JP2851441B2 - Method for producing solvent-based acrylic pressure-sensitive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solvent-type acrylic pressure-sensitive adhesive. In particular, the present invention relates to a method for producing a solvent-based acrylic pressure-sensitive adhesive, which can produce a pressure-sensitive adhesive having a small amount of residual monomer in a short time and can easily control the pressure-sensitive adhesive properties of the obtained pressure-sensitive adhesive.

[0002]

2. Description of the Related Art Solvent-type acrylic pressure-sensitive adhesives have an adhesive strength,
It has excellent adhesive properties such as cohesion, weather resistance, and oil resistance, and is widely used in adhesive tapes and adhesive sheets.

[0003] Such a solvent-type acrylic pressure-sensitive adhesive is generally prepared by using a polymerization initiator such as a peroxide or an azo compound in a suitable solvent with a vinyl-based monomer containing an alkyl (meth) acrylate as a main component. It is prepared by thermal polymerization. In such a thermal polymerization reaction, heat of polymerization is generated, so that it is difficult to appropriately control the reaction. If the reaction is not properly controlled, problems such as a rapid decomposition of the polymerization initiator, a decrease in the molecular weight of the resulting polymer, and a large amount of unreacted monomer remaining will occur. The monomer remaining in the adhesive reduces the adhesive properties of the adhesive,
It causes odor and contamination of adherend. If the reaction proceeds more rapidly, the polymerization reaction runs away, and there is a danger that the reaction vessel may burst. Therefore, this thermal polymerization reaction is generally carried out slowly for 7 to 8 hours by controlling the polymerization temperature within the range of about 60 to 120 ° C. or adding the polymerization initiator in a divided manner. It is a target. Therefore, this method has a problem that productivity is poor. further,
Even with such a method, it is difficult to sufficiently remove unreacted monomers.

[0004]

The object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to produce a solvent-type acrylic pressure-sensitive adhesive having high productivity and a small amount of residual monomer. The purpose is to provide a way to gain. Still another object of the present invention is to provide a method for producing a solvent-based acrylic pressure-sensitive adhesive, which can easily control the pressure-sensitive adhesive properties of the obtained pressure-sensitive adhesive.

[0005]

According to the present invention, there is provided a method for producing a solvent-type acrylic pressure-sensitive adhesive, comprising a vinyl monomer having an alkyl (meth) acrylate as a main component, a photopolymerization initiator, and a monomer containing a solvent. Irradiating the solution with ultraviolet light to perform a photopolymerization reaction; a first polymerization step; adding a thermal polymerization initiator to the photopolymerization reaction solution in advance or after the first polymerization step; And a second polymerization step of completing the polymerization reaction by thermally polymerizing the above monomer, whereby the above object is achieved.

In another method for producing a solvent-based acrylic pressure-sensitive adhesive of the present invention, a monomer solution containing a vinyl-based monomer having an alkyl (meth) acrylate as a main component, a thermal polymerization initiator, and a solvent is heated. To conduct a thermal polymerization reaction,
A first polymerization step; a photopolymerization initiator is added to the thermal polymerization reaction solution in advance or after the first polymerization step, and the mixture is irradiated with ultraviolet rays to photopolymerize unreacted monomers to complete the polymerization reaction. , A second polymerization step, whereby the object is achieved.

The vinyl monomers used in the present invention include 60 to 100% by weight of an alkyl (meth) acrylate and 0 to 40% by weight of another copolymerizable with an alkyl (meth) acrylate. A monomer containing a vinyl monomer may be used.

[0008] As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group having 1 to 14, preferably 4 to 12 carbon atoms is used. For example, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth)
Isooctyl acrylate, isononyl (meth) acrylate and the like are preferably used.

The vinyl monomers copolymerizable with the alkyl (meth) acrylate include acrylic acid, methacrylic acid, acrylamide, acrylonitrile, methacrylonitrile, N-substituted acrylamide, hydroxyethyl acrylate, N-vinylpyrrolidone, and maleic. Acid, itaconic acid, N-methylolacrylamide, hydroxyethyl methacrylate and the like are used. Alternatively, tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, and the like can also be used, and by using these monomers, a polymer having a low glass transition temperature can be obtained. Solvent-based acrylic pressure-sensitive adhesives are often used by blending a crosslinking agent when used in order to improve cohesive strength, solvent resistance, and the like. When used together with a crosslinking agent, a monomer having a carboxyl group or a hydroxyl group is used as a vinyl monomer other than the alkyl (meth) acrylate.

As the photopolymerization initiator used in the present invention, a photopolymerization initiator that absorbs ultraviolet rays having a wavelength of 300 to 400 nm and starts polymerization with high polymerization initiation efficiency is preferably used. For example, benzoin ethyl ether, benzoin isopropyl ether, hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal, and the like can be used. The addition amount of the photopolymerization initiator is 0.0001 to 1.0 with respect to 100 parts by weight of the total amount of the vinyl monomer.
Parts by weight are preferred. If the amount is less than 0.0001 part by weight, the polymerization time becomes longer. If the amount exceeds 1.0 part by weight, the odor due to the decomposition of the initiator during the reaction is severe, the molecular weight of the obtained polymer is reduced, and the adhesive properties are reduced.

Examples of the thermal polymerization initiator include acetyl peroxide, lauroyl peroxide, benzoyl peroxide, diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxy (2-ethylhexa). Noate), organic peroxides such as t-butyl perlaurate and t-butyl peroxyacetate, and azo compounds such as azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile) Is used. In particular, benzoyl peroxide and azobisisobutyronitrile are preferably used. The amount of the thermal polymerization initiator to be used is from 0.0001 to 0.001 parts by weight based on 100 parts by weight of the total amount of the vinyl monomer.
One part by weight is preferred. If the amount is less than 0.0001 part by weight, the polymerization time becomes longer. If the amount exceeds 0.1 parts by weight, the polymerization reaction runs away or the molecular weight of the obtained polymer is reduced, and the adhesive properties are reduced.

As the solvent used in the present invention, an organic solvent capable of dissolving the above-mentioned vinyl monomer is used.
Examples thereof include esters such as ethyl acetate, ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene, and cyclohexane. Further, two or more of these organic solvents may be used as a mixture. Such a solvent is generally used in a total amount of 1 to 1 of the above-mentioned vinyl monomer.
It is used in a proportion of 50 to 300 parts by weight with respect to 00 parts by weight. In order to adjust the viscosity of the reaction solution and the reactivity of the monomer, these solvents may be divided and administered to the reaction system.

According to the first method of the present invention, the solvent-based acrylic pressure-sensitive adhesive is prepared as follows. First,
The alkyl (meth) acrylate and, if necessary, other vinyl monomers and a photopolymerization initiator are dissolved in the above solvent to prepare a monomer solution. In the photopolymerization reaction, since the runaway of the polymerization reaction does not occur, a monomer solution containing a relatively high concentration of the monomer can be used. Since the reaction time can be shortened by increasing the monomer concentration, it is preferable to use a monomer solution having the highest possible concentration. For example, 50 to 30 parts by weight based on 100 parts by weight of the total amount of monomers
0 parts by weight of solvent are used. The photopolymerization initiator may be added to the solution at once before the reaction, or may be added separately during the reaction. This monomer solution is preferably purged with an inert gas such as nitrogen gas to remove dissolved oxygen. Alternatively, phenyldiisodecyl phosphite, triisodecyl phosphite,
A compound having an oxygen removing effect such as an octyltin compound may be added to the solution.

Next, as a first polymerization step, the monomer solution is irradiated with ultraviolet rays so that the polymerization rate is preferably 40%.
Photopolymerize until reaching ~ 95%. The polymerization rate can be determined based on the viscosity of the reaction solution and the like. As a light source used for ultraviolet irradiation, a light source having an emission spectrum in a wavelength region of 300 to 400 nm is used. For example, there are a chemical lamp, a black light lamp (trade name, manufactured by Toshiba Lighting & Technology Corporation), a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, and a metal halide lamp.
In the case of irradiating ultraviolet rays having relatively low light intensity, the former 2
In the case where one light source is preferably used and ultraviolet light having a relatively high light intensity is irradiated, the latter four light sources are used.
The light intensity is 300 to 400 nm ultraviolet light, 0.1 to 1
000 mW (milliwatt) / cm ² , preferably 0.1 to 1
It is in the range of 00 mW / cm ² . The irradiation time of the ultraviolet rays is closely related to the light intensity, but is preferably 0.5 to 4 hours. The detailed light intensity and ultraviolet light irradiation time are appropriately set according to the molecular weight and molecular weight distribution according to the quality required for the target pressure-sensitive adhesive. For example, when the light intensity is increased, the polymerization time is shortened, but the molecular weight distribution of the produced polymer is widened. Conversely, lowering the light intensity increases the polymerization time and narrows the molecular weight distribution. The reaction temperature in the first polymerization step does not need to be particularly controlled, but heating or cooling may be performed for the purpose of controlling the reaction rate.

Next, a thermal polymerization initiator is added to the reaction solution after the photopolymerization. The thermal polymerization initiator may be added when preparing the monomer solution. Then, when the mixed solution is heated and the unreacted monomer is thermally polymerized to complete the polymerization reaction, a target solvent-type acrylic pressure-sensitive adhesive is obtained. The reaction temperature and the amount of the thermal polymerization initiator to be added can be appropriately set in consideration of the quality and productivity required for the target pressure-sensitive adhesive. In the second polymerization step, since most of the monomers have already been polymerized, there is little danger that the polymerization reaction will run away. Therefore, the reaction temperature can be increased to near the boiling point of the solvent, and the thermal polymerization initiator A relatively large amount can also be used. Therefore, in this case, the amount of the thermal polymerization initiator to be added is 1 to the total amount of the vinyl monomer at the time of charging.
It is preferably 0.001 to 0.1 parts by weight based on 00 parts by weight. When such conditions are used, the polymerization reaction is considered to be almost completed in 1 to 3 hours.

The reaction vessel for carrying out the above polymerization reaction includes:
Those made of quartz glass or Pyrex glass that can transmit light are used. In particular, a reaction vessel made of Pyrex glass, which easily transmits ultraviolet light, is preferably used. Alternatively, a stainless steel reaction vessel having a window for ultraviolet irradiation made of such glass may be used. The method of irradiating the ultraviolet rays may be from outside or inside the reaction vessel, and may be appropriately selected depending on the shape of the reaction vessel.

In the method of the present invention, it is recommended to add a chain transfer agent to the monomer solution for the purpose of suppressing the dispersion of the polymerization reaction and appropriately adjusting the molecular weight of the obtained polymer. As the chain transfer agent, a thiol compound or a halogen compound having a high chain transfer property can be used. Examples of the thiol compound include n-dodecyl mercaptan, 2-mercaptoethanol, β-mercaptopropionic acid, octyl β-mercaptopropionate, methoxybutyl β-mercaptopropionate, and trimethylolpropanetris-
(β-thiopropionate), butyl thioglycolate,
There are propanethiols, butanethiols, thiophosphites and the like. Examples of the halogen compound include carbon tetrachloride. By adding a chain transfer agent, the molecular weight of the polymer can be precisely adjusted, and a pressure-sensitive adhesive having desired pressure-sensitive adhesive strength and cohesive strength can be obtained. Further, various additives may be added to the monomer solution for the purpose of improving the properties of the target pressure-sensitive adhesive. Such additives include thickeners, thixotropic agents, extenders, fillers and the like.
Examples of the thickener include acrylic rubber and epichlorohydrin rubber, and examples of the thixotropic agent include Aerosil and polyvinylpyrrolidone. As the extender, calcium carbonate, clay, etc. are used.As the filler, an inorganic hollow body such as a glass balloon, an organic spherical body such as a nylon bead, an organic hollow body such as an acrylic balloon, a single fiber made of polyester, etc. Used.

According to the first method, since photopolymerization in which the reaction is easily controlled is performed as the first polymerization step, the runaway of the polymerization reaction does not occur, the reaction can be performed safely, and the reaction time can be reduced. Can be shortened. Then, as the second polymerization step, the unreacted monomer can be rapidly polymerized by the thermal polymerization reaction, so that a solvent-type acrylic pressure-sensitive adhesive having a small amount of residual monomer and having good pressure-sensitive adhesive properties can be obtained.

According to the second method of the present invention, thermal polymerization is performed in the first polymerization step, and then photopolymerization is performed in the second polymerization step to produce a solvent-type acrylic pressure-sensitive adhesive. First, the alkyl (meth) acrylate and, if necessary, other vinyl monomers and a thermal polymerization initiator are dissolved in the above solvent to prepare a monomer solution. The thermal polymerization initiator may be added to the solution all at once before the reaction, or may be added separately during the reaction. This monomer solution is used after removing dissolved oxygen as described above. The container used for the reaction is not particularly limited,
Since ultraviolet irradiation is performed in the second polymerization step, the first polymerization is usually performed.
In the same manner as in the above method, a container made of a material that can transmit light is used.

Next, as a first polymerization step, the monomer solution is heated to 40 to 120 ° C., and a thermal polymerization reaction is performed until the polymerization rate reaches preferably 40 to 95%. The polymerization rate can be determined based on the viscosity of the reaction solution and the like. The reaction temperature and the amount of the thermal polymerization initiator to be added are set so as to have a molecular weight and a molecular weight distribution according to the quality required of the target pressure-sensitive adhesive within a range in which runaway of the polymerization reaction does not occur. Since the polymerization reaction does not need to be completed in this first polymerization step, 0.1.
With a reaction time of about 5 to 4 hours, the above polymerization rate is sufficiently achieved.

Next, a photopolymerization initiator is added to the reaction solution after the thermal polymerization. The photopolymerization initiator may be added when preparing the monomer solution when it is considered that the generation of heat-induced radicals is small. Then, when this mixed solution is irradiated with ultraviolet rays to photopolymerize unreacted monomers to complete the polymerization reaction, a target solvent-type acrylic pressure-sensitive adhesive is obtained. The light source and light intensity used for the irradiation of the ultraviolet rays are the same as those in the first method. This photopolymerization reaction proceeds rapidly, and the reaction is completed in 0.5 to 2 hours. In the second method, as in the first method, various chain transfer agents and additives can be used.

According to the second method, a photopolymerization initiator is added at a later stage of the thermal polymerization reaction to complete the polymerization by photopolymerization, so that the reaction can be completed quickly at a relatively low temperature. Therefore, the reaction time is reduced as compared with the conventional method in which all the steps are performed by thermal polymerization. Further, the amount of unreacted monomer remaining in the pressure-sensitive adhesive is greatly reduced, and a pressure-sensitive adhesive having good pressure-sensitive adhesive properties can be obtained.

As described above, according to the method of the present invention, a solvent type acrylic pressure-sensitive adhesive having a small amount of residual monomer can be produced with high productivity. Furthermore, since the polymerization reaction is carried out in two stages, it is easy to control the molecular weight and molecular weight distribution of the polymer, and it is possible to produce a pressure-sensitive adhesive having demands.

[0024]

Embodiments of the present invention will be described below.

For the solvent-based acrylic pressure-sensitive adhesives obtained in the following Examples and Comparative Examples, the weight-average molecular weight (Mw) of the polymer, the degree of dispersion of the molecular weight distribution (Mw / Mn), and the amount of the residual monomer were as follows: The method was evaluated.

(1) Dispersion of Weight Average Molecular Weight and Molecular Weight Distribution The molecular weight distribution of the polymer was measured by gel permeation chromatography with reference to standard crosslinked polystyrene, and the weight average molecular weight and number average molecular weight were calculated from the distribution curve. , And the degree of dispersion was calculated. Tetrahydrofuran was used as an eluent for gel permeation chromatography, and a differential refractometer was used as a detector.

(2) Amount of residual monomer Chromosomes supporting polyethylene glycol (20M)
Using a gas chromatograph (GC-6A, manufactured by Shimadzu Corporation) equipped with a separation column packed with a filler (manufactured by Shimadzu Corporation) obtained by treating the rb w with acid, and a flame ionization detector. The amount of monomer remaining in the agent was measured.

As a measurement sample, 100 mg of the adhesive sample from which the solvent was evaporated was dissolved in 5 ml of methyl acetate, and 2 ml of this solution was mixed with 2 ml of an internal standard solution in which 2-ethylhexyl methacrylate was dissolved in methyl acetate. The solution was used.

Example 1 A five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet was charged with 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of acrylic acid, and as a solvent. Charge 150 parts by weight of ethyl acetate,
0.1 parts by weight of benzyldimethyl ketal was added as a photopolymerization initiator, and the mixture was stirred to dissolve the monomer and the photopolymerization initiator. Nitrogen gas was blown into this monomer solution for 30 minutes to remove oxygen dissolved in the solution. Using a chemical lamp (manufactured by Toshiba Lighting & Technology Corp.), the monomer solution was irradiated with ultraviolet light having a wavelength of 360 nm at a light intensity of 4 mW / cm ² for 2 hours using a chemical lamp (manufactured by Toshiba Lighting & Technology Corp.) for 2 hours to photopolymerize the monomer ( First polymerization step).

Next, a solution prepared by dissolving 0.015 parts by weight of azobisisobutyronitrile, which is a thermal polymerization initiator, in 0.5 parts by weight of ethyl acetate was added to the above reaction solution using a dropping funnel. Was added each time. While stirring the reaction solution,
The mixture was heated to about 84 ° C., kept in a reflux state for 2 hours, and thermally unpolymerized in the first polymerization step (second polymerization step) to obtain a solvent-type acrylic pressure-sensitive adhesive. These two
The time required for the polymerization reaction in one polymerization step is a total of 4 hours 3
It was 0 minutes.

Table 1 shows the results of evaluating the obtained pressure-sensitive adhesives by the above-mentioned method, together with the evaluation results of the pressure-sensitive adhesives obtained in Examples 2 to 4 and Comparative Examples 1 to 3 described below.

Example 2 Example 1 was repeated except that in the second polymerization step, 0.013 parts by weight of benzoyl peroxide was used as the thermal polymerization initiator.
A solvent-type acrylic pressure-sensitive adhesive was prepared in the same manner as described above.

Example 3 Into the same reaction vessel as in Example 1, 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of acrylic acid, and 150 parts by weight of ethyl acetate as a solvent were charged, and the monomers were dissolved by stirring. . Nitrogen gas was blown into this monomer solution for 30 minutes to remove oxygen dissolved in the solution. While continuing to blow nitrogen gas, the monomer solution was heated to 60 ° C., and a solution prepared by dissolving 0.015 parts by weight of azobisisobutyronitrile, a thermal polymerization initiator, in 0.5 parts by weight of ethyl acetate was added dropwise. It was gradually dropped into the monomer solution by a funnel. Thermal polymerization was performed for 3 hours from the start of the dropwise addition while maintaining the temperature of the reaction solution at 60 ° C. (first polymerization step).

Next, a solution prepared by dissolving 0.1 part by weight of benzyldimethyl ketal, which is a photopolymerization initiator, in 0.5 part by weight of ethyl acetate was added to the above reaction solution from a dropping funnel. The reaction solution was irradiated with ultraviolet light having a wavelength of 360 nm at a light intensity of 8 mW / cm ² for 1 hour using an ultra-high pressure mercury lamp (manufactured by Oak Manufacturing Co., Ltd., jet cure), and the monomer which had not reacted in the first polymerization step was irradiated. Was subjected to photopolymerization (second polymerization step) to obtain a solvent-type acrylic pressure-sensitive adhesive. The time required for the polymerization reaction in these two polymerization steps was a total of 4 hours.

Example 4 In the first polymerization step, 0.013 parts by weight of benzoyl peroxide was used as a thermal polymerization initiator, and the reaction temperature of the thermal polymerization was 70 ° C.
A solvent-based acrylic pressure-sensitive adhesive was prepared in the same manner as in Example 3, except that

Comparative Example 1 In a reaction vessel similar to that in Example 1, 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of acrylic acid, and 150 parts by weight of ethyl acetate as a solvent were charged, and the monomers were dissolved by stirring. . Nitrogen gas was blown into this monomer solution for 30 minutes to remove oxygen dissolved in the solution. While continuing to blow nitrogen gas, the monomer solution is heated to 60 ° C., and a solution in which 0.015 part by weight of azobisisobutyronitrile is dissolved in 0.5 part by weight of ethyl acetate is added to the monomer solution by a dropping funnel. It was dropped slowly. Thermal polymerization was performed for 2 hours from the start of the dropwise addition while maintaining the temperature of the reaction solution at 60 ° C. Further, the same azobisisobutyronitrile solution as described above was gradually dropped again from the dropping funnel. After reacting for 1 hour, an azobisisobutyronitrile solution having a concentration 10 times higher than that described above (0.15 parts by weight of azobisisobutyronitrile dissolved in 1.5 parts by weight of ethyl acetate) is further added dropwise. , And gradually dropped. After completion of the dropping, the reaction solution was further maintained at 60 ° C. for 4 hours to complete the polymerization reaction, and a solvent-type acrylic pressure-sensitive adhesive was obtained. The time required for the polymerization reaction in this polymerization step was 7 hours.

Comparative Example 2 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of acrylic acid, and 85 parts by weight of ethyl acetate as a solvent were charged into the same reaction vessel as in Example 1, and the monomers were dissolved by stirring. . Nitrogen gas was blown into this monomer solution for 30 minutes to remove oxygen dissolved in the solution. While continuing to blow nitrogen gas, the monomer solution is heated to 70 ° C., and a solution in which 0.013 part by weight of benzoyl peroxide is dissolved in 0.5 part by weight of ethyl acetate is gradually dropped into the monomer solution by a dropping funnel. did. 2 hours from the start of dripping,
Thermal polymerization was performed while maintaining the temperature of the reaction solution at 70 ° C.
Further, the same amount of the above benzoyl peroxide solution was gradually dropped again from the dropping funnel. After reacting for one hour, a benzoyl peroxide solution (0.13 parts by weight of benzoyl peroxide) having a concentration ten times the above was gradually dropped from the dropping funnel. After the completion of the dropwise addition, the reaction solution was further added for 7
The polymerization reaction was completed by maintaining at 0 ° C. for 4 hours to obtain a solvent-type acrylic pressure-sensitive adhesive. The time required for the polymerization reaction in this polymerization step was 7 hours.

[0038]

[Table 1]

[0039]

As described above, according to the method of the present invention, a solvent type acrylic pressure-sensitive adhesive having a small amount of residual monomer can be produced with high productivity. Furthermore, by the method of the present invention, the polymerization reaction can be easily controlled, and the molecular weight and molecular weight distribution of the polymer can be adjusted to obtain a pressure-sensitive adhesive having desired pressure-sensitive adhesive properties. Therefore,
The solvent-based acrylic pressure-sensitive adhesive obtained by the method of the present invention can be widely used for various pressure-sensitive adhesive tapes or pressure-sensitive adhesive sheets.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-187483 (JP, A) JP-A-55-125117 (JP, A) JP-A-1-113402 (JP, A) JP-A 55-125 12687 (JP, A) JP-A-53-98339 (JP, A) JP-A-57-121009 (JP, A) JP-A-57-177008 (JP, A) JP-A-57-53508 (JP, A) JP-A-3-140313 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 133/04-133/14 C08F 2 / 48,2 / 50

Claims (2)

(57) [Claims] 1. A first polymerization step of irradiating a monomer solution containing a vinyl monomer mainly containing an alkyl (meth) acrylate, a photopolymerization initiator, and a solvent with ultraviolet rays to perform a photopolymerization reaction. And a second polymerization step in which a thermal polymerization initiator is added to the photopolymerization initiation reaction solution in advance or after the first polymerization step, and the mixture is heated to thermally polymerize unreacted monomers to complete the polymerization reaction. A method for producing a solvent-type acrylic pressure-sensitive adhesive, comprising: 2. A first polymerization step of heating a monomer solution containing a vinyl monomer containing an alkyl (meth) acrylate as a main component, a thermal polymerization initiator, and a solvent to carry out a thermal polymerization reaction; Adding a photopolymerization initiator to the thermal polymerization reaction solution in advance or after the first polymerization step, and irradiating ultraviolet rays to photopolymerize unreacted monomers to complete the polymerization reaction; A method for producing a solvent-type acrylic pressure-sensitive adhesive, including: