JP2009209321A - Adhesive sheet and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet which can paste a display panel with a protective plate with little air entangled between them and is excellent in wettability to adhere them, and further can endure severe conditions at a high temperature and a high humidity to bring about neither foaming nor peeling at the interface between them. <P>SOLUTION: The adhesive sheet, which is used to laminate a protective plate on the surface of a display panel in a display device, comprises an acrylic base adhesive agent which contains a copolymer of an alkyl (meth)acrylate, a polyfunctional (meth)acrylate, and a poly-dimethyl-siloxane having a radically polymerizable double bond, thereby to exhibit excellent wettability for the display panel and the protective plate. Therefore, the adhesive sheet can laminate strongly to unite the display panel and the protective plate with no stagnant air generated at their interface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an adhesive sheet used for integrating a display panel of a display device and a protective plate disposed on the display panel, and a display device using the same.

  Mobile communication terminals having a display device such as a mobile phone terminal such as a mobile phone or a PDA (Personal Digital Assistant) terminal are further reduced in thickness, weight, power consumption, high definition, and high brightness. It has been illustrated. In such a display device, in order to protect the display panel, a protective plate is usually attached and integrated through a frame-like pressure-sensitive adhesive layer formed on the outer peripheral edge of the display panel.

  In the display device having the above structure, since a space portion caused by the adhesive layer is formed between the protective plate and the display panel, when an external force is applied to the display device, the external force is absorbed by the presence of the space portion. It is alleviated and damage to the display device is prevented.

  However, there is a space between the opposing surfaces of the display panel and the protective plate, and light scattering occurs due to the air present in the space, thereby improving the display quality of the display device. There is a limit, and when a relatively large distortion occurs in the mobile communication terminal, there is a problem that the protective plate is cracked.

  Therefore, as a display device that can further improve the display quality of the display device and is excellent in durability against external force, the display panel and the protective plate are bonded to each other through a transparent double-sided adhesive sheet. Has been proposed. As such a transparent double-sided pressure-sensitive adhesive sheet, an acrylic resin is generally used. For example, Patent Documents 1 to 5 propose an acrylic transparent double-sided pressure-sensitive adhesive sheet or tape with improved adhesive force.

  However, in the acrylic transparent double-sided pressure-sensitive adhesive sheets described in Patent Documents 1 to 5, when the display device is placed in a harsh environment such as a high-temperature and high-humidity condition, the display panel, the protective plate, and the pressure-sensitive adhesive sheet There is a problem that bubbles and peeling occur at the interface of the display, and the visibility of the display device is lowered.

JP 2003-342542 A JP 2003-238915 A JP 2004-231723 A JP 2005-154581 A JP 2005-255877 A

  The present invention is used to join a display panel and a protective plate disposed on the display panel, and involves less air entrainment when the display panel and the protective plate are bonded to each other. Excellent wettability and adhesiveness. In addition, even under severe conditions under high temperature and high humidity, there are no bubbles or peeling at the interface between the display panel and the protective plate. An adhesive sheet capable of maintaining display quality over a long period of time and a display device using the same are provided.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet used for laminating and integrating a protective plate on the surface of a display panel of a display device. The pressure-sensitive adhesive sheet comprises an alkyl (meth) acrylate and a polyfunctional (meth) acrylate. And an acrylic pressure-sensitive adhesive containing a copolymer of polydimethylsiloxane having one radical polymerizable double bond. In addition, (meth) acrylate means an acrylate or a methacrylate.

  The alkyl (meth) acrylate that is the monomer component of the copolymer constituting the acrylic pressure-sensitive adhesive is not particularly limited, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl (meth). Acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) Acrylate, dode (Meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, and the like. Adjustment of glass transition temperature (Tg) and adhesive strength of the obtained acrylic adhesive, compatibility with other raw resin From the viewpoint, alkyl (meth) acrylates in which the alkyl group has 4 to 10 carbon atoms are preferred. In addition, alkyl (meth) acrylate may be used independently or 2 or more types may be used together.

  If the number of carbon atoms in the alkyl group of the alkyl (meth) acrylate is small, the acrylic pressure-sensitive adhesive may become too hard and the adhesion and adhesive strength may decrease. Alternatively, since the acrylic pressure-sensitive adhesive becomes hard and adhesion and adhesive strength may be reduced, 4 to 10 is preferable, and 4 to 8 is more preferable.

  If the content of the alkyl (meth) acrylate component in the copolymer constituting the acrylic pressure-sensitive adhesive is small, the pressure-sensitive adhesive strength of the acrylic pressure-sensitive adhesive decreases, and if it is large, the content is relatively polyfunctional (meth). When the content of acrylate is low, the adhesion durability of the pressure-sensitive adhesive sheet to the display panel and the protective plate is reduced, or when the content of polydimethylsiloxane is relatively low, the initial value for the display panel and the protective plate is reduced. Since adhesion wettability may fall, 85-99.48 weight% is preferable and 90-99 weight% is more preferable.

  The polyfunctional (meth) acrylate which is a monomer component of the copolymer constituting the acrylic pressure-sensitive adhesive refers to a compound having two or more (meth) acryloyl groups in one molecule. By including a polyfunctional (meth) acrylate component in the copolymer constituting the acrylic pressure-sensitive adhesive, the acrylic pressure-sensitive adhesive can form a high cross-linked structure, so the pressure-sensitive adhesive sheet has excellent heat resistance. It exhibits excellent durability by reliably maintaining adhesive strength even under high temperature and high humidity conditions.

  The polyfunctional (meth) acrylate is not particularly limited. For example, hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate , Tris (2-hydroxyethyl) isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, proximed trimethylolpropane triacrylate, proxiated glyceryl triacrylate, neopentyl glycol adipate diacrylate, polyethylene glycol di (meth ) Polymers such as acrylate and liquid hydrogenated 1,2 polybutadiene acrylate, etc. may be mentioned, and these may be used alone or in combination of two or more.

  As said polyfunctional (meth) acrylate, it is preferable that it is a polymer, It is preferable that the number average molecular weight of this polymer is 400 or more, It is more preferable that it is 800 or more, It is 1000-5000. Particularly preferred. This is because when the polyfunctional (meth) acrylate is a polymer, the molecular weight between the cross-linking points increases, thereby improving the stress dispersibility and improving the peeling force of the acrylic pressure-sensitive adhesive.

  In addition, the number average molecular weight of polyfunctional (meth) acrylate means the value measured as polystyrene conversion molecular weight by GPC (Gel Permeation Chromatography: Gel Permeation Chromatography) method, and details are a brand name "2690 Separations Model from Water company. The number average molecular weight of the polyfunctional (meth) acrylate is measured by using a gel permeation chromatograph commercially available in ”and using a differential refractometer as a detector at a sample flow rate of 1 ml / min and a column temperature of 40 ° C. Can be obtained.

  Even if the content of the polyfunctional (meth) acrylate component in the copolymer constituting the acrylic adhesive is at least, the durability of the acrylic adhesive and the adhesion to the display panel and the protective plate are Since it falls, 0.01 to 5 weight% is preferable and 0.02 to 5 weight% is more preferable.

  Further, the copolymer constituting the acrylic pressure-sensitive adhesive has a polydimethylsiloxane component having one radical polymerizable double bond as its monomer component. Therefore, the dimethylsiloxane skeleton is incorporated into the acrylic polymer skeleton, exhibits excellent wettability with respect to display panels and protective plates, exhibits excellent adhesion, and the surface panel and protective plate are adhesive sheets. Prevents air entrainment when stacking and integrating via the surface, and firmly stacking the surface panel and the protective plate via the adhesive sheet without generating air pockets between the surface panel and the protective plate and the adhesive sheet Can be integrated.

  In particular, it is preferable to have a radical polymerizable double bond at the terminal of polydimethylsiloxane. In this way, since the radical polymerizable double bond is bonded to the end of the molecular chain of polydimethylsiloxane, the main chain of the copolymer constituting the resulting acrylic pressure-sensitive adhesive is directly formed of polydimethylsiloxane. A chain of side chains is bound. Therefore, the side chain made of polydimethylsiloxane is in a state of being very mobile, and the acrylic pressure-sensitive adhesive exhibits better wettability with respect to the display panel and the protective plate.

  Polydimethylsiloxane has a radical polymerizable double bond, but the functional group containing such a radical polymerizable double bond is not particularly limited, and examples thereof include a vinyl group, a propenyl group, a styryl group, (Meth) acryloyl group, etc. are mentioned, it is excellent in compatibility with alkyl (meth) acrylate and polyfunctional (meth) acrylate, is easy to copolymerize, and is capable of efficiently introducing a dimethylsiloxane skeleton into an acrylic polymer skeleton ( A (meth) acryloyl group is preferred. In addition, (meth) acryloyl means acryloyl or methacryloyl.

  If the number average molecular weight of the polydimethylsiloxane having a radically polymerizable double bond is low, the wettability with respect to the display panel or the protective plate is lowered and the adhesion is lowered, and the surface panel and the protective plate are connected via the adhesive sheet. When the layers are integrated, air entrainment may occur, and if it is high, the adhesiveness of the acrylic pressure-sensitive adhesive decreases, so 500 to 20000 is preferable, and 1000 to 10,000 is more preferable.

  The polydimethylsiloxane having one radical polymerizable double bond is not particularly limited and includes α-styryl polydimethylsiloxane, α- (meth) acryloyloxypolydimethylsiloxane, and the like. Polydimethylsiloxane having one radical polymerizable double bond is commercially available from Chisso Corporation under the trade names “Silaplane FM-0711”, “Silaplane FM-0721”, and “Silaplane FM-0725”.

  If the content of the polydimethylsiloxane component having one radical polymerizable double bond in the copolymer constituting the acrylic pressure-sensitive adhesive is small, the wettability with respect to the display panel and the protective plate is lowered and the adhesion is lowered. Then, when the surface panel and the protective plate are laminated and integrated through the pressure-sensitive adhesive sheet, air entrainment may occur. When the surface panel and the protective plate are often integrated, the adhesiveness of the acrylic pressure-sensitive adhesive may be reduced. 8% by weight is preferred.

  Furthermore, the copolymer constituting the acrylic pressure-sensitive adhesive includes an alkyl (meth) acrylate component, a polyfunctional (meth) acrylate component, and polydimethyl for the purpose of adjusting the glass transition temperature and adhesive strength of the acrylic pressure-sensitive adhesive. In addition to the siloxane component, as monomer components, for example, styrene monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene; vinyl carboxylic acid esters such as vinyl acetate; (meth) acrylic acid, itaconic acid, etc. Carboxylic acid containing vinyl group; anhydride of dicarboxylic acid having vinyl bond such as maleic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate , Caprolactone-modified (meth) acrylate, Vinyl monomers having a hydroxyl group such as reoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate; (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinyllaurylactam, (meth) acryloylmorpholine , (Meth) acrylamide, dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, nitrogen-containing vinyl monomers such as dimethylaminomethyl (meth) acrylate, etc. Or two or more of them may be used in combination.

  If the content of these monomer components in the copolymer that constitutes the acrylic pressure-sensitive adhesive is large, the flexibility of the resulting pressure-sensitive adhesive sheet is reduced, and this may cause a decrease in the pressure-sensitive adhesive of the nunchaku sheet. 20 weight% or less is preferable and 0.1-10 weight% is more preferable.

  If necessary, the acrylic pressure-sensitive adhesive does not hinder the achievement of the subject of the present invention, thermoplastic resins, thermoplastic elastomers, crosslinked rubber, oligomers, inorganic compounds, nucleating agents, antioxidants, aging Conventionally known inhibitors, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, thickeners, flame retardant aids, antistatic agents, antifogging agents, fillers, softeners, plasticizers, colorants, etc. Additives may be blended.

  The copolymer constituting the acrylic pressure-sensitive adhesive has been described as having a polydimethylsiloxane component having one radical polymerizable double bond as its monomer component, but instead of this polydimethylsiloxane component, radical polymerizable It may have a polydimethylsiloxane component having two or more double bonds. In this case, the copolymer constituting the acrylic pressure-sensitive adhesive does not need to contain a polyfunctional (meth) acrylate component as the monomer component.

  That is, the case where the adhesive sheet is comprised from the acrylic adhesive containing the copolymer of alkyl (meth) acrylate and the polydimethylsiloxane which has two or more radically polymerizable double bonds may be sufficient.

  In addition, since it is the same as that of the above about alkyl (meth) acrylate, the description is abbreviate | omitted. Also, polydimethylsiloxane having two or more radical polymerizable double bonds is the same as polydimethylsiloxane having one radical polymerizable double bond except that it has two or more radical polymerizable double bonds. Therefore, the description will be omitted and only the differences will be described below.

  The number of radically polymerizable double bonds contained in polydimethylsiloxane may be two or more, but the gel fraction of the acrylic pressure-sensitive adhesive becomes too high, and adhesion and bonding reliability may decrease. Since it is, it is more preferable that it is 2-4.

  When polydimethylsiloxane has two or more radical polymerizable double bonds, a functional group having a radical polymerizable double bond is bonded to at least one end of the molecular chain of polydimethylsiloxane. It is preferable that it is bonded to both ends of the molecular chain of polydimethylsiloxane.

  The polydimethylsiloxane having two radically polymerizable double bonds is not particularly limited, and examples thereof include α, ω-distyrylpolydimethylsiloxane, α, ω-di (meth) acryloyloxypolydimethylsiloxane, and the like. It is done. Polydimethylsiloxane having two radically polymerizable double bonds is available from Chisso Corporation under the trade names “Silaplane FM-7711”, “Silaplane FM-7721”, and “Silaplane FM-7725”. It is commercially available from Dow Corning under the trade names “BY16-152” and “BY-152C”.

  If the content of the polydimethylsiloxane component having two or more radical polymerizable double bonds in the copolymer constituting the acrylic pressure-sensitive adhesive is small, the wettability with respect to the display panel and the protective plate is lowered and the adhesion is lowered. Then, when the surface panel and the protective plate are laminated and integrated through the pressure-sensitive adhesive sheet, air entrainment may occur. When the surface panel and the protective plate are often integrated, the adhesiveness of the acrylic pressure-sensitive adhesive may be reduced. 3% by weight is preferred.

  When the content of the alkyl (meth) acrylate component in the copolymer constituting the acrylic pressure-sensitive adhesive is small, the pressure-sensitive adhesive strength of the acrylic pressure-sensitive adhesive decreases, and when the content is large, the content of polydimethylsiloxane is relatively large. Since the initial adhesion wettability with respect to the display panel or the protective plate may be reduced by decreasing the amount, 90 to 99.5% by weight is preferable, and 95 to 99% by weight is more preferable.

  Next, the manufacturing method of the adhesive sheet of this invention is demonstrated. The method for producing the pressure-sensitive adhesive sheet is not particularly limited. For example, alkyl (meth) acrylate, polyfunctional (meth) acrylate, polydimethylsiloxane having one radical polymerizable double bond, and a photopolymerization initiator, if necessary. The other monomer and additive are added and a monomer composition containing no solvent is prepared. On the other hand, two transparent synthetic resin films whose one side is release-treated are prepared. After the monomer composition is applied to the release treatment surface in a general-purpose manner to form a monomer layer, the other synthetic resin film is overlaid on the monomer layer, and then the synthetic resin film is passed through the monomer layer and ultraviolet rays are passed. A method for producing a pressure-sensitive adhesive sheet composed of an acrylic pressure-sensitive adhesive by radical polymerization of a monomer composition by irradiating light such as And the like. In addition, as a transparent synthetic resin film, a polyethylene terephthalate film etc. are mentioned. When polydimethylsiloxane having two or more radical polymerizable double bonds is used, a monomer composition may be prepared by adding polyfunctional (meth) acrylate as necessary.

  The photopolymerization initiator is not particularly limited, and, for example, a ketone photopolymerization initiator such as 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (trade name “Darocur 2959” manufactured by Merck & Co., Inc.). , Α-hydroxy-α, α′-dimethyl-acetophenone (trade name “Darocur 1173” manufactured by Merck), methoxyacetophene, 2,2-dimethoxy-2-phenylacetophene (trade name “Irgacure 651” manufactured by Ciba Geigy) ), Acetophenone photopolymerization initiators such as 2-hydroxy-2-cyclohexylacetophenone (trade name “Irgacure 184” manufactured by Ciba Geigy), ketal photopolymerization initiators such as benzyldimethyl ketal, halogenated ketones, acylphosphinoxides, And acyl phosphonates That.

  The upper limit of the addition amount of the photopolymerization initiator is preferably 5 parts by weight and more preferably 1 part by weight with respect to 100 parts by weight of the total amount of monomers in the monomer composition. On the other hand, the lower limit of the addition amount of the photopolymerization initiator is preferably 0.01 parts by weight and more preferably 0.03 parts by weight with respect to 100 parts by weight of the total amount of monomers in the monomer composition.

  This is because if the amount of the photopolymerization initiator added is small, the polymerization of the monomer in the monomer composition becomes incomplete, and the required physical properties cannot be obtained due to a decrease in cohesive strength of the resulting acrylic pressure-sensitive adhesive. Because there are things.

  On the other hand, if the amount of photopolymerization initiator added is large, the amount of radicals generated increases when irradiated with light such as ultraviolet rays, the number average molecular weight and gel fraction of the acrylic adhesive decrease, and the display panel or protective plate at high temperatures. This is because many bubbles and peeling may occur at the interface with the adhesive sheet.

  The lamps used for light irradiation are not particularly limited, and examples thereof include those having a light emission distribution at a wavelength of 400 nm or less. Specific examples include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps. Since the light in the active wavelength region of the agent is efficiently emitted and light absorption in the monomer mixture excluding the photopolymerization initiator is small, the light reaches the inside of the monomer layer sufficiently and the monomer composition is effective. It is preferable because it can be polymerized automatically.

The light irradiation intensity to the monomer layer is a factor that affects the degree of polymerization of the polymer obtained by polymerization, and is appropriately controlled for each performance of the target product. When an acetophenone photopolymerization initiator is used as the photopolymerization initiator, the light intensity in the wavelength region effective for photolysis of the photopolymerization initiator (depending on the photopolymerization initiator, usually 365 nm to 420 nm) is 0.1. ˜100 mW / cm ² is preferred.

  If the gel fraction of the acrylic pressure-sensitive adhesive composing the pressure-sensitive adhesive sheet is low, the cohesive force of the acrylic pressure-sensitive adhesive is insufficient and the pressure-sensitive adhesive force is reduced. Under high temperature and high humidity, the display panel or protective plate When air bubbles are about to be generated at the interface with the pressure-sensitive adhesive sheet, they may not be able to resist the pressure and may float or peel off.If it is high, the pressure-sensitive adhesive sheet becomes too hard and stress dispersibility decreases. When air bubbles are about to be generated at the interface between the display panel or the protective plate and the pressure-sensitive adhesive sheet under high temperature and high humidity, the pressure cannot be dispersed and floating or peeling may occur. -90 weight% is preferable and 55-88 weight% is more preferable.

The gel fraction of the acrylic pressure-sensitive adhesive was measured as follows. First, an acrylic adhesive is weighed, and immersed in ethyl acetate at 23 ° C. for 24 hours, the insoluble matter is filtered through a 200 mesh wire mesh, and the residue on the wire mesh is dried at 110 ° C. under normal pressure. Then, the weight of the dry residue was measured (Bg) and calculated by the following formula.
Gel fraction (% by weight) = (B / A) × 100

  The total light transmittance in the 400 to 800 nm region of the pressure-sensitive adhesive sheet obtained as described above is preferably 85% or more, and preferably 90% or more. In addition, the total light transmittance of an adhesive sheet means what was measured using the integrating sphere type light transmittance apparatus based on JISK7105.

  The haze of the pressure-sensitive adhesive sheet is preferably 2.0% or less. In addition, the haze of an adhesive sheet means what was measured using the integrating sphere type light transmittance apparatus based on JISK7105.

  Next, the display apparatus A using the adhesive sheet of this invention is demonstrated. The pressure-sensitive adhesive sheet is used for stacking and integrating a protective plate on the surface of the display panel of the display device. First, as shown in FIG. 1, the backlight housing 1 of the display device A is formed in a rectangular frame shape made of synthetic resin, and has a flat rectangular frame shape for placing the display panel 2 on the upper end portion. The panel disposing step 11 is formed in an open state at the upper end surface of the backlight housing 1, and the reflecting plate disposing step 12 for disposing the reflecting plate 3 is provided at the lower end. A flat rectangular frame is formed in an open state at the end face.

  A flat rectangular display panel 2 having a size slightly smaller than the upper end opening of the backlight housing 1 is disposed on the panel placement step 11 of the backlight housing 1. In the backlight housing 1, a plurality of optical films such as a light guide plate 4, a diffusion sheet 5, and one or a plurality of prism sheets 6, 6. The display device 2 is configured by integrating the display panel 2, the optical film 6 facing the display panel 2, and the backlight housing 1 using a frame-like double-sided adhesive tape 7. In addition, the reflector 3 is disposed and integrated with the reflector-disposing step 12 of the backlight housing 1, and an LED (not shown) is disposed as a light source in the backlight housing 1. Has been.

  Further, a protective plate 8 is laminated and integrated on the surface of the display panel 2 of the display device A via an adhesive sheet 9. The protective plate 8 is made of a transparent synthetic resin plate such as polyethylene terephthalate, polycarbonate, or acrylic resin so that the display panel 2 can be visually recognized.

  However, the acrylic pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet 9 contains a copolymer containing a polydimethylsiloxane component having a radical polymerizable double bond as a monomer component, and is bonded to the main chain of this copolymer. Due to the side chain made of polydimethylsiloxane, the acrylic pressure-sensitive adhesive exhibits excellent wettability with respect to the protective plate 8 and the synthetic resin plate constituting the surface of the display panel 2, and the pressure-sensitive adhesive sheet 9 is used for the display panel 2 and the protection. The surface of the plate 8 is completely tightly integrated with no gap without involving air. Therefore, the display panel 2 and the protective plate 8 are firmly laminated and integrated through the adhesive sheet 9 without causing air accumulation at the interface between the display panel 2 and the protective plate 8 and the adhesive sheet 9.

  And the acrylic adhesive which comprises the adhesive sheet 9 contains polydimethylsiloxane which has two or more polyfunctional (meth) acrylate or radical polymerizable double bond as a monomer component, and is bridge | crosslinked moderately. Therefore, it also has excellent heat resistance, and exhibits excellent adhesive force even in harsh environments such as high temperature and high humidity, and the display panel 2 and the protective plate 8 are firmly integrated.

  In the above description, the optical film facing the display panel 2 is described as the prism sheet 6. However, the optical film facing the display panel 2 is not necessarily a prism sheet, and other optical films may be used. Good. In the above description, the display device A is a liquid crystal display device. However, the display device A may be a display device using an organic EL (electroluminescence) panel. In addition, when an organic EL panel is used, a light source is not necessary.

  In the display device A configured as described above, the protective plate 8 and the display panel 2 are laminated and integrated via the adhesive sheet 9, and an air layer is interposed between the protective plate 8 and the display panel 2. It does not exist, and deterioration of display quality due to refraction of light in the air layer can be prevented, so that the display device A exhibits excellent display performance.

  Even when a stress such as an unexpectedly large pressing force is applied to the protective plate 8, the protective plate 8 is entirely received by the adhesive sheet 9, and the stress is absorbed and relaxed by the adhesive sheet 9. Therefore, the situation where the protective plate 8 is unexpectedly broken can be generally prevented.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet used for laminating and integrating a protective plate on the surface of a display panel of a display device. The pressure-sensitive adhesive sheet comprises an alkyl (meth) acrylate and a polyfunctional (meth) acrylate. And an acrylic pressure-sensitive adhesive containing a copolymer of polydimethylsiloxane having a radical polymerizable double bond, or polydimethyl having an alkyl (meth) acrylate and two or more radical polymerizable double bonds Since it is composed of an acrylic pressure-sensitive adhesive containing a copolymer with siloxane, it exhibits excellent wettability with respect to display panels and protective plates. Can be firmly laminated and integrated without generating air pockets at the interface between them.

  And the acrylic adhesive which comprises the adhesive sheet of this invention contains the copolymer containing the polydimethylsiloxane component which has a polyfunctional (meth) acrylate component or two or more radically polymerizable double bonds as a monomer component. Therefore, the pressure-sensitive adhesive sheet has excellent heat resistance and maintains excellent pressure-sensitive adhesiveness even under high temperature and high humidity.Therefore, the pressure-sensitive adhesive sheet has a display panel and a protective plate under any circumstances. It is possible to firmly laminate and integrate over a long period of time without generating bubbles or peeling at the interface with them, and the display performance of the display device can be stabilized over a long period of time.

  In particular, when polydimethylsiloxane has two or more radically polymerizable double bonds, the pressure-sensitive adhesive sheet has better heat resistance and ensures excellent adhesive performance even under harsh conditions. To do.

  In the above pressure-sensitive adhesive sheet, when polydimethylsiloxane has a (meth) acryloyl group, the copolymer constituting the acrylic pressure-sensitive adhesive hardly affects the pressure-sensitive adhesive properties of the acrylic pressure-sensitive adhesive. A side chain made of polydimethylsiloxane can be effectively introduced therein.

  In the pressure-sensitive adhesive sheet, when the polydimethylsiloxane has a (meth) acryloyl group at the end of its molecular chain, a linear chain is formed on the main chain of the copolymer constituting the acrylic pressure-sensitive adhesive. The side chain made of polydimethylsiloxane can be bonded, and this easy-to-move side chain made of polydimethylsiloxane further improves the wettability of the adhesive sheet to the display panel and the protective plate. Can be more strongly integrated by the pressure-sensitive adhesive sheet.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

(Examples 1-16, Comparative Examples 1-3)
2-ethylhexyl acrylate, n-butyl acrylate, ethyl acrylate, dodecyl acrylate, liquid hydrogenated 1,2 polybutadiene acrylate (manufactured by Nippon Soda Co., Ltd., trade name “TEAI-1000”, number average molecular weight: 2250), ethoxylated trimethylolpropane Triacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name “SR502”, molecular weight: 692), hexanediol diacrylate (manufactured by Nippon Kayaku Co., Ltd., molecular weight: 226), polydimethylsiloxane 1 (trade name “Silaplane FM, manufactured by Chisso Corporation” -0721 ", polydimethylsiloxane having a methacryloyl group only at one end of the molecular chain, number average molecular weight: 5000, polydimethylsiloxane 2 (product name" Silaplane FM-0711 "manufactured by Chisso Corporation), molecular chain of methacryloyl group One end of Polydimethylsiloxane only in the number average molecular weight: 1000, polydimethylsiloxane 3 (manufactured by Chisso Corporation, trade name “Silaplane FM-0725”, polydimethylsiloxane having a methacryloyl group only at one end of the molecular chain, number average Molecular weight 10,000), polydimethylsiloxane 4 (product name “Silaplane FM-7721” manufactured by Chisso Corporation, polydimethylsiloxane having methacryloyl groups at both ends of the molecular chain, number average molecular weight: 5000), acrylic acid, 2,2- Dimethoxy-2-phenylacetophene (manufactured by Ciba Geigy, trade name “Irgacure 651”) and hydrophilic silica (trade name “Aerosil A-200”, manufactured by Nippon Aerosil Co., Ltd.) as a thickener are shown in Table 1 All units are “parts by weight”). Then, a monomer composition from which dissolved oxygen was removed by purging with nitrogen was prepared.

  Next, two 50 μm-thick polyethylene terephthalate films having one surface released from the mold were prepared, and the monomer composition was applied to the release-treated surface of one polyethylene terephthalate film using a doctor blade. After forming, the other polyethylene terephthalate film was overlaid on this monomer layer. A spacer member having a thickness of 0.3 mm was interposed between the opposed surfaces of the pair of polyethylene terephthalate films so that the thickness of the monomer layer was 0.3 mm.

Thereafter, the monomer composition was radically polymerized by irradiating with ultraviolet rays for 5 minutes so that the ultraviolet ray irradiation intensity was 3 mW / cm ² through a polyethylene terephthalate film through the monomer layer using a chemical lamp.

Furthermore, for the purpose of reducing the residual monomer, the monomer layer is irradiated with ultraviolet rays for 5 minutes so that the ultraviolet ray irradiation intensity is 20 mW / cm ² through a polyethylene terephthalate film through the monomer layer using a high pressure mercury lamp. The composition was radically polymerized to obtain an adhesive sheet having a thickness of 0.3 mm.

  The gel fraction of the obtained pressure-sensitive adhesive sheet was measured in the manner described above, and the air entrainment property, total light transmittance, haze, heat resistance and peeling force were measured in the manner shown below, and the results are shown in Table 1.

(Air entrainment)
A test piece having a plane rectangular shape of 40 × 50 mm was cut out from the pressure-sensitive adhesive sheet, and this test piece was adhered on a glass plate using a rubber roller. Next, an acrylic plate having a thickness of 0.5 mm is superimposed on the test piece, and a 0.5 kg rubber roller is reciprocated once so that the acrylic plate and the glass plate are laminated and integrated through the test piece. A sheet was produced.

  In the laminated sheet immediately after the production, the total number of bubbles entrained at the interface between the glass plate and the acrylic plate and the pressure-sensitive adhesive sheet was counted visually. Next, the same procedure as described above was performed except that the weight of the rubber roller was 2 kg and 5 kg, and the total number of bubbles entrained at the interface between the glass plate, the acrylic plate and the adhesive sheet was visually counted.

(Total light transmittance and haze)
The total light transmittance and haze of the pressure-sensitive adhesive sheet were measured using an integrating sphere light transmittance apparatus in accordance with JIS K 7105. However, since the pressure-sensitive adhesive sheet was very soft when used alone, measurement was performed with a polyethylene terephthalate film attached to both sides of the pressure-sensitive adhesive sheet, and a value obtained by sandwiching ethanol between the polyethylene terephthalate film was used as a reference value. The haze value (%) was calculated based on the following formula.
Haze value (%) = (H _d / H _t ) × 100
H _d : Diffuse transmittance (%)
H _t : Total light transmittance (%)

(Heat-resistant)
A test piece having a plane rectangular shape of 40 × 50 mm was cut out from the pressure-sensitive adhesive sheet, and this test piece was adhered on a glass plate using a rubber roller. Next, an acrylic plate having a thickness of 0.5 mm is superposed on the test piece, and a 2.0 kg rubber roller is reciprocated once to laminate the acrylic plate and the glass plate through the test piece. A sheet was produced.

  After this laminated sheet was cured at 23 ° C. for 24 hours, the laminated sheet was heated in a gear oven at 80 ° C. for 3 hours, and then the interface between the glass plate and the acrylic plate and the adhesive sheet The total number of bubbles entrained in was visually counted.

(5) Measurement of peel force After a polyethylene terephthalate film having a thickness of 25 μm was laminated and integrated on one surface of the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet was cut into a strip shape having a width of 10 mm to prepare a strip-shaped product. Prepare an acrylic resin plate, and stack the strips on the acrylic resin plate so that the adhesive sheet faces the acrylic resin plate, and then reciprocate a 2 kg rubber roller once to make a polyethylene terephthalate film and an acrylic resin. The plate was laminated and integrated through an adhesive sheet, and left at 23 ° C. for 24 hours. Thereafter, the peel force when peeling the strips from the acrylic resin plate is measured by performing a 180 ° peel test in a 23 ° C. atmosphere under a peel rate of 50 mm / min in accordance with JIS Z 0237. did.

It is the longitudinal cross-sectional view which showed the display apparatus. It is the disassembled perspective view which showed the display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight housing | casing 2 Display panel 3 Reflecting plate 4 Light guide plate 5 Diffusion sheet 6 Prism sheet 7 Double-sided adhesive tape 8 Protection plate 9 Adhesive sheet A Display device

Claims (9)

A pressure-sensitive adhesive sheet used for laminating and integrating a protective plate on the surface of a display panel of a display device, the pressure-sensitive adhesive sheet comprising an alkyl (meth) acrylate, a polyfunctional (meth) acrylate, and a radical polymerizable double-layer A pressure-sensitive adhesive sheet comprising an acrylic pressure-sensitive adhesive containing a copolymer with polydimethylsiloxane having one bond. A pressure-sensitive adhesive sheet used to laminate and integrate a protective plate on the surface of a display panel of a display device, the pressure-sensitive adhesive sheet comprising poly (dimethyl) acrylate and polydimethyl having two or more radical polymerizable double bonds A pressure-sensitive adhesive sheet comprising an acrylic pressure-sensitive adhesive containing a copolymer with siloxane. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the polydimethylsiloxane has a (meth) acryloyl group. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the polydimethylsiloxane has a (meth) acryloyl group at the end of its molecular chain. The acrylic pressure-sensitive adhesive has a weight ratio [polyfunctional (meth) acrylate component / alkyl (meth) acrylate component] of the alkyl (meth) acrylate component and the polyfunctional (meth) acrylate component] of 0.05 to 10. The pressure-sensitive adhesive sheet according to claim 1, which is characterized by: The pressure-sensitive adhesive sheet according to claim 1, wherein the polyfunctional (meth) acrylate is a polymer, and the number average molecular weight of the polymer is 400 or more. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the alkyl group of the alkyl (meth) acrylate has 4 to 10 carbon atoms. A display device in which a display panel of a display device and a protective plate disposed on the display panel are laminated and integrated via an adhesive sheet, the adhesive sheet comprising an alkyl (meth) acrylate, a polyfunctional ( A display device comprising an acrylic pressure-sensitive adhesive containing a copolymer of (meth) acrylate and polydimethylsiloxane having one radical polymerizable double bond. A display device in which a display panel of a display device and a protective plate disposed on the display panel are laminated and integrated via an adhesive sheet, the adhesive sheet comprising an alkyl (meth) acrylate and radically polymerizable A display device comprising an acrylic pressure-sensitive adhesive containing a copolymer with polydimethylsiloxane having two or more double bonds.

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