JP2001071420A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film excellent in handling properties at a time of use for protecting the self-adhesive layer of a liquid crystal polarizing plate, reduced in the precipitation quantity of an oligomer to the utmost, good in transparency and easy in the inspection accompanied by optical evaluation. SOLUTION: A release film is obtained by successively providing a polyvinyl alcohol-containing coating film and a release layer on the single surface of a biaxially stretched polyester film with a thickness of 9-50 μm. In this case, the release film satisfies formulae; (1) OL<=0.6, (2) 30<=Re<=10,000 and (3) 80<=TL [wherein OL is an amt. (mg/m2) of an oligomer extracted from the surface of the release layer of the release film by dimethylformamide after heat treatment at 150 deg.C for 10 min, Re is the retardation value (nm) of the biaxially stretched polyester film and TL is the total light transmissivity (%) of the release film] at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release film, and more particularly, to a release film for protecting a pressure-sensitive adhesive layer of a polarizing plate used in a liquid crystal display (hereinafter sometimes abbreviated as LCD).

[0002]

2. Description of the Related Art Conventionally, a release film based on a polyester film has been used for protecting an adhesive layer of a liquid crystal polarizing plate. However, oligomers deposited on the surface of the release layer at high temperatures cause various problems. Let me. The oligomer precipitated on the surface of the release layer is transferred to the surface of the other adhesive layer to which the adhesive is attached, and is obtained when an LCD is manufactured by attaching a polarizing plate with an adhesive layer to which the oligomer is attached to a glass substrate. Problems such as a decrease in the brightness of the LCD may occur.

In recent years, there has been a tendency to increase the brightness of the display screen for the purpose of improving the visibility of LCDs, and the above-mentioned problem has become a serious problem. In addition, with the aim of reducing the manufacturing cost due to the improvement in productivity, with the speeding up in the manufacturing process, there is a tendency to set the drying temperature particularly higher in the drying process, and the above-mentioned oligomer is more likely to precipitate. It is becoming.

On the other hand, in an inspection process involving optical evaluation of the display capability, hue, contrast, and contamination of a liquid crystal polarizing plate, measures have been taken to prevent outflow of defective products by visual observation or by using a magnifying glass. Due to the optical anisotropy of the polyester film that constitutes the mold film, there may be problems such as easy to overlook foreign matter contamination.Therefore, the release film must be peeled off at the time of inspection, and must be reattached after the inspection. I have a problem of not becoming.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal polarizing plate which has excellent handleability when used for protecting an adhesive layer.
An object of the present invention is to provide a release film having a minimum amount of oligomer precipitation, good transparency, and easy inspection involving optical evaluation.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above situation and found that the above-mentioned problems can be easily solved by using a release film having a specific structure. Was completed. That is, the gist of the present invention is a release film in which a coating layer containing polyvinyl alcohol and a release layer are sequentially provided on one surface of a biaxially stretched polyester film having a thickness of 9 to 50 μm, and the following formulas (1) to (3) A release film for protecting a pressure-sensitive adhesive layer of a liquid crystal polarizing plate which simultaneously satisfies (3).

OL ≦ 0.6 (1) 30 ≦ Re ≦ 10000 (2) 80 ≦ TL (3) (in the above formula, OL is the release layer of the release film after heat treatment at 150 ° C. for 10 minutes. The amount of oligomer (mg / m ² ) extracted from the surface with dimethylformamide and Re are the retardation values (n
m), TL represents the total light transmittance (%) of the release film)

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, the polyester used for the biaxially stretched polyester film may be a homopolyester or a copolyester. When a homopolyester is used, the polyester obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol is exemplified. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and the aliphatic glycol includes ethylene glycol,
Examples include diethylene glycol and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PE
N) and the like.

On the other hand, when a copolyester is used,
Copolymers containing 30 mol% or less of the third component can be exemplified. Examples of the dicarboxylic acid component of the copolymerized polyester include one or two of isophthalic acid, terephthalic acid phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). Species or more, as the glycol component, ethylene glycol, diethylene glycol, propylene glycol, butanediol,
One or more of 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be mentioned.

In any case, the polyester referred to in the present invention generally means polyethylene terephthalate having an ethylene terephthalate unit of at least 80 mol%, preferably at least 90 mol%, and polyethylene-2, an ethylene-2,6-naphthalate unit. Refers to polyester such as 6-naphthalate. In the biaxially stretched polyester film in the present invention, it is preferable to mix particles for the purpose of mainly providing lubricity. The type of particles to be blended is not particularly limited as long as the particles can impart lubricity, and specific examples thereof include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and magnesium phosphate oxidation. Examples include particles of silicon, kaolin, aluminum oxide, titanium oxide, and the like.

Further, heat-resistant organic particles described in JP-B-59-5216 and JP-A-59-217755 may be used. Examples of other heat-resistant organic particles include thermosetting urea resin, thermosetting phenol resin,
Thermosetting epoxy resin, benzoguanamine resin and the like can be mentioned. Further, during the polyester production process, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed can be used.

On the other hand, the shape of the particles to be used is not particularly limited, and any of spherical, massive, rod-like, flat, and the like may be used. There is no particular limitation on the hardness, specific gravity, color and the like. These series of particles may be used in combination of two or more as necessary. Further, the average particle size of the particles used is 0.01 to 3 μm, and more preferably 0.01 to
A range of 1 μm is preferred. When the average particle size is less than 0.01 μm, the particles are likely to aggregate, and the dispersibility may be insufficient. On the other hand, when the average particle size exceeds 3 μm, the surface roughness of the film becomes too coarse, and Problems may occur when a release layer is applied in the process.

Further, the content of particles in the polyester film is preferably in the range of 0.1 to 5% by weight, more preferably 0.1 to 3% by weight. When the particle content is less than 0.1% by weight, the lubricity may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the polyester film becomes insufficient. There are cases. The method for adding particles to the polyester film is not particularly limited, and a conventionally known method can be employed. For example, it can be added at any stage of producing the polyester, but preferably, the polycondensation reaction may be advanced after the esterification stage or after the transesterification reaction is completed.

A slurry of particles dispersed in ethylene glycol or water using a kneading extruder equipped with a vent.
And a polyester raw material, or a method of blending dried particles with a polyester raw material using a kneading extruder. In addition, conventionally known antioxidants, heat stabilizers, lubricants, dyes, pigments and the like can be added to the polyester film of the present invention, if necessary, in addition to the above-mentioned particles.

The thickness of the biaxially stretched polyester film constituting the release film in the present invention needs to be 9 to 50 μm, preferably 12 to 40 μm, from the viewpoint of film handling. 9μm film thickness
If it is less than 50 μm, the film handling property will be reduced, while if it exceeds 50 μm, the display performance of the liquid crystal polarizing plate, hue, contrast, optical contamination such as contamination, etc. A defect occurs when performing the inspection.

The biaxially oriented polyester film constituting the release film of the present invention must satisfy the above-mentioned film thickness and further have a retardation value (Re) in the range of 30 to 10,000. .
The Re value is preferably 50 to 5000 nm, more preferably 100 to 2000 nm. Re value is 30 nm
If it is less than 1, the chemical resistance of the film will be reduced. On the other hand, if it exceeds 10,000 nm, the cross Nicol between the polarizing plate and the release film will depend on the angle (θ3) of the orientation axis of the film. Since the state becomes a state (extinction state), when an optical inspection is performed, a problem such as that foreign matter is easily overlooked occurs.

Next, the production example of the biaxially stretched polyester film in the present invention will be described specifically, but it is not limited to the following production example. That is, a method in which an unstretched sheet is obtained by using the above-described polyester raw material and cooling and solidifying a molten sheet extruded from a die with a cooling roll using a cooling roll is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum, and the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

Next, the obtained unstretched sheet is stretched biaxially. First, the unstretched sheet is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 130 to 170 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, stretching is performed in a direction orthogonal to the stretching direction of the first stage. The stretching temperature is usually 130 to 170 ° C., and the stretching ratio is
It is usually 3.0 to 7 times, preferably 3.5 to 6 times. Subsequently, a heat treatment is performed at a temperature of 180 to 270 ° C. under tension or relaxation within 30% to obtain a biaxially oriented film. A so-called coating and stretching method (in-line coating) for treating the film surface during the stretching step can be applied. Although it is not limited to the following, in particular, the coating treatment can be performed before the first-stage stretching is completed and before the second-stage stretching.

In the above-mentioned stretching, the stretching in one direction is performed by 2
It is also possible to use a method of performing the above steps. In that case,
It is preferable that the stretching is performed so that the stretching ratio in the two directions finally falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area magnification becomes 10 to 40 times. Further, if necessary, the film may be stretched in the longitudinal and / or transverse directions again before or after the heat treatment.

When a coating layer is coated on a polyester film by the above-mentioned coating and stretching method, coating can be performed simultaneously with stretching, and the thickness of the coating layer can be reduced according to the stretching ratio. A film suitable as a biaxially stretched polyester film can be produced. In the release film of the present invention, the amount of oligomers extracted with dimethylformamide from the surface of the release layer after heat treatment at 150 ° C. for 10 minutes needs to be suppressed to 0.6 mg / m ² or less. The layer is applied on a polyester film. The coating layer is preferably applied on a polyester film by the above-mentioned coating and stretching method (in-line coating method).

The content of polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) in the coating layer constituting the release film of the present invention is not particularly limited, but is preferably 10 to 100% by weight, and more preferably 10 to 100% by weight. Preferably it is in the range of 20-90% by weight, most preferably 30-80% by weight. If the range is less than 10% by weight, the effect of preventing oligomer precipitation may be insufficient.

The degree of polymerization of PVA is not particularly limited, but is usually 100 or more, preferably 300 to 4
0000 is suitably used for applications. On the other hand, PV
The degree of saponification of A is not particularly limited, but is 70 mol% or more, preferably 80 mol% or more, and 99.9 mol%.
The following are preferably used, and specific examples thereof include saponified vinyl acetate.

In the coating layer constituting the release film of the present invention, other binder polymers may be used in addition to the above-mentioned PVA as long as the gist of the present invention is not impaired.
Specific examples of the binder polymer used in combination include polyacrylamide, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starch, polyurethane, polyester, polyacrylate, and chlorine-based polymer (polyvinyl chloride, vinyl chloride vinyl acetate copolymer). Coalescence), polyolefin and the like. Among them, when the PVA layer is applied by a coating and stretching method, nonionic, cationic, and amphoteric organic polymers that can be used as an aqueous solution or aqueous dispersion can be used. Among them, polyurethane and polyester can be used. When polyacrylate is used, the adhesion to the overcoat layer becomes good. These polymers are provided with hydrophilicity and can be dispersed in water by copolymerizing nonionic, cationic or amphoteric hydrophilic components as one component of the monomers.

Further, a crosslinking agent may be used in combination with the PVA coating layer. Specific examples thereof include methylolated or alkylolated urea-based, melamine-based, guanamine-based, acrylamide-based, polyamide-based compounds, epoxy compounds, Examples include an aziridine compound, a blocked polyisocyanate, a silane coupling agent, a titanium coupling agent, and a zircoaluminate coupling agent. These crosslinking components may be pre-bonded to the binder polymer.

The PVA coating layer may contain inorganic particles for the purpose of improving the fixability and the slipperiness. Specific examples thereof include silica, alumina, kaolin, calcium carbonate, and the like.
Titanium oxide, barium salt and the like can be mentioned. Furthermore, if necessary, an antifoaming agent, a coating improver, a thickener, an organic lubricant,
Organic polymer particles, antioxidants, ultraviolet absorbers, foaming agents, dyes and the like may be contained.

In the present invention, the coating amount of the PVA layer is 0.1.
01~5g / m ^2, more preferably in the range of 0.02 to 1 g / m ^2. When the coating amount is less than 0.01 g / m ² , the uniformity of the coating thickness may be insufficient.
In the case where the amount is more than g / m ² , a problem may occur due to a decrease in slipperiness. In the present invention, as a method of providing a PVA coating layer on a polyester film, a conventionally known coating method such as a bar coating method, a gravure coating method, or the like can be used as in the case of applying a release layer described later.

The release layer constituting the release film in the present invention is not particularly limited as long as it contains a material having a release property. Above all, those containing a curable silicone resin are preferred in that they have good releasability.
A type having a curable silicone resin as a main component or a modified silicone type obtained by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

As the type of the curable silicone resin, any of a curing reaction type such as an addition type, a condensation type, an ultraviolet curable type, an electron beam curable type, and a solventless type can be used. Specific examples include KS-774 and KS manufactured by Shin-Etsu Chemical Co., Ltd.
-775, KS-778, KS-779H, KS-84
7H, KS-856, X-62-2422, X-62-
2461, X-62-5039, X-62-5040 DKQ3-202, D manufactured by Dow Corning Asia Ltd.
KQ3-203, DKQ3-204, DKQ3-20
5, DKQ3-210, Toshiba Silicone Co., Ltd. YSR
-3022, TPR-6700, TPR-6720, T
PR-6721, SD manufactured by Dow Corning Toray Co., Ltd.
7220, SD7226 and SD7229. Further, a release control agent may be used in combination to adjust the release property of the release layer.

In the present invention, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, or doctor blade coating can be used as a method for applying a release layer to the biaxially stretched polyester film. The coating amount of the release layer is 0.01 to 5 g from the viewpoint of coatability.
/ M ^2, more preferably 0.01 to 1 g / m ² .
If the coating amount of the release layer is less than 0.01 g / m ² , stability may be lacked from the viewpoint of coatability, and it may be difficult to obtain a uniform coating film. On the other hand, when the thickness is more than 5 g / m ² , the adhesion of the release layer itself, the curability and the like may be reduced.

In the release film of the present invention, a coating layer such as an oligomer precipitation preventing layer, an adhesive layer, and an antistatic layer may be provided on a surface where the release layer is not provided, if necessary.
The biaxially stretched polyester film has a corona treatment,
Surface treatment such as plasma treatment may be performed. The amount of oligomer (OL) extracted with dimethylformamide from the surface of the release layer of the thus obtained release film after heat treatment at 150 ° C. for 10 minutes needs to be 0.6 mg / m ² or less. When OL exceeds 0.6 (mg / m ² ), the amount of oligomer on the surface of the release layer of the release film increases, and in the case of protecting the pressure-sensitive adhesive layer of a liquid crystal polarizing plate, the pressure-sensitive adhesive layer of the counterpart adhesive layer to be bonded is used. Problems such as a decrease in transparency or a decrease in the adhesive strength of the pressure-sensitive adhesive layer occur.

The total light transmittance (T) of the release film of the present invention is
L) needs to be 80% or more. If the TL is less than 80%, the transparency becomes insufficient, and in the inspection process involving optical evaluation, problems such as the inconvenience of foreign matter being easily overlooked occur. The residual adhesive ratio of the release film of the present invention is preferably 80% or more, because it suppresses the transfer or transfer of silicone to the surface of the counterpart adhesive layer to be bonded or to the surface of the transport roll in the manufacturing process. Preferably, 90% or more is good. When the residual adhesion ratio is less than 80%, in the manufacturing process, problems such as transfer of the silicone transfer component to the roll surface of the transport roll and reduction in the adhesive strength of the adhesive layer in contact with the release surface may occur. is there.

[0032]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the examples and comparative examples, “parts” means “parts by weight”. The measuring method used in the present invention is as follows. (1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester were removed was precisely weighed, and phenol / tetrachloroethane = 50/50 (weight ratio) mixed solvent 10
0 ml was added and dissolved, and the measurement was performed at 30 ° C.

(2) Measurement of average particle size (d ₅₀ : μm) Integration in equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation) (weight basis) ) The value of 50% was taken as the average particle size. (3) Measurement of the thickness of the biaxially stretched polyester film Muimetron “4M-100PT” manufactured by Citizen Watch Co., Ltd.
The film thickness was measured using "YPE V-2".

(4) Measurement of Retardation Value (Re) of Biaxially Stretched Polyester Film Using an Abbe refractometer manufactured by Atago Optical Co., Ltd., with the release layer surface side as a measurement surface, a base film constituting a release film , The maximum value nγ of the refractive index in the film plane and the refractive index nβ in the direction orthogonal thereto are measured, and the difference (nγ
−nβ) was calculated. The difference (nγ−nβ) was multiplied by the thickness of the film whose refractive index was measured to obtain a retardation value.

(5) The amount of oligomer (O) extracted from the surface of the release layer of the release film with dimethylformamide
Measurement of L) The release film after the heat treatment (at 150 ° C. for 10 minutes) is folded to form a square box so that the top is open and the area of the bottom is 250 cm ² . When a coating layer is provided, the coating layer face is on the inside. Next, 10 ml of DMF (dimethylformamide) is put in the box created by the above method, and left for 3 minutes. Then, DMF is collected. The recovered DMF is subjected to liquid chromatography (Shimadzu L
C-7A) to determine the amount of oligomer in DMF,
This value is divided by the area of the film contacted with DMF to obtain the amount of oligomer on the film surface (mg / m ² ).

The amount of oligomer in DMF was determined from the peak area ratio between the peak area of the standard sample and the peak area of the measurement sample (absolute calibration curve method). A standard sample was prepared by accurately weighing oligomers (cyclic trimers) collected in advance and dissolving them in accurately weighed DMF. The concentration of the standard sample is 0.0
A range from 01 mg / ml to 0.01 mg / ml is preferred. The conditions of the liquid chromatography were as follows.

Mobile phase A: acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS manufactured by Mitsubishi Chemical Corporation
1HU Column temperature: 40 ° C Flow rate: 1 ml / min Detection wavelength: 254 nm

(6) The total light transmittance (T) of the release film
Measurement of L) According to JIS-K-7105, the total light transmittance (%) of the release film was measured with a seat turbidimeter “NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd.

(7) Measurement of Residual Adhesion Rate of Release Film Residual Adhesion: Nitto Denko No. 31B pressure-sensitive adhesive tape was reciprocated one time with a 2 kg rubber roller, and heat-treated at 100 ° C. × 1 hour. Then, the sample film was peeled off from the pressure-bonded sample.
o. The adhesive strength of the 31B adhesive tape is measured according to the method of JIS-C-2107 (adhesive strength to stainless steel plate, 180 ° peeling method). This is defined as the residual adhesive force. Basic adhesive strength: The same tape as in the case of residual adhesive strength (No. 3)
No. 1B) on a stainless steel plate according to JIS-C-2107. The measurement is performed in the same manner by pressing the 31B pressure-sensitive adhesive tape. The value at this time is defined as the basic adhesive strength. Using these measured values, the residual adhesion rate is determined based on the following equation.

Residual adhesion rate (%) = (residual adhesive strength / basic adhesive strength) × 100 The measurement is performed at 20 ± 2 ° C. and 65 ± 5% RH.

(8) Measurement of Peeling Force (F) of Release Film A double-sided adhesive tape (“N
o. 502 "), 50mm x 300
After cutting to a size of mm, the peeling force after leaving for 1 hour is measured. As the peeling force, a 180 ° peeling was performed under a tensile speed of 300 mm / min using a tensile tester (“Intesco Model 2001” manufactured by Intesco Corporation).

(9) Evaluation of handleability of release film The handleability at the time of attaching the release film to a polarizing plate having an adhesive layer was evaluated according to the following criteria. 《Judgment criteria》 Good: no practical problem level Bad: practically problematic level

(10) Evaluation of quenching state of release film In a laminate in which the release film and the polarizing plate are bonded via the pressure-sensitive adhesive layer to which foreign matter is adhered, the light is viewed from the release film side through light. The presence or absence of the quenching state was observed.

(11) Evaluation of testability of release film In a laminate in which the release film and the polarizing plate are bonded via the pressure-sensitive adhesive layer to which foreign matter is adhered, when viewed through light from the release film side Was evaluated according to the following criteria. 《Judgment criteria》 Good: Inspection possible (no problem in practical use) Slightly poor: In some cases, inspection is difficult (problem in practical use)

<Production of Polyester> Production Example 1 (Polyethylene terephthalate A1) 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off. And
The transesterification reaction was performed, and the temperature was raised to 230 ° C. over 4 hours from the start of the reaction, and the transesterification reaction was substantially completed. Then, 0.04 parts of ethylene glycol slurry ethyl acid phosphate, 0.01 parts of germanium oxide
Parts, 0.1 part of silica particles having an average particle size of 0.1.54 μm was added, and after 100 minutes, the temperature was increased to 280 ° C. and the pressure was increased to 15 mmH.
g and then gradually reduce the pressure to 0.3 m
mHg. After 4 hours, the inside of the system was returned to normal pressure to obtain polyethylene terephthalate A1 having an intrinsic viscosity of 0.61.

Production Example 2 (Polyethylene terephthalate A)
2) Polyethylene terephthalate was prepared in the same manner as in Production Example 1 except that 1 part of titanium oxide particles having an average particle diameter of 0.27 μm was added instead of adding 0.1 parts of silica particles having an average particle diameter of 1.54 μm. A2 was obtained. <Production of biaxially stretched polyester film>

Production Example 3 (PET Film F1) The polyethylene terephthalate A1 produced in Production Example 1 was dried at 180 ° C. for 4 hours in an inert gas atmosphere, melted at 290 ° C. by a melt extruder, extruded from a die, and squeezed. The unstretched sheet was obtained by cooling and solidifying on a cooling roll having a surface temperature set to 40 ° C. by using an electric contact adhesion method. The obtained sheet was stretched 3.5 times in the longitudinal direction at 85 ° C. Next, after applying a coating agent having the following composition, the film was guided to a tenter and stretched 3.7 times in the transverse direction at 100 ° C.
And heat-fix at ℃, and the thickness of the coating layer after drying is 0.05
A PET film F1 coated with a coating layer having a thickness of 25 μm and a thickness of 25 μm was obtained. Examples of compounds constituting the coating layer are as follows.

(Examples of Compounds) PVA-based resin: A Polyvinyl alcohol having a saponification degree of 88 mol% and a polymerization degree of 500 Water-based polyester resin: B Polyester mainly containing isophthalic acid, ethylene glycol and diethylene glycol, neopentyl glycol, aliphatic Aqueous polyester obtained by neutralizing a polyester obtained by copolymerizing a dicarboxylic acid derivative having a dicarboxylic anhydride with an amine compound and converting it into an aqueous system. Crosslinkable compound: C hexamethoxymethylmelamine particles Silica sol having an average particle diameter of 65 nm

<< Coating Agent Composition >> 100% by weight of PVA resin (A) The concentration of the coating solution was 2% by weight.

Production Example 4 (PET film F2) to Production example 7 (PET film F5) PET film was produced in the same manner as in Production Example 3 except that the coating composition was changed to the coating composition shown in Table 1. F2 to PET film F5 were obtained. The properties of these PET films are as shown in Table 1 below.

Production Example 8 (PET Film F6) In Production Example 3, the coating composition was changed to the coating composition shown in Table 1, and the coating amount of the coating layer was 0.7 g / m ² (after drying). A PET film F6 was obtained in the same manner as in Production Example 3 except for performing the above. Table 1 shows the properties of the obtained film. Production Example 9 (PET Film F7) A PET film F7 was obtained in the same manner as in Production Example 3, except that the coating composition was changed to the coating composition shown in Table 1. Table 1 shows the properties of the obtained film.

Production Example 10 (PET Film F8) In the same manner as in Production Example 3, a layer having a thickness of 38
A μm PET film F8 was obtained. Table 1 shows the properties of the PET film. Production Example 11 (PET film F9) In the same manner as in Production Example 3, a coating layer was applied, and the thickness was 6 μm.
m of PET film F9 was obtained. Table 1 shows the properties of the PET film.

Production Example 12 (PET film F10) In the same manner as in Production Example 3, a film having a thickness of 75
A μm PET film F10 was obtained. Table 1 shows the properties of the PET film. Production Example 13 (PET film F11) A PET film F11 was obtained in the same manner as in Production Example 3, except that polyethylene terephthalate A2 was used instead of polyethylene terephthalate A1.
Table 1 shows the properties of the obtained film.

Production Example 14 (PET Film F12) The polyethylene terephthalate A1 produced in Production Example 1 was dried at 180 ° C. for 4 hours in an inert gas atmosphere, melted at 290 ° C. by a melt extruder, and extruded from a die. The unstretched sheet was obtained by cooling and solidifying on a cooling roll having a surface temperature set to 40 ° C. by using an applied contact method. Next, after applying a coating agent having the same composition as in Production Example 3 onto the obtained unstretched sheet, the film is guided to a tenter and dried at 80 ° C., and the thickness of the dried coating layer is 0.05 μm. Thus, a PET film F12 having a thickness of 50 μm was obtained. Table 1 shows the properties of the obtained film.

Production Example 15 (PET Film F13) In Production Example 3, the longitudinal stretching ratio was set to 5.0 times,
Produced in the same manner as in Production Example 3 except that the film is not stretched in the horizontal direction, and the thickness of the coating layer after drying is 0.05 μm.
A PET film F13 having a thickness of 50 μm was obtained. Table 1 shows the properties of the obtained film.

[0056]

[Table 1]

Example 1 A release layer having the following composition was further coated on the oligomer-prevention layer of the PET film F1 obtained in Production Example 3 so that the coating amount was 0.1 g / m ² (dry). Coating was performed to obtain a release film. << Composition of release agent >> Curable silicone resin (KS-847H: Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent 1500 parts

Example 2 In Example 1, PE film was used instead of PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F2 was used. Example 3 In Example 1, a PE film was used instead of the PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F3 was used.

Example 4 In Example 1, PE film was replaced with PE film instead of PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F4 was used. Example 5 In Example 1, a PE film was used instead of the PET film F1.
Using a T film F4, a release film was obtained in the same manner as in Example 1 except that the composition of the release agent was changed to the following release agent. << Release Agent Composition >> Curable Silicone Resin (KS-723A: Shin-Etsu Chemical) 100 parts Curable Silicone Resin (KS-723B: Shin-Etsu Chemical) 25 parts Curing Agent (PS-3: Shin-Etsu Chemical) 5 parts MEK / Toluene mixed solvent 1500 parts

Example 6 In Example 1, PE film was used instead of PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F8 was used. Example 7 A release film was obtained in the same manner as in Example 1, except that the composition of the release agent was changed to the following release agent. << Releasing Agent Composition >> Curable Silicone Resin (FSXK-2560: manufactured by Tow Corning Asia) 35 parts Curing Agent (FSK-1638: manufactured by Tow Corning Asia) 2 parts MEK / toluene mixed solvent 1400 parts Example 8 Example 8 1, in place of PET film F1, PE
A release film was obtained in the same manner as in Example 1 except that the T film F6 was used.

Comparative Example 1 In Example 1, PE film was used instead of the PET film F1.
Except for using the T film F5, in the same manner as in Example 1,
A release film was obtained. Comparative Example 2 In Example 1, PE film was used instead of the PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F12 was used. Comparative Example 3 In Example 1, PE was used instead of the PET film F1.
Except for using the T film F7, in the same manner as in Example 1,
A release film was obtained.

Comparative Example 4 In Example 1, PE film was used instead of the PET film F1.
Except for using the T film F9, in the same manner as in Example 1,
A release film was obtained. However, the entire film was wrinkled, which was at a practically problematic level. Comparative Example 5 In Example 1, PE film was used instead of the PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F10 was used. Comparative Example 6 In Example 1, PE was used instead of the PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F11 was used.

Comparative Example 7 In Example 1, PE film was used instead of the PET film F1.
A release film was obtained in the same manner as in Example 1 except that the T film F13 was used. The surface of the release surface of the obtained release film was poor, and was at a practically problematic level.
The properties of the release films obtained in the above Examples and Comparative Examples are shown in Tables 2 and 3 below.

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

The release film of the present invention has excellent handleability when used for protecting the pressure-sensitive adhesive layer of a liquid crystal polarizing plate, has a minimum amount of precipitated oligomers, has excellent transparency, and is inspected with optical evaluation. And its industrial value is extremely high.

Claims (3)

[Claims] 1. A release film comprising a biaxially stretched polyester film having a thickness of 9 to 50 μm, on which a coating layer containing polyvinyl alcohol and a release layer are sequentially provided on one side, and the following formulas (1) to (3): A release film for protecting the pressure-sensitive adhesive layer of a liquid crystal polarizing plate that simultaneously satisfies the above. OL ≦ 0.6 (1) 30 ≦ Re ≦ 10000 (2) 80 ≦ TL (3) (In the above formula, OL is dimethyl from the surface of the release layer of the release film after heat treatment at 150 ° C. for 10 minutes. The amount of oligomers extracted with formamide (mg / m ² ) and Re are the retardation values (n
m), TL represents the total light transmittance (%) of the release film) 2. The release film according to claim 1, wherein the content of polyvinyl alcohol in the coating layer is 10 to 100% by weight. 3. The release film according to claim 1, wherein the release layer contains a curable silicone resin.