Laser thermal transfer film

Abstract

The present invention aims to provide a laser thermal transfer film which improves transfer properties by using a bismaleimide resin having a large expansion rate as a binder. The laser thermal transfer film has a base material film, a light-heat conversion layer, and an adhesive layer, which are stacked in this order, the light-heat conversion layer being solid at ordinary temperature and containing an infrared absorber represented by general formula (1) and a bismaleimide resin represented by general formula (3) and / or a bismaleimide resin represented by general formula (4). In general formula (1), p is 1 or 2, R1 to R8 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms, and X － is a fluoroalkylphosphate anion represented by general formula (2).

Description

Technical Field

[0001] This invention relates to a laser thermal transfer film, which comprises a substrate film, a photothermal conversion layer and an adhesive layer stacked in sequence. The photothermal conversion layer heats up and expands when irradiated with a laser. Background Technology

[0002] Infrared-absorbing dyes, pigments, and metallic materials are used as light absorbers for photothermal conversion in photothermal transfer films. Infrared-absorbing dyes have the following advantages: they can be widely selected from the range of typical infrared laser wavelengths used in laser thermal transfer, i.e., the near-infrared region, where the peak of maximum absorbance is located, while exhibiting low absorbance in the visible light region below 700 nm.

[0003] For example, as materials suitable for use as imaging radiation absorbers for 808nm lasers, Patent Document 1 discloses Prussian blue (or Pigment Blue 27), copper phthalocyanine (Pigment Blue 15), polymethyl methacrylate dye, and cyanine dye.

[0004] On the other hand, as a dye for a specific photothermal conversion layer, whose maximum absorbance at wavelengths of 650-1200 nm is more than three times that of the maximum absorbance at wavelengths of 400-650 nm, Patent Document 2 discloses dyes of the indolium salt or benzo[e]indolium salt series. Examples of benzo[e]indolium salts are shown below.

[0005]

[0006] Patent document 3 discloses metal complexes of phthalocyanine series compounds as light absorbers for laser thermal transfer. Examples of phthalocyanine-metal complexes are shown below. However, due to insufficient transmittance in the visible light region when using the above-mentioned dyes, problems arise in the quality inspection of the resulting transfer film and its alignment with the receiving element.

[0007]

[0008] M represents several hydrogen atoms, a divalent metal, a trivalent metal derivative, or a tetravalent metal derivative; R1 to R8 represent alkyl or alkoxyalkyl groups, respectively; X1 to X8 represent sulfur or NR9, respectively; X1 = (any one of X3 or X4) = (any one of X5 or X6) = (any one of X7 or X8) = sulfur; and X2 = (the other of X3 and X4) = (the other of X5 and X6) = (the other of X7 and X8) = NR9; R9 represents hydrogen or an alkyl group. The above R1, etc., applies only to the above chemical formulas.

[0009] Patent document 4 discloses a photothermal transfer film composed of a photothermal conversion layer and an adhesive layer. In this patent, the photothermal conversion layer expands after being irradiated with an infrared laser, enabling the transfer material to be transferred to a specific location. Examples of adhesives include acrylic resins (such as polyacrylates, polymethacrylates, polyacrylic acid, or copolymers thereof with polyolefins, sometimes possessing hydrophilic functional groups such as -OH and -COOH, and sometimes not). These resins have low transfer capabilities due to insufficient heat resistance and a small coefficient of thermal expansion.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Korean Publication No. 2009-0034364

[0013] Patent Document 2: Korean Publication No. 2007-0067725

[0014] Patent Document 3: U.S. Patent No. 6,066,729

[0015] Patent Document 4: Korean Publication No. 2019-0106498 Summary of the Invention

[0016] The technical problem to be solved by the present invention

[0017] The present invention was made in view of the above circumstances, and its object is to provide a laser thermal transfer film that improves the transfer characteristics by using a bismaleimide resin with a high expansion rate as a binder for the photothermal transfer layer, thereby causing the photothermal transfer layer to expand significantly after being irradiated with a laser.

[0018] Technical means to solve technical problems

[0019] To solve the above-mentioned technical problems, the present invention provides a laser thermal transfer film, characterized in that it comprises three layers in sequence: a substrate film, a photothermal conversion layer, and an adhesive layer. The photothermal conversion layer is solid at room temperature and contains an infrared absorber represented by general formula (1) and a bismaleimide resin represented by general formula (3) and / or a bismaleimide resin represented by general formula (4).

[0020]

[0021] In general formula (1), p is 1 or 2, R1 to R8 are independently substituted or unsubstituted linear or branched alkyl groups having 1 to 10 carbon atoms, and are optionally substituted by cyano, nitro, carboxyl, sulfonyl, halogen atom, hydroxyl, alkoxy, alkoxyalkoxy, acyloxy or alkylamino groups having 1 to 8 carbon atoms, X － The fluoroalkyl phosphate anion is represented by the following general formula (2).

[0022]

[0023] In general formula (2), x is 0 or 1, y is 1, 2 or 3, z is 6-y, and R9~R 13 They are either hydrogen or fluorine, each independently.

[0024]

[0025] In general formula (3), A represents a tetravalent organic group containing an aromatic ring or an alicyclic ring, Q represents a straight-chain alkylene group with 6 or more carbon atoms, R represents a straight-chain or branched alkyl group with 6 or more carbon atoms, and n represents an integer from 1 to 10.

[0026]

[0027] In general formula (4), A' represents a tetravalent organic group containing an aromatic ring or an alicyclic ring, B is a divalent alkylene chain with an alicyclic ring having 6 to 18 carbon atoms, Q' represents a straight-chain alkylene chain with 6 or more carbon atoms, R' independently represents a straight-chain or branched alkyl group with 6 or more carbon atoms, n' represents an integer from 1 to 10, and m represents an integer from 1 to 10.

[0028] If it is this kind of laser thermal transfer film, then it is possible to provide a laser thermal transfer film with improved transfer characteristics.

[0029] Furthermore, in this invention, it is preferred that the adhesive constituting the adhesive layer is one or a combination of two or more selected from polyacrylate, polymethacrylate, epoxy, polystyrene, polyurethane, polysulfone, polyester, polyimide and silicone resin.

[0030] The above-mentioned adhesive is preferred as an adhesive for laser heat transfer films.

[0031] Furthermore, in this invention, it is preferred that the infrared absorber contained in the photothermal conversion layer has a content of 1-15% by mass, and the bismaleimide resin has a content of 85-99% by mass.

[0032] If it is this kind of laser heat transfer film, the infrared absorber can be appropriately dispersed in the binder resin, and can generate sufficient heat by irradiating with laser.

[0033] Furthermore, in this invention, it is preferred that the thickness of the adhesive layer is 1 to 10 μm.

[0034] If it is this kind of laser heat transfer film, the adhesion is sufficient, the transfer body can adhere well, and the transfer characteristics are easy to control after laser irradiation.

[0035] Furthermore, in this invention, it is preferred that the thickness of the photothermal conversion layer is 0.1–20 μm.

[0036] If it is this kind of laser heat transfer film, the photothermal conversion layer can be expanded by the localized heat absorption generated by irradiating the laser, thus making the transfer easy.

[0037] Furthermore, in this invention, it is preferred that the maximum absorption wavelength of the infrared absorber is in the range of 780 to 1500 nm.

[0038] If it is this type of laser thermal transfer film, the photothermal conversion efficiency using near-infrared light is high.

[0039] Furthermore, in this invention, it is preferred that the adhesive force of the adhesive layer is 0.1 to 10 N / 25 mm.

[0040] If it is this kind of laser thermal transfer film, the transfer material can be well transferred to the transfer substrate by irradiating with a laser.

[0041] Furthermore, in this invention, it is preferred that the substrate film is a transparent thermoplastic resin.

[0042] If it is this type of substrate film, then laser light can be irradiated from the substrate film side to cause the photothermal conversion layer to expand.

[0043] Furthermore, in this invention, it is preferred that the cured bismaleimide resin has a thermal decomposition initiation temperature of 300°C or higher and a glass transition temperature of 150°C or lower, and a coefficient of thermal expansion of 100 ppm / °C or higher above the glass transition temperature.

[0044] If it is this type of laser thermal transfer film, it can perform the transfer from the laser thermal transfer film to the transfer substrate with good precision.

[0045] Invention Effects

[0046] As described above, according to the present invention, a laser thermal transfer film can be provided in which a bismaleimide resin with a high expansion rate is used as the adhesive for the photothermal transfer layer, causing the photothermal transfer layer to expand significantly after laser irradiation, thereby reducing the adhesion area between the transfer body and the adhesive layer, adjusting the adhesion force to a specific range, and thus improving the transfer characteristics. Therefore, it is extremely useful as a laser thermal transfer film. Attached Figure Description

[0047] Figure 1 This is a schematic cross-sectional view illustrating an example of the laser thermal transfer film of the present invention.

[0048] Figure 2 This is a schematic diagram illustrating an example of the installation process of a laser thermal transfer film transfer element using the present invention.

[0049] Figure 3 A schematic diagram illustrating an example of measuring the expansion of the laser thermal transfer film of the present invention after irradiation with a laser using 3D (three-dimensional) methods and photographing it using a VHX digital microscope from KEYENCE.

[0050] Explanation of reference numerals in the attached figures

[0051] 1: Laser thermal transfer film; 11: Substrate film; 12: Photothermal conversion layer; 13: Adhesive layer; 14: Adhesive release layer; 15: Transfer substrate; 16: Solder; 17: Component; 18: Gap; 19: Expansion of photothermal conversion layer. Detailed Implementation

[0052] In order to solve the above-mentioned technical problems, the inventors of this application conducted in-depth research and found that the following laser thermal transfer film can solve the above-mentioned technical problems, thereby completing the present invention. The laser thermal transfer film is composed of three layers in sequence: a substrate film, a photothermal conversion layer, and an adhesive layer. The photothermal conversion layer contains an infrared absorber represented by the following general formula (1) and a bismaleimide resin represented by the following general formula (3) and / or a bismaleimide resin represented by the following general formula (4).

[0053] That is, the present invention is a laser thermal transfer film, characterized in that it comprises three layers in sequence: a substrate film, a photothermal conversion layer, and an adhesive layer. The photothermal conversion layer is solid at room temperature and contains an infrared absorber represented by general formula (1) and bismaleimide resin represented by general formula (3) and / or bismaleimide resin represented by general formula (4).

[0054]

[0055] In general formula (1), p is 1 or 2, R1 to R8 are independently substituted or unsubstituted linear or branched alkyl groups having 1 to 10 carbon atoms, and are optionally substituted by cyano, nitro, carboxyl, sulfonyl, halogen atom, hydroxyl, alkoxy, alkoxyalkoxy, acyloxy or alkylamino groups having 1 to 8 carbon atoms, X － The fluoroalkyl phosphate anion is represented by the following general formula (2).

[0056]

[0057] In general formula (2), x is 0 or 1, y is 1, 2 or 3, z is 6-y, and R9~R 13 They are either hydrogen or fluorine, each independently.

[0058]

[0059] In general formula (3), A represents a tetravalent organic group containing an aromatic ring or an alicyclic ring, Q represents a straight-chain alkylene group with 6 or more carbon atoms, R represents a straight-chain or branched alkyl group with 6 or more carbon atoms, and n represents an integer from 1 to 10.

[0060]

[0061] In general formula (4), A' represents a tetravalent organic group containing an aromatic ring or an alicyclic ring, B is a divalent alkylene chain with an alicyclic ring having 6 to 18 carbon atoms, Q' represents a straight-chain alkylene chain with 6 or more carbon atoms, R' independently represents a straight-chain or branched alkyl group with 6 or more carbon atoms, n' represents an integer from 1 to 10, and m represents an integer from 1 to 10.

[0062] As described above, the present invention relates to a laser thermal transfer film having a photothermal conversion layer and an adhesive layer stacked on a substrate film. The photothermal conversion layer contains an infrared absorber of a diamine series dye and a bismaleimide resin with a high coefficient of thermal expansion. The laser thermal transfer film has high transmittance in the visible light region, and the adhesive layer has an adhesion force within an appropriate range, thereby improving the transfer characteristics.

[0063] The photothermal conversion layer is a thin layer that is thermocured by infrared absorbers containing diammonium series dyes with a high coefficient of thermal expansion. The thickness of the adhesive layer is set to a specific range to adjust the adhesion. The photothermal conversion layer and the adhesive layer can expand and deform after being irradiated with a laser to reduce the ground plane of the semiconductor device, thereby reducing the adhesion and enabling the semiconductor device to be transferred onto a specific substrate.

[0064] The present invention will be described in detail below, but the present invention is not limited thereto.

[0065] Laser thermal transfer film

[0066] This invention relates to a laser thermal transfer film, which comprises three layers stacked sequentially: a substrate film, a photothermal conversion layer, and an adhesive layer. The photothermal conversion layer is solid at room temperature and contains a specific infrared absorber and a specific bismaleimide resin. Furthermore, in this invention, room temperature refers to 25°C.

[0067] like Figure 1 As shown, the laser thermal transfer film 1 of the present invention is formed by sequentially stacking three layers: a substrate film 11, a photothermal conversion layer 12, and an adhesive layer 13. The photothermal conversion layer 12 contains a specific infrared absorber and a specific bismaleimide resin. When the laser thermal transfer film 1 is irradiated with a laser, the photothermal conversion layer 12 is heated and expands, thereby causing the photothermal conversion layer 12 to push the adhesive layer 13 above it upwards, causing it to bulge.

[0068] The following is an explanation of each layer.

[0069] <Substrate Film>

[0070] The substrate film serves as a base plate that supports the photothermal conversion layer, the adhesive layer, and the transfer material attached to the adhesive layer.

[0071] The substrate film can be a polymer film. Suitable materials for use as the substrate film include, for example, polycarbonate, polyolefin, polyethylene resin, or polyester. The substrate film is preferably a transparent thermoplastic resin. Polyester films that combine light transmittance and thermal stability, such as polyethylene terephthalate or polyethylene naphthalate films, can be used, but are not limited to these; films with sufficient mechanical and thermal stability, and optical properties such as high transmittance for specific wavelengths of light, can also be used.

[0072] The thickness of the aforementioned substrate film is preferably 10–250 μm. For purposes such as improving adhesion to the photothermal conversion layer, it can undergo primer coating, roughening treatment, stretching or heat treatment to obtain thermal stability, and waterproofing treatment. Furthermore, to adjust light transmittance, it can contain a small amount of microparticles or filler materials. As the substrate film, for laser transmission, a 50–200 μm biaxially stretched polyethylene terephthalate (PET) film with a visible light transmittance of approximately 90% or more is preferred.

[0073] <Photothermal conversion layer>

[0074] The photothermal conversion layer is solid at room temperature and contains an infrared absorber represented by general formula (1) and a bismaleimide resin represented by general formula (3) and / or a bismaleimide resin represented by general formula (4). Utilizing one or more infrared absorbers contained within the photothermal conversion layer, light (laser) is absorbed and converted into heat, thereby causing the photothermal conversion layer to expand. Then, the physical force generated by the thermal expansion is used to transfer the semiconductor element to the transfer substrate.

[0075] The infrared absorber contained in the photothermal conversion layer is preferably 1-15% by mass, and the bismaleimide resin is preferably 85-99% by mass.

[0076] The photothermal conversion layer expands by utilizing localized heat absorption generated when irradiated with a laser. This makes the photothermal conversion layer easy to transfer, therefore, it is preferable to manufacture it as thin as possible, preferably with a thickness of 0.1 to 20 μm.

[0077] As the infrared absorber used in the photothermal conversion layer of the photothermal transfer film of the present invention, a series of diimonium salts dyes represented by the following general formula (1) are used.

[0078]

[0079] In general formula (1), p is 1 or 2, R1 to R8 are independently substituted or unsubstituted linear or branched alkyl groups having 1 to 10 carbon atoms, and are optionally substituted by cyano, nitro, carboxyl, sulfonyl, halogen atom, hydroxyl, alkoxy, alkoxyalkoxy, acyloxy or alkylamino groups having 1 to 8 carbon atoms, X － The fluoroalkyl phosphate anion is represented by the following general formula (2).

[0080]

[0081] In general formula (2), x is 0 or 1, y is 1, 2 or 3, z is 6-y, and R9~R 13 They are either hydrogen or fluorine, each independently.

[0082] In this invention, when a polyethylene terephthalate (PET) film with a thickness of, for example, 100 μm is used as the substrate film, the visible light transmittance of the biaxially stretched PET film can be set to about 90%. When the infrared absorber represented by the above general formula (1) is used in the substrate film, a photothermal transfer film that maintains transfer performance and has a visible light transmittance of more than 60% can be manufactured.

[0083] Visible light transmittance is inversely proportional to the concentration of the infrared absorber used in the photothermal conversion layer. The diammonium salt series organic dyes used as the infrared absorbers in this invention have higher absorbance in the near-infrared region, specifically in the 780–1500 nm wavelength range, than other organic dyes, thus resulting in high efficiency of photothermal conversion using near-infrared light. On the other hand, their absorbance in the visible light region is not high, and they exhibit high transparency in the visible light region. That is, it is preferable that the maximum absorption wavelength of the infrared absorber is in the range of 780–1500 nm.

[0084] To adjust the adhesion to the substrate film and / or adhesive layer, the aforementioned diammonium salt series dyes, used as infrared absorbers, are used in conjunction with an adhesive. Due to their excellent solubility in organic solvents, the diammonium salt series dyes can be uniformly dispersed in the bismaleimide resin used as an adhesive. As a result, because they are uniformly dispersed within the resin, the heat generated by the laser irradiation in a spot pattern becomes more uniform. Furthermore, this good dispersibility has the advantage of reducing thickness deviations in photothermal conversion layers with a thickness of less than 10 μm.

[0085] The bismaleimide resin used as the binder for the photothermal conversion layer is a solid bismaleimide resin at 25°C, and is a maleimide compound having at least one dimer acid backbone, at least one straight-chain alkylene group with 6 or more carbon atoms, and at least two maleimino groups in its molecule. Because it has a straight-chain alkylene group with 6 or more carbon atoms, it exhibits excellent heat resistance, and due to its large coefficient of thermal expansion, it expands significantly due to the heat generated by absorbing the laser, making transfer printing easy. In this invention, the bismaleimide resin represented by the following general formula (3) and / or the bismaleimide resin represented by general formula (4) are used as such bismaleimide resin.

[0086]

[0087] In general formula (3), A represents a tetravalent organic group containing an aromatic ring or an alicyclic ring, Q represents a straight-chain alkylene group with 6 or more carbon atoms, R represents a straight-chain or branched alkyl group with 6 or more carbon atoms, and n represents an integer from 1 to 10.

[0088]

[0089] In general formula (4), A' represents a tetravalent organic group containing an aromatic ring or an alicyclic ring, B is a divalent alkylene chain with an alicyclic ring having 6 to 18 carbon atoms, Q' represents a straight-chain alkylene chain with 6 or more carbon atoms, R' independently represents a straight-chain or branched alkyl group with 6 or more carbon atoms, n' represents an integer from 1 to 10, and m represents an integer from 1 to 10.

[0090] In general formula (3), Q and in general formula (4), Q' are straight-chain alkylene groups, and they have 6 or more carbon atoms, preferably 6 or more and 20 or less, more preferably 7 or more and 15 or less. In addition, in general formula (3), R and in general formula (4), R' have 6 or more carbon atoms, preferably 6 or more and 12 or less, and R and R' can be straight-chain or branched alkyl groups.

[0091] In general formula (3), A and in general formula (4) A' represent a tetravalent organic group containing an aromatic ring or an alicyclic ring, and are particularly preferred to be any one of the tetravalent organic groups represented by the following structural formulas.

[0092]

[0093] In addition, the bonding bonds of the unbonded substituents in the above structural formulas are bonded to the carbonyl carbons that form cyclic imide structures in general formulas (3) and (4).

[0094] Furthermore, B in general formula (4) is a divalent alkylene chain having an alicyclic ring optionally containing heteroatoms and having 6 to 18 carbon atoms, preferably having 8 or more and 15 or less carbon atoms. B in general formula (4) is preferably any one of the alkylene chains having an alicyclic ring represented by the following structural formulas.

[0095]

[0096] In addition, the unsubstituented bonds in the above structural formula are bonded to the nitrogen atom in general formula (4) to form a cyclic imide structure.

[0097] In general formula (3), n is an integer from 1 to 10, preferably an integer from 2 to 7. In general formula (4), n' is an integer from 1 to 10, preferably an integer from 2 to 7. In general formula (4), m is an integer from 1 to 10, preferably an integer from 2 to 7.

[0098] The weight-average molecular weight (Mw) of the bismaleimide resin is not particularly limited as long as it is solid at room temperature. Preferably, the weight-average molecular weight, calculated by gel permeation chromatography (GPC) and converted to polystyrene standards, is 2,000 to 50,000, particularly preferably 2,500 to 40,000, and more preferably 3,000 to 20,000. If the molecular weight is 2,000 or higher, the bismaleimide resin is solidified at room temperature. If the molecular weight is 50,000 or lower, there is no concern that the viscosity of the coating composition described later will become too high, leading to reduced flowability, resulting in good moldability.

[0099] In addition, Mw mentioned in this specification refers to the weight-average molecular weight obtained by GPC using polystyrene as a standard substance, measured under the following conditions.

[0100] <Measurement Conditions>

[0101] Developing solvent: Tetrahydrofuran (THF)

[0102] Flow rate: 0.35 mL / min

[0103] Detector: Differential Refractive Index Detector (RI)

[0104] Column: TSK Guardcolumn SuperH-L

[0105] TSKgel SuperHZ4000(4.6mmI.D.×15cm×1)

[0106] TSKgel SuperHZ3000(4.6mmI.D.×15cm×1)

[0107] TSKgel SuperHZ2000(4.6mmI.D.×15cm×2)

[0108] (All manufactured by TOSOH CORPORATION)

[0109] Column temperature: 40℃

[0110] Sample injection volume: 5 μL (0.2% by mass THF solution)

[0111] As the bismaleimide resin that can be used in this invention, commercially available resins such as SLK3000, SLK689, and SLK2600 from the SLK series (manufactured by Shin-Etsu Chemical Co., Ltd.) are preferred.

[0112] A coating composition in the form of a varnish-like solution is prepared, wherein the aforementioned infrared absorber, bismaleimide resin as a binder, and a curing catalyst are dissolved and dispersed in an organic solvent such as anisole. This varnish-like solution is then coated onto a substrate film and laminated. After coating, heat is applied in a heating bath to remove the solvent, causing the bismaleimide resin to dry and solidify. This results in the formation of a photothermal conversion layer on the substrate film that is solid at room temperature and contains the infrared absorber and maleimide resin.

[0113] The photothermal conversion layer can be solid at room temperature (25℃), and a curing catalyst can be added as needed. The curing catalyst can be imidazole catalysts, organic peroxides, etc., as long as it is a catalyst that enables the maleimide to react, there are no particular limitations.

[0114] The solids content of the coating composition is preferably 5 to 85% by mass, more preferably in the range of 5 to 60% by mass. If the solids content of the above composition is 5% by mass or more, it is easy to process to the desired coating thickness; if it is 85% by mass or less, the viscosity of the coating resin will not increase, and the surface after coating will not be rough, which is more suitable.

[0115] Furthermore, in the solid form of the above composition, the content of the infrared absorber (diammonium salt series dye) is preferably 1 to 15% by mass. If the content of the infrared absorber is 1% by mass or more, sufficient heat will be generated; if it is 15% by mass or less, the solubility of the infrared absorber will not decrease, and it is suitable for dispersion in the binder resin.

[0116] Since the resin is heated by heat generated by laser irradiation, the thermal decomposition initiation temperature of the cured bismaleimide resin is preferably 300°C or higher, more preferably 400°C or higher, and the glass transition temperature is preferably 150°C or lower, more preferably 100°C or lower, and even more preferably 50°C or lower.

[0117] The coefficient of thermal expansion of the cured bismaleimide resin is preferably 100 ppm / ℃ or less below the glass transition temperature, preferably 100 ppm / ℃ or more above the glass transition temperature, and more preferably 150 ppm / ℃ or more.

[0118] Generally, heat-resistant polyimide resins with a thermal decomposition initiation temperature of 300°C or higher have a glass transition temperature of 200°C or higher, and a coefficient of thermal expansion of 20 ppm / °C or lower below the glass transition temperature and 80 ppm / °C or lower above the glass transition temperature. Therefore, the expansion of the photothermal transfer layer of the polyimide resin after laser irradiation is less than that of the bismaleimide resin used in this invention, making it impossible to perform transfer from the laser thermal transfer film to the transfer substrate with good precision. Therefore, it is necessary to bring the transfer substrate, such as the transfer semiconductor element, as close as possible to the laser thermal transfer film beforehand. Consequently, it is difficult to control the transfer force during transfer from the laser thermal transfer film.

[0119] When using the laser thermal transfer film of the present invention, since it expands significantly due to laser irradiation, the transfer substrate and the laser thermal transfer film can be set separately. Furthermore, since the tip area of ​​the photothermal conversion layer, which expands to a convex shape due to thermal expansion, is reduced, the adhesion is further reduced, and semiconductor devices can be easily transferred to the transfer substrate.

[0120] The above coating composition may further contain crosslinking agents, humectants, surfactants, pH adjusters, viscosity adjusters, and cosolvents.

[0121] Lasers used for photothermal conversion include infrared lasers, visible lasers, UV lasers, and excimer lasers, among which infrared lasers are preferred.

[0122] <Adhesive layer>

[0123] The adhesive layer functions to attach semiconductor components to the laser thermal transfer film. The adhesive strength of this layer is designed with the adhesion strength of the transfer substrate in mind. By ensuring that the adhesive strength of the laser thermal transfer film and the transfer substrate are appropriately balanced, problems such as the transfer material gradually shifting to the transfer substrate side during film bonding, and the failure to transfer to the transfer substrate, are avoided. The adhesive strength of the laser transfer film is preferably 0.1 to 10 N / 25 mm in a 180° peel test (SUS substrate) according to JIS Z 0237, and can be adjusted within this range based on the adhesive strength on the transfer substrate side.

[0124] The thickness of the adhesive layer is preferably 1 to 10 μm. When the thickness of the adhesive layer is 1 μm or more, the adhesion will not decrease and the transfer body will adhere well. If the thickness is less than 10 μm, the transfer characteristics can be easily controlled after laser irradiation.

[0125] The adhesive layer is preferably selected from one or more of polyacrylate, polymethacrylate, epoxy, polystyrene, polyurethane, polysulfone, polyester, polyimide and silicone resin.

[0126] Among these, silicone adhesives with excellent heat resistance and stain resistance are preferred. Silicone adhesives are particularly suitable materials because they exhibit minimal transfer of the adhesive layer to the semiconductor device and excellent thermal stability. Examples of silicone adhesives include platinum addition-curing or condensation-curing types with MQ resin and high-viscosity vinylsiloxane as the main components; platinum addition-curing types, which cure rapidly after being coated onto the surface of the photothermal conversion layer, are preferred.

[0127] The above-mentioned organosilicon adhesive can be diluted with solvents such as toluene, and then coated onto the photothermal conversion layer at a thickness of 1 to 10 μm using a film coating machine and a glue coating machine, followed by solvent drying and adhesive curing.

[0128] The transfer material for laser thermal transfer film transfer is not particularly limited to any solid-shaped material such as a semiconductor element, a light-emitting element such as an LED, a substrate such as ceramic, a package containing a semiconductor element or an LED element made of plastic or ceramic, a ceramic substrate or resin sheet containing a phosphor, or a multilayer capacitor. In particular, by transferring micron-sized light-emitting diodes (Micro LEDs) or sub-millimeter-sized light-emitting diodes (Mini LEDs) onto a transfer substrate that serves as a display substrate and has solder bumps and anisotropic conductive layers, it is possible to manufacture display devices using LEDs.

[0129] <Transfer Process>

[0130] Figure 2 This is an example of the installation process of the laser thermal transfer film 1 transfer element using the present invention.

[0131] The laser thermal transfer film 1 has an adhesive release layer 14 stacked on the substrate film 11. The adhesive release layer 14 is formed by sequentially stacking a photothermal conversion layer 12 and an adhesive layer 13 from one side of the substrate film 11. On the other hand, solder 16 is provided on the part of the element to be transferred on one surface of the transfer substrate 15 by printing or the like.

[0132] After attaching component 17 to the adhesive layer surface of the adhesive release layer 14 of the laser thermal transfer film 1, the laser thermal transfer film 1 is placed in a laser irradiation device while the component 17 and solder 16 are facing each other and the distance (gap 18) between the laser thermal transfer film 1 and the transfer substrate 15 is set. Then, laser light is irradiated from the substrate film 11 side, causing the photothermal conversion layer to expand 19. At this time, the photothermal conversion layer 12 pushes the adhesive layer 13 above it upward, causing it to bulge, thereby transferring component 17 onto the solder 16 on the transfer substrate 15.

[0133] Example

[0134] The following examples and comparative examples illustrate the structure of the present invention and its effects in detail. However, these examples are used to illustrate the present invention in a more specific way, and the scope of the present invention is not limited to these examples.

[0135] The physical properties of the bismaleimide resins used in the examples / comparative examples are shown in Table 1.

[0136] [Table 1]

[0137] SLK3000 SLK689 SLK2600 polyimide Glass transition temperature 80℃ 30℃ 150℃ 230℃ Thermal decomposition onset temperature Above 400℃ Above 400℃ Above 400℃ 350℃ Coefficient of thermal expansion (above Tg) 150ppm / ℃ 170ppm / ℃ 150ppm / ℃ 80ppm / ℃

[0138] <Example 1>

[0139] (1) Substrate film: TORAY INDUSTRIES, INC. optical PET film (100 μm thick) is used as the substrate film.

[0140] (2) Photothermal conversion layer composition: The diimide series dye (made by Nippon Kayaku Co., Ltd., KAYASORB IRG-069), bismaleimide resin (SLK3000), and peroxide (diisopropylbenzene peroxide) as a curing catalyst are dissolved in anisole in the amounts listed in Table 2 to prepare the photothermal conversion layer composition (coating composition).

[0141] (3) Adhesive layer: Regarding the adhesive layer used to attach the transfer body, KR-3704 (manufactured by Shin-Etsu Chemical Co., Ltd.) and X-40-3237-1 (manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed in a ratio of 75:25 (mass ratio), and 0.5% of CATPL-50T manufactured by Shin-Etsu Chemical Co., Ltd. was further added, thereby preparing an adhesive with a solid content of 35% by mass.

[0142] Manufacturing of Laser Thermal Transfer Film

[0143] The photothermal transfer layer composition was applied to the substrate film using a Mayer bar and dried and cured at 150°C for 2 hours to form a photothermal transfer layer with an average thickness of 2.5 μm. Then, an adhesive was applied using a glue applicator and dried at 100°C for 3 minutes to form an adhesive layer with an average thickness of 3 μm (which showed an adhesion of 0.3 N / 25 mm in a 180° peel test (substrate SUS) according to JIS Z 0237), thus fabricating a laser thermal transfer film. Figure 1The transfer characteristics were evaluated using the methods described below. The results are recorded in Table 3.

[0144] <Example 2>

[0145] The amount of diammonium salt was varied, and the peroxide (diisopropylbenzene peroxide) used as a curing catalyst was dissolved in anisole in the amount described in Table 2 to prepare a composition for the photothermal conversion layer. Otherwise, a laser thermal transfer film was manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0146] <Example 3>

[0147] The amount of diammonium salt was varied, and the peroxide (diisopropylbenzene peroxide) used as a curing catalyst was dissolved in anisole in the amount described in Table 2 to prepare a composition for the photothermal conversion layer. Otherwise, a laser thermal transfer film was manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0148] <Example 4>

[0149] The bismaleimide resin was changed to SLK689 and SLK2600, and the peroxide (diisopropylbenzene peroxide) used as a curing catalyst was dissolved in anisole in the amounts described in Table 2, thereby preparing a composition for the photothermal conversion layer. Otherwise, a laser thermal transfer film was manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0150] <Example 5>

[0151] The amount of diammonium salt was varied, and the product was dissolved in anisole in the amounts described in Table 2 without the addition of peroxide (diisopropylbenzene peroxide) to prepare a composition for the photothermal conversion layer. A laser thermal transfer film was then manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0152] <Example 6>

[0153] The amount of diammonium salt was varied, and the peroxide (diisopropylbenzene peroxide) used as a curing catalyst was dissolved in anisole in the amount described in Table 2 to prepare a composition for the photothermal conversion layer. Otherwise, a laser thermal transfer film was manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0154] <Example 7>

[0155] The amount of diammonium salt was varied, and the amount of peroxide (diisopropylbenzene peroxide) used as a curing catalyst was dissolved in anisole as described in Table 2 to prepare a composition for photothermal conversion layer. A laser thermal transfer film was then manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0156] <Comparative Example 1>

[0157] The bismaleimide resin was replaced with a polyimide resin and dissolved in NMP (N-methylpyrrolidone) in the amounts described in Table 2 to prepare a composition for the photothermal transfer layer. Otherwise, a laser thermal transfer film was manufactured in the same manner as in Example 1, and the transfer characteristics were evaluated. The results are shown in Table 3.

[0158] <Evaluation of Transfer Properties>

[0159] A transfer substrate was fabricated by applying solder paste at a thickness of 20 μm onto designated electrodes on a PCB (printed circuit board) substrate using screen printing. Meanwhile, 100 evaluation optical semiconductor elements (500 μm square) were attached to a laser thermal transfer film consisting of a substrate, a photothermal conversion layer, and an adhesive layer, fabricated in the above embodiments and comparative examples. The distance between the laser thermal transfer film and the transfer substrate was set to 150 μm, and the film was placed in a laser irradiation device. A 1064 nm Nd:YAG laser was used to irradiate the laser thermal transfer film from the substrate side with a laser energy of 100 W. The expansion of the photothermal conversion layer transferred the optical semiconductor elements onto the solder paste on the transfer substrate. The number of optical semiconductor elements transferred to the transfer substrate was measured, and the transfer characteristics were evaluated.

[0160] <Example 8>

[0161] The expanded portion of the laser thermal transfer film of Example 1 after laser irradiation was photographed using a KEYENCE VHX digital microscope. The photographs are shown below. Figure 3 .

[0162] In this invention, the photothermal conversion layer contains a specific bismaleimide resin, thus enabling the achievement of this high elevation. The height of the expanded portion after laser irradiation was measured using 3D measurements and found to be 200 μm.

[0163] [Table 2]

[0164]

[0165] [Table 3]

[0166]

[0167] The laser thermal transfer films of Examples 1-7, which use bismaleimide resin as the resin in the composition for photothermal conversion layer, exhibit superior transfer characteristics compared to the laser thermal transfer film of Comparative Example 1, which uses polyimide resin as the resin in the composition for photothermal conversion layer. Therefore, using bismaleimide resin with a high expansion coefficient as the binder in the photothermal conversion layer is useful for providing laser thermal transfer films with improved transfer characteristics.

Claims

1. A laser heat transfer film characterized by, A substrate film, a photothermal conversion layer, and an adhesive layer are sequentially stacked, the photothermal conversion layer is solid at normal temperature and contains an infrared absorber represented by general formula (1) and a bismaleimide resin represented by general formula (3) and / or a bismaleimide resin represented by general formula (4), In general formula (1), p is 1 or 2, R1 to R8 are independently substituted or unsubstituted linear or branched alkyl groups having 1 to 10 carbon atoms, and are optionally substituted by cyano, nitro, carboxyl, sulfonyl, halogen atom, hydroxyl, alkoxy, alkoxyalkoxy, acyloxy or alkylamino groups having 1 to 8 carbon atoms, X － The fluoroalkyl phosphate anion is represented by the following general formula (2). In general formula (2), x is 0 or 1, y is 1, 2 or 3, z is 6-y, R9-R 13 are each independently hydrogen or fluorine, In general formula (3), A represents a 4-valent organic group including an aromatic ring or an alicyclic ring, Q represents a linear alkylene group having 6 or more carbon atoms, R each independently represents a linear or branched alkyl group having 6 or more carbon atoms, and n represents an integer of 1 to 10, In general formula (4), A' represents a 4-valent organic group including an aromatic ring or an alicyclic ring, B is a 2-valent alkylene chain having 6 to 18 carbon atoms having an alicyclic ring optionally including a hetero atom, Q' represents a linear alkylene group having 6 or more carbon atoms, R' each independently represents a linear or branched alkyl group having 6 or more carbon atoms, n' represents an integer of 1 to 10, and m represents an integer of 1 to 10.

2. The laser heat transfer film according to claim 1, wherein, The adhesive constituting the adhesive layer is one or a combination of two or more selected from the group consisting of polyacrylate, polymethacrylate, epoxy, polystyrene, polyurethane, polysulfone, polyester, polyimide, and silicone resin.

3. The laser heat transfer film according to claim 1, wherein, The content of the infrared absorber contained in the photothermal conversion layer is 1 to 15% by mass, and the bismaleimide resin is 85 to 99% by mass.

4. The laser heat transfer film according to claim 2, wherein, The content of the infrared absorber contained in the photothermal conversion layer is 1 to 15% by mass, and the bismaleimide resin is 85 to 99% by mass.

5. The laser heat transfer film according to claim 1, wherein, The thickness of the adhesive layer is 1 to 10 μm.

6. The laser heat transfer film according to claim 2, wherein, The thickness of the adhesive layer is 1 to 10 μm.

7. The laser heat transfer film according to claim 3, wherein, The thickness of the adhesive layer is 1 to 10 μm.

8. The laser heat transfer film according to claim 4, wherein, The thickness of the adhesive layer is 1 to 10 μm.

9. The laser heat transfer film according to claim 1, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

10. The laser heat transfer film according to claim 2, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

11. The laser heat transfer film according to claim 3, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

12. The laser heat transfer film according to claim 4, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

13. The laser heat transfer film according to claim 5, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

14. The laser heat transfer film according to claim 6, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

15. The laser heat transfer film according to claim 7, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

16. The laser heat transfer film according to claim 8, wherein, The thickness of the photothermal conversion layer is 0.1 to 20 μm.

17. The laser heat transfer film according to any one of claims 1 to 16, wherein, The maximum absorption wavelength of the infrared absorber is in the range of 780 to 1500 nm.

18. The laser heat transfer film according to any one of claims 1-16, wherein, The adhesive force of the adhesive layer is 0.1 to 10 N / 25 mm.

19. The laser heat transfer film according to any one of claims 1-16, wherein, The substrate film is a transparent thermoplastic resin.

20. The laser heat transfer film according to any one of claims 1-16, wherein, The cured product of the bismaleimide resin has a thermal decomposition initiation temperature of 300°C or higher and a glass transition temperature of 150°C or lower, and a thermal expansion coefficient of 100 ppm / °C or higher at or above the glass transition temperature.

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