JP5440082B2 - Additive for cellulose ester resin, cellulose ester resin composition and film using the same - Google Patents

Description

  The present invention relates to an additive for a cellulose ester resin comprising an ester compound capable of imparting excellent optical performance to an optical film such as a polarizer protective film when added to a cellulose ester resin, and a cellulose ester resin composition using the same And an optical film.

  In recent years, information devices such as notebook computers and televisions equipped with a liquid crystal display device capable of clearly displaying images and characters have been supplied to the market one after another. Consumers' demand for these information devices includes not only high functionality, but also a reduction in space and the diversification of the living environment. High contrast is required.

  The thinning of the information device is realized by reducing the depth (width) of the liquid crystal display device provided in the information device. The liquid crystal display device is generally composed of a laminated structure having a layer made of an electrode and a layer made of a liquid crystal substance between two glass substrates. The glass substrate has a polarizer attached to the surface opposite to the liquid crystal layer, and as this polarizer, a polarizer made of polyvinyl alcohol (PVA) with protective films attached to both sides is usually used. Has been. The polarizer protective film is generally a cellulose ester resin film having high transparency, moderate strength, and excellent adhesion to PVA.

  However, the cellulose ester resin film cannot sufficiently prevent moisture (moisture) from entering, and as a result, there is a problem in that the polarizer is deteriorated or peeling occurs between the polarizer and the film. . Therefore, as a polarizer protective film, conventionally, a film obtained by adding a plasticizer such as triphenyl phosphate to a cellulose ester resin has been used as a film having good moisture resistance.

  Further, as the polarizer protective film, a film having a film thickness of about 80 μm is usually used although it varies depending on the structure of the liquid crystal display device. In recent years, with the progress of thinning of liquid crystal display devices, the protective film has been further thinned, and as a guide, a film having a thickness of about 30 to 50 μm has been studied.

  In the course of studying such thinning, the conventional polarizer protective film containing the plasticizer and the cellulose ester resin has a remarkable moisture resistance when the film thickness is reduced to a required level. It had the problem of being lowered.

  In addition, since the plasticizer is not sufficiently compatible with the cellulose ester resin, the plasticizer may bleed from the film surface due to the influence of heat and humidity. Therefore, when used in a liquid crystal display device, the plasticizer bleeds on the surface of the film due to the influence of the heat of the backlight, etc., causing a problem that the image cannot be clearly displayed due to cloudiness.

  Further, the polarizer protective film is required to have excellent surface smoothness at a level that does not hinder the display of a clear image or the like. Therefore, the polarizer protective film is produced by a so-called solution casting method in which an organic solvent solution of the cellulose ester resin composition containing the plasticizer is cast into a film and then dried by heating in order to obtain surface smoothness. Is done. However, since the plasticizer is a low molecular weight compound, it tends to volatilize in the heating and drying step, and the volatilized plasticizer adheres to a web or a roll constituting the film manufacturing apparatus, thereby contaminating the apparatus. .

  The bleed and easiness of volatilization of the plasticizer has been conventionally regarded as a problem in applications where the cellulose ester resin is other than the polarizer protective film, such as toys and food utensils. As plasticizers for solving this problem, plasticizers mainly composed of sugar alcohol acetylated compounds and phthalic polyesters have been proposed (see, for example, Patent Documents 1 and 2).

  However, a resin containing, as a plasticizer, an acetylated product of the above sugar alcohol or a phthalic polyester obtained by reacting phthalic anhydride specifically described as a phthalic polyester and 1,3-butanediol. The film obtained by molding the composition does not have a level of moisture resistance that can be used as a polarizer protective film, and these plasticizers still tend to bleed under high temperature and high humidity. Had.

  In addition, it has been reported that a film containing an ester compound obtained by reacting 2-ethyl-2-butyl-1,3-propanediol and benzoic acid and a cellulose resin has excellent moisture resistance (for example, , See Patent Document 3).

  However, the film containing the ester compound and the cellulose resin is generally used at a thickness of about 80 μm, but when the film is thinned to about 40 to 50 μm, sufficient moisture resistance cannot be maintained. Therefore, it has not reached the practical level. In addition, since this ester compound is a relatively low molecular weight compound, it easily volatilizes in the heat drying step in the production of the film, and there is a problem of contaminating the rolls constituting the film production apparatus.

  By the way, in addition to the above-described thinning, information devices including a liquid crystal display device are required to have various characteristics depending on applications. In particular, liquid crystal televisions are strongly required to have a wide viewing angle with an increase in screen size.

  The wide viewing angle of liquid crystal display devices has been studied for some time. For example, a polarizer protective film made of a cellulose ester resin is provided with an optical compensation function that can contribute to a wide viewing angle. A method of adding an aromatic compound as an elevating agent has been proposed (see, for example, Patent Document 4).

  Here, the optical compensation film compensates for the phase difference caused by the liquid crystal material constituting the liquid crystal display device, and plays an important role in realizing “wide viewing angle”. If the phase difference is not compensated, there is a problem that the color and shape of an image displayed when the liquid crystal screen is viewed from an oblique direction looks different from the original one.

  Therefore, as the optical compensation film, a film having optical anisotropy is used in order to develop a wide viewing angle. Here, the optical performance referred to in the present invention refers to optical anisotropy, and generally the degree of optical anisotropy can be grasped by the retardation value. Among the retardation values of the optical compensation film, the retardation value in the thickness direction of the film (hereinafter referred to as “Rth value”) is generally adjusted to a desired anisotropy by adding a so-called retardation increasing agent. It is possible to adjust. However, the general retardation increasing agent as described in Patent Document 4 has insufficient compatibility with the cellulose ester resin, and therefore causes bleeding when the optical compensation film is left under high temperature and high humidity. There was a problem that transparency was impaired.

  The Rth value in the thickness direction is a value defined by the following formula (1).

Rth = {(nx + ny) / 2−nz} × d (nm) (1)
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, d Is the film thickness (nm).)

  Therefore, the present inventors have, as an additive that imparts excellent optical performance to the polarizer protective film, a diester compound having an aromatic group at both ends, and an aromatic cyclic structure at both ends and in the molecular chain. The ester compound which consists of a mixture with a polyester compound was proposed (refer patent document 5).

  However, the optical compensation film has been required to have a further excellent optical performance, that is, a high Rth value due to technological advancement. If an optical compensation film made of a cellulose ester resin having an excellent retardation compensation function can be obtained, the number of films that are usually required to be four can be further reduced, and the above-described film can be made thinner. Thus, an inexpensive and high-quality polarizing plate, and thus a liquid crystal display device can be provided, but such a material has not yet existed.

JP 2000-318771 A JP 61-276836 A JP 2003-096236 A JP 2000-284124 A JP 2008-069225 A

  The problem to be solved by the present invention is that it can impart excellent optical performance and moisture permeation resistance to a film made of cellulose ester resin, is excellent in bleed resistance under high temperature and high humidity, and volatilizes in the manufacturing process. It is providing the additive for cellulose ester resins which consists of a hard ester compound, and a cellulose-ester resin composition using the same.

  Moreover, this invention provides the film or optical film which consists of said cellulose-ester resin composition.

  As a result of diligent research, the present inventors have determined that an ester compound having a molecular weight in a specific range is used as an additive for a cellulose ester resin among ester compounds obtained by esterifying a diol and a specific aromatic dicarboxylic acid compound. When used, the cellulose ester resin can impart excellent optical performance and moisture permeability resistance to an optical film made of a cellulose ester resin, has excellent bleed resistance under high temperature and high humidity, and is less likely to volatilize in the film production process. It was found that an additive for use was obtained, and the invention was completed.

That is, the present invention provides at least one fragrance selected from the group consisting of diol (a1), terephthalic acid, terephthalic acid dialkyl ester, naphthalene dicarboxylic acid, naphthalene dicarboxylic acid dialkyl ester, biphenyl dicarboxylic acid and biphenyl dicarboxylic acid dialkyl ester. It is obtained by esterifying a group dicarboxylic acid compound (a2) and has a number average molecular weight in the range of 300 to 730. As the diol (a1), ethylene glycol (a1-1) and 1,2-propanediol (a1) -2) , the molar composition ratio (a-1) / (a-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) is 85/15 to 10/90. cellulose S., characterized in that an ester compound obtained in combination with a range (a) comprising The present invention provides an additive for tellur resin, a cellulose ester resin composition containing the additive, and a film and an optical film comprising the resin composition.

  The additive for cellulose ester resin of the present invention can impart excellent optical performance and moisture permeability resistance to the film by being added to the cellulose ester resin. Moreover, the additive for cellulose ester resins of the present invention has an excellent effect that it has bleed resistance under high temperature and high humidity and is less likely to volatilize in the film production process. Furthermore, the film comprising the cellulose ester resin composition containing the additive for cellulose ester resin of the present invention can be used for various optical films, and in particular for a polarizer protective film that requires an optical compensation function. Very useful.

  The ester compound (A) that is the additive for cellulose ester resin of the present invention will be described.

  The ester compound (A) of the present invention is characterized in that the terminal is a hydroxyl group or an alkyl ester group, and examples thereof include ester compounds having structures represented by the following general formulas (I) to (VI).

（上記一般式（Ｉ）中のＧはジオール（ａ１）の残基を表し、Ｔは芳香族ジカルボン酸化合物（ａ２）の残基を表し、Ｒはアルキル基を表す。また、ｎは繰り返し単位を表し、１以上の整数である。）

(G in the general formula (I) represents a residue of the diol (a1), T represents a residue of the aromatic dicarboxylic acid compound (a2), R represents an alkyl group, and n represents a repeating unit. Represents an integer of 1 or more.)

  The above “residue” means the following. The “residue” of the diol (a1) represents the remaining organic group excluding the two hydroxyl groups of the diol (a1). The “residue” of the aromatic dicarboxylic acid compound (a2) is the remaining organic group excluding the carboxyl group of the aromatic carboxylic acid when the aromatic dicarboxylic acid compound (a2) is an aromatic carboxylic acid. When the aromatic dicarboxylic acid compound (a2) is an aromatic carboxylic acid alkyl ester, it represents the remaining organic group excluding the alkoxycarbonyl group of the aromatic carboxylic acid alkyl ester.

More specifically, n in the general formulas (I) to (VI) may be an integer of 1 or more, but is preferably an integer in the range of 1 to 15. The ester compound (A) is usually a mixture of a plurality of ester compounds having different n numbers. For example, the ester compound (A1) in which n in the general formulas (I) to (VI) is 1 is in the range of 25 to 40% by mass with respect to the entire ester compound (A), in the general formulas (I) to (I). VI) The ester compound (A2) in which n is 2 is in the range of 20 to 40% by mass, and the ester compound (A3) in which n in the general formulas (I) to (VI) is 3 or more is 35 to 45% by mass. % Of the ester compound (A) contained in the range of cellulose ester resin can impart further superior optical performance and moisture permeability resistance, and is excellent in bleed resistance under high temperature and high humidity. And since an ester compound (A) is hard to volatilize in the manufacturing process of a film, it is preferable.

  The hydroxyl value of the ester compound (A) of the present invention is preferably in the range of 0.1 to 200, more preferably in the range of 1 to 150. If the hydroxyl value of the ester compound (A) is within this range, the bleed resistance and moisture permeability resistance of the optical film will be good. Moreover, when an optical film is used for a polarizer protective film, deterioration of a polarizer can be suppressed further. This hydroxyl value is derived from the terminal hydroxyl group of the ester compound (A) and the diol (a1) used as a raw material.

  The additive for cellulose ester resin of the present invention is required to have volatile resistance, particularly when used for an optical film. The volatilization resistance may be determined by measuring the heat loss value of the additive. For example, when used for a polarizer protective film of an optical film, the heat loss value of the additive for cellulose ester resin is 1.0. It is preferable that it is the range of 0.01 mass% or less and 0.01-1.0 mass%, It is more preferable that it is the range of 0.01-0.80 mass%, The range of 0.01-0.50 mass% It is particularly preferred that If the heating loss value is within this range, the polarizer protective film has excellent durability, moldability, and recyclability of the organic solvent used in film production by the solution casting method, and has problems in production and practical use. There is no level. The details of the measurement conditions for the heat loss value are described in the examples.

  The ester compound (A) which is an additive for cellulose ester resin of the present invention imparts volatility resistance, compatibility with the cellulose ester resin (B) and bleed resistance, and therefore its number average molecular weight is 300-3. , 000. The number average molecular weight is more preferably in the range of 330-2,700. An optical film made of a cellulose ester resin composition containing an ester compound (A) in the range of this number average molecular weight has excellent optical performance and moisture permeability, and even under high temperature conditions such as a film production process. Bleed of the ester compound (A) can be suppressed, and a film excellent in durability under wet heat conditions can be obtained.

  When the number average molecular weight of the ester compound (A) is 300 or less, a large amount of monomer components and low molecular weight substances remain, and the volatile resistance is remarkably deteriorated. On the other hand, if the number average molecular weight of the ester compound (A) is 3,000 or more, the compatibility with the cellulose ester resin (B) deteriorates, so that the transparency of the film is impaired and the use as an optical film is particularly difficult. It becomes.

  The number average molecular weight of the ester compound (A) is measured using gel permeation chromatography (GPC) using tetrahydrofuran (THF) as an eluent, and can be obtained as a value converted to standard polystyrene. . Detailed measurement conditions are described in the examples.

  The ester compound (A) is at least one selected from the group consisting of diol (a1) and terephthalic acid, dialkyl terephthalate, naphthalene dicarboxylic acid, naphthalene dicarboxylic acid dialkyl ester, biphenyl dicarboxylic acid and biphenyl dicarboxylic acid dialkyl ester. The aromatic dicarboxylic acid compound (a2) can be esterified.

  The reaction equipment for the ester compound (A) of the present invention can be produced by using a reaction equipment corresponding to pressurization and decompression. The reaction facility can be manufactured by using a general apparatus having a reactor, a stirrer, a rectifying column, a cooler, a pump for depressurizing, and the like.

  The ester compound (A) is prepared by, for example, charging the diol (a1) and the aromatic dicarboxylic acid compound (a2) in a reactor equipped with a thermometer, a stirrer, and a reflux condenser, An esterification catalyst is added in the middle of raising the temperature, and the reaction is carried out at a predetermined temperature. After the reaction, it can be obtained by performing a reduced pressure reaction for the purpose of accelerating the reaction with unreacted monomers and low molecular weight components.

  The diol (a1) used in the present invention will be specifically described below.

  Examples of the diol (a1) include ethylene glycol, 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol 1,12-dodecanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, 3,3-diethyl-1,3-propanediol, 3,3-dibutyl-1,3-propanediol, 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, n-butoxyethylene glycol, cyclohexanedimethanol, hydrogenated bisphenol A, dimer diol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexylene glycol Etc. These diols can be used alone or in combination of two or more.

  Moreover, aromatic diol can also be used as diol (a1). Examples of the aromatic diol include bisphenol A, an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct.

  Among the diols (a1), the most preferable diol includes those having 2 to 12 carbon atoms. Specifically, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4 -Butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,4-cyclohexanediol, 1,6-hexane Diol etc. are mentioned. These diols can be used alone or in combination of two or more.

  Furthermore, an ester compound (A) obtained by using a diol having a branched alkyl chain such as 1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, etc. is obtained by using a cellulose ester resin (B ) And excellent in bleed resistance in a high temperature and high humidity environment as an optical film.

  Moreover, when ethylene glycol (a1-1) and 1,2-propanediol (a1-2) are used in combination as the diol (a1), an optical film having excellent optical performance, that is, a polarizer protective film is obtained. Therefore, it is particularly preferable.

  When ethylene glycol (a1-1) and 1,2-propanediol (a1-2) are used in combination, ethylene glycol (a1-1) and 1,2-propanediol (a1- The molar composition ratio (a1-1) / (a1-2) of the structural unit derived from 2) is preferably in the range of 85/15 to 10/90 (mol%), and 80/20 to 15/85 (mol%). ) Is more preferable. When the molar composition ratio (a1-1) / (a1-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) is within this range, cellulose ester resin (B) In the case of producing a film by compatibility or a solution casting method, the solubility in an organic solvent becomes good, so that sufficient transparency can be imparted to the film. In addition, the optical performance is sufficiently developed.

  When the above-described ethylene glycol (a1-1) and 1,2-propanediol (a1-2) are used in combination, other alcohols other than these diols may be used. Specific examples of monoalcohols include methanol, ethanol, 1-butanol, 2-butanol, hexanol, cyclohexanol, amyl alcohol, octyl alcohol, lauryl alcohol, methyl lactate, ethyl lactate, and diols. 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1 , 8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, 3,3- Diethyl-1,3-propanediol, 3,3-dibuty -1,3-propanediol, 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, n-butoxyethylene glycol, cyclohexane Dimethanol, hydrogenated bisphenol A, dimer diol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexylene glycol, bisphenol A, ethylene oxide of bisphenol A Addendum, propylene oxide adducts and the like. Examples of other polyhydric alcohols include glycerin, sorbitol, ribitol, and pentaerythritol. These alcohols can be used alone or in combination of two or more.

  Next, one or more aromatic dicarboxylic acid compounds selected from the group consisting of terephthalic acid, terephthalic acid dialkyl ester, naphthalene dicarboxylic acid, naphthalene dicarboxylic acid dialkyl ester, biphenyl dicarboxylic acid and biphenyl dicarboxylic acid dialkyl ester used in the present invention (A2) will be specifically described below.

  The aromatic dicarboxylic acid compound (a2) used in the present invention is one selected from the group consisting of terephthalic acid, terephthalic acid dialkyl ester, naphthalene dicarboxylic acid, naphthalene dicarboxylic acid dialkyl ester, biphenyl dicarboxylic acid and biphenyl dicarboxylic acid dialkyl ester. That's it.

  Examples of the alkyl group of the terephthalic acid dialkyl ester, naphthalene dicarboxylic acid dialkyl ester, and biphenyl dicarboxylic acid dialkyl ester include those having 1 to 8 carbon atoms, and those having 3 or more carbon atoms are linear alkyl groups. May also 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. Further, the two alkyl groups of the aromatic dicarboxylic acid dialkyl ester may be the same or different. The aromatic dicarboxylic acid dialkyl ester can be used alone or in combination of two or more.

  Examples of the dialkyl terephthalate include dimethyl terephthalate, diethyl terephthalate, dipropyl terephthalate, dibutyl terephthalate, dipentyl terephthalate, dihexyl terephthalate, and diheptyl terephthalate. Among these dialkyl terephthalates, dimethyl terephthalate is capable of imparting excellent optical performance to an optical film made of a cellulose ester resin composition, and also has excellent bleed resistance in a high temperature and high humidity environment. Since the film which has property can be obtained, it is preferable.

  Examples of the naphthalene dicarboxylic acid dialkyl ester include dimethyl naphthalene dicarboxylate, diethyl naphthalene dicarboxylate, dipropyl naphthalene dicarboxylate, dibutyl naphthalene dicarboxylate, dipentyl naphthalene dicarboxylate, dihexyl naphthalene dicarboxylate, diheptyl naphthalene dicarboxylate and the like. In these naphthalene dicarboxylic acid dialkyl esters, there are various substitution positions of the carboxylic acid alkyl ester, but those in which the 2,6-position of naphthalene is a carboxylic acid alkyl ester are preferred, and the alkyl group is a methyl group. Some dimethyl 2,6-naphthalenedicarboxylate is more preferable.

  Examples of the dialkyl diphenyl dicarboxylate include dimethyl biphenyl dicarboxylate, diethyl biphenyl dicarboxylate, dipropyl biphenyl dicarboxylate, dibutyl biphenyl dicarboxylate, dipentyl biphenyl dicarboxylate, dihexyl biphenyl dicarboxylate, diheptyl biphenyl dicarboxylate, and the like. In addition, these biphenyl dicarboxylic acid dialkyl esters have various substitution positions of the carboxylic acid alkyl ester, but it is preferable that the 4,4′-position of biphenyl is a carboxylic acid alkyl ester, and the alkyl group is methyl. The group dimethyl 4,4′-biphenyldicarboxylate is more preferred.

  Furthermore, in the production of the ester compound (A), other dicarboxylic acids or their alkyl ester compounds or carbonate compounds can be used in combination as long as the present invention is not impaired. As said dicarboxylic acid or its alkylester compound, aliphatic dicarboxylic acid or aromatic dicarboxylic acid, or these alkylester 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 the aromatic dicarboxylic acid or its alkyl ester compound 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.

  When the diol (a1) and the aromatic dicarboxylic acid compound (a2) are esterified, the reaction can be performed in the presence of an esterification catalyst as necessary for the purpose of promoting the reaction.

  Examples of the esterification catalyst include at least one metal or organometallic compound selected from the group consisting of Groups 2, 3, and 4 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, zinc acetylacetonate, zirconium tetrachloride, zirconium tetrachloride, tetrahydrofuran complex, hafnium tetrachloride, hafnium tetrachloride tetrahydrofuran complex, germanium oxide, and tetraethoxygermanium. Among these, titanium alkoxide having good reactivity of diol (a1) and aromatic dicarboxylic acid compound (a2), ease of handling, and storage stability of ester compound (A) obtained by esterification reaction In particular, it is preferable to use titanium tetraisopropoxide, titanium tetrabutoxide, titanium oxyacetylacetonate or the like.

  In addition, the amount of the esterification catalyst used is usually an amount that can control the reaction between the diol (a1) and the aromatic dicarboxylic acid compound (a2) and can suppress the coloring of the ester compound (A). The range of 10 to 1000 ppm is preferable, the range of 20 to 500 ppm is more preferable, and the range of 30 to 300 ppm is particularly preferable with respect to the total amount of the diol (a1) and the aromatic dicarboxylic acid compound (a2). Since coloring of the ester compound (A) lowers the transparency of the film, it is necessary to pay particular attention to the optical film application that requires high transparency.

  The timing for adding the esterification catalyst may be added simultaneously with the preparation of the diol (a1) and the aromatic dicarboxylic acid compound (a2), or may be added during the temperature increase or at the start of pressure reduction. .

  In addition, when the diol (a1) and the aromatic dicarboxylic acid compound (a2) are reacted, the ester compound (A) is branched and has a high molecular weight as long as the effects of the present invention are not impaired. As examples, trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, trimellitic acid, and pyromellitic acid, and isocyanates such as carboxylic acid and hexamethylene diisocyanate may be used.

  The molar ratio [(a1) / (a2)] of the diol (a1) and the aromatic dicarboxylic acid compound (a2) in producing the ester compound (A) is 0.5 / 1 to 2/1. Is preferable, and the range of 0.8 / 1 to 1.5 / 1 is more preferable. If it is this range, the ester compound (A) which is an additive for cellulose-ester resins of this invention can be manufactured. In particular, when the charged molar ratio (a1) / (a2) is in the range of 0.5 / 1 to 1/1, the ratio of the terminal group of the ester compound (A) to the alkyl ester group increases. It is possible to obtain an optical film that is hardly affected by the influence of moisture and has a small fluctuation range of the Rth value.

  The reaction temperature when producing the ester compound (A) is determined while taking into consideration the boiling point, reactivity, sublimation, and hue of the resulting ester compound of the diol (a1) and aromatic dicarboxylic acid compound (a2) as raw materials. Although there will be no restriction | limiting if it is the range which (dehydration reaction or dealcoholization reaction) advances, The range of 120 to 300 degreeC is preferable, and the range of 150 to 280 degreeC is more preferable. The reaction time for producing the ester compound (A) is preferably 2 hours or more, and more preferably in the range of 4 to 100 hours. The degree of vacuum when producing the ester compound (A) is preferably 30,000 Pa or less, more preferably 25,000 Pa or less, and particularly preferably in the range of 5,000 Pa to 20,000 Pa. Within this range, unreacted monomers and low molecular weight components can be quickly removed, and the reaction can be promoted.

  The said ester compound (A) is good also as an additive for cellulose-ester resins of this invention, manufacturing a thing from which a kind differs, respectively, and then mixing them. Moreover, you may mix | blend additives other than ester compound (A) with the additive for cellulose-ester resins of this invention if it is in the range which does not impair the effect of this invention. Examples of the additive other than the ester compound (A) include a catalyst deactivator for deactivating the catalytic activity of the esterification catalyst, and an antioxidant for suppressing coloring of the ester compound (A). It is done.

  Examples of the catalyst deactivator include a chelating agent, and an organic chelating agent or an inorganic chelating agent 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 are preferably used by adding in the range of 10 to 2,000 ppm with respect to the total amount of the diol (a1) and the aromatic dicarboxylic acid compound (a2) as raw materials.

  Next, the cellulose ester resin composition containing the ester compound (A) will be described.

  The cellulose ester resin (B) used in the cellulose ester resin composition 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.

  Specific examples of the cellulose ester resin (B) include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, cellulose acetate phthalate, and cellulose nitrate. These cellulose ester resins can be used alone or in combination of two or more. When the film comprising the cellulose ester resin composition of the present invention is used as an optical film, particularly as a polarizer protective film, it is possible to obtain a film excellent in mechanical properties and transparency by using cellulose acetate. Therefore, it is preferable.

  The cellulose acetate preferably has an average degree of acetylation (bound acetic acid amount) in the range of 50.0 to 62.5% by mass, and an average degree of acetylation in the range of 52.5 to 61.5% by mass. Some cellulose triacetates are more preferred. By using cellulose acetate having an average degree of acetylation within this range, it is possible to improve moisture permeability of an optical film comprising the resulting cellulose ester resin composition. In addition, an average acetylation degree is a mass ratio of the acetic acid produced | generated by saponifying this cellulose acetate on the basis of the mass of a cellulose acetate.

  The number average molecular weight of the cellulose ester resin (B) is preferably 30,000 to 300,000, more preferably 50,000 to 200,000. By using cellulose acetate having a number average molecular weight within this range, the mechanical properties of the resulting film can be improved.

  The cellulose ester resin composition of the present invention preferably contains 0.5 to 50 parts by mass of the ester compound (A) with respect to 100 parts by mass of the cellulose ester resin (B). When the compatibility between the cellulose ester resin (B) and the ester compound (A) and the bleed resistance are further improved, the ester compound (A) is added to 1 part by mass with respect to 100 parts by mass of the cellulose ester resin (B). What contained in 40 mass parts is more preferable. When the cellulose ester resin composition containing the ester compound (A) is used in this range, an optical film having excellent optical performance, moisture permeability resistance, and bleed resistance under high temperature and high humidity can be obtained.

  Moreover, the cellulose-ester resin composition of this invention can add various additives other than ester compound (A) in the range which does not impair this invention.

  Examples of the various additives include modifiers (including plasticizers), ultraviolet absorbers, retardation increasing agents, resins, matting agents, deterioration inhibitors (eg, antioxidants, peroxide decomposition agents, radicals). Inhibitors, metal deactivators, acid scavengers, etc.) and additives such as dyes. Moreover, these additives can also be added together when the cellulose ester resin (B) and the ester compound (A) are dissolved and mixed in an organic solvent in the solution casting method described later.

  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, that is, the Rth value is increased. For example, a liquid crystal compound such as 4-cyano-4′-pentylbiphenyl, 1,4- Examples include a cyclohexanedicarboxylic acid ester compound and a compound having a 1,3,5-triazine ring. The 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 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 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).

  As the dye, a known and commonly used dye can be used, and the amount of the dye is not particularly limited as long as it does not impair the object of the present invention.

  The cellulose ester resin composition containing the additive for cellulose ester resin comprising the ester compound (A) of the present invention can be used for a film, and can also be used for an optical film.

  The film of the present invention can be obtained by molding the cellulose ester resin composition into a film. Examples of the molding method include a method in which the cellulose ester resin composition is melt-kneaded with an extruder or the like and molded into a film by using a T-die or the like.

  In addition to the molding method, the film of the present invention is a solution in which a resin solution obtained by uniformly dissolving and mixing the cellulose ester resin composition in an organic solvent is cast on a metal support and dried. It can also be obtained by molding by the casting method. When a film is obtained by the solution casting method, since the orientation of the cellulose ester resin (B) in the film during molding can be suppressed, the resulting film substantially exhibits optical isotropy. The film showing optical isotropy can be used as a member for a liquid crystal display or the like as an optical film, and is particularly useful as a polarizer protective film. Moreover, since the film obtained by this solution casting method has the characteristics that an unevenness | corrugation is hard to be formed in the surface and is excellent in surface smoothness, the solution casting method is a more preferable film forming method.

  The solution casting method is a first step in which the cellulose ester resin (B) and the ester compound (A) are dissolved in an organic solvent, and the resulting resin solution is cast on a metal support. The second step of drying the organic solvent contained in the resin solution to form a film and the third step of peeling the film formed on the metal support from the metal support and drying by heating.

  As the metal support used in the first step, an endless belt-shaped or drum-shaped metal such as stainless steel having a mirror-finished surface can be used. When casting the resin solution on the metal support, it is preferable to use a resin solution filtered with a filter in order to prevent foreign matters from being mixed into the resulting film.

  As a drying method in the second step, for example, by applying air in a temperature range of 30 to 50 ° C. to the upper and lower surfaces of the metal support, approximately 50 to 50 of the organic solvent contained in the cast resin solution. There is a method in which about 80% by mass is evaporated to form a film on the metal support.

  The third step is a step in which the film formed in the second step is peeled off from the metal support and is heat-dried at a higher temperature than in the second step. As the heat drying method, for example, a method of increasing the temperature stepwise in a temperature range of 100 to 160 ° C. is preferable in order to improve the dimensional stability. By heating and drying in the temperature range, the organic solvent remaining in the film obtained in the second step can be almost completely removed.

  As a solution density | concentration of the cellulose-ester resin composition in the said resin solution, the range of 3-50 mass% is preferable, and the range of 5-40 mass% is more preferable.

  The organic solvent is not particularly limited as long as it can dissolve the cellulose ester resin (B) and the ester compound (A). For example, when cellulose acetate is used as the cellulose ester resin (B), cellulose As a good solvent for acetate, for example, organic halogen compounds such as methylene chloride and dioxolanes can be used. In addition, it is preferable to use a poor solvent such as methanol, ethanol, 2-propanol, n-butanol, cyclohexane, and cyclohexanone in combination with the good solvent because the production efficiency of the film can be improved. The mass ratio in the case of using a mixture of a good solvent and a poor solvent is preferably in the range of good solvent / poor solvent = 75/25 to 95/5 (mass%).

  The film thickness of the film of the present invention is preferably in the range of 10 to 1,000 μm, more preferably in the range of 20 to 500 μm, and still more preferably in the range of 30 to 200 μm. Moreover, when using the film of this invention as an optical film, it is preferable that the film thickness is the range of 10-150 micrometers. When used as a polarizer protective film among optical films, the thickness of the liquid crystal display device can be reduced as long as the film thickness is in the range of 25 to 100 μm, and excellent film strength and wet heat change. Dimensional stability and moisture permeability resistance can be maintained. In the present invention, bleed resistance and dimensional stability are sometimes referred to as durability.

  The optical film of the present invention can also be used for a polarizer protective film that requires an optical compensation function. This polarizer protective film is required to have anisotropy in a specific range according to a liquid crystal display method such as TN (Twisted Nematic), VA (Vertically Aligned), OCB (Optically Compensatory Bend).

  The optical film of the present invention preferably has an Rth value of 100 nm or more, and having an Rth value in the range of 100 to 500 nm effectively compensates for a phase difference derived from a liquid crystal substance. Is more preferable because

  In order to obtain a polarizer protective film having desired optical anisotropy, it is possible to adjust the blending ratio of the additive for cellulose ester resin comprising the ester compound (A) of the present invention. In particular, since the additive for cellulose ester resin of the present invention can obtain a high Rth value by adding a small amount, a liquid crystal display device adopting a liquid crystal display system such as VA, OCB, and TN, which requires a relatively high Rth value. In addition, the desired Rth value can be adjusted while maintaining the bleed resistance.

  The reason why the optical film of the present invention exhibits excellent optical performance is considered to be due to the chemical structure of the ester compound (A) and its intermolecular interaction. Specifically, the diol (a1), which is a raw material for the additive for cellulose ester resin comprising the ester compound (A) of the present invention, and the aromatic dicarboxylic acid compound (a2) have a relatively high planar structure. It is considered that the electron density is increased because it is considered that a π-π bond is formed between molecules of the polyester due to the effect of the aromatic dicarboxylic acid compound (a2) in the ester compound. When the ester compound (A) having a high planarity and a high electron density is regarded as a refractive index ellipsoid, the ester compound (A) forms a highly anisotropic structure in the cellulose ester resin (B). Therefore, it is estimated that it has excellent optical performance.

  Further, ethylene glycol (a1-1) and 1,2-propanediol (a1-2) were used in combination as a diol (a1) which is a raw material of the additive for cellulose ester resin comprising the ester compound (A) of the present invention. In this case, 1,2-propanediol (a1-2) contributes to the compatibility between the ester compound (A) and the cellulose ester resin (B), and the improvement of the solvent solubility when the film is produced. On the other hand, ethylene glycol (a1-1) having a short C—C distance and a highly linear structure is considered to contribute to an improvement in optical anisotropy, that is, an Rth value. Accordingly, by using ethylene glycol (a1-1) and 1,2-propanediol (a1-2) in combination, the compatibility with the cellulose ester resin (B) or the solvent solubility when producing a film is improved. It is presumed that the effect of exhibiting excellent optical performance can be achieved at the same time.

The moisture permeability of the optical film of the present invention will be described. If the film thickness of the optical film of the present invention is 80 μm, the cellulose ester resin (B) film has a moisture permeability of, for example, about 800 to 900 g / m ² · 24 h. film is preferably less can be obtained in moisture permeability 600g / ^m 2 · 24h, and more preferable to obtain a moisture permeability ranging from 100~600g / ^m 2 · 24h. Within this range, even if the thickness of the obtained optical film is reduced to about 20 to 60 μm, it has excellent moisture resistance.

  The film of the present invention is excellent not only in optical performance but also in moisture permeation resistance, transparency, non-volatility, bleed resistance under high temperature and high humidity, and so on. It can be used as a material support. Here, examples of the optical film include a polarizer protective film, a retardation film, a reflector, a viewing angle improving film, an antiglare film, an antireflective film, an antistatic film, and a color filter. Among these optical films, a film having a high Rth value in addition to the excellent characteristics as described above can be used as a polarizer protective film having a viewing angle compensation function.

  The present invention will be specifically described below with reference to examples and comparative examples.

[Example 10] Production of ester compound (A-10) In a three-liter four-necked flask equipped with a thermometer, stirrer, rectifying column and reflux condenser, EG 140 g, PG 57 g and DMT 874 g were added. The temperature was raised. When the temperature in the flask reached 80 ° C., 60 ppm of tetraisopropyl titanate was added as an esterification catalyst to the total amount of EG, PG and DMT, and the temperature was increased at a rate of 10 ° C./hour while stirring in a nitrogen stream. The temperature was raised to 190 ° C. The reaction was carried out for 10 hours while distilling off the produced methanol. After the reaction, by reducing the pressure at about 18,000 Pa for 2 hours when the flask internal temperature reached 190 ° C., the ester compound (A-10) (acid) having a number average molecular weight of 730 and a weight average molecular weight of 1,220 was obtained. Value: 0.43, hydroxyl value: 121, heat loss value: 0.22% by mass). As a result of NMR spectrum measurement, the molar composition ratio (a1-1) / (a1-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) was 78/22 (mol%). Met.

[Example 13] Production of ester compound (A-13) EG (155 g), PG (190 g) and NDCM (610 g) were charged into a two-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser. did. When the temperature in the flask reached 80 ° C., 60 ppm of tetraisopropyl titanate was added as an esterification catalyst to the total amount of EG, PG and NDCM, and the temperature was increased at a rate of 10 ° C./hour while stirring in a nitrogen stream. The temperature was raised to 190 ° C. The reaction was carried out for 10 hours while distilling off the produced methanol. After the reaction, by reducing the pressure at about 18,000 Pa for 2 hours when the flask internal temperature reached 190 ° C., the ester compound (A-13) having a number average molecular weight of 360 and a weight average molecular weight of 390 (acid value: 0.43, hydroxyl value: 118, heat loss value: 0.34% by mass). As a result of NMR spectrum measurement, the molar composition ratio (a1-1) / (a1-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) was 50/50 (mol%). Met.

[Comparative Example 1] Production of ester compound (A-14) In a four-necked flask having an internal volume of 1 liter, 700 g of the ester compound (A-3) obtained in Example 3 was charged and the temperature was raised. When the temperature in the flask reaches 190 ° C., the pressure is reduced at about 133 Pa for 2 hours, whereby an ester compound (A-14) having a number average molecular weight of 3,300 and a weight average molecular weight of 9,600 (acid value: 0.45, hydroxyl value: 15) was obtained.

[Comparative Example 2] Production of ester compound (A-15) EG 186g, PG 228g and DMT 970g were placed in a two-liter four-necked flask equipped with a thermometer, stirrer, rectifying column and reflux condenser. The temperature was raised. When the temperature in the flask reached 80 ° C., 60 ppm of tetraisopropyl titanate was added as an esterification catalyst to the total amount of EG, PG and DMT, and the temperature was increased at a rate of 10 ° C./hour while stirring in a nitrogen stream. The temperature was raised to 190 ° C. The reaction was carried out for 10 hours while distilling off the produced methanol. After the reaction, by reducing the pressure at about 18,000 Pa for 3 hours when the temperature in the flask reaches 190 ° C., the ester compound (A-15) having a number average molecular weight of 3,150 and a weight average molecular weight of 8,200 (Acid value: 0.65, hydroxyl value: 15, heat loss value: 0.08 mass%) was obtained. As a result of NMR spectrum measurement, the molar composition ratio (a1-1) / (a1-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) was 51/49 (mol%). Met.

[Comparative Example 3] Production of ester compound (A-16) A three-liter four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 468 g of PG, 524 g of DMT and benzoic acid (hereinafter, “ BzA ")) 733 g was charged and the temperature was raised. When the temperature in the flask reaches 130 ° C., 60 ppm of tetraisopropyl titanate as an esterification catalyst is added to the total amount of PG, DMT, and BzA, and the mixture is stirred at 170 ° C. per hour for 10 hours while stirring in a nitrogen stream. The temperature was raised to 220 ° C. while distilling off water and methanol produced at a temperature rising rate of ° C. After the reaction for 10 hours, when the temperature inside the flask reached 190 ° C., the pressure was reduced at about 133 Pa for 4 hours, whereby the ester compound (A-16) having a number average molecular weight of 450 and a weight average molecular weight of 800 (acid value: 0.32 and hydroxyl value: 7) were obtained.

[Comparative Example 4] Production of ester compound (A-17) In a four-necked flask having an internal volume of 3 liters equipped with a thermometer, a stirrer, and a reflux condenser, 670 g of EG and adipic acid (hereinafter referred to as "AA") 1) 1461 g was charged and the temperature was raised. When the temperature in the flask reaches 70 ° C., 60 ppm of tetraisopropyl titanate as an esterification catalyst is added to the total amount of EG and AA, and the mixture is stirred at 150 ° C. for 15 hours under a nitrogen stream. The temperature was raised to 220 ° C. while distilling off the water produced at the rate of temperature rise. After the reaction for 7 hours, when the temperature inside the flask reached 195 ° C., the pressure was reduced at about 1330 Pa for 3 hours, thereby the ester compound (A-17) having a number average molecular weight of 1,000 and a weight average molecular weight of 1,850. (Acid value: 0.55, hydroxyl value: 113) was obtained.

[Comparative Example 5] Production of ester compound (A-18) 1,3-butanediol (hereinafter referred to as "1, 1") was added to a 3-liter four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser. 3-BD ”) and 461 g of phthalic anhydride (hereinafter referred to as“ PA ”) were charged and the temperature was raised. When the temperature in the flask reaches 70 ° C., tetraisopropyl titanate as an esterification catalyst is added at 60 ppm with respect to the total amount of 1,3- BD and PA, and the mixture is stirred from 150 ° C. under a nitrogen stream. The temperature was raised to 220 ° C. while distilling off the water produced at a rate of temperature rise of 15 ° C. per hour. After the reaction for 7 hours, when the temperature in the flask reached 195 ° C., the pressure was reduced at about 1330 Pa for 3 hours, whereby the ester compound (A-18) (acid) having a number average molecular weight of 710 and a weight average molecular weight of 1,350 was obtained. Value: 0.55, hydroxyl value: 123).

  Number average molecular weight (Mn), weight average molecular weight (Mw), acid value, hydroxyl value of ester compounds (A-1) to (A-18) obtained in Examples 1 to 13 and Comparative Examples 1 to 5 above. And the loss on heating was measured by the following method. The hydroxyl value was measured according to JIS K 0070-1992.

[Method for Measuring Number Average Molecular Weight (Mn) and Weight Average Molecular Weight (Mw) of Ester Compound]
Using a gel permeation chromatography (GPC) measuring device (“HLC-8330” manufactured by Tosoh Corporation), the number average molecular weight (Mn) and weight average molecular weight (Mw) of the ester compound in terms of standard polystyrene under the following measurement conditions: ) Was measured.
Column: “TSK gel SuperHZM-M” × 2 and “TSK gel SuperHZ-2000” × 2 Guard column: “TSK superH-H”
Developing solvent: Tetrahydrofuran Flow rate: 0.35 mL / min

[Method for measuring molar composition ratio (a-1) / (a-2) of ethylene glycol (a-1) and 1,2-propanediol (a-2)]
By analyzing the chloroform-d (CDCl ₃ ) solution of the ester compound using a ¹ H-NMR apparatus (JNM-LA300, manufactured by JEOL Ltd.), ethylene glycol (a- 1) The molar composition ratio (a-1) / (a-2) (unit: mol%) of the unit and 1,2-propanediol (a-2) unit was calculated.

[Measurement conditions for heat loss]
About 50 g of ester compound is put into a gear aging tester (model “SB-P” manufactured by Toyo Seiki Seisakusho Co., Ltd., internal volume 45 × 45 × 50 cm ³ ), and after heating at 140 ° C. for 60 minutes in a nitrogen atmosphere. The mass was measured, and the heat loss value was measured by the mass reduction rate before and after heating. In addition, when using for a polarizer protective film, it can be said that it is remarkably excellent in volatility if the heating loss value of an ester compound is about 0.5 mass% or less.

  The characteristic values of the ester compounds (A-1) to (A-18) obtained in Examples 1 to 13 and Comparative Examples 1 to 5 are shown in Tables 1 to 3.

[Production of Film for Evaluation Consisting of Cellulose Ester Resin Composition]
1 g of the ester compounds (A-1) to (A-18) obtained in Examples 1 to 13 and Comparative Examples 1 to 5 and 10 g of cellulose triacetate (acetylation degree 61 mass%, polymerization degree 265) were chlorinated. A dope solution was prepared by mixing in a mixed solvent consisting of 81 g of methylene and 9 g of methanol and stirring uniformly. Each of these dope solutions is cast on a glass plate to a thickness of about 1 mm, dried at room temperature for 16 hours, dried at 50 ° C. for 30 minutes, and further dried at 120 ° C. for 30 minutes. Thus, films for evaluation (F-1) to (F-18) having a film thickness of about 80 μm were obtained.

  Further, as Comparative Example 6, the same operation was performed using 1 g of triphenyl phosphate (hereinafter referred to as “TPP”) instead of the ester compound to obtain an evaluation film (F-19) having a thickness of about 80 μm. It was. Further, as Comparative Example 7, the same operation was carried out using only cellulose triacetate to obtain an evaluation film (F-20) having a film thickness of about 80 μm.

[Evaluation method of bleed resistance of film]
The obtained film was cut into a size of 30 mm × 40 mm, and left for 120 hours in constant temperature and humidity at a temperature of 85 ° C. and a relative humidity of 90%. Thereafter, the surface of the film was visually observed, and the presence or absence of bleeding such as an ester compound was evaluated according to the following criteria.
A: No bleed was observed on the surface of the film.
B: Bleed material was observed on the surface of the film.
A film in which no bleed or the like is observed is excellent in durability, and when used as a polarizer protective film, it can be said that the film is excellent in wet heat durability of the polarizer protective film.

  In addition, using the film after the bleed resistance test evaluation of the above film, the transparency of the film is measured with a turbidimeter (manufactured by Nippon Denshoku Industries Co., Ltd.) for the purpose of judging the compatibility between the cellulose ester resin and the esterified product. Using a model “ND-1001DP”), the haze value of the film was measured according to JIS K 7105. In addition, when it uses for a polarizer protective film, it is practically preferable that it is 1% or less, and it is more preferable practically that it is 0.5% or less.

[Measurement method of retardation value (Rth value) in thickness direction of film]
The retardation value (Rth value) in the thickness direction of the film was measured using an automatic birefringence meter (“KOBRA-WR” manufactured by Oji Scientific Instruments). Measurement conditions were as follows: humidity was adjusted for 12 hours or more in an environment of a temperature of 23 ° C. and a relative humidity of 20%, and then the measurement was performed in the same environment. Although the Rth value of the film varies depending on the application, it can be used as a polarizer protective film having an optical compensation function as long as it is approximately 130 nm or more.

[Measurement method of moisture permeability of film]
According to the method described in JIS Z 0208, the moisture permeability of the film was measured and converted to a thickness of 80 μm. The measurement conditions were a temperature of 25 ° C. and a relative humidity of 90%. In addition, since the moisture permeability of the film of only cellulose triacetate used in this example is about 800 g / m ² · 24 h (see Comparative Example 9 in Table 2), the additive for cellulose ester resin of the present invention is blended. If the moisture permeability of the film is less than this value, it can be said that the film has excellent moisture resistance as a polarizer protective film.

  Tables 1 and 2 show the evaluation results of films (F-1) to (F-13) using the additives for cellulose ester resin of the present invention obtained in Examples 1 to 13, respectively. Further, films (F-14) to (F-18) using the ester compounds obtained in Comparative Examples 1 to 5, films using TPP instead of the ester compounds (F-19; Comparative Example 6), and what Table 3 shows the evaluation results of the film (F-20; Comparative Example 7) which was not blended.

  From the results shown in Tables 1 and 2, it was found that the ester compound which is an additive for cellulose ester resin of the present invention has a very low heating loss value of 0.03 to 0.45% by mass. Moreover, the films (F-1) to (F-13) using the additive for cellulose ester resin of the present invention are excellent in bleed resistance and moisture permeability, and are highly transparent even when stored in a high temperature and high humidity environment. It was found to maintain. Furthermore, the Rth value of the film was as high as 115 to 291 nm, and it was found that the film was extremely useful as an optical film.

  Moreover, the following was found from the results shown in Table 3.

  Comparative Examples 1 and 2 are examples in which an ester compound exceeding 3,000 which is the upper limit of the number average molecular weight of the ester compound which is an additive for cellulose ester resin of the present invention is used. Films (F-14) and (F-15) containing this ester compound have the problem that the compatibility between the cellulose ester resin and the ester compound is very poor, so that the film becomes cloudy and the bleed resistance is poor. there were. The haze value of the film (F-14) and the Rth values of the films (F-14) and (F-15) were not measurable because the film was cloudy. Moreover, since these values were not measurable, moisture permeability was not measured.

  Comparative Example 3 is an example in which a terminal hydroxyl group is sealed using benzoic acid which is an aromatic monocarboxylic acid in addition to an aromatic dicarboxylic acid compound as a raw material of an ester compound which is an additive for cellulose ester resin of the present invention. It is. The film (F-16) containing this ester compound had good bleed resistance and moisture permeability resistance, but no improvement in Rth value was observed.

  Comparative Example 4 is an example of an ester compound in which an aliphatic dicarboxylic acid is used in place of the aromatic dicarboxylic acid compound used in the present invention as a raw material of an ester compound that is an additive for cellulose ester resin of the present invention. The film (F-17) blended with this ester compound had good bleed resistance and moisture permeability resistance, but no improvement in Rth value was observed.

  Comparative Example 5 is an example of an ester compound using an aromatic dicarboxylic acid compound different from the aromatic dicarboxylic acid compound defined in the present invention as a raw material of an ester compound that is an additive for cellulose ester resin of the present invention. The film (F-18) containing this ester compound had good bleed resistance and moisture permeability resistance, but no improvement in Rth value was observed.

  Comparative Example 6 is an example in which TPP was used instead of the ester compound that is the additive for cellulose ester resin of the present invention. It was found that the film (F-19) blended with this TPP had a problem that a large amount of TPP bleeds on the film surface even at room temperature. Moreover, the improvement of Rth value of the film was not recognized.

  Comparative Example 7 is an evaluation example of a film (F-20) in which no ester compound or the like was blended. Although this cellulose ester resin-only film is excellent in transparency, the Rth value is very low.

Claims (5)

Diol (a1) and at least one aromatic dicarboxylic acid compound (a2) selected from the group consisting of terephthalic acid, terephthalic acid dialkyl ester, naphthalene dicarboxylic acid, naphthalene dicarboxylic acid dialkyl ester, biphenyl dicarboxylic acid and biphenyl dicarboxylic acid dialkyl ester ) and the obtained by esterifying a number average molecular weight of from 300 to 730, and a diol (a1) as ethylene glycol (a1-1) and 1,2-propanediol (a1-2), Used together in a range where the molar composition ratio (a-1) / (a-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) is 85/15 to 10/90. An additive for cellulose ester resin, comprising the resulting ester compound (A). The molar composition ratio (a-1) / (a-2) of ethylene glycol (a1-1) and 1,2-propanediol (a1-2) is in the range of 80/20 to 15/85. The additive for cellulose ester resins described. Se relative to cellulose ester resin (B) 100 parts by weight of a cellulose ester resin composition, wherein the ester compound of claim 1, wherein the (A) containing 0.5 to 50 parts by weight.   A film comprising the cellulose ester resin composition according to claim 3.   An optical film comprising the cellulose ester resin composition according to claim 3.