JP4575802B2 - Optical film and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical film containing a modified α-1,4-glucan.

  Optical films are currently used in a wide variety of applications such as various display devices, optical disks for music or video, mirrors, and photographic films. The properties required for these optical films are generally diverse, such as film transparency, strength, flexibility, heat resistance, film forming properties and processability during film production. In a display device such as a liquid crystal display device, in general, a plurality of optical films having different properties are used in combination in order to develop required performance.

  A polarizer protective film is mentioned as an example of the optical film used for a display apparatus. In general, a polarizer is obtained by stretching a polyvinyl alcohol film and dyeing the obtained film with iodine. Generally, a polarizer protective film is provided on both sides of such a polarizer. A polarizer protective film has a role which reinforces the intensity | strength of a polarizer and protects the surface of a polarizer.

  Such a polarizer protective film is required to have characteristics such as high transparency and high strength. This polarizer protective film is further required to have a low birefringence. This is because, when the birefringence of the polarizer protective film is high, it causes optical distortion and deteriorates the image displayed on the display device. Currently, cellulose triacetate is widely used as a polarizer protective film.

  Moreover, a retardation film is mentioned as another example of the optical film used for a display apparatus. The retardation film is used for the purpose of color compensation or viewing angle expansion in a liquid crystal display device or the like. Currently, as the retardation film, various synthetic polymers or films obtained by stretching a film of cellulose triacetate are used.

  So far, cellulose triacetate has been widely used as an optical film such as the above-described polarizer protective film or retardation film. This is because the film of cellulose triacetate has a property of relatively high transparency and low birefringence.

  Cellulose triacetate is generally produced by reacting cellulose with acetic anhydride in the presence of an acidic catalyst. In this method, it is necessary to go through a two-step reaction in which the degree of substitution indicating the degree of reaction is once increased to around 3.0 and then deacetylated to achieve the desired degree of substitution. On the other hand, when cellulose triacetate is used as a retardation film, it is also known that birefringence characteristics change depending on the degree of substitution (Japanese Patent Laid-Open No. 2000-137116, Patent Document 1). In the above two-stage replacement method, it is difficult to strictly control the degree of substitution. Therefore, when the cellulose triacetate thus obtained is used, it is necessary to consider the problem of birefringence.

  Cellulose triacetate also has a problem of poor flexibility although it has strength as an optical film. The lack of flexibility of cellulose triacetate makes it difficult to sufficiently stretch the phase difference film. It is also difficult to realize a display device that is resistant to bending. As a method of improving the flexibility of cellulose triacetate, there is a method of adding flexibility by adding a plasticizer. However, the addition of a plasticizer can change the optical properties of the film. Furthermore, there is also a problem that the plasticizer contained in the film moves to the film surface over time.

  Another problem with cellulose triacetate is that it is made from natural cellulose. Such a natural product still has a broad molecular weight distribution even after purification, and therefore it is difficult to exhibit sufficient performance in terms of optical or strength.

  On the other hand, research using starch triacetate as an alternative material for these cellulose triacetates has also been conducted. However, such a starch triacetate has a problem of low strength although it is more flexible than cellulose triacetate. This low strength makes it difficult to use starch triacetate as an alternative to cellulose triacetate. For this reason, studies using starch triacetate as an optical film have not yet been made sufficiently. The low strength of starch triacetate is thought to be due to the fact that starch is a mixture of amylopectin with many branches and amylose with few branches, and a wide molecular weight distribution.

  WO02 / 06507 pamphlet (Patent Document 2), which is an invention by the present inventors, discloses a film made of enzyme-synthesized amylose (α-1,4-glucan) and a modified product thereof. However, this patent document does not mention use as an optical film.

JP 2000-137116 A WO02 / 06507 pamphlet

  The present invention solves the above-mentioned conventional problems, and the object thereof is an optical film having excellent transparency, strength, flexibility, etc., low birefringence, and excellent workability. In particular, it is to provide a polarizer protective film or a retardation film.

  The present invention provides an optical film containing a modified α-1,4-glucan, whereby the above object is achieved.

  The degree of substitution of the α-1,4-glucan modified product is preferably 2.5 to 3.0.

  The molecular weight of the α-1,4-glucan modified product is preferably 100 kDa to 6000 kDa.

  Further, the α-1,4-glucan modified product is one or more esterified α-1,4-glucans having one or more selected from the group consisting of acetyl group, butyryl group and propionyl group. It is preferable to include the above.

  Moreover, it is preferable that the transmittance | permeability of the said optical film is 90 to 100%.

The present invention also provides an optical film having an optical layer and a hydrophilic layer provided on at least one surface of the optical layer,
The optical layer includes α-1,4-glucan having one or more esterified α-1,4-glucans having one or more selected from the group consisting of an acetyl group, a butyryl group, and a propionyl group. A glucan modification product, and the hydrophilic layer contains α-1,4-glucan obtained by demodifying the α-1,4-glucan modification product contained in the optical layer.
An optical film is also provided.

  One embodiment of the optical film includes a polarizer protective film.

  Moreover, retardation film is mentioned as another one aspect | mode of the said optical film.

The present invention also provides a method for producing an optical film. As an example of the manufacturing method,
a solution preparation step of dissolving an α-1,4-glucan modified product in an organic solvent;
A solution casting step for casting the solution on a support, and a drying step;
The method of including is mentioned.

As another example of the manufacturing method,
a melting step of heating and melting the α-1,4-glucan modified product, and a melt casting step of casting the melt on a cooling roll;
The method of including is mentioned.

  The present invention also provides a liquid crystal display device on which the optical film is disposed.

  The optical film containing the α-1,4-glucan modified product has an advantage that the transmittance is very high. Furthermore, there is an advantage that the transmittance is high even for light of various wavelengths. Therefore, the optical film containing the α-1,4-glucan modified product of the present invention is a film excellent in transparency, which is a basic performance required for an optical film. Further, this film has an advantage that the birefringence causing optical distortion is low and the influence on the polarization component is small. For this reason, the optical film containing the α-1,4-glucan modified product is suitable as an optical film for liquid crystal display devices including a polarizer protective film. Even when the film is stretched to obtain a retardation film for a display device, since the original birefringence of the film is low, the retardation film having the desired performance can be obtained more easily. Have.

  The term “dispersion degree Mw / Mn” is the ratio of the number average molecular weight Mn to the weight average molecular weight Mw (ie, Mw ÷ Mn). Except for special cases such as proteins, a high molecular compound has a molecular weight that is not single and has a certain range regardless of whether it is derived from natural or non-natural origin. Therefore, in order to show the degree of dispersion of the molecular weight of the polymer compound, the dispersion degree Mw / Mn is usually used in the field of polymer chemistry. This degree of dispersion is an indicator of the breadth of the molecular weight distribution of the polymer compound. In the case of a polymer compound having a completely single molecular weight, Mw / Mn is 1, and Mw / Mn becomes a value larger than 1 as the molecular weight distribution increases. In this specification, the term “molecular weight” refers to weight average molecular weight (Mw) unless otherwise specified.

  The term “α-1,4-glucan”, as used herein, is a sugar having D-glucose as a constituent unit and linked only by α-1,4-glucoside bonds. Is a saccharide having at least two saccharide units. α-1,4-glucan is a linear molecule. α-1,4-glucan is also called linear glucan. The number of sugar units contained in one molecule of α-1,4-glucan is called the degree of polymerization. In this specification, the term “degree of polymerization” refers to the weight average degree of polymerization unless otherwise specified. In the case of α-1,4-glucan, the weight average degree of polymerization is calculated by dividing the weight average molecular weight by 162.

  The term “degree of substitution” represents the average number of substituted hydroxyl groups per anhydroglucose residue in the α-1,4-glucan modified product. There are three hydroxyl groups in the anhydroglucose residue. When all of them are substituted by chemical modification, the substitution degree is 3, and when two hydroxyl groups are substituted on average, the substitution degree is 2. When the chemical modification is acetylation, those with a substitution degree of 2 are called diacetates, and those with a substitution degree of 3 are called triacetates. As described above, the substitution degree is an average value, and an intermediate value can be taken.

Optical Film The optical film of the present invention contains an α-1,4-glucan modified product. The α-1,4-glucan constituting the α-1,4-glucan modified product is a polymer having a structure in which glucose is linearly bonded. This can be produced by a method known in the art, from natural starch, or enzymatically.

  As a method for obtaining α-1,4-glucan from natural starch, for example, isoamylase or pullulanase known as a debranching enzyme is used only for α-1,6-glucoside bond of amylopectin existing in natural starch. There is a method of obtaining amylose by selectively acting and decomposing amylopectin (so-called starch enzymatic decomposition method). Another example is a method in which an amylose / butanol complex is precipitated and separated from starch paste.

  In addition, α-1,4-glucan can be prepared using a known enzyme synthesis method. As an example of the enzyme synthesis method, there is a method in which amylosucrase (EC 2.4.1.4) is allowed to act using sucrose as a substrate.

  Another example of the enzyme synthesis method is a method using glucan phosphorylase (α-glucan phosphorylase, EC 2.4.1.1; usually referred to as phosphorylase). Phosphorylase is an enzyme that catalyzes a phosphorolysis reaction.

In the present invention, it is preferable to use enzyme-synthesized α-1,4-glucan, and it is particularly preferable to use α-1,4-glucan that is enzymatically synthesized using glucan phosphorylase. Enzymatic synthesis α-1,4-glucan synthesized with glucan phosphorylase has the following characteristics:
(1) Manufactured using carbohydrates, which are biological resources, as raw materials;
(2) It is composed of only glucose residues as in natural starch, and is not toxic to the environment and living organisms until α-1,4-glucan, its degradation intermediate, and final degradation product;
(3) A molecular weight distribution is narrow (Mw / Mn is 1.1 or less), and what has an arbitrary degree of polymerization (about 60 to about 37000) is obtained by appropriately controlling the production conditions;
(4) is completely linear and does not contain the slight branching structure found in amylose fractionated from natural starch;
(5) Chemical modification similar to starch is possible as required.

  The α-1,4-glucan modified product can be obtained by chemically modifying α-1,4-glucan. Examples of the chemical modification method include esterification, etherification, and crosslinking. The α-1,4-glucan modified product used in the optical film of the present invention is preferably an α-1,4-glucan modified product obtained by esterifying α-1,4-glucan.

  Esterification is performed by, for example, using α-1,4-glucan in various solvents or without solvent with an esterification reagent (for example, acid anhydride, organic acid, acid chloride, ketene, or other esterification reagent). It can be performed by reacting. Examples of the reaction include a heterogeneous reaction in an organic solvent or an aqueous solvent or in the absence of a solvent, or a homogeneous reaction in which the reaction is performed by dissolving in a solvent such as dimethyl sulfoxide. As a reaction reagent used for esterification, an acid anhydride, organic acid, acid chloride, ketene, or other esterification reagent corresponding to the type of ester to be introduced can be used. By such esterification, for example, a modified acylated ester such as acetate ester or propionate ester can be obtained. As an acyl group capable of substituting hydrogen of the hydroxyl group contained in the glucose residue constituting α-1,4-glucan by esterification, for example, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, Examples include isovaleryl group, pivaloyl group, lauroyl group, myristoyl group, benzoyl group, acryloyl group, and methacryloyl group.

  The modified α-1,4-glucan used in the present invention is an esterified α-1,4-glucan having one or more selected from the group consisting of an acetyl group, a butyryl group and a propionyl group. Is preferred. These chemical modifications having an acetyl group, a butyryl group, and a propionyl group can be performed singly or in combination. When the α-1,4-glucan modified product has an acetyl group, a butyryl group, or a propionyl group, the hygroscopicity of the optical film can be significantly reduced. Further, the dimensional stability and weather resistance of the optical film can be significantly improved. Furthermore, an optical film having strength characteristics suitable as an optical film can be obtained. These esterified glucans may be polymers composed of two or more modified glucose residues, that is, copolymers or terpolymers.

  The α-1,4-glucan modified product used in the present invention is preferably a product obtained by chemically modifying α-1,4-glucan within a substitution degree of 2.5 to 3.0. The α-1,4-glucan modified product having a substitution degree of 2.5 to 3.0 has an advantage of extremely low moisture permeability. By using a film containing such an α-1,4-glucan modified product as, for example, a polarizer protective film, it is possible to effectively prevent moisture from entering, and to improve moisture and heat resistance. A more preferable range of the degree of substitution of the α-1,4-glucan modified product is 2.7 to 3.0.

  The degree of substitution of the α-1,4-glucan modified product can be easily controlled in the range of 0 to 3.0 by changing the amount of reaction reagent, reaction time, reaction temperature, and the like. Therefore, a modified product having a desired substitution degree can be obtained by a one-step reaction. If necessary, the obtained α-1,4-glucan modified product can be demodified to reduce the degree of substitution. Examples of reagents that can be used to lower the degree of substitution include alkaline substances such as sodium hydroxide and sodium methoxide.

  The average molecular weight of the α-1,4-glucan used in the present invention is preferably 100 kDa to 6000 kDa, more preferably 300 to 3000 kDa, and further preferably 300 to 2000 kDa. If the average molecular weight is 100 kDa or less, it may be difficult to form a film having sufficient strength alone. On the other hand, if it is 6000 kDa or more, the yield in the enzyme synthesis is low and the viscosity is high, so that molding may be difficult. However, when α-1,4-glucan having two or more polymerization degrees is used in combination, for example, when using low molecular weight glucan and high molecular weight glucan having an average molecular weight other than the above range, or these and the above Even when a glucan having an average molecular weight within the range is used, good formability can be obtained. Further, when the optical film of the present invention is directly formed on an optical film having other functions by a method such as coating, it is not limited to the above range, and for example α-1,4- of 100 kDa or less. A modified glucan can also be used.

  Furthermore, the physical properties of the polarizing layer of the optical film can be controlled by using a mixture of two or more α-1,4-glucans having different molecular weights. By changing the molecular weight of the α-1,4-glucan to be mixed or the ratio of α-1,4-glucan used, physical properties such as flexibility and elongation of the obtained film can be controlled.

  The optical film of the present invention may contain various additives such as a plasticizer, a softening agent, a crosslinking agent, an ultraviolet absorber, and a stabilizer in addition to the α-1,4-glucan modified product.

  Examples of the plasticizer include glycerin, monoacetin, diacetin, triacetin, ethylene glycol, diethylene glycol, triethylene glycol, sucrose fatty acid ester, glycerin fatty acid ester and the like. By using a plasticizer, there is an advantage that the moldability of the film can be improved and stretching can be performed effectively.

  Examples of softening agents include, for example, glycerin derivatives such as glycerin, monoacetin, diacetin, and triacetin, ethylene glycol derivatives such as ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol, dextrin, glucose, fructose, and sucrose. And saccharides such as maltooligosaccharide, and fatty acid esters such as sucrose fatty acid ester and glycerin fatty acid ester. By using a softening agent, the film can be given flexibility and elongation can be improved.

  Further, an optical film may be prepared by mixing an α-1,4-glucan modified product with another polymer material. Examples of other polymeric materials that can be used include polysaccharides such as pullulan, alginic acid, carrageenan, guar gum, agar, chitosan, cellulose and derivatives thereof, dextrin, starches and derivatives thereof, and proteins such as gelatin, gluten And resins such as egg white, egg yolk, polyesters such as polylactic acid and poly-ε-caprolactone, polyethers such as polyethylene glycol, polyolefins such as polyvinyl alcohol and polyethylene, and polyamides. In particular, the physical properties and optical properties of the cellulose acetate film can be improved by mixing with a cellulose derivative such as cellulose acetate conventionally used as an optical film.

  The optical film of the present invention preferably has a film transmittance of 90 to 100%, more preferably 90 to 99.9%, and even more preferably 94 to 99.9%. And since the optical film of this invention has such a high transmittance | permeability, it is a film especially useful in an optical use. The transmittance can be measured by a method according to the Electronic Industries Association standard (LD-201).

  The optical film of the present invention preferably has a dimensional change rate of 0 to 4%, more preferably 0 to 3%. The optical film of the present invention is a film having such a low dimensional change rate and high dimensional stability required in optical applications. The dimensional change rate can be calculated by measuring the film thickness before and after the water absorption test.

  The optical film containing the α-1,4-glucan modified product has an advantage that the transmittance is very high. Furthermore, there is an advantage that the transmittance is high even for light of various wavelengths. Therefore, the optical film containing the α-1,4-glucan modified product of the present invention is a film excellent in transparency, which is a basic performance required for an optical film. In addition, since the birefringence that causes optical distortion is low, there is an advantage that the influence on the polarization component is small. The optical film containing the α-1,4-glucan modified product is suitable as an optical film for liquid crystal display devices including a polarizer protective film.

  Even when the film is stretched to obtain a retardation film for a display device, since the original birefringence of the film is low, the retardation film having the desired performance can be obtained more easily. Have.

  An optical film containing an α-1,4-glucan modified product has high strength and is highly flexible. Therefore, the durability against deformation of the film is excellent. Even when the film is subjected to a stretching process like a retardation film, a plasticizer is not required because of the high elongation rate of the film, or the amount used can be reduced compared to cellulose triacetate. it can.

  The α-1,4-glucan modified product can be obtained from α-1,4-glucan with a desired substitution degree in a one-step reaction. Therefore, the degree of substitution can be easily controlled as compared with the one that undergoes a two-step reaction such as cellulose triacetate, thereby improving the optical performance. Further, by not performing the two-step reaction, it is possible to suppress a decrease in strength due to decomposition of molecular chains that may occur during the reaction.

  The α-1,4-glucan, which is a linear polymer, which is a raw material for the optical film of the present invention, can be obtained by enzymatic synthesis. The α-1,4-glucan can be synthesized with a desired molecular weight, and has a feature that its molecular weight distribution is very narrow. Therefore, the problem of chain branching in starch and the like, and the problem of having a wide molecular weight distribution in cellulose and the like, which cause reduction in strength and optical performance of the optical film, do not occur. Further, since the molecular weight can be controlled to a desired value, viscosity adjustment, which is important at the time of film production, becomes easy. Furthermore, it is possible to easily control the solubility of the α-1,4-glucan modified product as a raw material and the physical properties of the resulting optical film.

  An excellent optical film can be provided by utilizing the above-described properties of the α-1,4-glucan modified product. As an optical film, it can be used for a polarizer protective film or retardation film for a liquid crystal display device, a photographic / movie film, an optical disk for music / video, a mirror, and the like. Moreover, it can be used also as an optical element which does not take the form as a film. For example, it can be used as an optical material such as a lens, a prism, or an optical fiber.

Method for Producing Optical Film As a method for producing the optical film of the present invention, a casting method, an extrusion method, a calendar method, or the like can be selected. Among these, it is preferable to use a casting method. This is because the optical film prepared by the casting method generates less distortion during molding and is more suitable for optical use.

  Examples of the casting method include a solution casting method and a melt casting method such as a T-die method. The solution casting method is a method for preparing a film by dissolving a resin such as a thermoplastic resin in a suitable solvent, casting the obtained solution on the surface of a support, and then heating to dry the film. An optical film can be obtained by peeling the film thus obtained from the support. The melt casting method is a method of forming a film by extruding a heat-melted thermoplastic resin into a film form from a mold, casting (casting) it onto the surface of the support, cooling it, and forming a film.

The solution cast method is
a solution preparation step of dissolving an α-1,4-glucan modified product in an organic solvent;
A solution casting step for casting the solution on a support, and a drying step;
It is a manufacturing method including.

  Various organic solvents can be used as a solvent used to dissolve the α-1,4-glucan modified product by the solution casting method. Examples of organic solvents that can be used include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone; diethyl ether, isopropyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and ethylene. Ether solvents such as glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, anisole, phenetol; esters such as methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, ethyl butyrate, ethyl lactate, ethylene glycol diacetate Solvents: dimethylformamide, diethylformamide, dimethylsulfoxide And amide solvents such as N-methylpyrrolidone; cellosolv solvents such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; alcohol solvents such as methanol, ethanol and propanol; halogen solvents such as dichloromethane, dichloroethane and chloroform; It is done. These solvents may be used alone or in combination.

  The method for dissolving the α-1,4-glucan modified product in the solvent is not particularly limited. For example, the α-1,4-glucan modified product is added to the solvent at once or little by little, and the solution is stirred. Obtainable.

  The concentration of the modified α-1,4-glucan contained in the solution of the modified α-1,4-glucan used in the solution casting method is preferably 3 to 50% by weight, and 5 to 30% by weight. It is more preferable that When the concentration of the α-1,4-glucan modified product is lower than 3% by weight, the surface performance of the obtained optical film may be deteriorated. On the other hand, if it is higher than 50% by weight, the change in the viscosity of the solution with time will become violent, which may make it difficult to cast the solution.

  The resulting solution is then cast on a support. The coater used for casting is not particularly limited as long as the solution can be cast on a support. As the coater, for example, a bar coater, a comma coater, a gravure coater, a mayer bar, a roll coater, a lip coater, a T die, a T die with a bar, or the like can be used.

  There is no restriction | limiting in particular in the support body to be used, A metal support body and a plastic support body can be used. Specific examples of the metal support include a support made of metal such as stainless steel, iron, and aluminum, and those metal surfaces subjected to chrome plating and mirror finished. Specific examples of the plastic support may include polyester, polyethylene terephthalate, polyethylene terephthalate, polyethylene, polypropylene, fluororesin, silicone resin, polyimide resin, and polyester subjected to chemical surface treatment.

  The film thickness of the optical film can be selected according to the application. The range of film thickness is generally 10 to 500 μm, preferably 20 to 300 μm, and more preferably 30 to 200 μm.

  Next, by drying the solution cast on the support, the solvent is removed and an optical film can be obtained. The drying conditions and method of the film are not particularly limited as long as the residual solvent amount can be 5% by weight or less, preferably 3% by weight or less. Examples of the drying conditions include a method of leaving under room temperature conditions, a method of heating to 30 to 70 ° C. and holding for 3 to 20 minutes, and a method of placing the obtained film under reduced pressure conditions. It is more preferable to dry without heating, so that the generation of strain can be suppressed.

The melt casting method is
a melting step of heating and melting the α-1,4-glucan modified product, and a melt casting step of casting the melt on a cooling roll;
It is a manufacturing method including.

  The α-1,4-glucan modified product varies depending on its molecular weight, but can generally be melted by heating to 150 to 250 ° C.

  The melt thus obtained is cast on a cooling roll. The die used for casting is not particularly limited as long as the solution can be cast on a support. As the die, for example, a T die, a T die with a bar, or the like can be used. The temperature during extrusion of the melt is preferably 100 to 250 ° C.

  The cooling roll to be used is not particularly limited, but a metallic cooling roll is mainly used. Examples of the cooling roll include a cooling roll made of metal such as stainless steel, iron, and aluminum, and those having the metal surface subjected to chrome plating or mirror finish. The temperature of the cooling roll is preferably 5 to 50 ° C, preferably 10 to 30 ° C.

  In the present invention, the film obtained by these methods can be subjected to an annealing treatment, if necessary. By performing an annealing process or the like, the distortion of the film can be removed. Moreover, it can also be extended | stretched to a uniaxial, a sequential biaxial, or simultaneous biaxial using the film obtained by these methods, and a common extending | stretching machine.

  In addition, although the optical film of this invention can manufacture an optical film by the said method normally using (alpha) -1, 4- glucan modified material, as an other method, it is unmodified alpha- beforehand. 1,4-glucan is formed into a film by a casting method or the like, and then α-1,4-glucan contained in the film is modified by esterification or the like in a gas phase or a liquid phase, and α-1,4- It can also be a glucan modified product. In such a case, when a solvent is required for film formation, it is preferable to use an aqueous solvent.

  Moreover, a film can also be directly formed by a solution casting method using another film material constituting a liquid crystal display device or the like as a support. By using such a method, the obtained optical film can be combined in advance. By combining the film by such a method, the manufacturing process of the display device can be simplified. Moreover, since the composite film obtained in this way has only a required optical layer, it can achieve thickness reduction or weight reduction of a display apparatus.

  One embodiment of the optical film of the present invention includes an optical film having an optical layer and a hydrophilic layer. Such an optical film has a hydrophilic layer on at least one surface of the hydrophobic layer. The optical layer includes one or more esterified α-1,4-glucans having one or more selected from the group consisting of an acetyl group, a butyryl group, and a propionyl group, α-1,4 -A layer containing a modified glucan. On the other hand, the hydrophilic layer is a layer containing α-1,4-glucan obtained by demodifying the α-1,4-glucan modified product contained in the optical layer.

  The optical film containing the α-1,4-glucan modified product of the present invention has a hydrophobic property as it is. Therefore, when the optical film of the present invention is combined with a hydrophilic adhesive or material, there may be a problem that the combination is not easy. In such a case, the composite can be made easier by modifying at least one surface of the optical layer constituting the optical film to a hydrophilic surface. In the present specification, the “optical layer” refers to a layer having properties required for the optical film of the present invention. For example, when the optical film of the present invention is a polarizer protective film, the optical layer means a polarizer protective layer.

  As a method for preparing an optical film having an optical layer and a hydrophilic layer, at least one surface of a film composed of a layer containing an α-1,4-glucan modified product (optical layer) is used as an alkaline solution, an alkali. It can be prepared by contacting with a catalyst solution or a mixture thereof and saponifying. Examples of the alkaline solution include a sodium hydroxide aqueous solution (for example, a 1N sodium hydroxide aqueous solution) and a potassium hydroxide aqueous solution (for example, a 1N potassium hydroxide aqueous solution). Examples of the alkali catalyst solution include a solution containing an alkali catalyst such as sodium methoxide or sodium ethoxide and an organic solvent such as alcohol. For example, after one surface of an acetylated α-1,4-glucan film is attached to a glass or plastic substrate and protected, only one surface can be saponified by contacting the film with an alkaline solution. Thus, an optical film having a hydrophilic layer only on one side of the optical layer can be obtained. Moreover, the optical structure which has a hydrophilic layer on both surfaces of an optical layer by immersing the film comprised from the layer (optical layer) containing an alpha-1, 4- glucan modification thing in these solutions for 1 to 30 minutes A film can be obtained.

  The optical film of the present invention obtained by the various methods described above and a film having other functions such as a polarizer can be combined. Examples of the composite method include a method using the solution cast method as described above, and a bonding with a film having a different function. As the adhesive used when laminating a plurality of films, an adhesive known in the art can be arbitrarily selected. Furthermore, α-1,4-glucan and / or a modified product thereof can be used as an adhesive. As another method, a method of forming a film by applying a melt of a modified α-1,4-glucan on a film having other functions such as a polarizer can be mentioned.

Liquid crystal display device The liquid crystal display device of the present invention includes a reflective liquid crystal display device, a transflective liquid crystal display device, and the like. The liquid crystal display device of the present invention has the optical film of the present invention. A liquid crystal display device generally includes a polarizing film, a liquid crystal cell, and, if necessary, a retardation film, a reflective layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, a color filter, etc. It consists of members. Here, the polarizing film is a film having a polarizer and a polarizer protective film. In the present invention, the member is not particularly limited except that it is essential to use the optical film of the present invention. The use position of the optical film of the present invention is not particularly limited, and may be one or more.

  The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used. The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. The electrode of the liquid crystal cell can usually be provided on the surface of the transparent substrate with which the liquid crystal layer is in contact. When a substrate having an alignment film is used, it can be provided between the substrate and the alignment film. The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal materials, polymer liquid crystal materials, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired.

  In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later. As a liquid crystal cell system, a TN (Twisted Nematic) system, an STN (Super Twisted Nematic) system, an ECB (Electrically Controlled Birefringence) system, an IPS (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, Method, PVA (Patterned Vertical Alignment) method, OCB (Optically Compensated Birefringence) method, HAN (Hybrid Aligned Nematic) (ASM) Various methods such as a display method using a method, a halftone gray scale method, a domain division method, or a ferroelectric liquid crystal or an antiferroelectric liquid crystal can be used. The driving method of the liquid crystal cell is not particularly limited, and a passive matrix method used for STN-LCD and the like, and an active matrix method using an active electrode such as a TFT (Thin Film Transistor) electrode and a TFD (Thin Film Diode) electrode, Any driving method such as a plasma addressing method may be used. Further, a field sequential method that does not use a color filter may be used.

  The optical film of the present invention is preferably used for reflective and transflective liquid crystal display devices. The reflective liquid crystal display device has a configuration in which a reflector, a liquid crystal cell, and a polarizing film are laminated in this order. The retardation film is disposed between the reflecting plate and the polarizing film (between the reflecting plate and the liquid crystal cell or between the liquid crystal cell and the polarizing film). The reflector may share the liquid crystal cell and the substrate. The transflective liquid crystal display device includes an electro-liquid crystal cell, a polarizing film disposed on the viewer side from the liquid crystal cell, at least one retardation film disposed between the polarizing film and the liquid crystal cell, and an observation At least a transflective layer disposed behind the liquid crystal layer as viewed from the viewer, and at least one retardation film and polarizing film behind the transflective layer as viewed from the viewer. In this type of liquid crystal display device, it is possible to use both a reflection mode and a transmission mode by installing a backlight.

  In such a liquid crystal display device, a retardation film that is one type of the optical film of the present invention and a polarizing film including a polarizer protective film that is one type of the optical film of the present invention can be used. The liquid crystal display device of the present invention uses at least one optical film of the present invention.

  The optical film of the present invention is not limited to the above applications, and can be used for various other applications. For example, it can be used for an antireflection film such as a host-guest type liquid crystal display device, a touch panel, an electroluminescence (EL) element, a reflective polarizing film, and the like.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on weight unless otherwise specified.

In the polymerization degree test example, a method for preparing a purified glucan phosphorylase derived from potato tuber, a method for preparing a sucrose phosphorylase derived from Streptococcus mutans, a method for calculating the yield (%) of α-1,4-glucan, a weight average molecular weight (Mw) and The method for measuring the number average molecular weight (Mn) was in accordance with the method known from JP-A-2002-345458. Specifically, the molecular weight of the synthesized glucan was measured as follows. First, the synthesized glucan is completely dissolved with 1N sodium hydroxide, neutralized with an appropriate amount of hydrochloric acid, and about 300 μg of glucan is subjected to gel filtration chromatography using a differential refractometer and a multi-angle light scattering detector in combination. To determine the weight average molecular weight. Specifically, Shodex SB806M-HQ (manufactured by Showa Denko) is used as a column, and a multi-angle light scattering detector (DAWN-EOS, manufactured by Wyatt Technology) and a differential refractometer (Shodex RI-71, manufactured by Showa Denko) are used as detectors. ) Were used in this order. The column was kept at 40 ° C., and 0.1 M sodium nitrate solution was used as an eluent at a flow rate of 1 mL / min. The obtained signals were collected using data analysis software (trade name ASTRA, manufactured by Wyatt Technology), and analyzed using the same software to determine the weight average molecular weight and the number average molecular weight.

Measurement of the degree of substitution The degree of substitution of acetylated α-1,4-glucan was measured by the following method according to the description of “Starch and related carbohydrate experiment method” (Nakamura et al., 1986, Japan Society for Publications). 1 g of the sample was precisely weighed into a 300 ml Erlenmeyer flask, and 50 ml of 75% ethanol was added and dispersed. To this was added 40 ml of 0.5N aqueous sodium hydroxide solution, which was sealed and shaken at room temperature for 48 hours. Excess alkali was titrated with 0.5N hydrochloric acid, and the degree of substitution (DS) was determined from the difference from the blank. The degree of substitution (DS) is the average number of substituted hydroxyl groups per anhydroglucose residue.

The tensile strength of the tensile test film was measured by the following method. A test piece having a width of 12.7 mm and a length of 152.4 mm was left in a constant temperature and humidity chamber at 26 ° C. and a relative humidity of 55% for one day, and then a tensile test was performed at the same place. A test piece whose thickness was measured in advance on a tensile tester (manufactured by Shimadzu Autograph AGS-H) was fixed so that the distance between handles was 100 mm, and was pulled until it broke at a speed of 10 mm / min. Five test results were averaged for each test piece, and excluded when cut inside the handle. The tensile strength was determined by dividing the load at break by the cross-sectional area of the film.

The water absorption and the dimensional change rate of the film were measured by the following method. A sample film having a thickness of about 100 μm was cut into 5 cm squares, dried by heating in a vacuum drier, and the weight was measured. This was immersed in distilled water for 24 hours, the surface water was wiped off, and the weight was measured again. The water absorption (%) was calculated from the weight change before and after the immersion. In the measurement of water absorption, the thickness of the film before and after immersion was measured, and the dimensional change rate (%) was calculated from the change.

The transmittance of the transmittance film was measured by the following method. Using an absorptiometer V-550 manufactured by JASCO Corporation, an absorbance spectrum was obtained in the wavelength range of 200 nm to 900 nm in 1 nm increments. From the value of the spectral spectrum, the transmittance was determined by a method according to the Electronic Industries Association standard (LD-201).

Production Example 1: Synthesis of α-1,4-glucan Reaction solution (1) containing 15 mM phosphate buffer (pH 7.0), 106 mM sucrose, and malto-oligosaccharide mixture (Tetrap H, manufactured by Hayashibara) 5.4 mg / liter Liters), purified glucan phosphorylase derived from potato tubers (1 unit / ml) and sucrose phosphorylase derived from Streptococcus mutans (1 unit / ml) were added and incubated at 37 ° C. for 16 hours. , 4-glucan yield (%), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined. As a result, α-1,4-glucan having a weight average molecular weight of 1250 kDa and a molecular weight distribution (Mw / Mn) of 1.03 was obtained.

Production Example 2: Production of acetylated α-1,4-glucan (degree of substitution: 2.1)
In a reaction vessel equipped with a refluxer, 1 L of pyridine was added so that the concentration of α-1,4-glucan obtained in Production Example 1 was 5% by weight, 50 ml of acetic anhydride was added dropwise, and the mixture was added at 100 ° C. for 60 minutes. Reacted. After the reaction, ethanol was added to precipitate the product. After filtration, the product was washed several times with water and purified. The degree of substitution of the obtained acetylated α-1,4-glucan was 2.1.

Production Example 3: Production of acetylated α-1,4-glucan (degree of substitution: 2.7)
In a reaction vessel equipped with a refluxer, 1 L of pyridine was added so that the concentration of α-1,4-glucan obtained in Production Example 1 was 5% by weight, 100 ml of acetic anhydride was added dropwise, and the mixture was added at 100 ° C. for 60 minutes. Reacted. After the reaction, ethanol was added to precipitate the product. After filtration, the product was washed several times with water and purified. The degree of substitution of the obtained acetylated α-1,4-glucan was 2.7.

Production Example 4: Production of acetylated α-1,4-glucan (degree of substitution: 2.9)
In a reaction vessel equipped with a refluxer, 1 L of pyridine was added so that the concentration of α-1,4-glucan obtained in Production Example 1 was 5% by weight, and 160 ml of acetic anhydride was added dropwise thereto at 100 ° C. for 60 min Reacted. After the reaction, ethanol was added to precipitate the product. After filtration, the product was washed several times with water and purified. The degree of substitution of the obtained acetylated α-1,4-glucan was 2.9.

Production Example 5: Preparation of acetylated high amylose starch Acetylation was carried out in the same manner as in Production Example 4 except that α-1,4-glucan was replaced with high amylose starch under the condition of dropping 160 ml of acetic anhydride. . An acetylated high amylose starch with a degree of substitution of 2.9 was obtained.

Reference Example 1: Production of cast film The acetylated α-1,4-glucan obtained in Production Example 3 was dissolved in chloroform at 5% by weight. This was cast on a polyester substrate and dried at room temperature to obtain a film of acetylated α-1,4-glucan having a substitution degree of 2.7 and a thickness of about 100 μm.

Reference Example 2: Production of cast film The acetylated α-1,4-glucan obtained in Production Example 4 was dissolved in chloroform at 5% by weight. This was cast on a polyester substrate and dried at room temperature to obtain a film of acetylated α-1,4-glucan having a substitution degree of 2.9 and a thickness of about 100 μm.

Example 3 Production of Cast Film Having Hydrophilic Layer The acetylated α-1,4-glucan obtained in Production Example 4 was dissolved in chloroform at 5% by weight. This solution was cast on a polyester substrate and dried at room temperature to obtain a film having a thickness of about 100 μm. The film was saponified by immersing in a 1N sodium hydroxide solution at 30 ° C. for 12 minutes without being peeled from the substrate, and then washed with running water. After drying with a dryer at 50 ° C., the film was peeled off from the substrate to obtain an acetylated α-1,4-glucan film having a hydrophilic layer and having one surface saponified.

Comparative Example 1: Production of Cast Film The acetylated α-1,4-glucan obtained in Production Example 2 was dissolved in acetone at 5% by weight. This was cast on a polyester substrate and dried at room temperature to obtain a film of acetylated α-1,4-glucan having a substitution degree of 2.1 and a thickness of about 100 μm.

Comparative Example 2: Production of Cast Film The acetylated high amylose starch obtained in Production Example 5 was dissolved in chloroform at 5% by weight. This was cast on a polyester substrate and dried at room temperature to obtain a film of acetylated high amylose starch having a thickness of about 100 μm and a substitution degree of 2.9.

Comparative Example 3: Production of Cast Film Using cellulose acetate having a substitution degree of 2.9 purchased from Wako Pure Chemical Industries, Ltd., a film was produced in the same manner as in Comparative Example 2 to obtain a cellulose acetate film.

  Table 1 shows the results of strength and elongation of the films obtained in Examples and Comparative Examples. Compared with acetylated high amylose starch and cellulose acetate, acetylated α-1,4-glucan had the same strength and greatly exceeded the elongation.

  Table 2 shows the measurement results of water absorption and dimensional change rate of the films obtained in Examples and Comparative Examples. Among the acetylated α-1,4-glucans, those having a substitution degree of 2.7 and 2.9 resulted in low water absorption and dimensional change rate.

  Table 3 shows the measurement results of the transmittance of the films obtained in Examples and Comparative Examples.

  As is clear from the results of the examples and comparative examples, the optical films of the present invention obtained by the examples have higher strength, elongation and transmittance than those of the comparative examples, and water absorption and dimensional stability. It was confirmed that the film was suitable as an optical film because of its low property.

  The optical film containing the α-1,4-glucan modified product has an advantage that the transmittance is very high. Furthermore, there is an advantage that the transmittance is high even for light of various wavelengths. Therefore, the optical film containing the α-1,4-glucan modified product of the present invention is a film excellent in transparency, which is a basic performance required for an optical film. Further, since the birefringence that causes optical distortion is low, there is an advantage that the influence on the polarization component is small. For this reason, the optical film containing the α-1,4-glucan modified product is suitable as an optical film for liquid crystal display devices including a polarizer protective film. Even when the film is stretched to obtain a retardation film for a display device, since the original birefringence of the film is low, the retardation film having the desired performance can be obtained more easily. Have.

An excellent optical film can be provided by utilizing the above-described properties of the α-1,4-glucan modified product. As an optical film, it can be used for a polarizer protective film or retardation film for a liquid crystal display device, a photographic / movie film, an optical disk for music / video, a mirror, and the like. Moreover, it can be used also as an optical element which does not take the form as a film. For example, it can be used as an optical material such as a lens, a prism, or an optical fiber.

Claims (9)

An optical film having an optical layer and a hydrophilic layer provided on at least one surface of the optical layer,
The optical layer is composed of one or more esterified α-1,4-glucans having one or more selected from the group consisting of acetyl group, butyryl group and propionyl group, α-1,4 -Containing a glucan modification, and
The hydrophilic layer contains α-1,4-glucan obtained by demodifying the α-1,4-glucan modified product contained in the optical layer.
Optical film.   The optical film according to claim 1, wherein the α-1,4-glucan modified product has a substitution degree of 2.5 to 3.0. The optical film according to claim 1 or 2 , wherein the α-1,4-glucan modified product has a molecular weight of 100 kDa to 6000 kDa. The optical film according to any one of claims 1 to 3 , wherein the optical film has a transmittance of 90 to 100%. A polarizer protecting film, an optical film according to any one of claims 1-4. The optical film according to any one of claims 1 to 4 , which is a retardation film. An α-1,4-glucan modified product comprising one or more esterified α-1,4-glucans having one or more selected from the group consisting of an acetyl group, a butyryl group and a propionyl group A solution preparation step for dissolving in a solvent,
The solution casting process of casting the solution on a support,
A drying step of drying to obtain an optical layer composed of a modified α-1,4-glucan ; and
By saponifying the α-1,4-glucan modified product by bringing at least one surface of the obtained optical layer composed of the α-1,4-glucan modified product into contact with an alkali solution, an alkali catalyst solution or a mixture thereof. Obtaining a hydrophilic layer;
A method for producing an optical film having an optical layer and a hydrophilic layer . Heating a modified α-1,4-glucan comprising one or more esterified α-1,4-glucans having one or more selected from the group consisting of an acetyl group, a butyryl group and a propionyl group Melting and melting process ,
The melt was cast onto a chill roll, the melt-casting to obtain an optical layer comprising a alpha-1,4-glucan modified product, and
By saponifying the α-1,4-glucan modified product by bringing at least one surface of the obtained optical layer composed of the α-1,4-glucan modified product into contact with an alkali solution, an alkali catalyst solution or a mixture thereof. Obtaining a hydrophilic layer;
A method for producing an optical film having an optical layer and a hydrophilic layer . The liquid crystal display device which has arrange | positioned the optical film in any one of Claims 1-6 .