JP2013189493A - Mold release film and molding method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve moldability and mold releasability of a mold release film in thermoforming.SOLUTION: A mold release film includes a crosslinked resin layer formed of a crosslinked thermoplastic resin.

Description

  The present invention relates to a release film and a molding method using the release film.

  In recent years, as electronic devices have higher functions and smaller sizes, and their rapid spread, smaller electronic components have been demanded in large quantities and at low cost. Under such circumstances, in the thermal processing step of electronic parts, it is required that parts having smaller shapes can be produced in large quantities and with high productivity. For example, in the case of LED parts, the package form has changed from a larger shell type to a small thin reflector type, and in the future, a large number of LED chips will be mounted on a substrate and then packaged and separated into individual pieces. The overmold type is expected to dominate the mainstream. Under such circumstances, release films used in the thermal processing steps of these electronic components are increasingly required to have higher processability such as higher moldability and higher release characteristics.

  Conventionally, it has been proposed as a release film of a tetrafluoroethylene-ethylene copolymer and a release film used for molding a printed circuit board (Patent Document 1).

  Further, there is a release film composed of a base film and an auxiliary layer, the base film having a compressive elastic modulus at 175 ° C. of 50 MPa or more, and using a fluororesin for the auxiliary layer (Patent Document 2).

  A release film comprising a composition containing a polymer having a 4-methyl-1-pentene content of 80% by mass or more, wherein the composition has a melting point of 170 to 240 ° C., and a half-crystallization time of 70 to 220 seconds. A release film is also disclosed (Patent Document 3). There is also a release film made of a resin composition containing a crosslinked cyclic olefin polymer and an elastomer that is incompatible with the polymer (Patent Document 4).

JP 2001-206913 A JP 2001-250838 A JP 2006-70252 A JP 2011-178953 A

  However, none of the release films described above is necessarily sufficient.

  Specifically, in the film of the tetrafluoroethylene-ethylene copolymer of Patent Document 1, polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), and polyimide are expensive and are discarded. In some cases, the incineration process is very difficult.

  In the release films of Patent Documents 2 and 3, the release film has an excessively high modulus of elasticity. Therefore, in the thermoforming process of electronic parts, wrinkles enter the molded product, and the release film has a sufficient mold shape. Cannot be reproduced. Since the release film of Patent Document 5 also lacks flexibility, the shape of the mold may not be reliably reproduced. It is said that improvement can be achieved by blending an elastomer that is incompatible with the crosslinked cyclic olefin polymer, but the mold release film still cannot sufficiently reproduce the shape of the mold.

  As described above, the conventional release film has a low flexibility in the general thermal processing process, and the release film cannot stick to the mold shape accurately. There is a problem that a cocoon enters. It is said that the mold release property for molds etc. is obtained by the fact that the release film does not melt, but in the current thermal processing process that requires molding of small parts or complicated bonding and molding When implemented, the release film melts, so that there is a problem that the release property is not exhibited with good reproducibility. This is because the melting point of the resin used in the conventional release film is 170 ° C. or more, and the temperature during the heat processing such as adhesion, molding, curing, etc. is lower than the resin melting point of the release film. This is thought to be due to what is being done in

  Then, the subject of this invention is mainly aiming at the further improvement of the moldability and mold release property of a release film in thermoforming.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have made the present invention. That is, the present invention is as follows.
[1] A release film comprising a crosslinked resin layer formed from a crosslinked thermoplastic resin.
[2] When the melting point of the uncrosslinked thermoplastic resin is Tm (° C.), the storage elastic modulus of the release film at Tm + 20 (° C.) relative to the storage elastic modulus of the release film at Tm (° C.) The release film according to [1], wherein the ratio is 50% or more.
[3] The release film according to [1] or [2], wherein the uncrosslinked thermoplastic resin has a melting point Tm of 170 ° C. or lower.
[4] The release film according to any one of [1] to [3], further comprising a release layer provided on at least one surface side of the crosslinked resin layer.
[5] The release film according to any one of [1] to [4], wherein the thermoplastic resin is a chain polyolefin.
[6] The release film according to any one of [1] to [5], wherein the release film has a gel fraction of 1% by mass to 80% by mass.
[7] The release film according to any one of [1] to [6], wherein the thermoplastic resin is crosslinked by electron beam irradiation.
[8] The release film according to any one of [1] to [8], which is for LED chip compression sealing molding.
[9] A molding method comprising thermoforming a molding material at a temperature higher than the melting point Tm of the uncrosslinked thermoplastic resin using the release film according to any one of [1] to [8]. .

  The release film according to the present invention includes polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), poly-4-methyl-1-pentene resin film, a crosslinked cyclic olefin polymer, and a crosslinked cyclic olefin polymer. Unlike conventional release films containing unionized elastomers and elastomers that are incompatible with the polymer, they exhibit heat resistance and release properties based on high melting point resins, whereas crosslinked thermoplastic resins are used. Use. Such a release film can have excellent heat resistance, flexibility, and release properties when used in a thermoforming process. Even in the processing conditions in the thermoforming process in the temperature range above the melting point of the thermoplastic resin, it is difficult for perforation, film breakage, etc. due to resin melting, and the flexibility of the release film can be further exhibited.

  According to the release film of the present invention, excellent heat resistance, flexibility and release properties can be exhibited during the thermoforming process. Therefore, in particular, the sealing process of semiconductors such as IC chips and LEDs of electronic components, the molding process in the production of multilayer printed wiring boards, the laminating hot pressing process, and the coverlay application process in the production of printed wiring boards, etc. It is useful in the thermal processing of electronic parts.

  Further, according to the release film of the present invention, even in a thermoforming process in a temperature range higher than the melting point of the thermoplastic resin, it is difficult for perforation or film breakage due to resin melting, and the release film exhibits further flexibility. Therefore, a molding method including thermoforming at a high temperature using a release film can be provided. Therefore, this method is suitable for thermoforming electronic parts and the like.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  The thermoplastic resin, which is the main component of the release film according to this embodiment, has a property of being elastic at room temperature and not easily deforming, but softening without causing a chemical reaction by heating, and solidifying again by cooling. . The thermoplastic resin is a synthetic resin that changes almost reversibly when heating and cooling are repeated and can be processed into various shapes. For example, as a thermoplastic resin, for example, polyolefin resin (polyethylene resin, polypropylene resin), polystyrene resin, methacrylic resin, polyvinyl chloride resin, polyamide resin, polycarbonate resin, polyester resin (polyethylene terephthalate) Resin, polybutylene terephthalate resin, etc.), and cellulose acetate resin.

  The thermoplastic resin which is the main component constituting the crosslinked resin layer of the release film according to this embodiment is crosslinked. From the viewpoint of ensuring good crosslinkability, flexibility, adhesion of the adherend and handleability, the thermoplastic resin is composed of ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene- At least one resin selected from the group consisting of aliphatic carboxylic acid ester copolymers, saponified ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate-acrylic acid ester copolymers, and polyolefin resins. Preferably there is.

  The ethylene-vinyl acetate copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and vinyl acetate. An ethylene-aliphatic unsaturated carboxylic acid copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acids. The ethylene-aliphatic unsaturated carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acid esters.

  The copolymerization can be performed by a known method such as a high pressure method or a melting method, and a multisite catalyst, a single site catalyst, or the like can be used as a catalyst for the polymerization reaction. Moreover, in the said copolymer, the bond shape of each monomer is not specifically limited, The polymer which has bond shapes, such as a random bond and a block bond, can be used.

  Examples of the ethylene-aliphatic unsaturated carboxylic acid copolymer include an ethylene-acrylic acid copolymer (hereinafter abbreviated as “EAA”) and an ethylene-methacrylic acid copolymer (hereinafter, “EMAA”). Abbreviated). Examples of the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include an ethylene-acrylic acid ester copolymer and an ethylene-methacrylic acid ester copolymer. Here, as acrylic acid ester and methacrylic acid ester, ester with C1-C8 alcohols, such as methanol and ethanol, is used suitably. These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers. Examples of the multi-component copolymer include a copolymer obtained by copolymerizing at least three types of monomers selected from ethylene, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester. In the ethylene-aliphatic unsaturated carboxylic acid copolymer, the proportion of the aliphatic unsaturated carboxylic acid in all monomers constituting the copolymer is preferably 3 to 35% by mass.

  Examples of the saponified ethylene-vinyl acetate copolymer include a partially saponified product of ethylene-vinyl acetate copolymer. Examples of the saponified ethylene-vinyl acetate-acrylic acid ester copolymer include a partially or completely saponified product of an ethylene-vinyl acetate-acrylic acid ester copolymer.

  As the polyolefin resin, a chain polyolefin is preferable, and a polyethylene resin, a polypropylene resin, and a polybutene resin are more preferable.

  Here, the polyethylene resin refers to a homopolymer of ethylene or a copolymer of ethylene and one or more other monomers. The polypropylene resin refers to a homopolymer of propylene or a copolymer of propylene and one or more other monomers. Examples of the polyethylene resin include polyethylene and ethylene-α-olefin copolymers.

  Examples of the polyethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and linear very low density polyethylene (referred to as “VLDPE” and “ULDPE”). In the case of a release film used for LED sealing, the molding temperature cannot be easily changed because the curing of the silicone resin also uses heat during molding. For this reason, if a very high level of molding is required, the mold release film should be thin, or a thermoplastic resin with a low melting point should be selected, and heat sufficient to enable moldability without changing the curing temperature. Can be supplied. When a polyethylene release film is used, the density of the thermoplastic resin constituting the release film is reduced by lowering the density of LDPE than HDPE, LLDPE than LDPE, VLDPE than LLDPE, and ULDPE than VLDPE. It becomes possible to lower the melting point.

  The ethylene-α-olefin copolymer is preferably a copolymer composed of ethylene and at least one selected from α-olefins having 3 to 20 carbon atoms, and ethylene and α having 3 to 12 carbon atoms. -More preferably, it is a copolymer comprising at least one selected from olefins. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-decene and 1-dodecene. , 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane, and the like, and these can be used alone or in combination of two or more. Moreover, it is preferable that the ratio (based on preparation monomer) of the alpha olefin in all the monomers which comprise a copolymer is 6-30 mass%. Furthermore, the ethylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  As the ethylene-α-olefin copolymer, a copolymer of ethylene and at least one comonomer selected from propylene comonomer, butene comonomer, hexene comonomer and octene comonomer is generally easily available and is preferably used. it can.

The polyethylene resin can be polymerized using a known catalyst such as a single-site catalyst or a multi-site catalyst, and is preferably polymerized using a single-site catalyst. From the viewpoint of flexibility, the polyethylene resin preferably has a density of 0.860 to 0.950 g / cm ³ , more preferably 0.870 to 0.945 g / cm ³ , and 0.870 to 0.970 g / cm ^3. More preferably, it is 0.940 g / cm ³ . These same types of polyethylene may be used alone or in combination.

  The polyethylene resin preferably has an MFR (190 ° C., 2.16 kg) of 0.5 g / 10 min to 30 g / 10 min, from 0.8 g / 10 min to 30 g / 10 min, from the viewpoint of processability of the release film. More preferably, it is 1.0 g / 10 min to 25 g / 10 min.

  As the polyethylene resin, a polyethylene copolymer in which the crystal / amorphous structure (morphology) is controlled in nano order can also be used.

  Examples of the polypropylene-based resin include polypropylene, propylene-α-olefin copolymer, and terpolymer of propylene, ethylene, and α-olefin. The propylene-α-olefin copolymer refers to a copolymer composed of at least one selected from propylene and α-olefin. The propylene-α-olefin copolymer is preferably a copolymer composed of propylene and at least one selected from ethylene and an α-olefin having 4 to 20 carbon atoms. Propylene, ethylene and 4 to 8 carbon atoms are preferable. A copolymer comprising at least one selected from α-olefins is more preferable. Examples of the α-olefin having 4 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene. , 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like, and these can be used alone or in combination.

  The content ratio of ethylene and / or α-olefin in all monomers constituting the propylene-α-olefin copolymer (based on charged monomers) is preferably 6 to 30% by mass. Furthermore, the propylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  As the propylene-α-olefin copolymer, a copolymer of propylene and at least one comonomer selected from ethylene comonomer, butene comonomer, hexene comonomer and octene comonomer is generally easily available and is preferably used. it can.

  The polypropylene resin can be polymerized using a known catalyst such as a single site catalyst or a multisite catalyst, and is preferably polymerized using a single site catalyst.

From the viewpoint of cushioning properties, the polypropylene resin preferably has a density of 0.860 to 0.920 g / cm ³ , more preferably 0.870 to 0.915 g / cm ³ , and 0.870 to More preferably, it is 0.910 g / cm ³ . When the density is 0.920 g / cm ³ or less, the cushioning property tends to be good. Note that if the density exceeds 0.920 g / cm ³ , the transparency may be lowered.

  The polypropylene resin preferably has an MFR (230 ° C., 2.16 kgf) of 0.3 g / 10 min to 15.0 g / 10 min, from 0.5 g / 10 min to 12 g / min, from the viewpoint of processability of the release film. 10 min is more preferable, and 0.8 g / 10 min to 10 g / 10 min is still more preferable.

  As the polypropylene resin, a polypropylene copolymer having a crystal / amorphous structure (morphology) controlled in nano order can be used. Polypropylene resins include copolymers of propylene and α-olefins such as ethylene, butene, hexene and octene, or ternary copolymers of propylene and ethylene and α-olefins such as butene, hexene and octene. A polymer etc. can be used conveniently. These copolymers may be in any form such as a block copolymer, a random copolymer, etc., preferably a random copolymer of propylene and ethylene, or a random copolymer of propylene, ethylene and butene. is there.

  The polypropylene resin may be not only a resin polymerized with a catalyst such as a Ziegler-Natta catalyst, but also a resin polymerized with a metallocene catalyst, for example, syndiotactic polypropylene or isotactic polypropylene can be used. .

  The proportion of propylene in all monomers constituting the polypropylene resin (based on the charged monomers) is preferably 60 to 80% by mass. Furthermore, from the viewpoint of excellent heat shrinkability, the propylene content ratio (based on the charged monomer) in all monomers constituting the polypropylene resin is 60 to 80% by mass, and the ethylene content ratio (based on the charged monomer) is 10 to 30. A ternary copolymer having a butene content ratio (based on charged monomers) of 5 to 20% by mass is preferable. As the polypropylene-based resin, a resin obtained by uniformly finely dispersing a rubber component having a high concentration of 50% by mass or less with respect to the total amount of the polypropylene-based resin can also be used.

  When the resin constituting the release film contains a polypropylene resin, characteristics such as hardness and heat resistance tend to be further improved.

  Since the polybutene resin is particularly excellent in compatibility with the polypropylene resin, it is preferably used in combination with the polypropylene resin for the purpose of adjusting the hardness and waist of the release film. The polybutene resin is crystalline, is a copolymer of at least one selected from butene, ethylene, propylene, and an olefin compound having 5 to 8 carbon atoms, and all of which constitutes the polybutene resin. A high molecular weight polybutene resin in which the butene content in the monomer is 70 mol% or more can be suitably used. The polybutene resin preferably has an MFR (190 ° C., 2.16 kg) of 0.1 g / 10 min to 10 g / 10 min. Moreover, it is preferable that a Vicat softening point is 40-100 degreeC. Here, the Vicat softening point is a value measured according to JIS K7206-1982.

  The release film according to the present embodiment is characterized in that the thermoplastic resin which is the main component as described above is crosslinked. By crosslinking, the thermoplastic resin does not melt and flow even when the melting point is higher than the melting point of the thermoplastic resin. Therefore, it is possible to prevent tearing due to the opening of the film or the melting of the resin. By using a cross-linked thermoplastic resin in the thermoforming process in an environment above the melting point, unprecedented flexibility can be exhibited, so that complicated mold shapes can be stably followed, so that mold reproducibility is excellent.

  Any known method may be used to crosslink the thermoplastic resin. For example, the thermoplastic resin can be cross-linked by irradiation with ionizing radiation such as α-rays, β-rays, γ-rays, neutron rays, and electron beams, or by using peroxide.

  Examples thereof include a crosslinking treatment with an organic peroxide and a crosslinking treatment by irradiation with ionizing radiation (electron beam, γ ray, ultraviolet ray, etc.), and these may be used in combination. The electron beam cross-linking treatment is preferable because the cross-linking component (so-called gel fraction) can be adjusted according to the electron beam irradiation conditions (irradiation environment: temperature and humidity, irradiation conditions: irradiation intensity, irradiation density, irradiation time). .

  The gel fraction is the ratio of the degree of crosslinking determined by the calculation formula described later. In the case of crosslinking using an electron beam, the degree of crosslinking varies depending on the type of resin and the environment at the time of irradiation, but it can be controlled to a desired gel fraction by the irradiation density and irradiation intensity of the electron beam.

  In particular, when polyolefin resin is used as the thermoplastic resin for the release film, when the electron beam irradiation conditions such as resin, irradiation temperature, and humidity are controlled, the reproducibility is relatively good and the gel fraction is within a certain range. Can be.

  For example, generally, in the case of low density polyethylene (LDPE) and ethylene-vinyl acetate copolymer resin (EVA), the irradiation density starts to be cross-linked from 20 kGy, and the gel fraction increases as the irradiation density increases. Further, when the irradiation density exceeds 200 kGy, the resin may be deteriorated or decomposed, and it is important to control the desired gel fraction in terms of ensuring the stability of physical properties.

  The gel fraction of a release film is 1-80 mass% on the basis of the mass of the whole release film, for example. When the gel fraction is 1% by mass or more, sufficient crosslinking characteristics can be obtained, and even when a release film is used at a mold temperature equal to or higher than the melting point of the thermoplastic resin before crosslinking, A hole can be prevented more effectively. Moreover, if the gel fraction is 80% by mass or less, the flexibility of the release film is particularly good. Accordingly, good mold reproducibility can be obtained. The gel fraction is preferably 1 to 70% by mass, and more preferably 1 to 65% by mass.

  Here, the melting point of the thermoplastic resin will be described. In the present embodiment, the melting point of the thermoplastic resin means the melting point before crosslinking.

  When the release film has a layer structure or is blended with a resin, the storage modulus of the release film is based on the melting point of the resin that has the highest usage ratio among the resins that make up the release film. Etc. are controlled.

  The release film according to the present embodiment maintains a storage elastic modulus of 50% or more at a temperature 20 ° C. higher than the melting point Tm of the thermoplastic resin before cross-linking compared to the melting point Tm of the thermoplastic resin. This indicates that the resin constituting the release film does not melt and flow in the temperature range above the melting point. The melting point is also calculated when the storage elastic modulus is measured. However, in the temperature range above the melting point, the resin molecular chain slips out, so that the storage elastic modulus is extremely lowered. This means that since the molecular chain is not fixed, it melts to generate a resin flow and cannot maintain a stable film state. On the other hand, the crosslinking treatment is to bond the molecular chains, and the crosslinking treatment prevents the molecular chains from slipping out even in the melting temperature range. Therefore, a stable film state can be maintained even in the melting temperature range. That is, the storage elastic modulus at a temperature 20 ° C. higher than the melting point is maintained at 50% or more as compared with the storage elastic modulus at the melting point, so that the molecular chain does not slip out even in the melting temperature range exceeding the melting point. Indicates that it is in a state. The storage elastic modulus at a temperature 20 ° C. higher than the melting point is preferably 60% or more, more preferably 80% or more with respect to the storage elastic modulus at the melting point.

  In the case of crosslinking by ionizing radiation, the storage elastic modulus can be adjusted by irradiation intensity (acceleration voltage) and irradiation density. The irradiation intensity (acceleration voltage) indicates how deep electrons can reach in the thickness direction of the sheet, and the irradiation density indicates how many electrons are irradiated per unit area. In the case of crosslinking with an organic peroxide, the storage elastic modulus can be adjusted by the content of the organic peroxide.

  You may utilize the difference of the crosslinking degree by the kind of resin, and the effect of the crosslinking promotion or crosslinking suppression by a transfer agent etc. In the case of crosslinking by irradiation with ionizing radiation, a method of irradiating the release film with ionizing radiation such as α-rays, β-rays, γ-rays, neutron beams, electron beams, and the like can be used. The acceleration voltage of ionizing radiation such as an electron beam may be selected according to the thickness of the release film. For example, in the case of a thickness of 50 μm, an acceleration voltage of 30 kV or more is required when the entire release film is crosslinked. is there. The acceleration voltage of ionizing radiation such as an electron beam can be appropriately adjusted according to the resin layer subjected to the crosslinking treatment. The irradiation dose of ionizing radiation varies depending on the resin used, but is generally less than 3 kGy. , It tends to be difficult to uniformly crosslink the entire release film.

  When the thermoplastic resin is crosslinked with an organic peroxide, thermal crosslinking is performed by blending or impregnating the organic peroxide in the resin as a crosslinking agent. In this case, an organic peroxide having a half-life at 100 to 130 ° C. of 1 hour or less is preferable. Examples of organic peroxides that have good compatibility and have the above half-life include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1 -Bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane and the like. The content of the organic peroxide is preferably 0 to 10% by mass and more preferably 0 to 5% by mass with respect to the resin constituting the release film. A release film containing an organic peroxide can provide a good release film because the sheet is softened without causing perforation even in a temperature range above the melting point, as in the case of an electron beam cross-linked release film. Has the advantage.

  As described above, “crosslinking” includes a method of irradiating with ionizing radiation and a method of using an organic peroxide. From the viewpoint that the method of crosslinking by irradiation with ionizing radiation can adjust the gel fraction. ,preferable. In addition, even if it is a case where a release film has any structure of the single layer structure or multilayer structure mentioned later, the said gel fraction is the average gel fraction (all layer gel fraction) of the whole release film. Mean value.

  170 degreeC or less may be sufficient as melting | fusing point of the uncrosslinked thermoplastic resin which forms the release film which concerns on this embodiment.

  The thermoplastic resin having a melting point of 170 ° C. or lower is the thermoplastic resin exemplified above, that is, among the synthetic resins that can be reversibly raised and processed into various shapes when repeated heating and cooling. The resin whose melting point by a measuring method is 170 degrees C or less is shown. The melting point of the uncrosslinked thermoplastic resin can be measured, for example, by DSC measurement. Specifically, 8 to 10 mg of an uncrosslinked thermoplastic resin sample is sealed in an aluminum pan, heated from -20 ° C to 200 ° C at a rate of 5 ° C / min, and then at a rate of 5 ° C / min at -20. The melting point can be measured by a method in which the temperature is lowered to 200 ° C., the temperature is raised again to 200 ° C. at a rate of 5 ° C./min, and the endothermic temperature at the second temperature rise is used as the melting point.

  For example, polyethylene resin (HDPE, LLDPE, LDPE, etc.), polypropylene resin (PP), polybutene-1 resin (PB), ethylene-vinyl acetate copolymer resin (EVA), ethylene-methyl methacrylate copolymer Resin (EMA etc.), ethylene-vinyl alcohol copolymer resin (EVOH etc.) and other polyolefin resin modified products (PO modified products), polyethylene terephthalate (modified) resins (PET etc.) melting point 170 Satisfies the following conditions.

  Polyolefin, which is a thermoplastic resin, is useful because it satisfies the above-mentioned melting point conditions, is inexpensive, and has a property of being easily cross-linked by an electron beam. Among them, polyethylene resins (HDPE, LLDPE, LDPE, etc.), polypropylene resins (PP), polybutene-1 resins (PB), ethylene-vinyl acetate copolymer resins (EVA), ethylene-methyl methacrylate copolymer resins (EMA etc.) are listed as preferred resins.

  Particularly in the case of sealing semiconductors such as LEDs, the processing temperature for thermally processing (thermoforming) a silicone resin used as an LED sealing agent using a mold is 120 to 130 ° C. from the viewpoint of moldability and curing. In the case of placing importance on the function of flexibility as the resin to be used, it is preferable from the viewpoint of moldability that the melting point of the resin to be used is equal to or lower than 120-130 ° C. Therefore, as the resin used, the above-described polyethylene resins (HDPE, LLDPE, LDPE, etc.), ethylene-polypropylene copolymer resin (EPC), polybutene-1 resin (PB), ethylene-vinyl acetate copolymer resin (EVA) ), Ethylene-methyl methacrylate copolymer resin (such as EMA) and the like.

  Furthermore, since these resins are cross-linked and can form a film without a hole or the like at 120-130 ° C. or higher, by performing the cross-linking treatment, the temperature is higher than the melting point of the base material (uncrosslinked thermoplastic resin). Even in the heat processing conditions of the region, it can have excellent heat resistance, flexibility and releasability.

  In the above, the thermoplastic resin which comprises the release film of this embodiment was demonstrated. Next, the structure of the release film of this embodiment is demonstrated.

  The release film of this embodiment mainly has a cross-linked resin layer formed from the above-described cross-linked thermoplastic resin. The release film of the present embodiment may have a single layer configuration or a multilayer configuration, if necessary. Also, regarding the resin of each layer, even if it is a single type of resin, as a mixed resin by blending or the like, if necessary. Also good.

  In the case of a multilayer structure, the release film may have a release layer provided on at least one surface of the crosslinked resin layer. In particular, industrially, since the above-described thermal processing step for electronic components is a repetitive operation, it is preferable to provide a release layer.

  It is preferable that the release film has a release layer having a release function for continuously peeling between the mold and the film on the surface on the mold side, and between the film and the molding material (resin etc.) It is more preferable to have a release layer having a release function. In order to make continuous peeling between the film and the resin and between the mold and the film, a release film having release layers on both surfaces is more preferable.

  For example, in the case of sealing a semiconductor such as an LED, the silicone resin used as an LED sealant is directly contacted with the mold during the process of molding and curing the silicone resin by thermal processing using a mold. In order to avoid this, a film made of fluorine resin or 4-methyl-1-pentene resin is usually used as a release layer.

  The release film of the present embodiment is useful as a release film used between the mold for heat transfer and molding and the silicone resin to be molded and cured as described above, and realizes repeated operations. Therefore, in order to make the peeling between the film and the resin and between the mold and the film continuous, as a release layer having a release function added to both surface layers, a fluororesin or a 4-methyl-1-pentene resin. A release film using this film can be obtained.

  The release layer having a release function may be applied using any known method such as resin coating, lamination, and bonding. Coating of fluorine resin such as PVDF, bar coating, etc., spray coating of silicon oil or silicone resin solution, lamination by coextrusion of fluorine resin such as ETFE, etc. Fluorine resin film such as ETFE already filmed Although lamination by dry lamination, etc. can be mentioned, it may be appropriately selected in terms of cost and performance.

  The cross-linked resin layer containing the cross-linked thermoplastic resin, which is the main component of the release film, is more preferably 40% by mass or less, and even more preferably 30% by mass of one or more other resins as long as the original properties are not impaired. % Or less, and more preferably 25% by mass or less.

  Although it does not specifically limit with other resin, For example, ethylene-vinyl acetate copolymer and its partially saponified product, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, ethylene-cyclic polyethylene random copolymer, ethylene-cyclic Polyethylene block copolymer, ionomer, high-pressure low-density polyethylene, highly branched ethylene polymer polymerized by transition metal catalyst (branching degree: 5-110 groups / 1000 carbons), styrene-conjugated diene copolymer and the copolymer Hydrogenated at least part of the above, or those obtained by modifying these resins by acid modification, etc., crystalline 1,2-polybutadiene, other petroleum resins such as hydrogenated polydicyclopentadiene, hydrogenated polyterpene, etc. Resins used for layers other than the target layer are listed.

  An ultraviolet absorber, an antioxidant, a discoloration inhibitor, and the like can be added to the release film in the present embodiment as long as the characteristics are not impaired. The addition amount is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total amount of resin to be added.

Examples of the ultraviolet absorber include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-5-sulfobenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2,2′-dihydroxy-4. , 4′-dimethoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and the like. Examples of the antioxidant include phenol-based, sulfur-based, phosphorus-based, amine-based, hindered phenol-based, hindered amine-based, and hydrazine-based antioxidants. These ultraviolet absorbers, antioxidants, discoloration inhibitors and the like are preferably added in an amount of 0 to 10% by mass, more preferably 0 to 5% by mass, in the resin constituting the release film. When added to an ethylene-based resin, adhesiveness can be further imparted by mixing a resin having a silanol group into a master batch. The addition method is not particularly limited, and examples thereof include a method of adding to a molten resin in a liquid state, directly kneading and adding to the target resin layer, and applying after sheeting.
In addition, when taking a multi-layer structure, it makes the whole object.

  The release film preferably has a thickness of 5 to 2000 μm, more preferably 10 to 1500 μm, and still more preferably 15 to 800 μm. If the thickness is less than 5 μm, from the viewpoint of workability, there is a tendency to cause a problem in strength such as tearing when contacting any corner. On the other hand, when the thickness exceeds 2000 μm, problems such as a decrease in productivity and poor shape reproducibility of the mold tend to occur. In the case of a release film having a multilayer structure, the total thickness is preferably within the above range.

  The release film of this embodiment has been described above. The use which can exhibit the effect of the release film of this embodiment effectively is demonstrated.

  The release film of this embodiment is useful for the heat processing step of an electronic component. Here, the thermal processing process of electronic components is the heat at the time of semiconductor encapsulation such as IC chips and LEDs, at the time of molding processing at the time of multilayer printed wiring board manufacturing, at the time of laminating hot pressing, at the time of applying the coverlay at the time of printed wiring board manufacturing. The process of performing bonding, molding, curing, etc. using the above.

  In these processes, the energy supply required for bonding, molding, curing, etc. is usually supplied as heat through the mold, but bonding and molding used in the thermoforming process of the heated mold and electronic parts In addition, a mold release film is interposed between a resin such as a cure and other molding materials such as a substrate resin to prevent direct contact between the mold and the molding material, and the mold becomes dirty with the resin. In order to prevent this, the release film of this embodiment is useful.

  And since the release film of this embodiment has a crosslinked thermoplastic resin as a main component, it has flexibility without causing problems such as opening even when the processing temperature is higher than the melting point of the uncrosslinked thermoplastic resin. The function of a release film with good mold reproducibility is demonstrated. Furthermore, the release layer provided as needed also has an effect in repeated processing.

  Next, the example of the manufacturing method of the release film of this embodiment is demonstrated.

  The release film of the present embodiment can be produced by molding the above-described thermoplastic resin by a known method such as a tubular method, a T-die method, or a cast method. Even if the crosslinking treatment is performed in the unstretched original state for stretching, or after the stretching, the crosslinking treatment may be performed before being used in the heat processing step.

  The release layer may also be applied at the same time by direct co-extrusion during or after stretching in an unstretched original fabric.

  An example of a method for producing a release film is shown below. This does not limit the invention.

  For example, when a tubular biaxial stretching method is used, the resin composition is melt-extruded from an extruder and an annular die, and quenched with a coolant such as water to produce a non-stretched tube. This non-stretched tube is irradiated with an electron beam and subjected to a crosslinking treatment, and then the melting point (Tm) before crosslinking of the resin mainly constituted by heating with hot air or radiation heating of an infrastructure heater, melting point + 50 ° C. After heating the tube to the following temperature, air is introduced into the tube, and the tube is preferably stretched three times or more in the longitudinal direction and the transverse direction. And after taking up the film after extending | stretching with a take-up roll, a release film is obtained with a winder.

  As post-treatment, for example, heat setting for dimensional stabilization, corona treatment, plasma treatment, and lamination with other films may be performed. Moreover, a release layer may be laminated by a coating treatment using PVDF latex and dried.

  As an example of another method for producing a release film, a resin composition can be melt extruded using a T-die to obtain an unstretched film, and then crosslinked by irradiation with an electron beam to obtain a crosslinked film. The post-treatment described above may be similarly performed on the film thus obtained.

  The conditions in the case of heat-processing using the release film manufactured as mentioned above are demonstrated.

  In the case of thermal processing using a mold, it is necessary that the release film is bonded to the mold without any gap and the mold shape is molded with good reproducibility. In order to transfer the mold shape of the mold, it is necessary that the release film has sufficient elongation and the release film does not pierce through the mold. In order to exhibit this performance in high-temperature thermal processing, it is required that the release film has sufficient flexibility and that the resin does not partially open even if the resin dissolves. . As a method for realizing this environment, a thermoplastic resin is crosslinked, and a release film can be used in thermoforming under a temperature condition higher than the melting point of the uncrosslinked thermoplastic resin by crosslinking.

  As already described, the application of the release film of the present embodiment includes a semiconductor sealing process such as an IC chip and an LED chip, a lamination process using a multilayer printed wiring board, a coverlay application process using a flexible wiring board, and the like. Although not particularly limited, a particularly preferred application is the use of an LED chip compression sealing process. In the compression sealing process of the LED chip, the release film is temporarily fixed on the lower mold having the concave hemispherical cavity by vacuum drawing, and after setting the LED mounting substrate downward on the upper mold, each mold After aligning the position of the upper and lower molds so that the LED chip is placed in the center of the tee, pouring sealing resin as a molding material into the cavity, the upper and lower molds are closed, and the molding is performed by pressurizing and heating. Done. The encapsulating resin is not limited to an epoxy resin, a silicone resin, or the like, but a silicone resin is preferably used as an encapsulating resin for a high power LED that particularly requires heat resistance. It is preferable to perform the molding by pouring the silicone resin precursor into the cavity and performing a curing reaction by heating in the mold. From the viewpoint of productivity, the mold is opened after the primary curing reaction is performed in the mold. After the release film is peeled off, it is preferable to perform a secondary curing reaction in an oven or the like.

  Hereinafter, the present invention will be described with specific examples and comparative examples. However, the present invention is not limited to only these examples.

<Density of ethylene polymer>
The density of the ethylene polymer (resins A to E described later) was measured according to JIS-K-7112.

<MFR of ethylene polymer>
The MFR (melt flow index) of the ethylene polymer (resins A to E described later) was measured according to JIS-K-7210. In the case of an ethylene polymer, values measured under conditions of 190 ° C. and 21.18 N, and in the case of a polypropylene resin, values measured under conditions of 230 ° C. and 21.18 N were used.

<Gel fraction>
A sample (release film) was extracted for 12 hours in boiling p-xylene, and the ratio of the insoluble part calculated by the following formula was determined as the gel fraction. This gel fraction was used as a measure of the degree of crosslinking of the film.
Gel fraction (wt%) = (sample mass after extraction / sample mass before extraction) × 100

<Storage modulus>
Using a dynamic viscoelastic device “RSA-II type” manufactured by Rheometric Co., Ltd., a sample (from −50 ° C. to 180 ° C. at a temperature rising rate of 2 ° C./min at a vibration frequency of 1 Hz and a strain of 0.1% ( The viscoelasticity of the release film) was measured. In the obtained viscoelastic curve, the ratio of the storage elastic modulus at a temperature 20 ° C. higher than the melting point Tm of the uncrosslinked ethylenic copolymers (resins A to E described later) to the storage elastic modulus at Tm is as follows: It was calculated by the following formula.
Ratio (%) = (Storage modulus at melting point Tm / Storage modulus at temperature 20 ° C. higher than melting point Tm) × 100

<LED overmold test>
A release film is set on a lower mold having 100 concave hemispherical cavities with a diameter of 2 mm and a lower mold having 100 concave hemispherical cavities with a diameter of 1 mm, and the lower mold is temporarily placed by vacuuming. Fixed. A metal base substrate (substrate size: 100 mm × 100 mm) on which 100 LED chips are mounted by wire bonding is set downward on the upper mold, and then the upper mold is arranged so that the LED chips are arranged in the center of each cavity. And the position of the lower mold was adjusted. In this state, a liquid silicone resin is poured into the cavity, the upper mold and the lower mold are closed, and the mold is clamped under a pressure of 3.0 MPa under a heating condition of 130 ° C. × 5 minutes, and compression molded. Went. Thereafter, the mold was opened, and the moldability and releasability were confirmed according to the following criteria. As the silicone resin as the sealing resin, KER-2500 manufactured by Shin-Etsu Chemical Co., Ltd., which is a dimethyl silicone type silicone resin, was used.
Judgment of moldability: A hemispherical silicone sealing resin for sealing each LED chip formed on a metal base substrate was observed with a microscope. “O” when 100 hemispherical silicone encapsulating resins do not contain any wrinkles, “△” when 10 or fewer encapsulating resins are formed with wrinkles, and sealing resins with wrinkles formed The case where there were 10 or more wrinkles was designated as “x”.
Judgment of releasability: When it is possible to peel the release film from the mold and the sealed substrate by hand and there is no residue of the release film on the mold and the sealing resin, Judged “O”. Although there was some residual of the release film, it was judged as “Δ” when it was practically acceptable. When a lot of release film residue remained, “x” was judged.

<Decision of disposal>
When the proportion of the halogen-based resin contained in the release film was less than 1%, the discardability was set to “◯”. When the proportion of the halogen-based resin is 1% or more and less than 20%, the disposal property is “Δ”, and when the proportion of the halogen-based resin exceeds 20%, the disposal property is “x”.

<Production of release film>
(Examples 1-12)
A release film composed of an inner layer and surface layers formed on both sides thereof was prepared using the resin shown in Table 1.

  Each resin is used in the combinations and mixing ratios (mass ratios) shown in Table 2 or Table 3. Using two extruders, it is melt-extruded into a tube shape from two types of three-layer annular dies, using a water-cooled ring Quenching was performed to obtain a tube-shaped raw material for drawing. The obtained raw material for stretching was irradiated with an electron beam accelerated at an acceleration voltage of 500 KV to carry out a crosslinking treatment. Subsequently, while being heated by radiant heating by an infrastructure heater, the stretching raw fabric is passed between two nip rolls, and air is injected into the stretching raw fabric according to the speed ratio of the two sets of nip rolls. The film formed by stretching was cooled by applying cold air to the bubbles with an air ring. The film is then folded and heat set at a hot air temperature of 45 ° C. and a relaxation rate in the MD direction (a method in which hot air is applied between the two sets of nip rolls), and the surface layer on both sides and the inner layer provided on the inside A structured release film was obtained. Tables 2 and 3 show the mixing ratio of the resin forming each layer, the layer constitution ratio of the surface layer and the inner layer, the irradiation amount and the thickness of the entire release film.

  In Examples 6 to 11, the post-treatment described in Table 3 was performed, and a release layer was further formed on the surface of the surface layer. In the table, when the release layer was formed by coater coating, it was described as “coater coating”, and the coating solution and coating film thickness were described. When the release layer was formed by spraying, it was described as “spray coating”, and the coating solution and coating thickness were described. A release layer containing polyvinylidene fluoride is formed by “PVDF Latex32”, a release layer containing polyvinylidene fluoride is formed by “Die-free GF-550”, and a release layer containing silicone is formed by “KF-96”. It is formed.

(Comparative Example 1)
An uncrosslinked 4-methyl-1-pentene film (manufactured by Mitsui Chemicals, Inc., Z-04, thickness 50 μm) was used as a release film, and the same evaluation as in the examples was performed.

(Comparative Example 2)
The same evaluation as in the example was performed using an uncrosslinked 4-methyl-1-pentene film (manufactured by Mitsui Chemicals, Inc., T-08, thickness 50 μm) as a release film.

(Comparative Example 3)
The same evaluation as in the example was performed using an uncrosslinked ethylene-tetrafluoroethylene copolymer (ETFE) film (Asahi Glass Co., Ltd., thickness: 50 μm).

  Tables 2 to 4 show the evaluation results of the physical properties of each film (melting point, gel fraction, ratio of storage elastic modulus at a temperature 20 ° C. higher than the melting point to the storage elastic modulus at the melting point), LED overmold test, and evaluation of disposal properties. Results are shown. The release film of each example showed good results with respect to moldability and release properties.

Claims (9)

  A release film comprising a crosslinked resin layer formed from a crosslinked thermoplastic resin.   When the melting point of the uncrosslinked thermoplastic resin is Tm (° C.), the ratio of the storage elastic modulus of the release film at Tm + 20 (° C.) to the storage elastic modulus of the release film at Tm (° C.) is 50. The release film according to claim 1, which is at least%.   The release film of Claim 1 or 2 whose melting | fusing point Tm of the uncrosslinked thermoplastic resin is 170 degrees C or less.   The release film according to any one of claims 1 to 3, further comprising a release layer provided on at least one surface side of the crosslinked resin layer.   The release film according to any one of claims 1 to 4, wherein the thermoplastic resin is a chain polyolefin.   The release film as described in any one of Claims 1-5 whose gel fraction of the said release film is 1 mass%-80 mass%.   The release film according to any one of claims 1 to 6, wherein the thermoplastic resin is crosslinked by electron beam irradiation.   The release film according to any one of claims 1 to 7, which is used for LED chip compression sealing molding.   A molding method comprising thermoforming a molding material at a temperature higher than the melting point Tm of the uncrosslinked thermoplastic resin using the release film according to any one of claims 1 to 8.