JP2008150550A - Adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition exhibiting strong adhesive strength even when a substrate is bent, not only causing no adhesive peeling of the substrate and no sealing defects such as cracks and gaps at sealed parts but also dispensing with a massive apparatus for processing. <P>SOLUTION: The adhesive composition is obtained by containing a polymer exhibiting rubber elasticity and a monofunctional acrylic (or methacrylic) monomer as principal constituents and a thermal radical generator. Preferably, it is used for manufacturing a flexible information display panel composed of flexible substrates bonded together. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention preferably relates to an adhesive composition that can be used as a sealant or an adhesive in the manufacture of flexible display panels.

  In recent years, the technology of thin information display panels has greatly advanced, and it is widely used as display panels for TVs, notebook computers, and mobile phones. The information display method is generally a method using liquid crystal, plasma, EL, etc. Recently, a charged particle in-air drive method, a charged particle electrophoresis method, and the like have been newly developed as a display method having a memory property. ing. In addition, as a recent large flow of thin information display panels, a flexible display that can be bent and is light and safe (not broken when dropped), so-called electronic paper, has attracted attention.

On the other hand, the adhesive plays an important role in the manufacture of such information display panels, such as adhesion of the substrate and moisture barrier by sealing the outer periphery of the display portion. Generally, a thermosetting one-component epoxy compound is widely used as a sealant for a display panel, particularly a sealant used for manufacturing a liquid crystal display (see, for example, Patent Document 1). Further, a sealing agent has been developed in which an acrylic polymerization monomer for shortening the curing time is mixed with a base polymer (epoxy acrylate or urethane acrylate) and cured with a photo radical generator (for example, Patent Document 2, Patent Document). 3). However, all of them are limited to information display panels made of rigid glass substrates, and there are no commercially available adhesives (or sealants) that are suitably used for information display panels made of flexible substrates. In addition, only a part of the patent document is disclosed (see Patent Document 4), and there are almost no examples.
JP 2000-347203 A Japanese Patent Laid-Open No. 7-13175 Japanese Patent No. 3162179 Japanese Patent Publication No. 6-90379

  Among the above-described prior arts, the example shown in Patent Document 1 has a problem that the epoxy material takes time for the curing reaction. They are hardened (formation of an excessive three-dimensional cross-linked structure) and are suitable for bonding to a glass substrate where the panel shape does not change, but for flexible displays made of film panels that undergo shape changes such as bending. As a sealing agent (or adhesive), there is a problem that the adhesive force is weak with respect to a bending shape change, and it is also weak against peeling. In addition, the example shown in Patent Document 2 or Patent Document 3 has a problem in that there is a restriction that it is necessary to install a large-scale ultraviolet light irradiation facility.

  The object of the present invention is not only to solve the above-mentioned problems, but to show a strong adhesive force even when the substrate is bent, and not only cause the substrate to peel off, but also cause a sealing failure such as a gap or a crack in the sealed portion. The present invention intends to provide an adhesive composition that does not require large-scale equipment for its construction.

  The adhesive composition of the present invention is characterized by comprising a polymer exhibiting rubber elasticity and a monofunctional acrylic (or methacrylic) monomer as a main component and a thermal radical generator.

  As a preferable example of the adhesive composition of the present invention, the monomer is 20 to 180 parts by weight with respect to 100 parts by weight of the polymer exhibiting rubber elasticity, and the polymer exhibiting rubber elasticity is butyl rubber, halogenated butyl rubber, It is an elastomer such as butadiene rubber, SBS (polystyrene = polybutadiene = polystyrene), SIS (polystyrene = polyisoprene = polystyrene), SEBS (polystyrene = poly (ethylene = butylene) = polystyrene), contains a crosslinking agent, silane It contains a coupling agent, is applied to a portion that requires flexibility, can be used for a flexible information display panel formed by bonding a flexible substrate, and at least one of two facing transparent sheets At least 1 in the space between the flexible substrates At least one type of display medium having optical reflectivity and chargeability composed of particles of at least one kind is encapsulated, and an electric field is applied to the display medium, whereby the display medium is moved to display information such as an image. It may be used for manufacturing information display panels.

  In the present invention, a composition comprising a polymer having rubber elasticity and a monofunctional acrylic (or methacrylic) monomer as a main component and a thermal radical generator is included, so that even when a flexible substrate is bent, strong adhesion is achieved. It is possible to obtain an adhesive composition that exhibits strength and does not cause adhesion peeling of the substrate or occurrence of sealing problems such as gaps and cracks in the sealed portion, and does not require extensive equipment for its construction.

  The adhesive composition of the present invention is suitable for bonding substrates of various information display panels, in particular, bonding of flexible information display panel substrates and sealing of the outer periphery of the display section. As an adherent portion, it can be suitably used not only for bonding flexible films as shown in FIG. 1 but also for a portion requiring flexibility, for example, bonding of a flexible film and a rigid partition wall.

  As an example of the information display panel, a charged particle driven flexible display panel is shown (FIG. 2). At least two or more kinds of display media 3 (here, white display medium 3W composed of particles of white display medium particles 3Wa and black display medium) which are composed of at least one kind of particles and have different optical reflectance and charging characteristics. In each cell formed with the partition walls 4, an electrode 5 (line electrode) provided on the flexible substrate 1 and an electrode 6 (line electrode) provided on the flexible substrate 2 are used to display a black display medium 3 </ b> B composed of particles of particles 3Ba. ) Between the substrates 1 and 2 according to the electric field generated by applying a voltage between them. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 2A, or white display is performed, or the black display medium 3B is visually recognized by the observer as shown in FIG. 2B. Are displayed in black. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted. Examples of the display medium include various display media such as a liquid crystal in which charged particles are enclosed in a microcapsule together with an insulating liquid in addition to the above-described charged particles, and the adhesive composition of the present invention may be any display. The present invention can also be applied to an information display panel using a medium.

  A feature of the present invention resides in an adhesive composition having a composition comprising a polymer having rubber elasticity and a monofunctional acrylic (or methacrylic) monomer as a main component and a thermal radical generator. In particular, in the production of information display panels having various configurations, as shown in FIG. 1, the adhesive composition of FIG. 1 is bonded between flexible upper and lower substrates, bonded between a flexible substrate and a rigid partition, and information display. It can be suitably used for a seal around the part.

  The adhesive composition of the present invention uses a monofunctional acrylic (or methacrylic) monomer as a polymerization monomer, thereby reducing the crosslink density of the cured product as compared with an epoxy adhesive. In addition, by using a polymer exhibiting rubber elasticity as a base polymer, a compound exhibiting strong adhesive strength against bending and peeling deformation of the substrate after bonding is obtained. Furthermore, by applying a polymerization reaction of olefin by thermal radical reaction, the curing time is shortened and the storage stability is improved as compared with the epoxy material.

  In the adhesive composition of the present invention, natural rubber or synthetic rubber such as butyl rubber, halogenated butyl rubber, butadiene rubber, SBS, SIS, SEBS, etc. can be applied as the base polymer having rubber elasticity. The molecular weight can be widely applied from oligomers of about 1000 to polymers of 1 million or more. As the monomer, various acrylic acid or methacrylic acid esters are used, and as the substituent, linear groups such as methyl group, ethyl group, butyl group, hexyl group, octyl group, decyl group, undecyl group, tetradecyl group, octadecyl group, etc. An alkyl group, one having a branched structure such as an isobutyl group or isopropyl group, and an alicyclic derivative such as a cyclohexyl group can be applied. An acrylate (or methacrylate) substituted with a benzyl group or a 2-hydroxyethyl group is not compatible with the above-mentioned base polymer alone and is difficult to handle. As for composition, it is desirable that a monomer is 20-180 weight part with respect to 100 weight part of base polymers. A bifunctional or polyfunctional monomer alone is not compatible with the above-mentioned base polymer, but can be used as a crosslinking agent for a monofunctional monomer compatible with the base polymer. If it is a polyfunctional monomer up to 5% by weight, it can be used up to about 5% by weight relative to the monofunctional monomer. As the crosslinking agent, a bifunctional or higher methacrylic (or acrylic) compound such as trimethylolpropane triacrylate or alkyldiol methacrylate can be used.

  In the adhesive composition of the present invention, a thermal radical generator (polymerization initiator) is added to the base polymer and monomer as main components, and a silane coupling agent is added as necessary.

  Here, as the thermal radical generator (polymerization initiator), thermo-cleavable peroxides such as benzoyl peroxide and t-butyl peroxyisopropyl monocarbonate can be applied, but storage stability and processing conditions are taken into consideration. Then, a one-hour half-life temperature of 70-100 degreeC is desirable. As the silane coupling agent, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and the like can be applied.

  The adhesive composition of the present invention can be adjusted in viscosity by appropriately mixing an organic solvent depending on the coating method. For example, when applying with a printing machine, it is used without a solvent, but when applying with a dispenser, it is necessary to lower the viscosity with a solvent. As the solvent, general-purpose organic solvents such as ethyl acetate, ethanol and toluene can be applied.

Hereinafter, an actual example will be described.

<Preparation of adhesive composition>
As polymers exhibiting rubber elasticity, butyl rubber 1 (average molecular weight 500,000), brominated butyl rubber 2 (average molecular weight 500,000), and SEBS 3 (average molecular weight 110,000) having the structure shown in the following chemical formula 1 are prepared, and monomers 2-ethylhexyl methacrylate 4, dodecyl methacrylate 5, benzyl methacrylate 6, glycidyl methacrylate 7, 2-hydroxy-3-phenoxypropyl acrylate 8, 2-methacryloyloxyethyl acid phosphate 9, and 2- Methacryloyloxyethylphthalic acid 10 is prepared, and 1,9-nonanediol diacrylate 11 and trimethylolpropane triacrylate 12 having the structure shown in the following chemical formula 3 are used as a crosslinking agent as a thermal radical generator (polymerization initiator). , Benzoyl peroxide 13 shown in Chemical formula 4 (1 hour half-life temperature 90 °) was prepared 3-methacryloyloxy trimethoxysilane 14 as the silane coupling agent. These were mixed by the compounding ratio shown in the following Tables 1 to 3, and the compound No. 1-1-No. A formulation of 3-10 was obtained. As a comparative example, polymethyl methacrylate 15 which is a polymer that does not exhibit rubber elasticity at room temperature and a commercially available one-part epoxy adhesive (a sealing agent for liquid crystal displays comprising an epoxy oligomer and a latent curing agent) Got ready. The formulation and results are shown in Table 1.

<Evaluation of adhesive composition>
Regarding the performance evaluation of the prepared blend, the adhesive strength to the plastic substrate, the moisture barrier property of the blend, the elastic modulus, and the strength at the time of preparing the flexible panel were examined.

  The adhesive strength was evaluated by a 180 ° peel test on the film substrate. A schematic diagram of the peel test is shown in FIG. The test piece was prepared by applying the composition on a film having a thickness of 125 mm and then heating and pressing (100 ° C., 1 hour) with the counter film while keeping the gap at 40 mm. The bonded film was cut into a width of 1 cm, and the upper and lower ends of the film were pulled at a rate of 5 cm / min by an autograph, and the average value of the stress was defined as the adhesive strength. Various plastic films such as polyethylene terephthalate (PET), polyethylene sulfate (PES), and coating (PC) can be applied to the film substrate. The results with PET films are shown in Tables 1 to 3.

  The moisture barrier property was measured by the MOCON method (conditions: 40 ° C., 90%) after film formation of the compound by a casting method (thickness of about 100 μm), after heating and curing (100 ° C., 1 hour).

  The elastic modulus was examined with a rheometer.

  The compatibility of the blend as a sealant and adhesive for flexible displays was evaluated by a repeated bending test as shown in FIG. In FIG. 4 (a), assuming a sealing agent, a sample is applied to a PET film substrate having a thickness of 125 mm as shown in FIG. And the gap between the film substrates was 40 mm). The produced overlapping panel was subjected to a bending tester and tested, and the number of bending tests until the film substrate and the adhesive were peeled was examined. Further, the adhesive force between the rigid wall space (thickness: 40 μm) and the flexible substrate was examined by a similar bending test in the empty panel with a partition wall that was not filled with the display medium having the configuration shown in FIG.

  From the results shown in Table 1, it was found that the adhesive strength was greatly increased by mixing the monofunctional monomer 4 in both the butyl rubber system and the SEBS system. Butyl rubber 1 alone (Table 1; Formulation No. 1-1) showed only an adhesive strength of 70 N / m, whereas as the monomer 4 was mixed, the adhesive strength increased and 1.4 times the weight was mixed. In the blends (Table 1; blend No. 1-5), 370 N / m and an adhesive force of 5 times or more were obtained. Also in the SEBS system, the adhesive strength by itself (150 N / m, formulation No. 1-7) was greatly increased by mixing the monomers (˜410 N.m, formulation No. 1-8 to No. 1). -11). In contrast, polymethyl methacrylate (PMMA) 15 (comparative example), which does not exhibit rubber elasticity in this test environment (room temperature), has a very weak single adhesive force, and even when a monomer is mixed, the adhesive strength to the film substrate is low. Little improvement was observed (Formulations No. 1-13 and No. 1-14). Furthermore, it was found that a commercially available epoxy adhesive (sealant for liquid crystal display) also had very weak peel adhesion to the film substrate (Table 1). This suggests that the elasticity of the rubbery polymer and the tackiness of the acrylic polymer play an important role in the adhesion of the film substrate. In particular, the elastic modulus of the cured product is considered to be important, and PMMA, which is a solid polymer, and commercially available epoxy adhesives are very hard materials, each having an elastic modulus on the order of 10 to the 9th power at room temperature. On the other hand (Table 1), the adhesive composition of the present invention is an extremely soft material having a modulus of elasticity at room temperature after curing, on the order of 10 5, and this characteristic disperses the stress generated when the film peels. It is thought that it absorbs (Table 1).

  When the compounding quantity of the monomer with respect to the base polymer was increased too much, it adversely affected the adhesive force (formulation No. 1-6, No. 1-12). The amount of monomer added is suitably 20 to 180 parts by weight per 100 parts by weight of the base polymer.

Regarding the moisture barrier property, the barrier property obtained with the base polymer alone was maintained even after mixing and curing of the monomers (Table 1). In particular butyl rubber, 8~9g ^/ m 2 · day and a commercially available epoxy adhesive is a sealant for a liquid crystal display ^(13g / m 2 · day) superior performance was observed. The present invention is a material having a very high barrier property as an organic adhesive compound, and is very useful as a sealant for a display.

  Table 2 shows the results of mixing various monofunctional monomers with the base polymer 2. When mixed at the blending ratio (base polymer: monofunctional monomer = 100: 140) at which the best adhesive strength was obtained in Table 1, monomers 4 and 5 substituted with aliphatic alkyl groups were base polymer 2 The benzene ring derivative 6 with stronger cohesion between monomers and polar sites in the molecule, while having a suitable adhesive strength (composition No. 2-1, No. 2-2) 7, 8, 9 and 10 having a ratio were not uniformly compatible with the base polymer. However, in Table 2, the formulation No. 2-8-No. As shown in 2-12, when a small amount of 7 to 10 was added to a monomer (here, 4) that is compatible with the base polymer using the monomer as a two-component system, a uniform mixture was obtained. In particular, in the case of a monomer having a higher polarity phosphate group or carboxyl group, it was found that it works favorably with respect to adhesive strength (No. 2-11, No. 2-12). Furthermore, the same tendency was observed when the monofunctional monomer was composed of three or more components.

  The effect of the crosslinking agent on the adhesive formulation is shown in Table 3. Regarding bifunctional 11 and trifunctional 12 alone, they are not compatible with the base polymer alone, but when added to the monofunctional monomer 4, the bifunctional crosslinker 11 is up to the same amount as the base polymer. The functional crosslinking agent 12 was compatible up to 5 parts by weight. In particular, Formulation No. 2 to which a bifunctional crosslinking agent was added. 3-1. In 3-4, the remarkable improvement of the adhesive force was observed. On the other hand, in the case of the trifunctional cross-linking agent, an effect was seen if it was added in a small amount (Compound No. 3-7), but when it was added in an amount of 3 parts by weight or more, the adhesive strength was greatly reduced (Compound No. 3-8, No. 3-9). Further, the elastic modulus increased about 10 times by mixing the cross-linking agent, but it is still sufficiently soft as compared with the solid polymer (formulation No. 1-13 and the sealing agent for liquid crystal display).

  The cure behavior of the formulation was confirmed by elastic modulus measurement. Formulation no. The measurement results of 3-7 are shown in FIG. An increase in elastic modulus was observed around 10 minutes after reaching 100 ° C., and it was found that the polymerization was almost completed in about 40 minutes. Also, the formulation No. Table 4 shows the results of 3-7 adhesion force acceleration test (reliability evaluation). The measurement was carried out after being placed in a thermostat having a temperature of 60 ° C. and a humidity of 90% for a predetermined time, and then allowed to stand in an environment of a temperature of 25 ° C. and a humidity of 50% for one day. Results, formulation no. 3-7 maintained the initial adhesive force even after 1000 hours, and was found to have high reliability.

  In order to examine the applicability to the sealing agent (or adhesive) for flexible displays of the present invention, a repeated bending test as shown in FIG. 5 was performed. In the system shown in FIG. 5 (a), the epoxy adhesive marketed as a sealant for liquid crystal displays has peeled off the upper and lower films after being bent about 50 times, whereas the adhesive composition of the present invention. For example, formulation no. In 3-7, the initial adhesive form was maintained without being peeled at all even after bending of 50,000 times or more. Even in the system of FIG. 5 (b), the adhesive composition of the present invention exhibited a bending durability of tens of thousands of times.

  The adhesive composition of the present invention is suitable for panel type products such as flexible display panels configured by bonding flexible plate materials, and products configured by bonding rigid objects on flexible plate materials. Used for.

It is a figure which shows an example of the application part in the information display panel of the adhesive composition of this invention. (A), (b) is a figure which shows an example of the panel for information displays using the adhesive composition of this invention, respectively. It is a schematic diagram for demonstrating a peel test. Formulation No. in Examples It is a graph which shows the hardening behavior of 3-7. (A), (b) is a schematic diagram for demonstrating the repeated bending test in an Example, respectively.

Explanation of symbols

1, 2 Flexible substrate 3 Display medium 3W White display medium 3Wa White particles for display 3B Black display medium 3Ba Black particles for display 4 Bulkhead 5, 6 Electrode

Claims (8)

An adhesive composition comprising a polymer having rubber elasticity and a monofunctional acrylic (or methacrylic) monomer as a main component and a thermal radical generator. The adhesive composition according to claim 1, wherein the monomer is 20 to 180 parts by weight with respect to 100 parts by weight of the polymer exhibiting rubber elasticity. Polymers exhibiting rubber elasticity are butyl rubber, halogenated butyl rubber, butadiene rubber, SBS (polystyrene = polybutadiene = polystyrene), SIS (polystyrene = polyisoprene = polystyrene), SEBS (polystyrene = poly (ethylene = butylene) = polystyrene), etc. The adhesive composition according to claim 1, wherein the adhesive composition is a synthetic rubber.   The adhesive composition according to any one of claims 1 to 3, further comprising a crosslinking agent.   A silane coupling agent is contained, The adhesive composition of any one of Claims 1-4 characterized by the above-mentioned.   The adhesive composition according to claim 1, wherein the adhesive composition is applied to a portion requiring flexibility.   The adhesive composition according to any one of claims 1 to 6, wherein the adhesive composition can be used for a flexible information display panel formed by bonding a flexible substrate.   At least one or more display media having optical reflectivity and chargeability composed of at least one kind of particles are sealed in a space between two opposing flexible substrates, at least one of which is transparent. The adhesive composition according to any one of claims 1 to 7, wherein the adhesive composition is used for manufacturing an information display panel that displays information such as an image by moving a display medium by applying an electric field. .

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