JP6016949B2 - Flame-retardant pressure-sensitive adhesive composition, flame-retardant heat-conductive pressure-sensitive adhesive composition, and pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to a flame retardant pressure-sensitive adhesive composition (pressure-sensitive adhesive), a flame-retardant and heat-conductive pressure-sensitive adhesive composition (pressure-sensitive adhesive), and a pressure-sensitive adhesive layer (pressure-sensitive) using these. The present invention relates to a pressure-sensitive adhesive sheet formed by forming an adhesive layer.

  In recent years, due to remarkable progress in electronics technology, higher integration and higher performance of electric, electronic, and OA devices are progressing. Along with this, in order to reduce the risk of ignition due to high temperature inside the product and heat storage, the adhesive member is also required to have high flame resistance. In addition, various researches have been made on the flame retardancy of plastic materials in various fields such as home appliances, vehicles, and building materials, and high flame retardancy is also required for adhesive members used for fixing them. In particular, in electronic parts and home appliances, measures are taken to prevent functional failure by dissipating heat by bonding heat countermeasure parts such as heat sinks with bonding members. This joining member is required to have high thermal conductivity, electrical insulation, and flame retardancy.

  Regarding flame retardancy, it is difficult to achieve both flame retardancy and the original purpose of adhesion performance by the flame retarding technique similar to that for plastic materials. Therefore, in general, flame-resistant pressure-sensitive adhesives have been obtained by using a halogen-based flame retardant or a combination of halogen-based / antimony. However, recently, from the viewpoint of environmental protection and human safety (suspected of carcinogenicity), there has been a movement to regulate the use of halogen-based flame retardants, and the demand for non-halogen-based flame retardants is increasing.

  On the other hand, a flame retardant adhesive containing red phosphorus and a nitrogen-containing phosphorus compound has a risk of ignition by red phosphorus and phosphine gas generation during the production of an adhesive tape. Moreover, although the flame-retardant adhesive containing the ammonium polyphosphate of a specific particle size is proposed, the flame retardance is inadequate. In addition, when using a hydrated metal compound as a flame retardant, it is necessary to add a large amount of hydrated metal compound to obtain the same flame resistance as a brominated flame retardant. The coexistence of the monomer and the hydrated metal compound inevitably causes a significant decrease in pressure-sensitive adhesive performance. That is, the addition of a hydrated metal compound causes a decrease in the adhesive performance of the pressure-sensitive adhesive such as adhesive strength, holding power, and tack. Thus, in the prior art, it is difficult to achieve both high flame retardancy and adhesive performance.

  In Patent Document 1, an acrylic acid ester copolymer [including acrylic acid (3.5%) and a crosslinking agent and a hydroxyl group-containing monomer (0.5%) of a reactive site] is added to a metal hydroxide, ammonium polyphosphate, Disclosed is a flame retardant double-sided pressure-sensitive adhesive tape having a good flame retardancy and adhesion by adding a polyhydric alcohol. However, good flame retardancy cannot be obtained unless 100 parts by mass or more of the total amount of metal hydroxide, ammonium polyphosphate, and polyhydric alcohol as flame retardants is added to 100 parts by mass of the acrylic ester copolymer. . Moreover, sufficient adhesive strength cannot be exhibited with this added amount.

  Patent Document 2 discloses that a double-sided pressure-sensitive adhesive sheet having good flame retardancy and adhesiveness can be obtained from a copolymer composed of an acrylate ester monomer, a nitrogen-containing acrylic monomer, and a carboxylic acid-containing monomer and a metal hydroxide. Yes. However, the Tg of the homopolymer is relatively high, and if nearly 20% of a nitrogen-containing acrylic monomer is added or about 130 parts of a metal hydroxide is added, sufficient adhesive strength cannot be exhibited. Further, when an acrylic acid-containing copolymer is mixed with a metal hydroxide or ammonium polyphosphate, it tends to thicken and gel, and is not suitable for applying an adhesive sheet.

  In Patent Document 3, it is assumed that a flame-retardant heat conductive pressure-sensitive adhesive sheet is made of an acrylic ester copolymer obtained by copolymerizing a polar monomer other than carboxylic acid and a metal hydrate, and a nitrogen-containing monomer and a hydroxyl group monomer are mentioned as polar monomers. ing. In the examples, 5 to 20% nitrogen-containing monomer, 1% hydroxyl-containing monomer (theoretical hydroxyl value: 4.9), 10% nitrogen-containing monomer (theoretical hydroxyl value: 0), 10% hydroxyl monomer (theoretical hydroxyl value: 48) and the like. However, according to the knowledge of the present inventors, since all have a low theoretical hydroxyl value, good flame retardancy cannot be obtained, and a large amount of flame retardant must be added. In this case, the adhesive properties are extremely lowered.

  In Patent Document 4, an acrylic polymer obtained by copolymerizing a monomer component containing (meth) acrylic acid alkyl ester as a main component, containing a polar group-containing monomer and substantially free of a carboxyl group-containing monomer, and hydration A flame-retardant heat conductive adhesive sheet provided with a flame-retardant heat conductive pressure-sensitive adhesive layer containing a metal compound has been proposed. However, according to the knowledge of the present inventors, since the theoretical hydroxyl value of the acrylic polymer is small, good flame retardancy cannot be obtained, and a large amount of flame retardant must be added. In this case, the adhesive properties are extremely lowered.

JP 2000-230162 A JP 2005-54006 A JP 2010-229265 A JP 2012-180495 A

  The present invention has been made to solve the above-described problems of the prior art. That is, the object of the present invention is to provide a flame retardant that achieves both high flame retardancy and excellent adhesiveness without using halogen-based flame retardants and antimony that have problems in environmental conservation and human safety (suspected of carcinogenicity). Another object of the present invention is to provide a heat-sensitive adhesive composition, a flame-retardant heat conductive pressure-sensitive adhesive composition imparted with high heat dissipation properties, and a pressure-sensitive adhesive sheet using them.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that it is very effective to use a (meth) acrylic acid alkyl ester copolymer having a specific theoretical hydroxyl value. It came to be completed.

The present invention is a flame retardant pressure-sensitive adhesive composition comprising 100 parts by mass of a (meth) acrylic acid alkyl ester copolymer having a theoretical hydroxyl value of 70 to 250, and 30 to 60 parts by mass of a non-halogen flame retardant. .

Moreover, this invention is a flame-retardant heat conductive adhesive composition which adds 100-300 mass parts of heat conductive particles with an average particle diameter of 1 micrometer- 100 micrometers further with respect to said flame-retardant adhesive composition. is there.

  Furthermore, this invention is an adhesive sheet formed by forming an adhesive layer on the one or both surfaces of a base material using said flame-retardant adhesive composition or a flame-retardant heat conductive adhesive composition.

  According to the present invention, a flame retardant pressure-sensitive adhesive composition having excellent flame retardancy and adhesive strength, a flame retardant heat conductive pressure-sensitive adhesive composition having excellent flame retardancy, thermal conductivity and adhesive strength, and An adhesive sheet using them can be provided. This pressure-sensitive adhesive sheet is very useful as a joining member that bonds, for example, an electronic member and a heat dissipation member (such as a heat sink).

  The theoretical hydroxyl value of the (meth) acrylic acid alkyl ester copolymer used in the present invention is 70 to 250, preferably 90 to 160. If the theoretical hydroxyl value is too low, sufficient flame retardancy cannot be obtained, and a large amount of flame retardant must be used, resulting in poor adhesive properties when used as an adhesive sheet. On the other hand, if the theoretical hydroxyl value is too high, the glass transition temperature of the (meth) acrylic acid ester copolymer becomes too high, and good adhesive properties cannot be obtained.

  In general, the hydroxyl value refers to the number of mg of potassium hydroxide required to neutralize acetic anhydride required for acetylating OH groups contained in 1 g of a sample. Specifically, OH groups in a sample are acetylated using acetic anhydride, and acetic acid that has not been used for acetylation is titrated with a potassium hydroxide solution for measurement. However, since the addition amount of the hydroxyl group-containing monomer is obvious when the copolymer is polymerized in the present invention, the hydroxyl value when the monomer charged in the polymerization reaction is 100% polymerized is calculated by the following formula ( This was determined by 1), and this was defined as the theoretical hydroxyl value.

Theoretical hydroxyl value = [Mass of hydroxyl group-containing monomer in 1 g of all charged monomers] / [Molecular weight of hydroxyl group-containing monomer] × [Molecular weight of KOH] × 1000 (1)
The theoretical hydroxyl value of the (meth) acrylic acid alkyl ester copolymer can be adjusted by the charge ratio of the hydroxyl group-containing monomer.

  In the prior art, a hydroxyl group-containing monomer has been used as a reaction site with a crosslinking agent (particularly an isocyanate-based crosslinking agent) or as a Tg regulator for a slight amount of polymer. In this case, the acrylic pressure-sensitive adhesive polymer contains about 0.1% (theoretical hydroxyl value: 0.48) to 1% (theoretical hydroxyl value: 4.8). On the other hand, the present inventors have found a flame retardant effect due to the hydroxyl group itself in the copolymer, and the effect is obtained by the copolymer obtained by containing the hydroxyl group-containing monomer in a completely different amount. I found out that And it becomes possible to reduce the quantity of a flame retardant significantly by this, and a favorable flame retardance and adhesiveness are obtained. Moreover, if the addition amount of a flame retardant is suppressed to a small amount, other functional fillers can be easily added, and a high-performance multifunctional adhesive sheet can be provided.

  The (meth) acrylic acid ester copolymer is obtained, for example, by copolymerizing a hydroxyl group-containing monomer and other (meth) acrylic acid ester monomers.

  Examples of the hydroxyl group-containing monomer include (meth) acrylic acid ester monomers having at least one hydroxyl group. Specific examples thereof include (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxybutyl, (meth) acrylic acid-4-hydroxybutyl, Examples include (meth) acrylic acid-2-hydroxyhexyl, monoesters of (meth) acrylic acid and polyethylene glycolicol or polypropylene glycol.

  Examples of other (meth) acrylic acid ester monomers include (meth) acrylic acid alkyl ester monomers having an alkyl group having 1 to 14 carbon atoms. Specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, Isobutyl (meth) acrylate, hexyl (meth) acrylate, isohexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, ( (Meth) acrylic acid ester monomers having an aliphatic group such as (meth) acrylic acid decyl, (meth) acrylic acid isodecyl, (meth) acrylic acid dodecyl, (meth) acrylic acid isododecyl; isobornyl (meth) acrylate, cyclohexyl (Meth) acrylate, benzyl (meth) acrylate (Meth) acrylic acid ester monomer having an alicyclic group or aromatic group such as phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, phenoxypropyl (meth) acrylate, phenoxypolypropylene glycol (meth) acrylate ;

  Furthermore, a monomer having a polar group other than a hydroxyl group can be used in combination for further improving the adhesive strength and heat resistance. For example, (meth) acrylamide, N-alkyl substituted (meth) acrylamide, N, N-dialkyl substituted (meth) acrylamide, and acryloylmorpholine are preferable.

  In order to produce a (meth) acrylic acid alkyl ester copolymer, for example, a monomer mixture is photopolymerized or thermally polymerized by a polymerization method such as solution polymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. Good. Polymerization by radiation such as gamma rays or polymerization by electron beams is also possible. In the photopolymerization, for example, the monomer mixture is irradiated with UV rays in the presence of a photopolymerization initiator. In thermal polymerization, for example, the monomer mixture is heated to about 50 to 200 ° C. in the presence of a thermal polymerization initiator. Photopolymerization is preferred because it can be carried out relatively easily. However, when the monomer mixture to be polymerized contains a relatively large amount of additives and UV light permeability is low, thermal polymerization may be preferable.

  The (meth) acrylic acid alkyl ester copolymer may be crosslinked using a crosslinking agent in order to improve cohesion. As the crosslinking agent used in the UV curing system, for example, a polyfunctional acrylate crosslinking agent such as 1,6-hexanedidiol diacrylate, an isocyanate crosslinking agent, and an epoxy crosslinking agent can be used. For example, the polyfunctional acrylate crosslinking agent may be added and photopolymerized when the monomer mixture is blended. As the crosslinking agent used in the solvent system, for example, an isocyanate crosslinking agent or an epoxy crosslinking agent can be used. For example, a crosslinking agent may be reacted with a (meth) acrylic acid alkyl ester copolymer containing a hydroxyl group or the like capable of reacting with these crosslinking agents. The amount of the crosslinking agent is preferably 0.01 to 10 parts by mass per 100 parts by mass of the monomer mixture or 100 parts by mass of the copolymer.

  The non-halogen flame retardant used in the present invention is a component that imparts flame retardancy to the pressure-sensitive adhesive composition. However, since the (meth) acrylic acid alkyl ester copolymer having a specific theoretical hydroxyl value is used in the present invention, the amount of the flame retardant blended may be relatively small.

  As the non-halogen flame retardant, for example, a phosphorus flame retardant, a melamine flame retardant, or a combination thereof can be used. Specific examples of phosphorus flame retardants include ammonium polyphosphate and phosphate esters. Specific examples of the melamine flame retardant include (poly) melamine phosphate and melamine sulfate. You may use these individually by 1 type or in mixture of 2 or more types. From the viewpoint of flame retardancy, ammonium polyphosphate is preferred. On the other hand, for example, in electrical insulation applications that require tracking resistance, phosphate esters and melamine flame retardants may be preferable to ammonium polyphosphate.

  The non-halogen flame retardant may be subjected to a surface treatment such as coating or microencapsulation using a thermosetting resin for improving water resistance. In addition, surface treatment such as coupling treatment or stearic acid treatment may be performed in order to improve dispersibility in the pressure-sensitive adhesive.

  The addition amount of the non-halogen flame retardant is 20 to 150 parts by mass, preferably 20 to 80 parts by mass, more preferably 30 to 60 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid alkyl ester copolymer. is there. In general, since the adhesiveness decreases as the amount of the flame retardant increases, a composition that can exhibit flame retardancy with a smaller amount of the flame retardant is preferable. And in this invention, since the (meth) acrylic-acid alkylester copolymer of a specific theoretical hydroxyl value is used, the compounding quantity of a flame retardant may be comparatively small, and sufficient adhesiveness can be ensured by that much.

  You may mix | blend the tackifier with the adhesive composition of this invention for the further adhesive improvement. For the copolymer obtained by solution polymerization, various tackifiers such as a rosin tackifier, a terpene resin, a petroleum resin, a terpene phenol resin, and a styrene resin can be used. On the other hand, when performing photopolymerization with UV light, it is necessary to use a resin that does not function as a chain transfer agent or a polymerization terminator for radical polymerization. For example, hydrogenated rosin tackifiers, terpene phenol tackifiers Agents can be used. The compounding amount of the tackifier is preferably 2 to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid alkyl ester copolymer.

  The thermally conductive particles used in the present invention are components that impart thermal conductivity to the pressure-sensitive adhesive composition. As the thermally conductive particles, for example, metal powder, metal oxide, metal hydroxide, boron nitride, silicon nitride, carbon nitride, and combinations thereof can be used. In order to improve dispersibility, surface treatment such as coupling treatment or stearic acid treatment may be performed. In the present invention, the metal hydroxide is used as the heat conductive particles, but may generally be used as a flame retardant. However, the flame retardant effect of metal hydroxide is much smaller than that of ordinary phosphorus or melamine flame retardants. For example, even if a large amount of metal hydroxide is added, in a severe flame retardant test such as UL94V-test, it melts together with the resin during flame contact to form a drop, and the absorbent cotton for labeling is ignited, It will be melted and will be rejected. Therefore, in the present invention, materials such as metal hydroxides can be used as thermally conductive particles, but are not flame retardants.

  The average particle diameter of the heat conductive particles is 1 μm to 100 μm, preferably 10 to 50 μm. The compounding quantity of a heat conductive particle is 50-300 mass parts per 100 mass parts of (meth) acrylic-acid alkylester copolymers, Preferably it is 100-200 mass parts.

  The pressure-sensitive adhesive sheet of the present invention is obtained by forming a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer) on one side or both sides of a substrate using the pressure-sensitive adhesive composition of the present invention. Examples of the method for forming the pressure-sensitive adhesive layer include a method in which the pressure-sensitive adhesive composition of the present invention is applied to a substrate and photocured, and the pressure-sensitive adhesive composition of the present invention is dissolved in a solvent, and this is applied to the substrate. There is a method of applying and drying. The thickness of the adhesive layer is preferably 0.05 to 2.0 mm, more preferably 0.05 to 1.0 mm.

  As a base material, various conventionally well-known base materials, such as paper materials, such as rayon paper, resin films, such as a polyethylene terephthalate, can be used, for example. If necessary, various release sheets such as conventionally known release papers can be used in combination.

  The pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present invention is not limited to the one having the above configuration. For example, a pressure-sensitive adhesive sheet without a substrate, that is, a pressure-sensitive adhesive sheet composed entirely of a pressure-sensitive adhesive composition, or only a pressure-sensitive adhesive sheet and a release sheet may be used.

  In order to obtain further high adhesiveness, an additional pressure-sensitive adhesive layer may be laminated on the pressure-sensitive adhesive sheet or pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. A flame retardant and heat conductive particles may be added to the additional adhesive layer, but it is preferable not to add them in order to obtain high adhesive strength. In this case, the additional pressure-sensitive adhesive layer is preferably thin so that the flame retardancy and thermal conductivity of the pressure-sensitive adhesive sheet do not decrease, and specifically, about 5 μm to 50 μm is preferable. For the additional adhesive layer, for example, an acrylic adhesive, a natural rubber adhesive, a synthetic rubber adhesive, or a silicone adhesive can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the following description, “part” and “%” mean “part by mass” and “% by mass”, respectively.

<Evaluation test>
(Theoretical hydroxyl value)
The theoretical hydroxyl value of the (meth) acrylic acid alkyl ester copolymer is the theoretical hydroxyl value = [the charged mass of the hydroxyl group-containing monomer in 1 g of all charged monomers] / [molecular weight of the hydroxyl group-containing monomer] × [ The molecular weight of KOH] × 1000.

(Flame retardance)
A pass / fail judgment was made according to the UL94 vertical combustion test method.

(180 ° adhesive strength)
According to JIS-Z-1528, 180 ° adhesive strength (N / 10 mm width) was measured using a SUS304 (surface BA treatment) plate as an adherend.

(90 ° adhesive strength)
In accordance with JIS-Z-1541, 90 ° adhesive strength (N / 10mm width) is measured using aluminum (0.130mm thickness) that has been bonded for backing and SUS304 (surface BA treatment) plate as the adherend. did.

(Holding power)
In accordance with JIS-Z-1528, aluminum (0.130 mm thick) that has been bonded for backing, and a stainless steel plate polished with water-resistant abrasive paper as the adherend, the affixed area is 20 mm × 20 mm, and a predetermined temperature A load of 4.9 N was applied vertically in the atmosphere, and the presence or absence of dropping after standing for 1 hour was measured.

(L-shaped holding force)
L-shaped metal fittings made of SUS (one piece 30 mm, thickness 3 mm, mass about 30 g) are affixed to an adherend (aluminum plate) with a tape sample 20 mm × 20 mm, and a load of 200 g is applied under a predetermined atmosphere for 24 hours. The presence or absence of the subsequent fall was measured.

(Thermal conductivity)
The sheet sample was measured using a rapid thermal conductivity meter (trade name QTM500, manufactured by Kyoto Electronics Industry Co., Ltd.) at an ambient temperature of 23 ° C. ± 2 ° C.

<Example 1>
(Preparation of acrylic syrup 1)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, UV lamp and nitrogen gas inlet, 70 parts of 2-ethylhexyl acrylate, 10 parts of methyl acrylate, 20 parts of 4-hydroxybutyl acrylate, photopolymerization initiator (BASF Japan) Made by the company, trade name DAROCURE 1173), 0.01 part of n-dodecyl mercaptan as a chain transfer agent, and irradiated with UV light in a nitrogen atmosphere, acrylic syrup 1 [(meth) acrylic acid alkyl ester co The theoretical hydroxyl value of the polymer: 77.9] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup 1 was about 13%, and the weight average molecular weight was about 1.5 million.

(Preparation of UV curable flame retardant adhesive composition 1)
For this acrylic syrup 1, 0.1 part of hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name NK Ester A-HD-N) as a cross-linking agent, photopolymerization initiator (manufactured by BASF Japan, trade name) Darocur 1173) 0.8 parts and 50 parts of ammonium polyphosphate (trade name Terrage C30, manufactured by Chisso Corporation) as a flame retardant were added and stirred uniformly. The air bubbles mixed during the stirring and mixing were removed by a defoaming operation to obtain a UV curable flame retardant pressure-sensitive adhesive composition 1.

(Preparation of flame retardant double-sided pressure-sensitive adhesive sheet 1)
The UV curable flame retardant pressure-sensitive adhesive composition 1 is based on rayon paper 14 g / m ² (MR base paper, manufactured by Miki Special Paper Co., Ltd.) so that the thickness after curing is 0.15 mm on both sides. The flame retardant double-sided pressure-sensitive adhesive sheet 1 was obtained by coating and coating with a 50 μm-thick polyethylene terephthalate (PET) film on which a release agent surface treatment was applied.

<Example 2>
(Preparation of acrylic syrup 2)
Acrylic syrup 2 [(meth) acrylic acid alkyl ester copolymer in the same manner as acrylic syrup 1 of Example 1 except that 20 parts of 2-hydroxyethyl acrylate was used instead of 20 parts of 4-hydroxyethyl acrylate. The theoretical hydroxyl value of 96.7] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup 2 was about 13%, and the weight average molecular weight was about 1.5 million.

(Preparation of UV curable flame retardant adhesive composition 2)
A UV curable flame retardant adhesive composition 2 was obtained in the same manner as the UV curable flame retardant adhesive composition 1 of Example 1 except that the acrylic syrup 2 was used.

(Preparation of flame retardant double-sided pressure-sensitive adhesive sheet 2)
A flame-retardant double-sided pressure-sensitive adhesive sheet 2 was obtained in the same manner as the pressure-sensitive adhesive sheet 1 of Example 1 except that the UV-curable flame-retardant pressure-sensitive adhesive composition 2 was used.

<Example 3>
(Preparation of acrylic syrup 3)
Acrylic syrup 3 [(meth) acrylic acid alkyl ester in the same manner as acrylic syrup 2 of Example 2 except that the amount of 2-ethylhexyl acrylate was changed to 60 parts and the amount of 2-hydroxyethyl acrylate was changed to 30 parts. The theoretical hydroxyl value of the copolymer: 145.1] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup 3 was about 13%, and the weight average molecular weight was about 1.5 million.

(Preparation of UV curable flame retardant adhesive composition 3)
The UV curable flame retardant composition was the same as the UV curable flame retardant pressure-sensitive adhesive composition 2 of Example 2 except that the acrylic syrup 3 was used and the amount of ammonium polyphosphate as a flame retardant was changed to 40 parts. A flammable pressure-sensitive adhesive composition 3 was obtained.

(Preparation of flame retardant double-sided pressure-sensitive adhesive sheet 3)
A flame-retardant double-sided pressure-sensitive adhesive sheet 3 was obtained in the same manner as the pressure-sensitive adhesive sheet 2 of Example 2 except that the UV curable flame-retardant pressure-sensitive adhesive composition 3 was used.

<Example 4>
(Preparation of acrylic syrup 4)
Example 2 except that the amount of 2-ethylhexyl acrylate was changed to 55 parts, the amount of 2-hydroxyethyl acrylate was changed to 30 parts, and 5 parts of acryloylmorpholine (trade name ACMO manufactured by Kojin Co., Ltd.) was also used. In the same manner as in Acrylic Syrup 2, Acrylic Syrup 3 [theoretical hydroxyl value of (meth) acrylic acid alkyl ester copolymer: 145.1] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup 3 was about 13%, and the weight average molecular weight was about 1.5 million.

(Preparation of UV curable flame retardant adhesive composition 4)
Acrylic syrup 4 was used, and the amount of flame retardant ammonium polyphosphate was changed to 40 parts, and 5 parts of terpene phenol resin (trade name YS Polystar N-125, manufactured by Yashara Chemical Co., Ltd.) was added as a tackifier. Except for the above, a UV curable flame retardant adhesive composition 4 was obtained in the same manner as in the UV curable flame retardant adhesive composition 2 of Example 2.

(Preparation of flame retardant double-sided pressure-sensitive adhesive sheet 4)
A flame-retardant double-sided pressure-sensitive adhesive sheet 4 was obtained in the same manner as the pressure-sensitive adhesive sheet 2 of Example 2 except that the UV curable flame-retardant pressure-sensitive adhesive composition 4 was used.

<Example 5>
(Preparation of acrylic syrup 5)
Acrylic syrup 5 [(meth) acrylic acid alkyl ester in the same manner as acrylic syrup 2 of Example 2 except that the amount of 2-ethylhexyl acrylate was changed to 40 parts and the amount of 2-hydroxyethyl acrylate was changed to 50 parts. The theoretical hydroxyl value of the copolymer: 241.8] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup 5 was about 10%, and the weight average molecular weight was about 1.3 million.

(Preparation of UV curable flame retardant adhesive composition 5)
The UV curable flame retardant 5 is the same as the UV curable flame retardant adhesive composition 2 of Example 2 except that the acrylic syrup 5 is used and the amount of ammonium polyphosphate, which is a flame retardant, is changed to 30 parts. A flammable pressure-sensitive adhesive composition 5 was obtained.

(Preparation of flame retardant double-sided pressure-sensitive adhesive sheet 5)
A flame-retardant double-sided pressure-sensitive adhesive sheet 5 was obtained in the same manner as the pressure-sensitive adhesive sheet 2 of Example 2 except that the UV curable flame-retardant pressure-sensitive adhesive composition 5 was used.

<Example 6>
(Preparation of UV curable flame retardant adhesive composition 6)
Using acrylic syrup 3 of Example 3, and 25 parts of melamine phosphate (trade name MPP-B, manufactured by Sanwa Chemical Co., Ltd.), 25 parts of melamine sulfate (trade name Apion 901, manufactured by Sanwa Chemical Co., Ltd.) as a flame retardant UV curable type in the same manner as UV curable flame retardant adhesive composition 3 of Example 3, except that 10 parts of aromatic condensed phosphate ester (trade name PX200, manufactured by Daihachi Chemical Industry Co., Ltd.) was used. A flame retardant pressure-sensitive adhesive composition 6 was obtained.

(Preparation of adhesive sheet 6)
A flame-retardant double-sided pressure-sensitive adhesive sheet 6 was obtained in the same manner as the pressure-sensitive adhesive sheet 3 of Example 3 except that the UV curable flame-retardant pressure-sensitive adhesive composition 6 was used.

<Example 7>
(Preparation of UV-curable flame retardant heat conductive adhesive composition 7)
Using acrylic syrup 3 of Example 3, 100 parts of aluminum hydroxide having an average particle diameter of 15 μm (trade name B153, manufactured by Nippon Light Metal Co., Ltd.) and magnesium oxide having a volume average particle diameter of 40 to 70 μm (Ube Materials) as a heat conductive agent UV curable flame retardant heat conductive adhesive composition as in UV curable flame retardant adhesive composition 3 of Example 3 except that 50 parts by the company, trade name RF-98) was also added. Product 7 was obtained.

<Preparation of flame-retardant heat conductive double-sided pressure-sensitive adhesive sheet 7>
The UV curable acrylic pressure-sensitive adhesive composition 7 was coated on a 50 μm thick polyethylene terephthalate (PET) film whose surface was treated with a release agent so that the thickness after curing was 0.25 mm. It was covered with a PET film having a thickness of 50 μm and irradiated with ultraviolet rays to obtain a flame-retardant heat conductive double-sided pressure-sensitive adhesive sheet 7.

<Example 8>
(Preparation of UV curable flame retardant heat conductive adhesive composition 8)
Using acrylic syrup 4 of Example 4, 100 parts of aluminum hydroxide having an average particle size of 15 μm (trade name B153, manufactured by Nippon Light Metal Co., Ltd.) and magnesium oxide having a volume average particle size of 40 to 70 μm (Ube Materials) as a thermal conductive agent UV curable type of Example 4 except that 50 parts by trade name, RF-98), and 5 parts terpene phenol resin (trade name YS Polystar N-125, made by Yasuhara Chemical Co., Ltd.) were also added as a tackifier. In the same manner as the flame-retardant pressure-sensitive adhesive composition 4, a UV-curable flame-retardant heat conductive pressure-sensitive adhesive composition 8 was obtained.

(Production of flame-retardant heat conductive double-sided pressure-sensitive adhesive sheet 8)
A flame-retardant heat-conductive double-sided pressure-sensitive adhesive sheet 8 was obtained in the same manner as the pressure-sensitive adhesive sheet 7 of Example 7 except that the UV-curable flame-retardant heat-conductive pressure-sensitive adhesive composition 8 was used.

<Example 9>
(Synthesis of solvent-type acrylic adhesive 1)
In a reaction vessel equipped with a condenser, a stirrer, and a thermometer, 60 parts of 2-ethylhexyl acrylate, 10 parts of methyl acrylate, 30 parts of 2-hydroxyethyl acrylate, and 2,2′-azobis as a polymerization initiator 0.2 part of isobutyronitrile was dissolved in 100 parts of ethyl acetate. After nitrogen substitution, polymerization was carried out at 68 ° C. for 4 hours, and further 0.2 part of 2,2′-azobisisobutyronitrile was added and polymerization was carried out at 80 ° C. for 2 hours. The theoretical hydroxyl value of the (meth) acrylic acid alkyl ester copolymer: 145.1] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the solvent-type acrylic pressure-sensitive adhesive 1 was about 50%, and the weight average molecular weight was about 800,000.

(Preparation of solvent-type flame retardant pressure-sensitive adhesive composition 1)
For 100 parts of the solid content of the acrylic ester copolymer of the solvent-type acrylic pressure-sensitive adhesive 1, 50 parts of ammonium polyphosphate (made by Chisso, trade name Terrage C30) as a flame retardant, isocyanate curing agent (made by Nippon Polyurethane, (Product name Coronate L) 0.2 part and ethyl acetate as a diluting solvent were added and stirred uniformly to obtain a solvent-type flame retardant pressure-sensitive adhesive composition 1.

(Preparation of flame retardant double-sided PSA sheet 9)
The solvent-type flame retardant pressure-sensitive adhesive composition 1 was coated on release paper so that the thickness after drying was 65 μm, dried, and then rayon paper 14 g / m ² (MR base paper: manufactured by Miki Special Paper Co., Ltd.) It laminated on both surfaces and the flame-retardant double-sided adhesive sheet 9 was obtained.

<Comparative Example 1>
<Preparation of acrylic syrup C1>
Acrylic syrup C1 [(meth) acrylic acid alkyl ester in the same manner as acrylic syrup 2 of Example 2 except that the amount of 2-ethylhexyl acrylate was changed to 85 parts and the amount of 2-hydroxyethyl acrylate was changed to 5 parts. The theoretical hydroxyl value of the copolymer: 24.2] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup C1 was about 15%, and the weight average molecular weight was about 1.3 million.

(Preparation of UV curable flame retardant adhesive composition C1)
A UV curable flame retardant pressure sensitive adhesive composition C1 was obtained in the same manner as the UV curable flame retardant pressure sensitive adhesive composition 2 of Example 2 except that the acrylic syrup C1 was used.

(Production of double-sided PSA sheet C1)
A double-sided pressure-sensitive adhesive sheet C1 was obtained in the same manner as the pressure-sensitive adhesive sheet 2 of Example 2 except that the UV-curable flame-retardant pressure-sensitive adhesive composition C1 was used.

<Comparative example 2>
(Preparation of UV curable flame retardant adhesive composition C2)
Except for using the acrylic syrup C1 of Comparative Example 1 and changing the amount of ammonium polyphosphate, which is a flame retardant, to 100 parts, in the same manner as the UV curable flame retardant adhesive composition C1 of Comparative Example 1, A UV curable flame retardant pressure-sensitive adhesive composition C2 was obtained.

(Production of double-sided pressure-sensitive adhesive sheet C2)
A double-sided pressure-sensitive adhesive sheet C2 was obtained in the same manner as the pressure-sensitive adhesive sheet C1 of Comparative Example 1 except that the UV curable flame-retardant pressure-sensitive adhesive composition C2 was used.

<Comparative Example 3>
<Preparation of acrylic syrup C3>
Furthermore, acrylic syrup C3 [(meth) acrylic acid alkyl ester copolymer] was used in the same manner as acrylic syrup C1 of Comparative Example 1 except that 5 parts of acryloylmorpholine (trade name ACMO, manufactured by Kojin Co., Ltd.) was also used. Theoretical hydroxyl value: 24.2] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup C3 was about 15%, and the weight average molecular weight was about 1.3 million.

(Preparation of UV curable flame retardant adhesive composition C3)
A UV curable flame retardant adhesive composition C3 was obtained in the same manner as the UV curable flame retardant adhesive composition C1 of Comparative Example 1 except that the acrylic syrup C3 was used.

(Production of double-sided PSA sheet C3)
A double-sided pressure-sensitive adhesive sheet C3 was obtained in the same manner as the pressure-sensitive adhesive sheet C1 of Comparative Example 1 except that the UV-curable flame-retardant pressure-sensitive adhesive composition C3 was used.

<Comparative example 4>
(Preparation of acrylic syrup C4)
Acrylic syrup C4 [(meth) acrylic acid alkyl ester in the same manner as the acrylic syrup C1 of Comparative Example 1 except that the amount of 2-ethylhexyl acrylate was changed to 80 parts and the amount of 2-hydroxyethyl acrylate was changed to 10 parts. The theoretical hydroxyl value of the copolymer: 48.4] was obtained. The concentration of the (meth) acrylic acid alkyl ester copolymer in the acrylic syrup C4 was about 15%, and the weight average molecular weight was about 1.3 million.

(Preparation of UV curable flame retardant adhesive composition C4)
A UV curable flame retardant adhesive composition C4 was obtained in the same manner as the UV curable flame retardant adhesive composition C1 of Comparative Example 1 except that acrylic syrup C4 was used.

(Production of double-sided PSA sheet C4)
A double-sided pressure-sensitive adhesive sheet C4 was obtained in the same manner as the pressure-sensitive adhesive sheet C1 of Comparative Example 1 except that the UV-curable flame-retardant pressure-sensitive adhesive composition C4 was used.

<Comparative Example 5>
(Preparation of UV curable flame retardant adhesive composition C5)
Using acrylic syrup C4 of Comparative Example 4, and 25 parts of melamine phosphate (trade name MPP-B, manufactured by Sanwa Chemical Co., Ltd.), 25 parts of melamine sulfate (trade name: Apinone 901, manufactured by Sanwa Chemical Co., Ltd.) as a flame retardant A UV curable type is the same as the UV curable flame retardant adhesive composition C4 of Comparative Example 4 except that 10 parts of an aromatic condensed phosphate ester (trade name PX200, manufactured by Daihachi Chemical Industry Co., Ltd.) is used. Flame retardant adhesive composition C5 was obtained.

(Production of double-sided PSA sheet C5)
A double-sided pressure-sensitive adhesive sheet C5 was obtained in the same manner as the pressure-sensitive adhesive sheet C4 of Comparative Example 4 except that the UV curable flame-retardant pressure-sensitive adhesive composition C5 was used.

<Comparative Example 6>
(Preparation of UV curable flame retardant adhesive composition C6)
The UV curable type of Example 3 except that the acrylic syrup 3 of Example 3 was used and 150 parts of aluminum hydroxide (trade name B153, manufactured by Nippon Light Metal Co., Ltd.) was used instead of ammonium polyphosphate as a flame retardant. In the same manner as the flame-retardant pressure-sensitive adhesive composition 3, a UV-curable flame-retardant pressure-sensitive adhesive composition C6 was obtained.

(Production of double-sided PSA sheet C6)
A double-sided pressure-sensitive adhesive sheet C6 was obtained in the same manner as the pressure-sensitive adhesive sheet 3 of Example 3 except that the UV-curable flame-retardant pressure-sensitive adhesive composition C6 was used.

<Comparative Example 7>
(Preparation of UV-curable flame retardant heat conductive adhesive composition C7)
Using the acrylic syrup C1 of Comparative Example 1 and changing the amount of ammonium polyphosphate, which is a flame retardant, to 40 parts, and aluminum hydroxide having an average particle size of 15 μm as a thermal conductive agent (trade name B153, manufactured by Nippon Light Metal Co., Ltd.) The UV curable flame retardant pressure-sensitive adhesive composition of Example 5 except that 100 parts and 50 parts of magnesium oxide having a volume average particle size of 40 to 70 μm (trade name RF-98, manufactured by Ube Materials Co., Ltd.) were also added. In the same manner as in No. 3, a UV curable flame retardant heat conductive adhesive composition C7 was obtained.

(Production of double-sided PSA sheet C7)
A double-sided pressure-sensitive adhesive sheet C7 was obtained in the same manner as the pressure-sensitive adhesive sheet 7 of Example 7 except that the UV-curable flame-retardant heat conductive pressure-sensitive adhesive composition C7 was used.

<Comparative Example 8>
(Preparation of UV curable flame retardant heat conductive adhesive composition C8)
The acrylic syrup C3 of Comparative Example 3 was used, and the amount of the ammonium polyphosphate as a flame retardant was changed to 40 parts. Further, as a tackifier, 5 parts of a terpene phenol resin (trade name YS Polystar N-125, manufactured by Yashara Chemical Co., Ltd.) In addition, 100 parts of aluminum hydroxide having an average particle diameter of 15 μm (trade name B153, manufactured by Nippon Light Metal Co., Ltd.) and magnesium oxide having a volume average particle diameter of 40 to 70 μm (trade name, manufactured by Ube Materials Co., Ltd.) RF-98) A UV curable flame retardant thermally conductive adhesive composition C8 was obtained in the same manner as the UV curable flame retardant adhesive composition C3 of Comparative Example 3 except that 50 parts were also added. .

(Production of double-sided PSA sheet C8)
A double-sided pressure-sensitive adhesive sheet C8 was obtained in the same manner as the pressure-sensitive adhesive sheet C7 of Comparative Example 7, except that the UV-curable flame-retardant heat conductive pressure-sensitive adhesive composition C8 was used.

<Comparative Example 9>
(Preparation of UV-curable flame-retardant heat conductive adhesive composition C9)
The acrylic syrup C3 of Comparative Example 3 was used, and the amount of ammonium polyphosphate, which is a flame retardant, was changed to 40 parts, and aluminum hydroxide having an average particle size of 15 μm as a thermal conductive agent (trade name B153, manufactured by Nippon Light Metal Co., Ltd.) The UV curable flame retardant pressure-sensitive adhesive composition of Comparative Example 3 except that 100 parts and 50 parts of magnesium oxide having a volume average particle size of 40 to 70 μm (trade name RF-98, manufactured by Ube Materials Co., Ltd.) were also added. In the same manner as C3, UV curable flame retardant heat conductive adhesive composition C9 was obtained.

(Production of double-sided PSA sheet C9)
A double-sided pressure-sensitive adhesive sheet C9 was obtained in the same manner as the pressure-sensitive adhesive sheet C3 of Comparative Example 3, except that the UV-curable flame-retardant heat conductive pressure-sensitive adhesive composition C9 was used.

<Evaluation>
The above-described evaluation tests were performed on the above examples and comparative examples. The results are shown in Tables 1-3. The composition values in the table are based on mass%.

各表中の略号は以下の化合物を示す。
「２ＥＨＡ」：２−エチルヘキシルアクリレート、
「ＭＡ」：メチルアクリレート、
「４ＨＢＡ」：４−ヒドロキシブチルアクリレート、
「ＨＥＡ」：２−ヒドロキシエチルアクリレート、
「ＡＣＭＯ」：アクリロイルモルフォリン。

The abbreviations in each table indicate the following compounds.
“2EHA”: 2-ethylhexyl acrylate,
“MA”: methyl acrylate,
“4HBA”: 4-hydroxybutyl acrylate,
“HEA”: 2-hydroxyethyl acrylate,
“ACMO”: acryloylmorpholine.

  As is clear from the results in each table, in Examples 1 to 9, high flame retardancy and excellent adhesive strength (adhesiveness) were obtained. In Example 4, since the monomer (ACMO) which has polar groups other than a hydroxyl group and the tackifier (terpene phenol resin) were also added, adhesive force improved further. In Example 5, since the Tg of the copolymer is high as an adhesive, the adhesive force is slightly lower, but there is no drop due to L-type holding force indicating adhesiveness and fixing force, and there is a problem in practical characteristics There was no. In Examples 7 and 8, since heat conductive particles were also added, good heat conductivity was also imparted.

  On the other hand, in Comparative Example 1, since the theoretical hydroxyl value of the (meth) acrylic acid alkyl ester copolymer was too low, the flame retardancy was inferior. Further, the holding power was insufficient.

  In Comparative Example 2, the theoretical hydroxyl value was too low as in Comparative Example 1, so the amount of flame retardant (ammonium polyphosphate) was increased to 100 parts to compensate for this. As a result, the flame retardancy was slightly improved as compared with Comparative Example 1, but the flame retardancy (equivalent to V-2) was inferior to that of Examples 1-9 (equivalent to V-0). Moreover, the adhesive strength has been reduced by the increase in the amount of the flame retardant.

  In Comparative Example 3, the theoretical hydroxyl value was too low as in Comparative Example 1, and therefore a monomer (ACMO) having a polar group other than the hydroxyl group was also used to compensate for this. However, even when compared with Comparative Example 1, the flame retardancy did not improve. From this result, it was found that polar groups other than hydroxyl groups do not affect flame retardancy.

  In Comparative Example 4, the theoretical hydroxyl value was slightly increased as compared with Comparative Example 1. However, since this theoretical hydroxyl value is still too low, the flame retardancy has not improved.

  In Comparative Example 5, as in Comparative Example 1, the theoretical hydroxyl value was too low. To compensate for this, a melamine flame retardant and a phosphate ester flame retardant were used in combination. However, even when compared with Comparative Example 1, the flame retardancy did not improve. Moreover, the flame retardancy was far inferior to Example 6 which used the same flame retardant together.

  In Comparative Example 6, the theoretical hydroxyl value was appropriate, but no non-halogen flame retardant was used. Instead, a large amount of aluminum hydroxide was added. However, the flame retardancy (equivalent to V-2) was inferior to that of Examples 1-9 (equivalent to V-0). Moreover, the adhesive strength was reduced by the addition of a large amount of aluminum hydroxide.

  In Comparative Examples 7 to 9, since the theoretical hydroxyl value of the (meth) acrylic acid alkyl ester copolymer was too low, the flame retardancy was inferior. Further, the holding power was insufficient. In particular, in Comparative Example 8, a monomer having a polar group other than a hydroxyl group (ACMO) was also used, but flame retardancy was not improved. In Comparative Examples 8 and 9, the monomer compositions described in Examples of Patent Document 4 were referred to.

  As described above, the pressure-sensitive adhesive composition of the present invention using a (meth) acrylic acid alkyl ester copolymer having a specific theoretical hydroxyl value exhibits good flame retardancy even if the amount of the flame retardant is small. Moreover, also from the viewpoint of adhesive properties, the adhesive composition of the present invention exhibits excellent holding power due to high cohesive strength without the addition of acrylic acid, high Tg monomer and the like. As a result, the adhesion to the adherend is improved and the L-type holding force is also improved.

  As described above, the pressure-sensitive adhesive composition of the present invention having both high flame retardancy and excellent adhesiveness and optionally having thermal conductivity is used in applications requiring such performance, for example, electronic parts and home appliances. In particular, it is very useful as a joining member for bonding an electronic member and a heat dissipation member.

Claims (10)

A flame retardant pressure-sensitive adhesive composition comprising 100 parts by mass of a (meth) acrylic acid alkyl ester copolymer having a theoretical hydroxyl value of 70 to 250 and 30 to 60 parts by mass of a non-halogen flame retardant.   The flame retardant pressure-sensitive adhesive composition according to claim 1, wherein the non-halogen flame retardant comprises a phosphorus flame retardant, a melamine flame retardant, or a combination thereof.   The phosphorous flame retardant is at least one flame retardant selected from the group consisting of ammonium polyphosphate and phosphate esters, and the melamine flame retardant is selected from the group consisting of (poly) melamine phosphate and melamine sulfate The flame-retardant pressure-sensitive adhesive composition according to claim 2, which is one or more flame retardants.   The flame retardant pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylic acid alkyl ester copolymer has a hydroxyl group and a polar group other than a hydroxyl group.   The polar group other than the hydroxyl group is a polar group other than one or more hydroxyl groups selected from the group consisting of (meth) acrylamide, N-alkyl substituted (meth) acrylamide, N, N-dialkyl substituted (meth) acrylamide and acryloylmorpholine. The flame retardant pressure-sensitive adhesive composition according to claim 4, which is a polar group derived from a containing acrylic monomer.   Furthermore, the flame-retardant adhesive composition of Claim 1 containing a tackifier. The flame-retardant heat conductive adhesive composition which adds 100-300 mass parts of heat conductive particles with an average particle diameter of 1 micrometer- 100 micrometers further with respect to the flame-retardant adhesive composition of Claim 1.   8. The flame-retardant heat conduction according to claim 7, wherein the thermally conductive particles are particles made of one or more materials selected from the group consisting of metals, metal oxides, metal hydroxides, boron nitride, silicon nitride, and carbon nitride. Adhesive composition.   A pressure-sensitive adhesive sheet formed by forming a pressure-sensitive adhesive layer on one side or both sides of a substrate using the flame retardant pressure-sensitive adhesive composition according to claim 1.   A pressure-sensitive adhesive sheet formed by forming a pressure-sensitive adhesive layer on one side or both sides of a substrate using the flame-retardant heat conductive pressure-sensitive adhesive composition according to claim 7.