JP5675975B2 - Adhesive composition and adhesive film - Google Patents

Description

  The present invention relates to an adhesive composition and an adhesive film. For example, the present invention relates to an adhesive composition and an adhesive film that are suitably used for connection between a signal drawing circuit of a touch panel and a flexible printed circuit board.

  An anisotropic conductive paste has been conventionally used for connection between a signal extraction circuit of a touch panel and a flexible printed circuit board. As for anisotropic conductive paste, improving the uniformity of film thickness has been a problem from the past, and nowadays, as the capacitance type touch panel is increasing, it is required to support connection to fine pitched parts. It has become to.

  As a conventional anisotropic conductive paste, a chloroprene type is generally used (for example, Patent Document 1). This type is tack-free and has the advantage that it can be stored at room temperature for a short period of time.

  However, due to recent environmental problems and increasing demands for safety, there is a strong demand for halogen-free adhesives. In addition, the conventional chloroprene type is not always satisfactory in terms of adhesive strength, long-term reliability, and workability depending on the application, and long-term reliability is particularly sufficient as an adhesive composition used for connecting substrates. There was a problem that could not be said.

  Therefore, the present inventors are a halogen-free anisotropic conductive paste having excellent adhesive strength, long-term reliability, workability, etc., and an adhesive composition that can be suitably used for connecting the above-described substrates. Have been proposed which comprises a polyetheresteramide and a styrene-isobutylene-styrene olefin elastomer (SIBS) (Patent Document 2).

  However, in recent years, electronic devices such as mobile phones have rapidly expanded in screen size, and accordingly, the bonding area connecting the signal drawing circuit of the touch panel and the flexible printed circuit board has been reduced. Nevertheless, since the adhesive is required to have the same or higher adhesiveness as before, there is an urgent need to further improve the adhesiveness of the adhesive.

  In addition, with the diversification of electronic products, the base materials and wiring materials of touch panels are diversified, and adhesives are required to be compatible with these various materials.

JP 2004-143219 A JP 2010-168510 A

  The present invention has been made in view of the above, and an object of the present invention is to provide an adhesive composition that is halogen-free and has improved adhesion to various materials and long-term reliability as compared with the prior art.

  As a result of intensive studies to solve the above problems, the present inventors have found that adhesion can be remarkably improved by adding a certain polyester resin based on a specific polyetheresteramide. The headline, the present invention has been completed.

  That is, the adhesive composition of the present invention contains 1 to 100 parts by weight of crystalline polyester and 20 to 110 parts by weight of silica with respect to 100 parts by weight of polyetheresteramide.

  The adhesive composition of the present invention may contain conductive particles. Metal conductive resin balls are preferably used as the conductive particles.

  In the adhesive composition of the present invention, the crystalline polyester has a molecular weight in the range of 10,000 to 35,000, a glass transition point in the range of −70 to 30 ° C., and a melting point in the range of 90 to 180 ° C. It is preferable to be within.

  The adhesive film of this invention shall consist of said adhesive composition.

  According to the present invention, it is possible to provide an adhesive composition that is halogen-free and has improved adhesiveness and long-term reliability as compared with conventional ones. In particular, the adhesion with nonpolar materials such as polyethylene terephthalate (hereinafter sometimes abbreviated as PET), which is a part of the touch panel substrate, can be greatly improved.

1 is a plan view showing a flexible printed circuit board (hereinafter sometimes abbreviated as FPC) 1 used in an embodiment of the present invention. It is a top view which shows the polymer thick film film (henceforth abbreviated as PTF) board | substrate 2 used in the Example of this invention. It is a top view which shows the connection position of the said FPC1 and PTF board | substrate 2 of the sample for a test. It is a top view which shows the measuring method of connection resistance. It is the perspective view and sectional drawing which show the test method of 90 degree | times peel strength.

  Hereinafter, the adhesive composition of the present invention will be described in detail.

  The polyether ester amide used in the present invention (hereinafter sometimes abbreviated as PEEA) has a melting point of 80 ° C. to 135 ° C. and a melt index of 5 g / 10 min to 100 g / 10 min (190 ° C., 21.18 N). And preferably soluble in a solvent. Conventionally, it has been difficult to form an elastomer film, but the use of a solvent-soluble type polyether ester amide makes it easy to form a thin film.

  As used herein, “elastomer” refers to a synthetic rubber material having thermoplasticity. Among these, it is preferable to use one having a structure composed of a hard segment having a large cohesive force and a flexible soft segment. The polyether ester amide has a structure in which a high melting point (Tm) polyamide is a hard segment and a low melting point or low glass transition point (Tg) polyether or polyester chain is a soft segment. Specific examples of PEEA hard segments include nylon 12 and nylon 6. Specific examples of the soft segment include aliphatic polyether or aliphatic polyester.

  PEEA is thought to contribute to the adhesion of polyimide, nickel-gold plated copper foil, ITO (indium tin oxide), silver paste, etc. of the touch panel.

  As described above, PEEA is preferably soluble in a solvent, but more specifically, PEEA is preferably soluble in an amine solvent, an alcohol solvent, or a ketone solvent.

  Amine solvents include diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, diisopropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, dibutylamine, diisobutylamine, tributylamine, pentylamine, dipentylamine , Tripentylamine, 2-ethylhexylamine, allylamine, aniline, N-methylaniline, ethylenediamine, propylenediamine, diethylenetriamine, formamide, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N -Methylacetamide, N, N-dimethylacetamide, N-methylpropionamide, 2-pyrrolidone, N-methyl Pyrrolidone, .epsilon.-caprolactam, carbamic acid ester and the like.

  Examples of the alcohol solvent include methanol, ethanol, isopropyl alcohol (IPA), and benzyl alcohol.

  Examples of ketone solvents include acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, methyl isobutyl ketone, 2-heptanone, 4-heptanone, diisobutyl ketone, acetonyl acetone, mesityl oxide, phorone, isophorone, cyclohexanone. And methylcyclohexanone.

As the polyether ester amide, those into which a functional group such as —NH ₂ or —COOH is introduced can be suitably used. By introducing an appropriate functional group according to the object to be bonded such as metal or resin, the adhesion can be further improved. In that case, it is desirable that the amine value is 20 or less and the acid value is 20 or less. If more functional groups are introduced, there is a risk of causing problems such as a decrease in peel strength and connection reliability in a moisture-resistant environment.

  Although PEEA can be manufactured by a well-known method, what is marketed can also be utilized. For example, TPAE series (solvent soluble grade, polyetheresteramide type) manufactured by T & K TOKA Co., Ltd. can be used. Among them, TPAE series TPAE-12, TPAE-31, TPAE-32, TPAE-826, PA-200, PA-201 and the like can be selected and used suitably. These polyether ester amides can be used in a blend of two or more.

  The adhesive composition of the present invention contains a predetermined amount of crystalline polyester. “Crystalline polyester” generally means a polyester having a melting point of 80 ° C. or higher. In the present invention, “crystalline polyester is soluble in a solvent and is gelled at room temperature (25 ° C.) in a state dissolved in a solvent. And a polyester that becomes liquid at 70 ° C. or higher ”. The crystalline polyester used in the present invention preferably has a number average molecular weight (Mn) of 10,000 to 35,000, a glass transition point (Tg) of preferably −70 to 30 ° C., and a melting point of 90 to 180. It is preferable that it is ° C. By using such crystalline polyester, it is possible to improve adhesion with a non-polar material such as PET which is a substrate material of the touch panel. It is also possible to improve the thixotropy of the adhesive composition and prevent the generation of bubbles during printing and coating operations.

  Examples of usable crystalline polyesters include acrylic / polyester hybrid curable resins, blocked isocyanate curable hydroxyl group-containing polyester resins, epoxy resin curable carboxyl group-containing polyester resins, and hydroxyalkylamide curable carboxyl group-containing polyester resins. Can be mentioned. These crystalline polyesters can also be produced by known methods, but commercially available ones can also be used. As a commercially available product, for example, DIC Corporation Fine Dick (registered trademark) series can be used. Among them, M-8010, M-8020, M-8021, M-8023, M-8076, M-8100, M-8230, M-8240, M-8250, M-8830, M-8842, M-8860, M-8630M-8961, M-8962, A-239-J, A-239-X, and M-8420 can be preferably used. Examples of the crystalline polyester include Byron (registered trademark) series GM-400, GM-415, GM-443, GM-480, GM-900, GM-913, GM-920, GM-925, and GM manufactured by Toyobo Co., Ltd. -990, GA-1200, GA-1300, GA-1310, GA-2310, GA-3200, GA-3410, GA-5300, GA-5310, GA-5410, GA-6300, GA-6400, 30P are used. be able to. Among these, GM-900, GM-913, GM-9200, and GA-5300 can be preferably used. In addition, as the crystalline polyester, Nichigo Polyester (registered trademark) series manufactured by Nippon Synthetic Chemical Industry Co., Ltd. can also be used. Among them, SP-180, SR-100, VR-300, HR-200, Z-1651ML. Z-1606ML can be preferably used.

  As for content of the said polyester resin, 1-100 weight part is preferable with respect to 100 weight part of polyetheresteramide. If the content is less than 1 part by weight, the effect of improving the adhesion cannot be obtained, and if it exceeds 100 parts by weight, the heat resistance may be lowered. The content is more preferably 2 parts by weight or more in consideration of the possibility of bubble generation during pressing, and more preferably 40 parts by weight or less in consideration of heat-resistant creep resistance.

  The method for blending the crystalline polyester is not particularly limited. For example, when the crystalline polyester is solid at room temperature, a method in which the crystalline polyester is dissolved in an appropriate solvent and mixed with PEEA can be used. As a solvent, the solvent which can dissolve PEEA mentioned above can be used. On the other hand, when it is liquid at normal temperature, it can be added and stirred as it is.

  The blended crystalline polyester is considered to contribute to improvement of thixotropy of the adhesive composition by forming a sea-island structure dispersed like a filler between PEEA molecules. Moreover, it is considered that it melts at the time of hot pressing and contributes to improvement in adhesion to PET or the like.

  The adhesive composition of the present invention further contains silica. By including a predetermined amount of silica, problems such as generation of bubbles during pressing can be solved. That is, when the melt viscosity of the PEEA resin is low, there are problems that the resin bleeds (resin flow) at the time of adhesion, and bubbles are generated at the time of printing, coating, and pressing. It is considered that these problems can be improved by adjusting the melt viscosity of the resin when an appropriate amount is used.

  As silica, for example, Admafine series from Admatechs Co., Ltd. and Aerosil (registered trademark) series from Nippon Aerosil Co., Ltd. can be used.

  The content of silica is preferably 20 to 110 parts by weight and more preferably 50 to 90 parts by weight with respect to 100 parts by weight of the polyetheresteramide. When the silica content is less than 20 parts by weight, the above-described bubble generation suppressing effect is insufficient, and when it exceeds 110 parts by weight, the heat aging resistance may be lowered.

  The adhesive composition of the present invention can be made into a conductive paste having anisotropic conductivity by adding conductive particles. As the conductive particles, metal-coated resin balls are preferably used.

  The metal-coated resin ball is obtained by applying a metal coating to the surface of a spherical resin, and in particular, a core portion made of polymethyl methacrylate (PMMA) and gold-coated through a nickel coating is preferably used. . Compared with metal powder, the metal-coated resin ball has an advantage that the particle size distribution is remarkably narrow and the core part is resin, so that it has elasticity and it is difficult to break glass and ITO that are in contact with it. Moreover, since specific gravity is small compared with metal powder, it also has the advantage that precipitation in a composition does not occur easily.

  Metal coated resin balls having various particle diameters can be used, but in the present invention, those having an average particle diameter of about 1 to 50 μm are usually used, and those having an average particle diameter of 10 to 35 μm can be suitably used. .

  In addition to the above metal-coated resin balls, the conductive particles include metal powders such as copper, silver, lead, zinc, iron and nickel, and inorganic powders such as these metal powders and glass powders, nickel, gold, silver, Particles plated with copper or the like can also be used. The shape of these conductive particles is not particularly limited, and any shape such as a spherical shape, a scale shape, a potato shape, a needle shape, or an indefinite shape can be used. preferable. The size is preferably in the range of an average particle size of 1 to 50 μm.

  The content of the conductive particles depends on the use of the adhesive composition, but usually it is preferably in the range of 1 to 100 parts by weight with respect to 100 parts by weight of the total resin solid content in the adhesive composition. .

  It is preferable to add a silane coupling agent to the silica and conductive particles. It is considered that the silane coupling agent has a reactive functional group and a hydrolyzable group (OR) and improves the dispersibility of the silica, thereby further improving the bubble generation suppression effect due to the silica blending. In addition, it is considered that the reactive functional group reacts with a resin component such as PEEA, and the hydrolyzable group is oriented on the surface of the conductive particles, thereby contributing to the suppression of bubble generation. When the silane coupling agent is used, the amount used is preferably 0.01 to 20% by weight with respect to silica or conductive particles.

  As a silane coupling agent, Shin-Etsu Silicone KBM-403 (Shin-Etsu Chemical Co., Ltd.) etc. can be used suitably by what is marketed.

  The adhesive composition of the present invention includes other components that may be used in the adhesive composition, that is, a tackifier, a stabilizer, an antioxidant, a reinforcing agent, a pigment, and an antifoaming agent. Etc. can be further added as needed.

  In order to obtain the adhesive composition of the present invention, for example, using a kneader such as a planetary kneader, a solvent may be added to the resin as a raw material, heated, and dissolved and mixed.

  Solvents used here include nitrogen or amide solvents such as N-methylpyrrolidone, hydrocarbon solvents such as hexane, heptane, decane, toluene, xylene, cyclohexane, benzyl alcohol, and solvent naphtha, and ketone solvents such as isophorone. Use ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate, ethyl cellosolve acetate, butyl cellosolve acetate, ether solvents such as ethyl cellosolve, butyl cellosolve, isopropyl cellosolve, t-butyl cellosolve, ethyl carbitol, butyl carbitol, etc. Can do.

  The amount of the solvent used is preferably in the range where the resin solid content concentration of the adhesive composition is 10 to 50% by weight. If the resin solid content concentration is less than 10% by weight, the coating thickness cannot be secured, and if it exceeds 50% by weight, the viscosity becomes too high and printing becomes difficult. Moreover, in the relationship with the said resin component, it is preferable that a solvent component exists in the range of 100-450 weight part with respect to 100 weight part of resin components.

  The adhesive film of the present invention can be obtained from any of the above-described adhesive compositions of the present invention.

  The method for obtaining an adhesive film from the above adhesive composition is not particularly limited, and the adhesive composition is applied on a support such as release paper to a predetermined thickness by various application methods and dried. Then, it can be obtained by peeling from the release paper or the like. Specifically, if necessary, an adhesive composition mixed with conductive particles is dissolved in an amine solvent or a ketone solvent to obtain a desired viscosity, and can be formed into a film by using a coating machine or the like. . The thickness of the adhesive film may be appropriately selected according to the use, but is usually about 10 to 50 μm.

  Moreover, when using the adhesive film of this invention, desired adhesive strength can be obtained by crimping | bonding for about 5 to 15 second at the temperature of 100-160 degreeC and the pressure of 1-4 MPa.

  According to the present invention, when a component is mounted on an FPC on a recent capacitive touch panel, the problem that paste printing after mounting is difficult is solved, and the connection material is transferred by transferring as a film type. It becomes possible to crimp on the touch panel.

  Examples of the present invention are shown below, but the present invention is not limited to the following examples.

[Examples 1-7, Comparative Examples 1-5]
The resin component and silica shown in Table 1 were blended and dispersed at the ratios (weight ratio, resin solid content conversion) shown in the table. Dispersion was performed by kneading for 3 hours using a planetary kneader at a heating temperature of 85 ° C. and a rotation speed of 50 rpm. Details of the resin components and silica shown in Table 1 are as follows.

PEEA: TPAE-32 (T & K TOKA Corporation)
Crystalline polyester: Byron GA-5300 (Toyobo Co., Ltd., Mn: 25000, glass transition point: -2 ° C, melting point: 114 ° C)
Polyurethane elastomer: Milactolan P485RSUI (Nippon Milactolan Co., Ltd.)
SIBS: Shibustar 103T (Kaneka Corporation)
Silica: Admafine SO-C2 (Admatechs Co., Ltd.)

The following components were added to and mixed with 100 parts by weight of the resin component (in terms of solid content) to prepare an adhesive composition.
Conductive particles: Metal-coated resin balls (core: PMMA, first layer: Ni, outermost layer: Au, average particle size 30 μm) 10 parts by weight Solvent: isophorone 300 parts by weight butyl cellosolve 50 parts by weight N-methylpyrrolidone 80 parts by weight Stabilizer: Irganox 1010 (Ciba Specialty Chemicals) 1.3 parts by weight

  About the obtained adhesive composition, connection resistance, 90 degree peel strength, and heat aging resistance were measured to evaluate the generation of bubbles during pressing. The measurement / evaluation method is as follows. The results are shown in Table 1.

  Samples for testing 90 degree peel strength, connection resistance, heat aging resistance, and heat creep are the flexible printed circuit board (FPC) 1 shown in FIG. 1 and the polymer thick film film (PTF) substrate shown in FIG. As shown in FIG. 3, 2 was connected by interposing an adhesive composition layer so that a part of the upper surface of the PTF substrate 2 was covered with the end portion of the FPC 1.

  For Examples 1, 2, 4, and 7 and Comparative Examples 2, 4, and 5, the paste-like adhesive composition was applied to a film thickness of 28 μm, and Examples 3, 5, 6, and Comparative Examples 1 and 3 were performed by press-bonding for 15 seconds at a pressure of 130 to 140 ° C. and a pressure of 3 MPa, with an adhesive composition previously formed into an adhesive film having a thickness of 28 μm.

<FPC: Nikkan Kogyo Co., Ltd.>
Composition: Polyimide 25 μm / Copper foil 18 μm
Electrode plating: Ni3μm / Au0.3μm
Pitch: 3mm
Electrode width (a): 10 mm
<PTF substrate>
Polymer: Polyethylene terephthalate (PET) 188 μm manufactured by Toray Industries, Inc.
Silver paste: about 10μm
* Resist coating on silver paste Pitch: 3mm

<Connection resistance>
As shown in FIG. 4, a low resistance meter (manufactured by HIOKI, DC method 3227 milliohm high tester) is used between FPC terminal terminals of FPC / PTF test samples, and ab, bc, cd The connection resistance between them was measured, and the average value was obtained.

<90 degree peel strength>
As shown in FIG. 5, the FPC / PTF test sample was peeled off at a tensile speed of 50 mm / min and a peeling direction of 90 degrees with a tensile testing machine (PT-200N manufactured by Minebea Co., Ltd.), and the maximum value at the time of breaking was determined. It was measured.

<Heat aging resistance>
As shown in FIG. 3, the FPC 1 and the PTF substrate 2 were connected and held at 80 ° C. for 1000 hours, and then the 90 ° peel strength was measured by the above method. If it is less than 5 N / cm, it shall be x, and if it is 5 N / cm or more, after further holding at 105 ° C. for 1000 hours, a 90 degree peel test is conducted in the same manner. If it was less than △, it was set as △.

<Heat resistant creep>
As shown in FIG. 3, the FPC 1 and the PTF substrate 2 connected are hung in an air oven, a weight of 600 g is attached to the FPC 1, and then heated at 1 ° C./90 seconds. Was measured for the temperature at which it separates at the bonding site. If it was 80 ° C. or higher, it was rated as “◯”, 60 ° C. or higher and lower than 80 ° C.

<Generation of bubbles during pressing>
188 μm PET is pasted on the circuit 4 of the flexible printed circuit board (FPC) 1 shown in FIG. 1, pressed at 150 ° C., and bubbles around the conductive particles are confirmed with an optical microscope from the PET surface side. If there was no problem in practical use, it was evaluated as △. If there was no problem in practical use, it was evaluated as △.

  The adhesive composition of the present invention is used for various applications such as connection of various substrates used in mobile phones, game machines, etc., that is, connection between a liquid crystal panel and a substrate, connection of a membrane switch, connection of terminals of an EL backlight, etc. Can be suitably used.

1 …… Flexible Printed Circuit Board (FPC)
2 ... Polymer thick film (PTF) substrate 3 ... Adhesive composition (paste or film)
4 …… Circuit

Claims (5)

  An adhesive composition comprising 1 to 100 parts by weight of crystalline polyester and 20 to 110 parts by weight of silica with respect to 100 parts by weight of polyetheresteramide.   The adhesive composition according to claim 1, further comprising conductive particles.   The adhesive composition according to claim 2, wherein the conductive particles are metal-coated resin balls.   The crystalline polyester has a number average molecular weight in the range of 10,000 to 35,000, a glass transition point in the range of −70 to 30 ° C., and a melting point in the range of 90 to 180 ° C. The adhesive composition according to any one of claims 1 to 3.   The adhesive film which consists of an adhesive composition of any one of Claims 1-4.

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