Modifier for cellulose ester resin, cellulose ester resin composition, optical film, and display device

Abstract

To provide a cellulose ester resin modifier that gives an optical film sufficient flexibility for improved processability, without spoiling the transparency of the optical film.SOLUTION: A cellulose ester resin modifier contains a polyester represented by the following general formula (1), and a diester compound represented by the following general formula (2) where B1 is an aliphatic monoalcohol residue, A is an aliphatic dicarboxylic acid residue, G1 is an alkylene glycol residue or oxyalkylene glycol residue, B2 is an aromatic monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, G2 is an alkylene glycol residue or oxyalkylene glycol residue.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a modifier for cellulose ester resin, a cellulose ester resin composition, an optical film, and a display device.

Background Art

[0002] Liquid crystal displays used in smartphones, notebook computers, televisions, etc. have been made larger, thinner, and lighter, and accordingly, the optical films used around the polarizing plate are also required to be made thinner.

[0003] Cellulose ester resin films such as cellulose acetate films used in the above optical films are generally hard and brittle. Therefore, when the film is made thinner, there are problems such as insufficient flexibility and easy breakage, and physical property changes such as dimensional changes are likely to occur due to high hygroscopicity.

[0004] Regarding the above problems, methods of adding various additives to the cellulose ester resin film to improve the physical properties have been proposed (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The above additives are, for example, plasticizers for cellulose ester resins, but the improvement of the flexibility of the film and the physical property changes due to moisture absorption is insufficient. In addition, when the compatibility of the additive with the cellulose ester resin is insufficient, there is also a problem that the additive bleeds out and the transparency of the optical film is significantly impaired.

[0007] The problem to be solved by the present invention is to provide a modifier for a cellulose ester resin that imparts sufficient flexibility to an optical film made of the cellulose ester resin to improve processability, imparts moisture absorption suppression and moisture and heat resistance to the optical film, and has sufficient compatibility with the cellulose ester resin so as not to impair the transparency of the optical film.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the present inventors have found that a modifier for a cellulose ester resin composed of a polyester having a specific structure and a diester compound having a specific structure imparts sufficient flexibility to a cellulose ester resin film to improve processability, suppresses the moisture absorption of the film, and can impart moisture and heat resistance, dimensional stability, etc. to the film. Further, it has been found that the modifier for the cellulose ester resin has sufficient compatibility with the cellulose ester resin, and the present invention has been completed.

[0009] That is, the present invention relates to a modifier for a cellulose ester resin containing a polyester represented by the following general formula (1) and a diester compound represented by the following general formula (2).

[0010]

Chemical formula

Advantages of the Invention

[0011] According to the present invention, a modifier for a cellulose ester resin can be provided that imparts moisture absorption suppression and moisture and heat resistance to an optical film of a cellulose ester resin and has sufficient compatibility with the cellulose ester resin so as not to impair the transparency of the optical film.

Modes for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within a range that does not impair the effects of the present invention.

[0013] [Modifier for Cellulose Ester Resin] The modifier for a cellulose ester resin of the present invention contains a polyester represented by the following general formula (1) (hereinafter sometimes referred to as "the polyester of the present invention") and a diester compound represented by the following general formula (2) (hereinafter sometimes referred to as "the diester compound of the present invention").

[0014]

Chemical formula

[0015] In the present invention, the "alcohol residue" refers to the remaining organic group obtained by removing the hydroxyl group from an alcohol. In the present invention, the "glycol residue" refers to the remaining organic group obtained by removing the hydroxyl group from a glycol. In the present invention, the "carboxylic acid residue" refers to the remaining organic group obtained by removing the carboxyl group from a carboxylic acid. Note that for the number of carbon atoms in the carboxylic acid residue, the carbon atom in the carboxyl group is not included.

[0016] In the modifier for the cellulose ester resin of the present invention, since the polyester itself has a flexible structure without an aromatic ring structure, it can function as a plasticizer that imparts flexibility to the cellulose ester resin. Further, by arranging the diester compound in the gaps of the cellulose ester resin, it is possible to suppress the moisture permeability of the cellulose ester film, improve the moisture and heat resistance and the dimensional stability, and also enhance the compatibility with the cellulose ester resin.

[0017] (Polyester) B 1 The aliphatic chain of the aliphatic monoalcohol residue of may be linear or branched, and may contain an alicyclic structure and / or an ether bond (-O-).

[0018] B 1 Examples of the aliphatic monoalcohol residue having 1 to 12 carbon atoms for B include methanol residue, ethanol residue, 1-propanol residue, 2-propanol residue, 1-butanol residue, 2-butanol residue, isobutanol residue, tert-butanol residue, 1-pentanol residue, 2-pentanol residue, 3-methyl-1-butanol residue, 1-hexanol residue, 2-hexanol residue, 1-heptanol residue, 1-octanol residue, 2-ethyl-1-hexanol residue, 3,3,5-trimethyl-1-hexanol residue, isononyl alcohol residue, 1-nonyl alcohol residue, cyclopentanol residue, cyclohexanol residue, methylcyclohexanol residue, trimethylcyclohexanol residue, and the like.

[0019] B 1 The aliphatic monoalcohol residue having 1 to 12 carbon atoms for B is preferably an aliphatic monoalcohol residue having 2 to 10 carbon atoms, and more preferably one or more selected from 1-butanol residue, 2-ethyl-1-hexanol residue, and isononyl alcohol residue.

[0020] The aliphatic chain of the aliphatic dicarboxylic acid residue having 1 to 6 carbon atoms of A may be linear or branched, and may contain an alicyclic structure and / or an ether bond (-O-).

[0021] Examples of the aliphatic dicarboxylic acid residue having 1 to 6 carbon atoms of A include succinic acid residue, adipic acid residue, maleic acid residue, pimelic acid residue, suberic acid residue, cyclohexanedicarboxylic acid residue, and the like.

[0022] The aliphatic dicarboxylic acid residue having 1 to 6 carbon atoms of A is preferably one or more selected from succinic acid residue and adipic acid residue.

[0023] G 1Examples of the alkylene glycol residue having 2 to 12 carbon atoms include ethylene glycol residue, 1,2-propylene glycol residue, 1,3-propanediol residue, 1,2-butanediol residue, 1,3-butanediol residue, 2-methyl-1,3-propanediol residue, 1,4-butanediol residue, 1,5-pentanediol residue, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) residue, 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane) residue, 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane) residue, 3-methyl-1,5-pentanediol residue, 1,6-hexanediol residue, 2,2,4-trimethyl 1,3-pentanediol residue, 2-ethyl-1,3-hexanediol residue, 2-methyl-1,8-octanediol residue, 1,9-nonanediol residue, 1,10-decanediol residue, 1,12-dodecanediol residue and the like.

[0024] G 1 The alkylene glycol residue having 2 to 12 carbon atoms may contain an alicyclic structure. Examples of the aliphatic diol residue having 2 to 12 carbon atoms and containing the alicyclic structure include 1,3-cyclopentanediol residue, 1,2-cyclohexanediol residue, 1,3-cyclohexanediol residue, 1,4-cyclohexanediol residue, 1,2-cyclohexanedimethanol residue, 1,4-cyclohexanedimethanol residue and the like.

[0025] G 1 The alkylene glycol residue having 2 to 12 carbon atoms is preferably an alkylene glycol residue having 2 to 4 carbon atoms, more preferably one or more selected from ethylene glycol residue, 1,2-propylene glycol residue, 1,3-propanediol residue, 1,2-butanediol residue, 2-methyl-1,3-propanediol residue.

[0026] G 1The oxyalkylene glycol residue having 4 to 12 carbon atoms is a group in which an ether bond (-O-) is inserted between any one of the carbon-carbon bonds of the alkylene glycol residue, and examples thereof include a diethylene glycol residue, a triethylene glycol residue, a tetraethylene glycol residue, a dipropylene glycol residue, a tripropylene glycol residue, and the like.

[0027] G 1 is preferably one or more selected from an ethylene glycol residue, a diethylene glycol residue, a 1,2-propylene glycol residue, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-butanediol, and a 1,3-butanediol residue, and more preferably an ethylene glycol residue, a diethylene glycol residue, or a 1,2-propylene glycol residue.

[0028] The repeating number of n is, for example, an integer in the range of 0 to 20. The average value of the repeating number of n is preferably in the range of 1.0 to 10.0, more preferably in the range of 1.0 to 8.0, and even more preferably in the range of 1.5 to 7.0. The average value of the repeating number of n can be calculated from the number average molecular weight of the polyester of the present invention.

[0029] The number average molecular weight (Mn) of the polyester of the present invention is, for example, in the range of 100 to 5,000, preferably in the range of 350 to 2,000, and more preferably in the range of 400 to 1,500. The above number average molecular weight (Mn) is a value converted to polystyrene based on gel permeation chromatography (GPC) measurement and is measured by the method described in the examples.

[0030] The acid value of the polyester of the present invention is, for example, 10 mgKOH / g or less, preferably 5 mgKOH / g or less, more preferably 3 mgKOH / g or less, and even more preferably 1 mgKOH / g or less. The lower limit of the acid value of the polyester of the present invention is not particularly limited, but is, for example, 0 mgKOH / g. The acid value of the above polyester is confirmed by the method described in the examples.

[0031] The properties of the polyester of the present invention vary depending on the number average molecular weight, composition, etc., but are usually liquid, solid, paste-like, etc. at normal temperature.

[0032] The polyester of the present invention that constitutes the modifier for the cellulose ester resin of the present invention may be any polyester that satisfies the general formula (1), and for example, two or more polyesters having different structures from each other may be used.

[0033] The polyester of the present invention is obtained by using reaction raw materials containing an aliphatic monoalcohol, an aliphatic dicarboxylic acid, and an alkylene glycol and / or an oxyalkylene glycol that constitute each residue. Here, the reaction raw material means a raw material that constitutes the polyester of the present invention, and does not include a solvent or a catalyst that does not constitute the polyester. The production method of the polyester of the present invention is not particularly limited, and it can be produced by a known method or by the production method described later.

[0034] The aliphatic monoalcohol used in the production of the polyester of the present invention is an aliphatic monoalcohol corresponding to the aliphatic monoalcohol residue having 1 to 12 carbon atoms of B 1 and the aliphatic monoalcohol used may be used alone or in combination of two or more. The aliphatic dicarboxylic acid used in the production of the polyester of the present invention is an aliphatic dicarboxylic acid corresponding to the aliphatic dicarboxylic acid residue having 1 to 6 carbon atoms of A, and the aliphatic dicarboxylic acid used may be used alone or in combination of two or more. The alkylene glycol used in the production of the polyester of the present invention is an alkylene glycol corresponding to the alkylene glycol residue having 2 to 12 carbon atoms of G 1 and the alkylene glycol used may be used alone or in combination of two or more. The oxyalkylene glycol used in the production of the polyester of the present invention is a 1 oxyalkylene glycol corresponding to an oxyalkylene glycol residue having 4 to 12 carbon atoms of G

[0035] In the production of the polyester of the present invention, any of the aliphatic monoalcohol, aliphatic dicarboxylic acid, alkylene glycol, and oxyalkylene glycol can be used in the form of its derivative. Examples of the derivative include esterified products, acid chlorides, cyclic esters, and the like.

[0036] The polyester of the present invention can be produced, for example, by reacting all at once under the condition that the equivalent amount of the hydroxyl group contained in the reaction raw materials, i.e., the aliphatic monocarboxylic acid, aliphatic dicarboxylic acid, alkylene glycol, and / or oxyalkylene glycol constituting each residue of the polyester of the present invention, is larger than the equivalent amount of the carboxyl group. The polyester of the present invention can also be produced, for example, by reacting the aliphatic dicarboxylic acid, alkylene glycol, and / or oxyalkylene glycol constituting each residue of the polyester of the present invention under the condition that the equivalent amount of the carboxyl group contained in the reaction raw materials is larger than the equivalent amount of the hydroxyl group to obtain a polyester having a carboxyl group at the terminal of the main chain, and then reacting the obtained polyester with an aliphatic monoalcohol.

[0037] In the production of the polyester of the present invention, the reaction of the reaction raw materials may be carried out, if necessary, in the presence of an esterification catalyst, for example, within a temperature range of 170 to 250°C for 10 to 25 hours for an esterification reaction. Incidentally, the conditions such as the temperature and time of the esterification reaction are not particularly limited and may be set as appropriate.

[0038] Examples of the esterification catalyst include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate; zinc-based catalysts such as zinc acetate; tin-based catalysts such as tin octylate and dibutyltin oxide; and organic sulfonic acid-based catalysts such as p-toluenesulfonic acid.

[0039] The amount of the esterification catalyst used may be appropriately set, but it is usually used in the range of 0.0001 to 0.1 parts by mass with respect to 100 parts by mass of the total amount of the reaction raw materials.

[0040] (Diester compound) B 2 Examples of the aromatic monocarboxylic acid residue having 6 to 12 carbon atoms of B include benzoic acid residue, dimethylbenzoic acid residue, trimethylbenzoic acid residue, tetramethylbenzoic acid residue, ethylbenzoic acid residue, propylbenzoic acid residue, butylbenzoic acid residue, cumic acid residue, para-tert-butylbenzoic acid residue, orthotoluic acid residue, metatoluic acid residue, para-toluic acid residue, ethoxybenzoic acid residue, propoxybenzoic acid residue, anisic acid residue, naphthoic acid residue, and the like.

[0041] B 2 Examples of the aliphatic monocarboxylic acid residue having 1 to 8 carbon atoms of B include acetic acid residue, propionic acid residue, butanoic acid residue, hexanoic acid residue, octanoic acid residue, octylic acid residue, and the like.

[0042] B 2 B is preferably one or more selected from a benzoic acid residue and a para-toluic acid residue.

[0043] G 2 Specific examples of the alkylene glycol residue having 2 to 12 carbon atoms of G and preferred alkylene glycol residues having 2 to 12 carbon atoms are the same as those of the alkylene glycol residue having 2 to 12 carbon atoms of G 1 in 1 .

[0044] G 2Specific examples of the oxyalkylene glycol residue having 4 to 12 carbon atoms and preferred oxyalkylene glycol residues having 4 to 12 carbon atoms are those of G 1 and are the same as the oxyalkylene glycol residues having 4 to 12 carbon atoms of

[0045] In addition, G 1 and G 2 may be the same as or different from each other.

[0046] The diester compound of the present invention constituting the modifier for cellulose ester resin may be any diester compound that satisfies the general formula (2), and may be, for example, two or more diester compounds having different structures from each other.

[0047] The diester compound of the present invention is obtained by using a reaction raw material containing an alkylene glycol or oxyalkylene glycol constituting each residue, and an aliphatic monocarboxylic acid and / or an aromatic monocarboxylic acid.

[0048] The diester compound of the present invention is preferably a diester of one or more selected from ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, diethylene glycol and dipropylene glycol, and one or more selected from benzoic acid and paratoluic acid.

[0049] The method for producing the diester compound of the present invention is not particularly limited, and it can be produced by a known method, or a commercially available product may be used.

[0050] In the modifier for cellulose ester resin of the present invention, the mass ratio (polyester / diester compound) of the polyester of the present invention to the diester compound of the present invention is preferably in the range of 95 / 5 to 30 / 70, more preferably in the range of 80 / 20 to 40 / 60.

[0051] [Cellulose Ester Resin Composition] The cellulose ester resin composition of the present invention is a composition containing a modifier for cellulose ester resin of the present invention and a cellulose ester resin. The content of the modifier for cellulose ester resin of the present invention (total amount of polyester and diester compound) is in the range of 1 to 30 parts by mass, preferably in the range of 1 to 20 parts by mass, more preferably in the range of 3 to 20 parts by mass with respect to 100 parts by mass of the cellulose ester resin.

[0052] Hereinafter, each component contained in the cellulose ester resin composition of the present invention will be described.

[0053] (Cellulose ester resin) Examples of the cellulose ester resin include cellulose acetate (CA), cellulose diacetate (DAC), cellulose triacetate (TAC), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), cellulose acetate phthalate, polycaprolactone grafted cellulose acetate, and the like. Among these, acetylated cellulose such as cellulose acetate, cellulose diacetate, and cellulose triacetate is preferred because of its good mechanical properties (tensile strength, flexural strength, flexural modulus, etc.). The cellulose ester resin can be used alone or in combination of two or more.

[0054] When the cellulose ester resin is acetylated cellulose, its degree of polymerization is preferably in the range of 250 to 400. Further, when the cellulose ester resin is acetylated cellulose, its degree of acetylation is preferably in the range of 54.0 to 62.5% by mass, more preferably in the range of 58.0 to 62.5% by mass. If the degree of polymerization and degree of acetylation of the cellulose acetate are within the above ranges, a film having excellent mechanical properties can be obtained. In the present invention, it is more preferable to use so-called cellulose triacetate. The degree of acetylation as used in the present invention is the mass ratio of acetic acid generated by saponifying the cellulose acetate to the total amount of the cellulose acetate.

[0055] The "average degree of polymerization" can be measured in accordance with the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, "Journal of the Fiber Society", Vol. 18, No. 1, pp. 105-120, 1962). Specifically, 0.2 g of absolutely dry cellulose ester is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride:ethanol = 9:1 (mass ratio). The dropping time of this solution is measured at a constant temperature of 25 °C in an Ostwald viscometer, and the average degree of polymerization is calculated by the following [Formula 1]. Average degree of polymerization = [η] / K m ···[Formula 1] [η] = (lnη rel ) / C η rel = T / T0 K m = 6×10 -4 T: dropping time of the measurement sample (seconds) T0: dropping time of the solvent (seconds) C: concentration of the sample (g / l)

[0056] The number average molecular weight of the cellulose ester resin is preferably in the range of 70,000 to 300,000, more preferably in the range of 80,000 to 200,000.

[0057] Cellulose ester resin may be a commercially available product. Examples of such commercially available products include cellulose diacetate such as "L-20" (average degree of acetyl substitution: 2.41, average degree of polymerization: 145), "L-30" (average degree of acetyl substitution: 2.41, average degree of polymerization: 160), "L-50" (average degree of acetyl substitution: 2.41, average degree of polymerization: 180), "L-70" (average degree of acetyl substitution: 2.41, average degree of polymerization: 190) manufactured by Daicel Corporation; and cellulose triacetate such as "LT-35" (average degree of acetyl substitution: 2.87, average degree of polymerization: 270), "LT-105" (average degree of acetyl substitution: 2.87, average degree of polymerization: 350) manufactured by Daicel Corporation.

[0058] In addition to using the above-mentioned commercially available products, synthesized cellulose ester resin can also be used. The cellulose ester resin can be synthesized by a known method, and the synthesis method is not particularly limited.

[0059] As a method for synthesizing cellulose ester resin, for example, it can be synthesized by esterifying all or some of the hydroxyl groups at the 2nd, 3rd, and 6th positions of glucose residues in cellulose molecules such as wood pulp (e.g., softwood pulp, hardwood pulp, etc.) and cotton linter.

[0060] When obtaining acetylated cellulose as the cellulose ester resin, it can be produced by known esterification of reacting cellulose with a predetermined amount of acetylating agent, and can be synthesized through an aging process, a precipitation process, a purification process, a drying process, etc. as necessary.

[0061] For example, it can be synthesized through a series of steps including: (1) After crushing pulp (cellulose), it is pre-treated and activated by spraying and mixing with monocarboxylic acids mainly composed of acetic acid, and then cellulose triacetate is prepared using a mono-carboxylic acid anhydride mainly composed of acetic anhydride and an esterification catalyst such as sulfuric acid; (2) An aging process of adjusting the obtained cellulose triacetate to a desired degree of acyl substitution by hydrolysis; and (3) A post-treatment process of filtering, separating by precipitation, washing with water, dehydrating, and drying the obtained cellulose acetylated product, etc.

[0062] Various conditions such as the type, usage amount, reaction temperature, and aging temperature of the esterification catalyst are not particularly limited. Also, when using an acid such as sulfuric acid as the esterification catalyst, the product may be treated with a base such as a metal salt of monocarboxylic acid to neutralize the remaining acid, and the type of base used for neutralization is not particularly limited.

[0063] (Other additives) The cellulose ester resin composition of the present invention may include the modifier for cellulose ester resin of the present invention and the cellulose ester resin, and may also contain other additives as long as the effects of the present invention are not impaired.

[0064] Examples of the other additives include other modifiers other than the modifier of the present invention, thermoplastic resins, ultraviolet absorbers, matting agents, stabilizers, deterioration inhibitors (such as antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, etc.), dyes, and the like.

[0065] Examples of the other modifiers include ester compounds other than the polyester and diester compounds of the present invention, phosphate esters such as triphenyl phosphate (TPP), tricresyl phosphate, and cresyl diphenyl phosphate, phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, trimethylolpropane tribenzoate, pentaerythritol tetraacetate, tributyl acetyl citrate, and the like.

[0066] Examples of the thermoplastic resin include polyester resins other than the ester resin of the present invention, polyester ether resins, polyurethane resins, acrylic resins, epoxy resins, toluenesulfonamide resins, and the like.

[0067] Examples of the ultraviolet absorber include oxybenzophenone-based compounds, benzotriazole-based compounds, salicylic acid ester-based compounds, benzophenone compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like. The ultraviolet absorber is preferably used in the range of 0.01 to 2 parts by mass with respect to 100 parts by mass of the cellulose ester resin.

[0068] Examples of the matting agent include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, kaolin, talc, and the like. The matting agent is preferably used in the range of 0.1 to 0.3 parts by mass with respect to 100 parts by mass of the cellulose ester resin.

[0069] Examples of the stabilizer include calcium hydroxide, calcium carbonate, fatty acid metal salts, and the like. The stabilizer is preferably used in the range of 50 to 5000 ppm with respect to 100 parts by mass of the cellulose ester resin.

[0070] The type, blending amount, etc. of the dye are not particularly limited as long as the effects of the present invention are not impaired.

[0071] [Optical film] The optical film of the present invention can be produced by using the cellulose ester resin composition of the present invention, and since it is excellent in elastic modulus, heat and humidity resistance, moisture permeability resistance, and dimensional stability, it can be used, for example, as an optical film for a display device. Examples of the optical film for the display device include a protective film for a polarizing plate, a retardation film, a reflection film, a viewing angle improvement film, an antiglare film, a non-reflection film, an antistatic film, a color filter, etc. Among them, it can be preferably used as a protective film for a polarizing plate.

[0072] The film thickness of the optical film of the present invention is preferably in the range of 20 to 120 μm, more preferably in the range of 25 to 100 μm, and particularly preferably in the range of 25 to 80 μm.

[0073] To obtain the optical film of the present invention, for example, methods such as extrusion molding and cast molding are used. Specifically, for example, an optical film in an unstretched state can be extrusion molded using an extruder equipped with a T-die, a circular die, etc. When obtaining the optical film of the present invention by extrusion molding, it is possible to use a resin composition obtained by previously melt-kneading an optical material resin such as the ester resin, ester resin mixture, cellulose ester resin, etc., and other additives, or it is also possible to melt-knead during extrusion molding and directly perform extrusion molding.

[0074] The optical film can also be obtained, for example, by casting a resin solution obtained by dissolving an optical material resin such as the cellulose ester resin composition in an organic solvent onto a metal support, and then removing the organic solvent by evaporation and drying, that is, by molding using a so-called solution casting method (solvent casting method).

[0075] The unstretched film obtained by the solution casting method substantially exhibits optical isotropy. The film exhibiting the optical isotropy can be used, for example, as an optical material for a liquid crystal display or the like, and is particularly useful as a protective film for a polarizing plate. Further, the film obtained by the above method is less likely to have irregularities formed on its surface and has excellent surface smoothness.

[0076] Generally, the solution casting method includes, for example, a first step of dissolving a cellulose ester resin and a modifier for the cellulose ester resin in a solvent and casting the obtained resin solution onto a metal support, a second step of distilling off and drying the organic solvent contained in the cast resin solution to form a film, and subsequently, a third step of peeling the film formed on the metal support from the metal support and heating and drying it.

[0077] Examples of the metal support used in the first step include endless belt-shaped or drum-shaped metal ones. For example, a stainless steel one with a mirror-finished surface can be used.

[0078] When casting the resin solution onto the metal support, it is preferable to use a resin solution filtered through a filter in order to prevent foreign substances from being mixed into the obtained film.

[0079] The drying method in the second step is not particularly limited. For example, a method of evaporating 50 to 80% by mass of the organic solvent contained in the cast resin solution by blowing air in the temperature range of 30 to 50 °C onto the upper surface and / or the lower surface of the metal support to form a film on the metal support can be mentioned.

[0080] Next, the third step is to peel the film formed in the second step from the metal support and heat-dry it under temperature conditions higher than those in the second step. As the heat-drying method, for example, a method of gradually increasing the temperature under temperature conditions of 100 to 160°C is preferable because good dimensional stability can be obtained. By heat-drying under the temperature conditions, almost all of the organic solvents remaining in the film after the second step can be removed.

[0081] In addition, in the first to third steps, the solvent can be recovered and reused.

[0082] The organic solvents that can be used when dissolving the cellulose ester resin and the modifier for cellulose ester resin are not particularly limited as long as they can dissolve them. For example, when using cellulose acetate as the resin for optical materials, it is preferable to use organic halogen compounds such as methylene chloride and dioxolanes as good solvents.

[0083] It is preferable to use a poor solvent such as methanol, ethanol, 2-propanol, n-butanol, cyclohexane, cyclohexanone, etc. in combination with the good solvent in order to improve the production efficiency of the film. The mixing ratio of the good solvent to the poor solvent is preferably in the range of a mass ratio of good solvent / poor solvent = 75 / 25 to 95 / 5.

[0084] The concentration of the cellulose ester resin in the resin solution is preferably in the range of 10 to 50% by mass, and more preferably in the range of 15 to 35% by mass.

[0085] In the present invention, for example, an unstretched optical film obtained by the above method can be stretched to obtain a stretched optical film by uniaxially stretching in the machine flow direction and then uniaxially stretching in a direction perpendicular to the machine flow direction as needed. Further, a biaxially stretched film can be obtained by stretching by a sequential biaxial stretching method of roll stretching and tenter stretching, a simultaneous biaxial stretching method by tenter stretching, a biaxial stretching method by tubular stretching, or the like. The stretching ratio is preferably at least 0.1% or more and 300% or less in at least one direction, more preferably 0.2% or more and 250% or less, and most preferably 0.3% or more and 200% or less. By designing within this range, a preferably stretched optical film can be obtained from the viewpoints of birefringence, heat resistance, and strength.

[0086] The optical film according to the present invention can be suitably used as an optical material for polarizing plates for polarizing lenses and sunglasses, polarizing plate protection films for liquid crystal display devices, plasma displays, organic EL displays, field emission displays, rear projection TVs, etc., quarter-wave plates, half-wave plates, viewing angle control films, retardation films such as liquid crystal optical compensation films, and display front panels. Further, the resin composition of the present invention can also be used for waveguides, lenses, optical fibers, substrates of optical fibers, coating materials, lenses of LEDs, lens covers, etc. in the fields of optical communication systems, optical switching systems, and optical measurement systems.

Examples

[0087] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. Note that the present invention is not limited to the following Examples.

[0088] In the examples of the present application, the values of the acid value and the hydroxyl value are the values evaluated by the following methods. [Method for measuring acid value] Measured by a method according to JIS K0070-1992. [Method for measuring hydroxyl value] It was measured by the method in accordance with JIS K0070-1992.

[0089] In the examples of the present application, the number average molecular weight of the polyester is a value converted to polystyrene based on GPC measurement, and the measurement conditions are as follows. [GPC measurement conditions] Measuring device: High-speed GPC device "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSK GURDCOLUMN SuperHZ-L" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation Detector: RI (differential refractometer) Data processing: "EcoSEC Data Analysis version 1.07" manufactured by Tosoh Corporation Column temperature: 40 °C Developing solvent: Tetrahydrofuran Flow rate: 0.35 mL / min Measurement sample: A solution obtained by dissolving 7.5 mg of the sample in 10 ml of tetrahydrofuran and filtering the resulting solution through a microfilter was used as the measurement sample. Sample injection volume: 20 μl Standard sample: The following monodisperse polystyrene with a known molecular weight was used in accordance with the measurement manual of the "HLC-8320GPC".

[0090] (Monodisperse polystyrene) "A-300" manufactured by Tosoh Corporation "A-500" manufactured by Tosoh Corporation "A-1000" manufactured by Tosoh Corporation "A-2500" manufactured by Tosoh Corporation "A-5000" manufactured by Tosoh Corporation "F-1" manufactured by Tosoh Corporation "F-2" manufactured by Tosoh Corporation "F-4" manufactured by Tosoh Corporation "F-10" manufactured by Tosoh Corporation "F-20" manufactured by Tosoh Corporation "F-40" manufactured by Tosoh Corporation "F-80" manufactured by Tosoh Corporation "F-128" manufactured by Tosoh Corporation "F-288" manufactured by Tosoh Corporation

[0091] (Synthesis Example 1: Synthesis of Polyester (P1)) Into a 2-liter four-necked flask, 216 g of 1,2-propylene glycol (hereinafter abbreviated as "PG") as the glycol component, 611 g of adipic acid (hereinafter abbreviated as "AA") as the dicarboxylic acid component, 462 g of 2-ethylhexanol as the monoalcohol component, and 0.081 g of tetraisopropyl titanate (hereinafter abbreviated as "TiPT") as the catalyst were charged. While introducing nitrogen through the nitrogen inlet tube and stirring, the temperature was gradually raised to 220 °C under a nitrogen stream. A condensation reaction was carried out at 220 °C for 13 hours. When the acid value reached 1.0 or less, unreacted components were removed from the reaction product under reduced pressure at 200 °C to obtain a transparent pale yellow liquid polyester (P1). The number average molecular weight of the obtained polyester (P1) was 760, the acid value was 0.3, and the hydroxyl value was 10.

[0092] (Synthesis Example 2: Synthesis of Polyester (P2)) Into a 2-liter four-necked flask, 83 g of ethylene glycol (hereinafter abbreviated as "EG") and 102 g of PG as the glycol components, 574 g of AA as the dicarboxylic acid component, 482 g of isononyl alcohol as the monoalcohol component, and 0.062 g of TiPT as the catalyst were charged. While introducing nitrogen through the nitrogen inlet tube and stirring, the temperature was gradually raised to 220 °C under a nitrogen stream. A condensation reaction was carried out at 220 °C for 13 hours. When the acid value reached 1.0 or less, unreacted components were removed from the reaction product under reduced pressure at 200 °C to obtain a transparent pale yellow liquid polyester (P2). The number average molecular weight of the obtained polyester (P2) was 1,190, the acid value was 0.3, and the hydroxyl value was 9.

[0093] (Synthesis Example 3: Synthesis of Polyester (P3)) A 2-liter four-necked flask was charged with 217 g of EG as a glycol component, 614 g of AA as a dicarboxylic acid component, 125 g of butanol as a monoalcohol component, and 0.057 g of TiPT as a catalyst. While introducing nitrogen through a nitrogen inlet tube and stirring, the temperature was gradually raised to 220 °C. A condensation reaction was carried out at 220 °C for 13 hours. When the acid value reached 1.0 or less, unreacted components were removed from the reaction product at 200 °C under reduced pressure to obtain a transparent pale yellow liquid polyester (P3). The number average molecular weight of the obtained polyester (P3) was 1,280, the acid value was 0.3, and the hydroxyl value was 12.

[0094] (Synthesis Comparative Example 1: Synthesis of Polyester (P1’)) A 2-liter four-necked flask was charged with 405 g of PG as a glycol component, 79 g of AA as a dicarboxylic acid, 240 g of phthalic anhydride, 586 g of benzoic acid (hereinafter abbreviated as “BzA”) as a monocarboxylic acid, and 0.08 g of TiPT as a catalyst. While introducing nitrogen through a nitrogen inlet tube and stirring, the temperature was gradually raised to 230 °C. A condensation reaction was carried out at 230 °C for 19 hours. When the acid value reached 1.0 or less, unreacted components were removed from the reaction product at 200 °C under reduced pressure to obtain a transparent pale yellow liquid polyester (P1’). The number average molecular weight (Mn) of the obtained polyester (P1’) was 405, the acid value was 0.2, and the hydroxyl value was 16.

[0095] (Synthesis Example 5: Synthesis of Diester (D1)) A 2-liter four-necked flask was charged with 900 g of BzA, 547 g of dipropylene glycol (hereinafter abbreviated as “DPG”), and 0.74 g of TiPT. After that, the temperature was raised to 220 °C and reacted for 11 hours. After the reaction, unreacted glycol was distilled off under reduced pressure at 200 °C. After the outflow of unreacted alcohol ceased, the reduced pressure was released and the temperature was lowered, and the reaction product was filtered out to obtain a transparent yellow liquid diester (D1). The number average molecular weight of the diester compound (D1) was 340, the acid value was 0.2, and the hydroxyl value was 5.

[0096] (Synthesis Example 6: Synthesis of Diester (D2)) After charging 900 g of BzA, 294 g of PG, 50 g of DPG, and 0.62 g of TiPT into a 2-liter four-necked flask, the temperature was raised to 220 °C and reacted for 11 hours. After the reaction, unreacted glycol was distilled off under reduced pressure at 200 °C. After the outflow of unreacted alcohol ceased, the reduced pressure was released and the temperature was lowered, and the reaction product was filtered out to obtain a transparent yellow liquid diester (D2). The number average molecular weight of the diester compound (D2) was 290, the acid value was 0.2, and the hydroxyl value was 5.

[0097] (Example 1: Production and Evaluation of Cellulose Ester Optical Film) 100 parts by mass of triacetyl cellulose resin ("LT-35" manufactured by Daicel Corporation), 6 parts by mass of polyester (P1), and 4 parts by mass of diester (D1) were added to a mixed solvent consisting of 810 parts of methylene chloride and 90 parts of methanol and dissolved to prepare a dope solution which is a cellulose ester resin composition. The obtained dope solution was cast on a glass plate and dried at room temperature for 16 hours, and then dried at 50 °C for 30 minutes and further at 120 °C for 30 minutes to obtain an optical film (film thickness: 40 μm). The following evaluations were carried out on the obtained film. The results are shown in Table 1.

[0098] (1) Moisture Permeability The moisture permeability of the optical film was measured by the method described in JIS Z 0208-1976. The measurement conditions were at a temperature of 40 °C and a relative humidity of 90%. The lower the obtained value of the moisture permeability, the better the moisture resistance.

[0099] (2) Haze Value The Haze value of the optical film was measured in accordance with JIS K 7105-1981 using a turbidimeter ("NDH 5000" manufactured by Nippon Denshoku Industries Co., Ltd.). The closer the obtained value of the Haze value is to 0%, the more transparent it is.

[0100] (3) Damp Heat Test An optical film with a film thickness of 40 μm was exposed to an environment of 85 °C and a relative humidity of 90% (humid and hot environment) for 120 hours. (3-1) State after the humid and hot test The state of the optical film after the humid and hot test was visually confirmed and evaluated according to the following criteria. A: No change in the film state before and after the humid and hot test B: Slight bleed-out was confirmed on the film surface. C: Obvious bleed-out was confirmed on the film surface. (3-2) HAZE value after the humid and hot test For the optical film after the humid and hot test, the HAZE value was measured by the same method as above. (3-3) Weight loss after the humid and hot test The weights of the optical film before the humid and hot test and after the humid and hot test were compared, and (mass of the optical film before the humid and hot test - mass of the optical film after the humid and hot test) / mass of the optical film before the humid and hot test was calculated to evaluate the weight loss of the optical film after the humid and hot test. The lower this value, the higher the non-volatility of the optical film, which is preferable.

[0101] (4) Elastic modulus The elastic modulus of the optical film was evaluated with the following apparatus and conditions. The smaller the value of the elastic modulus, the softer the film. Apparatus: Autograph AG-IS manufactured by Shimadzu Corporation Test piece: Strip-shaped with dimensions of 150 mm × 10 mm and a thickness of 40 μm Distance between chucks: 100 mm Test speed: 10 mm / min

[0102] (5) Elongation The elongation of the optical film was evaluated with the following apparatus and conditions. The larger the value of the elongation, the softer the film and the better its processability. Apparatus: Autograph AG IS manufactured by Shimadzu Corporation Test piece: Strip-shaped with dimensions of 150 mm × 10 mm and a thickness of 40 μm Distance between chucks: 100 mm Test speed: 10 mm / min

[0103] (6) Dimensional stability The dimensional change rate of the optical film was measured when the relative humidity was changed from 0% to 80%. The smaller the change rate, the better the dimensional stability. Apparatus: SIINT TMA / SS6100 + humidity control unit manufactured by Hitachi High-Tech Corporation Measurement temperature: Constant at 40 °C Relative humidity: 0% - 80% Measurement load: 50 mN Test piece film thickness: 40 μm

[0104] (Examples 2 - 6 and Comparative Examples 1 - 6: Production and evaluation of cellulose ester optical films) Optical films were produced and evaluated in the same manner as in Example 1, except that the polyesters and diesters shown in Table 1 were used as shown in Table 1. The results are shown in Table 1.

[0105]

Table 1

[0106] From the results in Table 1, it can be seen that in the optical films obtained using the compositions of Examples 1 - 5 containing specific polyesters and diesters, the moisture permeability is kept low, the transparency is not impaired, and the dimensional stability is excellent. On the other hand, in the optical films obtained using the compositions of Comparative Examples 2 - 4 which contain polyesters but do not contain diesters, the compatibility of the polyester is insufficient, bleeding out occurs, and transparency cannot be ensured. In the optical films obtained using the composition of Comparative Example 5 which contains both polyester and diester but the polyester contains an aromatic ring structure, no plasticizing effect is obtained. In addition, in the optical film obtained using the composition of Comparative Example 6 that contains diester but does not contain polyester, the weight loss after humidity and heat treatment is large, and the moisture and heat resistance is insufficient. In Comparative Example 1 that does not contain an additive and Comparative Example 7 that contains triphenyl phosphate, the moisture permeability resistance is insufficient. Incidentally, triphenyl phosphate is a plasticizer known for use in cellulose ester optical films (for example, Patent Document 1).

[0107] (Durability Evaluation) Regarding the optical film of Example 2 and the optical film of Comparative Example 7, a durability test was separately conducted. Specifically, 1.200 g of the film was placed in a 24 mL sealed container, and the film was sufficiently hydrated under the conditions of 85 °C and 90% humidity with the lid open. Then, the sealed container was sealed, and it was stored again under the conditions of 85 °C and 90% humidity for one week, and the amount of acetic acid generated from the film was measured using a gas detector tube (Kitagawa type gas detector tube 216S, gas sampler AP-20, manufactured by Komyo Rikagaku Kogyo Co., Ltd.). The results are shown in Table 2. Incidentally, the detection limit of the amount of acetic acid generated is 125 ppm. Since acetic acid is generated when the cellulose ester film undergoes hydrolysis, it can be said that the film with a lower amount of acetic acid generated is more excellent in durability.

[0108]

Table 2

[0109] In the optical film of Comparative Example 7 that contains triphenyl phosphate, the amount of acetic acid generated exceeds the detection limit, indicating that there is a problem with the durability of the film.

Claims

1. A modifier for cellulose ester resin containing a polyester represented by the following general formula (1) and a diester compound represented by the following general formula (2), wherein The modifier for cellulose ester resin in which the mass ratio (polyester / diester compound) of the polyester to the diester compound is in the range of 95 / 5 to 30 / 70. 【Chemical Formula 1】 (In the general formula (1), B １ is, independently of one another, an aliphatic monoalcohol residue having 1 to 12 carbon atoms, A is each independently an aliphatic dicarboxylic acid residue having 1 to 6 carbon atoms, G １ is an alkylene glycol residue having 2 to 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, n represents the number of repetitions. However, G within parentheses may be the same or different for each repeating unit. １ And A may be the same or different, respectively. In the general formula (2), B ２ is each independently an aromatic monocarboxylic acid residue having 6 to 12 carbon atoms or an aliphatic monocarboxylic acid residue having 1 to 8 carbon atoms, G ２ is an alkylene glycol residue having 2 to 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms.)

2. The modifier for cellulose ester resin according to claim 1, wherein A is a succinic acid residue or an adipic acid residue.

3. The modifier for cellulose ester resin according to claim 1 or 2, wherein the number average molecular weight of the polyester is in the range of 400 to 2,000.

4. The modifier for cellulose ester resin according to any one of claims 1 to 3, wherein the diester compound is a diester of one or more selected from ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, diethylene glycol and dipropylene glycol and one or more selected from benzoic acid and paratoluic acid.

5. The modifier for cellulose ester resin according to any one of claims 1 to 4, which is a plasticizer for cellulose ester resin.

6. A cellulose ester resin composition containing the modifier for cellulose ester resin according to any one of claims 1 to 5 and a cellulose ester resin, wherein the cellulose ester resin composition contains the modifier for cellulose ester resin in the range of 1 to 30 parts by mass with respect to 100 parts by mass of the cellulose ester resin.

7. An optical film containing the cellulose ester resin composition according to claim 6.

8. The optical film according to claim 7, which is for protecting a polarizing plate.

9. A display device having the optical film according to claim 7 or 8.

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