JP2006018106A - Manufacturing methods of optical alignment layer for liquid crystal display element and of liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical alignment layer for a liquid crystal display element having excellent practicality, wherein time for optical alignment treatment is reduced, and to provide a manufacturing method of the liquid crystal display element using substrates provided with the alignment layer obtained by the manufacturing method. <P>SOLUTION: In the manufacturing method of the optical alignment layer for the liquid crystal display element, an optical alignment layer containing a dichroic compound is formed on electrodes respectively provided on the substrates, the two substrates are opposed to each other at a fixed interval so that surfaces on which the optical alignment layer is formed are opposed to each other and the dichroic compound is aligned by irradiating surfaces of the substrates with non-polarized light from a direction oblique. In the manufacturing method of the liquid crystal display element, a liquid crystal material is injected into a gap between the two substrates provided with the optical alignment layer manufactured by the manufacturing method of the optical alignment layer for the liquid crystal display element, the liquid crystal material is sealed and then the liquid crystal material is aligned by heating the liquid crystal material up to a temperature at which the liquid crystal material shows isotropy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a photoalignment film for a liquid crystal element and a method for producing a liquid crystal display element. More specifically, the present invention relates to a method for producing a liquid crystal element by efficiently irradiating light during the alignment treatment of the photoalignment film. And a method for manufacturing a liquid crystal display element.

  In a liquid crystal display device, the state of molecular orientation of the liquid crystal is changed by the action of an electric field or the like, and the change in optical characteristics accompanying this is used for display. In many cases, the liquid crystal is used in a state of being sandwiched between two substrates. Here, in order to align liquid crystal molecules in a specific direction, an alignment process is performed on the inside of the substrate. Usually, this alignment treatment uses a method called rubbing, in which a polymer film such as polyimide is provided on a substrate such as glass and the like is rubbed with a cloth or the like in one direction.

  In recent years, as a method for producing a liquid crystal alignment film used for a liquid crystal display element, there is an alignment method capable of non-contact alignment treatment instead of the conventional rubbing method in which a film made of polyimide or the like is rubbed to perform alignment treatment. In particular, a photo-alignment method using an alignment film capable of aligning liquid crystals by irradiating ultraviolet polarized light or the like has been attracting attention.

Examples of such photo-alignment films include those by photodimerization reactions such as cinnamoyl group, coumarin group, chalcone group, and benzophenone group, those by photoisomerization of azobenzene, and those by photolysis of polyimide resin. ing.
For example, when a film containing an azobenzene derivative is irradiated with polarized light, the molecules are aligned in a certain direction with respect to the plane of polarization. 1). Although polarized light is used in this method, even when non-polarized light is irradiated from an oblique direction with respect to the film surface, the molecules are easily aligned and the liquid crystal alignment ability is obtained, so the light utilization efficiency is high and suitable for mass production. It is known that it can be a photo-alignment film.

In particular, it is known that a specific azobenzene derivative is aligned with a high order parameter even by irradiation with non-polarized ultraviolet rays, and a large alignment regulating force can be obtained for liquid crystals (for example, see Patent Document 2).
Japanese Laid-Open Patent Publication No. 2-277005 JP 2002-265442 A

  However, in the invention according to Patent Document 2, because of the limitation due to the output of the ultraviolet lamp, the light irradiation time by the ultraviolet irradiation device is longer than the rubbing time required for the conventional rubbing alignment film, and the productivity is lowered. was there. This is one of the reasons why the photo-alignment film is not widely used in the liquid crystal panel mass production process.

  The problem to be solved by the present invention is to propose a method for producing a photo-alignment film excellent in practicality with reduced photo-alignment processing time and alleviating the drawbacks of such photo-alignment method.

  Furthermore, the present invention proposes a method for manufacturing a liquid crystal display element using a substrate provided with the photo-alignment film obtained by the above-described manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors face two substrates on which a photo-alignment film containing a specific compound is formed facing each other on the surface on which the photo-alignment film is formed. The alignment process of the photo-alignment films on the two substrates can be performed at a time by irradiating the non-polarized ultraviolet rays from the oblique direction to the liquid crystal cells facing each other with a certain gap so as to be aligned. As a result, the present invention has been completed.

  That is, according to the present invention, a photo-alignment film containing a dichroic compound is formed on an electrode provided on a substrate, and the two surfaces of the substrate, on which the photo-alignment film is formed, face each other. A method for producing a photo-alignment film for a liquid crystal display device is provided, wherein the dichroic compound is oriented by irradiating the substrate surface with a non-polarized light from an oblique direction.

  Further, the present invention provides a liquid crystal material injected into a gap between two substrates provided with the photo-alignment film produced by the above-described method for producing a photo-alignment film for liquid crystal display elements, and sealed. There is provided a method for producing a liquid crystal display element, wherein the liquid crystal material is oriented by heating to a temperature exhibiting isotropic properties.

  According to the present invention, a liquid crystal cell is produced with a substrate coated with a photo-alignment film, and the dichroic compounds on the two substrates are aligned by simply irradiating non-polarized light once from one substrate side of the cell. Therefore, the photo-alignment treatment time, which has been a problem in mass production of liquid crystal elements using the photo-alignment film, can be shortened, and an efficient method for producing a photo-alignment film for liquid crystal elements can be provided.

  In addition, according to the present invention, after assembling the liquid crystal cell, the photo-alignment film is subjected to alignment treatment, and then the liquid crystal material is injected into the cell to align the liquid crystal material. Can be provided.

  Hereinafter, the present invention will be described in detail.

First, an embodiment of a photo-alignment film for a liquid crystal element manufactured according to the present invention will be described.
The photo-alignment film for a liquid crystal element of the present embodiment is generally composed of a photo-alignment film containing a dichroic compound formed on an electrode provided on a substrate. A liquid crystal cell having two substrates facing each other with a certain gap so that the surfaces on which the photo-alignment films are formed face each other is called a liquid crystal cell.

  The substrate used in the present invention is a substrate usually used for a liquid crystal display device having a liquid crystal alignment film, and examples thereof include a substrate such as glass, a polymer film, and a silicon wafer. It is preferable to have the heat resistance. In addition, at least one of the two substrates needs to be transparent to the light irradiated in the photo-alignment process.

As electrodes provided on substrates such as glass and plastic, in addition to ITO (indium tin oxide), which is currently most widely used, ATO (antimony tin oxide), TO (tin oxide), ZO (zinc oxide) , IZO (indium zinc oxide), FTO (fluorine tin oxide), and the like.
This electrode is preferably a transparent electrode. The substrate for irradiating non-polarized light has a transparent electrode, and ITO is particularly preferable. Moreover, it is preferable that the film thickness of this electrode is 200-2500 mm.

On this electrode, a photo-alignment film containing a dichroic compound is provided. The dichroic compound contained in the photo-alignment film used in the present invention has a large refractive index, is aligned with high order parameters even by irradiation with non-polarized ultraviolet rays, and has a large alignment regulating force for liquid crystals. Therefore, azobenzene derivatives are preferable.
As such an azobenzene derivative, a compound represented by the following general formula (1) is particularly preferable.

In the formula, R ¹ and R ² are each independently a hydroxy group, or a group consisting of a (meth) acryloyl group, a (meth) acryloyloxy group, a (meth) acrylamide group, a vinyl group, a vinyloxy group, and a maleimide group. Represents a polymerizable functional group to be selected.
X ¹ represents a single bond when R ¹ is a hydroxy group, and represents a linking group represented by — (A ¹ -B ¹ ) _m — when R ¹ is a polymerizable functional group, and X ² represents When R ² is a hydroxy group, it represents a single bond, and when R ² is a polymerizable functional group, it represents a linking group represented by — (A ² —B ² ) _n —. Here, A ¹ is bonded to R ¹ , A ² is bonded to R ^2, and B ¹ and B ² are bonded to adjacent phenylene groups.
A ¹ and A ² each independently represent a single bond or a divalent hydrocarbon group, and B ¹ and B ² each independently represent a single bond, —O—, —CO—O—, —OCO—, -CONH-, -NHCO-, -NHCO-O-, or -OCONH- is represented.
m and n each independently represents an integer of 0 to 4. However, when m or n is 2 or more, the plurality of A ¹ , B ¹ , A ² , and B ² may be the same group or different groups. However, A ¹ or A ² sandwiched between ^two B ¹ or B ² is not a single bond.
R ³ and R ⁴ each independently represent a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group, or a methoxycarbonyl group. The carboxy group may form a salt with an alkali metal.
R ⁵ and R ⁶ each independently represent a carboxyl group, a sulfo group, a nitro group, an amino group, or a hydroxy group. In addition, the carboxy group or the sulfo group may form a salt with the alkali metal.

  The azobenzene derivative represented by the general formula (1) is oriented so that the major axis direction of the molecule is perpendicular to the polarization direction by irradiation with linearly polarized light or elliptically polarized light, while non-polarized parallel light ultraviolet rays For the photo-alignment film used in the present invention because it has the property of being easily oriented so that the major axis direction of the molecules is parallel to the ultraviolet incident surface (surface perpendicular to the substrate surface). Particularly preferred as the dichroic compound.

In the general formula (1), R ¹ and R ² are each independently a hydroxy group, a (meth) acryloyl group, a (meth) acryloyloxy group, a (meth) acrylamide group, a vinyl group, a vinyloxy group, and It is a polymerizable functional group selected from the group consisting of maleimide groups. When R ¹ and R ² are polymerizable functional groups, the photo-alignment film having excellent heat resistance and light resistance can be obtained by fixing the orientation of the dichroic compound by thermal polymerization or photopolymerization after photo-alignment treatment. Is preferable. Among these, a (meth) acryloyloxy group or a (meth) acrylamide group is preferable.

In the general formula (1), the hydroxy group or polymerizable functional group represented by R ¹ and R ² is linked to the adjacent phenylene group via the linking group represented by X ¹ and X ² . . As the divalent hydrocarbon group represented by A ¹ or A ² among the linking group X ¹ and the linking group X ² , an alkylene group having 3 to 20 carbon atoms such as a propylene group and a heptylene group, a methylene group, 6 to 20 carbon atoms such as a polymethylene group having 1 to 20 carbon atoms such as a trimethylene group and a pentamethylene group, a cycloalkylene group having 3 to 20 carbon atoms such as a cyclopropylene group and a cyclohexylene group, a phenylene group and a naphthylene group And 20 arylene groups.

In the above general formula (1), the halogen atom of R ³ and R ⁴ is a fluorine atom or a chlorine atom, the halogenated methyl group is a trichloromethyl group or a trifluoromethyl group, and the halogenated methoxy group is And a chloromethoxy group and a trifluoromethoxy group. Among them, it is preferable that R ³ and R ⁴ are carboxy groups because a particularly large alignment regulating force can be obtained. The carboxy group may form a salt with an alkali metal such as lithium, sodium or potassium.

In the general formula (1), R ⁵ and R ⁶ are preferably a carboxy group or a sulfo group because adhesion to the substrate is increased. The carboxy group and the sulfo group may form a salt with an alkali metal such as lithium, sodium, or potassium.

  The compound represented by the above general formula (1) is easily oriented when irradiated with polarized light or light from an oblique direction with respect to the substrate surface, and has film formability and adhesion to a substrate such as glass or ITO. It is preferable that it is excellent in property. Specific examples include azobenzene derivatives having the following structure.

  For example, the azobenzene derivative represented by (a) can be obtained by reacting 2,2'-benzidinedisulfonic acid with sodium nitrite to form a diazonium compound and then reacting 2-hydroxybenzoic acid. The azobenzene derivative represented by (b) is obtained by reacting acrylic acid chloride with hydroxy groups at both ends of the azobenzene derivative represented by (a).

  Moreover, it is preferable that the film thickness of the photo-alignment film in this invention is 50-200 mm. This is because if the film thickness exceeds 200 mm, the dichroic compound contained in the photo-alignment film becomes colored and is not transparent, which is not preferable.

Next, an example of a method for producing the photo-alignment film for liquid crystal elements of the present invention will be described.
First, the composition for photo-alignment films containing the said dichroic compound is apply | coated on a board | substrate, and a photo-alignment film is created by drying. When the composition for photo-alignment film is applied on the substrate, it is used after being dissolved in an appropriate solvent. The solvent in this case is not particularly limited, but pyrrolidone, N-methylpyrrolidone, N, N-dimethylformamide, 2-butoxyethanol, 2-phenoxyethanol, γ-butyrolactone, chlorobenzene, dimethyl sulfoxide, dimethylacetamide, ethylene glycol, propylene glycol In general, isopropylene glycol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, 3-methoxy-3-methylbutanol and the like are generally used. Among them, a solution of 2-butoxyethanol, N-methylpyrrolidone, propylene glycol, N, N-dimethylformamide has a good coating property on the surface of glass, ITO, etc., and a uniform coating without unevenness can be obtained. Therefore, it is particularly preferable.
These solvents are preferably selected in consideration of applicability and volatilization rate after application, and two or more types can be mixed and used.

  In addition, as a method for applying the solution of the composition for photo-alignment film on the substrate, a spin coating method, a flexographic printing method, a micro gravure printing method, a die coating method, a dipping method, and the like can be used. The method and flexographic printing method are preferable because it is easy to obtain a uniform coating film.

  Next, these two substrates are bonded to each other through a spacer having a certain gap so that the surfaces on which the photo-alignment films are formed face each other, thereby obtaining a liquid crystal cell. Photo-alignment treatment is performed by irradiating light to the bonded liquid crystal cell. Light irradiation is performed by irradiating non-polarized light from an oblique direction to the substrate surface from the outside of the liquid crystal cell.

Next, a method for aligning the photo-alignment film will be described.
FIG. 1 shows that when non-polarized light is incident on the surface of a transparent layered medium from an oblique direction, the transmittance of the P-polarized component 1 and the S-polarized component 2 of the transmitted light and incident from the normal of the substrate surface It is a graph which shows the relationship with angle dependence. In general, when light is incident on the surface of a transparent medium from an oblique direction, if the incident angle of the light with respect to the surface normal is θ ₁ , the transmittance of the S-polarized component 2 of the incident light is the incident angle θ ₁ . Decreases with increase. On the other hand, the transmittance of the P-polarized component 1 increases as the incident angle θ ₁ increases until the Brewster angle is reached, and starts decreasing when the angle exceeds the Brewster angle. According to FIG. 1, although the light transmittance decreases as the incident angle (degrees) increases, the ratio of the P-polarized component 1 to the S-polarized component 2 in the transmitted light increases.

Further, the transmittance at the boundary surface in the transparent medium is expressed by the following equation for S-polarized light (t _s ) and P-polarized light (t _p ).

Here, θ ₁ and θ ₂ are an incident angle and a refraction angle with respect to each boundary surface. When the refractive index of the incident side of the medium and n _1, the refractive index of the refractive side of the medium and n _2, these and theta _1, relationship between theta _2, from Snell's law, expressed by the following equation.

For example, when n ₁ > n ₂ , θ ₂ > θ ₁ is satisfied. Equation (1) and _t p> _{t s} becomes from Equation (2), as the difference between the _{n 1} and _{n 2} is large, the intensity difference between the P-polarized light in the transmitted light _{(t p)} and S-polarized light _{(t s)} is increased .

FIG. 2 is an explanatory diagram showing the polarization direction of light and the direction in which the dichroic compound of the photo-alignment film is aligned when non-polarized parallel light is irradiated from an oblique direction to the substrate surface of the liquid crystal cell.
In the method for producing a photo-alignment film of the present invention, when light is applied to the liquid crystal cell 9 having two substrates facing each other, non-polarized light is applied to one substrate surface (hereinafter referred to as “upper substrate”). When irradiated from an oblique direction, as shown in FIG. 2, this non-polarized light 6 is incident in the order of 1) upper substrate 4, 2) transparent electrode 10, 3) photo-alignment film (upper substrate) 3, 4) air layer, Then, 5) photo-alignment film (lower substrate) 3 ′, 6) electrode 10 ′, 7) lower substrate 4 ′ of the other substrate (hereinafter referred to as “lower substrate”) is incident and passed through in this order.

Here, representative values of the refractive index of each layer are shown below.
0) Air Refractive index = 1
1) Upper substrate (glass, PC, PES, etc.) Refractive index = 1.5 to 1.7
2) Transparent electrode (ITO etc.) Refractive index = 1.8-2.0
3) Photo-alignment film (upper substrate) Refractive index = 1.6 to 1.8
4) Air Refractive index = 1
5) Photo-alignment film (lower substrate) Refractive index = 1.6 to 1.8
6) Electrode (lower substrate) Refractive index = 1.8 to 2.0
7) Lower substrate Refractive index = 1.5 to 1.7

  The light transmitted through the boundary surface changes in reflectance and transmittance depending on the refractive index of the adjacent medium at each boundary surface. Actually, since the light reflected and transmitted at the other interface is further reflected and transmitted to cause multiple reflection, it becomes more complicated, but the light reaching the photo-alignment film (upper substrate) 3 is air. The refractive index of each layer such as the upper substrate and the transparent electrode determines the ratio of the P-polarized light and the S-polarized light.

  The light that has passed through the photo-alignment film (upper substrate) 3 has a large difference in refractive index between the photo-alignment film (upper substrate) 3 and the air below it. The light reaching the alignment film (lower substrate) 3 ′ has a large P-polarized component.

The photo-alignment film used in the present invention contains a dichroic compound. In this dichroic compound, the absorption axis (major axis direction of the molecule) is parallel to the incident surface (surface perpendicular to the substrate surface) of the non-polarized light 6 when the non-polarized light 6 is irradiated from an oblique direction. It has the property of being oriented. Specifically, like the dichroic compound 5 of the photo-alignment film (upper substrate) 3 in FIG. 2, it is aligned parallel to the longitudinal direction of the substrate.
On the other hand, with respect to irradiation of polarized light, there is a property that the absorption axis (major axis direction of the molecule) is oriented so as to be perpendicular to the polarization direction. Specifically, it is aligned perpendicular to the longitudinal direction of the substrate, like the dichroic compound 7 of the photo-alignment film (lower substrate) 3 ′ in FIG.

By utilizing the characteristics of the photo-alignment film containing this dichroic compound, the non-polarized light is irradiated once from one substrate side, so that the photo-alignment film (upper substrate) and the photo-alignment film (lower substrate) The orientation directions of the dichroic compounds can be controlled so that in some cases, the dichroic compounds are in the same direction, and in other cases, the directions are perpendicular to each other.
That is, when both the photo-alignment film (upper substrate) and the photo-alignment film (lower substrate) are irradiated with P-polarized light, the dichroic compounds have the same orientation in each other. Therefore, when a liquid crystal material is injected into this liquid crystal cell and the liquid crystal molecules are aligned, a homogeneously aligned liquid crystal display element can be obtained.

  On the other hand, when the photo-alignment film (upper substrate) is irradiated with light close to non-polarized light, and the photo-alignment film (lower substrate) is irradiated with P-polarized light, the dichroic compounds have orientations in directions perpendicular to each other. For this reason, when a liquid crystal material is injected into this liquid crystal cell and the liquid crystal molecules are aligned, a twist-aligned TN liquid crystal display element is obtained.

  When the incident angle of non-polarized light with respect to the upper substrate and the refractive index of the photo-alignment film are appropriately selected, the photo-alignment film (upper substrate) provided on the substrate on which light is incident has the intensities of the P-polarized component and the S-polarized component. Light that is close to non-polarized light with a small difference is irradiated. On the other hand, the photo-alignment film (lower substrate) provided on the opposite substrate is irradiated with polarized light having a large intensity difference between the P-polarized component and the S-polarized component. Can be controlled. Alternatively, by changing the irradiation angle of non-polarized light with respect to the upper substrate, polarized light having a large intensity difference between the P-polarized component and the S-polarized component is irradiated to the photo-alignment film (upper substrate) provided on the substrate on which light is incident. In addition, it is possible to control the light alignment film (lower substrate) to be irradiated with polarized light having a large intensity difference between the P-polarized component and the S-polarized component.

As shown in FIG. 2, when the non-polarized light 6 is irradiated to the photo-alignment film (upper substrate) 3 provided on the substrate on the incident side from an oblique direction with respect to the substrate surface, the photo-alignment film (upper substrate) 3 The dichroic compound 5 is oriented parallel to the non-polarized incident surface (surface perpendicular to the substrate surface). The degree of polarization of light applied to the photo-alignment film (upper substrate) 3 can be obtained by calculation or simulation based on the irradiation angle of non-polarized light, the refractive index of the layer that passes before entering the photo-alignment film. it can.
On the other hand, the light transmitted through the upper substrate 4 and the photo-alignment film (upper substrate) 3 is reflected at the interface between the photo-alignment film (upper substrate) 3 and the air, so that the S-polarized component is relatively smaller than the P-polarized component. And it becomes elliptically polarized light. When this elliptically polarized light is irradiated to the opposing photo-alignment film (lower substrate) 3 ′, the dichroic compound 7 of the photo-alignment film (lower substrate) 3 ′ is oriented in a direction perpendicular to the major axis of the elliptically polarized light. As a result, the dichroic compound 5 of the photo-alignment film (upper substrate) 3 and the dichroic compound 7 of the photo-alignment film (lower substrate) 3 ′ are aligned substantially orthogonally. By injecting nematic liquid crystal into the liquid crystal cell 9 thus produced, a TN-aligned liquid crystal element can be obtained.

  The irradiation angle of non-polarized light on the substrate on the incident side when performing this photo-alignment treatment is an oblique direction with respect to the substrate surface, and the angle θ from the substrate surface normal is preferably 30 to 80 °, The angle is more preferably 45 to 80 ° from the viewpoint of obtaining good optical alignment, and the angle of 70 to 80 ° is most preferable from the viewpoint that the alignment can be performed efficiently. If the irradiation angle is smaller than 30 °, the photo-alignment efficiency with respect to the substrate surface decreases, and in order to obtain a sufficient alignment regulating force, a larger amount of light irradiation is required, and the alignment is uniform over the entire substrate surface. This is not preferable because the property is low. On the other hand, when the irradiation angle is larger than 80 °, the amount of light reflected between the substrate surface and the layers such as the photo-alignment film and the transparent electrode layer increases, so that the amount of light irradiated on the surface of the photo-alignment film is reduced and efficient. This is not preferable because optical alignment cannot be performed.

  The light irradiated in the photo-alignment treatment is preferably parallel light obtained from a light source using a collimator, and photo-alignment can be performed with relatively small irradiation energy.

  The light to be irradiated needs to be in a wavelength region in which the photo-alignment film has light absorption. In particular, when the photo-alignment film is composed of the azobenzene derivative represented by the general formula (1), the light having a wavelength of 300 to 500 nm is used. It is preferably ultraviolet light or visible light, and particularly preferably near ultraviolet light in the range of 350 to 400 nm. Examples of a light source that can obtain light having such a wavelength include ultraviolet lamps such as a xenon lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, and a metal halide lamp, and an ultraviolet laser such as a He-Cd laser. In particular, since the ultra-high pressure mercury lamp is close to a point light source, it is possible to easily obtain parallel light using a collimator composed of a lens or a concave mirror, and the absorption of the azobenzene derivative represented by the general formula (1) is high. This is particularly preferable because it has a strong emission spectrum in the vicinity of a large 365 nm and can perform efficient photo-alignment.

When the azobenzene derivative represented by the general formula (1) has a polymerizable functional group, it is preferable to polymerize the polymerizable functional group after the photo-alignment treatment. By polymerizing a polymerizable functional group, a photo-alignment film having excellent stability such as light resistance and moisture resistance can be obtained.
Examples of the polymerization method include thermal polymerization and photopolymerization. At this time, it is preferable to use a known and usual polymerization initiator as necessary. Examples of the thermal polymerization initiator include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,2′-azo. Examples thereof include bisisobutyronitrile and tetramethylthiuram disulfide. Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[(methylthio) phenyl] -2 morpholinopropane-1, benzyl dimethyl ketal, and acylphosphine oxide. It is done.

In the case where the polymerizable functional group is thermally polymerized, the composition for photo-alignment film is applied and dried, irradiated with light for alignment, and then heated. The heating temperature is preferably from 100 to 300 ° C, more preferably from 100 to 200 ° C.
On the other hand, when photopolymerizing a polymerizable functional group, it is preferable to irradiate light having a wavelength that is not absorbed by the photo-alignment film after coating and drying the composition for photo-alignment film and performing light irradiation for orientation. . For example, in the case of the azobenzene derivative represented by the general formula (1), photopolymerization is performed by irradiating light having a wavelength of 200 to 320 nm, which is a wavelength that is not absorbed by the azobenzene skeleton.

  Conventionally, before assembling the liquid crystal cell, each of the upper substrate and the lower substrate was irradiated with light and subjected to alignment treatment, and then the cell was assembled, whereas according to the present invention, after assembling the cell, The orientation can be imparted to both the upper substrate and the lower substrate by one irradiation, and the photo-alignment processing time can be shortened.

  In addition, the photo-alignment film containing the dichroic compound in the present invention does not generate a decomposition product by light irradiation for alignment control unlike the decomposition type photo-alignment film. It is not contaminated with decomposition products by irradiation.

  Further, in the photo-alignment film containing the dichroic compound in the present invention, the difference between the alignment direction of the dichroic compound with respect to the non-polarized irradiation from the oblique direction and the alignment direction of the dichroic compound with respect to the polarized light is different. The twist orientation or the homogeneous orientation can be appropriately selected using.

Next, an embodiment of a liquid crystal device manufactured according to the present invention will be described.
The liquid crystal element of this embodiment is roughly composed of a liquid crystal cell composed of two substrates provided with the above-described photo-alignment film, and liquid crystal injected between the two substrates. An electrode is provided on the substrate, and a photo-alignment film containing a dichroic compound is formed on the electrode. The liquid crystal cell has two substrates facing each other with a certain gap so that the surfaces on which the photo-alignment films are formed face each other, and a liquid crystal material is injected into this space.

The liquid crystal material to be used is not limited, and nematic liquid crystal, ferroelectric liquid crystal, or the like can be used. A nematic liquid crystal is preferable from the viewpoint of easy alignment.
This liquid crystal material preferably contains 2 to 40 kinds, particularly 4 to 30 kinds of liquid crystal compounds. Preferably, the liquid crystal compound includes a biphenyl compound, a terphenyl compound, a phenyl or cyclohexyl benzoate compound, a phenyl cyclohexane compound, a cyclohexyl biphenyl compound, a phenyl- or cyclohexyl pyrimidine compound, and a tolan compound. The 1,4-phenylene group present in these compounds is preferably a fluorinated compound.

The liquid crystal element of this embodiment is manufactured as follows.
First, after assembling a liquid crystal cell according to the above-described method for producing a photo-alignment film for a liquid crystal element, alignment treatment of the photo-alignment film is performed by light irradiation. A liquid crystal material is injected into the obtained empty cell by a known method such as a vacuum injection method using reduced pressure, an injection method using pressurization, or an injection method using capillary action, and the injection hole is formed by a thermosetting sealing material, Seal with a UV curable seal. As the thermosetting sealant and the ultraviolet curable seal, known ones may be used without any particular limitation.
Next, the obtained liquid crystal cell is heated to a temperature at which the liquid crystal material is isotropic, annealed at that temperature for 1 hour, and then gradually cooled to complete a liquid crystal display element.

  According to the method for manufacturing a liquid crystal element of the present invention, it is possible to efficiently manufacture a homogeneously aligned liquid crystal display element or a twist aligned TN liquid crystal display element by changing the irradiation angle of non-polarized light on the incident side substrate. it can.

  Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples.

[Example 1]
A 1.0 mass% N, N-dimethylformamide solution of an azobenzene derivative represented by the following chemical formula (2) was uniformly applied to the ITO electrode surface of the glass substrate with an ITO electrode using a spin coater. Next, the solvent was dried on a hot plate at 100 ° C. for 1 minute to obtain a photo-alignment film made of the azobenzene derivative. The film thickness of this photo-alignment film was 100 mm.
Next, a two-pack epoxy resin adhesive containing styrene beads having a diameter of 5 μm is applied to the outer edge of the substrate with a photo-alignment film so that the liquid crystal injection port remains, and another substrate with a photo-alignment film is formed. A liquid crystal cell was produced by overlapping and pressing the photo-alignment film faces to face each other and curing the adhesive.

  In addition, when the photo-alignment film was apply | coated to another glass substrate by the method similar to the above, and the refractive index of this photo-alignment film was measured using the ellipsometer, the refractive index was 1.72.

After the cell was fabricated, the photo-alignment film was irradiated with light. An ultra-high pressure mercury lamp is used as a light source for light irradiation, and ultraviolet light having a wavelength of 365 nm and an irradiation light amount of 40 mW / cm ² obtained through a band-pass filter and a collimator mirror is applied to the substrate surface from one substrate side of the cell. A light amount of 5 J / cm ² was irradiated from a direction of 75 ° with respect to the normal line.

Next, 4-n-pentyl-4′-cyanobiphenyl, which is a nematic liquid crystal composition, was injected into this liquid crystal cell by capillary action at room temperature and in vacuum. Thereafter, the injection port was sealed with an epoxy adhesive, heated to a temperature (50 ° C.) at which the liquid crystal material was isotropic, annealed at 50 ° C. for 1 hour, and then slowly cooled to obtain a liquid crystal element. The transition temperature from the nematic phase to the isotropic phase of this liquid crystal is 35 ° C.
When the liquid crystal element thus produced was placed between two polarizing plates with a crossed Nicols arrangement, it was found that light was transmitted. Further, when the twist angle was measured using a polarizing microscope, it was found that a TN orientation of approximately 90 ° was obtained.

[Example 2]
The azobenzene derivative represented by the following chemical formula (3) was dissolved in a mixed solvent composed of 50% by mass of N-methylpyrrolidone and 50% by mass of 2-butoxyethanol to obtain a 1.0% by mass solution. To this solution, 2.5% by mass of 1,1′-azobis (cyclohexane-1-carbonitrile) was added as a thermal polymerization initiator based on the mass of the azobenzene derivative.

A liquid crystal cell was produced in the same manner as in Example 1 using the composition solution for photo-alignment film thus produced. For the light irradiation after the cell preparation, the same ultraviolet light as in Example 1 was used, and a light amount of 5 J / cm ² was irradiated from a direction of 55 ° with respect to the normal to the substrate surface.
After light irradiation, heating was performed at 150 ° C. for 1 hour in a nitrogen stream, and thermal polymerization of the azobenzene derivative represented by the chemical formula (3) was performed.
When a liquid crystal element was produced from this liquid crystal cell by the same method as in Example 1 and the twist angle was measured, it was found that a TN alignment of approximately 90 ° was obtained.

[Example 3]
Using the azobenzene derivative represented by the chemical formula (2) shown in Example 1, a photoalignment film composition solution was prepared in the same manner as in Example 1, and a liquid crystal cell was further prepared.
The liquid crystal cell thus fabricated was irradiated with a light amount of 5 J / cm ² from a direction of 50 ° with respect to the substrate normal using the same light irradiation system as in Example 1.
When a liquid crystal element was produced from this liquid crystal cell in the same manner as in Example 1 and placed between two polarizing plates with a crossed Nicols arrangement, it was found that the liquid crystal was homogeneously oriented and the twist angle was 0 °. It was.

  From the above results, according to the present invention, after assembling the liquid crystal cell, orientation can be imparted to both the upper substrate and the lower substrate by one irradiation, and twist orientation or homogeneous orientation can be obtained depending on the incident angle of light. It was confirmed that a liquid crystal display element having controllability and twist alignment or homogeneous alignment could be obtained.

When non-polarized light is incident on the surface of the transparent layered medium from an oblique direction, the transmittance of the P-polarized component 1 and the S-polarized component 2 of the transmitted light and the incident angle dependence from the normal to the substrate surface It is a graph which shows the relationship. It is explanatory drawing which shows the polarization direction of the light at the time of irradiating the non-polarized parallel light from the diagonal direction with respect to the substrate surface of a liquid crystal cell, and the direction where the dichroic compound of a photo-alignment film aligns.

Explanation of symbols

3 Photo-alignment film (upper substrate)
3 'photo-alignment film (lower substrate)
4 Upper substrate 4 'Lower substrate 5 Dichroic compound of upper substrate 6 Non-polarized light 7 Dichroic compound of lower substrate 10 Electrode (upper substrate)
10 'electrode (lower substrate)

Claims (6)

Forming a photo-alignment film containing a dichroic compound on an electrode provided on a substrate;
Two of the substrates are opposed to each other with a certain gap so that the surfaces on which the photo-alignment films are formed face each other.
A method for producing a photo-alignment film for a liquid crystal display element, wherein a dichroic compound is aligned by irradiating non-polarized light from an oblique direction with respect to a substrate surface.   The method for producing a photo-alignment film for a liquid crystal display element according to claim 1, wherein the dichroic compound is an azobenzene derivative.   The method for producing a photo-alignment film for a liquid crystal display element according to claim 1, wherein the irradiation angle of the non-polarized light is 30 to 80 ° with respect to the normal to the substrate surface.   The alignment direction of the dichroic compound of an upper board | substrate and the dichroic compound of a lower board | substrate is substantially orthogonal, The optical orientation for liquid crystal display elements as described in any one of Claims 1-3 characterized by the above-mentioned. A method for producing a membrane. The said azobenzene derivative is represented by following General formula (1), The manufacturing method of the photo-alignment film for liquid crystal display elements as described in any one of Claims 2-4 characterized by the above-mentioned.

(Wherein R ¹ and R ² are each independently a hydroxy group, or a group consisting of a (meth) acryloyl group, a (meth) acryloyloxy group, a (meth) acrylamide group, a vinyl group, a vinyloxy group, and a maleimide group). Represents a polymerizable functional group selected from:
X ¹ represents a single bond when R ¹ is a hydroxy group, and represents a linking group represented by — (A ¹ -B ¹ ) _m — when R ¹ is a polymerizable functional group, and X ² represents When R ² is a hydroxy group, it represents a single bond, and when R ² is a polymerizable functional group, it represents a linking group represented by — (A ² —B ² ) _n —. Here, A ¹ is bonded to R ¹ , A ² is bonded to R ^2, and B ¹ and B ² are bonded to adjacent phenylene groups.
A ¹ and A ² each independently represent a single bond or a divalent hydrocarbon group, and B ¹ and B ² each independently represent a single bond, —O—, —CO—O—, —OCO—, -CONH-, -NHCO-, -NHCO-O-, or -OCONH- is represented.
m and n each independently represents an integer of 0 to 4. However, when m or n is 2 or more, the plurality of A ¹ , B ¹ , A ² , and B ² may be the same group or different groups. However, A ¹ or A ² sandwiched between ^two B ¹ or B ² is not a single bond.
R ³ and R ⁴ each independently represent a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group, or a methoxycarbonyl group. The carboxy group may form a salt with an alkali metal.
R ⁵ and R ⁶ each independently represent a carboxyl group, a sulfo group, a nitro group, an amino group, or a hydroxy group. In addition, the carboxy group or the sulfo group may form a salt with the alkali metal. ) After injecting a liquid crystal material into a gap between two substrates provided with a photo-alignment film manufactured by the method for manufacturing a photo-alignment film for a liquid crystal display element according to any one of claims 1 to 5, and sealing, A method for producing a liquid crystal display element, comprising: heating the liquid crystal material to a temperature at which the liquid crystal material is isotropic to align the liquid crystal material.

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