JP2009046531A - Modifier for cellulose ester resin, and cellulose ester optical film and polarizing plate protective film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a modifier for cellulose ester resin by which the thickness-direction retardation value (Rth) of a cellulose ester resin-containing film can be reduced to a practically adequate level and excellent moisture permeation resistance can be imparted to the film, and which is excellent in bleeding resistance and less liable to volatilize even under severe conditions of high temperature and high humidity, and to provide a cellulose ester optical film and a polarizing plate protective film using the modifier. <P>SOLUTION: The modifier for cellulose ester resin comprises an aliphatic polyester (A) having a number average molecular weight of 1,000-3,000 obtained by bringing a 2-4C glycol (a), a 2-6C aliphatic dicarboxylic acid (b) and a 4-9C monoalcohol and/or monocarboxylic acid (c) into a reaction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cellulose ester resin modifier that can be used in various applications including an optical film such as a polarizing plate protective film, a cellulose ester optical film containing the modifier, and a polarizing plate protection. Related to film.

  In recent years, information devices such as notebook computers, televisions, mobile phones, and the like equipped with a liquid crystal display device capable of clearly displaying images and characters have been supplied to the market one after another. Consumer demand for these information devices includes the provision of advanced high-performance functions. In particular, improving the visibility of the liquid crystal display device (widening the viewing angle) is important in determining the commercial value. It is strongly requested by consumers.

  The liquid crystal display device is generally a laminated structure having a layer made of an electrode and a layer made of a liquid crystal substance (liquid crystal layer) between two glass substrates. A polarizing plate is pasted on the surface of the glass substrate opposite to the liquid crystal layer, and a protective film is usually pasted on both sides of a polarizer made of polyvinyl alcohol (PVA) as the polarizing plate. Things are used. As the protective film for the polarizing plate, a cellulose ester film having high transparency and optical isotropy, an appropriate strength, and excellent adhesion to PVA has been conventionally used.

  However, the conventional cellulose ester film is excellent in optical isotropy in the film plane, but has optical anisotropy in the thickness direction. For this reason, when the liquid crystal screen using the cellulose ester film is viewed from an oblique direction, the color of the displayed image may appear different from the original color. Therefore, in order to optimize the visibility of the liquid crystal display device from an oblique direction, it is necessary to grasp the degree of optical anisotropy of the film and to perform optical design of the display device in consideration thereof.

  The degree of optical anisotropy of the optical film can be generally grasped from the retardation value. Of the retardation values of the optical film, the retardation value in the thickness direction of the film (hereinafter also referred to as “Rth”) is defined by the following formula (1).

Rth = {(n _x + _ny ) / 2−n _z } × d (1)
Wherein, n _x is a refractive index in a slow axis direction in the film plane, n _y is a refractive index in a fast axis direction in the film plane, n _z is a refractive index in the thickness direction of the film , D is the film thickness (nm). ]

  The cellulose ester optical film plays a role as a protective film for a polarizer, but a normal optical film cannot sufficiently prevent moisture (water) from entering the polarizer from the outside. In some cases, deterioration of the polarizer or peeling between the polarizer and the film may occur. Therefore, until now, by using a film obtained by adding a plasticizer such as triphenyl phosphate (TPP) to the cellulose ester resin, for example, as a “protective film for polarizing plate”, the moisture permeability resistance is improved. I was planning.

  However, conventional plasticizers such as TPP, which are widely used for cellulose ester optical films, are still inferior in compatibility with cellulose ester resin, volatilization resistance, and moisture permeability resistance, and Rth to a practically sufficient level. It did not lead to a decrease.

  Further, high visibility of liquid crystal display devices has been studied for some time. For example, a cellulose ester film containing a cellulose ester and a citrate ester that can contribute to optical isotropy has an optical anisotropy. It is known that it is relatively small and can be used for optical applications (see, for example, Patent Document 1).

  However, although the cellulose ester optical film obtained in Patent Document 1 shows a decrease in Rth, it has been difficult to use practically due to poor moisture permeation resistance and volatility resistance.

  Furthermore, a cellulose composition containing cellulose acylate and a compound having an aromatic hydrocarbon ring is known, and a cellulose film obtained using such a composition has good moisture resistance and Rth is Since it is relatively small and has good optical anisotropy, it can be used as a polarizing plate protective film, a liquid crystal display device, and a support for silver halide photographic light-sensitive materials (see, for example, Patent Document 2).

  However, since the cellulose composition obtained in Patent Document 2 is still insufficient in compatibility with the cellulose ester resin, it is easy to bleed and is not yet sufficiently resistant to volatility, and contamination of the manufacturing process equipment and working environment. There was a problem.

Japanese Patent Laid-Open No. 11-92574 JP 2005-89668 A

  An object of the present invention is to reduce the retardation value (Rth) in the thickness direction of a film containing a cellulose ester resin to a practically sufficient level, with small optical anisotropy and excellent moisture resistance. To provide a cellulose ester resin modifier that can be imparted to a film and has excellent bleed resistance even under severe conditions under high temperature and high humidity, and that does not easily volatilize, a cellulose ester optical film using the same, and a protective film for a polarizing plate. It is.

  As a result of intensive studies to solve the above problems, the present inventor has found that a glycol having 2 to 4 carbon atoms, an aliphatic dicarboxylic acid having 2 to 6 carbon atoms, a monoalcohol and / or a monocarboxylic acid having 4 to 9 carbon atoms. By using an aliphatic polyester having a number average molecular weight (Mn) of 1000 to 3000 obtained by reacting with an acid as a modifier for cellulose ester resin, (1) a cellulose ester optical film using a cellulose ester resin (2) The cellulose ester resin modifier is excellent in compatibility with the cellulose ester resin and excellent in bleed resistance under high temperature and high humidity, (3) The cellulose The ester resin modifier is excellent in volatility, and (4) the cellulose ester resin modifier and cellulose ester resin. Protective film for a polarizing plate obtained using the the optical anisotropy is excellent in practical use sufficiently small phase difference function, it was found.

  That is, the present invention comprises a glycol having 2 to 4 carbon atoms (a), an aliphatic dicarboxylic acid having 2 to 6 carbon atoms (b), a monoalcohol having 4 to 9 carbon atoms and / or a monocarboxylic acid (c). The present invention relates to a modifier for cellulose ester resin comprising an aliphatic polyester (A) having a number average molecular weight of 1000 to 3000, which is obtained by reaction.

  The present invention also relates to a cellulose ester optical film comprising the cellulose ester resin modifier and a cellulose ester resin.

  In the present invention, a resin solution obtained by dissolving the cellulose ester resin modifier and cellulose ester resin in an organic solvent is cast on a metal support, and then the organic solvent is distilled off and dried. It is related with the protective film for polarizing plates characterized by making it obtain.

  The number average molecular weight referred to in the present invention is a value measured by gel permeation chromatography (GPC) in terms of polystyrene using tetrahydrofuran (THF) as an eluent. Hereinafter, it may be abbreviated as “Mn”.

  According to the present invention, the modification for cellulose ester resin has small optical anisotropy, excellent moisture permeation resistance and bleed resistance under high temperature and high humidity, is less likely to volatilize in the film production process, and has less contamination of equipment and work environment. Agent can be provided. In addition, the cellulose ester optical film obtained by using the cellulose ester resin modifier and the cellulose ester resin can be used for various optical films and can sufficiently reduce the optical anisotropy. It is useful as a protective film for polarizing plates having.

  First, the modifier for cellulose ester resins of the present invention will be described.

  The modifier for cellulose ester resin of the present invention comprises a glycol (a) having 2 to 4 carbon atoms, an aliphatic dicarboxylic acid (b) having 2 to 6 carbon atoms, a monoalcohol and / or monocarboxylic acid having 4 to 9 carbon atoms. It is obtained by reacting with an acid (c) and consists of an aliphatic polyester (A) having a Mn of 1000 to 3000.

  Specific examples of the aliphatic polyester (A) include those having the structure represented by the following general formula (I) or (II), and these may be used alone or in combination of two or more.

[In the formulas (I) and (II), R1 and R2 each independently represents an alkyl group having 4 to 9 carbon atoms, and P1 and P2 each independently represent 3 to 3 carbon atoms. Represents an alkyl group of 8; G1 and G2 each independently represent an alkylene group having 2 to 4 carbon atoms. A1 and A2 each independently represent that an alkylene group having 1 to 4 carbon atoms or two carbonyl carbons are adjacent to each other and directly connected to each other. n represents an integer of 0 to 30. ]

  N in the general formulas (I) and (II) is preferably in the range of 0-30. In general, the modifier for cellulose ester resin of the present invention is usually a mixture of aliphatic polyesters (A) having different numbers of n, and n that can be produced when the aliphatic polyester (A) is produced. More than 30 aliphatic polyesters may be included as long as the effects of the present invention are not impaired.

  The aliphatic polyester (A) includes a glycol (a) having 2 to 4 carbon atoms, an aliphatic dicarboxylic acid (b) having 2 to 6 carbon atoms, a monoalcohol and / or a monocarboxylic acid (c) having 4 to 9 carbon atoms. ) Can usually be produced by an esterification reaction.

  The glycol having 2 to 4 carbon atoms (a) used for the production of the aliphatic polyester (A) constitutes the structures of G1 and G2 in the general formulas (I) and (II), for example, Ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methylpropanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol Among these, ethylene glycol is preferable for obtaining a cellulose ester resin modifier having excellent bleeding resistance under high temperature and high humidity and capable of imparting sufficient moisture permeability. These glycols may be used alone or in combination of two or more.

  Examples of the aliphatic dicarboxylic acid having 2 to 6 carbon atoms (b) used for the production of the aliphatic polyester (A) include oxalic acid (carbon number 2. The number in parentheses represents the number of carbon atoms in the molecule. The same meaning), malonic acid (3), succinic acid (4), glutaric acid (5), adipic acid (6), maleic acid (4), fumaric acid (4), etc. ) And (II) which constitute the structures of A1 and A2, and among them, the cellulose ester resin can be imparted with excellent moisture permeability resistance and has excellent bleed resistance under high temperature and high humidity. Acid and / or adipic acid are preferred. These aliphatic dicarboxylic acids may be used alone or in combination of two or more.

  Moreover, as said C2-C6 aliphatic dicarboxylic acid (b), instead of aliphatic dicarboxylic acid, carboxylic acid derivatives such as esterified products, acid chlorides, and acid anhydrides may be used alone or in combination of two or more. You may use together.

  In the monoalcohol having 4 to 9 carbon atoms and / or monocarboxylic acid (c) used for the production of the aliphatic polyester (A), examples of the monoalcohol having 4 to 9 carbon atoms include 1-butanol and 2-butanol. , Isobutanol, t-butanol, 1-pentanol, isopentyl alcohol, tert-pentyl alcohol, cyclopentanol, 1-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, iso Nonyl alcohol, 1-nonyl alcohol and the like constituting the structure of R1 and R2 in the general formula (I) are mentioned. Examples of the monocarboxylic acid having 4 to 9 carbon atoms include butanoic acid and pentane. Acid, hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexylic acid, nonanoic acid In which the structures of P1 and P2 in the general formula (II) are included, and these may be used alone or in combination of two or more thereof. Among these, 1-butanol, 1-hexanol, butane Acid is preferred. If such a compound is used as the monoalcohol and / or monocarboxylic acid (c), the cellulose ester resin can be imparted with excellent moisture permeability and low Rth, and is excellent in bleed resistance under high temperature and high humidity. An ester resin modifier can be obtained.

  The aliphatic polyester (A) is a glycol (a), an aliphatic dicarboxylic acid (b), a monoalcohol and / or a monocarboxylic acid (c), if necessary, in the presence of an esterification catalyst, for example, 180 It can manufacture by making it esterify within the temperature range of -250 degreeC for 10 to 25 hours. In addition, conditions, such as temperature of esterification reaction and time, are not specifically limited, You may set suitably.

  The esterification catalyst is not particularly limited, for example, a titanium-based catalyst such as tetraisopropyl titanate or tetrabutyl titanate; a tin-based catalyst such as dibutyltin oxide; an organic sulfonic acid-based catalyst such as p-toluenesulfonic acid.

  The amount of the esterification catalyst used may be set as appropriate, but is usually based on 100 parts by mass of the total amount of glycol (a), aliphatic dicarboxylic acid (b), monoalcohol and / or monocarboxylic acid (c). , Preferably in the range of 0.001 to 0.1 parts by mass.

  The number average molecular weight (Mn) of the aliphatic polyester (A) is in the range of 1000 to 3000, preferably in the range of 1200 to 2500, and more preferably in the range of 1300 to 2000. If the Mn of the aliphatic polyester (A) is within such a range, the modifier for cellulose ester resin is excellent in bleed resistance even under high temperature and high humidity, and is less likely to volatilize even under high temperature conditions including a film manufacturing process. It is possible to suppress and improve the contamination of the manufacturing process equipment and work environment.

  Moreover, the dispersity (Mw / Mn) of the aliphatic polyester (A) is preferably 1.0 to 3.0, more preferably 1.0 to 1.5. When the degree of dispersion of the aliphatic polyester (A) is within such a range, a modifier for cellulose ester resin excellent in compatibility with the cellulose ester resin and volatility resistance can be obtained.

  The dispersity is the value of the weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) in terms of polystyrene using tetrahydrofuran (THF) as an eluent (number average molecular weight ( Mn) divided by (Mw / Mn).

  The aliphatic polyester (A) has a hydroxyl value of 0 to 20 mgKOH / g, preferably an acid value of 0 to 1.0 mgKOH / g, and further has a hydroxyl value of 0 to 10, It is more preferable to have an acid value of 0 to 0.5.

  The acid value is derived from a polyester having a carboxyl group at the terminal, which can be generated when the glycol (a) and the aliphatic dicarboxylic acid (b) are reacted. In order to impart excellent moisture permeation resistance to the film and maintain the stability of the cellulose ester resin modifier itself, the terminal of the polyester having a carboxyl group at the end contained in the cellulose ester resin modifier is included. The content is preferably as small as possible. As a guide, the acid value is preferably within the above range.

  The hydroxyl value is derived from a hydroxyl group that is not blocked by the monocarboxylic acid (c) among the hydroxyl groups present at the end of the polyester that can be produced when the glycol (a) and the aliphatic dicarboxylic acid (b) react. Derived from an aliphatic polyester having one hydroxyl group at the end, which can be produced when the glycol (a) reacts with the monocarboxylic acid (c); derived from the unreacted hydroxyl group of the glycol used. And so on. Since the hydroxyl group has a strong affinity for water, the hydroxyl value is preferably within the above range in order to maintain moisture resistance of the resulting film.

  Furthermore, 0-3 mass% is preferable, as for the content rate of the diester body in the said aliphatic polyester (A), 0-2 mass% is more preferable, and 0-1 mass% is still more preferable. If the content of the diester in the aliphatic polyester (A) is within such a range, a modifier for cellulose ester resin that is superior in volatility resistance can be obtained. In addition, content of the diester body in aliphatic polyester (A) can be quantitatively analyzed by analytical methods, such as GPC and LC-MS, for example.

  Although it does not specifically limit as a processing method which can reduce content of the diester body in the said aliphatic polyester (A) to 0-3 mass%, For example, the distillation method by a thin film distillation apparatus, column adsorption method, solvent separation Examples of such methods include extraction methods, and among these methods, the distillation method using a thin-film distillation apparatus is short because there is no harmful effect such as an increase in molecular weight due to the progress of the transesterification reaction during the polyester treatment, decomposition reaction due to thermal history, or coloring. It is preferable because processing in time is possible.

  The modifier for cellulose ester resin of the present invention is composed of the aliphatic polyester (A), and when used in combination with the cellulose ester resin described later, the cellulose ester resin is excellent in compatibility with the cellulose ester resin. It is difficult to bleed, the retardation value (Rth) of the resulting film can be reduced, the optical anisotropy can be reduced, and the moisture permeability resistance of the film can be significantly improved.

  The properties of the modifier for cellulose ester resin of the present invention vary depending on factors such as Mn and composition of the aliphatic polyester (A) constituting the modifier, but are usually liquid, solid, paste, etc. at room temperature. It is.

  Next, a cellulose ester optical film comprising a cellulose ester resin and the cellulose ester resin modifier will be described.

  The cellulose ester optical film of the present invention is a film containing a cellulose ester resin, the cellulose ester resin modifier, and various other additives as required, and the film thickness is used. Generally, the range of 10 to 200 μm is preferable although it varies depending on the application.

  The cellulose ester optical film may have characteristics such as optical anisotropy or optical isotropy. However, when the optical film is used as a protective film for a polarizing plate, it does not inhibit light transmission. It is preferable to use an optically isotropic film.

  The cellulose ester optical film can be used in various applications. As the most effective use, for example, there is a protective film for a polarizing plate that requires optical isotropy of a liquid crystal display device, but it is also used for a support for a protective film for a polarizing plate that requires an optical compensation function. Can do.

  The cellulose ester optical film can be used for liquid crystal cells in various display modes. For example, IPS (In-Plane Switching), TN (Twisted Nematic), VA (Vertically Aligned): Examples include Vertically Aligned) and OCB (Optically Compensatory Bend), and it is particularly preferable to use the IPS mode.

  Examples of the cellulose ester resin contained in the cellulose ester optical film include those in which some or all of the hydroxyl groups of cellulose obtained from cotton linter, wood pulp, kenaf and the like are esterified. Among them, a film obtained by using a 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 the production efficiency of the film can be further improved. ,preferable.

  Examples of the cellulose ester resin include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose nitrate. When the cellulose ester optical film is used as a protective film for a polarizing plate, for example. It is preferable to use cellulose acetate because a film having excellent mechanical properties and transparency can be obtained. These cellulose ester resins may be used alone or in combination of two or more.

  The cellulose acetate preferably has a polymerization degree of 250 to 400, an acetylation degree of 54.0 to 62.5% by mass, and more preferably 58.0 to 62.5% by mass. If the cellulose acetate has a polymerization degree and an acetylation degree within a range, a film having excellent mechanical properties can be obtained. In the present invention, it is more preferable to use so-called cellulose triacetate. In addition, the acetylation degree said by this invention is the mass ratio of the acetic acid produced | generated by saponifying this cellulose acetate with respect to the whole quantity of a cellulose acetate.

  The Mn of the cellulose acetate is preferably in the range of 70,000 to 300,000, more preferably in the range of 80,000 to 200,000. If the Mn of the cellulose acetate is within such a range, a film having excellent mechanical properties can be obtained.

  Moreover, the range of 5-30 mass parts is preferable with respect to 100 mass parts of said cellulose ester resins, and the range of 5-15 mass parts is preferable for the said modifier for cellulose ester resins contained in the said cellulose-ester optical film. More preferred. If the cellulose ester resin modifier is used in such a range, a cellulose ester optical film having excellent moisture resistance, bleed resistance under high temperature and high humidity and low Rth can be obtained.

  The cellulose ester optical film is obtained by melt-kneading a cellulose ester resin composition containing a cellulose ester resin, a modifier for cellulose ester resin, and other various additives as necessary, for example, with an extruder or the like. And it can obtain by shape | molding into a film form using T die | dye.

  In addition to the molding method, the cellulose ester optical film is obtained by, for example, dissolving a resin solution obtained by uniformly dissolving and mixing the cellulose ester resin and the cellulose ester resin modifier in an organic solvent. It can be obtained by molding by a so-called solution casting method (solvent casting method), which is cast on a metal support and dried.

  According to the solution casting method, since the orientation of the cellulose ester resin in the film during molding can be suppressed, the resulting film substantially exhibits optical isotropy. The film showing optical isotropy can be used for an optical material such as a liquid crystal display, and is particularly useful as a protective film for a polarizing plate. Moreover, the film obtained by the said method cannot form an unevenness | corrugation on the surface, and is excellent in surface smoothness.

  The solution casting method generally includes a first step in which the cellulose ester resin and the cellulose ester resin modifier are dissolved in an organic solvent, and the resulting resin solution is cast on a metal support; A second step of forming a film by distilling off the organic solvent contained in the cast resin solution, followed by peeling the film formed on the metal support from the metal support and drying by heating. It consists of a 3rd process.

  Examples of the metal support used in the first step include endless belt-shaped or drum-shaped metal supports, for example, stainless steel with 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 entering the film obtained.

  Although it does not specifically limit as the drying method of the said 2nd process, For example, it includes in the said resin solution cast | casted by applying the wind of the temperature range of 30-50 degreeC to the upper surface and / or lower surface of the said metal support body. The method of evaporating 50-80 mass% of the organic solvent to be formed, and forming a film on the said metal support body is mentioned.

  Next, the third step is a step in which the film formed in the second step is peeled off from the metal support and heat-dried under a temperature condition higher than that in the second step. As the heat drying method, for example, a method in which the temperature is raised stepwise under a temperature condition of 100 to 160 ° C. is preferable because good dimensional stability can be obtained. The organic solvent remaining in the film after the second step can be almost completely removed by heating and drying under the temperature condition.

  In the first to third steps, the organic solvent can be recovered and reused.

  The organic solvent that can be used when the cellulose ester resin and the cellulose ester resin modifier are mixed and dissolved in an organic solvent is not particularly limited as long as they can be dissolved. Is preferably used as a good solvent, for example, an organic halogen compound such as methylene chloride or dioxolane.

  In addition, it is preferable to use a poor solvent such as methanol, ethanol, 2-propanol, n-butanol, cyclohexane, cyclohexanone or the like together with the good solvent in order to improve the production efficiency of the film.

  The mixing ratio of the good solvent and the poor solvent is preferably in the range of good solvent / poor solvent = 75/25 to 95/5 mass ratio.

  10-50 mass% is preferable and, as for the density | concentration of the cellulose ester resin in the said resin solution, 15-35 mass% is more preferable.

  Various additives can be used in the cellulose ester optical film as long as the object of the present invention is not impaired.

  Examples of the additive include other modifiers other than the modifier for cellulose ester resin of the present invention, thermoplastic resins, ultraviolet absorbers, matting agents, deterioration inhibitors (for example, antioxidants, peroxides). Decomposition agents, radical inhibitors, metal deactivators, acid scavengers, etc.) and dyes. These additives can be used together when the cellulose ester resin and the modifier for cellulose ester resin are dissolved and mixed in the organic solvent, and may be used separately. Not limited.

  Examples of other modifiers other than the cellulose ester resin modifier include phosphate esters such as triphenyl phosphate (TPP), tricresyl phosphate, and cresyl diphenyl phosphate, dimethyl phthalate, diethyl phthalate, and dibutyl phthalate. Phthalic acid esters such as di-2-ethylhexyl phthalate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, trimethylolpropane tribenzoate, pentaerythritol tetraacetate, tributyl acetylcitrate and the like can be used.

  Further, as other modifiers other than the modifier for cellulose ester resin, a compound in which the terminal is not blocked with monoalcohol and / or monocarboxylic acid (c) in the aliphatic polyester (A) is also the present invention. Can be used as long as the purpose of the above is not impaired.

  Although it does not specifically limit as said thermoplastic resin, For example, a polyester resin, a polyester ether resin, a polyurethane resin, an epoxy resin, toluenesulfonamide resin etc. are mentioned.

  The ultraviolet absorber is not particularly limited, and examples thereof include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. The ultraviolet absorber is preferably in the range of 0.01 to 2 parts by mass with respect to 100 parts by mass of the cellulose ester.

  The matting agent is not particularly limited, and examples thereof 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.

  The dye is not particularly limited in terms of type and blending amount as long as the object of the present invention is not impaired.

  The cellulose ester optical film of the present invention is excellent in moisture permeation resistance and transparency, and has a sufficiently small optical anisotropy in the thickness direction, so that it can be used for an optical film of a liquid crystal display device, for example. Examples of the optical film of the liquid crystal display device include a protective film for a polarizing plate, a retardation film, a reflective film, a viewing angle improving film, an antiglare film, an antireflective film, an antistatic film, and a color filter. Among these, the protective film for polarizing plates is preferable.

  The film thickness of the cellulose ester optical film is preferably in the range of 20 to 120 μm, more preferably in the range of 30 to 100 μm, and particularly preferably in the range of 30 to 90 μm. When the optical film is used as a protective film for a polarizing plate, a film thickness in the range of 30 to 90 μm is suitable for reducing the thickness of the liquid crystal display device, and is sufficient due to sufficient film strength and changes in wet heat. Excellent performance such as dimensional stability, Rth stability, and moisture permeability resistance can be maintained.

  In particular, since the protective film for polarizing plate of the present invention has a very small retardation value (Rth) of 0 to 15 nm, it is extremely useful as a material excellent in optical isotropy.

  In addition, since the polarizing plate protective film can be adjusted to a desired Rth without causing bleed under high temperature and high humidity, it can be widely used in various liquid crystal display systems depending on the application. Can do.

  The cellulose ester optical film and the protective film for polarizing plate are excellent in moisture permeability, transparency, volatilization resistance, bleed resistance under high temperature and high humidity, etc., and have a very small level of Rth and optical anisotropy. Therefore, it can be used for, for example, an optical film of a liquid crystal display device, a support for a silver halide photographic light-sensitive material, and the like. Although it does not specifically limit with the said optical film, For example, the protective film for polarizing plates, retardation film, a reflecting plate, a viewing angle improvement film, an anti-glare film, a non-reflective film, an antistatic film, a color filter etc. are mentioned. Among the cellulose ester optical films, in addition to the excellent properties as described above, a film having a low Rth is a protective film for a polarizing plate that requires optical isotropy and a polarizing plate having a viewing angle compensation function. It can be used as a support for a protective film.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited only to these examples. In the following, unless otherwise specified, “%” means mass%, and “part” means mass part. The measurement method and evaluation method used in the present invention are as follows.

[Method for creating evaluation film]
A dope solution was prepared by uniformly mixing and stirring a mixed solvent composed of 1 g of aliphatic polyester, 10 g of cellulose triacetate (acetylation degree 61 mass%, polymerization degree 265), 81 g of methylene chloride, and 9 g of methanol. The dope solution is cast on a glass plate to a thickness of 1.0 mm, dried at room temperature for 16 hours, then dried at 50 ° C. for 30 minutes, and further dried at 120 ° C. for 30 minutes. Obtained an 80 μm film. The following evaluation tests were performed using the film.

[Method of evaluating compatibility and bleed resistance]
The film prepared by the above method was cut into a size of 30 mm × 40 mm, and the HAZE value was measured with a turbidimeter (Nippon Denshoku Industries Co., Ltd., NDH 1000). Next, the film was left for 300 hours in a constant temperature and humidity of 85 ° C. and a relative humidity of 90%, and then the HAZE value of the film surface taken out was measured, and the difference in the HAZE value before and after the start of measurement was taken as the compatibility evaluation. Further, the degree of bleeding of the modifier visually was evaluated according to the following criteria.
Evaluation Criteria for Evaluation of Compatibility and Bleed Resistance ○: The difference in the HAZE value is less than 0.5 and there is no bleeding of the plasticizer (bleed).
X: The difference in the HAZE value is 0.5 or more, or there is bleeding of the plasticizer (bleed).

[Evaluation method for volatility]
Using a TG-DTA (differential thermothermal gravimetric simultaneous measurement device, manufactured by Seiko Instruments Inc., DMS6100), the mass reduction rate (mass%) after standing at 140 ° C. for 60 minutes in a nitrogen atmosphere is measured for the modifier sample. The volatilization resistance was evaluated according to the following criteria. In addition, although the target value of volatilization resistance changes a little with uses, in the case of the modifier used for the protective film for polarizing plates of this invention, it is less than 0.20 mass% in mass reduction rate.
Evaluation criteria for volatility ○: Mass reduction rate is less than 0.20% by mass.
X: Mass reduction rate is 0.20 mass% or more.

[Evaluation method of retardation value (Rth)]
Using the film, after conditioning for 12 hours or more in an environment of a temperature of 23 ° C. and a relative humidity of 20%, an automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR) was used in the same environment. Then, the retardation value (Rth) in the thickness direction of the film was measured. The Rth of the cellulose ester optical film of the present invention varies depending on the application, but particularly in the case of a protective film for a polarizing plate, it is characterized by excellent optical isotropy, and the Rth of the protective film for a polarizing plate is 15 nm or less. .

[Method of evaluating moisture permeability]
The moisture permeability of the film was measured under the conditions of a temperature of 40 ° C. and a relative humidity of 90% in accordance with the moisture permeability test method (cup method) of moisture-proof packaging material of JIS Z 0208. Although the moisture permeability of the cellulose ester optical film of the present invention varies depending on its use, in particular, in the case of a protective film for a polarizing plate, the moisture permeability is excellent if it is less than 650 g / m ² · 24 h.

[Example 1]
(1) Preparation of cellulose ester resin modifier (B1) 309 g of 1,2-propylene glycol as glycol (a), 562 g of succinic acid as aliphatic dicarboxylic acid (b), and 2-as monoalcohol (c) 331 g of ethyl-1-hexanol and 0.072 g of tetraisopropyl titanate (TIPT) as an esterification catalyst were charged into a 2-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, and a nitrogen stream Under stirring, the temperature was raised stepwise to 230 ° C., and then the reaction was continued at 230 ° C. to carry out a dehydration condensation reaction for a total of 17 hours. After the reaction, unreacted 1,2-propylene glycol and 2-ethyl-1-hexanol are distilled off under reduced pressure at 200 ° C., and the residue is further treated with a thin film distillation apparatus at 220 ° C. and 0.001 mmHg. To obtain 850 g of the cellulose ester resin modifier (B1) of the present invention consisting of aliphatic polyester (A1) (Mn 1800, acid value 0.19, hydroxyl value 6.0, diester content 0.8%). It was.

(2) Preparation and Evaluation of Cellulose Ester Optical Film (C1) Using Modifier (B1) For 1 g of the cellulose ester resin modifier (B1) obtained above, cellulose triacetate (degree of acetylation 61 mass) %, Polymerization degree 265) 10 g and a mixed solvent consisting of 81 g of methylene chloride and 9 g of methanol were mixed and stirred to prepare a dope solution. The dope solution is cast on a glass plate to a thickness of 1.0 mm, dried at room temperature for 16 hours, then dried at 50 ° C. for 30 minutes, and further dried at 120 ° C. for 30 minutes. Was 80 μm of the cellulose ester optical film (C1) of the present invention. The evaluation results of the modifier (B1) and film (C1) of the present invention are summarized in Table 1. The film (C1) prepared by adding the modifier (B1) of the present invention had a sufficiently low Rth, no bleeding, little volatilization, and excellent moisture resistance.

[Example 2]
(1) Preparation of cellulose ester resin modifier (B2) In the same manner as in Example 1, 252 g of ethylene glycol as glycol (a), 562 g of succinic acid as aliphatic dicarboxylic acid (b), monoalcohol As (c), 331 g of 2-ethyl-1-hexanol and 0.072 g of TIPT as an esterification catalyst were charged into a 2-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, While stirring under a nitrogen stream, the temperature was raised stepwise to 230 ° C., and then the reaction was continued at 230 ° C. for a dehydration condensation reaction for a total of 15 hours. After the reaction, unreacted ethylene glycol and 2-ethyl-1-hexanol are distilled off under reduced pressure at 200 ° C., and the residue is further treated with an thin-film distillation apparatus at 220 ° C. and 0.001 mmHg to obtain an aliphatic group. 780 g of a modifier (B2) for cellulose ester resin of the present invention comprising polyester (A2) (Mn 1450, acid value 0.08, hydroxyl value 4.5, diester content 0.7%) was obtained.

(2) Preparation and evaluation of cellulose ester optical film (C2) using modifier (B2) Using the modifier (B2) for cellulose ester resin obtained above, the same operation as in Example 1 was performed. The cellulose ester optical film (C2) of the present invention having a film thickness of 80 μm was obtained. The evaluation results of the modifier (B2) and film (C2) of the present invention are summarized in Table 1. The film (C2) prepared by adding the modifier (B2) of the present invention had a sufficiently low Rth, no bleeding, little volatilization, and excellent moisture resistance.

Example 3
(1) Preparation of cellulose ester resin modifier (B3) In the same manner as in Example 1, 608 g of 1,2-propylene glycol as glycol (a) and succinic acid as aliphatic dicarboxylic acid (b) 1062 g, 414 g of 1-butanol as the monoalcohol (c), and 0.125 g of TIPT as the esterification catalyst were charged into a three-liter four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, While stirring under a nitrogen stream, the temperature was raised stepwise to 220 ° C., and then the reaction was continued at 220 ° C. for a total of 23 hours of dehydration condensation reaction. After the reaction, unreacted 1,2-propylene glycol and 1-butanol are distilled off under reduced pressure at 200 ° C., and the residue is further treated with a thin film distillation apparatus under the conditions of 220 ° C. and 0.001 mmHg. 1100 g of cellulose ester resin modifier (B3) of the present invention comprising polyester (A3) (Mn 1500, acid value 0.09, hydroxyl value 3.5, diester content 0.5%) was obtained.

(2) Preparation and Evaluation of Cellulose Ester Optical Film (C3) Using Modifier (B3) Using the cellulose ester resin modifier (B3) obtained above, the same operation as in Example 1 was performed. The cellulose ester optical film (C3) of the present invention having a thickness of 80 μm was obtained. The evaluation results of the modifier (B3) and film (C3) of the present invention are summarized in Table 1. The film (C3) prepared by adding the modifier (B3) of the present invention had a sufficiently low Rth, no bleeding, little volatilization, and excellent moisture resistance.

Example 4
(1) Preparation of cellulose ester resin modifier (B4) In the same manner as in Example 1, 620 g of ethylene glycol as glycol (a), 1298 g of succinic acid as aliphatic dicarboxylic acid (b), monoalcohol (C) 6.4 g of 1-butanol and 0.143 g of TIPT as an esterification catalyst were charged into a 3-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, and a nitrogen stream Under stirring, the temperature was raised stepwise to 220 ° C., and then the reaction was continued at 220 ° C. for a total of 21 hours for dehydration condensation reaction. After the reaction, unreacted ethylene glycol and 1-butanol are distilled off at 200 ° C. under reduced pressure, and the residue is further treated with a thin-film distillation apparatus at 220 ° C. and 0.001 mmHg to obtain an aliphatic polyester (A4). 1335 g of the cellulose ester resin modifier (B4) according to the present invention (Mn 1750, acid value 0.11, hydroxyl value 6.6, diester content 0.4%) was obtained.

(2) Production and evaluation of cellulose ester optical film (C4) using modifier (B4) Using the modifier (B4) for cellulose ester resin obtained above, the same operation as in Example 1 was performed. The cellulose ester optical film (C4) of the present invention having a film thickness of 80 μm was obtained. The evaluation results of the modifier (B4) and film (C4) of the present invention are summarized in Table 1. The film (C4) prepared by adding the modifier (B4) of the present invention had a sufficiently low Rth, no bleeding, little volatilization, and excellent moisture resistance.

Example 5
(1) Preparation of cellulose ester resin modifier (B5) In the same manner as in Example 1, 342 g of 1,2-propylene glycol as glycol (a) and adipic acid as aliphatic dicarboxylic acid (b) 803 g, 546 g of 2-ethyl-1-hexanol as the monoalcohol (c), and 0.101 g of TIPT as the esterification catalyst, a three-liter four-necked interior with a thermometer, stirrer and reflux condenser The flask was charged and gradually heated to 230 ° C. while stirring under a nitrogen stream, and then the reaction was continued at 230 ° C. for a total of 16 hours for dehydration condensation. After the reaction, unreacted 1,2-propylene glycol and 2-ethyl-1-hexanol are distilled off under reduced pressure at 200 ° C., and the residue is further treated with a thin film distillation apparatus at 220 ° C. and 0.001 mmHg. By this, 973 g of the modifier (B5) for cellulose ester resin of the present invention consisting of aliphatic polyester (A5) (Mn 1550, acid value 0.15, hydroxyl value 12.1, diester content 0.8%) was obtained. It was.

(2) Preparation and Evaluation of Cellulose Ester Optical Film (C5) Using Modifier (B5) Using the modifier (B5) for cellulose ester resin obtained above, the same operation as in Example 1 was performed. A cellulose ester optical film (C5) of the present invention having a thickness of 80 μm was obtained. The evaluation results of the modifier (B5) and film (C5) of the present invention are summarized in Table 1. The film (C5) prepared by adding the modifier (B5) of the present invention had a sufficiently low Rth, no bleeding, little volatilization, and excellent moisture resistance.

Example 6
(1) Preparation of cellulose ester resin modifier (B6) In the same manner as in Example 1, 944 g of ethylene glycol as glycol (a), 944 g of succinic acid as aliphatic dicarboxylic acid (b), monocarboxylic acid 806 g of 2-ethylhexanoic acid as the acid (c) and 0.161 g of TIPT as the esterification catalyst were charged into a 5-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, While stirring under an air stream, the temperature was raised stepwise to 230 ° C., and then the reaction was continued at 230 ° C. for a dehydration condensation reaction for a total of 22 hours. After the reaction, unreacted 2-ethylhexanoic acid is distilled off at 200 ° C. under reduced pressure, and the residue is further treated with a thin-film distillation apparatus at 220 ° C. and 0.001 mmHg to obtain an aliphatic polyester (A6). 1480 g of the cellulose ester resin modifier (B6) according to the present invention (Mn 1500, acid value 0.21, hydroxyl value 9.8, diester content 0.6%) was obtained.

(2) Preparation and evaluation of cellulose ester optical film (C6) using modifier (B6) Using the modifier (B6) for cellulose ester resin obtained above, the same operation as in Example 1 was performed. A cellulose ester optical film (C6) of the present invention having a thickness of 80 μm was obtained. The evaluation results of the modifier (B6) and film (C6) of the present invention are summarized in Table 1. The film (C6) prepared by adding the modifier (B6) of the present invention had a sufficiently low Rth, no bleeding, little volatilization, and excellent moisture resistance.

[Comparative Example 1]
(1) Preparation of modifier (B7) and creation and evaluation of film (C7) The same operation as in Example 1 except that triphenyl phosphate (TPP) was used as the modifier (B7) for cellulose ester resin. Thus, a film (C7) was obtained. The evaluation results of the modifier (B7) and the film (C7) are shown in Table 2. However, the Rth was high, the optical anisotropy was large, and the compatibility, volatilization resistance and moisture permeability were inferior.

[Comparative Example 2]
(1) Preparation of modifier (B8) and creation and evaluation of film (C8) The same operation as in Example 1 except that tributyl acetyl citrate was used as the modifier for cellulose ester resin (B8). A film (C8) was obtained. The evaluation results of the modifier (B8) and the film (C8) are shown in Table 2, but were inferior in compatibility, volatility resistance and moisture permeability resistance.

[Comparative Example 3]
(1) Preparation of modifier (B9) and creation and evaluation of film (C9) In the same manner as in Example 1, except that triphenylmethanol was used as the modifier for cellulose ester resin (B9). A film (C9) was obtained. The evaluation results of the modifier (B9) and the film (C9) are shown in Table 2, but were inferior in compatibility and volatility resistance.

[Comparative Example 4]
(1) Preparation of modifier (B10) and creation and evaluation of film (C10) In the same manner as in Example 1 except that 1,6-hexanediol was used instead of 1,2-propylene glycol. A cellulose ester resin modifier (B10) consisting of aliphatic polyester (A10) (Mn 1300, acid value 0.25, hydroxyl value 11.0, diester content 4.6%) was prepared and used Thus, a film (C10) was obtained. The evaluation results of the modifier (B10) and the film (C10) are shown in Table 3, but were inferior in moisture permeability.

[Comparative Example 5]
(1) Preparation of modifier (B11) and production and evaluation of film (C11) Aliphatic polyester (A11) was prepared in the same manner as in Example 1 except that sebacic acid was used instead of succinic acid. A cellulose ester resin modifier (B11) consisting of (Mn 1500, acid value 0.28, hydroxyl value 9.8, diester content 3.4%) was prepared, and a film (C11) was obtained using this. It was. The evaluation results of the aliphatic polyester (A11), the modifier (B11), and the film (C11) are shown in Table 3, but were inferior in moisture resistance.

[Comparative Example 6]
(1) Preparation of modifier (B12) and production and evaluation of film (C12) The same method as in Example 1 except that the composition was the same as in Example 1 and the number average molecular weight was increased to 4000. A cellulose ester resin modifier (B12) comprising an aliphatic polyester (A12) (Mn 4000, acid value 0.35, hydroxyl value 12.0, diester content 1.5%) was prepared, To obtain a film (C12). The evaluation results of the aliphatic polyester (A12), the modifier (B12), and the film (C12) are shown in Table 3, but were inferior in compatibility and moisture permeability.

[Comparative Example 7]
(1) Preparation of cellulose ester resin modifier (B13) In the same manner as in Example 1, 486 g of 1,2-propylene glycol as glycol (a) and succinic acid as aliphatic dicarboxylic acid (b) 637 g, 912 g of dodecanoic acid as monocarboxylic acid (c), and 0.122 g of TIPT as an esterification catalyst were charged into a three-liter flask having an internal volume of 3 liters equipped with a thermometer, a stirrer and a reflux condenser. While stirring under a nitrogen stream, the temperature was raised stepwise to 230 ° C., and then the reaction was continued at 230 ° C. for a dehydration condensation reaction for a total of 26 hours. After the reaction, the unreacted dodecanoic acid is distilled off at 220 ° C. under reduced pressure to obtain an aliphatic polyester (A13) (Mn 1300, acid value 0.45, hydroxyl value 13.5, diester content 4.4%). 1012 g of the resulting cellulose ester resin modifier (B13) was obtained.

(2) Production and Evaluation of Film (C13) Cellulose ester optical film (C13) having a film thickness of 80 μm by the same operation as in Example 1 using the cellulose ester resin modifier (B13) obtained above. ) The evaluation results of the aliphatic polyester (A13), the modifier (B13), and the film (C13) are shown in Table 3, but were inferior in compatibility and moisture permeability.

Abbreviations in Tables 1 to 3 are as follows.
PG; 1,2-propylene glycol EG; ethylene glycol HD; 1,6-hexanediol SuA; succinic acid [structure formula: HOOC (CH ₂ ) ₂ COOH]
AdA: adipic acid [Structural Formula: HOOC (CH ₂ ) ₄ COOH]
SbA: Sebacic acid, [Structural formula: HOOC (CH ₂ ) ₈ COOH]
C4OH; 1-butanol C8OH; 2-ethyl-1-hexanol C7COOH; 2-ethylhexanoic acid C11COOH; dodecanoic acid

  The modifier for cellulose ester resin of the present invention is compatible with cellulose ester resin, excellent in bleed resistance under high temperature and high humidity, and volatile resistance, and excellent in cellulose ester optical film formed by using cellulose ester resin in combination. Moisture resistance can be imparted. Moreover, the protective film for polarizing plates of the present invention obtained using the modifier and the cellulose ester resin is, for example, a protective film for polarizing plates, a retardation plate, a reflective plate, a viewing angle improving film, an antiglare film, and an antireflective film. Although it can be used in a wide range of films, antistatic films, color filters, etc., it is particularly useful as a protective film for polarizing plates because of its small optical anisotropy in the thickness direction of the film.

Claims (8)

Obtained by reacting glycol (a) having 2 to 4 carbon atoms, aliphatic dicarboxylic acid (b) having 2 to 6 carbon atoms, monoalcohol and / or monocarboxylic acid (c) having 4 to 9 carbon atoms, A modifier for a cellulose ester resin comprising an aliphatic polyester (A) having a number average molecular weight of 1000 to 3000. The aliphatic dicarboxylic acid (b) having 2 to 6 carbon atoms is succinic acid and / or adipic acid, and the monoalcohol and / or monocarboxylic acid (c) having 4 to 9 carbon atoms is 1-butanol 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, isononyl alcohol, butanoic acid, 2-ethylhexyl acid, and nonanoic acid. The cellulose ester resin modifier according to claim 1. The modifier for a cellulose ester resin according to claim 1 or 2, wherein the aliphatic polyester (A) has a hydroxyl value of 0 to 20 mgKOH / g and an acid value of 0 to 1.0 mgKOH / g. The modifier for a cellulose ester resin according to any one of claims 1 to 3, wherein the content of the diester in the aliphatic polyester (A) is 0 to 2% by mass. A cellulose ester optical film comprising the cellulose ester resin modifier according to any one of claims 1 to 4 and a cellulose ester resin. The cellulose ester optical film according to claim 5, comprising 5 to 30 parts by mass of the modifier for cellulose ester resin with respect to 100 parts by mass of the cellulose ester resin. A resin solution obtained by dissolving the cellulose ester resin modifier and cellulose ester resin according to any one of claims 1 to 4 in an organic solvent is cast on a metal support, and then the organic A protective film for a polarizing plate obtained by distilling off the solvent and drying. The protective film for a polarizing plate according to claim 7, wherein the retardation value in the thickness direction measured using an automatic birefringence meter of a film having a thickness of 80 μm is in the range of 0 to 15 nm.