JP2001152109A - Pressure-sensitive adhesive composition and pressure- sensitive adhesive tapes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acrylic pressure-sensitive adhesive composition which can be polymerized by ultraviolet irradiation and can obtain high molecular weigh polymers in a short time, and a pressure-sensitive adhesive tape provided with a pressure-sensitive adhesive layer of the composition. SOLUTION: In polymerizing (a) a vinyl monomer having an alkyl (meth) acrylate as the major component by irradiation with ultraviolet rays, (b) a photopolymerization initiator containing nitrogen and, simultaneously, a number of conjugated electrons of 4n+2 (wherein (n) is a natural number) is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive composition polymerized by irradiation with ultraviolet rays, and a sheet or tape formed by providing the adhesive composition on one or both sides of a substrate. It relates to pressure-sensitive adhesive tapes.

[0002]

2. Description of the Related Art Pressure-sensitive adhesive tapes made of an acrylic polymer polymerized by irradiation with ultraviolet light have weather resistance, heat resistance,
Not only is it excellent in chemical resistance and the like, but it has the advantage that it can be manufactured without using an organic solvent that causes air pollution, which has recently become a problem.

However, the polymerization method by ultraviolet irradiation has a disadvantage that the polymerization rate is slowed down and the polymerization rate is not increased due to the influence of dissolved oxygen in the monomer and oxygen in the atmosphere. Therefore, in order to increase the polymerization rate, it is conceivable to increase the amount of the photopolymerization initiator or increase the illuminance of ultraviolet rays, but in this case, the molecular weight of the obtained polymer is reduced, and as a pressure-sensitive adhesive tape, Characteristics,
For example, there have been problems such as a decrease in heat resistance and holding characteristics.

[0004] Furthermore, once a usual photopolymerization initiator is decomposed to generate radicals, it does not have the ability to generate radicals again, and if radicals are rapidly generated in the initial stage of polymerization, they can be generated in the middle and late stages of polymerization. There was also a problem that the concentration of the initiator was insufficient and it was difficult to shorten the time required to reach a high polymerization rate as a result.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acrylic pressure-sensitive adhesive composition which can be polymerized by irradiation with ultraviolet rays and can obtain a high molecular weight polymer in a short time, and to provide the same in a pressure-sensitive adhesive layer. To provide pressure-sensitive adhesive tapes.

[0006]

Means for Solving the Problems As a result of various studies to solve the above problems, the present inventors have found that a vinyl monomer (a) containing an alkyl (meth) acrylate as a main component is polymerized by ultraviolet irradiation. In this case, nitrogen is contained and the number of electrons in the conjugated system is 4n + 2 (n is a natural number)
It has been found that a polymer composition can be obtained in a short polymerization time by using the photopolymerization initiator (b), and the present invention has been completed.

That is, the present invention provides (1) at least
Essentially a vinyl-based monomer (a) containing alkyl (meth) acrylate as a main component and a photopolymerization initiator (b) containing nitrogen and having a conjugated electron number of 4n + 2 (n is a natural number). A pressure-sensitive adhesive composition containing, as a main component, a polymer polymerized by irradiating the composition with ultraviolet light, and (2) at least a vinyl-based monomer (a) containing, as a main component, an alkyl (meth) acrylate. )When,
Containing nitrogen and having a conjugated electron number of 4n + 2 (n
(B) is a natural number) as an essential component, and a different type of photopolymerization initiator (c) from (b)
And / or a composition containing the photosensitizer (d), and a pressure-sensitive adhesive composition mainly containing a polymer polymerized by irradiation with ultraviolet light. (3) The above-mentioned (1) Or a pressure-sensitive adhesive tape provided with a layer of the pressure-sensitive adhesive composition according to (2).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The vinyl monomer of the component (a) used in the present invention is mainly composed of an alkyl (meth) acrylate, and specific examples thereof include a methyl group, an ethyl group and a propyl group. Group, butyl group, isobutyl group, pentyl group, isopentyl group, hexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, alkyl ester of acrylic acid or methacrylic acid having an alkyl group such as, Alternatively, one kind or two or more kinds in which a part of the alkyl group is substituted with a hydroxyl group is used.

In the present invention, a monoethylenically unsaturated monomer copolymerizable with the alkyl (meth) acrylate is added to improve the adhesiveness by introducing a functional group or a polar group. The glass transition temperature of the polymer may be controlled to improve or modify the cohesion and heat resistance.
Examples of the copolymerizable monoethylenically unsaturated monomer used for this purpose include monoethylenically unsaturated monomers having a functional group such as a carboxyl group, a hydroxyl group, and a glycidyl group. For example, acrylic acid, methacrylic acid and the like; hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate and 2-hydroxy-3-phenoxypropyl acrylate; and glycidyl group-containing monomers for glycidyl (meth) acrylate. One or more types are used.

[0010] In the vinyl monomer of the component (a),
The alkyl (meth) acrylate as the main component and the monoethylenically unsaturated monomer copolymerizable therewith are 70 to 100% by weight, preferably 85 to 95% by weight of the former, and 30 to 0% by weight of the latter. % By weight, preferably 15 to 5% by weight
It is preferable to use such a range, so that the adhesiveness, cohesive strength, and the like can be well balanced.

The photopolymerization initiator (b) used in the present invention contains nitrogen and has a conjugated electron number of 4n +.
2, wherein n is a natural number, preferably n is in the range of 1 to 10, for example, a carbazole-phenone-based initiator represented by the following structural formula (1): Used.

[0012]

Embedded image

Here, the number of electrons in the conjugated system is defined as follows. 1) When a double bond exists via one single bond, the two are considered to be conjugate and the number of electrons per double bond is counted as two. 2) When an atom having a lone electron pair is directly bonded to a carbon atom having a double bond, one lone electron pair is counted, and the number of electrons is counted as two. 3) When an atom having a lone pair is itself unsaturatedly bonded, the lone pair of the atom is not counted. 4) When the unsaturated bond is a triple bond, it is treated in the same way as a double bond, and the number of electrons per triple bond is counted as two. 5) When two or more single bonds are present between unsaturated bonds or between an unsaturated bond and a lone electron pair, they are not in a conjugate relationship and each separately counts the number of electrons in a conjugated system. .

Applying the above definition to the compound of (1), two carbonyl groups (4 electrons), two benzene rings (12 electrons) and a central nitrogen atom (2 electrons as a lone electron pair) , For a total of 18 electrons. this is,
4n + 2 corresponds to the case where n = 4.

In the present invention, the photopolymerization initiator of the component (b) is used in a total amount of 0.001 to 10 parts by weight, preferably 0.01 to 1 part by weight, per 100 parts by weight of the vinyl monomer of the component (a). Used in parts by weight. 0.001
If it is less than parts by weight, it is difficult to obtain the effect as a polymerization initiator,
If the amount is more than 10 parts by weight, a low molecular weight polymer tends to be formed.

In the present invention, when a photopolymerization initiator (b) containing nitrogen and having 4n + 2 (n is a natural number) electrons in a conjugated system is used, a polymer can be obtained in a short reaction time. The feature is that it can be done, but the reason is not clear. However, we think as follows.

1) Since the number of electrons in the conjugate system is 4n + 2, it has aromaticity according to the Huckel rule. 2) Therefore, the excited state at the time of absorbing ultraviolet light is stabilized. 3) Since the excited state is stabilized, the ability to cut and cleave a bond in the molecule is reduced, and the hydrogen abstraction reaction is likely to occur. 4) Since the hydrogen atom is easily extracted from the initiator in the ground state due to having a nitrogen atom in the molecule, the tendency is further increased. 5) The photoinitiator that participated in hydrogen abstraction gives a hydrogen atom to another molecule to maintain 4n + 2 aromaticity, and the initiator is regenerated. 6) Dissolved oxygen in the monomer is consumed by radicals generated by the photopolymerization initiator, and is less likely to inhibit polymerization. 7) Since the influence of oxygen is reduced and the photopolymerization initiator of the present invention is considered to be capable of generating a high concentration of radicals from the early stage to the late stage of the polymerization, the reaction time is suppressed while suppressing the decrease in the molecular weight of the produced polymer. Can be shortened.

In the present invention, a different type of photopolymerization initiator (c) and / or photosensitizer (d) may be used in combination with (b) for the purpose of cost reduction and molecular weight control. Examples of the photopolymerization initiator (c) include benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether; substituted benzoin ethers such as anisoin methyl ether; 2,2-diethoxysilane silane acetophenone; There are substituted acetophenones such as dimethoxy-2-phenone acetophenone and substituted α-ketols such as 2-methyl-2-hydroxypropiophenone, and one or more of these are used.

The photosensitizer (d) includes thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, and 2,4-dichlorothioxanthone. Song,
Examples thereof include thioxanthone-based photosensitizers such as 2,4-diethylthioxanthone and 2,4-diisopropylthioxanthone, and one or more of these are used.

The amount of the photopolymerization initiator (c) or the photosensitizer (d) is not particularly limited as long as the desired composition can be obtained. The total amount of the photopolymerization initiator (b) and the photopolymerization initiator (c) or the photosensitizer (d) is 0.001 to 10 parts by weight, preferably 0 to 100 parts by weight of the system monomer. .
It is used in the range of 01 to 1 part by weight. If the amount is less than 0.001 part by weight, it is difficult to obtain the effect as a polymerization initiator, and if it is more than 10 parts by weight, a low molecular weight polymer tends to be generated.
Further, the weight ratio of the photopolymerization initiator (b) to the photopolymerization initiator (c) or the photosensitizer (d) is 1: 0.1 to 2, preferably 1: 0.5 to 1. When the ratio is 0.1 or less, the effect of the polymerization initiator (c) or the photosensitizer (d) is hardly obtained. When the ratio is 2 or more, the effect of the photopolymerization initiator (b) tends to decrease.

In the present invention, a polyfunctional (meth) acrylate as a cross-linking agent can be added to prevent the adhesive of the pressure-sensitive adhesive from extruding. Examples of such polyfunctional (meth) acrylates include trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, and 1,6-hexanediol diacrylate. (Meth) acrylate and the like.

When these polyfunctional (meth) acrylates are added, 0.05 to 5 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the vinyl monomer (a).
Used in the range of 3 parts by weight. Within this range, 2
When the number of functional groups is large, the number of functional groups can be reduced when the number of functional groups is three or more. When gluing, glue is likely to run out.
If the amount is more than the weight part, the crosslinking density becomes too dense, and the adhesive strength is lowered, which is not preferable.

In the preparation of the pressure-sensitive adhesive composition of the present invention, first, a vinyl monomer (a) containing (meth) acrylic acid alkyl ester as a main component, nitrogen, and a conjugated system having 4n + 2 electrons are used. A certain photopolymerization initiator (b) and, if necessary, a different type of photopolymerization initiator (c) and / or photosensitizer (d) are mixed, and this premix is partially partially irradiated with light. Polymerized to a viscosity of about 500
Make a coatable syrup of ~ 7000 centipoise.

Next, a composition for photopolymerization is prepared by mixing a polyfunctional (meth) acrylate as a crosslinking agent and, if necessary, an additional photopolymerization initiator. In this composition, as long as the photopolymerizability is not impaired, a tackifying resin, a filler,
Known various additives such as a pigment, an antioxidant, and a silane coupling agent can be added as needed.

In the present invention, the composition adjusted as described above is applied to a release-treated film as a release liner, and subjected to a photopolymerization treatment by irradiation with ultraviolet rays to obtain a photopolymer. The photopolymerization treatment is performed in an atmosphere containing a small amount of oxygen replaced by an inert gas such as nitrogen gas, or in a state where the air is shut off by coating with an ultraviolet-permeable film.

The composition for photopolymerization may be applied onto the film by using a coating method such as roll coating, screen coating, or gravure coating. The coating thickness of the composition is
Although it is appropriately determined in consideration of the characteristics required for the purpose of use, it is usually about 10 to 200 μm.

The ultraviolet light used for photopolymerization has a wavelength range of about 1
Although it has an electromagnetic radiation of 80 to 460 nm, a longer or shorter wavelength electromagnetic radiation may be used. UV sources include mercury arcs, carbon arcs, low-pressure mercury lamps,
General lighting devices such as a medium / high pressure mercury lamp and a metal halide lamp are used. The intensity of the ultraviolet light can be appropriately determined in consideration of the adjustment of the distance to the irradiation object and the voltage and the irradiation time (productivity).

The pressure-sensitive adhesive tapes of the present invention are obtained by converting the pressure-sensitive adhesive composition formed by the above-described method into a sheet or tape. Alternatively, the pressure-sensitive adhesive composition may be provided on one or both sides of the substrate to form pressure-sensitive adhesive tapes with the substrate.

The substrate used herein is not particularly limited, and may be, for example, papers (Japanese paper, kraft paper, etc.), cloths (cotton, soft cloth, synthetic fiber, non-woven fabric, etc.), plastics (cellophane, polyethylene). , Polyester, polyvinyl chloride,
Acetate, polypropylene, polyethylene terephthalate, polystyrene, polyacrylonitrile, etc.), heat-resistant films (polyimide film, polytetrafluoroethylene film, polyetheretherketone film, polyethersulfone film, etc.), metal foil,
Alternatively, these plastic laminates and the like can be used. Further, a film or foam made of a polymer exhibiting rubber-like elasticity can also be used. The thickness can also be appropriately determined according to the type, use, and purpose of the base material used. Further, a substrate which has been subjected to a known treatment such as an undercoating treatment, a filling treatment, a corona treatment, and a back surface treatment can be used for the substrate.

In these cases, for example, a layer of the acrylic pressure-sensitive adhesive composition having a desired thickness is formed on a release liner by the above-mentioned method, and then the layer is transferred to one or both sides of a substrate. Can be. Alternatively, a 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. An appropriate method can be adopted depending on the type of the base material.

In the production of the pressure-sensitive adhesive tapes of the present invention thus constituted, the production speed can be made higher than before, and
In addition, the molecular weight of the pressure-sensitive adhesive composition can be made equal to or more than that.

EXAMPLES The present invention will now be described in more detail with reference to Examples, but the present invention is not limited thereto. In the following, “parts” means “parts by weight”.

Example 1 100 parts of butyl acrylate, carbazole / phenone-based initiator "ADEKA OPTOMER N-1414" (manufactured by Asahi Denka Kogyo KK) as a photopolymerization initiator (b) (the structural formula is the above chemical formula 1) The premix was prepared using 0.5 parts. This was partially irradiated with ultraviolet light in a nitrogen atmosphere to be partially photopolymerized to obtain a coatable syrup having a viscosity of about 5000 centipoise.

Example 2 100 parts of butyl acrylate, 0.3 part of N-1414 of Example 1 as the photopolymerization initiator (b), and 2,2-dimethoxy-2-phenylacetophenone as the photopolymerization initiator (c) Using 0.2 parts of "Irgacure 651" (manufactured by Ciba-Geigy Corporation), a coatable syrup having a viscosity of about 5000 centipoise was irradiated in the same manner as in Example 1 and then irradiated with ultraviolet rays.

Example 3 100 parts of butyl acrylate, 0.3 part of N-1414 of Example 1 as a photopolymerization initiator (b), and a photosensitizer (d)
As 2-chlorothioxathon "Kayacure CTX"
Using 0.2 part (manufactured by Nippon Kayaku Co., Ltd.), a coatable syrup having a viscosity of about 5000 centipoise was prepared in the same manner as in Example 1 and then subjected to ultraviolet irradiation.

COMPARATIVE EXAMPLE 1 Using 100 parts of butyl acrylate and 0.05 part of Irgacure 651 as a photopolymerization initiator, a coatable syrup having a viscosity of about 5000 centipoise was prepared in the same manner as in Example 1, and then irradiated with ultraviolet rays. Was done.

Comparative Example 2 Using 100 parts of butyl acrylate and 0.2 part of Irgacure 651 as a photopolymerization initiator, a coatable syrup having a viscosity of about 5000 centipoise was prepared in the same manner as in Example 1 and then irradiated with ultraviolet rays. Was done.

Comparative Example 3 Using 100 parts of butyl acrylate and 0.5 part of Irgacure 651 as a photopolymerization initiator, a coatable syrup having a viscosity of about 5000 centipoise was prepared in the same manner as in Example 1 and then irradiated with ultraviolet rays. Was done.

The reaction time and molecular weight of each of the syrups of Examples 1 to 3 and Comparative Examples 1 to 3 were measured by the following methods. These results were as shown in Table 1.

<Measurement of reaction time> The obtained syrup was irradiated with ultraviolet rays using a PDC (optical differential calorimeter, manufactured by Niseiko) under the following conditions, and the time from the start of irradiation until the exothermic curve returned to the baseline was measured. The reaction time was taken. Measurement conditions: illuminance 100mW / cm ² , ambient temperature 25 ° C, nitrogen flow rate 40ml / min

<Molecular Weight> The sample for which the above reaction time was determined was dissolved in THF so as to have a concentration of 0.1% by weight.
After leaving for 8 hours and filtering the insoluble matter with a filter,
The weight average molecular weight (Mw) was measured using a PC (HLC-8020 manufactured by Tosoh Corporation). Measurement conditions: standard polystyrene, eluent THF, liquid feed rate 0.5 ml / min, column temperature 40 ° C

[0041]

[Table 1]

As is evident from Table 1, the syrups of Examples 1 to 3 of the present invention can obtain a high molecular weight polymer although the reaction time is shorter than that of Comparative Example. On the other hand, in the syrups of Comparative Examples 1 to 3, when the amount of the initiator is increased to shorten the reaction time, the molecular weight decreases, and it is impossible to achieve both the short reaction time and the high molecular weight.

Next, Examples 1 to 3 of the present invention and Comparative Example 1
The characteristics when a pressure-sensitive adhesive sheet is formed using the syrups prepared in Steps 3 to 3 will be specifically described.

Example 4 To 100 parts of the syrup prepared in Example 1, 0.3 part of trimethylolpropane triacrylate as a crosslinking agent was added to prepare an adhesive solution. Next, after applying this adhesive solution on a release film composed of a polyethylene terephthalate film having a thickness of 50 μm, which has been subjected to silicone release treatment as a release liner, a cover is formed with a release film composed of a polyethylene terephthalate film. Irradiation with ultraviolet rays by a high-pressure mercury lamp with a light intensity of 100 mW / cm ² to prevent polymerization inhibition by oxygen and photopolymerization to give a thickness of 50 μm
To produce a pressure-sensitive adhesive sheet comprising the photopolymer. The irradiation time of the ultraviolet light was 5 based on the result of Example 1.
0 seconds.

Example 5 In the same manner as in Example 4, a pressure-sensitive adhesive sheet was produced using the syrup produced in Example 2. The irradiation time of the ultraviolet rays was set to 48 seconds based on the result of Example 2.

Example 6 In the same manner as in Example 4, a pressure-sensitive adhesive sheet was produced using the syrup produced in Example 3. The irradiation time of the ultraviolet rays was set to 55 seconds based on the result of Example 3.

Comparative Example 4 In the same manner as in Example 4, a pressure-sensitive adhesive sheet was produced using the syrup produced in Comparative Example 1. The irradiation time of the ultraviolet rays was set to 235 seconds based on the result of Comparative Example 1.

Comparative Example 5 In the same manner as in Example 4, a pressure-sensitive adhesive sheet was produced using the syrup produced in Comparative Example 2. The irradiation time of the ultraviolet rays was set to 103 seconds based on the result of Comparative Example 2.

Comparative Example 6 In the same manner as in Example 4, a pressure-sensitive adhesive sheet was produced using the syrup produced in Comparative Example 3. The irradiation time of the ultraviolet rays was set to 71 seconds based on the result of Comparative Example 3.

For each of the pressure-sensitive adhesive sheets of Examples 4 to 6 and Comparative Examples 4 to 6, the degree of polymerization and retention characteristics were measured by the following methods. These results were as shown in Table 2.

<Polymerization ratio> Initial weight X of obtained sample
_{From 1} (g) and the weight X ₂ (g) after drying this sample at 130 ° C. for 2 hours, the polymerization rate (%) = (X ₂ / X ₁ ) × 1
00 was calculated.

<Holding Characteristics> The above adhesive sheet was cut into an aluminum plate having a width / length / thickness of 25 mm / 80 mm / 0.4 mm as an adherend, and 15 mm × 15 mm was cut out, and one surface was pressed tightly with a hand roller. Peel off the release liner on the remaining surface,
Another adherend was prepared and bonded with one round trip of a 5 kg roller. After aging at 80 ° C. for 30 minutes, the sample was allowed to stand for 300 minutes in a 80 ° C. atmosphere while applying a load of 1 kg, and the presence or absence of load drop was measured.

[0053]

[Table 2]

As is clear from Table 2, in Examples 4 to 6 of the present invention, pressure-sensitive adhesive sheets having the same holding power can be obtained by irradiation with ultraviolet rays for a shorter time as compared with Comparative Examples 4 and 5. You can see that. On the other hand, in Comparative Example 6 in which the amount of the initiator was increased (see Comparative Example 3), although the irradiation time of the ultraviolet light could be shortened, the holding power was reduced due to the decrease in the molecular weight, and the irradiation time of the ultraviolet light was reduced Retention characteristics cannot be compatible.

[0055]

As described above, in the present invention, the vinyl monomer (a) containing an alkyl (meth) acrylate as a main component contains a nitrogen atom, and the number of conjugated electrons is 4n + 2. By adding a certain photopolymerization initiator (b), the reaction time can be reduced to about 1/2 and a polymer can be obtained, so that the production speed can be doubled.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Rie Mogi 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4J004 AA10 AB01 CA02 CA04 CA05 CA06 CB02 CB04 CC02 EA05 GA01 4J040 DF041 DF051 EC231 GA05 GA07 GA11 HB19 HB20 HC26 HD19 JA09 JB09 KA13 KA15 LA07 LA08 LA11

Claims (3)

[Claims] 1. Photopolymerization initiation at least comprising a vinyl-based monomer (a) containing an alkyl (meth) acrylate as a main component, nitrogen and a conjugated system having 4n + 2 electrons (n is a natural number). A pressure-sensitive adhesive composition comprising, as an essential component, an agent (b), and a polymer obtained by irradiating the composition with ultraviolet rays and polymerizing as a main component. 2. Photopolymerization initiation at least comprising a vinyl monomer (a) containing an alkyl (meth) acrylate as a main component and nitrogen and having a conjugated electron number of 4n + 2 (n is a natural number). A polymer containing a photopolymerization initiator (c) and / or a photosensitizer (d) of a type different from that of (b), containing an agent (b) as an essential component; A pressure-sensitive adhesive composition comprising as a main component. 3. A pressure-sensitive adhesive tape comprising a substrate and a layer of the pressure-sensitive adhesive composition according to claim 1 provided on one or both surfaces.