JP2006072272A - Method for manufacturing scattering polarizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scattering polarizer manufacturing method capable of efficiently and surely obtaining a scattering polarizer which is satisfactorily improved in terms of the angle dependency of transmitted light intensity, and which has a performance equivalent to that of a standard straight line polarizer. <P>SOLUTION: The scattering polarizer manufacturing method comprises a step of applying liquid solution containing mesomorphic polymer which has a nematic phase in a liquid crystal state, and also, which becomes in a vitreous state at a temperature equal to or below a glass transition point, and amorphous polymer on a substrate having an orientation control force, a step of orientating the mesomorphic polymer in a prescribed direction by the orientation control force of the substrate at a temperature where the mesomorphic polymer is made in the liquid crystal state, a step of applying a magnetic field on the mesomorphic polymer and still more orientating the mesomorphic polymer in the prescribed direction, and a step of cooling the mesomorphic polymer orientated in the prescribed direction so that the orientated state may be maintained, and making the polymer in the vitreous state, then, obtaining the scattering polarizer constituted of the mesomorphic polymer and the amorphous polymer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a scattering-type polarizing plate that can be used in a liquid crystal display device or the like.

  Liquid crystalline polymers exhibit various liquid crystal phases based on their unique alignment structures, and these liquid crystal structures can be fixed, so that optical recording elements, nonlinear optical materials, liquid crystal alignment films, optical fibers, and optical elements for liquid crystal display elements Active researches are being made in various functional material fields such as. Since such liquid crystalline polymers exhibit various orientations, the materials obtained by fixing these molecular orientations exhibit various optical properties such as refractive index and birefringence, and the phase of light. Since the polarization state and the like can be controlled, a wide range of applications are considered as optical materials.

  Among such optical materials, there are polarizing plates such as linearly polarizing plates, circularly polarizing plates, and elliptically polarizing plates as useful optical materials for widening the viewing angle in liquid crystal display devices and the like. As a material capable of improving the light utilization efficiency as compared with the above, a scattering-type polarizing plate has attracted attention.

  Under such circumstances, for example, in Japanese Patent Laid-Open No. 64-77001 (Patent Document 1), a blind layer structure having different refractive indexes is formed by phase separation, and a diffraction phenomenon caused by this layer structure is described. An anisotropic scattering element in which the anisotropy of light scattering is expressed by causing it to be disclosed is disclosed. However, this anisotropic scattering element has a practical problem that the anisotropic control of scattering is complicated and the thickness becomes large.

  Japanese Patent Application Laid-Open No. 11-29772 (Patent Document 2) discloses an anisotropic scattering element in which isotropic particles are dispersed in an anisotropic transparent medium. However, even in this anisotropic scattering element, control of the scattering direction is limited, and optical compensation is not sufficient.

Furthermore, JP-A-2004-70345 (Patent Document 3) discloses an anisotropic light scattering layer in which a second region having birefringence characteristics different from that of the first region is dispersed in the translucent first region. An anisotropic scattering element including a specific birefringent layer is disclosed. However, the anisotropic light scattering layer described in Patent Document 3 is substantially manufactured by stretching a polymer film, and even with such an anisotropic light scattering layer, there is a limit in improving the angle dependency of transmitted light intensity. It was extremely difficult to obtain performance as a polarizing plate equivalent to a standard linear polarizing plate.
JP-A 64-77001 JP 11-29772 A JP 2004-70345 A

  The present invention has been made in view of the above-mentioned problems of the prior art. The scattering-type polarizing plate has sufficiently improved angle dependency of transmitted light intensity and has performance as a polarizing plate equivalent to a standard linear polarizing plate. It is an object of the present invention to provide a method for producing a scattering-type polarizing plate capable of efficiently and reliably obtaining the above.

  As a result of intensive studies to achieve the above object, the present inventors have applied a solution containing a liquid crystalline polymer and an amorphous polymer on a substrate having an alignment regulating force, and then aligned the solution. The inventors have found that the above-mentioned object can be achieved by applying a magnetic field and further aligning, and have completed the present invention.

That is, the method for producing the scattering-type polarizing plate of the present invention includes:
A step of applying a solution containing a liquid crystalline polymer having a nematic phase in a liquid crystal state and becoming a glass state at a temperature below the glass transition point and a non-quality polymer onto a substrate having alignment control ability When,
Aligning the liquid crystalline polymer in a predetermined direction by the alignment regulating force of the substrate at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state;
Applying a magnetic field to the liquid crystalline polymer at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state, and further aligning the liquid crystalline polymer in the predetermined direction;
The liquid crystalline polymer aligned in the predetermined direction is cooled to be in a glass state so that the alignment state is maintained, and a scattering type polarizing plate composed of the liquid crystalline polymer and the amorphous polymer is obtained. Process,
It is the method characterized by including.

  In the method for producing a scattering type polarizing plate of the present invention, it is preferable to apply a magnetic field of 0.1 to 10 Tesla to the liquid crystalline polymer.

  In addition, while applying a magnetic field to the liquid crystalline polymer oriented in the predetermined direction, the glassy state is gradually cooled at a cooling rate of 0.1 to 10 ° C./min so as to maintain the orientation state. Is preferred.

  Further, the liquid crystalline polymer used in the present invention is preferably a main chain polyester liquid crystalline polymer, and the amorphous polymer used in the present invention is preferably a styrene random copolymer.

  According to the present invention, it is possible to efficiently and surely obtain a scattering-type polarizing plate that has sufficiently improved angle dependency of transmitted light intensity and has a performance as a polarizing plate equivalent to a standard linear polarizing plate. It becomes possible to provide the manufacturing method of a type polarizing plate.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

That is, the method for producing the scattering-type polarizing plate of the present invention includes:
A step of applying a solution containing a liquid crystalline polymer having a nematic phase in a liquid crystal state and becoming a glass state at a temperature below the glass transition point and an amorphous polymer on a substrate having an alignment regulating force. When,
Aligning the liquid crystalline polymer in a predetermined direction by the alignment regulating force of the substrate at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state;
Applying a magnetic field to the liquid crystalline polymer at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state, and further aligning the liquid crystalline polymer in the predetermined direction;
The liquid crystalline polymer aligned in the predetermined direction is cooled to be in a glass state so that the alignment state is maintained, and a scattering type polarizing plate composed of the liquid crystalline polymer and the amorphous polymer is obtained. Process,
It is the method characterized by including.

  The liquid crystalline polymer used in the present invention is not particularly limited as long as it has a nematic phase in a liquid crystal state and becomes a glass state at a temperature below the glass transition point. For example, polyester, polyamide, polycarbonate, Examples include main chain type liquid crystalline polymers such as polyesterimide, and side chain type liquid crystalline polymers such as polyacrylate, polymethacrylate, polymalonate, and polysiloxane. Among these, from the viewpoints of the refractive index, ease of synthesis, transparency, orientation, glass transition point, and the like, a main chain polyester liquid crystalline polymer is preferable.

  The structural unit of such a main-chain polyester-based liquid crystalline polymer is not particularly limited, but preferred examples include (a) units derived from dicarboxylic acids (hereinafter referred to as dicarboxylic acid units), ( b) units derived from diols (hereinafter referred to as diol units), (c) units derived from oxycarboxylic acids having a carboxyl group and a hydroxyl group simultaneously in one unit (hereinafter referred to as oxycarboxylic acid units). ) And the like. Such polyester structures include (a) + (b) type, (a) + (b) + (c) type, and (c) single type.

  Examples of the dicarboxylic acid unit (a) include the following.

(X is hydrogen, halogen (chlorine, bromine), C1-C4 alkyl group (methyl group, ethyl group, propyl group, isopropyl group, butyl group, t-butyl group, etc.), alkoxy group (methoxy group, Ethoxy group, prepoxy group, butoxy group and the like) or phenyl group, k is an integer of 0 to 2, and so on.

(* Indicates optically active carbon. The same applies hereinafter)
Moreover, as a diol unit of (b), the following are mentioned, for example.

  Furthermore, examples of the oxycarboxylic acid unit (c) include the following.

  The liquid crystalline polymer used in the present invention has a nematic phase in the liquid crystal state and is in a glass state at a temperature below the glass transition point. Therefore, when such an alignment structure of a liquid crystalline polymer is fixed, the polymer molecules are once aligned at a liquid crystal temperature and then cooled for fixing. In the case of a liquid crystalline polymer having a crystal phase, There is a possibility that the alignment state once obtained is destroyed. Therefore, it is preferable that the liquid crystalline polymer used in the present invention further includes a structural unit that suppresses crystallization, and in the case of a main-chain type polyester liquid crystalline polymer, further includes an ortho-substituted aromatic unit. It is preferable. The ortho-substituted aromatic unit here means a structural unit in which the bonds forming the main chain are ortho to each other. Specific examples of such ortho-substituted aromatic units include catechol units, salicylic acid units, phthalic acid units, and those having a substituent on the benzene ring of these groups, such as the following:

And the like are preferable, and among these, the following are particularly preferable.

  Furthermore, the liquid crystalline polymer used in the present invention may be an aromatic unit having a bulky substituent as shown below, or an aromatic unit having a fluorine or fluorine-containing substituent, instead of the above ortho-substituted aromatic unit. It may be included as a constituent component. By including such an aromatic unit, the obtained liquid crystalline polymer tends to be homeotropic. Examples of the aromatic unit having such a bulky substituent include the following.

(R represents an alkyl group having 3 to 12 carbon atoms, iPr represents isopropyl, and tBu represents tertiary butyl.)
Moreover, as an aromatic unit which has a fluorine or a fluorine-containing substituent, the following are mentioned, for example.

  The following liquid crystal polymers can be specifically exemplified as representative examples of the main-chain polyester liquid crystal polymer suitable for the present invention described above.

(Wherein, k, l and m are simply composition ratios (moles), k = 1 + m, 1 / m = 80/20 to 20/80, preferably 75 / 25-25 / 75)

(Wherein, k, l and m are simply composition ratios (moles), k = 1 + m, 1 / m = 80/20 to 20/80, preferably 75 / 25-25 / 75)

(Wherein, k, l and m are simply composition ratios (moles), k = 1 + m, 1 / m = 80/20 to 20/80, preferably 75 / 25-25 / 75)

(Wherein, k, l, m, n are simply composition ratios (moles), k = 1 + m + n, 1 / m = 80/20 to 20/80, preferably 75 / 25-25 / 75, l / n = 80 / 20-20 / 80, preferably 75 / 25-25 / 75)

(Wherein, k, l, m, and n are simply composition ratios (moles), k + 1 = m + n, k / 1 = 80/20 to 20/80, preferably 75 / 25-25 / 75, m / n = 80 / 20-20 / 80, preferably 75 / 25-25 / 75)

(Wherein, k, l and m are simply composition ratios (moles), k = 1 + m, 1 / m = 80/20 to 20/80, preferably 75 / 25-25 / 75)

(Wherein, k, l and m simply represent the composition ratio (mole), k / l = 80/20 to 20/80, preferably 75/25 to 25 / 75, l / m = 80/20 to 20/80, preferably 75/25 to 25/75)

(Wherein, k, l, m, and n are simply composition ratios (moles), k + 1 = m + n, k / 1 = 80/20 to 20/80, preferably 75 / 25-25 / 75, m / n = 80 / 20-20 / 80, preferably 75 / 25-25 / 75, p is 2-12)

(Wherein, k, l and m are simply composition ratios (moles), k + 1 = m, k / l = 80/20 to 20/80, preferably 75 / 25-25 / 75, p is 2-12).

  The molecular weight of the liquid crystalline polymer used in the present invention is not particularly limited, but the logarithmic viscosity measured at 30 ° C. in various solvents, for example, a mixed solvent of phenol / tetrachloroethane (60/40 (weight ratio)). Is preferably about 0.05 to 3.0, and more preferably about 0.07 to 2.0. When the logarithmic viscosity is less than 0.05, the strength of the obtained liquid crystalline polymer tends to be weak. There is a tendency that problems such as an increase in time required for orientation occur.

  In addition, the glass transition point of the liquid crystalline polymer used in the present invention is not particularly limited, but it generally affects the stability of the orientation after fixing the orientation, so that the glass transition point is generally 0 ° C. or higher. It is preferable that it is 20 degreeC or more.

  In addition, the method for synthesizing the liquid crystalline polymer used in the present invention is not particularly limited, and it is synthesized by a polymerization method known in the art, for example, a melt polymerization method or an acid chloride method using a corresponding acid chloride of a dicarboxylic acid. Is done. When synthesized by the melt polymerization method, for example, the acetylated product of the corresponding dicarboxylic acid and the corresponding diol can be produced by polymerization under high temperature and high vacuum, and the molecular weight can be controlled by controlling the polymerization time or the charged composition. A liquid crystalline polymer can be obtained. In order to accelerate the polymerization reaction, a conventionally known metal salt such as sodium acetate can also be used. Furthermore, when using the solution polymerization method, a predetermined amount of dicarboxylic acid dichloride and diol are dissolved in a solvent, and heated in the presence of an acid acceptor such as pyridine or N-methylimidazole, thereby increasing the target liquid crystallinity. A molecule can be obtained.

  The main chain polyester liquid crystalline polymer has a difference between the refractive index in the major axis direction (n //) and the refractive index in the minor axis direction (n⊥) when the refractive index ellipsoid is considered. In this respect, the main chain polyester liquid crystalline polymer is preferable.

  In the present invention, a solution containing the liquid crystalline polymer and the amorphous polymer is obtained. The amorphous polymer used in the present invention is not particularly limited. For example, styrene-based polymers such as polystyrene, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer; carbonate-based polymers such as polycarbonate Molecule: Polyolefin having norbornene structure; Acrylic polymer such as polymethyl methacrylate; Imide polymer; Polyethersulfone polymer; Polyphenylene sulfide polymer; Vinyl alcohol polymer; Vinyl butyrate polymer; A polymer based on polyoxymethylene; or a mixture thereof.

  Such an amorphous polymer is preferably one that forms a uniform phase separation structure with the liquid crystalline polymer, and the main chain polyester liquid crystalline polymer is used as the liquid crystalline polymer. In the case, a styrene random copolymer is more preferable. Such a styrenic random copolymer according to the present invention includes a styrene monomer and at least one monomer selected from the group consisting of acrylonitrile, maleic anhydride, methyl methacrylate, butadiene, acrylic acid, ethylene, and propylene. Of these, a random copolymer of a styrene monomer and an acrylonitrile monomer is particularly preferable from the viewpoint of forming a fine and uniform phase separation structure with a liquid crystalline polymer.

  In the present invention, an amorphous polymer having a refractive index relatively close to the refractive index (n⊥) in the minor axis direction or the refractive index (n //) in the major axis direction of the liquid crystalline polymer described above is used. Also in this respect, when using the above-mentioned main chain polyester liquid crystalline polymer, a styrene-acrylonitrile copolymer is preferable.

  In the present invention, when a styrene random copolymer is used as the amorphous polymer, the content of the styrene monomer is not particularly limited. However, in the case of a styrene-acrylonitrile copolymer, the styrene content is 25 to 90% by weight. (The acrylonitrile content is preferably 10 to 75% by weight), and the styrene content is particularly preferably 75 to 85% by weight (the acrylonitrile content is 15 to 25% by weight). When the content of styrene is less than the lower limit, it tends to be difficult to obtain a fine and uniform phase separation structure with the liquid crystalline polymer. It tends to be easily dissolved.

  Further, the blend ratio (weight basis) of the liquid crystalline polymer and the amorphous polymer used in the production method of the present invention is not particularly limited, but the former is a main chain polyester liquid crystalline polymer and the latter is styrene. -In the case of an acrylonitrile copolymer, the blend ratio (by weight) of a liquid crystalline polymer (hereinafter sometimes referred to as "LCP") and a styrene-acrylonitrile copolymer (hereinafter sometimes referred to as "SAN") is LCP / SAN = 9/1 to 1/9 is preferable, and LCP / SAN = 8/2 to 4/6 is more preferable. When the content of LCP is less than the lower limit, the polarization characteristics due to LCP tend to be sufficiently difficult to be obtained. On the other hand, when the content exceeds the upper limit, it is difficult to improve the angle dependency of transmitted light intensity. It is in.

  Whether or not the liquid crystalline polymer and the amorphous polymer form a fine and uniform phase separation structure can be confirmed by optical microscope observation, light scattering measurement, or the like.

  In the method for producing a scattering type polarizing plate of the present invention, first, a solution containing the liquid crystalline polymer and the amorphous polymer is prepared.

  The solvent used here may be any solvent that can dissolve the liquid crystalline polymer and the amorphous polymer, and is not particularly limited. Polar solvents such as hydrocarbons, mixed solvents of these and phenols, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, sulfolane, cyclohexane and the like can be used. The concentration of the solution is usually preferably in the range of 0.1 to 50% by weight and more preferably in the range of 5 to 20% by weight as the solid content concentration including the liquid crystalline polymer and the amorphous polymer.

  Next, in the method for producing a scattering-type polarizing plate of the present invention, after the solution is applied on a substrate having an orientation regulating force, the liquid crystalline polymer is subjected to the orientation regulating force of the substrate at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state. The liquid crystalline polymer is aligned in a predetermined direction. The step of applying the solution on the substrate and the step of aligning the liquid crystalline polymer by the alignment regulating force of the substrate may be performed in the same step, or the solution may be applied on the substrate and dried. After obtaining the film, it may be heated again to align the liquid crystalline polymer by the alignment regulating force of the substrate.

  Here, the method for applying the solution onto the substrate is not particularly limited, and for example, a spin coating method, a roll coating method, a gravure coating method, a curtain coating method, a slot coating method, a dip-up method, or the like may be appropriately employed. it can.

  In addition, the substrate having alignment regulating force used in the present invention is not particularly limited as long as it can align the liquid crystalline polymer in a predetermined direction. For example, a rubbing substrate is preferably used. As such a rubbing substrate, various conventionally known rubbing substrates can be used, and a glass substrate having a polyimide layer as having excellent orientation, heat resistance, solvent resistance, and peelability. And directly rubbed polyimide, polyetheretherketone, polyphenylene sulfide, polyethylene terephthalate film, and the like.

  Furthermore, in the method for producing a scattering type polarizing plate of the present invention, the liquid crystalline polymer is oriented in a predetermined direction at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state. The temperature at this time, that is, the temperature at which the liquid crystalline polymer exhibits a liquid crystal state differs depending on the characteristics of the liquid crystalline polymer used, but is above the glass transition point of the liquid crystalline polymer and isotropic phase-liquid crystal phase transition. Heat treatment is preferably performed at a temperature lower than the temperature. Such a temperature is generally preferably in the range of about 50 to 300 ° C, more preferably in the range of 100 to 250 ° C. In addition, the time required for such alignment treatment is not particularly limited, and varies depending on the composition of the liquid crystalline polymer, the molecular weight, etc., and cannot be generally stated, but when using a general rubbing substrate, it is about 10 seconds to 100 minutes. The range of about 30 seconds to 60 minutes is more preferable.

  Prior to the above alignment treatment, the solvent may be removed in advance from the solution applied on the substrate by performing a drying treatment as necessary. The temperature during the drying treatment is not particularly limited, but is preferably about the temperature between (the boiling point of the solvent minus 50 ° C.) and (the boiling point of the solvent).

  Next, in the method for producing a scattering type polarizing plate of the present invention, the liquid crystalline polymer subjected to the alignment treatment by the alignment regulating force of the substrate is set to a temperature at which it exhibits a liquid crystal state, and the liquid crystalline polymer is converted into the liquid crystalline polymer. A magnetic field is applied to further align the liquid crystalline polymer in the predetermined direction.

  The step of further aligning the liquid crystalline polymer with a magnetic field in this way is the same step as the step of applying the solution on the substrate and the step of aligning the liquid crystalline polymer with the alignment regulating force of the substrate, or It may be carried out in the same step as the step of aligning the liquid crystalline polymer by the orientation regulating force of the substrate, or after the liquid crystalline polymer is oriented by the orientation regulating force of the substrate and once cooled to the glass state, It may be heated again to apply a magnetic field to the liquid crystalline polymer for further alignment. From the viewpoint of improving the efficiency of the rubbing process, the step of aligning the liquid crystalline polymer by the alignment regulating force of the substrate and the step of further aligning by the magnetic field are performed in the same step, that is, the solution is applied onto the substrate. It is preferable that the orientation by the substrate and the orientation by the magnetic field proceed substantially simultaneously by applying heat treatment while applying a magnetic field after drying as necessary.

  Thus, the strength of the magnetic field applied in the step of further aligning the liquid crystalline polymer with a magnetic field is preferably 0.1 to 10 Tesla, and more preferably 1 to 5 Tesla. If the strength of the magnetic field is less than the above lower limit, the orientation of the liquid crystalline polymer by the magnetic field tends not to be sufficiently achieved. On the other hand, if the upper limit is exceeded, the amorphous polymer is aligned with the liquid crystalline polymer. Therefore, it is difficult to obtain a scattering type polarizing plate having good polarization characteristics.

  The temperature at which the liquid crystalline polymer is further aligned by a magnetic field is the same as the temperature in the step of aligning by the alignment regulating force of the substrate described above, and differs depending on the characteristics of the liquid crystalline polymer used. A temperature not lower than the glass transition point of the molecule and not higher than the isotropic phase-liquid crystal phase transition temperature is preferable. Such a temperature is generally preferably in the range of about 50 to 300 ° C, more preferably in the range of 100 to 250 ° C. Further, the time required for the alignment treatment by such a magnetic field is not particularly limited, and varies depending on the composition of the liquid crystalline polymer, the molecular weight, etc., and cannot be generally stated, but generally ranges from about 10 seconds to 100 minutes. The range of about 30 seconds to 60 minutes is more preferable.

  Next, in the method for producing a scattering type polarizing plate of the present invention, the liquid crystalline polymer subjected to the alignment treatment is cooled to a glass state so that the alignment state is maintained. That is, by cooling the liquid crystalline polymer in the alignment state to a temperature below its glass transition point, it can be fixed without impairing the alignment.

  Thus, the cooling rate at the time of cooling to a temperature below the glass transition point is not particularly limited, but it is preferable to gradually cool at a temperature lowering rate of 0.1 to 10 ° C./min. It is particularly preferable to cool slowly while applying a magnetic field of about Tesla. If the slow cooling rate is less than the lower limit, the slow cooling time tends to be unnecessarily long, and on the other hand, if the cooling is performed exceeding the upper limit, cracks and the like tend to occur in the obtained scattering type polarizing plate. It is in. In addition, by applying a magnetic field in the above slow cooling process, the orientation state in the slow cooling process is sufficiently prevented from being collapsed, and a scattering type polarizing plate in which the orientation state is maintained tends to be obtained more reliably. is there.

  By the method of the present invention described above, a scattering-type polarizing plate comprising the liquid crystalline polymer and the amorphous polymer and having the liquid crystalline polymer oriented in a predetermined direction can be obtained efficiently and reliably. It becomes like this.

  In the scattering-type polarizing plate obtained by the production method of the present invention, it is preferable that the liquid crystalline polymer and the amorphous polymer form a fine and uniform phase separation structure, and spinodal decomposition More preferably, a phase separation structure is formed.

  In addition, the directionality in which the liquid crystalline polymer is oriented is from the viewpoint of obtaining a scattering type polarizing plate that can be used in a liquid crystal display device or the like, from the orientation direction of the liquid crystalline polymer (the long axis direction of the polymer molecule). ) Is preferably homogeneous alignment substantially parallel to the substrate surface.

  Furthermore, the film thickness of the scattering-type polarizing plate of the present invention is not particularly limited, but is preferably in the range of about 1 to 100 μm, more preferably a so-called thick film range of about 20 to 100 μm. If the film thickness is smaller than the lower limit, the desired polarization effect by the scattering type polarizing plate tends not to be sufficiently obtained. On the other hand, if the film thickness exceeds the upper limit, the transmittance of polarized light itself is too low. There is a tendency.

  According to the manufacturing method of the present invention described above, a sufficient improvement in the angle dependency of the transmitted light intensity in the obtained scattering type polarizing plate is achieved, and the scattering type having the performance as a polarizing plate equivalent to a standard linear polarizing plate. A polarizing plate can be obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Synthesis of liquid crystalline polymer)
The polymerization reaction was allowed to proceed for 12 hours at 270 ° C. in a nitrogen atmosphere using 50 mmol of terephthalic acid, 50 mmol of 2,6-naphthalenedicarboxylic acid, 40 mmol of methylhydroquinone diacetate, 60 mmol of catechol diacetate and 60 mg of N-methylimidazole. Next, the obtained reaction product was dissolved in tetrachloroethane, and then purified by reprecipitation with methanol to obtain 14.7 g of a liquid crystal polyester having a wholly aromatic main chain type.

  This liquid crystalline polyester had a logarithmic viscosity of 0.17, a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 250 ° C. or higher, and a glass transition point of 115 ° C.

(Confirmation of phase separation structure)
As an amorphous polymer, a styrene-acrylonitrile copolymer (acrylonitrile content: 19 wt%, SAN19) having a refractive index relatively close to the refractive index in the minor axis direction of the liquid crystalline polyester (LCP) synthesized above. And using N-methyl-2-pyrrolidone (NMP) as a common solvent, an optical liquid crystal film was obtained as follows.

  That is, first, an N-methyl-2-pyrrolidone solution (LCP + SAN = 10% by weight) containing liquid crystalline polyester and styrene-acrylonitrile copolymer in the following mixing ratio (weight basis) was prepared.

LCP / SAN19
Sample 1 1/1
Sample 2 3/1
Sample 3 5/1
Sample 4 7/1
Sample 5 9/1.

  Next, each NMP solution obtained was spin cast (500 rpm, 30 s) at room temperature on a glass substrate that was rubbed in a direction parallel to the substrate surface with an imide film, and then at 200 ° C. for 10 minutes. By performing the heat treatment, an optical liquid crystal film having a film thickness of about 2 μm was obtained.

  Next, the optical liquid crystal films of Samples 1 to 5 were observed with a polarizing microscope using a sensitive color plate (retardation 530 nm) under crossed Nicols, and the liquid crystalline polyester and styrene-acrylonitrile copolymer in the optical liquid crystal film. The phase separation structure was evaluated. The obtained polarizing microscope photographs are shown in FIG. 1 (Sample 1), FIG. 2 (Sample 2), FIG. 3 (Sample 3), FIG. 4 (Sample 4), and FIG. 5 (Sample 5). As is clear from the results shown in FIGS. 1 to 5, it was confirmed that the optical liquid crystal films of Samples 1 to 5 were formed with a uniform phase separation structure with a minute size.

Example 1
Using the liquid crystalline polyester (LCP) synthesized above, the styrene-acrylonitrile copolymer (SAN19) corresponding to the sample 1, and N-methyl-2-pyrrolidone (NMP), the scattering type is performed as follows. A polarizing plate was obtained.

  That is, first, an NMP solution (LCP + SAN = 10% by weight) containing LCP and SAN19 at a mixing ratio (by weight) of 1: 1 was prepared. Next, the obtained NMP solution was spin-cast (500 rpm, 30 s) into a thick film at room temperature on a glass substrate that was rubbed in a direction parallel to the substrate surface with an imide film, and then 200 ° C. For 10 minutes, and then dried. Subsequently, the polymer film on the dried rubbing substrate was heat-treated at 230 ° C. for 30 minutes while applying a magnetic field of 1 Tesla so as to be parallel to the rubbing direction of the substrate surface. A scattering type polarizing plate having a film thickness of about 50 μm was obtained by cooling to room temperature at a temperature lowering rate of 1 to 2 ° C./min while applying the magnetic field.

(Comparative Examples 1-2)
Using the liquid crystalline polyester (LCP) synthesized above, the styrene-acrylonitrile copolymer (SAN19) corresponding to Sample 1 or Sample 2, and N-methyl-2-pyrrolidone (NMP) as follows: Thus, a scattering type polarizing plate was obtained.

  That is, first, an NMP solution (LCP + SAN = 10% by weight) containing LCP and SAN19 at a mixing ratio (weight basis) of 1: 1 (Comparative Example 1) or 3: 1 (Comparative Example 2) was prepared. Next, each obtained NMP solution was spin-cast (500 rpm, 30 s) into a thick film at room temperature on a glass substrate that was rubbed in a direction parallel to the substrate surface with an imide film, and then 200 A drying treatment was performed by maintaining at 10 ° C. for 10 minutes. Subsequently, a spacer having a thickness of 7.5 μm and a polymer film on a rubbed substrate subjected to a drying treatment are arranged between the two glass plates, and the two glass plates are about 10 mm from each other while being maintained at 250 ° C. A scattering type polarizing plate having a film thickness of about 7.5 μm was obtained by performing a heat treatment for 30 minutes while applying a shearing force to the polymer film by shifting in the parallel direction, and then rapidly cooling to room temperature.

<Orientation state confirmation test: deflection microscope observation>
The scattering type polarizing plate obtained in Example 1 and Comparative Example 2 is observed under a polarizing microscope using a sensitive color plate (phase difference 530 nm) under crossed Nicols, and the orientation of the liquid crystalline polyester in the scattering type polarizing plate. The condition was evaluated. Note that a polarizing microscope photograph taken by changing the angle (θ) between the polarization direction of the laser and the rubbing direction of the substrate and performing observation with a polarization microscope, and taking θ = 0 ° with respect to the scattering type polarizing plate of Example 1. FIG. 6 is a polarization microscope photograph taken at θ = 30 ° with respect to the scattering-type polarizing plate of Example 1, and FIG. 7 is a polarization photograph taken at θ = 30 ° with respect to the scattering-type polarizing plate of Comparative Example 2. The micrographs are shown in FIG.

  In this test, since a sensitive color plate (retardation 530 nm) was used, the color was given, but in the case of a sample having no birefringence, it should appear pink. However, in the scattering-type polarizing plate (FIGS. 6 to 7) obtained in Example 1, the pink color was not observed in any of the photographs, and the whole looked the same color uniformly. Were uniformly birefringent, that is, it was confirmed that the liquid crystalline polyester was sufficiently oriented in the rubbing direction (direction of applying a magnetic field). On the other hand, in the scattering-type polarizing plate obtained in Comparative Example 2 (FIG. 8), the entire region was non-uniform and pink regions and blue regions were observed, so the liquid crystalline polyester was completely in the rubbing direction. It was confirmed that it was not oriented.

<Polarization performance confirmation test: Transmitted light intensity measurement>
With respect to the scattering-type polarizing plates obtained in Example 1 and Comparative Examples 1 and 2, the performance as a polarizing plate was confirmed using the light scattering measurement system shown in FIG. In the figure, 1 is a He-Ne laser (wavelength 632.8 nm), 2 is a pinhole, 3 is a mirror, 4 is a sample cell, 5 is a photodiode (goniometer), 6 is an XY amplifier, and 7 is a computer. , 8 indicates a sample turntable (which can be rotated in the direction of the arrow in the figure).

  The scattering type polarizing plate obtained in Example 1 and Comparative Examples 1 and 2 is set in the sample cell of the light scattering measurement system shown in FIG. 9, and the scattering type polarizing plate is rotated by a certain angle in the direction of the arrow in the figure. The laser beam linearly polarized at each angle was vertically incident on the sample, and the transmitted light intensity at each angle was measured. FIG. 10 shows the angle dependency of the transmitted light intensity in the scattering type polarizing plate obtained in Example 1, and FIG. 11 shows the angle dependency of the transmitted light intensity in the scattering type polarizing plate obtained in Comparative Examples 1 and 2, respectively. Show. In addition, for comparison, results obtained using a standard linear polarizing plate (manufactured by Sumitomo Chemical Co., Ltd., trade name: SRW-862) are also shown in FIG.

  In FIG. 10, the arrangement where the polarization direction of the laser and the rubbing direction of the scattering type polarizing plate form an angle of about 90 ° is the initial position (0 °), but since the transmitted light intensity is strongest at this angle, the liquid crystal It was confirmed that the conductive polyester was oriented in the rubbing direction (magnetic field application direction). Furthermore, in the scattering type polarizing plate obtained in Example 1 in which the liquid crystalline polyester was aligned by a rubbing substrate and a magnetic field, the transmitted light intensity was almost 0 at 90 °, and a commercially available standard as a scattering type polarizing plate. It was confirmed that the polarizing plate had almost the same performance as a linear polarizing plate.

  On the other hand, in the scattering type polarizing plates obtained in Comparative Examples 1 and 2 in which the liquid crystalline polyester was aligned by the rubbing substrate and the shearing force, the transmitted light intensity at 90 ° was not sufficiently reduced. It was confirmed that the performance as a plate is not yet sufficient.

  According to the manufacturing method of the present invention described above, a scattering type polarizing plate having excellent angle dependency of transmitted light intensity can be obtained, and the scattering type having the performance as a polarizing plate equivalent to a standard linear polarizing plate. It is also possible to obtain a polarizing plate. Therefore, the scattering polarizing plate obtained by the production method of the present invention is a very useful optical material that can be used for a liquid crystal display device and the like.

2 is a polarizing micrograph of an optical liquid crystal film obtained using Sample 1. FIG. 2 is a polarizing micrograph of an optical liquid crystal film obtained using Sample 2. . 3 is a polarizing micrograph of an optical liquid crystal film obtained using Sample 3. FIG. 3 is a polarizing micrograph of an optical liquid crystal film obtained using Sample 4. FIG. 3 is a polarizing micrograph of an optical liquid crystal film obtained using Sample 5. FIG. 2 is a polarizing microscope photograph of a scattering type polarizing plate (θ = 0 °) obtained in Example 1. FIG. 2 is a polarizing microscope photograph of a scattering type polarizing plate (θ = 30 °) obtained in Example 1. FIG. 4 is a polarizing micrograph of a scattering type polarizing plate (θ = 30 °) obtained in Comparative Example 2. It is a schematic diagram which shows the structure of a light-scattering measurement system. 4 is a graph showing the results of angle dependence of transmitted light intensity in the scattering-type polarizing plate obtained in Example 1. It is a graph which shows the result of the angle dependence of the transmitted light intensity in the scattering type polarizing plate obtained by Comparative Examples 1-2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... He-Ne laser, 2 ... Pinhole, 3 ... Mirror, 4 ... Sample cell, 5 ... Photodiode (goniometer), 6 ... XY amplifier, 7 ... Computer, 8 ... Sample turntable.

Claims (5)

A step of applying a solution containing a liquid crystalline polymer having a nematic phase in a liquid crystal state and becoming a glass state at a temperature below the glass transition point and an amorphous polymer on a substrate having an alignment regulating force. When,
Aligning the liquid crystalline polymer in a predetermined direction by the alignment regulating force of the substrate at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state;
Applying a magnetic field to the liquid crystalline polymer at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state, and further aligning the liquid crystalline polymer in the predetermined direction;
The liquid crystalline polymer aligned in the predetermined direction is cooled to be in a glass state so that the alignment state is maintained, thereby obtaining a scattering type polarizing plate composed of the liquid crystalline polymer and the non-defective polymer. Process,
The manufacturing method of the scattering-type polarizing plate characterized by including.   The method for producing a scattering type polarizing plate according to claim 1, wherein a magnetic field of 0.1 to 10 Tesla is applied to the liquid crystalline polymer.   While applying a magnetic field to the liquid crystalline polymer oriented in the predetermined direction, the glassy state is obtained by slow cooling at a cooling rate of 0.1 to 10 ° C./min so as to maintain the orientation state. The manufacturing method of the scattering type polarizing plate of Claim 1 or 2.   The method for producing a scattering type polarizing plate according to any one of claims 1 to 3, wherein the liquid crystalline polymer is a main chain polyester liquid crystalline polymer.   The said amorphous polymer is a styrene random copolymer, The manufacturing method of the scattering type polarizing plate as described in any one of Claims 1-4 characterized by the above-mentioned.

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