TWI775784B - Liquid cristal display element - Google Patents

Abstract

The present invention greatly suppresses the occurrence of display defects related to alignment restraint force and alignment stability in a liquid crystal display element, and simultaneously improves problems such as transmittance and coloration. The present invention solves the above problems by utilizing a liquid crystal display element comprising at least a backlight, a polarizing film, a substrate with a liquid crystal alignment film, and a liquid crystal composition disposed from the backlight side, and characterized in that: The liquid crystal alignment film is produced by irradiating the liquid crystal alignment agent on the substrate with polarized light, and the optical axis of the polarized light irradiated when the liquid crystal alignment film is produced is parallel to the polarizing axis of the polarizing film.

Description

Liquid crystal display element

The present invention relates to a liquid crystal display element using photo-alignment technology, and more particularly, to a liquid crystal display element that is a horizontally aligned liquid crystal display mode and a lateral electric field driving mode.

As a method to achieve horizontal alignment, there is a conventional rubbing alignment technique in which the alignment direction of liquid crystal molecules is defined by rotating a roller on which a cloth such as cotton cloth or rayon is wound, and rubbing a liquid crystal alignment film formed on a substrate surface. .

However, when the substrate surface is rubbed with the cloth, dust from the cloth is generated, which contaminates the process line, resulting in a decrease in yield. Furthermore, the rubbing operation may cause unnecessary static electricity to the active matrix element, which may also cause pixel defects.

For these reasons, a method of specifying the alignment direction of liquid crystal molecules in a non-contact manner has been demanded instead of the rubbing alignment technique. In recent years, a method of specifying the alignment direction of liquid crystal molecules by irradiating a liquid crystal alignment film with polarized ultraviolet light for a fixed period of time has been promoted. Development of photo-alignment technology.

However, the alignment restraint force or its stability in the alignment direction of the liquid crystal molecules (the axis in which the long axes of the liquid crystal molecules are aligned with the alignment directions is generally referred to as the alignment easy axis. It will also be referred to as the "alignment easy axis" hereinafter) of the liquid crystal molecules. On the one hand, the photo-alignment technique studied so far is inferior to the rubbing alignment technique, so it has been a problem for a long time.

The inventors of the present invention have conducted various studies in order to solve the above-mentioned problems, and as a result, have found that a method in which the alignment axis of the liquid crystal alignment film (the optical axis of the polarized light irradiated when the liquid crystal alignment film is produced) is parallel to the polarizing axis of the polarizing film is utilized. The liquid crystal display element constructed can achieve the above-mentioned object, and the present invention has been completed.

Item 1. A liquid crystal display element comprising at least a backlight, a polarizing film, a substrate with a liquid crystal alignment film, and a liquid crystal composition from the backlight side, wherein the liquid crystal display element is characterized in that: the liquid crystal alignment film It is produced by irradiating polarized light to the liquid crystal alignment agent on the substrate, and the optical axis of the polarized light irradiated when producing the liquid crystal alignment film is parallel to the polarizing axis of the polarizing film.

Item 2. The liquid crystal display element according to Item 1, which is in a lateral electric field drive mode.

Item 3. The liquid crystal display element according to item 2, wherein the lateral electric field driving mode is a fringe field switching (Fringe Field Switching, FFS) mode.

Item 4. The liquid crystal display element according to any one of Items 1 to 3, wherein the liquid crystal aligning agent contains a photoisomerization type compound.

Item 5. The liquid crystal display element according to any one of Items 1 to 4, wherein the polarization axis of the polarizing film is orthogonal to the alignment direction (long axis direction) of the liquid crystal molecules in the liquid crystal composition Component configuration (O mode).

Item 6. The liquid crystal display element according to any one of Items 1 to 5, wherein the liquid crystal composition is subsequently configured with a substrate with other liquid crystal alignment films from the backlight side, the other liquid crystal alignment films The film thickness is smaller than that of the liquid crystal alignment film near the backlight.

Item 7. The liquid crystal display element according to Item 6, wherein the film thickness of the other liquid crystal alignment film is 30% or more and less than 100% of the film thickness of the liquid crystal alignment film near the backlight.

Item 8. The liquid crystal display element according to any one of Items 1 to 7, wherein the liquid crystal composition contains a liquid crystal compound having negative dielectric anisotropy.

Item 9. The liquid crystal display element according to Item 4, wherein the photoisomerization-type compound includes an azo group-containing compound.

Item 10. The liquid crystal display element according to item 4, wherein the photoisomerization type compound is a combination of at least one tetracarboxylic dianhydride selected from the following formulae (I) to (VII) and a A polyamide acid or its derivative obtained by reacting at least one diamine in the formula (I) to formula (VII).

[Chemical 13] R ² -C≡CR ³ (I) R ² -C≡CC≡CR ³ (II) R ² -C≡C-CH=CH-R ³ (III) R ² CCR ⁴ CCR ³ (IV ) R ² -C≡CR ⁴ -CH=CH-R ³ (V) R ² -CH=CH-R ³ (VI) R ² -NNR ³ (VII)

In formula (I) to formula (VII), R ² and R ³ are independently a monovalent organic group having -NH ₂ or -CO-O-CO-, and R ⁴ is a divalent organic group having an aromatic ring.

Item 11. The liquid crystal display element according to Item 10, wherein the tetracarboxylic dianhydride is at least one tetracarboxylic dianhydride selected from the following formula (PAN-1) and formula (PAN-2).

Item 12. The liquid crystal display element according to Item 10 or Item 11, wherein the diamine is at least one diamine selected from the following formulae (PDI-1) to (PDI-8).

In the formula (PDI-1) to the formula (PDI-8), the group whose bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary, and the formula (PDI-7 ), R ⁵ is independently -CH ₃ , -OCH ₃ , -CF ₃ , or -COOCH ₃ , and b is an integer of 0 to 2.

Item 13. The liquid crystal display element according to Item 12, wherein the diamine is at least one diamine selected from the group consisting of the following formula (PDI-6-1) and formula (PDI-7-1).

Item 14. The liquid crystal display element according to any one of Items 10 to 13, wherein the tetracarboxylic dianhydride other than the tetracarboxylic dianhydride is selected from the following formula (AN-I)～ At least one tetracarboxylic dianhydride of formula (AN-V) is reacted.

In formula (AN-I), formula (AN-IV) and formula (AN-V), X is independently a single bond or -CH ₂ -; in formula (AN-II), G is a single bond and has 1 to 1 carbon atoms. 20 alkylene, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -; formula (AN-II) ~ formula In (AN-IV), Y is independently a kind of in the group selected from the following trivalent group;

Any hydrogen of these groups can be substituted by methyl, ethyl or phenyl; and in formula (AN-III)～formula (AN-V), ring A is a monocyclic hydrocarbon group with 3 to 10 carbon atoms or A base of a condensed polycyclic hydrocarbon with a carbon number of 6 to 30, any hydrogen of the base can be substituted by methyl, ethyl or phenyl, the bond connected to the ring is connected to any carbon constituting the ring, and the two The root bond can be attached to the same carbon.

Item 15. The liquid crystal display element according to any one of Items 10 to 14, wherein the tetracarboxylic dianhydride other than the tetracarboxylic dianhydride is selected from the following formula (AN-1-1 ), formula (AN-1-13), formula (AN-2-1), formula (AN-3-1), formula (AN-3-2), formula (AN-4-5), formula (AN-4-5) -4-17), formula (AN-4-21), formula (AN-4-28), formula (AN-4-29), formula (AN-7-2), formula (AN-10), and At least one tetracarboxylic dianhydride in formula (AN-11-3) is reacted.

In formula (AN-4-17), m is an integer of 1-12.

Item 16. The liquid crystal display element according to any one of Items 10 to 15, wherein the diamine other than the diamine is selected from the following formulas (DI-1) to (DI-15) at least one of the diamines in the reaction.

In formula (DI-1), m is an integer from 1 to 12, and any hydrogen of alkylene can be replaced by -OH; in formula (DI-3) and formula (DI-5) to formula (DI-7) , G ²¹ is independently a single bond, -NH-, -O-, -S-, -SS-, -SO ₂ -, -CO-, -CONH-, -CONCH ₃ -, -NHCO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m' -, -O-(CH ₂ ) _m' -O-, -N(CH ₃ )-(CH ₂ ) _k -N (CH ₃ )-, or -S-(CH ₂ ) _m' -S-, m' is independently an integer of 1 to 12, and k is an integer of 1 to 5; formula (DI-6) and formula (DI-7 ), G ²² is independently a single bond, -O-, -S-, -CO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or an alkylene group having 1 to 10 carbon atoms ; Arbitrary hydrogen of cyclohexane ring and benzene ring in formula (DI-2)～formula (DI-7) can pass through -F, -CH ₃ , -OH, -CF ₃ , -CO ₂ H, -CONH ₂ , or benzyl substitution, in addition, in formula (DI-4), any hydrogen of cyclohexane ring and benzene ring can be selected from the following formula (DI-4-a)～formula (DI-4-c) ) is substituted with at least one group; [Chem. 21]

In formula (DI-4-a) and formula (DI-4-b), R ²⁰ is independently -H or -CH ₃ ; and in formula (DI-2) to formula (DI-7), the bonding position is not The group fixed on any carbon atom constituting the ring means that the bonding position on the ring is arbitrary, and the bonding position of -NH ₂ on the cyclohexane ring or the benzene ring is the bond other than G ²¹ or G ²² Any position other than the junction position.

In formula (DI-8), R ²¹ and R ²² are independently an alkyl group or phenyl group with 1 to 3 carbon atoms, and G ²³ is independently an alkylene group with 1 to 6 carbon atoms, a phenylene group or an alkyl group substituted with an alkyl group. Phenylidene, n is an integer from 1 to 10; In formula (DI-9), R ²³ is independently an alkyl group with 1 to 5 carbons, an alkoxy group with 1 to 5 carbons or -Cl, and p is independently 0 an integer of ~3, and q is an integer of 0 to 4; in formula (DI-10), R ²⁴ is -H, an alkyl group with 1 to 4 carbon atoms, a phenyl group, or a benzyl group; in formula (DI-11) , G ²⁴ is -CH ₂ - or -NH-; in formula (DI-12), G ²⁵ is a single bond, alkylene with 2 to 6 carbon atoms or 1,4-phenylene, and r is 0 or 1 In addition, in formula (DI-9), formula (DI-11) and formula (DI-12), the group whose bonding position is not fixed to any carbon atom constituting the ring represents the bonding position on the ring is arbitrary.

In formula (DI-13), G ³¹ is a single bond, an alkylene group having 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -; in formula (DI-14), ring B is a cyclohexane ring, a benzene ring or a naphthalene ring, and any hydrogen of the ring can be converted to a methyl group, an ethyl group, or a phenyl group Substitution; in formula (DI-15), ring C is independently a cyclohexane ring or a benzene ring, any hydrogen in the ring can be substituted by methyl, ethyl, or phenyl, and Y is a single bond, carbon 1-20 alkylene, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -; and the formula (DI- In 14) and formula (DI-15), the group whose bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary.

Item 17. The liquid crystal display element according to any one of Items 10 to 16, wherein the diamine other than the diamine is selected from the following formula (DI-1-3), formula (DI- 1-4), formula (DI-2-1), formula (DI-4-1), formula (DI-4-13), formula (DI-5-1), formula (DI-5-4), Type (DI-5-5), Type (DI-5-9), Type (DI-5-12), Type (DI-5-22), Type (DI-5-28), Type (DI-5) -30), formula (DI-5-31), formula (DI-7-3), formula (DI-9-1), formula (DI-13-1), formula (DI-13-2), formula (DI-14-1), at least one diamine in formula (DI-14-2) reacts.

In formula (DI-5-1), formula (DI-5-12), formula (DI-7-3) and formula (DI-13-2), m is an integer from 1 to 12; formula (DI-5 -30), k is an integer of 1 to 5; and in formula (DI-7-3), n is independently 1 or 2.

Item 18. The liquid crystal display element according to any one of Items 10 to 17, wherein the photoisomerization type compound is a polyamic acid or a derivative thereof having a photoisomerization structure in the main chain, so The liquid crystal alignment agent contains the polyamic acid or its derivatives and other polymers.

Item 19. The liquid crystal display element according to any one of Items 1 to 18, wherein the liquid crystal alignment film is formed through the steps of: coating the liquid crystal alignment agent on a substrate; and applying the coating After heating and drying the substrate of the liquid crystal aligning agent, it is a step of irradiating linearly polarized light or elliptically polarized light to impart alignment control ability to the liquid crystal.

Item 20. The liquid crystal display element according to any one of Items 1 to 18, wherein the liquid crystal alignment film is formed through the following steps: a step of coating the liquid crystal alignment agent on a substrate; The substrate of the alignment agent is heated and dried Then, the step of irradiating linearly polarized light or elliptically polarized light to give the liquid crystal alignment control ability; and then the step of heating and calcining the coating film.

Item 21. The liquid crystal display element according to any one of Items 1 to 18, wherein the liquid crystal alignment film is formed through the following steps: a step of coating the liquid crystal alignment agent on a substrate; The substrate of the alignment agent is heated and dried, and then heated and calcined; and the coating film is then irradiated with linearly polarized or elliptically polarized light to give liquid crystal alignment control ability.

According to the liquid crystal display element according to the preferred embodiment of the present invention, the alignment restraint force or the stability of the alignment direction of the liquid crystal molecules can be improved, and as a result, the display failure related to the alignment restraint force or the alignment stability can be greatly suppressed At the same time, photoisomerization compounds can be used to greatly improve the problems of transmittance and coloring. The liquid crystal display element of the preferred embodiment of the present invention further has the effects of improving the voltage holding ratio (VHR), improving the reliability of the VHR, and reducing the Vcom drift problem.

1: Liquid crystal display element

B: Backlight

F1: polarizing film

LC: liquid crystal composition

S1: Substrate with liquid crystal alignment film

S2: Substrate with other liquid crystal alignment films

FIG. 1 is a schematic cross-sectional view showing a liquid crystal display element according to an embodiment of the present invention.

<Configuration of the liquid crystal display element of the present invention>

As shown in FIG. 1 , the present invention is the following liquid crystal display element.

A liquid crystal display element comprising at least a backlight (B), a polarizing film (F1), a substrate (S1) with a liquid crystal alignment film (LO1), and a liquid crystal composition (LC) from the backlight (B) side. The liquid crystal display element (1), the liquid crystal display element is characterized in that: the liquid crystal alignment film (LO1) is produced by irradiating polarized light to the liquid crystal alignment agent on the substrate (S1), and the liquid crystal alignment film is produced. The optical axis of the polarized light irradiated at the time of (LO1) is parallel to the polarization axis of the polarizing film (F1).

In addition, the liquid crystal display element (1) is preferably a substrate (S2) provided with another liquid crystal alignment film (LO2) from the backlight (B) side to the liquid crystal composition (LC), and the other liquid crystal alignment The film thickness of the film (LO2) is smaller than the film thickness of the liquid crystal alignment film (LO1) near the backlight (B). Specifically, the film thickness of the other liquid crystal alignment films (LO2) is 30% or more and less than 100% of the film thickness of the liquid crystal alignment films (LO1) near the backlight (B), preferably 30% to 80%, and more The best is 30%~60%.

A more specific configuration of the liquid crystal display element is characterized by having a pair of substrates ( S1 and S2 ) arranged to face each other, and an electrode group formed on one or both of the facing surfaces of the pair of substrates. , a plurality of active elements connected to the electrode group, liquid crystal alignment films (LO1 and LO2) formed on the opposing surfaces of the pair of substrates, and a liquid crystal layer formed between the pair of substrates (LC), the liquid crystal configuration The alignment film, for example, contains (especially in the main chain of the polyamic acid or its derivative) a polyamic acid or its derivative having a photoisomerized structure such as an azo group, and the liquid crystal alignment film is irradiated with linearly polarized light or Elliptically polarized light is produced by the step of imparting alignment control ability, and the optical axis of the polarized light irradiated when the liquid crystal alignment film (LO1) close to the backlight (B) and the polarization axis of the polarizing film (F1) close to the backlight (B) are produced. parallel.

The driving mode of the liquid crystal display element is preferably a lateral electric field driving mode, more preferably an FFS mode.

The liquid crystal display element preferably has an element configuration (O mode) in which the polarization axis of the polarizing film (F1) is orthogonal to the alignment direction (long axis direction) of the liquid crystal molecules in the liquid crystal composition (LC).

Moreover, it is preferable that this liquid crystal display element contains the liquid crystal compound which has negative dielectric anisotropy in a liquid crystal composition (LC). The liquid crystal composition having negative dielectric anisotropy is sometimes simply expressed as "negative liquid crystal composition", and the liquid crystal composition having positive dielectric anisotropy is simply expressed as "positive liquid crystal composition". things".

A liquid crystal alignment film according to a preferred embodiment of the present invention is an alignment film formed using a liquid crystal alignment agent containing a photoisomerization type compound such as an azo group-containing compound, and is formed in a photodecomposition type, a photodimerization type, and a photodimerization type as described later. Among the various photo-alignment technologies such as the photo-isomerization type and the photo-isomerization type, in particular, the photo-isomerization type photo-alignment technology is used to impart the liquid crystal alignment control ability to the liquid crystal aligning agent. In the present invention, the characteristic element structure is used to Solve problems from this technology.

<About photo-alignment technology>

In the photo-alignment technology, as a method of specifying the easy axis of alignment, it is usually carried out by irradiating the liquid crystal alignment film with polarized ultraviolet light for a fixed period of time. Representative methods are as follows. In addition, the optical axis of polarized light in this specification means the axis along the straight line of linearly polarized light, or the axis along the long axis of elliptically polarized light.

<Photolysis type photoalignment technology>

In this technique, a liquid crystal aligning agent containing a compound decomposed by ultraviolet light is used, and the ultraviolet light to be irradiated is polarized, whereby the irradiation intensity is anisotropic in the long-axis direction and the short-axis direction of the optical axis of the polarized light, As a result, the liquid crystal aligning agent exhibits anisotropy due to the strength of the decomposition, and the indicated anisotropy causes anisotropy in the intermolecular interaction with the liquid crystal molecules, thereby determining the direction of the easy alignment axis.

<Photodimerization type photoalignment technology>

In this technique, the direction of the easy alignment axis is determined by adding a compound that causes a photodimerization reaction to a liquid crystal aligning agent, and using an anisotropic dimerization mechanism instead of the anisotropic decomposition mechanism.

<Photoisomerization type photoalignment technology>

In this technique, the direction of the alignment axis is determined by adding a compound that causes a photoisomerization reaction to a liquid crystal aligning agent and adding anisotropy.

With regard to the liquid crystal alignment films obtained by the above three photo-alignment techniques, by polarizing and irradiating light of a wavelength matching the light absorption mechanism of the compound of the material used in each mechanism, anisotropy is added to the liquid crystal alignment film, thereby specified alignment volume Easy shaft. The wavelength of light typically used for light absorption mechanisms is in the ultraviolet region. Furthermore, the ratio of the polarization axis to the absorption axis of the polarized ultraviolet light is referred to as the degree of polarization in polarized light, and it is advantageous that the degree of polarization is higher in terms of defining the easy axis of alignment.

The present invention relates to a photo-isomerization type photo-alignment technology among the three photo-alignment technologies. In the case of using this technology, the following problems are known in particular, but according to the preferred embodiments of the present invention, these problems can be solved.

<Issues about transmittance and coloring of liquid crystal display elements>

Compounds having dichroism are used in a large number of photoisomerizable materials. On the other hand, as in the present invention, when the optical axis of the polarized light irradiated to impart anisotropy to the liquid crystal aligning agent is aligned parallel to the optical axis of the polarized light originating from the polarizing film disposed on the backlight side, the liquid crystal aligning film The transmittance of the light-absorbing wavelength region increases, so the transmittance of the liquid crystal display element can be improved.

In the display mode of horizontal alignment, electrodes are generally provided on the liquid crystal side surface of the substrate on the backlight side. The light passing through the polarizing film arranged on the backlight side is approximately linearly polarized, but when liquid crystal is driven, the linearly polarized light depends on the difference between the ordinary light and the extraordinary light of the liquid crystal molecules that are driven (that is, the difference in refractive index Δ n), it becomes elliptically polarized light while passing through the liquid crystal layer. The elliptically polarized light as described above passes through the substrate on the opposite side of the backlight (hereinafter, referred to as the opposite substrate) with the liquid crystal layer at the center, passes through various films, and reaches the outside. The final transmitted light intensity is affected by the transmittance of the liquid crystal alignment film formed on the opposite substrate. On the other hand, in the present invention, the liquid crystal alignment film formed on the substrate on the opposite side can be made thinner as described later, so that the final intensity of transmitted light can be improved.

A liquid crystal alignment film formed of a photoisomerization-type material has light absorption on the short wavelength side of the visible light wavelength, that is, on the blue wavelength side, and the transmittance in the blue wavelength region decreases, resulting in a yellowish tinge. It's called the shading problem. If a coloring problem occurs in a liquid crystal display element, for example, when blue pixels, green pixels, and red pixels are driven for each pixel to synthesize the desired white color, the following problem occurs: along with blue transmission The transmittance of synthesized white decreases as the ratio decreases, or when a color coordinate area capable of color synthesis is drawn on the CIE1931 color coordinate, the area becomes narrower. Preferred embodiments of the present invention can improve this problem.

<About display failure of liquid crystal display element>

As described above, since the light reaching the opposite substrate becomes elliptically polarized light, it is affected by the coloring problem, but this problem can be improved as follows.

In terms of liquid crystal alignment force or alignment ease axis stability, it is advantageous to increase the amount or ratio of a liquid crystal alignment agent having, for example, an azobenzene-based compound as a photoisomerization material. , the coloring problem becomes larger, and there is a so-called trade-off problem.

In liquid crystal display elements, the degradation of display quality is often referred to as an afterimage problem, and when liquid crystal molecules are driven with electrical driving, torque stress and electric field stress originating from the liquid crystal molecules are applied to the easy alignment axis. When this state is maintained for a long time, an off-angle occurs with respect to the initial alignment easy axis, and when the driving voltage is gradually increased from a low voltage to a high voltage, a transmittance shift occurs in the vicinity of the threshold voltage at which the liquid crystal starts to drive. This transmittance shift leads to a decrease in the quality of the liquid crystal display. This reduction in display quality is often referred to as alternating current (AC) afterimage. For the driving voltage at this time, a rectangular wave AC voltage or active driving that simulates an actual liquid crystal display element is selected.

In the liquid crystal display element, such as an in-plane switching (IPS) driving mode or a fringe field switching (FFS) driving mode, which is a transverse electric field driving mode, only two substrates sandwiching the liquid crystal layer can be used. In a mode in which the electrodes of one-sided substrates perform liquid crystal display driving, an electric field for driving liquid crystals strongly acts between the liquid crystal molecules and the electrodes, and alignment due to AC afterimages occurs on the one-sided substrate on which the electrodes are provided. There is a problem of the axis shift of the easy axis, and these stresses are small in the liquid crystal alignment film on the substrate surface on the opposite side, so the easy axis shift of the alignment axis hardly becomes a problem.

This means that even if the amount of photoisomerization-type compounds such as azobenzene-based compounds used in the liquid crystal alignment film for the opposing substrate is reduced, it is difficult to cause insufficient alignment force or instability of the alignment axis. sexual issues.

Therefore, the usage amount of the photoisomerizable compound in the liquid crystal alignment film on the one-side substrate provided with the electrodes can be maintained as it is, and the usage amount of the photoisomerizable compound in the opposite substrate can be reduced, thereby It can effectively take into account the improvement of the transmittance with a trade-off relationship and the improvement of the AC afterimage problem.

As a method of reducing the usage-amount of a photoisomerization-type compound, there exist the method of reducing the usage-amount in the manufacturing stage of a liquid crystal aligning agent, and the method of thinning at the time of film formation. As a reduction method in the production stage, there is a method of reducing the mixing ratio of the photoisomerization type compound in a liquid crystal alignment film in which the photoisomerization type compound and two other liquid crystal aligning agents are mixed. When the mixing ratio is fixed, there is a method of reducing the usage ratio of the isomerized material in the production of the alignment layer. Here, polymerization in the alignment layer The ratio of the isomerized material in the material used in the production of the alignment layer polymer is reduced in a state where the mixing ratio of the polymer to the base layer polymer is fixed. For example, in the acid and diamine used in the production of the alignment layer polymer, when the diamine includes, for example, a diamine that causes isomerization and a diamine that does not cause isomerization, the amount of isomerization-causing diamine is reduced. The ratio of diamine increases the ratio of diamine that does not cause isomerization. In this way, the amount of the isomerized material to be used can be reduced and the alignment stability can be maintained, and as a result, the coloring (that is, the decrease in transmittance) that can be caused by using a large amount of the isomerized material can be suppressed. In the case where the same liquid crystal alignment film material is used for the one-side substrate provided with electrodes and the opposite-side substrate, it is often easier to reduce the amount of the photoisomerizable compound used when manufacturing the liquid crystal alignment agent. The reason is that the liquid crystal alignment film on the opposite side is thinner than that on the electrode side.

In addition, about increasing the ratio of the alignment layer of the liquid crystal alignment film on the one-side substrate provided with electrodes or increasing the azobenzene-based compound without reducing the amount of the azobenzene-based compound used in the liquid crystal alignment film of the opposite-side substrate In the case of the use amount of , it means that the transmittance remains as it is, but the AC afterimage problem that increases the alignment force can be further improved.

<About the reliability of liquid crystal display elements>

In the photoisomerization-type photoalignment technique, a compound having a site that causes a photoisomerization reaction when irradiated with ultraviolet light is used, and the irradiated ultraviolet light is irradiated with polarized light, thereby inducing photodifferentiation accompanying the compound. The anisotropy of the structure, thereby specifying the direction of the easy axis of alignment. However, as described above, the predetermined easy-to-align axis has problems with respect to the alignment restricting force and its stability. According to the preferred embodiment of the present invention, this problem can also be solved.

Photoisomerized materials have light-absorbing sites (such as azo groups), accompanied by There is photoelectric excitation, so when the backlight is irradiated for a long time, the liquid crystal alignment film may cause various deterioration processes. In addition, at the interface between the liquid crystal alignment film and the liquid crystal molecules, electric charges are accumulated at the interface due to excitation of electrons, which affects the polarization of the interface. When the interface polarization becomes large due to this influence, the liquid crystal molecules having a large dipole moment in the composition constituting the liquid crystal material are attracted, and as a result, the adsorption state between the liquid crystal alignment film material and the liquid crystal molecules is affected by coulomb interaction. .

It is considered that this adsorption state is usually mainly reversible physical adsorption in the initial state, but when the state of supplying excited electrons accompanying photoelectric excitation is continued for a long time, it is considered that it progresses to irreversible chemical adsorption accompanying chemical bonding. As for the progress toward such chemical adsorption, if the light irradiation from the backlight continues, the progress may be accelerated by the heat of the backlight.

When the mechanism progresses from the initial state of the liquid crystal display element to the state in which the display failure becomes obvious, the display failure is recognized first.

The mechanism described is only a hypothetical illustration of the reliability problem, and the performance mechanism is not limited to the description, and the reliability problem described above can also be improved according to the preferred embodiment of the present invention.

<About the problem of flickering and Vcom drift of liquid crystal display elements>

The liquid crystal display element is usually driven by an AC voltage, but when the driving state of the liquid crystal molecules is different at the + side and the - side of the AC driving voltage symbol, the transmitted light is different and becomes a flash to be recognized. It is the so-called flickering problem. In addition, although an alternating current voltage is active drive in an actual liquid crystal display element, in order to perform an evaluation test etc., an alternating rectangular wave voltage may be used for static drive.

This flicker problem in liquid crystal display elements can be ameliorated by applying a fixed DC voltage (Vcom voltage) to the common electrode, usually in the form of a bias voltage, thereby adjusting the voltage at which the flicker becomes the slightest (the voltage at which the flicker becomes the smallest). Voltage). However, even in the liquid crystal display element in which the flash is adjusted, there is a problem that the flash increases again in the state where the display is continued. This problem is called the Vcom drift problem. According to the preferred embodiment of the present invention, the Vcom drift problem can also be improved.

<About the O mode of the liquid crystal display element>

According to the preferred embodiment of the present invention, the problems of insufficient liquid crystal alignment force and instability of the easy axis of liquid crystal alignment are improved as follows.

In the photoisomerization-type photoalignment technology, when a liquid crystal alignment material having a photoisomerization-type compound such as an azobenzene-based compound is used, the alignment axis of the liquid crystal molecules is different from the irradiation for imparting anisotropy to the liquid crystal alignment material. The optical axis of the polarized ultraviolet light is orthogonal. The term "orthogonal" here means that the acute angle of the two intersecting axes is 80° to 90°, preferably 85° to 90°, more preferably 90°. On the other hand, "parallel" means that the acute angle of the two intersecting axes is 0° to 10°, preferably 0° to 5°, more preferably 0° (ie, the two axes do not intersect).

An element configuration in which the optical axis of the linearly polarized light transmitted from the polarizing film of the substrate arranged on the backlight side and the easy axis of alignment of the liquid crystal molecules is orthogonal to each other is called an O mode. Conversely, an element configuration in which the optical axis of the linearly polarized light transmitted from the polarizing film of the substrate disposed on the backlight side is parallel to the easy alignment axis of the liquid crystal molecules is called an E mode. Therefore, in the O-mode liquid crystal display element, the optical axis of the linearly polarized light of the backlight and the optical axis of the polarized ultraviolet light irradiated to impart anisotropy to the liquid crystal alignment film are aligned (parallel). By adopting such a configuration, for example, when the light quantity of the polarized ultraviolet light for adding anisotropy is insufficient, the linearly polarized light irradiated from the backlight can make up for the insufficient light quantity during use of the liquid crystal display element. As a result, it functions as an effect of repairing the unstable state of the alignment easy axis.

Instability of the easy alignment axis caused by the driving state of the liquid crystal display element causes the easy alignment axis to shift, but as described above, in the liquid crystal display element of the O mode, the linearly polarized light from the backlight in the driving state naturally decreases Small this offset, or play in the direction of return. That is, by continuously irradiating linearly polarized light from the backlight during use of the device, the stable state of the alignment axis can be improved while using the device. Regarding this effect, the liquid crystal alignment film produced in the photo-isomerization type photo-alignment technology can enjoy greater benefits than the liquid crystal alignment film produced in other photo-alignment technologies.

In this way, in the present invention, the problems of insufficient alignment force or alignment instability, which are problems in the photodecomposition type photoalignment technique or the photodimerization type photoalignment technique, are solved by adopting the photoisomerization type photoalignment technique. These problems are also solved in the photoisomerization-type photoalignment technology, such as the above-mentioned problems such as coloring.

<Liquid crystal alignment agent for forming liquid crystal alignment film>

The liquid crystal alignment film used in the liquid crystal display element contains the following reaction product, which is a polyamide acid or a derivative thereof having a photoisomerized structure such as an azo group in the main chain, and is used to convert light. The isomerized structure is introduced into the polymer main chain, and at least one of tetracarboxylic dianhydride having a photoisomerized structure or a diamine having a photoisomerized structure is used as an essential component, and other tetracarboxylic acids are used as appropriate. An acid dianhydride or other diamine etc. are also reacted and obtained.

Examples of other tetracarboxylic dianhydrides that do not have a photoisomerization structure include aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, aromatic tetracarboxylic dianhydrides, and the like. Moreover, as another diamine, the non-side chain type diamine, hydrazine etc. which do not have a photoisomerization structure, for example are mentioned.

Examples of derivatives of polyamides include soluble polyimides, polyamides, polyhydrazides, polyhydrazides, and polyhydrazides-hydrazides, and more specifically For example, 1) a polyimide obtained by dehydration ring-closure reaction of all the amine groups and carboxyl groups of polyamide acid, 2) a partial polyimide obtained by partially dehydration and ring-closure reaction of these, 3) the Polyamic acid ester obtained by converting the carboxyl group of polyamic acid into ester, 4) Polyamic acid ester obtained by reacting a part of acid dianhydride contained in tetracarboxylic dianhydride compound by substituting organic dicarboxylic acid for reaction Amino acid-polyamide copolymer, and 5) a polyamide imide obtained by subjecting a part or all of the polyamide acid-polyamide copolymer to a dehydration ring-closure reaction. As the polyamic acid or its derivatives, one compound may be used, or two or more compounds may be used simultaneously.

The liquid crystal alignment film used in the liquid crystal display element of the present invention is a liquid crystal alignment film that imparts alignment control ability by irradiating a liquid crystal alignment agent (liquid crystal alignment film) with linearly polarized or elliptically polarized light. In the step of imparting alignment control ability by light irradiation, the liquid crystal alignment agent is coated on the substrate, dried by preheating, and when linear or elliptically polarized light of ultraviolet rays is irradiated through a polarizing plate, the direction of polarization is substantially parallel to the direction of polarization. Photoisomerization is caused by the photosensitive groups of the polymer backbone. When the main chain of the polymer substantially parallel to the polarization direction is selectively photoisomerized, the main chain of the polymer forming the liquid crystal alignment film is oriented in the direction substantially orthogonal to the polarization direction of the irradiated ultraviolet rays. The directional component dominates. Therefore, the substrate is heated to dehydrate the polyamide acid. After the loop is closed to form a polyimide film, the long axis of the liquid crystal molecules of the liquid crystal composition injected into the cell assembled using this substrate is aligned in the direction orthogonal to the polarization direction of the irradiated ultraviolet rays. alignment. The step of irradiating the liquid crystal alignment film with linear or elliptically polarized light of ultraviolet rays may be performed before the heating step for polyimide, or may be performed after heating for polyimide.

<Tetracarboxylic dianhydride and diamine having a photoisomerized structure>

Terms used in the present invention will be described. "Arbitrary" used when defining a chemical structural formula means not only an arbitrary position but also an arbitrary number. In the chemical structural formula, the group surrounding the letter (eg, A) with a hexagon refers to the group (ring A) of a ring structure.

The tetracarboxylic dianhydride and diamine used for manufacture of the polyamic acid or its derivative|guide_body used for manufacture of the liquid crystal display element of this invention are demonstrated. Hereinafter, the description of "tetracarboxylic dianhydride" or "diamine" means not only the case where tetracarboxylic dianhydride or diamine is used alone, but also a plurality of tetracarboxylic dianhydride or diamine used as a mixture Case.

The polyamic acid or its derivatives having a photoisomerization structure can be obtained by making at least one tetracarboxylic dianhydride or diamine having a photoisomerization structure selected from the following formulas (I) to (VII) obtained by the reaction.

[Chemical 25] R ² -C≡CR ³ (I) R ² -C≡CC≡CR ³ (II) R ² -C≡C-CH=CH-R ³ (III) R ² CCR ⁴ CCR ³ (IV ) R ² -C≡CR ⁴ -CH=CH-R ³ (V) R ² -CH=CH-R ³ (VI) R ² -NNR ³ (VII)

In formula (I) ~ formula (VII), R ² and R ³ are independently monovalent organic groups with -NH ₂ (amine group) or -CO-O-CO- (carboxylic acid anhydride group), and R ⁴ is an aromatic group containing Ring divalent organic radical.

The liquid crystal alignment film used in the present invention can exhibit good photosensitivity by using at least one tetracarboxylic dianhydride or diamine having a photoisomerized structure selected from the above-mentioned formulas (I) to (VII). .

<Tetracarboxylic dianhydride having a photoisomerized structure>

As a tetracarboxylic dianhydride which has a preferable photoisomerization structure, the compound represented by following formula (PAN-1) or formula (PAN-2) is mentioned.

<Diamine having a photoisomerized structure>

As a diamine which has a preferable photoisomerization structure, the diamine represented by any one of following formula (PDI-1) - formula (PDI-8) is mentioned.

In the formula (PDI-1) to the formula (PDI-8), the group whose bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary, and the formula (PDI- In 7), R ⁵ is independently -CH ₃ , -OCH ₃ , -CF ₃ , or -COOCH ₃ , and b is an integer of 0 to 2.

<Diamine of formula (PDI-6-1) or formula (PDI-7-1)>

Furthermore, from the viewpoint of reactivity and photosensitivity, diamine represented by the following formula (PDI-6-1) or formula (PDI-7-1) is more preferable.

<Other tetracarboxylic dianhydride>

Tetracarboxylic dianhydrides other than the tetracarboxylic dianhydride having the above-mentioned photoisomerization structure can be further used, and can be selected from known tetracarboxylic dianhydrides without limitation. Such tetracarboxylic dianhydride may be an aromatic system (including heteroaromatic ring system) in which dicarboxylic dianhydride is directly bonded to an aromatic ring, and aliphatic in which dicarboxylic dianhydride is not directly bonded to an aromatic ring Tetracarboxylic dianhydrides in any group of families (including heterocyclic systems).

<Tetracarboxylic dianhydride of formula (AN-I) to formula (AN-V)>

As a preferable example of such a tetracarboxylic dianhydride, from the viewpoint of the ease of obtaining raw materials, the ease of polymerizing the polymer, and the electrical properties of the liquid crystal alignment film, the formula (AN-I)～ Tetracarboxylic dianhydride represented by any one of formula (AN-V).

In formula (AN-I), formula (AN-IV) and formula (AN-V), X is independently a single bond or -CH ₂ -; in formula (AN-II), G is a single bond and has 1 to 1 carbon atoms. 20 alkylene, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -; formula (AN-II) ~ formula In (AN-IV), Y is independently a kind of in the group selected from the following trivalent group;

Any hydrogen of these groups can be substituted by methyl, ethyl or phenyl; and in formula (AN-III)～formula (AN-V), ring A is a monocyclic hydrocarbon group with 3 to 10 carbon atoms or A base of a condensed polycyclic hydrocarbon with a carbon number of 6 to 30, any hydrogen of the base can be substituted by methyl, ethyl or phenyl, the bond connected to the ring is connected to any carbon constituting the ring, and the two The root bond can be attached to the same carbon.

<Tetracarboxylic dianhydride of formula (AN-1) to formula (AN-16-14)>

More specifically, the tetracarboxylic dianhydride represented by any one of the following formula (AN-1) - formula (AN-16-14) is mentioned.

<Tetracarboxylic dianhydride of formula (AN-1)>

In formula (AN-1), R ¹¹ is independently -H or -CH ₃ , and G ¹¹ is a single bond, an alkylene having 1 to 12 carbon atoms, a 1,4-phenylene, or a 1,4-ring extension hexyl. X ¹¹ is independently a single bond or -CH ₂ -. G ¹² is independently any one of the following trivalent groups.

When G ¹² is >CH-, the hydrogen of >CH- can be replaced by -CH ₃ . When G ¹² is >N-, G ¹¹ is not a single bond and -CH ₂ -, and X ¹¹ is not a single bond.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-1), the compound represented by the following formula is mentioned. In addition, in Formula (AN-1-2) and Formula (AN-1-14), m is an integer of 1-12.

<Tetracarboxylic dianhydride of formula (AN-2)>

In formula (AN-2), R ¹² is independently -H, -CH ₃ , -CH ₂ CH ₃ , or phenyl.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-2), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-3)>

In formula (AN-3), ring A ¹¹ is a cyclohexane ring or a benzene ring.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-3), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride represented by formula (AN-4)>

In formula (AN-4), ring A ¹¹ is each independently a cyclohexane ring or a benzene ring. G ¹³ can be bonded to any position of ring A ¹¹ , G ¹³ is a single bond, -CH ₂ -, -CH ₂ CH ₂ -, -O-, -S-, -C(CH ₃ ) ₂ -, - SO ₂ -, -CO-, -C(CF ₃ ) ₂ -, or a divalent group represented by the following formula (G13-1).

The phenylene in the formula (G13-1) is preferably 1,4-phenylene and 1,3-phenylene.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-4), the compound represented by the following formula is mentioned. In addition, in formula (AN-4-17), m is an integer of 1-12.

[Chemical 40]

[Chemical 42]

<Tetracarboxylic dianhydride of formula (AN-5)>

In formula (AN-5), R ¹¹ is independently -H or -CH ₃ . R ¹¹ whose bonding position is not fixed to the carbon atom constituting the benzene ring shows that the bonding position in the benzene ring is arbitrary.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-5), the compound represented by the following formula is mentioned.

[Chemical 45]

<Tetracarboxylic dianhydride of formula (AN-6)>

In formula (AN-6), X ¹¹ is independently a single bond or -CH ₂ -. X ¹² is independently -CH ₂ -, -CH ₂ CH ₂ - or -CH=CH-. n is 1 or 2.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-6), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-7)>

[Chemical 48]

In formula (AN-7), X ¹¹ is a single bond or -CH ₂ -.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-7), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-8)>

In formula (AN-8), X ¹¹ is a single bond or -CH ₂ -. R ¹² is -H, -CH ₃ , -CH ₂ CH ₃ , or phenyl, and ring A ¹² is a cyclohexane ring or a cyclohexene ring.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-8), the compound represented by the following formula is mentioned.

[Chemical 51]

<Tetracarboxylic dianhydride of formula (AN-9)>

In formula (AN-9), r is independently 0 or 1, respectively.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-9), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-10)>

<Tetracarboxylic dianhydride of formula (AN-11)>

[Chemical 55]

In formula (AN-11), ring A ¹¹ is independently a cyclohexane ring or a benzene ring.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-11), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-12)>

In formula (AN-12), ring A ¹¹ is each independently a cyclohexane ring or a benzene ring.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-12), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-13)>

In formula (AN-13), X ¹³ is an alkylene group having 2 to 6 carbon atoms, and Ph is a phenyl group.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-13), the compound represented by the following formula is mentioned.

<Tetracarboxylic dianhydride of formula (AN-15)>

In formula (AN-15), w is an integer of 1 to 10.

As an example of the tetracarboxylic dianhydride represented by Formula (AN-15), the compound represented by the following formula is mentioned.

[Chemical 62]

<Tetracarboxylic dianhydride of formula (AN-16)>

As the tetracarboxylic dianhydride other than the above, the following compounds can be mentioned.

When emphasis is placed on improving the alignment of the liquid crystal display element, among the acid dianhydrides, formula (AN-1-1), formula (AN-1-13), formula (AN-2-1), Compounds represented by formula (AN-3-1), formula (AN-4-17), formula (AN-4-28), and formula (AN-4-29).

When emphasis is placed on improving the transmittance of the liquid crystal display element, among the acid dianhydrides, formula (AN-1-1), formula (AN-1-13), formula (AN-2-1), Compounds represented by formula (AN-3-1), formula (AN-4-28), formula (AN-4-29), formula (AN-7-2) and formula (AN-10).

When emphasis is placed on improving the electrical properties of the liquid crystal display element, among the acid dianhydrides, those of formula (AN-3-2), formula (AN-4-5), formula (AN-4-17), Compounds represented by formula (AN-4-21), formula (AN-7-2), formula (AN-10), and formula (AN-11-3).

<Other diamines (1)>

When producing a polyamic acid or a derivative thereof, diamine compounds other than the above-mentioned diamine compound having a photoisomerized structure can be further used, and can be selected from known diamine compounds without limitation. At the time of this selection, it is preferable to select and use it for the purpose of improving the voltage holding ratio, the burn-mark characteristic, and the orientation of the liquid crystal.

<diamine of formula (DI-1) to formula (DI-15)>

As a known diamine, the diamine of the following formula (DI-1) - formula (DI-15) is mentioned. In addition, the group whose bonding position is not fixed to the carbon atom constituting the ring means that the bonding position on the ring is arbitrary. Furthermore, the bonding position of -NH ₂ on the cyclohexane ring or the benzene ring is any position other than the bonding position of G ²¹ or G ²² .

[Chemical 64]

In the formula (DI-1), m is an integer of 1 to 12, and any hydrogen in the alkylene group may be substituted by -OH.

In formula (DI-3) and formula (DI-5) to formula (DI-7), G ²¹ is independently a single bond, -NH-, -O-, -S-, -SS-, -SO ₂ -, -CO-, -CONH-, -CONCH ₃ -, -NHCO-, C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m' -, -O-(CH ₂ ) _m' -O-, -N(CH ₃ )-(CH ₂ ) _k -N(CH ₃ )-, or -S-(CH ₂ ) _m' -S-, m' is independently an integer from 1 to 12, k is an integer from 1 to 5.

In formula (DI-6) and formula (DI-7), G ²² is independently a single bond, -O-, -S-, -CO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or an alkylene group having 1 to 10 carbon atoms.

Arbitrary hydrogen of cyclohexane ring and benzene ring in formula (DI-2) ~ formula (DI-7) can pass through -F, -CH ₃ , -OH, -CF ₃ , -CO ₂ H, -CONH ₂ , or benzyl substitution, in addition, in formula (DI-4), any hydrogen of cyclohexane ring and benzene ring can be selected from the following formula (DI-4-a)～formula (DI-4-c) at least one group is substituted.

In formula (DI-4-a) and formula (DI-4-b), R ²⁰ is independently -H or -CH ₃ .

In formula (DI-8), R ²¹ and R ²² are independently an alkyl group or phenyl group with 1 to 3 carbon atoms, and G ²³ is independently an alkylene group with 1 to 6 carbon atoms, a phenylene group or an alkyl group substituted with an alkyl group. phenylene, n is an integer of 1-10.

In formula (DI-9), R ²³ is independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms or -Cl, p is independently an integer of 0 to 3, and q is an integer of 0 to 4. .

In formula (DI-10), R ²⁴ is -H, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a benzyl group.

In formula (DI-11), G ²⁴ is -CH ₂ - or -NH-.

In formula (DI-12), G ²⁵ is a single bond, an alkylene group having 2 to 6 carbon atoms or a 1,4-phenylene group, and r is 0 or 1.

In the formula (DI-9), the formula (DI-11) and the formula (DI-12), the group in which the bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary. .

In formula (DI-13), G ³¹ is a single bond, an alkylene group having 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, Or -C(CF ₃ ) ₂ -; in formula (DI-14), ring B is a cyclohexane ring, a benzene ring or a naphthalene ring, and any hydrogen in the ring can be substituted by methyl, ethyl, or phenyl In formula (DI-15), ring C is independently a cyclohexane ring or a benzene ring, any hydrogen in the ring can be substituted by methyl, ethyl or phenyl, Y is a single bond, and the number of carbon atoms is 1 ~20 alkylene, -CO-, -O-, -S-, _-SO2- , -C( _CH3 ) _2- , or -C( _CF3 ) _2- .

In addition, in the formula (DI-14) and the formula (DI-15), the group in which the bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary. meaning.

Specific examples of the following formulae (DI-1-1) to (DI-15-6) are exemplified as diamines of the above formulae (DI-1) to (DI-15).

<Specific diamine of formula (DI-1) to formula (DI-3)>

Examples of diamines represented by formula (DI-1) to formula (DI-3) are shown below.

<Specific diamine of formula (DI-4)>

Examples of the diamine represented by the formula (DI-4) are shown below.

[Chemical 69]

<The specific diamine of formula (DI-5)>

Examples of the diamine represented by the formula (DI-5) are shown below. In addition, in formula (DI-5-1), m is an integer of 1-12. In formula (DI-5-12) and formula (DI-5-13), m is an integer of 1-12. In formula (DI-5-16), v is an integer of 1-6. In formula (DI-5-30), k is an integer of 1-5.

[Chemical 70]

<Specific diamine of formula (DI-6)>

Examples of the diamine represented by the formula (DI-6) are shown below.

<Specific diamine of formula (DI-7)>

Examples of the diamine represented by the formula (DI-7) are shown below. In addition, in formula (DI-7-3) and formula (DI-7-4), m is an integer of 1-12, and n is 1 or 2 independently.

<Specific diamine of formula (DI-8)>

Examples of the diamine represented by the formula (DI-8) are shown below.

<Specific diamine of formula (DI-9)>

Examples of the diamine represented by the formula (DI-9) are shown below.

<The specific diamine of formula (DI-10)>

Examples of the diamine represented by the formula (DI-10) are shown below.

<Specific diamine of formula (DI-11)>

Examples of the diamine represented by the formula (DI-11) are shown below.

<The specific diamine of formula (DI-12)>

Examples of the diamine represented by the formula (DI-12) are shown below.

<The specific diamine of formula (DI-13)>

Examples of the diamine represented by the formula (DI-13) are shown below. In addition, in formula (DI-13-2), m is an integer of 1-12.

<The specific diamine of formula (DI-14)>

Examples of the diamine represented by the formula (DI-14) are shown below.

<The specific diamine of formula (DI-15)>

Examples of the diamine represented by the formula (DI-15) are shown below.

<Use of monoamine>

In each of the above-mentioned diamines, a part of the diamine may be substituted with a monoamine in a range in which the ratio of the monoamine to the diamine is 40 mol % or less. Such substitution can cause the termination of the polymerization reaction when the polyamic acid is produced, and can suppress the further progress of the polymerization reaction. Therefore, by such substitution, the molecular weight of the obtained polymer (polyamic acid or its derivative) can be easily controlled, for example, the coating properties of the liquid crystal aligning agent can be improved without impairing the effect of the present invention. As long as the effect of the present invention is not impaired, the diamine substituted into the monoamine may be one type or two or more types. Examples of the monoamine include aniline, 4-hydroxyaniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-decylamine Monoamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecamine, n-hexadecylamine, n-heptadecaamine, n-octadecylamine, and n-eicosamine.

<Use of monoisocyanate compound>

The polyamic acid or a derivative thereof may further contain a monoisocyanate compound in its monomer. By including a monoisocyanate compound in the monomer, the terminal of the obtained polyamic acid or its derivative is modified, and the molecular weight is adjusted. By using the terminal-modified polyamic acid or a derivative thereof, for example, the effect of the present invention can be impaired and the coating properties of the liquid crystal aligning agent can be improved. From this viewpoint, the content of the monoisocyanate compound in the monomer is preferable with respect to the total amount of the diamine and tetracarboxylic dianhydride in the monomer It is 1 mol% to 10 mol%. Examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.

<Preferred diamine>

Among the specific examples of the diamine, in the case of paying attention to further improving the alignment of liquid crystal molecules, the diamine is preferably the formula (DI-1-3), the formula (DI-5-1), the formula (DI-5) -12), a diamine represented by formula (DI-7-3), formula (DI-13-2), formula (DI-14-1) or formula (DI-14-2).

Among the specific examples of the diamine, the diamine is preferably the formula (DI-1-3), the formula (DI-1-4), and the formula (DI-2-1) when emphasis is placed on further improving the transmittance. , a diamine represented by formula (DI-13-1), formula (DI-13-2), formula (DI-14-1) or formula (DI-14-2).

Among the specific examples of the diamine, when further improvement in electrical properties is emphasized, the diamine is preferably the formula (DI-2-1), the formula (DI-4-1), and the formula (DI-4-13) , formula (DI-5-5), formula (DI-5-9), formula (DI-5-21), formula (DI-5-28), formula (DI-5-30), formula (DI- 5-31), the diamine represented by the formula (DI-9-1), the formula (DI-14-1), or the formula (DI-14-2).

<Production of Polyamide>

The polyamic acid used for the liquid crystal aligning agent used for manufacturing the liquid crystal aligning film used by this invention can be obtained by making an acid dianhydride component and a diamine component react in a solvent. In this synthesis reaction, except for the selection of raw materials, no special conditions are required, and the conditions in ordinary polyamic acid synthesis can be directly applied. The solvent to be used will be described later.

The liquid crystal aligning agent may be of a so-called blended type, may further contain a polyamic acid or a derivative thereof, and may further contain other components than a polyamic acid or a derivative thereof. The other ingredients may be one kind or two or more kinds.

In addition, for example, the liquid crystal aligning agent may further contain an acrylic polymer, an acrylic acid ester polymer in a range that does not impair the effect of the present invention (preferably in an amount within 20% by weight of the polyamic acid or its derivative). and other polymer components such as tetracarboxylic dianhydride, polyamide imide which is a reaction product of dicarboxylic acid or its derivative and diamine.

The polyamic acid or a derivative thereof can be produced in the same manner as a known polyamic acid or a derivative thereof used for the formation of a polyimide film. The total amount of tetracarboxylic dianhydride added is preferably approximately equal to the total molar number of diamine (the molar ratio is about 0.9 to 1.1).

The molecular weight of the polyamic acid or its derivative is preferably 10,000-500,000, more preferably 20,000-200,000, in terms of weight average molecular weight (Mw) in terms of polystyrene. The molecular weight of the polyamic acid or its derivative can be determined by measurement by colloidal permeation chromatography (Gel Permeation Chromatography, GPC).

The polyamide or its derivative can be confirmed by the following means: using infrared (Infrared, IR), nuclear magnetic resonance (Nuclear Magnetic Resonance, NMR) to make the polyamide or its derivative in the The solid content obtained by precipitation in a large amount of poor solvent was analyzed. In addition, the monomers used can be confirmed by gas chromatography (Gas Chromatography, GC), high performance liquid chromatography (High Performance Liquid Chromatography, HPLC) or Gas Chromatography-Mass Spectrometry (Gas Chromatography-Mass Spectrometry, GC-MS) is used to decompose the polyamic acid or its derivative with an aqueous solution of a strong base such as KOH or NaOH, and then use an organic solvent to decompose from it. The extracted extracts were analyzed.

<Solvent used in the production of polyamic acid or its coating>

Examples of the solvent include solvophiles for polyamic acid or its derivatives, and other solvents for the purpose of improving coatability.

Examples of aprotic polar organic solvents that are solvophilic to polyamic acid or derivatives thereof include N-methyl-2-pyrrolidone, dimethyl imidazolidinone, N-methylhexanone Lactamide, N-methylpropionamide, N,N-dimethylacetamide, dimethylsulfoxide, N,N-dimethylformamide, N,N-diethylformamide , Diethylacetamide, γ-butyrolactone and other lactones.

Examples of other solvents for the purpose of improving coatability and the like include: alkyl lactate, 3-methyl-3-methoxybutanol, tetralin, isophorone, ethylene glycol monobutyl ether such as ethylene glycol monoalkyl ethers, diethylene glycol monoalkyl ethers such as diethylene glycol monoethyl ether, ethylene glycol monoalkyl acetates or ethylene glycol monophenyl acetates, triethylene glycol mono Alkyl ethers, propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether and propylene glycol monobutyl ether, dialkyl malonates such as diethyl malonate, dipropylene glycol monoalkyl ethers such as dipropylene glycol monomethyl ether, these acetic acids Ester compounds such as esters.

Among these solvents, the solvent is particularly preferably N-methyl-2-pyrrolidone, dimethylimidazolidone, γ-butyrolactone, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and propylene glycol monobutyl ether , propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether.

The concentration of the polyamic acid in the liquid crystal alignment agent is preferably 0.1% by weight to 40% by weight. When this liquid crystal aligning agent is applied on a substrate, in order to adjust the film thickness, an operation of diluting the contained polyamic acid with a solvent in advance may be necessary.

The solid content concentration in the liquid crystal aligning agent is not particularly limited, and an optimum value may be selected according to the following various coating methods. Usually, in order to suppress unevenness, pinholes, etc. at the time of coating, it is preferably 0.1% by weight to 30% by weight, more preferably 1% by weight to 10% by weight, based on the weight of the varnish.

<Method for Forming Liquid Crystal Alignment Film>

The liquid crystal alignment film is a film formed by heating the coating film of the liquid crystal alignment agent. The liquid crystal alignment film can be obtained by a usual method of producing a liquid crystal alignment film from a liquid crystal alignment agent. For example, the liquid crystal alignment film can be obtained by going through a step of forming a coating film of a liquid crystal aligning agent, a step of heating and drying, and a step of heating and firing. In addition, anisotropy can be imparted by irradiating polarized light after the film coating step, the heating and drying step, or irradiating polarized light after the heating and firing step, if necessary.

A coating film can be formed by apply|coating a liquid crystal aligning agent to the board|substrate in a liquid crystal display element similarly to manufacture of a normal liquid crystal aligning film. The substrate may be provided with an indium tin oxide (Indium Tin Oxide, ITO) electrode, an indium zinc oxide (In ₂ O ₃ -ZnO, IZO) electrode, an indium gallium zinc oxide (In-Ga-ZnO ₄ , IGZO) electrode, or a color Glass substrates such as filters.

As a method of applying a liquid crystal aligning agent on a substrate, a spinner method, a printing method, a dipping method, a dropping method, an inkjet method, and the like are generally known. These methods can also be applied to the present invention in the same manner.

As the heat drying step, a method of heat treatment in an oven or an infrared furnace, a method of heat treatment on a hot plate, and the like are generally known. The heating and drying step is preferably carried out at a temperature within a range in which the solvent can evaporate, and more preferably carried out at a relatively low temperature with respect to the temperature in the heating and calcination step. Specifically, the heating and drying temperature is preferably in the range of 30°C to 150°C, and more preferably in the range of 50°C to 120°C.

The heating and calcining step can be carried out under the conditions required for the dehydration and ring-closure reaction of the polyamic acid or its derivatives. For the firing of the coating film, a method of heat treatment in an oven or an infrared furnace, a method of heat treatment on a hot plate, and the like are generally known. These methods can also be applied to the present invention in the same manner. Usually, it is preferable to carry out at a temperature of about 100°C to 300°C for 1 minute to 3 hours, more preferably 120°C to 280°C, and still more preferably 150°C to 250°C.

The photoisomerization treatment for the liquid crystal alignment film is performed by heating and drying the coating film of the liquid crystal alignment agent on the substrate, and then irradiating linearly polarized light or elliptically polarized light with radiation. As a result, anisotropy is imparted to the coating film, and By heating and calcining the film, a liquid crystal alignment film subjected to photoisomerization treatment can be formed. Alternatively, it can also be formed by irradiating the coating film with linearly polarized light or elliptically polarized light after heat-drying and heat-calcining the coating film. From the viewpoint of alignment, it is preferable to perform the radiation irradiation step before the heating and calcination step.

Furthermore, in order to improve the liquid crystal alignment ability of the liquid crystal alignment film, linear polarized light or elliptical polarized light of radiation may be irradiated while heating the coating film. Irradiation with radiation may be performed in the step of heating and drying the coating film, or the step of heating and calcining the coating film. It can be carried out in one step, and it can also be carried out between the heating drying step and the heating and calcining step. The heating and drying temperature in this step is preferably in the range of 30°C to 150°C, more preferably in the range of 50°C to 120°C. In addition, the heating and calcination temperature in this step is preferably in the range of 30°C to 300°C, more preferably in the range of 50°C to 250°C.

As the radiation, ultraviolet rays or visible light containing light having a wavelength of, for example, 150 nm to 800 nm can be used, and preferably ultraviolet rays containing light having a wavelength of 300 nm to 400 nm. Alternatively, linearly polarized light or elliptically polarized light can be used. These lights are not particularly limited as long as they can impart a liquid crystal alignment ability to the coating film, and linear polarized light is preferable when a strong alignment control force is to be exhibited to the liquid crystal.

The liquid crystal alignment film of the present invention can exhibit high liquid crystal alignment ability even under low-energy light irradiation. The irradiation amount of the linearly polarized light in the radiation irradiation step is preferably 0.05J/cm ² -20J/cm ² , more preferably 0.5J/cm ² -10J/cm ² . In addition, the wavelength of the linearly polarized light is preferably 200 nm to 400 nm, more preferably 300 nm to 400 nm. The irradiation angle of the linearly polarized light on the film surface is not particularly limited, but when a strong alignment restraining force is to be exhibited on the liquid crystal, it is preferably as perpendicular to the film surface as possible from the viewpoint of shortening the alignment treatment time. In addition, the liquid crystal alignment film of the present invention can align liquid crystal molecules (long axis direction) in a direction orthogonal to the polarization direction of the linearly polarized light by irradiating linearly polarized light.

When the pretilt angle is to be expressed, the light irradiated to the liquid crystal alignment film may be linearly polarized light or elliptically polarized light, as described above. In the case where the pretilt angle is to be exhibited, the irradiation amount of the light irradiated to the liquid crystal alignment film is preferably 0.05J/cm ² ~20J/cm ² , particularly preferably 0.5J/cm ² ~10J/cm ² , and its wavelength It is preferably 250 nm to 400 nm, particularly preferably 300 nm to 380 nm. When the pretilt angle is to be expressed, the irradiation angle of the light irradiated on the film with respect to the film surface is not particularly limited, but from the viewpoint of shortening the alignment treatment time, it is preferably 30 to 60 degrees.

Among the polarized ultraviolet light sources, ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, deep UV lamps, halogen lamps, metal halide lamps, high-power metal halide lamps, xenon lamps, mercury xenon lamps, Excimer lamps, KrF excimer lasers, fluorescent lamps, light emitting diode (LED) lamps, sodium lamps, microwave electrodeless lamps, etc.

The liquid crystal alignment film of the present invention can be preferably obtained by a method further including other steps than the above-mentioned steps. For example, although the step of cleaning the film after firing or radiation irradiation with a cleaning solution is not an essential step, a cleaning step may be provided depending on other steps.

As a cleaning method using a cleaning liquid, brushing, spraying, steam cleaning, ultrasonic cleaning, etc. are mentioned. These methods may be performed independently or may be used in combination. As the cleaning solution, pure water, various alcohols such as methanol, ethanol, and isopropanol, aromatic hydrocarbons such as benzene, toluene, and xylene, halogen-based solvents such as methylene chloride, acetone, methyl ethyl ketone, and the like can be used. Ketones, but are not limited to these cleaning solutions. Of course, as these cleaning liquids, sufficiently purified cleaning liquids with few impurities can be used. This cleaning method can also be applied to the cleaning step during the formation of the liquid crystal alignment film.

In order to improve the liquid crystal alignment ability of the liquid crystal alignment film, annealing treatment by heat or light may be used before and after the heating and firing step, or before and after irradiation of polarized ultraviolet light. In the annealing treatment, the annealing temperature is 30°C to 180°C, preferably 50°C to 150°C, and the time is preferably 1 minute to 2 hours. Moreover, UV lamps, fluorescent lamps, LED lamps, etc. are mentioned as annealing light used for an annealing process. The irradiation amount of light is preferably 0.3 J/cm ² to 10 J/cm ² .

The film thickness of the liquid crystal alignment film is not particularly limited, but for example, it is preferably 10 nm to 300 nm, and more preferably 30 nm to 150 nm, on the side of the substrate where the electrodes are provided. The film thickness of the liquid crystal alignment film can be measured by a known film thickness measuring apparatus such as a level difference meter or an ellipsometer.

The liquid crystal alignment film of the present invention is characterized by having a particularly large alignment anisotropy. The magnitude of such anisotropy can be evaluated by the method using polarized light IR described in Japanese Patent Laid-Open No. 2005-275364 and the like. In addition, it can also be evaluated by a method using ellipsometry.

<Liquid crystal composition>

The liquid crystal composition used for the liquid crystal display element of this invention is demonstrated. The liquid crystal composition includes a liquid crystal composition showing negative dielectric anisotropy and a liquid crystal composition showing positive dielectric anisotropy. Anisotropic liquid crystal composition.

The liquid crystal composition having negative dielectric anisotropy is characterized by containing, as a first component, at least one liquid crystal compound selected from the group of liquid crystal compounds represented by the following formula (1).

[Chemical 83]

Here, R ¹ and R ² are independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an arbitrary hydrogen group having 2 to 12 carbon atoms substituted with fluorine. Alkenyl of 12; Ring A and Ring B are independently 1,4-cyclohexylene, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, 1,4 -phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2-fluoro -3-Chloro-1,4-phenylene, 2,3-difluoro-6-methyl-1,4-phenylene, 2,6-naphthalenediyl, or 7,8-difluorochroman (chromane)-2,6-diyl, wherein at least one of ring A and ring B is 2,3-difluoro-1,4-phenylene, 2-fluoro-3-chloro-1,4- phenylene, 2,3-difluoro-6-methyl-1,4-phenylene, or 7,8-difluorochroman-2,6-diyl; Z ¹ is independently a single bond, -( _CH2 ) _2- , _-CH2O- , -COO-, or -CF2O-; j is 1, ₂ , or 3.

As a specific example of the liquid crystal compound of the said formula (1), the compound represented by any one of following formula (1-1) - formula (1-32) is mentioned.

In formulas (1-1) to (1-32), R ¹ and R ² are independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms in which any hydrogen is substituted by fluorine. In order to improve the stability to ultraviolet light or heat, the preferred R ¹ or R ² is an alkyl group having 1 to 12 carbon atoms, or in order to improve the absolute value of the dielectric anisotropy, the preferred R ¹ or R ² is An alkoxy group having 1 to 12 carbon atoms.

Preferred alkyl groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl. Further preferred alkyl groups are ethyl, propyl, butyl, pentyl, or heptyl in order to reduce viscosity.

Preferred alkoxy groups are methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, or heptyloxy. Further preferable alkoxy groups are methoxy groups or ethoxy groups in order to lower the viscosity.

Preferred alkenyl groups are vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-butenyl -Pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, or 5-hexenyl. Further preferred alkenyl groups are vinyl, 1-propenyl, 3-butenyl, or 3-pentenyl in order to lower the viscosity. The preferable steric configuration of -CH=CH- in these alkenyl groups depends on the position of the double bond. In terms of viscosity reduction and the like, in alkenyl groups such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl, 3-hexenyl and the like Preferred is trans. Cis is preferred among alkenyl groups such as 2-butenyl, 2-pentenyl, 2-hexenyl and the like. Among these alkenyl groups, straight-chain alkenyl groups are preferable to branched ones.

Preferable examples of the alkenyl in which any hydrogen is substituted with fluorine are 2,2-difluorovinyl, 3,3-difluoro-2-propenyl, 4,4-difluoro-3-butenyl, 5 , 5-difluoro-4-pentenyl, and 6,6-difluoro-5-hexenyl. In order to lower the viscosity, more preferable examples are 2,2-difluorovinyl and 4,4-difluoro-3-butenyl.

In formula (1), ring A and ring B are independently 1,4-cyclohexylene, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, 1, 4-phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2- Fluoro-3-chloro-1,4-phenylene, 2,3-difluoro-6-methyl-1,4-phenylene, 2,6-naphthalenediyl, 7,8-difluorochroman -2,6-diyl, where at least one of ring A and ring B is 2,3-difluoro-1,4-phenylene, 2-fluoro-3-chloro-1,4-phenylene , 2,3-difluoro-6-methyl-1,4-phenylene, 7,8-difluorochroman-2,6-diyl, when j is 2 or 3, any two rings A Can be the same or different. In order to improve the dielectric anisotropy, the preferred ring A and ring B are 2,3-difluoro-1,4-phenylene or tetrahydropyran-2,5-diyl, respectively. Desirable ring A and ring B are each 1,4-cyclohexylene.

In formulas (1-19) to (1-21), ring A ¹ , ring A ² , ring A ³ , ring B ¹ , and ring B ² are independently 1,4-cyclohexylene or 1,4-cyclohexylene phenyl. In order to reduce viscosity, preferable ring A ¹ , ring A ² , ring A ³ , ring B ¹ , and ring B ² are each 1,4-cyclohexylene.

In formula (1), Z ¹ is independently a single bond, -(CH ₂ ) ₂ -, -CH ₂ O-, -COO-, -CF ₂ O-, and when j is 2 or 3, any two Z ¹ It can be the same or different. In order to improve the dielectric anisotropy, the preferred Z ¹ is -CH ₂ O-, and in order to reduce the viscosity, the preferred Z ¹ is a single bond.

In formula (1-19) to formula (1-21), Z ¹¹ and Z ¹² are independently a single bond, -(CH ₂ ) ₂ -, -CH ₂ O-, or -COO-. In order to improve the dielectric anisotropy, the preferred Z ¹¹ and Z ¹² are -CH ₂ O-, and in order to reduce the viscosity, the preferred Z ¹¹ and Z ¹² are single bonds.

In formula (1), j is 1, 2, or 3. In order to lower the lower limit temperature, preferable j is 1, and in order to raise the upper limit temperature, preferable j is 2.

In the liquid crystal composition having negative dielectric anisotropy, the preferred compound (1) as the first component is formula (1-1), formula (1-4), formula (1-7) or A compound represented by formula (1-32).

Preferred examples of the liquid crystal composition having the negative dielectric anisotropy include Japanese Patent Laid-Open No. 57-114532, Japanese Patent Laid-Open No. 2-4725, and Japanese Patent Laid-Open No. Hei 4- Japanese Patent Laid-Open No. 224885, Japanese Patent Laid-Open No. Hei 8-40953, Japanese Patent Laid-Open No. Hei 8-104869, Japanese Patent Laid-Open No. 10-168076, Japanese Patent Laid-Open No. 10-168453, Japanese Patent Laid-Open No. Hei 10- Japanese Patent Laid-Open No. 236989, Japanese Patent Laid-Open No. 10-236990, Japanese Patent Laid-Open No. 10-236992, Japanese Patent Laid-Open No. 10-236993, Japanese Patent Laid-Open No. 10-236994, Japanese Patent Laid-Open No. 10-236994 Japanese Patent Laid-Open No. 237000, Japanese Patent Laid-Open No. 10-237004, Japanese Patent Laid-Open No. 10-237024, Japanese Patent Laid-Open No. 10-237035, Japanese Patent Laid-Open No. 10-237075, Japanese Patent Laid-Open No. 10-237075 Japanese Patent Laid-Open No. 237076, Japanese Patent Laid-Open No. 10-237448 (EP967261A1 Specification), Japanese Patent Laid-Open No. 10-287874, Japanese Patent Laid-Open No. 10-287875, Japanese Patent Laid-Open No. 10-291945, Japanese Patent Laid-Open No. 10-291945 Japanese Patent Laid-Open No. 11-029581, Japanese Patent Laid-Open No. 11-080049, Japanese Patent Laid-Open No. 2000-256307, Japanese Patent Laid-Open No. 2001-019965, Japanese Patent Laid-Open No. 2001-072626, Japanese Patent Laid-Open No. 2001 - 192657 Gazette, Japanese Patent Laid-Open No. 2010-037428 Gazette, International Publication No. 2011/024666 Handbook, International Publication No. 2010/072370 Handbook, Japanese Patent Publication No. 2010-537010, Liquid crystal compositions disclosed in Japanese Patent Laid-Open No. 2012-077201, Japanese Patent Laid-Open No. 2009-084362, and the like.

<Basic structure of liquid crystal display element>

The liquid crystal display element includes a pair of substrates arranged to face each other, an electrode group formed on one or both of the opposing surfaces of the pair of substrates, a plurality of active elements connected to the electrode group, A liquid crystal alignment film formed on each of the opposing surfaces of the pair of substrates, and a liquid crystal layer formed between the pair of substrates.

As the substrate, a glass substrate can be used, and the electrode is not particularly limited as long as it is an electrode formed on one surface of the substrate. Examples of such electrodes include ITO, IZO, IGZO, and metal vapor deposition films. In addition, the electrode may be formed on the entire surface of one surface of the substrate, or may be formed in a desired shape by, for example, patterning. The desired shape of the electrode includes, for example, a comb shape, a sawtooth structure, and the like. The electrodes may be formed on one of the pair of substrates, or may be formed on both substrates. The formation form of the electrodes differs depending on the type of liquid crystal display element. For example, in the case of an IPS type liquid crystal display element and an FFS type liquid crystal display element, the electrodes are arranged on one of the pair of substrates, and the electrodes are arranged on the other liquid crystal display elements. In this case, electrodes are arranged on both of the pair of substrates. The liquid crystal alignment film is formed on the substrate or electrode.

The liquid crystal layer is formed of a liquid crystal composition sealed in a gap between a pair of substrates facing each other so that the surface on which the liquid crystal alignment film of one of the pair of substrates is formed faces the other substrate.

The liquid crystal display element can be obtained by at least one of the pair of substrates. A liquid crystal alignment film is formed on one of them, the liquid crystal alignment film is turned inward, the obtained pair of substrates are opposed via a spacer, and the liquid crystal composition is enclosed in a gap formed between the substrates to form a liquid crystal layer. Further steps, such as attaching a polarizing film to a substrate, may be included if necessary at the time of manufacture of the liquid crystal display element.

The liquid crystal layer is formed in such a manner that a liquid crystal composition is sandwiched between the pair of substrates on which the liquid crystal alignment films are formed facing each other. In the formation of the liquid crystal layer, a spacer, such as fine particles or a resin sheet, may be used as necessary to form an appropriate interval between the pair of substrates.

[Example]

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.

1. Evaluation method of materials used

(1) Weight average molecular weight (Mw)

The weight-average molecular weight of polyamic acid was obtained by using the 2695 separation module. A 2414 differential refractometer (manufactured by Waters) was used for the measurement by the GPC method, and the polystyrene conversion was performed. The obtained polyamic acid was diluted with a phosphoric acid-dimethylformamide (DMF) mixed solution (phosphoric acid/DMF=0.6/100 in terms of weight ratio) so that the concentration would be about 2% by weight . As the column, HSPgel RT MB-M (manufactured by Waters) was used, and the mixed solution was used as a developing solvent, and the column temperature was measured at 50° C. and the flow rate was 0.40 mL/min. As the standard polystyrene, TSK standard polystyrene manufactured by Tosoh Co., Ltd. was used.

2. Evaluation method of liquid crystal display element

<About the transmitted light detection device>

The transmitted light is converted into electric current by photomultiplier tube (PMT) R374 manufactured by Hamamatsu photonics, and a predetermined voltage conversion is performed. The signal converted to voltage is digitized using a digital multimeter and a 14-bit, 10 MHz AD converter. In addition, when optical measurement is performed later, these photodetectors and the above-mentioned digitizer are used.

<About transmittance measurement>

Regarding the transmittance measurement of the liquid crystal display element, first, the electro-optical response (VT measurement) is measured using the above-mentioned transmitted light detection device, the voltage at which the transmittance becomes the maximum and the positional conditions of the polarizer and the analyzer are determined, and then the transmitted light is detected. The instrument used the spectrometer MCPC-7000 manufactured by Otsuka Electronics Co., Ltd., and the light source used the LED light source SLA-100 of Sigma Optical Co., Ltd. to measure the transmitted light intensity. By rotating the polarizing element to change the relative angle to the alignment axis of the liquid crystal molecules, the transmission spectrum for each angle was studied.

<About the driving of the liquid crystal test display element>

As a method of driving the liquid crystal display element, the evaluation was performed by static driving and active driving. In the case of static driving, a rectangular wave AC voltage is applied to the signal electrode terminal, the common electrode terminal is grounded, or a DC offset voltage is applied. On the other hand, in the case of active driving, by using a sample and hold circuit (sample hold circuit) sampling is performed at a small fixed time and held voltage to drive the liquid crystal evaluation cell.

<About O Mode>

Regarding the configuration of the liquid crystal display element using the O mode, from the backlight side, the backlight (B), polarizing film (F1), substrate with liquid crystal alignment film (S1), liquid crystal composition (LC), and liquid crystal alignment film In the liquid crystal display element constituted by the order of the substrate (S2) and the polarizing film (F2), the polarization axis direction of the ultraviolet rays irradiated to the liquid crystal alignment film of the substrate (S1) and the polarized light of the ultraviolet rays irradiated to the liquid crystal alignment film of the substrate (S2) The axis directions are parallel, so that the alignment direction (long axis direction) of the liquid crystal molecules in the liquid crystal composition (LC) is orthogonal to the polarization axis direction of the liquid crystal alignment film of the substrate (S1) and the substrate (S2), so that the polarizing film on the backlight side is The polarization axis of (F1) is parallel to the polarization axis direction of the ultraviolet rays irradiated to the liquid crystal alignment film of the substrate (S1). The O mode refers to an element configuration in which the polarization axis of the polarizing film (F1) on the backlight side is orthogonal to the alignment direction (long axis direction) of the liquid crystal molecules in the liquid crystal composition (LC).

<About E Mode>

Regarding the configuration of the liquid crystal display element using the E mode, from the backlight side, the backlight (B), polarizing film (F1), substrate with liquid crystal alignment film (S1), liquid crystal composition (LC), and liquid crystal alignment film In the liquid crystal display element constituted in the order of the substrate (S2) and the polarizing film (F2), the polarization axis direction of the ultraviolet rays irradiated to the liquid crystal alignment film of the substrate (S1) and the polarized light of the ultraviolet rays irradiated to the liquid crystal alignment film of the substrate (S2) The axis directions are parallel, so that the alignment direction (long axis direction) of the liquid crystal molecules in the liquid crystal composition (LC) is orthogonal to the polarization axis direction of the liquid crystal alignment film of the substrate (S1) and the substrate (S2), so that the polarizing film on the backlight side is The polarization axis of (F1) and the liquid irradiated to the substrate (S1) The direction of the polarization axis of the ultraviolet rays of the crystal alignment film is orthogonal to each other. The E mode refers to an element configuration in which the polarization axis of the polarizing film (F1) on the backlight side is parallel to the alignment direction (long axis direction) of the liquid crystal molecules in the liquid crystal composition (LC).

(1) Pre-tilt angle

Measurement and analysis were performed using a spectroscopic ellipsometer M-2000U (manufactured by J.A. Woollam Co. Inc.).

(2) Transmittance change rate (AC residual image evaluation)

The transmittance-voltage characteristics (TV characteristics) of the liquid crystal display element were measured in an arrangement of O mode (Example) or E mode (comparison), and both the polarizer and the analyzer were installed so that the transmittance was extremely small. Let this be the transmittance-voltage characteristic before stress application: T (before). Next, in the state of performing TV measurement in O mode or E mode, AC with amplitude V _0-P =4.5V, 60 Hz or 30 Hz was applied to the element with a rectangular wave waveform for 20 minutes, then short-circuited for 1 second, and the measurement was performed again. Transmittance-Voltage Characteristics (TV Characteristics). Let this be the transmittance-voltage characteristic after stress application: T (after). Based on these values, the transmittance change rate ΔT/T (%) was estimated using the following formula 1.

△T/T(%)=[T(rear)-T(front)]/T(front) (Formula 1)

These measurements were performed with reference to the description of International Publication No. 2000/43833 manual. When a voltage of 31 G is applied, it can be said that the smaller the value of ΔT/T (%), the more the generation of AC afterimages can be prevented.

Furthermore, the record of AC or AC drive and AC drive in the text refers to the Where there is no special description, the sampling and holding in the square wave AC voltage or active drive alternate, and have bipolar sampling characteristics.

(3) Liquid crystal alignment axis stability (alignment stability)

The rate of change of the easy axis of liquid crystal alignment on the electrode side of the liquid crystal display element was obtained. It was set to O mode (Example) or E mode (comparison), and the liquid crystal alignment easy axis angle Φ (front) on the electrode side before stress was measured. Then, in the configuration of the O mode or the E mode, the polarizing element and the analyzer are installed so that the transmittance is extremely small, and the amplitude V _0-P =4.5 V, 60 Hz or 30 Hz is applied to the element in a rectangular waveform for 20 minutes. After the alternating current, it was set to a short-circuit state, and the easy axis angle of the liquid crystal alignment on the electrode side was measured again. Let this be the liquid crystal alignment easy axis angle Φ (back) after stress is applied. Based on these values, the change ΔΦ (deg.) in the angle of the easy axis of liquid crystal alignment was estimated using the following formula 2.

△Φ(deg.)=Φ(back)-Φ(front) (Formula 2)

These measurements were made with reference to J. Hilfiker, B. Johs, C. Herzinger, J.F. Elman, E. Montbach, D. Bryant, and P.J. Bos, "Thin Solid Films", 455-456, (2004) 596-600. It can be said that a small ΔΦ results in a small change in the easy axis of liquid crystal alignment and good stability of the easy axis for liquid crystal alignment.

(4) Voltage holding ratio (VHR) and flicker

When the liquid crystal display element is actively driven, when the retention is not sufficient, the voltage drops due to the leakage current between the electrodes. An index indicating this voltage drop is the voltage holding ratio (VHR). When the VHR is significantly lowered, the display quality is lowered and flickering (flickering phenomenon) occurs. The flash period of the flicker caused by the influence of this voltage drop becomes half the drive period, and the frequency is doubled. For example, when the driving frequency is 30 Hz, the flashing frequency of the blinking is 60 Hz. On the other hand, the flicker due to the residual DC voltage appears repeatedly with peaks and valleys at the same cycle as the ± sign of the drive voltage, and has the same frequency. With respect to this driving period, the phenomenon of the same period and the double period is superimposed to cause flickering. Such flicker degrades the display quality, so it is required not to generate the flicker.

Furthermore, the measurement conditions of the VHR of the present embodiment are as follows:

Applied voltage: 5V

Hold Time: 167 ms

Measuring device: Model 6254 manufactured by Dongyang Technology

(5) Vcom drift voltage (DC afterimage evaluation)

When a rectangular wave AC voltage is applied to the signal electrode terminal to drive the liquid crystal, and a DC offset voltage (or a DC offset voltage is added to the rectangular wave AC voltage) is intentionally applied to the common electrode terminal, the applied DC offset voltage causes the liquid crystal to be driven. When the liquid crystal is driven by asymmetric AC, flickering occurs depending on the magnitude of the asymmetry. The generated flicker often has a maximum amplitude shortly after the DC offset voltage is applied, and the asymmetry of the AC drive is reduced due to the absorption of the applied DC offset voltage component in the liquid crystal display element, thereby reducing the amplitude of the flicker. . After applying this DC offset voltage for a fixed time and observing the absorption process, the DC offset voltage was set to 0V, the absorbed DC voltage was released, and the process was observed. When the DC offset voltage is set to 0V, as the absorbed DC voltage increases, the flicker increases depending on the magnitude, and is gradually alleviated. The observation of this absorption and relaxation process is called Vcom drift voltage measurement. In this Vcom drift voltage measurement, it can be said that the DC offset voltage has no absorption or that the lower the DC offset voltage, the better the Vcom tunability.

Incidentally, the Vcom drift voltage measurement or the evaluation of the behavior of the asymmetric DC offset voltage may be used in the same meaning as the DC afterimage evaluation.

The rectangular wave AC voltage is mostly selected to be about 63 degrees when γ=2.2.

In addition, in the FFS mode, the asymmetry of the electrode structure with respect to the liquid crystal driving also often results in asymmetric driving. As a result, flickering occurs also in rectangular wave AC driving in which a positive voltage and a negative voltage to which no DC offset voltage is applied are compared. In this case, a DC offset voltage is added to eliminate the asymmetry, thereby minimizing flicker. The DC offset voltage that minimizes this flicker is called the initial optimized Vcom voltage.

Good Vcom tunability by the evaluation means that it can be easily determined from the DC offset voltage added to minimize flicker, and the risk of re-generation of minimized flicker is low even under long-term driving . The smaller the initial optimized Vcom voltage is, the more difficult it is to cause problems caused by the flicker.

Regarding the DC offset absorption and release process, the time constant can be obtained by quantifying the effective value of the transmittance or the amplitude of flicker, and fitting the time change with the following equation 3. In flicker analysis, the AC drive voltage is in phase with the The polarity of the DC component of the asymmetric DC voltage can be discriminated by distinguishing the bit component and the half-cycle phase-shifted component, and the flicker of which the polarity is distinguished is defined as ±flicker. The ± scintillation was measured and analyzed.

AExp(-t/τ)+C (Equation 3)

A: Indicates the size of the absorption

τ: represents the time constant for absorption or relaxation

C: represents the fitting parameter that becomes the offset

t: Indicates time, DC offset voltage is applied at t=0.

Furthermore, fitting is performed using the least squares method.

When the time constant τ in Equation 3 is an index, when it is large, it means that the time taken for absorption and relaxation becomes longer, and conversely, when it is small, it means that the time required for absorption and relaxation is short. Generally, the time constant τ depends on the product of the resistance and capacitance of the material.

3. Solvents, additives and liquid crystal compositions

Solvents, additives, and liquid crystal compositions used in Examples will be described below.

(1) Solvent

NMP: N-methyl-2-pyrrolidone

BC: Butyl Cellosolve (ethylene glycol monobutyl ether)

(2) Additives

Additive (Ad1): bis[4-(allylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxy imide)phenyl]methane

Additive (Ad2): N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane

Additive (Ad3): 3-aminopropyltriethoxysilane

Additive (Ad4): 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane

(3) Liquid crystal composition

4. Liquid crystal alignment agent

The synthesis of the polyamic acid used to prepare the liquid crystal aligning agent used in the examples will be described below.

(1) Polyamide [A]

As the polyamic acid [A], various polyamic acid solutions PA1 to polyamic acid solutions PA6 were prepared.

[Synthesis Example 1]

Diamine (DI-5-1, m=2) 0.2102 g and diamine (DI-9-1) 0.0664 were put into a 50 mL brown four-necked flask equipped with a thermometer, a stirrer, a raw material injection port, and a nitrogen gas inlet. g, 0.2082 g of diamine (PDI-6-1), 0.5778 g of diamine (PDI-7-1), and dehydrated NMP (18.5 g) were stirred and dissolved under a stream of dry nitrogen gas. Then, 0.1268 g of tetracarboxylic dianhydride (AN-1-13), 1.8106 g of tetracarboxylic dianhydride (AN-4-17, m=8), and dehydrated NMP (18.5 g) were put, and the mixture was heated to room temperature. stirring was continued for 24 hours. BC (10.0 g) was added to this reaction solution to obtain a polyamic acid solution (PA1) having a polymer solid content concentration of 6% by weight. The weight average molecular weight of the polyamic acid contained in PA1 was 39,400.

[Synthesis Example 2 to Synthesis Example 6]

In accordance with Synthesis Example 1, except that the tetracarboxylic dianhydride and diamine were changed as shown in Table 1, a polyamic acid solution (PA2) to a polyamic acid solution (PA6) having a polymer solid content concentration of 6% by weight were prepared ).

Table 1 summarizes the measurement results of the weight average molecular weights of the polyamic acids obtained in Synthesis Example 1 and Synthesis Example 2 to Synthesis Example 6.

(2) Polyamide [B]

As the polyamic acid [B], various polyamic acid solutions PA7 to polyamic acid solutions PA22 were prepared.

[Synthesis Example 7]

Diamine (DI-4-1) 0.7349 g and dehydrated NMP (18.5 g) were put into a 50 mL brown four-necked flask equipped with a thermometer, a stirrer, a raw material input addition port, and a nitrogen gas introduction port, and dissolved by stirring under a stream of dry nitrogen. . Then, 0.6732 g of tetracarboxylic dianhydride (AN-1-1), 1.5918 g of tetracarboxylic dianhydride (AN-4-28), and dehydrated NMP (18.5 g) were put, and stirring was continued at room temperature for 24 Hour. BC (10.0 g) was added to this reaction solution to obtain a polyamic acid solution (PA7) having a polymer solid content concentration of 6% by weight. The weight average molecular weight of the polyamic acid contained in PA7 was 51,000.

[Synthesis Example 8 to Synthesis Example 22]

Except having changed the tetracarboxylic dianhydride and the diamine as shown in Table 2, according to Synthesis Example 7, the polymer solid content concentration is 6 weight % to prepare the polyamic acid solution (PA8) ~ the polyamic acid solution (PA22 ).

Table 2 summarizes the measurement results of the weight average molecular weights of the polyamic acids obtained in Synthesis Example 7 to Synthesis Example 22.

(3) Polyamide [A]+[B]

Polyamic acid [A] and [B] were mixed, and the solution PA23 of various polyamic acid - the solution PA37 of polyamic acid were prepared.

[Preparation Example 23]

The polyamic acid solution (PA1) as the polyamic acid [A] and the polyamic acid solution (PA9) as the polyamic acid [B] in the weight ratio [A]/[B]=3.0/7.0 mixed to prepare a polyamic acid solution (PA23).

[Preparation Example 24 to Preparation Example 37]

A polyamide having a polymer solid content concentration of 6 wt % was prepared in accordance with Preparation Example 23, except that the types of the polyamic acid [A] and the polyamic acid [B] and the mixing ratio of [A]/[B] were changed. Amino acid solution (PA24) ~ polyamide acid solution (PA37).

The details of Preparation Examples 23 to 37 are summarized in Table 3.

(4) Polyamic acid + additives

Polyamic acid and additives were mixed to prepare various polyamic acid solutions PA38 to polyamic acid solutions PA41.

[Preparation Example 38]

The additive (Ad1) was added to the polyamic acid solution (PA3) in a ratio of 5 wt % with respect to the polymer weight to prepare a polyamic acid solution (PA38).

[Preparation Example 39 to Preparation Example 41]

In addition to changing the types and addition ratios of polyamides and additives, according to the preparation Example 38 was used to prepare a polyamic acid solution (PA39) to a polyamic acid solution (PA41).

The details of Preparation Examples 38 to 41 are summarized in Table 4.

5. Characteristics of liquid crystal display elements

[Example 1]

A mixed solvent (NMP/BC=4/1 in weight ratio) was added to the polyamide solution (PA1) with a polymer solid content concentration of 6 wt %, and the polymer solid content concentration was diluted to 4 wt % And prepare a liquid crystal alignment agent. The liquid crystal aligning agent was applied to a glass substrate with column spacers and a glass substrate with ITO electrodes using a spinner (Mikasa Co., Ltd., spin coater 1H-DX2), and then heated. The plate (manufactured by ASONE Co., Ltd., EC hot plate EC-1200N) was heated and dried at 70° C. for 80 seconds. Next, using Multi-Light ML-501C/B manufactured by Ushio Electric Co., Ltd., linearly polarized light of ultraviolet rays was irradiated through a polarizing plate from a direction perpendicular to the plane of each substrate. The exposure energy at this time was measured to be 2.0 J/cm ² ±0.1 at a wavelength of 365 nm by measuring the amount of light using an ultraviolet cumulative light meter UIT-150 (photoreceiver UVD-S365) manufactured by Ushio Electric Co., Ltd. Adjust the exposure time in the way of J/cm ² . Next, in a clean oven (Espec Co., Ltd. make, clean oven PVHC-231), it heat-processed at 230 degreeC for 15 minutes, and formed the alignment film of film thickness 100nm±10nm on each substrate.

The two substrates are made to face each other in such a way that the formation surfaces of the alignment films face each other and the polarization directions of the ultraviolet rays irradiated to the alignment films become parallel, and then a space for injecting the liquid crystal composition is formed between the facing alignment films. Then, they were assembled into empty FFS cells with a cell thickness of 3.6 μm ± 0.3 μm. In addition, the liquid crystal injection port in the FFS cell is provided at a position where the injected liquid crystal flows in substantially parallel to the polarization direction of the alignment film. The negative liquid crystal composition A was vacuum-injected into the produced empty FFS cell to produce an FFS liquid crystal display element.

The pretilt angle of the FFS liquid crystal display element was measured and found to be 0.0°. In addition, the flow alignment was not confirmed, and the alignment was good.

In addition, when the transmittance change rate ΔT/T (%) was measured, it was 5.2% in the O mode and 9.5% in the E mode (comparison). In addition, when the liquid crystal alignment axis stability ΔΦ (deg.) was measured, it was 0.024 degrees in the O mode and 0.075 degrees in the E mode (comparison).

Furthermore, when a high-brightness LED light source was used as a backlight and the voltage holding ratio (VHR) was measured, it was 99.62% in the O mode, 99.58% in the E mode (comparison), and high in the O mode. In addition, the liquid crystal test evaluation samples of both the O mode and the E mode (comparison) were irradiated with LED backlight light for 1000 hours, and the voltage holding ratio was evaluated before and after. The results were 99.54% in the O mode and 99.54% in the E mode It is 99.35%, and the voltage holding ratio in the E mode has a larger drop than that in the O mode. From this result, it can be seen that the reliability characteristics against backlight light in the O mode are higher than those in the E mode (comparison).

[Example 2 to Example 21]

The FFS liquid crystal display element was produced by the method according to Example 1 except having changed the polyamic acid solution used as a liquid crystal aligning agent. In addition, the rotational speed of the spinner was adjusted according to the viscosity of the prepared liquid crystal aligning agent so that the film thickness of the alignment film was 100 nm±10 nm. In O mode and E mode, the transmittance change ratio ΔT/T (%), the liquid crystal alignment axis stability ΔΦ (deg.) and the voltage holding ratio (VHR) of the obtained FFS liquid crystal display element were measured. These results are summarized in Table 5.

[Example 22]

A FFS liquid crystal display element was produced by the method according to Example 1, except that the polyamic acid solution used as a liquid crystal aligning agent and the type of the liquid crystal composition injected between the cells were changed. However, the exposure time was adjusted so that the exposure energy at the time of ultraviolet irradiation of the Multi-Light manufactured by Ushio Motor Co., Ltd. was 0.7 J/cm ² ±0.1 J/cm ² at a wavelength of 365 nm. , and the temperature of the substrate during ultraviolet exposure was heated to 50°C, and the ultraviolet irradiation was performed by covering the entire device with an anti-ultraviolet film, and carried out at room temperature and in the air. In addition, the rotational speed of the spinner was adjusted according to the viscosity of the prepared liquid crystal aligning agent so that the film thickness of the alignment film was 100 nm±10 nm.

The pretilt angle of the FFS liquid crystal display element was measured and found to be 0.0°. In addition, the flow alignment was not confirmed, and the alignment was good.

In addition, when the transmittance change rate ΔT/T (%) was measured, it was 2.1% in the O mode and 4.7% in the E mode (comparison). In addition, when the liquid crystal alignment axis stability ΔΦ (deg.) was measured, it was 0.019 degrees in the O mode and 0.037 degrees in the E mode (comparison).

Furthermore, when a high-brightness LED light source was used as a backlight and the voltage holding ratio (VHR) was measured, it was 99.41% in the O mode, 99.34% in the E mode (comparison), and high in the O mode. In addition, the liquid crystal test evaluation samples of both the O mode and the E mode (comparison) were irradiated with LED backlight light for 1000 hours, and the voltage holding ratio was evaluated before and after. It is 99.18%, and the voltage holding ratio in the E mode has a larger drop than that in the O mode. From this result, it can be seen that the reliability characteristics against backlight light in the O mode are higher than those in the E mode (comparison).

[Example 23]

A FFS liquid crystal display element was produced by the method according to Example 1, except that the polyamic acid solution used as a liquid crystal aligning agent and the type of the liquid crystal composition injected between the cells were changed. However, the exposure time was adjusted so that the exposure energy at the time of ultraviolet irradiation of the Multi-Light manufactured by Ushio Motor Co., Ltd. was 1.0 J/cm ² ±0.1 J/cm ² at a wavelength of 365 nm. , The irradiation of ultraviolet rays is to cover the whole device with an anti-ultraviolet film, and it is carried out at room temperature and in the air. In addition, the rotational speed of the spinner was adjusted according to the viscosity of the prepared liquid crystal aligning agent so that the film thickness of the alignment film was 100 nm±10 nm.

The pretilt angle of the FFS liquid crystal display element was measured and found to be 0.0°. In addition, the flow alignment was not confirmed, and the alignment was good.

In addition, when the transmittance change rate ΔT/T (%) was measured, it was 2.3% in the O mode and 4.8% in the E mode (comparison). In addition, the liquid crystal alignment axis stability ΔΦ (deg.) was measured, and the result was 0.013 degrees in the O mode and 0.013 degrees in the E mode (comparison) Below is 0.035 degrees.

Furthermore, when a high-brightness LED light source was used as a backlight and the voltage holding ratio (VHR) was measured, it was 99.49% in the O mode, 99.2% in the E mode (comparison), and high in the O mode. In addition, the liquid crystal test evaluation samples of both the O mode and the E mode (comparison) were irradiated with LED backlight light for 1000 hours, and the voltage holding ratio was evaluated before and after. The results were 99.42% in the O mode and 99.42% in the E mode. It is 98.95%, and the voltage holding ratio in the E mode has a larger drop than that in the O mode. From this result, it can be seen that the reliability characteristics against backlight light in the O mode are higher than those in the E mode (comparison).

[Example 24]

A FFS liquid crystal display element was produced by the method according to Example 1, except that the polyamic acid solution used as a liquid crystal aligning agent and the type of the liquid crystal composition injected between the cells were changed. In addition, the rotational speed of the spinner was adjusted according to the viscosity of the prepared liquid crystal aligning agent so that the film thickness of the alignment film was 100 nm±10 nm.

The pretilt angle of the FFS liquid crystal display element was measured and found to be 0.0°. In addition, the flow alignment was not confirmed, and the alignment was good.

In addition, when the transmittance change rate ΔT/T (%) was measured, it was 2.5% in the O mode and 5.3% in the E mode (comparison). In addition, when the liquid crystal alignment axis stability ΔΦ (deg.) was measured, it was 0.024 degrees in the O mode and 0.042 degrees in the E mode (comparison).

Furthermore, when a high-brightness LED light source was used as a backlight and the voltage holding ratio (VHR) was measured, it was 99.62% in the O mode, 99.58% in the E mode (comparison), and high in the O mode. In addition, for both the O mode and the E mode (comparison) The liquid crystal test evaluation sample was irradiated with LED backlight light for 1000 hours, and the voltage retention rate was evaluated before and after it. The results were 99.54% in the O mode and 99.35% in the E mode. Compared with the O mode, the voltage in the E mode is 99.54%. The retention rate dropped significantly. From this result, it can be seen that the reliability characteristics against backlight light in the O mode are higher than those in the E mode (comparison).

[Example 25, Example 26]

A FFS liquid crystal display element was produced by the method according to Example 1, except that the polyamic acid solution used as a liquid crystal aligning agent and the type of the liquid crystal composition injected between the cells were changed. In addition, the rotational speed of the spinner was adjusted according to the viscosity of the prepared liquid crystal aligning agent so that the film thickness of the alignment film was 100 nm±10 nm. In the O mode and the E mode (comparison), the transmittance change rate ΔT/T (%), the liquid crystal alignment axis stability ΔΦ (deg.) and the voltage holding ratio (VHR) of the obtained FFS liquid crystal display element were measured. . These results are summarized in Table 5.

[Example 27, Example 28]

A FFS liquid crystal display element was produced by the method according to Example 1, except that the type of the polyamic acid solution used as a liquid crystal aligning agent and/or the liquid crystal composition injected between the cells was changed. In addition, the rotational speed of the spinner was adjusted according to the viscosity of the prepared liquid crystal aligning agent so that the film thickness of the alignment film was 100 nm±10 nm. In the O mode and the E mode (comparison), the transmittance change rate ΔT/T (%), the liquid crystal alignment axis stability ΔΦ (deg.) and the voltage holding ratio (VHR) of the obtained FFS liquid crystal display element were measured. . These results are summarized in Table 5.

[table 5]

According to the results of the Examples and Comparative Examples, it can be seen that the transmittance change rate ΔT/T (%) of the liquid crystal display element of the present invention is low, so the occurrence of AC afterimages can be further prevented, and the liquid crystal alignment axis stability ΔΦ (deg.) is small, so the stability of the easy axis of liquid crystal alignment is high. In addition, it can be seen that the O mode is more excellent than the E mode (comparison) in any of the characteristics. Furthermore, it was found that the liquid crystal display element of the present invention has a high voltage holding ratio (VHR). The voltage holding ratio is higher in the O mode than in the E mode (comparison), and the voltage holding ratio in the O mode is smaller than that in the E mode (comparison) among the changes before and after backlight irradiation. From this result, it can be seen that the reliability characteristics against backlight light in the O mode are higher than those in the E mode (comparison).

[Example 29]

Next, improvement of transmittance by thinning the alignment film of a liquid crystal display element was examined. In order to study the transmittance of the alignment film of the glass substrate with ITO electrode on the backlight side, the polarizing film disposed on the opposite side of the backlight was removed, and only the polarizing film on the backlight side was provided, and the O mode configuration and E mode configuration (comparison) Measurement of the transmitted light spectrum was performed. The transmitted light is the transmitted light in the blue region with a wavelength of 455 nm, the alignment film is the liquid crystal alignment agent (PA23) used in Example 3, and the liquid crystal composition is the negative liquid crystal composition used in Example 1. A.

The film thickness (100 nm±10 nm) of the alignment film of the glass substrate with ITO electrode on the backlight side was kept as it was, and the film thickness of the alignment film of the glass substrate with column spacer on the opposite side was reduced. In the O-mode configuration, the transmittance with respect to the wavelength of 455 nm of the alignment film of 100 nm is 90.5%, and the thinning is 40nm, the transmittance rises to 94.3% as a result. In addition, in the E-mode arrangement (comparison), the transmittance at a wavelength of 455 nm was 87.0% with respect to the alignment film of 100 nm, but increased to 91.3% at 40 nm. In this way, transmittance can be improved without sacrificing alignment with respect to liquid crystal. Furthermore, the transmittance of the O-mode configuration is higher than that of the E-mode configuration (comparison). The results are shown in the following figures and tables.

[Example 30]

Next, the improvement of transmittance by changing the content ratio of polyamic acid [A] and [B] which comprises a liquid crystal aligning agent was examined. Maintain the doping ratio of polyamide [A] and polyamide [B] in the alignment film of the glass substrate with ITO electrode on the backlight side, and reduce the doping ratio of the glass substrate with column spacers on the opposite side. The doping ratio of the polyamide [A] of the alignment film. In the O-mode configuration, the transmittance at a wavelength of 455 nm is 90.7% with respect to the alignment film of polyamide [A]/polyamide [B]=3/7, and the same doping ratio is reduced. To 1.5/8.5, the resultant transmittance rises to 92.5%. Also, in E-mode configuration In (comparison), the transmittance at a wavelength of 455 nm was 86.1% with respect to the alignment film with the same doping ratio of 3/7, but the same doping ratio was reduced to 1.5/8.5, and the result was increased to 89.2%. In this way, transmittance can be improved without sacrificing alignment with respect to liquid crystal. Furthermore, the transmittance is higher in the O-mode configuration than in the E-mode configuration (comparison). The results are shown below using figures and tables. Furthermore, the liquid crystal aligning agent used in Example 4 (the content ratio of [A] and [B] was changed on the basis of polyamic acid solution (PA24)) and the liquid crystal composition (negative liquid crystal composition A) were used. . In addition, the doping ratios 3 to 1.5 in each table represent the amount of the polyamic acid [A], and the amount of the polyamic acid [B] is represented by "10-[A]".

[Example 31]

Next, the Vcom drift voltage of the liquid crystal display element was measured. The Vcom shift voltage was measured for the liquid crystal compositions and liquid crystal aligning agents used in Example 1 and Comparative Example 1, and the time constants for absorption and relaxation were larger in the O mode than in the E mode (comparison). The evaluation results of the negative liquid crystal and the positive liquid crystal are shown in the following figures and tables.

[Example 32 to Example 34]

In accordance with Example 29, the change in transmittance due to the thinning of the alignment film was measured, except that the liquid crystal aligning agent and the liquid crystal composition used were changed. The liquid crystal aligning agent, the liquid crystal composition used, and the measurement results are shown in the table below. The transmittance is higher in the O-mode configuration than in the E-mode configuration (comparison).

[Industrial Availability]

According to a preferred embodiment of the present invention, an alignment film formed of a compound containing polyamic acid having a photoisomerized structure in the main chain or a derivative thereof, and liquid crystal molecules having negative dielectric anisotropy are used, A liquid crystal display element having excellent AC afterimage characteristics and DC afterimage characteristics and good alignment stability can be provided.

1‧‧‧LCD display element

B‧‧‧Backlight

F1‧‧‧Polarizing Film

LC‧‧‧liquid crystal composition

S1‧‧‧Substrate with liquid crystal alignment film

S2‧‧‧Substrate with other liquid crystal alignment films

Claims (18)

A liquid crystal display element, which is formed by at least disposing a backlight, a polarizing film, a substrate with a liquid crystal alignment film, and a liquid crystal composition from the backlight side, the liquid crystal display element is characterized in that: the liquid crystal alignment film The liquid crystal alignment agent on the substrate is produced by irradiating polarized light, and the optical axis of the polarized light irradiated when the liquid crystal alignment film is produced is parallel to the polarizing axis of the polarizing film, and the liquid crystal alignment agent contains a photoisomerization type compound, the liquid crystal composition is then disposed from the backlight side to the substrate with other liquid crystal alignment films, and the film thickness of the other liquid crystal alignment films is higher than that of the liquid crystal alignment films close to the backlight. small, the doping ratio of the photoisomerization type compound of the other liquid crystal alignment film is lower than that of the photoisomerization type compound of the liquid crystal alignment film close to the backlight, the light The isomerized compound is to react at least one tetracarboxylic dianhydride selected from the following formulas (I) to (VII) with at least one diamine selected from the following formulas (I) to (VII) And the obtained polyamic acid or its derivative, R ² -C≡CR ³ (I) R ² -C≡CC≡CR ³ (II) R ⁷ CC CH CH R ³ (III) R ² -C≡CR ⁴ -C≡CR ³ (IV) R ² CCR ⁴ CH-CH R ³ (V) R ² -CH CH-R ³ (VI) R ² NN R ³ (VII) in formula (I) to formula (VII) , R ² and R ³ are independently a monovalent organic group with -NH ₂ or -CO-O-CO-, and R ⁴ is a divalent organic group with an aromatic ring. The liquid crystal display element according to claim 1, which is in a transverse electric field driving mode. The liquid crystal display element according to claim 2, wherein the lateral electric field driving mode is a fringe field switching mode. The liquid crystal display element according to any one of claims 1 to 3 of the claimed scope, comprising an element having a polarization axis of the polarizing film orthogonal to the alignment direction of liquid crystal molecules in the liquid crystal composition. The liquid crystal display element according to claim 1, wherein the thickness of the other liquid crystal alignment films is 30% or more and less than 100% of the thickness of the liquid crystal alignment films near the backlight. The liquid crystal display element according to any one of claims 1 to 3, wherein the liquid crystal composition contains a liquid crystal compound having negative dielectric anisotropy. The liquid crystal display element according to claim 1, wherein the photoisomerization type compound includes an azo group-containing compound. The liquid crystal display element according to claim 1, wherein the tetracarboxylic dianhydride is at least one tetracarboxylic dianhydride selected from the following formulas (PAN-1) and (PAN-2),

The liquid crystal display element according to the claim 1, wherein the diamine is at least one diamine selected from the following formulas (PDI-1) to (PDI-8),

In the formula (PDI-1) to the formula (PDI-8), the group whose bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary, and the formula (PDI-7 ), R ⁵ is independently -CH ₃ , -OCH ₃ , -CF ₃ , or -COOCH ₃ , and b is an integer of 0 to 2. The liquid crystal display element according to claim 9, wherein the diamine is at least one diamine selected from the following formula (PDI-6-1) and formula (PDI-7-1),

The liquid crystal display element according to claim 1, wherein the tetracarboxylic dianhydride other than the tetracarboxylic dianhydride is selected from the following formulae (AN-I) to (AN-V) At least one of the tetracarboxylic dianhydrides in the reaction,

In formula (AN-I), formula (AN-IV) and formula (AN-V), X is independently a single bond or -CH ₂ -; in formula (AN-II), G is a single bond and has 1 to 1 carbon atoms. 20 alkylene, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -; formula (AN-II) ~ formula In (AN-IV), Y is independently a kind of in the group selected from the following trivalent group;

Any hydrogen of these groups can be substituted by methyl, ethyl or phenyl; and in formula (AN-III)～formula (AN-V), ring A is a monocyclic hydrocarbon group with 3 to 10 carbon atoms or A base of a condensed polycyclic hydrocarbon with a carbon number of 6 to 30, any hydrogen of the base can be substituted by methyl, ethyl or phenyl, the bond connected to the ring is connected to any carbon constituting the ring, and the two The root bond can be attached to the same carbon. The liquid crystal display element according to claim 1, wherein the tetracarboxylic dianhydride other than the tetracarboxylic dianhydride is selected from the following formula (AN-1-1), formula (AN- 1-13), formula (AN-2-1), formula (AN-3-1), formula (AN-3-2), formula (AN-4-5), formula (AN-4-17), Formula (AN-4-21), Formula (AN-4-28), Formula (AN-4-29), Formula (AN-7-2), Formula (AN-10), and Formula (AN-11- 3) at least one tetracarboxylic dianhydride in the reaction,

In formula (AN-4-17), m is an integer of 1-12. The liquid crystal display element according to claim 1, wherein at least one diamine selected from the following formulae (DI-1) to (DI-15) is used as the other diamine other than the diamine reaction,

In formula (DI-1), m is an integer from 1 to 12, and any hydrogen of alkylene can be replaced by -OH; in formula (DI-3) and formula (DI-5) to formula (DI-7) , G ²¹ is independently a single bond, -NH-, -O-, -S-, -SS-, -SO ₂ -, -CO-, -CONH-, -CONCH ₃ -, -NHCO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m' -, -O-(CH ₂ ) _m' -O-, -N(CH ₃ )-(CH ₂ ) _k -N (CH ₃ )-, or -S-(CH ₂ ) _m' -S-, m' is independently an integer of 1 to 12, and k is an integer of 1 to 5; formula (DI-6) and formula (DI-7 ), G ²² is independently a single bond, -O-, -S-, -CO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or an alkylene group having 1 to 10 carbon atoms ; Arbitrary hydrogen of cyclohexane ring and benzene ring in formula (DI-2)～formula (DI-7) can pass through -F, -CH ₃ , -OH, -CF ₃ , -CO ₂ H, -CONH ₂ , or benzyl substitution, in addition, in formula (DI-4), any hydrogen of cyclohexane ring and benzene ring can be selected from the following formula (DI-4-a)～formula (DI-4-c) ) is substituted with at least one group;

In formula (DI-4-a) and formula (DI-4-b), R ²⁰ is independently -H or -CH ₃ ; and in formula (DI-2) to formula (DI-7), the bonding position is not The group fixed on any carbon atom constituting the ring means that the bonding position on the ring is arbitrary, and the bonding position of -NH ₂ on the cyclohexane ring or the benzene ring is the bond other than G ²¹ or G ²² any position other than the knot position;

In formula (DI-8), R ²¹ and R ²² are independently an alkyl group or phenyl group with 1 to 3 carbon atoms, and G ²³ is independently an alkylene group with 1 to 6 carbon atoms, a phenylene group or an alkyl group substituted with an alkyl group. Phenylidene, n is an integer from 1 to 10; in formula (DI-9), R ²³ is independently an alkyl group with 1 to 5 carbons, an alkoxy group with 1 to 5 carbons or -Cl, and p is independently 0 an integer of ~3, and q is an integer of 0 to 4; in formula (DI-10), R ²⁴ is -H, an alkyl group with 1 to 4 carbon atoms, a phenyl group, or a benzyl group; in formula (DI-11) , G ²⁴ is -CH ₂ - or -NH-; in formula (DI-12), G ²⁵ is a single bond, alkylene with 2 to 6 carbon atoms or 1,4-phenylene, and r is 0 or 1 In addition, in formula (DI-9), formula (DI-11) and formula (DI-12), the group whose bonding position is not fixed to any carbon atom constituting the ring represents the bonding position on the ring is arbitrary;

In formula (DI-13), G ³¹ is a single bond, an alkylene group having 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -; in formula (DI-14), ring B is a cyclohexane ring, a benzene ring or a naphthalene ring, and any hydrogen of the ring can be converted to a methyl group, an ethyl group, or a phenyl group Substitution; in formula (DI-15), ring C is independently a cyclohexane ring or a benzene ring, any hydrogen in the ring can be substituted by methyl, ethyl, or phenyl, and Y is a single bond, carbon alkylene, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ - of numbers 1 to 20; and the formula (DI- In 14) and formula (DI-15), the group whose bonding position is not fixed to any carbon atom constituting the ring means that the bonding position on the ring is arbitrary. The liquid crystal display element according to claim 1, wherein the diamine other than the diamine is selected from the group consisting of the following formula (DI-1-3), formula (DI-1-4), formula (DI-2-1), formula (DI-4-1), formula (DI-4-13), formula (DI-5-1), formula (DI-5-4), formula (DI-5- 5), formula (DI-5-9), formula (DI-5-12), formula (DI-5-22), formula (DI-5-28), formula (DI-5-30), formula ( DI-5-31), formula (DI-7-3), formula (DI-9-1), formula (DI-13-1), formula (DI-13-2), formula (DI-14-1) ), at least one diamine reaction in the formula (DI-14-2),

In formula (DI-5-1), formula (DI-5-12), formula (DI-7-3) and formula (DI-13-2), m is an integer from 1 to 12; formula (DI-5 -30), k is an integer of 1 to 5; and in formula (DI-7-3), n is independently 1 or 2. The liquid crystal display element according to claim 1, wherein the photoisomerization compound is a polyamic acid or a derivative thereof having a photoisomerization structure in the main chain, and the liquid crystal aligning agent contains the Polyamic acid or its derivatives and other polymers. The liquid crystal display element according to any one of the claims 1 to 3, wherein the liquid crystal alignment film is formed through the following steps: The step of coating the liquid crystal alignment agent on the substrate; and the step of irradiating linearly polarized or elliptically polarized light after heating and drying the substrate coated with the liquid crystal alignment agent to give the liquid crystal alignment control ability. The liquid crystal display element according to any one of items 1 to 3 of the claimed scope, wherein the liquid crystal alignment film is formed through the following steps: the step of coating the liquid crystal alignment agent on the substrate; After the substrate coated with the liquid crystal alignment agent is heated and dried, it is irradiated with linearly polarized light or elliptically polarized light to give the liquid crystal alignment control ability; and then the coating film is heated and calcined. The liquid crystal display element according to any one of items 1 to 3 of the claimed scope, wherein the liquid crystal alignment film is formed through the following steps: the step of coating the liquid crystal alignment agent on the substrate; The substrate coated with the liquid crystal alignment agent is heated and dried, and then heated and calcined; and the coating film is irradiated with linearly polarized or elliptically polarized light to give the liquid crystal alignment control ability.

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