JP7719630B2 - Double-sided adhesive sheet for transfer - Google Patents

Description

The present invention relates to a double-sided pressure-sensitive adhesive sheet for transfer.

Conventionally, in the manufacturing process of semiconductor devices, etc., semiconductor chips obtained by dividing a semiconductor wafer are received on a double-sided adhesive sheet for transfer on a carrier substrate, and then transferred onto a mounting substrate (for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2005-263876

In the manufacturing process of semiconductor devices, etc., marking is sometimes performed on a double-sided pressure-sensitive adhesive sheet for transfer to provide identification when the sheet is transported after receiving a semiconductor chip. However, when an ultraviolet laser is used for such marking, as shown in Figure 5, there is a problem in that the first pressure-sensitive adhesive layer 11 peels off and lifts off the substrate 10, damaging the flatness of the double-sided pressure-sensitive adhesive sheet for transfer, which can easily cause misalignment of the electronic component 21 or poor transfer.

The present invention was made in consideration of the above problems, and aims to provide a double-sided pressure-sensitive adhesive sheet for transfer that is less likely to cause misalignment of electronic components even when irradiated with ultraviolet light, and can maintain transfer accuracy.

As a result of extensive research to achieve the above-mentioned objective, the inventors have discovered that by using a double-sided adhesive transfer sheet that has a first adhesive layer for receiving fine electronic components such as semiconductor chips, a base material, and a second adhesive layer for temporarily fixing the components to a carrier substrate, and in which the ratio of the lift height before irradiation to the lift height after irradiation with a specific ultraviolet laser is within a specific range, it is possible to suppress misalignment of electronic components and transfer failures even when marking is performed by ultraviolet laser irradiation. The present invention was completed based on these findings.

That is, the present invention provides a double-sided PSA sheet for transfer, in which a first PSA layer, a substrate, and a second PSA layer are laminated in this order,
the first pressure-sensitive adhesive layer is a low-tack pressure-sensitive adhesive layer,
the second pressure-sensitive adhesive layer is a peelable pressure-sensitive adhesive layer,
The double-sided pressure-sensitive adhesive sheet for transfer is provided, in which the ratio (R z 2 /R z ¹ ) of the lift height R _{z 2} after irradiation to the lift height R _{z 1} before irradiation of the first pressure-sensitive adhesive layer with an ultraviolet laser having a wavelength of 248 nm at a beam size of 130 × 105 μm, an output of _{100 mJ} /cm ₂ , a frequency of 100 Hz, and a pulse width of 10 ns is 0.2 to 1600.

When the first adhesive layer is irradiated with an ultraviolet laser having a wavelength of 248 nm with a beam size of 130 x 105 μm, an output of 100 mJ/cm ² , a frequency of 100 Hz, and a pulse width of 10 ns, it is preferable that the area ratio of the lifted area to the irradiated area is 20.0% or less.

The present invention also provides a double-sided PSA sheet for transfer, comprising a first PSA layer, a substrate, and a second PSA layer laminated in this order,
the first pressure-sensitive adhesive layer is a low-tack pressure-sensitive adhesive layer,
the second pressure-sensitive adhesive layer is a peelable pressure-sensitive adhesive layer,
The double-sided pressure-sensitive adhesive sheet for transfer has an area ratio of the lifted area to the total irradiated area of 20.0% or less when the first pressure-sensitive adhesive layer is irradiated with an ultraviolet laser having a wavelength of 248 nm with a beam size of 130 x 105 μm, an output of 100 mJ/cm ² , a pulse width of 10 ns, and a frequency of 100 Hz.

The ratio ( R _z2 /t ₁ ) of the floating height R _z2 (μm) to the thickness t ₁ (μm) of the first pressure-sensitive adhesive layer is preferably 1.0 or less.

The double-sided pressure-sensitive adhesive sheet for transfer of the present invention is less likely to lose its flatness even when irradiated with an ultraviolet laser, thereby preventing misalignment of electronic components and transfer failures and maintaining transfer accuracy.

1 is a cross-sectional view schematically illustrating one embodiment of a double-sided pressure-sensitive adhesive sheet for transfer according to the present invention. FIG. 2 is a cross-sectional view schematically illustrating another embodiment of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention. 2 is a cross-sectional view showing an embodiment of a first step in a method for mounting an electronic component on a mounting substrate using the double-sided pressure-sensitive adhesive sheet for transfer shown in FIG. 1. FIG. 2 is a cross-sectional view showing an embodiment of a second step in a method for mounting an electronic component on a mounting substrate using the double-sided pressure-sensitive adhesive sheet for transfer shown in FIG. 1. FIG. FIG. 1 is a cross-sectional view showing a double-sided pressure-sensitive adhesive sheet for transfer in which flatness has been impaired by irradiation with an ultraviolet laser, causing misalignment of the received electronic component.

[Double-sided adhesive sheet for transfer]
A double-sided pressure-sensitive adhesive transfer sheet according to one embodiment of the present invention has a laminated structure in which a first pressure-sensitive adhesive layer, a substrate, and a second pressure-sensitive adhesive layer are laminated in this order, and the ratio (R z 2 /R z 1 ) of the lift height R _{z 2} after irradiation of the first pressure-sensitive adhesive layer with an ultraviolet laser having a wavelength of 248 nm at a beam size of 130 × 105 μm, an output of 100 mJ/cm ² , a frequency of 100 Hz, _and a pulse width of 10 ns to the lift height R _{z 1 before} irradiation is 0.2 to 1600. One embodiment of the double-sided pressure-sensitive adhesive transfer sheet of the present invention will be described below with reference to the drawings, but the double-sided pressure-sensitive adhesive transfer sheet of the present invention is not limited to this embodiment. Figure 1 is a cross-sectional schematic diagram showing one embodiment of the double-sided pressure-sensitive adhesive transfer sheet of the present invention, in which 1 represents the double-sided pressure-sensitive adhesive transfer sheet, 10 represents the substrate, 11 represents the first pressure-sensitive adhesive layer, and 12 represents the second pressure-sensitive adhesive layer.

From the viewpoint of the positional accuracy of the electronic component received by the first pressure-sensitive adhesive layer, the ratio (R _{z 2} /R _{z 1} ) being 0.2 to 1600 is preferred, and is more preferably 0.4 to 1500, and even more preferably 0.5 to 1400. The floating heights R _z1 and R _z2 are the maximum heights of swelling in the vertical direction (Z-axis direction) of the irradiated area after laser irradiation, and can be obtained, for example, by analyzing a surface observation image obtained using a laser microscope (product name "VK-X100", manufactured by Keyence Corporation).

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, when the first pressure-sensitive adhesive layer is irradiated with an ultraviolet laser having a wavelength of 248 nm at a beam size of 130 × 105 μm, an output of 100 mJ/cm ² , a frequency of 100 Hz, and a pulse width of 10 ns, the area ratio of the lifted area to the irradiated area is preferably 20.0% or less. A configuration in which the area ratio is 20.0% or less is preferred from the viewpoint of the positional accuracy of the electronic components received by the first pressure-sensitive adhesive layer, and 15.0% or less is more preferred, and 10.0% or less is even more preferred. The lower limit of the area ratio is usually 0%. The lifted area is the area of the portion where the low-tack pressure-sensitive adhesive layer is peeled off from the substrate and lifted, and can be determined, for example, by analyzing a surface observation image taken using a microscope.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the ratio ( _Rz2 / _t1 ) of the floating height Rz2 ₍ μm) to the thickness _t1 (μm) of the first pressure-sensitive adhesive layer is preferably 1.0 or less. A configuration in which the ratio ( _Rz2 / _t1 ) is 1.0 or less is preferred from the viewpoint of the positional accuracy of the electronic component received by the first pressure-sensitive adhesive layer, and a ratio of 0.5 or less is more preferred, and 0.4 or less is even more preferred.

The above-mentioned lifting height _Rz2 after irradiation with an ultraviolet laser and the area ratio of the lifting area can be adjusted by adjusting the adhesive strength by adjusting the type, composition, degree of crosslinking, etc. of the adhesive constituting the first adhesive layer, and by adjusting the type and amount of ultraviolet absorber to suppress reaction of the substrate or adjust the adhesion between the adhesive and the substrate.

Another embodiment of the double-sided pressure-sensitive adhesive sheet for transfer according to the present invention has a laminated structure in which a first pressure-sensitive adhesive layer, a substrate, and a second pressure-sensitive adhesive layer are laminated in this order, and when the first pressure-sensitive adhesive layer is irradiated with an ultraviolet laser having a wavelength of 248 nm at a beam size of 130 × 105 μm, an output of 100 mJ/cm ² , a frequency of 100 Hz, and a pulse width of 10 ns, the area ratio of the lifted area to the irradiated area is 20.0% or less. The configuration in which this area ratio is 20.0% or less allows the positional accuracy of electronic components to be maintained. The area ratio is preferably 15.0% or less, and more preferably 10.0% or less.

<First adhesive layer>
In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the first pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer for receiving and holding electronic components, and is composed of a low-tack pressure-sensitive adhesive layer. The configuration in which the first pressure-sensitive adhesive layer is composed of a low-tack pressure-sensitive adhesive layer is advantageous in that it reduces the force applied to the electronic components during reception and suppresses damage to the electronic components. Furthermore, when the first pressure-sensitive adhesive layer receives an electronic component without contact, for example, the electronic component is peeled off from the dicing tape by pushing it with a pin member and then dropped onto the first pressure-sensitive adhesive layer. However, the dropped electronic component may bounce when received by the first pressure-sensitive adhesive layer, making it impossible to receive it accurately. If this phenomenon occurs, the positional accuracy of the electronic product may decrease, resulting in poor contact. The configuration in which the first pressure-sensitive adhesive layer is composed of a low-tack pressure-sensitive adhesive layer is also advantageous in that when the first pressure-sensitive adhesive layer receives an electronic component without contact, the electronic component is easily caught by the first pressure-sensitive adhesive layer without bouncing, allowing it to be received with high positional accuracy. Furthermore, this is also preferable in that when the electronic component received by the double-sided pressure-sensitive adhesive sheet for transfer is mounted on a mounting substrate, the electronic component can be easily peeled off from the first pressure-sensitive adhesive layer.

The first adhesive layer can be made into a low-tack adhesive layer by adjusting the type, composition, and degree of crosslinking of the adhesive that makes it up, or by forming a weak boundary layer (WBL) by incorporating a light release agent or plasticizer.

The 180° peel adhesive strength of the first adhesive layer against a PET film at 25°C is not particularly limited, but from the viewpoints of being able to receive electronic components with good positional accuracy without damage and of achieving good transferability to the mounting substrate, it is preferably 100 mN/25 mm or less, more preferably 50 mN/25 mm or less, and even more preferably 10 mN/25 mm. Furthermore, from the viewpoint of the adhesion of electronic components to the first adhesive layer, the 180° peel adhesive strength of the first adhesive layer against a glass plate at 25°C is preferably 0.1 mN/25 mm or more, more preferably 1 mN/25 mm or more.

The ratio (P1b/P1a) of the 180° peel adhesive strength of the first adhesive layer against a PET film at 25°C (hereinafter sometimes referred to as "P1a" herein) to the 180° peel adhesive strength of the first adhesive layer against a PET film at 25°C after the double-sided adhesive sheet for transfer is held at 160°C for 5 minutes (hereinafter sometimes referred to as "P1b" herein) is not particularly limited, but is preferably 3.0 or less, and more preferably 2.5 or less. A P1b/P1a ratio of 3.0 or less is preferable because, when an electronic component received by the double-sided adhesive sheet for transfer of the present invention is transferred onto a mounting substrate by thermocompression bonding and mounted, the adhesive strength of the first adhesive layer against the electronic component does not increase, allowing for smooth peeling and transfer to the mounting substrate.

The 180° peel adhesive strength at 25°C was measured by laminating the second adhesive layer of a double-sided adhesive sheet for transfer to a glass plate, laminating a PET film to the adhesive surface of the first adhesive layer, and then compressing the sheet using a 2 kg roller with one back-and-forth motion. The sheet was then aged for 30 minutes in an atmosphere at 23°C and 50% RH. After aging, the double-sided adhesive sheet for transfer was peeled from the adherend in accordance with JIS Z0237 at 25°C, 50% RH, at a tensile speed of 300 mm/min and a peel angle of 180°. The PET film used is not particularly limited as long as it is untreated PET, but an example is "Lumirror #25-S10, Thickness 23 μm" (manufactured by Toray Industries, Inc.) under the trade name "Lumirror #25-S10, Thickness 23 μm."

The surface strength of the first adhesive layer can be adjusted by the type and composition of the adhesive that makes it up, the degree of crosslinking, and additives such as fatty acid esters and fluorine-based surfactants.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the storage modulus (E'1a) of the first pressure-sensitive adhesive layer at a frequency of 1 Hz and 25°C as measured by AFM-DMA is preferably 50 MPa or less. This configuration is preferable for reliably adhering electronic components received by the first pressure-sensitive adhesive layer. If E'1a is too high, the adhesion of the electronic components to the first pressure-sensitive adhesive layer may decrease, resulting in problems such as misalignment or dropping of the electronic components. From the viewpoint of the adhesion of the electronic components to the first pressure-sensitive adhesive layer, E'1a is preferably 40 MPa or less, and more preferably 30 MPa or less. It may also be 20 MPa or less, or 10 MPa or less. On the other hand, from the viewpoint of transferability from the first pressure-sensitive adhesive layer to a circuit board, E'1a is preferably 0.1 MPa or more. If E'1a is too low, the adhesion of the electronic components to the first pressure-sensitive adhesive layer may be too high, impairing transferability when mounted to a mounting board. From the viewpoint of transferability of electronic components to mounting substrates, E'1a is preferably 0.2 MPa or more, and more preferably 0.5 MPa or more.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the storage modulus (E'1b) of the first pressure-sensitive adhesive layer measured by AFM-DMA at a frequency of 1 kHz and 25°C is preferably 100 MPa or less. This configuration is preferable because, when the first pressure-sensitive adhesive layer receives an electronic component without contact, the electronic component is not repelled from the surface of the first pressure-sensitive adhesive layer and can be received with good positional accuracy. If E'1b is too high, when an electronic component is dropped onto the surface of the first pressure-sensitive adhesive layer without contacting it, the electronic component is likely to be repelled and shifted from its predetermined position or turned upside down, resulting in a decrease in positional accuracy. From the perspective of positional accuracy of the electronic component relative to the first pressure-sensitive adhesive layer, E'1b is preferably 90 MPa or less, more preferably 80 MPa or less. It may also be 70 MPa or less, 60 MPa or less, 50 MPa or less, 40 MPa or less, or 30 MPa or less, and particularly 20 MPa or less. On the other hand, from the viewpoint of transferability from the first pressure-sensitive adhesive layer to the mounting substrate, E'1b is preferably 0.5 MPa or more. If E'1b is too low, the adhesion of the electronic component to the first pressure-sensitive adhesive layer will be high, and the electronic component may be buried in the first pressure-sensitive adhesive layer when dropped, impairing transferability when mounted on the mounting substrate. From the viewpoint of transferability of the electronic component to the mounting substrate, E'1b is preferably 0.7 MPa or more, and more preferably 1.0 MPa or more.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the ratio (E'1b/E'1a) of the storage modulus (E'1b) of the first pressure-sensitive adhesive layer measured by AFM-DMA at a frequency of 1 Hz and 25°C to the storage modulus (E'1a) of the first pressure-sensitive adhesive layer measured by AFM-DMA at a frequency of 1 Hz and 25°C is preferably greater than 1.00. This configuration is preferable in that it provides a good balance between the adhesion of electronic components to the first pressure-sensitive adhesive layer, positional accuracy, and transferability to mounting substrates. From the perspective of a balance between the adhesion of electronic components, positional accuracy, and transferability to mounting substrates, E'1b/E'1a is preferably 1.05 or greater, and more preferably 1.10 or greater. There is no particular upper limit to E'1b/E'1a, but from the perspective of this balance, it is preferably 3.00 or less.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the loss modulus (E"1a) of the first pressure-sensitive adhesive layer at a frequency of 1 Hz and 25°C as measured by AFM-DMA is preferably 7 MPa or less. This configuration is preferred from the viewpoint of excellent transferability of electronic components to mounting substrates. If E"1a is too high, the adhesion of the electronic component to the first pressure-sensitive adhesive layer may be too high, which may impair transferability when mounting the electronic component to a mounting substrate. From the viewpoint of transferability of the electronic component to a mounting substrate, E"1a is preferably 5 MPa or less, and more preferably 3 MPa or less. If E"1a is too low, the adhesion of the electronic component to the first pressure-sensitive adhesive layer may decrease, which may result in problems such as misalignment or falling of the electronic component. From the viewpoint of adhesion of the electronic component to the first pressure-sensitive adhesive layer, E"1a is preferably 0.01 MPa or more, and more preferably 0.03 MPa or more.

The storage modulus (E'1a) at a frequency of 1 Hz and 25°C, the storage modulus (E'1b) at a frequency of 1 kHz and 25°C, and the loss modulus (E"1a) at a frequency of 1 Hz and 25°C measured by AFM-DMA (nano Dynamic Mechanical Analysis (nDMA) using an atomic force microscope (AFM)) of the first adhesive layer can be adjusted by adjusting the type, composition, degree of crosslinking, etc. of the adhesive that constitutes the adhesive.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the tack strength of the first pressure-sensitive adhesive layer against a stainless steel plate (diameter 5 mm) is preferably 10 to 250 gf/Φ5mm SUS. A configuration in which the tack strength is 10 gf/Φ5mm SUS or more is preferred from the standpoint of adhesion and positional accuracy of electronic components to the first pressure-sensitive adhesive layer, with 20 gf/Φ5mm SUS or more being more preferred. On the other hand, a configuration in which the tack strength is 250 gf/Φ5mm SUS or less is preferred from the standpoint of transferability of electronic components to mounting substrates, with 200 gf/Φ5mm SUS or less being more preferred.

The tack strength of the first adhesive layer against a stainless steel plate (5 mm diameter) can be adjusted by the type and composition of the adhesive that makes it up, the degree of crosslinking, and additives such as fatty acid esters and fluorine-based surfactants.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the surface strength of the first pressure-sensitive adhesive layer is preferably -500 to -100 μN. A surface strength of -500 μN or more is preferred from the standpoints of adhesion and positional accuracy of electronic components to the first pressure-sensitive adhesive layer, with -400 μN or more being more preferred. On the other hand, a surface strength of -100 μN or less is preferred from the standpoint of transferability of electronic components to mounting substrates, with -150 μN or less being more preferred.

The surface strength of the first adhesive layer can be adjusted by the type and composition of the adhesive that makes it up, the degree of crosslinking, and additives such as fatty acid esters and fluorine-based surfactants.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the thickness _t1 of the first pressure-sensitive adhesive layer is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more. A thickness of at least a certain level is preferred because it makes it easier for the first pressure-sensitive adhesive layer to receive electronic components with precision. The upper limit of the thickness _t1 of the first pressure-sensitive adhesive layer is also not particularly limited, but is preferably 100 μm, more preferably 90 μm, and even more preferably 80 μm, 70 μm, 60 μm, or 50 μm. It is even more preferred to have a thickness of 45 μm, 40 μm, 35 μm, μm, 30 μm, 25 μm, 20 μm, 15 μm, or 10 μm. A thickness of at most a certain level is preferred because it makes it easier to transfer electronic components to a mounting substrate with precision.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the haze (according to JIS K7136) of the first pressure-sensitive adhesive layer is not particularly limited, but is preferably 10% or less, and more preferably 5.0% or less. A haze of 10% or less provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, a pattern (e.g., a marker indicating the transfer position of an electronic component) on the carrier substrate can be visually recognized. The haze can be measured, for example, by forming the first pressure-sensitive adhesive layer on a separator and leaving it at room temperature (23°C, 50% RH) for at least 24 hours, peeling off the separator, and bonding the resulting sample to a slide glass (e.g., one with a total light transmittance of 91.8% and a haze of 0.4%) using a haze meter (product name "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the total light transmittance (according to JIS K7361-1) of the first pressure-sensitive adhesive layer in the visible light wavelength range is not particularly limited, but is preferably 85% or higher, and more preferably 88% or higher. A total light transmittance of 85% or higher provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, a pattern (e.g., a marker indicating the transfer position of an electronic component) on the carrier substrate can be visually recognized. The total light transmittance can be measured, for example, by forming the first pressure-sensitive adhesive layer on a separator and leaving it at room temperature (23°C, 50% RH) for at least 24 hours, peeling off the separator, and bonding the resulting sample to a glass slide (e.g., one with a total light transmittance of 91.8% and a haze of 0.4%) using a haze meter (product name "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

The adhesive composition constituting the first adhesive layer is not particularly limited, but may include, for example, silicone-based adhesives, urethane-based adhesives, acrylic-based adhesives, rubber-based adhesives, polyester-based adhesives, polyamide-based adhesives, epoxy-based adhesives, vinyl alkyl ether-based adhesives, fluorine-based adhesives, etc. Among these, from the viewpoints of being able to hold electronic components with high positional accuracy without damaging them and further enabling good transferability to the mounting substrate, silicone-based adhesives, urethane-based adhesives, and acrylic-based adhesives are preferred, as they are easy to control to have low adhesion and low tack, with silicone-based adhesives and urethane-based adhesives being more preferred, and silicone-based adhesives being even more preferred.

(Silicone adhesive)
The silicone-based adhesive is not particularly limited, and known or commonly used silicone-based adhesives can be used, such as addition-type silicone-based adhesives, peroxide-curing silicone-based adhesives, and condensation-type silicone-based adhesives. The silicone-based adhesives may be either one-component or two-component. The silicone-based adhesives can be used alone or in combination of two or more.

The above-mentioned addition-type silicone-based pressure-sensitive adhesives are generally pressure-sensitive adhesives that produce a silicone-based polymer by subjecting an organopolysiloxane that has an alkenyl group, such as a vinyl group, on the silicon atom and an organopolysiloxane that has a hydrosilyl group to an addition reaction (hydrosilylation reaction) using a platinum compound catalyst, such as chloroplatinic acid. Peroxide-curing silicone-based pressure-sensitive adhesives are generally pressure-sensitive adhesives that produce a silicone-based polymer by curing (crosslinking) an organopolysiloxane with peroxide. Condensation-type silicone-based pressure-sensitive adhesives are generally pressure-sensitive adhesives that produce a silicone-based polymer by a dehydration or dealcoholization reaction between polyorganosiloxanes that have hydrolyzable silyl groups, such as silanol groups or alkoxysilyl groups, at the terminals.

Examples of silicone-based adhesives include those containing silicone rubber and silicone resin, which are easy to control to achieve low adhesion and low tack.

The silicone rubber is not particularly limited as long as it contains a silicone-based rubber component. For example, organopolysiloxanes whose main structural units are dimethylsiloxane, methylphenylsiloxane, etc. can be used. Depending on the type of reaction, silicone rubbers having alkenyl groups bonded to silicon atoms (alkenyl-group-containing organopolysiloxanes; addition reaction types), silicone rubbers having at least methyl groups (peroxide-curing types), and silicone rubbers having silanol groups or hydrolyzable alkoxysilyl groups at the terminals (condensation types) can be used. The weight-average molecular weight of the organopolysiloxane in the silicone rubber is typically 150,000 or higher, preferably 280,000 to 1,000,000, with 500,000 to 900,000 being particularly suitable.

The silicone resin is not particularly limited as long as it is a silicone resin used in silicone-based pressure-sensitive adhesives, and examples thereof include silicone resins made of organopolysiloxanes made of (co)polymers having at least one unit selected from M units made of the structural unit " _{R3Si1 / 2} ", Q units made of the structural unit "SiO2 _{", T units made of the structural unit "RSiO3/2 "} , and D units made of the structural unit "R2SiO". In the structural units, R represents a hydrocarbon group or a hydroxyl group. Examples of the hydrocarbon group include aliphatic hydrocarbon groups (e.g., alkyl groups such as methyl and ethyl), alicyclic hydrocarbon groups (e.g., cycloalkyl groups such as cyclohexyl), and aromatic hydrocarbon groups (e.g., aryl groups such as phenyl and naphthyl). The ratio (ratio) of the M units to at least one unit selected from Q units, T units, and D units is preferably, for example, a former/latter (molar ratio) of about 0.3/1 to 1.5/1 (preferably 0.5/1 to 1.3/1). Various functional groups, such as vinyl groups, may be introduced into the organopolysiloxane in such silicone resins, as necessary. The introduced functional groups may be functional groups capable of undergoing a crosslinking reaction. MQ resins composed of M units and Q units are preferred as silicone resins. The weight-average molecular weight of the organopolysiloxane in the silicone resin is typically 1,000 or more, preferably 1,000 to 20,000, and particularly preferably 1,500 to 10,000.

There are no particular restrictions on the blending ratio of silicone rubber to silicone resin, but because it is easier to control the adhesiveness and tackiness, it is preferable that the silicone resin be 100 to 220 parts by weight (particularly 120 to 180 parts by weight) per 100 parts by weight of silicone rubber.

In a silicone-based adhesive containing silicone rubber and silicone resin, the silicone rubber and silicone resin may be simply mixed together, or may have reacted with each other to form a condensation product (particularly a partial condensation product), a crosslinked reaction product, an addition reaction product, etc.

Furthermore, silicone-based pressure-sensitive adhesives containing silicone rubber and silicone resin typically contain a crosslinking agent to form a crosslinked structure, which makes it easier to control low adhesion and low tack. There are no particular restrictions on such crosslinking agents, but siloxane-based crosslinking agents (silicone-based crosslinking agents) and peroxide-based crosslinking agents are suitable. Crosslinking agents can be used alone or in combination of two or more.

As the siloxane-based crosslinking agent, for example, a polyorganohydrogensiloxane having two or more hydrogen atoms bonded to silicon atoms in the molecule can be suitably used. In such polyorganohydrogensiloxanes, the silicon atoms to which hydrogen atoms are bonded may have various organic groups bonded in addition to the hydrogen atoms. Examples of such organic groups include alkyl groups such as methyl and ethyl groups; aryl groups such as phenyl groups; and halogenated alkyl groups. However, from the standpoint of synthesis and handling, methyl groups are preferred. Furthermore, the skeletal structure of the polyorganohydrogensiloxane may be linear, branched, or cyclic, although linear structures are preferred.

Examples of the peroxide-based crosslinking agent that can be used include diacyl peroxides, alkyl peroxy esters, peroxydicarbonates, monoperoxycarbonates, peroxyketals, dialkyl peroxides, hydroperoxides, and ketone peroxides. More specific examples include benzoyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,4-dichloro-benzoyl peroxide, di-t-butylperoxy-diisopropylbenzene, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5-di-t-butylperoxyhexyne-3.

Addition-type silicone-based adhesives are commercially available under the trade names "KR-3700," "KR-3701," "X-40-3237-1," "X-40-3240," "X-40-3291-1," and "X-40-3306" (all manufactured by Shin-Etsu Chemical Co., Ltd.). Peroxide-curing silicone-based adhesives are commercially available under the trade names "KR-100," "KR-101-10," and "KR-130" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

The addition-type silicone adhesive preferably contains a curing catalyst such as a platinum catalyst. Commercially available platinum catalysts include those under the trade name "CAT-PL-50T" (manufactured by Shin-Etsu Chemical Co., Ltd.), "DOWSIL NC-25 Catalyst," and "DOWSIL SRX212 Catalyst" (all manufactured by Dow-Toray Industries, Inc.). From the perspective of balancing the first adhesive layer's ability to accept electronic components, positional accuracy, transferability to the mounting substrate, and tack, the content of the curing catalyst is preferably approximately 0.1 to 10 parts by weight per 100 parts by weight of the silicone polymer (including silicone rubber, silicone resin, etc.) used as the base polymer.

(urethane adhesive)
The urethane-based adhesive is not particularly limited, and any known or commonly used urethane-based adhesive can be used. A urethane-based adhesive containing a polyol, a polyfunctional isocyanate compound, and a catalyst is preferred because it is easy to control the adhesiveness and tackiness to be low.

Any suitable polyol having two or more hydroxyl groups can be used as the polyol. Examples of such polyols include polyols (diols) having two hydroxyl groups, polyols (triols) having three hydroxyl groups, polyols (tetraols) having four hydroxyl groups, polyols (pentaols) having five hydroxyl groups, and polyols (hexaols) having six hydroxyl groups. Polyols can be used alone or in combination of two or more.

The polyol preferably contains a polyol having a number average molecular weight (Mn) of 400 to 20,000. Furthermore, the content of polyols having a number average molecular weight (Mn) of 400 to 20,000 in the total amount of polyols is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, even more preferably 90 to 100% by weight, particularly preferably 95 to 100% by weight, and most preferably substantially 100% by weight. By adjusting the content of polyols having a number average molecular weight (Mn) of 400 to 20,000 in the polyols to fall within the above range, it is possible to provide, for example, a urethane-based adhesive with controlled low adhesion and low tackiness.

Examples of the polyols include polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, and castor oil-based polyols.

The above polyester polyol can be obtained, for example, by an esterification reaction between a polyol component and an acid component.

Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, and polypropylene glycol.

Examples of the acid component include succinic acid, methylsuccinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anhydrides of these acids.

Examples of the polyether polyols include those obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide using water, low-molecular-weight polyols (propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.), bisphenols (bisphenol A, etc.), and dihydroxybenzenes (catechol, resorcinol, hydroquinone, etc.) as initiators. Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Examples of the polycaprolactone polyol include caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

Examples of the polycarbonate polyols include polycarbonate polyols obtained by polycondensation of the polyol components with phosgene; polycarbonate polyols obtained by transesterification of the polyol components with carbonate diesters such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, and dibenzyl carbonate; copolymer polycarbonate polyols obtained by combining two or more of the polyol components; polycarbonate polyols obtained by esterification of the various polycarbonate polyols described above with carboxyl group-containing compounds; and various polycarbonate polyols described above. Examples include polycarbonate polyols obtained by etherifying polycarbonate polyols with hydroxyl group-containing compounds; polycarbonate polyols obtained by transesterifying the above-mentioned various polycarbonate polyols with ester compounds; polycarbonate polyols obtained by transesterifying the above-mentioned various polycarbonate polyols with hydroxyl group-containing compounds; polyester-based polycarbonate polyols obtained by polycondensation of the above-mentioned various polycarbonate polyols with dicarboxylic acid compounds; and copolymer polyether-based polycarbonate polyols obtained by copolymerizing the above-mentioned various polycarbonate polyols with alkylene oxides.

The castor oil-based polyol may be, for example, a castor oil-based polyol obtained by reacting a castor oil fatty acid with the polyol component. Specifically, for example, a castor oil-based polyol obtained by reacting a castor oil fatty acid with polypropylene glycol may be used.

From the viewpoint of low adhesion, low tackiness, wettability, etc. of the first pressure-sensitive adhesive layer to electronic components, it is preferable to use a polyol (triol) having three hydroxyl groups as an essential component of the polyol. The content of the polyol (triol) having three hydroxyl groups is preferably 50 to 100 wt %, and more preferably 70 to 100 wt %, of the total amount of components constituting the polyol.

Examples of the polyfunctional isocyanate compounds include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanate compounds.

Examples of the aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of the alicyclic polyisocyanates include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

Examples of the aromatic polyisocyanate include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

Among these, aliphatic polyisocyanates and their modified products are preferred. Compared to other isocyanate-based crosslinking agents, aliphatic polyisocyanates and their modified products have a highly flexible crosslinked structure, making it easier to control the adhesiveness and tackiness. Hexamethylene diisocyanate and its modified products are particularly preferred as aliphatic polyisocyanates and their modified products.

From the viewpoint of low adhesion, low tackiness, and wettability of the first pressure-sensitive adhesive layer to electronic components, the equivalent ratio (NCO/OH) of the isocyanate groups of the polyfunctional isocyanate compound and the hydroxyl groups of the polyol is preferably 1 to 5, more preferably 1.1 to 3, and even more preferably 1.2 to 2, for the polyfunctional isocyanate compound and the polyol.

The urethane-based adhesive preferably contains a catalyst such as an iron-based compound and/or a tin-based compound. Specifically, tin-based catalysts such as dibutyltin dilaurate and dioctyltin dilaurate, iron tris(acetylacetonate), iron tris(hexane-2,4-dionato), iron tris(heptane-2,4-dionato), iron tris(heptane-3,5-dionato), iron tris(5-methylhexane-2,4-dionato), iron tris(octane-2,4-dionato), iron tris(6-methylheptane-2,5-dionato), iron tris(6-methylheptane-2,6 ... ,4-dionato)iron, tris(2,6-dimethylheptane-3,5-dionato)iron, tris(nonane-2,4-dionato)iron, tris(nonane-4,6-dionato)iron, tris(2,2,6,6-tetramethylheptane-3,5-dionato)iron, tris(tridecane-6,8-dionato)iron, tris(1-phenylbutane-1,3-dionato)iron, tris(hexafluoroacetylacetonate) Iron-based catalysts include iron tris(ethyl acetoacetate), iron tris(n-propyl acetoacetate), iron tris(isopropyl acetoacetate), iron tris(n-butyl acetoacetate), iron tris(sec-butyl acetoacetate), iron tris(tert-butyl acetoacetate), iron tris(methyl propionylacetate), iron tris(ethyl propionylacetate), iron tris(n-propyl propionylacetate), iron tris(isopropyl propionylacetate), iron tris(n-butyl propionylacetate), iron tris(sec-butyl propionylacetate), iron tris(tert-butyl propionylacetate), iron tris(benzyl acetoacetate), iron tris(dimethyl malonate), iron tris(diethyl malonate), iron trimethoxy, iron triethoxy, iron triisopropoxy, and ferric chloride.

The catalyst content (amount used) in the urethane-based adhesive is preferably 0.002 to 0.5 parts by weight, more preferably 0.005 to 0.3 parts by weight, and even more preferably 0.01 to 0.1 parts by weight, per 100 parts by weight of polyol. Within this range, the crosslinking reaction rate is fast when the adhesive layer is formed, and the pot life of the adhesive composition is also long, making this a preferred embodiment.

Furthermore, as a urethane-based adhesive, a urethane-based adhesive containing a urethane prepolymer is also preferred, as it is easy to control the adhesiveness and tackiness.

Examples of urethane-based adhesives containing urethane prepolymers include adhesives containing polyurethane polyol as the urethane prepolymer and a polyfunctional isocyanate compound. Urethane prepolymers can be used alone or in combination of two or more types. Polyfunctional isocyanate compounds can be used alone or in combination of two or more types.

The polyurethane polyol used as a urethane prepolymer is preferably obtained by reacting a polyester polyol and a polyether polyol with an organic polyisocyanate compound in the presence or absence of a catalyst.

Any suitable polyester polyol can be used as the polyester polyol. Examples of such polyester polyols include polyester polyols obtained by reacting an acid component with a glycol component. Examples of acid components include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Examples of glycol components include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, and butylethylpentanediol. Examples of polyol components include glycerin, trimethylolpropane, and pentaerythritol. Other examples of polyester polyols include polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone.

Polyester polyols with molecular weights ranging from low to high can be used. The number average molecular weight of the polyester polyol is preferably 500 to 5,000. If the number average molecular weight is less than 500, the reactivity may be high and gelation may occur easily. If the number average molecular weight exceeds 5,000, the reactivity may decrease and the cohesive strength of the polyurethane polyol itself may become weak. The amount of polyester polyol used is preferably 10 to 90 mol % of the polyols that make up the polyurethane polyol.

Any suitable polyether polyol can be used as the polyether polyol. Examples of such polyether polyols include those obtained by polymerizing oxirane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using a low-molecular-weight polyol such as water, propylene glycol, ethylene glycol, glycerin, or trimethylolpropane as an initiator. Specific examples of such polyether polyols include polyether polyols with two or more functional groups, such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol.

Polyether polyols with molecular weights ranging from low to high can be used. The number average molecular weight of the polyether polyol is preferably 1,000 to 5,000. If the number average molecular weight is less than 1,000, the reactivity may be high and gelation may occur easily. If the number average molecular weight exceeds 5,000, the reactivity may decrease and the cohesive strength of the polyurethane polyol itself may become weak. The amount of polyether polyol used is preferably 20 to 80 mol % of the polyols that make up the polyurethane polyol.

If necessary, polyether polyols can be partially replaced with glycols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, and pentaerythritol, or polyamines such as ethylenediamine, N-aminoethylethanolamine, isophoronediamine, and xylylenediamine.

As the polyether polyol, only a bifunctional polyether polyol may be used, or a polyether polyol having a number-average molecular weight of 1000 to 5000 and at least three hydroxyl groups per molecule may be used in part or in whole. Using a polyether polyol having an average molecular weight of 1000 to 5000 and at least three hydroxyl groups per molecule in part or in whole can achieve a good balance between adhesive strength and removability. If such a polyether polyol has a number-average molecular weight of less than 1000, it may become highly reactive and prone to gelation. If such a polyether polyol has a number-average molecular weight of more than 5000, it may become less reactive and the cohesive strength of the polyurethane polyol itself may become weaker. The number-average molecular weight of such a polyether polyol is more preferably 2500 to 3500.

Any suitable organic polyisocyanate compound can be used as the organic polyisocyanate compound. Examples of such organic polyisocyanate compounds include aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates.

Examples of aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4',4"-triphenylmethane triisocyanate.

Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of aromatic aliphatic polyisocyanates include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

Examples of alicyclic polyisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, and 1,4-bis(isocyanatomethyl)cyclohexane.

Organic polyisocyanate compounds that can be used in combination include trimethylolpropane adducts, biuret compounds reacted with water, and trimers having an isocyanurate ring.

Any suitable catalyst can be used to obtain polyurethane polyol. Examples of such catalysts include tertiary amine compounds and organometallic compounds.

Examples of tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU).

Examples of organometallic compounds include tin-based compounds and non-tin-based compounds.

Examples of tin-based compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.

Non-tin compounds include, for example, titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc compounds such as zinc naphthenate and zinc 2-ethylhexanoate; and zirconium compounds such as zirconium naphthenate.

When using a catalyst to produce polyurethane polyol, in systems containing two types of polyols, polyester polyol and polyether polyol, differences in reactivity can easily lead to problems such as gelation and cloudy reaction solutions when using a single catalyst. Therefore, using two types of catalysts to produce polyurethane polyol makes it easier to control the reaction rate, catalyst selectivity, and other factors, thereby solving these problems. Examples of such combinations of two catalysts include tertiary amine/organometallic, tin/non-tin, and tin/tin. Tin/tin combinations are preferred, and a combination of dibutyltin dilaurate and tin 2-ethylhexanoate is even more preferred. The weight ratio of tin 2-ethylhexanoate/dibutyltin dilaurate is preferably less than 1, and more preferably 0.2 to 0.6. A ratio of 1 or more can lead to gelation due to the balance of catalytic activity.

When a catalyst is used to obtain polyurethane polyol, the amount of catalyst used is preferably 0.01 to 1.0% by weight based on the total amount of polyester polyol, polyether polyol, and organic polyisocyanate compound.

When a catalyst is used to obtain polyurethane polyol, the reaction temperature is preferably below 100°C, and more preferably between 85°C and 95°C. Temperatures above 100°C may make it difficult to control the reaction rate and crosslinking structure, making it difficult to obtain polyurethane polyol with the desired molecular weight.

When obtaining polyurethane polyol, it is not necessary to use a catalyst. In that case, the reaction temperature is preferably 100°C or higher, and more preferably 110°C or higher. Furthermore, when obtaining polyurethane polyol without a catalyst, it is preferable to carry out the reaction for 3 hours or more.

Methods for obtaining polyurethane polyol include, for example, 1) charging polyester polyol, polyether polyol, catalyst, and organic polyisocyanate into a volumetric flask, and 2) charging polyester polyol, polyether polyol, and catalyst into a flask and adding the organic polyisocyanate dropwise. Method 2) is preferred for obtaining polyurethane polyol in terms of reaction control.

Any suitable solvent can be used to obtain the polyurethane polyol. Examples of such solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Of these solvents, toluene is preferred.

The polyfunctional isocyanate compounds mentioned above can be used.

Any appropriate manufacturing method can be used to produce a polyurethane composition obtained from a composition containing a urethane prepolymer, as long as it is a method for producing a polyurethane resin composition using a so-called "urethane prepolymer" as a raw material.

(acrylic adhesive)
The acrylic pressure-sensitive adhesive is not particularly limited, and any known or commonly used acrylic pressure-sensitive adhesive can be used. For example, an acrylic pressure-sensitive adhesive containing an acrylic polymer as a base polymer is preferred because it is easy to control the adhesiveness and tackiness to be low.

The acrylic polymer is a polymer containing structural units derived from acrylic monomers (monomer components having a (meth)acryloyl group in the molecule) as structural units of the polymer. The acrylic polymer is preferably a polymer containing structural units derived from (meth)acrylic acid esters in the largest proportion by mass. Acrylic polymers can be used alone or in combinations of two or more. In this specification, "(meth)acrylic" refers to "acrylic" and/or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and similar terms apply to other polymers.

Examples of the (meth)acrylic acid ester include hydrocarbon group-containing (meth)acrylic acid esters. Examples of hydrocarbon group-containing (meth)acrylic acid esters include (meth)acrylic acid alkyl esters, (meth)acrylic acid cycloalkyl esters, and (meth)acrylic acid aryl esters. Examples of the (meth)acrylic acid alkyl esters include the methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester, isopentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester (lauryl ester), tridecyl ester, tetradecyl ester, hexadecyl ester, octadecyl ester, and eicosyl ester of (meth)acrylic acid. Examples of the (meth)acrylic acid cycloalkyl esters include the cyclopentyl ester and cyclohexyl ester of (meth)acrylic acid. Examples of the (meth)acrylic acid aryl ester include phenyl ester and benzyl ester of (meth)acrylic acid.

The above hydrocarbon group-containing (meth)acrylic esters can be used alone or in combination of two or more. Because the basic properties of the hydrocarbon group-containing (meth)acrylic ester, such as adhesion, are appropriately exhibited in the first adhesive layer and low adhesion and tackiness can be easily controlled, the proportion of the hydrocarbon group-containing (meth)acrylic ester in all monomer components used to form the acrylic polymer is preferably 40% by mass or more, and more preferably 60% by mass or more.

The acrylic polymer may contain structural units derived from other monomer components copolymerizable with the hydrocarbon group-containing (meth)acrylic acid ester to modify properties such as cohesive strength, heat resistance, adhesiveness, and tackiness. Examples of such other monomer components include carboxy group-containing monomers, acid anhydride monomers, hydroxy group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, functional group-containing monomers such as acrylamide and acrylonitrile, and vinyl ester monomers. Examples of the carboxy group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the acid anhydride monomers include maleic anhydride and itaconic anhydride. Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and methylglycidyl (meth)acrylate. Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid. Examples of the phosphate group-containing monomer include 2-hydroxyethyl acryloyl phosphate. Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl cyclohexanecarboxylate, and vinyl benzoate. The other monomer components can be used alone or in combination of two or more. To ensure that the basic properties of the hydrocarbon group-containing (meth)acrylic acid ester, such as adhesion, are appropriately exhibited in the first adhesive layer and to facilitate control of low adhesion and low tack, the total proportion of the other monomer components in all monomer components used to form the acrylic polymer is preferably 60% by mass or less, and more preferably 40% by mass or less.

The acrylic polymer may contain structural units derived from a polyfunctional monomer copolymerizable with the monomer components forming the acrylic polymer to form a crosslinked structure within the polymer backbone. Examples of polyfunctional monomers include monomers containing a (meth)acryloyl group and other reactive functional groups within the molecule, such as hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylate (e.g., polyglycidyl (meth)acrylate), polyester (meth)acrylate, and urethane (meth)acrylate. The polyfunctional monomers may be used alone or in combination. In order to ensure that the basic properties of the hydrocarbon group-containing (meth)acrylic acid ester, such as adhesion, are properly exhibited in the first adhesive layer and to facilitate control of low adhesion and low tackiness, the proportion of the above-mentioned polyfunctional monomer in all monomer components used to form the acrylic polymer is preferably 40% by mass or less, and more preferably 30% by mass or less.

Acrylic polymers are obtained by polymerizing one or more monomer components, including acrylic monomers. Polymerization methods include solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization.

The mass-average molecular weight of the acrylic polymer is preferably 100,000 or more, and more preferably 200,000 to 3,000,000. When the mass-average molecular weight is 100,000 or more, the amount of low-molecular-weight substances in the adhesive layer tends to be low, which can further reduce contamination of electronic components, etc.

The acrylic pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer may contain a crosslinking agent. For example, the acrylic polymer can be crosslinked to further reduce low-molecular-weight substances in the first pressure-sensitive adhesive layer. Furthermore, the weight-average molecular weight of the acrylic polymer can be increased to control low adhesion and low tack. Examples of the crosslinking agent include polyisocyanate compounds, epoxy compounds, polyol compounds (such as polyphenol compounds), aziridine compounds, and melamine compounds, with isocyanate-based crosslinking agents and/or epoxy-based crosslinking agents being preferred. When a crosslinking agent is used, the amount used is preferably approximately 10 parts by weight or less, more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the acrylic polymer.

Examples of isocyanate-based crosslinking agents include aliphatic isocyanates, alicyclic isocyanates, and aromatic isocyanates. Examples of aliphatic isocyanates include trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, and dimer acid diisocyanate. Examples of alicyclic isocyanates include cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane. Examples of aromatic isocyanates include 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate. Further examples of isocyanate-based crosslinking agents include a trimethylolpropane adduct of tolylene diisocyanate (trade name "Coronate L", manufactured by Tosoh Corporation) and an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation).

Examples of epoxy crosslinking agents (multifunctional epoxy compounds) include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol polyglycidyl ether. Examples of suitable crosslinking agents include glycerol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether. Examples of suitable crosslinking agents include epoxy resins having two or more epoxy groups in the molecule. An example of a commercially available epoxy crosslinking agent is "Tetrad C" manufactured by Mitsubishi Gas Chemical Company, Inc.

The adhesive composition constituting the first adhesive layer preferably contains a light release agent. By including a light release agent, a WBL (Weak Boundary Layer) is formed on the surface of the first adhesive layer, making it easier to control low adhesion and low tack.

The light release agent is not particularly limited, and any known light release agent can be used without restriction. Examples include silicone-based release agents, fluorine-based surfactants, and aliphatic esters. These can be used alone or in combination of two or more.

The silicone-based release agent is not particularly limited, but examples include heat-curable silicone-based release agents and ionizing radiation-curable silicone-based release agents. Silicone-based release agents may be either solvent-free, meaning they contain no solvent, or solvent-based, meaning they are dissolved or dispersed in an organic solvent. Silicone-based release agents can be used alone or in combination of two or more types.

The above-mentioned thermosetting silicone-based release agent is not particularly limited, but is preferably one containing an organohydrogenpolysiloxane and an organopolysiloxane having an aliphatic unsaturated group. Furthermore, the above-mentioned silicone-based release agent is preferably a thermal addition reaction-curable silicone-based release agent that cures by crosslinking caused by a thermal addition reaction.

The above-mentioned thermal addition reaction curable silicone release agent is not particularly limited, but preferred examples include release agents containing a polysiloxane having a hydrogen atom (H) bonded to a silicon atom (Si) in the molecule (Si-H group-containing polysiloxane) and a polysiloxane containing a functional group (Si-H group-reactive functional group) in the molecule that is reactive with Si-H bonds (covalent bonds between Si and H) (Si-H group-reactive polysiloxane). This release agent cures through crosslinking caused by an addition reaction between the Si-H group and the Si-H group-reactive functional group.

In the above-mentioned Si-H group-containing polysiloxane, the Si bonded to H may be either Si in the main chain or Si in the side chain. The above-mentioned Si-H group-containing polysiloxane is preferably a polysiloxane containing two or more Si-H groups in the molecule. Preferred examples of polysiloxanes containing two or more Si-H groups include dimethylhydrogensiloxane-based polymers such as poly(dimethylsiloxane-methylsiloxane).

Preferred examples of the Si-H group-reactive polysiloxane include polysiloxanes in which an Si-H group-reactive functional group or a side chain containing such a functional group is bonded to Si (e.g., Si at the terminal of the main chain, or Si within the main chain) that forms the main chain (skeleton) of the siloxane-based polymer. Among these, polysiloxanes in which the Si-H group-reactive functional group is directly bonded to Si in the main chain are preferred. Furthermore, preferred examples of the Si-H group-reactive polysiloxane include polysiloxanes containing two or more Si-H group-reactive functional groups in the molecule.

Examples of the Si-H group-reactive functional group in the Si-H group-reactive polysiloxane include alkenyl groups such as vinyl and hexenyl. Examples of the siloxane-based polymer that forms the main chain of the Si-H group-reactive polysiloxane include polydialkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane (wherein the two alkyl groups may be the same or different); polyalkylarylsiloxanes; poly(dimethylsiloxane-methylsiloxane); and polymers obtained by polymerizing multiple Si-containing monomers. Among these, polydimethylsiloxane is preferred as the siloxane-based polymer that forms the main chain.

In particular, the thermal addition reaction curable silicone release agent is preferably a thermal addition reaction curable silicone release agent that contains a polysiloxane containing two or more Si-H groups in the molecule and a polysiloxane containing two or more Si-H group reactive functional groups in the molecule.

The ionizing radiation-curable silicone-based release agent is not particularly limited, but a preferred example is a UV-curable silicone-based release agent that cures through a crosslinking reaction upon exposure to ultraviolet (UV) light.

The above-mentioned UV-curable silicone-based release agent is a release agent that cures through a chemical reaction such as cationic polymerization, radical polymerization, radical addition polymerization, or hydrosilylation reaction upon UV irradiation. Of the above-mentioned UV-curable silicone-based release agents, UV-curable silicone-based release agents that cure through cationic polymerization are particularly preferred.

Although not particularly limited, cationic polymerization type UV-curable silicone release agents include preferred release agents containing epoxy group-containing polysiloxanes in which at least two epoxy groups are bonded directly or via divalent groups (e.g., alkylene groups such as methylene and ethylene; alkyleneoxy groups such as ethyleneoxy and propyleneoxy) to silicon atoms forming the main chain (skeleton) of the siloxane polymer (e.g., silicon atoms at the terminals of the main chain, silicon atoms within the main chain) and/or silicon atoms contained in the side chains. The bonding modes of these at least two epoxy groups to the silicon atoms may be the same or different. That is, preferred release agents include polysiloxanes containing two or more types of epoxy group-containing side chains. Examples of epoxy group-containing side chains include glycidyl groups, glycidoxy groups (glycidyloxy groups), 3,4-epoxycyclohexyl groups, and 2,3-epoxycyclopentyl groups. The epoxy group-containing polysiloxanes may be linear, branched, or a mixture thereof.

In particular, in the double-sided adhesive tape for transfer of the present invention, from the viewpoint of making it easier to control the first adhesive layer to have low adhesiveness and low tackiness, it is preferable that the silicone-based adhesive contain a heat-curable silicone-based release agent, and it is even more preferable that it contain a thermal addition reaction-curable silicone-based release agent.

When the first pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive tape for transfer of the present invention contains a silicone-based pressure-sensitive adhesive, the content of the silicone-based release agent is not particularly limited, but is preferably 0.5 parts by weight or more and 100 parts by weight or less per 100 parts by weight of the silicone-based polymer base polymer. A content of 0.5 parts by weight or more makes it easier to achieve the effect of easily controlling the first pressure-sensitive adhesive layer to have low adhesion and low tackiness, and is more preferably 1 part by weight or more, and even more preferably 3 parts by weight or more. Furthermore, a content of 100 parts by weight or less makes it easier to suppress the problem of insufficient adhesion resulting in difficulty in receiving electronic components, and is more preferably 30 parts by weight or less, and even more preferably 25 parts by weight or less.

By using the above fluorosurfactants as light release agents, the low surface free energy of the fluorine moieties can be used to achieve a light release effect.

The fluorosurfactant is not particularly limited, but examples include fluorooligomers, perfluorobutanesulfonates, perfluoroalkyl group-containing carboxylates, hexafluoropentane trimer derivative-containing sulfonates, hexafluoropentane trimer derivative-containing carboxylates, hexafluoropentane trimer derivative-containing quaternary ammonium salts, hexafluoropentane trimer derivative-containing betaines, and hexafluoropentane trimer derivative-containing polyoxyethylene ethers, with fluorooligomers being preferred. The fluorosurfactants can be used alone or in combination of two or more.

Specific examples of the above-mentioned fluorine-based surfactants include, for example, commercially available products under the trade names "Megafac F-114" and "Megafac F-410" (both manufactured by DIC Corporation), "Surflon S-211," "Surflon S-221," "Surflon S-231," "Surflon S-232," "Surflon S-233," "Surflon S-241," "Surflon S-242," "Surflon S-243," and "Surflon S-420" (all manufactured by AGC Seimi Chemical Co., Ltd.), and products under the trade names "Ftergent 100," "Ftergent 100C," "Ftergent 110," "Ftergent 150," "Ftergent 150CH," "Ftergent 300," and "Ftergent Examples of suitable compounds include Ftergent 310, Ftergent 320, Ftergent 400SW, Ftergent 251, Ftergent 212M, Ftergent 215M, Ftergent 250, Ftergent 209F, Ftergent 222F, Ftergent 245F, Ftergent 208G, Ftergent 218GL, Ftergent 240G, Ftergent 212P, Ftergent 220P, Ftergent 228P, Ftergent FTX-218, and Ftergent DFX-18 (all manufactured by Neos Corporation). These compounds may be used alone or in combination of two or more.

The weight-average molecular weight (Mw) of the fluorine-based oligomer is preferably 3,500 or more, more preferably 5,000 or more, even more preferably 10,000 or more, and particularly preferably 20,000 or more. When the weight-average molecular weight of the fluorine-based oligomer is 3,500 or more, it is easier to control the adhesiveness and tackiness. Furthermore, a weight-average molecular weight of 20,000 or more is preferable because it can suppress foaming during blending of the adhesive (composition) and results in excellent appearance after application of the adhesive. The upper limit of the weight-average molecular weight (Mw) of the fluorine-based oligomer is preferably 200,000, and more preferably 100,000 or less. Setting the upper limit to 200,000 makes it easier for the fluorine-based oligomer to be unevenly distributed on the surface, making it easier to exhibit an easy release effect, which is preferable.

Furthermore, examples of the above-mentioned fluorine-based oligomers include commercially available products under the trade names "Megafac F-251," "Megafac F-253," "Megafac F-281," "Megafac F-410," "Megafac F-430," "Megafac F-444," "Megafac F-477," "Megafac F-510," "Megafac F-511," "Megafac F-551," "Megafac F-552," "Megafac F-553," "Megafac F-554," "Megafac F-555," "Megafac F-556," "Megafac F-557," "Megafac F-558," "Megafac F-559," "Megafac F-560," "Megafac F-561," and "Megafac F- 562," "Megafac F-563," "Megafac F-565," "Megafac F-568," "Megafac F-569," "Megafac F-570," "Megafac F-571," and "Megafac F-572" (all manufactured by DIC Corporation); trade names "Surflon S-611," "Surflon S-651," and "Surflon S-386" (all manufactured by AGC Seimi Chemical Co., Ltd.); trade names "Ftergent 610FM," "Ftergent 710FL," "Ftergent 710FM," "Ftergent 710FS," "Ftergent 730FL," and "Ftergent 730LM" (all manufactured by Neos Corporation). These compounds may be used alone or in combination of two or more.

When the first pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive tape for transfer of the present invention contains a fluororesin surfactant, the content of the fluororesin surfactant is not particularly limited, but is preferably 0.01 to 5 parts by weight per 100 parts by weight of the silicone polymer base polymer. A content of 0.01 parts by weight or more makes it easier to achieve the effect of easily controlling the first pressure-sensitive adhesive layer to have low adhesion and low tackiness, and is more preferably 0.05 parts by weight or more, and even more preferably 0.1 parts by weight or more. Furthermore, a content of 5 parts by weight or less makes it easier to prevent the problem of insufficient adhesion resulting in difficulty in receiving electronic components, and from the viewpoint of preventing a decrease in transparency, is more preferably 3 parts by weight or less, and even more preferably 2 parts by weight or less.

By including a fatty acid ester in the adhesive composition that constitutes the first adhesive layer, the first adhesive layer can be expected to have low adhesion, low tack, and wettability to electronic components.

Examples of the fatty acid esters include polyoxyethylene bisphenol A laurate, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, behenic acid monoglyceride, cetyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, cholesteryl isostearate, lauryl methacrylate, coconut fatty acid methyl ester, methyl laurate, methyl oleate, methyl stearate, myristyl myristate, octyldodecyl myristate, pentaerythritol monooleate, pentaerythritol monostearate, pentaerythritol tetrapalmitate, stearyl stearate, isotridecyl stearate, 2-ethylhexanoic acid triglyceride, butyl laurate, octyl oleate, and tridecyl isononanoate. The fatty acid esters can be used alone or in combination of two or more.

From the viewpoints of low adhesion, low tack, and wettability of the first pressure-sensitive adhesive layer to electronic components, as well as contamination of the adherend, the content of the fatty acid ester contained in the urethane-based pressure-sensitive adhesive composition is, for example, preferably 1 to 50 parts by weight, more preferably 2 to 40 parts by weight, and even more preferably 3 to 30 parts by weight, per 100 parts by weight of polyol.

When the adhesive composition constituting the first adhesive layer contains a light release agent, the content (total amount) thereof is, for example, preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 3 parts by weight or more, per 100 parts by weight of base polymer, from the viewpoints of low adhesion, low tack, wettability, and contamination prevention of the first adhesive layer to electronic components. From the viewpoint of preventing discoloration of the first adhesive layer, the content is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less.

The above-mentioned UV absorbers are not particularly limited, but examples include triazine-based UV absorbers, benzotriazole-based UV absorbers, benzophenone-based UV absorbers, oxybenzophenone-based UV absorbers, salicylic acid ester-based UV absorbers, and cyanoacrylate-based UV absorbers, which can be used alone or in combination of two or more. Of these, benzotriazole-based UV absorbers and triazine-based UV absorbers are preferred because of their high UV absorption ability at wavelengths around 250 nm.

Specific examples of triazine-based ultraviolet absorbers having two or less hydroxyl groups per molecule include 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name "Tinosorb S", manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (trade name "TINUVIN 460", manufactured by BASF), 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and [(C ₁₀ -C ₁₆ (mainly C ₁₂ -C ₁₃ 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol (trade name "TINUVIN 400", manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine), Examples of suitable esters include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-glycidic acid esters (trade name "TINUVIN 405", manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (trade name "TINUVIN 1577", manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (trade name "ADK STAB LA46", manufactured by ADEKA), and 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (trade name "TINUVIN 479", manufactured by BASF).

Furthermore, examples of benzotriazole-based ultraviolet absorbers having one benzotriazole skeleton per molecule include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 928", manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (trade name "TINUVIN PS", manufactured by BASF), benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy(C _7-9 side chain and straight chain alkyl) ester compound (trade name "TINUVIN 384-2", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 900", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 928", manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300 (trade name "TINUVIN 1130", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (trade name "TINUVIN P", manufactured by BASF), 2(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 234", manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (trade name "TINUVIN 326", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (trade name "TINUVIN 328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TIN methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (trade name "TINUVIN 213", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (trade name "TINUVIN 571", manufactured by BASF), and 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimido-methyl)-5-methylphenyl]benzotriazole (trade name "Sumisorb 250", manufactured by Sumitomo Chemical Co., Ltd.).

Furthermore, examples of the benzophenone-based UV absorbers (benzophenone-based compounds) and oxybenzophenone-based UV absorbers (oxybenzophenone-based compounds) include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (anhydrous and trihydrate), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, and 2,2'-dihydroxy-4,4-dimethoxybenzophenone.

Furthermore, examples of the salicylate ester-based UV absorbers (salicylate ester-based compounds) include phenyl-2-acryloyloxybenzoate, phenyl-2-acryloyloxy-3-methylbenzoate, phenyl-2-acryloyloxy-4-methylbenzoate, phenyl-2-acryloyloxy-5-methylbenzoate, phenyl-2-acryloyloxy-3-methoxybenzoate, phenyl-2-hydroxybenzoate, phenyl-2-hydroxy-3-methylbenzoate, phenyl-2-hydroxy-4-methylbenzoate, phenyl-2-hydroxy-5-methylbenzoate, phenyl-2-hydroxy-3-methoxybenzoate, and 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate (trade name "TINUVIN 120", manufactured by BASF).

Examples of the cyanoacrylate-based ultraviolet absorbers (cyanoacrylate-based compounds) include alkyl-2-cyanoacrylate, cycloalkyl-2-cyanoacrylate, alkoxyalkyl-2-cyanoacrylate, alkenyl-2-cyanoacrylate, and alkynyl-2-cyanoacrylate.

The above UV absorbers may be used alone or in combination of two or more.

The maximum absorption wavelength of the absorption spectrum of the above-mentioned UV absorber is preferably in the wavelength range of 200 to 400 nm, and more preferably in the wavelength range of 240 to 380 nm. Examples of such UV absorbers include "Tinuvin 384-2" (maximum absorption wavelength 345 nm, manufactured by BASF).

The ultraviolet transmittance _TUV1 of the first pressure-sensitive adhesive layer to ultraviolet light having a wavelength of 248 nm is preferably 75% or less (more preferably 70% or less, even more preferably 50% or less, with the lower limit typically being 5%), although this varies depending on the thickness of the first pressure-sensitive adhesive layer. The ultraviolet transmittance can be measured, for example, by measuring the transmittance of ultraviolet light having a wavelength of 248 nm incident perpendicularly on the first pressure-sensitive adhesive layer using a spectrophotometer (product name "U-4100", manufactured by Hitachi High-Tech Science Corporation).

Furthermore, the value (TUV ₁ /t ₁ ) obtained by dividing the ultraviolet transmittance TUV ₁ of ultraviolet light with a wavelength of 248 nm of the first adhesive layer by the thickness t ₁ of the first adhesive layer is preferably 5.00 or less, more preferably 4.90 or less, and even more preferably 4.80 or less, and the lower limit is preferably 0.50, more preferably 0.70, and even more preferably 1.00.

The content of the UV absorber in the pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer varies depending on the thickness of the first pressure-sensitive adhesive layer. For example, if the thickness is 15 μm, the content is preferably 0.05 to 1.5 parts by weight, more preferably 0.07 to 1.2 parts by weight, and even more preferably 1.0 to 1.0 parts by weight, per 100 parts by weight of the pressure-sensitive adhesive.

The pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer may contain an antioxidant. The inclusion of an antioxidant can suppress deterioration such as discoloration during storage of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, and can also improve processability, such as making the double-sided pressure-sensitive adhesive sheet for transfer easier to cut.

The antioxidant may be, for example, a phenol-based, phosphorus-based, sulfur-based, or amine-based antioxidant, and at least one selected from these may be used. Among these, phenol-based antioxidants are preferred, and hindered phenol-based antioxidants are particularly preferred.

Specific examples of phenolic antioxidants include monocyclic phenolic compounds such as 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, 2,6-dicyclohexyl-4-methylphenol, 2,6-diisopropyl-4-ethylphenol, 2,6-di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol, and 2,6-dicyclohexyl-4-n-octyl. phenol, 2-isopropyl-4-methyl-6-t-butylphenol, 2-t-butyl-4-ethyl-6-t-octylphenol, 2-isobutyl-4-ethyl-6-t-hexylphenol, 2-cyclohexyl-4-n-butyl-6-isopropylphenol, styrenated mixed cresols, DL-α-tocopherol, stearyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, etc., Examples of phenol compounds include 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2'-thiobis(4-methyl-6-t-butylphenol), 4,4'-methylenebis(2,6-di-t-butylphenol), and 2,2'-methylenebis[6-(1-methylcyclohexyl) -p-cresol], 2,2'-ethylidenebis(4,6-di-t-butylphenol), 2,2'-butylidenebis(2-t-butyl-4-methylphenol), 3,6-dioxaoctamethylenebis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol As tricyclic phenol compounds, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-t-butylbenzyl)isocyanurate, 1,3,5-tris[(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanurate, tris(4-t-butyl ... Examples of tetracyclic phenol compounds include tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, and examples of phosphorus-containing phenol compounds include bis(3,5-di-t-butyl-4-hydroxybenzylphosphonate)calcium and bis(3,5-di-t-butyl-4-hydroxybenzylphosphonate)nickel.

The antioxidants may be used alone or in combination of two or more. From the viewpoints of suppressing deterioration such as discoloration during storage and the processability of the double-sided pressure-sensitive adhesive sheet for transfer, the content of the deterioration inhibitor contained in the pressure-sensitive adhesive composition is, for example, preferably 0.01 to 10 parts by weight, more preferably 0.03 to 5 parts by weight, and even more preferably 0.1 to 3 parts by weight, per 100 parts by weight of the first pressure-sensitive adhesive composition.

The adhesive composition constituting the first adhesive layer may contain any appropriate other components as long as the effects of the present invention are not impaired. Examples of such other components include tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, plasticizers, conductive agents, surface lubricants, leveling agents, heat stabilizers, polymerization inhibitors, lubricants, and solvents.

<Second adhesive layer>
In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the second pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer for temporarily fixing to a carrier substrate, and is composed of a peelable pressure-sensitive adhesive layer. The configuration in which the second pressure-sensitive adhesive layer is composed of a peelable pressure-sensitive adhesive layer is preferable in that the second pressure-sensitive adhesive layer can be peeled off from the carrier substrate without leaving any contamination such as adhesive residue, thereby improving reworkability.

The second adhesive layer can be made into a releasable adhesive layer by adjusting the adhesiveness through the type, composition, and degree of crosslinking of the adhesive, or by lowering the adhesive strength through physical stimuli such as heat or electromagnetic waves such as ultraviolet rays.

The 180° peel adhesive strength of the second adhesive layer from a glass plate at 25°C is not particularly limited, but from the viewpoints of enabling peeling from the carrier substrate without leaving any contamination such as adhesive residue and improving reworkability, it is preferably 5000 mN/25 mm or less, more preferably 3000 mN/25 mm or less, and even more preferably 1000 mN/25 mm or less. Furthermore, from the viewpoint of adhesion of the carrier substrate to the second adhesive layer, the 180° peel adhesive strength of the second adhesive layer from a glass plate at 25°C is preferably 1 mN/25 mm or more, more preferably 5 mN/25 mm or more.

The ratio (P2b/P2a) of the 180° peel adhesive strength of the second adhesive layer against a glass plate at 25°C after the double-sided adhesive sheet for transfer is held at 160°C for 5 minutes (hereinafter sometimes referred to as "P2b") to the 180° peel adhesive strength of the second adhesive layer against a glass plate at 25°C (hereinafter sometimes referred to as "P2a") is not particularly limited, but is preferably 2 or less, and more preferably 2.5 or less. A P2b/P2a ratio of 3 or less is preferred because, when an electronic component received by the double-sided adhesive sheet for transfer of the present invention is transferred and mounted on a mounting substrate by thermocompression bonding, the adhesive strength of the second adhesive layer against the carrier substrate does not increase, allowing for good peeling and excellent reworkability.

The 180° peel adhesive strength of the second adhesive layer at 25°C can be measured in the same manner as for the first adhesive layer.

The adhesive strength of the second adhesive layer can be adjusted by adjusting the type, composition, and degree of crosslinking of the adhesive that makes it up, or by forming a weak boundary layer (WBL) by incorporating a light release agent or plasticizer.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the thickness of the second pressure-sensitive adhesive layer is not particularly limited, but is preferably 1 μm or more, and more preferably 3 μm or more. A thickness of at least a certain level makes it easier for the second pressure-sensitive adhesive layer to be stably fixed to the carrier substrate, which is preferable. Furthermore, the upper limit of the thickness of the second pressure-sensitive adhesive layer is not particularly limited, but is preferably 30 μm, and more preferably 20 μm. A thickness of less than a certain level makes it easier for the second pressure-sensitive adhesive layer to be peeled from the carrier substrate, improving reworkability, which is preferable.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the haze (according to JIS K7136) of the second pressure-sensitive adhesive layer is not particularly limited, but is preferably 10% or less, and more preferably 5% or less. A haze of 10% or less provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, a pattern on the carrier substrate (e.g., a marker indicating the receiving position of an electronic component) can be visually recognized. The haze can be measured, for example, by forming the second pressure-sensitive adhesive layer on a separator and leaving it at room temperature (23°C, 50% RH) for at least 24 hours, peeling off the separator, and bonding the resulting sample to a slide glass (e.g., one with a total light transmittance of 91.8% and a haze of 0.4%) using a haze meter (product name "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the total light transmittance (according to JIS K7361-1) of the second pressure-sensitive adhesive layer in the visible light wavelength range is not particularly limited, but is preferably 85% or higher, and more preferably 88% or higher. A total light transmittance of 85% or higher provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, a pattern on the carrier substrate (e.g., a marker indicating the receiving position of an electronic component) can be visually recognized. The total light transmittance can be measured, for example, by forming the second pressure-sensitive adhesive layer on a separator and leaving it at room temperature (23°C, 50% RH) for at least 24 hours, peeling off the separator, and bonding the resulting sample to a glass slide (e.g., one with a total light transmittance of 91.8% and a haze of 0.4%) using a haze meter (product name "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

The adhesive constituting the second adhesive layer is not particularly limited, but examples include the silicone-based adhesives, urethane-based adhesives, acrylic-based adhesives, rubber-based adhesives, polyester-based adhesives, polyamide-based adhesives, epoxy-based adhesives, vinyl alkyl ether-based adhesives, and fluorine-based adhesives used in the first adhesive layer. Among these, from the viewpoints of peeling from the carrier substrate without leaving any adhesive residue or other contamination and improving reworkability, silicone-based adhesives, urethane-based adhesives, and acrylic-based adhesives are preferred, with urethane-based adhesives and acrylic-based adhesives being more preferred, and acrylic-based adhesives being even more preferred.

The second adhesive layer in the double-sided adhesive sheet for transfer of the present invention may be an adhesive layer whose adhesive strength can be intentionally reduced by external action during use of the double-sided adhesive sheet for transfer (adhesion-reducible adhesive layer), or it may be an adhesive layer whose adhesive strength is hardly or not reduced at all by external action during use of the double-sided adhesive sheet for transfer (adhesion-non-reducible adhesive layer), and can be selected as appropriate depending on the method and conditions for transferring electronic components using the double-sided adhesive sheet for transfer of the present invention.

When the second adhesive layer is an adhesive strength-reducible adhesive layer, it is possible to selectively switch between a state in which the second adhesive layer exhibits relatively high adhesive strength and a state in which it exhibits relatively low adhesive strength during the manufacturing process and use of the double-sided adhesive sheet for transfer of the present invention. For example, during the process in which the first adhesive layer receives an electronic component during use of the double-sided adhesive sheet for transfer of the present invention, it is possible to suppress or prevent the double-sided adhesive sheet for transfer from lifting off the carrier substrate by utilizing the state in which the second adhesive layer exhibits relatively high adhesive strength. On the other hand, during the subsequent process of peeling the double-sided adhesive sheet for transfer of the present invention from the carrier substrate, it is possible to improve reworkability by reducing the adhesive strength of the second adhesive layer.

Examples of adhesives that form such an adhesive strength-reducible adhesive layer include radiation-curable adhesives and heat-foamable adhesives. The adhesives that form the adhesive strength-reducible adhesive layer can be used alone or in combination of two or more types.

The radiation-curable adhesive may be, for example, an adhesive that cures when irradiated with electron beams, ultraviolet rays, alpha rays, beta rays, gamma rays, or X-rays, and it is particularly preferable to use an adhesive that cures when irradiated with ultraviolet rays (ultraviolet-curable adhesive).

Examples of the radiation-curable adhesive include additive-type radiation-curable adhesives that contain a base polymer such as an acrylic polymer and a radiation-polymerizable monomer or oligomer component that has a functional group such as a radiation-polymerizable carbon-carbon double bond.

The base polymer can be the same acrylic polymer as in the first pressure-sensitive adhesive layer. Because the basic properties of the hydrocarbon group-containing (meth)acrylic acid ester, such as adhesion, can be appropriately expressed in the second pressure-sensitive adhesive layer and adhesion and peelability can be easily controlled, the proportion of the hydrocarbon group-containing (meth)acrylic acid ester in all monomer components used to form the acrylic polymer is preferably 40% by mass or more, and more preferably 60% by mass or more.

The acrylic polymer may contain a hydroxy group-containing monomer. When the acrylic polymer in the second pressure-sensitive adhesive layer contains a hydroxy group-containing monomer, the second pressure-sensitive adhesive layer is more likely to have adequate cohesive strength. From the perspective of achieving adequate adhesiveness and cohesive strength in the second pressure-sensitive adhesive layer, the proportion of the hydroxy group-containing monomer in the acrylic polymer is, for example, 0.1 to 30% by mass, and preferably 0.5 to 20% by mass.

The acrylic polymer may contain a carboxyl group-containing monomer. When the acrylic polymer in the second pressure-sensitive adhesive layer contains a carboxyl group-containing monomer, the second pressure-sensitive adhesive layer is more likely to have adequate adhesive reliability. From the perspective of achieving adequate adhesive reliability in the second pressure-sensitive adhesive layer, the proportion of the carboxyl group-containing monomer in the acrylic polymer is, for example, 0.1 to 30% by mass, and preferably 0.5 to 20% by mass.

The acrylic polymer may contain a vinyl ester monomer. When the acrylic polymer in the second pressure-sensitive adhesive layer contains a vinyl ester monomer, the second pressure-sensitive adhesive layer is more likely to have an appropriate cohesive strength. From the perspective of achieving an appropriate cohesive strength in the second pressure-sensitive adhesive layer, the proportion of the vinyl ester monomer in the acrylic polymer is, for example, 0.1 to 60% by mass, and preferably 0.5 to 50% by mass.

The acrylic pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer may contain a crosslinking agent. For example, by crosslinking the acrylic polymer, it is possible to further reduce the amount of low-molecular-weight substances in the second pressure-sensitive adhesive layer. Furthermore, by increasing the weight-average molecular weight of the acrylic polymer, it is possible to control low adhesion and releasability. Examples of the crosslinking agent include polyisocyanate compounds, epoxy compounds, polyol compounds (such as polyphenol compounds), aziridine compounds, and melamine compounds. Isocyanate-based crosslinking agents and/or epoxy-based crosslinking agents are preferred. When a crosslinking agent is used, the amount used is preferably about 10 parts by weight or less, more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the acrylic polymer.

The acrylic adhesive composition forming the second adhesive layer may contain a crosslinking accelerator. The type of crosslinking accelerator can be selected appropriately depending on the type of crosslinking agent used. In this specification, the term "crosslinking accelerator" refers to a catalyst that increases the rate of the crosslinking reaction caused by the crosslinking agent. Examples of such crosslinking accelerators include tin (Sn)-containing compounds such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, and trimethyltin hydroxide; amines such as N,N,N',N'-tetramethylhexanediamine and triethylamine; and N-containing compounds such as imidazoles. Among these, Sn-containing compounds are preferred. The use of these crosslinking accelerators is particularly effective when a hydroxyl group-containing monomer is used as the secondary monomer and an isocyanate-based crosslinking agent is used as the crosslinking agent. The amount of crosslinking accelerator contained in the pressure-sensitive adhesive composition can be, for example, approximately 0.001 to 0.5 parts by mass (preferably approximately 0.001 to 0.1 parts by mass) per 100 parts by mass of the acrylic polymer.

Examples of the radiation-polymerizable monomer component include urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Examples of the radiation-polymerizable oligomer component include various oligomers, such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers, with those having a molecular weight of approximately 100 to 30,000 being preferred. The content of the radiation-curable monomer component and oligomer component in the radiation-curable adhesive that forms the second adhesive layer is, for example, 5 to 500 parts by weight, and preferably approximately 40 to 150 parts by weight, per 100 parts by weight of the base polymer. Additionally, additive-type radiation-curable adhesives such as those disclosed in JP-A-60-196956 may be used.

The above-mentioned radiation-curable adhesives also include inherent radiation-curable adhesives containing a base polymer having a functional group such as a radiation-polymerizable carbon-carbon double bond on the polymer side chain, in the polymer main chain, or at the end of the polymer main chain. The use of such inherent radiation-curable adhesives tends to suppress unintended changes in adhesive properties over time due to the migration of low-molecular-weight components within the formed second adhesive layer.

The base polymer contained in the inherent radiation-curable adhesive is preferably an acrylic polymer. One method for introducing a radiation-polymerizable carbon-carbon double bond into an acrylic polymer involves, for example, polymerizing (copolymerizing) raw material monomers containing a monomer component having a first functional group to obtain an acrylic polymer, and then subjecting the acrylic polymer to a condensation reaction or addition reaction with a compound having a radiation-polymerizable carbon-carbon double bond and a second functional group reactive with the first functional group, while maintaining the radiation-polymerizability of the carbon-carbon double bond.

Examples of combinations of the first functional group and the second functional group include a carboxy group and an epoxy group, an epoxy group and a carboxy group, a carboxy group and an aziridyl group, an aziridyl group and a carboxy group, a hydroxy group and an isocyanate group, and an isocyanate group and a hydroxy group. Among these, from the perspective of ease of reaction tracking, a combination of a hydroxy group and an isocyanate group, and a combination of an isocyanate group and a hydroxy group are preferred. While producing a polymer containing a highly reactive isocyanate group is technically difficult, from the perspective of ease of production and acquisition of an acrylic polymer containing a hydroxy group, a combination in which the first functional group is a hydroxy group and the second functional group is an isocyanate group is preferred. Examples of compounds containing an isocyanate group and a radiation-polymerizable carbon-carbon double bond, i.e., radiation-polymerizable unsaturated functional group-containing isocyanate compounds, include, for example, methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Examples of acrylic polymers containing hydroxy groups include those containing structural units derived from the above-mentioned hydroxy group-containing monomers and ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether.

The radiation-curable adhesive preferably contains a photopolymerization initiator. Examples of the photopolymerization initiator include α-ketol compounds, acetophenone compounds, benzoin ether compounds, ketal compounds, aromatic sulfonyl chloride compounds, photoactive oxime compounds, benzophenone compounds, thioxanthone compounds, camphorquinone, halogenated ketones, acylphosphinoxides, and acylphosphonates. Examples of the α-ketol compounds include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone. Examples of the acetophenone-based compounds include methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1, and the like. Examples of the benzoin ether-based compounds include benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether. Examples of the ketal-based compounds include benzyl dimethyl ketal. Examples of the aromatic sulfonyl chloride-based compounds include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based compounds include 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime. Examples of the benzophenone-based compounds include benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone. Examples of the thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone. The content of the photopolymerization initiator in the radiation-curable adhesive is, for example, 0.05 to 20 parts by mass per 100 parts by mass of the base polymer.

The heat-foamable adhesive is an adhesive containing a component that foams or expands upon heating (foaming agent, heat-expandable microspheres, etc.). Examples of the foaming agent include various inorganic and organic foaming agents. Examples of the inorganic foaming agent include ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and azides. Examples of the organic blowing agent include fluorinated alkanes such as trichloromonofluoromethane and dichloromonofluoromethane; azo compounds such as azobisisobutyronitrile, azodicarbonamide and barium azodicarboxylate; hydrazine compounds such as paratoluenesulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 4,4'-oxybis(benzenesulfonylhydrazide) and allylbis(sulfonylhydrazide); semicarbazide compounds such as p-toluylenesulfonylsemicarbazide and 4,4'-oxybis(benzenesulfonylsemicarbazide); triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso compounds such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide. Examples of the heat-expandable microspheres include microspheres whose shell contains a substance that easily gasifies and expands when heated. Examples of the substance that easily gasifies and expands when heated include isobutane, propane, and pentane. Heat-expandable microspheres can be produced by encapsulating the substance that easily gasifies and expands when heated within a shell-forming substance using a coacervation method or interfacial polymerization method. Examples of the shell-forming substance include substances that exhibit thermal melting properties and substances that can be ruptured by the thermal expansion of the encapsulated substance. Examples of such substances include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone.

The non-reduced adhesive layer may be, for example, a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer includes an adhesive layer formed from the radiation-curable adhesive described above for the reducible adhesive layer, which is cured by irradiation while maintaining a certain level of adhesive strength. The adhesives forming the non-reduced adhesive layer may be used alone or in combination of two or more. The second adhesive layer may be entirely or partially composed of a non-reduced adhesive layer. For example, when the second adhesive layer has a monolayer structure, the entire second adhesive layer may be a non-reduced adhesive layer, or a specific portion of the second adhesive layer may be a non-reduced adhesive layer and other portions may be reducible adhesive layers. When the second adhesive layer has a laminated structure, all adhesive layers in the laminated structure may be non-reduced adhesive layers, or only a portion of the adhesive layers in the laminated structure may be non-reduced adhesive layers.

An adhesive layer (irradiated, radiation-cured adhesive layer) formed by previously curing an adhesive layer (unirradiated, radiation-cured adhesive layer) from a radiation-curable adhesive agent by irradiation exhibits adhesiveness attributable to the polymer components contained therein, even if its adhesive strength has been reduced by radiation irradiation, and is capable of exhibiting the minimum adhesive strength required for the double-sided adhesive sheet for transfer of the present invention. When an irradiated, radiation-cured adhesive layer is used, the entire second adhesive layer in the surface extension direction of the second adhesive layer may be an irradiated, radiation-cured adhesive layer, or a portion of the second adhesive layer may be an irradiated, radiation-cured adhesive layer and the remaining portion may be an unirradiated, radiation-cured adhesive layer. In this specification, the term "radiation-cured adhesive layer" refers to an adhesive layer formed from a radiation-curable adhesive, and includes both an unirradiated, radiation-cured adhesive layer that has radiation curability, and a radiation-cured, radiation-cured adhesive layer that is obtained after the adhesive layer has been cured by radiation exposure.

The adhesive that forms the pressure-sensitive adhesive layer can be a known or commonly used pressure-sensitive adhesive, and an acrylic adhesive that uses an acrylic polymer as the base polymer is preferably used. When the second adhesive layer contains an acrylic polymer as the pressure-sensitive adhesive, the acrylic polymer is preferably a polymer that contains a structural unit derived from a (meth)acrylic acid ester as the structural unit that is most abundant by mass. For example, the acrylic polymer that can be used as the acrylic polymer is one of the acrylic polymers described above as being capable of being contained in the additive-type radiation-curable adhesive.

<Base material>
The substrate in the double-sided pressure-sensitive adhesive sheet for transfer of the present invention is an element that functions as a support for the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer. Examples of the substrate include a plastic substrate (particularly a plastic film). The substrate may be a single layer or a laminate of the same or different substrates.

Examples of resins that may be used to form the plastic substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, very low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester (random, alternating) copolymers, ethylene-butene copolymers, and ethylene-hexene copolymers; polyurethanes; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonates; polyimides; polyether ether ketones; polyetherimides; polyamides such as aramids and wholly aromatic polyamides; polyphenyl sulfides; fluororesins; polyvinyl chloride; polyvinylidene chloride; cellulose resins; and silicone resins. When an electronic component received by the double-sided pressure-sensitive adhesive sheet for transfer of the present invention is transferred onto a mounting substrate by thermocompression bonding (e.g., at 150°C) for mounting, the substrate exhibits good heat resistance, making it less susceptible to thermal expansion or contraction, and enabling accurate mounting. From this viewpoint, the substrate preferably contains a heat-resistant resin such as polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide (PA), or polyether ether ketone (PEEK) as its main component, and more preferably contains polyimide as its main component. The main component of the substrate refers to the component that accounts for the largest mass percentage of the constituent components. The above resins can be used alone or in combination of two or more types. When the second pressure-sensitive adhesive layer is a radiation-curable pressure-sensitive adhesive layer as described above, the substrate is preferably radiation-transparent.

When the substrate is a plastic film, the plastic film may be non-oriented or oriented in at least one direction (uniaxial, biaxial, etc.), but non-oriented plastic films are preferred because they are less likely to exhibit heat shrinkage.

The surface of the substrate facing the first adhesive layer and/or second adhesive layer may be subjected to surface treatments, such as physical treatments such as corona discharge treatment, plasma treatment, sand matting, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, and ionizing radiation treatment, chemical treatments such as chromate treatment, coating agents (primers), and silicone primer treatments to enhance adhesion, in order to improve adhesion and retention with the adhesive layer. Furthermore, to impart antistatic properties, the substrate surface may be provided with a conductive vapor deposition layer containing a metal, alloy, or oxide thereof, or coated with a conductive polymer such as PEDOT-PSS. It is preferable that the surface treatment to improve adhesion be applied to the entire surface of the substrate facing the adhesive layer.

From the viewpoint of ensuring the strength required for the substrate to function as a support in the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the thickness of the substrate is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and particularly preferably 20 μm or more. Furthermore, from the viewpoint of achieving appropriate flexibility in the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the thickness of the substrate is preferably 200 μm or less, more preferably 180 μm or less, and even more preferably 150 μm or less.

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the haze of the substrate (in accordance with JIS K7136) is not particularly limited, but is preferably 10% or less, and more preferably 5.0% or less. A haze of 10% or less provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, patterns on the carrier substrate (e.g., markers indicating the receiving positions of electronic components) can be visually recognized. The haze can be measured using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory Co., Ltd.).

In the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, the total light transmittance (in accordance with JIS K7361-1) of the substrate in the visible light wavelength range is not particularly limited, but is preferably 85% or higher, and more preferably 88% or higher. A total light transmittance of 85% or higher provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, patterns on the carrier substrate (e.g., markers indicating the receiving positions of electronic components) can be visually recognized. The total light transmittance can be measured using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory Co., Ltd.).

<Separator>
The pressure-sensitive adhesive layer surface (the adhesive surface of the first pressure-sensitive adhesive layer and/or the second pressure-sensitive adhesive layer) of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention may be protected by a release liner (separator) until use. The separator is used as a protective material for the pressure-sensitive adhesive layer and is peeled off when the pressure-sensitive adhesive sheet is attached to an adherend. Figure 2 is a cross-sectional schematic diagram showing one embodiment of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention, in which 1 denotes the double-sided pressure-sensitive adhesive sheet for transfer, 10 denotes a substrate, 11 denotes the first pressure-sensitive adhesive layer, 12 denotes the second pressure-sensitive adhesive layer, and 110 and 120 denote separators. Note that the separator does not necessarily have to be provided.

Conventional release paper and the like can be used as the separator. Specific examples include substrates having a release treatment layer made from a release agent on at least one surface, low-adhesion substrates made from fluorine-based polymers (e.g., polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.), and low-adhesion substrates made from non-polar polymers (e.g., olefin-based resins such as polyethylene and polypropylene).

As the separator, for example, a separator having a release treatment layer formed on at least one surface of the separator substrate can be suitably used. Examples of such separator substrates include plastic substrate films (synthetic resin films) such as polyester films (polyethylene terephthalate films, etc.), olefin resin films (polyethylene films, polypropylene films, etc.), polyvinyl chloride films, polyimide films, polyamide films (nylon films), and rayon films; papers (high-quality paper, Japanese paper, kraft paper, glassine paper, synthetic paper, top-coated paper, etc.); and composites (2- to 3-layer composites) of these materials formed by lamination, co-extrusion, etc.

The release treatment agent constituting the release treatment layer is not particularly limited, but examples thereof include silicone-based release treatment agents, fluorine-based release treatment agents, long-chain alkyl-based release treatment agents, etc. The release treatment agents can be used alone or in combination of two or more.
Since the first pressure-sensitive adhesive layer is composed of a low-tack pressure-sensitive adhesive layer, it is also possible to use a substrate that is not treated with a release agent as the separator.

The above separator may have an antistatic layer formed on at least one surface of the separator substrate to prevent adverse effects on electronic components. The antistatic layer may be formed on one surface of the separator (the release-treated surface or the untreated surface), or on both surfaces of the separator (the release-treated surface and the untreated surface).

Antistatic agents contained in antistatic resins include cationic antistatic agents having cationic functional groups such as quaternary ammonium salts, pyridinium salts, and primary, secondary, and tertiary amino groups; anionic antistatic agents having anionic functional groups such as sulfonates, sulfate ester salts, phosphonates, and phosphate ester salts; amphoteric antistatic agents such as alkylbetaine and its derivatives, imidazoline and its derivatives, and alanine and its derivatives; nonionic antistatic agents such as aminoalcohols and their derivatives, glycerin and its derivatives, and polyethylene glycol and its derivatives; and ionic conductive polymers obtained by polymerizing or copolymerizing monomers having the above-mentioned cationic, anionic, or amphoteric ionic conductive groups. These compounds may be used alone or in combination.

The thickness of the separator is not particularly limited and can be selected appropriately from the range of 5 to 100 μm.

The method for producing the double-sided pressure-sensitive adhesive sheet for transfer of the present invention varies depending on the composition of the pressure-sensitive adhesive composition, etc., and is not particularly limited. Any known forming method can be used, and examples thereof include the following methods (1) to (4).
(1) A method for producing a pressure-sensitive adhesive sheet by applying (coating) the pressure-sensitive adhesive composition onto a substrate to form a composition layer, and curing the composition layer (for example, by heat curing or by irradiation with active energy rays such as ultraviolet rays) to form a pressure-sensitive adhesive layer. (2) A method for producing a pressure-sensitive adhesive sheet by applying (coating) the pressure-sensitive adhesive composition onto a separator to form a composition layer, and curing the composition layer (for example, by heat curing or by irradiation with active energy rays such as ultraviolet rays) to form a pressure-sensitive adhesive layer, and then transferring the pressure-sensitive adhesive layer onto a substrate. (3) A method for producing a pressure-sensitive adhesive sheet by applying (coating) the pressure-sensitive adhesive composition onto a substrate and drying it to form a pressure-sensitive adhesive layer. (4) A method for producing a pressure-sensitive adhesive sheet by applying (coating) the pressure-sensitive adhesive composition onto a separator and drying it to form a pressure-sensitive adhesive layer, and then transferring the pressure-sensitive adhesive layer onto a substrate.

As the curing method for (1) to (4) above, thermal curing is preferred because it is highly productive and can form a homogeneous adhesive layer with a smooth surface.

The method for applying (coating) the pressure-sensitive adhesive composition to a predetermined surface can be any known coating method, and includes, but is not limited to, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater, etc.

The thickness (total thickness) of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more. A thickness of at least a certain level is preferred as it makes it easier for the first pressure-sensitive adhesive layer to receive electronic components with precision. Furthermore, the upper limit of the thickness (total thickness) of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention is not particularly limited, but is preferably 500 μm, more preferably 300 μm. A thickness of at most a certain level is preferred as it makes it easier to transfer electronic components to a mounting substrate with precision. The thickness of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention does not include the thickness of the separator.

The haze (according to JIS K7136) of the double-sided pressure-sensitive adhesive transfer sheet of the present invention is not particularly limited, but is preferably 10% or less, and more preferably 5.0% or less. A haze of 10% or less provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive transfer sheet is attached to a carrier substrate, a pattern (e.g., a marker indicating the receiving position of an electronic component) on the carrier substrate can be visually recognized. The haze can be measured, for example, by leaving the double-sided pressure-sensitive adhesive transfer sheet at room temperature (23°C, 50% RH) for at least 24 hours, removing the separator, if any, and bonding the sheet to a slide glass (e.g., one with a total light transmittance of 91.8% and a haze of 0.4%). Using this as a sample, the sheet can be measured using a haze meter (product name "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

The total light transmittance (according to JIS K7361-1) in the visible light wavelength range of the double-sided pressure-sensitive adhesive sheet for transfer of the present invention is not particularly limited, but is preferably 85% or higher, and more preferably 88% or higher. A total light transmittance of 85% or higher provides excellent transparency, and is preferable because, for example, when the double-sided pressure-sensitive adhesive sheet for transfer is attached to a carrier substrate, a pattern on the carrier substrate (e.g., a marker indicating the receiving position of an electronic component) can be visually recognized. The total light transmittance can be measured, for example, by leaving the double-sided pressure-sensitive adhesive sheet for transfer at room temperature (23°C, 50% RH) for at least 24 hours, removing the separator, if any, and bonding the sheet to a slide glass (e.g., one with a total light transmittance of 91.8% and a haze of 0.4%). Using this as a sample, the sheet can be measured using a haze meter (product name "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

The double-sided pressure-sensitive adhesive sheet for transfer of the present invention is suitable for use in a method for mounting electronic components on a mounting substrate. The method for mounting electronic components on a mounting substrate using the double-sided pressure-sensitive adhesive sheet for transfer of the present invention preferably includes the following steps:
A step in which the diced electronic component is received by the first adhesive layer of the double-sided adhesive sheet for transfer (first step).
a step of transferring the electronic component received by the first adhesive layer to a mounting substrate (second step);

Figure 3 is a schematic cross-sectional view showing one embodiment of the first step in a method for mounting electronic components on a mounting substrate using the double-sided pressure-sensitive adhesive sheet for transfer of the present invention.

In Figure 3(a), the double-sided adhesive sheet for transfer 1 is attached to the carrier substrate 22 via the adhesive surface of the second adhesive layer 12. A marking pattern for arranging electronic components may be provided on the surface of the carrier substrate 22 that is attached to the second adhesive layer 12. Because the double-sided adhesive sheet for transfer 1 is highly transparent, the marking pattern provided on the carrier substrate 22 can be seen.

A plurality of electronic components 21, which have been diced into individual pieces, are attached to dicing tape 20 on top of the adhesive surface of the first adhesive layer 11 of the double-sided adhesive sheet 1, and are arranged facing and spaced apart from the adhesive surface of the first adhesive layer 11.

3(b), the pin member 23 pushes the electronic component 21 against the side of the dicing tape 20 to which the electronic component 21 is not attached, bringing the electronic component 21 close to the adhesive surface of the first adhesive layer 11, and the electronic component 21 is received by the adhesive surface of the first adhesive layer 11. The electronic component 21 may be received by contacting the first adhesive layer 11, or it may be received without contact. When receiving without contact, the electronic component 21 is pushed until it peels off the dicing tape 20, and then dropped onto the adhesive surface of the electronic component 21. When receiving by contact, the adhesive surface of the first adhesive layer 11 has low adhesiveness, so the stress applied when the electronic component 21 is received is low, and damage to the electronic component 21 can be suppressed. When receiving without contact, the adhesive surface of the first adhesive layer 11 has low adhesiveness, so the dropped electronic component 21 can be caught with high positional accuracy. Instead of using the pin members 23, the electronic components 21 may be peeled off from the dicing tape 20 by irradiating them with radiation such as ultraviolet light or laser light.

The electronic components 21 can be received individually on the first adhesive layer 11, or multiple components can be received together. Figure 3(c) is a schematic cross-sectional view showing the state in which all of the electronic components 21 on the dicing tape 20 have been received on the adhesive surface of the first adhesive layer 11 of the double-sided adhesive sheet 1 for transfer.

Figure 4 is a schematic cross-sectional view showing the second step in the method for mounting electronic components on a mounting substrate using the double-sided pressure-sensitive adhesive sheet for transfer of the present invention.

As shown in Figure 4(a), electronic components 21 are arranged on the adhesive surface of the first adhesive layer 11 of the double-sided adhesive sheet 1 for transfer, facing and spaced apart from the circuit surface 31 (circuit pattern not shown) of the mounting substrate 30. Next, as shown in Figure 4(b), the circuit surface 31 of the mounting substrate 30 and the electronic components 21 arranged on the adhesive surface of the first adhesive layer 11 of the double-sided adhesive sheet 1 for transfer are brought close together, so that the electronic components 21 and the circuit surface 31 of the mounting substrate 30 come into contact.

Transfer of the electronic component 21 to the circuit surface 31 of the mounting substrate 30 may be performed by thermocompression bonding (e.g., 150°C, 1 minute). The substrate 10, first adhesive layer 11, and/or second adhesive layer 12 that make up the double-sided adhesive sheet 1 for transfer have excellent heat resistance and are therefore less likely to expand, contract, or have their adhesive strength changed by thermocompression bonding, allowing for accurate transfer of the electronic component 21 to the circuit surface 31 of the mounting substrate 30.

Next, as shown in Figure 4(c), the double-sided adhesive sheet for transfer 1 and the mounting substrate 30 are separated, causing the electronic component 21 to peel from the first adhesive layer 11 and be transferred to the circuit surface 31 of the mounting substrate 30. Because the first adhesive layer 11 is composed of a low-tack adhesive layer, the electronic component 21 peels easily and can be efficiently mounted on the mounting substrate 30 without being damaged.

After the electronic component 21 has been mounted on the mounting substrate 30, the double-sided adhesive sheet 1 for transfer shown in Figure 4(c) may be peeled off from the carrier substrate 22 (not shown). Because the second adhesive layer 12 is composed of a peelable adhesive layer, it can be peeled off without leaving any adhesive residue, and its excellent reworkability allows the carrier substrate 22 to be easily reused.

The electronic components to be mounted on the mounting substrate are not particularly limited, but can be suitably used for fine, thin semiconductor chips and LED chips.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way.

Example 1
100 parts by weight of a silicone-based pressure-sensitive adhesive (addition reaction type silicone-based pressure-sensitive adhesive, product name "X-40-3306", manufactured by Shin-Etsu Chemical Co., Ltd.), 1.4 parts by weight of a platinum-based catalyst 1 (product name "CAT-PL-50T", manufactured by Shin-Etsu Chemical Co., Ltd.), 5 parts by weight of a silicone-based release agent 1 (an addition reaction type silicone-based release agent mainly composed of dimethylpolysiloxane, product name "KS-776A", manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.2 parts by weight of an ultraviolet absorber (product name "Tinuvin 384-2", maximum absorption wavelength 345 nm, manufactured by BASF) were blended, diluted with toluene to a total solids content of 25% by weight, and mixed using a disperser to prepare a silicone-based pressure-sensitive adhesive composition (1).

Silicone-based pressure-sensitive adhesive composition (1) was applied to the silicone-primed surface of a substrate film (polyester film with one side treated with a silicone primer, thickness 75 μm, product name "Diafoil MRF#75", manufactured by Mitsubishi Plastics, Inc.) so that the adhesive thickness after drying would be 15 μm, and the film was cured and dried at a drying temperature of 120°C for a drying time of 5 minutes. In this way, a film was obtained having a silicone-based pressure-sensitive adhesive layer on the silicone-primed layer of the substrate film.

A separator (1) (a polyethylene terephthalate film without release treatment, 25 μm thick, product name "Lumirror S10#25", manufactured by Toyobo Co., Ltd.) was laminated onto the adhesive surface of the silicone adhesive film to protect the silicone adhesive layer, thereby obtaining a laminate (1) having a laminate structure of [separator (1) layer]/[silicone adhesive (1) layer]/[base film layer].

Next, a four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 100 parts by weight of 2-ethylhexyl acrylate (2EHA) (manufactured by Nippon Shokubai Co., Ltd.), 4 parts by weight of 2-hydroxyethyl acrylate (HEA) (manufactured by Toagosei Co., Ltd.), 0.02 parts by weight of 2,2'-azobisisobutyronitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, and 180 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was maintained at around 65°C. A polymerization reaction was carried out for 6 hours, producing a solution of acrylic copolymer (solids content 35% by weight) with a weight-average molecular weight of 560,000.

To the prepared acrylic copolymer solution, 4.0 parts by solids of Coronate HX (manufactured by Tosoh Corporation) as a crosslinking agent and 0.02 parts by solids of Envirizer OL-1 (manufactured by Tokyo Fine Chemical Co., Ltd.) as a crosslinking catalyst were added per 100 parts by solids, and the mixture was diluted with toluene to a total solids content of 25% by weight. The resulting acrylic pressure-sensitive adhesive composition was stirred with a disperser and applied to the release-treated layer side of separator (2) (release-treated polyethylene terephthalate film, thickness 38 μm, product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) with a fountain roll to a dry thickness of 20 μm. The mixture was then cured and dried at a drying temperature of 130°C for 30 seconds. In this way, an acrylic pressure-sensitive adhesive layer was formed on separator (2).

Next, the substrate film side (the side not treated with silicone primer) of the laminate (1) obtained above was bonded to the surface of the acrylic pressure-sensitive adhesive layer, yielding a double-sided pressure-sensitive adhesive sheet for transfer having a laminate structure of [separator (1) layer]/[silicone pressure-sensitive adhesive (1) layer (first pressure-sensitive adhesive layer)]/[substrate film layer]/[acrylic pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer)]/[separator (2) layer].

<Examples 2 to 6, Comparative Examples 1 and 2>
In the same manner as in Example 1, a silicone-based pressure-sensitive adhesive composition containing an ultraviolet absorber (trade name "Tinuvin 384-2, maximum absorption wavelength 345 nm, manufactured by BASF) blended in the amount shown in Table 1 was used to form a first pressure-sensitive adhesive layer to the thickness shown in Table 1, thereby obtaining double-sided pressure-sensitive adhesive sheets for transfer.

<Evaluation>
The double-sided pressure-sensitive adhesive sheets for transfer obtained in the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 1.

(UV transmittance)
A thin section was cut out from the first pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet for transfer using a microtome, and the transmittance was measured in the wavelength range of 200 to 800 nm using a microscopic ultraviolet-visible-near-infrared spectrophotometer (product name "MSV-5200 DGK", manufactured by JASCO Corporation), and the value at a wavelength of 248 nm was taken as the ultraviolet transmittance TUV ₁ .

(floating height)
A double-sided pressure-sensitive adhesive sheet for transfer from which the separator (1) layer had been peeled was irradiated from the silicone-based pressure-sensitive adhesive layer side with an ultraviolet laser (wavelength 248 nm, laser beam spot cross-sectional area 15,300 μm ² , output 100 mJ/cm ² ) at a pulse time of 10 nsec, a frequency of 100 Hz, and 9 dots per mm ² (average irradiation area 15,300 μm ² ). Surface observation images of these 9 dots were obtained using a laser microscope (product name "VK-X100", manufactured by Keyence Corporation), and the lift height R _z2 after irradiation was calculated as the average of the maximum heights for each dot. Furthermore, the lift height R z1 before irradiation was similarly determined from surface observation images of the double-sided pressure-sensitive adhesive sheet for transfer before irradiation with the ultraviolet laser at locations corresponding to the 9 _dots .

(floating area)
The double-sided pressure-sensitive adhesive sheet for transfer from which the separator (1) layer had been peeled off was irradiated from the silicone-based pressure-sensitive adhesive layer side with an ultraviolet laser (wavelength 248 nm, laser beam size 130 × 105 μm (laser light spot cross-sectional area 13,650 μm ² , output 100 mJ/cm ² ) at a pulse time of 10 nsec and a frequency of 100 Hz so as to produce 9 dots per mm ² (average irradiation area 15,300 μm ² ). For each of these 9 dots, a surface observation image was taken at a magnification of 200x using a digital microscope (product name "VHX-700F", manufactured by Keyence Corporation). This was analyzed using image processing software ImageJ, and the area where lifting occurred (lifted area) was calculated as the average value of the 9 dots. The area percentage (%) of the lifted area was calculated as the area ratio of the lifted area to the laser irradiation area of 15,300 μm ² .

(transcription accuracy)
The double-sided adhesive sheet for transfer from which the separator (1) had been peeled off was attached to a dicing ring with the first adhesive layer facing outwards, and the surface of the double-sided adhesive sheet was diced to a depth of 10 μm, thereby making multiple markings with sides of 1 mm square.

A semiconductor wafer was pre-treated with laser light so that it would be cut into 1 mm x 1 mm pieces when expanded, and then polished to a thickness of 30 μm.It was then bonded to a dicing die-bonding film to obtain a dicing die-bonding film with a semiconductor wafer attached. The dicing die bond film with the semiconductor wafer attached was held in the dicing ring of a die separator (product name "DDS2300", manufactured by Disco Corporation) and subjected to cool expansion in a cool expander unit at an expansion temperature of -15°C, an expansion speed of 200 mm/sec, and an expansion amount of 11 mm. The semiconductor wafer and die bond layer were then cleaved, followed by room temperature expansion at an expansion speed of 1 mm/sec and an expansion amount of 7 mm. Furthermore, while maintaining the expanded state, the dicing tape around the outer periphery of the semiconductor chip was thermally shrunk at a heat temperature of 200°C, an air flow of 40 L/min, a heat distance of 20 mm, and a rotation speed of 3°/sec, resulting in a dicing die bond film with a semiconductor chip with a die bond layer, in which the semiconductor wafer and die bond layer remained cleaved.

A dicing die bond film with the side having the semiconductor chip with a die bond layer facing downwards and a double-sided adhesive sheet for transfer with the marked first adhesive layer facing upwards were placed opposite each other with a clearance of 1 mm, aligning the markings with the semiconductor chip with a die bond layer. A needle was used to push the dicing die bond film from the top (back) side, dropping 10 semiconductor chips with a die bond layer onto the adhesive surface of the first adhesive layer exactly at the marking positions, yielding a double-sided adhesive sheet for transfer bearing the semiconductor chips.

The double-sided adhesive sheet for transfer that received the semiconductor chip was irradiated with an ultraviolet laser (wavelength 248 nm, laser light spot cross-sectional area 15,300 μm ² , output 100 mJ/cm ² , frequency 100 Hz, pulse width 10 ns) to form an alignment mark on the area other than the area that received the semiconductor chip with a die bond layer, and a mounting substrate with a corresponding marking was placed and aligned using the alignment mark as a reference.The semiconductor chip with a die bond layer was transferred to the aligned mounting substrate, and the semiconductor chip with a die bond layer was checked using a microscope and evaluated according to the following criteria.

◯: No semiconductor chip with a die bond layer was found to be misaligned with respect to the marking position on the mounting substrate. ×: A semiconductor chip with a die bond layer was found to be misaligned with respect to the marking position on the mounting substrate.

The double-sided pressure-sensitive adhesive sheets for transfer of Examples 1 to 6, which had the configuration of the present invention, all suppressed misalignment of the semiconductor chip due to ultraviolet laser irradiation. In contrast, the double-sided pressure-sensitive adhesive sheets for transfer of Comparative Examples 1 and 2, which had ratios ( _Rz2 / _Rz1 ) outside the configuration of the present invention, caused misalignment of the semiconductor chip.

REFERENCE SIGNS LIST 1 double-sided adhesive sheet for transfer 10 substrate 11 first adhesive layer 12 second adhesive layer 110, 120 separator 20 dicing tape 21 electronic component 22 carrier substrate 23 pin member 30 mounting substrate 31 circuit surface

Claims (4)

a double-sided PSA sheet for transfer in which a first PSA layer, a substrate, and a second PSA layer are laminated in this order;
the first adhesive layer is a low-tack adhesive layer containing an adhesive and an ultraviolet absorber, and having a 180° peel adhesive strength from a glass plate at 25°C of 0.1 mN/25 mm or more ;
the second pressure-sensitive adhesive layer is a releasable pressure-sensitive adhesive layer having a 180° peel adhesive strength from a glass plate at 25°C of 1 mN /25 mm or more ;
The double-sided pressure-sensitive adhesive sheet for transfer has a ratio (R z 2 /R z 1 ) of a lift height R _{z 2} after irradiation of the first pressure-sensitive adhesive layer with an ultraviolet laser having a wavelength of 248 nm at a beam size of 130 × 105 μm, an output of 100 _mJ /cm ² , a pulse width of 10 ns, and a frequency of 100 Hz to a lift height R _{z 1 before} irradiation , of 0.2 to 1600. The double-sided adhesive sheet for transfer according to claim 1, wherein when the first adhesive layer is irradiated with an ultraviolet laser having a wavelength of 248 nm with a beam size of 130 x 105 μm, an output of 100 mJ/cm ² , a pulse width of 10 ns, and a frequency of 100 Hz, the area ratio of the lifted area to the total irradiated area is 20.0% or less. a double-sided PSA sheet for transfer in which a first PSA layer, a substrate, and a second PSA layer are laminated in this order;
the first adhesive layer is a low-tack adhesive layer containing an adhesive and an ultraviolet absorber, and having a 180° peel adhesive strength from a glass plate at 25°C of 0.1 mN/25 mm or more ;
the second pressure-sensitive adhesive layer is a releasable pressure-sensitive adhesive layer having a 180° peel adhesive strength from a glass plate at 25°C of 1 mN /25 mm or more ;
A double- ^{sided pressure-sensitive adhesive sheet for transfer, in which when the first pressure-sensitive adhesive layer is irradiated with an ultraviolet laser having a wavelength of 248 nm with a beam size of 130 x 105 μm, an output of 100 mJ/cm 2} , a pulse width of 10 ns, and a frequency of 100 Hz, the area ratio of the lifted area to the total irradiated area is 20.0% or less. The double-sided pressure-sensitive adhesive sheet for transfer according to claim 1 or 2, wherein the ratio (R _z2 /t ₁ ) of the floating height R _z2 (μm) to the thickness t ₁ (μm) of the first pressure-sensitive adhesive layer is 1.0 or less.