JP7385053B2 - Adhesive tape - Google Patents

Description

The present invention relates to an adhesive tape.

In the process of polishing semiconductor wafers, liquid crystal glass substrates, etc. to a predetermined thickness (for example, the chemical-mechanical-polishing (CMP) process), a polishing pad (polishing cloth) fixed to the surface plate of a polishing machine is used. Polishing is performed using Double-sided adhesive tape is usually used to secure the polishing pad to the surface plate of the polishing machine. This double-sided adhesive tape for fixing polishing pads is required to have sufficient adhesive strength to prevent the polishing pad from peeling off during polishing, and to be able to be re-peeled from the surface plate without leaving any adhesive residue when replacing the used polishing pad. It will be done.

As a double-sided adhesive tape for fixing a polishing pad, for example, Patent Documents 1 and 2 disclose that a specific heat-activated adhesive is provided on one side of a plastic film support, and a removable adhesive is provided on the other side of the plastic film support. A double-sided adhesive tape for fixing an abrasive material is described in which a heat-activated adhesive layer is provided, and the heat-activated adhesive layer serves as a bonding surface to the abrasive material.

Japanese Patent Application Publication No. 6-145611 Japanese Unexamined Patent Publication No. 6-172721

The performance required of double-sided adhesive tapes for fixing polishing pads is becoming more sophisticated year by year. For example, in order to increase the polishing rate in order to improve the polishing efficiency, it is necessary to increase the amount of strongly acidic or strongly alkaline slurry liquid used during polishing and to use a soft polishing pad. As such a soft polishing pad, for example, polyurethane foam and the like are being considered. However, since the soft polishing pad has many cavities on its surface and has a rough surface, there is a problem in that the adhesion of the double-sided adhesive tape for fixing the polishing pad is poor and the adhesive force is insufficient.
Another problem is that when the polishing speed is increased to improve polishing efficiency, the pressure-sensitive adhesive layer is likely to shift or peel due to increased temperature due to frictional heat or application of strong shearing force. Double-sided adhesive tapes for fixing polishing pads are also required to have excellent resistance to displacement or peeling (creep resistance) when strong shearing force is applied at high temperatures.

An object of the present invention is to provide an adhesive tape that has high adhesive strength to rough surfaces and excellent shear strength at high temperatures. In particular, an object of the present invention is to provide an adhesive tape that has high adhesive strength to a polishing pad having a rough surface and has excellent shear strength at high temperatures.

The present disclosure 1 is an adhesive tape having a base material and an adhesive layer, wherein the adhesive layer contains a (meth)acrylic copolymer and a crosslinking agent, and the sol component of the adhesive layer has a differential refractive index. When performing GPC measurement using total RI detection, in the region of molecular weight 5000 or more, the proportion of molecular weights of 100,000 or less is 5% or more and 75% or less, and the proportion of molecular weights of 600,000 or more is 0.5% or more and 16% or less. The adhesive tape has a (meth)acrylic monomer content of 2.5% by weight or less in the adhesive layer.
The present disclosure 2 is the adhesive tape of the present disclosure 1, in which the proportion of molecular weights of 150,000 or less in the region of molecular weights of 5,000 or more is 5% or more and 65% or less when the GPC measurement is performed.
Present disclosure 3 is the adhesive tape of present disclosure 1 or 2, in which the ratio of molecular weights of 500,000 or more is 1% or more and 20% or less in the region of molecular weights of 5000 or more when the GPC measurement is performed.
Present disclosure 4 is the adhesive tape of present disclosure 1, 2, or 3, wherein the content of the (meth)acrylic monomer in the adhesive layer is 0.1% by weight or more.
This disclosure 5 discloses the peak of the molecular weight distribution (Mp (UV)) when the sol component of the adhesive layer is subjected to GPC measurement using ultraviolet (UV) detection with an absorption wavelength of 254 nm, and the sol component of the adhesive layer. The adhesive tape according to Present Disclosure 1, 2, 3, or 4, wherein the difference Mp (UV-RI) from the peak of molecular weight distribution (Mp (RI)) when GPC measurement is performed using differential refractometer RI detection is 5000 or more. It is.
Present disclosure 6 provides that when the sol component of the adhesive layer is subjected to GPC measurement using differential refractometer RI detection, the peak of the molecular weight distribution (Mp(RI)) is 100,000 to 400,000 in the molecular weight region of 5,000 or more. The adhesive tape of the present disclosure 1, 2, 3, 4 or 5 is
The present disclosure 7 is the adhesive tape of the present disclosure 1, 2, 3, 4, 5, or 6, wherein the adhesive layer has a gel fraction of 15% by weight or more and 70% by weight or less.
Present disclosure 8 provides the present disclosure 1, 2, 3, 4, 5, 6 or 7, wherein the adhesive layer has a storage modulus G' (100° C.) of 3.5×10 ⁴ Pa or more. This is an adhesive tape.
Present disclosure 9 provides that the adhesive layer further includes a tackifying resin, the softening temperature of the tackifying resin is 100°C or more and 180°C or less, and the content of the tackifying resin is equal to or less than the (meth)acrylic. The adhesive tape according to the present disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the amount is 10 parts by weight or more and 60 parts by weight or less based on 100 parts by weight of the polymer.
This disclosure 10 provides the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9 adhesive tape.
Present disclosure 11 provides that the (meth)acrylic copolymer has a content of structural units derived from an alkyl (meth)acrylate having an alkyl group having 4 or less carbon atoms of 25% by weight or more and 70% by weight or less, and Present Disclosures 1, 2, 3, 4, 5, 6, 7, 8, wherein the content of the structural unit derived from an alkyl (meth)acrylate having an alkyl group of 6 or more is 22% by weight or more and 67% by weight or less , 9 or 10 adhesive tape.
The present disclosure 12 is the adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the adhesive layer has a thickness of 10 μm or more and 150 μm or less.
Present disclosure 13 is the adhesive tape of present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, which has the adhesive layer on both sides of the base material.
Present disclosure 14 is an adhesive according to present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, which is used for fixing a polishing pad to a surface plate of a polishing machine. It's a tape.
The present invention will be explained in detail below.

The present inventors have developed a (meth)acrylic copolymer and a cross-linked adhesive layer that can be used as an adhesive layer for fixing a polishing pad to a surface plate of a polishing machine, and in particular, as an adhesive layer that can be used on the surface to be bonded to the polishing pad. We investigated optimizing the molecular weight distribution of the sol component of the adhesive layer by using an adhesive layer containing the adhesive. Specifically, when performing GPC measurement using differential refractometer RI detection on the sol component of the adhesive layer, in the region of molecular weight 5,000 or more, the proportion of low molecular weight components with molecular weight of 100,000 or less, and the proportion of low molecular weight components with molecular weight of 60,000 or less. We considered adjusting the proportion of high molecular weight components of 10,000 or more to a specific range. Furthermore, the present inventors investigated suppressing the content of (meth)acrylic monomer in the adhesive layer to a certain value or less. The present inventors have discovered that an adhesive tape having such an adhesive layer has high adhesive strength to rough surfaces and has excellent shear strength at high temperatures, and in order to complete the present invention. It's arrived.

The adhesive tape of the present invention is an adhesive tape having a base material and an adhesive layer, and the adhesive layer contains a (meth)acrylic copolymer and a crosslinking agent.
When the sol component of the adhesive layer is subjected to GPC measurement using differential refractometer RI detection, the adhesive layer has a molecular weight of 5% or more and 75% or less in a region of molecular weight 5000 or more, and The proportion of molecular weight of 600,000 or more is 0.5% or more and 16% or less.
Note that (meth)acrylic in this specification means acrylic or methacryl.

Here, the "sol component" means a component obtained by removing the "gel component" from the adhesive layer. That is, the relationship "Sol fraction (wt%) = 100 (wt%) - Gel fraction (wt%)" holds true. In addition, the "gel component" is a component with low fluidity in which the above-mentioned (meth)acrylic copolymer, tackifier resin, etc. blended as necessary build a crosslinked structure via the above-mentioned crosslinking agent, The "sol component" is a highly fluid component that does not participate in such a crosslinked structure.

The sol component of the adhesive layer can be obtained, for example, by immersing the adhesive layer in tetrahydrofuran (THF) at 23°C for 24 hours, and removing insoluble matter by filtering through a 200-mesh wire mesh. .
When performing GPC measurement using differential refractometer RI detection for the sol component of the adhesive layer, for example, the following method can be adopted. That is, using column LF-804 manufactured by SHOKO Co., Ltd. as a column, the sol component of the adhesive layer was analyzed by gel permeation chromatography (GPC) (manufactured by Waters Co., Ltd., 2690 Separations Model), and the molecular weight distribution in terms of polystyrene was determined. Measure.
Eluent: Tetrahydrofuran (THF)
Flow rate: 0.4mL/min
Detector: Differential refractometer RI
Column temperature (measurement temperature): 40°C
Injection volume: 20μL
In addition, in GPC measurement using differential refractometer RI detection, it is possible to mainly know the molecular weight distribution of the (meth)acrylic copolymer contained in the sol component of the adhesive layer. On the other hand, in GPC measurement using ultraviolet (UV) detection, which will be described later, components that exhibit ultraviolet (UV) absorption (e.g., components with aromatic rings in their molecules, more specifically, e.g., sol components of the adhesive layer) (crosslinking agents, tackifying resins, molecules having structures derived from these, etc.) can be detected.

When the proportion of the molecular weight of 100,000 or less (proportion of low molecular weight components) is 5% or more, the bulk fluidity of the pressure-sensitive adhesive layer increases and it can have high adhesive strength to rough surfaces. When the proportion of the molecular weight of 100,000 or less is 75% or less, the bulk cohesive force of the adhesive layer does not decrease more than necessary, so that the shear strength of the adhesive layer at high temperatures is improved. The preferable lower limit of the proportion of the molecular weight of 100,000 or less is 10%, the preferable upper limit is 70%, the more preferable lower limit is 20%, and the more preferable upper limit is 65%.

If the proportion of the molecular weight of 600,000 or more (proportion of high molecular weight components) is 0.5% or more, the bulk cohesive force of the pressure-sensitive adhesive layer increases, and the shear strength at high temperatures improves. If the proportion of the molecular weight of 600,000 or more is 16% or less, the bulk fluidity of the adhesive layer will not decrease more than necessary, and the adhesive layer will have high adhesive strength to rough surfaces. can have The preferable lower limit of the proportion of the molecular weight of 600,000 or more is 2%, the preferable upper limit is 15%, the more preferable lower limit is 3%, and the more preferable upper limit is 10%.

The proportion of the molecular weight of 150,000 or less is not particularly limited, but is preferably 5% or more and 65% or less. If the proportion of the molecular weight of 150,000 or less is 5%, the bulk fluidity of the pressure-sensitive adhesive layer will further increase, and it can have even higher adhesive strength to rough surfaces. When the proportion of the molecular weight of 150,000 or less is 65% or less, the bulk cohesive force of the adhesive layer does not decrease more than necessary, so that the shear strength of the adhesive layer at high temperatures is further improved. A more preferable lower limit of the proportion of the molecular weight of 150,000 or less is 15%, a more preferable upper limit is 60%, an even more preferable lower limit is 25%, and an even more preferable upper limit is 55%.

The proportion of the molecular weight of 500,000 or more is not particularly limited, but is preferably 1% or more and 20% or less. If the proportion of the molecular weight of 500,000 or more is 1% or more, the bulk cohesive force of the pressure-sensitive adhesive layer will further increase, and the shear strength at high temperatures will further improve. If the proportion of the molecular weight of 500,000 or more is 20% or less, the bulk fluidity of the adhesive layer will not decrease more than necessary, and the adhesive layer will have even higher adhesive strength to rough surfaces. can have. A more preferable lower limit of the proportion of the molecular weight of 500,000 or more is 2.5%, a more preferable upper limit is 15%, an even more preferable lower limit is 4%, and an even more preferable upper limit is 10%.

The proportion of the molecular weight of 100,000 to 600,000 is not particularly limited, but is preferably 9% or more and 94.5% or less. If the ratio of the molecular weight of 100,000 to 600,000 is 9% or more and 94.5% or less, the bulk fluidity and bulk cohesive force of the adhesive layer will not decrease more than necessary, so In addition to having high adhesive strength, the shear strength of the adhesive layer at high temperatures is improved. A more preferable lower limit of the above molecular weight ratio of 100,000 to 600,000 is 15%, a more preferable upper limit is 88%, an even more preferable lower limit is 25%, and an even more preferable upper limit is 77%.

The proportion of the molecular weight of 150,000 to 500,000 is not particularly limited, but is preferably 15% or more and 94% or less. When the ratio of the molecular weight of 150,000 to 500,000 is 15% or more and 94% or less, it has even higher adhesive strength to rough surfaces and further improves the shear strength of the pressure-sensitive adhesive layer at high temperatures. A more preferable lower limit of the above molecular weight ratio of 150,000 to 500,000 is 17.5%, a more preferable upper limit is 75%, an even more preferable lower limit is 35%, and an even more preferable upper limit is 71%.

The adhesive layer has a molecular weight distribution peak (Mp(RI)) of 100,000 to 400,000 in a molecular weight region of 5,000 or more when the sol component of the adhesive layer is subjected to GPC measurement using differential refractometer RI detection. It is preferable that it is below.
If the peak of the molecular weight distribution (Mp(RI)) is 100,000 or more, the proportion of high molecular weight components increases and the proportion of low molecular weight components decreases, so the bulk cohesive force of the adhesive layer increases. , the shear strength at high temperatures is further improved. If the peak of the molecular weight distribution (Mp(RI)) is 400,000 or less, the proportion of high molecular weight components decreases and the proportion of low molecular weight components increases, so the bulk fluidity of the adhesive layer increases. , can have higher adhesion to rough surfaces. A more preferable lower limit of the peak of the molecular weight distribution (Mp(RI)) is 120,000, a more preferable upper limit is 350,000, an even more preferable lower limit is 150,000, and an even more preferable upper limit is 300,000.
Note that the peak of molecular weight distribution (Mp(RI)) means the molecular weight at the highest peak in the molecular weight distribution curve. Even if there is a shoulder or two or more peaks in the molecular weight distribution curve, the peak of the molecular weight distribution (Mp(RI)) means the molecular weight at the highest peak in the molecular weight distribution curve.

The adhesive layer has a molecular weight distribution peak (Mp (UV)) when the sol component of the adhesive layer is subjected to GPC measurement using ultraviolet (UV) detection with an absorption wavelength of 254 nm, and a sol component of the adhesive layer. It is preferable that the difference Mp (UV-RI) between the peak of the molecular weight distribution (Mp (RI)) when GPC measurement using differential refractometer RI detection is performed for 5000 or more.
Here, in the GPC measurement using differential refractometer RI detection, the entire (meth)acrylic copolymer is detected. On the other hand, in GPC measurement using ultraviolet (UV) detection, components exhibiting ultraviolet (UV) absorption (for example, components having an aromatic ring in the molecule, more specifically, for example, components contained in the sol component of the adhesive layer), Only crosslinking agents, tackifying resins, molecules with structures derived from these, etc.) are detected.
The sol component of the adhesive layer may contain many molecular chains of the (meth)acrylic copolymer having a relatively small molecular weight. This is because molecular chains with relatively small molecular weights have a relatively low content of structural units derived from crosslinkable functional group-containing monomers due to the heterogeneity of the polymerization reaction, making it difficult to bond to gel components, resulting in a crosslinked structure. This is thought to be due to the fact that it is difficult to be taken into account. The low molecular chains contained in such a sol component have functional groups introduced at their ends, and the low molecular chains having the functional groups are blended with each other via the above-mentioned crosslinking agent or with the above-mentioned crosslinking agent as necessary. It is preferable to form a conjugate (for example, a dimer, etc.) via a conjugate with a tackifier resin.
The combination of low molecular chains in the sol component of the adhesive layer includes a component that absorbs ultraviolet (UV) light. As the amount of the above-mentioned low molecular chain conjugates increases, the peak of the molecular weight distribution (Mp(UV)) detected by GPC measurement using ultraviolet (UV) detection will be lower than that when performing GPC measurement using differential refractometer RI detection. The peak of the molecular weight distribution (Mp(RI)) is shifted to the higher molecular weight side.

If the difference Mp (UV-RI) is 5000 or more, it can be determined that the sol component of the pressure-sensitive adhesive layer contains a sufficient amount of the low molecular chain bond. That is, it can be said that the (meth)acrylic copolymer contained in the sol component of the pressure-sensitive adhesive layer has a high molecular weight as a whole. Therefore, the ratio of the molecular weight of 150,000 or less tends to be within the above range, and the bulk cohesive force of the pressure-sensitive adhesive layer is further increased, and the shear strength at high temperatures is further improved. In addition, when the molecular weight of the (meth)acrylic copolymer increases in this way, the shear strength at high temperatures improves even if the molecular weight of the (meth)acrylic copolymer used as a raw material is adjusted to a relatively low range. Therefore, the molecular weight of the (meth)acrylic copolymer used as a raw material can be adjusted to a relatively low range. Therefore, the adhesive layer can also have higher adhesive strength to rough surfaces. A more preferable lower limit of the difference Mp (UV-RI) is 10,000, and an even more preferable lower limit is 30,000.

When performing GPC measurement using ultraviolet (UV) detection with an absorption wavelength of 254 nm for the sol component of the adhesive layer, for example, the following method can be adopted. That is, using column LF-804 manufactured by SHOKO Co., Ltd. as a column, the sol component of the adhesive layer was analyzed by gel permeation chromatography (GPC) (manufactured by Waters Co., Ltd., 2690 Separations Model), and the molecular weight distribution in terms of polystyrene was determined. Measure.
Eluent: Tetrahydrofuran (THF)
Flow rate: 0.4mL/min
Detector: UV detector (absorption wavelength 254nm)
Column temperature (measurement temperature): 40°C
Injection volume: 20μL

In the adhesive tape of the present invention, the upper limit of the content of the (meth)acrylic monomer in the adhesive layer is 2.5% by weight.
When the content of the monomer is 2.5% by weight or less, the glass transition temperature (Tg) of the pressure-sensitive adhesive layer increases, thereby increasing the bulk cohesive force and improving the shear strength at high temperatures. Furthermore, since the content of the above monomer is 2.5% by weight or less, the shear strength at high temperatures is improved even if the molecular weight of the (meth)acrylic copolymer used as a raw material is adjusted to a relatively low range. , the molecular weight of the (meth)acrylic copolymer used as a raw material can be adjusted to a relatively low range. Therefore, the adhesive layer can also have higher adhesive strength to rough surfaces. A preferable upper limit of the content of the monomer in the adhesive layer is 1.5% by weight, and a more preferable upper limit is 1% by weight.
The lower limit of the content of the monomer in the adhesive layer is not particularly limited, but from the viewpoint of ensuring bulk fluidity of the adhesive layer and improving adhesive strength to rough surfaces, the lower limit is preferably 0.1 weight %.
The monomer may be an unreacted monomer that remains without being incorporated into the polymerization during the production of the (meth)acrylic copolymer. By increasing the polymerization efficiency during production of the (meth)acrylic copolymer, the amount of the monomer can be controlled within a predetermined range.

The content of the monomer in the adhesive layer can be determined, for example, by performing GC-MS (gas chromatograph mass spectrometer) measurement on the adhesive layer. For example, an adhesive is weighed out from the adhesive layer of an adhesive tape, and the adhesive is immersed in a solvent such as chloroform. The monomer concentration contained in the sample can be determined by performing GC-MS measurement on the dissolved components under the following conditions and determining the peak area value of each monomer in the total ion chromatogram. From this monomer concentration, the monomer content contained in the weighed adhesive can be calculated. It is preferable to perform measurement and calculation using a calibration curve between the concentration of each monomer and the peak area value.
(Measurement condition)
GC-MS device GC: 78906B (manufactured by Agilent technology), MS: JMS-Q1500 (manufactured by JEOL Ltd.)
Column: SLBTM-5ms (slightly polar) 0.25mmφ x 30m x 0.25μm
Inlet temperature: 250℃
He flow rate: 1.0mL/min (split ratio 1:50)
Column temperature: After holding at 40°C for 3 minutes, increase the temperature at 10°C/min. Thereafter, the temperature was maintained at 300°C for 10 minutes.
MS measurement range: 35-800amu
Ionization voltage: 70eV, ionization method: EI method, measurement mode: scan Ion source temperature: 230°C, interface temperature: 250°C

Regarding the sol component of the adhesive layer, the above ratio of molecular weight is 100,000 or less, the above molecular weight is 150,000 or less, the above molecular weight is 500,000 or more, the above molecular weight is 600,000 or more, and the above molecular weight is 100,000 to 600,000. , the ratio of the molecular weight of 150,000 to 500,000, the peak of the molecular weight distribution (Mp(RI)), and the difference Mp(UV-RI) are adjusted to the above ranges, and the monomer in the adhesive layer is The method for adjusting the content within the above range is not particularly limited. Specifically, for example, a method using a (meth)acrylic copolymer obtained by living radical polymerization, free radical polymerization, etc. can be mentioned. Among these, from the viewpoint of reducing reaction time and cost, a method using a (meth)acrylic copolymer obtained by free radical polymerization is preferred.

Among the above-mentioned free radical polymerization methods, a method using a (meth)acrylic copolymer obtained under relatively mild polymerization conditions such as keeping the polymerization temperature and the concentration of the monomer mixture constant is preferred. This makes the composition of the (meth)acrylic copolymer more uniform and increases the ratio (Mw/Mn) of the weight average molecular weight (Mw) to number average molecular weight (Mn) of the (meth)acrylic copolymer. This makes it easier to adjust the molecular weight distribution of the sol component of the adhesive layer to the above range. Polymerization methods that require relatively mild polymerization conditions include, for example, free radical constant temperature polymerization, free radical boiling point polymerization, and polymerization in which half of the monomer mixture and a polymerization initiator are charged into a reaction vessel. After starting the process, the remaining half of the monomer mixture is added dropwise or all at once.

The polymerization reaction time of the above-mentioned free radical polymerization is not particularly limited, but is preferably relatively short, with a preferable lower limit being 2 hours and a preferable upper limit being 10 hours. If the polymerization reaction time of the free radical polymerization is within the above range, the content of the monomer in the pressure-sensitive adhesive layer can be easily adjusted within the above range. A more preferable lower limit of the polymerization reaction time of the free radical polymerization is 3 hours, and a more preferable upper limit is 8 hours.

Examples of the polymerization initiator used in the free radical polymerization include organic peroxides, azo compounds, and the like.
The above azo compound is not particularly limited as long as it is commonly used in radical polymerization, and examples thereof include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), ), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexane-1-carbonitrile) ), 1-[(1-cyano-1-methylethyl)azo]formamide, 4,4'-azobis(4-cyanovaleric acid), dimethyl-2,2'-azobis(2-methylpropionate), Dimethyl-1,1'-azobis(1-cyclohexanecarboxylate), 2,2'-azobis{2-methyl-N-[1,1'-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'- Azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis[2-(2-imidazolin-2-yl)propane ] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis[2-(2- imidazolin-2-yl)propane], 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2'-azobis(2,4,4-trimethylpentane), and the like. These azo compounds may be used alone or in combination of two or more.
Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5 -dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. These organic peroxides may be used alone or in combination of two or more.

Among these, it is preferable to use a polymerization initiator having a functional group.
By using the polymerization initiator having the above functional group, it becomes easy to adjust the molecular weight distribution of the sol component of the pressure-sensitive adhesive layer to the above range.
That is, by using a polymerization initiator having the above-mentioned functional group, a functional group can be introduced into the terminal of the above-mentioned (meth)acrylic copolymer. A functional group can also be introduced at the end of a molecular chain that does not have a structural unit derived from a functional group-containing monomer and has a relatively small molecular weight (non-crosslinkable low molecular chain). By having a functional group at the end, such a low molecular chain is incorporated into the crosslinked structure via the crosslinking agent, thereby further increasing the bulk cohesive force of the adhesive layer and further improving the shear strength at high temperatures. . In addition, even if it does not participate in the crosslinking structure, the low molecular chain has a functional group at the end and can be used via the crosslinking agent or with a tackifying resin that is blended with the crosslinking agent as necessary. The low molecular chains can form a conjugate (for example, a dimer, etc.) with each other through a conjugate with such as. In such a case, it can be said that the (meth)acrylic copolymer contained in the sol component of the pressure-sensitive adhesive layer has a high molecular weight as a whole. Therefore, the ratio of the molecular weight of 150,000 or less tends to be within the above range, and the bulk cohesive force of the pressure-sensitive adhesive layer is further increased, and the shear strength at high temperatures is further improved.
The above-mentioned functional groups are not particularly limited, and include, for example, a hydroxyl group, a carboxy group, a silyl group, a glycydicyl group, an amino group, an amide group, a nitrile group, an alkoxy group, an acetoacetyl group, and the like. Among them, hydroxyl group and carboxy group are preferred. Among the polymerization initiators mentioned above, examples of the polymerization initiator having the above-mentioned functional group include 2,2'-azobis{2-methyl-N-[1,1'-bis(hydroxymethyl)-2-hydroxyethyl ] propionamide}, 4,4'-azobis(4-cyanovaleric acid (valeric acid)), and the like. Polymerization initiators having these functional groups may be used alone or in combination of two or more.

The amount of the polymerization initiator added is not particularly limited, but a preferable lower limit is 0.01 part by weight and a preferable upper limit is 0.5 part by weight based on 100 parts by weight of the monomer mixture. By setting the amount of the polymerization initiator added within the above range, the ratio of the molecular weight of the sol component of the adhesive layer to 150,000 or less, the ratio of the molecular weight of 500,000 or more, and the peak of the molecular weight distribution (Mp ) can be easily adjusted to the above range. A more preferable lower limit of the amount of the polymerization initiator added is 0.02 parts by weight, and a more preferable upper limit is 0.3 parts by weight.

In the above free radical polymerization, a chain transfer agent may be used.
The chain transfer agent is not particularly limited, and examples include lauryl mercaptan, mercaptopropionic acid, mercaptosuccinic acid, 3-mercapto-1,2-propanediol, 1-butanethiol, cyclohexyl 3-mercaptopropionate, and 2-mercaptoacetate. Examples include thiol compounds such as ethylhexyl, 1-hexadecanethiol, 2-mercaptoethanol, mercaptoacetic acid, ethyl mercaptoacetate, 1-octanethiol, tridecyl 3-mercaptopropionate, and thiophenol. Also included are 2,4-diphenyl-4-methyl-1-pentene and the like. These chain transfer agents may be used alone or in combination of two or more.

Among these, it is preferable to use a chain transfer agent having a functional group.
By using a chain transfer agent having the above functional group, it becomes easier to adjust the molecular weight distribution of the sol component of the pressure-sensitive adhesive layer to the above range.
That is, by using a chain transfer agent having the above-mentioned functional group, it is possible to introduce a functional group to the end of the above-mentioned low molecular chain in the same way as when using a polymerization initiator having the above-mentioned functional group, and as a result, , the bulk cohesive force of the adhesive layer is further increased, and the shear strength at high temperatures is further improved.
The above-mentioned functional groups are not particularly limited, and include, for example, a hydroxyl group, a carboxy group, a silyl group, a glycydicyl group, an amino group, an amide group, a nitrile group, an alkoxy group, an acetoacetyl group, and the like. Among these, hydroxyl group and carboxy group are preferable, and hydroxyl group is more preferable. The number of functional groups of the chain transfer agent having the above-mentioned functional group is not particularly limited, but it should be multivalent because the crosslinked structure tends to become higher-dimensional and networked, and the bulk cohesive force of the pressure-sensitive adhesive layer increases. is preferred. Among the chain transfer agents mentioned above, examples of the chain transfer agent having the above functional group include mercaptopropionic acid, mercaptosuccinic acid, 3-mercapto-1,2-propanediol, and the like. Chain transfer agents having these functional groups may be used alone or in combination of two or more.

The amount of the chain transfer agent added is not particularly limited, but the preferable lower limit is 0.01 part by weight and the preferable upper limit is 0.5 part by weight based on 100 parts by weight of the monomer mixture. By setting the amount of the chain transfer agent added within the above range, the ratio of the molecular weight of the sol component of the adhesive layer to 150,000 or less, the ratio of the molecular weight of 500,000 or more, and the peak of the molecular weight distribution (Mp ) can be easily adjusted to the above range. A more preferable lower limit of the amount of the chain transfer agent added is 0.02 parts by weight, and a more preferable upper limit is 0.3 parts by weight.

In the above free radical polymerization, a dispersion stabilizer may be used. Examples of the dispersion stabilizer include polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, ethylcellulose, poly(meth)acrylic acid, poly(meth)acrylic acid ester, polyethylene glycol, and the like.
When using a polymerization solvent in the above free radical polymerization, the polymerization solvent is not particularly limited, and examples thereof include nonpolar solvents such as hexane, cyclohexane, octane, toluene, and xylene, water, methanol, ethanol, propanol, butanol, acetone, Highly polar solvents such as methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, and N,N-dimethylformamide can be used. These polymerization solvents may be used alone or in combination of two or more.
Further, the polymerization temperature is preferably 0 to 110°C from the viewpoint of polymerization rate.

The above (meth)acrylic copolymer is not particularly limited, but preferably contains a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 4 or less carbon atoms.
The alkyl (meth)acrylate having an alkyl group having 4 or less carbon atoms is not particularly limited, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, butyl Examples include (meth)acrylate. These alkyl (meth)acrylates having an alkyl group having 4 or less carbon atoms may be used alone, or two or more types may be used in combination. Among them, butyl (meth)acrylate is preferred.

The content of the structural unit derived from the alkyl (meth)acrylate having an alkyl group having 4 or less carbon atoms is not particularly limited, but the preferable lower limit is 25% by weight, and the preferable upper limit is 70% by weight. If the content is 25% by weight or more, the glass transition temperature (Tg) of the (meth)acrylic copolymer will be sufficiently high, which will further increase the bulk cohesive strength of the adhesive layer and reduce shear resistance at high temperatures. Strength is further improved. If the content is 70% by weight or less, the glass transition temperature (Tg) of the (meth)acrylic copolymer will not become too high, the bulk fluidity of the adhesive layer will increase, and the rough surface will be improved. It is possible to have higher adhesive force against A more preferable lower limit of the content is 30% by weight, a more preferable upper limit is 65% by weight, an even more preferable lower limit is 35% by weight, and an even more preferable upper limit is 60% by weight.

The (meth)acrylic copolymer preferably contains a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms.
The alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms is not particularly limited, and the alkyl group preferably has 6 or more carbon atoms and 16 or less carbon atoms, and the alkyl group has 6 or more carbon atoms and 12 or less carbon atoms. is more preferable. Further, in the alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms, the alkyl group may or may not have a branch, but it is preferable that the alkyl group does not have a branch. Because the alkyl group of the alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms has a linear structure, the adhesive layer has a low storage modulus at low to room temperatures, but a storage modulus at high temperatures. is higher, the shear strength at high temperatures is further improved, and it is possible to have higher adhesive strength to rough surfaces.
Specific examples of the alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms include n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-octyl (meth)acrylate, and isooctyl (meth)acrylate. ) acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, isostearyl acrylate, arachidyl (meth)acrylate, and the like. These alkyl (meth)acrylates having an alkyl group having 6 or more carbon atoms may be used alone, or two or more types may be used in combination. Among them, n-heptyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred.
Note that (meth)acrylate in this specification means acrylate or methacrylate.

The content of the structural unit derived from the alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms is not particularly limited, but the preferable lower limit is 22% by weight, and the preferable upper limit is 67% by weight. If the content is 22% by weight or more, the glass transition temperature (Tg) of the (meth)acrylic copolymer will be sufficiently low, so the bulk fluidity of the adhesive layer will increase, and it will can have higher adhesive strength. If the content is 67% by weight or less, the glass transition temperature (Tg) of the (meth)acrylic copolymer will not become too low, the bulk cohesive strength of the adhesive layer will increase, and Shear strength is further improved. A more preferable lower limit of the content is 27% by weight, a more preferable upper limit is 62% by weight, an even more preferable lower limit is 32% by weight, and an even more preferable upper limit is 57% by weight.

The (meth)acrylic copolymer preferably has a structural unit derived from a crosslinkable functional group-containing monomer.
Since the (meth)acrylic copolymer has a structural unit derived from the crosslinkable functional group-containing monomer, the (meth)acrylic copolymer, the tackifier resin, etc. that are blended as needed can be used as the crosslinking agent. By constructing a crosslinked structure through the adhesive layer, the bulk cohesive force of the adhesive layer is further increased, and the shear strength at high temperatures is further improved. Examples of the crosslinkable functional group include a hydroxyl group, a carboxy group, a silyl group, a glycydicyl group, an amino group, an amide group, a nitrile group, an alkoxy group, and an acetoacetyl group. Among these, hydroxyl groups and carboxy groups are preferred because the bulk cohesive force of the pressure-sensitive adhesive layer can be easily adjusted.

Examples of the hydroxyl group-containing monomer include (meth)acrylic acid esters having a hydroxyl group, such as 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate.
Examples of the carboxy group-containing monomer include (meth)acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, and fumaric acid. Among them, acrylic acid is preferred.
Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate.
Examples of the amide group-containing monomer include hydroxyethylacrylamide, isopropylacrylamide, dimethylaminopropylacrylamide, and the like.
Examples of the nitrile group-containing monomer include acrylonitrile.

The content of the structural unit derived from the crosslinkable functional group-containing monomer is not particularly limited, but the preferable lower limit is 0.05% by weight, and the preferable upper limit is 20% by weight. When the content is 0.05% by weight or more, the bulk cohesive force of the pressure-sensitive adhesive layer is further increased, and the shear strength at high temperatures is further improved. When the content is 20% by weight or less, the bulk fluidity of the pressure-sensitive adhesive layer increases, and it can have higher adhesive strength to rough surfaces. A more preferable lower limit of the content is 0.1% by weight, and a more preferable upper limit is 15% by weight.
In particular, when the (meth)acrylic copolymer contains a structural unit derived from the carboxy group-containing monomer, the preferable lower limit of the content of the structural unit is 8% by weight. If the content is 8% by weight or more, the glass transition temperature (Tg) of the (meth)acrylic copolymer will be sufficiently high, which will further increase the bulk cohesive strength of the adhesive layer and reduce shear resistance at high temperatures. Strength is further improved. Furthermore, if the content is 8% by weight or more, the polarity of the (meth)acrylic copolymer increases, so the adhesive layer has higher adhesive strength to highly polar adherends. Can be done. A more preferable lower limit of the content of the structural unit derived from the carboxy group-containing monomer is 9% by weight, and an even more preferable lower limit is 10% by weight.

Moreover, when the above-mentioned (meth)acrylic copolymer contains a structural unit derived from the above-mentioned hydroxyl group-containing monomer, the preferable upper limit of the content of the structural unit is 0.5% by weight. If the content is 0.5% by weight or less, the reaction between the (meth)acrylic copolymer and the crosslinking agent proceeds mildly, so that the molecular weight of the sol component of the adhesive layer is 150,000 or less. It becomes easier to adjust the ratio of , the ratio of the molecular weight of 500,000 or more, and the difference Mp (UV-RI) to the above range. A more preferable upper limit of the content of the structural unit derived from the hydroxyl group-containing monomer is 0.1% by weight. The lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer is not particularly limited, and is preferably closer to 0% by weight, and may be 0% by weight.

The (meth)acrylic copolymer may optionally contain the above alkyl (meth)acrylate having an alkyl group having 4 or less carbon atoms, the above alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms, and the above-mentioned alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms. It may contain structural units derived from other copolymerizable monomers other than the structural units derived from the crosslinkable functional group-containing monomer.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer is not particularly limited, but from the viewpoint of adjusting the molecular weight distribution of the sol component of the adhesive layer within the above range, the preferable lower limit is 150,000, and the preferable upper limit is 45,000. The more preferable lower limit is 170,000, and the more preferable upper limit is 400,000.
Further, the ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the above-mentioned (meth)acrylic copolymer is not particularly limited, but the molecular weight distribution of the sol component of the above-mentioned adhesive layer is From the viewpoint of adjusting the range, the upper limit is preferably 10, and the upper limit is more preferably 5.
The weight average molecular weight (Mw) and the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) of the above-mentioned (meth)acrylic copolymer are measured based on the pressure-sensitive adhesive layer. This can be carried out in the same manner as when performing GPC measurement using differential refractometer RI detection for the sol component.

The crosslinking agent is not particularly limited, and depending on the type of crosslinkable functional group of the (meth)acrylic copolymer, for example, an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, a metal chelate type crosslinking agent. Select and use etc. Among these, isocyanate-based crosslinking agents are preferred because they can selectively crosslink hydroxyl groups and carboxyl groups and the crosslinked structure can be easily controlled. Examples of the isocyanate-based crosslinking agent include Coronate HX (manufactured by Nippon Polyurethane Industries, Ltd.), Coronate L (manufactured by Nippon Polyurethane Industries, Ltd.), Mytech NY260A (manufactured by Mitsubishi Chemical Corporation), and the like.
By appropriately adjusting the type or amount of the crosslinking agent, the bulk cohesive force of the pressure-sensitive adhesive layer can be easily adjusted.
The number of functional groups in the crosslinking agent is not particularly limited, but it is preferably multivalent, since the crosslinked structure tends to have higher dimensions and network formation, and the bulk cohesive force of the pressure-sensitive adhesive layer increases.

The content of the crosslinking agent is not particularly limited, but is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the (meth)acrylic copolymer.

It is preferable that the pressure-sensitive adhesive layer further contains a tackifying resin.
By containing the tackifying resin in the adhesive layer, the adhesive layer can have higher adhesive strength to the adherend.

The softening temperature of the tackifying resin is not particularly limited, but a preferable lower limit is 100°C, and a preferable upper limit is 180°C. When the softening temperature is 100° C. or higher, the heat resistance of the adhesive layer increases, so that the shear strength at high temperatures is further improved. When the softening temperature is 180° C. or less, the adhesive layer becomes easily flexible and can have higher adhesive strength to rough surfaces. A more preferable lower limit of the softening temperature is 110°C, a more preferable upper limit is 170°C, an even more preferable lower limit is 120°C, and an even more preferable upper limit is 165°C.
Note that the softening temperature is a softening temperature measured by the JIS K2207 ring and ball method.

The hydroxyl value of the tackifier resin is not particularly limited, but the lower limit is preferably 25 mgKOH/g, the upper limit is 150 mgKOH/g, the lower limit is more preferably 30 mgKOH/g, and the upper limit is 100 mgKOH/g.
Note that the hydroxyl value can be measured according to JIS K1557 (phthalic anhydride method).

The above-mentioned tackifier resin is not particularly limited, and examples include rosin resins such as rosin ester resins, terpene resins such as terpene phenol resins, petroleum resins, and the like. Among these, rosin ester resins, terpene phenol resins, and combinations thereof are preferred, and terpene phenol resins are more preferred.
The terpene phenol resin has good compatibility with the (meth)acrylic copolymer, is easily grafted with the (meth)acrylic copolymer, and is easily incorporated into the adhesive layer. Therefore, the surface of the pressure-sensitive adhesive layer becomes polymer-rich and flexible, and can have higher adhesive strength to rough surfaces. On the other hand, since the bulk cohesive force of the adhesive layer is further increased by grafting the terpene phenol resin and the (meth)acrylic copolymer, the shear strength of the adhesive layer at high temperatures is further improved.

The above-mentioned rosin ester resins are rosin resins whose main component is abietic acid, disproportionated rosin resins, hydrogenated rosin resins, dimers of resin acids such as abietic acid (polymerized rosin resins), etc., which are esterified with alcohol. This is a resin obtained by A part of the hydroxyl group of the alcohol used for esterification is not used for esterification and is contained in the resin, so that the hydroxyl value is adjusted to the above range. Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.
Furthermore, resin obtained by esterifying rosin resin is called rosin ester resin, resin obtained by esterifying disproportionated rosin resin is called disproportionated rosin ester resin, resin obtained by esterifying hydrogenated rosin resin is called hydrogenated rosin ester resin, and polymerized rosin resin. A resin obtained by esterifying a resin is a polymerized rosin ester resin.
The above-mentioned terpene phenol resin is a resin obtained by polymerizing terpene in the presence of phenol.

Examples of the above-mentioned disproportionated rosin ester resin include Superester A75 manufactured by Arakawa Chemical Co., Ltd. (hydroxyl value 23 mgKOH/g, softening temperature 75°C), Superester A100 manufactured by Arakawa Chemical Co., Ltd. (hydroxyl value 16, softening temperature 100°C), Superester A115 (hydroxyl value: 19 mgKOH/g, softening temperature: 115°C) manufactured by the same company, Superester A125 (hydroxyl value: 15 mgKOH/g, softening temperature: 125°C), and the like. Examples of the hydrogenated rosin ester resin include Pine Crystal KE-359 manufactured by Arakawa Chemical Co., Ltd. (hydroxyl value 42 mgKOH/g, softening temperature 100°C), Ester Gum H manufactured by the same company (hydroxyl value 29 mgKOH/g, softening temperature 70°C). ) etc. Examples of the polymerized rosin ester resin include Pencel D135 manufactured by Arakawa Chemical Industry Co., Ltd. (hydroxyl value 45 mgKOH/g, softening temperature 135°C), Pencel D125 manufactured by Arakawa Chemical Co., Ltd. (hydroxyl value 34 mgKOH/g, softening temperature 125°C), Pencel manufactured by Arakawa Chemical Co., Ltd. D160 (hydroxyl value: 42 mgKOH/g, softening temperature: 160° C.) and the like.
Examples of the above-mentioned terpene resin include YS Polyster G150 manufactured by Yasuhara Chemical Co., Ltd. (hydroxyl value 140 mgKOH/g, softening temperature 150°C), YS Polyster T100 manufactured by Yasuhara Chemical Co., Ltd. (hydroxyl value 60 mgKOH/g, softening temperature 100°C), YS Polyster manufactured by Yasuhara Chemical Co., Ltd. G125 (hydroxyl value 140mgKOH/g, softening temperature 125°C), YS Polyster T115 manufactured by the same company (hydroxyl value 60mgKOH/g, softening temperature 115°C), YS Polyster T130 manufactured by the same company (hydroxyl value 60mgKOH/g, softening temperature 130°C), Examples include YS Polyster T160 manufactured by the same company (hydroxyl value 60 mgKOH/g, softening temperature 160° C.).
These tackifying resins may be used alone or in combination of two or more.

The content of the tackifier resin is not particularly limited, but the lower limit is preferably 10 parts by weight and the upper limit is 60 parts by weight based on 100 parts by weight of the (meth)acrylic copolymer. When the content is 10 parts by weight or more, the glass transition temperature (Tg) of the pressure-sensitive adhesive layer increases, thereby increasing the bulk cohesive force and further improving the shear strength at high temperatures. When the content is 60 parts by weight or less, the pressure-sensitive adhesive layer is prevented from becoming too hard due to an increase in glass transition temperature (Tg), and the pressure-sensitive adhesive layer can have sufficient adhesive strength. A more preferable lower limit of the content is 15 parts by weight, a more preferable upper limit is 50 parts by weight, an even more preferable lower limit is 20 parts by weight, and an even more preferable upper limit is 45 parts by weight.

The adhesive layer may contain other resins such as plasticizers, emulsifiers, softeners, fillers, pigments, dyes, silane coupling agents, antioxidants, and other additives, if necessary. good.

The gel fraction of the pressure-sensitive adhesive layer is not particularly limited, but a preferable lower limit is 15% by weight, and a preferable upper limit is 70% by weight. When the gel fraction is 15% by weight or more, the bulk cohesive force of the pressure-sensitive adhesive layer is further increased, and the shear strength at high temperatures is further improved. When the gel fraction is 70% by weight or less, the adhesive layer has sufficient flexibility and can have higher adhesive strength to rough surfaces. A more preferable lower limit of the gel fraction is 20% by weight, a more preferable upper limit is 65% by weight, an even more preferable lower limit is 25% by weight, and an even more preferable upper limit is 60% by weight.

For example, the following method can be employed to measure the gel fraction of the adhesive layer. That is, first, W ₁ (g) of the adhesive layer was collected, the collected adhesive layer was immersed in ethyl acetate at 23°C for 24 hours, and the insoluble matter was filtered through a 200-mesh wire mesh. The residue on the wire mesh is heated and dried at 110°C, and the weight W ₂ (g) of the obtained dried residue is measured. The gel fraction (degree of crosslinking) is calculated using the following formula (1).
Gel fraction (weight %) = 100 x W ₂ /W ₁ (1)

Although the storage elastic modulus of the adhesive layer is not particularly limited, it is preferable that the storage elastic modulus G' (100°C) is 3.5×10 ⁴ Pa or more. If the storage elastic modulus G' (100°C) is 3.5×10 ⁴ Pa or more, the bulk cohesive force of the pressure-sensitive adhesive layer at high temperatures will further increase, and the shear strength at high temperatures will further improve. A more preferable lower limit of the storage modulus G' (100°C) at 100°C is 4×10 ⁴ Pa, and an even more preferable lower limit is 4.5×10 ⁴ Pa.
The upper limit of the storage modulus G' at 100°C (100°C) is not particularly limited, but if it is too high, the storage modulus at room temperature will also increase and the adhesive strength to rough surfaces will decrease, so the preferable upper limit is 2.0 ×10 ⁵ Pa.

For example, the following method can be adopted to measure the storage modulus G' (100°C) of the adhesive layer at 100°C. That is, first, samples of the above-mentioned pressure-sensitive adhesive layers are stacked on top of each other to produce a laminate with a thickness of about 1 mm, and the laminate is cut into a size of 6 mm x 10 mm to obtain a test piece. Using a dynamic viscoelasticity measurement device (IT Keizai Control Co., Ltd., DVA-200), the measurement temperature was -40 to 140°C in a nitrogen atmosphere in shear mode, the heating rate was 5°C/min, the frequency was 10Hz, and the strain was 0. Measurements are made on specimens at 0.08%.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferable lower limit is 10 μm and a preferable upper limit is 150 μm. If the thickness is 10 μm or more, the pressure-sensitive adhesive layer will have an increased ability to penetrate into the adherend and will have a high peel resistance, so it can have high adhesive strength to rough surfaces. When the thickness is 150 μm or less, the amount of displacement when shearing force is applied to the adhesive layer is reduced, so that the shear strength of the adhesive layer at high temperatures is further improved. A more preferable lower limit of the thickness of the adhesive layer is 20 μm, a more preferable upper limit is 120 μm, an even more preferable lower limit is 40 μm, and an even more preferable upper limit is 100 μm.

The base material is not particularly limited, but a resin film is preferred. The resin film is not particularly limited, and examples thereof include polyester resin film, polypropylene resin film, and the like. Among these, polyester resin films are preferred because they are flat, have small thickness fluctuations, and have high strength. Among polyester resin films, polyethylene terephthalate films are more preferred.
The base material may contain additives such as a filler, an ultraviolet absorber, a light stabilizer, and an antistatic agent within a range that does not impair its physical properties.
The thickness of the base material is not particularly limited, but a preferable lower limit is 10 μm, a preferable upper limit is 200 μm, a more preferable lower limit is 15 μm, and a more preferable upper limit is 150 μm.

The adhesive tape of the present invention is not particularly limited as long as it has the above-mentioned base material and the above-mentioned adhesive layer, and may have the above-mentioned adhesive layer only on one side of the above-mentioned base material, or The base material may have the above adhesive layer on both sides. Among these, it is preferable to have the adhesive layer on both sides of the base material.

The method for producing the adhesive tape of the present invention is not particularly limited, and for example, when the base material has adhesive layers having the same composition and thickness on both sides, the following method may be used.
First, a pressure-sensitive adhesive solution containing a (meth)acrylic copolymer, a crosslinking agent, and, if necessary, other components such as a tackifying resin is prepared. Next, the adhesive solution obtained above is applied to the release-treated side of the release film, one side of which has been subjected to the release treatment, and dried to produce a laminate sheet having an adhesive layer on the release-treated side of the release film. Create. A total of two laminated sheets are prepared in the same manner. Next, the pressure-sensitive adhesive layers of the two laminated sheets are transferred to the base material and laminated together to obtain a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the base material.

Applications of the adhesive tape of the present invention are not particularly limited, but it has high adhesion to rough surfaces, especially polishing pads with rough surfaces, and has excellent shear strength at high temperatures. It is preferable to use it for fixing a polishing pad to a surface plate of a polishing machine in the process of polishing a substrate or the like to a predetermined thickness. Examples of such a polishing process include a chemical-mechanical-polishing (CMP) process.
The adhesive tape of the present invention is more preferably used for the surface to be bonded to a polishing pad than to the surface to be bonded to the surface plate of a polishing machine.
The above-mentioned polishing pad is not particularly limited, and may be any polishing pad made of absorbent material, nonwoven fabric, polyurethane foam, etc. and fixed to the surface plate of the polishing machine. The adhesive tape of the present invention can have high adhesive strength even to a soft polishing pad made of polyurethane foam or the like, that is, a polishing pad having many cavities on the surface and having a rough surface.

According to the present invention, it is possible to provide an adhesive tape that has high adhesive strength to rough surfaces and has excellent shear strength at high temperatures.

FIG. 2 is a schematic diagram showing a method for measuring the shear strength (creep resistance test) of double-sided adhesive tapes obtained in Examples and Comparative Examples.

The embodiments of the present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

(Preparation of (meth)acrylic copolymer A (free radical boiling point polymerization))
A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared, and a total of 50 parts by weight of the monomer mixture and 90 parts by weight of ethyl acetate were added into the reactor. As the monomer mixture, 22 parts by weight of butyl acrylate (BA), 22 parts by weight of 2-ethylhexyl acrylate (2EHA), and 6 parts by weight of acrylic acid (AAc) were used. After purging with nitrogen, the reactor was heated to start reflux. Thirty minutes after the ethyl acetate boiled, 0.03 parts by weight of chain transfer agent 3-mercapto-1,2-propanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and V-60 (as polymerization initiator 1) was added. 0.04 parts by weight of 2,2'-azobisisobutyronitrile (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added, and polymerization was started under reflux. After 30 minutes, a total of 50 parts by weight of the monomer mixture was added dropwise to the reactor using a dropping funnel over a period of 1 hour. As the monomer mixture, 22 parts by weight of butyl acrylate (BA), 22 parts by weight of 2-ethylhexyl acrylate (2EHA), and 6 parts by weight of acrylic acid (AAc) were used. After that, 0.15 parts by weight of V-60 (2,2'-azobisisobutyronitrile, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added as a polymerization initiator 2, and the polymerization reaction was continued for a total of 6 hours from the start of polymerization. A solution containing (meth)acrylic copolymer A was obtained.

(Preparation of (meth)acrylic copolymers B to J and a to d (free radical boiling point polymerization))
(meth)acrylic copolymer A was prepared in the same manner as (meth)acrylic copolymer A except that the monomer composition, the amount of initiator, the type and amount of chain transfer agent, and the amount of solvent were changed as shown in Table 1. Acrylic copolymers BJ and ad were prepared.

(Preparation of (meth)acrylic copolymer K (free radical constant temperature polymerization))
A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared, and a total of 100 parts by weight of the monomer mixture, 30 parts by weight of ethyl acetate, and 90 parts by weight of toluene were added into the reactor. The monomer mixture used was 44 parts by weight of butyl acrylate (BA), 44 parts by weight of 2-ethylhexyl acrylate (2EHA), and 12 parts by weight of acrylic acid (AAc). Argon gas was introduced into the reactor to remove dissolved oxygen, and the reactor was heated to bring the solution temperature to 60°C. Subsequently, 0.03 parts by weight of chain transfer agent 3-mercapto-1,2-propanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the reactor, and V-60 (2,2 parts by weight) was added as a polymerization initiator. 0.05 part by weight of '-azobisisobutyronitrile (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added, and polymerization was started under reflux. A polymerization reaction was carried out for 6 hours from the start of polymerization to obtain a (meth)acrylic copolymer K-containing solution.

(Preparation of (meth)acrylic copolymers L to Q and e (free radical constant temperature polymerization))
(meth)acrylic copolymer K was prepared in the same manner as (meth)acrylic copolymer K except that the monomer composition, type and amount of chain transfer agent, amount of initiator, and amount of solvent were changed as shown in Table 2. Acrylic copolymers L to Q and e were prepared.

(Example 1)
(1) Production of adhesive tape Ethyl acetate was added to 100 parts by weight of the non-volatile content of the obtained (meth)acrylic copolymer-containing solution and stirred. 40 parts by weight of ``T160'') and 6 parts by weight of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name ``Coronate L45'') were added and stirred to obtain an adhesive solution.

A polyethylene terephthalate film whose one side was subjected to mold release treatment was prepared. The adhesive solution obtained above was applied to the release-treated surface of this polyethylene terephthalate film so that the thickness after drying would be 80 μm, and it was dried at 110°C for 5 minutes, and the (meth)acrylic copolymer-containing solution Crosslinking of the (meth)acrylic copolymer therein was progressed to produce a laminated sheet having an adhesive layer on the release-treated surface of the polyethylene terephthalate film. One more laminated sheet was produced in the same manner to obtain a total of two laminated sheets.
Next, a polyethylene terephthalate film (thickness: 50 μm) was prepared as a base material. One of the laminated sheets was laminated on one surface of this base material from the adhesive layer side, so that the adhesive layer was transferred and laminated onto the base material. The other laminated sheet was laminated on the other surface of the base material from the pressure-sensitive adhesive layer side, so that the pressure-sensitive adhesive layer was transferred and laminated onto the base material. As a result, a double-sided adhesive tape was obtained in which adhesive layers with a thickness of 80 μm were provided on both sides of the base material.

(2) GPC measurement of sol components (RI and UV)
The adhesive layer of the double-sided adhesive tape was immersed in tetrahydrofuran (THF) at 23° C. for 24 hours, and insoluble matter was removed by filtration through a 200-mesh wire mesh to obtain a sol component of the adhesive layer.
The sol component of the obtained adhesive layer was subjected to GPC measurement using differential refractometer RI detection in the following manner. That is, the sol component of the obtained adhesive layer was analyzed by gel permeation chromatography (GPC) (manufactured by Waters, 2690 Separations Model) using column LF-804 manufactured by SHOKO Co., Ltd. as a column, and the sol component was analyzed in terms of polystyrene. The molecular weight distribution was measured.
Eluent: Tetrahydrofuran (THF)
Flow rate: 0.4mL/min
Detector: Differential refractometer RI
Column temperature (measurement temperature): 40°C
Injection volume: 20μL

In the obtained molecular weight distribution, the proportion of molecular weight of 100,000 or less, the proportion of molecular weight of 150,000 or less, the proportion of molecular weight of 500,000 or more, the proportion of molecular weight of 600,000 or more, the proportion of molecular weight of 100,000 to 600,000, and the proportion of molecular weight of 150,000 to 500,000. The ratio and the peak of molecular weight distribution (Mp(RI)) are shown in Table 3.

Further, the sol component of the obtained adhesive layer was subjected to GPC measurement using ultraviolet (UV) detection with an absorption wavelength of 254 nm by the following method. That is, the sol component of the obtained adhesive layer was analyzed by gel permeation chromatography (GPC) (manufactured by Waters, 2690 Separations Model) using column LF-804 manufactured by SHOKO Co., Ltd. as a column, and the sol component was analyzed in terms of polystyrene. The molecular weight distribution was measured.
Eluent: Tetrahydrofuran (THF)
Flow rate: 0.4mL/min
Detector: UV detector (absorption wavelength 254nm)
Column temperature (measurement temperature): 40°C
Injection volume: 20μL

From the obtained molecular weight distribution, the difference between the peaks of the molecular weight distribution (Mp (UV-RI)) was determined and shown in Table 3.

(3) Measurement of storage modulus The storage modulus G' (100°C) of the adhesive layer of the double-sided adhesive tape was measured by the following method. That is, first, samples of the adhesive layer were stacked together to produce a laminate with a thickness of about 1 mm, and the laminate was cut into a size of 6 mm x 10 mm to obtain a test piece. Using a dynamic viscoelasticity measurement device (IT Keizai Control Co., Ltd., DVA-200), the measurement temperature was -40 to 140°C in a nitrogen atmosphere in shear mode, the heating rate was 5°C/min, the frequency was 10Hz, and the strain was 0. Measurements were made on specimens at 0.08%.

(4) Measurement of Gel Fraction The gel fraction of the adhesive layer of the double-sided adhesive tape was measured by the following method. That is, first, W ₁ (g) of the adhesive layer was collected, the collected adhesive layer was immersed in ethyl acetate at 23°C for 24 hours, and the insoluble matter was filtered through a 200-mesh wire mesh. The residue on the wire mesh was dried by heating at 110° C., and the weight W ₂ (g) of the obtained dried residue was measured. The gel fraction (degree of crosslinking) was calculated using the following formula (1).
Gel fraction (weight %) = 100 x W ₂ /W ₁ (1)

(5) Measurement of monomer content The adhesive layer of the double-sided adhesive tape was subjected to GC-MS (gas chromatograph mass spectrometer) measurement under the following conditions to determine the monomer content in the adhesive layer.
(Measurement condition)
GC-MS device GC: 78906B (manufactured by Agilent technology), MS: JMS-Q1500 (manufactured by JEOL Ltd.)
Column: SLBTM-5ms (slightly polar) 0.25mmφ x 30m x 0.25μm
Inlet temperature: 250℃
He flow rate: 1.0mL/min (split ratio 1:50)
Column temperature: After holding at 40°C for 3 minutes, increase the temperature at 10°C/min. Thereafter, the temperature was maintained at 300°C for 10 minutes.
MS measurement range: 35-800amu
Ionization voltage: 70eV, ionization method: EI method, measurement mode: scan Ion source temperature: 230°C, interface temperature: 250°C

(Examples 2 to 20, Comparative Examples 1 to 5)
A double-sided adhesive tape was obtained in the same manner as in Example 1, except that the types or amounts of the (meth)acrylic copolymer, tackifying resin, and crosslinking agent were changed as shown in Tables 3 and 4.
In addition, "T130" in Tables 3 and 4 is a terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "T130") which is a tackifying resin, and "D135" is a polymerized rosin ester resin which is a tackifying resin. (manufactured by Arakawa Chemical Industries, Ltd., Pencel D135), "KE388" is a hydrogenated rosin ester resin (manufactured by Arakawa Chemical Industries, Ltd., Pine Crystal KE-388), which is a tackifying resin, and "KE359" is a tackifying resin. The tackifying resin is hydrogenated rosin ester resin (Pine Crystal KE-359, manufactured by Arakawa Chemical Co., Ltd.), and "G150" is a terpene resin (Yasuhara Chemical Co., Ltd., YS Polyster G150), which is the tackifying resin.

<Evaluation>
The double-sided adhesive tapes obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 3 and 4.

(1) Adhesion to the polishing pad As the polishing pad, a polyurethane foam sliced to a thickness of 3 mm (mainly containing PPG as the polyether polyol, TDI as the isocyanate, and MOCA as the curing agent) was used. When this polyurethane foam was observed using a laser microscope, the surface roughness Sa was 3.99 μm and the contact area ratio was 77%.

The double-sided adhesive tape was cut into strips with a width of 25 mm to prepare test pieces. The release PET film on one side of the test piece was peeled off to expose the adhesive layer. After washing with ethanol, the test piece was placed on the above-mentioned polishing pad that had been wiped dry with the adhesive layers facing each other. A 2 kg rubber roller was moved back and forth over the test piece at a speed of 300 mm/min to bond the test piece and the polishing pad together. This laminate was passed through a laminator (Multi Laminator GDRH355 A3, manufactured by Aco Brands Japan Co., Ltd.) once under the conditions of a roll temperature of 85° C., a roll gap of 2 mm, and a speed of 7.5 rpm, and was pressed under a pressure of 1.2 MPa. Thereafter, the sample was allowed to stand for 24 hours at a temperature of 23° C. and a relative humidity of 50% to obtain a test sample.
A 180° peel test was performed on the test sample using a tensile testing machine in accordance with JIS Z0237 at a peeling rate of 300 mm/min and a peeling angle of 180°.

(2) Measurement of shear strength (creep resistance test)
FIG. 1 is a schematic diagram showing a method for measuring the shear strength (creep resistance test) of the double-sided adhesive tapes obtained in Examples and Comparative Examples.
A double-sided adhesive tape was cut out to a width of 10 mm and a length of 120 mm and lined with a PET film having a thickness of 25 μm to prepare a test piece 1. As shown in FIG. 1, the test piece 1 was attached to the stainless steel measurement terminal portion 2 of the tester with an adhesive area of 10×10 mm. The temperature of the stainless steel measurement terminal portion 2 was set at 60°C. A mirror-treated quartz block 3 (chromium-deposited quartz glass) was placed on the attachment surface of the test piece 1, and a weight 5 of 50 gf was attached to the test piece 1. Three minutes after applying the load with the weight 5, the amount of displacement (deviation amount) (μm) in the direction of the arrow in the figure was measured using a laser interferometer 4 (manufactured by Keyence Corporation, SI-F10). The amount of movement of the treated quartz block 3 was measured and used as a cohesive force displacement value.

(3) Comprehensive evaluation If the adhesive force to the polishing pad measured in (1) above is 50 N/25 mm or more, and the cohesive force displacement value measured in (2) above is 50 μm or less, 〇 is adhesive strength. is 45 N/25 mm or more and less than 50 N/25 mm, and the cohesive force displacement value is 50 μm or less, △, and the case where the adhesive force is less than 45 N/25 mm, or the cohesive force displacement value is less than 50 μm, is evaluated as ×. did.

According to the present invention, it is possible to provide an adhesive tape that has high adhesive strength to rough surfaces and has excellent shear strength at high temperatures.

1 Test piece 2 Stainless steel measurement terminal part 3 Mirror-treated quartz block 4 Laser interferometer 5 Weight (50 gf)

Claims (14)

An adhesive tape having a base material and an adhesive layer,
The adhesive layer contains a (meth)acrylic copolymer and a crosslinking agent,
The weight average molecular weight of the (meth)acrylic copolymer is 450,000 or less,
When the sol component of the adhesive layer is subjected to GPC measurement using differential refractometer RI detection, in the region of molecular weight 5000 or more, the proportion of molecular weight of 100,000 or less is 5% or more and 75% or less, and the proportion of molecular weight of 600,000 or more is 0.5% or more and 16% or less,
An adhesive tape characterized in that the content of (meth)acrylic monomer in the adhesive layer is 2.5% by weight or less. The adhesive tape according to claim 1, wherein when the GPC measurement is performed, the proportion of molecular weights of 150,000 or less in the region of molecular weights of 5,000 or more is 5% or more and 65% or less. The adhesive tape according to claim 1 or 2, wherein when the GPC measurement is performed, the proportion of molecular weights of 500,000 or more in the region of molecular weights of 5000 or more is 1% or more and 20% or less. The adhesive tape according to claim 1 or 2, wherein the content of the (meth)acrylic monomer in the adhesive layer is 0.1% by weight or more. The peak of the molecular weight distribution (Mp (UV)) when the sol component of the adhesive layer is measured by GPC using ultraviolet (UV) detection with an absorption wavelength of 254 nm, and the RI detection using a differential refractometer for the sol component of the adhesive layer. The adhesive tape according to claim 1 or 2, wherein the difference Mp (UV-RI) from the peak of molecular weight distribution (Mp (RI)) when measured by GPC is 5000 or more. Claim: When the sol component of the adhesive layer is subjected to GPC measurement using differential refractometer RI detection, the peak of the molecular weight distribution (Mp(RI)) is 100,000 to 400,000 in a molecular weight region of 5,000 or more. Adhesive tape according to 1 or 2. The adhesive tape according to claim 1 or 2, wherein the adhesive layer has a gel fraction of 15% by weight or more and 70% by weight or less. The adhesive tape according to claim 1 or 2, wherein the adhesive layer has a storage modulus G' (100°C) of 3.5×10 ⁴ Pa or more. The adhesive layer further includes a tackifying resin, the softening temperature of the tackifying resin is 100°C or more and 180°C or less, and the content of the tackifying resin is 100 parts by weight of the (meth)acrylic copolymer. The adhesive tape according to claim 1 or 2, wherein the adhesive tape contains 10 parts by weight or more and 60 parts by weight or less. The adhesive tape according to claim 1 or 2, wherein the (meth)acrylic copolymer contains 8% by weight or more of structural units derived from a carboxy group-containing monomer. The (meth)acrylic copolymer has a content of structural units derived from an alkyl (meth)acrylate having an alkyl group having 4 or less carbon atoms of 25% by weight or more and 70% by weight or less,
The adhesive tape according to claim 1 or 2, wherein the content of the structural unit derived from an alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms is 22% by weight or more and 67% by weight or less. The adhesive tape according to claim 1 or 2, wherein the adhesive layer has a thickness of 10 μm or more and 150 μm or less. The adhesive tape according to claim 1 or 2, wherein the adhesive layer is provided on both sides of the base material. The adhesive tape according to claim 1 or 2, which is used for fixing a polishing pad to a surface plate of a polishing machine.

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