JP2010194905A - Mold release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release film with excellent releasability in a printing process for shallow draw and middle draw, with excellent heat dimensional change and printability, excellent moldability because of extending easily with low stress, and providing a molded article with excellent low glossiness. <P>SOLUTION: The mold release film has a release layer on one face of the film face, and has a longitudinal heat contraction rate of the release film of 3.0% or less at 180°C for 5 minutes, and a lateral heat contraction rate of 0.5% or less. In the tensile test at 25°C, 5% elongation stress in the longitudinal direction of the release film is 90-120 MPa, and 100% elongation stress is 200 MPa or less in both longitudinal and lateral directions, and a center line-average roughness (Ra) of the release layer surface is 0.30-0.70 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the printing process for shallow drawing to medium drawing use, the thermal dimensional change is good, the printing property is excellent, the moldability is good because it easily stretches with low stress, and the molded product is excellent in low gloss. The present invention relates to a release film having good release properties.

  Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, etc. Used for applications.

  However, as the applications diversify, the film processing conditions and usage conditions tend to diversify. As an example, a release film for producing an in-mold transfer foil can be mentioned. The structure of the transfer foil using the release film includes a transfer layer such as a design print layer and an adhesive layer sequentially on one side of the release layer. Generally, it has a laminated structure, and a hard coat layer, a metal vapor deposition layer, or the like is laminated on the transfer layer according to the purpose. Further, a functional agent such as an antistatic agent or an antibacterial agent is added to the release layer or the transfer layer to give a function as a transfer foil.

  With regard to the transfer foil transfer method described above, the transfer foil is set in an injection mold and a resin molded product is molded. A so-called in-mold transfer method (simultaneous molding transfer method) in which a design is transferred and decorated is widely known (Patent Documents 1 to 4).

  Such a transfer method is a method in which a plurality of laminated transfer foils including an adhesive layer on the surface of a polyester base material are used and transferred to an object to be transferred via the adhesive layer. It is used in a wide range of applications for the purpose of surface treatment such as decoration and surface protection on the surface of a wide variety of resin molded products such as automobile parts, cosmetic containers, and toys.

  On the other hand, as one of the design properties of a molded product, a molded product having a low gloss feeling may be required. As a means for giving a molded article a low gloss feeling, for example, a method in which a product is directly coated with a matte paint, a base material surface is used to make a matte state using various means, and the cosmetic material is used as a product. Examples thereof include a method of attaching to the surface, a transfer method of transferring the matte resin layer by transferring the transfer foil to a product using a transfer foil on which a matte resin layer has been formed in advance.

  In the molding application, the diaphragm in the molding process varies greatly depending on various applications, such as cellular phones and electric products, such as those with a shallow diaphragm during molding and those with a large diaphragm during molding, such as automobiles. The drawing in this forming process is classified into shallow drawing, medium drawing, and deep drawing, and a suitable base film is selected and used according to the intended application.

  As a necessary requirement for the release film, thermal dimensional changes due to stretch deformation and width shrinkage occur in the release film due to the influence of drying temperature and tension in coating and printing processes such as pattern printing and adhesive layer, printing displacement, There may be a problem such as a decrease in flatness.

  As the necessary characteristics of the release film, certain thermal dimensional stability and mechanical characteristics are required. However, the transfer foil laminated using this release film also has high mechanical strength, so the deformation stress is high during in-mold molding, the followability with the mold is poor, and the printing is clear. There is a problem that chipping phenomenon and molding breakage are likely to occur.

  In this deep drawing mold release film, the mold release film itself has soft characteristics in terms of film design. Therefore, in consideration of this point, the film is processed at a low temperature such as 80 to 100 ° C. which does not hinder elongation deformation. . In many cases, the pattern to be painted is one-step full surface printing such as woodgrain, and it is used for transfer foils that do not interfere with the quality of the pattern even if some thermal dimensional change or elongation deformation occurs. Yes.

  However, in many applications, such as shallow drawing to medium drawing, patterns to be painted are often printed in multiple colors, such as three to seven colors, and stretch deformation due to the influence of drying temperature and processing tension due to such high temperatures. In other words, there is a situation where the width shrinkage occurs and printing misalignment or flatness deteriorates, resulting in a fatal defect in the quality of the transfer foil.

  As countermeasures against the above problems, conventionally, release films for shallow drawing to medium drawing have been given mechanical strength so as to suppress elongation deformation in the vertical direction in coating and printing. However, the transfer foil obtained using such a release film also has high mechanical strength, so it has high deformation stress at the time of in-mold molding, poor followability with the mold, and clear printing. There is a problem that a phenomenon lacking in the thickness and molding breakage are likely to occur.

  Further, as a means for giving a low gloss feeling to a molded product, a method using a transfer foil having a matte resin layer formed in advance, which can reduce the processing step, is desirable. It is believed that the number of processing steps can be further reduced if it can be blended.

  However, when a matting agent is blended in the release film, there may be a problem that the continuity during film formation is poor or a molding break that occurs when used as a transfer foil.

  Furthermore, in the same application, the release layer is generally provided off-line, but since the release layer has a coating thickness of several μm level, the release layer is formed on the roughened polyester film substrate surface. Is provided off-line, the protrusion on the surface of the film is buried by the release layer, so that it may be difficult to obtain a desired low gloss feeling.

Japanese Patent Laid-Open No. 7-196821 JP 7-237283 A JP 2007-181978 A JP 2004-9596 A

  The present invention has been made in view of the above circumstances, and the solution is to form in a printing process for shallow drawing to medium drawing applications because the thermal dimensional change is good, the printability is excellent, and the film easily stretches with low stress. An object of the present invention is to provide a release film having good release properties, which is good and can provide a molded product excellent in low gloss.

  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, a release film suitable for in-mold transfer can be provided without impairing excellent film properties. As a result, the present invention has been completed.

  That is, the gist of the present invention is a release film having a release layer on one film surface, and the longitudinal heat shrinkage of the release film at 180 ° C. for 5 minutes is 3.0% or less. The thermal shrinkage rate is 0.5% or less, and in the tensile test at 25 ° C., the 5% elongation stress in the longitudinal direction of the release film is 90 to 120 MPa, and the 100% elongation stress is 200 MPa or less in both the longitudinal and transverse directions. It exists in the release film characterized by centerline average roughness (Ra) of the mold layer surface being in the range of 0.30 to 0.70 μm.

Hereinafter, the present invention will be described in detail.
The polyester film constituting the release film referred to in the present invention is a film that is melt-extruded from an extrusion die, cooled after being melted by a so-called extrusion method, and stretched and heat-treated as necessary. is there.

  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 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.

  Inorganic particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, lithium fluoride, etc. Is mentioned. Examples of the organic salt particles include terephthalate such as calcium oxalate, calcium, barium, zinc, manganese, and magnesium. Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers of divinylbenzene, styrene, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin may be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  The average particle size of the particles used in the present invention is usually preferably 3 to 8 μm. If the average particle size is less than 3 μm, the ability to form protrusions on the surface may be insufficient, which does not meet the object of the present invention. On the other hand, if the average particle size exceeds 8 μm, the film breaks when stretched. Etc. occur frequently and products cannot be collected stably.

  Furthermore, the particle content in the polyester is usually 0.1 to 5% by weight, preferably 0.2 to 3% by weight. When the particle content is less than 0.1% by weight, the number of protrusions on the film is insufficient, so that the appearance of the molded product having low gloss tends to be rough. On the other hand, if it exceeds 5% by weight, breakage and the like frequently occur during film stretching, and stable production may be lost.

  The center line average roughness (Ra) of the release film of the present invention needs to be in the range of 0.30 to 0.70 μm. When Ra is less than 0.30 μm, the low gloss feeling of the molded product molded using the release film becomes insufficient. On the other hand, in order to make Ra larger than 0.70 μm, it is necessary to blend a large amount of coarse particles, and breakage and the like frequently occur during film stretching, resulting in lack of stable production.

  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 converted into chips after melt polymerization, and further solid phase polymerization may be performed 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 12 to 100 μm, preferably from the viewpoint of mechanical strength, handling properties and productivity, It is the range of 25-75 micrometers.

  Next, although the manufacturing method of the 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 of dimethyl terephthalate and ethylene glycol is carried out, the product is transferred to a polymerization tank, the temperature is increased while reducing the pressure, and finally vacuum is applied. Under heating to 280 ° C., the polymerization reaction proceeds 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.

With respect to the release film in the present invention, the melting peak temperature (Tm) measured by a differential scanning calorimeter is preferably 220 to 260 ° C., preferably 230, from the viewpoints of heat resistance, molding processability and dimensional stability. ~ 255 ° C. When Tm is less than 220 ° C., the heat resistance and dimensional stability are inferior, and thus wrinkles are generated in the printing process, and the film surface after molding is swollen, so that the design of the design pattern is impaired. May cause problems. On the other hand, when Tm exceeds 260 ° C., moldability and productivity may be lowered.
Moreover, regarding the release film in this invention, the secondary transition temperature (Tg) obtained from a differential scanning calorimeter is preferably 50 ° C to 90 ° C, more preferably 55 ° C to 80 ° C. When Tg is 50 ° C. or lower, heat resistance tends to be poor, and when it exceeds 90 ° C., moldability tends to be poor.

  The release film of the present invention needs to have a heat shrinkage rate of 3.0% or less in the vertical direction and 0.5% or less in the horizontal direction after heat treatment at 180 ° C. for 5 minutes, preferably in the vertical direction. 2.5% or less, and 0.3% or less in the lateral direction. When the thermal contraction rate in the vertical direction is larger than 3.0%, the flatness (single tarmi) considered to be affected by the thermal contraction difference in the width direction is likely to deteriorate. On the other hand, when the thermal contraction rate in the horizontal direction exceeds 0.5%, the width shrinkage becomes large, and a printing misalignment problem occurs in the width direction.

  From the viewpoint of processability to a transfer foil, the release film of the present invention needs to have a 5% elongation stress in the range of 90 to 120 MPa, preferably 95 to 115 in a longitudinal tensile test at 25 ° C. The range is good. If the 5% elongation stress is lower than 90 MPa in the tensile test in the longitudinal direction, film elongation occurs in a processing step such as printing, and problems such as printing misalignment tend to occur in the longitudinal direction. On the other hand, if the 5% elongation stress exceeds 120 MPa in the longitudinal direction, the mechanical strength of the base film finished on the transfer foil is maintained, so the deformation stress during in-mold molding increases, ensuring good moldability. Difficult to do.

  Furthermore, the release film in the present invention needs to have a 100% elongation stress of 200 MPa or less in both the longitudinal and transverse directions at 25 ° C. in the tensile test from the viewpoint of moldability. The 100% elongation stress is preferably 180 MPa or less. If the 100% elongation stress exceeds 200 MPa in the vertical and horizontal directions at 25 ° C., the deformation stress increases during in-mold molding, and the followability with the so-called mold deteriorates, and the decorative printed surface becomes clear. Chipping phenomenon or molding breakage occurs.

  The basis for specifying the 5% elongation stress is that the elongation deformation rate in the longitudinal direction that occurs in the coating process or the printing process is substantially less than 3%. It is a thing. Also, when the molding elongation rate was converted from the thickness change after shallow drawing to middle drawing at 100% elongation stress, the deformation rate was in the range of 70 to 130%. Is. These measurement temperatures vary depending on the application, but generally the film temperature at the drying temperature (80 ° C. to 180 ° C.), the molding temperature (120 ° C. to 160 ° C.), etc. in the coating or printing process is used. A high temperature test method can be considered. However, in this method, crystallization proceeds in the process of raising the film temperature, and it is difficult to know the exact mechanical characteristics of the polyester film for transfer foil. Therefore, the measurement temperature is measured with the mechanical characteristics at room temperature (JIS C 2318). Compliant).

Next, the manufacturing method of the film of this invention is demonstrated.
First, a polyester chip 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 to melt. 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, it is possible to give what is called in-line coating which processes a film surface during 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 the release film in the present invention, since it is necessary to provide a thin release layer on the roughened polyester film, the release layer is coated and stretched (in-line coating). It is an essential requirement to be provided above.

  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 process may be performed before the second stage of stretching. it can. When a release layer is provided on a polyester film by a coating 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, and is suitable as a polyester film. Can be manufactured.

  The release layer constituting the release film in the present invention contains at least one selected from a fluorine compound, a long-chain alkyl compound and a wax as a constituent material. These release agents may be used alone or in combination.

  The fluorine compound in the present invention is a compound containing a fluorine atom in the compound. Organic fluorine compounds are preferably used in terms of planarity due to in-line coating, and examples thereof include perfluoroalkyl group-containing compounds, polymers of olefin compounds containing fluorine atoms, and aromatic fluorine compounds such as fluorobenzene. . In view of heat resistance and contamination due to transfer, a polymer compound is preferable.

  The long-chain alkyl compound in the present invention is a compound having a linear or branched alkyl group having 6 or more, particularly preferably 8 or more carbon atoms. Specific examples include, but are not limited to, long-chain alkyl group-containing polyvinyl resins, long-chain alkyl group-containing acrylic resins, long-chain alkyl group-containing polyester resins, long-chain alkyl group-containing amine compounds, long-chain alkyl groups. And an ether compound, a long-chain alkyl group-containing quaternary ammonium salt, and the like. In consideration of the transfer of the component derived from the release layer to the surface of the counterpart base material bonded when the release film is peeled off, a polymer compound is preferable.

  The wax in the present invention is a wax selected from natural waxes, synthetic waxes, and blended waxes. Natural waxes are plant waxes, animal waxes, mineral waxes, and petroleum waxes. Examples of plant waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil. Animal waxes include beeswax, lanolin, and whale wax. Examples of the mineral wax include montan wax, ozokerite, and ceresin. Examples of petroleum wax include paraffin wax, microcrystalline wax, and petrolatum. Synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, esters, and ketones. As synthetic hydrocarbons, Fischer-Tropsch wax (also known as Sazoir wax) and polyethylene wax are famous, but in addition to this, low molecular weight polymers (specifically, polymers having a viscosity number average molecular weight of 500 to 20000) Some of the following polymers are also included. That is, there are polypropylene, ethylene / acrylic acid copolymer, polyethylene glycol, polypropylene glycol, polyethylene glycol and polypropylene glycol block or graft conjugate. Examples of the modified wax include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. The derivative here is a compound obtained by purification, oxidation, esterification, saponification treatment, or a combination thereof. Hydrogenated waxes include hardened castor oil and hardened castor oil derivatives.

  Various known resins can be used as the thermosetting compound used in the release layer of the present invention, and examples include melamine compounds, epoxy compounds, oxazoline compounds, and isocyanate compounds. A melamine compound is more preferable in that it has excellent heat resistance during heat transfer and does not lower the releasability.

  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 polymers and derivatives thereof.

  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) according to 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 is usually 0.005 to 0.5 g / m ² , preferably 0.005 to 0.2 g / m ² , more preferably 0.005 to 0, from the viewpoint of coating properties. The range is 1 g / 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.

  With respect to the release film in the present invention, a coating layer such as an antistatic layer, an adhesive layer, and an oligomer precipitation preventing layer may be provided on the surface on which 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.

  With respect to the release film in the present invention, so-called visibility, which is confirmed through the film, may be required with respect to the printed pattern on the surface of the opposite molded product to be bonded during the processing step. In order to cope with such a process, the transmission density (OD) of the release film in the present invention is preferably 0.25 or less in order to ensure good visibility. The OD is more preferably 0.20 or less. When OD exceeds 0.25, even if it is going to confirm the printed design of the other party molded product bonded together through a release film, visibility may fall and it may not be visible.

  The release film of the present invention has a good thermal dimensional change and excellent printability in a printing process for shallow drawing to medium drawing applications, good moldability because it easily stretches at low stress, and excellent in low gloss. This is a release film with good releasability, and the industrial value of the present invention is very large.

  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) Measurement of Melting Peak Temperature (Tm) of Release Film Using a differential scanning calorimeter “MDSC 2920 type” manufactured by TI Instruments, about 5 mg of polyester resin from 0 ° C. to 300 ° C. at 20 ° C./min The temperature of the endothermic peak that accompanies the melting obtained when the temperature was raised at a rate of T was defined as Tm.

(4) Measurement of secondary transition temperature (Tg) of release film Using a differential scanning calorimeter “MDSC 2920 type” manufactured by TI Instruments, about 5 mg of polyester resin from 0 ° C. to 300 ° C. at 20 ° C. / The glass transition observed when the temperature was raised at a rate of 5 minutes, melted and held at 300 ° C. for 5 minutes, rapidly cooled to below 0 ° C., and then raised to 0 to 300 ° C. at 20 ° C./minute to 300 ° C. The accompanying transition point was defined as Tg.

(5) Measurement of surface roughness (Ra) of release surface of release film The surface roughness is defined as the center line average roughness Ra (nm). It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, the center line of the extracted portion is the x axis, and the direction of the vertical magnification is the y axis. When represented by (x), the value given by the following equation is represented by [nm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portion obtained from 10 cross section curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.
Ra = (1 / L) ∫ 0 L | f (x) | dx

(6) Measurement of 5% elongation stress of release film Using an Intesco tensile tester, Intesco Model 2001, a sample film having a length of 50 mm and a width of 15 mm at a temperature of 25 ° C. at a speed of 200 mm / min. A tensile test was performed to determine the stress at 5% elongation in the longitudinal direction.

(7) Measurement of 100% elongation stress of release film By the measurement method of (6) above, the sample piece was pulled in the vertical and horizontal directions, and the stress at 100% elongation was determined.

(8) Breaking elongation measurement of release film By the measuring method of (6) above, the sample piece was pulled in the vertical direction and the horizontal direction, and the breaking elongation of the sample piece was determined.

(9) Measurement of heat shrinkage rate of release film Using a hot air circulating furnace (manufactured by Taibai Seisakusho), heat-treated the film in a tension-free state for 5 minutes in an atmosphere of 180 ° C. The length before and after the heat treatment was measured, calculated by the following formula, and expressed as an average value for each of the five samples.
Thermal contraction rate (%) = (L ₀ −L ₁ ) × 100 / L ₀
In the above formula, L ₀ represents the sample length (mm) before the heat treatment, and L ₁ represents the sample length (mm) after the heat treatment. However, when L ₀ is smaller than L ₁ (when the film expands), the value of the thermal contraction rate is represented by − (minus).

(10) Peeling property evaluation (practical property substitution evaluation)
Regarding the sample film, a top coat layer having the following coating composition was coated on the release surface under the following coating conditions, and then the peelability between the top coat layer and the release layer was determined according to the following criteria.
<Topcoat composition>
In a 2 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, 60 g of 2-hydroxyethyl acrylate (hereinafter referred to as 2-HEA), and 3.0 g of n-dodecyl mercaptan were added, and the flask was heated to 55 ° C. while the air in the flask was replaced with nitrogen. Then, 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) as a polymerization initiator 025 g was added under stirring and mixed uniformly.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., 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. Then, after cooling to 55 ° C., the temperature was maintained and 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 the initiator is charged, 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 acrylic syrup A. This syrup had a monomer concentration of 50% and a polymer concentration of 50%, and the weight average molecular weight by GPC of the polymer was 50,000. 1,6 hexanediol diacrylate (trade name Light Acrylate 1,6HX-A; manufactured by Kyoeisha Chemical Co., Ltd .: hereinafter referred to as HX-A) to 1.0 part by mass (100 parts by mass of the monomer mixture) 18. 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) 8 parts by mass, silica particles (trade name Typaque R-972; manufactured by Tegusa: hereinafter referred to as R-972) 6.0 parts by mass, peroxide-based initiator: cumyl-peroxy-neodecanoate (trade name Park Mill ND; Nippon Oil & Fat Co., Ltd .: 2.0 parts by mass, hereinafter referred to as initiator ND, 1,1,3,3-tetramethylbutyl-peroxy-2-ethylhexanoate (trade name Perocta O; Nippon Oil & Fats ( 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) 12 parts by mass was added and mixed and defoamed to prepare thermopolymerizable composition A-1.

<Application conditions>
Drying conditions: 120 ° C. × 10 minutes Application amount (g / m ² ): 80 μm (after drying)
Application method: Bar coat method

<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.

(11) Evaluation of printability of release film <Print deviation>
A roll-shaped film sample was unwound at a tension of 8 MPa, subjected to four-color gravure printing, and then dried at 180 ° C. for 30 seconds to prepare a pattern printing film. The printing misalignment of the resulting pattern printing film was visually observed and judged according to the following criteria.
<Criteria>
A: No occurrence of printing misalignment (elongation and shrinkage of the film) is observed. O: Slight printing misalignment is observed, but is practically usable level. X: Printing misalignment is observed, and practically unusable. (failure)
Among the above judgment criteria, “◯” or more is a level that can be used practically without any problem.

<Flatness (single tarmi)>
The pattern printed film prepared above was drawn out to a length of 2 m from the roll, visually observed for the flatness of the one piece, and judged according to the following criteria.
<Criteria>
◎: The flatness of the piece tarmi is hardly observed on the pattern printing film. ○: The piece tarmi is slightly observed but is practically usable. ×: The piece tarmi is slightly conspicuous and the sheet-like appearance is poor. (failure)
Among the above judgment criteria, “◯” or more is a level that can be used practically without any problem.

(12) Evaluation of moldability of release film The pattern printing film prepared in (11) above is continuously molded at a rate of 100 pieces / min into a cylindrical shape having a bottom diameter of 50 mm and a depth of 5 mm using a male and female mold. did. The state of the obtained sample was visually observed and judged according to the following criteria.
<Criteria>
A: 95 or more out of 100 films are uniformly formed without tearing of the film. O: 80 or more of 100 films are uniformly formed without generating a film tear. X: 21 out of 100 films. Film breakage occurs at more than one piece, and many defective parts are observed. Among the above judgment criteria, ○ or more is a level that can be used practically without any problem.

(13) Low glossiness of transfer molded products (practical property substitution evaluation)
The glossiness was measured according to the method of JIS-Z-8741 using a gloss meter “VG-107 type” manufactured by Nippon Denshoku Co., Ltd. at the bottom of the sample film obtained in (12) above. . The reflectance of the sample was determined based on the reflectance of the black standard plate at an incident angle and a reflection angle of 60 degrees, and the gloss was determined. The determination was made according to the following criteria.
<Criteria>
：: 0 or more and less than 20 ○: 20 or more and less than 30 ×: 30 or more Among the above criteria, ◯ or more is a level that can be used practically without any problem.

(14) Evaluation of transmission density (OD) of release film The transmission density of the sample film was measured using a Macbeth transmission densitometer “TD504”.

(15) Visibility evaluation of release film (practical property substitution evaluation)
After pasting the sample film on the surface of the molded article subjected to character printing, whether or not the character can be read through the sample film was determined according to the following criteria.
<Criteria>
○: Characters can be read ×: Characters are difficult to read In the above criteria, ○ is a level that can be used practically without problems.

(16) Comprehensive evaluation Comprehensive evaluation was performed on the release film according to the following criteria.
<Criteria>
○: All items of releasability, printability, moldability, low gloss, and visibility are ○
Δ: At least one item among the releasability, printability, moldability, low gloss, and visibility is Δ
×: At least one of the releasability, printability, moldability, low gloss, and visibility is ×
Among the above judgment criteria, Δ or more is a level that can be used practically without any problem.

Examples 1, 3-7:
<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 0.66 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (A). The intrinsic viscosity of this polyester was 0.66.

<Manufacture of polyester (B)>
In the production method of polyester (A), polyester (A) was added except that after adding ethyl acid phosphate, organic particles of an alkyl methacrylate-styrene copolymer having an average particle diameter of 4.5 μm were added to 10% by weight. A polyester (B) was obtained using a method similar to the production method of A). The obtained polyester (B) had an intrinsic viscosity of 0.66.

<Manufacture of polyester (C)>
In the production method of the polyester (B), the addition particles are amorphous silicaum particles having an average particle diameter of 2.5 μm, and the content with respect to the polyester is 0.6% by weight. Polyester (C) was obtained using the method described above. The obtained polyester (C) had an intrinsic viscosity of 0.66.

<Manufacture of polyester (D)>
In the method for producing polyester (A), polyester (D) is produced using the same method as the method for producing polyester (A) except that 100 parts by weight of dimethyl terephthalate and 22 parts by weight of isophthalic acid are used as the dicarboxylic acid component. Obtained. The obtained polyester (D) had an intrinsic viscosity of 0.60.

<Manufacture of film>
A mixed raw material obtained by mixing the polyester (A) chip and the polyester (B), (C), and (D) chips in the proportions shown in Tables 1 and 2 is used as a raw material for the outermost layer (surface layer) and the intermediate layer. Each was supplied to two extruders, 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, the film was stretched 3.2 times in the longitudinal direction at 95 ° C., and then a coating solution composed of the composition described in Table 1 below was applied so that the coating amount (after drying) was 0.030 g / m ² . Thereafter, the film was subjected to a preheating step in a tenter and subjected to transverse stretching of 4.2 times at 110 ° C., followed by heat treatment at 250 ° C. for 10 seconds, and 10% relaxation was added in the width direction. The total thickness was 50 μm, and the thickness of each layer was 5 μm / 40 μm / 5 μm.

Examples of compounds constituting the release layer are as follows.
(Compound example)
Fluorine compound (a1):
In a glass reaction vessel, CF3 (CF2) nCH2CH2OCOCH = CH2 (n = 5 to 11, n average = 9) 80.0 g, acetoacetoxyethyl methacrylate 20.0 g, dodecyl mercaptan 0 0.8 g, 354.7 g of deoxygenated pure water, 40.0 g of acetone, 1.0 g of C16H33N (CH3) 3Cl and 3.0 g of C8H17C6H4O (CH2CH2O) nH (n = 8) were added, and azobisisobutylamidine dihydrochloride 0. 5 g was added and a copolymerization reaction was carried out at 60 ° C. for 10 hours while stirring under a nitrogen atmosphere to obtain a copolymer emulsion.

Long chain alkyl compound (a2):
To a four-necked flask, 200 parts of xylene and 600 parts of otadecyl isocyanate were added and heated with stirring. From the time when xylene began to reflux, 100 parts of polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 88 mol% was added in small portions over a period of about 2 hours. After the addition of polyvinyl alcohol, the reaction was completed by further refluxing for 2 hours. When the reaction mixture was cooled to about 80 ° C. and added to methanol, the reaction product was precipitated as a white precipitate. This precipitate was filtered off, added with 140 parts of xylene, and heated to dissolve completely. After repeating the operation of adding methanol again to precipitate several times, the precipitate was washed with methanol and dried and ground.

-Wax (a3):
An emulsification facility with an internal volume of 1.5 L equipped with a stirrer, thermometer, temperature controller, melting point 105 ° C., acid value 16 mgKOH / g, density 0.93 g / mL, average molecular weight 5000 oxidized polyethylene wax 300 g, ion-exchanged water 650 g 50 g of decaglycerin monooleate surfactant and 10 g of 48% potassium hydroxide aqueous solution were added and replaced with nitrogen, then sealed, stirred at 150 ° C for 1 hour at high speed, cooled to 130 ° C, and passed through a high-pressure homogenizer at 400 atm. And cooled to 40 ° C. to obtain a wax emulsion.

-Thermosetting compound (b):
Crosslinkable resin of alkylol melamine / urea copolymer (Beckamine manufactured by Dainippon Ink and Chemicals: “J101”)

-Binder polymer (c1):
Polyvinyl alcohol binder polymer (c2) having a saponification degree of 88 mol% and a polymerization degree of 500:
Acrylic resin (Nicazole manufactured by Nippon Carbide Industries: RX7013ED)

  The obtained release film had good printing misalignment, flatness and formability, and was excellent in low gloss and visibility.

Example 2:
In Example 1, a release film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the weight ratio of polyesters A and B was 7: 3.

Comparative Example 1:
A film was obtained in the same manner as in Example 1 except that the release layer was not provided in Example 1. The properties were good except that the releasability was insufficient.

Comparative Example 2:
A film was obtained in the same manner as in Example 1 except that the type of the release layer was changed in Example 1. The properties were good except that the releasability was insufficient.

Comparative Example 3:
In Example 1, polyester B and polyester D were blended at a weight ratio of 1: 4, melted in an extruder, supplied to a single-layer die, extruded into a film, and cast on a cooling drum at 35 ° C. Then, it was cooled and solidified to produce an unstretched film. Next, after preheating with a heating roll at 80 ° C., using an infrared heater and a heating roll in combination, the film is stretched 3.0 times in the vertical direction between 85 ° C. rolls, and then charged to a thickness of 5 μm with a gravure coater on one side of the film. After performing the prevention coating, the film end is held by a clip and guided into a tenter, and stretched 3.5 times in the horizontal direction while being heated at a temperature of 100 ° C., and subjected to a heat treatment at 195 ° C. for 10 seconds, A polyester film composed of a single layer film having a thickness of 50 μm was obtained by relaxing 3% in the width direction at 170 ° C. The properties of the obtained film were as shown in Table 1. From this result, the print misalignment in the longitudinal direction and the misalignment in the width direction due to the width shrinkage, which are considered to be caused by the lack of the 5% elongation stress in the vertical direction, are conspicuous. Furthermore, since the vertical shrinkage was somewhat large, a slight deterioration in flatness was observed. In terms of moldability, a good molded product was obtained without any problem of mold breaking.

Comparative Example 4:
In Comparative Example 3, the polyester was adjusted to a thickness of 50 μm in the same manner as in Comparative Example 1 except that only the vertical magnification was increased from 3.0 to 3.5 and the relaxation in the width direction was changed from 3% to 4%. A film was obtained. Although the printability of the obtained film improved, flatness deterioration was observed due to an increase in the vertical shrinkage rate. As for the moldability, a good molded product was obtained without any problem as in Comparative Example 1. However, the visibility was poor, and the printed pattern on the surface of the opposite molded product to be bonded was not visible through the release film.

Comparative Example 5:
In Example 1, a 50 μm thick polyester film was prepared in the same manner as in Example 1 except that the stretching in the longitudinal direction was 3.8 times, heat treatment was performed at 230 ° C. for 10 seconds, and then 3% was relaxed in the width direction at 190 ° C. Obtained. Although the printing deviation of the obtained film was very good, many breaks occurred in the formability, and the molded article was partially observed to have a defect of lack of clear printing at the corner. Furthermore, the visibility was poor, and the printed pattern on the surface of the counterpart molded product to be bonded was not visible through the release film.

Comparative Example 6:
A polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the raw material composition supplied to the surface layer in Example 1 was changed to 7: 3 by weight ratio of polyesters A and C. The obtained film was inferior in low gloss, and the target film excellent in low gloss could not be obtained.

The release film of the present invention can be suitably used, for example, for producing a molded simultaneous transfer foil.

Claims (2)

A release film having a release layer on one side of the film. The heat shrinkage in the vertical direction of the release film at 180 ° C. for 5 minutes is 3.0% or less, and the heat shrinkage in the horizontal direction is 0.5%. In the tensile test at 25 ° C., the 5% elongation stress in the longitudinal direction of the release film is 90 to 120 MPa, and the 100% elongation stress is 200 MPa or less in both the longitudinal and lateral directions. A release film having a thickness (Ra) in the range of 0.30 to 0.70 μm. 2. The release film according to claim 1, wherein the release film is used for producing a molded simultaneous transfer foil.