In-mold transfer molding film and manufacturing method for molded products

Abstract

Provided is an in-mold transfer molding film, which has excellent moldability, post-molding electroconductivity and electromagnetic wave shielding properties and that features good productivity. Also provided is a method for manufacturing a molded article. The in-mold transfer molding film comprises a substrate film, a release layer, and an electroconductive layer, in this order. The electroconductive layer contains, with respect to the electroconductive layer which is 100 mass%, particles at 60-91 mass%, and contains a resin at 9-40 mass%. The weight average molecular weight of the resin is at least 5,000 but less than 10,000. The particles include at least one type selected from the group consisting of non-valent carbon, silver, gold, copper, nickel, chrome, palladium, indium, aluminum, zinc and platinum.

Description

[Technical Field]

[0001] The present invention relates to an in-mold transfer molding film and a method for producing a molded product. [Background technology]

[0002] In recent years, with the expansion of the IoT society, there has been an increasing demand for electromagnetic wave shielding performance in fields such as mobile phones, electrical appliances, and automobile parts. When using resin for housings, known methods include plating or conductive coating of molded products. However, these conventional methods require environmental measures such as wastewater treatment and post-treatment of solvents, and various attempts have been made to improve this aspect.

[0003] For example, Patent Document 1 discloses a technique for in-mold transfer molding of a molding film having a conductive layer containing resin and conductive fine particles, and Patent Document 2 discloses a technique related to an in-mold transfer molding film having a conductive layer made of metal or conductive polymer resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-192960 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-297642 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in Patent Document 1 has a problem in that when in-mold transfer molding is performed, in-plane variations occur in the conductive layer, resulting in deterioration of conductivity and electromagnetic wave shielding properties.On the other hand, the technology described in Patent Document 2 has a problem in terms of moldability, because cracks and tears occur in the conductive layer when the molded product has a complex shape.

[0006] The present invention aims to improve upon the problems of the prior art and to provide an in-mold transfer molding film that has excellent moldability, conductivity and electromagnetic wave shielding properties after molding processing, and good productivity, as well as a method for producing a molded product. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the present inventors have found that the problems can be solved as follows, and have arrived at the present invention. That is, a preferred embodiment of the in-mold transfer molding film and the method for producing a molded product of the present invention has the following configuration. (1) An in-mold transfer molding film having a base film, a release layer, and a conductive layer in this order, wherein the conductive layer contains particles in an amount of 60% by mass or more and 91% by mass or less, based on 100% by mass of the conductive layer; the conductive layer contains a resin in an amount of 9% by mass or more and 40% by mass or less, the resin having a weight-average molecular weight of 5,000 or more and less than 10,000; and the particles contain one or more metals selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum. (2) The in-mold transfer molding film according to (1), wherein the thickness of the conductive layer is 5 μm or more and 15 μm or less. (3) The in-mold transfer molding film according to (1) or (2), wherein the conductive layer has a glass transition temperature of 40°C or higher and 100°C or lower when heated from 20°C to 250°C at a rate of 20°C / min under a nitrogen atmosphere using a differential scanning calorimeter. (4) The in-mold transfer molding film according to any one of (1) to (3), which comprises the base film, the release layer, the conductive layer, and an adhesive layer in this order. (5) The in-mold transfer molding film according to any one of (1) to (4), wherein the release layer contains a silicone resin as a main component. (6) The in-mold transfer molding film according to (5), wherein the release layer is mainly composed of an alkyd-modified silicone resin. (7) The in-mold transfer molding film according to any one of (1) to (6), wherein the resin is a polyester resin. (8) The in-mold transfer molding film according to (7), wherein the acid value of the polyester resin is 5 mgKOH / g or more and 20 mgKOH / g or less. (9) The in-mold transfer molding film according to any one of (1) to (8), wherein the particles are first particles having an aspect ratio of 1 or more and less than 2, and second particles having an aspect ratio of 2 or more. (10) An in-mold transfer molding film according to any one of (1) to (9), which has an electromagnetic wave shielding effect of 40 dB or more when measured using the KEC method (electric field) for electromagnetic waves with a frequency of 300 MHz. (11) The in-mold transfer molding film according to any one of (1) to (10), wherein the base film is a polyethylene terephthalate film. (12) A method for producing a molded product, comprising the steps of placing the in-mold transfer molding film according to any one of (1) to (11) in a mold, and then injecting a molding resin and / or a molding resin precursor into the mold. [Effects of the Invention]

[0008] The present invention can provide an in-mold transfer molding film and a method for producing a molded product that are excellent in moldability, conductivity after molding, and electromagnetic wave shielding properties, and that have good productivity. DETAILED DESCRIPTION OF THE INVENTION

[0009] A preferred embodiment of the in-mold transfer molding film of the present invention comprises, in this order, a base film, a release layer, and a conductive layer, wherein the conductive layer contains particles in an amount of 60% by mass to 91% by mass, based on 100% by mass of the conductive layer, and the conductive layer contains a resin in an amount of 9% by mass to 40% by mass, the resin having a weight-average molecular weight of 5,000 or more and less than 10,000, and the particles contain one or more metals selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum. The in-mold transfer molding film of the present invention will now be described in detail.

[0010] [Conductive layer] In a preferred embodiment of the conductive layer of the present invention, the conductive layer contains particles in an amount of 60% by mass to 91% by mass, and the conductive layer contains resin in an amount of 9% by mass to 40% by mass. By adopting such a configuration, even if the conductive layer is subjected to a step in which it is heated during molding, fine cracks do not occur, and excellent moldability can be achieved.

[0011] Furthermore, by setting the weight average molecular weight of the resin to 5,000 or more but less than 10,000 and the particles containing one or more metals selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum, the in-plane variation of the conductive layer can be reduced even after the conductive layer has been heated during molding, resulting in a product with excellent conductivity and electromagnetic wave shielding properties after molding.

[0012] From the above viewpoint, by including particles in an amount of 60% by mass or more, the particle component ratio in the conductive layer can be increased, thereby improving the conductivity and electromagnetic wave shielding properties after molding. From the same viewpoint, a content of 65% by mass or more is more preferable, and a content of 70% by mass or more is even more preferable.

[0013] Furthermore, by containing 91% by mass or less of particles, the resin component ratio in the conductive layer can be increased, thereby improving moldability. From the same viewpoint, the content is more preferably 87% by mass or less, and even more preferably 85% by mass or less.

[0014] From the above viewpoints, when all components constituting the conductive layer are taken as 100% by mass, the particles in the present invention preferably comprise 65% by mass or more and 87% by mass or less, and even more preferably comprise 70% by mass or more and 85% by mass or less.

[0015] From the viewpoint of improving the electrical conductivity and electromagnetic wave shielding properties after molding, the particles in the present invention preferably contain one or more metals selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum, and more preferably one or more metals selected from the group consisting of gold, silver, silver-plated copper powder, and silver-copper alloy, from the viewpoint of improving the electrical conductivity and electromagnetic wave shielding properties as the resistivity decreases. The term "zero-valent" refers not only to the initial carbon but also to all metal elements.

[0016] Whether or not the particles listed above contain a zero-valent metal element can be determined by performing energy dispersive X-ray spectroscopy mapping analysis (hereinafter referred to as EDX mapping analysis) on a cross section obtained by cutting an in-mold transfer molding film and determining whether or not a zero-valent metal element is detected in the particle portion. EDX mapping analysis can be performed, for example, using a scanning electron microscope (FEI, XL30 SFEG) equipped with an energy dispersive X-ray spectrometer (EDAX, NEW XL30 132-2.5) at an acceleration voltage of 20 kV and a magnification of 20,000x. The in-mold transfer molding film can be cut using a "Cross Section Polisher" (registered trademark) SM-09010 (JEOL), or similar. When using this device, samples are obtained by treating with argon gas at an acceleration voltage of 4 kV and a current of 70 μA for 10 hours. Regarding carbon particles, this refers to particles that have been qualitatively analyzed by microscopic Raman mapping analysis on a cross section obtained using the same method as above. The microscopic Raman mapping analysis can be performed using, for example, a microscopic laser Raman spectrometer (manufactured by Horiba, Ltd., "LabRAM" (registered trademark) HR Evolution).

[0017] By containing first particles having an aspect ratio of 1 or more but less than 2 and second particles having an aspect ratio of 2 or more, the overlap between particles in the conductive layer after molding can be maintained, thereby further improving the electromagnetic wave shielding properties after molding.

[0018] From the same viewpoint as above, it is preferable that the content of the first particles is 20% by mass or more and 70% by mass or less, and the content of the second particles is 10% by mass or more and 60% by mass or less, when all components constituting the conductive layer are 100% by mass.

[0019] In the present invention, particles refer to primary particles. Therefore, first particles refer to primary particles having an aspect ratio of 1 or more and less than 2, and second particles refer to primary particles having an aspect ratio of 2 or more. The average particle size of the primary particles can be calculated, for example, using a scattering-type particle size distribution analyzer (LA-960V2, manufactured by Horiba, Ltd.).

[0020] The particle aspect ratio here can be calculated as the average major axis / average minor axis of the particles. For example, a scanning electron microscope (FEI, XL30 SFEG) is used to observe the cross section of the conductive layer obtained by cutting the in-mold transfer molding film at an acceleration voltage of 20 kV and a magnification of 100,000 times. 50 particles are extracted from the obtained image, each of which is approximated as an ellipse. The aspect ratio is calculated by taking the average of the maximum length as the average major axis and the minimum length as the average minor axis. Furthermore, as a cutting means for the in-mold transfer molding film, for example, a manual rotary microtome (Leica Microsystems, "HistoCore BIOCUT" (registered trademark) R) can be used to obtain a sample.

[0021] Furthermore, by containing 40% by mass or less of resin, the ratio of particles to all components constituting the conductive layer can be increased, thereby improving the conductivity and electromagnetic wave shielding properties after molding. From the same viewpoint, the resin content is more preferably 25% by mass or less, and even more preferably 20% by mass or more.

[0022] Furthermore, by containing 9% by mass or more of the resin, the dispersibility of particles in the conductive layer and the moldability and flexibility of the entire conductive layer can be improved, thereby improving moldability. From the same viewpoint, the resin content is more preferably 10% by mass or more, and even more preferably 13% by mass or more.

[0023] From the above viewpoints, the resin content in the present invention is more preferably 10% by mass to 25% by mass, and even more preferably 13% by mass to 20% by mass, based on 100% by mass of the conductive layer.

[0024] The resin preferably has a weight average molecular weight of 5,000 or more and less than 10,000, from the viewpoint of improving moldability and electrical conductivity and electromagnetic wave shielding properties after molding.

[0025] By setting the weight-average molecular weight of the resin to 5,000 or more, the viscosity of the resin increases, stabilizing the fluidity of the conductive layer during the molding process, thereby reducing in-plane variations in the conductive layer and resulting in excellent conductivity and electromagnetic wave shielding properties. From the same perspective, it is more preferable that the weight-average molecular weight of the resin be 7,500 or more.

[0026] Furthermore, by making the weight-average molecular weight of the resin less than 10,000, the fluidity of the resin in the molding process can be increased, resulting in excellent moldability. From the same viewpoint, it is more preferable that the weight-average molecular weight of the resin be 9,000 or less, and even more preferable that it be 8,500 or less.

[0027] From the above viewpoint, the weight average molecular weight of the resin in the present invention is more preferably 7,500 or more and 9,000 or less.

[0028] The weight-average molecular weight of a resin can be calculated from the styrene-equivalent molecular weight measured by GPC (gel permeation chromatography). The method for measuring the weight-average molecular weight of a resin using GPC is as follows.

[0029] A high-speed GPC system (HLC-8220, Tosoh Corporation) with two separation columns (PLgel 5μm MiniMIX-D, Agilent Technologies, Inc.) connected in series was used as the measurement device. Standard samples, polystyrene standards (weight average molecular weights: 5,000, 10,000, and 30,000), were placed in chloroform and stirred at 20°C for 10 minutes. The standard sample solution was then filtered through a 0.45 μm membrane filter and analyzed to create a calibration curve. 5 mg of conductive layer was then placed in 2 mL of chloroform and stirred at 20°C for 10 minutes. The sample was then filtered through a 0.45 μm membrane filter and analyzed to calculate the resin's weight average molecular weight. The flow rate through the separation column was 0.35 mL / min, the column temperature was 40°C, and a differential refractometer (RI detector, Tosoh Corporation) was used as the detector. The resin content was determined by collecting and weighing each peak.

[0030] From the viewpoint of satisfying moldability and the electrical conductivity and electromagnetic wave shielding properties after molding processing, it is preferable that the conductive layer of the present invention has a glass transition temperature observed between 40°C and 100°C when heated from 20°C to 250°C at a rate of 20°C / min in a nitrogen atmosphere using a differential scanning calorimeter.

[0031] When the glass transition temperature of the conductive layer is observed at 100°C or lower, the conductive layer can exhibit sufficient flexibility in the molding process, resulting in excellent moldability. From the same viewpoint, it is more preferable that the glass transition temperature of the conductive layer is observed at 80°C or lower.

[0032] Furthermore, when the glass transition temperature of the conductive layer is observed at 40°C or higher, the fluidity of the conductive layer is stabilized during the molding process, thereby reducing in-plane variations in the conductive layer, resulting in excellent conductivity and electromagnetic shielding properties after molding. From the above viewpoints, it is more preferable that the glass transition temperature of the conductive layer is observed at 60°C or higher.

[0033] From these viewpoints, it is more preferable that the glass transition temperature of the conductive layer in the present invention is observed at 60°C or higher and 80°C or lower.

[0034] The glass transition temperature of the conductive layer can be measured using a known differential scanning calorimeter. Specifically, the method for measuring the glass transition temperature of the conductive layer using a differential scanning calorimeter is to use a differential scanning calorimeter (RDC220, manufactured by Seiko Instruments Inc.) and perform measurement and analysis using the following method in accordance with JIS K7121 (2012).

[0035] The conductive layer alone is scraped off from the in-mold transfer molding film, and the resulting conductive layer is heated at 100°C for 4 hours in a nitrogen atmosphere, then cooled to 25°C to prepare a 5 mg sample. The sample is heated from 20°C to 250°C at a rate of 20°C / min in a nitrogen atmosphere, and the change in specific heat due to the transition from the glassy state to the rubbery state is read. The glass transition temperature is determined as the midpoint between the line equidistant from the extended line of each baseline in the vertical axis (axis indicating heat flow) and the curve representing the stepwise change in the glass transition.

[0036] The resin in the conductive layer preferably contains a polyester resin as a main component from the viewpoint of improving moldability and conductivity and electromagnetic shielding properties after molding. The resin in the conductive layer containing a polyester resin as a main component means that the conductive layer contains 50% by mass or more of polyester resin when the content of the resin in the conductive layer is 100% by mass. This embodiment can improve the flexibility of the resin and the dispersibility of particles, thereby achieving excellent moldability and conductivity and electromagnetic shielding properties after molding. From the same viewpoint, the resin more preferably contains 80% by mass or more of polyester resin when the content of the resin is 100% by mass. From the above viewpoint, it is even more preferable that the resin contained in the conductive layer is a polyester resin. From the same viewpoint, it is also preferable that the polyester resin is a saturated polyester resin, and from the viewpoint of durability, it is even more preferable that the polyester resin is a thermoplastic saturated polyester resin.

[0037] The polyester resin preferably has an acid value of 5 mgKOH / g or more and 20 mgKOH / g or less, from the viewpoint of improving moldability and electrical conductivity and electromagnetic wave shielding properties after molding.

[0038] By setting the acid value of the polyester resin to 5 mgKOH / g or more, adhesion to the release layer is improved, and in-plane variations in the conductive layer after the molding process can be reduced, resulting in excellent conductivity and electromagnetic wave shielding properties. From the same perspective, it is more preferable that the acid value of the polyester resin be 7 mgKOH / g or more.

[0039] Furthermore, by setting the acid value of the polyester resin to 20 mgKOH / g or less, the dispersibility of the particles and the polyester resin is improved, resulting in excellent moldability. From the same viewpoint, it is more preferable that the acid value of the polyester resin be 15 mgKOH / g or less.

[0040] From the above viewpoint, it is more preferable that the acid value of the polyester resin is 5 mgKOH / g or more and 20 mgKOH / g or less, and the weight average molecular weight is 7,500 or more and 9,000 or less.

[0041] One method for qualitative and quantitative analysis of polyester resin is to scrape off only the conductive layer from an in-mold transfer molding film, freeze-dry the resulting sample of the conductive layer, and then perform qualitative and quantitative analysis of the recovered dried material using gas chromatography mass spectrometry (P&T-GC / MS) equipped with a purge and trap sampler (thermal desorption device).

[0042] The acid value of the polyester resin can be measured in accordance with the titration method of JIS K 5601-2-1 (1999). Specifically, for example, a sample is dissolved in a mixed solvent of toluene / ethanol = 2 / 1 by volume, and titrated with a potassium hydroxide solution using phenolphthalein as an indicator, and the acid value can be measured in accordance with the titration method of JIS K 5601-2-1 (1999) using the following formula: Acid value (mgKOH / g)=56.1×V×C / m V: titrant volume (ml), C: titrant concentration (mol / l), m: sample solid mass (g).

[0043] The thickness of the conductive layer in the present invention is preferably 5 μm or more and 15 μm or less from the viewpoint of satisfying the conductivity and electromagnetic wave shielding properties after molding. When the thickness of the conductive layer is 15 μm or less, the conductive layer is stably heated during the molding process, thereby reducing in-plane variations in the conductive layer, and thus the conductive layer can have excellent conductivity and electromagnetic wave shielding properties after molding. From the same viewpoint, the thickness of the conductive layer is more preferably 12 μm or less. Furthermore, when the thickness of the conductive layer is 5 μm or more, the particle content in the conductive layer increases and the resistivity of the conductive layer decreases, thereby allowing the conductive layer to fully exhibit conductivity and electromagnetic wave shielding properties, and the conductive layer can have excellent conductivity and electromagnetic wave shielding properties after molding. From the same viewpoint, the thickness of the conductive layer is more preferably 7 μm or more.

[0044] [Electromagnetic wave shielding] By adopting the above-described configuration, the in-mold transfer molding film of the present invention can achieve an electromagnetic wave shielding effect of 40 dB or more when measured using the KEC method (electric field) for electromagnetic waves with a frequency of 300 MHz.

[0045] The KEC method, established by the Kansai Electronics Industry Development Center, evaluates the shielding effectiveness of electromagnetic waves generated in the near field by separating them into electric and magnetic fields. Measurements using this method can be performed by transmitting electromagnetic waves from a transmitting antenna (transmitting fixture) through an electromagnetic shielding film (measurement sample) and receiving them with a receiving antenna (receiving fixture). The KEC method measures the electromagnetic waves that pass through (transmitted by) the electromagnetic shielding film at the receiving antenna. In other words, it measures how much the transmitted electromagnetic waves (signal) are attenuated by the electromagnetic shielding film at the receiving antenna side. Therefore, the electromagnetic shielding ability to block (shield) electromagnetic waves can be determined by combining the reflective component that reflects the electromagnetic waves and the absorbing component that absorbs the electromagnetic waves.

[0046] The in-mold transfer molding film of the present invention preferably has an electromagnetic wave shielding effect of 40 dB or more when measured using the KEC method (electric field) for electromagnetic waves with a frequency of 300 MHz.

[0047] [Release layer] The release layer in the present invention is not particularly limited as long as it is a layer for peeling the conductive layer from the base film, but from the viewpoint of improving productivity, it is preferable that the release layer contains a silicone resin as its main component. When the release layer contains a silicone resin as its main component, more preferably when the content of the silicone resin in the release layer is 80 mass % or more, the adhesive force between the base film and the conductive layer can be controlled, and therefore, both the processability of the conductive layer and the releasability of the base film in the molding step can be achieved.

[0048] As the silicone resin, from the viewpoint of controlling the adhesive strength with the conductive layer, polyester-modified silicone resin, acrylic-modified silicone resin, urethane-modified silicone resin, epoxy-modified silicone resin, and alkyd-modified silicone resin, which are silicones modified by graft polymerization with an organic resin or the like, are more preferred, and alkyd-modified silicone resin is even more preferred from the viewpoint of controlling the adhesive strength with the polyester resin.

[0049] [Base film] The substrate film in the present invention has good dimensional stability and durability, and from the viewpoint of improving productivity, is preferably a plastic film made of polyester, such as polyethylene terephthalate, polyethylene 2,6-naphthalate, polyethylene α,β-bis(2-chlorophenoxy)ethane 4,4′-dicarboxylate, polybutylene terephthalate, etc. Among these, a film made of polyethylene terephthalate is particularly preferred from the viewpoint of excellent processability in the lamination and molding steps of the release layer and conductive layer, and from the same viewpoint, biaxially oriented polyethylene terephthalate is most preferred.

[0050] [In-mold transfer molding film] The in-mold transfer molding film of the present invention has excellent moldability and excellent electrical conductivity and electromagnetic shielding properties after molding processing, making it possible to easily add electrical conductivity or an electromagnetic shielding layer to molded articles having, for example, curved surfaces, uneven ribs, hinges, bosses, or hollow shapes. That is, since the in-plane variation in electrical conductivity and electromagnetic shielding properties is small, the film can be more suitably used as an in-mold transfer molding film for imparting electrical conductivity or electromagnetic shielding properties to molded articles, and since the in-plane variation in electromagnetic shielding properties is particularly small, the film can be even more suitably used as an in-mold transfer molding film for imparting electromagnetic shielding properties to molded articles.

[0051] From the above viewpoint, the applications are not limited as long as the effects of the present invention are not impaired. For example, the composition can be suitably used to impart electromagnetic wave shielding properties to personal computers, displays, office automation equipment, mobile phones, personal digital assistants, optical equipment, audio equipment, air conditioners, lighting equipment, entertainment equipment, toys, other home appliances, electronic equipment, semiconductor materials, electrical components and internal parts of automobiles, electrical components and internal parts of aircraft, electrical components and internal parts of motorcycles, etc.

[0052] From the viewpoint of adhering the conductive layer to the resin and / or resin precursor, the in-mold transfer molding film of the present invention preferably has a base film, a release layer, a conductive layer, and an adhesive layer in this order, with the adhesive layer being the outermost layer.

[0053] The resin used in the adhesive layer in the in-mold transfer molding film of the present invention, i.e., the resin contained in the adhesive layer, can be a heat-sensitive resin or a pressure-sensitive resin, and the material of the adhesive layer can be appropriately selected according to the material of the resin and / or resin precursor.

[0054] The resin contained in the adhesive layer is preferably, for example, an acrylic resin, a polyester resin, a polyphenylene oxide-polystyrene resin, a polycarbonate resin, a polystyrene resin, a styrene copolymer resin, a polyamide resin, a chlorinated polyolefin resin, a chlorinated vinyl acetate copolymer resin, a cyclized rubber, a coumarone-indene resin, or the like, which may be used alone or in combination.

[0055] [Manufacturing method for in-mold transfer molding film] The method for producing the in-mold transfer molding film can include, for example, the following exemplary materials, amounts used, processing contents, processing procedures, etc.

[0056] The in-mold transfer molding film of the present invention can be produced, for example, by applying a coating composition for the release layer and a coating composition for the conductive layer in that order to one side of a substrate film, and then subjecting the film to heat treatment.

[0057] The coating composition for the release layer of the present invention can be obtained by mixing a silicone resin and an organic solvent. The organic solvent used in the coating composition for the release layer of the present invention is preferably 50% by mass or more and 99% by mass or less, when the total components of the resin mixture constituting the silicone resin and the organic solvent are taken as 100% by mass, in order to improve the coatability to the substrate film. Examples of organic solvents that can be used to improve the coatability of the coating composition for the release layer include ethyl methyl ketone, methyl isobutyl ketone, butyl acetate, ethyl acetate, methanol, isopropanol, cyclohexanone, toluene, and xylene. Furthermore, inorganic particles, organic particles, leveling agents, etc. can be blended into the coating composition, as long as the effects of the present invention are not impaired, in order to prevent blocking when wound onto a film roll and to improve coatability to the substrate film.

[0058] The coating composition for the conductive layer of the present invention can be obtained by mixing particles, a resin, and a mixing organic solvent to obtain a resin mixture, and then mixing with a dilution organic solvent. The particles used in the resin mixture of the present invention preferably contain 60% by mass or more and 91% by mass or less of particles when the total components constituting the particles and resin are taken as 100% by mass. Furthermore, the resin used in the resin mixture of the present invention preferably contains 9% by mass or more and 40% by mass or less of resin when the total components constituting the particles and resin are taken as 100% by mass. The mixing organic solvent used in the resin mixture for the conductive layer of the present invention preferably contains 5% by mass or more and 50% by mass or less of the mixing organic solvent when the total components of the resin mixture constituting the particles, resin, and mixing organic solvent are taken as 100% by mass, in order to improve the mixing and dispersion of the particles and resin. From the viewpoint of suppressing evaporation of the organic solvent for mixing when mixing the particles and resin and suppressing thickening of the resin mixture, it is more preferable to use, alone or in combination, the following organic solvents for mixing: N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone, dimethyl sulfoxide, γ-butyrolactone, ethyl lactate, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ethylene glycol mono-n-propyl ether, diacetone alcohol, tetrahydrofurfuryl alcohol, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether acetate (hereinafter referred to as "DMEA"), diethylene glycol monobutyl ether, diethylene glycol, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.

[0059] In the present invention, the dilution organic solvent is preferably 10% by mass or more and 80% by mass or less, from the viewpoint of achieving both coatability when the conductive layer is applied to the release layer and a desired thickness, when the total mass of the resin composition constituted by the resin mixture and the dilution organic solvent is taken as 100. Examples of the dilution organic solvent include ethyl methyl ketone, methyl isobutyl ketone, butyl acetate, ethyl acetate, methanol, isopropanol, cyclohexanone, toluene, and xylene.

[0060] In the resin mixture of the present invention, the particles, urethane resin, and mixing organic solvent can be mixed using known mixing and dispersing methods such as a three-roll mill, ultrasonic disperser, sand mill, attritor, pearl mill, super mill, ball mill, impeller, desparger, KD mill, colloid mill, dynatron, planetary mill, and pressure kneader.

[0061] In the resin composition, the resin mixture and the organic solvent for dilution can be mixed by known mixing and dispersing methods such as a magnetic stirrer, a homodisper, ultrasonic irradiation, vibration dispersion, and manual mixing and dispersing.

[0062] As a method for applying the coating composition for the release layer and the coating composition for the conductive layer in that order to one side of the substrate film, it is preferable to form the release layer and the conductive layer by applying them by a comma coating method, an applicator method, a dip coating method, a roller coating method, a wire bar coating method, a reverse coating method, a kiss coating method, a gravure coating method, or a die coating method (U.S. Pat. No. 2,681,294), etc., and from the viewpoint of processability, the applicator method, the comma coating method, the reverse coating method, and the die coating method are more preferred.

[0063] The in-mold transfer molding film of the present invention is preferably used for in-mold transfer because it has excellent moldability, conductivity after molding, and electromagnetic wave shielding properties, and improves productivity.

[0064] In other words, it is preferable that the in-mold transfer molding film is used in a manufacturing method for a molded product, which includes a step of placing the in-mold transfer molding film in a mold and then injecting a resin and / or a resin precursor.

[0065] This process can be carried out using a known injection molding machine and film delivery machine; for example, an S-2000 model (manufactured by Fanuc Corporation) can be used as the injection molding machine, and a roll-type foil stamping machine (Horikin Foil Powder Co., Ltd.) can be used as the film delivery machine.

[0066] [Molded product manufacturing method: In-mold transfer injection molding] The method for producing a molded article of the present invention can preferably take an embodiment including a step of placing the in-mold transfer molding film in a mold and then injecting a molding resin and / or a molding resin precursor into the mold.

[0067] Specifically, for example, a preferred method is to pass the in-mold transfer molding film of the present invention through the mold of an injection molding machine, position the conductive layer side of the molding film so that it faces into the cavity of the in-mold transfer injection molding mold, and then injection mold the injection resin as the molding resin and / or molding resin precursor therein, thereby transferring the conductive layer of the molding film to the surface of the injected resin, cool the injected resin, open the injection molding mold, and peel off the base film of the molding film to obtain a molded product in this order.

[0068] The molding resin and / or molding resin precursor in the present invention is preferably a thermoplastic resin or elastomer, and more preferably polybutylene terephthalate (PBT), polyphenylene sulfide, polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polyacrylate, polyamide, polypropylene, acrylic, polystyrene, polyacrylonitrile-styrene, polyacrylonitrile-butadiene-styrene (ABS), epoxy, or other resins used alone or in combination. Furthermore, glass fiber or inorganic fillers can also be added to the resin as a reinforcing material. [Example]

[0069] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples.

[0070] The measurement and evaluation methods used in the present examples are as follows.

[0071] (1) Thickness of the conductive layer and adhesive layer The thickness (μm) of the conductive layer and adhesive layer was determined by cutting the in-mold transfer molding film perpendicular to the thickness using a manual rotary microtome (Leica Microsystems, "HistoCore BIOCUT" (registered trademark) R) to obtain a cross-section of the in-mold transfer molding film, observing the cross-section of the conductive layer using a scanning electron microscope (FEI, XL30 SFEG) at an accelerating voltage of 20 kV and an observation magnification of 100,000 times, and measuring any five points on the cross-sectional photograph and calculating the average value obtained.

[0072] (2) Particle aspect ratio In method (1), 50 particles were extracted from the obtained scanning electron microscope image, each of which was approximated as an ellipse, and the aspect ratio of each particle was calculated by taking the maximum length as the major axis and the minimum length as the minor axis. Next, a histogram was created in increments of 0.1 using the obtained aspect ratios, and the peak value was calculated as the aspect ratio of the second particle. When there were two peaks, the peak with the smaller value was taken as the aspect ratio of the first particle, and the peak with the larger value was taken as the aspect ratio of the second particle.

[0073] (3) Glass transition temperature of the conductive layer Measurements and analyses were carried out using a differential scanning calorimeter (Seiko Instruments Inc., RDC220) according to the following method in accordance with JIS K7121 (2012).

[0074] A 5 mg sample of the conductive layer or thermoplastic resin was used. When evaluating the conductive layer or thermoplastic resin, the conductive layer or thermoplastic resin was heated to 100°C for 4 hours in a nitrogen atmosphere, then cooled to 25°C to prepare a 5 mg sample. The sample was heated from 20°C to 250°C at a rate of 20°C / min in a nitrogen atmosphere, and the specific heat change due to the transition from the glassy state to the rubbery state was measured. The glass transition temperature was determined as the midpoint between the line equidistant from the extended line of each baseline in the vertical axis (axis indicating heat flow) and the curve representing the stepwise change in the glass transition.

[0075] (4) Weight-average molecular weight of resin The molecular weight of the thermoplastic resin contained in the conductive layer was analyzed by the following method, and the weight average molecular weight was evaluated from the detected peak area.

[0076] <Molecular weight analysis method> A high-speed GPC system (HLC-8220, Tosoh Corporation) connected in series with two separation columns (PLgel 5 μm MiniMIX-D, Agilent Technologies, Inc.) was used as the measurement system. Standard samples (polystyrene standards: 5,000, 10,000, and 30,000) were added to chloroform, stirred at 20 °C for 10 min, and filtered through a 0.45 μm membrane filter. A calibration curve was then generated by measuring the standard sample solution. 5 mg of the conductive layer was then added to 2 mL of chloroform, stirred at 20 °C for 10 min, and filtered through a 0.45 μm membrane filter. The flow rate through the separation column was 0.35 mL / min, the column temperature was 40 °C, and a differential refractometer (RI detector, Tosoh Corporation) was used as the detector.

[0077] (5) Electromagnetic wave shielding effect of in-mold transfer molding film The in-mold transfer molding film was cut into a 120mm x 120mm piece and measured using the KEC method (electric field), and the electromagnetic wave shielding effectiveness (dB) at a frequency of 300MHz was calculated using a spectrum analyzer. The results obtained are shown in the table below. The higher the electromagnetic wave shielding effectiveness of the in-mold transfer molding film, the better the electromagnetic wave shielding properties.

[0078] (6) Electromagnetic wave shielding effect of in-mold transfer molding film when stretched 1.1 times vertically and 1.1 times horizontally The in-mold transfer molding film was cut into 120mm x 120mm pieces and subjected to simultaneous biaxial stretching of 1.1 times lengthwise and 1.1 times widthwise using a Bruckner KARO 5.0 lab stretcher to create samples. Measurements were performed using the KEC method (electric field), and the electromagnetic shielding effectiveness (dB) at a frequency of 1 GHz was measured using a spectrum analyzer. The results obtained were taken as the electromagnetic shielding effectiveness at a frequency of 1 GHz. The higher the electromagnetic shielding effectiveness, the better the electromagnetic shielding properties.

[0079] (7) Processing suitability for molding process The film roll of in-mold transfer molding film was attached to a roll-type foil stamping machine (Horikin Foil Powder Co., Ltd.), which is a film delivery machine attached to an injection molding machine ROBO SHOT S2000i 150A (manufactured by Fanuc Corporation), and then passed through the injection molding mold, with the conductive layer side of the in-mold transfer molding film facing inside the cavity of the in-mold transfer injection molding mold (tile-shaped molded product 30 mm wide, 300 mm long, and 10 mm high, processing temperature: 80°C). Polybutylene terephthalate resin (Toray Industries, Inc.'s "Toraycon" (registered trademark) 1101G) was used as molding resin A, and polyacrylonitrile butadiene styrene resin (Toyolac (registered trademark) 100) was used as molding resin B. These molding resins were then injection molded to transfer the conductive layer of the in-mold transfer molding film onto the surface of the injected resin. After cooling, the injection mold was opened, and the base film of the in-mold transfer molding film was peeled off to obtain a molded product. The processability of the molding process was evaluated according to the following criteria, depending on the state of the conductive layer when the injection mold was opened.

[0080] When molding resin A was polybutylene terephthalate resin (Toray Industries, Inc.'s "Treycon" (registered trademark) 1101G), the melting temperature of the injected resin was 260°C, the injection speed was 8 mm / sec, and the cooling time was 25 seconds. When molding resin B was polyacrylonitrile butadiene styrene resin (Toyolac (registered trademark) 100) manufactured by Toray Industries, Inc., the melting temperature of the injected resin was 230°C, the injection speed was 8 mm / sec, and the cooling time was 25 seconds. A: There was no abnormality between the molded product and the base film, and the conductive layer was transferred to the surface of the molded product. B: After the injection mold is opened, there is unevenness in the conductive layer transferred to the surface of the molded product, or less than 20% of the surface of the molded product where the conductive layer should be transferred has not been transferred. C: The conductive layer is not transferred to 20% or more of the surface of the molded product to which it should be transferred.

[0081] (8) Formability of in-mold transfer molding film In the method (7), the injection mold was opened, and the in-mold transfer molding film was visually observed before the base film was peeled off, and evaluated according to the following criteria. A: The conductive layer and base film conform to the molded product. Good results. B: The conductive layer and base film conform to the molded product, but cracks are observed in some parts of the conductive layer or base film. This does not pose a problem for practical use. C: The conductive layer and base film do not conform to the molded product, or tears are observed in the conductive layer or base film. Not suitable for practical use.

[0082] (9) Uneven thickness of the conductive layer The thickness unevenness of the conductive layer was evaluated by cutting any five points of the molded product obtained by method (7) perpendicularly to the thickness of the molded product using a manual rotary microtome (Leica Microsystems, "HistoCore BIOCUT" (registered trademark) R) to obtain a cross-section of the molded product, and observing the cross-section of the conductive layer using a scanning electron microscope (FEI, XL30 SFEG) at an accelerating voltage of 20 kV and an observation magnification of 100,000 times.The standard deviation of the measured values ​​was calculated and evaluated according to the following criteria. A: The standard deviation is 1.5 or less, which is a good result. B: The standard deviation is greater than 1.5 and less than 2.5, and there is no problem in practical use. C: Standard deviation is greater than 2.5, not practical (10) In-plane variation in electromagnetic wave shielding effect Measurements were performed using the KEC method (electric field) at five random locations on the molded product obtained by method (7), and the electromagnetic wave shielding effect (dB) at a frequency of 300 MHz was calculated using a spectrum analyzer. The measured values ​​were evaluated according to the following criteria. A: The difference between the maximum and minimum values ​​is 5 or less, which is a good result. B: The difference between the maximum and minimum values ​​is greater than 5 and less than 10, and there is no practical problem. C: The difference between the maximum and minimum values ​​is greater than 10, making it unusable.

[0083] The materials used are as follows:

[0084] (Silicone resin A) Alkyd-modified silicone resin (X-62-900B manufactured by Shin-Etsu Chemical Co., Ltd.).

[0085] (Silicone resin B) Addition reaction type silicone resin ("DOWSIL" (registered trademark) LTC750A manufactured by Dow-Toray Industries, Inc.).

[0086] (Particle A) Silver particles (Fukuda Metal Foil and Powder Co., Ltd., AgG-204B, average particle size 1.8 μm, kidney-shaped, aspect ratio 2.2).

[0087] (Particle B) Silver particles (DOWA Electronics Co., Ltd., AG-2-1C, average particle size 0.8 μm, spherical, aspect ratio 1.0).

[0088] (Polyester Resin A) Saturated copolymer polyester resin (manufactured by Unitika Ltd., "Elite" (registered trademark) XA-0847, glass transition temperature 58°C, weight average molecular weight 8,000, acid value 10 mg / KOH).

[0089] (Polyester resin B) Urethane-modified polyester resin (manufactured by Toyobo Co., Ltd., "Vylon" (registered trademark) UR-4800, glass transition temperature 106°C, weight average molecular weight 25,000, acid value 4 mg / KOH).

[0090] (Polyester resin C) Saturated copolymer polyester resin (manufactured by Unitika Ltd., "Elite" (registered trademark) UE-3320, glass transition temperature 38°C, weight average molecular weight 1,800, acid value 1 mg / KOH).

[0091] (Polyester Resin D) Saturated copolymer polyester resin (manufactured by Toyobo Co., Ltd., "Vylon" (registered trademark) GK-810, glass transition temperature 46°C, weight average molecular weight 6,000, acid value 5 mg / KOH).

[0092] (Polyester Resin E) Saturated copolymer polyester resin (manufactured by Unitika Ltd., "Elite" (registered trademark) KA-5034, glass transition temperature 67°C, weight average molecular weight 9,000, acid value 7 mg / KOH).

[0093] (acrylic resin) Acrylic resin (manufactured by Taisei Fine Chemical Co., Ltd., 8DL-100, glass transition temperature 90°C, weight average molecular weight 8,000, acid value 1 mg / KOH).

[0094] (Injection resin A) Polybutylene terephthalate resin ("Trecon" (registered trademark) 1101G manufactured by Toray Industries, Inc.).

[0095] (Injection resin B) Polyacrylonitrile butadiene styrene resin ("Toyolac" (registered trademark) 100 manufactured by Toray Industries, Inc.).

[0096] [Example 1] <Preparation of release layer laminated film> The materials for the release layer composition shown in Table 1 were dissolved in methyl ethyl ketone, and the raw materials were mixed and dispersed using a Homodisper (manufactured by Primix Corporation) to obtain a coating composition for the release layer with a solid content of 3.0% by mass.The above coating composition for the release layer was applied by gravure coating using a 38 μm thick biaxially oriented polyethylene terephthalate film ("Lumilar" (registered trademark) S10, manufactured by Toray Industries, Inc.) as the base film, and after drying at 120°C, a release layer laminate film with a release layer thickness of 0.05 μm was obtained, which was then wound into a roll.

[0097] <Production of in-mold transfer molding film> The raw materials for the conductive layer, with the composition shown in Table 1, were dispersed or dissolved in DMEA as an organic solvent and kneaded on a three-roll mill to obtain a resin mixture for the conductive layer. Next, the resin mixture and ethyl methyl ketone were mixed and dispersed using a Homodisper (Primix Corporation) to obtain a conductive layer coating composition with a solids content of 30.0% by mass. The conductive layer coating composition was gravure coated onto the release layer surface of the release layer laminate film and dried at 120°C to form a 10 μm-thick conductive layer. An adhesive layer coating composition (vinyl chloride / vinyl acetate copolymer adhesive K588HP, manufactured by Toyo Ink Co., Ltd.) was then gravure coated, dried, and cured to form a 10 μm-thick adhesive layer, obtaining an in-mold transfer molding film, which was then wound into a roll.

[0098] <Production of molded products> Molded products were produced by the method described in "(7) Processing suitability of molding process." The obtained conductive layer, resin, in-mold transfer molding film, and molded product were evaluated for each evaluation item. The evaluation results are shown in Table 1.

[0099] [Examples 2 to 11, Comparative Examples 1 to 3] An in-mold transfer molding film and a molded product were produced in the same manner as in Example 1, except that the release layer, particles, resin, injected resin, and adhesive layer were as shown in Tables 1 and 2. Note that no release layer was provided in Comparative Example 1. The evaluation results of the in-mold transfer molding film and the molded product are shown in Tables 1 and 2.

[0100] [Table 1]

[0101] [Table 2]

Claims

1. The substrate film has a base film, a release layer, and a conductive layer in this order, the conductive layer has a thickness of 5 μm or more and 12 μm or less; the conductive layer contains particles in an amount of 60% by mass or more and 91% by mass or less based on 100% by mass of the conductive layer; the conductive layer contains a resin in an amount of 9% by mass or more and 40% by mass or less, The weight average molecular weight of the resin is 5,000 or more and less than 10,000, the conductive layer has a glass transition temperature of 40° C. or higher and 100° C. or lower when heated from 20° C. to 250° C. at a rate of 20° C. / min in a nitrogen atmosphere using a differential scanning calorimeter; the particles contain one or more metals selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum; the particles are first particles having an aspect ratio of 1 or more and less than 2, and second particles having an aspect ratio of 2 or more; The release layer has a silicone resin content of 80% by mass or more, The in-mold transfer molding film, wherein the base film is a polyester film.

2. The in-mold transfer molding film according to claim 1 , comprising the base film, the release layer, the conductive layer, and an adhesive layer in this order.

3. 2. The in-mold transfer molding film according to claim 1, wherein the release layer is mainly composed of an alkyd-modified silicone resin.

4. The in-mold transfer molding film according to claim 1 , wherein the resin is a polyester resin.

5. 5. The in-mold transfer molding film according to claim 4, wherein the acid value of the polyester resin is 5 mgKOH / g or more and 20 mgKOH / g or less.

6. 2. The in-mold transfer molding film according to claim 1, wherein the electromagnetic wave shielding effect of the in-mold transfer molding film is 40 dB or more when measured using the KEC method (electric field) for electromagnetic waves with a frequency of 300 MHz.

7. 2. The in-mold transfer molding film according to claim 1, wherein the base film is a polyethylene terephthalate film.

8. A method for producing a molded product, comprising the steps of placing the in-mold transfer molding film according to claim 1 in a mold and then injecting a molding resin and / or a molding resin precursor into the mold.

Images