Cellulose resins and optical films using the same

Abstract

To provide an optical film that comprises a resin composition having excellent phase difference characteristics and wavelength dispersion characteristics, the film being free of whitening at high temperatures and high humidity.SOLUTION: A cellulose resin has a salt content of 0.03% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a cellulose resin and an optical film using the same. More specifically, it relates to an optical film for liquid crystal displays and organic EL displays that has excellent phase difference characteristics, wavelength dispersion characteristics, and resistance to moisture and heat. [Background technology]

[0002] In recent years, the demands for display performance and durability in various displays have increased, and challenges have arisen in improving response speed and compensating for a wider viewing angle, such as contrast and color balance when viewing the displayed image from an oblique angle. To solve these problems, VA (Vertical Alignment), OCB (Optical Compensated Bend), and IPS (In-Plane Switching) display elements have been developed, and optical compensation film materials with various phase difference characteristics are required according to each liquid crystal method.

[0003] Conventional optical films include stretched films made from cellulose resins, polycarbonates, and cyclic polyolefins. Stretched films made from cellulose resins, particularly cellulose acylates, are widely used as optical compensation films for liquid crystal display devices due to their transparency, toughness, and the moisture permeability and low wavelength dispersion required for the process.

[0004] However, optical films made of cellulose resin have several challenges. For example, cellulose resin films can be processed into optical compensation films with phase difference values ​​suited to various displays by adjusting the stretching conditions. However, the three-dimensional refractive index of a film obtained by uniaxial or biaxial stretching of a cellulose resin film is ny≧nx>nz. To manufacture optical compensation films with other three-dimensional refractive indices, such as ny>nz>nx or ny=nz>nx, a special stretching method is required, such as bonding a heat-shrinkable film to one or both sides of the film and then heat-stretching the laminate to apply a shrinking force in the thickness direction of the polymer film. Controlling the refractive index (phase difference value) is also difficult (see, for example, Patent Documents 1-3). Here, nx is the refractive index in the phase-advancing axis direction (the direction with the smallest refractive index) within the film plane, ny is the refractive index in the phase-slow axis direction (the direction with the largest refractive index) within the film plane, and nz is the refractive index outside the film plane (in the thickness direction).

[0005] Furthermore, cellulose resin films are generally manufactured by solvent casting, but cellulose resin films formed by casting have an out-of-plane phase difference (Rth) of about 40 nm in the film thickness direction, which causes problems such as color shift in IPS mode liquid crystal displays and organic EL displays. Here, the out-of-plane phase difference (Rth) is the phase difference value shown by the following formula.

[0006] Rth = [(nx + ny) / 2 - nz] × d (In the formula, nx represents the refractive index in the phase-advancing axis direction within the film plane, ny represents the refractive index in the phase-lagging axis direction within the film plane, nz represents the refractive index outside the film plane, and d represents the film thickness.) Furthermore, a phase difference film (optical compensation film) made of a fumarate ester resin has been proposed (see, for example, Patent Document 4).

[0007] Furthermore, the three-dimensional refractive index of a stretched film made of fumarate ester resin is nz > ny > nx, and in order to obtain an optical film exhibiting the above three-dimensional refractive index, lamination with other optical films or the like is necessary.

[0008] Therefore, resin compositions and optical films using the same have been proposed as optical compensation films exhibiting the above-mentioned three-dimensional refractive index (see, for example, Patent Documents 5 to 7).

[0009] In general, optical films are used as anti-reflective layers for reflective liquid crystal displays, touch panels, and organic EL displays. For these applications, optical compensation films (hereinafter referred to as "reverse wavelength dispersion films") with particularly large phase differences in the longer wavelength range are required. For example, when a reverse wavelength dispersion film is used as the optical film for a circular polarizer for organic EL displays, the phase difference is preferably about 1 / 4 of the measurement wavelength λ, and the ratio of the phase difference at 450 nm to the phase difference at 550 nm, Re(450) / Re(550), is preferably close to 0.81. Furthermore, considering the trend towards thinner display devices, the reverse wavelength dispersion films used must also be thin. Various optical films have been developed to meet these required characteristics.

[0010] A phase difference film containing a cellulose resin and a fumarate ester polymer has been proposed as a phase difference film (optical compensation film) that exhibits the above three-dimensional refractive index and is used as an inverse wavelength dispersion film (see, for example, Patent Document 8). However, the phase difference film described in Patent Document 8 has problems with the durability of the resulting film in high temperature and high humidity environments, and there is a need for an optical film that is more stable under higher temperature and high humidity conditions.

[0011] Furthermore, cellulose resins are manufactured using pulp and cotton linters as raw materials, and it is known that cellulose fibers derived from the raw materials and impurities during the manufacturing process can affect the transparency and other qualities of the film (see, for example, Patent Document 9). [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 2818983 [Patent Document 2] Japanese Patent Application Laid-Open No. 5-297223 [Patent Document 3] Japanese Patent Application Laid-Open No. 5-323120 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-64817 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-28741 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-125609 [Patent Document 7] Japanese Patent Application Laid-Open No. 2014-125610 [Patent Document 8] Japanese Patent Application Laid-Open No. 2015-157928 [Patent Document 9] Japanese Patent Application Laid-Open No. 2002-40244 [Summary of the Invention] [Problems to be Solved by the Invention]

[0013] The present invention has been made in view of the above problems, and an object thereof is to provide a resin that has excellent retardation characteristics and wavelength dispersion characteristics when formed into a film, and that does not turn white (the increase in haze after a heat and humidity resistance test is small) even under high temperature and high humidity conditions when the resin is formed into a film. [Means for Solving the Problems]

[0014] As a result of intensive studies to solve the above problems, the present inventors have found that when a cellulose-based resin with a low salt content is formed into a film, whitening can be suppressed even under high temperature and high humidity conditions, and have thus found a solution to the above problems and completed the present invention.

[0015] That is, the present invention relates to a cellulose-based resin having a salt content of 0.03% or less. [Effects of the Invention]

[0016] The resin and film using the present invention can suppress whitening even under high temperature and high humidity conditions, making them suitable for use in polarizing plates, liquid crystal displays, organic EL displays, and the like, and exhibiting excellent display performance and high stability under high temperature and high humidity conditions. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows the relationship between the film density and molecular weight of ethylcellulose. [Modes for carrying out the invention]

[0018] The details of the present invention will be described below.

[0019] The cellulose resin of the present invention has a salt content of 0.03% or less, preferably 0.020% or less, and particularly preferably 0.015% or less.

[0020] The cellulose-based resin of the present invention preferably has a constituent unit represented by the following formula (1).

[0021] [ka]

[0022] (In the formula, R1, R2, and R3 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms or an acyl group.) Examples of cellulose-based resins of the present invention include cellulose ethers and cellulose ether esters. The cellulose-based resin of the present invention may be one of these cellulose-based resins, or it may be a composition containing two or more of these cellulose-based resins.

[0023] The cellulose resin of the present invention exhibits excellent resistance to moisture and heat, as well as superior mechanical properties and moldability during film formation. Therefore, the weight-average molecular weight (Mw) on a standard polystyrene basis, obtained from the elution curve measured by gel permeation chromatography (GPC), is 5 × 10⁻⁶.3 ~3×10 5 Preferably, 1 × 10 4 ~2.5×10 5 This is particularly preferable. Regarding the molecular weight dependence of whitening after the moist heat test, there is a tendency for density to decrease with increasing molecular weight, and it is presumed that the free volume in the low-temperature range increases and the cohesive force decreases with increasing molecular weight, thereby promoting whitening after the moist heat test with higher molecular weight. Figure 1 shows the relationship between the film density and molecular weight of ethyl cellulose.

[0024] The cellulose-based resin of the present invention is preferred because it exhibits excellent compatibility with ester-based resins that show negative birefringence (described later), has a large in-plane phase difference Re, and has excellent stretchability.

[0025] The following describes preferred cellulose ethers as cellulose-based resins of the present invention.

[0026] Cellulose ethers are polymers in which β-glucose units are polymerized in a linear chain, and are polymers in which some or all of the hydroxyl groups at the 2nd, 3rd, and 6th positions of the glucose units are etherified. Examples of cellulose ethers of the present invention include alkylcellulose such as methylcellulose, ethylcellulose, and propylcellulose; hydroxyalkylcellulose such as hydroxyethylcellulose and hydroxypropylcellulose; aralkylcellulose such as benzylcellulose and tritylcellulose; cyanoalkylcellulose such as cyanoethylcellulose; carboxyalkylcellulose such as carboxymethylcellulose and carboxyethylcellulose; carboxyalkylalkylcellulose such as carboxymethylmethylcellulose and carboxymethylethylcellulose; and aminoalkylcellulose such as aminoethylcellulose.

[0027] The degree of substitution (degree of etherification) of the hydroxyl groups of cellulose in the cellulose ether, via the oxygen atom, refers to the proportion of hydroxyl groups of cellulose that are etherified at positions 2, 3, and 6, respectively (100% etherification corresponds to a degree of substitution of 3). From the viewpoint of solubility, compatibility, and stretchability, the total degree of substitution DS of the ether group is preferably 1.5 to 3.0 (1.5 ≤ DS ≤ 3.0), and more preferably 1.8 to 2.8.

[0028] When the cellulosic resin of the present invention is a cellulose ether, R1 to R3 in formula (1) are hydrogen atoms or hydrocarbon groups having 1 to 12 carbon atoms. From the viewpoint of solubility and compatibility, it is preferable that the cellulose ether has hydrocarbon groups having 1 to 12 carbon atoms. Examples of hydrocarbon groups having 1 to 12 carbon atoms include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decanyl group, dodecanyl group, isobutyl group, t-butyl group, cyclohexyl group, phenonyl group, benzyl group, naphthyl group, etc. Among these, from the viewpoint of solubility and compatibility, methyl group, ethyl group, propyl group, butyl group, and pentyl group, which are alkyl groups having 1 to 5 carbon atoms, are preferred. The cellulose polymer used in the present invention may have only one type of ether group, or it may have two or more types of ether groups. In addition, it may also have ester groups in addition to ether groups.

[0029] Cellulose ethers are generally synthesized by alkaline decomposing cellulose pulp obtained from wood or cotton, and then etherifying the resulting cellulose pulp. Suitable alkalis include hydroxides of alkali metals such as lithium, potassium, and sodium, as well as ammonia. These alkalis are generally used as aqueous solutions. The alkaline cellulose pulp is then etherified by contact with an etherifying agent, which is used depending on the type of cellulose ether. Examples of etherifying agents include alkyl halides such as methyl chloride and ethyl chloride; aralkyl halides such as benzyl chloride and trityl chloride; halocarboxylic acids such as monochloroacetic acid and monochloropropionic acid; and alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide. These etherifying agents can be used individually or in combination of two or more.

[0030] Generally, after the etherification reaction is complete, cellulose ether is treated with hydrogen chloride, hydrogen bromide, hydrochloric acid, or sulfuric acid to adjust viscosity and neutralize the reaction. Since the cellulose ether obtained after this reaction and neutralization process contains a large amount of by-product salts, the resin is washed with water or the like after the reaction to reduce the amount of salts contained in the resin and obtain cellulose ether.

[0031] For example, if sodium hydroxide is used as the alkali for producing ethylcellulose, ethyl chloride as an etherifying agent, and hydrogen chloride is used for viscosity adjustment or neutralization, the by-product sodium chloride is included.

[0032] The cellulose-based resin of the present invention is a polymer in which β-glucose units are polymerized in a linear chain, and may also be a polymer in which some or all of the hydroxyl groups at positions 2, 3, and 6 of the glucose units are esterified with acyl groups. Examples include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, and cellulose acetate propionate.

[0033] The degree of acylation refers to the percentage of esterification of the hydroxyl groups of cellulose at positions 2, 3, and 6 (100% esterification corresponds to a degree of substitution of 3), and the total degree of substitution DS of the acyl group is preferably 1.5 ≤ DS ≤ 3.0, and more preferably 1.8 to 2.8. Cellulose resins preferably have acyl groups having 2 to 12 carbon atoms as substituents. Examples of acyl groups having 2 to 12 carbon atoms include acetyl, propionyl, butyryl, heptanol, hexanoyl, octanoyl, decanoyl, dodecanoyl, isobutanoyl, t-butyryl, cyclohexanecarbonyl, benzoyl, naphthylcarbonyl, and cinnamoyl groups. Among these, acetyl, propionyl, butyryl, and pentyl groups, which are acyl groups having 2 to 5 carbon atoms, are particularly preferred. The cellulose resin used in this invention may contain only one type of acyl group, or two or more types of acyl groups may be used.

[0034] In the acylation of cellulosic resins, when acid anhydrides or acid chlorides are used as acyling agents, organic acids such as acetic acid and methylene chloride are used as the reaction solvent. As a catalyst, when the acyling agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acyling agent is an acid chloride (e.g., propionyl chloride), a basic compound is preferably used. The most common industrial synthesis method for mixed fatty acid esters of cellulose is to acylate cellulose with a mixed organic acid component containing fatty acids (acetic acid, propionic acid, butyric acid, valeric acid, etc.) or their acid anhydrides that correspond to the acetyl group and other acyl groups.

[0035] The general method for producing cellulose esters involves first crushing cellulose material such as pulp, followed by a pretreatment step in which organic acids such as acetic acid, propionic acid, and butyric acid (with or without a sulfuric acid catalyst) are added. Then, acylation is carried out by adding organic acids such as acetic acid, propionic acid, and butyric acid, acetic anhydride, and a sulfuric acid catalyst. After the acylation reaction, a neutralizing agent such as an aqueous magnesium acetate solution is added to induce hydrolysis. Subsequently, a large amount of water, a dilute aqueous acetic acid solution, etc., is added to precipitate the cellulose ester, which is then washed and dried to obtain the cellulose ester.

[0036] In the present invention, the term "salt" is not particularly limited as long as it is an ionic substance in which anions and cations are electrically bonded and have a neutral effective charge. Examples include metal salts such as sodium, potassium, and cesium salts; alkaline earth metal salts such as calcium and magnesium salts; organic amine salts such as triethylamine, guanidine, and N-substituted guanidine salts, acetamidine and N-substituted acetamidine, pyridine, picoline, ethanolamine, triethanolamine, dicyclohexylamine, and N,N'-dibenzylethylenediamine salts and imidazole salts; inorganic acid salts such as hydrochloride, hydrobromide, sulfate, and phosphate; organic acid salts such as trifluoroacetate and maleate; sulfonates such as methanesulfonate, ethanesulfonate, benzenesulfonate, p-toluenesulfonate, camphorsulfonate, and naphthalenesulfonate; amino acid salts such as arginate, alanate, aspartate, and glutamate; and hydrocarbon salts such as glucuronate and galacturonate. Examples of sodium salts, ammonium salts, and potassium salts include sodium chloride, ammonium chloride, and potassium chloride; sodium acetate, ammonium acetate, and potassium acetate; sodium butyrate, ammonium butyrate, and potassium butyrate; sodium citrate, ammonium citrate, and potassium citrate; sodium phosphate, ammonium phosphate, and potassium phosphate; sodium fluoride, ammonium fluoride, and potassium fluoride; sodium bromide, ammonium bromide, and potassium bromide; and sodium iodide, ammonium iodide, and potassium iodide. The salt is preferably one of the group consisting of sodium chloride, ammonium chloride, potassium chloride, sodium acetate, ammonium acetate, potassium acetate, sodium butyrate, and potassium butyrate. These salts may be present individually or in groups of two or more, as long as their total amount in the cellulosic resin is less than or equal to a predetermined amount.

[0037] Next, a resin composition, which is one aspect of the present invention, will be described.

[0038] The present invention relates to a composition comprising 50 to 99% by weight of the cellulose-based resin and 1 to 50% by weight of an ester-based resin exhibiting negative birefringence having cinnamic acid ester residue units represented by the following formula (2), fumarate ester residue units represented by the following formula (3), and residue units represented by the following formula (4). Preferably, the composition comprises 60 to 90% by weight of the cellulose-based resin and 10 to 40% by weight of an ester-based resin exhibiting negative birefringence having cinnamic acid ester residue units represented by the following formula (2), fumarate ester residue units represented by the following formula (3), and residue units represented by the following formula (4).

[0039] [ka]

[0040] (In the formula, R4 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. R5 to R9 represent one of the groups consisting of a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, a phenyl group, a thiol group, an amide group, an amino group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. Y represents one of the groups consisting of a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, or a thiol group.)

[0041] [ka]

[0042] (In the formula, R 10、 R 11 Each of these independently represents either a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.

[0043] [ka]

[0044] (In the formula, R 12This represents a five-membered heterocyclic residue or a six-membered heterocyclic residue containing one or more nitrogen or oxygen atoms as heteroatoms (the five-membered heterocyclic residue and the six-membered heterocyclic residue may form a fused ring structure with other cyclic structures). The ester resin exhibits negative birefringence. This is due to the presence of a residue unit represented by one of the group consisting of formulas (2), (3), and (4).

[0045] Here, the positive and negative signs of birefringence are defined as follows.

[0046] Negative birefringence occurs when the stretching direction is aligned with the phase-advancing axis, while positive birefringence occurs when the direction perpendicular to the stretching direction is aligned with the phase-advancing axis. In other words, resins that exhibit positive birefringence when uniaxially stretched have a smaller refractive index in the direction perpendicular to the stretching axis (phase-advancing axis: direction perpendicular to the stretching direction), while resins that exhibit negative birefringence when uniaxially stretched have a smaller refractive index in the direction of the stretching axis (phase-advancing axis: direction of stretching). Furthermore, the high likelihood of negative birefringence in ester resins allows for the thinning of films.

[0047] In formula (2), R4 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. Examples of alkyl groups having 1 to 12 carbon atoms include methyl, ethyl, isopropyl, n-propyl, n-butyl, s-butyl, t-butyl, and ethylhexyl groups.

[0048] In formula (2), R5 to R9 each independently represent one of the group consisting of a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, a phenyl group, a thiol group, an amino group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

[0049] In formula (2), Y represents one of the groups consisting of a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, or a thiol group.

[0050] Specific residue units represented by formula (2) include, for example, cinnamic acid ester residue units such as methyl cinnamate residue, ethyl cinnamate residue, isopropyl cinnamate residue, n-propyl cinnamate residue, n-butyl cinnamate residue, sec-butyl cinnamate residue, tert-butyl cinnamate residue, and 2-ethylhexyl cinnamate residue; cinnamic acid residue units; 4-methyl methoxycinnamate residue, 4-ethyl methoxycinnamate residue, 4-isopropyl methoxycinnamate residue, 4-n-propyl methoxycinnamate residue, 4-n-butyl methoxycinnamate residue, and 4-methyl methoxycinnamate residue. sec-butyl ethyl cinnamate residue, tert-butyl 4-methoxycinnamate residue, 2-ethylhexyl 4-methoxycinnamate residue, methyl 4-ethoxycinnamate residue, ethyl 4-ethoxycinnamate residue, isopropyl 4-ethoxycinnamate residue, n-propyl 4-ethoxycinnamate residue, n-butyl 4-ethoxycinnamate residue, sec-butyl 4-ethoxycinnamate residue, tert-butyl 4-ethoxycinnamate residue, 2-ethylhexyl 4-ethoxycinnamate residue, methyl 4-isopropoxycinnamate residue, ethyl 4-isopropoxycinnamate residue, 4- Isopropyl sopropoxycinnamate residue, n-propyl 4-isopropoxycinnamate residue, n-butyl 4-isopropoxycinnamate residue, sec-butyl 4-isopropoxycinnamate residue, tert-butyl 4-isopropoxycinnamate residue, 2-ethylhexyl 4-isopropoxycinnamate residue, methyl 4-n-propoxycinnamate residue, ethyl 4-n-propoxycinnamate residue, isopropyl 4-n-propoxycinnamate residue, n-propyl 4-n-propoxycinnamate residue, n-butyl 4-n-propoxycinnamate residue, 4-n-propoxycinnamate sec-butyl cinnamate residue, tert-butyl 4-n-propoxycinnamate residue, 2-ethylhexyl 4-n-propoxycinnamate residue, methyl 4-n-butoxycinnamate residue, ethyl 4-n-butoxycinnamate residue, isopropyl 4-n-butoxycinnamate residue, n-propyl 4-n-butoxycinnamate residue, n-butyl 4-n-butoxycinnamate residue, sec-butyl 4-n-butoxycinnamate residue, tert-butyl 4-n-butoxycinnamate residue, 2-ethylhexyl 4-n-butoxycinnamate residue, methyl 4-sec-butoxycinnamate residue,4-sec-ethyl butoxycinnamate residue, 4-sec-isopropyl butoxycinnamate residue, 4-sec-n-propyl butoxycinnamate residue, 4-sec-n-butyl butoxycinnamate residue, 4-sec-sec-butyl butoxycinnamate residue, 4-sec-tert-butyl butoxycinnamate residue, 4-sec-2-ethylhexyl butoxycinnamate residue, 4-tert-methyl butoxycinnamate residue, 4-tert-ethyl butoxycinnamate residue, 4-tert-isopropyl butoxycinnamate residue, 4-tert-n-propyl butoxycinnamate 4-alkoxycinnamic acid ester residue units such as pyrus residues, 4-tert-butoxycinnamate n-butyl residues, 4-tert-butoxycinnamate sec-butyl residues, 4-tert-butoxycinnamate tert-butyl residues, 4-tert-butoxycinnamate 2-ethylhexyl residues; 4-alkoxycinnamic acid residue units; 3-methoxycinnamate methyl residues, 3-methoxycinnamate ethyl residues, 3-methoxycinnamate isopropyl residues, 3-methoxycinnamate n-propyl residues, 3-methoxycinnamate n-butyl residues, 3-methoxycinnamate sec-butyl residues Base, 3-methoxycinnamate tert-butyl residue, 3-methoxycinnamate 2-ethylhexyl residue, 3-ethoxycinnamate methyl residue, 3-ethoxycinnamate ethyl residue, 3-ethoxycinnamate isopropyl residue, 3-ethoxycinnamate n-propyl residue, 3-ethoxycinnamate n-butyl residue, 3-ethoxycinnamate sec-butyl residue, 3-ethoxycinnamate tert-butyl residue, 3-ethoxycinnamate 2-ethylhexyl residue, 3-isopropoxycinnamate methyl residue, 3-isopropoxycinnamate ethyl residue, 3-isopropoxycinnamate Sopropyl residue, n-propyl 3-isopropoxycinnamate residue, n-butyl 3-isopropoxycinnamate residue, sec-butyl 3-isopropoxycinnamate residue, tert-butyl 3-isopropoxycinnamate residue, 2-ethylhexyl 3-isopropoxycinnamate residue, methyl 3-n-propoxycinnamate residue, ethyl 3-n-propoxycinnamate residue, isopropyl 3-n-propoxycinnamate residue, n-propyl 3-n-propoxycinnamate residue, n-butyl 3-n-propoxycinnamate residue, sec-butyl 3-n-propoxycinnamate residue,3-n-propoxycinnamate tert-butyl residue, 3-n-propoxycinnamate 2-ethylhexyl residue, 3-n-butoxycinnamate methyl residue, 3-n-butoxycinnamate ethyl residue, 3-n-butoxycinnamate isopropyl residue, 3-n-butoxycinnamate n-propyl residue, 3-n-butoxycinnamate n-butyl residue, 3-n-butoxycinnamate sec-butyl residue, 3-n-butoxycinnamate tert-butyl residue, 3-n-butoxycinnamate 2-ethylhexyl residue, 3-sec-butoxycinnamate methyl residue, 3-sec-butoxy Ethyl cinnamate residue, 3-sec-isopropyl butoxycinnamate residue, 3-sec-n-propyl butoxycinnamate residue, 3-sec-n-butyl butoxycinnamate residue, 3-sec-sec-butyl butoxycinnamate residue, 3-sec-tert-butyl butoxycinnamate residue, 3-sec-3-ethylhexyl butoxycinnamate residue, 3-tert-methyl butoxycinnamate residue, 3-tert-ethyl butoxycinnamate residue, 3-tert-tert-isopropyl butoxycinnamate residue, 3-tert-n-propyl butoxycinnamate residue, 3-ter 3-alkoxycinnamic acid residue ester units such as n-butyl t-butoxycinnamate residue, sec-butyl 3-tert-butoxycinnamate residue, tert-butyl 3-tert-butoxycinnamate residue, 2-ethylhexyl 3-tert-butoxycinnamate residue; 3-alkoxycinnamic acid residue units; methyl 2-methoxycinnamate residue, ethyl 2-methoxycinnamate residue, isopropyl 2-methoxycinnamate residue, n-propyl 2-methoxycinnamate residue, n-butyl 2-methoxycinnamate residue, sec-butyl 2-methoxycinnamate residue, 2-methoxy tert-butyl cinnamate residue, 2-ethylhexyl methoxycinnamate residue, methyl 2-ethoxycinnamate residue, ethyl 2-ethoxycinnamate residue, isopropyl 2-ethoxycinnamate residue, n-propyl 2-ethoxycinnamate residue, n-butyl 2-ethoxycinnamate residue, sec-butyl 2-ethoxycinnamate residue, tert-butyl 2-ethoxycinnamate residue, 2-ethylhexyl 2-ethoxycinnamate residue, methyl 2-isopropoxycinnamate residue, ethyl 2-isopropoxycinnamate residue, isopropyl 2-isopropoxycinnamate residue,n-propyl residue of 2-isopropoxycinnamate, n-butyl residue of 2-isopropoxycinnamate, sec-butyl residue of 2-isopropoxycinnamate, tert-butyl residue of 2-isopropoxycinnamate, ethylhexyl residue of 2-isopropoxycinnamate, methyl residue of 2-n-propoxycinnamate, ethyl residue of 2-n-propoxycinnamate, isopropyl residue of 2-n-propoxycinnamate, n-propyl residue of 2-n-propoxycinnamate, n-butyl residue of 2-n-propoxycinnamate, sec-butyl residue of 2-n-propoxycinnamate, 2-n-propoxy tert-butyl oxycinnamate residue, 2-n-ethylhexyl propoxycinnamate residue, 2-n-methyl butoxycinnamate residue, 2-n-ethyl butoxycinnamate residue, 2-n-isopropyl butoxycinnamate residue, 2-n-n-propyl butoxycinnamate residue, 2-n-n-butyl butoxycinnamate residue, 2-n-sec-butyl butoxycinnamate residue, 2-n-tert-butyl butoxycinnamate residue, 2-n-ethylhexyl butoxycinnamate residue, 2-sec-methyl butoxycinnamate residue, 2-sec-ethyl butoxycinnamate residue, 2-sec-isopropyl butoxycinnamate residue, 2-sec-n-propyl butoxycinnamate residue, 2-sec-n-butyl butoxycinnamate residue, 2-sec-sec-butyl butoxycinnamate residue, 2-sec-tert-butyl butoxycinnamate residue, 2-sec-ethylhexyl butoxycinnamate residue, 2-tert-methyl butoxycinnamate residue, 2-tert-ethyl butoxycinnamate residue, 2-tert-isopropyl butoxycinnamate residue, 2-tert-n-propyl butoxycinnamate residue, 2-tert-butoxycinnamate 2-alkoxycinnamic acid ester residue units such as alkoxycinnamic acid ester residue units selected from n-butyl residues, 2-tert-butoxycinnamate sec-butyl residues, 2-tert-butoxycinnamate tert-butyl residues, and 2-tert-butoxycinnamate 2-ethylhexyl residues; 2-alkoxycinnamic acid residue units; 4-methyl methyl cinnamate residues, 4-methyl methyl cinnamate residues, 4-methyl methyl cinnamate isopropyl residues, 4-methyl methyl cinnamate n-propyl residues, 4-methyl methyl cinnamate n-butyl residues, 4-methyl cinnamate sec-butyl residues,4-methylcinnamate tert-butyl residue, 4-methylcinnamate 2-ethylhexyl residue, 4-ethylcinnamate methyl residue, 4-ethylcinnamate ethyl residue, 4-ethylcinnamate isopropyl residue, 4-ethylcinnamate n-propyl residue, 4-ethylcinnamate n-butyl residue, 4-ethylcinnamate sec-butyl residue, 4-ethylcinnamate tert-butyl residue, 4-ethylcinnamate 2-ethylhexyl residue, 4-isopropylcinnamate methyl residue, 4-isopropylcinnamate ethyl residue, 4-isopropylcinnamate isopropyl residue, 4-isopropyl n-propyl cinnamate residue, n-butyl 4-isopropylcinnamate residue, sec-butyl 4-isopropylcinnamate residue, tert-butyl 4-isopropylcinnamate residue, 2-ethylhexyl 4-isopropylcinnamate residue, methyl 4-n-propylcinnamate residue, ethyl 4-n-propylcinnamate residue, isopropyl 4-n-propylcinnamate residue, n-propyl 4-n-propylcinnamate residue, n-butyl 4-n-propylcinnamate residue, sec-butyl 4-n-propylcinnamate residue, tert-butyl 4-n-propylcinnamate residue Group, 4-n-propylcinnamate 2-ethylhexyl residue, 4-n-butylcinnamate methyl residue, 4-n-butylcinnamate ethyl residue, 4-n-butylcinnamate isopropyl residue, 4-n-butylcinnamate n-propyl residue, 4-n-butylcinnamate n-butyl residue, 4-n-butylcinnamate sec-butyl residue, 4-n-butylcinnamate tert-butyl residue, 4-n-butylcinnamate 2-ethylhexyl residue, 4-sec-butylcinnamate methyl residue, 4-sec-butylcinnamate ethyl residue, 4-sec-butylcinnamate isopropyl residue, 4 -sec-butylcinnamate n-propyl residue, 4-sec-butylcinnamate n-butyl residue, 4-sec-butylcinnamate sec-butyl residue, 4-sec-butylcinnamate tert-butyl residue, 4-sec-butylcinnamate 2-ethylhexyl residue, 4-tert-butylcinnamate methyl residue, 4-tert-butylcinnamate ethyl residue, 4-tert-butylcinnamate isopropyl residue, 4-tert-butylcinnamate n-propyl residue, 4-tert-butylcinnamate n-butyl residue, 4-tert-butylcinnamate sec-butyl residue,Alkyl cinnamic acid ester residue units such as tert-butyl residue of 4-tert-butylcinnamate, 2-ethylhexyl residue of 4-tert-butylcinnamate; alkyl cinnamic acid residue units; methyl 4-nitrocinnamate residue units, ethyl 4-nitrocinnamate residue units, isopropyl 4-nitrocinnamate residue units, n-propyl 4-nitrocinnamate residue units, 4-nitro, Nitrocinnamic acid ester residue units such as n-butyl nitrate residue units, sec-butyl 4-nitrocinnamate residue units, tart-butyl 4-nitrocinnamate residue units, and 2-ethylhexyl 4-nitrocinnamate residue units; nitrocinnamic acid residue units; methyl 4-bromocinnamate residue units, ethyl 4-bromocinnamate residue units, isopropyl 4-bromocinnamate residue units, n-propyl 4-bromocinnamate residue units, n-butyl 4-bromocinnamate residue units, and sec-butyl 4-bromocinnamate residue units. Bromocinnamic acid ester residue units such as 4-bromocinnamate tart-butyl residue units and 4-bromocinnamate 2-ethylhexyl residue units; bromocinnamic acid residue units; 4-iodocinnamate methyl residue units, 4-iodocinnamate ethyl residue units, 4-iodocinnamate isopropyl residue units, 4-iodocinnamate n-propyl residue units, 4-iodocinnamate n-butyl residue units, 4-iodocinnamate sec-butyl residue units, 4-iodocinnamate tart-butyl residue units, 4-iodocinnamate Iodocinnamic acid ester residue units such as 2-ethylhexyl acid residue units; iodocinnamic acid residue units; cyanocinnamic acid ester residue units such as methyl 4-cyanocinnamic acid residue units, ethyl 4-cyanocinnamic acid residue units, isopropyl 4-cyanocinnamic acid residue units, n-propyl 4-cyanocinnamic acid residue units, n-butyl 4-cyanocinnamic acid residue units, sec-butyl 4-cyanocinnamic acid residue units, tart-butyl 4-cyanocinnamic acid residue units, and 2-ethylhexyl 4-cyanocinnamic acid residue units; Cyanocinnamic acid residue units; methyl 4-sulfonic acid cinnamate residue units, ethyl 4-sulfonic acid cinnamate residue units, isopropyl 4-sulfonic acid cinnamate residue units, n-propyl 4-sulfonic acid cinnamate residue units, n-butyl 4-sulfonic acid cinnamate residue units, sec-butyl 4-sulfonic acid cinnamate residue units, tart-butyl 4-sulfonic acid cinnamate residue units, 2-ethylhexyl 4-sulfonic acid cinnamate residue units, and other sulfonic acid cinnamate ester residue units; sulfonic acid cinnamate residue units;Carboxylic acid ester residue units such as ethyl 4-carboxycinnamate residue units, isopropyl 4-carboxycinnamate residue units, n-propyl 4-carboxycinnamate residue units, n-butyl 4-carboxycinnamate residue units, sec-butyl 4-carboxycinnamate residue units, tart-butyl 4-carboxycinnamate residue units, and 2-ethylhexyl 4-carboxycinnamate residue units; carboxycinnamate residue units; methyl 4-phenylcinnamate residue units, ethyl 4-phenylcinnamate residue units, and 4-phenylcinnamate residue units. Phenyl transcinnamic acid ester residue units such as isopropyl phenylcinnamate residue units, n-propyl 4-phenylcinnamate residue units, n-butyl 4-phenylcinnamate residue units, sec-butyl 4-phenylcinnamate residue units, tart-butyl 4-phenylcinnamate residue units, and 2-ethylhexyl 4-phenylcinnamate residue units; phenyl transcinnamic acid residue units; methyl α-cyano-2-hydroxycinnamate residue units, methyl α-cyano-3-hydroxycinnamate residue units, and methyl α-cyano-4-hydroxycinnamate Residue unit, α-cyano-2-hydroxycinnamate ethyl residue unit, α-cyano-3-hydroxycinnamate ethyl residue unit, α-cyano-4-hydroxycinnamate ethyl residue unit, α-cyano-2-hydroxycinnamate n-propyl residue unit, α-cyano-3-hydroxycinnamate n-propyl residue unit, α-cyano-4-hydroxycinnamate n-propyl residue unit, α-cyano-2-hydroxycinnamate n-butyl residue unit, α-cyano-3-hydroxycinnamate n-butyl residue unit, α-cyano-4-hydroxy α-cyano-hydroxycinnamate ester residue units such as n-butyl cyanathenate residue units, isobutyl α-cyano-2-hydroxycinnamate residue units, isobutyl α-cyano-3-hydroxycinnamate residue units, isobutyl α-cyano-4-hydroxycinnamate residue units, t-butyl α-cyano-2-hydroxycinnamate residue units, t-butyl α-cyano-3-hydroxycinnamate residue units, t-butyl α-cyano-4-hydroxycinnamate residue units, and methyl α-cyano-2,4-dihydroxycinnamate residue units;α-cyano-carboxycinnamic acid ester residue units such as α-cyano-4-carboxycinnamic acid methyl residue units, α-cyano-4-carboxycinnamic acid ethyl residue units, α-cyano-2,3-dicarboxycinnamic acid methyl residue units, and α-cyano-2,3-dicarboxycinnamic acid ethyl residue units; α-cyano-carboxy-hydroxycinnamic acid ester residue units such as α-cyano-2-carboxy-3-hydroxycinnamic acid methyl residue units and α-cyano-2-carboxy-3-hydroxycinnamic acid ethyl residue units; hydroxybenzylidenemalonate diester residue units such as hydroxybenzylidenemalonate dimethyl residue units, hydroxybenzylidenemalonate diethyl residue units, hydroxybenzylidenemalonate di-n-propyl residue units, and hydroxybenzylidenemalonate diisopropyl residue units;Examples of the carboxybenzylidene malonic acid diester residue unit include a dimethyl carboxybenzylidene malonate residue unit, a diethyl carboxybenzylidene malonate residue unit, a di-n-propyl carboxybenzylidene malonate residue unit, and a diisopropyl carboxybenzylidene malonate residue unit. Among them, a cinnamic acid ester residue unit, an alkoxycinnamic acid ester residue unit, and an α-cyano-hydroxycinnamic acid ester residue unit are preferable, and an α-cyano-2-hydroxycinnamic acid methyl residue unit, an α-cyano-3-hydroxycinnamic acid methyl residue unit, an α-cyano-4-hydroxycinnamic acid methyl residue unit, an α-cyano-2-hydroxycinnamic acid ethyl residue unit, an α-cyano-3-hydroxycinnamic acid ethyl residue unit, an α-cyano-4-hydroxycinnamic acid ethyl residue unit, an α-cyano-2-hydroxycinnamic acid n-propyl residue unit, an α-cyano-3-hydroxycinnamic acid n-propyl residue unit, an α-cyano-4-hydroxycinnamic acid n-propyl residue unit, an α-cyano-2-hydroxycinnamic acid isopropyl residue unit, an α-cyano-3-hydroxycinnamic acid isopropyl residue unit, an α-cyano-4-hydroxycinnamic acid isopropyl residue unit, an α-cyano-2-hydroxycinnamic acid n-butyl residue unit, an α-cyano-3-hydroxycinnamic acid n-butyl residue unit, an α-cyano-4-hydroxycinnamic acid n-butyl residue unit, an α-cyano-2-hydroxycinnamic acid isobutyl residue unit, an α-cyano-3-hydroxycinnamic acid isobutyl residue unit, an α-cyano-4-hydroxycinnamic acid isobutyl residue unit, an α-cyano-4-hydroxycinnamic acid t-butyl residue unit, an α-cyano-2-hydroxycinnamic acid t-butyl residue unit, an α-cyano-3-hydroxycinnamic acid t-butyl residue unit, and an α-cyano-4-hydroxycinnamic acid t-butyl residue unit are particularly preferable.;

[0051] In the ester resin, the residue unit represented by the formula (2) may contain one kind of the residue units exemplified above, or may contain two or more kinds of the residue units.;

[0052] R in the formula (3) 10 , R 11Each of these independently represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. Examples of alkyl groups having 1 to 12 carbon atoms include methyl, ethyl, isopropyl, n-propyl, n-butyl, s-butyl, t-butyl, and ethylhexyl groups.

[0053] Specific examples of residue units represented by formula (3) include, for example, monomethyl fumarate residue units, monoethyl fumarate residue units, mono-n-propyl fumarate residue units, monoisopropyl fumarate residue units, mono-n-butyl fumarate residue units, mono-sec-butyl fumarate residue units, mono-tert-butyl fumarate residue units, mono-2-ethylhexyl fumarate residue units, monocyclopropyl fumarate residue units, monocyclopentyl fumarate residue units, monocyclohexyl fumarate residue units, and other fumarate monoester residue units; dimethyl fumarate residue units, diethyl fumarate residue units Examples include fumarate di-n-propyl fumarate, fumarate diisopropyl fumarate, fumarate di-n-butyl fumarate, fumarate di-sec-butyl fumarate, fumarate di-tert-butyl fumarate, fumarate di-2-ethylhexyl fumarate, fumarate dicyclopropyl fumarate, fumarate dicyclobutyl fumarate, fumarate dicyclopentyl fumarate, fumarate dicyclohexyl fumarate, fumarate diester

[0054] Among these, monomethyl fumarate, monoethyl fumarate, monoisopropyl fumarate, mono-tert-butyl fumarate, mono-n-butyl fumarate, monoisobutyl fumarate, dimethyl fumarate, diethyl fumarate, diisopropyl fumarate, di-tert-butyl fumarate, di-n-butyl fumarate, and diisobutyl fumarate are preferred.

[0055] In ester resins, the residue unit represented by formula (3) may contain one of the residue units in the above example, or it may contain two or more types.

[0056] R in equation (4) 12 This represents a five-membered heterocyclic residue or a six-membered heterocyclic residue containing one or more nitrogen or oxygen atoms as heteroatoms (the five-membered heterocyclic residue and the six-membered heterocyclic residue may form a fused ring structure with other cyclic structures).

[0057] Specific residue units represented by formula (4) include, for example, 1-vinylpyrrole residue units, 2-vinylpyrrole residue units, 1-vinylindole residue units, 9-vinylcarbazole residue units, 2-vinylquinoline residue units, 4-vinylquinoline residue units, N-vinylphthalimide residue units, N-vinylsuccinimide residue units, 2-vinylfuran residue units, 2-vinylbenzofuran residue units, styrene residue units, and 2-vinylnaphthalene residue units, with 9-vinylcarbazole residue units and N-vinylphthalimide residue units being more preferred.

[0058] In addition to the above formulas (2), (3), and (4), the ester resin may also have residue units represented by the following formula (5).

[0059] [ka]

[0060] (In the formula, R 13 , R 14 Each of these independently represents one of the groups consisting of a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms. R 13 , R 14 Examples of linear alkyl groups having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl groups.

[0061] R 13 , R 14Examples of branched alkyl groups having 3 to 12 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, and the like.

[0062] R 13 , R 14 Examples of cyclic alkyl groups having 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, and cyclohexyl groups.

[0063] R in equation (5) 13 , R 14 As such, hydrogen atoms, methyl groups, ethyl groups, propyl groups, isopropyl groups, butyl groups, isobutyl groups, sec-butyl groups, tert-butyl groups, pentyl groups, isopentyl groups, sec-pentyl groups, 3-pentyl groups, neopentyl groups, hexyl groups, isohexyl groups, and neohexyl groups are preferred, and hydrogen atoms, methyl groups, ethyl groups, propyl groups, isopropyl groups, butyl groups, isobutyl groups, sec-butyl groups, and isobutyl groups are even more preferred.

[0064] The residue unit represented by formula (5) is preferably an acrylic resin residue unit. Specific examples of acrylic resin residue units represented by formula (5) include acrylic acid residue units, methacrylic acid residue units, 2-ethyl acrylic acid residue units, 2-propyl acrylic acid residue units, 2-isopropyl acrylic acid residue units, 2-pentyl acrylic acid residue units, 2-hexyl acrylic acid residue units, methyl acrylate residue units, ethyl acrylate residue units, n-propyl acrylate residue units, isopropyl acrylate residue units, n-butyl acrylate residue units, isobutyl acrylate residue units, sec-butyl acrylate residue units, n-pentyl acrylate residue units, isopentyl acrylate residue units, sec-pentyl acrylate residue units, 3-pentyl acrylate residue units, neopentyl acrylate residue units, n-hexyl acrylate residue units, isohexyl acrylate residue units, neohexyl acrylate residue units, methyl methacrylate residue units, and Examples include ethyl methacrylate residue units, n-propyl methacrylate residue units, isopropyl methacrylate residue units, n-butyl methacrylate residue units, isobutyl methacrylate residue units, sec-butyl methacrylate residue units, n-pentyl methacrylate residue units, isopentyl methacrylate residue units, sec-pentyl methacrylate residue units, 3-pentyl methacrylate residue units, neopentyl methacrylate residue units, n-hexyl methacrylate residue units, isohexyl methacrylate residue units, neohexyl methacrylate residue units, methyl 2-ethylacrylate residue units, ethyl 2-ethylacrylate residue units, n-propyl 2-ethylacrylate residue units, isopropyl 2-ethylacrylate residue units, n-butyl 2-ethylacrylate residue units, isobutyl 2-ethylacrylate residue units, and sec-butyl 2-ethylacrylate residue units.

[0065] Among these, the ratio Re(450) / Re(550) of the in-plane phase difference (Re) at a wavelength of light of 450 nm to the in-plane phase difference (Re) at a wavelength of light of 550 nm becomes smaller, resulting in the following residue units: methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, Isobutyl methacrylate residue units, sec-butyl methacrylate residue units, methyl methacrylate residue units, ethyl methacrylate residue units, n-propyl methacrylate residue units, isopropyl methacrylate residue units, n-butyl methacrylate residue units, isobutyl methacrylate residue units, and sec-butyl methacrylate residue units are preferred, and methyl acrylate residue units, ethyl acrylate residue units, n-propyl acrylate residue units, isopropyl acrylate residue units, n-butyl acrylate residue units, isobutyl acrylate residue units, and sec-butyl acrylate residue units are even more preferred.

[0066] In ester resins, when the cinnamic acid ester residue unit of formula (2) and formula (4) are included, it is preferable that the monomer component related to the cinnamic acid ester residue unit of formula (2) is present in an amount of 21 mol% to 50 mol% of the total monomer components. It is preferable that the residue unit represented by formula (4) is present in an amount of 21 mol% to 65 mol% of the total monomer components.

[0067] When the ester resin contains residue units of formula (2) and formula (3), the monomer component related to formula (2) is preferably present in an amount of 21 mol% to 70 mol%, and more preferably 35 mol% to 60 mol%, relative to 100 mol% of the total of formulas (2) and (3).

[0068] When the ester resin contains residue units of formulas (2), (4), and (5), the content of each residue unit component is Formula (2) 21 mol% or more and 49 mol% or less Formula (4) 35 mol% or more and 60 mol% or less Formula (5) 1 mol% or more and 30 mol% or less This is preferable. This results in superior phase difference characteristics when the resin composition of the present invention is used as a film.

[0069] Here, the composition ratio of the ester resin is: 1 It can be measured by 1H-NMR.

[0070] Ester resins may contain monomer residue units other than those of formulas (2) to (5) above. Examples of such monomer residue units include one or more of the following: styrene residues such as styrene residues and α-methylstyrene residues; acrylic acid residues; acrylic acid ester residues; methacrylic acid residues; methacrylic acid ester residues; vinyl ester residues such as vinyl acetate residues and vinyl propionate residues; vinyl ether residues such as methyl vinyl ether residues, ethyl vinyl ether residues, and butyl vinyl ether residues; N-substituted maleimide residues such as N-methyl maleimide residues, N-cyclohexyl maleimide residues, and N-phenyl maleimide residues; acrylonitrile residues; methacrylonitrile residues; and olefin residues such as ethylene residues and propylene residues.

[0071] Ester resins exhibit particularly excellent mechanical properties and superior moldability during film formation. Therefore, the weight-average molecular weight (Mw) on a standard polystyrene basis, obtained from the elution curve measured by gel permeation chromatography (GPC), is 3 × 10⁻⁶. 3 ~5×10 6 It is preferable that it be of the type 5×10 3 ~1 × 10 6 It is even more preferable that this be the case.

[0072] As for the method of producing the ester resin, any method is acceptable as long as the resin can be obtained, and it can be produced by radical polymerization.

[0073] Any of the following methods can be used for radical polymerization: bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization, emulsion polymerization, etc.

[0074] The cellulose resin of the present invention may contain other polymers, surfactants, polymer electrolytes, conductive complexes, pigments, dyes, antistatic agents, antiblocking agents, lubricants, etc., to the extent that it does not exceed the spirit of the invention.

[0075] The cellulose resin of the present invention may contain antioxidants to improve thermal stability. Examples of antioxidants include hindered phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, lactone antioxidants, amine antioxidants, hydroxylamine antioxidants, vitamin E antioxidants, and other antioxidants. These antioxidants may be used individually or in combination of two or more.

[0076] The cellulose resin of the present invention may contain a hindered amine-based light stabilizer or an ultraviolet absorber to enhance weather resistance. Examples of ultraviolet absorbers include benzotriazole, benzophenone, triazine, and benzoate-based absorbers.

[0077] In the present invention, a composition comprising a cellulose resin and an ester resin exhibiting negative birefringence having at least one residue unit from the group consisting of cinnamic acid ester residue units represented by formula (2), fumarate ester residue units represented by formula (3), and residue units represented by formula (4) can be produced by blending the cellulose resin and the ester resin. Methods for blending include melt blending and solution blending. Melt blending is a method of production in which the resin is melted by heating and kneaded. Solution blending is a method of blending in which the resin is dissolved in a solvent. Any solvent that can dissolve the resin can be used as the solvent for solution blending, but in order to minimize residual solvent in the film-forming process, the boiling point of the solvent is preferably 200°C or lower, and more preferably 170°C or lower.

[0078] Examples of solvents include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenols such as phenol and parachlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, mesitylene, and 1,2-dimethoxybenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, and N-methyl-2-pyrrolidone; and ethyl acetate and butyl acetate. Examples of solvents include ether-based solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol; amide-based solvents such as dimethylformamide and dimethylacetamide; nitrile-based solvents such as acetonitrile and butyronitrile; ether-based solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; and solvents such as carbon disulfide, ethyl cellsolve, and butyl cellsolve, either alone or in combination.

[0079] An optical film, which is one aspect of the present invention, will be described.

[0080] The optical film of the present invention comprises the cellulose-based resin. Preferably, the composition comprises the cellulose-based resin and the ester-based resin exhibiting the negative phase difference.

[0081] Any method may be used to manufacture the film using the cellulose resin of the present invention, but it is preferable to manufacture it by the solution casting method. Here, the solution casting method is a method in which a resin solution (generally called dope) is cast onto a support substrate, and then the solvent is evaporated by heating to obtain a film. The coating method is not particularly limited, and conventional methods can be used. For example, T-die method, doctor blade method, bar coater method, slot die method, lip coater method, reverse gravure coating method, microgravure method, spin coating method, brush coating method, roll coating method, flexographic printing method, etc. Furthermore, there are no particular limitations on the support substrate used, but examples include polymer substrates made of polyester, polycarbonate, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, triacetylcellulose, polyvinyl alcohol, polyimide, polyarylate, polysulfone, polyethersulfone, epoxy resins, etc., glass substrates such as glass plates and quartz substrates, metal substrates such as aluminum, stainless steel, and ferrotype, and inorganic substrates such as ceramic substrates. The above-mentioned substrate is preferably a polymer substrate or a metal substrate.

[0082] The viscosity of the resin solution used to produce an optical film using the cellulose-based resin of the present invention can be adjusted by the molecular weight, concentration, and type of solvent of each component. There are no particular restrictions on the viscosity of the resin solution, but to facilitate film coating, it is preferably 100 to 30,000 cps, and more preferably 300 to 20,000 cps.

[0083] The drying method in the drying process of the coating solution is not particularly limited, and conventional heating methods can be used. Examples include hot air blowers, heating rolls, and far-infrared heaters.

[0084] In the film manufacturing method using the cellulose resin of the present invention, the drying temperature may be set to a single stage, or it may be a multi-stage drying method in which the first stage is dried at a low temperature and the second and subsequent stages are dried at a high temperature in order to maintain the appearance and shorten the drying time.

[0085] In the present invention, the concentrations of the cellulose resin and the ester resin exhibiting negative birefringence are not particularly limited as long as dissolution and film formation are possible. The method for dissolving the cellulose resin and the ester resin exhibiting negative birefringence may be carried out to a predetermined concentration during the dissolution stage, or a low-concentration solution may be prepared in advance and then adjusted to a predetermined high-concentration solution in a concentration step. Furthermore, a high-concentration resin solution of the cellulose resin and the ester resin exhibiting negative birefringence may be prepared in advance, and then various additives may be added to obtain a predetermined low-concentration resin solution.

[0086] The method for producing an optical film using the resin of the present invention is not particularly limited in terms of how to produce a phase difference, but in order to effectively orient the molecular chains of the cellulose resin and produce a high phase difference, uniaxial stretching or unbalanced biaxial stretching is preferred. As for the stretching method, longitudinal uniaxial stretching by roll stretching, transverse uniaxial stretching or oblique stretching by tenter stretching, or unbalanced sequential biaxial stretching or unbalanced simultaneous biaxial stretching by combinations thereof can be used.

[0087] The thickness of the unstretched film before stretching is preferably 5 to 200 μm, more preferably 10 to 150 μm, and particularly preferably 20 to 120 μm, from the viewpoint of ease of stretching and suitability for thinning of optical components.

[0088] Furthermore, the thickness of the stretched optical film is preferably 5 to 100 μm, and more preferably 5 to 60 μm, in order to make the image display device thinner.

[0089] There are no particular restrictions on the stretching temperature, but it is preferably 50 to 200°C, and more preferably 100 to 200°C, as good phase difference characteristics can be obtained. There are no particular restrictions on the stretching ratio for uniaxial stretching, but it is preferably 1.05 to 4.0 times, and more preferably 1.1 to 3.5 times, as good phase difference characteristics can be obtained. There are no particular restrictions on the stretching ratio for unbalanced biaxial stretching, but it is preferably 1.05 to 4.0 times in the length direction, and more preferably 1.1 to 3.5 times, as excellent optical properties can be obtained. The phase difference can be controlled by the stretching temperature, stretching ratio, etc.

[0090] In the optical film using the resin of the present invention, the phase difference can be adjusted by the cellulose resin content, the total degree of substitution of the contained cellulose resin, the degree of substitution distribution of the substituents at positions 2, 3, and 6, and the stretching conditions.

[0091] The phase difference characteristics of an optical film using the resin of the present invention vary depending on the target optical film. For example, in applications of circular polarizer phase difference films, the phase difference (Re) shown in formula (A) below is preferably 30 to 300 nm, more preferably 100 to 300 nm, and particularly preferably 120 to 280 nm, and the Nz coefficient shown in formula (B) below is preferably 0.3 to 1.3, more preferably 0.4 to 0.8, that is, the phase difference (Rth) shown in formula (C) below is preferably -60 to 240 nm, and more preferably -30 to 90 nm. The phase difference characteristics in this case are measured using a fully automatic birefringent (manufactured by Oji Instruments Co., Ltd., product name KOBRA-21ADH) at a measurement wavelength of 589 nm.

[0092] These materials possess phase difference characteristics that are difficult to achieve with conventional optical films made of cellulose resins.

[0093] Re = (ny - nx) × d (A) Nz = (ny - nz) / (ny - nx) (B) Rth = [(nx + ny) / 2 - nz] × d (C) (In the formula, nx represents the refractive index in the advancing axis direction within the film plane, ny represents the refractive index in the retarding axis direction within the film plane, nz represents the refractive index outside the film plane, and d represents the film thickness.) As the wavelength dispersion characteristics of the optical film of the present invention, for suppressing color shift, preferably 0.60 < Re(450) / Re(550) < 1.05, more preferably 0.70 < Re(450) / Re(550) < 1.02, and particularly preferably 0.75 < Re(450) / Re(550) < 1.00.

[0094] When the cellulose-based resin of the present invention is used alone, an optical film with low wavelength dispersion can be provided. A resin composition in which an ester-based resin showing negative birefringence with respect to the stretching direction is blended with this film can generally provide an optical film showing inverse wavelength dispersion characteristics.

[0095] Satisfying these retardation characteristics and wavelength dispersion characteristics simultaneously is generally difficult to achieve in an optical film using a cellulose-based resin, but the optical film according to the present invention satisfies these characteristics simultaneously.

[0096] In order to avoid a decrease in the amount of light of the image display device, the transmittance of the optical film using the resin of the present invention when formed into a film is preferably 87% or more, more preferably 90% or more.

[0097] The haze of the optical film using the resin of the present invention is preferably 1.5% or less, more preferably 1.0% or less. By controlling the haze within the above range, a high-contrast image can be obtained when incorporated into a display device as a retardation film.

[0098] In order to avoid a decrease in the amount of light of the screen display device in a high-temperature and high-humidity environment and maintain a high-contrast image, the haze after 500 hours in an environment of 65°C and 90% relative humidity is preferably 1.5% or less, and the transmittance is preferably 87% or more. More preferably, the haze is 1.0% or less and the transmittance is 90% or more.

[0099] The optical film of the present invention preferably exhibits a haze increase rate of 1.0% or less and a decrease in total light transmittance of less than 2% after 500 hours in an environment of 65°C and 90% relative humidity.

[0100] The optical film using the resin of the present invention can be laminated with a film containing other resins as needed. Examples of other resins include polyethersulfone, polyarylate, polyethylene terephthalate, polynaphthalene terephthalate, polycarbonate, cyclic polyolefin, maleimide resin, fluororesin, and polyimide. It is also possible to laminate a liquid crystal layer, a hard coat layer, a gas barrier layer, and a refractive index-controlled layer (low-reflection layer).

[0101] The optical film of the present invention can be suitably used as a component of a polarizing plate, that is, as a polarizing plate equipped with the optical film.

[0102] The optical film using the resin of the present invention is suitably used in polarizing plates and optical compensation films for applications such as liquid crystal displays and organic EL displays. Furthermore, the polarizing plate is suitably used as an image display device. The optical compensation film is characterized by having excellent moisture and heat resistance, phase difference characteristics, and wavelength dispersion characteristics. [Examples]

[0103] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0104] The physical properties shown in the examples were measured by the following method. <Measuring molecular weight> The values ​​were determined using a gel permeation chromatography (GPC) apparatus (Tosoh Corporation, column GMHHR-H) at 40°C with stabilizer-containing tetrahydrofuran as the solvent, and calculated from the equivalent values ​​for standard polystyrene. <Measurement of Chloride Content> The quantitative determination method for chlorides in ethylcellulose is specified in the Japanese Pharmacopoeia. Yes, they are.

[0105] Based on the Japanese Pharmacopoeia, the chloride content was determined by potentiometric titration using a potentiometric titrator (HIRANUMA, COM-1600). A 10 vol% ethanol solution of 70% concentrated nitric acid and 50 ppm sodium chloride aqueous solution (volume ratio) was used as the blank solution. A 5 vol% ethanol solution of 70% concentrated nitric acid and 50 ppm sodium chloride aqueous solution (volume ratio) was used as the sample solution. Ethyl cellulose was dissolved in this solution, and the ethyl cellulose concentration was adjusted to 1.0 wt%. Both the sample solution and the blank solution were titrated with 0.02 mol / L silver nitrate solution (F=1.000). All chlorides were converted to sodium chloride, and the chloride content was calculated using the following formula (6).

[0106] Sodium chloride content (%) = [(Sample solution titration volume (mL) - Blank solution titration volume (mL))] [×0.02×58.45×0.10] / sample weight (g) Formula (6) <Measurement of acetate and butyrate content> The quantitative determination method for sodium acetate is specified in the Japanese Pharmacopoeia and JIS K 8371, and the measurement was performed in accordance with JIS K 8371 (2006 edition).

[0107] The acetic acid content was determined by potentiometric titration using a potentiometric titrator (HIRANUMA, COM-1600). 50 mL of acetic acid was used as the blank solution, and a solution prepared by dissolving cellulose sylate in 50 mL of acetic acid and adjusting the cellulose acylate concentration to 1.0% by weight was used as the sample solution. 0.1 mol / L perchloric acid-acetic acid solution (F=1.000) was titrated against the sample solution and blank solution, and all acetic acid was converted to sodium acetate, which was then calculated using the following formula (7). For cellulose acetate butyrate, acetic acid or butyrate was converted to sodium acetate and sodium butyrate, which were then calculated using the following formula (8).

[0108] Sodium acetate content (%) = [(Sample solution titration volume (mL) - Blank solution titration volume (mL))] [82.03 × 1.00 × 0.10] / (Sample weight (g) × 10) Equation (7) Sodium acetate and sodium butyrate content (%) = [(Sample solution titration volume (mL) - Blank solution titration volume (mL)) × 99.53 × 1.00 × 0.10] / (Sample weight (g) × 10) Equation (8) <Measurement of Phase Difference Characteristics> The phase difference characteristics of the phase difference film were measured using light at a wavelength of 589 nm with a sample tilt type automatic birefringent (manufactured by Oji Instruments Co., Ltd., product name: KOBRA-WR). <Measurement of total light transmittance and haze> The total light transmittance and haze of the prepared film were measured using a haze meter (manufactured by Nippon Denshoku Industries, product name: NDH5000, light source: white LED (5V3W, wavelength range 380nm to 780nm, total light transmittance and haze value are the sum of values ​​within this range)). Total light transmittance was measured in accordance with JIS K 7361-1 (1997 edition), and haze was measured in accordance with JIS-K 7136 (2000 edition). <Heat and moisture resistance test> The heat resistance was measured by examining the total light transmittance and haze after 500 hours in a high-temperature, high-humidity environment of 65°C and 90% relative humidity using a constant temperature and humidity chamber (manufactured by Yamato Scientific Co., Ltd., product name: IG400) (hereinafter referred to as the "heat resistance test").

[0109] Synthesis Example 1 (Synthesis of an ester resin (1) exhibiting negative birefringence (diisopropyl fumarate / monoethyl fumarate resin)) 42 g of diisopropyl fumarate, 7.7 g of monoethyl fumarate, and 0.66 g of tert-butyl peroxypivalate (a polymerization initiator) were placed in a 75 mL glass ampoule. After repeated nitrogen purging and pressure release, the ampoule was sealed under reduced pressure. Radical polymerization was carried out by placing this ampoule in a 55°C constant temperature bath and maintaining it for 24 hours. After the polymerization reaction was complete, the polymer was removed from the ampoule and dissolved in 200 g of tetrahydrofuran. This polymer solution was precipitated by dropwise addition to 4 L of hexane, and then vacuum-dried at 80°C for 10 hours to obtain 27 g of a negatively birefringent ester resin (1) (yield 54%). The weight-average molecular weight of the obtained negatively birefringent ester resin (1) was 95,000, with 82 mol% diisopropyl fumarate residue units and 18 mol% monoethyl fumarate residue units.

[0110] Synthesis Example 2 (Synthesis of an ester resin exhibiting negative birefringence (2) (9-vinylcarbazole / α-cyano-4-hydroxycinnamate isobutyl / acrylate isobutyl)) 50 mL glass ampoules were filled with 5.0 g (0.020 mol) of 9-vinylcarbazole, 3.2 g (0.013 mol) of isobutyl α-cyano-4-hydroxycinnamate, 1.7 g (0.013 mol) of isobutyl acrylate, 0.093 g (0.00022 mol) of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (a polymerization initiator), and 24.6 g of ethyl cellosolve. After repeated nitrogen purging and pressure release, the ampoules were sealed under reduced pressure. Radical polymerization was carried out by placing these ampoules in a 47°C constant temperature bath and maintaining the temperature for 24 hours. After the polymerization reaction was complete, the polymer was removed from the ampoule, 41 g of tetrahydrofuran was added, and this polymer solution was added dropwise to 330 g of methanol / water mixed solvent (weight ratio 80 / 20) to precipitate. After filtration, the filtrate was washed five times with 45 g of methanol / water mixed solvent (weight ratio 90 / 10) and filtered. The obtained resin was vacuum-dried at 80°C for 10 hours to obtain 9.2 g of negative birefringence ester resin (2) (yield: 94%). The weight-average molecular weight of the obtained negative birefringence ester resin (2) was 230,000, and the ratio of residue units was 50 mol% 9-vinylcarbazole residue units, 25 mol% α-cyano-4-hydroxy-cinnamate isobutyl residue units, and 25 mol% isobutyl acrylate residue units.

[0111] Example 1 50.0 g of ethylcellulose (Ethocel Standard 100, manufactured by Dow Chemical, with molecular weight Mn=58,000, molecular weight Mw=181,000, Mw / Mn=3.1, degree of total substitution DS=2.51, and sodium chloride content of 0.082% by weight) was used as a cellulosic resin. After washing it five times with 250 g of deionized water with an electrical conductivity of 0.01 mS / m, it was vacuum-dried at 60°C until there was no further weight loss, and the sodium chloride content was measured to be 0.013% by weight. 40.0 g of the obtained resin was dissolved in a toluene / ethyl acetate = 8 / 2 (by weight ratio) solution to make a 12% by weight resin solution, which was then poured onto a polyethylene terephthalate film using a coater. After drying at 40°C and then in two stages at 155°C, a film with a width of 150 mm was obtained.

[0112] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 150°C (resulting in a film thickness of 30 μm).

[0113] The phase difference and wavelength dispersion characteristics of the obtained film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 93% and a haze of 0.2%. After the humid heat resistance test, the light transmittance was 93% and the haze was 0.4%, with a decrease of 0% in total light transmittance and an increase of 0.2% in haze.

[0114] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0115] [Table 1]

[0116] Example 2 50.0 g of ethylcellulose (Ethocel Standard 300, manufactured by Dow Chemical, with molecular weight Mn=87,000, molecular weight Mw=269,000, Mw / Mn=3.1, degree of total substitution DS=2.52, and sodium chloride content of 0.054 wt%) was used as a cellulosic resin. After washing five times with 250 g of deionized water with an electrical conductivity of 0.01 mS / m, the resin was vacuum-dried at 60°C until no further weight loss occurred, and the sodium chloride content was measured to be 0.015 wt%. 40.0 g of the obtained resin was dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to obtain a 12 wt% resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at 40°C and then in two stages at 155°C, a film with a width of 150 mm was obtained.

[0117] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 150°C (resulting in a film thickness of 30 μm).

[0118] The phase difference and wavelength dispersion characteristics of the obtained optical compensation film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the humid and heat resistance test, the light transmittance was 92% and the haze was 0.6%, resulting in a decrease of 1% in total light transmittance and an increase of 0.3% in haze.

[0119] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0120] Example 3 As the cellulosic resin, 24.00 g of ethylcellulose (Ethocel standard 100, manufactured by Dow Chemical, molecular weight Mn=58,000, molecular weight Mw=181,000, Mw / Mn=3.1, degree of total substitution DS=2.51, sodium chloride content 0.013 wt%), which had been washed in the same manner as in Example 1, and 16.00 g of the ester resin (1) exhibiting negative birefringence obtained in Synthesis Example 1 were dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to make a 15 wt% resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at a drying temperature of 40°C, it was dried in two stages at 155°C to obtain a film (resin composition) with a width of 150 mm (cellulosic resin: 60.00 wt%, ester resin exhibiting negative birefringence: 40.00 wt%).

[0121] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 140°C (resulting in a film thickness of 30 μm).

[0122] The light transmittance, haze, phase difference characteristics, wavelength dispersion characteristics, and heat and humidity resistance of the obtained film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the heat and humidity resistance test, the light transmittance was 93% and the haze was 0.4%, with a decrease of 0% in total light transmittance and an increase of 0.1% in haze.

[0123] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0124] Example 4 As the cellulosic resin, 31.20 g of ethylcellulose (Ethocel standard 100, manufactured by Dow Chemical, molecular weight Mn=58,000, molecular weight Mw=181,000, Mw / Mn=3.1, degree of total substitution DS=2.51, sodium chloride content 0.013 wt%), which had been washed in the same manner as in Example 1, and 8.80 g of the negative birefringence ester resin (2) obtained in Synthesis Example 2 were dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to make a 15 wt% resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at a drying temperature of 40°C, it was dried in two stages at 155°C to obtain a film (resin composition) with a width of 150 mm (cellulosic resin: 78.0 wt%, negative birefringence ester resin: 22.0 wt%).

[0125] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 157°C (resulting in a film thickness of 30 μm).

[0126] The light transmittance, haze, phase difference characteristics, wavelength dispersion characteristics, and heat and humidity resistance of the obtained film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the heat and humidity resistance test, the light transmittance was 93% and the haze was 0.5%, with a decrease of 0% in total light transmittance and an increase of 0.2% in haze.

[0127] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0128] Example 5 As a cellulose-based resin, 31.20 g of ethylcellulose (Ethocel standard 300, manufactured by Dow Chemical, molecular weight Mn=87,000, molecular weight Mw=269,000, Mw / Mn=3.1, degree of total substitution DS=2.52, sodium chloride content 0.015 wt%), which had been washed in the same manner as in Example 2, and 8.80 g of the negative birefringence ester resin (2) obtained in Synthesis Example 2 were dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to make a 15 wt% resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at a drying temperature of 40°C, it was dried in two stages at 155°C to obtain a film (resin composition) with a width of 150 mm (cellulose-based resin: 78.0 wt%, negative birefringence ester resin: 22.0 wt%).

[0129] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 157°C (resulting in a film thickness of 30 μm).

[0130] The light transmittance, haze, phase difference characteristics, wavelength dispersion characteristics, and heat and humidity resistance of the obtained film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the heat and humidity resistance test, the light transmittance was 92% and the haze was 0.6%, resulting in a decrease of 1% in total light transmittance and an increase of 0.3% in haze.

[0131] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0132] Example 6 As a cellulose-based resin, cellulose acetate butyrate (manufactured by Sigma-Aldrich, molecular weight Mn=27,000, molecular weight Mw=73,000, Mw / Mn=2.7, degree of acetyl substitution DS) is used. acetyl =1.05, butyl substitution degree DS butyl50.0 g of the resin (sodium acetate and sodium butyrate content 0.042 wt%) was washed five times with 250 g of deionized water with an electrical conductivity of 0.01 mS / m, then vacuum-dried at 60°C until weight loss ceased, and the sodium acetate content was measured to be 0.013 wt%. 40.0 g of the obtained resin was dissolved in a toluene / methanol = 8 / 2 (weight ratio) solution to make a 30 wt% resin solution, which was then poured onto a polyethylene terephthalate film using a coater, and after drying at 40°C and then in two stages at 130°C, a film with a width of 150 mm was obtained.

[0133] The obtained film was cut into 50 mm squares, then uniaxially stretched to 1.5 times its original size at 130°C (resulting in a film thickness of 30 μm).

[0134] The phase difference and wavelength dispersion characteristics of the obtained film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the humid and heat resistance test, the light transmittance was 93% and the haze was 0.4%, with a decrease of 0% in total light transmittance and an increase of 0.1% in haze.

[0135] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0136] Example 7 As the cellulose-based resin, cellulose acetate butyrate (manufactured by Sigma-Aldrich, molecular weight Mn=27,000, molecular weight Mw=73,000, Mw / Mn=2.7, degree of acetyl substitution DS) was washed in the same manner as in Example 7. acetyl =1.05, butyl substitution degree DS butyl36 g of 1.74% sodium acetate and sodium butyrate (containing 0.013% by weight), 4.00 g of the negatively birefringent ester resin (2) obtained by Synthesis Example 2, and 0.4 g of 2-hydroxy-4-methoxybenzophenone were dissolved in a toluene / methanol = 8 / 2 (weight ratio) solution to make a 32% by weight resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at a drying temperature of 40°C followed by two-stage drying at 130°C, a film (resin composition) with a width of 150 mm was obtained (cellulose resin: 89.1% by weight, negatively birefringent ester resin: 9.9% by weight, 2-hydroxy-4-methoxybenzophenone: 1.0% by weight).

[0137] The obtained film was cut into 50 mm squares, then uniaxially stretched to 1.5 times its original size at 130°C (resulting in a film thickness of 30 μm).

[0138] The light transmittance, haze, phase difference characteristics, wavelength dispersion characteristics, and heat and humidity resistance of the obtained film were measured. The results are shown in Table 1. The obtained film had a light transmittance of 92% and a haze of 0.7%. After the heat and humidity resistance test, the light transmittance was 92% and the haze was 0.9%, with a decrease of 0% in total light transmittance and an increase of 0.2% in haze.

[0139] The resulting film exhibited high light transmittance, low haze, and high resistance to humidity and heat.

[0140] Comparative Example 1 As a cellulosic resin, ethylcellulose (Ethocel standard 100, manufactured by Dow Chemical, molecular weight Mn=58,000, molecular weight Mw=181,000, Mw / Mn=3.1, degree of total substitution DS=2.51, sodium chloride content 0.082 wt%) used in Example 1 was not washed with deionized water. 40.0 g of the resin was dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to obtain a 12 wt% resin solution, which was then poured onto a polyethylene terephthalate film using a coater. After drying at a temperature of 40°C and then in two stages at 155°C, a film with a width of 150 mm was obtained.

[0141] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 150°C (resulting in a film thickness of 30 μm).

[0142] The phase difference and wavelength dispersion characteristics of the obtained film were measured. The results are shown in Table 2. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the humid and heat resistance test, the light transmittance was 89% and the haze was 3.5%, resulting in a decrease of 4% in total light transmittance and an increase of 3.2% in haze.

[0143] The resulting film had low light transmittance, high haze, and poor resistance to humidity and heat.

[0144] [Table 2]

[0145] Comparative Example 2 40.0 g of ethylcellulose (Ethocel Standard 300, manufactured by Dow Chemical, molecular weight Mn=87,000, molecular weight Mw=269,000, Mw / Mn=3.1, degree of total substitution DS=2.52, sodium chloride content 0.054 wt) used in Example 2 as a cellulosic resin was dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution without washing with deionized water to obtain a 12 wt% resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at 40°C and then in two stages at 155°C, a film with a width of 150 mm was obtained.

[0146] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 150°C (resulting in a film thickness of 30 μm).

[0147] The phase difference and wavelength dispersion characteristics of the obtained film were measured. The results are shown in Table 2. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the humid and heat resistance test, the light transmittance was 91% and the haze was 1.7%, resulting in a decrease of 2% in total light transmittance and an increase of 1.4% in haze.

[0148] The resulting film had low light transmittance, high haze, and poor resistance to humidity and heat.

[0149] Comparative Example 3 28.00 g of ethylcellulose (Ethocel standard 100, manufactured by Dow Chemical, molecular weight Mn=58,000, molecular weight Mw=181,000, Mw / Mn=3.1, degree of total substitution DS=2.51, sodium chloride content 0.082% by weight), which was used as the cellulosic resin in Comparative Example 1, and 12.00 g of the ester resin (1) exhibiting negative birefringence obtained by Synthesis Example 1 were dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to obtain a 15% by weight resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at a drying temperature of 40°C, it was dried in two stages at 155°C to obtain a film (resin composition) with a width of 150 mm (cellulosic resin: 70.00% by weight, ester resin exhibiting negative birefringence: 30.00% by weight).

[0150] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 140°C (resulting in a film thickness of 30 μm).

[0151] The light transmittance, haze, phase difference characteristics, wavelength dispersion characteristics, and heat and humidity resistance of the obtained film were measured. The results are shown in Table 2. The obtained film had a light transmittance of 93% and a haze of 0.4%. After the heat and humidity resistance test, the light transmittance was 91% and the haze was 1.6%, resulting in a decrease of 2% in total light transmittance and an increase of 1.2% in haze.

[0152] The resulting film had low light transmittance, high haze, and poor resistance to humidity and heat.

[0153] Comparative Example 4 31.20 g of ethylcellulose (Ethocel standard 300, manufactured by Dow Chemical, molecular weight Mn=87,000, molecular weight Mw=269,000, Mw / Mn=3.1, degree of total substitution DS=2.52, sodium chloride content 0.054 wt%) used in Example 2 as a cellulosic resin, and 8.80 g of the negative birefringence ester resin (2) obtained in Synthesis Example 2 were dissolved in a toluene / ethyl acetate = 8 / 2 (weight ratio) solution to obtain a 15 wt% resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at a drying temperature of 40°C, it was dried in two stages at 155°C to obtain a film (resin composition) with a width of 150 mm (cellulosic resin: 78.0 wt%, negative birefringence ester resin: 22.0 wt%).

[0154] The obtained film was cut into 50 mm squares, then uniaxially stretched to 2.0 times its original size at 157°C (resulting in a film thickness of 30 μm).

[0155] The light transmittance, haze, phase difference characteristics, wavelength dispersion characteristics, and heat and humidity resistance of the obtained film were measured. The results are shown in Table 2. The obtained film had a light transmittance of 93% and a haze of 0.4%. After the heat and humidity resistance test, the light transmittance was 91% and the haze was 1.6%, resulting in a decrease of 2% in total light transmittance and an increase of 1.2% in haze.

[0156] The resulting film had low light transmittance, high haze, and poor resistance to humidity and heat.

[0157] Comparative Example 5 As the cellulose-based resin used in Example 6, cellulose acetate butyrate (manufactured by Sigma-Aldrich, molecular weight Mn=27,000, molecular weight Mw=73,000, Mw / Mn=2.7, degree of acetyl substitution DS) was used. acetyl =1.05, butyl substitution degree DS butyl40.0 g of the solution (1.74% sodium acetate and sodium butyrate content, 0.042% by weight) was dissolved in a toluene / methanol = 8 / 2 (weight ratio) solution without washing with deionized water to obtain a 30% by weight resin solution. This solution was then poured onto a polyethylene terephthalate film using a coater, and after drying at 40°C followed by two-stage drying at 130°C, a film with a width of 150 mm was obtained.

[0158] The obtained film was cut into 50 mm squares, then uniaxially stretched to 1.5 times its original size at 130°C (resulting in a film thickness of 30 μm).

[0159] The phase difference and wavelength dispersion characteristics of the obtained film were measured. The results are shown in Table 2. The obtained film had a light transmittance of 93% and a haze of 0.3%. After the humid and heat resistance test, the light transmittance was 91% and the haze was 2.0%, resulting in a decrease of 2% in total light transmittance and an increase of 1.7% in haze.

[0160] The resulting film had low light transmittance, high haze, and poor resistance to humidity and heat.

[0161] Films containing the cellulose resin obtained in Examples 1 to 7 of the present invention, or compositions containing the cellulose resin and an ester resin exhibiting a negative birefringence, are suitable for optical films, particularly optical compensation films, because they exhibit a small increase in haze (suppression of whitening) after heat and humidity resistance tests, a small decrease in light transmittance, and high resistance to heat and humidity.

Claims

1. An optical film containing one of the following cellulosic resins, with a salt content of 0.020% or less: methylcellulose, ethylcellulose, propylcellulose, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, or cellulose acetate propionate.

2. A cellulose-based resin comprising 50 to 99% by weight of any of the following, having a salt content of 0.020% or less: methylcellulose, ethylcellulose, propylcellulose, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, or cellulose acetate propionate. An optical film comprising a composition containing 1 to 50% by weight of an ester resin exhibiting negative birefringence, having at least one residue unit from the group consisting of a cinnamic acid ester residue unit represented by the following formula (2), a fumarate ester residue unit represented by the following formula (3), and a residue unit represented by the following formula (4). 【Chemistry 1】 (In the formula, R ４ R represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. ５ ~R ９ Each of these independently represents one of the groups consisting of a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, a phenyl group, a thiol group, an amide group, an amino group, a hydroxyl group, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms. Y represents one of the groups consisting of a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, or a thiol group. 【Chemistry 2】 (In the formula, R １０、 R １１ Each of these independently represents either a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. 【Transformation 3】 (In the formula, R １２ This represents a five-membered heterocyclic residue or a six-membered heterocyclic residue containing one or more nitrogen or oxygen atoms as heteroatoms (the five-membered heterocyclic residue and the six-membered heterocyclic residue may form a fused ring structure with other cyclic structures).

3. The optical film according to claim 1 or 2, wherein the increase in haze after 500 hours in an environment of 65°C and 90% relative humidity is 1.0% or less, and the decrease in total light transmittance is less than 2%.

4. The optical film according to claim 1 or 2, wherein the phase difference (Re) shown by the following formula (A) is 30 to 300 nm, the Nz coefficient shown by the following formula (B) is 0.3 to 1.3, and the ratio of the phase difference at 450 nm to the phase difference at 550 nm, Re(450) / Re(550), is 0.60 < Re(450) / Re(550) < 1.

05. Re=(ny-nx)×d (A) Nz=(ny-nz) / (ny-nx) (B) (In the formula, nx represents the refractive index in the phase-advancing axis direction within the film plane, ny represents the refractive index in the phase-lagging axis direction within the film plane, nz represents the refractive index outside the film plane, and d represents the film thickness.)

5. A polarizing plate comprising the optical film according to claim 1 or 2.

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