JP5331274B2 - Release film - Google Patents

Description

  The present invention relates to a release film whose color tone is changed by laser irradiation.

  Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, etc. It is used in applications. However, as the use diversifies, the processing conditions and usage conditions of the film diversify. For example, when using as a release film in which a release layer is provided on a polyester film, Some marking processing, such as positioning, may be required.

  In response to such a request, for example, when a belt-like print layer is provided in advance as a mark on a polyester film (for example, Patent Document 1), it is necessary to provide a belt-like print layer on the film when producing a release film. The manufacturing process will increase by one.

Japanese Patent Laid-Open No. 10-230576

  The present invention has been made in view of the above problems, and the solution is to include a laser marking pigment in a polyester film as a release film, and the treatment region can be visually identified by a color tone change by laser irradiation. The object is to provide a release film that can be manufactured without increasing the manufacturing process as much as possible and has good transparency.

  As a result of intensive studies in view of the above problems, the present inventors have found that a release film made of a polyester film having a specific configuration is suitable for various mold releases without impairing excellent film properties. It has been found that the present invention can be provided, and the present invention has been completed.

That is, the gist of the present invention resides in a release film comprising a release layer containing a curable silicone resin on at least one surface of a polyester film containing a copper compound and a molybdenum compound as a metal oxide .

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.

  Further, the polyester film constituting the polyester film of the present invention may be a single layer structure or a multilayer structure, and may be a four-layer or a multilayer unless the gist of the present invention is exceeded other than the two-layer or three-layer structure. It may be a multilayer having more than that, and is not particularly limited.

  The polyester constituting the film of 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.

  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 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. The content of the film layer to which these particles are added is usually 1% by weight or less, preferably 0.01 to 1% by weight, and more preferably 0.02 to 0.6% by weight. When the content of the particles is small, the film surface is flattened, and in the film production process, the surface is liable to be scratched and the winding property tends to be 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 is 0.02 to 2 μm, preferably 0.1 to 1.8 μm, more preferably 0.2 to 1.6 μm. When the particle size is less than 0.02 μm, the film surface becomes flat and the winding properties in the film production process tend to be inferior. When the particle diameter exceeds 2 μm, it may be difficult to cope with the formation of a flat resin sheet. On the other hand, in order to improve the transparency of the film, when a laminated film of 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 for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, 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 may be chipped 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.

  The total thickness of the film of the present invention is not particularly limited as long as it can be formed as a film, but is usually 9 to 350 μm, preferably 12 to 250 μm, and more preferably 25 to 188 μm. is there.

  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.

  With respect to the release film of the present invention, it is an essential requirement that the polyester film contains a material whose color tone is changed by laser irradiation, that is, a so-called laser marking pigment, in order to impart visual discrimination.

As a specific example of the laser marking pigment, the metal oxide is preferably at least one selected from a copper compound, a molybdenum compound, an iron compound, a nickel compound, a chromium compound, a zirconium compound and an antimony compound. More preferably, it is at least one selected from compounds. In addition, supplementary use and use of inorganic metal compounds such as titanium oxide, zinc sulfide, zinc oxide, precipitated barium sulfate, barium carbonate and precipitated calcium carbonate and dyes such as carbon black, graphite and black lake, and leuco dye It is desirable to select and use it according to the environment.

  In the polyester film constituting the release film in the present invention, the total content of the laser marking pigment in the polyester layer is preferably in the range of 0.025 to 0.25% by weight. When the said range is less than 0.025 weight%, the color tone change after laser irradiation is scarce, and it may become difficult to identify a process part visually. On the other hand, if it exceeds 0.25% by weight, the transparency may be insufficient, and it may be difficult to cope with applications in which so-called visibility is emphasized.

  Next, the kneading of the laser marking pigment into the polyester in the present invention will be described. The above-mentioned laser marking pigment may be any method such as a method of using as a master batch kneaded in a polyester resin, or directly adding a laser marking pigment to a polyester resin, and is not particularly limited.

  For example, a 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.

  In the polyester film which comprises the release film of this invention, if it is a range which does not impair the effect of this invention, you may give what is called the coating extending | stretching method (inline coating) which processes a film surface in a extending process. Although it is not limited to the following, for example, after the first stage of stretching is completed, before the second stage of stretching, improvement of antistatic property, slipperiness, adhesion, etc., secondary workability improvement, weather resistance, etc. In order to improve the property and surface hardness, a coating treatment with an aqueous solution, an aqueous emulsion, an aqueous slurry, or the like can be performed.

Next, formation of the release layer in the present invention will be described.
As a required characteristic for a release film in the present invention, for example, when used as a process paper in a processing step, it is required that the film flatness is good. As a specific example, for example, a wider release film may be required in applications where the screen collection efficiency needs to be further improved as the screen size increases, such as a liquid crystal display.

  As a method for simultaneously satisfying the above-mentioned required characteristics, it is preferable that the release layer in the present invention is provided with a release layer on the polyester film by a coating stretching method (in-line coating).

  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 is particularly finished and the coating process is performed before the second stage of stretching. Can do. 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.

  Regarding the release layer constituting the release film in the present invention, it is an essential requirement to contain a curable silicone resin as a constituent material in order to improve release properties.

  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, Momentive YSR-3022, TPR-6700, TPR-6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, Toray Dow Corning SRX357, SR manufactured by 211, SD7220, LTC750A, LTC760A, SP7259, BY24-468C, SP7248S, BY24-452, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, etc. DKQ3-210 are exemplified. Further, a release control agent may be used in combination to adjust the release property of the release layer.

  Moreover, regarding the release layer which comprises the release film in this invention, when apply | coating by the apply | coating extending | stretching method (in-line coating), it is preferable to contain an emulsion type curable silicone resin. It may be a type mainly composed of an emulsion type curable silicone resin, or a modified silicone type by graft polymerization with an organic resin such as urethane resin, epoxy resin, alkyd resin, etc. within a range not impairing the gist of the present invention. May be used.

  Specific examples of the emulsion-type curable silicone resin include Dehesive 430, Dehesive 440 made by Asahi Kasei Wacker Silicone, Silicone 902 made by Arakawa Chemical, and the like.

  Various known resins can be used as the thermosetting compound used in the release layer of the present invention, and examples thereof include melamine compounds, epoxy compounds, oxazoline compounds, isocyanate compounds, and the like.

  Examples of the melamine compound in the present invention include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. .

  As an epoxy compound in this invention, the compound containing an epoxy group in a molecule | numerator, its prepolymer, and hardened | cured material are mentioned, for example. A typical example is a condensate of epichlorohydrin and bisphenol A. In particular, a reaction product of a low molecular polyol with epichlorohydrin gives an epoxy resin having excellent water solubility.

  The oxazoline compound in the present invention is a compound having an oxazoline ring in the molecule, and includes a monomer having an oxazoline ring and a polymer synthesized using the oxazoline compound as one of raw material monomers.

  The isocyanate compound in the present invention refers to a compound having an isocyanate group in the molecule, specifically, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tolylene diisocyanate. And their polymers and derivatives.

  These thermosetting compounds may be used alone or in combination of two or more. It can also be used with a catalyst to promote thermosetting. Furthermore, when consideration is given to application to in-line coating, it is preferable to have water solubility or water dispersibility.

  In the release film of the present invention, a binder polymer can be used in combination for the purpose of improving the adhesion between the polyester film and the release layer or improving the coated surface of the release layer.

  The “binder polymer” used in the present invention is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) in accordance with a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). ) Is a polymer compound having a molecular weight of 1000 or more and having a film forming property.

  Specific examples of the binder polymer include polyester resin, acrylic resin, urethane resin, polyvinyl, polyalkylene glycol, polyalkyleneimine, celluloses, and starches.

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

  Furthermore, as long as it does not impair the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc. May be contained.

  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. For example, when the release layer is provided by a coating stretching method (in-line coating), it is usually 170 to 280. The heat treatment may be performed for 3 to 40 seconds at a temperature, preferably 200 to 280 ° C. for a time of 3 to 40 seconds. 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 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 to 0.5 / ^{m 2,} preferably in the range of 0.005~0.2g / ^{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, in the case of thick coating exceeding 0.5 g / m ² , the coating film adhesion, curability and the like 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.
Surprisingly, the inventors of the present invention have a release film composed of a polyester film containing a laser marking pigment. When laser irradiation such as YAG or YVO ₄ is performed from the release surface side, the laser marking pigment is It was found that the release layer of the laser irradiated part would be heavily peeled because the release layer was affected by the heat energy generated in the process of changing the color tone.

  As an application of such a heavy peeling phenomenon, for example, in the same mold release surface, a part of the mold release surface is partially irradiated with a laser to make it a heavy release, so that it can be applied from the mold release surface in a scene that does not need to be peeled off originally. It is preferable at the point which can newly provide the release film with the function which can suppress that the other party base material to match | combine easily peels.

  In order to realize the partial delamination, the release film in the present invention preferably has a peeling force change of 2 times or more before and after laser irradiation. Moreover, if the partial laser irradiation technique of a mold release surface is used, conventionally, for example, as there is an example described in Patent Document 1, it is not necessary to provide an extra print layer on the polyester film for partial heavy peeling.

As the release film, the side of the release surface is irradiated with laser using YAG, YVO ₄ or the like, so that the processing area changes color tone, so that it can be visually identified. Can be suitably used when some marking process such as positioning is required. As an additional effect, the release surface of the laser processing section has the effect of heavy peeling, so there is no need to provide an extra print layer for peeling, and it can be bonded together in situations where it is not necessary to peel off. It is possible to prevent the opposite base material from being easily peeled off from the release surface, and supports various release applications such as adhesive layer protection, transfer foil production, green sheet production, and resin sheet molding. 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 diameter (d50)
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.

(3) Visual distinguishability (color tone change) evaluation of release film After the laser beam was irradiated on the release surface side of the sample film under the following measurement conditions, visual determination was performed according to the following criteria.
<Laser irradiation conditions>
Model: Keyence YVO ₄ laser "MD-V9900"
Laser wavelength: 1064 nm
Average output: 13W
Q switch frequency: CW, 1 to 400 kHz
Irradiation speed: 1500mm / sec

<Criteria>
◯: Good distinguishability △: Discrimination is possible but color tone change is small ×: Color tone does not change In the above criteria, Δ or higher is a level that can be used practically without problems.

(4) Transparency evaluation of release film After irradiating the sample film with laser, the total light transmittance was measured with an integrating sphere turbidimeter “NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS-K-7105. Measurement was made and judged according to the following criteria.
<Criteria>
○: Good transparency (compared to Comparative Example 2, the decrease in total light transmittance is 2% or less)
Δ: Insufficient in some cases (compared to Comparative Example 2, decrease in total light transmittance exceeds 2% and 4% or less)
X: Face-to-face is difficult to see through the sample film (compared to Comparative Example 2, the decrease in total light transmittance exceeds 4%)
Among the above judgment criteria, Δ or more is a level that can be used practically without any problem.

(5) Peeling property evaluation (practical property substitution evaluation)
For the sample film, a top coat layer composed of the following coating composition was applied to the release surface and dried (using a hot air circulation furnace manufactured by Espec) under the following coating conditions, and then the top coat layer and the release layer were peeled off. The sex was determined according to the following criteria.
<Topcoat composition>
In a two-liter four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and cooling tube, 340 g of 2-ethylhexyl acrylate (hereinafter referred to as 2-EHA) and isobornyl acrylate (hereinafter referred to as iBoA) ) 600 g, 2-hydroxyethyl acrylate (hereinafter referred to as 2-HEA) 60 g, and 3.0 g of n-dodecyl mercaptan were charged, and the flask was heated to 55 ° C. while the air in the flask was replaced with nitrogen. Next, 2,2′azobis (4-methoxy-2,4-dimethylvaleronitrile) (trade name V-70; manufactured by Wako Pure Chemical Industries, Ltd. (hereinafter referred to as V-70) 0.025 g as a polymerization initiator. After the polymerization initiator was added, the temperature of the reaction system rose, but when the polymerization reaction was continued without cooling, the temperature of the reaction system reached 120 ° C, and then When the temperature of the reaction system dropped to 115 ° C., 68.0 g of 2-EHA, 120.0 g of iBoA, 12.0 g of 2-HEA, and 1.5 g of n-dodecyl mercaptan were added. After cooling to 55 ° C., the temperature was maintained and the mixture was stirred for 30 minutes while purging with nitrogen, then 0.05 g of V-70 was added as a polymerization initiator under stirring and mixed uniformly. After charging, the temperature of the reaction system is The temperature rose to 115 ° C. and then gradually began to drop, and when the temperature of the reaction system dropped to 110 ° C., 102.0 g of 2-EHA, 180.0 g of iBoA, and 18.0 g of 2-HEA were added. Then, cooling was performed to obtain an acrylic syrup A. This syrup had a monomer concentration of 50% and a polymer concentration of 50%, and the polymer had a weight average molecular weight by GPC of 50,000.

  1,200 hexanediol diacrylate (trade name Light Acrylate 1,6HX-A; manufactured by Kyoeisha Chemical Co., Ltd .: hereinafter referred to as HX-A) with respect to 200 parts by mass of syrup A (100 parts by mass of monomer mixture). ) 1.0 part by mass (1.8 parts by mass with respect to 100 parts by mass of iBoA), isocyanurate HDI (trade name Duranate TPA100; manufactured by Asahi Kasei Co., Ltd .: hereinafter referred to as TPA), 18.8 parts by mass, silica particles (product) Name typec R-972; manufactured by Tegusa Co., Ltd .: hereinafter referred to as R-972) 6.0 parts by mass, peroxide-based initiator: cumyl-peroxy-neodecanoate (trade name Park Mill ND; manufactured by Nippon Oil & Fats Co., Ltd .: 2.0 parts by mass of 1,1,3,3-tetramethylbutyl-peroxy-2-ethylhexanoate (trade name Perocta O; This oil and fat Co., Ltd .: 3.0 parts by mass, hereinafter referred to as initiator PO, tin-based curing accelerator (trade name Neostan U-340; Nitto Kasei Co., Ltd .: hereinafter referred to as U-340) ) 0.12 parts by mass was added, and mixed and defoamed to prepare a thermopolymerizable composition A-1.

<Application conditions>
Sample size: A4 cut size Drying conditions: 120 ° C. × 10 minutes Application amount (g / m ² ): 80 μm (after drying)
Application method: Baker type applicator <Criteria>
○: Good peelability Δ: Slightly heavy peelability but peelable ×: Difficult to peel Out of the above criteria, Δ or higher is a level that can be used practically without problems.

(6) Peelability evaluation after laser irradiation of release surface of release film Before and after laser release of release surface of sample film in advance, double-sided adhesive tape (“No. .502 "), after being cut into a size of 50 mm x 300 mm, the peel strength after standing for 1 hour at room temperature 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 the condition of a tensile speed of 300 mm / min.

Thereafter, the determination was made according to the following criteria.
<Criteria>
○: peeling force after laser irradiation is 2 times or more before irradiation ×: peeling force after laser irradiation is less than 2 times before irradiation In the above criteria, ○ is a level that can be used practically without problems.

(7) Comprehensive evaluation Comprehensive evaluation was performed on the sample film according to the following criteria.
<Criteria>
○: Visibility, transparency and heavy release are all “○”
Δ: At least one item among the visibility, transparency, and heavy release is “△”
×: At least one item among the visibility, transparency, and heavy release is “×”
In the above criteria, ○ is a level that can be used practically without any problem.

Examples 1-5 and Comparative Examples 1-4:
<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)>
The polyester (A) and the laser marking pigment CuO.xMoO3 were dry blended at a ratio of 99.97: 0.03 (parts by weight).

<Manufacture of polyester (C)>
The polyester (A) and the laser marking pigment CuO.xMoO3 were dry blended at a ratio of 99.77: 0.3 (parts by weight).

<Manufacture of polyester (D)>
Polyester (A) and laser marking pigment CuO.xMoO3 were dry blended at a ratio of 99.57: 0.5 (parts by weight).

<Manufacture of polyester (E)>
The polyester (A) and the laser marking pigment CuO.xMoO3 were dry blended at a ratio of 99.98: 0.02 (parts by weight).

<Manufacture of film>
A mixed raw material obtained by mixing the polyester (A) chip and the polyester (B) chip to the polyester (E) chip in the proportions shown in Tables 2 and 3 is used as a raw material for the outermost layer (surface layer) and the intermediate layer. Each was supplied to an extruder, melt-extruded at 290 ° C., and then cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched sheet. Next, after stretching 2.8 times in the longitudinal direction at 100 ° C., a coating liquid composed of the composition described in Table 1 below was applied so that the coating amount (after drying) was 0.020 g / m ² . Then, after a preheating step in a tenter and 4.0 times transverse stretching at 120 ° C., heat treatment was performed at 225 ° C. for 10 seconds, and then 2% relaxation was added in the width direction to obtain a polyester film. . The total thickness of the obtained film was 100 μm, and the thickness of each layer was 5 μm / 90 μm / 5 μm.

  Examples of compounds constituting the release layer are as follows.

a1: Curing type silicone resin (Dehesive 430: manufactured by Asahi Kasei Wacker Silicone)
a2: Curable silicone resin (Dehesive 440: manufactured by Asahi Kasei Wacker Silicone)
a3: Curable silicone resin (Silicolys 902: Arakawa Chemical)
a4: Platinum catalyst (Silicolyse 903: Arakawa Chemical)
a5: Curable silicone resin (KS-779H: manufactured by Shin-Etsu Chemical)
a6: Platinum catalyst (PL-50T: manufactured by Shin-Etsu Chemical)

The release film of the present invention can be suitably used for various release applications, for example, for protecting an adhesive layer, for transferring, and for producing a green sheet.

Claims (1)

A release film comprising a release layer containing a curable silicone resin on at least one surface of a polyester film containing a copper compound and a molybdenum compound as a metal oxide .