JP2008143047A - Release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a release film having excellent optical characteristics essential for films used in liquid crystal display or the like and giving high precision in detecting defects in a film test, more specifically, a release film which copes with high-precision inspection allowing the easy detection of defects in a cross Nicol's prism method. <P>SOLUTION: The release film has an applied layer containing an organic compound containing one or more metal elements selected from aluminum, titanium and zirconium and a release layer formed in this order on one side of a polyester film. The amount of oligomer extracted from the surface of the release layer with dimethyl formamide after 10-min heat treatment at 180°C is ≤2.2 mg/m<SP>2</SP>, the average particle size of particles contained in the polyester film is 0.2-1.5 μm, and a particle size distribution value (d25/d75) is 1.0-2.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a release film that has a small amount of oligomer precipitation, suppresses generation of bright spots caused by particles in the film in a foreign matter inspection process, and can be used for a highly accurate inspection method. (Hereinafter, abbreviated as “LCD”) For manufacturing LCD components such as polarizing plates and retardation plates, for plasma display panel (hereinafter, abbreviated as “PDP”) components, organic electroluminescence (hereinafter, “organic EL”) (Abbreviated) The present invention provides a release film suitable for manufacturing various display components, such as for manufacturing components, and for various optical applications.

  Conventionally, release films based on polyester films have been used for various types of display components such as LCD polarizing plates, retardation plate components, PDP components, organic EL components, etc. It is used for optical applications. A problem in using the release film is that oligomers precipitated on the surface of the release layer at high temperatures cause various problems in the production process.

  In recent years, with the advancement of the IT (Information Technology) field, various defects associated with the precipitation of oligomers have become apparent along with the improvement of the quality of release films used when manufacturing display members such as LCDs, PDPs, and organic ELs.

  In order to cope with the various uses described above, it is desired not only to have excellent mold releasability, but also to minimize foreign matter on the film surface. In other words, since it is also an application that places importance on so-called visibility, especially through light transmission, even a foreign matter on the film surface that is not a problem at all in a normal film application becomes a serious problem.

  For example, when the manufacturing process of a polarizing plate for LCD is given as an example, the manufacturing process includes a process in which a release film and a polarizing plate are bonded together via an adhesive layer and wound into a roll. Is considered to be deposited through a drying step after the pressure-sensitive adhesive is applied to the surface of the release layer of the film. The oligomer deposited on the surface of the release layer is obtained when the LCD is manufactured by transferring the polarizing plate with the pressure-sensitive adhesive layer to which the oligomer is adhered to the glass substrate, by transferring to the surface of the opposite pressure-sensitive adhesive layer. In some cases, the brightness of the LCD is reduced.

  In recent years, there is a tendency to increase the brightness of the display screen for the purpose of improving the visibility of the LCD, and the above-mentioned problems have become serious problems.

  On the other hand, with the aim of reducing the manufacturing cost accompanying productivity improvement, there is a tendency to set the drying temperature higher in the drying process, especially with the speeding up of the manufacturing process, and the above-mentioned oligomer is more likely to precipitate. It has become.

  The polarizing plate inspection process involves optical evaluation of LCD display performance, hue, contrast, foreign matter, etc., and measures to prevent the outflow of defective products using visual or magnifying glass have been taken. In the case of using a release film to which is attached, there is a problem in that it is determined as a defective product due to mixing of foreign matters, resulting in problems such as a decrease in product yield.

  Furthermore, in recent years, in the foreign substance inspection of the polarizing plate, the particle component in the polyester film constituting the release film becomes a bright spot, which may cause problems such as a decrease in inspection accuracy.

  Conventionally, the particles in the polyester film are used for the purpose of ensuring the slipperiness and winding characteristics of the film, but the desired slipperiness cannot be ensured unless the appropriate particle size and blending amount are satisfied, or the winding characteristics. In some cases, problems such as worsening occur. However, when the particle size and blending amount are in the range normally used, as described above, when the particle-containing polyester film is used as the release film for the polarizing plate, the particles are bright spots in the foreign matter inspection process. In some cases, the inspection accuracy may be degraded.

Furthermore, there is a tendency to increase the brightness of the display screen for the purpose of improving the visibility of the LCD, and even a very small size foreign matter that has not been a problem in the conventional low-brightness type LCD is regarded as a problem. . For this reason, while taking measures to prevent contamination by foreign matter in the manufacturing process, even if foreign matter is mixed in the product, it is possible to reliably detect foreign matter as a defect, and can be used for high-precision inspection. There is a situation where a film is needed.
Japanese Patent Laid-Open No. 6-16941 JP-A-7-3215 JP 2000-44904 A JP 2000-238441 A JP 2000-338327 A

  The present invention has been made in view of the above-mentioned circumstances, and the problem to be solved is that the amount of oligomer precipitation is as small as possible, and in the foreign matter inspection process, generation of bright spots due to particles in the film is suppressed. An object of the present invention is to provide a release film capable of handling a highly accurate foreign object inspection in the inspection by the crossed Nicols method.

  As a result of intensive studies in view of the above problems, the present inventors have found that according to a release film having a specific configuration, it is particularly suitable for producing a liquid crystal component without impairing excellent film characteristics. The present invention has been completed.

That is, the gist of the present invention is that a coating layer containing an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium and a release layer are sequentially provided on one side of a polyester film. The release film is a release film, and after heat treatment at 180 ° C. for 10 minutes, the amount of oligomer extracted from the release layer surface with dimethylformamide is 2.2 mg / m ² or less, and the average particle size of the particles contained in the polyester film The present invention resides in a release film having a diameter in the range of 0.2 to 1.5 μm and a particle size distribution value (d25 / d75) in the range of 1.0 to 2.0.

Hereinafter, the present invention will be described in detail.
The polyester film referred to in the present invention is a film which is melt-extruded from an extrusion die, and is subjected to stretching and heat treatment as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method.

  The polyester constituting the polyester film used in the present invention is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. The polyester used may be a homopolyester or a copolyester. In the case of a copolyester, it may be a copolymer containing 30 mol% or less of the third component.

  The dicarboxylic acid component of the copolymerized polyester is selected from isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more selected from ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dl / g or more, and preferably 0.40 to 0.90 dl / g.

  In the present invention, it may be a film having a structure obtained by coextrusion laminating a polyester having a low oligomer content on the surface of at least one side of a layer composed of a polyester having a normal oligomer content. In the mold release film obtained by this invention, it uses suitably from a viewpoint of the bright spot generation | occurrence | production prevention by oligomer precipitation.

  In the polyester obtained by the present invention, a weathering agent, a light-proofing agent, an antistatic agent, a lubricant, a light-shielding agent, an antioxidant, a fluorescent whitening agent, a matting agent, and a heat-stabilizing agent as long as the gist of the present invention is not impaired. You may mix | blend an agent and coloring agents, such as dye and a pigment.

  Examples of the particles to be blended in the polyester film include silicon oxide, alumina, calcium carbonate, kaolin, titanium oxide, and crosslinked polymer fine powder as described in JP-B-59-5216. These particles may be used alone or in combination of two or more components. And the content is 1 weight% or less normally, Preferably it is 0.01 to 1 weight%, More preferably, it is the range of 0.02 to 0.6 weight%. When the content of the particles is small, the film surface is flattened, and there is a tendency that scratches on the surface in the film production process are likely to occur or the winding properties are inferior. Further, when the content of the particles exceeds 1% by weight, the degree of roughening of the film surface becomes too large, and the transparency may be impaired.

  The average particle size of the particles contained in the polyester film needs to be in the range of 0.2 to 1.5 μm. When the average particle size is less than 0.2 μm, the film surface is flattened and the film is produced. The winding characteristics in the process are inferior. On the other hand, when the average particle size exceeds 1.5 μm, when used as a release film for protecting the pressure-sensitive adhesive layer of a polarizing plate, the occurrence of bright spots due to particles contained in the film causes troubles in foreign matter inspection. The

  Moreover, the particle size distribution of the particles contained in the polyester film in the present invention needs to be sharp. Specifically, the particle size distribution value, which is an index representing the sharpness of the particle size distribution, needs to be 1.0 to 2.0, preferably 1.1 to 1.8. The “particle size distribution value” referred to in the present invention is a particle size distribution value d25 / d75 (d25 and d75 are calculated by calculating the integrated volume of the particle group from the large particle side and correspond to 25% and 75% of the total volume, respectively. It means a value defined by particle size (μm). When the particle size distribution value (d25 / d75) exceeds 2.0, bright spots due to coarse particles are generated, which impedes foreign matter inspection.

  On the other hand, in the present invention, in order to improve the transparency of the polyester film, when a laminated polyester film having two or more layers is used, a method of blending particles only in the surface layer is also preferably employed. The surface layer in this case is at least one of the front and back layers, and of course, particles can be blended in both the front and back layers.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage of producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or the stage after the transesterification reaction and before the start of the polycondensation reaction. The condensation reaction may proceed. A method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder Etc.

  The polyester film constituting the release film in the present invention preferably has a variation range of the orientation angle in the film plane of 3 degrees / 500 mm or less. More preferably, it is 2 degrees / 500 mm or less. When the fluctuation range of the orientation angle exceeds 3 degrees / 500 mm, the transmitted light intensity varies depending on the position of the polarizing plate during the polarizing plate inspection, which may obstruct the polarizing plate inspection.

  The polyester film constituting the release film in the present invention preferably has a refractive index (nβ) in the direction perpendicular to the film in-plane direction of 1.640 or less with respect to the main orientation axis, and nβ is 1.640. In the case of exceeding, the fluctuation of the orientation angle of the film tends to increase, which becomes an obstacle to the stable inspection of the polarizing plate, and the formation of voids in the particles becomes remarkable, and it appears as a bright spot during the inspection of the polarizing plate. It may be an obstacle to inspection.

  The thickness of the polyester film constituting the release film of the present invention is not particularly limited as long as it can be formed as a film, but is usually 4 to 100 μm, preferably 9 to 50 μm.

  Next, although the manufacturing method of the polyester film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

  First, the preferable example of the manufacturing method of polyester used by this invention is demonstrated. Here, an example in which polyethylene terephthalate is used as the polyester is shown, but the production conditions differ depending on the polyester used. According to a conventional method, esterification from terephthalic acid and ethylene glycol, or transesterification reaction between dimethyl terephthalate and ethylene glycol, the product is transferred to a polymerization tank, and the temperature is increased while reducing the pressure. The polymerization reaction is advanced by heating to 280 ° C. under vacuum to obtain a polyester.

  The intrinsic viscosity of the polyester used in the present invention is usually in the range of 0.40 to 0.90, preferably 0.45 to 0.80, and more preferably 0.50 to 0.70. When the intrinsic viscosity is less than 0.40, the mechanical strength of the film tends to be weakened. When the intrinsic viscosity is more than 0.90, the melt viscosity becomes high, the load on the extruder is increased, and the production cost is increased. Problems may occur.

Next, for example, the polyester chip obtained as described above and dried by a known method is supplied to a melt-extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer and melted. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. In the present invention, the sheet thus obtained is stretched biaxially to form a film.
Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary. Furthermore, it is also possible to perform simultaneous biaxial stretching of the unstretched sheet so that the area magnification is 10 to 40 times.

  Furthermore, a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step can be applied. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, producing a film suitable as a polyester film. it can.

  Next, formation of the coating layer which comprises the release film in this invention is demonstrated. Regarding the coating layer, the above-described coating stretching method (in-line coating) may be used, so-called off-line coating that is applied outside the system on a once produced film may be employed, and any method may be employed. .

  In the present invention, it is an essential requirement that the coating layer contains an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium. Only one kind of these metal organic compounds may be used, or two or more kinds may be appropriately mixed and used.

  Specific examples of the organic compound having an aluminum element include aluminum tris (acetylacetonate), aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum-di-n-butoxide-monoethylacetoacetate, aluminum di- Examples include iso-propoxide-monomethyl acetoacetate.

  Specific examples of the organic compound having a titanium element include, for example, titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate; titanium acetylacetonate, Examples thereof include titanium chelates such as titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamate, and titanium ethylacetoacetate.

  Specific examples of the organic compound having a zirconium element include zirconium acetate, zirconium normal propyrate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate and the like.

  Among them, it is preferable to use an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium, more preferably an organic compound having a chelate structure, particularly in terms of good oligomer precipitation preventing performance. Compounds are preferred. Specific examples of the compounds are described in "Crosslinking Agent Handbook" (Yamashita Shinzo, Kaneko Tosuke Editor, Taiseisha, 1990).

  The coating layer constituting the release film in the present invention preferably uses a silane alkoxy oligomer in combination in order to improve the oligomer precipitation preventing property and to improve the coating film adhesion between the release layer and the polyester film.

  Silane alkoxy oligomers are represented, for example, by the following average composition formula (1), and are specifically exemplified in JP-A-2002-88155, JP-A-2005-8755, and the like.

_{^{R k R 1 m Si (OR}} 2) n O (4-k-m-n) / 2 ... (1)
(In the above formula, R is one or more groups selected from unsubstituted or substituted alkyl groups and aryl groups, R ¹ is an aliphatic unsaturated double bond-containing group, and R ² is a group having 1 to ² carbon atoms. Represents an alkyl group having 3 carbon atoms, an acyl group having 2 or 3 carbon atoms, or an alkoxyalkyl group having 3 to 5 carbon atoms, and k, m, and n are numbers that simultaneously satisfy the following relational expression: 0 ≦ k <1 .5, 0.01 ≦ m ≦ 1, 0.5 ≦ k + m ≦ 1.8, 0.01 ≦ n ≦ 2.5, 1 ≦ k + m + n ≦ 3)

  Specific examples of R include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, octyl and decyl, cycloalkyl such as cyclohexyl, alkenyl such as vinyl and allyl, phenyl Groups, aryl groups such as tolyl groups, or chloromethyl groups, chloropropyl groups, trifluoropropyl groups, etc., in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, cyanoethyl groups substituted with cyano groups, etc. Glycidoxypropyl group substituted by epoxy group, epoxycyclohexylethyl group, etc., methacryloxypropyl group substituted by (meth) acryl group, acryloxypropyl group, etc., aminopropyl group substituted by amino group, aminoethylaminopropyl group And a mercaptopropyl group substituted with a mercapto group. Specific examples of R1 include aliphatic groups such as vinyl group, allyl group, isopropenyl group, 1-butenyl group, 2-butenyl group and 3-butenyl group, 2-cyclohexenyl group, 3-cyclohexenyl group, 2- Contains an alicyclic group such as vinylcyclohexenyl group, an aromatic group such as 2-vinylphenyl group, 3-vinylphenyl group and 2-allylphenyl group, and a substituent such as 3- (meth) acryloxypropyl group. Etc. are exemplified.

  Specific products include KR-401N, X-40-9227, X-40-9247, KR-510, KR-9218, KR-213, KR-217, X-41-1053, X-manufactured by Shin-Etsu Chemical Co., Ltd. 40-1056, X-41-1805, X-41-1810, X-40-2651, X-40-2652B, X-40-2655A, X-40-2761, X-40-2672, and the like.

  In the coating layer, a crosslinking agent may be used in combination as long as the gist of the present invention is not impaired, and specific examples include methylolated or alkylolated urea, melamine, guanamine, acrylamide, and polyamide. Examples of the compound include an epoxy compound, an aziridine compound, a block polyisocyanate, a silane coupling agent, a titanium coupling agent, and a zirco-aluminate coupling agent. These crosslinking components may be previously bonded to the binder polymer.

  Further, inorganic particles may be contained for the purpose of improving the adhesion and slipperiness of the coating layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like.

  Moreover, an antifoamer, a coating property improving agent, a thickener, an organic lubricant, organic polymer particles, an antioxidant, a UV absorber foaming agent, a dye, and the like may be contained as necessary.

  In the range not exceeding the gist of the present invention, only one type of organic solvent may be used for the purpose of improving dispersibility, improving film forming property, etc., and two or more types may be used as appropriate.

The coating amount of the coating layer provided on the polyester film constituting the release film of the present invention (after drying) is generally 0.005~1g / ^{m 2,} the range preferably from 0.005 to 0.5 / ^{m 2} It is. When the coating amount is less than 0.005 g / m ² , the uniformity of coating thickness may be insufficient, and the amount of oligomer deposited from the coating layer surface after heat treatment may increase. On the other hand, when the coating is applied in excess of 1 g / m ² , problems such as a decrease in slipperiness may occur.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. As for the coating method, there is a description example in “Coating method” published by Yoji Harasaki in 1979.

  In the present invention, the curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, usually at 60 to 200 ° C. for 3 to 40 seconds. The heat treatment is preferably performed at 80 to 180 ° C. for 3 to 40 seconds as a guide. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed.

Next, formation of the release layer in the present invention will be described.
The release layer constituting the release film in the present invention refers to a layer having releasability. Specifically, the peel force (F) between the acrylic adhesive tape and the release layer is 5 to 500 mN / It is preferable for use of the present invention to be cm.

  The release layer constituting the release film in the present invention may be provided on the polyester film in the film production process such as the above-described coating stretching method (inline coating), and is applied outside the system on the once produced film. So-called off-line coating may be employed, and any method may be employed. The coating stretching method (in-line coating) is not limited to the following, but for example, in sequential biaxial stretching, the first stage of stretching may be completed and the coating treatment may be performed before the second stage of stretching. it can. When a release layer is provided on a polyester film by a coating and stretching method, the film can be applied simultaneously with stretching, and the thickness of the release layer can be reduced according to the stretching ratio. Can be manufactured.

  Moreover, it is preferable that the release layer which comprises the release film in this invention contains a curable silicone resin in order to make mold release property favorable. A type having a curable silicone resin as a main component may be used, or a modified silicone type 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 the curing reaction types 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, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, X manufactured by Shin-Etsu Chemical Co., Ltd. -62-1387, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B, X-62-7052, X-62-7028A / B, X-62-7619, X-62 -7213, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210 manufactured by Dow Corning Asia Co., Ltd. YSR-3022, TPR-6700, TPR-6720 manufactured by GE Toshiba Silicone Co., Ltd. , TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775 XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, manufactured by Dow Corning Toray Co., Ltd. SRX357, SRX211, SD7220, LTC750A, LTC760A, SP7259, BY24-468C, SP7248S, etc. BY24-452 are exemplified. Further, a release control agent may be used in combination to adjust the release property of the release layer.

  In the present invention, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like can be used as a method for providing a release layer on the polyester film. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

In the present invention, the curing conditions for forming the release layer on the polyester film are not particularly limited, and when providing the release layer by off-line coating, usually at 120 to 200 ° C. for 3 to 40 seconds, The heat treatment is preferably performed at 100 to 180 ° C. for 3 to 40 seconds as a guide. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. In addition, a conventionally well-known apparatus and an energy source can be used as an energy source for hardening by active energy ray irradiation. The coating amount of the release layer from the viewpoint of coating property, usually 0.005~1g / ^{m 2,} preferably in the range from 0.005 to 0.5 / ^{m 2.} If the coating amount is less than 0.005 g / m ² , the coating property may be less stable and it may be difficult to obtain a uniform coating film. On the other hand, when the coating is thicker than 1 g / m ² , the coating layer adhesion and curability of the release layer itself may be lowered.

  Regarding the release film in the present invention, a coating layer such as an adhesive layer, an antistatic layer and an oligomer precipitation preventing layer may be provided on the surface where the release layer is not provided, as long as the gist of the present invention is not impaired.

  Further, the polyester film constituting the release film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  In the present invention, when a release layer is provided on the coating layer, the film may be temporarily wound after the coating layer is provided, and the release layer may be provided again. After the coating layer is provided, the release layer is continuously provided. A mold layer may be provided on the coating layer, and any method may be adopted.

After heat-treating the release film of the present invention at 180 ° C. for 10 minutes, the amount of oligomer (OL) extracted from the release layer surface with dimethylformamide is 2.2 mg / m ² or less, preferably 1.5 mg / m ^2. m ² or less. When OL exceeds 2.2 mg / m ² , for example, when used for the purpose of protecting the pressure-sensitive adhesive layer during the manufacture of LCD components, the transparency of the pressure-sensitive adhesive is reduced, or the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer is reduced. Cause problems such as

  In the present invention, “oligomer” is defined as a cyclic trimer of low molecular weight substances that crystallize and precipitate on the film surface after heat treatment.

  When the release film in the present invention is used as a release film for protecting a pressure-sensitive adhesive layer such as a polarizing plate or a retardation plate, the film has as few bright spots as possible in the foreign substance inspection process, and can cope with high precision foreign substance inspection. A release film can be provided, and the industrial value of the present invention is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. 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 was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measurement was performed at 30 ° C.

(2) Average particle size (d50) and particle size uniformity (d25 / d75)
The average particle size d50 was defined as the particle size having an integrated volume fraction of 50% in an equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (SA-CP3 type) manufactured by Shimadzu Corporation. In addition, the ratio d25 / d75 of the diameter of the point having a weight fraction of 25% and the diameter of the point having a weight fraction of 75%, integrated from the large particle side, was used as the particle size distribution value.

(3) Measurement of the variation width of the orientation angle in the film plane of the polyester film constituting the release film In the width direction of the sample film, from the center position toward the both ends in the width direction, the position every 500 mm, and The samples at the extreme ends were cut out, and the change in the orientation angle for every 500 mm in the film width direction was determined using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Scientific Instruments. When calculating the variation in the orientation angle including the positions at the extreme ends, if the distance between the sample positions is less than 500 mm, the variation width of the orientation angle every 500 mm is calculated by proportional calculation. Subsequently, a 3 m length was cut out in the longitudinal direction of the film, and a sample was cut out from a total of 7 positions every 500 mm (including both ends) in the longitudinal direction from the center in the film width direction, and the orientation angle was determined. Thus, the fluctuation width of the orientation angle for every 500 mm in the width direction and the longitudinal direction was determined, and the maximum fluctuation value was set as the fluctuation width of the orientation angle of the film. Further, in the measurement, it is important to make the reference axis of the orientation angle the same in all samples, and the reference axis can be arbitrarily determined.

(4) Refractive index (nβ) of the polyester film constituting the release film
In the width direction of the sample film, the position at every 500 mm toward the both ends in the width direction from the center position and the sample at the outermost ends are cut out, and the main orientation axis in the film plane is obtained using an Abbe refractometer manufactured by Atago Optical Co., Ltd. The refractive index in the direction perpendicular to the surface was measured at each position, and the average value was obtained and defined as nβ.

(5) Evaluation of release film peeling force (F) After attaching one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the surface of the release layer of the sample film, cut into a size of 50 mm × 300 mm Then, the peel strength after standing at room temperature for 1 hour is measured. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under a tensile speed of 300 mm / min.

(6) Measurement of oligomer extracted from surface of release layer of release film An unheat-treated release film is heated in air at 180 ° C. for 10 minutes in advance. Thereafter, the heat-treated film is brought into close contact as much as possible with the inner surface of a box having a top and width of 10 cm and a height of 3 cm so as to form a box shape. When the coating layer is provided, the coating layer surface is set to the inside. Next, 4 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of oligomer in DMF, and this value was divided by the film area in contact with DMF to obtain the amount of film surface oligomer (mg / M ² ).

  The oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml.

The conditions for the liquid chromatograph were as follows.
Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(7) Visual inspection property under crossed Nicols The sample film was adhered to the polarizing film through the adhesive so that the width direction of the sample film was parallel to the orientation axis of the polarizing film, and the polarizing film was adhered. A polarizing plate for inspection is superimposed on the sample film so that the orientation axis is orthogonal to the film width direction, white light is irradiated from the polarizing plate side, and 10 inspectors are visually inspected from the polarizing plate for inspection. Observation and visual inspection under crossed Nicols were evaluated according to the following criteria. At the time of measurement, A4 size samples were cut out from locations corresponding to positions of 10, 50, and 90% of the film width in the film width direction from the end of the obtained release film. Carried out.
<Criteria for visual inspection under crossed Nicols>
(Good inspection) ◎>○>△>×> XX (Inspection failure)
Among the above judgment criteria, those above Δ are the levels where actual use is possible.

(8) Foreign matter recognition A sample film is adhered to a polarizing film through a known acrylic pressure-sensitive adhesive so that the width direction of the sample film is parallel to the orientation axis of the polarizing film, thereby creating a polarizing plate with a release film. did. Here, when the polarizing plate was prepared, black metal powder (foreign matter) having a size of 50 μm or more was mixed between the pressure-sensitive adhesive and the polarizing film so as to be 50 / m ² . A polarizing plate for inspection is superimposed on the polarizing plate release film mixed with the foreign matter thus obtained so that the orientation axis is orthogonal to the width direction of the release film, and white light is irradiated from the polarizing plate side. Ten inspectors visually observed from the polarizing plate for inspection, and evaluated whether the foreign matter mixed between the adhesive and the polarizing film could be found by the following classification. In the measurement, the film was evaluated using a total of three films at the center and both ends of the obtained film, and the result of the point where the visual inspection property was the best was obtained. It was cognitive.
<Foreign substance recognition classification criteria>
(Good foreign body recognition) ◎ ＞ ○ ＞ △ ＞ × (foreign body poor recognition)
Among the above judgment criteria, those above ◯ are the levels where actual use is possible.

(9) Coating film adhesion promotion evaluation of release film (practical property substitution evaluation)
The sample film was left in a constant temperature and humidity chamber at 60 ° C. and 70% RH for 48 hours, and then the sample film was taken out. Thereafter, the release surface of the sample film was rubbed with a tentacle five times, and the degree of release of the release layer was determined according to the following criteria.
<Criteria>
○: No dropout of the coating film (practical level)
Δ: The coating film turns white but does not fall off (practical level)
×: Detachment of the coating film was confirmed (practically difficult level)

<Manufacture of polyester (A)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, and 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C.
On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (A). The intrinsic viscosity of this polyester was 0.63.

<Manufacture of polyester (B)>
In the method for producing polyester (A), after adding ethyl acid phosphate, the content of synthetic calcium carbonate particles having an average particle size of 0.8 μm and a particle size distribution value of 1.6 in an amount of 1 wt. The polyester (B) was obtained using the same method as the production method of the polyester (A) except that the addition was made so as to be%. The obtained polyester (B) had an intrinsic viscosity of 0.63.

<Manufacture of polyester (C)>
In the production method of the polyester (B), the additive particles are synthetic calcium carbonate particles having an average particle size of 0.5 μm and a particle size distribution value of 1.7, and the content with respect to the polyester is 1 wt%. A polyester (C) was obtained using a method similar to the production method of B). The obtained polyester (C) had an intrinsic viscosity of 0.63.

<Manufacture of polyester (D)>
In the method for producing polyester (B), the additive particles are synthetic calcium carbonate particles having an average particle size of 1.4 μm and a particle size distribution value of 1.9, and the content of the polyester is 1% by weight. Polyester (D) was obtained using the same method as the production method of B). The obtained polyester (D) had an intrinsic viscosity of 0.63.

<Manufacture of polyester (E)>
In the production method of the polyester (B), the additive particles are silica particles having an average particle size of 2.5 μm and a particle size distribution value of 1.3, and the content of the polyester is 0.6% by weight. A polyester (E) was obtained using a method similar to the production method of B). The obtained polyester (E) had an intrinsic viscosity of 0.63.

<Manufacture of polyester (F)>
In the method for producing polyester (B), the additive particles are natural calcium carbonate particles having an average particle diameter of 0.8 μm and a particle size distribution value of 2.5, and the content of the polyester is 1% by weight. A polyester (F) was obtained using a method similar to the production method of B). The obtained polyester (F) had an intrinsic viscosity of 0.63.

<Manufacture of polyester (G)>
In the method for producing polyester (B), polyester (B) is used except that the additive particles are silica particles having an average particle size of 0.12 μm and a particle size distribution value of 2.0, and the content with respect to the polyester is 0.3% by weight. A polyester (G) was obtained using a method similar to the production method of B). The obtained polyester (G) had an intrinsic viscosity of 0.63.
<Manufacture of film>

Example 1:
A mixed raw material obtained by mixing the polyester (A) chip and the polyester (B) chip at a ratio shown in Table 2 below is used as a raw material for the A layer, and a raw material of 100% polyester (A) chip is used as a raw material for the B layer. Each was supplied to two extruders and melt-extruded at 290 ° C., and then the surface temperature was set to 40 ° C. using an electrostatic application adhesion method with the A layer as the outermost layer (surface layer) and the B layer as the intermediate layer. It cooled and solidified on the cooling roll and the unstretched sheet was obtained. Next, a polyester film having a width of 3000 mm was obtained under the conditions shown in Table 2 below for the longitudinal stretching ratio, the longitudinal stretching temperature, the lateral stretching ratio, the lateral stretching temperature, and the heat treatment temperature (main crystal temperature). The total thickness of the obtained film was 40 μm, and the thickness of each polyester layer was 4 μm / 32 μm / 4 μm (A / B / A). Next, an application layer composed of the following application agent composition was applied off-line by a reverse gravure coating method so that the application amount (after drying) was 0.05 g / m ^2, and then heat-treated at 120 ° C. for 10 seconds.

<< Coating composition >>
Examples of compounds constituting the coating layer are as follows.
(Compound example)
Organic compound having zirconium element (A1): Zirconium tetraacetylacetonate Organic compound having titanium element (A2): Titanium tetraacetylacetonate Organic compound having aluminum element (A3): Aluminum tris (acetylacetonate G)
・ Alkoxysilane oligomer (B1): X-41-1056 (manufactured by Shin-Etsu Chemical)
・ Alkoxysilane oligomer (B2): X-40-2652B (manufactured by Shin-Etsu Chemical)
Crosslinking agent (C): γ-glycidoxypropyltrimethoxysilane Particle (D): silica sol (average particle size 60 nm)

(Coating agent composition ratio)
Organic compound having zirconium element (A1): 20% by weight
Alkoxysilane oligomer (B1): 80% by weight
The coating agent was diluted with a toluene / MEK mixed solvent (mixing ratio was 1: 1) to obtain 4% by weight.

Thereafter, a release agent having the following release agent composition was applied on the coating layer by a reverse gravure coating method so that the coating amount (after drying) was 0.1 g / m ² and heat-treated at 120 ° C. for 30 seconds. A release film was obtained later.
<Releasing agent composition>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical): 99% by weight
Curing agent (PL-50T: manufactured by Shin-Etsu Chemical): 1% by weight
The release agent was diluted with a MEK / toluene mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 2% by weight.

Examples 2-11 and Comparative Examples 1-3:
In Example 1, the polyester film constituting the release film was produced in the same manner as in Example 1 except that the raw material constituting the polyester film or the composition of the coating layer was different to obtain a release film. The characteristics of the obtained release film are shown in Tables 2 and 3.

Comparative Example 4
In Example 1, since the polyester raw material was changed, and the polyester film using the polyester (A) and (G) chips as the film surface layer had a surface shape that became extremely flat and slipperiness deteriorated, after stretching and heat treatment When the polyester film was wound into a roll, it could not be wound well, and scratches were generated on the entire surface of the film, which could not be a product. The properties of the obtained release film are shown in Table 3.

Comparative Example 5
In Example 1, the polyester film constituting the release film was produced in the same manner as in Example 1 except that the raw material constituting the polyester film or the composition of the coating layer was different to obtain a release film. The properties of the obtained release film are shown in Table 3.

  The release film of the present invention has an extremely small amount of oligomer precipitation, suppresses the generation of bright spots due to particles in the film in the foreign substance inspection process, and is particularly suitable for protecting the adhesive layer of a liquid crystal polarizing plate. In the inspection process by the Nicol method, it is possible to deal with highly accurate foreign matter inspection, and its industrial value is high.

Claims (1)

180. A release film in which a coating layer containing an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium and a release layer are sequentially provided on one side of a polyester film. After heat treatment at 10 ° C. for 10 minutes, the amount of oligomer extracted from the release layer surface with dimethylformamide is 2.2 mg / m ² or less, and the average particle size of the particles contained in the polyester film is 0.2 to 1. A release film having a range of 5 μm and a particle size distribution value (d25 / d75) of 1.0 to 2.0.