JP6152757B2 - Method for producing retardation film - Google Patents

Description

  The present invention relates to a method for producing a retardation film, a retardation film, and a polarizing plate.

  In recent years, polarizing plates obtained by laminating a retardation film and a polarizer using an adhesive have been widely used as components of liquid crystal display devices such as liquid crystal televisions, liquid crystal monitors, and personal computers. Among these, in particular, those using a cyclic olefin resin-based retardation film as a retardation film are often used because birefringence hardly occurs. However, if the adhesive strength between the retardation film and the polarizer is weak, peeling or the like occurs at the interface between the two, causing a product defect. Therefore, the improvement of the adhesive strength between retardation film and a polarizer is calculated | required.

  In response to the above requirements, a method for producing a retardation film in which a specific organic solvent or an aqueous solution thereof is brought into contact with a cyclic olefin resin-based retardation film has been developed (Japanese Patent Laid-Open No. 2012-177890 and Korean Patent Publication No. 2012). No. 92265). However, the above manufacturing method is not always satisfactory under the situation where higher adhesive strength is required as in the present day, and appearance failure of the retardation film occurs due to excessive contact of the organic solvent with the retardation film. There is also an inconvenience.

JP 2012-177890 A Korean Published Patent No. 2012-92265

  The present invention has been made in view of the above disadvantages, and an object of the present invention is to provide a method for producing a retardation film excellent in adhesive strength and appearance when used as a polarizing plate.

  The invention made in order to solve the above problems is a method for producing a retardation film comprising a step of bringing an organic solvent into contact with a cyclic olefin resin retardation film, wherein the organic solvent comprises an ester organic solvent and an alcohol solvent. It is a manufacturing method of retardation film characterized by including an organic solvent.

  Another invention made to solve the above problems is a retardation film obtained by bringing an organic solvent into contact with a cyclic olefin resin retardation film, wherein the organic solvent comprises an ester organic solvent and an alcohol organic solvent. And a retardation film.

  Another invention made to solve the above problems is a polarizing plate obtained by laminating the retardation film and a polarizer using an adhesive.

  Here, the “organic group” refers to a group containing at least one carbon atom. The “hydrocarbon group” includes a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. The “hydrocarbon group” may be a saturated hydrocarbon group or an unsaturated hydrocarbon group.

  By using the manufacturing method of the said retardation film, the retardation film excellent in the adhesive strength at the time of setting it as a polarizing plate and an external appearance can be provided. Therefore, the retardation film can be suitably used as a member for a polarizing plate.

<Method for producing retardation film>
The method for producing a retardation film is a method for producing a retardation film comprising a step (contact step) of bringing an organic solvent into contact with a cyclic olefin resin phase difference film, wherein the organic solvent is an ester organic solvent and an alcohol. And an organic solvent.

The method for producing the retardation film includes the following steps:
Before the contacting step, a step of stretching the cyclic olefin resin composition (stretching step);
A step of drying the retardation film (drying step) may optionally be provided after the contacting step. Hereinafter, each process and its raw material are explained in full detail.

(Cyclic olefin resin composition)
The cyclic olefin-based resin composition used in the stretching step contains a cyclic olefin-based resin and may optionally contain other components as long as the effects of the present invention are not impaired.

(Cyclic olefin resin)
Since the cyclic olefin-based resin composition contains a cyclic olefin-based resin, birefringence due to molecular orientation hardly occurs when the molecules are oriented, and in addition to thermoplasticity, transparency, heat resistance, chemical resistance Etc. In addition, 1 type (s) or 2 or more types can be used for cyclic olefin resin.

  The cyclic olefin-based resin is not particularly limited as long as it has a structural unit derived from a cyclic olefin (cycloolefin) -based monomer, but a structural unit derived from another monomer unless the effect of the present invention is impaired. It may optionally be included.

As the cyclic olefin monomer, for example,
A cyclic olefin having one double bond such as cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclododecene, norbornene, or a substituted product thereof;
Examples thereof include cyclic olefins having a plurality of double bonds such as 1,4-cyclooctadiene, dicyclopentadiene and cyclododecatriene, or substituted products thereof.

  The cyclic olefin-based resin can be produced according to a known method, but a commercially available product may be used. Commercially available products of cyclic olefin resins include, for example, “TOPAS” from Polyplastics, “ARTON” from JSR, “Arton Film” from Zeon, “ZEONOR” from ZEON, "ZEONOR FILM" of the company, "ZEONEX" of the company, "Appel" of Mitsui Chemicals, "Essina" of Sekisui Chemical Co., Ltd., "SCA40" of the company.

  As the cyclic olefin-based resin, a cyclic olefin-based resin having a structural unit represented by the structural unit represented by the following formula (1) is preferable from the viewpoint of better adhesive strength when used as a polarizing plate.

In the above formula (1), m is 0, 1 or 2. X is —CH═CH— or —CH ₂ CH ₂ —. R ^{1 to} R ⁴ are each independently a hydrogen atom, a halogen atom, an organic group having 1 to 10 carbon atoms, or a polar group. However, at least one of R ^{1 to} R ⁴ is a polar group and an organic group having 1 to 10 carbon atoms.

The polar group represented by R ^{1 to} R ¹⁴ is preferably a group represented by the following formula (2).

  In said formula (2), p is an integer of 0-5. R ′ is a hydrocarbon group having 1 to 9 carbon atoms. However, carbon number contained in the said Formula (2) is 1-10.

  As p, 0 or 1 is preferable from the viewpoint of increasing the glass transition temperature of the cyclic olefin resin and improving the heat resistance.

  R ′ is preferably an alkyl group having 1 to 3 carbon atoms from the same viewpoint.

  The structural unit represented by the above formula (1) is, for example, a cyclic olefin monomer represented by the following formula (1 ′) (hereinafter also referred to as “cyclic olefin monomer (1)”). It can be obtained by ring-opening copolymerization or further hydrogenation.

In said formula (1 '), m and R < ¹ > -R < ⁴ > are synonymous with said formula (1).

  The copolymerization ratio of the cyclic olefin monomer (1) is usually 50 to 90 parts by mass of the cyclic olefin monomer (1) when the total of all monomers is 100 parts by mass. It is preferable that a system monomer (1) is 50-80 mass parts. When the amount of the cyclic olefin monomer (1) exceeds 90 parts by mass, the glass transition temperature of the resulting polymer becomes too high, and molding may be difficult.

  The number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) of a cyclic olefin resin is usually from 8,000 to 1,000,000, and from 10,000 to 500,000. The following is preferable, and 10,000 or more and 100,000 or less are more preferable.

  The weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of a cyclic olefin resin is usually 10,000 or more and 3,000,000 or less, and 20,000 or more and 1,000. Is preferably 30,000 or less and more preferably 30,000 or more and 500,000 or less.

  When the molecular weight is less than the above lower limit, the strength of the obtained film may be low. On the other hand, when the molecular weight exceeds the above upper limit, the solution viscosity becomes too high, and the productivity and workability of the cyclic olefin resin may be deteriorated.

  The molecular weight distribution (Mw / Mn) of the cyclic olefin-based resin is usually from 1.5 to 10, preferably from 1.7 to 8, more preferably from 1.9 to 5.

Mw and Mn of the polymer in this specification are values measured using gel permeation chromatography (GPC) under the following conditions.
GPC column: 2 "G2000HXL" from Tosoh Corporation, 1 "G3000HXL" from the company, 1 "G4000HXL" from the company Column temperature: 40 ° C
Elution solvent: Tetrahydrofuran (Wako Pure Chemical Industries)
Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

  The glass transition temperature (Tg) of the cyclic olefin resin is usually 110 ° C. or higher and 250 ° C. or lower, preferably 115 ° C. or higher and 220 ° C. or lower, and more preferably 120 ° C. or higher and 200 ° C. or lower. By setting Tg within the above range, the cyclic olefin-based resin tends to have excellent heat resistance. When Tg is less than 110 ° C., the heat distortion temperature is lowered, which may cause a problem in heat resistance, and the change in optical characteristics due to temperature in the obtained film may be increased. On the other hand, when Tg exceeds 250 ° C., the processing temperature becomes too high during the stretching process, and the cyclic olefin-based resin may be thermally deteriorated.

  The cyclic olefin-based resin preferably has a DSC differential differential scanning calorific curve having a single peak, and a Tg distribution which is a rising temperature width of the peak having a narrow distribution of 40 ° C. or less. The differential scanning calorimetric curve of DSC used in the present invention is obtained by measuring in a nitrogen atmosphere at a temperature rising rate of 20 ° C./min. The peak rising temperature width is the width between the inflection points where the peak rises from the baseline. Furthermore, the Tg of the cyclic olefin-based ring-opening copolymer is plotted on the differential scanning calorie curve with the maximum peak temperature (point A) of the differential differential scanning calorific value and the temperature 20 points lower than the maximum peak temperature (point B), It is obtained as the intersection of the tangent line on the baseline starting from point B and the tangent line starting from point A.

Other monomers include, for example,
Chain olefins such as ethylene and propylene;
Examples thereof include aromatic monomers such as styrene and α-methylstyrene.

  When the cyclic olefin-based resin contains other monomers, the content ratio of the structural unit derived from the cyclic olefin-based monomer in the cyclic olefin-based resin is usually 10 mol% or more, and 10 mol% or more and 95 mol% or less. Preferably, 15 mol% or more and 85 mol% or less are more preferable. When the content is within the above range, the adhesive strength tends to be more excellent when a polarizing plate is obtained. There exists a possibility that the said adhesive strength may become inadequate that the said content is less than the said minimum.

  The cyclic olefin-based resin may be a ring-opened polymer of a cyclic olefin-based monomer or a hydrogenated product of the above-mentioned ring-opened polymer as long as the effects of the present invention are not impaired.

  As long as the effect of this invention is not impaired, the cyclic olefin resin may have the hydrogen atom substituted by the polar group. Examples of the polar group include a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group.

(Other ingredients)
The cyclic olefin-based resin composition may contain other components as long as the effects of the present invention are not impaired.

As other components, for example,
Other resin components such as polycarbonate, polymethyl methacrylate and polystyrene;
Lubricants such as silicon dioxide, titanium dioxide, magnesium oxide;
UV absorbers such as oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds;
Examples thereof include layered crystal compounds, inorganic fine particles, heat stabilizers, light stabilizers, weather stabilizers, plasticizers, dyes, pigments, and antistatic agents.

(Stretching process)
In this step, the cyclic olefin resin phase difference film can be obtained by stretching the cyclic olefin resin composition. More specifically, the cyclic olefin-based resin composition may be stretched (stretch orientation treatment) to align the molecular chain in a certain direction and to provide a retardation film having a function of giving a retardation to transmitted light. it can.

  The stretching method may be uniaxial stretching or biaxial stretching. More specifically, for example, a horizontal uniaxial stretching method by a tenter method, a compression stretching method between rolls, a vertical uniaxial stretching method using two sets of rolls having different circumferences, and a biaxial stretching in which a horizontal uniaxial and a vertical uniaxial are combined And a stretching method by an inflation method.

  The draw ratio is usually 1.01 to 10 times, preferably 1.03 to 5 times.

  The thickness of the obtained cyclic olefin resin-based retardation film is usually from 5 μm to 200 μm, preferably from 7 μm to 150 μm, and more preferably from 10 μm to 100 μm.

(Contact process)
In this step, a retardation film can be obtained by bringing an organic solvent containing an ester organic solvent and an alcohol organic solvent into contact with the cyclic olefin resin retardation film. The retardation film thus obtained is excellent in adhesive strength and appearance when used as a polarizing plate.

  Although it is not necessarily clear why the manufacturing method of the retardation film has the above-described configuration, the following effects can be inferred. That is, the ester organic solvent is excellent in affinity with the cyclic olefin resin. Therefore, when the organic solvent contains only an ester organic solvent, the orientation of the surface of the cyclic olefin resin phase difference film can be greatly relaxed. May cause defects. On the other hand, although the alcohol organic solvent is inferior in affinity with the cyclic olefin resin, it has excellent compatibility with the ester organic solvent, and therefore has high uniformity as a mixed solvent. Therefore, the organic solvent contains an ester organic solvent and an alcohol organic solvent, so that only the surface layer of the cyclic olefin resin retardation film can be uniformly and gently relaxed. As a result, a retardation film excellent in adhesive strength and appearance when used as a polarizing plate can be obtained by an easy adhesion treatment in which an organic solvent is brought into contact with the cyclic olefin resin phase difference film. Moreover, the fall of the phase difference of a retardation film and an in-plane retardation value can also be suppressed by reducing an external appearance defect. The orientation relaxation can be monitored by a change in front phase difference.

  The organic solvent includes an ester-based organic solvent and an alcohol-based organic solvent, but may optionally include other organic solvents as long as the effects of the present invention are not impaired. In addition, the organic solvent can use 1 type (s) or 2 or more types.

Examples of ester organic solvents include:
Carbonates such as diethyl carbonate and propylene carbonate;
Methyl acetate, ethyl acetate, γ-butyrolactone, γ-valerolactone, n-propyl acetate, iso-propyl acetate, n-butyl acetate, iso-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, n-nonyl acetate, methyl acetoacetate, ethyl acetoacetate, ethylene glycol monomethyl ether, acetic acid Ethylene glycol monoethyl ether, acetic acid diethylene glycol monomethyl ether, acetic acid diethylene glycol monoethyl ether, acetic acid diethylene glycol mono-n-butyl ether, acetic acid propylene glycol monomethyl ether, Acetate esters such as propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, glycol diacetate, methoxytriglycol acetate;
Propionate esters such as ethyl propionate, n-butyl propionate, iso-amyl propionate;
Oxalates such as diethyl oxalate and di-n-butyl oxalate;
Lactic acid esters such as methyl lactate, ethyl lactate, n-butyl lactate, and n-amyl lactate;
Malonic acid esters such as diethyl malonate;
And phthalic acid esters such as dimethyl phthalate and diethyl phthalate.

  Among these ester-based organic solvents, acetate esters are preferable from the viewpoint of further relaxing the orientation of the surface of the cyclic olefin resin-based retardation film, and ethyl acetate, n-propyl acetate, iso-propyl acetate, N-butyl acetate, iso-butyl acetate, and sec-butyl acetate are more preferable, and n-butyl acetate, iso-butyl acetate, and sec-butyl acetate are more preferable.

  The boiling point of the ester organic solvent is usually 30 ° C. or higher and 140 ° C. or lower, and preferably 40 ° C. or higher and 130 ° C. or lower. There is a tendency that the orientation can be sufficiently relaxed by setting the boiling point of the ester organic solvent in the above range. When the boiling point of the ester organic solvent exceeds the above upper limit, it may take a long time to dry the ester organic solvent. If the boiling point of the ester organic solvent is less than the above lower limit, orientation relaxation may be insufficient.

Examples of alcohol-based organic solvents include:
Methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, n-pentanol, iso-pentanol, 2-methylbutanol, sec-pentanol, tert- Pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, 3-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n- Nonyl alcohol, 2,6-dimethyl-4-heptanol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, furf Alcohol, phenol, cyclohexanol, methyl cyclohexanol, 3,3,5-trimethyl cyclohexanol, benzyl alcohol, monoalcohols such as diacetone alcohol;
Ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2 Polyhydric alcohols such as ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, and polyhydric alcohol partial ether and dipropylene glycol monopropyl ether.

  Of these, monoalcohols are preferable from the viewpoint of compatibility with ester organic solvents, and alcohols such as ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol are preferable. Tert-butanol is more preferable, and n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, and tert-butanol are more preferable.

  The boiling point of the alcohol organic solvent is usually 70 ° C. or higher and 130 ° C. or lower, and preferably 80 ° C. or higher and 120 ° C. or lower. By setting the boiling point of the alcohol-based organic solvent in the above range, there is a tendency that the orientation relaxation can be sufficiently performed when the ester-based solvent and the mixed solvent are used. If the boiling point of the alcoholic organic solvent exceeds the above upper limit, it may take a long time to dry the alcoholic organic solvent. If the boiling point of the alcohol-based organic solvent is less than the above lower limit, orientation relaxation may be nonuniform.

  The boiling point of the ester organic solvent is preferably higher than the boiling point of the alcohol organic solvent, and the boiling point of the ester organic solvent is preferably higher than the boiling point of the alcohol organic solvent within 45 ° C. Since the boiling point of the ester organic solvent is higher than the boiling point of the alcohol organic solvent, orientation relaxation can be sufficiently performed. When the boiling point of the ester organic solvent is higher than 45 ° C. from the boiling point of the alcohol organic solvent, there is a possibility that a poor appearance of the retardation film may occur.

  The volume mixing ratio of the ester organic solvent to the alcohol organic solvent is preferably from 5/95 to 60/40, more preferably from 15/85 to 55/45. By setting the volume mixing ratio in the above range, only the surface layer of the cyclic olefin resin phase difference film can be more uniformly and gently relaxed. When the volume mixing ratio exceeds the upper limit, there is a possibility that a poor appearance of the retardation film may occur. If the volume mixing ratio is less than the lower limit, orientation relaxation may be insufficient.

  Examples of other organic solvents include ether solvents, ketone organic solvents, amide solvents, hydrocarbon solvents, and the like. The other organic solvent may be contained in an amount of generally 40% by volume or less, preferably 20% by volume or less in the total organic solvent including the ester organic solvent and the alcohol organic solvent.

  Examples of the contact method include known methods such as a casting method, a bar coating method, a gravure coating method, a comma coating method, a doctor blade method, a die coating method, a dip coating method, and a spraying method. Among these, the bar coating method and the die coating method are preferable.

  The contact may be performed on both surfaces of the cyclic olefin resin-based retardation film, or may be performed only on the surface to be bonded to the polarizer.

(Drying process)
In this step, the retardation film from which the organic solvent has been removed can be obtained by drying the retardation film.

  Examples of the drying method include heat drying, natural drying, and air drying. In these, heat drying is preferable and heat drying below the glass transition point of cyclic olefin resin is more preferable. In addition, you may perform this process in a contact process.

<Phase difference film>
The retardation film is a retardation film obtained by bringing an organic solvent containing an ester organic solvent and an alcohol organic solvent into contact with the cyclic olefin resin retardation film. Therefore, the retardation film is excellent in adhesive strength and appearance when used as a polarizing plate.

  The haze value of the retardation film is preferably 0.5% or less, and more preferably 0.4% or less.

  The retardation change rate of the in-plane retardation value (Re) of the retardation film is preferably 5% or less, and more preferably 4% or less. The “in-plane retardation value (Re) retardation change rate” refers to the change rate of the in-plane retardation value before and after contact with the organic solvent.

The in-plane retardation value (Re) is nx for the refractive index in the in-plane slow axis direction of the film, ny for the in-plane fast axis direction (direction perpendicular to the slow axis in the plane), and thickness. Where d is a value defined by the following equation.
Re = (nx−ny) × d

  When the phase difference film has a haze value of 0.5% or less and a retardation change rate of 5% or less, it can be more suitably used as a component of a liquid crystal display device.

  The thickness of the retardation film is usually from 5 μm to 200 μm, preferably from 10 μm to 150 μm, and more preferably from 20 μm to 100 μm.

<Polarizing plate>
If an example is given, the said polarizing plate can be obtained with the manufacturing method provided with the process obtained by bonding together the retardation film and polarizer which concern on this invention using an adhesive agent. That is, the polarizing plate is a polarizing plate obtained by bonding the retardation film and a polarizer using an adhesive. Since the retardation film has the above-described properties, the polarizing plate is excellent in adhesive strength.

The polarizer is, for example,
A step of dyeing a resin film with a dichroic dye (dyeing step);
A step of treating a resin film dyed with a dichroic dye with a boric acid aqueous solution (boric acid aqueous solution treatment step);
It can obtain by the manufacturing method of a polarizer provided with the process (water-washing process) of washing the resin film processed with the boric acid aqueous solution.

  Examples of the resin film include a polyvinyl alcohol (PVA) film, an ethylene-vinyl acetate film, a polyethylene terephthalate (PET) film, and a triacetyl cellulose (TAC) film.

  Among these, a polyvinyl alcohol film and a triacetyl cellulose film that are excellent in dyeability with a dichroic material are preferable as the resin film.

  Examples of the method for producing the resin film include a casting method, a casting method, and an extrusion method. The resin film may be stretched before, during or after the dyeing process.

  Examples of the dichroic dye include iodine, a disazo compound, a trisazo compound, a tetrakisazo compound, and the like. One or two or more dichroic dyes can be used.

  The thickness of the polarizer is usually 5 μm or more and 40 μm or less, and preferably 6 μm or more and 30 μm or less.

  The bonded surfaces of the polarizer and the retardation film may be subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, frame treatment, and saponification treatment from the viewpoint of improving adhesive strength.

  A polarizer may be manufactured according to the said manufacturing method, and a commercial item may be used for it.

  Examples of the adhesive include a polyvinyl alcohol-based adhesive, an epoxy-based adhesive, and a urethane-based adhesive. Of these, polyvinyl alcohol adhesives and epoxy adhesives are preferable. 1 type (s) or 2 or more types can be used for an adhesive agent.

  The adhesive may contain a silane coupling agent, a plasticizer, an antistatic agent, and the like as long as the effects of the present invention are not impaired.

  The polarizing plate may be applied using a known method such as a casting method, a bar coating method, a gravure coating method, a comma coating method, a doctor blade method, a die coating method, a dip coating method, or a spraying method. Is applied to the surface of a retardation film or a polarizer, the retardation film and the polarizer are bonded together, and then the adhesive is dried.

  The drying temperature is usually 40 ° C. or higher and 100 ° C. or lower, and preferably 50 ° C. or higher and 90 ° C. or lower. The drying time is usually from 20 seconds to 1200 seconds, and preferably from 30 seconds to 1000 seconds.

  The polarizing plate is excellent in adhesive strength. Specifically, the adhesive strength of the polarizing plate is preferably 0.4 N / 25 mm or more, more preferably 0.8 N / 25 mm or more, and further preferably 1.0 N / 25 mm or more.

  In the polarizing plate, a protective film may be further bonded to the surface where the retardation film of the polarizer is not bonded.

  Examples of the protective film include a cellulose acetate resin film, a polyolefin resin film, an acrylic resin film, a polyimide resin film, a polycarbonate resin film, and a polyester resin film.

  As thickness of a protective film, they are 10 micrometers or more and 200 micrometers or less normally, and 20 micrometers or more and 150 micrometers or less are preferable.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. The evaluation method is shown below.

<Evaluation method>
(appearance)
Appearance was evaluated as follows by bringing the organic solvent into contact with the cyclic olefin resin-based retardation film, and then visually observing the contact surface of the retardation film.
○: Roughness cannot be confirmed on the surface.
Δ: Minute roughness (unevenness) can be confirmed on the surface.
X: Roughness (unevenness) can be confirmed on the surface.

(Haze value (%))
The haze value (%) is determined using a haze / transmittance meter (“HAZEMETAR HM-150” manufactured by Murakami Color Research Laboratory Co., Ltd.) according to JIS K 7136: 2000 “Plastics—How to Obtain Haze of Transparent Materials”. It was measured.

(In-plane retardation value (Re) (nm))
The in-plane retardation value (Re) (nm) was measured using a phase difference measuring apparatus (“KOBRA-21ADH” manufactured by Oji Scientific Instruments).

(Adhesive strength (N / 25mm))
The adhesive strength (N / 25 mm) was measured in accordance with JIS K 8654-1: 1999 “Adhesive—Peeling peel strength test method—Part 1: 90 ° C. peeling”. Specifically, after the corona treatment was applied to the surface of the cyclic olefin resin “ARTON” (weight average molecular weight (Mw) 50,000) having a polar group of JSR as a cyclic olefin resin retardation film The adhesive composition prepared in Production Example 1 below was applied to the corona-treated surface in an atmosphere at 23 ° C. A cellulose acetate-based resin film (triacetyl cellulose (TAC) -based film) as a polarizer was bonded to the adhesive application surface, and a drying process was performed at a temperature of 80 ° C. for 5 minutes with a dryer. After the drying treatment, the mixture was allowed to stand for 1 day at a temperature of 23 ° C. The obtained laminated film (polarizing plate) was cut into a test piece having a width of 25 mm and a length of 100 mm, and one end in the length direction of the test piece (“AG-1” manufactured by Shimadzu Corporation) was used ( A cellulose acetate-based resin film having a width of 25 mm is gripped and peeled at 90 ° C. at a crosshead speed of 200 mm / min under conditions of a temperature of 23 ° C. (JIS K 8654-1: 1999 “Adhesive— The adhesion strength between the cyclic olefin-based resin and the cellulose acetate-based resin was evaluated.

[Production Example 1] Preparation of adhesive composition Polyvinyl alcohol ("KL-318" manufactured by Kuraray Co., Ltd.) was dissolved in pure water to prepare a 30% by mass aqueous solution. To this polyvinyl alcohol aqueous solution, an epoxy resin (“Srz.650” from Taoka Chemical Industry Co., Ltd.) serving as a cross-linking agent is added in an amount of polyvinyl alcohol: epoxy resin = 2.5: 1.0 at a solid content concentration, and water is further added. It diluted with the pure water so that polyvinyl alcohol might be 2.5 mass parts with respect to 100 mass parts, and prepared the adhesive composition.

[Example 1]
Mixing obtained by mixing on the surface of the cyclic olefin resin with n-butyl acetate: 2-propanol = 3: 7 (volume ratio) using a coating machine (“AUTOMATIC FILM APPLICATOR” manufactured by Yasuda Seiki Seisakusho) A solvent was applied, and a drying process was performed at 80 ° C. for 3 minutes in a dryer to obtain a retardation film. Table 1 shows the measurement results of the in-plane retardation value and haze value of the treated cyclic olefin-based resin. After the corona treatment was performed on the treated surface of the solvent-treated cyclic olefin resin film, the cyclic olefin resin and the cellulose acetate resin were bonded together, and the adhesive strength of the polarizing plate was evaluated. The evaluation results are shown in Table 1.

[Example 2]
The same procedure as in Example 1 was performed except that the mixed solution was changed to n-butyl acetate / 1-butanol = 1: 9 (volume ratio).

[Example 3]
The same procedure as in Example 1 was performed except that the mixed solution was changed to n-butyl acetate / ethanol = 3: 7 (volume ratio).

[Example 4]
The same procedure as in Example 1 was performed except that the mixed solution was changed to ethyl acetate / 2-propanol = 3: 7 (volume ratio).

[Comparative Example 1]
It implemented like Example 1 except not having used an organic solvent.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the mixed solution was changed to n-propyl acetate / ethylcyclohexane = 7: 3 (volume ratio).

[Comparative Example 3]
The same procedure as in Example 1 was performed except that the mixed solution was changed to n-butyl acetate / methyl ethyl ketone = 3: 7 (volume ratio).

[Comparative Example 4]
The same procedure as in Example 1 was performed except that the mixed solution was changed to ethanol / ethylcyclohexane = 7: 3 (volume ratio).

  Table 1 shows the organic solvents used in Examples and Comparative Examples and the evaluation results. “-” In Table 1 indicates that the corresponding organic solvent was not used.

  As is apparent from the results in Table 1, in the examples, the adhesive strength and appearance when used as polarizing plates were excellent, whereas in the comparative examples, these performances were insufficient.

  By using the manufacturing method of the said retardation film, the retardation film excellent in the adhesive strength at the time of setting it as a polarizing plate and an external appearance can be provided. Therefore, the retardation film can be suitably used as a member for a polarizing plate.

Claims (5)

A method for producing a retardation film comprising a step of bringing an organic solvent into contact with a single-layered cyclic olefin resin-based retardation film,
A method for producing a retardation film, wherein the organic solvent contains an ester organic solvent and an alcohol organic solvent. 2. The method for producing a retardation film according to claim 1, wherein a change rate of an in-plane retardation value of the cyclic olefin resin-based retardation film before and after contact with an organic solvent is 5% or less. The method for producing a retardation film according to claim 1 or 2 , wherein a volume mixing ratio of the ester organic solvent to the alcohol organic solvent is 5/95 or more and 60/40 or less. The method for producing a retardation film according to claim 1 , wherein the ester organic solvent has a boiling point higher than that of the alcohol organic solvent. The method for producing a retardation film according to claim 1, wherein the cyclic olefin resin-based retardation film has a haze value of 0.5% or less after contact with an organic solvent.