JP2004347698A - Retardation plate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation plate excellent in adhesion between base material and an optical anisotropic layer and excellent in cost and manufacture efficiency, and its manufacturing method. <P>SOLUTION: Transparent base material having liquid crystal alignment regulating force is coated with a silane coupling agent or the like so as to form a surface modified layer, which is coated with a liquid crystal compound. Then, the aligned state is fixed to form an optical anisotropic layer, whereby the object retardation plate is obtained. In the retardation plate, the optical anisotropic layer is not directly laminated on the surface having the liquid crystal alignment regulating force but laminated through the surface modified layer. Therefore, an alignment film is omitted. Even if the alignment film is provided, it is directly provided on the surface of the transparent base material differently from the conventional technology, whereby a manufacturing stage is simplified. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００８９】
一方、トリアセチルセルロース（ＴＡＣ）フィルム（富士写真フィルム社製、商品名Ｔ８０ＵＺ、厚み８０μｍ）を準備し、これを、１０重量％濃度の水酸化ナトリウム水溶液中、６０℃で１分間煮沸して表面をケン化処理し、さらにラビング処理して透明基材とした。
【００９０】
他方、シランカップリング剤原液（信越化学工業株式会社製、商品名ＫＢＭ５１０３）を、２重量％酢酸水溶液で希釈して３０分間攪拌し、２重量％シランカップリング剤水溶液を調製した。次に、前記透明基材のラビング処理面上に、前記２重量％のシランカップリング剤水溶液を、第一理化株式会社製バーコーター♯３（商品名）を用いて塗布し、１２０℃のオーブン中で５分間静置して乾燥および熱処理して表面改質層を形成させた。
【００９１】
さらに、前記表面改質層上に、前記塗工液Ａを、第一理化株式会社製バーコーター♯５（商品名）を用いて塗布し、これを１２０℃で２分間加熱して乾燥させて液晶化合物含有層を形成させた。その後、室温環境下で放冷し、前記液晶化合物含有層の温度が約４０℃となるまで冷却した。さらに、前記液晶化合物含有層に紫外線を積算光量で２００ｍＪ／ｃｍ^２照射し、前記液晶化合物を重合させて光学異方性層として目的の位相差板を得た。
【００９２】
（比較例）
前記透明基材（ケン化処理およびラビング処理したＴＡＣフィルム）上に前記表面改質層を形成させず、直接液晶化合物溶液を塗布して光学異方性層を形成させる以外は前記実施例と同様にして位相差板を製造した。
【００９３】
（液晶配向性の評価）
実施例および比較例のそれぞれの位相差板について、日本分光株式会社製Ｍ２２０型自動波長走査型エリプソメータ（商品名）を用いて波長５９０ｎｍの光で位相差測定を行なった。その結果、実施例の位相差板における光学異方性層は面内位相差１３４ｎｍのＡ−ｐｌａｔｅであり、比較例の位相差板における光学異方性層は面内位相差１１９ｎｍのＡ−ｐｌａｔｅであったことから、いずれも液晶化合物が規則的に配向していることが分かった。また、実施例の位相差板は、液晶化合物を含む光学異方性層と透明基材との間に表面改質層が存在しても前記透明基材表面の液晶配向規制力が阻害されていないことが分かった。
【００９４】
（透明基材と光学異方性層との密着性評価）
実施例および比較例のそれぞれの位相差板について、ＪＩＳ Ｋ５４００−１９９０の試験方法により前記透明基材と前記光学異方性層との密着性を試験した。その結果、実施例の位相差板では面積比で７０％の光学異方性層が透明基材上に密着したままであったが、比較例の位相差板では１００％の光学異方性層が剥離してしまった。
【００９５】
以上の通り、実施例の位相差板は、光学異方性層中の液晶化合物が規則的に配向しており、しかも光学異方性層と透明基材との密着性が高いことが分かった。これに対し、比較例の位相差板は、光学異方性層中の液晶化合物が規則的に配向しているが、光学異方性層と透明基材との密着性が低いことが分かった。
【００９６】
【発明の効果】
以上説明した通り、本発明によれば、基材と光学異方性層との密着性に優れ、かつコストと製造効率にも優れる位相差板およびその製造方法を提供できる。本発明の位相差板は、各種光学素子や画像表示装置等に広く使用することができ、特に、液晶ディスプレイの薄型化等に大いに寄与することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a retardation plate preferably used for an image display device, for example, a liquid crystal display device (LCD) and a method for manufacturing the same.
[0002]
[Prior art]
A retardation plate (also referred to as an optical compensator, an optical compensatory sheet or the like) is an important member that realizes improvement in contrast and expansion of a viewing angle range in an image display device such as a liquid crystal display device by optical compensation. The retardation plate may be one in which a polymer film is stretched to impart optical anisotropy, or one in which an optically anisotropic layer containing a liquid crystal compound is coated on a transparent substrate such as glass or a polymer film. is there. In particular, the latter has attracted attention due to recent thinning of liquid crystal display devices and the like.
[0003]
In the production of a retardation plate, in order to form an optically anisotropic layer containing a liquid crystal compound, the orientation of all the molecules of the liquid crystal compound or the mesogenic portion exhibiting liquid crystallinity is changed in a fixed direction or continuously. It is necessary to orient regularly. As a specific method therefor, first, a liquid crystal compound solution or melt is applied on an alignment substrate such as a uniaxially stretched polymer film to form a liquid crystal compound-containing layer, and the liquid crystal compound is further aligned. Then, there is a method of forming the optically anisotropic layer (for example, see Patent Document 1). Second, the transparent substrate surface is treated to give a liquid crystal alignment regulating force, and a liquid crystal compound solution or melt is applied thereon to form a liquid crystal compound-containing layer, and the liquid crystal compound is further aligned. There is also a method of forming an optically anisotropic layer (see, for example, Patent Document 2). In the first method, generally, as a transparent substrate, an optically isotropic polymer film or an optically anisotropic film having an optical axis different from the liquid crystal compound orientation direction of the optically anisotropic layer. It is separately prepared, and the optically anisotropic layer is transferred thereon. This is because it is difficult to use the oriented substrate as it is as the transparent substrate from the viewpoint of optical anisotropy and transparency. On the other hand, the second method does not require the transfer step, and therefore has advantages over the first method in terms of cost and manufacturing efficiency, and is often used. In this method, as a method for providing the liquid crystal alignment regulating force, for example, a method of directly rubbing the surface of the transparent substrate, or forming a film on the surface of the transparent substrate, rubbing or polarizing the film. There is a method of performing an ultraviolet irradiation treatment or the like to form an alignment film. In particular, the rubbing treatment is a frequently used method because it can easily provide a liquid crystal alignment regulating force.
[0004]
One of the important factors in the retardation plate manufactured in this way is the adhesion between the layers, for example, between the transparent substrate and the optically anisotropic layer. For example, the retardation plate is often bonded to a polarizing plate or the like to produce an optical element, and the optical element is often bonded to a glass surface of a liquid crystal cell for use. In the step of bonding such an optical element to the glass surface or the like, reworkability of the optical element may be required. However, since the optical element has a multilayer structure, if the adhesion is low at any of the layer interfaces, for example, at the interface between the transparent base material and the optically anisotropic layer, there is a possibility that the optical element may peel off from the interface during rework. is there.
[0005]
There is known a method of providing an adhesion improving layer in order to enhance the adhesion between the layers in the retardation plate. For example, in Patent Document 3, an adhesion improving layer is formed on a transparent substrate made of a polymer film, an alignment film is formed thereon, and a discotic compound is further applied thereon to form an optically anisotropic layer. It is formed to manufacture a phase difference plate. However, this method has problems in terms of cost and production efficiency because it is necessary to form at least three layers of an adhesion improving layer, an alignment film, and an optically anisotropic layer on a transparent substrate.
[0006]
[Patent Document 1]
Japanese Patent No. 2631015
[0007]
[Patent Document 2]
JP-A-2002-14233
[0008]
[Patent Document 3]
JP-A-7-333433
[0009]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a retardation plate which is excellent in adhesion between a substrate and an optically anisotropic layer, and which is excellent in cost and production efficiency, and a method for producing the same.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the retardation plate of the present invention includes a transparent substrate having at least one surface having a liquid crystal alignment regulating force, a surface modification layer, and an optically anisotropic layer containing a liquid crystal compound, The surface modifying layer is laminated on a surface of the transparent substrate having a liquid crystal alignment regulating force, and the optically anisotropic layer is laminated on the transparent substrate via the surface modifying layer. It is a phase difference plate.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described.
[0012]
(Phase plate)
In the prior art using the adhesion improving layer, since it is necessary to directly laminate the optically anisotropic layer on the surface having the liquid crystal alignment regulating force, the adhesion improving layer, the alignment film, and the optically anisotropic layer on a transparent substrate. And at least three layers were required except for the transparent substrate. However, according to the present invention, an optically anisotropic layer can be laminated on a surface having a liquid crystal alignment regulating force via a surface modification layer. For this reason, it is also possible to provide a liquid crystal alignment regulating force by directly rubbing the surface of the transparent substrate or the like and omit the alignment film. Also in the case where an alignment film is provided, unlike the prior art, it can be provided directly on the surface of the transparent base material, so that the manufacturing process is simple. For these reasons, the retardation plate of the present invention is excellent in adhesion between the transparent substrate and the optically anisotropic layer, and is also excellent in cost and production efficiency. Hereinafter, each of the components in the retardation plate of the present invention will be specifically described.
[0013]
The thickness of the transparent base material is not particularly limited, but is preferably as thin as possible, for example, 20 to 120 μm, preferably 20 to 80 μm, and more preferably 20 to 40 μm in order to reduce the thickness of the retardation plate.
[0014]
“Transparent” in the transparent substrate means that the transparent substrate has a light transmittance that can be applied to a retardation plate. The light transmittance is not particularly limited as long as it is in a range suitable for practical use. The higher the transmittance, the more advantageous from the viewpoint of the function of the retardation plate, and ideally 100%.
[0015]
The transparent substrate may be optically isotropic, but the transparent substrate may have optical anisotropy depending on a function required for a liquid crystal display device equipped with a retardation plate. Is preferred. Although the optical anisotropy in this case is not particularly limited, for example, optical anisotropy exhibiting a positive or negative A-Plate retardation characteristic, optical anisotropy exhibiting a positive or negative C-Plate retardation characteristic Optical anisotropy exhibiting a positive or negative O-Plate phase difference characteristic, biaxial optical anisotropy having a refractive index anisotropy in different directions (that is, having two optical axes), and the like are possible. is there. Note that A-plate, C-plate and O-plate all refer to a layer having so-called uniaxial optical anisotropy. The A-plate has a positive (positive) A-plate when the optical axis exists in the in-plane direction and the optical characteristic condition satisfies the following formula (I), and a negative A-plate when the optical characteristic condition satisfies the following formula (II) Called (negative) A-plate.
[0016]
nx> ny = nz (I)
nx <ny = nz (II)
[0017]
The C-plate has a positive (positive) C-plate when the optical axis exists in the Z-axis direction, that is, the thickness direction, and the optical characteristic condition satisfies the following formula (III), and the following formula (IV). If it satisfies, it is called Negative C-plate.
[0018]
nx = ny <nz (III)
nx = ny> nz (IV)
[0019]
In the above formulas (I) to (IV), nx, ny and nz indicate the refractive index of the layer in the X-axis, Y-axis and Z-axis directions. However, one of the X axis and the Y axis is an axial direction indicating the maximum refractive index in the plane of the layer, and the other is an axial direction in the plane perpendicular to the axis. The Z axis indicates a thickness direction perpendicular to the X axis and the Y axis. In the O-plate, the optical axis direction is inclined when viewed from the in-plane direction and the Z-axis direction (the thickness direction perpendicular to the in-plane direction). The means for imparting optical anisotropy is not particularly limited, and a known method may be appropriately applied.For example, the optically anisotropic transparent film is subjected to stretching treatment or the like to impart optical anisotropy. It can be a transparent substrate.
[0020]
Although the material of the transparent substrate is not particularly limited, for example, glass, a polymer film, or the like can be used. The polymer that can be used for the polymer film is not particularly limited. For example, polyethylene-based polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetyl cellulose and triacetyl cellulose; and acrylic polymers such as polymethyl methacrylate. Polystyrene, styrene-based polymer such as acrylonitrile-styrene copolymer (AS resin), polycarbonate-based polymer such as bisphenol A-carbonic acid copolymer, linear or branched such as polyethylene, polypropylene, ethylene-propylene copolymer Polyolefins containing cyclo structures such as polyolefins and polynorbornenes, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamides, imide polymers, and sulfone polymers Polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, and epoxy polymer. Preferably, these may be used alone or in combination of two or more. Among the above polymers, more preferred are cellulosic polymers such as triacetyl cellulose, polycarbonate polymers such as bisphenol A / carbonic acid copolymer, polyolefins having a cyclo structure such as polynorbornene, and amides such as aromatic polyamide. Polymers and imide polymers are particularly preferable, and a cellulose polymer (cellulose derivative) is particularly preferable.
[0021]
Examples of the material of the transparent substrate include a polymer film described in JP-A-2001-343529 (WO01 / 37007). Examples of the polymer material include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a cyano group in a side chain. For example, a resin composition having an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be used. The polymer film may be, for example, an extruded product of the resin composition.
[0022]
The transparent base material needs to have a liquid crystal alignment regulating force, but the method of imparting the liquid crystal alignment regulating force is not particularly limited, and a known method can be appropriately used. For example, the transparent substrate may be one in which a polymer film surface is directly rubbed to impart a liquid crystal alignment regulating force, or an alignment film is provided on the surface of glass or a polymer film, and further subjected to rubbing treatment or polarized ultraviolet irradiation. A liquid crystal alignment regulating force may be imparted by the method described above. The material and manufacturing method of the alignment film are not particularly limited, and known materials and manufacturing methods can be appropriately used. In addition, a polymer film provided with optical anisotropy by stretching or the like can be used as a transparent substrate having a liquid crystal alignment regulating force without surface treatment in some cases. Among these transparent substrates, those in which the surface of the polymer film is directly subjected to a rubbing treatment to impart a liquid crystal alignment regulating force are preferred because the treatment is simple and the liquid crystal alignment regulating force is excellent.
[0023]
In addition, it is preferable that the transparent base material contains a hydrophilic group, for example, a hydroxyl group or the like on the surface, since the adhesion to the surface modified layer is further improved. Even if the material of the transparent substrate is a material such as triacetyl cellulose that does not contain a hydrophilic group, for example, the surface is subjected to a saponification treatment or the like to express a hydrophilic group, and the adhesiveness with the surface-modified layer. Can be increased.
[0024]
Next, the surface modified layer will be described.
[0025]
The surface modification layer is not particularly limited, but preferably contains an organic silicon compound, and can be formed using, for example, a surface modification agent called a silane coupling agent or a silane coupler. The thickness of the surface modification layer is not particularly limited as long as the adhesion between the liquid crystal and the substrate is maintained and the liquid crystal alignment regulating force of the substrate is not lost. A surface-modified layer using a surface-modifying agent such as a silane coupling agent is generally used to enhance the adhesion between materials that are not easily compatible with each other, for example, glass and an organic material. However, the present inventor has found that this can be applied to the surface of the transparent substrate having a liquid crystal alignment regulating force to improve the adhesion to a liquid crystal compound.
[0026]
The silane coupling agent used for the surface-modified layer of the present invention is not particularly limited, and a known silane coupling agent can be appropriately used. The silane coupling agent is represented by a general formula such as the following formula (V).
Y- (CH ₂ ) _n Six ₃ (V)
In the formula (V), n is an integer of 1 or more, and is preferably in a range of 1 or more and 3 or less. In the above formula (V), X is a hydrolyzable substituent such as an alkoxy group or a halogen, and Y is a substituent that easily reacts with an organic substance such as a vinyl group, an epoxy group or an amino group. The silane coupling agent that can be used in the present invention is not limited to this, and any silane coupling agent can be used. In such a case, it is preferable that an unsaturated bond between carbon atoms is included in the molecule because a chemical bond between the liquid crystal molecule and the silane coupling agent is possible. The silane coupling agent containing an unsaturated bond between carbon atoms in the molecule includes, for example, a silane coupling agent containing a vinyl group, but is not limited thereto.
[0027]
Next, the optically anisotropic layer containing the liquid crystal compound will be described.
[0028]
The thickness of the optically anisotropic layer is not particularly limited, but is preferably as thin as possible for thinning the retardation plate, for example, 0.5 to 10 μm, preferably 1 to 10 μm, more preferably 2 to 8 μm. . The orientation direction of the liquid crystal compound in the optically anisotropic layer is not particularly limited, and may be appropriately set so as to obtain optimal optical compensation. For example, so-called homogenous tilt alignment, hybrid alignment, chiral nematic alignment, or homogeneous horizontal alignment Orientation, homeotropic orientation and the like are preferred. The control method is not particularly limited, and can be controlled similarly to the conventional method by appropriately selecting the type of the liquid crystal compound, the state of the surface having the liquid crystal alignment regulating force, and the like. In the retardation plate of the present invention, the optically anisotropic layer is laminated on a surface of the transparent substrate having a liquid crystal alignment regulating force via the surface modification layer, but the alignment direction of the liquid crystal compound is Control can be performed according to the same rule as in the case of directly laminating without interposing the surface modified layer.
[0029]
The liquid crystal compound contained in the optically anisotropic layer is not particularly limited, and various known liquid crystal compounds can be appropriately used. For example, a rod-shaped liquid crystal compound, a flat liquid crystal compound, and a polymer thereof are used. And may be used alone or in combination of two or more. The liquid crystal compounds include, for example, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines And liquid crystal compounds such as phenyldioxane, tolane, alkenylcyclohexylbenzonitrile and the like, and polymers thereof, among which benzoic acid esters are preferable. In addition, the liquid crystal compound preferably contains a nematic liquid crystal compound because of good alignment properties and few alignment defects. For example, a VA-type liquid crystal display device or the like has a negative C-plate. It is preferable to include a cholesteric liquid crystal compound because it is effective for compensating the viewing angle. The liquid crystal compound preferably contains, for example, a polymer of a liquid crystal monomer or a liquid crystal prepolymer from the viewpoint of easy formation of the optically anisotropic layer, but may contain a liquid crystal polymer. Further, the optically anisotropic layer may appropriately contain a substance other than the liquid crystal compound, for example, a photopolymerization initiator, a leveling agent, a viscosity modifier and the like, as long as the function of the retardation plate is not impaired.
[0030]
(Method of manufacturing retardation plate)
Next, a method for manufacturing a retardation plate of the present invention will be described.
[0031]
The method for producing the retardation plate of the present invention is not particularly limited, and may be produced by any method. For example, it can be produced by a production method including the following steps (1) to (4).
(1) A step of forming a surface-modified layer on a surface of a transparent substrate having at least one surface having a liquid crystal alignment regulating force on a surface having a liquid crystal alignment regulating force.
(2) A step of forming a liquid crystal compound-containing layer on the surface modified layer.
(3) A step of regularly aligning the liquid crystal compound contained in the liquid crystal compound-containing layer.
(4) a step of fixing the alignment state of the liquid crystal compound to form an optically anisotropic layer.
[0032]
Hereinafter, the manufacturing method will be described more specifically.
[0033]
First, the manufacturing method preferably further includes, for example, a step of rubbing the surface of the transparent base material to impart a desired liquid crystal alignment regulating force prior to the step (1). The reason why a rubbing treatment is preferable as a method for imparting a liquid crystal alignment regulating force to the transparent substrate is as described above. However, as described above, the method of imparting the liquid crystal alignment regulating force is not limited to the rubbing treatment, but may be any method. Preferably, prior to the step (1), a step of expressing a hydrophilic group on the surface of the transparent substrate on which the surface-modified layer is formed is preferable. The method for expressing the hydrophilic group is not particularly limited, and includes, for example, a method such as a saponification treatment as described above. Either the step of expressing the hydrophilic group or the step of imparting the liquid crystal alignment regulating force may be performed first, but it is preferable to perform the step of imparting the liquid crystal alignment regulating force as soon as possible immediately before the step (1).
[0034]
Next, the surface modified layer is formed in the step (1). This formation method is not particularly limited, either, the transparent substrate is immersed in a solution of a silane coupling agent, or a solution of the silane coupling agent is applied on a surface of the transparent substrate having a liquid crystal alignment regulating force, Thereafter, it is preferable that the silane coupling agent solution is dried. The silane coupling agent that can be used is not particularly limited as described above, but a silane coupling agent containing an unsaturated bond between carbon atoms in the molecule is more preferable. Although the coating method is not particularly limited, for example, a spin coating method, a roll coating method, a flow coating method, a printing method, a dip coating method, a casting film forming method, a bar coating method, a gravure printing method, and the like are more preferable. The solvent of the solution is not particularly limited, and a known solvent can be used. For example, acidic water or an alcohol solvent is particularly preferable because the solubility of the silane coupling agent is high. Further, it is particularly preferable to further heat the silane coupling agent solution after drying it, because the affinity between the transparent substrate and the surface modified layer is further increased. The heating temperature is not particularly limited, but is, for example, 60 to 150 ° C, preferably 80 to 120 ° C, and more preferably 100 to 120 ° C. The heating time is also not particularly limited, but is, for example, 1 to 5 minutes, preferably 3 to 5 minutes. The drying and heating may be performed separately or simultaneously.
[0035]
Subsequently, in the step (2), the liquid crystal compound-containing layer is formed on the surface modified layer. The method for forming the liquid crystal compound-containing layer is also not particularly limited, and is a method in which a solution of the liquid crystal compound is applied to the transparent substrate and dried, or a method in which a melt of the liquid crystal compound is applied to the transparent substrate. Is preferred from the viewpoint of simplicity of production and the like. In the present invention, “molten” for a liquid crystal compound means that the compound is in a liquid crystal state or a liquefied state.
[0036]
Here, the liquid crystal compound may be a liquid crystal polymer, but more preferably contains at least one of a liquid crystal prepolymer and a liquid crystal monomer from the viewpoint of low alignment temperature and easy processing. When at least one of a liquid crystal prepolymer and a liquid crystal monomer is contained, it is more preferable to polymerize the compound later by a method such as photopolymerization to obtain a polymer. Otherwise, the type of the liquid crystal compound is not particularly limited, and is as described above.
[0037]
The range of the temperature at which the liquid crystal compound-containing layer exhibits a liquid crystal state (liquid crystal temperature) is appropriately determined depending on the type of the liquid crystal compound and the like. The liquid crystal temperature range is not particularly limited, and may be appropriately set in consideration of the manufacturing and use convenience of the retardation plate, etc. Preferably not too high. When the liquid crystal compound is a liquid crystal monomer or a liquid crystal prepolymer, the liquid crystal temperature range is, for example, 20 to 150 ° C, preferably 20 to 120 ° C, particularly preferably 20 to 80 ° C. For example, the range is 100 to 200 ° C, preferably 100 to 150 ° C.
[0038]
When the liquid crystal compound contains a liquid crystal prepolymer or a liquid crystal monomer and is subsequently photopolymerized, it is particularly preferable to add a photopolymerization initiator. The photopolymerization initiator is not particularly limited. For example, Irgacure 907, Irgacure 369, Irgacure 184 (all trade names) manufactured by Ciba Specialty Chemicals, or a mixture thereof is preferable. The addition amount of the photopolymerization initiator is not particularly limited either, but is, for example, 0.1 to 5% by weight, and preferably 0.1 to 1% by weight, based on the liquid crystal prepolymer and the liquid crystal monomer. In the solution of the liquid crystal compound, the solvent is not particularly limited. However, a solvent that easily dissolves the liquid crystal compound and does not easily erode the surface modified layer or the transparent substrate is preferable. As the solvent, for example, ketones such as methyl ethyl ketone, cyclopentanone, cyclohexanone, esters such as ethyl acetate, and hydrocarbons such as toluene can be used. Further, a leveling agent, a viscosity adjusting agent, and the like may be appropriately added to the solution or the melt of the liquid crystal compound as needed.
[0039]
The method for applying the solution or the melt of the liquid crystal compound is not particularly limited. For example, a spin coating method, a roll coating method, a flow coating method, a printing method, a dip coating method, a casting film forming method, a bar coating method, a gravure method A printing method or the like is preferred.
[0040]
Next, in the step (3), the liquid crystal compound contained in the liquid crystal compound-containing layer is regularly aligned. Although this method is not particularly limited, a method in which the liquid crystal compound-containing layer is heated to the liquid crystal temperature, or a method in which the layer is once heated to a temperature higher than the liquid crystal temperature and then cooled to the liquid crystal temperature is preferable. The liquid crystal temperature range is as described above. After heating or cooling to the liquid crystal temperature, the time required for regularly aligning the liquid crystal compound is not particularly limited, but is, for example, 10 to 120 seconds, and preferably 30 to 60 seconds. Note that the step (2) and the step (3) can be performed simultaneously by applying the liquid crystal compound which is in a liquid crystal state by melting on the surface modification layer.
[0041]
Then, in the step (4), the alignment state of the liquid crystal compound is fixed to form an optically anisotropic layer, thereby obtaining a target retardation plate. As described above, it is more preferable that the liquid crystal compound includes at least one of a liquid crystal prepolymer and a liquid crystal monomer, and the fixing of the alignment state is performed by a method of photopolymerizing the liquid crystal compound. The irradiation light in this case is not particularly limited, but is preferably, for example, ultraviolet light, and the wavelength of the ultraviolet light is more preferably 200 to 400 nm. The light intensity, irradiation time, and integrated light amount of the irradiation light are not particularly limited as long as the alignment state is sufficiently fixed.
[0042]
Further, when the liquid crystal compound is a liquid crystal polymer, the fixing of the alignment state is preferably performed by a method of cooling the liquid crystal compound-containing layer to a temperature lower than the liquid crystal temperature. The liquid crystal temperature range is as described above. The cooling method is not particularly limited, and may be simply left under room temperature conditions, or may be rapidly cooled using an appropriate cooler.
[0043]
The retardation plate of the present invention can be manufactured as described above, but the manufacturing method of the present invention is not limited to the above description, and can be modified in any manner without departing from the gist of the present invention.
[0044]
(Optical element and image display device)
The application of the retardation plate of the invention is not particularly limited, and can be widely used for various optical elements and image display devices. Hereinafter, the optical element and the image display device of the present invention will be described.
[0045]
First, the optical element of the present invention is an optical element including the retardation plate of the present invention and a polarizer. Other than this, the optical element of the present invention is not particularly limited. For example, it is preferable that the optical element further includes an adhesive layer, and the retardation plate and the polarizer are laminated via the adhesive layer. It is preferable that a protective film is further included, and the retardation plate and the polarizer are laminated via the transparent protective film. For example, the optical element of the present invention may be an optical element in which the retardation plate and the polarizer are directly bonded by the bonding layer. Further, the optical element of the present invention is an optical element in which the retardation plate of the present invention is further laminated on a polarizing plate in which a transparent protective film is laminated on a polarizer, wherein the polarizer, the transparent protective film and the retardation plate are Each may be laminated via an adhesive layer. Further, the optical element of the present invention may appropriately include optional components other than the polarizer and the transparent protective film. Hereinafter, each component of the optical element of the present invention will be described more specifically.
[0046]
The polarizer is not particularly limited, but a stretched film is preferable because good optical characteristics are easily obtained. For example, a film prepared by adsorbing a dichroic substance such as iodine or a dichroic dye on various films by a conventionally known method, dyeing the film, crosslinking, stretching, and drying can be used. Among these, a film that transmits linearly polarized light when natural light is incident thereon is preferable, and a film that is excellent in light transmittance and polarization degree is preferable. Examples of the various films on which the dichroic substance is adsorbed include, for example, polyvinyl alcohol (PVA) -based films, partially formalized PVA-based films, ethylene-vinyl acetate copolymer-based partially saponified films, and cellulose-based films. Molecular films and the like, and besides these, for example, oriented polyene films such as dehydrated PVA and dehydrochlorinated polyvinyl chloride can also be used. Among these, a polyvinyl alcohol-based polarizing film is preferable because good optical characteristics are easily obtained. The thickness of the polarizer is, for example, in the range of 1 to 80 μm, but is not limited thereto.
[0047]
The transparent protective film is not particularly limited, and a conventionally known transparent film can be used. For example, a film having excellent transparency, mechanical strength, heat stability, moisture barrier properties, isotropy, and the like is preferable. Specific examples of the material of such a transparent protective film include, for example, polyethylene-based polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetyl cellulose and triacetyl cellulose; acrylic polymers such as polymethyl methacrylate; and polystyrene. Styrene polymers such as acrylonitrile / styrene copolymer (AS resin), polycarbonate polymers such as bisphenol A / carbonic acid copolymer, linear or branched polyolefins such as polyethylene, polypropylene, ethylene / propylene copolymer; Polyolefins having a cyclo structure such as polynorbornene, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, polyethers Sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, etc. Further, a thermosetting resin such as an acrylic, urethane, acrylic urethane, epoxy, or silicone resin or an ultraviolet curable resin may also be used. These may be used alone or in combination of two or more. Among them, a TAC film whose surface is saponified with an alkali or the like is preferable from the viewpoint of polarization characteristics and durability. In addition, a polymer film described in JP-A-2001-343529 (WO 01/37007) can also be preferably used.
[0048]
Further, it is preferable that the transparent protective film has no coloring, for example. Specifically, the retardation value (Rth) in the film thickness direction is preferably in the range of -90 nm to +75 nm, more preferably in the range of -80 nm to +60 nm, and particularly preferably in the range of -70 nm to +45 nm. . When the retardation value is in the range of -90 nm to +75 nm, coloring (optical coloring) due to the protective film can be sufficiently eliminated. However, Rth in this case is represented by the following formula (VI). In the formula (VI), the definitions of nx, ny and nz are the same as those in the formulas (I) to (IV), and d indicates the thickness of the transparent protective film.
[0049]
Rth = [(nx + ny) / 2-nz] × d (VI)
[0050]
The thickness of the transparent protective film is not particularly limited and can be appropriately determined depending on, for example, a retardation and a protection strength, but is usually 500 μm or less, preferably 5 to 300 μm, more preferably 5 to 150 μm. It is.
[0051]
The transparent protective film can be appropriately formed by a conventionally known method such as a method of applying the various transparent resins to a polarizer, a method of laminating the transparent resin film on the polarizer, or use a commercially available product. You can also. Further, the transparent substrate in the retardation plate of the present invention may also serve as the transparent protective film.
[0052]
The transparent protective film may be further subjected to, for example, a hard coat treatment, an anti-reflection treatment, a treatment for preventing sticking and diffusion, an anti-glare, and the like. The hard coat treatment is a process for forming a cured film having excellent hardness and slipperiness, which is made of a curable resin on the surface of the transparent protective film, for the purpose of, for example, preventing scratches on the surface. . As the curable resin, for example, an ultraviolet curable resin such as a silicone-based, urethane-based, acrylic-based, or epoxy-based resin can be used, and the treatment can be performed by a conventionally known method. The purpose of preventing sticking is to prevent adhesion between adjacent layers. The antireflection treatment is for the purpose of preventing external light from being reflected on the polarizing plate surface, and can be performed by forming a conventionally known antireflection layer or the like.
[0053]
The anti-glare treatment is for the purpose of preventing obstruction of transmitted light due to reflection of external light and the like, for example, by forming a fine uneven structure on the surface of the transparent protective film by a conventionally known method. It can be done by doing. Examples of a method of forming such a concavo-convex structure include a method of forming a surface by sandblasting or embossing, and a method of forming the transparent protective film by blending transparent fine particles with the transparent resin as described above. Can be
[0054]
Examples of the transparent fine particles include, for example, silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like.In addition, inorganic fine particles having conductivity, and crosslinked or uncrosslinked. Organic fine particles composed of polymer particles or the like can also be used. The average particle size of the transparent fine particles is not particularly limited, but is, for example, in a range of 0.5 to 20 μm. The mixing ratio of the transparent fine particles is not particularly limited, but is generally preferably in the range of 2 to 70 parts by mass, more preferably in the range of 5 to 50 parts by mass per 100 parts by mass of the transparent resin as described above.
[0055]
The antiglare layer containing the transparent fine particles may be used, for example, as a transparent protective film itself, or may be formed as a coating layer on the surface of the transparent protective film. Further, the anti-glare layer may also serve as a diffusion layer (a visual compensation function or the like) for diffusing transmitted light and expanding a viewing angle.
[0056]
The anti-reflection layer, anti-sticking layer, diffusion layer, anti-glare layer and the like are separately formed from the transparent protective film, for example, as an optical layer composed of a sheet provided with these layers, laminated on a polarizing plate. May be.
[0057]
Further, the polarizing plate may further include other optical layers, for example, various conventionally known optical layers used for forming a liquid crystal display device such as a reflector, a semi-transmissive reflector, and a brightness enhancement film. One of these optical layers may be used, two or more of them may be used in combination, one layer may be used, or two or more layers may be laminated. Hereinafter, such an integrated polarizing plate will be described.
[0058]
First, an example of a reflective polarizing plate or a transflective polarizing plate will be described. In the reflective polarizing plate, a reflective plate is further laminated on the polarizer and the transparent protective film, and in the semi-transmissive reflective polarizing plate, a semi-transmissive reflective plate is further laminated on the polarizer and the transparent protective film.
[0059]
The reflection type polarizing plate is disposed, for example, on the back side of a liquid crystal cell, and can be used for a liquid crystal display device (reflection type liquid crystal display device) that reflects incident light from the viewing side (display side) to display. Such a reflective polarizer can omit the incorporation of a light source such as a backlight, for example, and thus has advantages such as enabling the liquid crystal display device to be thinner.
[0060]
The reflective polarizing plate can be manufactured by a conventionally known method such as a method of forming a reflective plate made of metal or the like on one surface of a polarizing plate exhibiting an elastic modulus. Specifically, for example, one surface (exposed surface) of the transparent protective film in the polarizing plate is subjected to a mat treatment as needed, and a metal foil or a vapor-deposited film made of a reflective metal such as aluminum is coated on the surface. And the like.
[0061]
Further, as described above, a reflective polarizing plate, which includes a transparent protective film in which fine particles are contained in various transparent resins to form a fine uneven structure on the surface and a reflective plate reflecting the fine uneven structure is formed on the transparent protective film. Can be A reflector having a fine uneven structure on its surface has an advantage that, for example, incident light is diffused by irregular reflection, directivity and glare can be prevented, and uneven brightness can be suppressed. Such a reflection plate, for example, on the uneven surface of the transparent protective film, a vacuum deposition method, an ion plating method, a deposition method such as a sputtering method or a plating method, a conventionally known method, directly, the metal foil or It can be formed as a metal deposition film.
[0062]
Further, instead of a method in which the reflective plate is directly formed on the transparent protective film of the polarizing plate as described above, a reflective sheet or the like provided with a reflective layer on an appropriate film such as the transparent protective film is used as the reflective plate. May be. Since the reflection layer in the reflection plate is usually made of a metal, for example, for example, prevention of a decrease in reflectance due to oxidation, a long-term persistence of initial reflectance, and a point of avoiding separate formation of a transparent protective film, etc. It is preferable that the mode of use is such that the reflection surface of the reflection layer is covered with the film, the polarizing plate, or the like.
[0063]
On the other hand, the transflective polarizing plate has a transflective reflecting plate in place of the reflecting plate in the reflecting type polarizing plate. Examples of the semi-transmissive reflection plate include a half mirror that reflects light on a reflection layer and transmits light.
[0064]
The transflective polarizing plate is provided, for example, on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, an image is displayed by reflecting incident light from the viewing side (display side). However, in a relatively dark atmosphere, the present invention can be used for a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of a transflective polarizing plate. That is, the transflective polarizing plate can save energy for use of a light source such as a backlight in a bright atmosphere, and can be used with the built-in light source even in a relatively dark atmosphere. It is useful for formation of etc.
[0065]
Next, an example of a polarizing plate in which a brightness enhancement film is further laminated on the polarizer and the transparent protective film will be described.
[0066]
The brightness enhancement film is not particularly limited, for example, a multilayer thin film of a dielectric, such as a multilayer laminate of thin film having different refractive index anisotropy, transmitting linearly polarized light of a predetermined polarization axis, Other light that shows a characteristic of reflecting light can be used. Examples of such a brightness enhancement film include “D-BEF” (trade name, manufactured by 3M). In addition, a cholesteric liquid crystal layer, in particular, an oriented film of a cholesteric liquid crystal polymer, and a film in which the oriented liquid crystal layer is supported on a film substrate can be used. These reflect one of the left and right circularly polarized light and show the property of transmitting the other light. For example, Nitto Denko's product name "PCF350", Merck's product name "Transmax", etc. can give.
[0067]
The method for producing the optical element of the present invention is not particularly limited and can be produced by a conventionally known method. For example, each component (a retardation plate, a polarizer, a transparent protective film, etc.) It can be manufactured by a method of laminating through the like. The adhesive layer is not particularly limited, and may be, for example, a layer formed from various adhesives, adhesives, and the like. For example, first, a retardation plate of the present invention and a polarizer to which a transparent protective film is adhered are prepared, and then an adhesive is applied to one side of the retardation plate or the transparent protective film, Further, the target optical element can be manufactured by laminating the retardation plate on the transparent protective film. The type of the pressure-sensitive adhesive or the adhesive is not particularly limited and can be appropriately determined depending on the material of each of the constituent elements. For example, acrylic, vinyl alcohol, silicone, polyester, polyurethane, and polyether-based And a rubber-based adhesive. In the present invention, there is no clear distinction between "adhesive" and "adhesive", but among the adhesives, those which are relatively easy to peel and re-adhesively adhere to each other are referred to as "adhesives". Call. The above-mentioned pressure-sensitive adhesives and adhesives are hardly peeled off by the influence of, for example, humidity or heat, and are excellent in light transmittance and polarization degree. Specifically, when the polarizer is a PVA-based film, for example, a PVA-based adhesive is preferable from the viewpoint of the stability of the bonding treatment and the like. These adhesives and pressure-sensitive adhesives, for example, may be applied directly to the surface of the polarizer or the transparent protective film, or a layer such as a tape or sheet composed of the adhesive or pressure-sensitive adhesive is disposed on the surface. May be. Further, for example, when prepared as an aqueous solution, another additive or a catalyst such as an acid may be blended as necessary. When the adhesive is applied, for example, another additive or a catalyst such as an acid may be added to the aqueous solution of the adhesive. The thickness of such an adhesive layer is not particularly limited, but is, for example, 1 nm to 500 nm, preferably 10 nm to 300 nm, and more preferably 20 nm to 100 nm.
[0068]
Each layer such as a polarizer, a transparent protective film, an optical layer and a pressure-sensitive adhesive layer forming the optical element of the present invention as described above is, for example, a salicylate compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound. Alternatively, those having an ultraviolet absorbing ability by appropriately treating with an ultraviolet absorbing agent such as a nickel complex compound may be used.
[0069]
The optical element of the present invention can also be manufactured by, for example, a method in which components are sequentially and separately stacked on a liquid crystal cell surface or the like in a manufacturing process of a liquid crystal display or the like. However, it is better to laminate the above-mentioned components in advance and provide the optical element of the present invention to manufacture a liquid crystal display device or the like, for example, because it is excellent in quality stability and assembly workability, etc. This is preferable because there is an advantage that the efficiency can be improved.
[0070]
The optical element of the present invention further includes, for example, a layer of the pressure-sensitive adhesive or the adhesive on one or both outer surfaces thereof, since the lamination to another member such as a liquid crystal cell is facilitated. Is preferred. The pressure-sensitive adhesive layer or the like may be, for example, a single-layer body or a laminate. As the laminate, for example, a laminate in which different compositions or different types of single layers are combined may be used. When the optical elements are arranged on both sides, for example, they may be the same pressure-sensitive adhesive layer, or may have different compositions or different types of pressure-sensitive adhesive layers. When the surface of the pressure-sensitive adhesive layer or the like provided on the optical element is thus exposed, the surface may be covered with a separator for the purpose of preventing contamination or the like until the pressure-sensitive adhesive layer or the like is put to practical use. preferable. This separator can be formed by, for example, providing an appropriate film with a release coat using a release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. The material of the film is not particularly limited, and for example, the same material as the transparent protective film can be used.
[0071]
The method of using the optical element of the present invention is not particularly limited, but is suitable for use in various image display devices such as, for example, disposing it on the surface of a liquid crystal cell.
[0072]
Next, the image display device of the present invention will be described. The image display device of the present invention is an image display device including the retardation plate of the present invention or the optical element of the present invention. Other than this, the image display device of the present invention is not particularly limited, and its manufacturing method, structure, usage method, and the like are arbitrary, and conventionally known modes can be appropriately applied.
[0073]
Although the type of the image display device of the present invention is not particularly limited, for example, a liquid crystal display device is preferable. For example, the retardation plate or the optical element of the present invention is arranged on one or both sides of a liquid crystal cell to form a liquid crystal panel, and can be used for a liquid crystal display device of a reflection type, a semi-transmission type, or a transmission / reflection type. The type of the liquid crystal cell forming the liquid crystal display device can be arbitrarily selected, for example, an active matrix driving type typified by a thin film transistor type, a simple matrix driving type typified by a twisted nematic type or a super twisted nematic type. Various types of liquid crystal cells can be used.
[0074]
The liquid crystal cell usually has a structure in which liquid crystal is injected into a gap between opposing liquid crystal cell substrates. The liquid crystal cell substrate is not particularly limited, and for example, a glass substrate or a plastic substrate can be used. The material of the plastic substrate is not particularly limited, and may be a conventionally known material.
[0075]
Further, the optical element of the present invention may be provided on one side or both sides of the liquid crystal cell. When members such as the optical element are provided on both sides of the liquid crystal cell, they may be of the same type or different. You may. Further, when manufacturing a liquid crystal display device, for example, one or more layers of appropriate components such as a prism array sheet, a lens array sheet, a light diffusion plate, and a backlight can be arranged at appropriate positions.
[0076]
The structure of the liquid crystal panel in the liquid crystal display device of the present invention is not particularly limited, and includes, for example, a liquid crystal cell, a retardation plate of the present invention, a polarizer and a transparent protective film, and the retardation plate is provided on one surface of the liquid crystal cell. It is preferable that the polarizer and the transparent protective film are laminated in this order. Further, the arrangement of the retardation plate of the present invention is not particularly limited. For example, an arrangement in which the optically anisotropic layer side faces the liquid crystal cell and the transparent base material side faces the polarizer. can give.
[0077]
When the liquid crystal display device of the present invention further includes a light source, the light source is not particularly limited. For example, a planar light source that emits polarized light is preferable because light energy can be used effectively.
[0078]
Further, the image display device of the present invention is not limited to the liquid crystal display device as described above, and includes, for example, an organic electroluminescence (EL) display, a plasma display (PD), an FED (Field Emission Display), and the like. The self-luminous display device may be used. When used in a self-luminous flat display, for example, by setting the in-plane retardation value of the optically anisotropic layer of the retardation plate of the present invention to λ / 4, circularly polarized light can be obtained. Can be used as a prevention filter.
[0079]
Hereinafter, the electroluminescent (EL) display device of the present invention will be described. The EL display device of the present invention is a display device having the retardation plate or the optical element of the present invention. The EL display device may be either an organic EL display device or an inorganic EL display device.
[0080]
In recent years, it has been proposed to use, for example, an optical film such as a polarizer or a polarizing plate together with a λ / 4 plate in an EL display device to prevent reflection from an electrode in a black state. The retardation plate and the optical element of the present invention are particularly suitable when the EL layer emits any one of linearly polarized light, circularly polarized light or elliptically polarized light, or obliquely emits natural light in the front direction. This is very useful when the emitted light is partially polarized.
[0081]
First, a general organic EL display device will be described. The organic EL display generally includes a light-emitting body (organic EL light-emitting body) in which a transparent electrode (anode), an organic light-emitting layer, and a metal electrode (cathode) are stacked in this order on a transparent substrate. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Various combinations such as a stacked body of a light emitting layer and an electron injection layer made of a perylene derivative or the like, and a stacked body of the hole injection layer, the light emitting layer, and the electron injection layer are given.
[0082]
The light emission principle of such an organic EL display device is as follows. That is, by applying a voltage to the anode and the cathode, holes and electrons are injected into the organic light emitting layer, and energy is generated by the recombination of the holes and electrons. Then, the fluorescent substance is excited by the energy, and emits light on the principle that the fluorescent substance emits light when returning to the ground state. The mechanism of the recombination of holes and electrons is the same as that of a general diode, and the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.
[0083]
In the organic EL display device, at least one electrode is required to be transparent in order to extract light emitted from the organic light emitting layer. Therefore, the organic EL display device is usually formed of a transparent conductor such as indium tin oxide (ITO). A transparent electrode is used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually a metal electrode such as Mg-Ag or Al-Li is used.
[0084]
In the organic EL display device having such a configuration, it is preferable that the organic light emitting layer is formed of, for example, an extremely thin film having a thickness of about 10 nm. This is because light is transmitted almost completely in the organic light emitting layer as in the case of the transparent electrode. As a result, when light is not emitted, light that enters from the surface of the transparent substrate, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode exits to the surface of the transparent substrate again. Therefore, when viewed from the outside, the display surface of the organic EL display device looks like a mirror surface.
[0085]
In the organic EL display device of the present invention, for example, it is preferable that the retardation plate or the optical element of the present invention is disposed on the surface of the transparent electrode. With this configuration, an organic EL display device has an effect of suppressing external reflection and improving visibility. For example, the optical element of the present invention including the retardation plate and the polarizing plate has a function of polarizing light incident from the outside and reflected by the metal electrode. This has the effect of not allowing visual recognition from the user. In particular, if the phase difference plate of the present invention is a quarter-wave plate and the angle between the polarization directions of the polarizing plate and the phase difference plate is adjusted to π / 4, the mirror surface of the metal electrode can be completely completed. Can be shielded. That is, only linearly polarized light components of the external light incident on the organic EL display device are transmitted by the polarizing plate. The linearly polarized light is generally converted into elliptically polarized light by the retardation plate. In particular, when the retardation plate is a 波長 wavelength plate and the angle is π / 4, the linearly polarized light is circularly polarized light.
[0086]
This circularly polarized light, for example, passes through a transparent substrate, a transparent electrode, an organic thin film, is reflected by a metal electrode, again passes through an organic thin film, a transparent electrode, a transparent substrate, and is again linearly polarized by the retardation plate. Become. And, since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate, and as a result, the mirror surface of the metal electrode can be completely shielded as described above. .
[0087]
【Example】
Next, examples of the present invention will be described.
[0088]
(Example)
A retardation plate was manufactured as follows. That is, first, toluene was added to 1 g of an ultraviolet-polymerizable nematic liquid crystal compound represented by the following chemical formula (VII) and 0.05 g of a photopolymerization initiator (Irgacure 907 (trade name) manufactured by Ciba Specialty Chemicals), followed by stirring for 10 minutes. Then, the solid was completely dissolved to prepare a solution of the liquid crystal compound (hereinafter referred to as coating liquid A). At this time, the amount of toluene added was adjusted so that the concentration of the solute was 20% by weight.
Embedded image

[0089]
On the other hand, a triacetylcellulose (TAC) film (trade name: T80UZ, manufactured by Fuji Photo Film Co., Ltd., thickness: 80 μm) was prepared and boiled in a 10% by weight aqueous sodium hydroxide solution at 60 ° C. for 1 minute to form a surface. Was subjected to a saponification treatment, followed by a rubbing treatment to obtain a transparent substrate.
[0090]
On the other hand, a silane coupling agent stock solution (trade name: KBM5103, manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with a 2% by weight aqueous acetic acid solution and stirred for 30 minutes to prepare a 2% by weight silane coupling agent aqueous solution. Next, the 2% by weight aqueous solution of the silane coupling agent was applied onto the rubbed surface of the transparent substrate using a bar coater # 3 (trade name) manufactured by Daiichi Rika Co., Ltd. And left to stand for 5 minutes in a vacuum oven to dry and heat-treat to form a surface-modified layer.
[0091]
Further, the coating liquid A was applied on the surface modified layer using a bar coater # 5 (trade name) manufactured by Daiichi Rika Co., Ltd., and dried by heating at 120 ° C. for 2 minutes. A liquid crystal compound-containing layer was formed. Thereafter, the mixture was allowed to cool in a room temperature environment until the temperature of the liquid crystal compound-containing layer reached about 40 ° C. Further, an ultraviolet ray was applied to the liquid crystal compound-containing layer at an integrated light amount of 200 mJ / cm ² Irradiation was performed to polymerize the liquid crystal compound to obtain a target retardation film as an optically anisotropic layer.
[0092]
(Comparative example)
Same as the above example except that the liquid crystal compound solution is directly applied to form an optically anisotropic layer without forming the surface modified layer on the transparent base material (TAC film subjected to saponification treatment and rubbing treatment). To produce a phase difference plate.
[0093]
(Evaluation of liquid crystal orientation)
For each of the retardation plates of the example and the comparative example, the retardation was measured with light having a wavelength of 590 nm using an M220 type automatic wavelength scanning ellipsometer (trade name) manufactured by JASCO Corporation. As a result, the optically anisotropic layer in the retardation plate of the example was an A-plate with an in-plane retardation of 134 nm, and the optically anisotropic layer in the retardation plate of the comparative example was an A-plate with an in-plane retardation of 119 nm. , It was found that the liquid crystal compounds were regularly aligned. Further, in the retardation plate of the example, even if a surface modifying layer is present between the optically anisotropic layer containing the liquid crystal compound and the transparent substrate, the liquid crystal alignment regulating force on the surface of the transparent substrate is hindered. I knew it wasn't.
[0094]
(Evaluation of adhesion between transparent substrate and optically anisotropic layer)
With respect to each of the retardation plates of the examples and the comparative examples, the adhesion between the transparent substrate and the optically anisotropic layer was tested by a test method according to JIS K5400-1990. As a result, in the retardation plate of the example, the optically anisotropic layer having an area ratio of 70% was kept in close contact with the transparent substrate, but in the retardation plate of the comparative example, the optically anisotropic layer was 100%. Has peeled off.
[0095]
As described above, in the retardation plates of the examples, it was found that the liquid crystal compounds in the optically anisotropic layer were regularly oriented, and that the adhesion between the optically anisotropic layer and the transparent substrate was high. . On the other hand, in the retardation plate of the comparative example, although the liquid crystal compound in the optically anisotropic layer was regularly oriented, it was found that the adhesion between the optically anisotropic layer and the transparent substrate was low. .
[0096]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a retardation plate excellent in adhesion between a substrate and an optically anisotropic layer, and excellent in cost and production efficiency, and a method for producing the same. INDUSTRIAL APPLICABILITY The retardation plate of the present invention can be widely used for various optical elements, image display devices, and the like, and in particular, can greatly contribute to thinning of a liquid crystal display and the like.

Claims (22)

At least one surface includes a transparent substrate having a liquid crystal alignment regulating force, a surface modified layer, and an optically anisotropic layer containing a liquid crystal compound, wherein the surface modified layer has a liquid crystal alignment regulating force of the transparent substrate. A retardation plate, wherein the optically anisotropic layer is laminated on the transparent substrate via the surface modifying layer. The retardation plate according to claim 1, wherein the transparent substrate is a substrate obtained by directly rubbing the surface of a polymer film. The retardation plate according to claim 1, wherein the transparent substrate is formed of a cellulose derivative. The retardation plate according to any one of claims 1 to 3, wherein the surface modification layer contains an organosilicon compound. The retardation plate according to any one of claims 1 to 4, wherein the liquid crystal compound contained in the optically anisotropic layer contains a polymer of a liquid crystal monomer or a liquid crystal prepolymer. The retardation plate according to any one of claims 1 to 5, wherein the liquid crystal compound contained in the optically anisotropic layer includes a liquid crystal polymer. The retardation plate according to any one of claims 1 to 6, wherein the liquid crystal compound contained in the optically anisotropic layer includes a nematic liquid crystal compound. The retardation plate according to claim 1, wherein the liquid crystal compound contained in the optically anisotropic layer includes a cholesteric liquid crystal compound. An optical element comprising the retardation plate according to claim 1 and a polarizer. The optical element according to claim 9, further comprising an adhesive layer, wherein the retardation plate and the polarizer are laminated via the adhesive layer. The optical element according to claim 9, further comprising a transparent protective film, wherein the retardation plate and the polarizer are laminated via the transparent protective film. An image display device comprising the retardation plate according to any one of claims 1 to 8, or the optical element according to any one of claims 9 to 11. A method for manufacturing a retardation plate, comprising the following steps (1) to (4).
(1) A step of forming a surface-modified layer on a surface of a transparent substrate having at least one surface having a liquid crystal alignment regulating force on a surface having a liquid crystal alignment regulating force.
(2) A step of forming a liquid crystal compound-containing layer on the surface modified layer.
(3) A step of regularly aligning the liquid crystal compound contained in the liquid crystal compound-containing layer.
(4) a step of fixing the alignment state of the liquid crystal compound to form an optically anisotropic layer. 14. The manufacturing method according to claim 13, further comprising a step of rubbing the surface of the transparent base material to impart a desired liquid crystal alignment regulating force prior to the step (1). The method according to claim 13 or 14, further comprising, prior to the step (1), a step of expressing a hydrophilic group on the surface of the transparent substrate on which the surface-modified layer is formed. In the step (1), the method for forming the surface-modified layer may include immersing the transparent substrate in a solution of a silane coupling agent, or forming the silane on a surface of the transparent substrate having a liquid crystal alignment regulating force. The production method according to any one of claims 13 to 15, wherein the method is a method of applying a solution of a coupling agent and thereafter drying the silane coupling agent solution. The method according to claim 16, wherein the silane coupling agent solution is further heated after being dried. The method according to claim 16 or 17, wherein the silane coupling agent contains an unsaturated bond between carbon atoms in the molecule. In the step (2), the method of forming the liquid crystal compound-containing layer on the surface modified layer may be a method of applying a solution of the liquid crystal compound to the transparent substrate and drying the solution, or a method of melting the liquid crystal compound. The method according to any one of claims 13 to 18, which is a method of applying a liquid to the transparent substrate. In the step (3), the method of regularly aligning the liquid crystal compound contained in the liquid crystal compound-containing layer may be a method of heating the liquid crystal compound-containing layer to the liquid crystal temperature, or a method of temporarily exceeding the liquid crystal temperature. The method according to any one of claims 13 to 19, wherein the method is a method of heating to a temperature of the liquid crystal and thereafter cooling to a liquid crystal temperature. The liquid crystal compound according to claim 13, wherein the liquid crystal compound includes at least one of a liquid crystal prepolymer and a liquid crystal monomer, and in the step (4), the fixing of the alignment state is performed by a method of photopolymerizing the liquid crystal compound. The production method according to any one of the above. 22. The method according to claim 13, wherein the liquid crystal compound is a liquid crystal polymer, and in the step (4), the alignment state is fixed by a method of cooling the liquid crystal compound-containing layer to a temperature lower than the liquid crystal temperature. The production method according to any one of the above.