JP2003207631A - Optical film, polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical film by which an improved utilization factor of the light is obtained, scattering characteristics are easily controlled and which exhibits uniform and further prominent scattering characteristics over a large area. <P>SOLUTION: In the optical film comprising a polarization selecting layer selectively transmitting specified polarized light and selectively reflecting or scattering other polarized light formed on a transparent supporting body, a compound expressed by a formula (I) is added to the polarization selecting layer. (I) R<SP>1</SP>-äL<SP>1</SP>-(Ar<SP>1</SP>)<SB>l</SB>}<SB>s</SB>-C≡C-(Ar<SP>2</SP>)<SB>m</SB>-C≡C-(Ar<SP>3</SP>)<SB>n</SB>-C≡C-ä(Ar<SP>4</SP>)<SB>p</SB>-L<SP>2</SP>}<SB>t</SB>-R<SP>2</SP>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transparent support,
The present invention relates to an optical film having a polarization selection layer that selectively transmits predetermined polarized light and selectively reflects or scatters other polarized light, and a polarizing plate and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art Although natural light such as sunlight and light from an ordinary artificial light source such as a lamp are unpolarized (random polarized), they can be polarized (linearly polarized, circularly polarized, elliptically polarized) by using a polarizing plate. The polarized light component can be extracted. The extracted polarized light can be used for various optical devices. It can be said that the liquid crystal display device that is widely used at present is a device that displays an image by utilizing the property of polarized light. The broadly defined polarizing plate includes a linear polarizing plate, a circular polarizing plate and an elliptically polarizing plate. However, the ordinary (narrowly defined) polarizing plate means a linear polarizing plate. Also in the present specification, a "polarizing plate" not particularly specified
Means a linear polarizing plate. The linear polarizing plate is the most basic polarizing plate. Circular polarizers are generally linear polarizers and λ
It is a laminate of a linear polarizing plate with a / 4 plate. The elliptically polarizing plate is
Generally, it is a laminated body of a linear polarizing plate and a retardation plate other than a λ / 4 plate. Therefore, in various (broadly defined) polarizing plates,
The optical function of the linear polarizing plate is important.

As the linear polarizing plate, a light absorbing type polarizing plate made of a polyvinyl alcohol film is generally used. The polyvinyl alcohol-based polarizing plate is produced by stretching a polyvinyl alcohol-based film and adsorbing iodine or a dichroic dye. The transmission axis (polarization axis) of the polarizing plate corresponds to the direction perpendicular to the stretching direction of the film.
The light absorption type polarizing plate transmits only the polarization component parallel to the polarization axis and absorbs the polarization component in the direction orthogonal thereto. Therefore,
The utilization efficiency of light is theoretically 50% or less (actually lower value).

In order to improve the light utilization efficiency of the polarizing plate,
It has been proposed to use a light scattering type polarizing plate instead of the light absorbing type polarizing plate or in addition to the light absorbing type polarizing plate.
The light-scattering type polarizing plate, like the light-absorption type polarizing plate, transmits only the polarization component parallel to the polarization axis. However, in the light-scattering type polarizing plate, the polarization component in the direction orthogonal to the polarization axis is not absorbed but is scattered forward or backward to improve the light utilization efficiency of the polarizing plate. There are a plurality of mechanisms for improving the light use efficiency by the light-scattering polarizing plate as follows.

(A) Depolarization of forward scattered light In a light-scattering type polarizing plate, a polarization component orthogonal to the polarization axis is scattered forward or backward. Of these, the light scattered forward is depolarized, and the polarization direction of the forward scattered light rotates from the polarization direction of the incident light, so that the polarization component in the polarization axis direction of the light-scattering polarizing plate increases more than the incident light. In the light-scattering polarizer, when a large number of particles are present in the thickness direction, the degree of depolarization becomes strong due to multiple scattering. As described above, when the scattering type polarizing plate is used, the light utilization efficiency is improved by depolarizing the forward scattered light as compared with the case where only the light absorbing type polarizing plate is used.

(B) Reuse of backscattered light (depolarization) The backscattered light of the polarization components in the direction orthogonal to the polarization axis of the light scattering polarizing plate is depolarized when it is backscattered. It The back-scattered light is reflected by the metal reflection plate arranged on the back surface of the backlight, which is the light source, and is incident on the light-scattering polarizing plate again. Here, the re-incident light undergoes depolarization when it is backscattered, and a polarization component parallel to the polarization axis of the scattering polarizing plate is generated, and this polarization component passes through the scattering polarizer. As described above, the light utilization efficiency can be improved by repeating the backscattering by the light-scattering polarizer and the reflection by the metal reflector.

(C) Reuse of backscattered light (rotation of polarization direction) An optical system in which a λ / 4 plate and a metal reflection plate are arranged so that the slow axis of the λ / 4 plate forms 45 °. When linearly polarized light is incident on, the incident light and the reflected light whose polarization direction is rotated by 90 ° return. A λ / 4 plate is provided between the light-scattering polarizing plate and the metal reflecting plate (located on the back surface of the backlight) so that the polarization axis of the light-scattering polarizing plate and the slow axis of the λ / 4 plate are 45 °. By arranging so as to achieve the same effect as above. The distribution of the polarization direction of the light backscattered in the light scattering type polarizing plate is
The direction perpendicular to the polarization axis of the light scattering polarizing plate is large. The distribution of the polarization direction of the backscattered light that passes through the λ / 4 plate, is reflected by the metal reflection plate, and is incident on the light-scattering polarizing plate again is parallel to the polarization axis of the light-scattering polarizing plate. The polarized light component, which has a large size and is parallel to the polarization axis, passes through the light scattering type polarizing plate. Thus, by disposing the λ / 4 plate between the light-scattering type polarizing plate and the metal reflection plate, it is possible to improve the light utilization efficiency.

Regarding the light-scattering type polarizing plate, JP-A-8-7
6114, 9-274108, 9-29720.
No. 4, Tokuyohei 11-502036, No. 11-5090
14 and US Pat. Nos. 5,783,120 and 5,
Nos. 825543 and 586316 are described.

[0009]

Among the conventional light-scattering polarizing plates, JP-A-8-76114 and JP-A-9-274108.
No. 11-502036 and 11-50901
4 and US Pat. Nos. 5,783,120 and 58.
The light-scattering type polarizing plates disclosed in the specifications of No. 25543 and No. 5867316 are manufactured by stretching a polymer film similarly to the light-absorbing type polarizing plate. In these methods, it is necessary to highly control the refractive indexes of the binder and dispersed particles. Specifically, it is necessary to match the refractive indexes of the two on the side where the polarized light is transmitted, and it is necessary to increase the refractive index difference on the side where the polarized light is scattered. In the methods described in the above-mentioned publication and specification, these performances are insufficient, and sufficient utilization efficiency of light cannot be improved. In the light-scattering type polarizing plate described in JP-A-11-502036, an optically anisotropic compound (liquid crystal) is aligned by a method in which a liquid crystal is dispersed in a polymer film and an electric field or a magnetic field is applied. However, it is difficult to uniformly apply an electric field or magnetic field to a large area,
It is also difficult to obtain uniform scattering characteristics over a large area. Moreover, the non-uniformity of the in-plane scattering characteristics of the light-scattering type polarizing plate as described above leads to unevenness of the in-plane brightness of the liquid crystal display device. An object of the present invention is to improve the light utilization efficiency of a polarizing plate, to easily control the scattering property thereof, and to show a uniform and large scattering property over a large area, and a novel polarization-selective optical film for achieving these. To provide such a compound.

[0010]

The objects of the present invention are achieved by the following optical films (1) to (9), the following polarizing plate (10) and the following liquid crystal display devices (11) and (12). It was (1) Selectively transmitting predetermined polarized light on a transparent support,
An optical film in which a polarization selective layer that selectively reflects or scatters other polarized light is formed, wherein the polarization selective layer contains a compound represented by the following formula (I): (I) R ^1- {L ^1- (Ar ¹ ) _l } _s -C≡C- (A
r ² ) _m- C≡C- (Ar ³ ) _n- C≡C-{(A
r ⁴ ) _p −L ² } _t −R ² [wherein, R ¹ and R ² are each independently an alkyl group or an aromatic group; L ¹ and L ² are each independently —C≡ C- or -CR ³ = CR ⁴ - and a, R ³ and R ⁴ are each independently hydrogen atom or an alkyl ^{group; Ar 1, Ar 2, Ar} 3 and a
r ⁴ is each independently a divalent aromatic group;
m, n and p are each independently 1, 2 or 3; and s and t are each independently 0 or 1.

(2) The optical film as described in (1), wherein the polarization selection layer comprises an optically isotropic phase and an optically anisotropic phase. (3) The optical film according to (2), wherein the optically anisotropic phase contains a compound represented by the formula (1). (4) The maximum total light transmittance is 75% or more and the minimum total light transmittance is 6 in the plane of polarization perpendicular to the film surface.
The optical film according to (1), which is less than 0%. (5) The optical film according to (2), wherein the minimum refractive index difference between the optically isotropic phase and the optically anisotropic phase is less than 0.05 in the in-plane direction of the film.

(6) The optical film as described in (1), wherein the compound represented by the formula (I) has a polymerizable group. (7) One of the optically isotropic phase and the optically anisotropic phase is a discontinuous phase, and the circle-approximate average particle size of the discontinuous phase is 0.01 to 10.0 μm. The described optical film. (8) The optical film according to (2), wherein the optically isotropic phase is a continuous phase and the optically anisotropic phase is a discontinuous phase. (9) The optical film as described in (1), wherein the polarization selection layer is formed by stretching at 10.0 times or less.

(10) Light having a light-scattering-type polarization selection element having the polarization selection layer described in (1) above and a polarization selection layer that selectively transmits a predetermined polarization and selectively absorbs another polarization. A polarizing plate in which an absorption type polarization selection element is laminated, wherein the polarization selection layer of the light scattering type polarization selection element comprises an optically isotropic phase and an optically anisotropic phase. In the polarization plane perpendicular to the film surface of the device, the maximum total light transmittance is 75% or more and the minimum total light transmittance is 60%.
And a transmission axis of the light absorption type polarization selection element is substantially parallel to an axis having a polarization plane that maximizes the total light transmittance. (11) A liquid crystal display device comprising a pair of substrates having transparent electrodes and pixel electrodes, a liquid crystal cell in which a liquid crystalline compound is sealed between the substrates, and a pair of polarizing plates arranged outside the liquid crystal cell. A liquid crystal display device, characterized in that the optical film according to the above (1) is arranged between the backlight side polarizing plate and the backlight.

(12) A liquid crystal display device in which a backlight, a polarizing plate, a liquid crystal cell, and a polarizing plate are laminated in this order, wherein the polarizing plate between the backlight and the liquid crystal cell is as described in (1) above. Polarized light in which a light-scattering polarization selection element having a polarization selection layer and a light absorption polarization selection element having a polarization selection layer that selectively transmits predetermined polarized light and selectively absorbs other polarized light are stacked. The plate, the polarization selection layer of the light-scattering polarization selection element is composed of an optically isotropic phase and an optically anisotropic phase, in the polarization plane perpendicular to the film surface of the light-scattering polarization selection element, A total light transmittance of 75% or more, a minimum total light transmittance of less than 60%, and
A liquid crystal display device, wherein an axis having a polarization plane that maximizes the total light transmittance and a transmission axis of a light absorption type polarization selection element are substantially parallel to each other. In the present specification, “optical isotropic” means that the birefringence is less than 0.05, and “optical anisotropy” means that the birefringence is 0.05 or more. means.

[0015]

The polarization selective layer of the present invention comprises an optically isotropic phase and an optically anisotropic phase, and either the optically isotropic phase or the optically anisotropic phase is a discontinuous phase. , The other is the continuous phase. In the present invention, the optically anisotropic phase is preferably a discontinuous phase. Explaining such a form as an example, the coating liquid in which the liquid crystal represented by the formula (I) is dispersed in advance causes phase separation by coating alone or by heat or light irradiation, and becomes cloudy. Of these, the continuous phase has optical isotropy with a birefringence of less than 0.05,
The discontinuous phase (dispersed phase) has optical anisotropy with birefringence of 0.05 or more, but refraction of a phase in which the refractive index viewed from one axis of the anisotropy is optically isotropic. If the ratio is almost the same, a given polarized light is transmitted without scattering in the plane in which the plane of polarization includes its axis. On the other hand, polarized light having a polarization plane orthogonal to this polarized light is scattered due to the difference in refractive index between the optically anisotropic phase and the optically isotropic phase. With respect to the optical anisotropy in the discontinuous phase, when a liquid crystalline compound represented by the formula (I) is used, it is spontaneously oriented by stretching 5.0 times or less, so that a large birefringence can be easily obtained. However, since the scattering property of the scattering axis increases as the difference between the refractive index of the optically isotropic phase and the refractive index of the optically anisotropic phase in the scattering axis increases, the optical film of the present invention has a large polarization selectivity. can get. In the optical film of the present invention, the stretching step can be performed at a stretching ratio of 10.0 times or less, preferably 5.0 times or less, so that uniform scattering characteristics can be obtained over a large area. This method can easily orient in a large area as compared with the manufacturing method using an electric field or a magnetic field, and moreover can easily obtain large birefringence of a discontinuous phase as compared with other manufacturing methods, resulting in a large area. A uniform and large scattering characteristic can be obtained over the entire range.

As described above, in the optical film of the present invention, the optical properties required for the light-scattering type polarizing plate can be easily achieved by stretching 10.0 times or less. By using a light-scattering polarizing plate that has achieved the required optical characteristics, the efficiency of light utilization of the polarizing plate is significantly improved by any of the forward scattering depolarizing type, backscattering depolarizing type, and backscattering polarization rotating type. can do.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that the polarization selection layer contains a compound represented by the following formula (I). (I) R ^1- {L ^1- (Ar ¹ ) _l } _s -C≡C- (A
r ² ) _m- C≡C- (Ar ³ ) _n- C≡C-{(A
_{^{r 4) p -L 2} t}} -R 2 In formula (I), R ¹ and R ² are each independently an alkyl group or an aromatic group. The alkyl group preferably has 1 to 30 carbon atoms. Examples of alkyl groups include methyl, propyl, hexyl, octyl and dodecyl.

The aromatic group is an aryl group or an unsubstituted aromatic heterocyclic group. Examples of aryl groups are phenyl,
1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-
Included are phenanthryl and 9-phenanthryl.
Phenyl, 2-naphthyl, 2-anthryl and 2-phenanthryl are preferred, and phenyl is more preferred.

R ¹ and R ² may further have a substituent, and examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), cyano, and 1 carbon atom. To 20 (preferably 1 to 12) alkyl groups (eg,
(Methyl, ethyl, hexyl, dodecyl), alkenyl group having 2 to 20 (preferably 2 to 12) carbon atoms (eg vinyl, propenyl, hexenyl), 2 to 20 (preferably 2 to 12) carbon atoms An alkynyl group (eg, ethynyl, propynyl, hexynyl), an aryl group having 6 to 20 (preferably 6 to 12) carbon atoms (eg, phenyl, naphthyl), and 1 to 20 carbon atoms.
(Preferably 1 to 12) alkoxy group (eg, methoxy, ethoxy, hexyloxy, octyloxy), aryloxy group having 6 to 20 (preferably 6 to 12) carbon atoms (eg, phenoxy, naphthoxy), An alkylthio group having 1 to 20 (preferably 1 to 12) carbon atoms (eg, methylthio, butylthio, hexylthio, decylthio), an arylthio group having 6 to 20 (preferably 6 to 12) carbon atoms (eg, phenylthio) , Naphthylthio), an acyl group having 1 to 20 (preferably 1 to 12) carbon atoms (eg, acetyl, isobutyryl, lauroyl, acryloyl, benzoyl), and 2 carbon atoms.
To 20 (preferably 2 to 12) alkoxycarbonyl groups (eg, methoxycarbonyl, ethoxycarbonyl, hexyloxycarbonyl), and acyloxy groups having 2 to 20 (preferably 2 to 12) carbon atoms (eg,
Acetyloxy, acryloyloxy, methacryloyloxy, hexanoyloxy), C2 to C20
(Preferably 2 to 12) amide group (eg, acetamide, acrylamide, methacrylamide, hexanamide), carbamoyl, alkyl-substituted carbamoyl group having 2 to 20 (preferably 2 to 12) carbon atoms (eg,
Methylcarbamoyl, diethylcarbamoyl, octylcarbamoyl), and aryl-substituted carbamoyl groups having 7 to 20 (preferably 7 to 12) carbon atoms (eg, phenylcarbamoyl).

[0020] In the formula (I), L ¹ and L ² are each independently, -C≡C- or -CR ³ = CR ⁴ - a. R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group. R ³ and R ⁴ are preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom. Is most preferred.

In the formula (I), Ar ¹ , Ar ² and Ar
³ and Ar ⁴ are each independently a divalent aromatic group. The divalent aromatic group means a divalent aromatic hydrocarbon group or a divalent aromatic heterocyclic group. Examples of the divalent aromatic hydrocarbon group include phenylene, naphthylene, anthrylene and phenanthrylene. 1,4-phenylene, 2,6-naphthylene, 2,6-anthrylene and 2,7-phenanthrylene are preferable, 1,4-phenylene and 2,6-naphthylene are more preferable,
Most preferred is 1,4-phenylene. The aromatic heterocycle of the divalent aromatic heterocycle group is preferably a 5-membered ring or a 6-membered ring. Examples of the divalent aromatic heterocyclic group are shown below.

[0022]

[Chemical 1]

[0023]

[Chemical 2]

[0024]

[Chemical 3]

[0025]

[Chemical 4]

[0026]

[Chemical 5]

The divalent aromatic hydrocarbon group and the divalent aromatic heterocyclic group may have a substituent. Examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), cyano, and a carbon atom number of 1 to 20.
(Preferably 1 to 12) alkyl group (eg, methyl, ethyl, hexyl, dodecyl), having 2 to 20 carbon atoms
(Preferably 2 to 12) alkenyl group (eg, vinyl, propenyl, hexenyl), having 2 to 2 carbon atoms
0 (preferably 2 to 12) alkynyl group (eg, ethynyl, propynyl, hexynyl), aryl group having 6 to 20 carbon atoms (preferably 6 to 12) (eg, phenyl, naphthyl), 1 carbon atom To 20 (preferably 1 to 12) alkoxy groups (eg, methoxy, ethoxy, hexyloxy, octyloxy), aryloxy groups having 6 to 20 (preferably 6 to 12) carbon atoms (eg, phenoxy, naphthoxy). ), An alkylthio group having 1 to 20 (preferably 1 to 12) carbon atoms (eg,
Methylthio, butylthio, hexylthio, decylthio), having 6 to 20 carbon atoms (preferably 6 to 1)
2) an arylthio group (eg, phenylthio, naphthylthio), having 1 to 20 carbon atoms (preferably 1 to 1)
2) an acyl group (eg, acetyl, isobutyryl, lauroyl, acryloyl, benzoyl), an alkoxycarbonyl group having 2 to 20 (preferably 2 to 12) carbon atoms (eg, methoxycarbonyl, ethoxycarbonyl,
Hexyloxycarbonyl), having 2 to 20 carbon atoms
(Preferably 2 to 12) acyloxy group (eg, acetyloxy, acryloyloxy, methacryloyloxy, hexanoyloxy), amide group having 2 to 20 (preferably 2 to 12) carbon atoms (eg, acetamide, acrylamide, Methacrylamide, hexanamide),
Carbamoyl having 2 to 20 carbon atoms (preferably 2 carbon atoms)
To 12) alkyl-substituted carbamoyl groups (eg, methylcarbamoyl, diethylcarbamoyl, octylcarbamoyl) and aryl-substituted carbamoyl groups having 7 to 20 (preferably 7 to 12) carbon atoms (eg, phenylcarbamoyl).

The number of substituents contained in the divalent aromatic hydrocarbon group and the divalent aromatic heterocyclic group is preferably 3 or less, more preferably 2 or less.

In the formula (I), l, m, n and p
Are each independently 1, 2 or 3. l, m,
It is preferable that n and p are each independently 1 or 2. In formula (I), s and t are each independently 0 or 1. At least one of s and t is preferably 0, and more preferably both s and t are 0.

When it is necessary to suppress the variation in liquid crystallinity due to temperature, the compound represented by the formula (I) preferably has a polymerizable group. As the polymerizable group, an unsaturated polymerizable group, an epoxy group or an azirinidyl group is preferable, an unsaturated polymerizable group is more preferable, and an ethylenically unsaturated polymerizable group is most preferable. From the viewpoint of the liquid crystallinity of the rod-shaped liquid crystalline molecule and the alignment fixing by polymerization, it is preferable that the polymerizable groups are provided at both ends of the rod-shaped liquid crystal structure.

Examples of the compound represented by the formula (I) are shown below.

[0032]

[Chemical 6]

[0033]

[Chemical 7]

[0034]

[Chemical 8]

[0035]

[Chemical 9]

[0036]

[Chemical 10]

[0037]

[Chemical 11]

[0038]

[Chemical 12]

[0039]

[Chemical 13]

The compound represented by the formula (I) is, for example, M
acromolecules, 26, 5840 (1
993) and the method described in JP-A No. 2000-198755.

[Synthesis Example 1] Synthesis of compound (1-f)

[0042]

[Chemical 14]

70 mmol of compound (1-a), 70 mmol of compound (1-b), 150 ml of acetonitrile,
A mixture of 280 mmol of piperidine, 0.2 mmol of compound (1-c), 1.04 mmol of compound (1-d) and 0.26 mmol of compound (1-e) was reacted at room temperature for 12 hours under a nitrogen atmosphere. It was After that, 300 ml of ethyl acetate was added, and the reaction solution was added with 0.5N hydrochloric acid water and water.
Washed with brine. The organic layer was concentrated and then purified by silica gel column chromatography (eluent: hexane) to obtain the compound (1-f) at a yield of 53%.

Synthesis of compound (1-h)

[0045]

[Chemical 15]

35 mmol of compound (1-f), 35 mmol of compound (1-g), 80 ml of acetonitrile, 140 mmol of piperidine, 0.1 mmol of compound (1-c), 0.52 mmol of compound (1-d) and A mixture of 0.13 mmol of compound (1-e) was reacted at 50 ° C. for 4 hours under a nitrogen atmosphere. Then, the compound (1
-G) 35 mmol was added and the mixture was refluxed for 4 hours. After cooling to room temperature, 150 ml of ethyl acetate was added, and the reaction solution was added with 0.5N.
It was washed with hydrochloric acid water, water and brine. After concentrating the organic layer, the compound (1-h) was purified to 83% by silica gel column chromatography (eluent: hexane).
It was obtained in a yield of.

Synthesis of compound (1-i)

[0048]

[Chemical 16]

28 mmol of the compound (1-h) and 35 mmol of potassium carbonate were reacted in 60 ml of methanol at room temperature for 6 hours. 60 ml of ethyl acetate was added and the reaction solution was filtered. After the filtrate was concentrated, the residue was purified by silica gel column chromatography (eluent: hexane) to obtain the compound (1-i) in a yield of 94%.

Synthesis of compound (1)

[0051]

[Chemical 17]

Compound (1-f) 4 mmol, compound (1
-I) 4 mmol, acetonitrile 20 ml, piperidine 16 mmol, compound (1-c) 0.024 mmol, compound (1-d) 0.032 mmol and compound (1-e) 0.12 mmol were mixed with nitrogen. Refluxed for 2 hours under atmosphere. After cooling to room temperature, hexane 50m
1, and the reaction solution was washed with 0.5 N hydrochloric acid water, water and saline. After concentrating the organic phase, silica gel column chromatography (eluent: hexane / methylene chloride = 20/1,
52% of compound (1) by purifying by volume ratio)
It was obtained in a yield of. The phase transition temperature was as follows. Here, C represents a crystalline phase, N represents a nematic phase, and Iso represents an isotropic phase. Numbers represent C to N, N to Iso phase transition temperatures.

C → 86.0 ° C. → N → 225.8 ° C. → Is
o

[Synthesis example 2] Synthesis of compound (2)

[0055]

[Chemical 18]

Compound (2) was synthesized by the same method as in Synthesis Example 1 according to the above synthesis route. The phase transition temperature was as follows.

[0057] C → 127.5 ° C. → N → 275.7 ° C. → Iso

[Synthesis Example 3] Synthesis of compound (17)

[0059]

[Chemical 19]

Compound (17) was synthesized by the same method as in Synthesis Example 1 according to the above synthetic route. The phase transition temperature was as follows.

[0061] C → 56.4 ° C. → N → 92.7 ° C. → Iso

[Structure of Optical Film] FIG. 1 is a schematic sectional view showing the basic structure of the optical film. In each of the optical films shown in FIG. 1, the polarization selective layer (12) is phase-separated into a discontinuous phase (13) and a continuous phase (14) on the transparent support (11). The discontinuous phase (13) is composed of an optically anisotropic compound having birefringence, and the two refractive indices n1 and n2 of the discontinuous phase depend on the properties of the optically anisotropic compound used or the degree of orientation in the discontinuous phase. different. In order for the optical film to function as a polarization-selective optical film, it is necessary that one of n1 and n2 has a value substantially equal to the refractive index of the continuous phase, that is, less than 0.05. The direction of n1 or n2 in which the refractive indices are substantially equal corresponds to the transmission axis of the polarization selection layer.

FIG. 2 is a schematic diagram showing the structure of the most basic liquid crystal display device. A general liquid crystal display device uses an edge light type backlight light source (2
1) is arranged, and is composed of a light guide plate (23) and a reflection plate (22) that sequentially emits light of the backlight from the back surface to the front surface. The optical film according to the present invention is also effective for a direct type backlight that does not use a light guide plate. Above the light source, there is a liquid crystal cell (26) sandwiched between two conventional light absorbing polarizing plates (24, 25) on both sides, which has an image display function. Since the light emitted from the light source is absorbed by at least 50% by the lower polarizing plate (24), theoretically, the light utilization efficiency of 50% or more cannot be obtained in this configuration.

FIG. 3 is a schematic view showing various structural examples of a liquid crystal display device using an optical film. FIG. 3A shows
It is a simple configuration example showing the effect of the optical film. The optical film (31) selectively transmits polarized light in the same direction as the transmission axis of the light-absorption type polarizing plate (24), and part of the polarized light orthogonal to the polarizing plate transmission axis is a polarization plane due to depolarization by forward scattering. Are used in the transmission axis direction, the utilization efficiency is improved, and part of the light is returned to the light source side by backscattering, depolarized by the light guide plate, reflected by the reflection plate, and returned to the optical film (31) again. Utilization improves the utilization efficiency.

FIG. 3B shows a constitutional example in which a light-scattering type polarizing plate using an optical film as a protective film of a polarizing plate is combined with a film having another function. The light emitted from the light source has an in-plane brightness uniformized by the scattering sheet (33), and the film (34) having a function of condensing the light in a predetermined direction prevents the observer from seeing it in an extremely oblique direction. The light of. Concentrate near the front to improve usage efficiency. On the contrary, in this film, light in a slightly oblique direction from the front, which may be seen by the user, is reduced, but it is appropriately diffused by the polarizing plate of the present invention, and the brightness is improved by the same principle as that of FIG. At the same time, a viewing angle distribution with natural brightness can be obtained. Further, in FIG. 3A, the light utilization efficiency is about 10 because there is reflection on the surface of the optical film (31) opposite to the polarization selection layer and the surface of the light absorption type polarizing plate.
%, But the use of this as a protective film for a polarizing plate eliminates this reflective surface, and this alone increases the light utilization efficiency by about 10%.

FIG. 3C is a structural example of a liquid crystal display device in which the function of improving the brightness of the optical film or the polarizing plate is further improved. By providing the antireflection layer (35) on the surface of the polarization selection layer directly or via another layer, the reflection on the surface can be reduced and the amount of light entering the polarization selection layer can be increased. Further, by using a λ / 4 plate (36) below the polarizing plate (32) as in the backscattering / polarization rotating type, the polarized light orthogonal to the transmission axis of the backscattered light scattering type polarizing plate is 2 By passing through the λ / 4 plate, the light-scattering type polarizing plate is rotated so that the transmission axis has a polarization plane, and the light utilization efficiency can be improved.

[Transparent Support] The light transmittance of the transparent support is preferably 80% or more. It is preferable that the transparent support has optical isotropy when viewed from the front. Therefore, the transparent support is preferably a material having a small intrinsic birefringence. As such a material, Zeonex,
Zeonor (manufactured by Nippon Zeon Co., Ltd.), ARTON (JSR
Commercially available products such as Fuji Tack (manufactured by Fuji Photo Film Co., Ltd.) and Fuji Tac (manufactured by Fuji Photo Film Co., Ltd.) can be used. Further, even for a material having a large intrinsic birefringence such as polycarbonate, polyester, polyarylate, polysulfone and polyethersulfone, the conditions such as solution casting and melt extrusion, and the stretching conditions in the longitudinal and transverse directions are appropriately set. Can be obtained. When a protective film for protecting the polarizing layer of the polarizing plate is used as the transparent support, triacetyl cellulose is particularly preferable. The thickness of the transparent support is preferably 10 to 500 μm, particularly preferably 40 to 200 μm.

An undercoat layer may be provided on the transparent support in order to impart adhesion to an adjacent layer. The material for forming such an undercoat layer is not particularly limited. For example, on triacetyl cellulose, gelatin, poly (meth) acrylate resin and its substitution product, styrene-
Butadiene resin or the like is used. Further, surface treatment such as chemical treatment, mechanical treatment, corona treatment and glow discharge treatment may be performed.

[Discontinuous Phase of Polarization Selective Layer] The discontinuous phase includes
Included are compounds of formula (I). The discontinuous phase is 2 to 95% by mass of the polarization selection layer, preferably 3 to 50% by mass.
It is contained in an amount of 3% by mass, more preferably 3 to 30% by mass. As the discontinuous phase, other optically anisotropic compound may be used together with the compound represented by the formula (I). As such an optically anisotropic compound, a rod-shaped liquid crystal is preferable, and azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted Examples include phenylpyrimidines, phenyldioxanes, tolans and alkenylcyclohexylbenzonitriles. Specific examples thereof include Quarterly Chemistry Review Volume 22, Liquid Crystal Chemistry (1994), Chapters 4, 7 and 11 of the Chemical Society of Japan, and Liquid Crystal Device Handbook, Chapter 142 of the Japan Society for the Promotion of Science. It is described in Chapter 3. From the viewpoint of obtaining excellent light scattering properties, the size of the discontinuous phase is preferably in the range of 0.01 to 10 μm as an average diameter of an approximate circle in which each region is approximated by a circle having substantially the same area, and Preferably 0.05-5.
It is in the range of 0 μm.

[Continuous Phase of Polarization Selection Layer] The optically isotropic compound contained in the continuous phase is not limited as long as it is optically isotropic in the polarization selection layer. Here, the optical isotropy refers to a birefringence of less than 0.05. That is, if the optically anisotropic compound is also isotropic in the polarization selection layer, it can be used as the optically isotropic compound. Among them, a polymer compound or a monomer that is polymerized by irradiation with heat or ionizing radiation is preferable because it can be used also as a binder for forming a layer. Also, since most of the liquid crystalline compounds used for the discontinuous phase are soluble in organic solvents, in order to obtain a phase-separated structure only by coating, a coating liquid in which liquid crystals are dispersed in an aqueous phase containing a water-soluble polymer compound. Should be used. In addition, since the use of water as the solvent has a small effect on the environment, a water-soluble polymer compound is particularly preferable. Further, from the viewpoint of dispersion stability and liquid crystal alignment during stretching, polyvinyl alcohol or modified polyvinyl alcohol is most preferable. It is preferable that the continuous phase is crosslinked, since it is preferable that the continuous phase is not affected by the external environment such as temperature and humidity.

The polymer compound may be water-soluble or organic solvent-soluble. Examples of water-soluble polymer compounds include gelatin, agarose, cellulose, polyvinyl alcohol and their derivatives, or polyacrylic acid,
Examples thereof include polygalacturonic acid, polyalginic acid and salts thereof. Examples of organic solvent-soluble polymer compounds include:
Cellulose ester (eg, triacetyl cellulose, diacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose), polyamide, polycarbonate, polyester (eg, polyethylene terephthalate, polyethylene naphthalate, poly-1,4-cyclohexanediene) Methylene terephthalate, polyethylene-1,2-diphenoxyethane-4,4′-dicarboxylate, polybutylene terephthalate), polystyrene (eg syndiotactic polystyrene), polyolefin (eg polypropylene, polyethylene, polymethylpentene), Polysulfone, polyether sulfone, polyarylate,
Included are polyetherimides, polymethylmethacrylates and polyetherketones.

Examples of the monomer polymerized by irradiation with heat or ionizing radiation include ethylenically unsaturated polymerizable group, isocyanate group, epoxy group, aziridine group, oxazoline group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, In addition to the methylol group and the active methylene group, compounds including vinyl sulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, metal alkoxide such as tetramethoxysilane and the like can be mentioned. Among them, a compound containing an ethylenically unsaturated polymerizable group is preferable because it can be easily polymerized by light, and a compound containing two or more ethylenically unsaturated polymerizable groups is particularly preferable from the viewpoint of reducing the influence of heat after polymerization. . Examples of the compound containing two or more ethylenically unsaturated polymerizable groups include esters of polyhydric alcohols and (meth) acrylic acid (eg, ethylene glycol di (meth) acrylate, 1,4-dichlorohexane diacrylate, Pentaerythritol tetra (meth) acrylate), pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) ) Acrylate, pentaerythritol hexa (meth) acrylate, 1,3,5-cyclohexanetriol triacrylate, polyurethane polyacrylate, polyester polyacrylate), vinylbenzene and its Derivatives (eg 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (eg divinyl sulfone), acrylamide (eg methylenebisacrylamide) and methacryl Examples include amides.

When a water-soluble polymer compound is used in the continuous phase, a surfactant may be added in order to reduce the dispersed particle size and impart dispersion stability. The surfactant is not particularly limited, and any of nonionic and ionic (anion, cation, betaine) can be used. As the nonionic surfactant, polyoxyethylene, polyoxypropylene, polyoxybutylene, polyglycidyl or sorbitan is a surfactant having a nonionic hydrophilic group, specifically, polyoxyethylene alkyl ether, poly Oxyethylene alkyl phenyl ether, polyoxyethylene-polyoxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, fatty acid diethanolamide, triethanolamine A fatty acid partial ester may be mentioned. The anionic surfactants are carboxylates, sulfates, sulfonates, and phosphoric acid ester salts, and representative ones are fatty acid salts, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, α-olefin sulfonate, dialkylsulfosuccinate, α
-Sulfonated fatty acid salt, N-methyl-N-oleyl taurine, petroleum sulfonate, alkyl sulfate, sulfated oil, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate,
Examples thereof include polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, and naphthalene sulfonate salt formaldehyde condensate. Examples of the cationic surfactants include amine salts, quaternary ammonium salts, pyridium salts, and the like. First to third fatty amine salts, quaternary ammonium salts (tetraalkyl ammonium salts,
Trialkylbenzylammonium salt, alkylpyridinium salt, alkylimidazolium salt and the like). Examples of the amphoteric surfactant include carboxybetaine and sulfobetaine, and N, N, N-trialkyl-N-carboxymethylammonium betaine, N, N, N-trialkyl-N-sulfoalkyleneammonium betaine and the like. Is mentioned.

These surfactants are described in Application of Surfactants (Koshobo, Takao Karime, published September 1, 1980). In the present invention, the preferred amount of the surfactant is not particularly limited as long as it is used, as long as the desired surfactant properties are obtained. The amount of these surfactants used is 0.001 g per 1 g of the discontinuous phase liquid crystal.
1 to 1 g is preferable. 0.01 to 0.1 g is particularly preferable.

The polarization selection layer is applied by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method or an extrusion coating method (US Pat. No. 2,681,294). Can be formed by. Two or more layers may be applied simultaneously. The simultaneous coating method is described in US Pat. Nos. 2,761,791 and 2,942,898.
Nos. 3508947 and 3526528 and Yuji Harasaki, Coating Engineering, page 253, Asakura Shoten (1973). The polarization selection layer preferably has a thickness of 1 to 100 μm, more preferably 10 to 70 μm.

The polarization selection layer may be applied to an endless support such as a band or a drum or a transparent support by the above-mentioned method, and then peeled off and stretched to be laminated on the transparent support. After being applied to the body, it may be stretched and used as it is, or laminated with another transparent support or transferred to another transparent support to be formed. From the viewpoint of productivity, the draw ratio is preferably 10.0 times or less,
It is more preferably 5.0 times or less. Further, from the viewpoint of the stretching effect, the stretching ratio is preferably 1.01 times or more.

In order to facilitate the stretching process, a compound which lowers the glass transition temperature of the continuous phase compound may be added. The compound that lowers the glass transition temperature of the continuous phase compound is not particularly limited, and examples thereof include dibutyl phthalate, triphenyl phosphate, and glycerin. Glycerin is particularly preferable when a water-soluble polymer compound is used in the continuous phase.

The refractive index (n1) in the axial direction including the polarization plane of the polarized light having the maximum total light transmittance of the polarization selection layer of the discontinuous phase and the axial direction including the polarization plane of the polarized light having the minimum total light transmittance. Birefringence (| n1-, which is the absolute value of the difference from the refractive index (n2) of
n2 |) is preferably 0.05 to 1.0, more preferably 0.10 to 1.0,
Most preferably, it is 0.15 to 1.0. The continuous phase may have a birefringence of less than 0.05, and as a refractive index, a difference from either n1 or n2 of the optically anisotropic compound is less than 0.05, preferably less than 0.01, more preferably It may be less than 0.001. When the relationship between the refractive index of the continuous phase and the refractive index of the discontinuous phase satisfies the above relationship, the optical film functions as a polarization-selective optical film. A value in which the refractive indices of the continuous phase and the discontinuous phase are substantially equal to each other, that is, the direction in which the refractive index is less than 0.05 corresponds to the transmission axis of the polarization selection layer.

[Polarizing Plate] A light-scattering polarizing plate using a polarization-selective optical film is generally used by laminating it with a light-absorbing polarizing plate. The light-scattering type polarizing plate and the light absorbing type polarizing plate are laminated so that their transmission axes are substantially parallel to each other. And the polarization selective layer of the polarizing plate is arranged toward the backlight side. In addition, a metal reflector is arranged on the back surface of the backlight.

An antireflection layer can be provided on the surface of the light-scattering type polarizing plate on the side of the polarization selection layer. The antireflective layer reduces surface reflections, which can result in increased display brightness. This antireflection layer is described, for example, in the Journal of the Photographic Society of Japan, Vol. 137 (1966), a laminate of a low refractive index layer and a high refractive index layer may be used, or a single low refractive index layer may be provided.

It is preferable to dispose a λ / 4 plate between the laminate of the light scattering type polarizing plate and the light absorbing type polarizing plate and the backlight. Here, the transmission axis of the light scattering polarizing plate and the light absorbing polarizing plate and the slow axis of the λ / 4 plate are substantially 4
By arranging so as to be 5 °, it is possible to increase the light utilization efficiency in the backscattering and polarization rotation type.

[Liquid Crystal Display Device] By using a polarization-selective optical film or a light-scattering type polarizing plate in a liquid crystal display device, the utilization efficiency of light is increased, and as a result, the brightness of the display is increased. In order to increase the brightness, the transmittance Tmax at the polarization plane where the total light transmittance is maximum is 7
5% or more, the minimum transmittance Tmin on the plane of polarization is 60
% Or less, Tmax of 80% or more,
Tmin is more preferably 50% or less, and Tm
It is particularly preferable that ax is 85% or more and Tmin is 40% or less.

The polarization-selective optical film is a liquid crystal display including a pair of substrates having transparent electrodes and pixel electrodes, a liquid crystal cell in which a liquid crystalline compound is sealed between the substrates, and a pair of polarizing plates arranged outside the liquid crystal cell. In the device, the liquid crystal cell can be used by adhering it to the surface of the polarizing plate on the backlight side using an adhesive or the like. The light-scattering type polarizing plate is a liquid crystal display device including a pair of substrates having a transparent electrode and a pixel electrode, a liquid crystal cell in which a liquid crystalline compound is sealed between the substrates, and a pair of polarizing plates arranged outside the liquid crystal cell. It can be used as a polarizing plate on the backlight side of the liquid crystal cell and can be used by arranging the polarization selective layer facing the backlight side. Further, the polarization-selective optical film or the light-scattering type polarizing plate is disclosed in Japanese Patent Application Laid-Open No. 2-160204 and Tokubo 2587.
It can also be used in combination with a viewing angle compensation film as described in Japanese Patent No. 398.

[0084]

EXAMPLES [Example 1] Coating liquids A to F for polarization selection layer and a coating liquid R-1 for comparison were prepared as follows. (Preparation of Coating Liquid A for Polarization Selective Layer) 48 g of Compound (1) was dissolved in 150 g of ethyl acetate and filtered through a polypropylene filter having a pore size of 30 μm to prepare a polymerizable liquid crystal solution O-1 liquid for discontinuous phase. . On the other hand, polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.) 20 mass% aqueous solution 2
To 000 g, 4.0 g of sodium dodecylbenzenesulfonate as a surfactant was added and dissolved, and then the pore size was 30 μm.
Was filtered through a polypropylene filter to prepare a continuous-phase aqueous solution W-1 liquid. O-1 liquid 40g and W-1 liquid 2
A liquid in which 00 g was mixed was dispersed by ultrasonic dispersion to prepare a coating liquid A for a polarization selection layer.

(Preparation of Coating Liquid B for Polarization Selective Layer) 48 g of the compound (2) was dissolved in 150 g of ethyl acetate to give a pore size of 30.
The mixture was filtered through a polypropylene filter of μm to prepare a polymerizable liquid crystal solution O-2 liquid for discontinuous phase. O-2 liquid 40
g and the liquid W-1 (200 g) were ultrasonically dispersed to prepare a coating liquid B for the polarization selection layer.

(Preparation of Coating Liquid C for Polarization Selective Layer) 48 g of Compound (16) was dissolved in 150 g of ethyl acetate to give a pore size of 3
The mixture was filtered through a 0 μm polypropylene filter to prepare a polymerizable liquid crystal solution O-3 liquid for discontinuous phase. O-3 liquid 4
A liquid in which 0 g and 200 g of the W-1 liquid were mixed was ultrasonically dispersed to prepare a coating liquid C for the polarization selection layer.

(Preparation of Coating Liquid D for Polarization Selective Layer) 48 g of Compound (17) was dissolved in 150 g of ethyl acetate to give a pore size of 3
The mixture was filtered through a 0 μm polypropylene filter to prepare a polymerizable liquid crystal solution O-4 liquid for discontinuous phase. O-4 liquid 4
A liquid obtained by mixing 0 g and 200 g of the W-1 liquid was dispersed by ultrasonic dispersion to prepare a coating liquid D for the polarization selection layer.

(Preparation of Coating Liquid E for Polarization Selective Layer) 48 g of Compound (20), 1.0 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.), photopolymerization Initiator (Irgacure 907, manufactured by Ciba Geigy)
1.0g dissolved in 150g ethyl acetate, pore size 30μm
The mixture was filtered through a polypropylene filter to prepare a polymerizable liquid crystal solution O-5 liquid for discontinuous phase. A liquid obtained by mixing 40 g of the O-5 liquid and 200 g of the W-1 liquid was ultrasonically dispersed to prepare a coating liquid E for the polarization selection layer.

(Preparation of Coating Liquid F for Polarization Selective Layer) 48 g of Exemplified Compound (22), 1.0 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.), light Polymerization initiator (Irgacure 907, manufactured by Ciba Geigy)
1.0g dissolved in 150g ethyl acetate, pore size 30μm
The mixture was filtered through a polypropylene filter to prepare a polymerizable liquid crystal solution O-6 liquid for discontinuous phase. A liquid prepared by mixing 40 g of the O-6 liquid and 200 g of the W-1 liquid was dispersed by ultrasonic dispersion to prepare a coating liquid F for the polarization selection layer.

(Preparation of Coating Solution R-1 for Comparative Polarization Selective Layer) 4'-Pentyl-4-biphenylcarbonitrile 4
8 g was dissolved in 150 g of ethyl acetate and filtered through a polypropylene filter having a pore size of 30 μm to prepare a liquid crystal solution for discontinuous phase RO-1 liquid. RO-1 liquid 40 g and the W
The liquid in which 200 g of the liquid-1 was mixed was dispersed by ultrasonic dispersion to prepare a coating liquid R-1 for the polarization selection layer. An optical film was prepared by using these polarization selective layer coating solutions.

(Preparation of Optical Film P-1) The coating solution F for polarizing layer is applied onto a polyethylene terephthalate film (PET) having a thickness of 6 μm by using a die and dried so that the polarizing layer has a thickness of 100 μm. did. PET polarizing layer
Then, the film was peeled off and stretched 2.5 times at 80 ° C./50% RH to prepare an optical film P-1.

(Preparation of Optical Films P-2 to P-4) Using Coating Liquids B to D for Polarizing Layer, the optical films P-2 (Coating Liquid B) and P-3 were prepared in the same manner as in P-1. (Coating liquid C),
P-4 (Coating liquid D) was prepared.

(Preparation of Optical Film P-5) The coating solution E for the polarizing layer was applied onto a polyethylene terephthalate film (PET) having a thickness of 6 μm using a die and dried to make the thickness of the polarizing layer 100 μm. did. PET polarizing layer
Peeled off and stretched 2.5 times at 80 ° C / 50% RH,
After aging at 120 ° C for 2 minutes, 160 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.,
(Wavelength range 200 to 500 nm, maximum wavelength 365 nm), illuminance 200 mW / cm2, irradiation amount 400 mJ /
The discontinuous phase was cured by irradiating with an ultraviolet ray of cm 2 to prepare an optical film P-5.

(Preparation of Optical Film P-6) Using Coating Solution F for Polarizing Layer, Optical Film P was prepared in the same manner as in P-5.
-6 (Coating liquid F) was prepared.

(Preparation of Optical Film R-1) An optical film R-1 was prepared in the same manner as in P-6 using the polarizing layer coating liquid R-1.

(Evaluation of Polarization Selective Optical Film) 1. Birefringence of the birefringent continuous phase is MD and T for films drawn at the same draw ratio for films that do not contain a discontinuous phase.
The refractive index in the D direction was measured with an Abbe refractometer.

2. Light transmittance and light scattering (haze) The light transmittance and light scattering (haze) of the obtained film were measured using a haze meter MODEL 1001DP (Nippon Denshoku Industries Co., Ltd.). The measurement is performed by inserting a polarizer between the light source and the film, and the transmittances of all light rays are defined as those in which the transmission axis of the polarizer and the transmission axis of the polarization selection layer are the same, and those orthogonal are orthogonal. The transmittance was evaluated using the haze as an index for the light scattering property. In the case of polarization selectivity, the parallel one has lower transmittance and higher haze than the orthogonal one.

3. Discontinuous phase particle size The discontinuous phase particle size of the obtained polarization-selective layer of the film was cut by a scanning electron microscope at a cross section of 50.
From the photograph observed at 00 times, 100 discontinuous phases were arbitrarily extracted and converted into equivalent circle radii for measurement.

The evaluation results are shown in Table 1. P-1 of the present invention
The transmittances of P6 to P-6 were 46% or less in the parallel direction and 91% or more in the orthogonal direction, showing high polarization selectivity with respect to the comparative sample R-1. Thus, the usefulness of the liquid crystal of the present invention was clear. Further, the optical film (P-
5), (P-6) under high humidity of 40 ℃, 80% RH 3
When stored for a day, the polarization selectivity did not change at all. This is because the alignment fixation using the polymerizable liquid crystal is sufficiently occurring. On the other hand, (P-1) to (P-
4) and the comparative sample (R-1) show a marked deterioration in the polarization selectivity, and there is no polymerizable group in the liquid crystal molecule, so that immobilization cannot be achieved.

[0100]

[Table 1] Table 1 ──────────────────────────────────── Optical total light transmittance Haze no Film of continuous phase Birefringence Parallel Parallel Cross Parallel Parallel Particle size (μm) ─────────────────────────────────── -P-1 <0.01 44.1 93.4 88.4 12.9 0.28 P-2 <0.01 44.3 93.3 88.3 13.2 0.29 P-3 <0 .01 45.1 92.6 87.6 13.7 0.31 P-4 <0.01 44.8 93.1 88.0 13.1 0.32 P-5 <0.01 44.7 92 .9 88.1 13.2 0.26 P-6 <0.01 44.9 93.1 88.0 13.3 0.31 R-1 <0.01 49.9 90.1 81.9 18 .3 0.28 ── ───────────────────────────────────

[Example 2] A protective film on one side of a commercially available iodine-based polarizing plate was adhered to a polarizing layer containing iodine so that the saponified triacetylcellulose surface without a polarization selection layer was laminated. The light-scattering polarizing plate of Example 2 was prepared by replacing the optical film P-5.

Example 3 The coating solution A for polarizing layer was cast on a band using a die and dried to a thickness of 40 μm. Peel this film off the band and dry 25
It was stretched 2.5 times at ° C. Then, it is laminated only by pressure bonding with a polyvinyl alcohol film which has already been stretched 6 times and which has adsorbed iodine.
It was immersed in an aqueous solution of g / l at 70 ° C. for 5 minutes, further washed with water in a water-washed layer at 20 ° C. for 10 seconds, further dried at 80 ° C. for 5 minutes, and saponified as it was. Polyvinyl alcohol (PVA117, Kuraray Co., Ltd.) 5% by mass aqueous solution was used as a paste and laminated on both sides. 1 of this film
It dried at 20 degreeC and created the light-scattering polarizing plate of Example 3.

When the light-scattering polarizing plate of Examples 2 and 3 and the ordinary polarizing plate were placed on a reflecting plate made of aluminum with the polarization selection layer facing the reflecting plate, the light-scattering polarizing plate was found to be better. The reflector looked bright. This is because the external light is reflected by the reflection plate, the reflected light transmits only the polarization of the transmission axis in the polarization selection layer, and the backscattered light is reflected again by the reflection plate and reaches the polarization selection layer. Has been raised. In addition, these light-scattering polarizing plates are placed at 40 ° C. and 8
When stored for 3 days under high humidity of 0% RH, there was no change in the brightness increasing effect. This indicates that alignment can be fixed by boric acid crosslinking even if the liquid crystal has no polymerizable group.

[Examples 4, 5 and Comparative Example 1] Using the optical film P-5 of Example 1, a liquid crystal display device of Example 4 was prepared as shown in FIG. Further, using the light-scattering polarizing plate of Example 3, a liquid crystal display device of Example 5 was prepared as shown in FIG. A commercially available brightness enhancement film (DBEF, manufactured by 3M) having a polarization selection layer due to optical interference was used as the polarization selection optical film in FIG. 3 to prepare a liquid crystal display device of Comparative Example 1. As a result, the one using the optical film of the present invention showed a large increase in luminance when viewed obliquely as compared with the one of Comparative Example 1, and the usefulness of the present invention was clear.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an optical film.

FIG. 2 is a schematic cross-sectional view showing a basic liquid crystal display device.

FIG. 3 is a schematic view showing various structural examples of a liquid crystal display device using an optical film.

[Explanation of symbols]

11 Transparent support 12 Polarization selection layer 13 continuous phase 14 Discontinuous phase 21 Backlight light source 22 Reflector 23 Light guide plate 24 Lower side light absorption type polarizing plate 25 Upper light absorption type polarizing plate 26 Liquid crystal cell 31 Polarization Selective Optical Film 32 light scattering type polarizing plate 33 Scattering sheet 34 Light-collecting film 35 Antireflection Layer 36 λ / 4 plate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 G02F 1/1335 510 510 1/13357 1/13357 F term (reference) 2H049 BA03 BA05 BA07 BA43 BA44 BB03 BB42 BC03 BC05 BC22 2H091 FA08X FA08Z FA11X FA11Z LA30 4F071 AA14 AA22 AA29 AA32 AA33 AA43 AA60 AA62 AA64.

Claims (12)

[Claims] 1. An optical film comprising a transparent support and a polarization selection layer which selectively transmits predetermined polarized light and selectively reflects or scatters other polarized light. An optical film containing a compound represented by the following formula (I): (I) R ^1- {L ^1- (Ar ¹ ) _l } _s -C≡C- (A
r ² ) _m- C≡C- (Ar ³ ) _n- C≡C-{(A
r ⁴ ) _p −L ² } _t −R ² [wherein, R ¹ and R ² are each independently an alkyl group or an aromatic group; L ¹ and L ² are each independently —C≡ C- or -CR ³ = CR ⁴ - and a, R ³ and R ⁴ are each independently hydrogen atom or an alkyl ^{group; Ar 1, Ar 2, Ar} 3 and a
r ⁴ is each independently a divalent aromatic group;
m, n and p are each independently 1, 2 or 3; and s and t are each independently 0 or 1. 2. The optical film according to claim 1, wherein the polarization selection layer comprises an optically isotropic phase and an optically anisotropic phase. 3. The optical film according to claim 2, wherein the optically anisotropic phase contains a compound represented by formula (1). 4. The optical film according to claim 1, which has a maximum total light transmittance of 75% or more and a minimum total light transmittance of less than 60% in a plane of polarization perpendicular to the film surface. 5. The minimum refractive index difference between the optically isotropic phase and the optically anisotropic phase in the in-plane direction of the film is 0.05.
The optical film according to claim 2, which is less than 3. 6. The optical film according to claim 1, wherein the compound represented by the formula (I) has a polymerizable group. 7. An optically isotropic phase or an optically anisotropic phase is a discontinuous phase, and the discontinuous phase has an approximate circular average particle diameter of 0.01 to 10.0 μm. The optical film described in 2. 8. The optical film according to claim 2, wherein the optically isotropic phase is a continuous phase and the optically anisotropic phase is a discontinuous phase. 9. The optical film according to claim 1, wherein the polarization selection layer is formed by stretching at 10.0 times or less. 10. A light-scattering polarization selection element having the polarization selection layer according to claim 1, and selectively transmitting a predetermined polarization,
A polarizing plate in which a light absorption type polarization selection element having a polarization selection layer that selectively absorbs other polarized light is laminated, wherein the polarization selection layer of the light scattering type polarization selection element is an optically isotropic phase. In the polarization plane perpendicular to the film surface of the light scattering type polarization selection element, which has an optically anisotropic phase, the maximum total light transmittance is 75% or more and the minimum total light transmittance is less than 60%. A polarizing plate, wherein an axis having a polarization plane that maximizes the total light transmittance and a transmission axis of the light absorption type polarization selection element are substantially parallel to each other. 11. A liquid crystal display device comprising a pair of substrates each having a transparent electrode and a pixel electrode, a liquid crystal cell in which a liquid crystalline compound is sealed between the substrates, and a pair of polarizing plates arranged outside the liquid crystal cell. A liquid crystal display device comprising the optical film according to claim 1 disposed between a backlight side polarizing plate of a cell and the backlight. 12. A polarization selection device according to claim 1, wherein the polarizing plate between the backlight and the liquid crystal cell is a liquid crystal display device in which a backlight, a polarizing plate, a liquid crystal cell, and a polarizing plate are laminated in this order. A light-scattering polarization selection element having a layer,
A polarizing plate in which a light absorption type polarization selection element having a polarization selection layer that selectively transmits a predetermined polarized light and selectively absorbs another polarized light is laminated, and a polarization selection of a light scattering type polarization selection element. The layer consists of an optically isotropic phase and an optically anisotropic phase,
In the polarization plane perpendicular to the film plane of the light scattering polarization selection element, the maximum total light transmittance is 75% or more, the minimum total light transmittance is less than 60%, and the maximum light transmittance is maximum. A liquid crystal display device, wherein an axis having a polarization plane to be and a transmission axis of the light absorption type polarization selection element are substantially parallel to each other.