotropy and adjusting the amount of the chiral agent to be added so that the chiral pitch is 18 μm was used. As calculation conditions, liquid crystal physical properties: Δ ∈ =3.0, Δ n =0.127, cell gap: 4.5 μm, pretilt angle: measured value (in example 5, both TFT substrate side and opposing substrate side are 90.0 °), applied voltage: 6V. The light transmittance of the liquid crystal display element of the example was calculated as 0.286 by simulation. In addition, almost no dark line was observed in the pixel (see fig. 4 (v)).

Comparative example 1

A liquid crystal display element was produced in the same manner as in example 1, except that the chiral agent was not added to the liquid crystal material, the refractive index anisotropy Δ n of the liquid crystal was set to 0.100, the cell thickness d was set to 3.2 μm, and the exposure orientation of the photo alignment film on the counter substrate side was set to be antiparallel to the exposure orientation of the photo alignment film on the TFT substrate side. In comparative example 1, the retardation (d · Δ n) was set to 320nm in order to optimize the transmittance. In general, in a vertical alignment liquid crystal display element, it is known that a liquid crystal composition represented by d · Δ n: about 320nm to 340 nm. The exposure orientation of the photo-alignment film on the TFT substrate side was the same as in example 1.

The liquid crystal display element of comparative example 1 was evaluated for transmittance characteristics by simulation in the same manner as in example 1. As a result, the transmittance was 0.216 in the above example. In addition, as shown in fig. 4 (i), it was confirmed that a dark line extending in the short-side direction of the pixel (DL 1 in fig. 4) and a dark line extending in the long-side direction of the pixel (DL 2 in fig. 4) were generated at one end portion in the pixel in the boundary portion between the adjacent domains in the analysis result of the dark line in the pixel by simulation.

Comparative example 2

A liquid crystal display element was produced in the same manner as in example 2, except that the chiral agent was not added to the liquid crystal material, d · Δ n was 320nm, and the exposure orientation of the photo alignment film on the counter substrate side was antiparallel to the exposure orientation of the photo alignment film on the TFT substrate side. The liquid crystal display element was evaluated for transmittance characteristics by simulation in the same manner as in example 1. The exposure orientation of the photo-alignment film on the TFT substrate side was the same as in example 2. As a result, the transmittance was 0.234 in the above example. In addition, as shown in fig. 4 (ii), the analysis result of the dark line in the pixel by simulation confirmed the dark line having the same shape as that of comparative example 1.

Comparative example 3

A liquid crystal display element was produced in the same manner as in example 3, except that the chiral agent was not added to the liquid crystal material, and d · Δ n was 320nm. The liquid crystal display element was evaluated for transmittance characteristics by simulation in the same manner as in example 1. As a result, the transmittance was 0.192 in the above example. In addition, as shown in (iii) of fig. 4, a dark line having the same shape as that of comparative example 1 was confirmed in the analysis result of the dark line in the pixel by simulation.

Comparative example 4

A liquid crystal display element was produced in the same manner as in example 4, except that the chiral agent was not added to the liquid crystal material, and d · Δ n was 320nm. The liquid crystal display element was evaluated for transmittance characteristics by simulation in the same manner as in example 1. As a result, the transmittance was 0.219 in the above example. In addition, as shown in (iv) of fig. 4, the dark line having the same shape as that of comparative example 1 was confirmed in the analysis result of the dark line in the pixel by simulation.

Comparative example 5

A liquid crystal display element was produced in the same manner as in example 5, except that the chiral agent was not added to the liquid crystal material, and d · Δ n was 320nm. The liquid crystal display element was evaluated for transmittance characteristics by simulation in the same manner as in example 1. As a result, the transmittance was 0.219 in the above example. In addition, as shown in fig. 4 (v), it is confirmed that, in the analysis result of the dark line in the pixel by simulation, the dark line DL3 extending along the boundary portion is generated at the boundary portion of the orientation division, and the dark line DL4 extending in the direction from each side of the pixel 30 toward the inner side of the pixel is generated.

The results of calculating the conditions and the transmittances of the liquid crystal display elements of examples 1 to 5 and comparative examples 1 to 5 are summarized in table 1 below. In examples 1 to 5, the increase rate Δ Q of transmittance relative to comparative example 1 is also shown in table 1.

As shown in table 1 and fig. 4, in examples 1 to 5 in which the chiral agent was added to the liquid crystal having negative dielectric anisotropy, no dark line was observed in the pixel region, and high transmittance was exhibited. On the other hand, in comparative examples 1 to 5 in which no chiral agent was added to the liquid crystal having negative dielectric anisotropy, dark lines were clearly seen in the pixel regions, and the transmittance was also lower than that of the examples. As is clear from these results, by adding a chiral agent to a liquid crystal having negative dielectric anisotropy, the generation of dark lines in the pixel region can be suppressed.

< relationship between d.DELTA.n and p and transmittance characteristics accompanying addition of chiral reagent >

[ examples 6 to 15]

Next, in order to further verify the effect of transmittance improvement accompanying suppression of dark line generation, the retardation (d · Δ n) and the chiral pitch (p) were changed in the liquid crystal display element having the pixel structure of example 1 (the electrode structure of fig. 2 (i) and the exposure azimuth of fig. 3 (i)), and the influence on transmittance was examined. In each example, light transmittance of the liquid crystal display element was calculated by simulation using an epsipret (Expert) LCD manufactured by linkgobular (linkgobular) 21, with d · Δ n, and p being changed. In addition, for each example, the reciprocal (1/(p/d)) of the value of the chiral pitch (p) with respect to the cell thickness (d) was calculated. The results of the simulation are shown in table 2.

[ Table 2]

Further, in the examples of table 2, the horizontal axis is plotted as 1/(p/d), and the vertical axis is plotted as d · Δ n, and as a result, it is understood that the relationships shown in fig. 5 exist between 1/(p/d), d · Δ n, and the transmittance. In fig. 5, a curve a is a function in which the increase rate Δ Q of the transmittance is about 3.0% with respect to the transmittance of comparative example 1, and is represented by the following equation (3). Curve B is a function in which the increase rate Δ Q of the transmittance with respect to the transmittance of comparative example 1 is about 6.0%, and is represented by the following equation (4). The open circles in fig. 5 are drawn for the results of examples 6 to 10, the black circles are drawn for the results of examples 11 to 15, and the black triangles are drawn for the results of examples 1 to 5. In examples 1 to 5, the coordinates were the same. Each of the curve a and the curve B is obtained by polynomial approximation.

y＝4661.2x ² -2431.5x+723.0…(3)

y＝5140.4x ² -2758.3x+787.1…(4)

As can be seen from FIG. 5, if 1/(p/d) and d.DELTA.n are located in the upper region of the boundary line including the curve A (y.gtoreq.4661.2 x) ² Coordinates of-2431.5x + 723.0), the generation of dark lines in the pixel region can be sufficiently suppressed, and a liquid crystal display element excellent in transmittance characteristics can be obtained. Furthermore, it can be said that if 1/(p/d) and d.DELTA.n are within a region located above the boundary line including the curve B (y.gtoreq.5140.4 x) ² Coordinates of-2758.3x + 787.1), a liquid crystal display element having more excellent transmittance characteristics can be obtained.

[ example 16]

A liquid crystal display device was manufactured in the same manner as in example 1, except that the TFT substrate was subjected to the photo-alignment treatment in the second domain 32 and the fourth domain 34, the counter substrate was subjected to the photo-alignment treatment in the first domain 31 and the third domain 33, and the exposure azimuth was set to the pixel horizontal direction (see fig. 7 (i) and 8 (i)). In addition, the transmittance characteristics of the manufactured liquid crystal display element were evaluated by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was 0.296. In addition, almost no dark line was observed in the pixel (see fig. 9 (i)).

[ example 17]

A liquid crystal display element was produced in the same manner as in example 1, except that the TFT substrate was subjected to the photo-alignment treatment in the second domain 32 and the fourth domain 34, and the counter substrate was subjected to the photo-alignment treatment in the first domain 31 and the third domain 33, and that the TFT substrate and the counter substrate were exposed so that the liquid crystal molecules present in the vicinity of the TFT substrate and the liquid crystal molecules present in the vicinity of the counter substrate were aligned at ± 15 ° from the pixel horizontal direction during the photo-alignment treatment (see (ii) of fig. 7 and (ii) of fig. 8). In addition, the transmittance characteristics of the manufactured liquid crystal display element were evaluated by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was 0.299. In addition, almost no dark line was observed in the pixel (see (ii) of fig. 9).

Comparative example 6

A liquid crystal display element was produced in the same manner as in example 16, except that the chiral agent was not added to the liquid crystal material, and d · Δ n was 320nm. The liquid crystal display element was evaluated for transmittance characteristics by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was as low as 0.135. In addition, as shown in fig. 9 (i), dark lines were clearly confirmed in the pixel analysis results by simulation.

Comparative example 7

A liquid crystal display element was produced in the same manner as in example 17, except that the chiral agent was not added to the liquid crystal material, and d · Δ n was 320nm. The liquid crystal display element was evaluated for transmittance characteristics by simulation in the same manner as in example 1. As a result, in the above example, the transmittance was as low as 0.191. In addition, as shown in fig. 9 (ii), dark lines were clearly confirmed in the pixel analysis results by simulation.

As described above, in examples 16 and 17 in which a chiral agent was added to a liquid crystal having negative dielectric anisotropy, no dark line was observed in the pixel region, and high transmittance was exhibited. On the other hand, in comparative examples 6 and 7 in which no chiral agent was added to the liquid crystal having negative dielectric anisotropy, dark lines were clearly observed in the pixel region, and the transmittance was lower than that of the examples. From these results, it is understood that the generation of dark lines in the pixel region can be suppressed by adding a chiral agent to the liquid crystal having negative dielectric anisotropy. In the liquid crystal display elements 10 of examples 16 and 17, the orientation direction of the liquid crystal layer 13 can be set to about 45 degrees with respect to the transmission axis of the first polarizing plate 27 and the transmission axis of the second polarizing plate 28, and liquid crystal orientation with respect to the transmission axis of the polarizing plate having the highest transmittance in the optically active mode can be realized.

[ examples 18 to 20]

Next, in order to further verify the effect of transmittance improvement accompanying suppression of dark line generation, the retardation (d · Δ n) and the chiral pitch (p) were changed in the liquid crystal display element having the pixel structure of example 16 (the electrode structure of fig. 7 (i) and the exposure azimuth of fig. 8 (i)), and the influence on the transmittance was examined. In each example, the retardation (d · Δ n) and the chiral pitch (p) were changed, and the light transmittance of the liquid crystal display element was calculated by simulation using an epstein barr (Expert) LCD manufactured by linkgglobal 21. The conditions of the liquid crystal display element and the simulation results are shown in table 3. In examples 16 to 20, the increase rate Δ Q of transmittance relative to comparative example 1 is also shown in table 3.

Fig. 10 shows the results obtained by plotting d · Δ n on the abscissa and transmittance on the ordinate for each of examples 16, 18 to 20 in table 3. The solid 16, the solid 18 to the solid 20 in the open circle symbols in fig. 10 are graphs in which the results of example 16 and example 18 to example 20 are plotted, respectively. From the results shown in Table 3 and FIG. 10, it can be said that in the liquid crystal display element having the pixel structure of example 16, if d.DELTA.n.gtoreq.370 nm, the increase rate Δ Q of the transmittance was 3.0% or more relative to comparative example 1, and the effect of improving the transmittance was high, and the transmittance characteristics were excellent. Further, it can be said that if d.DELTA.n is 380nm or more, a liquid crystal display element having more excellent transmittance characteristics can be obtained.

< relationship between twist angle and liquid crystal orientation deviation angle of liquid crystal and transmittance characteristics with addition of chiral agent >

[ examples 21 to 46]

Liquid crystal display elements were produced in the same manner as in examples 16 and 17, except that the cell thickness (d), the refractive index anisotropy (Δ n) of liquid crystal, the chiral pitch (p), and the liquid crystal azimuthal shift angle (v) were changed as shown in table 4 (see fig. 7 and 8). In addition, the liquid crystal display elements of the respective examples were evaluated for transmittance characteristics by simulation in the same manner as in example 16. The results are shown in table 4.

The liquid crystal azimuth shift angle v will be described with reference to fig. 11. Fig. 11 (a) shows the side of the photo-alignment film formed on the TFT substrate, and fig. 11 (b) shows the photo-alignment film formed on the counter substrate. In FIG. 11 (a), (a-1) shows one pixel, and (a-2) and (a-3) are enlarged views of X in (a-1). In FIG. 11 (b), (b-1) shows one pixel, and (b-2) and (b-3) are enlarged views of X in (b-1). The arrows in (a-2), (a-3), (b-2) and (b-3) indicate the orientation directions of the liquid crystal molecules.

As shown in fig. 11, the liquid crystal azimuth shift angle v represents a shift angle of the alignment azimuth with respect to the pixel horizontal direction in the liquid crystal molecules present in the vicinity of the alignment film having a pretilt angle of less than 90 degrees, among the optical alignment films formed on the TFT substrate and the counter substrate. In this embodiment, the liquid crystal azimuth shift angle v is a shift amount in the counterclockwise direction indicated by a positive value on the TFT substrate side as shown in fig. 11 (a), and a shift amount in the clockwise direction indicated by a positive value on the opposite substrate side as shown in fig. 11 (b). For example, the liquid crystal azimuth shift angle v of example 16 is 0 degrees, and the liquid crystal azimuth shift angle v of example 17 is +15 degrees. The liquid crystal azimuth shift angle v on the TFT substrate side and the liquid crystal azimuth shift angle v on the counter substrate side are the same value.

[ Table 4]

	p(μm)	w：360/(p/d)	v: liquid crystal azimuth offset angle	Transmittance of light	Rate of increase Δ Q
						Example 21	28.8	40	20.0	0.230	6.3％
Example 22	25.6	45	18.0	0.234	8.2％
						Example 23	23.0	50	3.2	0.230	6.3％
Example 24	23.0	50	5.0	0.235	8.6％
						Example 25	23.0	50	30.0	0.233	8.0％
Example 26	23.0	50	32.6	0.229	6.0％
						Example 27	19.2	60	-6.9	0.230	6.3％
Example 28	19.2	60	-6.2	0.234	8.1％
						Example 29	19.2	60	34.1	0.234	8.3％
Example 30	16.5	70	-17.8	0.230	6.4％
						Example 31	14.4	80	-25.7	0.230	6.4％
Example 32	14.4	80	39.0	0.234	8.4％
						Example 33	14.4	80	47.1	0.230	6.3％
Example 34	12.8	90	-25.0	0.230	6.2％
						Example 35	12.8	90	-19.5	0.234	8.3％
Example 36	12.8	90	38.7	0.234	8.2％
						Example 37	12.8	90	44.2	0.229	6.0％
Example 38	11.5	100	-11.7	0.234	8.1％
						Example 39	11.5	100	30.0	0.234	8.3％
Example 40	11.5	100	33.5	0.230	6.2％
						Example 41	10.7	108	2.3	0.234	8.2％
Example 42	10.5	110	0	0.229	6.0％
						Example 43	11.5	100	-30.0	0.223	3.2％
Example 44	12.8	90	50	0.224	3.8％
						Example 45	16.5	80	-30	0.225	3.8％
Example 46	28.8	40	30	0.223	3.4％

Further, in examples 21 to 42 shown in table 4, the horizontal axis is represented by 360/(p/d), and the vertical axis is represented by the liquid crystal azimuth offset angle v (see fig. 12 and 13). In addition, the results of examples 21 to 42 in which the transmittance was improved by about 6% were plotted by the square marks in fig. 12, and the results of examples 43 to 46 were plotted by the circular marks. Examples 43 to 36 are examples in which the increase rate Δ Q of transmittance was less than 6%. In addition, the results of examples 21 to 42 in which the effect of improving the transmittance was about 8% were plotted by square marks in fig. 13. Here, "360/(p/d)" represents the twist angle of the liquid crystal. As a result of the above-described plotting, it is understood that the relationship shown in fig. 12 and 13 exists between 360/(p/d) and the liquid crystal azimuth offset angle.

Curves P1 and P2 shown in fig. 12 are functions in which the increase rate Δ Q of the transmittance is about 6.0% with respect to the transmittance of comparative example 1, and are represented by the following numerical expressions (5) and (6). The curves P1 and P2 are obtained by polynomial approximation.

v＝0.0263w ² -4.2945w+151.89…(5)

v＝-0.0337w ² +4.8753w-123.82…(6)

(in the numerical expressions (5) and (6), w represents 360/(p/d) and v represents the liquid crystal azimuth offset angle)

From fig. 12, it can be said that if 360/(P/d) and the liquid crystal azimuth offset angle v are coordinates in a region located inside a boundary line including the curves P1 and P2 (i.e., in a region satisfying the following expression (7)), dark lines in the pixel region can be sufficiently suppressed, and a liquid crystal display element having excellent transmittance characteristics can be obtained.

0.0263w ² -4.2945w+151.89≤v≤-0.0337w ² +4.8753w-123.82…(7)

The curves R1 and R2 shown in fig. 13 are functions in which the increase rate Δ Q of the transmittance is about 8.0% with respect to the transmittance of comparative example 1, and are represented by the following numerical expressions (9) and (10).

v＝0.0306w ² -4.9416w+177.88…(9)

v＝-0.0309w ² +4.5561w-124.28…(10)

(in the numerical expressions (9) and (10), w represents 360/(p/d) and v represents the liquid crystal azimuth offset angle)

From fig. 13, it can be said that if 360/(p/d) and the liquid crystal azimuth offset angle v are coordinates in a region located inside a boundary line including the curves R1 and R2 (i.e., in a region satisfying the following expression (11)), dark lines in the pixel region can be further suppressed, and a liquid crystal display element having more excellent transmittance characteristics can be obtained.

0.0306w ² -4.9416w+177.88≤v≤-0.0309w ² +4.5561w-124.28…(11)

Description of the symbols

10: liquid crystal display element

11: first substrate

12: second substrate

13: liquid crystal layer

15: pixel electrode

19: opposite electrode

22: first alignment film

23: second alignment film

30: pixel

Claims

1. A liquid crystal display element comprising:

a first substrate;

a second substrate disposed to face the first substrate; and

a liquid crystal layer disposed between the first substrate and the second substrate and including liquid crystal molecules having negative dielectric anisotropy,

the liquid crystal display element has a plurality of pixels,

a photo-alignment film is formed on at least one of the first substrate and the second substrate, or a polymer layer formed by polymerization of a photopolymerizable monomer is provided at a boundary portion between the first substrate and the liquid crystal layer and a boundary portion between the second substrate and the liquid crystal layer,

each of the plurality of pixels has a plurality of alignment regions in which alignment orientations of liquid crystal molecules are different,

the liquid crystal layer comprises a chiral agent,

the liquid crystal molecules are twisted and aligned between the first substrate and the second substrate in a state where a voltage is applied, and the twist directions of the liquid crystal molecules in the plurality of alignment regions are the same.

2. The liquid crystal display element according to claim 1, wherein d · Δ n is 405nm or more, where d is a thickness of the liquid crystal layer and Δ n is refractive index anisotropy of the liquid crystal.

3. The liquid crystal display element according to claim 1 or 2, wherein the following expression (1) is satisfied where d is a thickness of the liquid crystal layer, Δ n is a refractive index anisotropy of the liquid crystal, p is a chiral pitch of the liquid crystal, x is 1/(p/d), and y is d · Δ n,

y≥4661.2x ² -2431.5x+723.0 …(1)。

4. the liquid crystal display element according to any one of claims 1 to 3, wherein a photo-alignment film is formed on each of the first substrate and the second substrate,

a pretilt angle defined by the optical alignment film formed on the first substrate and a pretilt angle defined by the optical alignment film formed on the second substrate are each less than 90 degrees,

a twist angle of the liquid crystal molecules in a state where a voltage is applied to the liquid crystal layer is 60 to 120 degrees,

in each of the plurality of pixels, an azimuth of projecting a long axis direction of liquid crystal molecules present in the vicinity of a center in a thickness direction of the liquid crystal layer onto the first substrate is ± 15 degrees with respect to a horizontal direction of a display surface of the liquid crystal display element, or ± 15 degrees with respect to a vertical direction of the display surface.

5. The liquid crystal display element according to any one of claims 1 to 3, wherein a photo-alignment film is formed on at least one of the first substrate and the second substrate,

one of a pretilt angle defined by the liquid crystal alignment film formed on the first substrate and a pretilt angle defined by the liquid crystal alignment film formed on the second substrate is smaller than 90 degrees and the other is substantially 90 degrees,

the alignment azimuth of the liquid crystal molecules present in the vicinity of the alignment film having a pretilt angle of less than 90 degrees is 30 to 60 degrees with respect to the horizontal direction of the display surface of the liquid crystal display element.

6. The liquid crystal display element according to claim 5, wherein in each of the plurality of pixels, an orientation in which a long axis direction of liquid crystal molecules existing in the vicinity of a center in a thickness direction of the liquid crystal layer is projected onto the first substrate is ± 15 degrees with respect to a horizontal direction of the display surface, or ± 15 degrees with respect to an up-down direction of the display surface.

7. The liquid crystal display element according to any one of claims 1 to 6, wherein a photo-alignment film is formed over at least one of the first substrate and the second substrate,

the plurality of alignment regions are arranged in a row along a predetermined direction.

8. The liquid crystal display element according to claim 1, wherein a photo alignment film is formed on each of the first substrate and the second substrate,

among the plurality of alignment regions, a pretilt angle defined by the optical alignment film formed on the first substrate is less than 90 degrees and a pretilt angle defined by the optical alignment film formed on the second substrate is substantially 90 degrees, and among the remaining alignment regions, a pretilt angle defined by the optical alignment film formed on the first substrate is substantially 90 degrees and a pretilt angle defined by the optical alignment film formed on the second substrate is less than 90 degrees.

9. The liquid crystal display element according to claim 8, wherein an alignment azimuth of liquid crystal molecules present in the vicinity of the alignment film having a pretilt angle of less than 90 degrees is 0 degree or more and 50 degrees or less with respect to a horizontal direction of a display surface of the liquid crystal display element.

10. The liquid crystal display element according to claim 8 or 9, wherein d · Δ n is 370nm or more where d is a thickness of the liquid crystal layer and Δ n is refractive index anisotropy of the liquid crystal.

11. The liquid crystal display element according to any one of claims 8 to 10, wherein when a shift angle of an alignment azimuth with respect to a horizontal direction of a display surface of the liquid crystal display element of liquid crystal molecules present in the vicinity of an alignment film having a pretilt angle of less than 90 degrees is represented by v (wherein a shift angle in a predetermined rotational direction is represented by a positive value for the first substrate side, and a shift angle in a direction opposite to the predetermined rotational direction is represented by a positive value for the second substrate side), a thickness of the liquid crystal layer is represented by d, a chiral pitch of the liquid crystal is represented by p, and 360/(p/d) is represented by w, the following expression (7) is satisfied,

0.0263w ² -4.2945w+151.89≤v≤-0.0337w ² +4.8753w-123.82 …(7)。

12. the liquid crystal display element according to any one of claims 8 to 11, wherein the plurality of alignment regions are arranged in a line along a prescribed direction.

13. The liquid crystal display element according to any one of claims 1 to 12, wherein the plurality of pixels are arranged in a matrix shape including a plurality of rows and a plurality of columns,

each of the plurality of pixels displaying a color corresponding to the pixel,

the pixels of the same color are arranged in a stripe shape extending in a row direction or a column direction.