JP4940851B2 - Method for producing retardation film - Google Patents

Description

  The present invention relates to a method for producing a retardation film used in a liquid crystal display device or the like.

Since the liquid crystal display device has features such as power saving, light weight, thinness, etc., the conventional C
Instead of RT display, it has been rapidly spreading in recent years. As a typical liquid crystal display device, for example, as shown in FIG. 3, a liquid crystal display device having an incident side polarizing plate 102 </ b> A, an outgoing side polarizing plate 102 </ b> B, and a liquid crystal cell 104 can be cited. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light having a vibration surface in a predetermined vibration direction (in the drawing, the vibration direction of light is schematically illustrated by an arrow), They are arranged opposite to each other in a crossed nicols state so that the respective vibration directions are perpendicular to each other. The liquid crystal cell 104 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  On the other hand, the liquid crystal display device has the advantages as described above, but as a particular problem, there is a problem of viewing angle dependency due to the refractive index anisotropy of the liquid crystal cell. This problem of viewing angle dependency is a problem in which the color and contrast of a visually recognized image change between when the liquid crystal display device is viewed from the front and when viewed from an oblique direction. Such a problem of viewing angle characteristics has become more important as the liquid crystal display device has recently been enlarged.

  In order to improve such a problem of viewing angle dependency, various techniques have been developed so far, and a representative method is a method using a retardation film. In the method using this retardation film, as shown in FIG. 3, the retardation film 30 having predetermined optical characteristics is disposed between the liquid crystal cell 104 and the polarizing plate 102B, thereby causing a problem of viewing angle dependency. It is a way to improve. Since this method can improve the viewing angle dependency only by incorporating the retardation film 30 in the liquid crystal display device, it is widely used as a method for easily obtaining a liquid crystal display device having excellent viewing angle characteristics. Has come to be.

  Here, as the retardation film, for example, one having a configuration in which a retardation layer containing an optically anisotropic material having refractive index anisotropy is formed on a transparent substrate, or a stretched film is used. Is generally known. Among them, a retardation film having a configuration in which a retardation layer containing the optically anisotropic material is formed has excellent retardation, and thus becomes a major form of today's retardation film. Yes. Regarding the retardation film having such a configuration, for example, in Patent Document 1 or Patent Document 2, an optically anisotropic layer having a cholesteric regular molecular structure (an optically anisotropic layer exhibiting birefringence) is an alignment film. There is disclosed a retardation film formed on a substrate having the following. Patent Document 3 discloses a retardation film in which an optically anisotropic layer (an optically anisotropic layer exhibiting birefringence) made of a discotic compound is formed on a substrate having an alignment film. .

By the way, in a retardation film having a configuration in which a retardation layer is formed on the transparent substrate, usually, the optically anisotropic material is regularly arranged in the retardation layer to exhibit a predetermined retardation. Designed to be. For this reason, when manufacturing the retardation film having the above-described configuration, a method is used in which the optically anisotropic material is regularly arranged in the stretching direction by stretching the retardation layer together with the transparent substrate. There are many.
However, when the optically anisotropic material is arranged by such a method, either one of the retardation layer or the transparent substrate is cracked or one of them is broken. Some problems have been pointed out.
In addition, it has been pointed out that a retardation film produced by using the stretching method as described above may have a large amount of retardation change with time.

  For this reason, the method of expressing retardation by stretching described above has the advantage that the retardation layer can be easily imparted to the retardation layer, but it is not necessarily excellent in retardation stability over time. It was not possible to manufacture with high productivity.

JP-A-3-67219 JP-A-4-322223 Japanese Patent Laid-Open No. 10-312166

  The present invention has been made in view of the above problems, and is a method for producing a retardation film having a configuration in which a retardation layer containing an optically anisotropic material is laminated on a transparent substrate, the retardation film comprising: It is a main object of the present invention to provide a method for producing a retardation film, which can produce a retardation film having excellent stability over time with high productivity.

  In order to solve the above-mentioned problems, the present invention uses a transparent substrate, and coats a coating solution for forming a retardation layer containing an optically anisotropic material having refractive index anisotropy on the transparent substrate. By stretching the optical laminate formed by the optical laminate forming step and the optical laminate forming step of forming the optical laminate in which the retardation layer forming layer is laminated on the transparent substrate. Producing a retardation film in which a retardation layer containing the optically anisotropic material is laminated on the transparent substrate. A method for producing a retardation film, wherein the ratio of the tensile elongation at break of the layer for forming the retardation layer to the tensile elongation at break of the transparent substrate (the tensile elongation at break of the layer for forming the retardation layer / the transparent substrate) The tensile elongation at break) is in the range of 1-30. To provide a method of manufacturing a difference film.

According to the present invention, the optical laminate is stretched in the stretching treatment step because the ratio of the tensile elongation at break of the retardation layer forming layer and the transparent substrate constituting the optical laminate is within the above range. In this case, it is possible to prevent breakage or cracks from occurring in either the transparent substrate or the retardation layer forming layer. For this reason, according to the present invention, a retardation film can be produced with high productivity.
Further, according to the present invention, the retardation film produced according to the present invention is aged over time because the ratio of the tensile elongation at break of the retardation layer forming layer and the transparent substrate constituting the optical laminate is within the above range. The dimensional change can be reduced. For this reason, according to the present invention, a retardation film having excellent retardation stability with time can be produced.
For this reason, according to the present invention, a retardation film containing an optically anisotropic material is laminated on a transparent substrate, and a retardation film excellent in retardation stability with time is increased. Can be manufactured with productivity.

  In the present invention, the tensile elongation at break of the retardation layer forming layer is preferably in the range of 150% to 250%. Moreover, in this invention, it is preferable that the breaking tensile elongation of the said transparent substrate exists in the range of 5%-250%. Depending on the use of the retardation film produced by the present invention, the retardation layer forming layer and the transparent substrate each have a tensile elongation at break within the above range. This is because it becomes easy to adjust the stretch ratio in the stretching step so that the predetermined retardation can be imparted.

  Moreover, in this invention, it is preferable that the draw ratio of the said optical laminated body in the said extending process process exists in the range of 1.01 times-2 times. Since the stretching ratio is within such a range, it is possible to further prevent cracks and breaks from occurring in either the retardation layer forming layer or the transparent substrate in the stretching treatment step. This is because the method for producing the retardation film can be made more productive.

  The present invention has a configuration in which a retardation layer containing an optically anisotropic material is laminated on a transparent substrate, and a retardation film excellent in retardation stability over time can be produced with high productivity. There is an effect.

  Hereinafter, the manufacturing method of the retardation film of this invention is demonstrated.

  The method for producing a retardation film of the present invention comprises using a transparent substrate, and coating a coating solution for forming a retardation layer containing an optically anisotropic material having refractive index anisotropy on the transparent substrate. An optical laminate forming step of forming an optical laminate in which a retardation layer forming layer is laminated on a transparent substrate; and the retardation layer is formed by stretching the optical laminate formed by the optical laminate forming step. And a stretching treatment step for expressing retardation in the forming layer, and producing a retardation film in which a retardation layer containing the optically anisotropic material is laminated on the transparent substrate. The ratio of the breaking tensile elongation of the retardation layer forming layer to the breaking tensile elongation of the transparent substrate (breaking tensile elongation of the retardation layer forming layer / breaking tensile elongation of the transparent substrate) is 1 to 1. It is within the range of 30.

The method for producing the retardation film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of a method for producing a retardation film of the present invention. As illustrated in FIG. 1, the method for producing a retardation film of the present invention uses a transparent substrate 1 (FIG. 1A), and an optically anisotropic material having refractive index anisotropy on the transparent substrate 1. An optical laminate forming step for forming an optical laminate 10 ′ in which a retardation layer forming layer 2 ′ is laminated on the transparent substrate 1 by applying a retardation layer forming coating solution containing 1 (b)) and an optical laminate 10 ′ formed by the optical laminate forming process, thereby stretching the retardation layer forming layer 2 ′ to develop retardation (FIG. 1). (C)), and a retardation film 10 in which a retardation layer 2 containing the optically anisotropic material is laminated on the transparent substrate 1 is manufactured (FIG. 1D). .
In such an example, the method for producing a retardation film of the present invention includes the breaking tensile elongation of the retardation layer forming layer 2 ′ in the optical laminate 10 ′ and the breaking tensile elongation of the transparent substrate 1. The ratio (breaking tensile elongation of the retardation layer forming layer / breaking tensile elongation of the transparent substrate) is in the range of 1 to 30.

According to the present invention, when the ratio of the tensile elongation at break of the retardation layer forming layer and the transparent substrate constituting the optical laminate is within the above range, the retardation layer forming layer and the transparent substrate The tensile elongation at break can be close to each other. For this reason, when extending | stretching the said optical laminated body in the said extending | stretching process process, it can prevent that a fracture | rupture or a crack arises in either one of the said transparent substrate or the said phase difference layer formation layer. Therefore, according to the present invention, a retardation film can be produced with high productivity.
Further, according to the present invention, the retardation film produced according to the present invention is aged over time because the ratio of the tensile elongation at break of the retardation layer forming layer and the transparent substrate constituting the optical laminate is within the above range. The dimensional change can be reduced. For this reason, according to the present invention, a retardation film having excellent retardation stability with time can be produced.
For this reason, according to the present invention, a retardation film containing an optically anisotropic material is laminated on a transparent substrate, and a retardation film excellent in retardation stability with time is increased. Can be manufactured with productivity.

The manufacturing method of the retardation film of this invention has at least the said optical laminated body formation process and the said extending | stretching process process.
Hereinafter, each process used for the manufacturing method of the retardation film of this invention is demonstrated in order.

1. Optical Laminate Forming Process First, the optical laminate forming process used in the present invention will be described. This step uses a transparent substrate and coats the transparent substrate with a retardation layer forming coating solution containing an optically anisotropic material having refractive index anisotropy on the transparent substrate. An optical laminate in which a forming layer is laminated, wherein a ratio of a breaking tensile elongation of the retardation layer forming layer to a breaking tensile elongation of the transparent substrate (a breaking tensile elongation of the retardation layer forming layer) Degree / breaking tensile elongation of the transparent substrate) is a step of producing an optical laminate having a range of 1 to 30.
Hereinafter, such an optical layered body forming step will be described in detail.

(1) Optical laminated body First, the optical laminated body formed in this process is demonstrated. The optical laminate formed in this step has a configuration in which a transparent substrate and a retardation layer forming layer are laminated, and the tensile elongation at break of the retardation layer forming layer is as described above. The ratio of the tensile elongation at break of the transparent substrate (the tensile elongation at break of the layer for forming the retardation layer / the tensile elongation at break of the transparent substrate) (hereinafter sometimes simply referred to as “the ratio of the tensile elongation at break”). It is within the range of 1-30.

  The above-mentioned fracture tensile elongation ratio of the optical laminate formed in this step is within the above range because the fracture tensile elongation ratio is out of the above range and is formed by this step in the stretching treatment step described later. This is because, when the optical laminate is stretched, cracks or breaks are likely to occur in either the transparent substrate or the retardation layer forming layer. In addition, when the breaking tensile elongation ratio is out of the above range, the retardation film produced according to the present invention is likely to undergo dimensional change over time, so that the change in retardation over time is large. Because it becomes.

The above-mentioned breaking tensile elongation ratio of the optical laminate formed in this step is not particularly limited as long as it is within the range of 1 to 30, and can be arbitrarily determined according to the stretching ratio in the stretching treatment step described later. That's fine. In particular, the optical laminate formed in this step preferably has a breaking tensile elongation ratio in the range of 1-20.
Here, the breaking tensile elongation ratio is, for example, based on JIS-K-6781, and using a tensile testing machine (Shimadzu Autograph: AGS-D), the breaking tension of the transparent substrate and the retardation layer forming layer. After measuring the elongation, it can be calculated from the measured value. Here, the tensile elongation at break of the retardation layer forming layer is obtained by measuring the tensile elongation at break of the optical laminate by the method described above, and then calculating the measured value of the tensile elongation at break of the transparent substrate from the measured value. It can be determined by subtracting.

The optical layered product formed by this step preferably has a tensile elongation at break of the retardation layer forming layer in the range of 150% to 250%, and more preferably in the range of 150% to 220%. It is preferable that it is in the range of 150% to 200%.
The optical laminate formed by this step preferably has a breaking tensile elongation of the transparent substrate in the range of 5% to 50%, and more preferably in the range of 5% to 45%. In particular, it is preferably in the range of 5% to 40%. When the breaking tensile elongation of the retardation layer forming layer and the transparent substrate is within the above range, the retardation layer has a predetermined position depending on the use of the retardation film produced by the present invention. It is because it becomes easy to adjust the draw ratio in the said extending process process so that phase difference can be provided.

  Further, the optical laminate formed by this step has a configuration in which a retardation layer forming layer is laminated on a transparent substrate, but the retardation layer forming layer is laminated on the transparent substrate. The aspect may be an aspect in which the transparent substrate and the retardation layer forming layer are laminated as independent layers, or a clear interface between the transparent substrate and the retardation layer forming layer. There may be a mode in which the layers are laminated so that the content of the optically anisotropic material continuously changes between them.

  Such an aspect in which the transparent substrate and the retardation layer forming layer are laminated will be described with reference to the drawings. FIG. 2 is a schematic view showing an example of an aspect in which the transparent substrate and the retardation layer forming layer are laminated in the optical laminate formed by this step. As illustrated in FIG. 2, the optical layered body 10 ′ formed by this step may have a mode in which the transparent substrate 1 and the retardation layer forming layer 2 ′ are stacked as independent layers. (FIG. 2 (a)), or there is no clear interface between the transparent substrate 1 and the retardation layer forming layer 2 ′, and the content of the optically anisotropic material is continuously between the two. The layers may be stacked so as to change (FIG. 2B).

(2) Manufacturing method of optical laminated body Next, in this step, by applying a retardation layer forming coating solution containing an optically anisotropic material having refractive index anisotropy on the transparent substrate. A method for forming the optical laminate will be described.

a. Retardation layer forming coating solution The retardation layer forming coating solution used in this step contains an optically anisotropic material having refractive index anisotropy, and is usually the above optically anisotropic material. Is dissolved in a solvent.

(Optically anisotropic material)
The optically anisotropic material used in this step is capable of forming a retardation layer forming layer having refractive index anisotropy and capable of setting the above-described breaking tensile elongation ratio within the range specified in the present invention. There is no particular limitation. Examples of such an optically anisotropic material include a polymerizable optically anisotropic material having a polymerizable functional group, an optically anisotropic polymer material, and the like. Among these, in the present step, it is preferable to use the polymerizable optically anisotropic material. The polymerizable optically anisotropic material can be easily polymerized with each other via the polymerizable functional group, so that the tensile elongation at break of the phase difference layer forming layer can be easily controlled within the range specified in the present invention. This is because it has advantages. In addition, the polymerizable optically anisotropic material is fixed in a state where the optically anisotropic material is arranged by, for example, polymerizing after the optically anisotropic material is arranged in the stretching direction in a stretching process described later. This is because there is an advantage that the arrangement state of the optically anisotropic material can be prevented from changing over time.
Here, the above-mentioned “refractive index anisotropy” means that the refractive index varies depending on the incident direction of light.

The polymerizable optically anisotropic material is not particularly limited as long as it has a polymerizable functional group and can impart desired retardation to the retardation film produced according to the present invention. Among these, examples of the polymerizable optically anisotropic material suitably used in this step include a polymerizable liquid crystal material and a urethane acrylate monomer.
Here, since the polymerizable liquid crystal material has a large refractive index anisotropy, a retardation layer forming layer having excellent retardation can be obtained even if the retardation layer forming layer is thin. It has the advantage that it can be formed. In addition, the urethane acrylate monomer has a urethane bond part (—O—CO—N <) in which the wavelength dependency of the retardation value indicates a reverse dispersion type, and therefore the wavelength dependency of the retardation value is a reverse dispersion type. There is an advantage that a certain phase difference layer forming layer can be formed.

  As the polymerizable liquid crystal material, those having a polymerizable functional group capable of three-dimensional crosslinking in the molecule are more preferably used. Examples of the polymerizable functional group include polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat. Representative examples of these polymerizable functional groups include radically polymerizable functional groups or cationic polymerizable functional groups. Further, representative examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups having or not having substituents, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given. Moreover, an epoxy group etc. are mentioned as a specific example of the said cation polymerizable functional group. In addition, examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. Among these, from the viewpoint of the process, a functional group having an ethylenically unsaturated double bond is preferably used.

  Further, the liquid crystal phase exhibited by the polymerizable liquid crystal material used in this step is not particularly limited, and may be any of the polymerizable liquid crystal materials exhibiting a liquid crystal phase such as a nematic phase, a cholesteric phase, and a smectic phase. However, it can be suitably used. In particular, in this step, it is preferable to use a polymerizable liquid crystal material exhibiting a nematic phase. This is because a polymerizable liquid crystal material exhibiting a nematic phase is easily arranged regularly as compared with polymerizable liquid crystal materials exhibiting other liquid crystal phases.

  Further, as the polymerizable liquid crystal material exhibiting the nematic phase, it is preferable to use a material having spacers at both ends of the mesogen. This is because the polymerizable liquid crystal material having spacers at both ends of the mesogen is excellent in flexibility, and the retardation film produced according to the present invention can be made excellent in transparency by using such a polymerizable liquid crystal material. .

  Specific examples of such polymerizable liquid crystal materials include compounds represented by the following formulas (1) to (6).

  Here, the polymerizable liquid crystal materials represented by the chemical formulas (1), (2), (5) and (6) are disclosed in DJ Broer et al., Makromol. Chem. 190, 3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190, 2250 (1989), or can be prepared similarly. The preparation of polymerizable liquid crystal materials represented by the chemical formulas (3) and (4) is disclosed in DE 195,04,224.

  Specific examples of the nematic polymerizable liquid crystal material having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17).

  In addition, the polymeric liquid crystal material used for this process may be only 1 type, or 2 or more types. For example, when the polymerizable liquid crystal material is a mixture of a polymerizable liquid crystal material having one or more polymerizable functional groups at both ends and a polymerizable liquid crystal material having one or more polymerizable functional groups at one end. The polymerization density (crosslinking density) and optical characteristics can be arbitrarily adjusted by adjusting the blending ratio of the two, which is preferable.

  When the polymerizable liquid crystal material is used as the optically anisotropic material, the retardation layer of the retardation film produced according to the present invention contains a polymer of the polymerizable liquid crystal material. become.

The urethane acrylate used in this step is not particularly limited as long as it has a urethane bond and an acryloyl group.
Here, the number of acryloyl groups contained in the urethane acrylate monomer may be one or plural.
Further, the number of urethane bond portions contained in the urethane acrylate monomer may be one or plural.

  The urethane acrylate monomer used in this step preferably has an atomic group having refractive index anisotropy between the urethane bond and the acryloyl group. The urethane acrylate obtained by polymerizing such a urethane acrylate monomer can be arranged in one direction by stretching the atomic group having the above refractive index anisotropy, and thus has excellent retardation. is there.

  In addition, as the urethane acrylate monomer having an atomic group having the refractive index anisotropy, the total atomic weight of the elements constituting the atomic group having the refractive index anisotropy is preferably in the range of 100 to 1000, Especially, it is preferable to be in the range of 200 to 600, and it is particularly preferable to be in the range of 400 to 600. If the sum of the atomic weights is less than the above range, the number of atomic groups contributing to the development of retardation will be reduced, and as a result, it will be difficult to impart the desired retardation to the retardation film produced according to the present invention. Because there is a possibility. Further, if the amount is larger than the above range, the number of urethane bond portions present in the urethane acrylate obtained by polymerization of the urethane acrylate monomer is reduced, so that the wavelength dependency of the retardation value of the retardation film produced according to the present invention is desired. This is because it may be difficult to mold.

  The type of atomic group having the refractive index anisotropy is not particularly limited as long as a desired retardation can be imparted depending on the use of the retardation film produced according to the present invention. . Examples of the atomic group having such refractive index anisotropy include an ester atomic group including an ester bond, an ether atomic group including an ether bond, and the like. In this step, any of the above-mentioned atomic groups can be suitably used, but it is particularly preferable to use an ester-based atomic group. This is because by using the ester group, the retardation layer forming layer formed in this step can be made more excellent in retardation. Moreover, since the urethane acrylate monomer which has the said ester system atomic group can be synthesize | combined comparatively easily, it is because the productivity of the manufacturing method of the retardation film of this invention can be improved more.

  The ester group used in this step includes a lactone group containing a lactone constituent unit, a polycarbonate group containing a polycarbonate constituent unit, and an adipate group containing an adipate constituent unit. Can be mentioned. Any of these atomic groups can be suitably used in this step, but among them, a lactone group is preferably used. This is because the lactone-based atomic group has a high refractive index anisotropy and an excellent retardation property.

Furthermore, in this step, it is preferable to use a caprolactone-modified atomic group containing a caprolactone constituent unit among the above lactone group. This is because the caprolactone-modified atomic group has a larger refractive index anisotropy, so that the retardation of the retardation layer forming layer can be further improved.
Here, the caprolactone-modified atomic group may include a single caprolactone constituent unit or may include a plurality of caprolactone constituent units. When the caprolactone-modified atomic group includes a plurality of caprolactone structural units, the number of caprolactone structural units contained in the caprolactone-modified atomic group is preferably in the range of 2 to 5.

  When the urethane acrylate monomer is used as the optically anisotropic material, the retardation layer of the retardation film produced according to the present invention contains urethane acrylate obtained by polymerizing the urethane acrylate monomer. Will be.

  On the other hand, as the optically anisotropic polymer material used in this step, a liquid crystalline resin such as a polymer of the polymerizable liquid crystal material, a urethane acrylate obtained by polymerizing the urethane acrylate monomer, a polyurethane, or the like. Mention may be made of urethane resins.

  Further, as the optically anisotropic material used in this step, in addition to the materials described above, acicular crystals such as strontium carbonate and boehmite alumina, and organic clay composites such as smectite and mica can also be used.

(solvent)
The solvent used for the retardation layer forming coating solution is not particularly limited as long as it can dissolve the optically anisotropic material or the like at a desired concentration. Examples of such solvents include alcohol solvents such as methanol, ethanol, butanol and diacetone alcohol; hydrocarbon solvents such as benzene and hexane; methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, methylcyclohexanone, and the like. Ketone solvents; ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane; alkyl halide solvents such as chloroform and dichloromethane; ester solvents such as methyl acetate, butyl acetate and propylene glycol monomethyl ether acetate; N, N- Examples thereof include amide solvents such as dimethylformamide, and sulfoxide solvents such as dimethyl sulfoxide. Among these, in this step, it is preferable to use methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone.

  The solvent used in this step may be a single solvent or a mixed solvent of a plurality of solvents.

(Other)
The retardation layer forming coating solution used in this step may contain other compounds than the optically anisotropic material and the solvent as long as the object of the present invention is not impaired. . As such another compound, a compound having a desired function can be used according to the use of the retardation film produced according to the present invention. Examples of such other compounds include compounds having a refractive index anisotropy that contributes to the development of retardation in the retardation film produced according to the present invention. By using such a compound, for example, when it is difficult to express a desired retardation with only the optically anisotropic material, there is an advantage that the retardation can be increased.

  Examples of the compound having refractive index anisotropy used in this step include liquid crystal compounds and inorganic compounds having refractive index anisotropy.

  Moreover, when using a polymerizable optically anisotropic material as the optically anisotropic material used in this step, it is preferable to use a photopolymerization initiator as the other compound. Examples of the photopolymerization initiator used in this step include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino acetophenone, 4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpro Piophenone, p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethyl ketal, benzylmethoxyethyla Tar, benzoin methyl ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberon, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis ( p-azidobenzylidene) cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione 2- (o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o- Nzoyl) oxime, Michler's ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone , Naphthalene sulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, Adeca N1717, carbon tetrabromide And a combination of a photoreductive dye such as tribromophenylsulfone, benzoin peroxide, eosin, and methylene blue with a reducing agent such as ascorbic acid and triethanolamine. In this step, these photopolymerization initiators can be used alone or in combination of two or more.

  When using the said photoinitiator, it is preferable to use a photoinitiator adjuvant together. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

  In addition, the amount of the optically anisotropic material contained in the retardation layer forming coating solution used in this step depends on the type of the optically anisotropic material, etc., and the retardation produced by the present invention. It can adjust arbitrarily within the range which can provide desired retardation property to a film.

b. Transparent substrate Next, the transparent substrate used for this process is demonstrated. The transparent substrate used in this step is not particularly limited as long as the ratio of the tensile elongation at break can be within the range defined by the present invention, depending on the type of the optically anisotropic material. . Examples of such transparent substrates include cellulose derivatives, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, modified acrylic polymer, polystyrene, epoxy resin, polycarbonate, and polyester. And substrates made of cycloolefin polymers such as norbornene polymers. In particular, in this step, it is preferable to use a transparent substrate made of a cellulose derivative or a cycloolefin resin. Since the cellulose derivative is excellent in optical isotropy, the use of a transparent substrate made of such a cellulose derivative has the advantage that the optical properties of the retardation film produced according to the present invention can be easily designed. It is. In addition, since the cycloolefin-based resin is excellent in gas barrier properties and heat-and-moisture resistance, the retardation film produced according to the present invention has an advantage that it can have excellent temporal stability of optical properties in a high-temperature and high-humidity atmosphere. It is because it has.

  As the cellulose derivative, cellulose esters are preferably used, and among the cellulose esters, cellulose acylates are preferably used. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  Moreover, as said cellulose acylates, C2-C4 lower fatty acid ester is preferable. The lower fatty acid ester may include only a single lower fatty acid ester such as cellulose acetate, and may include a plurality of fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate. There may be.

In this step, cellulose acetate can be particularly preferably used among the above lower fatty acid esters. As the cellulose acetate, it is most preferable to use triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). This is because triacetylcellulose is excellent in optical isotropy, so that the design of the optical properties of the retardation film produced according to the present invention becomes easier. In addition, since triacetyl cellulose has a molecular structure having a relatively bulky side chain, in the retardation film produced according to the present invention, a transparent substrate can be obtained by using such a transparent substrate made of triacetyl cellulose. This is because the adhesion between the film and the retardation layer can be improved.
The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose, and is determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (testing method for cellulose acetate, etc.). Can do. The degree of acetylation of the triacetyl cellulose constituting the triacetyl cellulose film can be determined by the above method after removing impurities such as a plasticizer contained in the film.

  On the other hand, the cycloolefin-based resin means a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Examples of the monomer composed of the cyclic olefin include norbornene and polycyclic norbornene-based monomers. Can be mentioned. The cycloolefin resin used in this step may be a homopolymer of a monomer comprising the above cyclic olefin, or may be a copolymer.

The cycloolefin resin used in this step is not particularly limited as long as it can obtain a transparent substrate having desired transparency. Among them, the cycloolefin resin used in this step preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and particularly preferably in the range of 0.1% by mass to 0.7% by mass. This is because by using such a cycloolefin-based resin, the retardation film produced according to the present invention can be made less susceptible to changes in optical properties and dimensions due to water absorption.
Here, the saturated water absorption is obtained by immersing in 23 ° C. water for 1 week according to ASTM D570 and measuring the increased weight.

  Moreover, as for the cycloolefin type resin used for this process, what has a glass transition point in the range of 100 to 200 degreeC is preferable, and what is in the range of 100 to 180 degreeC is preferable especially, and also 100 degreeC What is in the range of -150 degreeC is preferable. This is because by using such a cycloolefin-based resin, the retardation film produced according to the present invention can be made more excellent in heat resistance and processability.

  Examples of such a cycloolefin resin include those having a structural unit represented by the following formula (a) or the following formula (b).

Here, in the above formula (a), t and u each independently represent 0 or a positive integer, except when t and u are 0 at the same time. A represents an ethylene group or a vinylene group, and R ^{11 to} R ¹⁴ are each independently a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or — (CH ₂ ) n—COOR ( n represents 0 to 5, and R represents an alkyl group having 1 to 12 carbon atoms.
Here, R ¹¹ or R ¹² and R ¹³ or R ¹⁴ may be bonded to each other to form a carbocyclic or heterocyclic ring. Furthermore, the carbocycle or heterocycle may be a monocyclic structure or a polycyclic structure.

In the above formula (b), B represents an ethylene group or a vinylene group. R ^{15 to} R ¹⁸ each independently represent a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 30 carbon atoms. Further, R ¹⁵ and R ¹⁶ , or R ¹⁷ and R ¹⁸ may be integrated to form a divalent hydrocarbon group.

  Specific examples of the transparent substrate made of cycloolefin-based resin used in this step include, for example, Ticona Topas, JSR Arton, ZEON Corporation ZEONOR, ZEON Corporation ZEONEX, Mitsui Chemicals Appel, etc. Can be mentioned.

The transparent substrate used in this step preferably has a transmittance in the visible light region of 80% or more, more preferably 90% or more. When the transmittance in the visible light region is within such a range, for example, when the retardation film produced according to the present invention is used as an optical compensation film for a liquid crystal display device, the visibility of the image is reduced. It is because it can prevent.
Here, the transmittance of the transparent substrate can be measured by JIS K7361-1 (Testing method for total light transmittance of plastic-transparent material).

The retardation value of the transparent substrate used in this step is not particularly limited as long as it is within a range in which a desired retardation value can be imparted to the retardation film produced according to the present invention. In particular, the transparent substrate used in this step preferably has a retardation value at a wavelength of 550 nm in the range of 0 nm to 50 nm, particularly preferably in the range of 0 nm to 40 nm.
Here, the retardation value (Re) depends on the refractive index nx in the slow axis direction in the plane, the refractive index ny in the fast axis direction in the plane, and the thickness d (nm) of the transparent substrate. = (Nx−ny) × d is a value represented by the formula, and can be measured by, for example, the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

The wavelength dependency of the retardation value of the transparent substrate may be a reverse dispersion type, a normal dispersion type, or a flat type.
Here, in general, a type of chromatic dispersion in which the retardation value is smaller on the short wavelength side than on the long wavelength side (that is, the retardation value is an increasing function of the wavelength) is referred to as “reverse dispersion type”. The “reverse dispersion type” in the invention is a ratio (Re ₄₅₀ / Re ₅₅₀ ) of a retardation value (Re ₄₅₀ ) at a wavelength of ₄₅₀ nm and a retardation value (Re ₅₅₀ ) at a wavelength of 550 nm (hereinafter simply referred to as “Re ratio”). ) Is less than 1.
A type of chromatic dispersion in which the retardation value is generally larger on the short wavelength side than on the long wavelength side (that is, the retardation value is a decreasing function of the wavelength) is referred to as “positive dispersion type”. “Positive dispersion type” means that the Re ratio is greater than 1.
Furthermore, a type of chromatic dispersion in which the retardation value does not have wavelength dependency is generally referred to as a “flat type”. In the present invention, the “flat type” means that the Re ratio is approximately 1. Shall.

Further, the transparent substrate used in this step preferably has a thickness direction retardation (Rth) at a wavelength of 550 nm in the range of 0 nm to 100 nm, and more preferably in the range of 0 nm to 60 nm. This is because when the Rth is in such a range, the retardation film produced according to the present invention can be made suitable as an optical compensation film for a liquid crystal display device.
Here, the retardation in the thickness direction (Rth) is the in-plane slow axis direction refractive index nx, the in-plane fast axis direction refractive index ny, the thickness direction refractive index nz, and the transparent substrate. It is a value represented by the formula of Rth = {(nx + ny) / 2−nz} × d by the thickness d (nm) of, and can be measured by, for example, KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd. .

The configuration of the transparent substrate used in this step is not limited to a configuration composed of a single layer, and may have a configuration in which a plurality of layers are stacked.
Moreover, when it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, or the several layer which has a different composition may be laminated | stacked.

The thickness of the transparent substrate used in this step is not particularly limited as long as necessary self-supporting properties can be obtained according to the use of the retardation film produced according to the present invention. In particular, the thickness of the transparent substrate used in this step is preferably in the range of 10 μm to 188 μm, particularly preferably in the range of 20 μm to 125 μm, and more preferably in the range of 30 μm to 100 μm. . This is because if the thickness of the transparent substrate is thinner than the above range, the necessary self-supporting property may not be imparted to the retardation film produced according to the present invention. Further, if the thickness is thicker than the above range, for example, when cutting the retardation film produced according to the present invention, the processing waste may increase or the cutting blade may be worn quickly. It is.
Here, when the transparent substrate used in this step has a configuration in which a plurality of layers are laminated, the above thickness means the sum of the thicknesses of the respective layers.

c. Method for Applying Retardation Layer Forming Coating Liquid Next, a method for applying the retardation layer forming coating liquid on the transparent substrate will be described. In this step, the method of coating the retardation layer forming coating solution on the transparent substrate is not particularly limited as long as it is a method capable of coating a predetermined amount of the retardation layer forming coating solution. Absent. As such a coating method, for example, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, immersion pulling method , Curtain coating method, die coating method, casting method, bar coating method, extrusion coating method, E-type coating method, and the like.

  Moreover, generally used drying methods, such as a heat drying method, a reduced pressure drying method, a gap drying method, can be used for the drying method of the coating film of the said retardation layer forming coating liquid. Also, the drying method used in this step is not limited to a single method, and adopts a plurality of drying methods, for example, by sequentially changing the drying method according to the amount of solvent remaining in the coating film. Also good.

d. Others When the polymerizable optically anisotropic material is used as the optically anisotropic material, usually, after forming a coating film of the retardation layer forming coating solution on the transparent substrate in this step, the polymerization is performed. A polymerization treatment step for polymerizing the functional group is performed. What is necessary is just to determine arbitrarily as said polymerization process according to the kind of polymeric functional group which the said optically anisotropic material has. Examples of such a polymerization process include a process of irradiating active radiation such as ultraviolet rays, a heat treatment, and the like.

2. Stretching process Next, the stretching process used in the present invention will be described. This step is a step of causing the retardation layer forming layer to exhibit retardation by stretching the optical laminate formed by the optical laminate formation step. Further, in this step, the optical layered body is stretched, and the optically anisotropic material contained in the retardation layer forming layer is arranged along the stretching direction, whereby the retardation layer forming layer is formed. It can also be said that this is a step of imparting phase difference.
Here, since the optical laminate that is stretched in this step has the above-described breaking tensile elongation ratio within the range specified in the present invention, the retardation layer forming layer or the transparent substrate in this step The optical layered body can be stretched without any crack or breakage in either one of the above.
In addition, the optical laminated body stretched in this step is a retardation having a configuration in which a retardation layer is laminated on a transparent substrate by stretching the retardation layer forming layer to impart retardation. Become a film.
Hereinafter, such a stretching process will be described in detail.

  The aspect of stretching the optical layered body in this step is not particularly limited as long as it is within a range in which a desired retardation can be imparted to the retardation film produced according to the present invention. Therefore, the stretching mode in this step may be uniaxial stretching or biaxial stretching.

  Moreover, it does not specifically limit as a draw ratio which extends | stretches an optical laminated body in this process, if it exists in the range which can provide desired phase difference to the phase difference film manufactured by this invention. Especially, it is preferable that the draw ratio in this process exists in the range of 1.01 times-2 times. Since the stretching ratio is within such a range, in this step, it is possible to further prevent cracks from occurring in either the retardation layer forming layer or the transparent substrate. This is because the method for producing the retardation film can be made more productive.

  In this step, the method for stretching the retardation layer is not particularly limited as long as it can impart desired retardation to the retardation film produced according to the present invention. In particular, in this step, nx> ny ≧ between the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction. It is preferable to stretch so that the nz relationship is established. By stretching in this way, the retardation film produced according to the present invention can be made suitable as a viewing angle compensation film for a liquid crystal display device.

  In this step, as a mode of stretching the retardation layer so that the relationship of nx> ny ≧ nz is established between nx, ny, and nz, uniaxial stretching can be performed between nx, ny, and nz. A mode (first mode) of stretching so that a relationship of nx> ny = nz is established and a relationship of nx> ny> nz is established between nx, ny, and nz by biaxial stretching. Thus, an aspect (second aspect) of stretching can be mentioned.

  The method for stretching the retardation layer in the first aspect and the second aspect is not particularly limited as long as the retardation layer can be stretched to a desired stretching ratio. Examples of such a method include a roll stretching method, a long gap stretching method, a tenter stretching method, and a tubular stretching method.

  In this step, the retardation layer is usually stretched in a heated state, but the heating temperature at this time is particularly limited as long as the retardation layer can be stretched at a desired magnification. Not. In particular, in the present invention, it is usually not lower than the glass transition temperature and not higher than the melting point temperature.

3. Other Steps The method for producing a retardation film of the present invention may have other steps in addition to the retardation layer forming step and the stretching treatment step. As such other steps, those capable of producing a retardation film having a desired function can be appropriately selected and used according to the use of the retardation film produced according to the present invention.

  Moreover, if the manufacturing method of the retardation film of this invention is implemented, if the said retardation layer forming process and the said extending | stretching process process are implemented, it will not specifically limit. As such an embodiment, for example, a long-formed transparent substrate is used, and a roll-to-roll process (a belt-shaped film supplied in a winding form is unwound and traveled to be continuously processed. The phase difference layer forming step and the stretching treatment step may be continuously carried out by a later winding method), or a transparent substrate processed into a predetermined size (sheet) is used. The phase difference layer forming step and the stretching step may be performed while sequentially moving the transparent substrate.

4). Retardation Film The retardation film produced according to the present invention has a transparent substrate and a retardation layer formed on the transparent substrate and containing an optically anisotropic material having refractive index anisotropy. .

  The wavelength dependency of the retardation value of the retardation film produced according to the present invention may be a normal dispersion type, a reverse dispersion type, or a flat type.

Moreover, the Nz factor of the retardation film manufactured by this invention is not specifically limited, It can adjust arbitrarily according to the use of retardation film. For example, when the retardation film produced according to the present invention is used as a viewing angle compensation film for an IPS liquid crystal display device, the Nz factor is preferably in the range of 0.5 to 1.0, while the present invention is When the retardation film produced by the above is used as a viewing angle compensation film (A plate) of a VA liquid crystal display device, the Nz factor is preferably in the range of 1.0 to 2.0.
Here, the Nz factor is a parameter that defines the shape of the refractive index ellipsoid, and the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the thickness direction. And the refractive index nz are represented by the following formula.
Nz = (nx-ny) / (nx-nz)

  Further, when the retardation film produced according to the present invention is used as a viewing angle compensation film for a liquid crystal display device, the refractive index nx in the slow axis direction in the in-plane direction and the refractive index ny in the fast axis direction in the in-plane direction. And the refractive index nz in the thickness direction, it is preferable that a relationship of nx> ny ≧ nz holds. This is because when such a relationship is established among the above nx, ny and nz, the film can be suitably used as a viewing angle compensation film of a liquid crystal display device.

  As an aspect in which the relationship of nx> ny ≧ nz is established in nx, ny and nz, a uniaxial retardation film in which the relationship of nx> ny = nz is established and the relationship of nx> ny> nz is established. Biaxial retardation film can be mentioned.

When the retardation film produced according to the present invention is the uniaxial retardation film, the retardation (Re) at a wavelength of 550 nm is preferably in the range of 0 nm <Re ₅₅₀ <300 nm.
Further, the thickness direction retardation (Rth) at a wavelength of 550 nm is preferably in the range of 0 nm to 150 nm.

On the other hand, when the retardation film produced by the present invention is the biaxial retardation film, the retardation (Re) at a wavelength of 550 nm is preferably in the range of 0 nm <Re ₅₅₀ <300 nm.
Further, the thickness direction retardation (Rth) at a wavelength of 550 nm is preferably in the range of 0 nm to 300 nm.

  In addition, the form of the retardation film manufactured by this invention can be made into a desired form according to the use etc. of retardation film. Therefore, for example, it may be formed in a long shape and wound into a roll shape, or may be in a sheet shape cut into a predetermined size.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to examples.

1. Example 1
(1) Optical layered product forming step Caprolactone-modified urethane acrylate is used as an optically anisotropic material, dissolved in methyl ethyl ketone so as to be 40% by mass, and further a polymerization initiator is added by 4% by mass with respect to the solid content. Thus, a coating solution for forming a retardation layer was prepared.

As the transparent substrate, a TAC (triacetylcellulose) film having a breaking tensile elongation of 30% was used, and the retardation layer forming coating solution was applied to the surface of the TAC film by bar coating. Subsequently, the solvent is removed by heating at 90 ° C. for 4 minutes, and the optically anisotropic material is fixed by irradiating the coated surface with ultraviolet rays, thereby forming a 6 μm thick retardation layer on the TAC film. An optical laminate in which layers were laminated was produced.
In addition, the breaking tensile elongation of the phase difference layer forming layer formed in the present example was 160%, and the breaking tensile elongation ratio of the optical laminate was 5.3.

(2) Stretching treatment step Next, the optical film is uniaxially stretched in the in-plane direction while being heated at 165 ° C. so that the stretching ratio is 1.3 times by a stretching experiment machine, thereby forming a retardation film. Produced. At this time, the optical layered product was stretchable without the retardation layer forming layer being peeled off from the TAC film.

2. Example 2
A retardation film was produced in the same manner as in Example 1 except that urethane acrylate was used as the optically anisotropic material.
As a result, the optical laminate was stretchable without the retardation layer forming layer being peeled off from the TAC film.
In addition, the breaking tensile elongation of the phase difference layer forming layer formed in this example was 350%, and the breaking tensile elongation ratio of the optical laminate was 8.

3. Example 3
A retardation film was produced in the same manner as in Example 1 except that a PMMA film having a breaking tensile elongation of 10% was used as the base material as the transparent substrate.
As a result, the optical laminate was stretchable without the retardation layer forming layer being peeled off from the PMMA film.
In addition, the fracture tensile elongation ratio of the optical layered body formed in this example was 16.

4). Example 4
A retardation film was produced in the same manner as in Example 1 except that a norbornene-based resin film (trade name: Arton JSR) having a breaking tensile elongation of 13% was used as the transparent substrate.
As a result, the optical laminate was stretchable without the retardation layer forming layer being peeled off from the norbornene-based resin film.
In addition, the breaking tensile elongation ratio of the optical laminated body formed in the present Example was 12.3.

5. Comparative Example 1
A retardation film was produced in the same manner as in Example 1 except that isocyanuric acid EO-modified diacrylate was used as the optically anisotropic material.
As a result, when the optical laminate was stretched, peeling occurred at the interface between the TAC film and the retardation layer forming layer.
In addition, the fracture tensile elongation of the phase difference layer forming layer formed in the comparative example was 2%, and the fracture tensile elongation ratio of the optical laminate was 0.06.

6). Comparative Example 2
A retardation film was produced in the same manner as in Example 1 except that urethane acrylate was used as the optically anisotropic material and a PMMA film having a tensile elongation at break of 10% was used as the transparent substrate.
As a result, when the optical layered body was stretched, cracks occurred in the retardation layer forming layer.
In addition, the breaking tensile elongation of the phase difference layer forming layer formed in this example was 350%, and the breaking tensile elongation ratio of the optical laminate was 35.

It is the schematic which shows an example of the manufacturing method of the retardation film of this invention. It is the schematic which shows an example of the optical laminated body in this invention. It is the schematic which shows an example of a common liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Phase difference layer 2 '... Phase difference layer formation layer 10 ... Phase difference film 10' ... Optical laminated body 30 ... Phase difference film 100 ... Liquid crystal display device 102A, 102B ... Polarizing plate 104 ... Liquid crystal cell

Claims (3)

Using a transparent substrate, a retardation layer forming layer is formed on the transparent substrate by coating a retardation layer forming coating solution containing an optically anisotropic material having refractive index anisotropy on the transparent substrate. An optical laminate forming step of forming an optical laminate in which is laminated,
A stretching treatment step of causing the retardation layer forming layer to exhibit retardation by stretching the optical layered body formed by the optical layered body forming step, and forming the optical difference on the transparent substrate. A method for producing a retardation film, comprising producing a retardation film in which a retardation layer containing an anisotropic material is laminated,
The ratio of the breaking tensile elongation of the retardation layer forming layer to the breaking tensile elongation of the transparent substrate (breaking tensile elongation of the retardation layer forming layer / breaking tensile elongation of the transparent substrate) is 1 to 30. range der of is,
The break tensile elongation of the retardation layer forming layer, characterized in der Rukoto the range of 150% to 250%, method for producing a retardation film. The method for producing a retardation film according to claim 1, wherein the tensile elongation at break of the transparent substrate is in the range of 5% to 50%. The stretching ratio of the optical laminate in the stretching treatment step is in the range of 1.01 times to 2 times,
Method for producing a retardation film according to claim 1 or claim 2, wherein the optically anisotropic material is polymerizable optically anisotropic material.

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