JP2001049215A - Adhesive composition and adhesive tape or sheet prepared by using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition which exerts a stable adhesive strength and cohesion and an adhesive tape or sheet prepared by using this composition. SOLUTION: This composition is prepared by copolymerizing an alkyl (meth) acrylate (a) having a 2-14C alkyl group and 0.05 to 80 wt.% alkyl (meth)acrylate (b) which has a carboxy group or hydroxy group at the end and a 3-14C alkyl group as its ester side chain. Especially, a monomer (b) having an alkyl group with a carbon number either smaller by 1 than that of the monomer (a) or identical to or larger than that of the monomer (a), is used to maximize the intrinsic effect of the functional group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet such as a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet using the same, and more particularly, to a monomer terminal used for obtaining the pressure-sensitive adhesive composition. The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape or sheet capable of maximizing the effects of a functional group.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesive tapes and sheets (hereinafter referred to as pressure-sensitive adhesive sheets) in which a pressure-sensitive adhesive layer is provided on one or both sides of a support made of paper, plastic film, or the like have been widely used for various purposes. . The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer is also various depending on the application, and natural rubber-based or synthetic rubber-based, acrylic-based, vinyl ether-based, and silicone-based are commonly used. . Among these pressure-sensitive adhesives, acrylic pressure-sensitive adhesives have excellent adhesive properties such as adhesive strength and tackiness (tack), cohesive strength, and deterioration resistance properties such as weather resistance, solvent resistance, and heat resistance. It is one of the representative adhesives.

In general, acrylic pressure-sensitive adhesives are mainly composed of a (meth) acrylic acid alkyl ester having a low glass transition temperature as a main monomer in order to impart tackiness, and are copolymerized with a monomer having a functional group. When a small monomer is subjected to stress for a long time,
Insufficient cohesive strength, which tends to cause slippage and breakage, insufficient adhesive properties at high temperatures, and changes in adhesive strength over time,
Depending on the application, there are still many points to be improved.

[0004] Since the acrylic pressure-sensitive adhesive can be prepared by a copolymerization reaction as described above, a polar monomer having a functional group such as a carboxyl group or a hydroxyl group may be copolymerized, or di (meth) acrylate or di (meth) acrylate may be used. By copolymerizing a polyfunctional internal crosslinking monomer such as glycidyl (meth) acrylate, it is relatively easy to improve the adhesiveness and cohesiveness.

[0005] However, when such a polar monomer is copolymerized, the glass transition temperature of the resulting pressure-sensitive adhesive (copolymer) increases, and the tackiness, particularly the initial adhesion (tack), tends to decrease. Further, as the glass transition temperature rises, there is a possibility that the adhesive properties at low temperatures may also decrease, and there is a limit to the copolymerization ratio of such a polar monomer. In order to improve the cohesiveness of the pressure-sensitive adhesive by post-crosslinking, a solution prepared by dissolving the copolymer and the cross-linking agent in any solvent is applied and dried to obtain pressure-sensitive adhesive sheets. When a functional group in the copolymer to be formed is incorporated into the molecular chain of the copolymer, a rapid crosslinking reaction does not occur, and the crosslinking property progresses with time, thereby changing the adhesive properties. Therefore, in order to obtain pressure-sensitive adhesive sheets that are stable in quality, a sufficient aging operation is required, and it cannot be said that this is a favorable one in terms of improving productivity.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the above-mentioned conventional acrylic pressure-sensitive adhesive composition,
An object of the present invention is to provide a pressure-sensitive adhesive composition that stably exhibits excellent adhesive strength and cohesive strength.

Another object of the present invention is to provide pressure-sensitive adhesive sheets using the above-mentioned pressure-sensitive adhesive composition.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted various studies to achieve the above object, and as a result, have found that a monomer copolymerizable with an alkyl (meth) acrylate as a tackifier is mainly used. By using a functional (meth) acrylic acid alkyl ester having a specific side chain as a functional group, a functional group in a copolymer is effectively acted on to obtain a pressure-sensitive adhesive composition having excellent adhesiveness and cohesiveness. And found that the present invention was completed.

That is, the present invention relates to a pressure-sensitive adhesive composition obtained by copolymerizing the following monomers (a) and (b) as essential components, wherein the pressure-sensitive adhesive composition comprises the monomers (a) and (b) When the alkyl group is a linear alkyl group, the number of carbon atoms of the alkyl group of the monomer (b) is one less than or equal to the number of carbon atoms of the alkyl group of the monomer (a). In the case where at least one alkyl group of the monomer (a) and the monomer (b) is a branched alkyl group, the number of carbon atoms of the alkyl group having a functional group of the monomer (b) is The pressure-sensitive adhesive composition, wherein the number of carbon atoms of the longest alkyl straight chain in the alkyl group of the monomer (a) is one less or the same or more. (A) The total number of carbon atoms of the alkyl group as the ester side chain is 2
(Meth) acrylic acid alkyl ester 30 to 14
~ 99.95% by weight. (B) having a carboxyl group or a hydroxyl group at the terminal, and having an alkyl group as an ester side chain having a total carbon number of 3 to
(Meth) acrylic acid alkyl ester which is 14 0.0
5 to 70% by weight.

Further, the present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer obtained from the above-mentioned pressure-sensitive adhesive composition formed on at least one surface of a support.

The monomer (a) used in the pressure-sensitive adhesive composition of the present invention is an alkyl (meth) acrylate having an alkyl group having a total carbon number of 2 to 14 as an ester side chain, and is obtained. It is a component that mainly imparts adhesive properties to the composition. The total carbon number of the alkyl group as the ester side chain needs to be 2 to 14 from the viewpoint of initial adhesiveness, tackiness, and adhesiveness. Specifically, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylate
Pentyl acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate,
Octyl (meth) acrylate, Nonyl (meth) acrylate, Decyl (meth) acrylate, Undecyl (meth) acrylate, (Meth)
Examples include dodecyl acrylate, tridecyl (meth) acrylate, and tetradecyl (meth) acrylate. These may be linear esters or branched esters as structural isomers. More than one species can be used in combination.

From the viewpoint of the properties as a pressure-sensitive adhesive, the monomer (a) is present as an essential component in all the monomers in an amount of 20 to 99.9.
It is copolymerized in an amount of 5% by weight, preferably 30 to 99.95% by weight.

On the other hand, as the monomer (b), a (meth) acrylic acid alkyl ester having a carboxyl group or a hydroxyl group at the terminal and having an alkyl group having a total carbon number of 3 to 14 as an ester side chain. Is used. This monomer (b) has an alkyl group as an ester side chain similarly to the monomer (a), but has a carboxyl group or a hydroxyl group as a functional group at a terminal of the side chain. The polarity is increased by the functional group at the terminal, and the adhesive properties such as adhesiveness and cohesiveness are improved. In addition, the methylene chain between the acryloyl group, which is the main chain of the obtained copolymer, and the functional group at the terminal acts as a spacer to give the copolymer main chain a degree of freedom, and the glass transition of the copolymer. It has the effect of reducing the rise in temperature. Further, by making an alkyl group having a total carbon number of 3 to 14 an ester side chain, preferably by making it larger than the total carbon number of the alkyl group in the monomer (a), the molecular chain of the copolymer is increased. The functional group can be prevented from being taken into the inside, and the effect of the functional group can be effectively exhibited. In order to provide the above-mentioned effects, particularly to impart an appropriate degree of freedom to the copolymer main chain, the total number of carbon atoms of the alkyl group in the monomer (b) needs to be 3 or more. In addition, the total carbon number is 14
If it exceeds, the side chain of the ester is too long, which may cause a phenomenon in which the functional group at the end of the side chain is incorporated into the molecular chain, or may cause a decrease in the adhesiveness.

Specific examples of such a monomer (b) include (meth) acrylic acid 3-carboxypropyl ester, (meth) acrylic acid 4-carboxybutyl ester, and (meth) acrylic acid 5-carboxypentyl ester. 6-carboxyhexyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-methyl-3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Examples thereof include 6-hydroxyhexyl (meth) acrylate and 8-hydroxyoctyl (meth) acrylate, and these may be used alone or in combination of two or more.

The monomer (b) is used as an essential component in an amount of 0.05 to 80% by weight, preferably 0.05 to 7% by weight of all the monomers.
It is copolymerized in the range of 0% by weight. When the amount is less than 0.05% by weight, the effect of the functional group contained in the monomer (b) cannot be sufficiently radiated.
It is not preferable because the copolymerization amount of the monomer (a) becomes small and the adhesive properties such as initial adhesive strength as a pressure-sensitive adhesive decrease. The copolymerization range of the monomer (b) is relatively wide, but when a functional group acts as a crosslinking point, the copolymerization amount can be reduced within the above range.
However, when the functional group is used not for the crosslinking point but for the purpose of improving the cohesive strength of the obtained pressure-sensitive adhesive, the copolymerization amount can be increased. Therefore, the range is as described above.

Further, the above-mentioned monomer (a) and monomer (b) to be copolymerized as essential components in the pressure-sensitive adhesive composition of the present invention preferably have the following relationship:

When the alkyl groups of the monomers (a) and (b) are linear alkyl groups, the monomer (b)
The number of carbon atoms of the alkyl group of (a) is one less than or equal to the number of carbon atoms of the alkyl group of the monomer (a).

When at least one of the alkyl groups of the monomer (a) and the monomer (b) is a branched alkyl group, an alkyl straight-chain carbon atom for growing the functional group of the monomer (b) is used. The number is one less than or equal to or greater than the carbon number of the longest alkyl straight chain of the alkyl group of the monomer (a).

That is, when the monomer (a) and the monomer (b) satisfy the above or the above relation, the monomer (b)
Since the functional group at the end of the polymer has a long methylene chain as a spacer in the side chain, the amount of the functional group incorporated into the molecular chain of the copolymer is reduced, and the functional group is used as a polarizer or a crosslinking point. It is possible to effectively emit the function and effect originally possessed by.

The pressure-sensitive adhesive composition of the present invention may be copolymerized with another copolymerizable monomer (c) in addition to the monomers (a) and (b). By using such a copolymerizable monomer (c), desired properties can be imparted to the obtained pressure-sensitive adhesive composition according to the intended use. And the adhesiveness can be improved.

Specific examples of the copolymerizable monomer (c) include (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid and carboxyethyl (meth) acrylate. A carboxyl group-containing monomer, a sulfoxyl group-containing monomer such as 2-acrylamido-2-methylpropanesulfonic acid, a phosphoxyl group-containing monomer such as 2-hydroxyethylacryloyl phosphate, 2-hydroxypropylacryloyl phosphate, ) Acrylamide, N-substituted (meth) acrylamide, 3-acryloyloxypropylamide, 4-acryloyloxybutylamide, 5-acryloyloxypentylamide, 4-acryloyloxyhexylamide, N-methyl-3-acryloyloxypropylamide, N N- dimethyl-3-acryloyloxy propyl amide, N- vinyl-2-pyrrolidone,
Amide monomers such as N-vinyl carboxylic acid amide, vinyl monomers such as vinyl acetate, styrene, α-methylstyrene, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (Meth) acrylate, methyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate,
Polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, 1-acetoxy-4-acryloyloxypentane, 6-acryloyloxy-ethylhexanoate, fluorine-containing (meth)
Functional group-containing (meth) acrylates such as acrylate and silicon-containing (meth) acrylate are exemplified. Also, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, Polyfunctional monomers for internal crosslinking such as pentaerythritol hexa (meth) acrylate, polyester (meth) acrylate, urethane (meth) acrylate, and the like can also be used.

The copolymerizable monomer (c) is also selected so as to have a side chain alkyl group relationship as in the monomer (a) and the monomer (b) in the present invention. The function and effect originally possessed by the functional group in the copolymerizable monomer (c) can be maximized.

The copolymerizable monomer (c) is selected so as not to impair the properties of the monomers (a) and (b).
One or more copolymers can be copolymerized in an amount of 30% by weight or less, preferably 25% by weight or less of the total amount of the monomers.

The pressure-sensitive adhesive composition of the present invention comprises the monomer (a)
And the monomer (b) as an essential component, and if necessary, the monomer (c) is also blended and copolymerized, and the polymerization method is not particularly limited. Specifically, known polymerization methods such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a suspension polymerization method can be employed.In the bulk polymerization method which is a solventless polymerization method, from the viewpoint of controlling the reaction. It is preferable to carry out a polymerization operation by irradiation with radiation such as ultraviolet rays. In addition, a polymerization initiator is used in the above polymerization, and an azo-based or peroxide-based thermal polymerization initiator, an acetophenone-based, benzoin ether-based, ketal-based photopolymerization initiator, or the like can be used.

The pressure-sensitive adhesive composition of the present invention may further contain, if necessary, various fillers such as glass fibers and glass beads, metal powders and inorganic powders, tackifying resins such as natural resins and synthetic resins, oils and fats. Various additives such as a surfactant, a surfactant, a pigment and a colorant can be blended in an amount of 200 parts by weight or less per 100 parts by weight of the copolymer.

The pressure-sensitive adhesive composition of the present invention can be used on at least one surface of a support made of various plastic films or sheets, paper, woven fabric, nonwoven fabric, various foam films or sheets, metal foil, or a laminate thereof. A pressure-sensitive adhesive sheet such as a pressure-sensitive adhesive tape or a pressure-sensitive adhesive sheet can be formed into a layer with a thickness of about 5 to 2000 μm. The obtained pressure-sensitive adhesive sheets of the present invention may be coated on a back surface of a support with a known release agent such as a silicone-based resin or a fluorine-based resin and wound into a roll, or may be exposed on the exposed surface of a formed pressure-sensitive adhesive layer. Can be coated with a known separator coated with a release agent.

Further, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present invention may be subjected to a crosslinking treatment in addition to the provision of the cross-linking point and the improvement of the cohesive force by the monomer (b). Examples of the crosslinking treatment include a method of copolymerizing an internally crosslinkable monomer such as the polyfunctional (meth) acrylate exemplified as the monomer (c), a melamine resin or an isocyanate compound as an external crosslinker, An epoxy compound, an aziridine-based compound, a peroxide, a metal chelate compound, or the like can be blended with the copolymer and subjected to a method such as heating. Further, instead of the above-mentioned crosslinking means, a crosslinking means for irradiating with an actinic ray such as an electron beam or an ultraviolet ray to perform crosslinking can be employed.

By performing the cross-linking treatment, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present invention has an improved internal cohesive force and emits excellent adhesive properties. The degree of cross-linking is appropriately adjusted according to the application. For example, it is preferable to adjust the gel fraction to 30 to 90% for bonding and to 60% or more for re-peeling. The gel fraction in this case is the ratio of the pressure-sensitive adhesive (residual content) that was not dissolved after immersing the pressure-sensitive adhesive layer in ethyl acetate for 1 week at room temperature.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these, and various modifications can be made without departing from the technical idea of the present invention. It is. In the following text, “part” means “part by weight”.

EXAMPLE 1 150 parts of ethyl acetate and n-acrylic acid were placed in a polymerization reaction vessel.
-95 parts of butyl ester, 5 parts of acrylic acid 5-carboxypentyl ester, and 0.5 parts of azobisisobutyronitrile as a polymerization initiator are charged, and the mixture is heated at 60 ° C for 4 hours in an inert gas atmosphere. At 80 ° C. for 2 hours to prepare a copolymer solution (99% polymerization rate).

To 100 parts of the solid content of the obtained copolymer solution, 5 parts of a trimethylolpropane-tolylenediisocyanate adduct as a crosslinking agent was added to prepare a solution of the pressure-sensitive adhesive composition of the present invention. .

This solution was applied on a 25 μm-thick polyester film so that the thickness after drying was 50 μm.
The resultant was dried by heating at 120 ° C. for 5 minutes to prepare a pressure-sensitive adhesive sheet having a crosslinked pressure-sensitive adhesive layer.

Example 2 In Example 1, n-butyl acrylate 75
Parts, and a copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Example 1 except that acrylic acid 5-carboxypentyl ester was changed to 25 parts, and a crosslinking agent was added in the same manner as in Example 1. Thus, an adhesive sheet was prepared.

Example 3 In Example 1, n-butyl acrylate 40
Parts, a copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Example 1 except that acrylic acid 5-carboxypentyl ester was 60 parts, and a crosslinking agent was added in the same manner as in Example 1. Thus, an adhesive sheet was prepared.

COMPARATIVE EXAMPLE 1 In Example 1, 95-acrylic acid n-butyl ester was used.
And a copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Example 1 except that 5 parts of acrylic acid was used instead of 5-carboxypentyl acrylate. Similarly, a pressure-sensitive adhesive sheet was prepared by adding a crosslinking agent.

Comparative Example 2 In Comparative Example 1, 90 parts of n-butyl acrylate was used.
And a copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Comparative Example 1, except that 10 parts of acrylic acid were used.
Further, a cross-linking agent was added in the same manner as in Comparative Example 1 to produce a pressure-sensitive adhesive sheet.

COMPARATIVE EXAMPLE 3 In Comparative Example 1, n-butyl acrylate was added at 75
And a copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Comparative Example 1, except that 25 parts of acrylic acid were used.
Further, a cross-linking agent was added in the same manner as in Comparative Example 1 to produce a pressure-sensitive adhesive sheet.

The following properties of the pressure-sensitive adhesive sheets obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were measured. The results are shown in Table 1.

<Initial Adhesion> The initial adhesion was measured by finger tack. Defective indicates that there is almost no tack by finger touch and temporary fixing (immediate fixing) cannot be performed.

<Initial Adhesive Strength> The pressure-sensitive adhesive sheet obtained in each of the above Examples and Comparative Examples was cut into a width of 20 mm, and the surface was polished with sandpaper (# 280).
The plates were bonded to four plates, reciprocated one time with a roller having a load of 2 kg, and pressed, and then left for 20 minutes. Next, this sample was subjected to a 180-degree peeling test at a peeling speed of 300 mm / min using a tensile tester according to JIS-Z-0237, and the adhesive strength was measured.

<Average Adhesive Strength> The same sample as used in the above initial adhesive strength test was stored in a thermostat at 50 ° C. for one day, and the same test as the initial adhesive strength test was performed. <Aqueous Shochu> The same sample used in the initial adhesive strength test was immersed in water at room temperature for 3 days, and then subjected to a 180 ° peel test at a peel rate of 300 mm / min using a tensile tester to measure the adhesive strength. did.

[0042]

[Table 1]

As is evident from Table 1, the products of Examples have good initial adhesiveness and do not decrease in initial adhesiveness even if the copolymerization amount of 5-carboxypentyl acrylate is increased. On the other hand, in the comparative example product, when the copolymerization amount of acrylic acid having no methylene spacer increases, the initial adhesiveness and the initial adhesive strength become poor.

The daily adhesive strength after aging at 50 ° C. for one day shows a tendency to increase in both the product of the example and the product of the comparative example, and the product of the comparative example also exhibits a sufficient adhesive strength. However, the comparative example product was not practical because it could not be temporarily fixed because the initial adhesiveness was insufficient. This is considered to be due to the fact that the pressure-sensitive adhesive composition of the present invention is improved in cohesiveness and the methylene spacer alleviates the worsening glass transition temperature.

However, in the water resistance test, even in the case of the product of the example, when the amount of the copolymer component was excessive, the balance of the practical characteristics tended to be gradually lost.

Example 4 150 parts of ethyl acetate and n-acrylic acid were placed in a polymerization reaction vessel.
-99.9 parts of butyl ester, 0.1 part of 6-hydroxyhexyl acrylate, and 0.5 part of azobisisobutyronitrile as a polymerization initiator were added, and the mixture was heated at 60 ° C in an inert gas atmosphere. The polymerization reaction was carried out for 4 hours and subsequently at 80 ° C. for 2 hours to prepare a copolymer solution (polymerization rate: 99%).

To 100 parts of the solid content of the obtained copolymer solution, 0.1 part of a trimethylolpropane-tolylene diisocyanate adduct as a crosslinking agent was added to prepare a solution of the pressure-sensitive adhesive composition of the present invention. did.

This solution was applied on a polyester film having a thickness of 25 μm so that the thickness after drying was 50 μm.
The resultant was dried by heating at 120 ° C. for 5 minutes to prepare a pressure-sensitive adhesive sheet having a crosslinked pressure-sensitive adhesive layer. Similarly, a pressure-sensitive adhesive layer was separately formed on release paper.

Example 5 In Example 4, n-butyl acrylate was used.
8 parts, acrylic acid 6-hydroxyhexyl ester
A copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Example 4 except that the amount was 2 parts, and a crosslinking agent was further added in the same manner as in Example 4 to produce an adhesive sheet.

Example 6 In Example 4, n-butyl acrylate was used.
5 parts, acrylic acid 6-hydroxyhexyl ester
A copolymer solution (polymerization rate: about 99%) was prepared in the same manner as in Example 4 except that the amount was changed to 5 parts, and a crosslinking agent was further added in the same manner as in Example 4 to prepare an adhesive sheet.

Comparative Example 4 A copolymer solution was prepared in the same manner as in Example 4 except that 2-hydroxyethyl acrylate was used in place of 6-hydroxyhexyl acrylate. ) Was prepared, and a crosslinking agent was further added in the same manner as in Example 4 to prepare a pressure-sensitive adhesive sheet.

Comparative Example 5 A copolymer solution was prepared in the same manner as in Example 5 except that 2-hydroxyethyl acrylate was used instead of 6-hydroxyhexyl acrylate (polymerization rate: about 99%). ) Was prepared, and a crosslinking agent was further added in the same manner as in Example 5 to prepare an adhesive sheet.

Comparative Example 6 A copolymer solution was prepared in the same manner as in Example 6 except that 2-hydroxyethyl acrylate was used instead of 6-hydroxyhexyl acrylate. ) Was prepared, and a crosslinking agent was further added in the same manner as in Example 6 to prepare an adhesive sheet.

The following characteristics of the pressure-sensitive adhesive sheets obtained in Examples 4 to 6 and Comparative Examples 4 to 6 were measured. Table 2 shows the results.

<Holding force> The adhesive sheet obtained in each of the above Examples and Comparative Examples was heated at 50 ° C. for 7 days, and then heated for 20 m.
Laminated on a belite plate with an area of mx 10mm,
After reciprocating one time with a roller of 2kg load and pressing, 20
Then, a load of 500 g was hung on the longitudinal end of the bonded sheet, and the sheet was left in an atmosphere of 40 ° C. to measure the time until the pressure-sensitive adhesive sheet dropped.
In addition, when the pressure-sensitive adhesive sheet did not drop even after 1 hour, the displacement movement distance after 1 hour was measured.

<Gel Fraction> After the adhesive layer formed on the release paper obtained in each of the above Examples and Comparative Examples was aged at 50 ° C. for 7 days, a part of the adhesive layer was cut into 2 cm 2 squares, It was immersed in ethyl acetate for one week at room temperature in a bag made of a polytetrafluoroethylene porous membrane having a pore size of 0.2 μm. The weight of the bag alone was measured in advance, the weight of the pressure-sensitive adhesive layer before immersion and the dry weight after immersion were determined, and the ratio of the undissolved component (gel component) in the pressure-sensitive adhesive layer was measured.

[0057]

[Table 2]

As is evident from Table 2 above, the product of the example shows a sufficient cross-linking reaction even with the copolymerization of a small amount of 6-hydroxyhexyl acrylate, and exhibits excellent adhesive properties (cohesiveness). On the other hand, in the comparative example, acrylic acid 2-hydroxyethyl ester, which should be introduced in a stoichiometrically large amount, is used, but the crosslinking reaction is not performed sufficiently as compared with the example, and as a result, the cohesive force is reduced. Shortage.

As described above, from the results in Tables 1 and 2,
It is clear that in the product of the present invention, the alkyl group in the monomer (b) acts as a spacer, and the terminal functional group sufficiently exhibits its introduction effect.

Examples 7 to 9 Examples 7 to 9 correspond to Examples 4 to 6, respectively, except that n-butyl acrylate used in each example was replaced with isooctyl acrylate. In the same manner as in the above, an adhesive sheet was produced.

For the pressure-sensitive adhesive sheets obtained in Examples 7 to 9, the holding power and the gel fraction were measured in the same manner as described above, and the results are shown in Table 3.

[0062]

[Table 3]

Example 10 An adhesive sheet was produced in the same manner as in Example 3 except that the amount of 5-carboxypentyl acrylate used in Example 3 was 55 parts and 5 parts of acrylic acid was further added.

Example 11 An adhesive sheet was produced in the same manner as in Example 2 except that no crosslinking agent was added to Example 2.

The adhesive sheets obtained in Examples 10 and 11 were measured for initial adhesiveness, initial adhesive strength, aging adhesive strength and water resistance in the same manner as described above, and the results are shown in Table 4.

[0066]

[Table 4]

[0067]

As described above, the pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive tape or sheet using the composition have a functional group present in a monomer depending on the combination of specific monomers. It is capable of maximally and effectively exerting its inherent effects, and exhibits excellent cohesiveness, tackiness, and adhesion properties such as adhesiveness that have solved the drawbacks of conventional acrylic pressure-sensitive adhesives. .

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuo Omata 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Eiichiro Fukusaki 1-1-2, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (4)

[Claims] 1. A pressure-sensitive adhesive composition obtained by copolymerizing the following monomers (a) and (b) as essential components, wherein the alkyl groups of the monomers (a) and (b) are When it is a linear alkyl group, the number of carbon atoms of the alkyl group of the monomer (b) is one less than or equal to the number of carbon atoms of the alkyl group of the monomer (a), and When at least one alkyl group of the monomer (a) and the monomer (b) is a branched alkyl group, the alkyl group having a functional group of the monomer (b) has a carbon number of the monomer One less than the carbon number of the longest alkyl straight chain of the alkyl group in (a),
Alternatively, the pressure-sensitive adhesive composition is at least the same number. (A) The total number of carbon atoms of the alkyl group as the ester side chain is 2
(Meth) acrylic acid alkyl ester 30 to 14
~ 99.95% by weight. (B) having a carboxyl group or a hydroxyl group at the terminal, and having an alkyl group as an ester side chain having a total carbon number of 3 to
(Meth) acrylic acid alkyl ester which is 14 0.0
5 to 70% by weight. 2. The method according to claim 1, wherein the copolymerizable monomer (c) other than the monomers (a) and (b) is copolymerized within a range of 30% by weight or less based on the total amount of the monomers. The pressure-sensitive adhesive composition as described in the above. 3. A pressure-sensitive adhesive tape or sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 on at least one surface of a support. 4. The pressure-sensitive adhesive layer is cross-linked.
The adhesive tape or sheet according to the above.