JP2000119624A - Thermally active adhesive composition and film adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermally active adhesive composition which is useful for forming a film adhesive having a substantially nonsticky surface by compounding a sticky polymer containing a polymer having hydroxyl and phenyl groups with a polyester. SOLUTION: An example of the sticky polymer containing a polymer having hydroxyl and phenyl groups is an acrylic copolymer obtained from a phenoxyalkyl acrylate (e.g. phenoxyethyl acrylate) and a monomer having a hydroxyl group (e.g. 2-hydroxy-3-phenoxypropyl acrylate). A preferable polyester is polycaprolactone. The content of the polyester is preferably 5-50 wt.% based on the adhesive composition; and that of the sticky polymer is preferably 50-95 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-active adhesive composition and a film adhesive capable of forming a film adhesive having a surface having substantially no tackiness.

[0002]

2. Description of the Related Art An adhesive containing a tacky polymer as a main component is also called a pressure-sensitive adhesive (adhesive), and can be easily and strongly bonded only by applying pressure. However, due to the adhesiveness, workability such as punching is poor, and alignment is difficult.

[0003] Therefore, a number of techniques have been proposed for controlling the adhesiveness of an adhesive film (having an adhesive layer made of an adhesive). For example, a method of reducing the apparent tackiness by embossing the tacky surface by embossing, and smoothing by heating to increase the adhesive strength (JP-A-4-309)
No. 583 and the like. ). That is, during processing or alignment, the adhesive surface is maintained in an uneven state having a low adhesive force to the adherend, and at the stage of completing the adhesion, the adhesive surface is smoothed to increase the adhesive force.

[0004] Further, as an adhesive film having an adhesive layer containing a crystalline component, International Publication No. WO97 / 46.
No. 633 is disclosed. In the adhesive layer of the adhesive film, a crystalline acrylate component is introduced as a continuous phase into the adhesive polymer. Even with this adhesive layer, it is relatively difficult to completely eliminate the adhesiveness without reducing the adhesive strength, and the adhesive surface (adhesive surface) usually has adhesiveness. Therefore, by making use of the shape memory property and changing the adhesive face having the irregularities as the secondary shape to the smooth adhesive face which is the memory shape (primary shape), the workability and the position can be improved in the same manner as described above. Easy to match.

However, these adhesive films cannot form a film adhesive having a smooth adhesive surface from the stage of processing and alignment (initial stage). When the adhesive surface has tackiness and has a concavo-convex structure, it is difficult to remove dust attached during processing or alignment. In addition, a special liner (such as one having a concave-convex structure on the peeling surface) is required to reliably protect such an uneven adhesive surface, and there has been a difficulty in economy. Further, the Tg of the adhesive polymer itself is relatively low, and the heat resistance is also low.

On the other hand, a so-called heat-active adhesive which develops or increases tackiness by heating is also known. The heat activated adhesive is also called a hot melt film adhesive or a heat sensitive adhesive. It is also known to combine an adhesive polymer and a thermoplastic resin in order to increase the adhesive strength.

[0007] The thermoplastic resin used in the heat-activated adhesive is diversified. For example, polyester can be used. For example, Japanese Patent Publication No. 56-501131 discloses that
A heat activated adhesive composition having improved heat resistance is disclosed as follows. That is, (i) about 100 parts by weight of a thermoplastic polymer, and (ii) a cross-linking agent (cross-linking agent).
And (iii) about 1 to 100 parts by weight of an organic polymer having a plurality of functional groups available for performing a cross-linking reaction with the cross-linking agent. As the thermoplastic polymer, polyester, polyurethane or the like can be used, and as the organic polymer, polyalcohols or polyamines can be used. Further, diisocyanate or polyisocyanate can be used as the cross-linking agent. The heat-activated adhesive composition thus cross-linked is
Heat resistance can be effectively increased. In addition, such a heat-activated adhesive usually has no tackiness at room temperature,
Workability and ease of positioning can be improved. However, since the adhesive composition disclosed herein does not contain a tacky polymer, it is difficult to increase the adhesive strength.

On the other hand, JP-A-8-134428 discloses a hot melt adhesive composition containing a thermoplastic binder and a tacky polymer. This publication exemplifies polyester as a thermoplastic binder and isooctyl acrylate-acrylic acid copolymer as an adhesive polymer. In this composition,
The tacky polymer and the thermoplastic binder must be phase separated. The reason for this is to enhance the coating properties when applying the hot melt adhesive in a liquid state, and to maintain the tackiness for a relatively long time after coating (even after cooling and apparently solidifying). is there. That is, this composition is more suitable for use as an adhesive of the type that is liquefied than for use as a film adhesive whose adhesiveness is increased by heating.

JP-A-6-256746 and JP-A-5-256746
JP-A-339556 discloses a heat-active film adhesive formed from a composition containing an adhesive acrylic polymer, a phenoxy resin as a thermoplastic resin, an epoxy resin, and a crosslinking agent thereof. ing. It is considered that the adhesive acrylic polymer preferably has a carboxyl group, a hydroxyl group, or an epoxy group in the molecule.

[0010]

The film adhesive (film adhesive) used for electrical applications is usually used for positioning after punching and for bonding electronic parts and the like. The properties (adhesion at room temperature and about 25 ° C.) are preferably as low as possible, and those having substantially no tackiness are particularly preferable. In addition, since adhesives for electric use often require heat resistance, ordinary pressure-sensitive adhesives were not suitable for this use.

On the other hand, in the case of a combination of a usual adhesive polymer and a thermoplastic resin, it is inevitable that the adhesive surface of the film adhesive has adhesiveness. The film adhesive having an adhesive surface cannot solve the above-mentioned problem of the adhesive film. Further, it is difficult to increase the adhesive strength unless the tacky polymer is used effectively.

Accordingly, an object of the present invention is to form a film adhesive having substantially no tackiness (so-called “tack-free”) on the surface, and to solve the above-mentioned problem with the tacky film. Another object of the present invention is to provide a heat-activated adhesive composition which can easily increase the adhesive strength.

[0013]

According to the present invention, there is provided a heat-active adhesive composition comprising a tacky polymer and a polyester, wherein the tacky polymer has a hydroxyl group in the molecule. Provided is a heat-active adhesive composition, comprising a polymer having a group and a phenyl group.

The heat-activable adhesive composition of the present invention is characterized in that the tacky polymer used in combination with the polyester comprises a polymer having a hydroxyl group and a phenyl group in the molecule. Such a tacky polymer has high compatibility with the polyester, can substantially eliminate the tackiness of the adhesive composition at room temperature, and has higher heat resistance than a normal pressure-sensitive adhesive. On the other hand, since the adhesiveness is high when heated, the adherends can be adhered to each other with a high adhesive force by a heat-pressing operation.

The content of the polyester in the whole adhesive composition is usually 5 to 50% by weight, preferably 10 to 50% by weight.
~ 45% by weight. If the amount of polyester is too small, the tackiness of the adhesive composition at room temperature cannot be substantially eliminated. If the amount is too large, high adhesive strength may not be exhibited immediately after pressure bonding. On the other hand, the ratio of the adhesive polymer containing the above two functional groups (hydroxy group and phenyl group) to the whole adhesive composition is usually 50%.
It is at least 95% by weight, preferably 55 to 89% by weight.

The polyester is not particularly limited as long as it is substantially non-tacky at room temperature (about 25 ° C.) and has crystallinity that can be melted by heating. However, preference is given to polycaprolactone. Polycaprolactone refers to (i) a polyester obtained by polymerizing a starting material containing caprolactone, or (ii)
It is a polyester containing in its molecule a polymerized unit (unit) obtained by ring-opening polymerization of caprolactone. In the composition containing the above-mentioned adhesive polymer and polycaprolactone, the crystallization of polycaprolactone has little tackiness at normal temperature, but the polycaprolactone is melted by heating, and a strong adhesive force can be exhibited. Such an effect is particularly enhanced when the adhesive polymer having both a hydroxy group and a phenyl group in the molecule is an acrylic polymer. This is because the compatibility between such an acrylic polymer and polycaprolactone is specifically excellent.

The heat-active adhesive composition of the present invention preferably contains a crosslinking agent. Thereby, heat resistance required as an adhesive for electric use, particularly solder heat resistance, can be effectively improved.

The heat-active adhesive composition of the present invention can be used as an adhesive of the type which is liquefied by heating and used, but is used as a film adhesive which increases the adhesiveness of the bonding surface by heating. It is preferred to do so. That is, one embodiment of the present invention provides a film adhesive having the predetermined thickness, which is made of the heat-active adhesive composition. Such a film adhesive can substantially eliminate the tackiness at room temperature and has higher heat resistance than a normal pressure-sensitive adhesive. On the other hand, since the adhesiveness is high when heated, the adherends can be adhered to each other with a high adhesive force by a heat-pressing operation.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The tacky polymer used in the present invention is a polymer which exhibits tackiness at normal temperature (about 25 ° C.),
There is no particular limitation as long as it comprises a polymer having a hydroxyl group and a phenyl group in the molecule. For example, an acrylic polymer, a nitrile-butadiene-based copolymer (such as NBR), a styrene-butadiene-based copolymer (such as SBR), polyurethane, and a silicone-based polymer. The adhesive polymer is composed of one of these polymers alone or a mixture of two or more thereof.

The polymer containing the above functional group in the molecule can be obtained by polymerizing a starting material containing a monomer having a hydroxy group in the molecule and a monomer having a phenyl group in the molecule. . Alternatively, after the polymerization, another functional group (for example, a carboxyl group) in the molecule may be reacted to be converted into a hydroxy group and a phenyl group.

Here, a preferred example of the acrylic polymer that can be used in the present invention will be described. Starting materials containing (A) one or more phenoxyalkyl acrylates, (B) a monomer having a hydroxyl group in the molecule, and optionally (C) an alkyl (meth) acrylate as starting monomers, The usual way,
For example, it can be prepared by copolymerization by emulsion polymerization, solution polymerization, bulk polymerization, suspension polymerization and the like.

As the component (A), for example, phenoxyethyl acrylate, phenoxypropyl acrylate and the like can be used. Examples of the component (B) include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxymethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and hydroxy-3 -Phenoxypropyl acrylate and the like. Further, examples of the component (C) include n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and the like.

The component (B) includes hydroxy-3
Monomers containing both hydroxyl and phenyl groups in the molecule, such as phenoxypropyl acrylate, are preferred. This makes it possible to particularly effectively increase the compatibility of the adhesive polymer with the polyester.

Occupying the whole polymerized unit of the adhesive polymer,
A monomer unit containing the above two functional groups (ie,
The ratio (weight ratio) of the (units derived from the components (A) and (B)) is usually 70% by weight or more, preferably 80% by weight.
% By weight or more, particularly preferably 90% by weight or more. If the number of the units containing the above two functional groups is too small, the compatibility with the polyester may be reduced. The proportion of the unit derived from the component (B) in the polymerized units of the whole polymer is 0.5 mol% or more, preferably 1 mol% or more, and particularly preferably 5 to 15 mol%. If the number of units derived from the component (B) is too small, it may be disadvantageous to develop a sufficiently high adhesive force (for example, 0.5 kg / cm or more) immediately after the pressure bonding, and may be derived from the component (B). If there are too many units, the compatibility with the polyester may be reduced.

[0025] The adhesive polymer used in the present invention may be, in addition to the polymer containing the above two functional groups (hydroxy group and phenyl group), unless the effects of the present invention are impaired.
A polymer without the above two functional groups can also be included. However, the proportion of the polymer containing the above two functional groups (hydroxy group and phenyl group) in the whole adhesive polymer is usually 70% by weight or more, preferably 80% by weight or more.
% By weight or more, particularly preferably 90% by weight or more.

The molecular weight of the pressure-sensitive adhesive polymer may be within a range in which a predetermined adhesive force is exhibited, and is usually in the range of 10,000 to 100,000 in terms of weight average molecular weight.
Also, as with the conventional pressure-sensitive adhesive, a tackifier can be used together with the tacky polymer. In addition, as long as the effects of the present invention are not impaired, the adhesive polymer may be a crosslinkable polymer by heat or radiation (ultraviolet rays, electron beams, etc.). Crosslinking of the tacky polymer can be performed before or / and after adhesion to the adherend.

On the other hand, the molecular weight of the polyester may be within a range in which a predetermined adhesive force can be exhibited and the tackiness of the composition at room temperature can be substantially eliminated, and the weight average molecular weight is usually 500 to 200,000. , Usually 1,000-100,0
00 in the range. If the molecular weight is too small, the adhesive strength may be reduced.On the other hand, if the molecular weight is too large, the compatibility with the tacky polymer may be reduced, and it may be difficult to eliminate the tack at room temperature of the composition. .

The heat-active adhesive composition of the present invention can be prepared by mixing the respective raw materials uniformly by a usual mixing operation. For example, an adhesive polymer, polyester, a solvent, additives such as a crosslinking agent that is added as needed, a homomixer,
By mixing with a mixing device such as a planetary mixer and dissolving or dispersing each material uniformly, a liquid composition can be prepared.

This liquid composition is usually mixed with a first solution containing the above-mentioned adhesive polymer dissolved therein and a second solution containing the above-mentioned crystalline polymer dissolved therein. The precursor solution can be prepared by uniformly dissolving the reactive polymer, and the precursor solution can be dried to form a heat-active adhesive composition comprising a dried product of the precursor solution. In this manner, a unique morphology (interconnection structure) between crystalline polycaprolactone and an adhesive polymer having a hydroxy group and a phenyl group can be formed, and the above-described performance (non-adhesiveness at room temperature and High adhesion) can be exerted particularly effectively.
When a cross-linking agent is added, the third
The solution is added to the precursor solution.

The liquid composition prepared as described above is
It can be coated on a substrate and dried to form a film adhesive comprising the adhesive composition. Known means such as a knife coater, a roll coater, a die coater, and a bar coater can be used as the application means. As the base material, a releasable material such as a liner, an adherend to be bonded, a support for an adhesive sheet, and the like can be used. When a releasable material such as a liner is used, a film adhesive composed of the adhesive composition can be easily isolated and obtained.

The drying for forming the film adhesive is usually performed at a temperature of 60 to 180 ° C. The drying time is usually several tens of seconds to several minutes. The thickness of the film adhesive is 10 to 1,000 μm, preferably 20 to 500 μm.
m, particularly preferably 50 to 100 μm.

The film adhesive of the present invention can be used as an adhesive layer of an adhesive sheet. That is, the present invention provides an adhesive sheet having a support and an adhesive layer made of a heat-active adhesive composition fixed on one main surface of the support. The support is not particularly limited, but is usually used as a base film of a conventional adhesive sheet and has flexibility. For example, paper, metal film, plastic film and the like can be used. As the plastic, synthetic polymers such as polyimide, polyvinyl chloride, acrylic polymer, fluorine polymer, polyester (PET or the like), and polyurethane can be used.

The support may be one that transmits visible light or ultraviolet light, one that is colored, one that is decorated by printing or the like. Further, a metal-deposited film may be provided to give a metallic gloss appearance. Furthermore, in order to provide an optical function to the adhesive sheet, a polarizing film, a dielectric reflection film, a retroreflection film, a prism film, a fluorescent film, a film-like electroluminescence element, or the like can be used as a support. On the other hand, in order to increase the stain resistance of the support surface, a photocatalyst layer can be formed on the support surface. Further, the support may be composed of two or more different layers. The thickness of the support is usually 5 to 500 µm, preferably 10 to 300 µm. If the thickness is too small, the mechanical strength of the adhesive sheet is reduced, and the durability may be reduced. On the other hand, if the thickness is too large, the flexibility and the flexibility of the entire adhesive sheet are reduced, and the attaching work becomes difficult. Could be.

A primer layer may be provided on the side of the support on which the adhesive layer is to be formed. In general, a primer is prepared by preparing a coating solution containing a material to be a primer and applying the coating solution on one main surface of a support to form a primer layer.

The adhesive surface of the adhesive layer is usually protected by a liner. The liner is usually formed from a paper, a plastic film, or a film in which both are laminated.

Further, conventionally known additives can be added to the adhesive composition of the present invention as long as the effects of the present invention are not impaired. For example, viscosity control agents, defoaming agents, leveling agents, ultraviolet absorbers, antioxidants, pigments, fungicides, inorganic particles such as glass beads, elastic microspheres made of sticky polymers or non-sticky rubber-based polymers And so on.

As described above, the adhesive composition of the present invention preferably contains a crosslinking agent. The crosslinking agent can enhance the heat resistance of the adhesive composition. As the crosslinking agent, for example, an isocyanate compound, a melamine compound, an epoxy compound, a poly (meth) acrylate compound and the like can be used. The proportion of the crosslinking agent in the entire adhesive composition is usually 2
It is 0% by weight or less, preferably 0.2 to 10% by weight, particularly preferably 0.5 to 5% by weight. If too little crosslinking agent is used,
There is a possibility that the heat resistance cannot be increased, and if it is too large, the adhesive strength may be reduced.

The adhesive composition can be crosslinked before and / or after bonding to the adherend. However,
If the adhesive composition is cross-linked before being applied to the adherend, the adhesive composition must be heated so that it exhibits sufficient thermal tack. Further, the crosslinking of the adhesive composition,
Usually, it is carried out by crosslinking the adhesive polymer.

[0039]

EXAMPLES (Examples 1 to 10) First, an ethyl acetate solution containing a tacky polymer (nonvolatile content concentration = 30% by weight)
A precursor solution was formed by mixing with a toluene solution containing polycaprolactone (nonvolatile content: 30% by weight). This precursor solution was applied on a release film (PET film) and dried to form a film adhesive having a thickness of 70 μm on the release film. Table 1 shows the composition of the film adhesive. In Examples 5 to 8, a predetermined amount of the isocyanate-based crosslinking agent was added to the precursor solution, and the solution after the addition was applied and dried to form a film adhesive.

In the film adhesives of all the examples, 2
At 5 ° C., it was confirmed that it had no tackiness (by finger tack test). Also, the film adhesives of all examples were heat-activatable at 120 ° C.

The adhesive polymer in each of the examples is a monomer having a phenoxy group in the molecule (phenoxyethyl acrylate: "(product name)" manufactured by Osaka Organic Chemical Industry Co., Ltd.
Biscoat # 192 ") and a monomer having a phenoxy group and a hydroxy group in the molecule (2-hydroxy-3-
Phenoxypropyl acrylate: A starting monomer consisting of "(product name) Alonix M-5700" manufactured by Toa Gosei Chemical Industry Co., Ltd.) was prepared by solution polymerization in an ethyl acetate solvent. In each example, a monomer having a phenoxy group in the molecule (# 192) and a monomer having a phenoxy group and a hydroxy group in the molecule (M570)
0) was as shown below.

Comparative Example 1 On the other hand, a film adhesive of Comparative Example 1 was formed in the same manner as in Example 1 except that the adhesive polymer contained neither a phenoxy group nor a hydroxy group in the molecule. Table 1 shows the composition of the film adhesive. The film adhesive of Comparative Example 1 had tackiness (by finger tack test) at 25 ° C.

[Table 1] Composition Table Example 1 PS1 / PCL = 70/30 Example 2 PS2 / PCL = 70/30 Example 3 PS2 / PCL = 85/15 Example 4 PS2 / PCL = 55/45 Example Example 5 PS2 / PCL / L45 = 70/30 / 0.7 Example 6 PS2 / PCL / L45 = 70/30 / 1.5 Example 7 PS2 / PCL / L45 = 70/30 / 2.3 Example 8 PS2 / PCL / L45 = 70/30 / 4.5 Example 9 PS3 / PCL = 70/30 Example 10 PS4 / PCL = 70/30 Comparative Example 1 PS5 / PCL = 70/30 Note) All the above amounts Parts by weight. PCL: polycaprolactone, manufactured by Daicel Chemical Industries, Ltd. “(Product name) Praxel H7; molecular weight = 70,000” PS1: # 192: M5700 = 95: 5 (molar ratio) PS2: # 192: M5700 = 90: 10 (molar ratio) PS3: # 192: M5700 = 99: 1 (molar ratio) PS4: # 192: M5700 = 97: 3 (molar ratio) PS5: 2-ethylhexyl acrylate: acrylic acid = 90:10 (weight ratio) L45: isocyanate -Based cross-linking agent, Nippon Polyurethane Co., Ltd. “(Product name) Colonate”

The film adhesive of each example shown in Table 2 was sandwiched between two 25 μm polyimide films.
° C., and pressed for 1 minute at 5 kg / cm ^2, was evaluated the adhesion immediately after bonding. Table 2 shows the results. The adhesive strength is 50
It is a peeling speed in a peeling test in a direction of 180 ° in a peeling speed of mm / min.

[Table 2] Adhesive force (immediately after pressure bonding) # 192 / M5700 Adhesive force [kg / cm] Example 1 95/5 0.55 Example 2 90/10 0.57 Example 9 99/1 0. 21 Example 10 97/3 0.43 Comparative Example 1-> 0.1

Further, from these results, it was found that 0.1 mm was obtained immediately after crimping.
In order to obtain an adhesive force of 5 kg / cm or more, it was found that the content of the monomer unit having a phenyl group and a hydroxyl group in the adhesive polymer is preferably 5 mol% or more.

On the other hand, a film adhesive of each example shown in Table 3 was sandwiched between a 2 mm-thick polyetherimide plate and a 25 μm-thick polyimide film.
g / cm ² , pressure bonding for 1 minute, and heating (aging or post-curing) at 150 ° C. for 30 minutes were evaluated for adhesive strength. Table 3 shows the results. Further, the presence or absence of foaming when the film adhesive of each example was placed on a 260 ° C. solder bath for 1 minute was examined, and the solder heat resistance was evaluated. The case where there was no foaming was judged as "pass". Similarly, the results are shown in Table 3.

[Table 3] Adhesive force (post-cure after crimping) and solder heat resistance (260 ° C./1 minute) Adhesive force [kg / cm] Solder heat resistance Crosslinking agent parts by weight Example 2 2.0 Foaming 0 Example 3 1.3 With foaming 0 Example 4 2.0 With foaming 0 Example 5 2.2 Passed 0.7 Example 6 2.7 Passed 1.5 Example 7 1.8 Passed 2.3 Performed Example 8 1.6 Pass 4.5

From these results, in order to realize particularly good solder heat resistance (heat resistance test under relatively severe conditions of 260 ° C./1 minute), it is preferable to add a crosslinking agent. Do you get it.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jin Yamaguchi 3-8-8 Minamihashimoto, Sagamihara City, Kanagawa Prefecture Within Sumitomo 3M Limited (72) Inventor Akito Muramatsu 3-8-8 Minamihashimoto, Sagamihara City, Kanagawa Prefecture Sumitomo 3M shares In-house F-term (reference) 4J004 AA02 AA05 AA10 AA11 AA14 AA15 AB01 AB03 BA02 CA02 CA03 CA05 CA06 CA08 CB02 CC02 FA05 4J040 CA071 CA081 DF061 DF062 ED011 ED012 EF001 EK031 GA05 GA07 JA09 JB01 LA06

Claims (3)

[Claims] 1. A heat-active adhesive composition comprising an adhesive polymer and a polyester, wherein the adhesive polymer comprises a polymer having a hydroxyl group and a phenyl group in a molecule. A heat activated adhesive composition. 2. The heat activated adhesive composition according to claim 1, wherein said polyester is polycaprolactone. 3. A film adhesive comprising the heat-active adhesive composition according to claim 1.