阅读说明：本技术 酯树脂、反增塑剂、纤维素酯树脂组合物、光学膜和液晶显示装置 (Ester resin, anti-plasticizer, cellulose ester resin composition, optical film, and liquid crystal display device ) 是由 尾崎知代 田尻裕辅 于 2019-08-08 设计创作，主要内容包括：本发明提供一种加工成薄膜状时的强度、耐热性、尺寸稳定性的平衡性优异、能够适合作为对光学用树脂的反增塑剂使用的酯树脂、包含其的树脂组合物、使用该树脂组合物而得到的光学膜以及使用其的液晶显示装置。具体地,本发明提供一种酯树脂、包含其的树脂组合物、使用该组合物而得到的光学膜、以及使用该光学膜的液晶显示装置,该酯树脂的特征在于,其由通式H-(G～1-A)-n-G～1-H(I)表示,式(I)中,G～1为亚烷基二醇残基、氧亚烷基二醇残基或芳基二醇残基,A为二羧酸残基,且A的总计摩尔数的25摩尔％以上为间苯二甲酸残基,n为重复单元数,每个重复单元中,G～1、A可以相同也可以不同,并且多个G～1可以相同也可以不同。(The invention provides an ester resin which has excellent balance of strength, heat resistance and dimensional stability when processed into a film shape and can be suitably used as a plasticizer for an optical resin, a resin composition containing the ester resin, an optical film obtained by using the resin composition and a liquid crystal display using the optical filmProvided is a device. Specifically, the present invention provides an ester resin, a resin composition comprising the same, an optical film obtained using the composition, and a liquid crystal display device using the optical film, wherein the ester resin is represented by the general formula H- (G) 1 ‑A) n ‑G 1 H (I) represents, in the formula (I), G 1 Is an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue, A is a dicarboxylic acid residue, 25 mol% or more of the total number of moles of A is an isophthalic acid residue, n is the number of repeating units, and in each repeating unit, G is 1 A may be the same or different, and G's may be plural 1 May be the same or different.)

1. An ester resin, characterized by being represented by the following general formula (I):

H-(G¹-A)_n-G¹-H(I)

in the formula (I), G¹Is an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue, A isDicarboxylic acid residues, wherein 25 mol% or more of the total moles of A are isophthalic acid residues, n is the number of repeating units, and G is the number of repeating units¹A may be the same or different, and G's may be plural¹May be the same or different.

2. The ester resin according to claim 1,

g in the general formula (I)¹Is an alkylene glycol residue having 2 to 12 carbon atoms, an oxyalkylene glycol residue having 4 to 12 carbon atoms or an aryl glycol residue having 6 to 18 carbon atoms, and the average value of n is 1.0 to 10.0.

3. The ester resin according to claim 1 or 2, wherein,

the number average molecular weight of the ester resin is in a range of 350-2000.

4. The ester resin according to any one of claims 1 to 3, wherein,

g in the general formula (I)¹Is a residue of one or more selected from the group consisting of ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol and 2-methyl-1, 3-propanediol, A is a residue of one or more selected from the group consisting of succinic acid, adipic acid, dicarboxylcyclohexane, phthalic acid, terephthalic acid and isophthalic acid, and 25 mol% or more of the total mole number of A is an isophthalic acid residue.

5. The ester resin according to any one of claims 1 to 4, wherein,

40 to 100 mol% of the total mole number of A in the general formula (I) is an isophthalic acid residue.

6. The ester resin according to any one of claims 1 to 5, wherein,

the amount of residual diol in the ester resin is 1.5% by mass or less.

7. An ester resin mixture, comprising:

an ester resin of any one of claims 1 to 6; and a diester compound represented by the following general formula (II),

B-G²-B(II)

in the formula (II), B is an aryl monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, G²The plural groups B may be the same or different and are alkylene glycol residues, oxyalkylene glycol residues or aryl glycol residues.

8. The ester resin mixture according to claim 7,

the diester compound is a diester of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 2-methyl-1, 3-propylene glycol, diethylene glycol or dipropylene glycol with benzoic acid or p-toluic acid.

9. The ester resin mixture according to claim 7 or 8,

the ester resin and the diester compound are contained in a mass ratio (ester resin/diester compound) of 95/5-50/50.

10. An anti-plasticizer for a resin for optical materials, characterized in that:

consisting of an ester resin according to any of claims 1 to 6 or an ester resin mixture according to any of claims 7 to 9.

11. A cellulose ester resin composition characterized in that:

the cellulose ester resin composition containing the antiplasticizer according to claim 10 and 1 to 30 parts by mass of the antiplasticizer per 100 parts by mass of the cellulose ester resin.

12. An optical film, characterized in that:

comprising the cellulose ester resin composition according to claim 11.

13. The optical film of claim 12, which is used to protect a polarizer.

14. A liquid crystal display device, characterized in that:

having the optical film of claim 12 or 13.

Technical Field

The present invention relates to an ester resin and an ester resin mixture suitable as a plasticizer for an optical material resin, a cellulose ester resin composition containing the ester resin and the ester resin mixture, an optical film obtained using the resin composition, and a liquid crystal display device using the optical film.

Background

In recent years, liquid crystal displays have been made thinner, and polarizer protective films have been made thinner from 80 μm to 60 μm and further from 40 to 25 μm. Conventionally, triacetyl cellulose resin (hereinafter, referred to as TAC) has been used in many cases as a protective film for a polarizer, from the viewpoint of easy adhesion to a polarizer.

However, TAC has a problem that TAC is hard and brittle and therefore has insufficient strength when formed into a film, and is easily broken. Further, TAC has high moisture permeability and moisture absorption, and is likely to undergo dimensional change due to moisture permeability and moisture absorption, and therefore, it is necessary to provide various additives by suppressing moisture permeability and moisture absorption with an additive (for example, see patent document 1).

In general, when an additive is added to suppress moisture permeation and moisture absorption, plasticization of the resin occurs at the same time, and it is difficult to achieve both physical properties such as strength and heat resistance and dimensional stability of the obtained film. Therefore, it is required to develop an additive capable of providing a film excellent in elastic modulus, heat resistance and dimensional stability.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-151699

Disclosure of Invention

Problems to be solved by the invention

In view of the above circumstances, an object to be solved by the present invention is to provide an ester resin and an ester resin mixture which are excellent in balance among strength, heat resistance and moisture absorption dimensional stability when processed into a film form and which can be suitably used as an anti-plasticizer for an optical resin, a cellulose ester resin composition containing the same, an optical film obtained using the resin composition, and a liquid crystal display device using the same.

Means for solving the problems

The present inventors have conducted intensive studies and as a result, have found that the above problems can be solved by using a specific dicarboxylic acid component as a raw material of an ester resin, and have completed the present invention.

That is, the present invention provides an ester resin, an ester resin mixture containing the same, a plasticizer composed of the same, a cellulose ester resin composition, an optical film obtained using the composition, and a liquid crystal display device using the optical film, the ester resin being characterized by being represented by the following general formula (I):

H-(G¹-A)_n-G¹-H (I)

in the formula (I), G¹Is an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue, A is a dicarboxylic acid residue, 25 mol% or more of the total number of moles of A is an isophthalic acid residue, n is the number of repeating units, and in each repeating unit, G is¹A may be the same or different, and G's may be plural¹May be the same or different.

Effects of the invention

According to the present invention, an ester resin and an ester resin mixture which are excellent in balance among strength, heat resistance and dimensional stability when processed into a film form and which can be suitably used as a plasticizer for an optical resin can be provided. In addition, by using the specific ester resin or the mixture thereof, particularly in an optical film containing a cellulose ester resin, it is possible to achieve both improvement of elastic modulus and heat resistance and dimensional stability without impairing transparency, and it is possible to suitably use the optical film as an optical film used in a liquid crystal display device.

Detailed Description

The ester resin of the present invention is characterized by being represented by the following general formula (I):

H-(G¹-A)_n-G¹-H (I)

in the formula (I), G¹Is an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue, A is a dicarboxylic acid residue, 25 mol% or more of the total number of moles of A is an isophthalic acid residue, n is the number of repeating units, and in each repeating unit, G is¹A may be the same or different, and G's may be plural¹May be the same or different.

G in the above general formula (I)¹Is an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue. The diol residue refers to a group obtained by removing a hydrogen atom from a hydroxyl group.

The alkylene glycol residue is preferably an alkylene glycol residue having 2 to 12 carbon atoms from the viewpoint of more easily exhibiting the effects of the present invention, and examples thereof include ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 2-methyl-1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 2-dimethyl-1, 3-propanediol (neopentyl glycol), 2-diethyl-1, 3-propanediol (3, 3-dimethylolpentane), 2-n-butyl-2-ethyl-1, 3-propanediol (3, 3-dimethylolheptane), 3-methyl-1, 5-pentanediol, 3-dimethylolheptane, 1, 3-butanediol, 2-butanediol, 1, residues of 1, 6-hexanediol, 2, 4-trimethyl-1, 3-pentanediol, 2-ethyl-1, 3-hexanediol, 2-methyl-1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol, 1, 12-dodecanediol, and the like may be used alone or in combination of two or more. Among these, from the viewpoint of an ester resin having more excellent compatibility when mixed with a cellulose ester resin described later, a group having 3 or less carbon atoms without a branch between OH groups is preferable, and among these, a residue of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, or 2-methyl-1, 3-propylene glycol is preferable, a residue of ethylene glycol or 1, 2-propylene glycol is more preferable, and a residue of 1, 2-propylene glycol is most preferable.

The oxyalkylene glycol residue is preferably an oxyalkylene glycol residue having 4 to 12 carbon atoms from the viewpoint of more easily exhibiting the effect of the present invention, and examples thereof include residues of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like, and two or more of them may be used alone or in combination.

The above-mentioned aryl diol residue is preferably an aryl diol residue having 6 to 18 carbon atoms from the viewpoint of more easily exhibiting the effect of the present invention, and examples thereof include residues of hydroquinone, resorcinol, bisphenol a, an alkylene oxide adduct of bisphenol a, bisphenol F, an alkylene oxide adduct of bisphenol F, biphenol, an alkylene oxide adduct of biphenol, and the like, and may be used alone or in combination of two or more thereof.

Further, a in the above general formula (I) is a dicarboxylic acid residue, specifically, an alkylene dicarboxylic acid residue (a1) or an aryl dicarboxylic acid residue (a2) is mentioned, and the mole number of the isophthalic acid residue in the total mole number of a must be 25 mole% or more. Here, the dicarboxylic acid residue means a group other than-OH in the carboxyl group.

Among the ester resins represented by the above general formula (I), isophthalic acid is used in a large amount as a raw material dicarboxylic acid, and when the ester resin is mixed with an optical resin described later, the optical resin, particularly a cellulose ester resin, is not plasticized, and when the ester resin is processed into a film, the elastic modulus can be improved and heat resistance can be imparted, and the ester resin can be suitably used for an optical film application for advancing a film formation without impairing the transparency inherent in the optical resin.

From the viewpoint of exerting the above-mentioned effects, the number of moles of isophthalic acid residues in the dicarboxylic acid residues must be 25 mol% or more, and particularly from the viewpoint of further exerting the effects, the content of isophthalic acid residues is preferably in the range of 25 to 100 mol%, more preferably in the range of 40 to 100 mol%, and most preferably in the range of 70 to 90 mol%.

The above-mentioned alkylenedicarboxylic acid residue (a1) which can be used in combination with an isophthalic acid residue is preferably an alkylenedicarboxylic acid residue having 2 to 12 carbon atoms from the viewpoint of more easily exhibiting the effects of the present invention, and examples thereof include residues of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, 1, 2-dicarboxycyclohexane, 1, 2-dicarboxycyclohexene and the like, and two or more thereof may be used alone or in combination. Among them, from the viewpoint of obtaining an optical film having more excellent transparency of a film, the residue of succinic acid, adipic acid, and 1, 2-dicarboxycyclohexane is preferable, and the residue of adipic acid is most preferable.

Examples of the aryldicarboxylic acid residue (a2) that can be used in combination with an isophthalic acid residue include residues of phthalic acid, terephthalic acid, 1, 4-naphthalenedicarboxylic acid, 2, 3-naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, 2, 7-naphthalenedicarboxylic acid, 1, 8-naphthalenedicarboxylic acid, and the like, and these may be used alone or in combination of two or more. Among them, from the viewpoint of obtaining an optical film having higher strength, the residue of phthalic acid or terephthalic acid is preferable, and the residue of phthalic acid is most preferable.

In the present invention, the ester resin represented by the above general formula (I) may be represented by G¹A is the same substance composition and only n is a mixture of compounds with different numbers of repeating units, and may be G in the general formula (I)¹A and n are each a mixture of different compounds.

From the viewpoint of further exhibiting the effect of the present invention, in the general formula (I), G is preferably¹Residues of ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 2-methyl-1, 3-propanediol, A1 which may be used in combination is the residue of succinic acid, adipic acid, 1, 2-dicarboxycyclohexane, A2 is the residue of phthalic acid, terephthalic acid, in particular, G is most preferred¹Residues of ethylene glycol, 1, 2-propanediol, a1, which may be used in combination, is the residue of adipic acid and a2 is the residue of phthalic acid.

In the present invention, in order to reduce nonvolatile components in the film production process and obtain an optical film having excellent moisture absorption dimensional stability in an optical film obtained by mixing with a resin for an optical material described later, particularly a cellulose ester resin, it is desirable to reduce the amount of residual diol in the ester resin represented by the above general formula (I) by distillation or the like. The amount of residual diol in the ester resin is preferably 1.5% by mass or less, and most preferably 1.0% by mass or less. The residual diol content can be measured by gas chromatography.

In addition, from the viewpoint of compatibility and film properties, the ester resin of the present invention preferably has a number average molecular weight in the range of 350 to 2000, particularly preferably in the range of 400 to 1500, and most preferably in the range of 500 to 1200. The average value of the number n of repeating units in the general formula (I) is preferably in the range of 1.0 to 10.0, more preferably in the range of 1.0 to 8.0, and most preferably in the range of 1.5 to 7.0, from the viewpoint of compatibility and film properties. The average value of the number average molecular weight and n is a value measured by GPC measurement.

In the present invention, GPC measurement is performed under the following conditions.

[ GPC measurement conditions ]

A measuring device: high-speed GPC apparatus "HLC-8320 GPC" manufactured by Tosoh corporation "

Column: "TSK GURDCOLUMN SuperHZ-L" manufactured by Tosoh corporation, "TSK gel SuperHZM-M" manufactured by Tosoh corporation "+ TSK gel SuperHZ-2000" manufactured by Tosoh corporation "

A detector: RI (differential refractometer)

Data processing: "EcoSEC Data Analysis version 1.07" manufactured by Tosoh corporation "

Column temperature: 40 deg.C

Developing agent: tetrahydrofuran (THF)

Flow rate: 0.35 mL/min

Measurement of the sample: a7.5 mg sample was dissolved in 10ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to obtain a measurement sample.

Sample injection amount: 20 μ l

Standard sample: following the manual for the determination of "HLC-8320 GPC" mentioned above, the following monodisperse polystyrene of known molecular weight was used.

(monodisperse polystyrene)

"A-300" manufactured by Tosoh corporation "

"A-500" manufactured by Tosoh corporation "

"A-1000" manufactured by Tosoh corporation "

"A-2500" manufactured by Tosoh corporation "

"A-5000" manufactured by Tosoh corporation "

"F-1" manufactured by Tosoh corporation "

"F-2" manufactured by Tosoh corporation "

"F-4" manufactured by Tosoh corporation "

"F-10" manufactured by Tosoh corporation "

"F-20" manufactured by Tosoh corporation "

"F-40" manufactured by Tosoh corporation "

"F-80" manufactured by Tosoh corporation "

"F-128" manufactured by Tosoh corporation "

"F-288" manufactured by Tosoh corporation "

Further, the acid value of the ester resin of the present invention is preferably 5 or less, more preferably 1 or less, from the viewpoint of better compatibility with the resin for an optical material.

The ester resin of the present invention can be produced, for example, by subjecting the above raw materials to an esterification reaction at a temperature of, for example, 180 to 250 ℃ for 10 to 25 hours in the presence of an esterification catalyst, if necessary. Conditions such as the temperature and time of the esterification reaction are not particularly limited and may be appropriately set. The monocarboxylic acid and the dicarboxylic acid may be used as the raw materials, and an acid itself, an esterified product thereof, an acid chloride thereof, an acid anhydride of a dicarboxylic acid, or the like may be used as the raw materials.

Examples of the esterification catalyst include titanium catalysts such as tetraisopropyl titanate and tetrabutyl titanate, tin catalysts such as dibutyltin oxide, and organosulfonic acid catalysts such as p-toluenesulfonic acid.

The amount of the esterification catalyst used may be appropriately set, but is preferably in the range of 0.001 to 0.1 part by mass per 100 parts by mass of the total amount of raw materials.

The ester resin of the present invention varies in properties depending on factors such as the number average molecular weight and the combination of raw materials, but is usually liquid, solid, paste-like at ordinary temperature.

More specifically, the method for producing the ester resin includes a method of reacting a compound having a hydroxyl group at the terminal obtained by using the above-mentioned alkylene glycol, oxyalkylene glycol or aryl glycol and dicarboxylic acid with monocarboxylic acid. The alkylene glycol, oxyalkylene glycol or aryl glycol may be put into the reaction system together with the dicarboxylic acid and monocarboxylic acid and reacted with each other, or may be a series reaction in which a compound having a hydroxyl group at the terminal obtained by using the alkylene glycol, oxyalkylene glycol or aryl glycol and dicarboxylic acid is obtained and then the monocarboxylic acid is put into the reaction system.

In the present invention, the above-mentioned ester resin may be used alone and added to a resin for optical materials such as a cellulose ester resin described later, or may be used in combination with a diester compound represented by the following general formula (II).

B-G²-B(II)

In the formula (II), B is an aryl monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, G²The plural groups B may be the same or different and are alkylene glycol residues, oxyalkylene glycol residues or aryl glycol residues.

In the above general formula (II), B is a monocarboxylic acid residue, and specifically, an aryl monocarboxylic acid residue or an aliphatic monocarboxylic acid residue may be mentioned. Here, the "carboxylic acid residue" means a group other than-OH in the carboxyl group. The aryl monocarboxylic acid residue is preferably an aryl monocarboxylic acid residue having 6 to 12 carbon atoms from the viewpoint of ease of raw material acquisition and ease of esterification, and from the viewpoint of easily achieving a balance among moisture permeation resistance, elastic modulus and dimensional stability when mixed with a cellulose ester resin described later, and examples thereof include benzoic acid, dimethylbenzoic acid, trimethylbenzoic acid, tetramethylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, cuminic acid, p-tert-butylbenzoic acid, o-methylbenzoic acid, m-methylbenzoic acid, p-toluic acid, ethoxybenzoic acid, propoxybenzoic acid, anisic acid, naphthoic acid, and the like, and may be used alone or in combination of two or more. In particular, from the viewpoint of more easily exhibiting the effects of the present invention, the residue of benzoic acid, p-toluic acid, or dimethylbenzoic acid is preferable, and the residue of benzoic acid, or p-toluic acid is more preferable. The number of carbon atoms herein does not include the carbon atoms in the carboxyl group. Further, the residue may be a residue of aromatic nicotinic acid, furoic acid or the like optionally having a substituent.

The aliphatic monocarboxylic acid residue is preferably an aliphatic monocarboxylic acid residue having 1 to 8 carbon atoms from the viewpoints of easiness of raw material acquisition and esterification reaction, and easiness of obtaining a balance among moisture permeability resistance, elastic modulus and dimensional stability when mixed with a cellulose ester resin described later, and examples thereof include residues of acetic acid, propionic acid, butyric acid, caproic acid, caprylic acid, octylic acid and the like, and two or more thereof may be used alone or in combination, and particularly, acetic acid is preferably used. The number of carbon atoms herein does not include the carbon atoms in the carboxyl group.

G in the above general formula (II)²Is an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue. The diol residue refers to a group obtained by removing a hydrogen atom from a hydroxyl group.

The alkylene glycol residue is preferably an alkylene glycol residue having 2 to 12 carbon atoms from the viewpoint of more easily exhibiting the effects of the present invention, and examples thereof include ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 2-methyl-1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 2-dimethyl-1, 3-propanediol (neopentyl glycol), 2-diethyl-1, 3-propanediol (3, 3-dimethylolpentane), 2-n-butyl-2-ethyl-1, 3-propanediol (3, 3-dimethylolheptane), 3-methyl-1, 5-pentanediol, 3-dimethylolheptane, 1, 3-butanediol, 2-butanediol, 1, residues of 1, 6-hexanediol, 2, 4-trimethyl-1, 3-pentanediol, 2-ethyl-1, 3-hexanediol, 2-methyl-1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol, 1, 12-dodecanediol, and the like may be used alone or in combination of two or more. Among them, from the viewpoint of enhancing the strength of the film, preferred are residues of ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 2-methyl-1, 3-propanediol, and 1, 5-pentanediol.

The oxyalkylene glycol residue is preferably an oxyalkylene glycol residue having 4 to 12 carbon atoms from the viewpoint of more easily exhibiting the effect of the present invention, and examples thereof include residues of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like, and two or more of them may be used alone or in combination.

The above-mentioned aryl diol residue is preferably an aryl diol residue having 6 to 18 carbon atoms from the viewpoint of more easily exhibiting the effect of the present invention, and examples thereof include residues of hydroquinone, resorcinol, bisphenol a, an alkylene oxide adduct of bisphenol a, bisphenol F, an alkylene oxide adduct of bisphenol F, biphenol, an alkylene oxide adduct of biphenol, and the like, and may be used alone or in combination of two or more thereof.

In the general formula (II), from the viewpoint of further exhibiting the effect of the present invention, it is preferable that B is a residue of benzoic acid or p-toluic acid, and G is²Is the residue of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 2-methyl-1, 3-propylene glycol, diethylene glycol or dipropylene glycol.

The diester compound (II) may be a synthetic product or a commercially available product, and in the synthesis, the reaction conditions (catalyst, temperature, time, etc.) used in the synthesis of the ester resin (I) used in the present invention may be used, for example.

The ester resin mixture of the present invention preferably contains the ester resin (I) and the diester compound (II) in a mass ratio [ ester resin/diester compound ] 100/0 to 50/50, from the viewpoint of being suitably used as an anti-plasticizer for an optical resin described later.

When such a diester compound (II) is contained, it is appropriately disposed in the gap of the resin for an optical material, particularly a cellulose ester resin, and as a result, the effects of improving moisture permeation resistance, elastic modulus, and dimensional stability are further exhibited, and compatibility with the resin for an optical material can be secured, and transparency usable as an optical film can be more effectively maintained.

From the viewpoints of further exhibiting these effects, suppressing contamination of a production line and the like due to volatilization, easily maintaining transparency of an optical film, and the like, the proportion of the ester resin (I) in the total mass of the ester resin (I) and the diester compound (II) is preferably 50 to 100 mass%, more preferably 60 to 95 mass%, and most preferably 65 to 90 mass%.

The ester resin mixture of the present invention may be composed of only the ester resin (I) and the diester compound (II), or may contain a polyester other than the ester resin (I) and a diester compound other than the diester compound (II). The resin composition may contain a substance known as a modifier for a so-called optical resin other than the ester resin (I) and the diester compound (II), or may contain an unreacted material of a raw material used for producing the ester resin (I) and the diester compound (II).

The ester resin or ester resin mixture of the present invention obtained by such a method or the like can be blended with a resin for an optical material to obtain a film having an excellent balance among an elastic modulus, heat resistance and dimensional stability, and can be used as a so-called anti-plasticizer, and the obtained film is particularly suitable as an optical film.

The resin for optical materials is not particularly limited as long as it is a resin having high transparency and capable of being processed into a film, and examples thereof include (meth) acrylic resins, cycloolefin resins, polycarbonate resins, and cellulose ester resins. In particular, from the viewpoint of further exhibiting the effect of the present invention, it is preferable to use a cellulose ester resin.

The amount of the ester resin or the ester resin mixture to be blended with the resin for optical materials of the present invention may be determined depending on the desired performance (e.g., elastic modulus, heat resistance, etc.), and is, for example, in the range of 0.1 to 50 parts by mass, preferably in the range of 1 to 30 parts by mass, and particularly preferably in the range of 3 to 20 parts by mass, based on 100 parts by mass of the resin for optical materials.

Examples of the cellulose ester resin include resins obtained by esterifying a part or all of the hydroxyl groups of cellulose obtained from cotton linter, wood pulp, kenaf, and the like.

Examples of the cellulose ester resin include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose nitrate, and when used as a protective film for a polarizer, cellulose acetate is preferably used 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 degree of polymerization of 250 to 400, and a degree of acetylation of 54.0 to 62.5 mass%, more preferably 58.0 to 62.5 mass%. When the degree of polymerization and the degree of acetylation of the cellulose acetate are in such ranges, a film having excellent mechanical properties can be obtained. In the present invention, so-called triacetylcellulose is more preferably used. The acetylation degree in the present invention means a mass ratio of acetic acid generated by alkalinizing the cellulose acetate to the total amount of the cellulose acetate.

The number average molecular weight of the cellulose acetate is preferably 70000 to 300000, more preferably 80000 to 200000. When the number average molecular weight of the cellulose acetate is in this range, a film having excellent mechanical properties can be easily obtained.

The optical film of the present invention is a resin composition containing the ester resin or ester resin mixture of the present invention and a resin for optical materials such as cellulose ester resin, and may be a resin composition containing other various additives as required.

To obtain the optical film of the present invention, for example, extrusion molding, casting molding, or the like can be used. Specifically, for example, an optical film in an unstretched state can be extrusion-molded using an extruder equipped with a T-die, a circular die, or the like. When the optical film of the present invention is obtained by extrusion molding, a resin composition obtained by melt-kneading a resin for an optical material such as the above-mentioned ester resin, ester resin mixture, cellulose ester resin, and other additives may be used in advance, and the resin composition may be subjected to melt-kneading at the time of extrusion molding and may be directly subjected to extrusion molding.

Examples of the additives include the ester resin of the present invention, modifiers other than diester compounds, thermoplastic resins, ultraviolet absorbers, delustering agents, stabilizers, deterioration inhibitors (for example, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers), dyes, and the like.

The other modifiers may be ester resins other than the diester compounds, phosphate esters such as triphenyl phosphate (TPP), tricresyl phosphate and cresyldiphenyl phosphate, phthalate esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate and di-2-ethylhexyl phthalate, ethyl phthalate ethyl glycolate, butyl phthalate butyl glycolate, trimethylolpropane tribenzoate, pentaerythritol tetraacetate, and acetyl tributyl citrate, which are specified in the present invention, within a range not to impair the effects of the present invention.

The thermoplastic resin is not particularly limited, but examples thereof include polyester resins, polyether ester resins, polyurethane resins, acrylic resins, epoxy resins, and toluene sulfonamide resins other than the ester resin of the present invention.

The ultraviolet absorber is not particularly limited, but examples thereof include hydroxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, and the like. Preferably, the ultraviolet absorber is used in the range of 0.01 to 2 parts by mass per 100 parts by mass of the cellulose ester resin.

Examples of the matting agent include silica, titanium oxide, alumina, calcium carbonate, calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, kaolin, talc, and the like. Preferably, the matting agent is used in an amount of 0.1 to 0.3 parts by mass based on 100 parts by mass of the cellulose ester resin.

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

The type and amount of the dye are not particularly limited as long as the dye does not interfere with the object of the present invention.

Further, the optical film can be obtained by molding, for example, a so-called solution casting method (solvent casting method) as follows, in addition to the molding method described above: a resin solution obtained by dissolving a resin for an optical material such as the cellulose ester resin composition in an organic solvent is cast on a metal support, and then the organic solvent is distilled off and dried.

According to the solution casting method, the orientation of the resin for an optical material such as the cellulose ester resin in the film during the molding process can be suppressed, and therefore, the obtained film can exhibit substantial optical isotropy. The film exhibiting the above optical isotropy is useful as an optical material for, for example, a liquid crystal display, and is useful as a protective film for a polarizer. The film obtained by the above method has a surface which is less likely to have irregularities and has excellent surface smoothness.

The above solution casting method generally consists of the following steps: a first step of dissolving the resin composition in an organic solvent and casting the obtained resin solution on a metal support; a second step of forming a thin film by distilling off and drying the organic solvent contained in the resin solution after casting; and a subsequent third step of peeling the thin film formed on the metal support from the metal support and drying the peeled thin film by heating.

As the metal support used in the first step, a metal support in a ring belt shape or a drum shape can be exemplified, and for example, a support made of stainless steel and having a mirror-finished surface can be used.

In the case of casting a resin solution on the metal support, it is preferable to use a resin solution filtered through a filter in order to prevent foreign matter from being mixed into the obtained film.

The drying method in the second step is not particularly limited, and examples thereof include a method of forming a thin film on the metal support by blowing air at a temperature of 30 to 50 ℃ to the upper surface and/or the lower surface of the metal support to evaporate 50 to 80 mass% of the organic solvent contained in the resin solution after casting.

Next, the third step is a step of peeling the thin film formed in the second step from the metal support and drying the film by heating at a temperature higher than that in the second step. The heat drying method is preferably a method of raising the temperature stepwise at a temperature of 100 to 160 ℃, for example, because good dimensional stability can be obtained. By heating and drying under the above temperature conditions, the organic solvent remaining in the film after the second step can be removed substantially completely.

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

The organic solvent that can be used when the resin composition is mixed and dissolved in an organic solvent is not particularly limited as long as it can dissolve the resin composition, and for example, when cellulose acetate is used as the resin for an optical material, an organic halogen compound such as dichloromethane or a dioxolane is preferably used as a good solvent.

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

The mixing ratio of the good solvent and the poor solvent is preferably good solvent/poor solvent

The mass ratio is 75/25-95/5.

The concentration of the resin for optical materials in the resin solution is preferably 10 to 50% by mass, and more preferably 15 to 35% by mass.

In the present invention, for example, the optical film in an unstretched state obtained by the above-described method may be uniaxially stretched in the longitudinal direction in the machine flow direction and uniaxially stretched in the transverse direction in the direction orthogonal to the machine flow direction as necessary to obtain a stretched optical film. Further, a biaxially stretched film can be obtained by stretching by a sequential biaxial stretching method of roll stretching and tenter stretching, a simultaneous biaxial stretching method based on tenter stretching, a biaxial stretching method based on tubular stretching, or the like. The stretch ratio is preferably 0.1% to 300%, more preferably 0.2% to 250%, and most preferably 0.3% to 200% in at least one direction. By designing in this range, a stretched optical film preferable from the viewpoint of birefringence, heat resistance, and strength can be obtained.

The optical film of the present invention is excellent in elastic modulus, heat resistance, moisture permeation resistance and dimensional stability, and therefore 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 polarizer, a retardation film, a reflective film, a viewing angle improving film, an antiglare film, a non-reflective film, an antistatic film, a color filter, and the like, and among them, the optical film is preferably used as a protective film for a polarizer.

The thickness of the optical film is preferably in the range of 20 to 120 μm, more preferably in the range of 25 to 100 μm, and particularly preferably in the range of 25 to 80 μm. When the optical film is used as a protective film for a polarizer, if the film thickness is in the range of 25 to 80 μm, the optical film is suitable for thinning a liquid crystal display device, and can maintain sufficient film strength, Rth stability, moisture permeation resistance and other excellent performances.

The optical film of the present invention is characterized in that the elastic modulus is higher than that in the case where the ester resin is not blended. In general, a polyester resin blended for the purpose of improving the processability of a cellulose ester resin is sometimes referred to as a "plasticizer", but the ester resin of the present invention has a performance different from that of a conventional one in that it is used as a counter plasticizer in comparison with a plasticizing effect from the viewpoint of improving the strength of the resin for an optical material.

Further, the protective film for a polarizer can adjust a desired retardation without bleeding under high temperature and high humidity conditions, and thus can be widely used in various liquid crystal display systems depending on the application.

Examples of the liquid crystal display mode include IPS (In-Plane Switching), TN (Twisted Nematic), VA (vertical alignment), OCB (Optically compensated Bend) and the like.

The optical film of the present invention can be suitably used as an optical material for protective films for polarizers used in displays such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, rear projection televisions, etc., retardation films such as 1/4 wave plates, 1/2 wave plates, viewing angle control films, liquid crystal optical compensation films, etc., front panels of displays, etc. The resin composition of the present invention can be used for waveguides, lenses, optical fibers, optical fiber substrates, coating materials, lenses for LEDs, lens covers, and the like in the fields of optical communication systems, optical switching systems, and optical measurement systems.

Examples

The present invention will be described in more detail with reference to examples. In the examples, the amounts of the components and% are based on mass unless otherwise specified.

Example 1

In a1 liter four-necked flask, 346g of 1, 2-propanediol (hereinafter abbreviated as "PG") as a diol component, 376g of isophthalic acid (hereinafter abbreviated as "IPA") as a dicarboxylic acid component, 110g of adipic acid (hereinafter abbreviated as "AA") and 0.05g of tetraisopropyl titanate (hereinafter abbreviated as "TIPT") as a catalyst were charged, and the temperature was raised to 230 ℃ in a stepwise manner under a nitrogen flow from a nitrogen introduction tube. The condensation reaction was carried out at 230 ℃ for 8 hours, and it was confirmed that the acid value was 1.0 or less. The excess diol was removed under reduced pressure at 150 ℃ to thereby obtain ester resin (1) of the present invention. The obtained ester resin (1) was a pale yellow liquid at room temperature, and had an acid value of 0.25, a hydroxyl value of 135, a number average molecular weight of 920, and a residual PG amount of 0.2 mass%.

Example 2

In a1 liter four-necked flask, 352g of PG as a diol component, 257g of IPA and 226g of AA as dicarboxylic acid components, and 0.05g of TIPT as a catalyst were charged, and the temperature was gradually raised to 230 ℃ under a nitrogen flow from a nitrogen introduction pipe. The condensation reaction was carried out at 230 ℃ for 8 hours, and it was confirmed that the acid value was 1.0 or less. The excess diol was removed under reduced pressure at 150 ℃ to thereby obtain ester resin (2) of the present invention. The obtained ester resin (2) was a pale yellow liquid at room temperature, and had an acid value of 0.27, a hydroxyl value of 135, a number average molecular weight of 950, and a residual PG amount of 0.2 mass%.

Comparative example 1

In a 3 liter four-necked flask, PG 922g as a diol component, phthalic anhydride (hereinafter abbreviated as "PA") 944g as a dicarboxylic acid component, AA 310g, and TIPT 0.13g as a catalyst were charged, and the temperature was gradually raised to 220 ℃ under a nitrogen flow from a nitrogen introduction tube. The condensation reaction was carried out at 220 ℃ for 8 hours, and when the acid value became 1 or less, the reaction product was filtered and taken out to obtain an ester resin (1'). The obtained ester resin (1') was a pale yellow liquid at room temperature, and had an acid value of 0.50, a hydroxyl value of 163, a number average molecular weight of 790, and a residual PG amount of 3.0 mass%.

Comparative example 2

The ester resin (1 ') was subjected to removal of excess diol under reduced pressure at 150 ℃ to thereby obtain an ester resin (2'). The obtained ester resin (2') was a pale yellow liquid at room temperature, and had an acid value of 0.18, a hydroxyl value of 147, a number-average molecular weight of 800 and a residual PG amount of 0.5 mass%.

Examples 3 to 4 and comparative examples 3 to 4

< preparation of cellulose ester optical film >

100 parts of triacetylcellulose resin ("LT-35" manufactured by Daluosite, Ltd.), 10 parts of the ester resins (1) to (2) and the ester resins (1 ') to (2') were dissolved in a mixed solvent composed of 810 parts of methylene chloride and 90 parts of methanol to prepare a coating solution as a cellulose ester resin composition. These coating liquids were cast on a glass plate to a thickness of 0.8mm or 0.5mm, dried at room temperature for 16 hours, then dried at 50 ℃ for 30 minutes, and further dried at 120 ℃ for 30 minutes, to obtain an optical film (60 μm or 40 μm). The physical properties of the obtained film were measured in the following manner, and the results are shown in table 1.

< measurement of elastic modulus of optical film >

The device comprises the following steps: AUTOGRAPH AG-IS manufactured by SHIMADZU

Test piece: rectangle 150mm 10mm thick 40 μm

And (3) spacing of the clamps: 100mm

Test speed: 10 mm/min

The greater the elastic modulus, the harder the film.

< method for evaluating elastic modulus >

X: the elastic modulus is 4600MPa or less.

O: the elastic modulus is greater than 4600MPa and is 4650MPa or less.

Very good: the elastic modulus is higher than 4650 MPa.

< measurement of Heat resistance of optical film >

The device comprises the following steps: RSA-III tensile mode manufactured by TA instruments

Temperature rise rate: 3 ℃ per minute

Frequency: 1Hz

Load strain: 0.1 percent of

Test piece film thickness: 60 μm

the peak top of tan δ is Tg, and a higher Tg indicates more excellent heat resistance.

< method for evaluating Heat resistance >

X: tg is 182 ℃ or lower.

O: tg higher than 182 ℃.

< measurement of dimensional stability of optical film >

The device comprises the following steps: SIINT TMA/SS6100+ humidity control unit manufactured by Hitachi high and New technology Co

Measuring temperature: constant at 40 deg.C

Relative humidity: 0 to 80 percent

And (3) measuring the load: 50mN

Test piece film thickness: 60 μm

The dimensional change rate was measured so that the relative humidity was 0% to 80%. The smaller the change rate, the more excellent the dimensional stability.

< method for evaluating dimensional stability >

X: the dimensional change rate is greater than 0.45%.

O: the dimensional change rate is 0.40% or more and 0.45% or less.

Very good: the dimensional change rate is less than 0.40%.

<HAZE>

The HAZE value was measured in accordance with JIS K7105 using a HAZE meter ("NDH 5000" manufactured by Nippon Denshoku industries Co., Ltd.). The closer the value obtained is to 0%, the more transparent it is.

< method for evaluating transparency >

X: the HAZE value is greater than 1.0%.

O: the HAZE value is 1.0% or less.

< measurement of moisture permeability of optical film >

The measurement was carried out according to the method described in JIS Z0208. The measurement conditions were carried out at a temperature of 40 ℃ and a relative humidity of 90%. The smaller the value obtained, the more excellent the moisture permeation resistance.

< method for evaluating moisture permeation resistance >

X: the moisture permeability is more than 600g/m²·24h。

O: the moisture permeability is 600g/m²24h or less.

< evaluation of non-volatility >

The amount of change in mass of the film when exposed to an environment of 85 ℃ and 90% relative humidity (in a moist heat environment) for 120 hours was measured. The smaller the value obtained, the more excellent the non-volatility.

< method for evaluating non-volatility >

X: the damp-heat loss is more than 1.5 percent.

O: the wet heat loss is 1.5% or less.

[ Table 1]

By using isophthalic acid in the dicarboxylic acid component of the ester resin (I), the elastic modulus and Tg are improved. Further, by reducing the amount of residual glycol in the ester resin (I), dimensional change in moisture absorption is suppressed, and moisture permeability resistance and non-volatility under a moist heat environment are improved.

Synthesis example 1

1906g of p-toluic acid as a monocarboxylic acid component, 639g of PG as a diol component, and 0.153g of TiPT as a catalyst were put into a 3-liter four-necked flask, and then the temperature was raised to 220 ℃ to cause a reaction for 11 hours. After the reaction, the unreacted diol was distilled off under reduced pressure at 200 ℃. Then, the reduced pressure was released and the temperature was reduced, and the reaction product was filtered and taken out to obtain a transparent yellow liquid diester compound (a). The diester compound (a) had a number average molecular weight (Mn) of 310, an acid value of 0.10 and a hydroxyl value of 4.

Synthesis example 2

900g of benzoic acid (hereinafter, abbreviated as "BzA") as a monocarboxylic acid component, 294g of PG as a diol component, 50g of dipropylene glycol and 0.62g of TiPT as a catalyst were put into a 2-liter four-necked flask, and then the temperature was raised to 220 ℃ to react for 11 hours. After the reaction, the unreacted diol was distilled off under reduced pressure at 200 ℃. After the unreacted alcohol did not flow out any more, the pressure was released and the temperature was reduced, and the reaction product was filtered and taken out to obtain a transparent yellow liquid diester compound (b). The diester compound (b) had a number average molecular weight (Mn) of 300, an acid value of 0.07 and a hydroxyl value of 7.

Synthesis example 3

BzA 952g of a monocarboxylic acid component, PG 124g of a diol component, diethylene glycol 281g and TiPT 0.68g of a catalyst were put into a 2-liter four-necked flask, and then heated to 220 ℃ to react for 11 hours. After the reaction, the unreacted diol was distilled off under reduced pressure at 200 ℃. After the unreacted alcohol did not flow out any more, the pressure was released and the temperature was reduced, and the reaction product was filtered and taken out to obtain a transparent yellow liquid diester compound (c). The diester compound (c) had a number average molecular weight (Mn) of 350, an acid value of 0.05 and a hydroxyl value of 3.

Examples 5 to 11 and comparative examples 5 to 7

< preparation of cellulose ester optical film >

A coating solution as a cellulose ester resin composition was prepared by adding and dissolving 100 parts of triacetylcellulose resin ("LT-35" manufactured by Daluosite, Ltd.), 10 parts of ester resins (1) to (2), ester resins (1 ') to (2'), and diester compounds (a) to (c) in combination in the proportions shown in tables 2 to 3 in a mixed solvent composed of 810 parts of methylene chloride and 90 parts of methanol. These coating liquids were cast on a glass plate to a thickness of 0.8mm or 0.5mm, dried at room temperature for 16 hours, then dried at 50 ℃ for 30 minutes, and further dried at 120 ℃ for 30 minutes, to thereby obtain an optical film (60 μm or 40 μm) of the present invention. The physical properties of the obtained film were measured as described above, and the results are shown in tables 2 to 3.

[ Table 2]

[ Table 3]

By adding the diester compound (II), the elastic modulus, the dimensional stability and the moisture permeation resistance are greatly improved. Both had a low HAZE value and had sufficient transparency as an optical film.