JPH08157782A - Preparation of pressure-sensitive adhesive sheet - Google Patents

Abstract

PURPOSE: To provide a process for preparing a pressure-sensitive adhesive sheet wherein the viscosity of a photopolymerizable compsn. is always regulated in a viscosity range suitable for coating without undergoing any influence of temperature and humidity conditions of the atmosphere. CONSTITUTION: A substrate is coated with a photopolymerizable compsn. comprising 100 pts.wt. photopolymerizable monomer, 1 to 10 pts.wt. silica thixotropy agent having a water content of not more than 1wt% and possessing high hydrophilicity, and 0.10 to 0.60 pt.wt. water or 0.1 to 0.9 pt.wt. polyhydric alcohol.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an adhesive sheet.

[0002]

2. Description of the Related Art A coating film obtained by polymerizing a photopolymerizable monomer is used as a supporting base material or a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet. The photopolymerizable monomer is generally used as a base material or pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet. Its viscosity is remarkably low as compared with other materials used, and when the photopolymerizable composition containing the photopolymerizable monomer is applied, the viscosity of the coating liquid is 1.00.
When it is less than 0 cps, a method of adding a thixotropy-imparting agent such as fumed silica to impart thixotropy suitable for coating is adopted (Japanese Patent Publication No. 57-17030). Further, as the thixotropic agent,
In addition to the above fumed silica, trade name Aerosil # 200 and #
300 (manufactured by Aerosil), trade name Nipsil VN3 (manufactured by Nippon Silica Industry Co., Ltd.) and the like are known (Japanese Patent Laid-Open No. 2-11).
684).

Silica having high hydrophilicity which has been used in the above-mentioned technique has a water content depending on environmental humidity in the atmosphere during storage period or during mixing and adjusting work with photopolymerizable monomer due to its high hydrophilicity. And the viscosity of the photopolymerizable composition fluctuates greatly. Therefore, in the above conventional technique, the viscosity of the photopolymerizable composition is in a range suitable for application (generally 2,500 to 3,5) without being affected by atmospheric conditions.
It was very difficult to constantly control the temperature within 100 cps.

[0004]

The present invention overcomes the above-mentioned drawbacks of the prior art. The object of the present invention is to apply the viscosity of a photopolymerizable composition without being affected by the temperature and humidity conditions of the atmosphere. Suitable range (generally 2,500-3,5
The present invention is to provide a method for producing a pressure-sensitive adhesive sheet, which is constantly controlled within 100 cps.

[0005]

The present invention comprises 100 parts by weight of a photopolymerizable monomer, 1 to 10 parts by weight of a highly hydrophilic silica-based thixotropic agent having a water content of 1% by weight or less, and 0.1 to 10 parts of water. A method for producing a pressure-sensitive adhesive sheet is characterized in that a photopolymerizable composition comprising 0.6 parts by weight or 0.1 to 0.9 parts by weight of a polyhydric alcohol is applied onto a substrate. is there.

The photopolymerizable monomer used in the present invention is selected from those polymerizable monomers which are excited by irradiation with light such as ultraviolet rays and decompose into radicals to initiate radical polymerization or ionic polymerization. If it is not particularly limited, for example, (meta)
N-butyl acrylate, hexyl (meth) acrylate,
2-Ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic 50 (meth) acrylic acid esters such as acid dodecyl
To 98% by weight, a monomer containing a carboxyl group such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid or the anhydride thereof, (meth) acrylonitrile, N-
Vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropylacrylamide and other nitrogen-containing monomers, 2-hydroxyethyl (meth) acrylate, 4 2 to 20% by weight of a polar copolymerizable monomer composed of a hydroxyl group-containing monomer such as hydroxybutyl acrylate, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, and caprolactone modified (meth) acrylate. In addition to acrylic acid ester and polar copolymerizable monomer, copolymers other than the two such as vinyl acetate, vinyl propionate, styrene, and isobornyl (meth) acrylate can be copolymerized. Those like blended with 30 wt% or less Nomar the like.

The above-mentioned (meth) acrylic acid ester, polar copolymerizable monomer and copolymerizable monomer other than the two types may be used singly or in a mixture of two or more kinds. May be. Further, a crosslinked structure can be introduced into the above copolymer by adding a crosslinkable monomer and polymerizing.

Examples of the crosslinkable monomer include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate. , Pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate,
Vinyl (meth) acrylate, divinylbenzene and other epoxy acrylates, polyester acrylates, urethane acrylates and the like can be preferably used.

The amount of the crosslinkable monomer added is 0.01, based on 100 parts by weight of the total amount of the (meth) acrylic acid ester and the polar copolymerizable monomer in the copolymer.
To about 1.0 part by weight, preferably 0.02 to 0.
It is added in an amount of about 8 parts by weight.

When the above monomers are photopolymerized, a photopolymerization initiator may be further added. Examples of these photopolymerization initiators include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α′-dimethylacetophenone, methoxyacetophenone, and 2,2-. Examples thereof include acetophenone-based compounds such as dimethoxy-2-phenylacetophenone and 2-hydroxy-2-cyclohexylacetophenone, ketal-based compounds such as benzyldimethylketal, and other halogenated ketones, acylphosphinoxides, acylphosphonates and the like.

The amount of the photopolymerization initiator added is 0.01 to 5 parts by weight based on 100 parts by weight of the total amount of the (meth) acrylic acid ester of the alcohol and the polar copolymerizable monomer in the copolymer. It is about 0, preferably 0.
It is added in an amount of about 05 to 3 parts by weight.

Water content used in the present invention 1% by weight
The following silica-based thixotropy-imparting agents include, for example, the thixotropy of the photopolymerizable monomer obtained by drying white carbon or carbon black having an average particle size of 5 to 50 μm at a temperature of 100 ° C. or higher for 2 hours or more. Is an additive for imparting and improving.

The apparatus used for the above drying is not particularly limited as long as commercially available white carbon, carbon black, etc., which generally have a high water content, can be made to have a water content of 1% by weight or less, and the apparatus can be used at a temperature of 100 ° C. or more for a long time. Any material can be used as long as it can be stably heated for a long time.

The amount of the silica-based thixotropy imparting agent having a water content of 1% by weight or less is such that the photopolymerizable monomer 100 is added.
When the amount is less than 1 part by weight, the photopolymerizable composition containing the photopolymerizable monomer is not provided with sufficient thixotropy, and when the amount exceeds 10 parts by weight, the light containing the photopolymerizable monomer is added. The viscosity of the polymerizable composition becomes too high, and neither can form a uniform coating film.

The water used in the present invention is added in an amount of 0.1 to 10 parts by weight of a silica-based thixotropy-imparting agent having a water content of 1% by weight or less with respect to 100 parts by weight of the photopolymerizable monomer. Although 0.6 part by weight is added, by adding it in this range, the viscosity of the photopolymerizable composition of the present invention can be maintained in a range where a uniform coating film can be always formed with high accuracy.

1 to 10 parts by weight of a silica-based thixotropic agent having a water content of 1% by weight or less is added to 100 parts by weight of the above photopolymerizable monomer.
Instead of 0.6 part by weight, polyhydric alcohols 0.1 to 0.
Even if 9 parts by weight is added, the viscosity of the photopolymerizable composition of the present invention can be maintained in a range where a uniform coating film can always be formed with high accuracy.

The above-mentioned polyhydric alcohols have 2 in the same molecule.
Alcohols having at least one hydroxyl group and derivatives thereof, for example, ethylene glycol, propylene glycol, salicyl alcohol, dihydric alcohols such as pinacol, trihydric alcohols such as glycerin and trimethanolamine, tetrahydric alcohols such as pentaerythritol, etc. However, the present invention is not limited to these.

The above-mentioned polyhydric alcohols are compatible with or dissolved in, for example, a photopolymerizable composition mainly containing acrylic acid esters as a photopolymerizable monomer. Preferably there is.

If necessary, fine particles or hollow fine particles having an average particle size of about 1 to 150 μm may be added to the photopolymerizable composition used in the present invention. Examples of the fine particles include glass balloons, shirasu balloons, fly ash balloons, and other inorganic hollow particles, polymethyl methacrylate, acrylonitrile-vinylidene chloride copolymer, polystyrene, organic hollow particles made of phenolic resin, glass beads, and silica. Examples thereof include inorganic fine particles such as beads and synthetic mica, and organic fine particles such as polyethyl acrylate, polyurethane, polyethylene and polypropylene. These fine particles or hollow fine particles have the effect of improving the stress relaxation characteristics of the base material layer.

In addition to the above, a tackifying resin, a softening agent, a heat stabilizer, an antioxidant, a lubricant, a filler, a colorant and the like may be added to the above-mentioned photopolymerizable composition, if necessary.

The above-mentioned photopolymerizable composition used in the present invention is prepared by homogeneously mixing the above respective materials, but the apparatus used for mixing is not particularly limited, and for example,
Depending on the viscosity, a kneader, a mixing roll, a triple roll, a sand mill, a ball mill, a homomixer, an ultrasonic mixer, a disperser, a homogenizer, a dissolver and the like can be used alone or in combination of two or more kinds.

The substrate used in the present invention may be a sheet having a releasable surface which is temporarily used for forming a coating film of the photopolymerizable composition, Further, it may be a supporting base material of an adhesive sheet.

As the sheet having a surface having a releasing property, a sheet having a high light ray transmittance, particularly a short wavelength light ray transmittance, and a tough and smooth surface, can be used so that photopolymerization can be efficiently carried out. For example, without limitation,
Examples thereof include a polyethylene terephthalate (PET) film and a biaxially oriented polypropylene (OPP) film whose surface is subjected to silicone release treatment. The thickness of the sheet having a surface having these releasability is 30 to 70.
Those having a size of about μm are preferably used.

When the above-mentioned base material is a support base material for a pressure-sensitive adhesive sheet, the base material is not particularly limited as long as it can be used as a support base material for a pressure-sensitive adhesive sheet. In the photopolymerizable composition used in the above, fine particles or hollow fine particles having an average particle diameter of about 1 to 150 μm are 3 parts by weight per 100 parts by weight of the photopolymerizable monomer.
When a supporting base material added with 0 to 150 parts by weight is used, it can be suitably used as a structural pressure-sensitive adhesive sheet with improved stress relaxation characteristics.

[0025]

The silica-based thixotropy-imparting agent used in the present invention is always used in the state where the water content is 1% by weight or less as described above, and water or polyhydric alcohols to which a necessary amount is precisely measured is added. Therefore, the photopolymerizable composition can fully utilize the flow characteristics of the silica-based thixotropic agent having high hydrophilicity without being affected by the temperature and humidity conditions of the atmosphere.

In the photopolymerizable composition used in the present invention, the amount of water added and the like can be accurately set as described above, and the viscosity of the photopolymerizable composition can be controlled without being affected by the temperature and humidity conditions of the atmosphere. It can be set and controlled arbitrarily, and in the adhesive tape manufacturing process, the optimum conditions of the coating process can be always set according to the application.Therefore, in the coating method such as a roll coater that controls the coating film with its slit shape, It is possible to provide a method for producing a pressure-sensitive adhesive sheet capable of giving a coating film shape.

[0027]

EXAMPLES The present invention will be specifically described based on the following examples.

(Preparation of silica-based thixotropy-imparting agent-1) A silica-based thixotropy-imparting agent (Aerosil # 200, manufactured by Aerosil Co., Ltd.) is dried by heating in a thermostatic chamber at 110 ° C. for 5 hours to obtain silica-based thixotropy. Giving agent-1 (hereinafter simply referred to as "giving agent-1") was prepared.
The water content after drying is as shown in Table 2.

(Silica-based thixotropic agent-2)
The silica-based thixotropy imparting agent (manufactured by Aerosil Co., Ltd., trade name: Aerosil # 200) and water content were measured before compounding and described in Table 2 in the same manner as above. (Hereinafter, simply referred to as "adding agent-2").

In addition to the above, the contents and composition of each material used in Examples and Comparative Examples of the present invention are shown below.

(Photopolymerizable monomer) 90.0 parts by weight of 2-ethylhexyl acrylate, 6.0 parts by weight of acrylic acid, 4.0 parts by weight of N-vinylpyrrolidone.

(Photopolymerization initiator) 2,2-dimethyl-2-
Phenyriacetophenone (Ciba Geigy, trade name:
Irgacure 651) 1.5 parts by weight.

(Filler) 30.0 parts by weight of high-density polyethylene powder (manufactured by Mitsui Petrochemical Co., Ltd., trade name: Miperon MX220, density 0.94 g / cm ³ , bulk specific gravity 0.4).

The water content and viscosity of the above materials and the photopolymerizable composition of the present invention were measured by the following methods. 1. Moisture content of silica-based thixotropy imparting agent: Measured immediately before the preparation of the photopolymerizable composition by an absolute dry weight method.

2. Water content of photopolymerizable composition: Immediately before the addition of water at the time of preparation of the photopolymerizable composition by the Karl Fischer method and after sufficient stirring and mixing of water (at the completion of preparation of the photopolymerizable composition ) Was measured.

3. Viscosity of photopolymerizable composition: using a B-type viscometer, rotor No. Measured at the number of revolutions of 3 at 6 rpm, just before the water was added during the preparation of the photopolymerizable composition, and after the water was added and sufficiently stirred and mixed (at the completion of the preparation of the photopolymerizable composition). did.

Table 1 shows the temperature and humidity (temperature and humidity conditions) of the atmosphere of the work place where the materials of Examples and Comparative Examples of the present invention were temporarily stored and the photopolymerizable composition was prepared.

[0038]

[Table 1]

(Examples 1 to 6), (Comparative Examples 1 to 6) (Preparation of Photopolymerizable Composition-1) 100 parts by weight of a photopolymerizable monomer and an imparting agent-in a compounding tank purged with nitrogen gas. 1
(Examples 1 to 6) or imparting agent-2 (Comparative Examples 1 to 6) 4.
5 parts by weight were added, and the mixture was stirred and mixed for 4 hours.
Add 0.0 parts by weight and 1.5 parts by weight of a photopolymerization initiator,
Stir and mix for hours. After that, 0.25 part by weight of water was added (Examples 1 to 6) and mixed by stirring for 30 minutes to prepare a photopolymerizable composition. However, since the conventional method has no idea of adding water in the preparation of the photopolymerizable composition, the step of adding 0.25 part by weight of water in the latter half of Examples 1 to 6 is omitted as described above. . Table 2 shows the preparation stages of the materials and the photopolymerizable composition of the above Examples and the above performance of the finished products.

(Examples 7 to 12) (Preparation of Photopolymerizable Composition-2) 100 parts by weight of photopolymerizable monomer and Additive-1 in a compounding tank purged with nitrogen gas.
After adding 4.5 parts by weight of the mixture and stirring and mixing for 4 hours, 30 parts by weight of the filler and 1.5 parts by weight of the photopolymerization initiator are added, and the mixture is stirred and mixed for 1 hour. After that, 0.40 parts by weight of glycerin was added and mixed by stirring for 30 minutes to prepare a photopolymerizable composition. Table 3 shows the preparation stages of the materials and the photopolymerizable composition of the above Examples and the above performance of the finished products.

[0041]

[Table 2]

[0042]

[Table 3]

As shown in Table 2, the photopolymerizable composition of the present invention has a water content of 0.13 to 0. It is controlled to 16%, and its viscosity is 2430-
3370 cps, 2830 to 3350 as shown in Table 3.
cps, which matches the target viscosity of 2500 to 3500 cps at the time of manufacturing the base film of the adhesive tape.

On the other hand, in the conventional methods shown in Comparative Examples 1 to 6, the water content of the silica-based thixotropic agent was 1.
It shows a large variation of 1 to 5.6%, the water content of the photopolymerizable composition is 0.05 to 0.17%, and as a result, its viscosity is 860 to 4240 cps and its range (R) is 338.
The R of the viscosity of the photopolymerizable composition of the above-mentioned embodiment of the present invention is large without needing to be compared with 940 cps, and both the upper limit and the lower limit of the desirable viscosity range of 2500 to 3500 cp are greatly protruded.

(Applicability of Photopolymerizable Composition) On the polyethylene terephthalate film having a thickness of 38 μm obtained by releasing treatment of the photopolymerizable composition prepared as described above, the thickness at the end of the polymerization was 1.0 ±. It is coated with a roll coater so as to have a thickness of 0.1 mm, and the coated surface is covered with a polyethylene terephthalate film having the same thickness as the above film so that the release treated surface is in contact with the coated surface. The cover polyethylene terephthalate film was irradiated for 8 minutes at an irradiation intensity of ² mw / cm ² to produce an adhesive sheet.

According to the present invention, as shown in Table 1, the temperature and humidity (temperature and humidity conditions) of the atmosphere for temporary storage of materials and preparation of photopolymerizable composition in the workplace are greatly changed in a very short period depending on weather and day / night. In some cases, the applicability of the photopolymerizable composition should be evaluated using Examples 1 to 6 and Comparative Examples 1 to 6 as a group. For reference, the release treatment in each Example was performed. The coating property of the photopolymerizable composition on a polyethylene terephthalate film having a thickness of 38 μm was measured for the thickness variation of the coating film with a dial gauge, and the target thickness of 1.0 ± 0.1 mm and ± 0. Evaluation by comparing with 15 mm, surface smoothness of film thickness (whether bubbles are generated, coating unevenness such as streaks, etc.), leakage of the photopolymerizable composition from the glue reservoir weir at the coating portion is visually observed. , Overall, about individual examples ○: good, ×: evaluated in two stages of failure, are shown in Tables 4 and 5.

[0047]

[Table 4]

[0048]

[Table 5]

As is clear from Tables 4 and 5, each of the pressure-sensitive adhesive sheets of Examples 1 to 12 of the present invention had a small variation in film thickness, no bubble generation, and uneven coating such as streaks. A coating film having good surface smoothness was formed, and even if the temperature and humidity conditions changed significantly, the photopolymerizable composition did not leak from the glue reservoir of the coating section, and a very smooth coating operation could be carried out. On the other hand, in Comparative Examples, only two of Comparative Examples 4 and 5 showed good coatability, but the other 4 Examples showed leakage of the photopolymerizable composition from the glue reservoir of the coating part and generation of bubbles. There was uneven coating such as stains and streaks, and there was a large variation in the film thickness of the coating film.

[0050]

The photopolymerizable composition used in the present invention is a silica-based composition having a high hydrophilicity because the amount of water added or the content of polyhydric alcohols to be added is accurately set and controlled as described above. A thixotropy imparting agent can be used, and its flow characteristics can be fully utilized without being affected by the temperature and humidity conditions of the atmosphere.

In the photopolymerizable composition used in the present invention, the amount of water to be added can be accurately set as described above, and the viscosity of the photopolymerizable composition can be adjusted to any desired value without being affected by the temperature and humidity conditions of the atmosphere. Since the optimum conditions of the coating process can always be set according to the application in the adhesive tape manufacturing process, it is possible to precisely control the coating method such as a roll coater by controlling the slit shape. It is possible to provide a method for producing a pressure-sensitive adhesive sheet capable of giving a film shape.

Claims (1)

[Claims] 1. A photopolymerizable monomer of 100 parts by weight, a highly hydrophilic silica-based thixotropy imparting agent having a water content of 1% by weight or less, 1 to 10 parts by weight, and water of 0.1 to 0.6 parts by weight or polyvalent. A method for producing a pressure-sensitive adhesive sheet, which comprises coating a substrate with a photopolymerizable composition comprising 0.1 to 0.9 parts by weight of alcohols.