JP2010195971A - Self-adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self-adhesive sheet which is excellent in processing easiness and durability. <P>SOLUTION: A self-adhesive 7 constituting the self-adhesive sheet is charged in a gap between an image display module 4 and a surface protection plate 1 in an image display 11 and allows the image display module 4 and the surface protection plate 1 to adhere to each other. The self-adhesive 7 includes at least a cross-linking agent and an acrylic polymer obtained by copolymerizing two or more monomers, wherein at least one of the monomers is an acrylic acid ester having an aromatic ring. By using the self-adhesive 7 having such a constitution, it becomes possible to improve the durability of the image display 11. Further, it becomes possible to easily allow the image display module 4 and the surface protection plate 1 to adhere to each other, and the productivity of the image display device 11 is enhanced by using the self-adhesive 7 as the self-adhesive sheet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesive sheet. More specifically, the present invention relates to an adhesive sheet used to fill a gap between a surface protection plate of an image display device and an image display module.

  2. Description of the Related Art Conventionally, an image display device used for a mobile phone, a mobile terminal, a touch panel, or the like is configured by an image display module such as a liquid crystal module or electroluminescence, and a surface protection plate that protects the image display module. An air layer having a certain thickness is provided between the image display module and the surface protection plate. The air layer is provided for the purpose of preventing the impact from being directly transmitted to the image display module when the image display device receives some impact from the outside. For example, an air layer of about 0.5 mm is usually provided between the liquid crystal cell and the protective panel.

  When an air layer is provided between the surface protection plate and the image display module, light scattering due to a difference in refractive index between the surface protection plate and the air layer occurs, and the visibility of the image display device is lowered. On the other hand, a resin, a structure, and a device that improve optical characteristics by filling a resin or the like having an impact absorbing action and a refractive index equivalent to that of the surface protection plate instead of the air layer have been proposed. For example, there has been proposed an optical confusion prevention structure that fills a gap between a liquid crystal cell and a protective panel with a silicone gel that is cured by ultraviolet rays (see Patent Document 1). A display device in which a gap between the liquid crystal display panel and the touch panel on the surface layer is filled with a polymerizable resin composition has been proposed (see Patent Document 2). In addition, an image display device and a light-transmitting pressure-sensitive adhesive sheet in which a gel-like light-transmitting pressure-sensitive adhesive sheet such as silicone gel is disposed between a liquid crystal display panel and a transparent protective plate have been proposed (see Patent Document 3).

JP-A-6-337411 JP-A-2004-77887 JP 2006-290960 A

  However, in the structures and apparatuses described in Patent Document 1 and Patent Document 2, for example, a polymerizable resin composition in a liquid state is filled between a liquid crystal display panel and a transparent protective substrate, and then irradiated with light such as ultraviolet rays. The resin must be cured with Therefore, there is a problem that bubbles are mixed in the process of filling the polymerizable resin in a liquid state. In addition, there is a problem in that a difference in the degree of curing due to variations in light irradiation intensity occurs in the step of curing the polymerizable resin with light irradiation equipment. In addition, there is a problem in that yield is lowered due to distortion caused by volume shrinkage during resin curing.

  In addition, for example, the light-transmitting pressure-sensitive adhesive sheet described in Patent Document 3 has a function as an impact absorbing material, but bubbles are likely to be mixed at the time of bonding, even when autoclaving treatment by heating and pressurization is performed. However, there is a problem that bubbles in the printed step portion remain. In addition, there is a problem that floating and peeling are likely to occur in a high temperature and high humidity environment as compared with the polymerizable resin.

  The present invention has been made to solve the above-described problems, and when used in an application in which an air layer between a surface protection plate and an image display module is filled, the visibility and resistance of the image display device are improved. An object of the present invention is to provide a pressure-sensitive adhesive sheet having excellent properties in terms of impact, processability, stability, and durability.

In order to solve the above-mentioned problems, the pressure-sensitive adhesive sheet of the invention according to claim 1 is a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive containing at least a crosslinking agent and an acrylic polymer copolymerized with two or more monomers, 4. A pressure-sensitive adhesive sheet comprising a release sheet releasably attached to at least one surface of the pressure-sensitive adhesive layer, wherein the crosslinking agent is 0.1 parts by weight or more in solid content in the pressure-sensitive adhesive. Less than 0 part by weight, at least one of the monomers is an acrylate ester having an aromatic ring, and the adhesive has a storage elastic modulus at 25 ° C. of 9.0 × 10 ^{4 to} 2.0 × 10 ⁵ Pa. It is characterized by being.

  The pressure-sensitive adhesive sheet of the invention according to claim 2 is characterized in that, in addition to the structure of the invention of claim 1, the acrylic ester having an aromatic ring is phenoxyethyl acrylate.

  The pressure-sensitive adhesive sheet of the invention according to claim 3 is characterized in that, in addition to the structure of the invention according to claim 1 or 2, the thickness of the pressure-sensitive adhesive layer is 100 μm or more.

The pressure-sensitive adhesive sheet of the invention according to claim 1 includes a pressure-sensitive adhesive layer and a release sheet that is detachably attached to at least one surface of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive containing at least a crosslinking agent and an acrylic polymer obtained by copolymerization of two or more monomers (at least one acrylic ester having an aromatic ring). Further, the content of the crosslinking agent is less than 0.1 part by weight to 5.0 parts by weight, the storage elastic modulus and ^{9.0 × 10 4 ~2.0 × 10 5} Pa. Such an adhesive is excellent in impact resistance and durability. Therefore, the pressure-sensitive adhesive sheet in which this pressure-sensitive adhesive is used as a pressure-sensitive adhesive layer is used for the purpose of filling a gap provided between the image display module and the surface protection plate in the image display device. Protect the module. Further, the image display module and the surface protection plate are attached by an adhesive constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, and the gap between the image display module and the surface protection plate is filled. Therefore, it is possible to easily realize the adhesive processing between the image display module and the surface protection plate in the process of creating the image display device.

  In addition to the effect of the invention of claim 1, the pressure-sensitive adhesive sheet of the invention of claim 2 uses an image display module and a surface protection plate by using phenoxyethyl acrylate as an acrylic ester having an aromatic ring. When it is bonded between the two, it exhibits good shock absorption characteristics and durability. Accordingly, it is possible to improve durability in a high temperature and high humidity environment required as an image display device while protecting the image display module from external impacts.

  In the pressure-sensitive adhesive sheet of the invention according to claim 3, in addition to the effect of the invention according to claim 1 or 2, by setting the thickness of the pressure-sensitive adhesive layer to 100 μm or more, good shock absorption characteristics are obtained. It is done. At the same time, even if there is a step on the surface protection plate surface, it is possible to favorably adhere the surface protection plate and the image display module.

2 is a cross-sectional view showing a physical configuration of the pressure-sensitive adhesive sheet 10. FIG. 3 is a cross-sectional view showing a physical configuration of the image display device 11. FIG.

  Hereinafter, an adhesive sheet 10 according to an embodiment of the present invention will be described with reference to the drawings. These drawings are used to explain the technical features that can be adopted by the present invention, and the configuration of the apparatus described is limited to that unless otherwise specified. It is not an intent but merely an illustrative example.

  With reference to FIG. 1, the physical structure of the adhesive sheet 10 is demonstrated. As shown in FIG. 1, the pressure-sensitive adhesive sheet 10 includes a pressure-sensitive adhesive layer 3, and a release sheet 5 and a release sheet 6 that are attached to the pressure-sensitive adhesive layer 3 so as to sandwich the pressure-sensitive adhesive layer 3. The pressure-sensitive adhesive layer 3 is composed of a pressure-sensitive adhesive 7 including at least an acrylic polymer and a crosslinking agent.

  The pressure-sensitive adhesive layer 3 will be described. First, the acrylic polymer constituting the pressure-sensitive adhesive 7 will be described. In the present embodiment, the acrylic polymer is a copolymer composed of a plurality of types of monomers, and contains an acrylic ester having an aromatic ring as an essential component. Examples of the acrylate ester having an aromatic ring include benzyl acrylate and phenoxyethyl acrylate. When used for filling the air layer between the surface protection plate and the image display module, impact resistance In order to obtain a pressure-sensitive adhesive sheet having excellent durability and durability, it is preferable to use phenoxyethyl acrylate. The kind of at least one acrylic monomer that can be used in combination with an acrylic ester having an aromatic ring is not particularly limited, and is methyl methacrylate, ethyl methacrylate, n-butyl acrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate. 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate, which are hydroxyalkyl esters of acrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 4-hydroxy, which are hydroxyalkyl esters of methacrylic acid Butyl methacrylate, unsaturated aliphatic carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid It can be of use known ones. In particular, the use of n-butyl acrylate (Tg = −55 ° C.) or 2-ethylhexyl acrylate (Tg = −70 ° C.) having a low glass transition point (Tg), which has adhesive strength even at low temperatures, This is preferable because the effect of synergistically improving the adhesion to the image display module, the impact resistance, and the durability under a high temperature and high humidity environment can be obtained.

  In the present embodiment, it is preferable that an acrylic ester having an aromatic ring that can be suitably used as an essential component among monomers constituting the acrylic polymer is contained in the pressure-sensitive adhesive within a range of 15 to 35% by weight. If it is less than 15% by weight, the embedding property and impact resistance of the surface protection plate in the printed step portion are good, but foaming is observed in the pressure-sensitive adhesive layer after a long period of time in a high temperature and high humidity environment. For this reason, application to an image display device is not preferable. In addition, when the content is 35% by weight or more, the embedding property and impact resistance of the surface protection plate, which is the subject of the present invention, are good, but the miscibility with the additive component is reduced in a high temperature and high humidity environment. Coloring due to the occurrence occurs. For this reason, application to an image display device is not preferable.

  More preferably, phenoxyethyl acrylate and n-butyl acrylate are preferably blended at a ratio of 1: 9 to 5: 5. This is because the embedding property and impact resistance of the surface protection plate in the printed step portion are ensured, and there is no foaming even after a long time in a high temperature and high humidity environment.

  A method for producing the acrylic polymer will be described. The acrylic polymer constituting the pressure-sensitive adhesive 7 can be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method can be appropriately selected. As the polymerization initiator, azo polymerization initiators such as azobisisobutyronitrile (AIBN), peroxide compounds such as lauroyl peroxide and benzoyl peroxide (BPO), benzophenone initiators such as benzophenone, 2-methyl Thioxanthone initiators such as thioxanthone, benzoin ether initiators such as benzoin ethyl ether, and the like can be used. Of these, an azo polymerization initiator such as azobisisobutyronitrile is particularly preferred from the viewpoint of polymerizability. Then, an acrylic polymer solution is prepared by dissolving the acrylic polymer produced by the above method in a solvent such as toluene, ethyl acetate, or methyl ethyl ketone.

  The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, but is preferably 300,000 to 2,000,000, particularly preferably 800,000 to 1.3 million. When the molecular weight is less than 300,000, when used as an image display device that is expected to be used in severe environments such as high-temperature and high-humidity, such as mobile phones, mobile terminals, touch panels, etc., the adhesive layer is likely to foam, float, and peel off. Therefore, it is not preferable. When the molecular weight exceeds 2 million, the initial adhesion to the surface protective plate or the image display module is lowered, and bubbles are likely to remain, such being undesirable. In the present embodiment, the weight average molecular weight (Mw) is a value in terms of polystyrene measured by gel permeation chromatography (GPC method). In addition, the storage elastic modulus mentioned later can be adjusted also with the weight average molecular weight of an acrylic polymer.

  In the above-mentioned acrylic polymer solution, in addition to the above-mentioned components, a tackifier silane coupling agent, a colorant, a plasticizer, a filler, an antistatic agent, an antioxidant, an ultraviolet absorber, etc. These additives may be added as appropriate.

  The crosslinking agent added to the above acrylic polymer solution will be described. A solution of the pressure-sensitive adhesive 7 constituting the pressure-sensitive adhesive layer 3 (hereinafter referred to as “pressure-sensitive adhesive solution”) is created by adding a crosslinking agent to the above-mentioned acrylic polymer solution. Examples of the crosslinking agent suitably used in the present invention include isocyanate-based crosslinking agents that are compounds having two or more isocyanate groups in one molecule. For example, isocyanates such as tolylene diisocyanate, 4-4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine isocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, Moreover, the product of these isocyanates and a polyalcohol, the polyisocyanate produced | generated by condensation of isocyanate, etc. can be used. Moreover, the crosslinking agent (Nippon Polyurethane Industry Co., Ltd. product "Coronate L") which has trimethylol propane tolylene diisocyanate as a main ingredient can be used.

  Further, if necessary, the isocyanate-based crosslinking agent and / or the following compounds may be used in combination of two or more as crosslinking agents. Types of crosslinking agents used in combination with isocyanate crosslinking agents include bisphenol A, epichlorohydrin type epoxy resin, epoxy compounds such as ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether; hexamethylenediamine Amine compounds such as aluminum, iron, copper, zinc, tin, titanium, nickel, etc .; metal chelate compounds in which polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium and nickel are coordinated to acetylacetone and ethyl acetoacetate; N, N′-diphenylmethane -4,4'-bis (1-aziridinecarboxide), N, N'-toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methyla) Lysine), of the aziridine compound such as tri-1-aziridinyl phosphine oxide, can be suitably used one or more.

  The predetermined adhesion performance and storage elastic modulus can be adjusted by cross-linking the acrylic polymer with a crosslinking agent. The blending ratio of the acrylic polymer and the isocyanate-based crosslinking agent is not particularly limited, but from the viewpoint of securing excellent properties in terms of printing step embedding, impact relaxation, and durability of the surface protection plate, The addition amount of the crosslinking agent is preferably 0.1 parts by weight or more and less than 5.0 parts by weight, and more preferably 0.5 to 1.0 parts by weight in terms of solid content with respect to 100 parts by weight of the acrylic polymer. If it is less than 0.1 part by weight, the resulting adhesive 7 becomes soft due to insufficient cohesive force. For this reason, the adhesive 7 protrudes from the end face during sheet processing, or the adhesive 7 tends to protrude due to heat inside an electronic display such as an LCD or PDP. Moreover, when it is 5.0 weight or more, it becomes difficult to laminate | stack two or more adhesive layers by insufficient adhesive force. Or the possibility that the surface protection plate of the image display device and the image display module may be unexpectedly peeled off increases.

  The cross-linking reaction can be suitably controlled by the temperature and time for drying after applying the adhesive solution to the release liner. The crosslinking temperature is appropriately adjusted according to the type of the pressure-sensitive adhesive composition, but generally 70 to 150 ° C. is preferable. Moreover, it is preferable that the crosslinking time is generally terminated in about 1 to 5 minutes.

  A tackifier is added to the pressure-sensitive adhesive solution prepared as described above as necessary for the purpose of improving the adhesion to the surface protection plate and the image display module. As the tackifier, rosin-based, terpene-based, aliphatic hydrocarbon-based, aromatic hydrocarbon-based, polystyrene-based, or the above-mentioned acrylic polymer can be used. In view of the goodness, styrene tackifiers such as polystyrene, poly-α-methylstyrene, and styrene-α-methylstyrene copolymers are particularly preferable. It is preferable that the addition amount of a tackifier is 10.0 weight part or less in conversion of solid content with respect to 100 weight part of solid content of the said acrylic polymer solution. When the addition amount of the tackifier exceeds 10.0 parts by weight, the pressure-sensitive adhesive layer may be yellowed or whitened over time, which is not preferable. Although it does not specifically limit to the weight average molecular weight (Mw) of a tackifier, Since tackifying performance falls as molecular weight becomes large, Preferably it is 200-50,000, Most preferably, it is 1,000-10,000.

  The storage elastic modulus obtained by the viscoelasticity test depends on the acrylic polymer configured as the main component. In order to ensure excellent properties in terms of printing step embedding on the surface protection plate, impact resistance, and durability in high-temperature and high-humidity environments, crosslinkers and acrylic esters with aromatic rings are essential components. In addition to the acrylic polymer to be included, the additive is added to adjust. The storage elastic modulus can be set by appropriately adjusting the additive within a predetermined range.

A pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive containing at least a crosslinking agent and an acrylic polymer copolymerized with two or more monomers, wherein the crosslinking agent is 0.1 parts by weight or more in solid content in the pressure-sensitive adhesive A pressure-sensitive adhesive layer containing less than 5.0 parts by weight and at least one of the monomers being an acrylic ester having an aromatic ring is used. More preferably, the acrylic ester having an aromatic ring is phenoxyethyl acrylate, and the thickness of the pressure-sensitive adhesive layer is 100 μm or more. The storage elastic modulus at 25 degreeC of the adhesive which comprises such an adhesive layer is set to 9.0 * 10 < ⁴ > -2.0 * 10 < ⁵ > Pa. The pressure-sensitive adhesive having the storage elastic modulus has good adhesion and impact resistance to the surface protective plate and the image display module. Moreover, durability in a high temperature and high humidity environment can be improved.

  In the pressure-sensitive adhesive solution prepared as described above, a colorant such as a dye or a pigment is added as necessary when there is a demand for fine adjustment of color tone as an image display device. As the dye, one or more selected from basic dyes, acid dyes, direct dyes, acid mordant dyes, or mordant dyes can be used. There are various types of dyes, and chemical structures include azo dyes, anthraquinone dyes, triphenylmethane dyes, pyrazolone dyes, stilbene dyes, diphenylmethane dyes, azomethine dyes, xanthene dyes, alizarin dyes, acridine dyes, quinone imines. Examples include dyes (azine dyes, oxazine dyes, thiazine dyes), cyanine dyes, quinoline dyes, thiazole dyes, methine dyes, and nitro dyes. Examples of the pigment include azo pigment, anthraquinone pigment, indigo pigment, thioindigo pigment, perylene / perinone pigment, quinacridone pigment, dioxazine pigment, quinophthalone pigment, isoindolinone pigment, pyrrole pigment, phthalocyanine pigment, aniline black pigment. , Organic pigments such as carbon black pigments, metal oxide pigments such as titanium oxide pigments and iron oxide pigments, chromate pigments, sulfide pigments, silicate pigments, carbonate pigments, ferrocyanians Examples thereof include inorganic pigments such as compounds. It is preferable to use a pigment having an average particle diameter of 0.03 to 0.30 μm. This is because a desired storage modulus can be obtained and can be uniformly dispersed in the pressure-sensitive adhesive layer. Any one or two or more colorants such as dyes and pigments can be used in appropriate combination. The color tone can be adjusted by the blending ratio of the colorant to be combined.

  Although coloring agents, such as dye and a pigment, are not specifically limited, For example, a coloring agent is added about 0.1-10 weight part in conversion of solid content with respect to 100 weight part of adhesive polymers. This impairs excellent properties such as reduced adhesion to the surface protection plate and image display module, suitability for embedding the surface protection plate in printing steps, impact resistance, and durability in high-temperature and high-humidity environments. In addition, the color tone required for the image display apparatus can be appropriately corrected while maintaining the light transmission performance.

  The release sheet 5 and the release sheet 6 will be described. As release sheet 5 and release sheet 6, synthetic resin films such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, rubber sheet, foam sheet, metal foil, paper, non-woven fabric Alternatively, an appropriate thin leaf made of a laminate or the like can be used. The surfaces of the release sheet 5 and the release sheet 6 may be subjected to release treatment such as silicone treatment, long-chain alkyl treatment, and fluorine treatment as necessary in order to enhance the peelability from the pressure-sensitive adhesive layer 3. The peelability of the release sheet 5 and the release sheet 6 can be controlled by adjusting at least one parameter of the type of chemical used for the release treatment and the coating amount.

  A method for forming the pressure-sensitive adhesive layer 3 will be described. The method for forming the pressure-sensitive adhesive layer 3 is not particularly limited. For example, the pressure-sensitive adhesive solution prepared as described above may be a known method such as a gravure printing method, a spray method, a dipping method, a roll coater method, or a die coater method. The release sheet 5 is coated by the method. After drying, it is bonded to a release sheet 6 having a different peeling force. Thereby, the adhesive sheet 10 which is a double-sided adhesive sheet without a core material can be created.

  The thickness of the pressure-sensitive adhesive layer 3 is preferably 100 μm or more and 500 μm or less. If the thickness is less than 100 μm, unintentional peeling or peeling occurs due to insufficient adhesive force when the printing unit 2 (see FIG. 2; described later) is printed on the surface protection plate 1 (see FIG. 2, described later) to form a step. Cheap. When it exceeds 500 μm, the light transmittance of the pressure-sensitive adhesive layer 3 is reduced, and the pressure-sensitive adhesive layer 3 protrudes easily during processing.

  The pressure-sensitive adhesive sheet 10 is preferably produced in a roll shape from the viewpoint of work efficiency in continuous production. Thereafter, it can be formed into a predetermined shape for incorporation into an image display device used in a mobile phone, a portable terminal, a touch panel, or the like by a technique such as punching or laser cutting.

  The usage pattern of the adhesive sheet 10 will be described. FIG. 2 shows a cross-sectional configuration when the adhesive 7 constituting the adhesive layer 3 of the adhesive sheet 10 is used in the image display device 11. As shown in FIG. 2, the image display device 11 includes an image display module 4 and a surface protection plate 1 disposed on a side (upper side in FIG. 2) on which an image is displayed in the image display module 4. . The adhesive 7 is filled in a portion sandwiched between the image display module 4 and the surface protection plate 1. The printing unit 2 is printed on the surface of the surface protection plate 1 that is close to the image display module 4 (the surface that contacts the adhesive 7). The printing unit 2 is printed on the surface protection plate 1 when, for example, a frame-shaped outer peripheral frame is formed on the display unit of the image display device 11. The printing unit 2 has a predetermined thickness (for example, 10 μm).

  The surface protection plate 1 will be described. The material and shape of the surface protection plate 1 are not particularly limited as long as they are a light-transmitting sheet or plate-shaped body. Specifically, polyethylene terephthalate (PET) resin, polymethyl methacrylate (PMMA) resin, polycarbonate (PC) resin, triacetyl cellulose (TAC) resin, polyvinyl alcohol (PVA) resin, norbornene resin, cycloolefin (grease Ring) transparent resin such as resin, synthetic resin mainly composed of at least one of the group consisting of translucent resin such as polyethylene resin, polypropylene resin and silicone resin, or soda lime glass, alkali-free glass, tempered glass, Inorganic materials such as heat-resistant glass can be used. From the viewpoint of weight reduction and thickness reduction, a resin material such as a transparent resin or a translucent resin is preferable. PMMA resin, PC resin, soda lime glass, non-alkali glass, and tempered glass are particularly preferable from the viewpoint of molding processability and durability.

  As the surface protection plate 1, a sheet-like molded body having a thickness of 12 to 300 μm or a plate-shaped molded body having a thickness of 0.3 to 10.0 mm can be used. In particular, a sheet-like molded body having a thickness of 38 to 300 μm is preferable. Alternatively, a plate-like formed body having a thickness of 0.3 to 3.0 mm, particularly 0.8 mm to 1.2 mm is preferable.

  In addition, as long as the present invention is not hindered, functional layers such as an antiglare layer, an antireflection layer, an antistatic treatment layer, a hard coat layer, an antifouling layer, and an antibacterial layer are formed on the surface layer of the surface protective plate 1 or an optical function. It is possible to bond the film which coat | covered the layer through an adhesive layer. In this case, surface treatment such as corona treatment, alkali treatment, plasma treatment, and easy-adhesion resin layer coating treatment may be performed in order to improve the adhesion between the functional layer, the optical functional layer, and the like and the other layers.

  As described above, the printing unit 2 may be provided on the surface of the surface protection plate 1. The printing unit 2 is often so-called frame printing.

  The image display module 4 will be described. As the image display module 4, various types of image display modules such as a liquid crystal method and an organic EL method can be used. The image display device 11 may be an image display device to which a touch panel function is added.

  Of the image display module 4, the surface in contact with the pressure-sensitive adhesive 7 is made of polyethylene terephthalate (PET) resin, polymethyl methacrylate (PMMA) resin, polycarbonate (PC) resin, triacetyl cellulose (TAC) resin, polyvinyl alcohol (PVA). ) Resin, norbornene resin, functional film resin layer made of transparent resin such as cycloolefin (alicyclic) resin, or special coating layer such as easy-adhesion coat layer, conductive coat layer made of acrylic resin, polyurethane resin, etc. Is placed.

  A method for creating the image display device 11 using the adhesive sheet 10 will be described. The release sheet 6 of the pressure-sensitive adhesive sheet 10 is peeled off. Next, the surface of the pressure-sensitive adhesive layer 3 that is exposed when the release sheet 6 is peeled off is attached to the image display module 4. Next, the release sheet 5 is peeled off from the pressure-sensitive adhesive layer 3. Next, the surface protection plate 1 is attached to the surface of the pressure-sensitive adhesive layer 3 that is exposed when the release sheet 5 is peeled off. As described above, the image display module 4 and the surface protection plate 1 are bonded together to create the image display device 11.

  It is preferable that the above-described production process is performed in a vacuum environment, whereby the occurrence of foaming, peeling, and floating of the pressure-sensitive adhesive 7 can be suppressed. Moreover, when the image display module 4 and the surface protection board 1 are bonded together with the adhesive 7, a heat-pressing process is performed after bonding. Thereby, generation | occurrence | production of foaming, peeling, etc. of the adhesive 7 by bonding can be suppressed. In addition, durability in a high temperature and high humidity state (for example, 60 ° C. 95% RH, left for 168 hours) can be improved.

  As described above, the pressure-sensitive adhesive sheet 10 exhibits excellent impact resistance and durability when used for the purpose of filling the space between the image display module 4 and the surface protection plate 1. As a result, the surface protection plate 1 and the image display module 4 can be adhered well. Moreover, since the adhesive 7 absorbs the impact applied to the surface protection plate 1 satisfactorily, it is possible to prevent the impact from being transmitted to the image display module 4. Moreover, since the surface protection board 1 and the image display module 4 are bonded by the adhesive 7 which comprises the adhesive layer 3 of the adhesive sheet 10, while being able to produce the image display apparatus 11 easily, the adhesive 7 It is possible to prevent air bubbles from entering the inside. Furthermore, since the adhesive 7 shows high permeability, it becomes possible to improve the visibility of the image displayed on the display module 4.

The present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited by these. Hereinafter, 1. Details of evaluation sample, 2. 2. Evaluation method, It demonstrates in order of an evaluation result.
1. Evaluation sample details

  First, the adjustment method of an adhesive solution is demonstrated. Acrylic monomer having a weight average molecular weight (Mw) of 1 million (n-butyl acrylate (denoted as “BA”), phenoxyethyl acrylate (denoted as “PEA”), methyl acrylate (denoted as “MA”) ), Methyl methacrylate (referred to as “MMA”), 2-hydroxyethyl acrylate (referred to as “2HEA”), acrylic acid (referred to as “AA”)) in a predetermined weight% ( See Table 1 and described in detail later). Then, 0.6 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator was added to the blended acrylic monomer and copolymerized. Next, 30 parts by weight of the polymer produced by copolymerization is dissolved in 70 parts by weight of solvent (a solvent in which 30 parts by weight of toluene and 40 parts by weight of ethyl acetate are mixed) to obtain an acrylic polymer solution having a solid content of 30% by weight. It was. Next, predetermined 100 parts by weight of trimethylolpropane tolylene diisocyanate as a crosslinking agent (see Table 1, detailed later) was added to 100 parts by weight of the solid content of the obtained acrylic polymer solution to obtain an adhesive solution.

  Next, the manufacturing method of the adhesive sheet 10 is demonstrated. A release sheet 5 made of a PET film having a thickness of 75 μm and having a silicone resin coated on one side was prepared. Next, the pressure-sensitive adhesive solution prepared above was applied to the silicone resin-coated surface of the release sheet 5 and dried at 100 ° C. for 3 minutes. As a result, the pressure-sensitive adhesive layer 3 having a predetermined thickness after drying (see Table 1, details will be described later) was formed.

  Next, the release sheet 6 made of a PET film having a thickness of 38 μm was bonded to the surface of the pressure-sensitive adhesive layer 3 opposite to the side on which the release sheet 5 was applied, and aged at room temperature for 1 week. The relationship between the release forces of the release sheets 5 and 6 was set to “release sheet 5> release sheet 6”. In this way, an adhesive sheet 10 for evaluation was obtained.

  Subsequently, the obtained adhesive sheet 10 was used and the sample for evaluation was created. Either of two types of surface protection plates 1 (soda lime glass plate (hereinafter simply referred to as “glass plate”) or PMMA resin plate (hereinafter referred to as “acrylic plate”)) on which the frame-shaped printing unit 2 is printed. Two pieces were prepared and bonded using the prepared adhesive sheet 10. A total of 14 shown below was prepared as samples.

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 75 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 1").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of the pressure-sensitive adhesive layer 3 of 100 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 2").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a pressure-sensitive adhesive layer 3 having a thickness of 150 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 3").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 4").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of the pressure-sensitive adhesive layer 3 of 200 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 5").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 3.0 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 6").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.1 parts by weight of a cross-linking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 7").

  The acrylic polymer to be blended was blended at a ratio of BA: 85% by weight, PEA: 10% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 8").

  The acrylic polymer to be blended was blended at a ratio of BA: 80% by weight, PEA: 15% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 9").

  The acrylic polymer to be blended was blended at a ratio of BA: 60% by weight, PEA: 35% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.7 parts by weight of a crosslinking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. And the sample was created using the created adhesive sheet 10 (it is set as "Example 10").

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, and AA: 1% by weight, and 5.1 parts by weight of a cross-linking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. A sample was prepared using the prepared adhesive sheet 10 (referred to as “Comparative Example 1”).

  The acrylic polymer to be blended was blended at a ratio of BA: 70% by weight, PEA: 25% by weight, 2HEA: 4% by weight, AA: 1% by weight, and 0.05 parts by weight of a cross-linking agent was added in terms of solid content. Using the pressure-sensitive adhesive solution, the pressure-sensitive adhesive sheet 10 having a thickness of 175 μm was prepared. A sample was prepared using the prepared adhesive sheet 10 (referred to as “Comparative Example 2”).

  The acrylic polymer to be blended is blended at a ratio of BA: 63% by weight, MA: 10% by weight, MMA: 25% by weight, 2HEA: 1% by weight, and AA: 1% by weight. A pressure-sensitive adhesive sheet 10 having a thickness of the pressure-sensitive adhesive layer 3 of 100 μm was prepared using a pressure-sensitive adhesive solution having a configuration with 0.0 part by weight added. And the sample was created using the created adhesive sheet 10 (it is set as "Comparative example 3").

２．評価方法及び評価結果 A pressure-sensitive adhesive solution having a composition in which an acrylic polymer to be blended is blended at a ratio of BA: 65% by weight, MA: 30% by weight, 2HEA: 5% by weight, and 0.4 parts by weight of a cross-linking agent is added in terms of solid content. Using, the adhesive sheet 10 whose thickness of the adhesive layer 3 is 100 micrometers was created. A sample was prepared using the prepared adhesive sheet 10 (referred to as “Comparative Example 4”). Table 1 summarizes the parameters described above. Table 1 shows the details of the composition and composition of the prepared samples.

2. Evaluation method and evaluation results

About the sample (Examples 1-10, Comparative Examples 1-4) created as mentioned above and the adhesive 7 which comprises these, (1) Storage elastic modulus measurement, (2) Impact relaxation test, (3) Adhesion (4) Durability evaluation was performed. Details of the measurement and evaluation methods are shown below.
(1) Storage elastic modulus measurement

The storage elastic modulus of the pressure-sensitive adhesive 7 was measured for the purpose of evaluating the properties of the pressure-sensitive adhesive 7 constituting the prepared sample as a viscoelastic body. Storage elastic modulus (G ′) at 25 ° C. and 1 Hz of the pressure-sensitive adhesive 7 constituting the pressure-sensitive adhesive tape 10 used in preparing each sample using a viscoelasticity measuring device (manufactured by Nippon Sebel Hegner, product number: MCR301). Was measured. The results are shown in Table 2.
(2) Impact relaxation test

（３）密着性評価 When a steel ball (diameter φ = 50 mm, weight = 510 g) was dropped onto a test piece bonded to a glass plate with the adhesive 7 for the purpose of evaluating the impact relaxation properties of the adhesive 7 constituting the prepared sample, The height (mm) when the glass plate was broken was measured. The results are shown in Table 2.

(3) Adhesion evaluation

  In order to confirm the adhesiveness of the pressure-sensitive adhesive 7 to the surface protection plate 1 in the prepared sample, an evaluation was made to visually check the state after the surface protection plates 1 were bonded together with the pressure-sensitive adhesive 7.

  A glass plate and an acrylic plate were used as the surface protection plate 1. And the state immediately after sticking of the surface protection plates 1 and the state after performing the heating and pressurizing treatment (50 ° C., 5 atm, 30 minutes) are observed, and bubbles are mixed, floated, and peeled off. Judged whether or not. The results are shown in Table 3.

In Table 3, “◯” indicates that bubbles are not mixed, floated, or peeled off immediately after sticking. “Δ” indicates that air bubbles are mixed, floated, and peeled immediately after sticking, and that air bubbles are not mixed, floated, and peeled after the heat and pressure treatment. “X” indicates that bubbles were mixed, floated, and peeled off in both the state immediately after pasting and the state after the heat and pressure treatment.
(4) Durability test

  In order to confirm the durability of the prepared sample, the sample after the surface protective plates 1 were attached to each other was placed in a constant temperature and humidity chamber, and an evaluation was performed by visually checking the state after setting to a predetermined temperature and humidity. .

  A glass plate and an acrylic plate were used as the surface protection plate 1. By the same method as the sample preparation method in (3), the pressure-sensitive adhesive sheet 10 in which the surface protection plates 1 were prepared was used for bonding. Then, this sample is placed in a constant temperature and humidity chamber, (A) left at a temperature of 80 ° C. and humidity of 0% for 1,000 hours, (B) left at a temperature of 60 ° C. and humidity of 95% for 1,000 hours, ( C) After leaving at a temperature of −40 ° C. for 1,000 hours, it was determined whether or not bubbles were generated, floated or peeled, and whether or not there was a change in color tone that could be visually determined. The results are shown in Table 3.

３．評価結果
（１）貯蔵弾性測定結果について In Table 3, “◯” indicates that no bubbles are generated, floated or peeled off after being placed in the above-described environment, and there is no change in color tone that can be visually discerned. “Δ” indicates that no bubble generation, floating, or peeling occurred, but there was a change in color tone that could be visually discerned. “X” indicates that bubbles were generated, floated, and peeled after being placed in the above-described environment.

3. Evaluation results (1) Storage elastic measurement results

When the pressure-sensitive adhesive 7 is used for the purpose of filling the space between the surface protection plate 1 with a printed step and the image display module 4, the pressure-sensitive adhesive 7 needs to have an appropriate elastic modulus as a viscoelastic body. When the storage elastic modulus is larger than 2.0 × 10 ⁵ , it becomes impossible to follow the uneven shape on the printing step portion of the surface protection plate 1, and a problem of entraining bubbles at the time of bonding occurs. Further, when the storage elastic modulus was smaller than 9.0 × 10 ⁴ , the adhesive 7 protruded from the end portion, and the workability was remarkably lowered. Here, from the results of Table 2, the addition amount of the crosslinking agent was 0.1 parts by weight (Example 7), 0.7 parts by weight (Examples 1 to 5, Examples 8 to 10), 3.0 parts by weight ( In the case of Example 6), it was found that the storage elastic modulus was within the range of 9.0 × 10 ^{4 to} 2.0 × 10 ⁵ . On the other hand, in Comparative Example 1 in which the addition amount of the crosslinking agent is 5.1 parts by weight, the storage elastic modulus is larger than 2.0 × 10 ⁵ , and the addition amount of the crosslinking agent is 0.1 parts by weight. In smaller Comparative Example 2 (0.05 parts by weight), it was found that the storage elastic modulus was smaller than 9.0 × 10 ⁴ . From this result, it became clear that the addition amount of the crosslinking agent should be at least 0.1 parts by weight and less than 5.0 parts by weight.
(2) Impact relaxation test

  When the adhesive 7 is used for the purpose of filling the space between the surface protection plate 1 with a printed step and the image display module 4, the adhesive 7 does not receive an impact when the image display device receives some impact from the outside. In order not to be transmitted directly to the image display module 4, it is necessary to have a performance of absorbing impact. When a steel ball having a diameter φ = 50 mm and a weight = 510 g is dropped directly onto a glass plate from a height of 20 mm, the glass plate is broken. On the other hand, when the glass plate is bonded to the glass plate with the adhesive 7 as in Examples 1 to 10, the glass plate is not damaged even when the hard sphere is dropped onto the glass plate from a height of 20 mm or more. It was. From this result, it became clear that the pressure-sensitive adhesive 7 has the ability to mitigate the impact of dropping the steel ball.

As a result of confirming the height at which the steel ball is dropped in the impact relaxation test, the thickness of the pressure-sensitive adhesive 7 is preferably 100 μm or more (Examples 2 to 10, height: 30 mm or more) from the viewpoint of impact relaxation. It was found that the thickness was preferably 150 to 200 μm (Examples 3 to 10, height: 40 mm or more).
(3) Results of adhesion evaluation

  When the thickness of the adhesive layer 3 was 75 micrometers (Example 1), it turned out that the tendency for the adhesiveness to the surface protection board 1 with a printing level | step difference to fall arises. When the thickness of the pressure-sensitive adhesive layer 3 is 100 μm (Example 2), the adhesiveness is good. Therefore, when the thickness of the pressure-sensitive adhesive layer 3 is 100 μm or more, good adhesiveness is exhibited. It became clear.

Moreover, when phenoxyethyl acrylate was not used as a monomer which comprises an acryl-type polymer (Comparative Example 3 and Comparative Example 4), it turned out that adhesiveness deteriorates. When phenoxyethyl acrylate is used as a monomer constituting an acrylic polymer under the same thickness (100 μm) of the pressure-sensitive adhesive layer 3 (Example 2), good adhesion to the surface protection plate 1 with a printed step Therefore, it has been clarified that by using phenoxyethyl acrylate as a monomer constituting the acrylic polymer, good adhesion is exhibited.
(4) Durability test

  When a glass plate or an acrylic plate was used as the surface protection plate 1, it was found that the durability of Comparative Examples 1 and 2 deteriorated. In Comparative Example 1 and Comparative Example 2, 5.1 and 0.05 parts by weight of a crosslinking agent were added, respectively, and a sample (Example 6) in which the addition amount of the crosslinking agent was 3.0 parts by weight, And since the sample (Example 7) which is 0.1 weight part has shown favorable durability, the addition amount of a crosslinking agent shall be at least 0.1 weight part or more and less than 5.0 weight part. As a result, it became clear that good durability was exhibited.

  Moreover, it turned out that durability of the comparative example 3 and the comparative example 4 in which the acrylic ester which has aromatic rings, such as a phenoxyethyl acrylate, is not used as a monomer which comprises an acryl-type polymer deteriorates. Samples (Example 1 to Example 10) in which phenoxyethyl acrylate is used as a monomer constituting the acrylic polymer exhibit good durability. Therefore, good durability can be obtained by using phenoxyethyl acrylate. It became clear to show.

  In Example 8 containing 10% by weight of phenylethyl acrylate in the weight% of the pressure-sensitive adhesive composition, although the embedding property and impact resistance of the surface protection plate in the printed stepped portion are good, it has passed for a long time in a high-temperature and high-humidity environment. Then, the foaming of the grade which can be visually confirmed slightly was seen in the adhesive layer. Further, in Example 10 containing 35% by weight of phenylethyl acrylate, the embedding property and impact resistance of the surface protective plate in the printing step portion are good, but the mixing property with the additive component is reduced in a high temperature and high humidity environment. The coloring caused by the above occurred at a level that can be visually discerned. From this result, it is preferable to contain phenylethyl acrylate in the range of 10 to 35, more preferably 15 to 25% by weight in the weight% of the pressure-sensitive adhesive composition.

3 Adhesive layers 5 and 6 Release sheet 7 Adhesive 10 Adhesive sheet

Claims (3)

A pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive containing at least a crosslinking agent and an acrylic polymer obtained by copolymerization of two or more monomers;
A pressure-sensitive adhesive sheet comprising a release sheet releasably attached to at least one surface of the pressure-sensitive adhesive layer,
The crosslinking agent is contained in the pressure-sensitive adhesive in a solid content of 0.1 part by weight or more and less than 5.0 parts by weight,
At least one of the monomers is an acrylic ester having an aromatic ring,
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive has a storage elastic modulus at 25 ° C. of 9.0 × 10 ^{4 to} 2.0 × 10 ⁵ Pa.   The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic ester having an aromatic ring is phenoxyethyl acrylate.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a thickness of 100 µm or more.

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