JP2013049755A - Method of manufacturing dope solution, method of manufacturing optical thin film, and optical thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a dope solution by a uniform dissolution method in which an undissolved matter is not detected when solvent-dissolving a fumaric acid diester-based resin, and to provide a method of manufacturing an optical thin film.SOLUTION: The method of manufacturing a dope solution comprises as follows. A fumaric acid diester based resin having an average particle size of 50-300 μm and including a diisopropyl fumarate residue unit and a fumaric acid diester residue unit having a 1-2C alkyl group, when the agitated flow amount Q shown by (Formula 1) is in the range of 0.15-3.5 L/sec, and the value shown by the ratio (Q/V) of the agitated flow amount Q to the solution volume V is in the range of 1-25 sec., is inputted in a solvent in the time of 3 minutes from a stirring initiation, and is stirred for 0.5-4 hours. Q=Nq×n×d×10(Formula 1). In the formula, Q denotes the amount of the agitated flow, Nq denotes the agitated flow amount coefficient, n denotes the number of revolutions [rps], and d denotes a stirring impeller diameter [m].

Description

  The present invention relates to a method for producing a dope solution and a method for producing an optical thin film, and more particularly to a method for producing a resin solution (dope solution) used for film formation and a method for producing an optical thin film such as a retardation film.

  Liquid crystal displays (hereinafter referred to as LCDs) are widely used as the most important display devices in the multimedia society, including cellular phones, computer monitors, notebook computers, and televisions. Many optical films are used for LCD to improve display characteristics. In particular, a retardation film is used to compensate for contrast and color tone when the LCD is viewed from the front or obliquely, and plays an important role. As the retardation film, a film made of a fumaric acid ester resin in addition to the conventional polycarbonate and cyclic polyolefin has been proposed (see, for example, Patent Document 1). The optical compensation film described in Patent Document 1 is characterized in that the refractive index in the thickness direction of the film is large and has a certain amount of out-of-plane retardation.

  Normally, film and sheets that require high quality, such as optical compensation films, require uniform film manufacturing technology, but optical film materials made of fumarate-based resins have a high molecular molecular skeleton. Since it is rigid, it is difficult to prepare a uniform solution by a dissolving operation in a solvent, and an undissolved residue tends to be formed after dissolution.

  However, in Patent Document 1, for example, there is no description for preparing a solution in which resin undissolved material does not remain in a method for preparing a dope solution for producing an optical thin film.

JP 2008-112141 A

  An object of the present invention is to provide a method for producing a dope solution and a method for producing an optical thin film by a uniform dissolution method in which undissolved substances are not detected when a fumaric acid diester resin is dissolved in a solvent.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by stirring and mixing under specific conditions as a method of dissolving a specific fumaric acid diester resin in a solvent, The present invention has been completed. That is, the present invention shows a fumaric acid diester resin having an average particle size of 50 to 300 μm and containing a fumaric acid diester residue unit having a diisopropyl fumarate residue unit and an alkyl group having 1 or 2 carbon atoms according to a predetermined formula. Stirring flow rate Q is 0.15 to 3.5 L / sec. The value indicated by the ratio (Q / V) of the stirring flow rate Q to the solution volume V is 1 to 25 sec. ^In the range of ^-1 , the dope solution is produced by adding it into the solvent within 3 minutes from the start of stirring and stirring for 0.5 to 4 hours.

  The present invention is described in detail below.

  The fumaric acid diester resin used in the method for producing the dope liquid (resin solution for producing an optical thin film) of the present invention is a fumaric acid diester having a diisopropyl fumarate residue unit and an alkyl group having 1 or 2 carbon atoms. It includes residue units.

  Here, the alkyl group having 1 or 2 carbon atoms in the fumaric acid diester residue unit having an alkyl group having 1 or 2 carbon atoms is independent, and examples thereof include a methyl group and an ethyl group. These may be substituted with halogen groups such as fluorine and chlorine; ether groups; ester groups or amino groups. Examples of the fumaric acid diester residue unit having an alkyl group having 1 or 2 carbon atoms include a dimethyl fumarate residue unit and a diethyl fumarate residue unit. These may be contained alone or in combination of two or more.

  Specific examples of the fumaric acid diester resin include diisopropyl fumarate / dimethyl fumarate copolymer, diisopropyl fumarate / diethyl fumarate copolymer, and the like.

  The ratio of the copolymer composition in the fumaric acid diester resin is such that the phase difference characteristics and strength in the case of an optical thin film are excellent, so that the diisopropyl fumarate residue unit is 50 to 99 mol% and the carbon number is 1 or 1 to 50 mol% of a fumaric acid diester residue unit having 2 alkyl groups is preferred, and since the phase difference characteristics and strength are more excellent, 60 to 95 mol% of diisopropyl fumarate residue unit and 1 or more carbon atoms The fumaric acid diester residue unit having 2 alkyl groups is more preferably 5 to 40 mol%.

  The fumaric acid diester resin may contain other monomer residue units as long as it does not exceed the scope of the present invention. Examples of other monomer residue units include styrene residue units, Styrene residue units such as α-methylstyrene residue units; (meth) acrylic acid residue units; (meth) methyl acrylate residue units, (meth) ethyl acrylate residue units, (meth) acrylate butyl (Meth) acrylic acid ester residue units such as residue units; vinyl ester residue units such as vinyl acetate residue units and vinyl propionate residue units; acrylonitrile residue units; methacrylonitrile residue units; methyl Vinyl ether residue units such as vinyl ether residue units, ethyl vinyl ether residue units, butyl vinyl ether residue units; N-methylmaleimide residue units, N-cyclohexylma N-substituted maleimide residue units such as imide residue units and N-phenylmaleimide residue units; olefin residue units such as ethylene residue units and propylene residue units; di-n-butyl fumarate residue units 1 type, or 2 or more types selected from fumaric acid diester residue units other than the fumaric acid diester residue units such as bis (2-ethylhexyl) fumarate residue units.

  The fumaric acid diester resin has an average particle size of 50 to 300 μm. When the average particle size is smaller than 50 μm, the powder tends to float easily and is difficult to handle, and agglomeration at the time of solvent dissolution becomes significant. When the average particle diameter exceeds 300 μm, the powder is difficult to float and handling is not a problem. However, when it is agglomerated when dissolved in a solvent, the solubility is significantly deteriorated.

  The fumaric acid diester resin preferably has a standard polystyrene equivalent number average molecular weight of 50,000 to 250,000 obtained from an elution curve measured by gel permeation chromatography (GPC).

  The fumarate diester resin may be produced by any method as long as the fumarate diester resin is obtained. For example, diisopropyl fumarate and a fumaric acid diester having an alkyl group having 1 or 2 carbon atoms may be used. It can be produced by performing radical polymerization or the like.

  For the radical polymerization, any known polymerization method such as bulk polymerization method, solution polymerization method, suspension polymerization method, precipitation polymerization method, emulsion polymerization method and the like can be adopted, but the polymerization can be performed by controlling the particle size. A suspension polymerization method that can be easily recovered is preferred.

  As a polymerization catalyst when performing radical polymerization, for example, benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, organic peroxides such as t-butylperoxyacetate and t-butylperoxybenzoate; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-butyronitrile), 2, Examples thereof include azo initiators such as 2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, and 1,1′-azobis (cyclohexane-1-carbonitrile).

  And there is no restriction | limiting in particular as a solvent which can be used in solution polymerization method, suspension polymerization method, precipitation polymerization method, emulsion polymerization method etc., For example, aromatic solvents, such as benzene, toluene, xylene; Methanol, ethanol, propanol, butanol Examples include alcohol solvents such as cyclohexane, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, dimethylformamide, isopropyl acetate, and water, and a mixed solvent thereof can also be used.

  The polymerization temperature at the time of performing radical polymerization can be appropriately set according to the decomposition temperature of the polymerization initiator, and is generally preferably in the range of 30 to 150 ° C.

In the method for producing a dope solution of the present invention, the stirring flow rate Q shown in Formula 1 is 0.15 to 3.5 L / sec. In this range, the value indicated by the ratio (Q / V) of the stirring flow rate Q to the solution volume V is 1 to 25 sec. ^In the range of ^-1 , the above-mentioned fumaric acid diester resin is introduced into the stirring solvent within 3 minutes from the start of stirring, and mixed and stirred for 0.5 to 1 hour to obtain a dope solution exhibiting uniform solubility. Can be obtained.

Q = Nq × n × d ³ × 10 ³ (Formula 1)
(In the formula, Q represents the stirring flow rate, Nq represents the stirring flow coefficient, n represents the rotational speed [rps], and d represents the stirring blade diameter [m].)
The stirring flow rate Q is 0.15 L / sec. Is smaller than the above, the stirring is not sufficient, and the uneven distribution of the fluidized portion and the staying portion in the solution becomes remarkable, and the lump remains as an undissolved material in the staying portion, which is not preferable. On the other hand, the stirring flow rate Q is 3.5 L / sec. In the case of larger than that, the liquid level is unstable because the stirring is too strong, and the solvent volatilization is remarkable due to the heat generation of the solution.

  When the value indicated by the ratio (Q / V) of the stirring flow rate Q to the solution volume V is less than 1, the stirring is not sufficient and the uneven distribution of the fluidized portion and the staying portion in the solution becomes remarkable. Since a thing remains as an undissolved substance, it is not preferable. On the other hand, when the Q / V value exceeds 25, almost the same uniform solubility as in the range of 1 to 25 can be obtained, but the solution heat generation during stirring is large, and the solvent tends to volatilize.

  The fumaric acid diester resin is charged into the stirring solvent within 3 minutes. It is not preferable to add the fumaric acid diester resin for more than 3 minutes because aggregation occurs. As long as the charging can be completed in a shorter time, the faster one is preferable for the purpose of suppressing aggregation.

  The stirring time after charging the resin is 0.5 to 4 hours. If it is less than 0.5 hour, the circulation of the solution inside the stirring vessel cannot be said to be sufficient, and a minute amount of undissolved matter on the vessel wall surface or the like may remain. However, the dissolution effect is not different from the case of about 1 hour. Therefore, the stirring time is preferably 0.5 to 1 hour.

  As the solvent for dissolving the fumaric acid diester resin, any solvent can be used as long as it dissolves, for example, tetrahydrofuran, ethyl acetate, butyl acetate, acetic acid isobutyl ester, cellosolve acetate, acetone, MEK (methyl ethyl ketone). , MIBK (methyl isobutyl ketone), cyclohexanone, methanol, ethanol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, toluene, xylene, cyclohexane, cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbi Toll, methylene chloride and the like can be mentioned, and these can be used alone or in combination.

The apparatus for preparing the dope solution has a stirring flow rate Q of 0.15 to 3.5 L / sec. Q / V value is 1 to 25 sec. Any one from a small mixer to a large mixer may be used as long as the range of ⁻¹ can be obtained. As a kind of mixer, there are, for example, a batch type mixing method and a circulation type in-line mixing method, and as a shape of a stirring blade, for example, a propeller type, an axial flow turbine type, a radiation turbine type, an impeller type, a sawtooth blade type , Closed rotor type, rotor / stator type, and the like.

  In addition, it is effective to dissolve the resin over time while dividing the resin and adding it to the solvent little by little in the operation of dissolving the resin, which is usually not so high in solubility in a solvent and easily forms an aggregated mass. However, in the production method of the present invention, if the resin solids are divided and added to the solvent little by little while being dissolved over time, a lot of aggregates are generated instead. .

  As described above, the dope solution prepared so as not to remain undissolved may be filtered using a filter in order to remove dust, foreign substances, etc. In addition, no undissolved material is found on the filter after filtration. Here, a filter having an opening size that can be used for optical purposes can be used, and a typical opening having a size of about 0.5 to 20 μm can be used in various combinations.

  As a method for producing an optical thin film of the present invention, a film can be formed by a solution coating method or the like produced by casting the dope solution obtained by the above method on a supporting substrate and then removing the solvent. .

  The solution coating method is, for example, a method of forming an optical thin film by casting a dope solution on a supporting substrate and then removing the solvent by heating or the like. In that case, as a method of casting the dope solution on the support substrate, for example, a T-die method, a gravure roll method, a doctor blade method, a bar coat method, a roll coater method, a lip coater method, or the like can be used. In particular, industrially, a gravure in which the dope solution is scooped up onto a belt-shaped or drum-shaped support substrate by coating from a die and applied to the T-die method or a concavo-convex pattern roll and transferred to the support substrate side. The roll method is most commonly used.

  Examples of the supporting substrate used include polarized light such as TAC film, acrylic resin film, cyclic olefin film, PP film composed of a glass substrate, a triacetyl cellulose composition constituting a laminated polarizing plate, and the like. There are films for the purpose of protecting the child and imparting a retardation, and the like. The film is not limited to those mentioned here, and can be widely used as a supporting substrate for coating. Moreover, in order to obtain sufficient adhesion strength between the optical thin film of the present invention and the supporting base material, an adhesive treatment, a base material surface treatment or the like may be performed, and known materials and techniques can be used.

  In this case, the coating thickness of the optical thin film is preferably 20 μm or less, more preferably 1 to 20 μm, and particularly preferably 5 to 20 μm in order to obtain a thin film having excellent coating appearance and high uniformity in the dried state.

  The viscosity of the dope liquid used in the method for producing an optical thin film of the present invention is only required to have a solution characteristic capable of forming an optical thin film, and the solution viscosity is preferably 50 to 10,000 cP, preferably 50 to More preferred is 3,000 cP.

  The optical thin film of the present invention may contain an antioxidant and an ultraviolet stabilizer for coating film formation or to increase the thermal stability of the optical thin film itself. Examples of the antioxidant include hindered phenol antioxidants, phosphorus antioxidants, and other antioxidants, and these antioxidants may be used alone or in combination of two or more. In particular, in order to improve the synergistic antioxidant action, it is preferable to use a hindered phenol-based antioxidant and a phosphorus-based antioxidant in combination, for example, phosphorus-based with respect to 100 parts by weight of the hindered phenol-based antioxidant. An antioxidant is contained in a ratio of 100 to 500 parts by weight, and 0.01 to 10 parts by weight of the antioxidant is preferable, and 0.5 to 1 part by weight is further added per 100 parts by weight of the fumaric acid diester resin. preferable. Examples of the ultraviolet stabilizer include benzotriazole, benzophenone, triazine, benzoate and the like.

  The optical thin film of the present invention may contain a plasticizer for the purpose of manipulating optical properties and mechanical properties. Examples of the plasticizer include a phthalate ester plasticizer, an adipate ester plasticizer, and a phosphate plasticizer. These plasticizers may be used alone or in combination.

  The optical thin film of the present invention contains additives such as other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, antistatic agents, antiblocking agents, lubricants and the like within the scope of the invention. May be.

  In order to suppress optical loss, the optical thin film of the present invention preferably has a total light transmittance of 85% or more, more preferably 90% or more.

  The optical thin film of the present invention can be used as an integrated polarizing plate laminate by directly coating and integrating a polarizing plate, or by laminating a pre-coated support substrate with a polarizing plate.

  The optical thin film of the present invention is useful as a laminate with a polarizing plate for a liquid crystal display, an organic EL display, a brightness enhancement film, and the like. Furthermore, the optical thin film obtained by the present invention can be laminated with other retardation films.

  According to the present invention, a uniform dope solution of a fumaric acid diester copolymer can be obtained, and it is possible to prepare a solution in which no undissolved lump remains on the filter even after filter filtration. Therefore, it can be easily filtered and is useful as a method for producing an optical thin film such as a liquid crystal display.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

  Hereafter, the method used for evaluation and measurement of an Example is shown.

<Measurement of number average molecular weight>
It measured using the gel permeation chromatography (GPC) apparatus (The Tosoh make, brand name: C0-8011), and computed as a standard polystyrene conversion value.

<Confirmation of composition of fumaric acid diester resin>
It was derived from proton nuclear magnetic resonance spectroscopy (1H-NMR) spectrum analysis using a nuclear magnetic resonance measuring apparatus (trade name: JNM-GX270, manufactured by JEOL Ltd.).

<Measurement of solution viscosity>
It measured at 25 degreeC using the rotational viscometer (The Toki Sangyo make, brand name: TV-20 type | mold viscosity meter).

<Measurement of light transmittance of optical thin film>
Based on JIS-K-7361-1, it measured with the haze meter (Nippon Denshoku Industries make, brand name: NDH5000).

<Measurement of birefringence and retardation of optical thin film>
Measurement was performed using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, trade name: KOBRA-21ADH).

  Here, the birefringence of the optical thin film refers to the refractive index in the two axial directions in the thin film plane with respect to the film forming direction, the reference axis as the slow axis nx, the fast axis ny orthogonal thereto, and the thin film thickness direction. When the axis is nz and the thickness of the thin film is d, the absolute value | nx−ny | of the difference in the average refractive index in the plane expressed as the birefringence Δn in the thin film plane is expressed. The in-plane retardation (Re) of the thin film is (nx−ny) × d, the out-of-plane birefringence (ΔP) of the thin film is ((nx + ny) / 2−nz), and the out-of-plane retardation (Rth) of the thin film is (( nx + ny) / 2−nz) × d.

Synthesis Example 1 (Synthesis of fumaric acid diester resin (diisopropyl fumarate / diethyl fumarate copolymer))
Hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metrolose 60SH-50) 2 g, water 600 g, diisopropyl fumarate 365 g, diethyl fumarate 35 g and polymerization start in a 1 L autoclave equipped with a stirrer, a condenser, a nitrogen inlet tube and a thermometer 3 g of t-butyl peroxypivalate was added as an agent, nitrogen bubbling was carried out for 1 hour, and then the suspension was kept at 45 ° C. for 24 hours while stirring at 400 rpm to carry out radical suspension polymerization. After cooling to room temperature, the resulting suspension containing the polymer particles was filtered and washed with water and methanol to obtain a fumaric acid diester resin (diisopropyl fumarate / diethyl fumarate copolymer) (yield) : 65%).

  The number average molecular weight of the obtained fumaric acid diester resin was 132,000, and the average particle diameter was 130 μm. Moreover, the resin composition was a diisopropyl fumarate residue unit / diethyl fumarate residue unit = 91/9 (mol%) by 1H-NMR measurement.

Synthesis Example 2 (Synthesis of fumaric acid diester resin (diisopropyl fumarate / diethyl fumarate copolymer))
Hydroxypropylmethylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metrolose 60SH-50) 2 g, water 600 g, diisopropyl fumarate 330 g, diethyl fumarate 70 g and polymerization start in a 1 L autoclave equipped with a stirrer, condenser, nitrogen inlet tube and thermometer 3 g of t-butyl peroxypivalate was added as an agent, nitrogen bubbling was performed for 1 hour, and then radical suspension polymerization was performed by maintaining at 45 ° C. for 36 hours while stirring at 400 rpm. After cooling to room temperature, the resulting suspension containing the polymer particles was filtered and washed with water and methanol to obtain a fumaric acid diester resin (diisopropyl fumarate / diethyl fumarate copolymer) (yield) : 75%).

  The number average molecular weight of the obtained fumaric acid diester resin was 120,000, and the average particle size was 110 μm. Moreover, the resin composition was the diisopropyl fumarate residue unit / diethyl fumarate residue unit = 84/16 (mol%) by 1H-NMR measurement.

Example 1
136 g of a mixed solvent of toluene and MIBK (toluene / MIBK = 20/80 weight ratio) is a small sawtooth blade type mixer (Primics Co., Ltd., TK-Robomix, stirring flow coefficient (Nq value): 0.3, stirring blade diameter: While stirring at a rotation speed of 1,400 rpm at 32 mm), 24 g of the fumaric acid diester resin of Synthesis Example 1 (diisopropyl fumarate residue unit / diethyl fumarate residue unit = 91/9 (mol%)) was started. The mixture was stirred for 1 minute and stirred for 1 hour to prepare a dope solution (solution volume (based on raw material charge, converted to volume from 20 ° C. density, the same applies hereinafter) V: 0.19 L). The stirring flow rate Q at this time is 0.23 L / sec. , Q / V value is 1.21 sec. ^-1 .

  No undissolved resin mass was found in the obtained dope solution. When this dope solution was filtered using a 3 μm membrane filter, no undissolved material was found on the filter. The solution viscosity of the dope solution was 1,050 cP.

Example 2
In Example 1, 148.6 g of MIBK alone as a solvent was stirred at a rotation speed of 1,400 rpm with a small sawtooth blade type mixer (manufactured by Primics Co., Ltd., TK-Robomix). 11.4 g of diisopropyl residue unit / diethyl fumarate residue unit = 91/9 (mol%)) was added for 2 minutes and 50 seconds from the start of stirring, and stirred for 1 hour to prepare a dope solution (solution volume V: 0.197L). The stirring flow rate Q at this time is 0.23 L / sec. , Q / V value is sec. ^-1 .

  No undissolved resin mass was found in the obtained dope solution. When this dope solution was filtered using a 3 μm membrane filter, no undissolved material was found on the filter. The solution viscosity of the dope solution was 950 cP.

Comparative Example 1
In Example 1, instead of a small sawtooth blade type mixer (manufactured by PRIMIX Co., Ltd., TK-Robomix), synthesis was performed while stirring at a rotational speed of 270 rpm with a three-one motor equipped with three propeller type stirring blades (stirring blade diameter: 42 mm). A dope solution was prepared in the same manner except that the fumaric acid diester resin of Example 1 was added for 1 minute from the start of stirring and stirred for 1 hour (solution volume V: 0.19 L). The stirring flow rate Q at this time is 0.1 L / sec. , Q / V value is 0.52 sec. ^-1 .

  In the obtained dope solution, several lumps of undissolved material of about several mm were observed, and it was confirmed that the undissolved material remained on the filter when the dope solution was filtered through a 3 μm filter.

Comparative Example 2
A dope solution was prepared in the same manner except for stirring for 8 hours in Comparative Example 1 (solution volume V: 0.19 L). As in Comparative Example 1, the stirring flow rate Q at this time was 0.1 L / sec. , Q / V value is 0.52 sec. ^-1 .

  The undissolved substance in the obtained dope liquid still remained, and when the dope liquid was filtered through a 3 μm filter, it was confirmed that the undissolved substance still remained on the filter.

Example 3
A dope solution was prepared in the same manner as in Example 1 except that the rotation speed was 6,000 rpm (solution volume V: 0.19 L). The stirring flow rate Q at this time is 0.98 L / sec. , Q / V value is 5.15 sec. ^-1 .

  No undissolved resin mass was found in the obtained dope solution. When this dope solution was filtered using a 3 μm membrane filter, no undissolved material was found on the filter. The solution viscosity of the dope solution was 980 cP.

Example 4
In Example 1, 765 g of a mixed solvent of toluene and MIBK (toluene / MIBK = 20/80 weight ratio) was stirred with a sawtooth blade mixer (Primix Co., TK homodisper, stirring flow coefficient (Nq value): 0. 3. A dope solution was prepared in the same manner except that 135 g of the fumaric acid diester resin of Synthesis Example 1 was added during stirring at a rotation speed of 600 rpm using a stirring blade diameter: 100 mm) (solution volume V: 1. 075L). The stirring flow rate Q at this time is 3 L / sec. , Q / V value is 2.79 sec. ^-1 .

  No undissolved resin mass was found in the obtained dope solution. When this dope solution was filtered using a 3 μm membrane filter, no undissolved material was found on the filter.

Comparative Example 3
A dope solution was prepared in the same manner as in Example 4 except that the number of revolutions of the stirring blade was 1,000 rpm (solution volume V: 0.84 L). The stirring flow rate Q at this time is 5 L / sec. , Q / V value is 5.95 sec. ^-1 .

  Although no undissolved resin lump was found in the obtained dope solution, the solution heat generation is remarkable, and the solvent easily evaporates, making it difficult to control the solvent concentration and temperature. When this dope solution was filtered using a 3 μm membrane filter, no undissolved material was found on the filter, and the solution viscosity was 980 cP.

Comparative Example 4
In Example 1, the fumaric acid diester resin was changed from that of Synthesis Example 1 to that of Synthesis Example 2, and this resin was gradually added over 3 minutes 30 seconds while stirring the solvent. A dope solution was prepared in the same manner except for stirring for 1 hour (solution volume V: 0.19 L). The stirring flow rate Q at this time is 0.23 L / sec. , Q / V value is 1.20 sec. ^-1 .

  Many undissolved lumps of about several mm were observed in the obtained dope solution. When this dope solution was filtered using a 3 μm membrane filter, undissolved substances were confirmed on the filter. The solution viscosity of the dope solution was 820 cP.

Example 5
A 15 μm-thick optical thin film was formed on the 140 μm glass substrate using the spin coater from the dope solution prepared in Example 1, and immediately blown and dried at 80 ° C. for 2 minutes and 130 ° C. for 8 minutes. The obtained optical thin film has a light transmittance of 91%, an in-plane retardation (Re) of 0 nm, an out-of-plane birefringence (ΔP) of −0.0047 (absolute value: 0.0047), and an out-of-plane retardation (Rth). ) Was -71 nm.

  The refractive index of the optical thin film was nx = 1.46844, ny = 1.46844, nz = 1.47311, and the relationship was nz> nx = ny.

Example 6
A dope solution was prepared in the same manner as in Example 1 except that the fumaric acid diester resin of Synthesis Example 1 was pulverized in a mortar and an average particle size of 65 μm was used (solution volume V: 0.19 L). The stirring flow rate Q at this time is 0.23 L / sec. , Q / V value is 1.21 sec. ^-1 .

  No undissolved substance was found in the obtained dope solution, and no undissolved substance was confirmed on the filter even in 3 μm filter filtration.

Example 7
A 15 μm-thick optical thin film was formed on the 140 μm glass substrate using the blade coater from the dope solution prepared in Example 1, and immediately blown and dried at 80 ° C. for 4 minutes and at 130 ° C. for 6 minutes. The obtained optical thin film has a light transmittance of 91%, an in-plane retardation (Re) of 0 nm, an out-of-plane birefringence (ΔP) of −0.0047 (absolute value: 0.0047), and an out-of-plane retardation (Rth). ) Was -71 nm.

The refractive index of the optical thin film was nx = 1.46844, ny = 1.46844, nz = 1.47311, and the relationship was nz> nx = ny Comparative Example 5
In Example 1, the fumaric acid diester resin of Synthesis Example 1 (diisopropyl fumarate residue unit / diethyl fumarate residue unit = 91/9 (mol%)) was previously pulverized using a freeze pulverizer, and sieved. A dope solution was prepared in the same manner except that a product having an average particle size of 35 μm was prepared and used by separation (solution volume V: 0.19 L). The stirring flow rate Q at this time is 0.23 L / sec. , Q / V value is 1.21 sec. ^-1 . When the fumaric acid diester resin is introduced, the powder particle size is small, so it easily floats and adheres to the wall of the upper part of the container, making it difficult to completely inject into the solvent. A lump was formed.

  Many undissolved substances were found in the obtained dope solution, and it was difficult to filter through a 3 μm filter.

Claims (4)

A fumaric acid diester resin having an average particle size of 50 to 300 μm and containing a fumaric acid diester residue unit having a diisopropyl fumarate residue unit and an alkyl group having 1 or 2 carbon atoms has a stirring flow rate Q of 0. 15-3.5 L / sec. In this range, the value indicated by the ratio (Q / V) of the stirring flow rate Q to the solution volume V is 1 to 25 sec. ^In the range of ^-1 , the dope liquid manufacturing method characterized by throwing into a solvent within 3 minutes from the start of stirring, and stirring for 0.5 to 4 hours.
Q = Nq × n × d ³ × 10 ³ (Formula 1)
(In the formula, Q represents the stirring flow rate, Nq represents the stirring flow coefficient, n represents the rotational speed [rps], and d represents the stirring blade diameter [m].) A fumaric acid diester resin having an average particle size of 50 to 300 μm and containing a fumaric acid diester residue unit having a diisopropyl fumarate residue unit and an alkyl group having 1 or 2 carbon atoms has a stirring flow rate Q of 0. 15-3.5 L / sec. In this range, the value indicated by the ratio (Q / V) of the stirring discharge Q and the solution volume V is 1 to 25 sec. An optical thin film characterized in that it is poured into a solvent within 3 minutes from the start of stirring in the range of ^-1 , and the dope solution obtained by stirring for 0.5 to 4 hours is cast on a support substrate and dried. Manufacturing method.
Q = Nq × n × d ³ × 10 ³ (Formula 1)
(In the formula, Q represents the stirring flow rate, Nq represents the stirring flow coefficient, n represents the rotational speed [rps], and d represents the stirring blade diameter [m].) 3. The method for producing an optical thin film according to claim 2, wherein an undissolved substance of the fumaric acid diester resin is not detected in a 3 [mu] m filter filtration of the dope solution. An optical thin film obtained by the method for producing an optical thin film according to claim 1 or 2.