JPWO2013027793A1 - Optical film, retardation film and wave plate - Google Patents

Abstract

An object of the present invention is to provide a thin optical film with high birefringence, and the substitution degree of propionyl group or butyryl group is within the range of 0.1 to 2.2 substitution degree of acetyl group. Cellulose acylate (A) having a substitution degree in the range of 0.5 to 2.7, a substitution degree of the hydroxyl group in the range of 0.1 to 1, and a total of these substitution degrees of 3 and 2 carbon atoms Ester compound (8) obtained by esterifying -8 linear or branched alkylene diol (b1) with an aromatic dicarboxylic acid (b2) selected from terephthalic acid or naphthalenedicarboxylic acid or a dialkyl ester compound thereof ( B) is an optical film obtained by heating and stretching a cellulose ester resin composition containing the cellulose ester resin composition, and the content of the ester compound (B) in the cellulose ester resin composition is cellulosic. In Suashireto (A) 7 to 30 parts by weight per 100 parts by weight, the stretching ratio during the heating stretching to provide an optical film is 1.7 to 4 times.

Description

  The present invention relates to a retardation film used for flat panel displays (liquid crystal displays, organic EL displays, etc.), and more particularly to an optical film that can be suitably used as a wave plate.

  In recent years, demand for flat panel displays such as mobile terminals, tablet terminals, personal computer monitors, and liquid crystal televisions is increasing. In this flat panel display, an optical film such as a retardation film is used to control light. Examples of the retardation film include a wave plate such as a quarter wave plate, a viewing angle compensation film, and the like.

  The quarter-wave plate has a phase difference value of a quarter wavelength of the light wavelength, and has a function of converting the polarization state of the light. In a terminal that is often used outside, such as a mobile terminal and a tablet-type terminal, image quality deteriorates due to reflection of external light, and thus it is necessary to suppress external light reflection. In order to effectively suppress this external light reflection, a circularly polarizing plate combining a polarizing plate and a quarter wave plate is used.

  A circularly polarizing plate is an essential member for a display device that uses circularly polarized light. Examples of such a display device include a reflective liquid crystal display (hereinafter abbreviated as a reflective LCD) and a transflective liquid crystal display (hereinafter referred to as a reflective liquid crystal display). Abbreviated as transflective LCD). In addition, it is used to prevent external light reflection in a touch panel that has a remarkable decrease in visibility due to external light reflection due to a multilayer structure and an organic light emitting diode (OLED) display device that has a significant decrease in visibility due to external light reflection by a metal electrode. Has been. In these display devices, a circularly polarizing plate in which a polarizing plate and a quarter-wave plate are combined is disposed so that the polarizing plate is disposed on the outermost surface of the display device, for example. A protective layer having antireflection ability and scratch resistance is formed on the surface of the polarizing plate as necessary.

  The viewing angle compensation film is not disposed on the surface of the display device like the circularly polarizing plate. For example, the viewing angle compensation film is inserted between the liquid crystal cell and the polarizer film, and the phase difference of the light that has passed through the liquid crystal cell. And the function of correcting the distortion of light derived from the liquid crystal cell.

  In recent years, due to the demand for cost reduction and thickness reduction of flat panel displays (FPDs), members have been actively studied for the circularly polarizing plate.

  A polarizing plate, which is a member of a circularly polarizing plate, usually has protective films attached to both sides of a polarizer film obtained by stretching a film of polyvinyl alcohol to which iodine is added (hereinafter abbreviated as “PVA”). Things are used. As the polarizer protective film, a cellulose ester resin film having generally high transparency, moderate strength, and excellent adhesiveness with PVA is used.

Moreover, the quarter wavelength plate which is a member of a circularly-polarizing plate is a retardation film having a retardation value of a quarter wavelength of light as described above, and has a function of converting the polarization state of light. The retardation value of the film is an index of optical anisotropy, and the retardation can be expressed by the following formula.
Phase difference (nm) = birefringence Δn × thickness d (nm)
Birefringence Δn = Nx−Ny
(However, Nx: Refractive index of slow axis in film plane, Ny: Refractive index of fast axis in film plane, Nx> Ny)

  The quarter wave plate can convert linearly polarized light into circularly polarized light by having a phase difference value of ¼ of the wavelength. In order to express a large retardation value, polycarbonate or the like, which is a raw material having a large optical anisotropy, is used in the current retardation film.

  Conventionally, a polycarbonate resin used as a wave plate has a characteristic that the birefringence decreases as the measurement wavelength becomes longer. When a film having such a characteristic is used, for example, the retardation value is 1 at 588 nm. Even when the wavelength is optimized to / 4 wavelength, the phase difference value is shifted from the ¼ wavelength on the short wavelength side and the long wavelength side, which causes a problem such as light leakage. In order to solve this problem, a film having a characteristic (reverse wavelength dispersion) in which birefringence increases as the measurement wavelength becomes longer is required.

  Here, the cellulose ester resin is known to exhibit birefringent reverse wavelength dispersibility, and is suitable for quarter wave plate applications. Moreover, since it is the same material as the conventional polarizer protective film, cost reduction and thickness reduction by combining the members can be expected. Furthermore, among cellulose ester resins, cellulose acetate propionate, cellulose acetate butyrate, and the like can use a melt-extrusion method with high productivity as a film forming method, and have an advantage that they can be produced at low cost.

  With the recent thinning of LCDs, there has been a demand for thinner retardation films. As described above, since the retardation value of the retardation film is determined by the product of the birefringence and the thickness of the film, the birefringence Δn is increased in order to reduce the thickness and obtain an equivalent retardation value. It will be necessary. Thermal stretching is known as a technique for increasing the birefringence of a resin film, but it has been difficult to develop birefringence in an isotropic cellulose ester resin by this technique.

  Therefore, as a technique for developing birefringence in a cellulose ester resin, for example, by adding a specific compound to cellulose acetate propionate into a film by a melt extrusion method, and increasing the birefringence by thermally stretching the film. (For example, refer to Patent Documents 1 and 2). Specifically, for example, Patent Document 2 discloses a film obtained using a resin composition containing 100 parts by mass of cellulose acetate propionate resin and 10 parts of phthalic polyester. However, the films described in Patent Documents 1 and 2 have low birefringence, and it has not been possible to realize sufficient thinning as a wave plate.

  Further, in the field of viewing angle compensation film which is an example of a phase difference film, in order to express the phase difference necessary for viewing angle compensation, 100 parts by mass of cellulose acetate propionate resin and 1.5 parts of terephthalic acid polyester are added. A film obtained by hot-stretching a resin composition containing it is disclosed (for example, see Patent Document 3). However, the film described in Patent Document 3 has low birefringence, and it has not been possible to realize sufficient thinning as a wave plate.

JP 2008-291246 A JP 2011-021182 A JP 2011-121327 A

  The problem to be solved by the present invention is to provide an optical film (retardation film) that can obtain a high birefringence and can be thinned, and can be suitably used particularly as a wave plate.

  As a result of intensive studies, the present inventors have found that alkylene diols having a specific number of carbon atoms, terephthalic acid, and naphthalenedicarboxylic acid with respect to 100 parts by mass of cellulose acylate disclosed in Patent Documents 2 and 3 above. A cellulose ester resin composition containing 7 to 30 parts by mass of a polyester obtained by using an aromatic dicarboxylic acid or an alkyl ester thereof selected from the above is obtained by heating and stretching in a range of a stretching ratio of 1.7 to 4 times. The film thus obtained has high birefringence, and it has been found that the retardation film (particularly a wave plate) can be thinned, and the invention has been completed.

  That is, in the present invention, the substitution degree of the acetyl group is in the range of 0.1 to 2.2, the substitution degree of the propionyl group or the substitution degree of the butyryl group is in the range of 0.5 to 2.7, and the substitution degree of the hydroxyl group. Is a cellulose acylate (A) having a total substitution degree of 3, a linear or branched alkylene diol (b1) having 2 to 8 carbon atoms, and terephthalate. Obtained by heating and stretching a cellulose ester resin composition containing an ester compound (B) obtained by esterifying an aromatic dicarboxylic acid (b2) selected from an acid or naphthalenedicarboxylic acid or a dialkyl ester compound thereof. It is an optical film, and the content of the ester compound (B) in the cellulose ester resin composition is 7 to 30 parts by mass with respect to 100 parts by mass of the cellulose acylate (A). Stretching ratio during stretching is to provide an optical film which is a 1.7 to 4-fold.

  The present invention also provides a retardation film comprising the optical film.

  Furthermore, the present invention provides a wave plate comprising the optical film.

  The optical film of the present invention can be easily produced by various methods such as a melt extrusion method, and has a high birefringence by thermally stretching the film. An optical film that exhibits the function of the film can be obtained. Therefore, the optical film of the present invention can be used for various optical films, and is particularly useful as a retardation film used for a circularly polarizing plate, specifically as a wave plate.

  The cellulose acylate (A) used in the optical film of the present invention is obtained by esterifying part or all of the hydroxyl groups of cellulose obtained from cotton linter, wood pulp, kenaf and the like. Among these, a film obtained by using cellulose ester resin obtained by esterifying cellulose obtained from cotton linter is easy to peel off from the metal support constituting the film production apparatus, and improves the production efficiency of the film. It is preferable because it becomes possible.

  The cellulose molecule is a polysaccharide in which D-glucose, which is a basic unit, is connected in a straight chain with β-1,4 bonds. The glucose unit constituting cellulose has three hydroxyl groups at positions 2, 3, and 6, and these hydroxyl groups can be esterified. The esterification of cellulose can be performed by a known method. For example, cellulose is treated with a strong caustic soda solution and then acylated with an acid anhydride. The degree of substitution of the obtained cellulose acylate is about 3. By hydrolyzing this, a cellulose acylate having the desired degree of substitution can be produced. The type and degree of substitution of the cellulose acylate substituent can be determined by ASTM-D817.

  The cellulose acylate (A) has an acetyl group substitution degree in the range of 0.1 to 2.2 and a propionyl group substitution degree or a butyryl group substitution degree in the range of 0.5 to 2.7. The substitution degree of the hydroxyl group is in the range of 0.1 to 1, and the total of these substitution degrees is 3. Since the birefringence develops well, the substitution degree of the acetyl group is in the range of 0.1 to 1.5, and the substitution degree of the propionyl group or the substitution degree of the butyryl group is 1.0 to 2.7. More preferably, the hydroxyl group substitution degree is in the range of 0.1 to 1, and the total of these substitution degrees is 3. Specific examples of the cellulose acylate (A) include cellulose acetate propionate and cellulose acetate butyrate.

  The number average molecular weight of the cellulose acylate (A) is preferably from 30,000 to 200,000, more preferably from 50,000 to 100,000, since the mechanical properties are good.

  The ester compound (B) used for the optical film of the present invention is an aromatic dicarboxylic acid (b2) selected from linear or branched alkylene diol (b1) having 2 to 8 carbon atoms and terephthalic acid or naphthalenedicarboxylic acid. ) Or a dialkyl ester compound thereof is an ester compound obtained by an esterification reaction.

  Examples of the ester compound (B) include an ester compound having a structure represented by the following general formula (I) and having hydroxyl groups at both ends.

（上記一般式（Ｉ）中のＧはアルキレンジオール（ｂ１）の残基を表し、Ｔは芳香族ジカルボン酸化合物（ｂ２）の残基を表す。また、ｎは繰り返し数を表し、１以上の整数である。）

(G in the general formula (I) represents a residue of the alkylene diol (b1), T represents a residue of the aromatic dicarboxylic acid compound (b2), n represents the number of repetitions, and 1 or more. (It is an integer.)

  The above “residue” means the following. The “residue” of the alkylene diol (b1) represents the remaining organic group excluding the two hydroxyl groups that the alkylene diol (b1) has before the reaction. The “residue” of the aromatic dicarboxylic acid (b2) represents the remaining organic group excluding the carboxyl group of the aromatic dicarboxylic acid (b2). Further, n in the general formula (I) is an integer of 1 or more, preferably 30 or less, more preferably 20 or less, and still more preferably 10 or less.

  Examples of the alkylene diol (b1) include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, , 8-octanediol and other linear alkylene diols; propylene glycol (1,2-propanediol), 2-methyl-1,3-propanediol, neopentyl glycol, 3,3-diethyl-1,3-propane Diol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 2-methyl-2 , 4-pentanediol, 3-methyl-1,5-pentanediol, 1,4-pentanediol, 1,2 Hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, etc. And branched alkylene diols. These alkylene diols (b1) can be used alone or in combination of two or more. Among these alkylene diols (b1), a linear or branched alkylene diol having 2 to 6 carbon atoms is preferable because of its good compatibility with the cellulose acylate (A). Since high birefringence can be provided, propylene glycol, 2-methyl-1,3-propanediol and 3-methyl-1,5-pentanediol are more preferable.

  Here, in order to obtain high birefringence, 1. 1. refractive index anisotropy of additive molecules; The nematic interaction between the resin and the additive is important. 1. With regard to, short-chain glycol is advantageous because the aromatic ring concentration of the additive contributing to the expression of refractive index heterogeneity increases. In addition, 2. The nematic interaction is an interaction between molecules that induces molecular orientation. Specifically, the orientation of the polymer chain (resin) during the stretching is an interaction that induces the orientation of the low molecular compound (additive). The additive structure having a larger interaction increases the birefringence expression at the time of stretching. The nematic interaction is maximum within a specific range of the glycol chain length, and a high nematic interaction can be expected if the alkylene diol (b1) is within the above range.

  The aromatic dicarboxylic acid (b2) or its dialkyl ester compound used in the present invention is terephthalic acid or naphthalene dicarboxylic acid, and its dialkyl ester compound. These aromatic dicarboxylic acids can be used alone or in combination of two or more.

  When the dialkyl ester compound of the aromatic dicarboxylic acid (b2) is used, examples of the alkyl group include those having 1 to 8 carbon atoms, and those having 3 or more carbon atoms may be linear alkyl groups. It may be a branched alkyl group. Examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, and an octyl group. Two alkyl groups may be the same as or different from each other.

  Specific examples of the dialkyl ester compound of terephthalic acid include dimethyl terephthalate, diethyl terephthalate, dipropyl terephthalate, dibutyl terephthalate, dipentyl terephthalate, dihexyl terephthalate, and diheptyl terephthalate.

  Specific examples of the dialkyl ester compound of naphthalene dicarboxylic acid include dimethyl naphthalene dicarboxylate, diethyl naphthalene dicarboxylate, dipropyl naphthalene dicarboxylate, dibutyl naphthalene dicarboxylate, dipentyl naphthalene dicarboxylate, dihexyl naphthalene dicarboxylate, diheptyl naphthalene dicarboxylic acid Etc.

  Of the above aromatic dicarboxylic acids (b2) or dialkyl ester compounds thereof, naphthalenedicarboxylic acid or dialkyl ester compounds thereof are preferred. Specifically, 1,4-naphthalenedicarboxylic acid or dialkyl ester compounds thereof, 1,5 -Naphthalenedicarboxylic acid or its dialkyl ester compound, 1,8-naphthalenedicarboxylic acid or its dialkyl ester compound, 2,3-naphthalenedicarboxylic acid or its dialkyl ester compound, 2,6-naphthalenedicarboxylic acid or its dialkyl ester compound are preferred . Among these, 2,6-naphthalenedicarboxylic acid or a dialkyl ester compound thereof is more preferable, and dimethyl 2,6-naphthalenedicarboxylic acid is more preferable.

  As the ester compound used in the present invention, the linear or branched alkylene diol (b1) having 2 to 8 carbon atoms, the aromatic dicarboxylic acid (b2) selected from terephthalic acid or naphthalenedicarboxylic acid, or a dialkyl ester thereof. In addition to the compound, an ester compound obtained by further esterifying an aromatic monocarboxylic acid (b3) or an alkyl ester compound thereof can also be used. By using such a terminal aromatic sealing type ester compound, an effect of imparting moisture permeability resistance to the cellulose ester film can be obtained. Examples of such ester compounds include ester compounds having a structure represented by the following general formula (II).

（上記一般式（Ｉ）中のＲはアルキレンジオール（ｂ１）の残基を表し、Ｔは芳香族ジカルボン酸（ｂ２）の残基を表し、Ａは芳香族モノカルボン酸（ｂ３）の残基を表す。また、ｎは繰返し数を表し、０以上の整数である。）

(R in the general formula (I) represents a residue of an alkylene diol (b1), T represents a residue of an aromatic dicarboxylic acid (b2), and A represents a residue of an aromatic monocarboxylic acid (b3). In addition, n represents the number of repetitions and is an integer of 0 or more.)

  The aromatic monocarboxylic acid (b3) or an alkyl ester compound thereof is a compound having one carboxyl group in an aromatic ring or an alkyl ester compound. Among the aromatic monocarboxylic acids (b3), benzoic acid or a derivative thereof can be preferably exemplified. Examples of benzoic acid derivatives include dimethyl benzoic acid, trimethyl benzoic acid, tetramethyl benzoic acid, ethyl benzoic acid, propyl benzoic acid, butyl benzoic acid, cumic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, Examples include p-toluic acid, ethoxybenzoic acid, propoxybenzoic acid, methoxybenzoic acid, dimethoxybenzoic acid, trimethoxybenzoic acid, cyanobenzoic acid, hydroxybenzoic acid, and cinnamic acid. These aromatic monocarboxylic acids (b3) or alkyl ester compounds thereof can be used alone or in combination of two or more. Among these, p-toluic acid and benzoic acid are preferable because of excellent compatibility with the cellulose ester resin.

  In the present invention, a monoalcohol or a polyhydric alcohol may be used in addition to the above alkylene diol (b1) within a range not impairing the effects of the present invention. Examples of the monoalcohol include methanol, ethanol, 1-butanol, 2-butanol, hexanol, cyclohexanol, pentyl alcohol, octyl alcohol, lauryl alcohol, methyl lactate, and ethyl lactate. Examples of the polyhydric alcohol include glycerin, sorbitol, ribitol, pentaerythritol, dipentaerythritol and the like. These monoalcohols and polyhydric alcohols can be used alone or in combination of two or more. In order to impart high birefringence to the optical film of the present invention, the amount of the alkylene diol (b1) used is 95 in a total of 100 parts by mass of the alkylene diol (b1) and monoalcohol or polyhydric alcohol. It is preferable to set it as a mass part or more.

  Furthermore, in the production of the ester compound (B), a dicarboxylic acid other than the aromatic dicarboxylic acid (b2) or an alkyl ester compound thereof, or a carbonate compound may be used in combination as long as the effects of the present invention are not impaired. it can. As said dicarboxylic acid or its alkyl ester compound, aliphatic dicarboxylic acid, aromatic dicarboxylic acids other than aromatic dicarboxylic acid (b2), or these alkyl ester compounds can be used. Examples of the aliphatic dicarboxylic acid or its alkyl ester compound include succinic acid, dimethyl succinate, glutaric acid, dimethyl glutarate, adipic acid, dimethyl adipate, diethyl adipate, dibutyl adipate, pimelic acid, dimethyl pimelate. , Suberic acid, dimethyl suberate, azelaic acid, dimethyl azelate, sebacic acid, dimethyl sebacate, decanedicarboxylic acid, dimethyl decanedicarboxylate, cyclohexanedicarboxylic acid, dimethyl cyclohexanedicarboxylate, dimer acid, dimethyl dimer acid, fumaric acid, And dimethyl fumarate. Examples of aromatic dicarboxylic acids other than aromatic dicarboxylic acid (b2) or alkyl ester compounds thereof include phthalic acid, dimethyl phthalate, isophthalic acid, dimethyl isophthalate, and the like. Furthermore, examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, and dibutyl carbonate. These other dicarboxylic acids or their alkyl ester compounds or carbonate compounds can be used alone or in combination of two or more. In order to impart high birefringence to the optical film of the present invention, use of the aromatic dicarboxylic acid compound (b2) in a total of 100 parts by mass of the aromatic dicarboxylic acid compound (b2) and other dicarboxylic acids and the like The amount is preferably 95 parts by mass or more.

  The ester compound (B) used in the present invention contains, in a reactor, an alkylene diol (b1), an aromatic dicarboxylic acid (b2) selected from terephthalic acid or naphthalenedicarboxylic acid or a dialkyl ester compound thereof, It can be obtained by charging an aromatic monocarboxylic acid (b3) or its alkyl ester compound and heating to cause esterification.

  The reaction equipment used for producing the ester compound (B) is preferably a reaction equipment corresponding to pressurization and depressurization, equipped with a reactor, a stirrer, a rectifying column, a reflux condenser, a pump for depressurizing, and the like. Other common devices can be used.

  In producing the ester compound (B), an esterification catalyst is preferably used for the purpose of promoting the esterification reaction. Examples of the esterification catalyst include at least one metal or organometallic compound selected from the group consisting of Group 2, Group 3, Group 12, Group 13, and Group 14 of the Periodic Table. More specifically, for example, metals such as titanium, tin, zinc, aluminum, zirconium, magnesium, hafnium, germanium; titanium tetraisopropoxide, titanium tetrabutoxide, titanium oxyacetylacetonate, tin octoate, 2-ethyl Examples thereof include metal compounds such as hexanetin, acetylacetonate zinc, zirconium tetrachloride, zirconium tetrachloride tetrahydrofuran complex, hafnium tetrachloride, hafnium tetrachloride, hafnium tetrachloride complex, germanium oxide, and tetraethoxygermanium. Among these, titanium alkoxides are preferable because the reactivity can be improved, the handling is easy, and the storage stability of the ester compound (B) obtained by the esterification reaction is good. It is preferable to use titanium tetraisopropoxide, titanium tetrabutoxide, titanium oxyacetylacetonate or the like.

  The esterification catalyst may be used in an amount that can control the esterification reaction and suppress the coloring of the resulting ester compound (B). The alkylene diol (b1) and the aromatic dicarboxylic acid may be used. The range of 10 to 1,000 ppm is preferable and the range of 20 to 500 ppm is more preferable with respect to the total amount of the acid (b2) or its dialkyl ester compound and the aromatic monocarboxylic acid (b3) that may be used as necessary. A range of 30 to 300 ppm is particularly preferable. Since coloring of the ester compound (B) lowers the transparency of the film, it is necessary to pay particular attention to the optical film application that requires high transparency.

  When the ester compound (B) is produced, the esterification catalyst is added to the reactor with the alkylene diol (b1) and the aromatic dicarboxylic acid (b2) which is terephthalic acid or naphthalenedicarboxylic acid or a dialkyl ester thereof. It may be added at the same time as the compound is charged, may be added during the temperature increase, at the start of pressure reduction, or the esterification catalyst may be added in portions.

  Further, when the alkylene diol (b1), the aromatic dicarboxylic acid (b2) or a dialkyl ester compound thereof, and the aromatic monocarboxylic acid (b3) or the alkyl ester compound used as necessary are reacted, A trihydric or higher polyhydric alcohol such as glycerin, pentaerythritol, trimellitic acid, pyromellitic acid or carboxylic acid is used for the purpose of branching and increasing the molecular weight of the ester compound (B) within a range not inhibiting the effects of the invention. Acid; polyisocyanate such as hexamethylene diisocyanate may also be used.

  The reaction temperature at the time of producing the ester compound (B) is such that the alkylene diol (b1) as a raw material and the aromatic dicarboxylic acid (b2) which is terephthalic acid or naphthalenedicarboxylic acid or its dialkyl ester compound are evaporated or sublimated. The range of 120 ° C. to 300 ° C. is preferable, and the range of 150 ° C. to 280 ° C. is more preferable because the reaction is promoted while suppressing the thermal decomposition and coloring of the ester compound (B) produced by the reaction. . Further, the reaction time for producing the ester compound (B) is preferably 2 hours or more, and more preferably in the range of 4 to 100 hours.

  Furthermore, when manufacturing the said ester compound (B), it is preferable to carry out under reduced pressure from the middle of reaction for the objective of removing the unreacted raw material and a low molecular-weight product, or the objective of promoting reaction. The degree of vacuum when producing the ester compound (B) is preferably 3,000 Pa or less because unreacted raw materials and low molecular weight products can be removed quickly and the reaction can be promoted. 2,000 Pa or less is more preferable, and a range of 10 to 1,000 Pa is more preferable.

  As the ester compound (B), different ester compounds (B) may be produced separately and then used together. In addition, the ester compound (B) used in the present invention is mixed with the cellulose acylate (A) to obtain a cellulose ester resin composition, so long as the effects of the present invention are not impaired. You may mix | blend an additive with ester compound (B). Examples of the additive that can be added to the ester compound (B) include a catalyst deactivator for deactivating the catalytic activity of the esterification catalyst, and an antioxidant for suppressing coloring of the ester compound (B). It is done.

  Examples of the catalyst deactivator include chelating agents, and organic chelating agents or inorganic chelating agents can be used. Examples of organic chelating agents include amino acids, phenols, hydroxycarboxylic acids, diketones, amines, oximes, phenanthrolines, pyridine compounds, dithio compounds, diazo compounds, thiols, porphyrins, and nitrogen as a coordinating atom. Examples thereof include phenols having atoms and carboxylic acids. Examples of the inorganic chelating agent include phosphorus compounds such as phosphoric acid, phosphoric acid ester, phosphorous acid, and phosphorous acid ester. These chelating agents are in the range of 10 to 2,000 ppm with respect to the total amount of the alkylene diol (b1) and the aromatic dicarboxylic acid (b2) which is terephthalic acid or naphthalenedicarboxylic acid or a dialkyl ester compound thereof. It is preferable to add and use.

  The hydroxyl value of the ester compound represented by the general formula (I), which is an example of the ester compound (B) used in the present invention, can prevent deterioration of the resin composition when melted at a high temperature. Some are preferable, more preferably in the range of 40 to 320, and still more preferably in the range of 60 to 280. This hydroxyl value is derived from the terminal hydroxyl group of the ester compound (B), that is, the hydroxyl group of the alkylene diol (b1) used as a raw material.

  Moreover, the hydroxyl value of the ester compound represented by the general formula (II) which is an example of the ester compound (B) used in the present invention is in the range of 0 to 40 because an optical film excellent in moisture permeability resistance can be easily obtained. Some are preferred, those in the range of 0-30 are more preferred, and those in the range of 0-20 are even more preferred. The hydroxyl value is derived from a hydroxyl group that is not blocked by the aromatic monocarboxylic acid (b3) among the hydroxyl groups present at the terminal of the polyester that can be generated, or the alkylene diol (b1) and the aromatic monocarboxylic acid. This is derived from an ester compound having one hydroxyl group at the terminal which can be produced when the carboxylic acid (b3) reacts. Here, the ester compound (B) having a hydroxyl value in such a range includes, for example, the alkylene diol (b1), the aromatic dicarboxylic acid (b2) or its dialkyl ester compound, and the aromatic monocarboxylic acid (b3). ) Or an alkyl ester compound thereof can be easily obtained by an esterification reaction.

  The number average molecular weight of the ester compound (B) is 300 to 5,000 because the compatibility with the cellulose acylate (A) is good and the smoothness and transparency of the optical film of the present invention are good. Is preferable, the range of 350 to 3,000 is more preferable, and the range of 400 to 2,000 is more preferable.

  In addition, the number average molecular weight of the ester compound (B) in the present invention is measured using a gel permeation chromatograph (GPC) using tetrahydrofuran (THF) as an eluent, and converted into standard polystyrene. Can be obtained. The measurement conditions are as follows.

[Measurement conditions of number average molecular weight (Mn) of ester compound (B)]
Measuring device: High-speed GPC device “HLC-8320GPC” manufactured by Tosoh Corporation
Column: “TSK GARDCOLUMN SuperHZ-L” manufactured by Tosoh Corporation
+ "TSK gel SuperHZM-M" manufactured by Tosoh Corporation
+ "TSK gel SuperHZM-M" manufactured by Tosoh Corporation
+ Tosoh Corporation “TSK gel SuperHZ-2000”
+ Tosoh Corporation “TSK gel SuperHZ-2000”
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 Sample for measurement: 15 mg of sample was dissolved in 10 ml of tetrahydrofuran, and the obtained solution was filtered through a microfilter to obtain a sample for measurement.
Sample injection volume: 20 μl
Standard sample: The following monodisperse polystyrene having a known molecular weight was used according to the measurement manual of “HLC-8320GPC”.

(Monodispersed 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

  The cellulose ester resin composition used in the present invention contains 5 to 30 parts by mass of the ester compound (B) with respect to 100 parts by mass of the cellulose acylate (A). By setting the content of the ester compound in the above range, an optical film having high birefringence can be obtained. The content of the ester compound (B) is more preferably 7 to 22 parts by mass with respect to 100 parts by mass of the cellulose acylate (A).

  Moreover, various additives other than the said cellulose acylate (A) and ester compound (B) can be mix | blended with the cellulose-ester resin composition used by this invention in the range which does not impair this invention.

  Examples of the additive include additives such as a modifier (including a plasticizer), an ultraviolet absorber, a retardation increasing agent, a thermoplastic resin, a matting agent, a deterioration preventing agent, and a dye.

  Examples of the modifier (including a plasticizer) include phosphate esters such as triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate; dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and the like. Phthalic acid esters of; ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, trimethylolpropane tribenzoate, pentaerythritol tetraacetate, tributyl acetylcitrate and the like.

  Examples of the ultraviolet absorber include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. It is preferable that the compounding quantity of this ultraviolet absorber is the range of 0.01-2 mass parts with respect to 100 mass parts of said cellulose-ester resin (B).

  The retardation increasing agent is not particularly limited as long as the retardation value increases, and examples thereof include a compound having a 1,4-cyclohexanedicarboxylic acid ester compound and a 1,3,5-triazine ring. It is done. The blending amount of the retardation increasing agent is preferably in the range of 0.01 to 20 parts by mass, more preferably in the range of 1 to 10 parts by mass with respect to 100 parts by mass of the cellulose ester resin (B).

  Examples of the thermoplastic resin include polyester resins (for example, polyethylene terephthalate, polymethyl methacrylate, etc.), polycarbonate resins, polyester ether resins, polyurethane resins, epoxy resins, toluenesulfonamide resins, and the like.

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

  Examples of the deterioration inhibitor include hindered phenol antioxidants, acid scavengers, hindered amine light stabilizers, peroxide decomposers, radical inhibitors, metal deactivators, and the like. In particular, the cellulose ester resin composition used in the present invention includes a hindered phenol antioxidant, an acid scavenger, a hindered amine light stabilizer, and the like as a deterioration preventing agent for stabilization at the time of heat melting when producing a film. It is preferable to mix.

  The said dye can be used as needed, The compounding quantity should just be a range which does not impair the effect of this invention.

  As a method for producing the cellulose ester resin composition used in the present invention, the cellulose acylate (A) and the ester compound (B) are melt kneaded with an internal mixer, a roll kneader, a single screw or twin screw extruder, or the like. Is mentioned. In this case, the melt kneading temperature is preferably in the range of 120 to 300 ° C, more preferably in the range of 150 to 260 ° C. In order to prevent deterioration of the raw material, the melt kneading time is preferably within 5 minutes. Further, when the resin composition is produced, since the smoothness and transparency of the optical film of the present invention are improved, volatile components such as moisture and organic solvent contained in each component are previously dried and removed. It is preferable to keep it.

  The optical film of the present invention is an optical film obtained by heating and stretching the cellulose ester resin composition, and the stretching ratio at this time is 1.7 to 4 times. Thus, an optical film having high birefringence can be obtained by heating and stretching at a high magnification. Among the draw ratios, a high birefringence film can be obtained without fear of breaking, and the range of 1.7 to 3.5 times is preferable, and the range of 1.8 to 3 times is more preferable.

  The optical film of the present invention can be obtained, for example, by forming the cellulose ester resin composition into a film and stretching it by heating.

  Examples of the method for forming the cellulose ester resin composition into a film include a method of forming a film by a compression molding method, a method of melt-kneading with an extruder or the like, and forming into a film using a T die or the like. Can be mentioned. When a film is produced by these molding methods, the molding temperature is preferably in the range of 120 to 300 ° C, more preferably in the range of 150 to 260 ° C.

  Moreover, the said cellulose-ester resin composition can be melt | dissolved in the organic solvent in which each component melt | dissolves, and a film can also be manufactured with a solution casting method.

  As a method for producing a film by the solution casting method, for example, a cellulose ester resin composition is dissolved in an organic solvent, and the obtained resin solution is cast on a support such as a glass plate or a metal. There is a method in which about 50 to 80% by mass of the organic solvent contained in the cast resin solution is evaporated and then peeled and further dried to completely remove the organic solvent and obtain a film.

  The film obtained by the above production method can be further heated and stretched to obtain the optical film of the present invention. The temperature during the heat stretching is preferably in the temperature range of −18 ° C. to + 25 ° C. of the glass transition temperature of the cellulose ester resin composition used as a raw material of the optical film because an optical film having high birefringence can be obtained without fear of breaking. A temperature range of −15 ° C. to + 10 ° C. of the glass transition temperature is more preferable.

  Here, the glass transition temperature (hereinafter abbreviated as “Tg”) of the cellulose ester resin composition (C) in the present invention is determined by the dynamic viscoelasticity measurement at 10 Hz and the dynamic storage elastic modulus (E ′). This is the peak top temperature of tan δ obtained from the respective ratios obtained by measuring the dynamic loss modulus (E ″). The dynamic viscoelasticity measurement can be performed, for example, with a forced vibration type dynamic viscoelasticity measuring apparatus (“Rheogel-E4000” manufactured by UBM Co., Ltd.).

  In addition, as a stretching method, uniaxial stretching that stretches in either the MD direction or TD direction of the film according to the characteristics of the retardation to be imparted to the optical film; biaxial stretching that stretches in both the MD and TD directions. Either can be selected. When biaxial stretching is performed, any of sequential biaxial stretching and simultaneous biaxial stretching can be used.

  The film thickness of the optical film of the present invention is preferably in the range of 20 to 300 μm, and more preferably in the range of 20 to 90 μm from the viewpoint of thinning. Among the optical films, when the present invention is used as a quarter-wave plate for a circularly polarizing plate, if the film thickness is 20 μm, the strength as a polarizing plate can be maintained. As a result, a sufficient phase difference can be obtained.

  The optical film of the present invention can be applied to a melt film-forming method and has excellent birefringence, so that it can be used, for example, as an optical film for a display device of a flat panel display. Here, as an optical film, the retardation film (especially wavelength plate) essential for a circularly-polarizing plate, the polarizer protective film with viewing angle compensation, etc. are mentioned. Since the optical film of the present invention is a cellulose ester resin, a conventional polarizer bonding process can be applied in the polarizing plate production process, and high birefringence can be easily imparted to the film, which is very advantageous industrially. .

  The present invention will be specifically described below with reference to examples and comparative examples. In addition, the acid value of the ester compound synthesize | combined in the following synthesis examples 1-5, a hydroxyl value, and a number average molecular weight are measured on condition of the following.

[Measurement conditions for acid value and hydroxyl value]
The acid value and hydroxyl value of each ester compound were measured according to JIS K 0070-1992.

[Measurement conditions for number average molecular weight (Mn)]
Measuring device: High-speed GPC device “HLC-8320GPC” manufactured by Tosoh Corporation
Column: “TSK GARDCOLUMN SuperHZ-L” manufactured by Tosoh Corporation
+ "TSK gel SuperHZM-M" manufactured by Tosoh Corporation
+ "TSK gel SuperHZM-M" manufactured by Tosoh Corporation
+ Tosoh Corporation “TSK gel SuperHZ-2000”
+ Tosoh Corporation “TSK gel SuperHZ-2000”
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 Sample for measurement: 15 mg of sample was dissolved in 10 ml of tetrahydrofuran, and the obtained solution was filtered through a microfilter to obtain a sample for measurement.
Sample injection volume: 20 μl
Standard sample: The following monodisperse polystyrene having a known molecular weight was used according to the measurement manual of “HLC-8320GPC”.

(Monodispersed 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

Synthesis Example 1 [Preparation of ester compound (B)]
In a four-necked flask with an internal volume of 3 liters equipped with a thermometer, a stirrer and a reflux condenser, 776.7 g of dimethyl terephthalate, 1081.4 g of 2-methyl-1,3-propanediol and tetraisopropyl as an esterification catalyst The titanate 0.11g was prepared, it heated up in steps until it became 210 degreeC, stirring under nitrogen stream, and it was made to react for a total of 10 hours. After the reaction, the unreacted 2-methyl-1,3-propanediol is removed under reduced pressure at 160 ° C. to obtain an ester compound (B1) (acid value: 0.17, hydroxyl value: 273, number average) that is a room temperature liquid. Molecular weight: 500) was obtained.

Synthesis example 2 (same as above)
In a four-necked flask with an internal volume of 2 liters equipped with a thermometer, a stirrer, and a reflux condenser, 388.4 g of dimethyl terephthalate, 709.1 g of 1,6-hexanediol, and 0.07 g of tetraisopropyl titanate as an esterification catalyst. Was stirred in a nitrogen stream, the temperature was raised stepwise until reaching 200 ° C., and the reaction was carried out for a total of 17 hours. After the reaction, unreacted 1,6-hexanediol is removed under reduced pressure at 180 ° C., whereby the ester compound (B2) which is a solid at normal temperature (acid value: 0.24, hydroxyl value: 187, number average molecular weight: 720) Got.

Synthesis example 3 (same as above)
In a four-necked flask with an internal volume of 3 liters equipped with a thermometer, a stirrer and a reflux condenser, 776.7 g of dimethyl terephthalate, 1418.2 g of 3-methyl-1,5-pentanediol and tetraisopropyl as an esterification catalyst The titanate 0.132g was prepared, it heated up in steps until it became 230 degreeC, stirring under nitrogen stream, and it was made to react for a total of 16 hours. After the reaction, the unreacted 3-methyl-1,5-pentanediol is removed under reduced pressure at 170 ° C. to obtain an ester compound (B3) (acid value: 0.30, hydroxyl value: 205, number average) which is a solid at room temperature. Molecular weight: 650) was obtained.

Synthesis example 4 (same as above)
In a four-necked flask with an internal volume of 3 liters equipped with a thermometer, stirrer and reflux condenser, 659.4 g of dimethyl 2,6-naphthalenedicarboxylate, 58.3 g of dimethyl terephthalate, 684.8 g of propylene glycol and esterification As a catalyst, 0.084 g of zinc acetate dihydrate was charged, and the temperature was raised stepwise to 210 ° C. while stirring under a nitrogen stream, and the reaction was conducted for a total of 13 hours. After the reaction, unreacted propylene glycol was removed under reduced pressure at 160 ° C. to obtain an ester compound (B4) (acid value: 0.08, hydroxyl value: 213, number average molecular weight: 590) which is a solid at normal temperature.

Synthesis example 5 (same as above)
In a three-liter flask with an internal volume of 3 liters equipped with a thermometer, stirrer and reflux condenser, 1,553.4 g of dimethyl terephthalate, 1,241.4 g of ethylene glycol and zinc acetate dihydrate as an esterification catalyst 0.168 g of the product was charged, and the temperature was raised stepwise to 210 ° C. while stirring under a nitrogen stream, and the reaction was performed for a total of 18 hours. After the reaction, unreacted ethylene glycol was removed under reduced pressure at 160 ° C. to obtain an ester compound (B5) (acid value: 0.12, hydroxyl value: 195, number average molecular weight: 580) which is a solid at room temperature.

Synthesis example 6 (same as above)
In a four-necked flask with an internal volume of 2 liters equipped with a thermometer, a stirrer and a reflux condenser, 349.5 g of dimethyl terephthalate, 377.0 g of 2-methyl-1,3-propanediol, 488.5 g of benzoic acid and 0.073 g of tetraisopropyl titanate was charged as an esterification catalyst, and the temperature was raised stepwise to 230 ° C. while stirring under a nitrogen stream, and the reaction was conducted for a total of 13 hours. After the reaction, unreacted 2-methyl-1,3-propanediol is removed under reduced pressure at 200 ° C., whereby the ester compound (B6) (acid value: 0.07, hydroxyl value: 13.3, Number average molecular weight: 490) was obtained.

Synthesis example 7 (same as above)
A three-liter four-necked flask equipped with a thermometer, stirrer and reflux condenser was charged with 349.5 g of dimethyl terephthalate, 494 g of 1,6-hexanediol, 488.5 g of benzoic acid and tetraisopropyl as an esterification catalyst. 0.08 g of titanate was charged, the temperature was raised stepwise to 230 ° C. while stirring under a nitrogen stream, and the reaction was allowed to proceed for a total of 15 hours. After the reaction, unreacted 1,6-hexanediol is removed under reduced pressure at 230 ° C., whereby the ester compound (B7) (acid value: 0.12, hydroxyl value: 15.6, number average molecular weight: solid at room temperature) 550).

Synthesis example 8 (same as above)
A four-necked flask with an internal volume of 3 liters equipped with a thermometer, a stirrer and a reflux condenser was charged with 524.4 g of dimethyl terephthalate, 741.1 g of 3-methyl-1,5-pentanediol, 816.9 g of p-toluic acid and Tetraisopropyl titanate (0.125 g) was charged as an esterification catalyst, and the temperature was raised stepwise to 230 ° C. while stirring under a nitrogen stream, and the reaction was performed for a total of 16 hours. After the reaction, the unreacted 3-methyl-1,5-pentanediol is removed under reduced pressure at 200 ° C. to give an ester compound (B8) (acid value: 0.12, hydroxyl value: 15.3, liquid at room temperature). Number average molecular weight: 490) was obtained.

Synthesis example 9 (same as above)
In a four-necked flask having an internal volume of 3 liters equipped with a thermometer, a stirrer and a reflux condenser, 439.6 g of dimethyl 2,6-naphthalenedicarboxylate, 329.7 g of propylene glycol, 488.4 g of benzoic acid and an esterification catalyst As a starting material, 0.075 g of tetraisopropyl titanate was charged, and the temperature was raised stepwise to 230 ° C. while stirring under a nitrogen stream, and the reaction was allowed to proceed for a total of 15 hours. After the reaction, unreacted propylene glycol is removed under reduced pressure at 200 ° C. to obtain an ester compound (B9) (acid value: 0.16, hydroxyl value: 15.9, number average molecular weight: 470) which is a solid at room temperature. It was.

Synthesis Example 10 [Preparation of ester compound for comparison (B ′)]
Into a 2 liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, 485.5 g of dimethyl terephthalate, 1201.9 g of 1,9-nonanediol and 0.10 g of tetraisopropyl titanate as an esterification catalyst The mixture was heated stepwise until it reached 210 ° C. while stirring under a nitrogen stream, and reacted for a total of 8 hours. After the reaction, a thin-film distillation treatment was performed at 200 ° C., and unreacted 1,9-nonanediol was removed under reduced pressure, whereby a comparative ester compound (B′1) (acid value: 0.10, solid at room temperature) was obtained. Hydroxyl value: 167, number average molecular weight: 790).

Synthesis example 11 (same as above)
In a four-necked flask with an internal volume of 2 liters equipped with a thermometer, a stirrer, and a reflux condenser, 244.7 g of dimethyl terephthalate, 468.9 g of 1,9-nonanediol, 341.9 g of benzoic acid and an esterification catalyst 0.063 g of tetraisopropyl titanate was charged, the temperature was raised stepwise to 230 ° C. while stirring under a nitrogen stream, and the reaction was allowed to proceed for a total of 15 hours. After the reaction, unreacted 1,9-nonanediol was removed under reduced pressure at 230 ° C., whereby a comparative ester compound (B′2) (acid value: 0.23, hydroxyl value: 19.4, which is a solid at room temperature). , Number average molecular weight: 650).

Synthesis example 12 (same as above)
In a three-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, 415.4 g of isophthalic acid, 433.7 g of propylene glycol, 610.6 g of benzoic acid, and tetraisopropyl titanate as an esterification catalyst were added. 088 g was charged and the temperature was raised stepwise to 230 ° C. while stirring under a nitrogen stream, and the reaction was carried out for a total of 14 hours. After the reaction, unreacted propylene glycol is removed under reduced pressure at 200 ° C., whereby a comparative ester compound (B′3) (acid value: 0.30, hydroxyl value: 12.0, number, which is a room temperature high viscosity liquid) Average molecular weight: 470) was obtained.

Synthesis example 13 (same as above)
Into a 2-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser is charged 370 g of phthalic anhydride, 433.2 g of propylene glycol, 610 g of benzoic acid and 0.170 g of tetraisopropyl titanate as an esterification catalyst. While stirring under a nitrogen stream, the temperature was raised stepwise until reaching 230 ° C., and the reaction was carried out for a total of 17 hours. After the reaction, unreacted propylene glycol is removed under reduced pressure at 200 ° C. to obtain an ester compound (B′4) (acid value: 0.19, hydroxyl value: 10, number average molecular weight: 480) which is a room temperature liquid. It was.

Synthesis example 14 (same as above)
A three-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser was charged with 600 g of succinic acid, 560 g of propylene glycol and 0.07 g of tetra-n-butyl titanate as an esterification catalyst under a nitrogen stream. The temperature was raised stepwise until the temperature reached 220 ° C. with stirring for a total of 9 hours. After the reaction, the unreacted propylene glycol is removed under reduced pressure at 220 ° C. to obtain an ester compound (B′5) that is a room temperature liquid (acid value: 0.24, hydroxyl value: 129, number average molecular weight: 1,100). Got.

  Raw material components, acid value, hydroxyl value and number average molecular weight of the ester compounds (B1) to (B9) obtained in the synthesis examples 1 to 14 and the ester compounds for comparison (B′1) to (B′5). Are summarized in Tables 1 to 3. In addition, the symbol in Table 1 is as follows.

PG: propylene glycol 2MPD: 2-methyl-1,3-propanediol 3MPD: 3-methyl-1,5-pentanediol 1,6HD: 1,6-hexanediol 1,9ND: 1,9-nonanediol DMT: Dimethyl terephthalate NDCM: Dimethyl 2,6-naphthalenedicarboxylate iPA: Isophthalic acid BzA: Benzoic acid PTA: Paratoluic acid PA: Phthalic anhydride SuA: Succinic acid

Preparation Example 1 (Preparation of cellulose ester resin composition)
Cellulose acetate propionate (“CAP-482-20” manufactured by Eastman Chemical Co., Ltd .; acetyl group substitution degree 0.2, propionyl group substitution degree 2.5, hydroxyl group substitution degree 0.3, number average molecular weight 75, 000; hereinafter abbreviated as “CAP”.) 100 parts by mass and 10 parts by mass of the ester compound (B1) obtained in Synthesis Example 1 were used at 200 ° C. using a lab plast mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.). And mixing at 30 rpm for 5 minutes to obtain a resin composition (C1).

Preparation Examples 2 to 13 (same as above)
Cellulose ester resin compositions (C2) to (C13) were obtained in the same manner as in Preparation Example 1 except for the formulations shown in Tables 4 and 5.

Footnotes in Tables 4 and 5 CAP: cellulose acetate propionate ("CAP-482-20" manufactured by Eastman Chemical Co., Ltd.); substitution degree of acetyl group: 0.2, substitution degree of propionyl group: 2.5, hydroxyl group Degree of substitution 0.3, number average molecular weight 75,000.)
CAB: cellulose acetate butyrate (“CAB-381-20” manufactured by Eastman Chemical Co., Ltd .; substitution degree of acetyl group 1.0, substitution degree of butyryl group 1.7, substitution degree of hydroxyl group 0.3, number average molecular weight 70 , 000.)

Comparative Preparation Examples 1-3
Comparative control cellulose ester resin compositions (C′1) to (C′7) were obtained in the same manner as in Preparation Example 1 except for the formulation shown in Table 6.

Footnotes in Table 6 TCP: tricresyl phosphate

  Tg of the cellulose ester resin composition obtained above was measured by dynamic viscoelasticity measurement at 10 Hz to measure dynamic storage elastic modulus (E ′) and dynamic loss elastic modulus (E ″). The peak top temperature of tan δ obtained from In addition, the dynamic viscoelasticity measurement was performed using a forced vibration type dynamic viscoelasticity measuring apparatus (“Rheogel-E4000” manufactured by UBM Co., Ltd.).

Example 1
The cellulose ester resin composition (C1) obtained in Preparation Example 1 was molded with a compression molding machine heated to 200 ° C. and cooled at 25 ° C. to obtain a film having a thickness of about 200 μm. Next, this film is uniaxially stretched by a heating uniaxial stretching machine at a stretching temperature of 138 ° C. (Tg + 2 ° C.) so as to be twice the initial length (stretching ratio is 2 times), and the optical film (1) of the present invention is obtained. Obtained.

(Evaluation of birefringence of optical film)
In order to evaluate the birefringence of the optical film obtained above, the retardation value at 588 nm was measured with a retardation measuring device KOBRA-WR (manufactured by Oji Scientific Instruments). Birefringence of the optical film was obtained by dividing the obtained retardation value by the thickness of the stretched film.

(Calculation of 1 / 4λ retardation film thickness)
Using the birefringence value obtained above, the thickness in the case of a 1 / 4λ retardation film was calculated by the following formula (1). The phase difference value required for 1 / 4λ is 588/4 = 147 nm.

    The evaluation results are shown in Table 7.

Examples 2-43
Optical films (2) to (43) were obtained in the same manner as in Example 1 except that the film was stretched at the stretching temperatures shown in Tables 7 to 17. Evaluation similar to Example 1 was performed, and the results are shown in Tables 7-17.

Comparative Examples 1-16
Comparative optical films (1 ′) to (16 ′) were obtained in the same manner as in Example 1 except that the film was stretched at the stretching temperatures shown in Tables 18 to 21. The same evaluation as in Example 1 was performed, and the results are shown in Tables 18-21.

The results shown in Table 7 are examples using the cellulose ester resin composition (C1), but the Tg of the cellulose ester resin compositions (C1) of Examples 1 to 4 is a temperature of -15 ° C to + 2 ° C. The birefringence of the film stretched by heating in the range shows a high birefringence of 18.8 × 10 ^{−4 to} 24.6 × 10 ^−4, and it is found that a thinner film can be formed when a retardation film is used. It was.

Although the result shown in Table 8 is an example using a cellulose ester resin composition (C2), the temperature of −13 ° C. to + 8 ° C. of Tg of the cellulose ester resin composition (C2) of Examples 5 to 8 The birefringence of the film stretched by heating in the range shows a high birefringence of 18.8 × 10 ^{−4 to} 25.9 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

The results shown in Table 9 are examples in which the cellulose ester resin composition (C3) was used, but the Tg of the cellulose ester resin compositions (C3) of Examples 9 to 12 was from −14 ° C. to + 1 ° C. The birefringence of the film stretched by heating in the range shows a high birefringence of 17.0 × 10 ^{−4 to} 25.3 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

Although the result shown in Table 10 is an example using a cellulose ester resin composition (C4), the temperature of −9 ° C. to + 10 ° C. of Tg of the cellulose ester resin compositions (C4) of Examples 13 to 16 The birefringence of the film stretched by heating in the range shows a high birefringence of 27.7 × 10 ^{−4 to} 34.1 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

Although the result shown in Table 11 is an example using a cellulose ester resin composition (C5), the temperature of −15 ° C. to + 7 ° C. of Tg of the cellulose ester resin compositions (C5) of Examples 17 to 20 The birefringence of the film stretched by heating in the range shows a high birefringence of 24.3 × 10 ^{−4 to} 29.7 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

The results shown in Table 12 are examples using the cellulose ester resin compositions (C6), (C7) and (C8), but the cellulose ester resin compositions (C6) and (C7 of Examples 21 to 23). ) And (C8) Tg of the film stretched by heating in the temperature range of −3 ° C. to + 3 ° C. shows high birefringence of 14.8 × 10 ^{−4 to} 44.7 × 10 ⁻⁴ , It has been found that a thinner film can be formed when the phase difference film is used.

The results shown in Table 13 are examples in which the cellulose ester resin composition (C9) was used, but the Tg of the cellulose ester resin compositions (C9) of Examples 24-27 was a temperature of −13 ° C. to + 8 ° C. The birefringence of the film stretched by heating in the range shows a high birefringence of 14.3 × 10 ^{−4 to} 20.0 × 10 ^−4, and it is found that a thinner film can be formed when a retardation film is used. It was.

The result shown in Table 14 is an example using the cellulose ester resin composition (C10), but the Tg of the cellulose ester resin composition (C10) of Examples 28 to 31 is a temperature of -11 ° C to + 20 ° C. The birefringence of the film stretched by heating in the range shows a high birefringence of 15.8 × 10 ^{−4 to} 20.7 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

The results shown in Table 15 are examples using the cellulose ester resin composition (C11), but the Tg of the cellulose ester resin compositions (C11) of Examples 32 to 35 is a temperature of −16 ° C. to + 5 ° C. The birefringence of the film stretched by heating in the range shows a high birefringence of 15.9 × 10 ^{−4 to} 21.1 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

The results shown in Table 16 are examples using the cellulose ester resin composition (C12), but the Tg of the cellulose ester resin compositions (C9) of Examples 36 to 39 is a temperature of -14 ° C to + 4 ° C. The birefringence of the film stretched by heating in the range shows a high birefringence of 24.0 × 10 ^{−4 to} 30.2 × 10 ^−4, and it is understood that a thinner film can be formed when a retardation film is used. It was.

The results shown in Table 17 are examples using the cellulose ester resin composition (C13), but the temperatures of -13 ° C. to + 9 ° C. of Tg of the cellulose ester resin compositions (C13) of Examples 40 to 43. The birefringence of the film stretched by heating in the range shows a high birefringence of 19.8 × 10 ^{−4 to} 25.2 × 10 ^−4, and it is found that a thinner film can be formed when a retardation film is used. It was.

The results shown in Table 18 are examples using a cellulose ester resin composition (C′1) containing an ester compound (B′1) using a C9 alkylene diol as a raw material, but a comparative example. The birefringence of the film produced by heating and stretching at a temperature higher or lower than Tg of the cellulose ester resin composition (C′1) of 1 to ⁴ is 7.8 × 10 ^{−4 to} 11.7 × 10 ⁻⁴ . It was found that the birefringence of the optical film of the present invention using the cellulose ester resin compositions (C1) to (C13) was lower.

The results shown in Table 19 are examples using a cellulose ester resin composition (C′2) containing an ester compound (B′2) using a C9 alkylene diol as a raw material, but a comparative example. The birefringence of the film produced by heating and stretching at a temperature higher or lower than the Tg of the cellulose ester resin composition (C′2) of 5 to 8 is 5.8 × 10 ^{−4 to} 9.1 × 10 ⁻⁴ . It was found that the birefringence of the optical film of the present invention using the cellulose ester resin compositions (C1) to (C13) was lower.

The results shown in Table 20 show that the ester compound (B'3) using isophthalic acid as a raw material, the ester compound (B'4) using phthalic anhydride as a raw material, and the ester compound (B'5 using succinic acid as a raw material) ) Containing cellulose ester resin compositions (C′3), (C′4) and (C′5), but cellulose ester resin compositions (C′3) of Comparative Examples 9 to 11 The birefringence of the film produced by heating and stretching at a temperature higher or lower than the Tg of (C′4) and (C′5) is 4.3 × 10 ^{−4 to} 9.9 × 10 ⁻⁴ , cellulose. It was found to be lower than the birefringence of the optical film of the present invention using the ester resin compositions (C1) to (C13). Further, the birefringence of the film prepared in Comparative Example 12 using the cellulose ester resin composition (C′7) to which no modifier was added was 7.7 × 10 ⁻⁴ and the cellulose ester resin composition (C1). It was found to be lower than the birefringence of the optical film of the present invention using ~ (C13).

The results shown in Table 21 are examples in which the cellulose ester resin composition (C′6) containing TCP was used instead of the ester compound (B) used in the present invention, but the cellulose esters of Comparative Examples 13 to 16 The birefringence of the film produced by heating and stretching at a temperature higher or lower than the Tg of the resin composition (C′6) is 11.4 × 10 ^{−4 to} 13.7 × 10 ^−4, and the cellulose ester resin composition It was found that the birefringence of the optical film of the present invention using (C1) to (C13) was lower.

Example 44 and Comparative Example 17
An optical film (44) and a comparative optical film (16 ') were obtained in the same manner as in Example 1 except that the stretching temperature and the stretching ratio shown in Table 21 were used. The same evaluation as in Example 1 was performed, and the results are shown in Table 21. From this result, it can be seen that the birefringence increases due to the difference in the draw ratio.

Claims (9)

  The degree of substitution of the acetyl group is in the range of 0.1 to 2.2, the degree of substitution of the propionyl group or the degree of substitution of the butyryl group is in the range of 0.5 to 2.7, and the degree of substitution of the hydroxyl group is 0.1 to 1. In the range, the cellulose acylate (A) having a total degree of substitution of 3, a linear or branched alkylene diol (b1) having 2 to 8 carbon atoms, and terephthalic acid or naphthalenedicarboxylic acid An optical film obtained by heating and stretching a cellulose ester resin composition containing an ester compound (B) obtained by esterifying a selected aromatic dicarboxylic acid (b2) or a dialkyl ester compound thereof, The content of the ester compound (B) in the cellulose ester resin composition is 7 to 30 parts by mass with respect to 100 parts by mass of the cellulose acylate (A). Optical film rate is characterized in that it is a 1.7 to 4-fold.   The optical film according to claim 1, wherein a draw ratio in the heat drawing is 1.7 to 3.5 times.   The optical film according to claim 1, wherein the content of the ester compound (B) is 7 to 22 parts by mass with respect to 100 parts by mass of the cellulose acylate (A).   2. The optical film according to claim 1, wherein the heat stretching is performed in a temperature range of −18 ° C. to + 25 ° C. of the glass transition temperature of the cellulose ester resin composition.   The optical film according to claim 1, wherein the naphthalenedicarboxylic acid is 2,6-naphthalenedicarboxylic acid.   The ester compound (B) is an aromatic dicarboxylic acid (b2) selected from linear or branched alkylene diol (b1) having 2 to 8 carbon atoms and terephthalic acid or naphthalenedicarboxylic acid, or a dialkyl ester compound thereof. The optical film according to claim 1, wherein the optical film is obtained by an esterification reaction between an aromatic monocarboxylic acid (b3) or an alkyl ester compound thereof.   The optical film according to claim 6, wherein the aromatic monocarboxylic acid (b3) is benzoic acid or a derivative thereof.   A retardation film comprising the optical film according to claim 1.   A wave plate comprising the optical film according to claim 1.