JP2017025121A - Imide structure-containing acrylic resin and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imide structure-containing acrylic resin which has high heat resistance and low birefringence, and has a little high molecular weight body that may cause a foreign matter and has little foaming during heat residence, and to provide a method for producing the same.SOLUTION: There are provided a method for producing an imide structure-containing acrylic resin obtained by imidizing an amide group-containing acrylic resin obtained by copolymerization of an acrylic monomer having an amide group containing 1 mass% or less of a carboxylic compound and an acrylic monomer having an ester group in the molecule; and an imide structure-containing acrylic resin in which Tg is 130°C or higher, an absolute value is a stress optical coefficient (Cr) of 0.3×10Paor less, a high molecular weight body having a molecular weight of 2,000,000 is 1% or less in terms of GPC area, and the number of air bubbles during heat residence is less than 20 pieces/g.SELECTED DRAWING: None

Description

  The present invention relates to an imide structure-containing acrylic resin and a method for producing the same.

  In recent years, there has been a demand for image display devices to develop optical materials having advanced optical characteristics in response to a demand for improvement in image sharpness. As one of the advanced optical characteristics, low birefringence is required. In general, a polymer compound used for an optical material has birefringence because the refractive index in the main chain direction of the molecule is different from the refractive index in the direction perpendicular to the main chain direction. As a polymer material for an optical film having a small birefringence, a cellulose-based resin such as triacetyl cellulose has been proposed (for example, see Patent Document 1). However, an optical film made of a cellulose-based resin produces a phase difference with respect to obliquely incident light, and the phase difference with respect to the obliquely incident light adversely affects viewing angle characteristics in a large liquid crystal display. Have

  On the other hand, polymethyl methacrylate has been conventionally proposed as an optical material having excellent moldability, high surface hardness, high light transmittance, low birefringence, and low wavelength dependency (see, for example, Patent Document 2). . However, since polymethyl methacrylate has a low glass transition temperature (Tg) of about 100 ° C. and is inferior in heat resistance, it is difficult to use it in applications requiring heat resistance, for example, image display devices. Therefore, an imide structure-containing acrylic resin has been proposed as an acrylic resin having excellent heat resistance and high optical properties. For example, Patent Documents 3 and 4 disclose a method for producing an imide structure-containing acrylic resin by reacting an acrylic ester (co) polymer with an amine as an imidizing agent. Further, Patent Document 5 discloses a method for producing an imide structure-containing acrylic resin by melt-kneading a polymer containing an amide group-containing vinyl monomer and an unsaturated carboxylic ester unit to cause an intramolecular cyclization reaction. It is disclosed.

JP 2009-265174 A Japanese Patent Laid-Open No. 06-102547 International Publication No. 2005/054311 Pamphlet JP2011-225699A JP 2008-255175 A

  However, in the imide structure-containing acrylic resin, conventionally, it has been difficult to suppress the formation of a high molecular weight substance that causes foreign matters and the foaming during heat retention while realizing both high heat resistance and low birefringence. The present invention has been made in view of the above circumstances, and the object thereof is an imide that has high heat resistance and low birefringence, and has a small proportion of high molecular weight substances that can cause foreign substances and low foaming due to heat retention. The object is to provide a structure-containing acrylic resin and a method for producing the same.

  When the present inventors examined the above-mentioned problem, in order to achieve both high heat resistance and low birefringence of the imide structure-containing acrylic resin, a ring structure group-bonded imide structure such as N-arylimide is introduced. Although it is effective, when it has a ring structure group, imidization reactivity (imidation rate) falls. This is particularly noticeable when the ring structure group is an aromatic group. Furthermore, when producing an amide group-containing acrylic resin before intramolecular cyclization of the imide structure-containing acrylic resin, a carboxylic acid compound is included as an impurity contained in the acrylic monomer having an amide group as a raw material. In the case where a large amount is contained, it has been clarified that the polymerization rate and imidation rate of the acrylic monomer having an amide group during the polymerization are remarkably lowered. As a result, not only the heat resistance of the imide structure-containing acrylic resin obtained by imidizing the amide group-containing acrylic resin becomes insufficient, but the unreacted amide group reacts during the molding process, so that coloring and May cause problems such as gelation and foaming. In addition, impurities such as acrylic monomers with unreacted amide groups and radical non-reactive amide compounds contained therein volatilize during the imidization process and block the vacuum line, resulting in productivity during continuous production. Decreases. Therefore, as a result of the study by the present inventors, an amide group-containing product obtained by copolymerizing an acrylic monomer having an amide group containing 1% by mass or less of a carboxylic acid compound and an acrylic monomer having an ester group. If an acrylic resin is subjected to a cyclocondensation reaction in a molten state, even if the amide group of the acrylic resin has a nitrogen atom and a substituent having a ring structure such as an aryl group, the cyclization condensation is performed. It has been clarified that the reaction proceeds suitably, and an imide structure-containing acrylic resin having a low birefringence while having high heat resistance can be easily obtained. Further, it was found that the imide structure-containing acrylic resin obtained in this way has a high molecular weight that causes gel foreign substances and a low ratio of foaming.

That is, the method for producing an imide structure-containing acrylic resin of the present invention includes copolymerizing an acrylic monomer having an amide group containing 1% by mass or less of a carboxylic acid compound and an acrylic monomer having an ester group. The amide group-containing acrylic resin thus obtained is intramolecularly imidized. The obtained imide structure-containing acrylic resin has a Tg of 130 ° C. or higher, an absolute value of stress optical coefficient (Cr) of 0.3 × 10 ⁻⁹ Pa ⁻¹ or lower, and a high molecular weight of 2 million or higher. Since the body is 1% or less in terms of GPC area and the number of bubbles during heat retention is less than 20 / g, the imide structure-containing acrylic resin of the present invention has high heat resistance, Not only the birefringence becomes small, but also the generation of foreign matters and foaming can be suppressed.

  The acrylic monomer having an amide group used as a monomer component is a compound represented by the following formula (1), and the acrylic monomer having an ester group is a compound represented by the following formula (2). Preferably there is.

[In Formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R ⁵ represents a hydrogen atom, a straight chain having 1 to 18 carbon atoms, A cyclic or branched alkyl group (including an alkyl group having an aromatic ring) or an aryl group having 6 to 10 carbon atoms is represented. ]

[In Formula (2), R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R ⁶ represents a hydrogen atom, a straight chain having 1 to 18 carbon atoms, A cyclic or branched alkyl group (including an alkyl group having an aromatic ring) or an aryl group having 6 to 10 carbon atoms is represented. ]
Further, the present invention is an imide structure-containing acrylic resin having a Tg of 130 ° C. or higher, an absolute value of stress optical coefficient (Cr) of 0.3 × 10 ⁻⁹ Pa ⁻¹ or lower, and a molecular weight of 200 It is an imide structure-containing acrylic resin having a ratio of 10,000 or more high molecular weight substances of 1% or less in terms of GPC area, and the number of bubbles measured by the following method is less than 20 / g.
Number of bubbles: Acrylic resin dried in an oven at 80 ° C. for 24 hours was loaded into a melt indexer cylinder specified in JIS K7210, held at 260 ° C. for 5 minutes, extruded into a strand, and melted into a melt indexer. The number of bubbles present in the strand extruded between the piston upper standard line and the lower standard line was counted and converted into the number per 1 g of resin.

  In the present specification, “acrylic” means “acrylic” or “methacrylic”.

According to the method for producing an imide structure-containing acrylic resin of the present invention, Tg is 130 ° C. or higher, the absolute value of stress optical coefficient (Cr) is 0.3 × 10 ⁻⁹ Pa ⁻¹ or lower, and the molecular weight is 200. It is possible to obtain a resin having a high molecular weight of 10,000 or more in terms of GPC area of 1% or less and having a number of bubbles during heat retention of less than 20 / g with good productivity. The imide structure-containing acrylic resin obtained by the production method of the present invention has not only high heat resistance and low birefringence, but also can suppress the generation of foreign matter and foaming.

■ Overall explanation of manufacturing method of imide structure-containing acrylic resin ■
The method for producing the imide structure-containing acrylic resin of the present invention (hereinafter also referred to as an acrylic resin having a glutarimide structure in the main chain or simply referred to as a glutarimide resin) will be described first. The method for producing an imide structure-containing acrylic resin of the present invention is obtained by copolymerizing an acrylic monomer having an amide group containing 1% by mass or less of a carboxylic acid compound and an acrylic monomer having an ester group. In the production method, the obtained amide group-containing acrylic resin is intramolecularly imidized. The obtained imide structure-containing acrylic resin has a Tg of 130 ° C. or higher, an absolute value of stress optical coefficient (Cr) of 0.3 × 10 ⁻⁹ Pa ⁻¹ or lower, and a high molecular weight of 2 million or higher. The body is 1% or less in terms of GPC area, and the number of bubbles during heat retention is less than 20 / g. The imide structure-containing acrylic resin of the present invention has high heat resistance, Not only the birefringence becomes small, but also the generation of foreign matters and foaming can be suppressed. Hereinafter, the manufacturing method of the imide structure containing acrylic resin of this invention is demonstrated in detail.

■ Description of polymerization process ■
In the polymerization step, a monomer component containing an acrylic monomer having an amide group and an acrylic monomer having an ester group is copolymerized in an organic solvent to obtain an amide group-containing acrylic resin. The acrylic monomer used in the polymerization step is preferably an acrylic acid compound, but is not limited thereto, and α, β-unsaturated carbonyl compounds other than the acrylic acid compound can be widely used. The α, β-unsaturated carbonyl compound other than acrylic acid may have a substituent other than a hydrogen atom bonded to the β-position carbon, and a substituent other than a hydrogen atom or a methyl group bonded to the α-position carbon. Also good. In addition, as a substituent other than the hydrogen atom which may be couple | bonded with (beta) -position carbon, a C1-C8 alkyl group is mentioned, for example. Examples of the substituent other than the hydrogen atom and the methyl group that may be bonded to the α-position carbon include an alkyl group having 2 to 8 carbon atoms. In the case of an acrylic monomer having an amide group, the carbonyl group of the α, β-unsaturated carbonyl compound has an amide group (that is, an amide group) and an acrylic group having an ester group. In the case of a monomer, the carbonyl group is esterified (that is, an ester group).

  As the acrylic monomer having an amide group, a compound represented by the following formula (1) (hereinafter sometimes referred to as “α, β-unsaturated carboxylic acid amide”) is preferably used.

In Formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, isopentyl group, n- Examples include a hexyl group, an isohexyl group, an n-heptyl group, an isoheptyl group, an n-octyl group, and a 2-ethylhexyl group. Among these, as R ¹ and R ² , a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is preferable, whereby an imide structure-containing acrylic resin having high heat resistance and a small absolute value of stress optical coefficient (Cr) is used. When an optical film is produced by forming an imide structure-containing acrylic resin into a film, an optical film having high heat resistance and low birefringence is easily obtained. From the viewpoint of ease of production of the α, β-unsaturated carboxylic acid amide of the formula (1), R ¹ and R ² are preferably a hydrogen atom or a methyl group, R ¹ is a hydrogen atom, and R ² Is more preferably a hydrogen atom or a methyl group. That is, as the α, β-unsaturated carboxylic acid amide of the formula (1), (meth) acrylic acid amide is preferable.

In Formula (1), R ⁵ represents a hydrogen atom, a linear, cyclic, or branched alkyl group having 1 to 18 carbon atoms (including an alkyl group having an aromatic ring), or an aryl group having 6 to 10 carbon atoms. Represent. Note that the alkyl group or aryl group of R ⁵ may also include an ester group. Examples of the alkyl group having 1 to 18 carbon atoms of R ⁵ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, and an isopentyl group. , N-hexyl group, isohexyl group, n-heptyl group, isoheptyl group, n-octyl group, 2-ethylhexyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, benzyl group and the like. Examples of the aryl group having 6 to 10 carbon atoms of R ⁵ include phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, 2,3-xylyl group, 2,4-xylyl group, 2,5- Examples include xylyl group, 2,6-xylyl group, 3,4-xylyl group, 3,5-xylyl group, 1-naphthyl group, 2-naphthyl group, biphenyl group and the like. Among these, as R ⁵ , a cycloalkyl group having 3 to 12 carbon atoms or an aryl group having 6 to 10 carbon atoms is preferable. As a result, an imide structure-containing acrylic resin having a small absolute value of stress optical coefficient (Cr) is obtained. It becomes easy to obtain. R ⁵ is more preferably an aryl group having 6 to 10 carbon atoms, more preferably a phenyl group, a tolyl group or a naphthyl group, and particularly preferably a phenyl group.

As the α, β-unsaturated carboxylic acid amide of the formula (1), only one type may be used, or two or more types may be used in combination. As the α, β-unsaturated carboxylic acid amide of the formula (1), R ⁵ has 3 to 12 carbon atoms because an imide structure-containing acrylic resin having a small absolute value of the stress optical coefficient (Cr) is easily obtained. It is preferable to use (meth) acrylamide which is a cycloalkyl group or an aryl group having 6 to 10 carbon atoms, and (meth) acrylamide which R ⁵ is an aryl group having 6 to 10 carbon atoms is more preferable.

  At this time, as an impurity contained in the acrylic monomer having an amide group, the carboxylic acid compound is 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.3% by mass or less. Examples of carboxylic acid compounds include acetic acid, acrylic acid, methacrylic acid and the like. When the amount of the carboxylic acid compound exceeds 1% by mass, the polymerization rate of the acrylic monomer having an amide group is remarkably lowered, so that an acrylic monomer having an unreacted amide group increases and an imide structure-containing acrylic type is obtained. In addition to being unable to obtain sufficient heat resistance in the resin, it may cause coloring. Further, when the acrylic monomer having an amide group is a solid, it is not preferable because it may cause clogging of the vent line in the imidization step. In addition, when the carboxylic acid compound exceeds 1% by mass, imidization is difficult to proceed (the imidization rate becomes low), and thus the heat resistance of the imide structure-containing acrylic resin becomes insufficient, or during the molding process. The reaction of unreacted amide groups may cause foreign matters due to gelation or the like, which is not preferable. Examples of the method for removing the carboxylic acid compound contained in the acrylic monomer having an amide group include distillation under reduced pressure, crystallization, washing with water, column, etc., preferably crystallization, washing with water, and column. Most preferred is crystallization.

  As impurities other than the carboxylic acid compound contained in the acrylic monomer having an amide group, the radical non-reactive amide compound is preferably 4% by mass or less, preferably 2% by mass or less, and preferably 1% by mass or less. More preferred. The radical non-reactive amide compound is a compound that does not react under radical polymerization conditions, and examples thereof include methylacetamide, ethylacetamide, acetanilide, tolylacetamide, naphthylacetamide, and the like. If the non-reactive amide compound exceeds 4% by mass, not only will it cause coloration, but if the non-reactive amide compound is solid, it will cause clogging of the vent line in the imidization process and productivity will be increased during continuous production. It is not preferable because it causes a decrease. Examples of a method for reducing the radical non-reactive amide compound contained in the acrylic monomer having an amide group include, for example, a method for increasing the purity of (meth) acrylic anhydride as a precursor, a column, and crystallization. There are methods for purification by washing with water, etc., preferably a method for increasing the purity of (meth) acrylic anhydride as a precursor, a method for purification by column and crystallization. In addition, the impurity contained in the acryl-type monomer which has an amide group is calculated | required based on the method as described in an Example.

  As the acrylic monomer having an ester group, a compound represented by the following formula (2) (hereinafter sometimes referred to as “α, β-unsaturated carboxylic acid ester”) is preferably used.

In Formula (2), R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms of R ³ and R ⁴ include the alkyl groups exemplified as the alkyl group having 1 to 8 carbon atoms of R ¹ and R ² described above. Among these, as R ³ and R ⁴ , a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is preferable, and thus an imide structure-containing acrylic resin having high heat resistance and a small absolute value of stress optical coefficient (Cr) is used. When an optical film is produced by forming an imide structure-containing acrylic resin into a film, an optical film having high heat resistance and low birefringence is easily obtained. From the viewpoint of ease of production of the α, β-unsaturated carboxylic acid ester of the formula (4), R ³ and R ⁴ are preferably a hydrogen atom or a methyl group, R ³ is a hydrogen atom, and R ⁴ Is more preferably a hydrogen atom or a methyl group. That is, as the α, β-unsaturated carboxylic acid ester of the formula (4), a (meth) acrylic acid ester is preferable.

In Formula (2), R ⁶ represents a hydrogen atom, a linear, cyclic, or branched alkyl group having 1 to 18 carbon atoms (including an alkyl group having an aromatic ring), or an aryl group having 6 to 10 carbon atoms. Represent. Examples of the alkyl group having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, isopentyl group, n- Examples include hexyl group, isohexyl group, n-heptyl group, isoheptyl group, n-octyl group, 2-ethylhexyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, benzyl group and the like. Examples of the aryl group having 6 to 10 carbon atoms of R ⁶ include phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, 2,3-xylyl group, 2,4-xylyl group, 2,5-xylyl group, Examples include xylyl group, 2,6-xylyl group, 3,4-xylyl group, 3,5-xylyl group, 1-naphthyl group, 2-naphthyl group, biphenyl group and the like. Among these, R ^6, preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, a methyl group or an ethyl group An n-butyl group is even more preferable, and a methyl group or an ethyl group is particularly preferable. This makes it easy to proceed with the imidization reaction, and can improve the heat resistance of the imide structure-containing acrylic resin. The α, β-unsaturated carboxylic acid ester of the formula (4) may be used alone or in combination of two or more.

  The monomer component used for the polymerization may contain a monomer other than an acrylic monomer having an amide group and an acrylic monomer having an ester group. In producing an imide structure-containing acrylic resin, it is preferable to configure the monomer component so that an acrylic monomer having an amide group and an acrylic monomer having an ester group are the main components. Therefore, the blending amount of the acrylic monomer having an amide group and the acrylic monomer having an ester group in 100% by mass of all the monomer components is preferably 50% by mass or more. More preferably, it is 90 mass% or more, and 95 mass% or more is especially preferable.

  The mixing ratio of the acrylic monomer having an amide group and the acrylic monomer having an ester group is determined based on the imide structure (glutarimide structure) unit and α, β-unsaturation contained in the resulting imide structure-containing acrylic resin. The mixing ratio (molar basis) of the acrylic monomer having an amide group / the acrylic monomer having an ester group may be appropriately adjusted depending on the desired amount of the unit derived from the carboxylic acid ester. The above is preferable, 8/92 or more is more preferable, 10/90 or more is more preferable, 70/30 or less is preferable, 60/40 or less is more preferable, and 50/50 or less is more preferable. When the acrylic monomer having an amide group / the acrylic monomer having an ester group is within the above range, the heat resistance is high, the absolute value of the stress optical coefficient (Cr) is small, and the flexibility of the resin is high. An imide structure-containing acrylic resin is obtained.

  The monomer component includes a carboxyl group and an acid anhydride from the viewpoint of increasing the polymerization rate and imidization rate of the acrylic monomer having an amide group and reducing the acid value of the resulting imide structure-containing acrylic resin. It is preferable that many acrylic monomers having a group are not contained. Accordingly, in 100% by mass of all monomer components, the blending amount of the acrylic monomer having a carboxyl group or an acid anhydride group is preferably 5% by mass or less, more preferably 2% by mass or less, and 1% by mass. % Or less is more preferable.

  The monomer component may contain styrene as a monomer other than the acrylic monomer having an amide group and the acrylic monomer having an ester group, but the absolute value of the stress optical coefficient (Cr) From the viewpoint of easily obtaining a glutarimide resin having a small value, it is preferable not to use much styrene. Therefore, in 100% by mass of all monomer components, the amount of styrene is preferably 5% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less.

  The polymerization of the monomer component is preferably performed in an organic solvent. As the organic solvent, a solvent used in a normal radical polymerization reaction can be used. Specifically, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and anisole; acetic acid Ester solvents such as ethyl, butyl acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate; Alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether; acetonitrile, propionitrile , Nitrile solvents such as butyronitrile, benzonitrile, chloroform, dimethyl Sulfoxides and the like. These solvents may use only 1 type and may use 2 or more types together.

  The organic solvent contains at least one selected from aromatic hydrocarbons, ketones, ethers, esters and nitriles from the viewpoint that it is easy to obtain a glutarimide resin having a small absolute value of the stress optical coefficient (Cr). It is preferable. In order to obtain an imide structure-containing acrylic resin having a small absolute value of the stress optical coefficient (Cr), as an acrylic monomer having an amide group, a cycloalkyl group having 3 to 12 carbon atoms or a nitrogen atom of the amide group or It is effective to use an α, β-unsaturated carboxylic acid amide to which an aryl group having 6 to 10 carbon atoms is bonded, but the organic solvent for the polymerization reaction is selected from aromatic hydrocarbons, ketones, ethers, esters and nitriles. If the solvent containing at least one kind is used, an α, β-unsaturated carboxylic acid amide in which a cycloalkyl group having 3 to 12 carbon atoms or an aryl group having 6 to 10 carbon atoms is bonded to the nitrogen atom of the amide group was used. In some cases (especially even when an α, β-unsaturated carboxylic acid amide to which an aryl group having 6 to 10 carbon atoms is bonded) is used, an acrylic monomer having an amide group and Amide group-containing acrylic resin is sufficiently soluble in the solvent, preferably facilitate the polymerization reaction. Specifically, the polymerization rate of each monomer can be improved while lowering the viscosity of the polymerization solution, and the composition distribution of the polymer can be reduced. As a result, the heat resistance is high and the stress optical coefficient (Cr) is low. It becomes easy to obtain a gimide structure-containing acrylic resin having a small absolute value, excellent transparency, and less gelation and foaming by a process with excellent productivity. In addition, it is easy to prevent problems such as coloring, gelation, and foaming due to the reaction of unreacted residual amide groups during the molding process.

  The organic solvent used in the polymerization reaction preferably contains at least one selected from aromatic hydrocarbons, ketones, ethers, esters and nitriles at a concentration of 20% by mass or more, more preferably 30% by mass or more, and 40% by mass. % Or more is more preferable. In addition, the said density | concentration means these total density | concentrations, when the organic solvent used by a polymerization reaction contains 2 or more types chosen from a ketone, ether, ester, and a nitrile. Among these, as the organic solvent, it is preferable to use toluene, a mixed solvent of toluene and methanol, a mixed solvent of toluene and butanol, methyl isobutyl ketone, anisole or ethyl acetate.

  The concentration of the monomer component in the organic solvent may be appropriately set according to the polymerization conditions, the desired molecular weight of the resulting amide group-containing acrylic resin, the viscosity of the polymerization solution, and the like. The concentration of the monomer component in the organic solvent is, for example, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 300 parts by mass or less, and 200 parts by mass with respect to 100 parts by mass of the organic solvent. Part or less is more preferable.

  The temperature of the polymerization reaction may be appropriately adjusted according to the type of organic solvent and the progress of the polymerization reaction. For example, it is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, and preferably 160 ° C. or lower, preferably 145 ° C. The following is more preferable. The polymerization reaction time may be appropriately adjusted according to the degree of progress of the polymerization reaction. For example, the polymerization reaction time may be 1 to 48 hours (preferably 3 to 24 hours).

  In the polymerization, a known polymerization initiator may be used. Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, dimethyl-2,2′-azobis (2-methylpropyl). Azo compounds such as 4,4′-azobis (4-cyanopentanoic acid); persulfates such as potassium persulfate; cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, Peroxides such as lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyoctoate, t-amylperoxyisononanoate Etc. can be used. These may use only 1 type and may use 2 or more types together. It is preferable that the usage-amount of a polymerization initiator shall be 0.01-3 mass parts with respect to 100 mass parts of monomer components, for example.

■ Explanation of cyclization condensation process ■
The amide group-containing acrylic resin obtained in the polymerization step is then subjected to a cyclization condensation step. In the cyclocondensation step, the amide group-containing acrylic resin is melted and subjected to cyclocondensation (imidation reaction) between the amide group and ester group of the amide group-containing acrylic resin. obtain.

  In the cyclization condensation step, the imidation reaction is performed in a molten state of the amide group-containing acrylic resin. By performing the imidization reaction in the molten state of the amide group-containing acrylic resin, even when the amide group-containing acrylic resin has a low nucleophilicity, the imidization reaction (that is, the amide group and the ester group Condensation reaction) can be suitably carried out. As a result, an imide structure-containing acrylic resin having a small absolute value of the stress optical coefficient (Cr) can be easily produced.

  The melting of the amide group-containing acrylic resin may be performed by heating at or above the softening point of the amide group-containing acrylic resin. The heating temperature (reaction temperature) is preferably 180 ° C or higher, more preferably 220 ° C or higher, and 240 ° C. The above is more preferable. By heating and melting the amide group-containing acrylic resin at such a temperature, the imidization reaction can be suitably performed. On the other hand, the temperature of the amide group-containing acrylic resin (reaction) is suppressed from the point that it suppresses the decomposition of the acrylic resin due to excessive thermal history, and suppresses the transparency and molecular weight reduction of the imide structure-containing acrylic resin and the resin coloring. The temperature is preferably 380 ° C. or less, more preferably 360 ° C. or less, further preferably 340 ° C. or less, and particularly preferably 320 ° C. or less.

  In the cyclization condensation step, it is preferable to devolatilize the amide group-containing acrylic resin, thereby removing the organic solvent brought in from the polymerization step, alcohol produced as a by-product by the condensation reaction between the amide group and the ester group, and the like. can do. In particular, by removing the alcohol by-produced by the condensation reaction between the amide group and the ester group, the reaction equilibrium in the condensation reaction between the amide group and the ester group is shifted to the imide formation side, and the resulting imide structure-containing acrylic resin It is possible to increase the imidization ratio of the.

  In the cyclization condensation step, it is preferable to melt the amide group-containing acrylic resin under reduced pressure from the viewpoint of efficient devolatilization. The reduced pressure in the cyclization condensation step is preferably, for example, 80 kPa or less as an absolute pressure, more preferably 65 kPa or less, and further preferably 50 kPa or less. On the other hand, the absolute pressure during decompression is preferably 1 kPa or more, more preferably 10 kPa or more, and even more preferably 20 kPa or more from the viewpoint that the equipment for realizing the decompressed state is not over-specification and the equipment cost is kept low. Note that the reduced pressure in the cyclization condensation step may be realized in at least a part of the cyclization condensation step. For example, by reducing the pressure at the end of the cyclization condensation step, the organic solvent brought in from the polymerization step and the alcohol by-produced by the condensation reaction between the amide group and the ester group may be devolatilized together. The organic solvent brought in from the polymerization step may be devolatilized first by reducing the pressure at the beginning of the cyclization condensation step. Moreover, you may perform pressure reduction over the whole cyclization condensation process. Among these, in order to advance the cyclization condensation step efficiently, the organic solvent is devolatilized at least at the beginning of the cyclization condensation step and alcohol by-produced by the condensation reaction is removed at the end of the cyclization condensation step. preferable.

  The time for the cyclization condensation step (heating time) is preferably 10 seconds or longer, more preferably 30 seconds or longer from the viewpoint of sufficiently performing the imidization reaction. The upper limit of the time may be set as appropriate while watching the degree of progress of the cyclization condensation reaction, and is not uniquely determined, but considering the production efficiency of glutarimide resin, for example, preferably 60 minutes or less, 30 minutes or less is more preferable, and 15 minutes or less is more preferable.

  A catalyst is preferably used for the cyclization condensation reaction. The catalyst is preferably added to the amide group-containing acrylic resin prior to melting of the amide group-containing acrylic resin. As a catalyst for the cyclocondensation reaction, at least one selected from the group consisting of acids, bases and salts thereof can be used. Kinds of acids, bases and salts thereof are not particularly limited.

  Examples of the acid include hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, phosphoric acid, phosphorous acid, phenylphosphonic acid, methyl phosphate, and the like. Examples of the base include metal hydroxide, amine, imine, metal alkoxide, ammonium hydroxide salt and the like. Examples of the acid and base salts include organic acid metal salts such as metal acetates and metal stearates; metal carbonates and the like. Among these catalysts, a compound having an alkali metal is preferable because an excellent reaction promoting effect is exhibited in a small amount. Examples of the compound having an alkali metal include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; sodium methoxide, sodium ethoxide, sodium phenoxide, potassium methoxide, potassium ethoxide and potassium phenoxide. And alkali metal alkoxides such as organic acid alkali metal salts such as lithium acetate, sodium acetate, potassium acetate and sodium stearate. Among these compounds having an alkali metal, sodium hydroxide, sodium methoxide, lithium acetate and sodium acetate are preferable, and sodium methoxide and lithium acetate are more preferable.

  The amount of the catalyst is not particularly limited, but the imidization is sufficiently progressed, and the resulting imide structure-containing acrylic resin has no adverse effects such as coloring, foreign matter derived from a high molecular weight substance, foaming, and the like. It is preferable to use it within a range where the transparency of the resin is not lowered. The amount of the catalyst is preferably about 0.001 to 0.4 parts by mass with respect to 100 parts by mass of the amide group-containing acrylic resin, for example.

  The reactor for performing the imidization reaction may be a batch reactor or a continuous reactor, but is preferably provided with a vent for releasing volatile components and the like in the reactor. The vent may be a simple opening, but is preferably provided with a decompression means such as a vacuum pump.

  As the batch reactor, a pressure vessel equipped with a stirring means can be used. For example, a horizontal biaxial reactor (manufactured by Sumitomo Heavy Industries, Ltd., trade name: Vivolac), vertical concentric biaxial agitator ( It is preferable to use a reactor that can cope with high viscosity such as that manufactured by Sumitomo Heavy Industries, Ltd. (trade name: Super Blend).

  As the continuous reactor, an extruder or the like can be used. The extruder preferably includes a cylinder and a screw provided in the cylinder, and includes a heating unit. Depending on the number of screws, there are various types of extruders, such as single screw extruders, twin screw extruders, and multi screw extruders. However, amide group-containing acrylic resins can be mixed efficiently. It is preferable to use a screw extruder. Examples of the twin screw extruder include, for example, a non-meshing type co-rotating twin screw extruder, a meshing type co-rotating twin screw extruder, a non-meshing different direction rotating twin screw extruder, and a meshing type. A different direction rotation type twin screw extruder etc. are mentioned. These extruders may be used singly or two or more may be connected in series. Among the twin screw extruders, the meshing type co-rotating twin screw extruder is preferable because it can rotate at high speed and can be mixed efficiently.

  The extruder is preferably provided with a vent in order to remove (devolatilize) the organic solvent brought in from the polymerization step and alcohol produced as a by-product by the condensation reaction between the amide group and the ester group. The vent is preferably one that can be depressurized to atmospheric pressure or lower. The number of vents may be only one or plural. The vent may be provided at least on the downstream side of the raw material charging part (the place where the amide group-containing acrylic resin is supplied into the reactor) with respect to the transfer direction of the amide group-containing acrylic resin in the extruder. Preferably, it may also be provided upstream of the raw material charging unit.

  The imidation of the amide group-containing acrylic resin is performed by supplying the amide group-containing acrylic resin from the raw material charging part of the extruder, heating and melting the amide group-containing acrylic resin, and filling the cylinder. be able to. At this time, the imidization reaction proceeds in the process of transferring the amide group-containing acrylic resin supplied into the extruder from the upstream side to the downstream side of the extruder while kneading with a screw, and glutarimide from the downstream side of the extruder. Resin is discharged. It is preferable that a die portion for discharging the imide structure-containing acrylic resin from the extruder is provided on the downstream side of the extruder. By discharging the imide structure-containing acrylic resin from the die portion, a predetermined shape ( It can be formed into a film shape or a rod shape. For example, pellets can be produced by finely cutting an imide structure-containing acrylic resin shaped like a rod.

  In addition, when implementing a cyclization condensation process using an extruder, the pressure reduction degree (pressure in the case of pressure reduction) means the suction pressure in a vent. Moreover, the time of a cyclization condensation process means the residence time from a raw material injection | throwing-in part to a discharge part (die part), when an extruder performs only an imidation reaction.

  According to the method for producing an imide structure-containing acrylic resin of the present invention, an amide group-containing acrylic resin obtained by copolymerizing an acrylic monomer having an amide group and an acrylic monomer having an ester group is obtained. By carrying out the cyclization condensation reaction in the molten state, even when the amide group-containing acrylic resin has a low nucleophilicity, the cyclization condensation reaction can proceed suitably, and the imide structure has low birefringence. The containing acrylic resin can be easily obtained.

■ Overall explanation of imide structure-containing acrylic resin ■
Next, the imide structure-containing acrylic resin of the present invention will be described. The imide structure-containing acrylic resin of the present invention has a Tg of 130 ° C. or higher, an absolute value of stress optical coefficient (Cr) of 0.3 × 10 ⁻⁹ Pa ⁻¹ or lower, and a molecular weight of 2 million or higher. Is 1% or less in terms of GPC area, and the number of bubbles measured under specific heat retention conditions is less than 20 / g. The imide structure-containing acrylic resin of the present invention can be easily produced by the production method described above. Since the imide structure-containing acrylic resin of the present invention has a Tg of 130 ° C. or higher and an absolute value of the stress optical coefficient (Cr) of 0.3 × 10 ⁻⁹ Pa ⁻¹ or less, the heat resistance is high and the birefringence is high. It will be small. Moreover, since the ratio of the high molecular weight polymer having a molecular weight of 2 million or more is 1% or less in terms of GPC area and the foaming under heat retention is small, the generation of foreign matters can be suppressed.

The absolute value of the stress optical coefficient (Cr) of the imide structure-containing acrylic resin is 0.2 from the viewpoint of suppressing the birefringence by suppressing the anisotropy of the refractive index of the stretched film obtained by stretching the resin. × 10 ⁻⁹ Pa ⁻¹ or less is more preferable. The stress optical coefficient (Cr) of the imide structure-containing acrylic resin is determined based on the method described in the examples.

■ Explanation of the structure of acrylic resin containing imide structure ■
The imide structure-containing acrylic resin is not particularly limited as long as it is an imide structure-containing acrylic resin having a glutarimide structure in the main chain, but the repeating unit represented by the following formula (3) (hereinafter, It may preferably be referred to as “glutarimide unit”.

In the glutarimide unit of the formula (3), R ¹ , R ² , R ³ , R ⁴ and R ⁵ represent the same meaning as described above. That is, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ⁵ is a hydrogen atom or a straight chain having 1 to 18 carbon atoms. , A cyclic or branched alkyl group (including an alkyl group having an aromatic ring) and an aryl group having 6 to 10 carbon atoms. As the glutarimide unit of the formula (3), R ¹ , R ² , R ³ and R ⁴ are preferably hydrogen atoms or methyl groups, R ¹ and R ³ are hydrogen atoms, R ² and R ⁴ Is more preferably a hydrogen atom or a methyl group. This makes it easy to obtain an optical film having high heat resistance and low birefringence when an imide structure-containing acrylic resin is formed into a film to produce an optical film. The production of the structure-containing acrylic resin is also facilitated. R ⁵ is preferably a cycloalkyl group having 3 to 12 carbon atoms or an aryl group having 6 to 10 carbon atoms, more preferably an aryl group having 6 to 10 carbon atoms, thereby further improving heat resistance. It is easy to obtain an imide structure-containing acrylic resin having a high stress optical coefficient (Cr) and a small absolute value. The imide structure-containing acrylic resin may contain only one type of glutarimide unit of the formula (3), or may contain two or more types.

  The imide structure-containing acrylic resin is a repeating unit represented by the following formula (4) in addition to the glutarimide unit of the formula (3) (hereinafter referred to as “unit derived from an α, β-unsaturated carboxylic acid ester”). Preferably).

In the unit derived from the α, β-unsaturated carboxylic acid ester of the formula (4), R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms of R ³ and R ⁴ include the alkyl groups exemplified as the alkyl group having 1 to 8 carbon atoms of R ¹ and R ² . Among these, as R ³ and R ⁴ , a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is preferable, and thereby an imide structure-containing acrylic resin having high heat resistance and a small absolute value of stress optical coefficient (Cr) is used. When an optical film is produced by forming an imide structure-containing acrylic resin into a film, an optical film having high heat resistance and low birefringence is easily obtained. From the viewpoint of ease of production of the imide structure-containing acrylic resin, R ³ and R ⁴ are preferably a hydrogen atom or a methyl group, R ³ is a hydrogen atom, and R ⁴ is a hydrogen atom or a methyl group. It is more preferable.

In the unit derived from the α, β-unsaturated carboxylic acid ester of the formula (4), R ⁶ represents the same meaning as described above. That is, R ⁶ represents a hydrogen atom, a linear, cyclic, or branched alkyl group having 1 to 18 carbon atoms (including an alkyl group having an aromatic ring), or an aryl group having 6 to 10 carbon atoms. R ⁶ is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, still more preferably an alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group or an n-butyl group. Is more preferable, and a methyl group or an ethyl group is particularly preferable, which facilitates the imidization reaction.

  The imide structure-containing acrylic resin may contain only one type of unit derived from the α, β-unsaturated carboxylic acid ester of the formula (4), or may contain two or more types.

  If the imide structure-containing acrylic resin has a unit derived from the α, β-unsaturated carboxylic acid ester of the formula (4) in addition to the glutarimide unit of the formula (3), the imide structure-containing acrylic resin It becomes easy to improve heat resistance and transparency, and it becomes easy to make birefringence small. That is, this imide structure-containing acrylic resin exhibits weak positive birefringence based on glutarimide units, and weak negative birefringence based on units derived from α, β-unsaturated carboxylic acid esters. Cancel each other, so that the whole exhibits low birefringence. Moreover, the moldability to a film etc. improves and it becomes easy to raise mechanical strength.

  In the imide structure-containing acrylic resin, the content of the glutarimide unit of the formula (3) is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and 85% by mass. The following is preferable, 80% by mass or less is more preferable, and 75% by mass or less is more preferable. If the content rate of the glutarimide unit of Formula (1) is 5 mass% or more, heat resistance and transparency will improve and it will become easy to make birefringence small. If the content of the glutarimide unit is 85% by mass or less, the moldability to a film or the like is improved, the mechanical strength is easily increased, and the birefringence is easily reduced.

  In the imide structure-containing acrylic resin, the content of the unit derived from the α, β-unsaturated carboxylic acid ester of the formula (4) is preferably 15% by mass or more, more preferably 20% by mass or more, and 25% by mass. The above is more preferable, 95% by mass or less is preferable, 90% by mass or less is more preferable, and 85% by mass or less is more preferable. If the content of the unit derived from the α, β-unsaturated carboxylic acid ester is 15% by mass or more, the moldability to a film or the like is improved, the mechanical strength is easily increased, and the birefringence can be reduced. It becomes easy. If the content rate of the unit derived from the α, β-unsaturated carboxylic acid ester is 95% by mass or less, the heat resistance and transparency are improved, and birefringence can be easily reduced.

The content ratio of the glutarimide unit of the formula (3), the unit derived from the α, β-unsaturated carboxylic acid ester of the formula (4) and the unit derived from the acrylic monomer having an amide group is ¹ H-NMR. Can be sought. Specifically, an amide proton of a unit derived from an acrylic monomer having an amide group, a proton of a substituent R ⁵ on N of the acrylic monomer having an amide group and formula (1), and a formula It can be determined from the ratio of protons on carbon adjacent to oxygen in the ester group of (2). The imide structure-containing acrylic resin may contain a repeating unit other than the glutarimide unit of the formula (1) and the unit derived from the α, β-unsaturated carboxylic acid ester of the formula (2). The imide structure-containing acrylic resin preferably contains a glutarimide unit and a unit derived from an α, β-unsaturated carboxylic acid ester as main components. Therefore, in the imide structure-containing acrylic resin, the glutarimide unit and α , Β-unsaturated ester combined content is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. . The imide structure-containing acrylic resin may have, for example, a unit derived from styrene as a repeating unit, but a unit derived from styrene from the point that a glutarimide resin having a small absolute value of stress optical coefficient (Cr) is easily obtained. It is preferable not to contain so much. Accordingly, the content of styrene-derived units in the imide structure-containing acrylic resin is preferably 5% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less.

■ Other explanation of acrylic resin containing imide structure ■
The weight average molecular weight of the imide structure-containing acrylic resin is preferably 10,000 or more, more preferably 30,000 or more, and molding into a film or the like from the viewpoint of increasing mechanical strength when being molded into a film or the like. From the viewpoint of improving the workability at the time, 500,000 or less is preferable, and 300,000 or less is more preferable. The weight average molecular weight of the imide structure-containing acrylic resin is determined based on the method described in the examples.

  The ratio of the high molecular weight polymer of the imide structure-containing acrylic resin is 1% or less in terms of GPC area, and is preferably 0.8% or less from the viewpoint of reducing foreign matter that becomes a problem when formed into a film or the like. 0.5% or less is more preferable, and 0.2% or less is more preferable. In addition, the ratio of a high molecular weight body is calculated | required based on the method as described in an Example. That is, using standard polystyrene, which is a standard sample, a calibration curve of retention time and molecular weight is created in terms of polystyrene, and a retention time with a molecular weight of 2,000,000 is obtained. Subsequently, an imide structure-containing acrylic system obtained by sample measurement The peak is divided with the retention time at which the molecular weight of the resin GPC chart (detector: RI) is 2 million as a boundary, and the ratio of the area having a molecular weight of 2 million or more to the entire peak is determined.

  The imidization ratio of the imide structure-containing acrylic resin is preferably 90% or more and 92% or more from the viewpoint of increasing the heat resistance of the imide structure-containing acrylic resin, suppressing coloring, and increasing the productivity during continuous production. More preferred is 95% or more. The imidization rate is determined based on the method described in the examples. That is, by dissolving an imide structure-containing acrylic resin in heavy acetone, the peak area A derived from the proton on N of N-substituted (meth) acrylamide and the proton of the substituent on N of N-substituted (meth) acrylamide The ratio of peak area B derived from the above (peak area A / peak area B)] is calculated.

  The imide structure-containing acrylic resin has a glass transition temperature of 130 ° C. or higher, more preferably 135 ° C. or higher, and further preferably 140 ° C. or higher. If the imide structure-containing acrylic resin has such a glass transition temperature, the imide structure-containing acrylic resin can be applied to applications requiring heat resistance, such as image display devices. The upper limit of the glass transition temperature of the imide structure-containing acrylic resin is preferably 250 ° C. or lower, more preferably 230 ° C. or lower, further preferably 210 ° C. or lower, from the viewpoint of improving the molding processability to a film or the like. 200 degrees C or less is especially preferable. The glass transition temperature of the imide structure-containing acrylic resin is determined based on the method described in the examples.

  The thermal decomposition starting temperature of the imide structure-containing acrylic resin is 330 ° C. from the viewpoint of enhancing the heat resistance of the imide structure-containing acrylic resin, suppressing foaming at the time of molding and making it easy to select balanced molding conditions. The above is preferable, 340 ° C. or higher is more preferable, and 350 ° C. or higher is further preferable. The thermal decomposition starting temperature of the imide structure-containing acrylic resin is determined based on the method described in the examples.

  The imide structure-containing acrylic resin preferably has a water absorption rate of 3.0% by mass or less when molded into an unstretched film having a thickness of 200 μm from the viewpoint of improving moldability. The following is more preferable, and 2.0% by mass or less is more preferable. The water absorption is determined based on the method described in the examples.

  The imide structure-containing acrylic resin preferably has a haze of 3.0% or less, more preferably 2.0% or less when molded into an unstretched film having a thickness of 100 μm, from the viewpoint of enhancing transparency. 1.0% or less is more preferable. A haze is calculated | required based on the method as described in an Example.

  The imide structure-containing acrylic resin is preferably as colorless as possible when assuming application to an optical film. Therefore, the glutarimide resin has a b * value of 5 when molded into an unstretched film having a thickness of 100 μm. Is preferably 0.0 or less, more preferably 2.0 or less, and even more preferably 1.0 or less. The b * value is determined based on the method described in the examples.

  The number of air bubbles in the imide structure-containing acrylic resin is less than 20 / g, and it is 15 from the viewpoint of suppressing foaming at the time of molding of the imide structure-containing acrylic resin and making it easy to select balanced molding conditions. The number is preferably less than 5 / g, more preferably less than 10 / g, and still more preferably less than 5 / g. The number of bubbles is determined based on the method described in the examples. That is, an imide structure-containing acrylic resin dried in an oven at 80 ° C. for 24 hours is loaded into a cylinder of a melt indexer specified in JIS K7210, held at 280 ° C. for 5 minutes, extruded into a strand, and melted. The number of bubbles present in the strand extruded between the piston upper benchmark and the lower benchmark of the indexer is counted and converted to the number per 1 g of resin.

  The imide structure-containing acrylic resin may be used together with other thermoplastic resins, for example, a polymer blend or a polymer alloy. Other thermoplastic resins include, for example, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride, and the like. Vinyl halide polymer; acrylic polymer such as polymethyl methacrylate; styrene polymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer Polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; cellulose acylates such as cellulose triacetate, cellulose acetate propionate and cellulose acetate butyrate; nylon 6, nylon Polyamide, Polyamide oxide, Polyphenylene sulfide, Polyphenylene sulfide, Polyether ether ketone, Polysulfone, Polyethersulfone, Polyoxybenzylene, Polyamideimide, ABS resin blended with polybutadiene rubber or acrylic rubber And rubbery polymers such as ASA resin.

  The imide structure-containing acrylic resin may contain various additives. Examples of additives include antioxidants such as hindered phenol antioxidants, phosphorus antioxidants, sulfur antioxidants; stabilization of light stabilizers, weather stabilizers, heat stabilizers, etc. Agents: Reinforcing materials such as glass fibers and carbon fibers; near infrared absorbers; ultraviolet absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; anionic surfactants, cationic interfaces Antistatic agents such as activators and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; fillers such as organic fillers and inorganic fillers; resin modifiers; plasticizers; lubricants and the like .

■ Explanation of optical film ■
The imide structure-containing acrylic resin of the present invention can be suitably used as a raw material for, for example, a lens material or an optical film. The optical film can be produced by using an imide structure-containing acrylic resin, for example, by a melt extrusion molding method such as a T-die method or an inflation method, a cast molding method, a press molding method, or the like. When manufacturing an optical film by a melt extrusion method, a single screw extruder, a twin screw extruder, etc. can be used, for example.

  The optical film is preferably uniaxially or biaxially stretched, and more preferably biaxially stretched from the viewpoint of increasing mechanical strength or achieving a predetermined retardation. Examples of the method for biaxially stretching the optical film of the present invention include a sequential biaxial stretching method and a simultaneous biaxial stretching method.

  The stretching temperature at the time of stretching the optical film is that the glass transition from a temperature 20 ° C. lower than the glass transition temperature of the imide structure-containing acrylic resin from the viewpoint of stretching the optical film without breaking and sufficient molecular orientation. It is preferably a temperature range up to a temperature that is 50 ° C. higher than the temperature, more preferably a temperature from a temperature that is 10 ° C. lower than the glass transition temperature of the imide structure-containing acrylic resin to a temperature that is 30 ° C. higher than the glass transition temperature. It is a range.

  The stretching ratio of the optical film is about 1.5 to 3 times from the viewpoint of increasing the mechanical strength and adjusting the phase difference in both the longitudinal direction and the transverse direction perpendicular to the longitudinal direction. It is preferable that it is about 1.5 to 2.5 times.

  The dimensional change rate of the stretched optical film is preferably 1.0% or less and 0.7% or less from the viewpoint of improving the durability of a film subjected to secondary processing such as an ITO film. More preferably, it is more preferably 0.5% or less, and particularly preferably 0.2% or less. The dimensional change rate of the optical film is determined based on the method described in the examples.

  Since the thickness of the optical film varies depending on the application, it cannot be determined unconditionally. For example, when the optical film is used for a protective film, an antireflection film, a polarizing film or the like used in an image display device such as a liquid crystal display device or an organic EL display device, the thickness of the optical film is 1 μm or more. Is preferably 10 μm or more, more preferably 20 μm or more, further preferably 250 μm or less, more preferably 100 μm or less, and further preferably 80 μm or less. For example, when the optical film is used for applications such as a transparent conductive film used for an ITO film, a silver nanowire film, a metal mesh film, etc., the thickness of the optical film is preferably 20 μm or more, and 30 μm or more. Is more preferable, 40 μm or more is further preferable, 400 μm or less is preferable, 350 μm or less is more preferable, and 300 μm or less is more preferable.

The in-plane retardation Re of the optical film is preferably 20 nm or less, more preferably 10 nm or less, further preferably 5 nm or less, and further preferably 3 nm or less from the viewpoint of suppressing the refractive index anisotropy of the optical film and reducing the birefringence. Is particularly preferred. The absolute value of the thickness direction retardation Rth of the optical film is preferably 20 nm or less from the viewpoint of suppressing the anisotropy of the refractive index of the optical film and reducing the birefringence, as in the in-plane retardation Re. 10 nm or less is more preferable, 5 nm or less is further more preferable, and 3 nm or less is especially preferable. For example, the absolute value of the thickness direction retardation Rth of the optical film after biaxial stretching is controlled by controlling the absolute value of the stress optical coefficient (Cr) described above to 0.3 × 10 ⁻⁹ Pa ⁻¹ or less. Can be made 20 nm or less.

  The in-plane retardation Re and the thickness direction retardation Rth of the optical film were measured under the conditions of a light having a wavelength of 590 nm and an incident angle of 40 ° using a retardation film / optical material inspection apparatus (Otsuka Electronics Co., Ltd., RETS-100). Obtained by measuring with The in-plane retardation Re of the optical film is expressed by the formula: Re = (nx−ny) × d (where nx is the direction of the slow axis for light having a wavelength of 590 nm (the direction showing the maximum refractive index in the plane of the optical film). ), Ny is the refractive index in the fast axis direction (direction perpendicular to nx in the plane of the optical film), and d is the thickness (nm) of the optical film. The thickness direction phase difference Rth is expressed by the formula: Rth = {(nx + ny) / 2−nz} × d (where nx is the refractive index in the slow axis direction with respect to light having a wavelength of 590 nm, and ny is in the fast axis direction) Nz is a refractive index in the thickness direction of the film, and d is a thickness (nm) of the film).

The absolute value of the photoelastic coefficient of the optical film is preferably 10 × 10 ⁻¹² Pa ⁻¹ or less, preferably 6 × 10 ⁻¹² Pa ⁻¹ , from the viewpoint of suppressing light leakage, particularly light leakage in a high temperature and high humidity environment. The following is more preferable. The photoelastic coefficient of the optical film is determined according to the following method. That is, the sample was cut into 20 mm × 50 mm with the extending direction of the optical film as the long side, and this sample was mounted on a photoelasticity measurement unit of an ellipsometer (manufactured by JASCO Corporation, product number: M-150). The birefringence is measured at three points while applying a stress load of 5 to 25 N in parallel with the light, and the inclination of the birefringence with respect to the stress is obtained as a photoelastic coefficient using light having a wavelength of 590 nm.

The linear expansion coefficient in the temperature range of 60 to 100 ° C. of the optical film is preferably 80 × 10 ⁻⁶ K ⁻¹ or less, and preferably 70 × 10 ⁻⁶ K ⁻¹ or less from the viewpoint of suppressing dimensional changes in a high temperature environment. More preferred. The linear expansion coefficient at 60 to 100 ° C. of the optical film was increased from 60 ° C. to 100 ° C. at a measurement load of 5 g and a heating rate of 5 ° C./min using a thermomechanical measuring device (manufactured by Shimadzu Corporation, TMA-60). Calculated as the slope when heating. The sample for measurement is prepared by cutting the optical film into a size of 5 mm × 20 mm with the stretching direction as the long side, pretreating it at 60 ° C. for 15 hours, and then cooling to room temperature.

  The water absorption rate of the optical film is preferably 3.0% or less, more preferably 2.5% or less, and even more preferably 2.0% or less, for example, from the viewpoint of improving the moldability to an ITO film. The water absorption rate of the optical film is determined by the following method. That is, after the optical film is dried at 80 ° C. for 24 hours, its mass X is measured. Next, the dried optical film is absorbed in water by storing it in a thermostatic bath at 85 ° C. and a relative humidity of 85%, taken out of the thermostatic bath after 250 hours, and the mass Y of the optical film after water absorption is measured. From the measured values of mass X and Y, the water absorption is determined based on the formula: {(Y−X) / X} × 100.

  The optical film preferably has high transparency. Therefore, the haze is preferably 3.0% or less, more preferably 2.0% or less, and further preferably 1.0% or less. A haze is calculated | required based on the method as described in an Example. A haze is calculated | required based on the prescription | regulation of JISK7136 using a turbidimeter (Nippon Denshoku Industries make, NDH-5000).

  The optical film is preferably as colorless as possible. Therefore, the b * value is preferably 5.0 or less, more preferably 2.0 or less, and even more preferably 1.0 or less. The b * value is determined based on the method described in the examples. The b * value is determined using a spectral color difference meter (Nippon Denshoku Industries Co., Ltd., SE-6000) in accordance with the provisions of JIS Z 8730.

■ Explanation of application of optical film ■
A coating layer may be formed on at least one surface of the optical film as necessary. Examples of the coating layer include an antistatic layer, an adhesive layer, an adhesive layer, an easy-adhesion layer, an antiglare layer (non-glare) layer, a photocatalyst layer, an antifouling layer, an antireflection layer, a hard coat layer, an ultraviolet shielding layer, and a heat ray. Examples thereof include a shielding layer, an electromagnetic shielding layer, and a gas barrier layer.

  The optical film is, for example, a protective film for an optical disc, a polarizer protective film used for a polarizing plate of an image display device such as a liquid crystal display device, a retardation film, a viewing angle compensation film, a light diffusion film, a reflective film, an antireflection film, It is expected to be used for applications such as antiglare films, brightness enhancement films, conductive films for touch panels, diffusion plates, light guides, and prism sheets. Therefore, the optical film can be suitably used for applications such as an image display device such as a liquid crystal display device.

  An optical film having a transparent conductive layer formed on the surface of the optical film can be used as a transparent conductive film. Examples of the transparent conductive layer include an inorganic compound layer having a property of reflecting infrared rays, such as an indium-tin oxide (ITO) layer, and a metal mesh layer made of a metal such as silver, copper, nickel, and tungsten. . The transparent conductive layer may be formed on at least one surface of the optical film.

  An optical adjustment layer may be formed on the surface of the optical film. The optical adjustment layer is a layer for appropriately adjusting the transmittance or reflectance of incident light. As described in, for example, Japanese Patent Application Laid-Open No. 2006-201450, the optical adjustment layer is formed by alternately arranging a low refractive index layer having a relatively low refractive index and a high refractive index layer having a relatively high refractive index. It can be formed by laminating.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.
[Amount of impurities contained in acrylic monomer having amide group]
Gas chromatography (Agilent Technologies, 6890N) was used for determination of the amount of impurities contained in the acrylic monomer having an amide group. The measurement conditions are as follows.

Detector: FID
Column: InertCap Pure WAX 0.25mmID 30m
Temperature: 50 ° C. (5 min hold) + 50 ° C. to 240 ° C. (10 ° C./min)+240° C. (6 min hold)
Inlet temperature: 280 ° C
Detector temperature: 320 ° C
Carrier gas: helium (column flow 1.30 mL / min)
Injection volume: 1.0 μL
Internal standard sample: Diethylene glycol diethyl ether Diluting solvent: Acetonitrile Specifically, a calibration curve solution in which each component and the internal standard sample are dissolved in acetonitrile is prepared and measured by the above gas chromatography, and a calibration curve is obtained from the peak area. Created. Then, the sample solution which melt | dissolved the composition and the internal standard sample in acetonitrile was created, and it measured similarly. The content of each component in the composition was determined by an internal standard method.

[Weight average molecular weight]
The weight average molecular weight (Mw) and the amide group-containing acrylic resin and the imide structure-containing acrylic resin were determined in terms of polystyrene using gel permeation chromatography (GPC). The apparatus and measurement conditions used for the measurement are as follows.

System: Tosoh GPC system HLC-8320
Detector: RI
Measurement side column configuration:
Guard column (manufactured by Tosoh, TSK guard column Super HZ-L)
-Two separation columns (Tosoh, TSKgel SuperHZM-M) connected Reference column configuration:
・ Reference column (manufactured by Tosoh Corporation, TSKgel SuperH-RC)
Developing solvent: THF (made by Wako Pure Chemical Industries, special grade)
Flow rate of developing solvent: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Vial filling pretreatment: Filter the sample solution with a non-aqueous syringe filter (model 25N, 0.45 μm) manufactured by GL Science

[Measurement of high molecular weight ratio]
Using the GPC apparatus and conditions used for the molecular weight measurement, the ratio of the molecular weight of 2 million or more to the whole imide structure-containing acrylic resin was calculated from the area ratio. Specifically, using standard polystyrene as a standard sample, a calibration curve of retention time and molecular weight was created in terms of polystyrene, and the retention time at which the molecular weight was 2 million was determined. Subsequently, the peak is divided with the retention time at which the molecular weight is 2 million of the GPC chart (detector: RI) of the imide structure-containing acrylic resin obtained by the sample measurement as a boundary, and the area having a molecular weight of 2 million or more is included in the entire peak. The proportion of the total was calculated. That is, the high molecular weight ratio (area%) is expressed by the formula: [high molecular weight ratio (area%)] = {(area of molecular weight of 2 million or more) / (area of molecular weight of 2 million or more + area of molecular weight of less than 2 million) } It calculated | required based on * 100.

[Polymerization rate]
For the polymerization rate of each monomer, gas chromatography (manufactured by Shimadzu Corporation, GC2010) was used. The measurement conditions are as follows.

Detector: FID
Column: RESTEK Rxi-624Sil MS 0.25mmID 30m
Temperature: 40 ° C. (5 min hold) + 40 ° C. to 310 ° C. (10 ° C./min)+310° C. (10 min hold)
Inlet temperature: 250 ° C
Detector temperature: 315 ° C
Carrier gas: helium (column flow rate 1.27 mL / min)
Injection volume: 1.0 μL
Internal standard sample: Dimethyl succinate Diluting solvent: Acetone Specifically, a calibration curve solution in which each monomer and internal standard sample are dissolved in acetone is prepared, measured by the above gas chromatography, and a calibration curve is obtained from the peak area. Created. Thereafter, a sample solution in which the polymerization solution and the internal standard sample were dissolved in acetone was prepared and measured in the same manner. The content of each monomer in the polymerization solution was determined by an internal standard method, and the polymerization rate was calculated from the theoretical value.

[Imidation rate]
The imidation ratio of the imide structure-containing acrylic resin was determined by measuring a ¹ H-NMR spectrum using an NMR measurement apparatus (manufactured by Varian, trade name: Unity Plus 400). Specifically, an imide structure-containing acrylic resin is dissolved in heavy acetone, and the peak area A derived from protons on N of N-substituted (meth) acrylamide and substitution on N of N-substituted (meth) acrylamide. The ratio of imidization was calculated from the ratio to the peak area B derived from the proton of the group (peak area A / peak area B)].

For example, when R ^{5 of the} repeating unit represented by the formula (1) is a phenyl group, the imidization rate is expressed by the formula: [imidization rate (%)] = [ ^1/5 (peak area A / peak area B) )] × (100 × 5).
[Glass transition temperature (Tg)]
The glass transition temperature (Tg) of the imide structure-containing acrylic resin was determined in accordance with the provisions of JIS K7121. Specifically, using a differential scanning calorimeter (Rigaku, Thermo plus EVO DSC-8230), a sample of about 10 mg was heated from room temperature to 200 ° C. (heating rate 20 ° C./min) in a nitrogen gas atmosphere. From the DSC curve obtained in this way, the starting point method was used for evaluation. Α-alumina was used as a reference.
[Pyrolysis start temperature (Td)]
The thermal decomposition starting temperature (Td) of the imide structure-containing acrylic resin was determined from dynamic TG measurement. Specifically, it is as follows. Using a differential type differential thermal balance device (Rigaku, Thermo Plus2 TG-8120), a 10 mg sample was heated from room temperature to 500 ° C. in a nitrogen gas atmosphere. At this time, when the sample mass reduction rate is 0.005% by mass / second or less, the rate of temperature increase is 10 ° C./min. When the sample mass decrease rate during temperature increase exceeds 0.005% by mass / second The temperature was increased by using stepwise isothermal control so that the speed was maintained at 0.005 mass% / second or less. The temperature at which stepwise isothermal control was first performed in order to maintain the mass reduction rate (the lowest temperature at which stepwise isothermal control was performed) was defined as Td of the resin composition. In addition, when Td based on mass reduction due to impurity volatilization was clearly confirmed, a temperature with stepwise isothermal control on the higher temperature side than the Td was also obtained (in the Td column of the table below, The temperature is shown in parentheses).

[Haze]
Using a manual heating press (manufactured by Imoto Seisakusho Co., Ltd., IMC-180C type), the imide structure-containing acrylic resin was melt-pressed at a pressure of 40 MPa at a temperature of 280 ° C. for 2 minutes, and the thickness was 100 μm. An unstretched film was produced. The haze of the produced unstretched film was calculated | required based on the prescription | regulation of JISK7136 using the turbidimeter (Nippon Denshoku Industries make, NDH-5000).
[B * value]
Using a manual heating press (manufactured by Imoto Seisakusho Co., Ltd., IMC-180C type), the imide structure-containing acrylic resin was melt-pressed at a pressure of 40 MPa at a temperature of 280 ° C. for 2 minutes, and the thickness was 100 μm. The b * value of the produced unstretched film produced from the unstretched film was determined using a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., ZE6000) in accordance with the provisions of JIS Z8730.
[Film thickness]
The thickness of the film obtained by molding the imide structure-containing acrylic resin was determined with a Digimatic micrometer (Mitutoyo).

[Stress optical coefficient (Cr)]
Using a manual heating press (manufactured by Imoto Seisakusho Co., Ltd., IMC-180C type), the imide structure-containing acrylic resin was melt-pressed at a pressure of 40 MPa at a temperature of 280 ° C. for 2 minutes, and the thickness was 100 μm. An unstretched film was produced. For the stress optical coefficient (Cr) of the imide structure-containing acrylic resin, the unstretched film is cut into a 60 mm × 20 mm rectangle, the weight is selected so that the stress is 1 N / mm ² or less, and the lower end of the unstretched film (short Attached to the side). This unstretched film was set at a temperature of 3 ° C. higher than the glass transition temperature of the imide structure-containing acrylic resin at a constant temperature dryer (manufactured by ASONE, product number: DOV-450A) with a distance between chucks of 40 mm. After stretching by holding for about 30 minutes, heating was stopped and cooling was performed at a cooling rate of about 1 ° C./min until the temperature became 40 ° C. lower than the glass transition temperature of the imide structure-containing acrylic resin. Then, the obtained stretched film was taken out from the constant temperature dryer, and the length, thickness and weight of the stretched film were measured, and the in-plane retardation Re of the stretched film was measured. Further, the length, thickness and weight of the stretched film were measured in the same manner as described above using four kinds of weights so that the stress was 1 N / mm ² or less. In-plane retardation Re was measured. Based on the above results, based on the measurement method described in Polymer Science Society, “Frontier of Transparent Plastics (Polymer Frontier 21 Series)”, NTS, October 2006, pages 37-44. The stress optical coefficient (Cr) was calculated. More specifically, Δn (nx−ny) is plotted on the y-axis, σ is plotted on the x-axis, the slope of the straight line obtained by the least square method is obtained, and the value of the slope is expressed as the stress optical coefficient (Cr). did. Note that nx is the refractive index in the slow axis direction in the plane of the film (direction showing the maximum refractive index in the film plane), and ny is the fast axis direction in the plane of the film (perpendicular to nx in the film plane). The refractive index in the direction), σ, is the stress (N / m ² ) on stretching.

[Water absorption rate]
Using a manual heating press machine (IMC-180C type, manufactured by Imoto Seisakusho Co., Ltd.), the imide structure-containing acrylic resin was melt-pressed at a pressure of 20 MPa at a temperature of 240 ° C. for 2 minutes, and the thickness was 300 μm. An unstretched film was produced. The obtained unstretched film was dried at 80 ° C. for 24 hours, and then its mass (X) was measured. Next, the unstretched film obtained above is absorbed in water by storing it in a thermostatic bath at 85 ° C. and a relative humidity of 85%, taken out from the thermostatic bath after 250 hours, and the mass of the unstretched film after water absorption (Y ) Was measured. The water absorption of the unstretched film was determined based on the formula: [Water absorption (mass%)] = [(Y−X) / X] × 100.
[Measure the number of bubbles]
An acrylic resin containing an imide structure dried in an oven at 80 ° C. for 24 hours is loaded into a cylinder of a melt indexer specified in JIS K7210, held at 280 ° C. for 5 minutes, and then extruded into a strand shape. The number of bubbles present in the strand extruded between the piston upper standard line and the lower standard line was counted and converted into the number per 1 g of resin.

(Synthesis Example 1)
In a 300 mL four-necked flask equipped with a rectifying column, a Dimroth, a reflux drum, a stirrer chip, a thermometer, and an air blowing tube, 138 g (1.6 mol) of methacrylic acid, 40.8 g (0.4 mol) of acetic anhydride, Nickel acetate tetrahydrate 40 mg (0.0002 mol) and phenothiazine 0.24 g were charged. After stirring with heating at an internal temperature of 75 ° C. for 2 hours, the pressure was reduced to 50 torr to obtain a total reflux state. After 1 hour and a half, 14.8 g of the content liquid in the reflux drum was withdrawn, the pressure was lowered to 40 torr, and the total reflux state was resumed. After 1 hour, 11.3 g of the content liquid in the reflux drum was extracted. Thereafter, the pressure was gradually reduced to 20 torr to obtain a total reflux state, and after 1 hour, 14.9 g of the content liquid of the reflux drum was extracted. Thereafter, 37.2 g (0.4 mol) of aniline was added dropwise to the reaction solution in the flask to produce N-phenylmethacrylamide with a reaction yield of 90.5% (based on acetic anhydride). N-phenylmethacrylamide was precipitated by adding an excessive amount of hexane to the reaction solution, and an N-phenylmethacrylamide composition having a purification yield of 85% was obtained by filtration. This composition contained 0.2% by weight of methacrylic acid and 0.4% by weight of acetanilide.

(Synthesis Example 2)
The N-phenylmethacrylamide composition obtained in Synthesis Example 1 was purified on a silica gel column using a developing solvent of ethyl acetate: hexane = 4: 1. Both methacrylic acid and acetanilide contained in the obtained N-phenylmethacrylamide composition were below the detection limit (10 ppm) in terms of mass.

(Synthesis Example 3)
In a 300 mL four-necked flask equipped with a rectifying column, a Dimroth, a reflux drum, a stirrer chip, a thermometer, and an air blowing tube, 138 g (1.6 mol) of methacrylic acid, 40.8 g (0.4 mol) of acetic anhydride, Nickel acetate tetrahydrate 40 mg (0.0002 mol) and phenothiazine 0.21 g were charged. After stirring with heating at an internal temperature of 75 ° C. for 2 hours, the pressure was reduced to 50 torr to obtain a total reflux state. After 1 hour and a half, 14.5 g of the content liquid in the reflux drum was withdrawn, the pressure was lowered to 40 torr, and the total reflux state was resumed. After 1 hour, 13.8 g of the content liquid in the reflux drum was extracted. Thereafter, 37.2 g (0.4 mol) of aniline was added dropwise to the reaction solution in the flask to produce N-phenylmethacrylamide with a reaction yield of 78% (based on acetic anhydride). N-phenylmethacrylamide was precipitated by adding an excessive amount of hexane to the reaction solution, and an N-phenylmethacrylamide composition having a purification yield of 80% was obtained by filtration. This composition contained 1.2% by weight of methacrylic acid and 4.3% by weight of acetanilide.

Example 1
In a reaction kettle equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen gas introduction pipe, 35 parts by mass of N-phenylmethacrylamide (PMAM) obtained in Synthesis Example 1, 52 parts by mass of methyl methacrylate (MMA), toluene And 57.5 parts by mass of a mixed solvent of methanol and methanol (toluene / methanol = 8/2 (mass ratio)) and 0.05 part by mass of an antioxidant (manufactured by ADEKA, trade name: ADK STAB 2112) were reacted. The temperature was raised to 76 ° C. while passing nitrogen gas through the kettle. Subsequently, 0.15 parts by mass of dimethyl-2,2′-azobis (2-methylpropionate) [manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-601] as a polymerization initiator was placed in the reaction kettle. In addition to the addition of 28.4 parts by mass of a mixed solvent of toluene and methanol (toluene / methanol = 8/2 (mass ratio)), dimethyl-2,2′-azobis (2-methylpropionate) [Wako Pure Chemical Industries, Ltd. (Product name: V-601), 0.25 parts by mass of solution and 13 parts by mass of MMA were added dropwise to the reaction kettle over 2 hours, respectively, and refluxed at about 70 to 77 ° C. Solution polymerization was carried out. 1 hour after the completion of dropwise addition of dimethyl-2,2′-azobis (2-methylpropionate) and MMA, 35.6 parts by mass of methyl ethyl ketone was added for dilution, and after 3 hours, 27.8 parts by mass of methyl ethyl ketone were added. Aged for 2 hours after dilution. Subsequently, 2,2′-azobis (2,4-dimethylvaleronitrile) [manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-65] was added by 0.05 part by mass, and further aged for 4 hours, A polymerization liquid of an amide group-containing acrylic resin was obtained.

  Next, a solution obtained by dissolving 0.1 part by mass of sodium methoxide (NaOMe) as a cyclization catalyst in 9.9 parts by mass of methanol was dropped into the polymerization solution in the reaction kettle at a temperature of about 60 ° C. A polymerization solution was obtained. The obtained polymerization solution was heated at 240 ° C. under vacuum for 1 hour to obtain an imide structure-containing acrylic resin. At this time, no obstruction was found in the mouth of the vacuum trap. Further, when the molecular weight of the imide structure-containing acrylic resin was measured, the filter was not clogged in the pre-filling treatment of the vial, and it was not necessary to replace the filter before obtaining 2 ml of filtrate. Table 1 shows the physical properties of the resulting imide structure-containing acrylic resin.

Example 2
In Example 1, except for using PMAM obtained in Synthesis Example 2 instead of PMAM obtained in Synthesis Example 1, the same operation as in Example 1 was performed to obtain an imide structure-containing acrylic resin. At this time, no obstruction was found in the mouth of the vacuum trap. Further, when the molecular weight of the imide structure-containing acrylic resin was measured, the filter was not clogged in the pre-filling treatment of the vial, and it was not necessary to replace the filter before obtaining 2 ml of filtrate. Table 1 shows the physical properties of the resulting imide structure-containing acrylic resin.

Example 3
In Example 2, except that the amount of NaOMe was changed from 0.1 parts by mass to 0.02 parts by mass, the same operation as in Example 2 was performed to obtain an imide structure-containing acrylic resin. At this time, no obstruction was found in the mouth of the vacuum trap. Further, when measuring the molecular weight of the acrylic resin containing the imido structure, the filter was not clogged in the pre-filling treatment, and it was not necessary to replace the filter until 2 ml of filtrate was obtained. Table 1 shows the physical properties of the resulting imide structure-containing acrylic resin.

Comparative Example 1
In Example 1, except for using PMAM obtained in Synthesis Example 3 instead of PMAM obtained in Synthesis Example 1, the same operation as in Example 1 was performed to obtain an imide structure-containing acrylic resin. At this time, an obstruction was observed at the mouth of the vacuum trap. Further, when the molecular weight of the imide structure-containing acrylic resin was measured, the filter was not clogged in the pre-filling treatment of the vial, and it was not necessary to replace the filter before obtaining 2 ml of filtrate. Table 1 shows the physical properties of the resulting imide structure-containing acrylic resin.
Comparative Example 2
In Comparative Example 1, the same operation as in Example 2 was performed except that the amount of NaOMe was changed from 0.1 parts by mass to 0.02 parts by mass to obtain an imide structure-containing acrylic resin. At this time, an obstruction was observed at the mouth of the vacuum trap. In addition, when measuring the molecular weight of the imide structure-containing acrylic resin, clogging occurred during filtration of the vial pre-treatment. Table 1 shows the physical properties of the resulting imide structure-containing acrylic resin.

  The imide structure-containing acrylic resin obtained by the production method of the present invention is provided in an image display device such as a protective film for a substrate of an optical disk such as VD, CD, DVD, MD, and LD, and a liquid crystal display device such as an LCD. Optical protective films such as polarizer protective films used for polarizing plates, antireflection films used for organic EL displays (OLEDs), and optical films such as transparent conductive films formed with transparent conductive layers such as ITO layers It can be suitably used as a raw material, lens material, and the like.

Claims (7)

  A method for producing an imide structure-containing acrylic resin having a glutarimide structure in the main chain, which is a copolymerization of a monomer component containing an acrylic monomer having an amide group and an acrylic monomer having an ester group A process for producing an imide structure-containing acrylic resin, wherein the acrylic monomer having an amide group contains 1% by mass or less of a carboxylic acid compound.   The method for producing an imide structure-containing acrylic resin according to claim 1, wherein the acrylic monomer having an amide group contains 4% by mass or less of a radical non-reactive amide compound. The acrylic monomer having the amide group is a compound represented by the following formula (1), and the acrylic monomer having the ester group is a compound represented by the following formula (2). Or the manufacturing method of imide structure containing acrylic resin of 2.

[R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ⁵ and R ⁶ each independently represent a hydrogen atom or carbon number 1 to 18 linear, cyclic and branched alkyl groups (including alkyl groups having an aromatic ring) and aryl groups having 6 to 10 carbon atoms. ]   A step of copolymerizing a monomer component containing an acrylic monomer having an amide group and an acrylic monomer having an ester group in an organic solvent to obtain an amide group-containing acrylic resin; The method includes the step of melting the acryl-containing acrylic resin and cyclizing and condensing the amide group and ester group of the amide group-containing acrylic resin in the presence of a basic compound. A method for producing an imide structure-containing acrylic resin. It is an imide structure-containing acrylic resin having a glutarimide structure in the main chain, has a glass transition temperature (Tg) of 130 ° C. or higher, and an absolute value of stress optical coefficient (Cr) of 0.3 × 10 ⁻⁹ Pa ^{−. An} imide structure-containing acrylic resin having a molecular weight of ¹ or less, a molecular weight of 2 million or more in terms of GPC area of 1% or less, and a number of bubbles measured by the following method of less than 20 / g.
Number of bubbles: (meth) acrylic resin dried in an oven at 80 ° C. for 24 hours was loaded into a cylinder of a melt indexer specified in JIS K7210, held at 280 ° C. for 5 minutes, and then extruded into a strand. The number of air bubbles present in the strand extruded between the upper index line and the lower index line of the melt indexer was counted and converted to the number per 1 g of resin. The imide structure containing (meth) acrylic resin of Claim 5 which has a repeating unit represented by following formula (3), and a repeating unit represented by following formula (4).

[R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ⁵ and R ⁶ each independently represent a hydrogen atom or carbon number 1 to 18 linear, cyclic and branched alkyl groups (including alkyl groups having an aromatic ring) and aryl groups having 6 to 10 carbon atoms. ] The imide structure-containing (meth) acrylic resin according to claim 5 or 6, wherein in the formula (3), R ⁵ is an aryl group having 6 to 10 carbon atoms.