Liquid crystal display device

Abstract

The present invention provides a liquid crystal display device that can suppress light leakage and contrast reduction caused by unevenness on the substrate. [Solution] A liquid crystal display device comprising a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and an alignment film disposed between at least one of the pair of substrates and the liquid crystal layer, wherein at least one of the pair of substrates has a step on the surface in contact with the alignment film, the alignment film comprises a base layer disposed on the substrate side and a liquid crystal alignment layer disposed on the liquid crystal layer side, the base layer and the liquid crystal alignment layer have a structure derived from a polymer having crosslinkable functional groups, and the base layer and the liquid crystal alignment layer have a structure derived from a specific crosslinking material.

Description

[Technical Field]

[0001] This disclosure relates to a liquid crystal display device. [Background technology]

[0002] Liquid crystal display devices are display devices that utilize liquid crystal compositions for display. A typical display method involves irradiating a liquid crystal panel, which contains a liquid crystal composition sealed between a pair of substrates, with light from a backlight. By applying a voltage to the liquid crystal composition and changing the orientation of the liquid crystal material, the amount of light transmitted through the liquid crystal panel is controlled. Such liquid crystal display devices have features such as being thin, lightweight, and low power consumption, and are therefore used in electronic devices such as smartphones, tablet PCs, and car navigation systems.

[0003] Furthermore, as a display method for liquid crystal displays, the transverse field type display mode, which controls the orientation of the liquid crystal material mainly by rotating it in a plane parallel to the substrate surface, is attracting attention for reasons such as the ease of obtaining wide viewing angle characteristics. Examples of transverse field type display modes include in-plane switching (IPS) mode and fringe field switching (FFS) mode. It is known that optical films and liquid crystal alignment layers are used in liquid crystal displays, and for example, Patent Document 1 proposes an optical compensation film using a specific compound. Patent Document 2 describes a liquid crystal alignment agent containing a specific polyimide precursor or polyimide and a compound having two or more crosslinkable groups. Furthermore, Patent Document 3 describes a liquid crystal display element having a liquid crystal alignment layer formed by a liquid crystal alignment agent containing a polymer with a weight-average molecular weight of 30,000 or more. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-089855 [Patent Document 2] International Publication No. 2023 / 013622 [Patent Document 3] Japanese Patent Publication No. 2016-173544 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] On the other hand, in liquid crystal displays for head-mounted displays (HMDs), FFS (Full-Frequency Shift) is commonly used as the display mode to suppress color shift within the viewing angle. Furthermore, from the perspective of securing aperture area in line with higher resolution, forming a color filter on the array substrate is advantageous. However, forming a color filter on the array substrate makes oblique color mixing more likely, so a portion of the display area is covered with a light-shielding film. In liquid crystal displays for HMDs with a light-shielding film, irregularities are formed on the substrate due to the light-shielding film and electrode slits, and particularly large steps are formed where the edges of the light-shielding film and the boundaries of the electrode slits overlap. When an alignment film is formed in such stepped areas, a deviation occurs from the original alignment direction of the alignment film, resulting in problems such as light leakage and reduced contrast when displaying black.

[0006] This invention has been made in view of the above-mentioned circumstances, and aims to provide a liquid crystal display device that can suppress light leakage and contrast reduction caused by steps on the substrate. [Means for solving the problem]

[0007] The present invention consists of the following disclosures 1 to 14. The present invention will be described in detail below. [Disclosure 1] A liquid crystal display device having a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and an alignment film disposed between at least one of the pair of substrates and the liquid crystal layer, At least one of the pair of substrates has a step on the surface that contacts the alignment film, The alignment film comprises a base layer disposed on the substrate side and a liquid crystal alignment layer disposed on the liquid crystal layer side. The base layer and the liquid crystal alignment layer have a structure derived from a polymer having crosslinkable functional groups. A liquid crystal display device characterized in that the base layer and the liquid crystal alignment layer have a structure derived from a crosslinking material represented by the following structural formula (1). [ka] Here E 1 , E 2 and E 3 Each of these independently represents an amino group, a methylamino group, or a hydroxyl group. w1, w2, and w3 each independently represent an integer between 1 and 18. [Disclosure 2] The liquid crystal display device according to Disclosure 1, wherein w1, w2, and w3 in the above structural formula (1) are each independent integers between 4 and 18. [Disclosure 3] E of the above structural formula (1) 1 , E 2 and E 3 The liquid crystal display device according to disclosure 1 or 2, wherein each is independently an amino group or a methylamino group. [Disclosure 4] The liquid crystal display device according to any one of disclosures 1 to 3, wherein the weight ratio of the structure derived from the crosslinking material to the total weight ratio of the structure derived from the polymer constituting the base layer and the liquid crystal alignment layer is 20% or more and 80% or less. [Disclosure 5] A liquid crystal display device according to any one of disclosures 1 to 4, wherein the height of the step is greater than the thickness of the alignment film. [Disclosure 6] A liquid crystal display device according to any one of disclosures 1 to 5, wherein the height of the step is 200 nm or more and 1000 nm or less. [Disclosure 7] The liquid crystal display device according to any one of disclosures 1 to 6, wherein the liquid crystal alignment layer is a photo-alignment film that has undergone photo-alignment treatment. [Disclosure 8] The liquid crystal alignment layer has a structure derived from a polymer of polyimide, polyamic acid, polysiloxane, polyacrylic acid, or polymethacrylic acid having an epoxy group in the side chain, and the liquid crystal display device according to any one of Disclosures 1 to 7. [Disclosure 9] The liquid crystal alignment layer has a structure derived from a polyimide or polyamic acid horizontal alignment polymer represented by the following structural formula (2) or (3), and the liquid crystal display device according to Disclosure 8. [Chemical formula] Here, X 1 , X 2 each independently represents any one of the following structural formulas (X-a1) to (X-a13), (X-b1) to (X-b)Y 1 represents any one of the following structural formulas (Y-a1) to (Y-a14), (Y-b1) to (Y-b8), and Y[[ID=1十八]] 2 represents any one of (Y-c1) to (Y-c16), (Y-d1) to (Y-d8). Z 1 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number from 0 to 0.5, and p represents an integer of 1 or more. [Chemical formula] Here, X 1 , X 2 each independently represents any one of the following structural formulas (X-a1) to (X-a13), (X-b1) to (X-b4). Y 1 represents any one of the following structural formulas (Y-a1) to (Y-a14), (Y-b1) to (Y-b8), and Y 2 represents any one of (Y-c1) to (Y-c16), (Y-d1) to (Y-d8). Zs 1 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number from 0 to 0.5, and p represents an integer of 1 or more. <000022記載の液晶表示装置。[Chemical formula] [[ID=4記載の液晶表示装置。 [Chemical formula] [ka] [ka] [ka] [ka] [Disclosure 10] The liquid crystal display device according to disclosure 8, wherein the liquid crystal alignment layer has a structure derived from a polyimide-based or polyamic acid-based vertically oriented polymer represented by the following structural formula (2') or (3'). [ka] Here X 3 , X 4 Each of these independently represents one of the following structural formulas: (X-a1)~(X-a13) or (X-b1)~(X-b4). 3 This represents a structure in which one of the following structural formulas (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8) is bonded to one of the side chains represented by the following structural formulas (Z-a1)~(Z-a21). 4 This represents one of the following structural formulas: (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8). 2 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. [ka] Here X 3 , X 4 Each of these independently represents one of the following structural formulas: (X-a1)~(X-a13) or (X-b1)~(X-b4). 3 This represents a structure in which one of the following structural formulas (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8) is bonded to one of the side chains represented by the following structural formulas (Z-a1)~(Z-a21). 4This represents one of the following structural formulas: (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8). 2 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater. [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [Disclosure 11] The liquid crystal display device according to disclosure 8, wherein the liquid crystal alignment layer has a structure derived from a polysiloxane-based vertically oriented polymer represented by the following structural formula (4) or (5). [ka] Here, α independently represents a hydrogen atom, a methyl group, or a methoxy group. β 1 , β 2 Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.3 (inclusive). r represents a numerical value greater than 0 and less than or equal to 0.6 (inclusive). p represents an integer greater than or equal to 1 (inclusive). [ka] Here, α independently represents a hydrogen atom, a methyl group, or a methoxy group. β 1 , β2 Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.3 (inclusive). r represents a numerical value greater than 0 and less than or equal to 0.6 (inclusive). p represents an integer greater than or equal to 1 (inclusive). [ka] [Disclosure 12] The liquid crystal display device according to disclosure 8, wherein the liquid crystal alignment layer has a structure derived from a polyacrylic acid-based or polymethacrylic acid-based vertically oriented polymer represented by the following structural formula (6). [ka] Here, γ independently represents either a hydrogen atom or a methyl group. β 1 , β 2 Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.3 (inclusive). r represents a numerical value greater than 0 and less than or equal to 0.6 (inclusive). p represents an integer greater than or equal to 1 (inclusive). [ka] [Disclosure 13] The liquid crystal display device according to any one of disclosures 1 to 12, wherein the base layer has a structure derived from a polyimide-based or polyamic acid-based polymer represented by the following structural formula (7) or (8). [ka] Here, X 5 , X 6 Each of these independently represents one of (X-c1) to (X-c11). 5 Y represents one of (Y-a1) to (Y-a14). 6 This represents one of (Y-c1) to (Y-c16). 3 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater. [ka] Here, X5 , X 6 Each of these independently represents one of (X-c1) to (X-c11). 5 Y represents one of (Y-a1) to (Y-a14). 6 This represents one of (Y-c1) to (Y-c16). 3 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater. [ka] [ka] [ka] [Disclosure 14] The liquid crystal display device according to any one of disclosures 1 to 12, wherein the base layer has a structure derived from a polyimide-based or polyamic acid-based polymer represented by the following structural formulas (7') and (8'). [ka] Here, X 7 , X 8 Each of these independently represents one of the following structural formulas (X-c1) to (X-c11). 7 This represents a structure in which one of the following structural formulas (Y-c1) to (Y-c16) is bonded to one of the side chains represented by the following structural formulas (Z-b1) to (Z-b7). 8 This represents one of the following structural formulas (Y-c1) to (Y-c16). 4 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater. [ka] Here, X 7 , X 8 Each of these independently represents one of the following structural formulas (X-c1) to (X-c11). 7This represents a structure in which one of the following structural formulas (Y-c1) to (Y-c16) is bonded to one of the side chains represented by the following structural formulas (Z-b1) to (Z-b7). 8 This represents one of the following structural formulas (Y-c1) to (Y-c16). 4 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater. [ka] [ka] [ka] [Effects of the Invention]

[0008] The liquid crystal display device of the present invention can suppress light leakage and contrast reduction caused by steps in the substrate. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic plan view of a substrate having steps in the liquid crystal display device of this embodiment. [Figure 2] This is a schematic cross-sectional view of a substrate having steps in the liquid crystal display device of this embodiment. [Figure 3] This is a schematic cross-sectional view showing the area around the alignment film in a liquid crystal display device where a conventional alignment film is formed on a substrate with steps. [Figure 4] This is a schematic cross-sectional view showing the area around the alignment film in the liquid crystal display device of this embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below. The present invention is not limited to the embodiments described below, and design modifications can be made as appropriate within the scope of satisfying the configuration of the present invention.

[0011] The liquid crystal display device of this embodiment comprises a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and an alignment film disposed between at least one of the pair of substrates and the liquid crystal layer. The pair of substrates described above are a TFT substrate and a counter substrate. The liquid crystal layer can be the same as that used in conventional liquid crystal display devices.

[0012] At least one of the pair of substrates has a step on the surface that is in contact with the orientation film. Here, Figure 1 shows a schematic plan view of the stepped substrate of the liquid crystal display device of this embodiment, and Figure 2 shows a cross-sectional view. For clarity, some layers are omitted in Figure 1. Figure 2 shows a cross-sectional view between B1 and B2 in Figure 1. The substrate 1 of the liquid crystal display device in this embodiment, like the substrates of general liquid crystal display devices, has layers such as a gate wiring layer 12, a first insulating layer 13A, a semiconductor layer (not shown), a source wiring layer 14, and a second insulating layer 13B stacked in order from the support substrate 11 toward the observation surface. However, unlike the substrates of general liquid crystal display devices, the substrate 1 of the liquid crystal display device in this embodiment has a color filter 15 consisting of a red color filter 15R, a green color filter 15G, and a blue color filter 15B stacked on the second insulating layer 13B. By having a structure with a color filter 15 on the substrate (Color filter On Array (COA) structure), the aperture area can be secured even when the liquid crystal display device is made high-resolution. Furthermore, a first electrode 17, an insulating layer 13C, a second electrode 18, and a light-shielding film 19 are stacked in order on the color filter 15 with a planarization layer 16 in between, and the second electrode 18 is provided with a longitudinally shaped opening 18X. By providing a light-shielding film 19 on the substrate 1, oblique color mixing can be suppressed even when a color filter 15 is formed on the substrate 1. Furthermore, since the substrate 1 has a region where the outermost surface is an insulating layer 13C (the region within the opening 18X), a region where the second electrode 18 is formed, and a region where the light-shielding film 19 is formed, a step 1S is created between each region. There are three types of step 1S: a step between the insulating layer 13C, which is the outermost surface due to the opening 18X, and the second electrode 18; a step between the second electrode 18 and the light-shielding film 19; and a step between the insulating layer 13C and the light-shielding film 19.

[0013] The height of the step mentioned above is, for example, greater than the thickness of the alignment film. In substrates where the height of the step exceeds the thickness of the alignment film, light leakage and contrast reduction are more likely to occur. However, in this embodiment, even in substrates with such large step differences, light leakage and contrast reduction can be suppressed.

[0014] The height of the step mentioned above is, for example, in the range of 200 nm to 1000 nm. As described above, the step in the substrate originates from the opening of the second electrode in FFS mode. By making the step height 200 nm or more, the light-shielding film can be made thicker, which further suppresses oblique color mixing. In addition, the electrode can also be made thicker, which reduces the electrode resistance and allows for the application of a larger electric field. The step height is more preferably 250 nm or more, and even more preferably 300 nm or more. On the other hand, if the thickness of the light-shielding film and the electrode is too thick, the above effect will saturate, so the step height is preferably 1000 nm or less at most, more preferably 950 nm or less, and even more preferably 900 nm or less. Even with step heights within the above range, light leakage and a decrease in contrast can be suppressed in this embodiment.

[0015] The alignment film comprises a base layer disposed on the substrate side and a liquid crystal alignment layer disposed on the liquid crystal layer side, and the base layer and the liquid crystal alignment layer have a structure derived from a polymer having crosslinkable functional groups. The inventors investigated the cause of light leakage and contrast reduction when a conventional alignment film is laminated on a substrate having steps as shown in Figures 1 and 2 in a liquid crystal display device. As a result, they found that the cause is the existence of a region near the top of the step where the thickness of the alignment film is extremely thin. Here, Figure 3 shows a schematic cross-sectional view of the area around the alignment film in a liquid crystal display device in which a conventional alignment film is formed on a substrate having steps, and Figure 4 shows a schematic cross-sectional view of the area around the alignment film in the liquid crystal display device of this embodiment. Note that in Figures 3 and 4, unlike Figure 2, there is a region in the opening where the first electrode is not present, and a step is also formed at the boundary between the region where the first electrode is present and the region where it is not. Also, the color filter and the layers below the planarization layer are simplified. As shown in Figure 3, when a conventional alignment film 2 is formed on the surface of a substrate 1 with steps, the conventional alignment film 2 formed near the top of the step flows to lower areas over time, and the thicknesses d2 and d3 of the conventional alignment film 2 formed in the stepped portion become thinner than the thickness d1 of the conventional alignment film 2 formed in the non-stepped portion of the substrate 1. Furthermore, when the thickness of the conventional alignment layer 2 is reduced, the alignment direction deviates from the intended direction, resulting in light leakage and a decrease in contrast when displaying black. In particular, the decrease in thickness becomes more pronounced as the step height increases and closer to the step height, and at d3, where the step height is the highest, the thickness becomes extremely thin, which was a major cause of the decrease in contrast.

[0016] On the other hand, as shown in Figure 4, the alignment film 3 of this embodiment includes two layers: a base layer 32 and a liquid crystal alignment layer 31. The base layer 32 and the liquid crystal alignment layer 31 have a structure derived from a polymer having crosslinkable functional groups. Furthermore, these crosslinkable functional groups are crosslinked by a crosslinking material described later. This crosslinking makes it difficult for the alignment film 3 of this embodiment to flow away from the coated position, so that the thickness of the alignment film 3 of this embodiment can be maintained within a certain range even if the substrate 1 has steps. As a result, light leakage and a decrease in contrast can be suppressed even when there are steps on the substrate. Furthermore, one possible method to eliminate the above-mentioned light leakage and decrease in contrast is to increase the viscosity of the alignment film formed near the top of the step, from the viewpoint of preventing it from flowing downwards. However, simply increasing the viscosity of the alignment film makes it difficult to coat the alignment film with a uniform thickness. In this embodiment, since the alignment film is made less likely to flow by crosslinking, it is not necessary to make the viscosity of the polymer having crosslinkable functional groups extremely high, and therefore the polymer having crosslinkable functional groups can be coated with a uniform thickness when forming the alignment film.

[0017] The crosslinkable functional group contained in the polymer having the above-mentioned crosslinkable functional group is not particularly limited as long as it can be crosslinked by the crosslinking material, and examples include epoxy groups and isocyanate groups. Among these, epoxy groups are preferred because they possess both high thermal stability and sufficient reactivity.

[0018] Examples of polymers having the above-mentioned crosslinkable functional groups include polyimide polymers, polyamic acid polymers, polyamide polymers, polymaleimide polymers, poly(meth)acrylic acid polymers, polysiloxane polymers, polysilsesquioxane polymers, polyphosphozene polymers, or copolymers thereof.

[0019] The above-mentioned liquid crystal alignment layer is preferably subjected to an alignment treatment. The alignment treatment method is not particularly limited, and methods such as rubbing and photo-alignment can be used. In particular, the above-mentioned liquid crystal alignment layer is preferably a photo-alignment film that aligns liquid crystals by light irradiation, that is, a photo-alignment film that has undergone a photo-alignment treatment, in order to further enhance contrast. Examples of materials for the above-mentioned photo-alignment film include polymers having photoreactive functional groups. Specific examples of the above-mentioned photoreactive functional groups include azobenzene groups, chalcone groups, cinnamate groups, coumarin groups, tran groups, stilbene groups, and the like. The above-mentioned liquid crystal alignment layer may be vertically oriented or horizontally oriented.

[0020] The above liquid crystal alignment layer preferably has a structure derived from a polyimide-based, polyamic acid-based, polysiloxane-based, polyacrylic acid-based, or polymethacrylic acid-based polymer having epoxy groups in its side chains. By having a structure derived from the above polymers, the thickness of the alignment film can be maintained more uniformly, and light leakage and contrast reduction can be further suppressed. In particular, since light leakage and contrast reduction can be further suppressed, the above liquid crystal alignment layer preferably has a structure derived from a polyimide-based or polyamic acid-based horizontally oriented polymer represented by the following structural formula (2) or (3), a structure derived from a polyimide-based or polyamic acid-based vertically oriented polymer represented by the following structural formula (2') or (3'), a structure derived from a polysiloxane-based vertically oriented polymer represented by the following structural formula (4) or (5), or a structure derived from a polyacrylic acid-based or polymethacrylic acid-based vertically oriented polymer represented by the following structural formula (6).

[0021] [ka] Here X 1 , X 2 Each of these independently represents one of the following structural formulas: (X-a1)~(X-a13) or (X-b1)~(X-b4). 1 Y is one of the following structural formulas (Y-a1)~(Y-a14) or (Y-b1)~(Y-b8). 2 This represents either (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8). 1 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater.

[0022] [ka] Here X 1 , X 2 Each of these independently represents one of the following structural formulas: (X-a1)~(X-a13) or (X-b1)~(X-b4). 1Y is one of the following structural formulas (Y-a1)~(Y-a14) or (Y-b1)~(Y-b8). 2 This represents either (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8). 1 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater.

[0023] [ka] Here X 3 , X 4 Each of these independently represents one of the following structural formulas: (X-a1)~(X-a13) or (X-b1)~(X-b4). 3 This represents a structure in which one of the following structural formulas (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8) is bonded to one of the side chains represented by the following structural formulas (Za-1)~(Z-a21). 4 This represents one of the following structural formulas: (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8). 2 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater.

[0024] [ka] Here X 3 , X 4 Each of these independently represents one of the following structural formulas: (X-a1)~(X-a13) or (X-b1)~(X-b4). 3 This represents a structure in which one of the following structural formulas (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8) is bonded to one of the side chains represented by (Z-a1)~(Z-a21). 4 This represents one of the following structural formulas: (Y-c1)~(Y-c16) or (Y-d1)~(Y-d8). 2represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater.

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka] Here, α independently represents a hydrogen atom, a methyl group, or a methoxy group. β 1 , β 2 Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.3 (inclusive). r represents a numerical value greater than 0 and less than or equal to 0.6 (inclusive). p represents an integer greater than or equal to 1 (inclusive).

[0036] [ka] Here, α independently represents a hydrogen atom, a methyl group, or a methoxy group. β 1 , β 2 Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.3 (inclusive). r represents a numerical value greater than 0 and less than or equal to 0.6 (inclusive). p represents an integer greater than or equal to 1 (inclusive).

[0037] [ka] Here, γ independently represents either a hydrogen atom or a methyl group. β 1 , β 2 Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.3 (inclusive). r represents a numerical value greater than 0 and less than or equal to 0.6 (inclusive). p represents an integer greater than or equal to 1 (inclusive).

[0038] [ka]

[0039] In the above structural formulas (4), (5), and (6), r is more preferably 0.2 or greater, and more preferably 0.5 or less. When r is within the above range in these structural formulas, light leakage and contrast reduction can be further suppressed.

[0040] The weight-average molecular weight of the polymer having crosslinkable functional groups that serves as the raw material for the above-mentioned liquid crystal alignment layer should be such that it does not easily flow down to the underside of the step when applied and can be applied to a uniform thickness. For example, it is preferably 10,000 or more, more preferably 30,000 or more, preferably 1,000,000 or less, and more preferably 500,000 or less.

[0041] The above-mentioned base layer is not particularly limited as long as it has a structure derived from a polymer having crosslinkable functional groups, but it is preferable that it has a structure derived from a polyimide-based or polyamic acid-based polymer represented by the following structural formulas (7), (8), (7'), and (8') in order to form a film with high thermal stability and high electrical insulation properties.

[0042] [ka] Here, X 5 , X 6 Each of these independently represents one of the above structural formulas (X-c1) to (X-c11). 5 Y represents one of the above structural formulas (Y-a1) to (Y-a14). 6 This represents one of the above structural formulas (Y-c1) to (Y-c16). 3 represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or greater.

[0043] [ka] Here, X 5 , X 6 Each of these independently represents one of the above structural formulas (X-c1) to (X-c11). 5 Y represents one of the above structural formulas (Y-a1) to (Y-a14). 6 This represents one of the above structural formulas (Y-c1) to (Y-c16). 3represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number from 0 to 0.5, and p represents an integer of 1 or more.

[0044]

Chemical formula

[0045]

Chemical formula

[0046]

Chemical formula

[0047]

Chemical formula

[0048] The weight-average molecular weight of the polymer having crosslinkable functional groups that serves as the raw material for the base layer described above should be such that it does not easily flow down the step when applied and can be applied to a uniform thickness. For example, it is preferably 10,000 or more, more preferably 30,000 or more, preferably 1,000,000 or less, and more preferably 500,000 or less.

[0049] The base layer and the liquid crystal alignment layer preferably each contain 20% to 80% by weight of a structure derived from the polymer having the crosslinkable functional group. By setting the proportion of structures derived from the polymer having the crosslinkable functional group in the base layer and the liquid crystal alignment layer to the above range, the crosslinking effect of the crosslinking material described later is further enhanced, and light leakage and contrast reduction can be further suppressed. The proportion of structures derived from the polymer having the crosslinkable functional group in the base layer and the liquid crystal alignment layer is more preferably 25% by weight or more, and more preferably 75% by weight or less, respectively.

[0050] The above-mentioned base layer and liquid crystal alignment layer have a structure derived from a crosslinking material represented by the following structural formula (1). By crosslinking the crosslinkable functional groups of the polymers that serve as raw materials for the base layer and liquid crystal alignment layer using a crosslinking material represented by the following structural formula (1), the alignment film formed near the top of the step can be made less likely to flow downwards, and the thickness of the alignment film can be maintained within a certain range. Furthermore, since the alignment film becomes less likely to flow after crosslinking, it is not necessary to make the viscosity of the polymer itself that has the crosslinkable functional groups very high, so a uniform thickness can be achieved.

[0051] [ka] Here E 1 , E 2 and E 3 Each of these independently represents an amino group, a methylamino group, or a hydroxyl group. 1, w 2 and w 3 Each of these independently represents an integer between 1 and 18, inclusive.

[0052] E of the above structural formula (1) 1 , E 2 and E 3 Preferably, each of these is an amino group or a methylamino group, independently of the others. E 1 ~E 3 Because the functional group is as described above, the thermal reactivity is increased, and the voltage retention rate can be further improved.

[0053] In the above structural formula (1), it is preferable that w1, w2, and w3 are each independent integers between 4 and 18. Especially E 1 ~E 3 When using an amino group or methylamino group, there is an advantage in that the thermal reactivity is higher than when using a hydroxyl group, resulting in a higher voltage retention rate. On the other hand, if unreacted amino groups or methylamino groups remain and react when used in a liquid crystal display device, their high thermal reactivity may cause orientation changes such as changes in the pre-tilt angle. When w1 to w3 are integers within the above range, that is, longer alkyl groups, the amino group or methylamino group bonded to the end of the alkyl chain reacts more easily, making it less likely for unreacted amino groups or methylamino groups to remain. As a result, the voltage retention rate can be further increased while suppressing orientation changes caused by unreacted amino groups or methylamino groups. It is more preferable that w1, w2, and w3 are each independently 12 or less.

[0054] Preferably, the weight ratio of the structure derived from the above-mentioned crosslinking material to the total weight of the structure derived from the polymer constituting the base layer and the above-mentioned liquid crystal alignment layer is 20% or more and 80% or less. When the weight ratio of the structure derived from the crosslinking material to the total structure derived from the polymer constituting the base layer and the liquid crystal alignment layer is within the above range, the crosslinking material can sufficiently crosslink the polymer constituting the base layer and the liquid crystal alignment layer, making it more difficult for the liquid crystal alignment layer and the base layer to flow down to the lower side of the step. The weight ratio of the structure derived from the crosslinking material to the total structure derived from the polymer constituting the base layer and the liquid crystal alignment layer is more preferably 25% or more, even more preferably 30% or more, more preferably 75% or less, and even more preferably 70% or less.

[0055] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0056] (Example 1) (1) Preparation of liquid crystal alignment layer, base layer and crosslinking material As a polymer having crosslinkable functional groups that serves as a material for the liquid crystal alignment layer, it has the structure of the above structural formula (3), and X 1 , X 2 X-a1, Y 1 Y-a9, Y 2 Y-C11, Z 1 A polyamic acid-based horizontally oriented polymer was prepared, having direct bonding with epoxy groups, m = 0.5, and a weight-average molecular weight of approximately 50,000. Furthermore, a polymer having crosslinkable functional groups to serve as the base layer material was prepared, having the structure of structural formula (7) above, and X 5 , X 6 X-C1, Y 5 Y-a9, Y 6 Y-C11, Z 3 A polyimide polymer was prepared with direct bonding to an epoxy group, m = 0.5, and a weight-average molecular weight of approximately 50,000. Furthermore, as a crosslinking material, it has the structure of the above structural formula (1), where w1 to w3 are 6 and E 1 ~E 3 A compound in which the group is an amino group was prepared.

[0057] (2) Manufacturing of liquid crystal displays A substrate with a resolution of 1400 ppi and a 250 nm step was prepared, with pixel electrodes, a common electrode, a color filter, and a light-shielding film to prevent color mixing of the color filters, as shown in Figures 1 and 2. First, a mixture of a polymer having crosslinkable functional groups to be used as the base layer material, a polymer having crosslinkable functional groups to be used as the liquid crystal alignment layer material, and the crosslinking material was coated onto the stepped surface of the substrate to a thickness of 300 nm. The weight ratio of the coated polymer having crosslinkable functional groups to be used as the liquid crystal alignment layer material and the polymer having crosslinkable functional groups to be used as the base layer material was 1:1. The content (weight ratio) of the crosslinking material was set to 20% of the total weight of the polymer having crosslinkable functional groups to be used as the liquid crystal alignment layer material and the polymer having crosslinkable functional groups to be used as the base layer material. Next, a firing process was performed at 230°C for 40 minutes, and the liquid crystal alignment layer and the base layer were formed by crosslinking the polymer having crosslinkable functional groups to be used as the liquid crystal alignment layer material and the polymer having crosslinkable functional groups to be used as the base layer material with the crosslinking material and separating the layers. After the firing process, polarized UV light (250nm peak) at 500mJ / cm² is applied to the liquid crystal alignment layer for photo-alignment treatment. 2 Irradiation was performed. Subsequently, a positive-type liquid crystal was dropped onto the liquid crystal alignment layer using the liquid crystal drop method (ODF), and the opposing substrate was bonded to obtain a liquid crystal display device in FFS mode. The minimum thickness of the alignment film at the stepped portion of the obtained liquid crystal display device was measured using an electron microscope and found to be 10 nm.

[0058] (3) Measurement of luminance The brightness of the obtained liquid crystal display was measured before the drive test using a luminance meter (Topcon SR-5000). Then, after the liquid crystal display was driven for 1000 hours, the brightness was measured again using the same method to measure the brightness after the drive test. The results are shown in Table 1.

[0059] (4) Measurement of contrast For the obtained liquid crystal display devices, the luminance in bright and dark states was measured using a luminance meter (Topcon SR-5000), and the contrast before the drive test was calculated from the ratio of the two obtained luminance values. Next, the contrast was calculated in the same way after the liquid crystal display device was driven for 1000 hours, and the contrast after the drive test was calculated. The results are shown in Table 1.

[0060] (Examples 2-4, Comparative Example 1) Liquid crystal display devices were fabricated in the same manner as in Example 1, except that the crosslinking material content (by weight) was set to 0%, 40%, 60%, and 80%, and the brightness and contrast were measured. The results are shown in Table 1.

[0061] [Table 1]

[0062] (Example 5) (1) Preparation of liquid crystal alignment layer, base layer and crosslinking material As a polymer having crosslinkable functional groups that serves as a material for the liquid crystal alignment layer, it has the structure of the above structural formula (3') and X 3 , X 4 X-a3, Y 3 Y-b1, Y 4 Y-d1, Z 2 A polyamic acid-based horizontally oriented polymer was prepared, having direct bonding with epoxy groups, m = 0.5, and a weight-average molecular weight of approximately 50,000. Furthermore, a polymer having crosslinkable functional groups to serve as the base layer material was prepared, having the structure of structural formula (7) above, and X 5 , X 6 X-C1, Y 5 Y-a9, Y 6 Y-C11, Z 3 A polyimide polymer was prepared with direct bonding to an epoxy group, m = 0.5, and a weight-average molecular weight of approximately 50,000. Furthermore, as a crosslinking material, it has the structure of the above structural formula (1), where w1 to w3 are 6 and E 1 ~E 3 A compound in which the group is a hydroxyl group was prepared.

[0063] (2) Manufacturing of liquid crystal display devices and measurement of brightness and contrast A liquid crystal display device was obtained in the same manner as in Example 1, except that a polymer having a crosslinkable functional group was used as the material for the liquid crystal alignment layer, a polymer having a crosslinkable functional group was used as the material for the base layer, and a crosslinking material was used. Brightness and contrast were measured in the same manner as in Example 1. The results are shown in Table 2.

[0064] (Examples 6-8, Comparative Example 2) Liquid crystal display devices were fabricated in the same manner as in Example 5, except that the crosslinking material content (by weight) was set to 0%, 40%, 60%, and 80%, and the brightness and contrast were measured. The results are shown in Table 2.

[0065] [Table 2]

[0066] (Example 9) (1) Preparation of liquid crystal alignment layer, base layer and crosslinking material As a polymer having crosslinkable functional groups that serves as a material for the liquid crystal alignment layer, it has the structure of the above structural formula (4), where α is a methoxy group and β 1 β-1, β 2 A polysiloxane-based vertically oriented polymer was prepared with β-2, n = 0.25, r = 0.5, and a weight-average molecular weight of approximately 50,000. In addition, a polymer having crosslinkable functional groups to serve as the base layer material was prepared, having the structure of structural formula (7) above, X 5 , X 6 X-C1, Y 5 Y-a9, Y 6 Y-C11, Z 3 A polyimide polymer was prepared with direct bonding to an epoxy group, m = 0.5, and a weight-average molecular weight of approximately 50,000. Furthermore, as a crosslinking material, it has the structure of the above structural formula (1), where w1 to w3 are 6 and E 1 ~E 3 A compound in which the group is a hydroxyl group was prepared.

[0067] (2) Manufacturing of liquid crystal display devices and measurement of brightness and contrast A liquid crystal display device was obtained in the same manner as in Example 1, except that a polymer having crosslinkable functional groups was used as the material for the liquid crystal alignment layer, a polymer having crosslinkable functional groups was used as the material for the base layer, and a crosslinking material was used. Brightness and contrast were measured in the same manner as in Example 1. The results are shown in Table 3.

[0068] (Examples 10-11, Comparative Example 3) Liquid crystal display devices were fabricated in the same manner as in Example 9, except that the crosslinking material content (by weight) was set to 0%, 40%, and 60%, and the brightness and contrast were measured. The results are shown in Table 3.

[0069] [Table 3] [Explanation of Symbols]

[0070] 1 circuit board 11 Support substrate 12 gate wiring layers 13A First insulating layer 13B Second insulating layer 13C insulating layer 14 Source Wiring Layers 15 Color Filters 15R Red Color Filter 15G Green Color Filter 15B Blue Color Filter 16 Planarization layer 17 1st electrode 18 2nd electrode 18X opening 19. Light-shielding film 1S step 2 Conventional alignment film 3. Alignment film of this embodiment 31 Liquid crystal alignment layer 32 Base Layer

Claims

1. A liquid crystal display device having a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and an alignment film disposed between at least one of the pair of substrates and the liquid crystal layer, At least one of the pair of substrates has a step on the surface that contacts the alignment film, The alignment film comprises a base layer disposed on the substrate side and a liquid crystal alignment layer disposed on the liquid crystal layer side. The base layer and the liquid crystal alignment layer have a structure derived from a polymer having crosslinkable functional groups. A liquid crystal display device characterized in that the base layer and the liquid crystal alignment layer have a structure derived from a crosslinking material represented by the following structural formula (1). 【Chemistry 1】 Here E １ , E ２ and E ３ Each of these independently represents an amino group, a methylamino group, or a hydroxyl group. w1, w2, and w3 each independently represent an integer between 1 and 18.

2. The liquid crystal display device according to claim 1, wherein w1, w2, and w3 in the structural formula (1) are each independent integers between 4 and 18.

3. E of the above structural formula (1) １ , E ２ and E ３ The liquid crystal display device according to claim 1 or 2, wherein each is independently an amino group or a methylamino group.

4. The liquid crystal display device according to claim 1 or 2, wherein the weight ratio of the structure derived from the crosslinking material to the total of the structures derived from the polymer constituting the base layer and the liquid crystal alignment layer is 20% or more and 80% or less.

5. The liquid crystal display device according to claim 1 or 2, wherein the height of the step is greater than the thickness of the alignment film.

6. The liquid crystal display device according to claim 1 or 2, wherein the height of the step is 200 nm or more and 1000 nm or less.

7. The liquid crystal display device according to claim 1 or 2, wherein the liquid crystal alignment layer is a photo-alignment film that has undergone photo-alignment treatment.

8. The liquid crystal display device according to claim 1 or 2, wherein the liquid crystal alignment layer has a structure derived from a polyimide-based, polyamic acid-based, polysiloxane-based, polyacrylic acid-based, or polymethacrylic acid-based polymer having epoxy groups in its side chains.

9. The liquid crystal display device according to claim 8, wherein the liquid crystal alignment layer has a structure derived from a polyimide-based or polyamic acid-based horizontally oriented polymer represented by the following structural formula (2) or (3). 【Chemistry 2】 Here, X １ , X ２ each independently represents any one of the following structural formulas (X-a1) to (X-a13), (X-b1) to (X-b4). Y １ represents any one of the following structural formulas (Y-a1) to (Y-a14), (Y-b1) to (Y-b8), and Y ２ represents any one of the following structural formulas (Y-c1) to (Y-c16), (Y-d1) to (Y-d8). Z １ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number from 0 to 0.5, and p represents an integer of 1 or more. 【Transformation 3】 Here X １ , X ２ Each of these independently represents one of the following structural formulas: (X-a1) to (X-a13) or (X-b1) to (X-b4). １ Y is one of the following structural formulas (Y-a1) to (Y-a14), (Y-b1) to (Y-b8), Y ２ This represents one of the following structural formulas: (Y-c1) to (Y-c16), (Y-d1) to (Y-d8). １ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】

10. The liquid crystal display device according to claim 8, wherein the liquid crystal alignment layer has a structure derived from a polyimide-based or polyamic acid-based vertically oriented polymer represented by the following structural formula (2') or (3'). 【Chemistry 10】 Here X ３ , X ４ Each of these independently represents one of the following structural formulas: (X-a1) to (X-a13) or (X-b1) to (X-b4). ３ This represents a structure in which one of the following structural formulas (Y-c1) to (Y-c16) or (Y-d1) to (Y-d8) is bonded to one of the side chains represented by the following structural formulas (Za-1) to (Za-a21). ４ This represents one of the following structural formulas: (Y-c1) to (Y-c16), (Y-d1) to (Y-d8). ２ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 11】 Here X ３ , X ４ Each of these independently represents one of the following structural formulas: (X-a1) to (X-a13) or (X-b1) to (X-b4). ３ This represents a structure in which one of the following structural formulas (Y-c1) to (Y-c16) or (Y-d1) to (Y-d8) is bonded to one of the side chains represented by the following structural formulas (Z-a1) to (Z-a21). ４ This represents one of the following structural formulas: (Y-c1) to (Y-c16), (Y-d1) to (Y-d8). ２ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 [Chemistry 18] 【Chemistry 19】

11. The liquid crystal display device according to claim 8, wherein the liquid crystal alignment layer has a structure derived from a polysiloxane-based vertically oriented polymer represented by the following structural formula (4) or (5). 【Chemistry 20】 Here, α independently represents a hydrogen atom, a methyl group, or a methoxy group. β １ , β ２ Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.

3. r represents a numerical value greater than 0 and less than or equal to 0.

6. p represents an integer greater than or equal to 1. 【Chemistry 21】 Here, α independently represents a hydrogen atom, a methyl group, or a methoxy group. β １ , β ２ Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.

3. r represents a numerical value greater than 0 and less than or equal to 0.

6. p represents an integer greater than or equal to 1. 【Chemistry 22】

12. The liquid crystal display device according to claim 8, wherein the liquid crystal alignment layer has a structure derived from a polyacrylic acid-based or polymethacrylic acid-based vertically oriented polymer represented by the following structural formula (6). 【Chemistry 23】 Here, γ independently represents either a hydrogen atom or a methyl group. β １ , β ２ Each of these independently represents the following structural formula (β-1) or (β-2). n represents a numerical value between 0 and 0.

3. r represents a numerical value greater than 0 and less than or equal to 0.

6. p represents an integer greater than or equal to 1. 【Chemistry 24】

13. The liquid crystal display device according to claim 1 or 2, wherein the base layer has a structure derived from a polyimide-based or polyamic acid-based polymer represented by the following structural formula (7) or (8). 【Chemistry 25】 Here, X ５ , X ６ Each of these independently represents one of the following structural formulas (X-c1) to (X-c11). ５ Y represents one of the following structural formulas (Y-a1) to (Y-a14). ６ This represents one of the following structural formulas (Y-c1) to (Y-c16). ３ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 26】 Here, X ５ , X ６ Each of these independently represents one of the following structural formulas (X-c1) to (X-c11). ５ Y represents one of the following structural formulas (Y-a1) to (Y-a14). ６ This represents one of the following structural formulas (Y-c1) to (Y-c16). ３ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 27】 【Chemistry 28】 【Chemistry 29】

14. The liquid crystal display device according to claim 1 or 2, wherein the base layer has a structure derived from a polyimide-based or polyamic acid-based polymer represented by the following structural formulas (7') and (8'). 【Transformation 30】 Here, X ７ , X ８ Each of these independently represents one of (X-c1) to (X-c11). ７ Y represents a structure in which one of the following structural formulas (Y-c1) to (Y-c16) is bonded to one of the side chains represented by the following structural formulas (Z-b1) to (Z-b7). ８ This represents one of the following structural formulas (Y-c1) to (Y-c16). ４ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 31】 Here, X ７ , X ８ Each of these independently represents one of (X-c1) to (X-c11). ７ Y represents a structure in which one of the following structural formulas (Y-c1) to (Y-c16) is bonded to one of the side chains represented by the following structural formulas (Z-b1) to (Z-b7). ８ This represents one of the following structural formulas (Y-c1) to (Y-c16). ４ represents a direct bond with an epoxy group or a linear or branched alkylene group having 1 to 12 carbon atoms. m represents a number between 0 and 0.5, and p represents an integer of 1 or more. 【Chemistry 32】 【Transformation 33】 【Transformation 34】

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