JP3093874B2 - Pressure sensitive adhesives and their adhesive sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a photopolymerizable pressure-sensitive adhesive, and a method of providing the adhesive on one or both surfaces of a substrate.
The present invention relates to an adhesive sheet in the form of a sheet or a tape.

[0002]

2. Description of the Related Art In recent years, photopolymerizable pressure-sensitive adhesives have been proposed from the viewpoint of safety and environmental hygiene caused by the use of organic solvents. For example, US Pat. No. 4,181,752 discloses a method of obtaining a pressure-sensitive adhesive without using an organic solvent by photopolymerizing an alkyl acrylate and a modifying monomer on a substrate. Have been. Also,
A transfer-type pressure-sensitive adhesive in which the same adhesive is obtained on a release liner and is transferred onto a substrate is also known.

In this type of pressure-sensitive adhesive, polymerization is inhibited by oxygen during the process of irradiating the monomer composition coated on the base material with ultraviolet rays to perform photopolymerization, and the polymerization becomes impossible or the polymerization cannot be performed. Progression becomes very slow. When a large amount of the photopolymerization initiator is added, the polymerization rate is improved to some extent.

In view of the above, conventionally, the oxygen concentration has been reduced as low as possible by avoiding photopolymerization in the air and blowing an inert gas such as nitrogen gas or covering the substrate-coated surface with a film. A high polymerization rate is obtained by performing photopolymerization in a suppressed state.

[0005]

However, the photopolymerization method as described above has the disadvantages that it is inferior in the workability of manufacturing a pressure-sensitive adhesive, requires a large-scale apparatus, and is expensive.

In view of the above circumstances, the present invention can obtain a high polymerization rate by ordinary ultraviolet irradiation even in an atmosphere having a relatively high oxygen concentration, and has excellent adhesive strength and holding power after photopolymerization. It is intended to provide a pressure-sensitive adhesive and its adhesive sheet.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and have found that when a specific nitrogen-containing monomer is added to a monomer composition to be photopolymerized. In addition, the effect of polymerization inhibition by oxygen during ultraviolet irradiation is greatly suppressed, a high polymerization rate is obtained even in an atmosphere having a high oxygen concentration, and a pressure-sensitive adhesive having excellent adhesive strength and holding power after photopolymerization. Was found, and the present invention was completed.

That is, the present invention relates to the following three components a to c: a) a monomer mainly composed of an alkyl (meth) acrylate having 2 to 14 carbon atoms in an alkyl group; 0.5 to 100 parts by weight of the component monomer
A pressure-sensitive adhesive comprising a photopolymer of a composition containing 15 parts by weight of N - monosubstituted aminoalkyl (meth) acrylate c) a photopolymerization initiator; The present invention relates to an adhesive sheet in which a layer is provided on one side or both sides of a substrate. In addition,
The above "adhesive sheet" usually includes a wide adhesive sheet.
Or, it usually includes a narrow adhesive tape. Smell this meaning
Therefore, in this specification, the above “adhesive sheet” is referred to as “adhesive sheet”.
Sometimes referred to as "class."

[0009]

DETAILED DESCRIPTION OF THE INVENTION The alkyl (meth) acrylate used in the composition of the present invention is the main component of the monomer of the component a, and is preferably non-tertiary.
Monofunctional unsaturated (meth) acrylates of alkyl alcohols
And the alkyl group is selected from those having 2 to 14 carbon atoms. Such monomers include, for example,
Ethyl (meth) acrylate, butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate , Isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and the like,
One or more of these are used.

In addition to the alkyl (meth) acrylate, a monoethylenically unsaturated monomer copolymerizable therewith may be used. This monomer has the above (meth)
By copolymerizing with alkyl acrylate,
It is used to improve the adhesion by introducing a functional group or a polar group, or to improve and modify the cohesive strength and heat resistance by controlling the glass transition temperature of the copolymer. Examples of such a monomer include acrylic acid, itaconic acid, sulfopropyl acrylate, hydroxyalkyl acrylate, cyanoalkyl acrylate, acrylonitrile, 2-methoxyethyl acrylate, acryl Glycidyl acid, vinyl acetate and the like.
Use species or two or more.

In the monomer of the component a, the above (meth)
The proportion of the alkyl acrylate and the monoethylenically unsaturated monomer copolymerizable therewith is such that the alkyl (meth) acrylate as the main component is 70 to 100% by weight, preferably 85 to 95% by weight. The amount of the monoethylenically unsaturated monomer copolymerizable therewith may be 30 to 0% by weight, preferably 15 to 5% by weight. By using in such a range, the balance between adhesiveness, cohesive strength, and the like can be well balanced.

The monomer of the component b used in the composition of the present invention is an N - monosubstituted aminoalkyl (meth) acrylic acid.
G, that is, the following general formula; (Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² is an alkylene group, R ³ is hydrogen atom, R ⁴ is an alkyl group) a nitrogen-containing monomer represented by, and specific examples thereof are ,
N-tert-butylaminoethyl (meth) acryle
And the like.

When the monomer of the component (b) is added to the monomer of the component (a) and irradiated with ultraviolet rays, the monomer acts as a reducing agent for oxygen present in the polymerization system, thereby inhibiting polymerization by oxygen. Effectively suppress. Such an effect can be obtained, for example, by adding a non-polymerizable low-molecular-weight amine. However, this low-molecular-weight amine bleeds over time on the surface of the adhesive layer after photopolymerization, and the adhesive strength is reduced. And lowering the holding power. On the other hand, since the monomer of the component b is integrated into the polymer molecule as one component of the polymer chain after photopolymerization, there is no problem of a bridge such as a low molecular weight amine, and Does not adversely affect the adhesion or holding power of the polymer.

The monomer of the component (b) is used in an amount of 0.5 to 15 parts by weight, particularly preferably 3 to 10 parts by weight, based on 100 parts by weight of the monomer of the component (a). It is good to use within the range. If the amount is less than 0.5 part by weight, the effect of scavenging oxygen cannot be obtained, and if the amount is more than 15 parts by weight, the adhesive strength and the holding power decrease.

The photopolymerization initiator of component c used in the composition of the present invention includes benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, and substituted benzoin ethers such as anisoin methyl ether. -Substituted acetophenones such as ters, 2.2-diethoxyacetophenone, 2.2-dimethoxy-2-phenoneacetophenone, and substituted -α-keto such as 2-methyl-2-hydroxypropiophenone , Aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, 1
-Photoactive oximes such as -phenone-1-1-propanedione-2- (o-ethoxycarbonyl) oxime.

These photopolymerization initiators are usually used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the monomer of the component a. If the amount is too small, a large amount of monomer tends to remain. On the other hand, if the amount is too large, the molecular weight of the polymer decreases and the cohesive force of the adhesive tends to decrease.

In order to increase the shear strength of the adhesive, a small amount of a polyfunctional (meth) acrylate as a crosslinking agent can be added to the composition of the present invention, if necessary. Such polyfunctional (meth) acrylates include:
For example, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1.2-ethylene glycol di (meth) acrylate, 1.6-hexanediol di (meth) acrylate ―
And the like.

When these polyfunctional (meth) acrylates are added, they are usually used in an amount of 0.02 to 5 parts by weight based on 100 parts by weight of the monomer of the component a. Within this range, it is sufficient to increase the number of functional groups in the case of bifunctional and to reduce the number of functional groups in the case of trifunctional or higher.

In preparing the composition of the present invention, first,
The monomer of the component a and the photopolymerization initiator of the component c are mixed together, and the premix is partially polymerized by irradiation with ultraviolet rays to have a viscosity in the range of about 500 to 5,000 centipoise. Make a syrup that can be coated. Alternatively, a thixotropic agent such as fumed silica may be mixed with the premix of the monomer and the photopolymerization initiator to form a coatable syrup.

Next, a composition for photopolymerization is prepared by mixing the monomer of the component b with a polyfunctional (meth) acrylate as a cross-linking agent, if necessary, and an additional photopolymerization initiator. Is done. If necessary, various known additives such as a filler, a pigment, an antioxidant, and a tackifying resin can be added to the composition as long as the photopolymerization by irradiation with ultraviolet rays is not hindered.

In the present invention, the composition thus prepared is irradiated with ultraviolet rays to form a photopolymer. At this time, it is not particularly necessary to suppress the oxygen concentration as much as possible by blowing an inert gas or coating with an ultraviolet-permeable film as in the past, and the oxygen concentration is usually 20,000 ppm or less, particularly preferably 10,000 ppm or less. In the atmosphere, photopolymerization can be performed without any trouble.

The ultraviolet light used for photopolymerization has a wavelength range of about 1
Although the electromagnetic radiation is 80 to 460 nm (nanometer), electromagnetic radiation having a longer or shorter wavelength may be used. UV light source is mercury arc, carbon arc
General irradiation devices such as a lamp, a low-pressure mercury lamp, a medium / high-pressure mercury lamp, and a metal halide lamp are used. The intensity of the ultraviolet light can be appropriately set by adjusting the distance to the irradiation object and the voltage.

The photopolymer thus obtained can be widely used in various fields as a pressure-sensitive adhesive having good adhesive strength and holding power.

The adhesive sheets of the present invention can be prepared by providing a pressure-sensitive adhesive formed by the above-mentioned method on one or both sides of a substrate for each purpose of use. It is in the form of a letter. Here, as the substrate, a porous material such as a nonwoven fabric or paper, or a plastic film such as a polyester film or a polyimide film is used. The thickness of these substrates is usually about 25 to 125 μm,
The thickness of the pressure-sensitive adhesive layer provided on the substrate is usually about 10 to 100 μm.

In the production of the adhesive sheet of the present invention, for example, a layer of a pressure-sensitive adhesive having a desired thickness is formed on a release liner by the above-mentioned method, and this is then applied to one or both sides of a substrate. The transfer can be carried out. Alternatively, the composition for photopolymerization may be directly applied or impregnated onto a substrate without using a release liner, and the composition may be irradiated with ultraviolet rays to perform photopolymerization. An appropriate method can be adopted depending on the type of the base material and the like.

[0026]

As described above, in the present invention, by adding a specific nitrogen-containing monomer to the monomer composition to be photopolymerized, polymerization inhibition by oxygen at the time of ultraviolet irradiation is prevented. A pressure-sensitive adhesive that is effectively suppressed and can achieve a high polymerization rate even in an atmosphere with a high oxygen concentration, and has excellent adhesive strength and holding power after photopolymerization and its adhesive sheet.
Can provide.

[0027]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”.

[0028]

[0029]

[0030]

Example 1 90 parts of 2-ethylhexyl acrylate, acrylic acid 1
0 parts, 2.2-dimethoxy-2- as photopolymerization initiator
Phenylacetophenone (Ciba-gei-gi-co-pole-shiyo)
Premix was prepared using 0.05 parts of Irgaki Yua 651 (trade name, manufactured by Nippon Kayaku) . This was partially exposed to ultraviolet light in a nitrogen gas atmosphere to partially polymerize to obtain a coatable syrup having a viscosity of about 3,000 centipoise.

To 100 parts of the partially polymerized syrup was added N
1 part of tert-butylaminoethyl methacrylate, 0.1 part of trimethylolpropane triacrylate as a cross-linking agent, and 0.1 part of additional Irgakiurea 651 (the above-mentioned photopolymerization initiator) Parts of the mixture were mixed and the composition was coated on a polyimide film having a thickness of 25 μm.
Oxygen concentration of 10,000 ppm or 5,000 pp
m to be photopolymerized by irradiation with ultraviolet light
Thus, a layer of a photopolymer having a thickness of 50 μm was formed, and an adhesive sheet was produced.

[0033]

[0034]

Comparative Example 1 An adhesive sheet was prepared in the same manner as in Example 1 except that 1 part of N-tert-butylaminoethyl methacrylate was not added.

With respect to each of the adhesive sheets of Example 1 and Comparative Example 1 , the polymerization rate, adhesive strength and holding power of the photopolymer were examined in the following manner. The results are shown in Table 1 below. In Table 1, "A" in the column of ultraviolet irradiation atmosphere means that the oxygen concentration is 10,000 ppm, and "B" means that the concentration is 5,000 ppm.

<Polymerization rate> A sample X ₁ g (about 0.1 g) whose polymerization rate is to be measured is taken and stored in a dryer at 130 ° C. for 3 hours, and then the weight X ₂ g of the sample is measured again. I do. From the weights of X ₁ and X ₂ , the polymerization rate = (X ₂ /
X ₁ ) × 100 (%).

<Adhesive force> According to JIS Z-1522,
The measurement was performed using a stainless steel plate as an adherend. The adhesive strength was expressed in g / 20 mm width.

<Holding force> One end in the longitudinal direction of a mirror-finished stainless steel plate (30 mm × 120 mm × 3.0 mm)
Affix an adhesive sheet (width 10 mm) so that the adhesive area is 15 mm x 15 mm, leave for 30 minutes,
A load of 500 g was applied at 0 ° C., and the presence or absence of a drop in 30 minutes was observed.

[0040]

As is clear from the results in Table 1 above,
It can be seen that the adhesive sheet of Example 1 of the present invention has a high polymerization rate and satisfies both adhesive strength and holding power even in an atmosphere having a high oxygen concentration.

Continuation of front page (56) References JP-A-2-3481 (JP, A) JP-A-60-99183 (JP, A) JP-A-60-248786 (JP, A) JP-A-5-65317 (JP, A) JP-A-2-15878 (JP, A) U.S. Pat. No. 4,181,752 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 133/06-133/14 C09J 7/02

Claims (2)

(57) [Claims] 1. The following three components a to c: a) a monomer mainly composed of an alkyl (meth) acrylate having an alkyl group having 2 to 14 carbon atoms; b) a monomer of the component a) 0.5 to 100 parts by weight of body
C) A pressure-sensitive adhesive comprising a photopolymer of a composition containing a N - monosubstituted aminoalkyl (meth) acrylate in a proportion of 15 parts by weight. C) A photopolymerization initiator. 2. An adhesive sheet comprising a substrate and the pressure-sensitive adhesive layer according to claim 1 provided on one or both surfaces thereof .