JP2000212310A - Oriented film, its production and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject oriented film capable of promoting the orientation accompanying a pretilt angle of a liquid crystal sealed in a liquid crystal panel without any coloring, excellent in light and heat resistances and useful for liquid crystal displays, etc., by passing a specific polymer through a step for coating the top surface of a substrate with the polymer. SOLUTION: This oriented film is prepared by a step for coating the top surface of a substrate with a polymer having side chains containing a mesogen structure and a step including operations to irradiate the coated polymer with ultraviolet rays preferably from the oblique direction. The side chains of the polymer preferably have photoreactivity and the polymer preferably contains at least a structure represented by formula I or formula II or formula III. The main chain represented by formula IV [x:y:z is (100-0):(100-0):(99-0); (x+y+z) is 100; n, m, j and k are each 1-12; X, Y and Z are each none, COO or the like; R1 to R10 are each H, a halogen or the like; R11 is H, CN or the like] is preferably a homopolymer or a copolymer of a hydrocarbon, an acrylate, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a polymer film which promotes the orientation of a liquid crystal encapsulated in a liquid crystal panel by irradiating a polymer film having a side chain containing a mesogen structure with ultraviolet rays. This is useful for improving the method of manufacturing a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, in order to align a liquid crystal enclosed in a liquid crystal panel, as shown in FIG. 2, a polymer compound 22 such as polyimid is applied to a substrate 21 and a cloth whose surface is planted with nylon or polyester fibers is used. A method such as a method of forming an extremely fine groove on the surface by rubbing with the wound drum 23, or extending and orienting the silicon oxide (SiO) obliquely on a substrate, and a method such as a SiO oblique evaporation method. Has been used. In such a precedent,
The method of physically rubbing the polymer compound surface with a flocking cloth is
This causes a discharge due to fine dust or static electricity, which has been a problem in a liquid crystal panel manufacturing process. In addition, the oblique deposition of SiO has problems that it is difficult to maintain the uniformity of the deposition angle and the film thickness on the substrate, and the process becomes large. In recent years, in order to solve the above-described problems, a technique of irradiating linearly polarized ultraviolet light (hereinafter, referred to as “polarized light”) to align liquid crystals has been attracting attention as a method for producing a non-rubbing alignment film. I have. Examples of the liquid crystal photo-alignment technique include a technique using a photodimerization reaction and a technique using photoisomerization of an azo polymer. In these methods, unlike the rubbing treatment, the orientation of the liquid crystal can be controlled in two or more directions within one pixel by mask exposure, and the viewing angle dependence of the liquid crystal display device can be reduced. In these methods, it is necessary to convert natural light into linearly polarized light for irradiation. As a general dichroic polarizer used for such polarization conversion, there is a sheet obtained by impregnating a sheet obtained by uniaxially stretching PVA (polyvinyl alcohol) with iodine with TAC (triacetyl cellulose). However, such a dichroic polarizer has a low transmittance of light in the ultraviolet region and a low heat resistance, and thus cannot withstand the use of the liquid crystal light alignment technology. For this reason, birefringent prisms are used to polarize light in the ultraviolet region.However, since birefringent prisms use natural crystals of calcite as prisms, they irradiate the entire surface of a substrate such as that used for LCDs. There is no large prism that can be made. On the other hand, a method has been proposed in which anisotropy is generated on the surface of an irradiation object without using polarization conversion means. In JP-A-10-104626, non-polarized ultraviolet light (hereinafter, referred to as "natural light") is irradiated onto an irradiation target surface coated with an azo-based polymer or a polymerizable prepolymer at an incident angle of 45 ° or more, A method has been proposed in which a relatively large amount of S-waves are reflected and the proportion of P-waves in transmitted light is enhanced, so that anisotropy of the photoreaction, such as cutting of conjugated systems, is expressed in the film and the liquid crystal is aligned. . However, in the proposed material, the direction of the electric field of the P-wave is perpendicular to the direction of the liquid crystal alignment, so that it is difficult to develop a pretilt angle that prevents defects in the liquid crystal alignment in the liquid crystal panel. As the only method of irradiating non-polarized light to develop a pretilt angle, the orientation of azobenzene-based polymer materials has been reported (Appl. Phys. Lett.,
Vol 73, No. 7, 17 August 1998). However, since the transmitted light is colored due to light absorption in the visible region, it is not suitable for use in a full-color LCD. Further, since the photoisomerization reaction is used, there is a problem in light resistance and heat resistance.
As a material for the photo-alignment film used for the LCD, a compound which does not absorb light in the visible region and is sensitive to light having a wavelength of 400 nm or less is suitable.

[0003]

The liquid crystal photo-alignment technology proposed so far requires irradiation of polarized light in order to provide a liquid crystal alignment regulating force. This utilizes the difference in the photoreactivity of the alignment film material between the direction of the electric field oscillation of the irradiation light and the direction perpendicular thereto, so that the irradiation light has to be linearly polarized through a polarizing element. The most common means of obtaining linearly polarized light from natural light is a dichroic polarizer in which uniaxially stretched PVA sheet is impregnated with iodine.However, it is not suitable for this application in terms of absorption in the ultraviolet region and durability. No The only way to convert ultraviolet light into linearly polarized light is to use a birefringent prism using calcite crystals that do not absorb in the ultraviolet region. However, it is difficult to increase the size of such a birefringent prism, and there is a problem when using it for irradiation with a large area. As described above, in the conventional liquid crystal photo-alignment technology that attempts to use the linear polarization of the irradiation light, it is necessary to develop a practical polarizing element. In addition, in the orientation film irradiated by natural light, there are problems such as the absence of a pretilt angle and the coloring of transmitted light. The present invention encapsulates a liquid crystal panel by irradiating natural light to a polymer film having a side chain containing a structure in which a liquid crystal mesogen component and a photosensitive group are bonded, without utilizing the polarization property of irradiation light. The present invention promotes the alignment of a liquid crystal with a pretilt angle, provides a polymer film free from coloring and excellent in light resistance and heat resistance, and is useful for improving a method of manufacturing a liquid crystal display.

[0004]

In view of the above problems, the present invention is directed to a polymer comprising at least one structure represented by the chemical formula 1, 2, or 3 in a side chain, wherein the main chain is a hydrocarbon, Provided are an alignment film using a homopolymer or a copolymer represented by Chemical Formula 4, which is acrylate, methacrylate, or siloxane, and a method for producing the same.

Embedded image However, x: y: z = 100-0: 100-0: 99-0
(Where x + y + z = 100), n = 1 to 12, m =
1-12, j = 1-12, k = 1-12, X, Y, Z =
none, -COO, -OCO-, -N = N-, -C = C-or-C6H4
-, -R1 to -R10 = -H, an alkyloxy group such as a halogen group or a methoxy group, and -R11 = -H, -C
N or an alkyloxy group such as a methoxy group.
The side chain type polymer has a substituent such as biphenyl, terphenyl, phenylbenzoate, or azobenzene which is frequently used as a mesogen component of a liquid crystalline polymer in a side chain.
It is a polymer having a structure such as a hydrocarbon, acrylate, methacrylate, or siloxane in the main chain. Also, if necessary, a structure in which a photosensitive group such as a cinnamic acid group (or a derivative group thereof) is bonded to the mesogen component of the side chain, or a structure having a side chain containing a photosensitive group and the bonding of the photosensitive group is provided. It contains a certain proportion of untreated side chains. As shown in FIG. 1, a polymer coating film 12 is formed by applying (spin coating or casting) a solution of the polymer on a substrate 11. By irradiating natural light L to the coating film of the polymer compound, a film in which dimerization of cinnamic acid (or a derivative thereof) groups is suppressed can be formed, and an alignment film can be formed. Furthermore, this solution eliminates the need to generate fine dust and static electricity and to perform a large-scale process when physically rubbing the surface of the polymer compound. Further, since the liquid crystal alignment by natural light is possible, the optical alignment can be realized without using a polarizing element, and the biggest problem in the conventional technology is solved.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. A solution of the above-mentioned homopolymer or copolymer is applied (spin-coated or cast) on a substrate to form a polymer coating film. The inside of the polymer coating film is not oriented at the time of film formation, and the side chain portion does not face a specific direction. When the film is irradiated with ultraviolet light, the side chain portion directed in the direction perpendicular to the direction of the irradiation ultraviolet light is more sensitive than the side chain portion directed in the parallel direction, and thus becomes an anisotropic film. The conjugated mesogen side chain containing a benzene ring etc. extends in the long axis direction of the side chain,
The electrons move in this direction. As shown in FIG. 3, when such a side chain is placed in a radiation field irradiated with natural light L, the direction of the electric field oscillation of light coincides with the long axis direction of the side chain.
The interaction is maximized, and the interaction is minimized in the component 3b in which the light traveling direction coincides with the long axis direction of the side chain. When liquid crystal molecules are brought into contact with the surface of the alignment film, the reaction amount of the side chain is different in direction, and the liquid crystal molecules are aligned under the influence of the reaction.

In order to promote the dimerization of the photosensitive group in the side chain,
Light of a wavelength suitable for the reaction of this part is irradiated. This wavelength varies depending on the structure represented by Formula 1 or 2, but is generally 200-500 nm when biphenyl is used as the mesogenic component or cinnamic acid group (or a derivative thereof) is used as the photosensitive group. In particular, the effectiveness of 250-450 nm is often high.

In the conventional optical alignment technology, the alignment direction of the liquid crystal is parallel to the S-wave electric field oscillation direction of the irradiation light, and it is difficult to develop a pretilt angle for preventing a defect in the liquid crystal alignment in the liquid crystal panel. In contrast, the polymer of the present invention can exhibit a pretilt angle because the orientation direction of the liquid crystal is parallel to the direction of the electric field oscillation of the P-wave component in the irradiation light. Further, the orientation direction and density of the unreacted side chain can be controlled by the irradiation direction of the irradiation light and the irradiation light amount, and the magnitude of the pretilt angle and the direction in which the pretilt angle appears can be arbitrarily set by the irradiation direction and the irradiation light amount of the irradiation light. FIGS. 4 and 5 show different polymers (x: y: z = 100: 0: 0, n = 6, m = 2, X =
none, -R1--R5 = -H, and x: y: z = 0: 1
00: 0, k = 6, Z = none, -R6 to -R10 = -H)
3 shows the change of the pretilt angle with respect to the irradiation time when natural light is irradiated to the light emitting element. Using a high-pressure mercury lamp as the light source of the irradiation light,
The irradiation angles are 60 ° and 35
°, 45 °, and 55 °. It was confirmed that when the irradiation time was increased, the pretilt angle showed an irradiation time dependency that gradually decreased from 90 °, and that there was also an irradiation angle dependency.

For the measurement of the pretilt angle of the liquid crystal molecules, a crystal rotation method for measuring the transmission intensity of He-Ne laser light having a wavelength of 633 nm while rotating a measurement sample inserted between a pair of polarizers was used. In the measurement method,
The three-dimensional birefringence of the measurement sample can be measured from the angle dependence of the transmittance of the He-Ne laser light.

From the above, the polymer material of the present invention is applied (spin-coated or cast) to a substrate to form a film, and the substrate surface is irradiated with natural light from a specific direction to form the film. The photoreaction of only the polymer side chain in the direction can be suppressed. The density of the unreacted side chains can be arbitrarily set by changing the irradiation amount of irradiation light. When a substrate having this alignment film is used for a liquid crystal cell, liquid crystal molecules can be set to a desired pretilt angle by interaction with the side chain, so that various modes of LCD such as TN, VA, and IPS modes are used.
Can be used as an alignment film. In addition, in the photo-alignment film and the method of manufacturing the same according to the present invention, since a process such as physically rubbing the substrate surface is unnecessary, static electricity, dust and the like are not generated, and the liquid crystal can be aligned by natural light. Therefore, a liquid crystal display device can be provided without using a polarizing element.

A method for synthesizing a raw material compound of a polymer material will be described below. (Monomer 1) 4,6-dibromohexane is reacted with 4,4′-biphenyldiol under alkaline conditions,
(6-Bromohexyloxy) -4′-biphenol was synthesized. Next, lithium methacrylate was reacted to synthesize 4-hydroxy-4 ′-(6′-biphenyloxyhexyl) methacrylate. Finally, under basic conditions, cinnamoyl chloride is added,
Was synthesized.

Embedded image

(Monomer 2) 4-Hydroxy-4'-hydroxyethoxybiphenyl was synthesized by heating 4,4'-biphenyldiol and 2-chloroethanol under alkaline conditions. This product was reacted with 1,6-dibromohexane under alkaline conditions to obtain 4- (6
-Bromohexyloxy) -4'-hydroxyethoxybiphenyl was synthesized. Next, lithium methacrylate was reacted to give 4-hydroxyethoxy-4 ′-(6 ′).
-Biphenyloxyhexyl) methacrylate was synthesized. Finally, cinnamoyl chloride was added under basic conditions to synthesize a methacrylic ester represented by Chemical Formula 6.

Embedded image

(Monomer 3) 1,4-Dibromohexane was reacted with 4,4'-biphenyldiol under alkaline conditions to synthesize 4- (6-bromohexyloxy) -4'-hydroxybiphenyl. . Subsequently, lithium methacrylate was reacted to give 4-hydroxy-4 ′-(6 ′
-Biphenyloxyhexyl) methacrylate was synthesized. Finally, under basic conditions, 2-methoxycinnamoyl chloride was added to synthesize a methacrylic acid ester represented by Chemical Formula 7.

Embedded image

(Monomer 4) 4-Hydroxy-4'-hydroxyhexyloxybiphenyl was synthesized by heating 4,4'-biphenyldiol and 2-chlorohexanol under alkaline conditions. The product is reacted with 1,6-dibromohexane under alkaline conditions,
4- (6-Bromohexyloxy) -4′-hydroxyhexyloxybiphenyl was synthesized. Next, lithium methacrylate was reacted to synthesize 4-hydroxyhexyloxy-4 ′-(6′-biphenyloxyhexyl) methacrylate. Finally, under basic conditions, 2-methoxycinnamoyl chloride was added to obtain a compound of formula 8
Was synthesized.

Embedded image

(Monomer 5) 4-Hydroxy-4'-cyanobiphenyl is reacted with 1,6-dibromohexane under alkaline conditions to give 4- (6-bromohexyloxy)-
4′-cyanobiphenyl was synthesized. Next, lithium methacrylate was reacted to obtain 4-cyano-4 ′-(6 ′).
-Biphenyloxyhexyl) methacrylate was synthesized. A methacrylic ester represented by Chemical Formula 9 was synthesized.

Embedded image

(Polymer 1) Polymer 1 was obtained by dissolving this monomer 1 in tetrahydrofuran, adding AIBN (azobisisobutyronitrile) as a reaction initiator and polymerizing. This polymer 1 exhibited liquid crystallinity in a temperature range of 144 to 219 ° C.

(Polymer 2) Polymer 2 is dissolved by dissolving monomer 2 in tetrahydrofuran and adding AIBN (azobisisobutyronitrile) as a reaction initiator to carry out polymerization.
I got This polymer 2 also exhibited liquid crystallinity in a temperature range of 47 to 75 ° C.

(Polymer 3) Polymer 4 is dissolved by dissolving monomer 4 in tetrahydrofuran and adding AIBN (azobisisobutyronitrile) as a reaction initiator to carry out polymerization.
I got This polymer 3 also exhibited liquid crystallinity in a temperature range of 92 to 116 ° C.

(Polymer 4) 1: 1 of monomer 2 and monomer 5
Was dissolved in tetrahydrofuran at a ratio of, and polymer 4 was obtained by adding AIBN (azobisisobutyronitrile) as a reaction initiator and polymerizing. This polymer 4 also exhibited liquid crystallinity. This polymer 4 exhibited liquid crystallinity in a temperature range of 44-99 ° C.

Example 1 Polymer 1 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). The substrate was placed at an angle of 55 degrees with respect to the horizontal plane, and was irradiated with non-polarized ultraviolet light at room temperature for 120 seconds from a direction perpendicular to the horizontal plane. By preparing two such substrates and filling the liquid crystal ZLI2061, a TN type liquid crystal cell having a thickness of 4.5 μm was assembled. The driving voltage of this TN type liquid crystal cell was 2V. Further, when the pretilt angle was measured by a crystal rotation method as an anti-parallel cell, the pretilt angle was 6 °.

Example 2 Polymer 2 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). The substrate was arranged so as to be tilted by 60 degrees with respect to the horizontal plane, and irradiated with ultraviolet rays at a room temperature for 200 seconds from a direction perpendicular to the horizontal plane. Two such substrates were produced to produce an anti-parallel cell, which was filled with liquid crystal ZLI2061. When the pretilt angle was measured by the crystal rotation method, the pretilt angle was 45.
°.

Example 3 The polymer 2 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). The substrate was arranged so as to be inclined by 60 degrees with respect to the horizontal plane, and irradiated with ultraviolet rays at room temperature for 180 seconds from a direction perpendicular to the horizontal plane. Two such substrates were produced to produce an anti-parallel cell, which was filled with liquid crystal ZLI2061. When the pretilt angle was measured by the crystal rotation method, the pretilt angle was 55.
°.

Example 4 Polymer 2 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). The substrate was arranged so as to be inclined by 60 degrees with respect to the horizontal plane, and ultraviolet rays were irradiated from a direction perpendicular to the horizontal plane at room temperature for 90 seconds. An anti-parallel cell is manufactured by manufacturing two such substrates, and a liquid crystal is manufactured.
ZLI2061 was filled. When the pretilt angle was measured by the crystal rotation method, the pretilt angle was 88 °.
Met.

Example 5 The polymer 4 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and irradiated with ultraviolet rays at room temperature for 500 seconds from a direction perpendicular to the horizontal plane. Two such substrates were produced to produce an anti-parallel cell, which was filled with liquid crystal ZLI2061. When the pretilt angle was measured by the crystal rotation method, the pretilt angle was 82.
°.

Example 6 The polymer 4 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and irradiated with ultraviolet rays at room temperature for 700 seconds from a direction perpendicular to the horizontal plane. Two such substrates were produced to produce an anti-parallel cell, which was filled with liquid crystal ZLI2061. When the pretilt angle was measured by the crystal rotation method, the pretilt angle was 59.
°.

[0025]

As described above, according to the present invention, an alignment film which exhibits a pretilt angle of liquid crystal molecules by irradiating natural light can be obtained, and this film is applied to an alignment film for a liquid crystal display. it can. This eliminates the need for a polarizing element that is indispensable in the conventional optical alignment technology.
In addition, in this orientation, the orientation direction of the liquid crystal and the magnitude of the pretilt angle can be arbitrarily set according to the irradiation direction and the irradiation amount of light, so that the alignment film is used in LCDs of various modes such as TN, VA, and IPS modes. Can be used as. Further, by exposing using a mask, films having different pretilt angles can be formed on the same substrate. In order to increase the viewing angle in a liquid crystal display device, a pixel division orientation that allows the liquid crystal to exhibit an alignment state with a low tilt angle and a high tilt angle within one pixel or inverts the alignment of the liquid crystal within one pixel is an effective technology. is there. The polymer material of the present invention also enables the pixel division alignment by light irradiation. Furthermore, since an alignment film that does not require an operation for aligning liquid crystal molecules, such as rubbing, is prepared, defects generated in the assembly process of the liquid crystal display are significantly reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a method for manufacturing an alignment film according to the present invention.

FIG. 2 is an example showing a conventional method for manufacturing an alignment film.

FIG. 3 is a schematic diagram showing reactivity depending on arrangement of irradiation light and side chains.

FIG. 4 shows the relationship between irradiation time and tilt angle.

FIG. 5 shows the relationship between irradiation time, irradiation angle, and tilt angle.

[Explanation of symbols]

 11: substrate 12: polymer coating film L: natural light

Continued on the front page F term (reference) 2H090 HB13Y HB17Y HC05 HC11 KA05 LA16 MA10 MB14 4D075 BB18Z BB22X BB46Z CA50 DA04 DB13 DC22 EA05 EB22 EB42 4F073 AA14 BA34 BB01 CA45

Claims (6)

[Claims] 1. A method comprising the steps of: applying a polymer having a side chain containing a mesogen structure onto a substrate; and irradiating the applied polymer with ultraviolet light. An alignment film and a method of manufacturing the same. 2. A process comprising applying the polymer according to claim 1 onto a substrate and irradiating the applied polymer with ultraviolet light obliquely. , Alignment film and method for producing the same. 3. An alignment film and a method for producing the alignment film, wherein the side chains of the polymer according to claim 1 and 2 have photoreactivity. 4. A side chain comprising at least a structure represented by Formula 1 or Formula 2 or Formula 3, wherein a main chain represented by Formula 4 is a homopolymer or copolymer such as hydrocarbon, acrylate, methacrylate, or siloxane. An alignment film and a method for producing the alignment film, which are produced in a step of applying the union onto a substrate and a step of irradiating the applied compound with light. Embedded image Embedded image Embedded image Embedded image However, in the chemical formulas 1 to 4, x: y: z = 100
0: 100-0: 99-0 (where x + y + z = 1
00), n = 1 to 12, m = 1 to 12, j = 1 to 12,
k = 1 to 12, X, Y, Z = none, -COO, -OCO-,-
N = N-, -C = C-or-C6H4-, -R1--R10 = -H,
An alkyloxy group such as a halogen group or a methoxy group, and an alkyloxy group such as -R11 = -H, -CN, or a methoxy group. 5. The method according to claim 1, 2 or 3.
5. The method of claim 4, wherein the method includes the steps of heating and cooling the substrate. 5. 6. The method according to claim 1, wherein said first and second means are different from each other.
6. A liquid crystal display device produced by the production method according to claim 4 or 5, wherein liquid crystal alignment is achieved by an alignment film.