JP2017014458A - Conductive adhesive tape for display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive adhesive tape for a display device that is suitably used for removal of static electricity and shielding of electromagnetic wave, is excellent in step followability when laminated, hardly causes floating and peeling over a long period of time and can maintain excellent electrical characteristics.SOLUTION: The conductive adhesive tape for a display device has an acrylic adhesive layer on at least one surface of a conductive base material having a plastic film and a metal thin film. The acrylic adhesive layer contains an acrylic copolymer and a metal filler and has a degree of crosslinking of 20 to 45 wt% and a storage elastic modulus G' at 25°C of 1.8×10to 4.0×10GPa. The conductive adhesive tape for a display device has a probe tack of 10 N/mmor more, a low-speed peeling force to the vertical direction of 20 N/cmor more and a length of shear displacement at 85°C of 2 mm or less.SELECTED DRAWING: Figure 1

Description

The present invention is suitably used for static electricity removal and electromagnetic wave shielding in a display device, has excellent step-following properties at the time of bonding, and does not easily lift off over a long period of time, and can maintain excellent electrical characteristics. It relates to an adhesive tape.

In a display device such as a liquid crystal display or an organic EL display, it is required to release and remove static electricity charged around the display screen. As a method of removing static electricity, for example, a method in which a conductive portion is provided near the display screen, the conductive portion is electrically connected to a printed circuit board provided at the lower portion of the display screen, and the charged static electricity is grounded. Has been adopted. Such a conductive portion has been conventionally formed by applying a silver paste.

In recent years, display devices have been increased in screen size, and materials that are easily affected by static electricity have increased as materials for display devices. Therefore, it is required to more efficiently remove static electricity. For this reason, it replaces with silver paste and the electroconductive adhesive tape by which the adhesive layer was laminated | stacked on metal foil, such as copper foil and aluminum foil, is used. The conductive adhesive tape is effective not only for removing static electricity but also for shielding (shielding) noise electromagnetic waves from the outside. For example, Patent Document 1 describes that a conductive tape in which an adhesive layer is laminated on a metal foil is used for a conductive portion of a display device.

In many cases, a conductive adhesive tape is bonded to a bent surface with a narrow adhesive area in a display device. In conventional conductive adhesive tapes in which an adhesive layer is laminated on a metal foil, the step following ability at the time of bonding is insufficient, so peeling due to uneven bonding occurs and it is difficult to exert sufficient electrical characteristics. It was. Moreover, the conductive adhesive tape in which a pressure-sensitive adhesive layer is laminated on a conventional metal foil has been exfoliated due to repulsion after a long period of time in an environment of high temperature, high temperature and high humidity, and electrical characteristics have deteriorated.

JP 2011-209334 A

The present invention is suitably used for static electricity removal and electromagnetic wave shielding in a display device, has excellent step-following properties at the time of bonding, and does not easily lift off over a long period of time, and can maintain excellent electrical characteristics. An object is to provide an adhesive tape.

The present invention relates to a conductive pressure-sensitive adhesive tape for a display device having an acrylic pressure-sensitive adhesive layer on at least one surface of a conductive substrate having a plastic film and a metal thin film, wherein the acrylic pressure-sensitive adhesive layer is an acrylic copolymer. And the degree of cross-linking of the acrylic pressure-sensitive adhesive layer is 20 to 45% by weight, and the storage elastic modulus G ′ at 25 ° C. is 1.8 × 10 ^{5 to} 4.0 × 10 ⁵ Gpa, Conductive pressure-sensitive adhesive tape for display device has a probe tack of 10 N / mm ² or more, a low-speed peel force in the vertical direction of 20 N / cm ² or more, and a shear deviation length at 85 ° C. of 2 mm or less. It is a tape.
The present invention is described in detail below.

The present inventor uses a conductive substrate having a plastic film and a metal thin film in a conductive pressure-sensitive adhesive tape for a display device having an acrylic pressure-sensitive adhesive layer on at least one surface of the conductive substrate. By adjusting the degree of cross-linking and storage elastic modulus G ′ at 25 ° C., probe tack of conductive adhesive tape for display device, low-speed peeling force in the vertical direction, and shear deviation length at 85 ° C. to specific ranges In addition, it is possible to improve the step following ability at the time of bonding of the conductive adhesive tape for display device, and further to suppress the peeling of the conductive adhesive tape for display device over a long period of time and to maintain excellent electrical characteristics. The headline and the present invention have been completed.

The conductive pressure-sensitive adhesive tape for display device of the present invention has an acrylic pressure-sensitive adhesive layer on at least one surface of a conductive substrate having a plastic film and a metal thin film.
The conductive substrate has a plastic film excellent in flexibility and a thin metal film having high strength and is difficult to be stressed. For this reason, by having the said electroconductive base material, the electroconductive adhesive tape for display apparatuses of this invention can maintain the outstanding electrical property which is hard to produce peeling off over a long period of time. In addition, in the conductive adhesive tape in which the pressure-sensitive adhesive layer is laminated on the conventional metal foil, the metal foil as the conductive base material is hard and has high resilience. Gets worse.

Although the said plastic film is not specifically limited, For example, transparent plastics, such as a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polycarbonate (PC) film, an expanded polypropylene (OPP) film, a triacetyl cellulose (TAC) film A film is preferred. Among these, a PET film is more preferable because of excellent heat resistance, dimensional stability, and mechanical strength.

The metal thin film is preferably a thin film made of a metal such as nickel, silver, copper, or aluminum formed on the plastic film by a sputtering method, a vacuum deposition method, or the like. Especially, since the stable resistance value and electromagnetic wave shielding characteristics are stable in each frequency band, a thin film made of silver or copper is more preferable.

The thickness of the plastic film is not particularly limited, but a preferable lower limit is 6 μm, a preferable upper limit is 38 μm, a more preferable lower limit is 12 μm, and a more preferable upper limit is 25 μm.
Although the thickness of the said metal thin film is not specifically limited, A preferable minimum is 0.01 micrometer and a preferable upper limit is 0.3 micrometer, A more preferable minimum is 0.1 micrometer, A more preferable upper limit is 0.2 micrometer.
If the plastic film or the metal thin film is too thin, the strength of the conductive pressure-sensitive adhesive tape for display device may be reduced, and may be destroyed when a strong impact is applied. If the plastic film or the metal thin film is too thick, the conductive adhesive tape for display device may be lifted off due to repulsion after a long period of time, and the electrical characteristics of the adhesive tape may be deteriorated.

As a method for producing the conductive substrate, for example, a method of forming the metal thin film on the plastic film by a sputtering method, a vacuum deposition method, or the like, or a plating of the metal thin film on the plastic film by an electroless plating method. Methods and the like.

If the conductive adhesive tape for display devices of the present invention has an acrylic pressure-sensitive adhesive layer on at least one surface of the conductive substrate, either the metal thin film side or the plastic film side of the conductive substrate is used. You may have an acrylic adhesive layer.
The conductive adhesive tape for display device of the present invention may have an acrylic adhesive layer on both the metal thin film side and the plastic film side of the conductive substrate, The composition may be the same or different.

The acrylic pressure-sensitive adhesive layer contains an acrylic copolymer and a metal filler, has a crosslinking degree of 20 to 45% by weight, and a storage elastic modulus G ′ at 25 ° C. of 1.8 × 10 ⁵ to 4. It is 0 × 10 ⁵ Gpa.
By having the acrylic pressure-sensitive adhesive layer, the conductive pressure-sensitive adhesive tape for display device of the present invention improves the step following property at the time of bonding, and does not easily peel off due to uneven bonding. Moreover, by having the said acrylic adhesive layer, the electroconductive adhesive tape for display apparatuses of this invention can maintain the electrical property which was hard to produce floating peeling over a long period of time, and was excellent.

If the degree of cross-linking of the acrylic pressure-sensitive adhesive layer is less than 20% by weight, the acrylic pressure-sensitive adhesive layer becomes too soft and the cohesive force is lowered. Peeling occurs and the electrical properties of the adhesive tape are deteriorated. Even if the cross-linking degree of the acrylic pressure-sensitive adhesive layer exceeds 45% by weight, the acrylic pressure-sensitive adhesive layer becomes too hard and the adhesive strength is lowered. Peeling occurs and the electrical properties of the adhesive tape are deteriorated. Moreover, since the said acrylic adhesive layer will become hard when the crosslinking degree of the said acrylic adhesive layer exceeds 45 weight%, the level | step following followability at the time of bonding of the electroconductive adhesive tape for display apparatuses will fall, and uneven bonding will be carried out. Peeling easily occurs. The preferred lower limit of the degree of crosslinking of the acrylic pressure-sensitive adhesive layer is 25% by weight, the preferred upper limit is 40% by weight, the more preferred lower limit is 30% by weight, and the more preferred upper limit is 35% by weight.
The degree of cross-linking of the acrylic pressure-sensitive adhesive layer was determined by taking W1 (g) of the acrylic pressure-sensitive adhesive layer and immersing this acrylic pressure-sensitive adhesive layer in ethyl acetate at 23 ° C. for 24 hours to make the insoluble matter 200 mesh wire mesh. The residue on the wire mesh is vacuum-dried, and the weight W2 (g) of the dried residue is measured, and calculated by the following formula (1).
Crosslinking degree (% by weight) = 100 × W2 / W1 (1)

When the storage elastic modulus G ′ at 25 ° C. of the acrylic pressure-sensitive adhesive layer is less than 1.8 × 10 ⁵ Gpa, the acrylic pressure-sensitive adhesive layer becomes too soft and the cohesive force decreases, so that a long time elapses. The conductive adhesive tape for display device is lifted off due to the repulsion, and the electrical properties of the adhesive tape are deteriorated. Even when the storage elastic modulus G ′ at 25 ° C. of the acrylic pressure-sensitive adhesive layer exceeds 4.0 × 10 ⁵ Gpa, the acrylic pressure-sensitive adhesive layer becomes too hard and the adhesive force is reduced. The conductive adhesive tape for display device is lifted off due to the repulsion, and the electrical properties of the adhesive tape are deteriorated. Further, when the storage elastic modulus G ′ at 25 ° C. of the acrylic pressure-sensitive adhesive layer exceeds 4.0 × 10 ⁵ Gpa, the acrylic pressure-sensitive adhesive layer becomes hard, and therefore when the conductive pressure-sensitive adhesive tape for display device is bonded. The step following ability is reduced, and peeling due to uneven bonding tends to occur. The preferable lower limit of the storage elastic modulus G ′ at 25 ° C. of the acrylic pressure-sensitive adhesive layer is 2.0 × 10 ⁵ Gpa, the preferable upper limit is 3.8 × 10 ⁵ Gpa, and the more preferable lower limit is 2.5 × 10 ^5. Gpa, more preferably the upper limit is 3.5 × 10 ⁵ Gpa.
In addition, the storage elastic modulus G ′ at 25 ° C. of the acrylic pressure-sensitive adhesive layer is measured under a condition of a measurement frequency of 10 Hz by shear deformation using a dynamic viscoelasticity measuring device (for example, (DVA-200 manufactured by IT Corporation)). The dynamic viscoelastic spectrum of the acrylic pressure-sensitive adhesive layer is measured and determined.

As a method for adjusting the crosslinking degree of the acrylic pressure-sensitive adhesive layer and the storage elastic modulus G ′ at 25 ° C. to the above range, for example, a method for adjusting the weight average molecular weight of the acrylic copolymer, added to the acrylic pressure-sensitive adhesive layer And a method for adjusting the content of the tackifier resin to be formed, a method for adjusting the content of a crosslinking agent for forming a crosslinked structure in the acrylic pressure-sensitive adhesive layer, and the like.

The acrylic copolymer is preferably a copolymer obtained by copolymerizing a monomer mixture containing butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). The content of butyl acrylate in the total monomer mixture and the content of 2-ethylhexyl acrylate are not particularly limited, but the preferable content of butyl acrylate is 50 to 90% by weight, and the preferable content of 2-ethylhexyl acrylate is 10 to 10%. 50% by weight.

The monomer mixture may contain other polymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate as necessary.
Examples of other polymerizable monomers that can be copolymerized include, for example, carbon number of alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate. 1 to 3 (meth) acrylic acid alkyl ester, tridecyl methacrylate, and (meth) acrylic acid alkyl ester having 13 to 18 carbon atoms such as stearyl (meth) acrylate, hydroxyalkyl (meth) acrylate , Glycerin dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid and the like.

In order to copolymerize the monomer mixture to obtain the acrylic copolymer, the monomer mixture may be radically reacted in the presence of a polymerization initiator. As a method of radical reaction of the monomer mixture, that is, a polymerization method, a conventionally known method is used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
The said polymerization initiator is not specifically limited, For example, an organic peroxide, an azo compound, etc. are mentioned. Examples of the organic peroxide include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5 -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

The acrylic copolymer preferably has a weight average molecular weight (Mw) of 400,000 to 1,200,000. When the weight average molecular weight is less than 400,000, the acrylic pressure-sensitive adhesive layer becomes too soft and the cohesive force is reduced. The electrical properties of the adhesive tape may deteriorate. Even if the weight average molecular weight exceeds 1,200,000, the acrylic pressure-sensitive adhesive layer becomes too hard and the adhesive strength is reduced. The electrical properties of the adhesive tape may deteriorate. Further, when the weight average molecular weight exceeds 1,200,000, the acrylic pressure-sensitive adhesive layer becomes hard, so that the step following property at the time of bonding of the conductive pressure-sensitive adhesive tape for display device is lowered, and peeling due to uneven bonding is likely to occur. May be. The minimum with said more preferable weight average molecular weight is 500,000, and a more preferable upper limit is 700,000.
In order to adjust the weight average molecular weight to the above range, polymerization conditions such as a polymerization initiator and a polymerization temperature may be adjusted.
In addition, a weight average molecular weight (Mw) is a weight average molecular weight of standard polystyrene conversion by GPC (Gel Permeation Chromatography: gel permeation chromatography).

The said metal filler will not be specifically limited if electroconductivity can be provided to the said acrylic adhesive layer, For example, the particle | grains which consist of metals, such as nickel, silver, copper, gold | metal | money, aluminum, iron, a tin alloy, and titanium, are mentioned.
The shape of the metal filler is not particularly limited, and the average particle diameter in the case of a spherical shape is not particularly limited, but the preferable lower limit of the average particle diameter is 1 μm, and the preferable upper limit is 20 μm. When the average particle diameter is less than 1 μm, a conductive path may not be formed and the resistance value may increase. When the average particle diameter exceeds 20 μm, the conductive particles may aggregate. A more preferable lower limit of the average particle diameter is 10 μm, and a more preferable upper limit is 12 μm.

Although content of the said metal filler is not specifically limited, The preferable minimum with respect to 100 weight part of said acrylic copolymers is 20 weight part, and a preferable upper limit is 80 weight part. When the content is less than 20 parts by weight, it may be difficult to form a conductive path. When the content exceeds 80 parts by weight, the contact resistance at the interface may affect the resistance value. A more preferable lower limit of the content is 30 parts by weight, and a more preferable lower limit is 60 parts by weight.

The acrylic pressure-sensitive adhesive layer preferably contains a tackifier resin.
Examples of the tackifier resins include rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, and C9 resins. Examples thereof include petroleum resins and C5-C9 copolymer petroleum resins. These tackifying resins may be used alone or in combination of two or more.

The tackifier resin is preferably highly polar from the viewpoint of improving adhesiveness and dispersibility of the metal filler. The preferred lower limit of the hydroxyl value is 20, the preferred upper limit is 200, and the more preferred lower limit is 30. A more preferred upper limit is 150.

Although content of the said tackifying resin is not specifically limited, The preferable minimum with respect to 100 weight part of said acrylic copolymers is 5 weight part, and a preferable upper limit is 40 weight part. When the content is less than 5 parts by weight, the adhesive strength of the acrylic pressure-sensitive adhesive layer is lowered. Therefore, when a long period of time elapses, the conductive pressure-sensitive adhesive tape for display device is lifted off due to repulsion, and the electric power of the pressure-sensitive adhesive tape is reduced. Characteristics may deteriorate. Even if the content exceeds 40 parts by weight, the acrylic pressure-sensitive adhesive layer becomes too hard and the adhesive strength is lowered, so that the conductive adhesive tape for display device is lifted off due to repulsion after a long period of time, The electrical properties of the adhesive tape may deteriorate. A more preferable lower limit of the content is 10 parts by weight, and a more preferable lower limit is 30 parts by weight.

In the acrylic pressure-sensitive adhesive layer, a crosslinking structure is formed between the main chains of the resin (the acrylic copolymer and / or the tackifying resin) constituting the acrylic pressure-sensitive adhesive layer by adding a crosslinking agent. It is preferable.
The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Of these, isocyanate-based crosslinking agents are preferred. By adding an isocyanate-based crosslinking agent to the acrylic pressure-sensitive adhesive layer, the isocyanate group of the isocyanate-based cross-linking agent reacts with the alcoholic hydroxyl group in the resin constituting the acrylic pressure-sensitive adhesive layer, and the acrylic pressure-sensitive adhesive layer. The cross-linking becomes loose. Therefore, since the acrylic pressure-sensitive adhesive layer can disperse the peeling stress applied intermittently, the conductive pressure-sensitive adhesive tape for a display device can hardly float and can maintain excellent electrical characteristics over a long period of time.
The addition amount of the crosslinking agent is preferably 0.01 to 10 parts by weight and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

The acrylic pressure-sensitive adhesive layer may contain plasticizers, emulsifiers, softeners, fillers, additives such as pigments and dyes, and other resins such as rosin resins, if necessary.

Although the thickness (thickness of one side) of the said acrylic adhesive layer is not specifically limited, A preferable minimum is 20 micrometers and a preferable upper limit is 60 micrometers. When the thickness is less than 20 μm, the adhesive strength of the acrylic pressure-sensitive adhesive layer is reduced, so that the conductive adhesive tape for display device is lifted off due to repulsion after a long period of time, and the electrical properties of the adhesive tape deteriorate. There are things to do. When the said thickness exceeds 60 micrometers, the rework property or re-peelability of the electroconductive adhesive tape for display apparatuses may be impaired. The more preferable lower limit of the thickness is 30 μm, and the more preferable upper limit is 42 μm.

The conductive adhesive tape for display device of the present invention may further have a light shielding layer on the plastic film side of the conductive substrate.
The said light shielding layer is not specifically limited, For example, the insulating light shielding layer printed with the black ink etc. on the plastic film side of the said electroconductive base material, the insulating light shielding layer printed with UV hardening ink, etc. are mentioned. In addition to printing, a black PET film kneaded with carbon black can be used as the light shielding layer.

Although the thickness of the said light shielding layer is not specifically limited, A preferable minimum is 1 micrometer and a preferable upper limit is 5 micrometers. If the thickness is less than 1 μm, pinholes (color loss) and appearance irregularities may occur. When the thickness exceeds 5 μm, blocking may occur. The more preferable lower limit of the thickness is 2 μm, and the more preferable upper limit is 4 μm.

In FIG. 1, sectional drawing which shows typically an example of the electroconductive adhesive tape for display apparatuses of this invention is shown.
A conductive adhesive tape 1 for a display device shown in FIG. 1 has an acrylic adhesive layer 4 on one surface (metal thin film 3 side) of a conductive base material having a plastic film 2 and a metal thin film 3. A light shielding layer 5 is further provided on the other surface (plastic film 2 side) of the conductive substrate.

The conductive adhesive tape for display device of the present invention has a probe tack of 10 N / mm ² or more. When the probe tack is less than 10 N / mm ² , the conductive adhesive tape for display device is lifted off due to repulsion after a long period of time, and the electrical properties of the adhesive tape are deteriorated. The probe tack is preferably 12 N / mm ² or more, and more preferably 15 N / mm ² or more.
The upper limit of the probe tack is not particularly limited, but if the probe tack is too high, the reworkability or removability of the conductive pressure-sensitive adhesive tape for display device is impaired, so the preferable upper limit is 20 N / mm ² .
The probe tack of the conductive adhesive tape for display device is 1 mm in size made of SUS with respect to the acrylic adhesive layer of the conductive adhesive tape for display device fixed on the support plate so that the acrylic adhesive layer is exposed. When a x1 mm x 1 mm probe is brought into contact at a speed of 300 mm / min, the probe is left in contact with the acrylic pressure-sensitive adhesive layer for 3 seconds, and then the probe is peeled off from the acrylic pressure-sensitive adhesive layer at a speed of 300 mm / min. Measure the peel strength of

The conductive adhesive tape for a display device of the present invention has a low-speed peeling force in the vertical direction of 20 N / cm ² or more. When the low-speed peeling force in the vertical direction is less than 20 N / cm ² , the conductive adhesive tape for display device is easily peeled off against the peeling force at a low speed in the vertical direction. The adhesive tape is lifted and peeled off, and the electrical properties of the adhesive tape are deteriorated. Slow release force to said vertical direction is preferably 23N / cm ² or more, 28N / cm ² or more is more preferable.
The upper limit of the low speed peel force to said vertical direction is not particularly limited, considering reworkability, the preferred upper limit is 40N / cm ^2, and more preferable upper limit is 30 N / cm ^2.
In addition, the low speed peeling force to the orthogonal | vertical direction of the electroconductive adhesive tape for display apparatuses can be measured as follows. That is, as an example of the conductive adhesive tape, a test piece obtained by cutting a conductive single-sided adhesive tape into 30 mm square is prepared. A polycarbonate plate (PC plate) of 30 mm × 30 mm × 2 mm is attached to the back surface of the conductive single-sided adhesive tape using a commercially available double-sided tape. A 20 mm square hole is made in the center of a stainless steel plate (SUS plate), and a conductive single-sided adhesive tape with a PC plate is manually attached to the periphery of the stainless steel plate so that the attachment width is constant. Tensilon (for example, manufactured by Shimadzu Corporation) can be used to determine the low-speed peel force in the vertical direction of the conductive single-sided adhesive tape.

The conductive adhesive tape for a display device of the present invention has a shear deviation length of 2 mm or less at 85 ° C. When the shear displacement length at 85 ° C. exceeds 2 mm, the conductive adhesive tape for display device tends to be displaced in the shear direction at high temperature, and the adhesive tape is lifted off due to repulsion after a long period of time, The electrical properties of the adhesive tape deteriorate. The shear deviation length at 85 ° C. is preferably 1.0 mm or less, and more preferably 0.5 mm or less.

In FIG. 2, the schematic diagram which shows the measuring method of the shear shift | offset | difference length in 85 degreeC of the electroconductive adhesive tape for display apparatuses is shown.
First, a conductive adhesive tape for a display device having an acrylic adhesive layer on both sides is cut into a plane rectangular shape of 25 mm × 50 mm to produce a test piece, and the release films on both sides are peeled and removed (referred to as test piece B). ). As shown in FIG. 2, a PET film C having a thickness of 25 μm with respect to the acrylic adhesive layer on the upper surface of the test piece B, and a metal base D (made of SUS) having a length of 25 mm and a width of 25 mm with respect to the acrylic adhesive layer on the lower surface. ) Are pasted to prepare test samples. A 50 g load is applied in the horizontal direction (arrow direction) to the PET film C on the upper surface of the test sample by a weight E and pulled for 3 minutes. The measurement is performed at 85 ° C. Then, one end (fixed) of the acrylic pressure-sensitive adhesive layer bonded to the PET film C on the upper surface with reference to the position of one end (end on the fixing jig side) of the acrylic pressure-sensitive adhesive layer bonded to the metal base D on the lower surface The distance L at which the end on the jig side is displaced in the pulling direction of the PET film C on the upper surface is measured.
In addition, the upper surface PET film C is affixed on the acrylic adhesive layer of the test piece B so that the acrylic adhesive layer adhering to the metal pedestal D on the lower surface and the PET film C on the upper surface are flush with each other. A detector (not shown) that can measure the amount of movement of one end of the PET film C on the upper surface in units of μm is installed.

As a method for adjusting the probe tack of the conductive pressure-sensitive adhesive tape for display device of the present invention, the low-speed peel force in the vertical direction, and the shear deviation length at 85 ° C. to the above ranges, for example, the weight average molecular weight of the acrylic copolymer A method for adjusting the content, a method for adjusting the content of the tackifying resin added to the acrylic pressure-sensitive adhesive layer, and an isocyanate-based cross-linking agent or an epoxy-based cross-linking agent for forming a cross-linked structure in the acrylic pressure-sensitive adhesive layer A method for adjusting the amount is exemplified.

Although the total thickness of the electroconductive adhesive tape for display devices of the present invention is not particularly limited, the preferred lower limit is 20 μm and the preferred upper limit is 80 μm. When the total thickness is less than 20 μm, handling by hand may be difficult. When the total thickness exceeds 80 μm, the pressure-sensitive adhesive tends to ooze out during processing, and processing conditions may be limited. The minimum with said more preferable total thickness is 48 micrometers, and a more preferable upper limit is 60 micrometers.

As a manufacturing method of the electroconductive adhesive tape for display apparatuses of this invention, the following methods are mentioned, for example.
First, a solvent is added to an acrylic copolymer, a metal filler, a tackifier resin, a cross-linking agent, etc. as necessary to prepare a solution of the adhesive a, and the solution of the adhesive a is applied to the surface of the conductive substrate. The acrylic adhesive layer a is formed by applying and completely removing the solvent in the solution by drying. Next, the release film is superposed on the formed acrylic pressure-sensitive adhesive layer a so that the release treatment surface faces the acrylic pressure-sensitive adhesive layer a.
Next, a release film different from the above release film is prepared, a solution of the adhesive b is applied to the release treatment surface of the release film, and the solvent in the solution is completely removed by drying, thereby releasing the release film. A laminated film having the acrylic pressure-sensitive adhesive layer b formed on the surface of the mold film is produced. The obtained laminated film is overlaid on the back surface of the conductive base material on which the acrylic pressure-sensitive adhesive layer a is formed, with the acrylic pressure-sensitive adhesive layer b facing the back surface of the conductive base material to produce a laminate. The laminate is pressed by a rubber roller or the like, thereby having an acrylic pressure-sensitive adhesive layer on both surfaces of the conductive base material, and the surface of the acrylic pressure-sensitive adhesive layer covered with a release film. An adhesive tape can be obtained.

In addition, two sets of laminated films are produced in the same manner, and these laminated films are superposed on both sides of the conductive substrate, with the acrylic adhesive layer of the laminated film facing the conductive substrate. A display in which a laminate is prepared, and the laminate is pressed by a rubber roller or the like to have an acrylic pressure-sensitive adhesive layer on both sides of the conductive substrate, and the surface of the acrylic pressure-sensitive adhesive layer is covered with a release film. You may obtain the electroconductive adhesive tape for apparatuses.

The use of the conductive adhesive tape for display device of the present invention is not particularly limited, but it is preferably used for static elimination and electromagnetic wave shielding in the display device. The conductive pressure-sensitive adhesive tape for display device of the present invention is excellent in step followability at the time of bonding even when bonded to a bent surface in a display device with a narrow adhesive area, and is excellent in being difficult to lift off for a long period of time. The electrical characteristics can be maintained.
The shape of the conductive adhesive tape for display device of the present invention in these applications is not particularly limited, and examples thereof include a rectangle, a frame shape, a circle, an ellipse, and a donut shape.

According to the present invention, it is suitably used for static electricity removal and electromagnetic wave shielding in a display device, has excellent step followability at the time of bonding, and does not easily float off for a long period of time and can maintain excellent electrical characteristics. A conductive adhesive tape can be provided.

It is sectional drawing which shows typically an example of the electroconductive adhesive tape for display apparatuses of this invention. It is a schematic diagram which shows the measuring method of the shear shift | offset | difference length in 85 degreeC of the electroconductive adhesive tape for display apparatuses.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

Example 1
(1) Production of conductive single-sided adhesive tape Acrylic copolymer (monomer: 30% by weight of 2-ethylhexyl acrylate (2-EHA), 60% by weight of butyl acrylate (BA), 6.7% by weight of cyclohexyl methacrylate (CHMA), 3% by weight of acrylic acid (AAC), 0.3% by weight of 4-butylhydroxyacrylate (4-HBA), 100 parts by weight of weight average molecular weight (Mw): 1,200,000, nickel particles as metal filler (average particle diameter 2 μm, Fukuda Metal Foil Co., Ltd., Ni255) 20 parts by weight, tackifier resin terpene resin (hydroxyl value 130, Yashara Chemical Co., G-150) 10 parts by weight, crosslinker isocyanate crosslinker (Tosoh Corp., Coronate L45) ) 1.4 parts by weight and 50 parts by weight of ethyl acetate as a solvent with stirring and mixing, pressure-sensitive adhesive solution It was prepared.
The adhesive solution obtained above is applied to the copper thin film side of a conductive substrate on which a 0.1 μm thick copper thin film is formed by sputtering on a polyethylene terephthalate (PET) film having a thickness of 16 μm, and 100 ° C. And dried for 5 minutes to form an acrylic adhesive layer having a thickness of 30 μm. Subsequently, black ink was printed on the PET film side of the conductive substrate to form an insulating light-shielding layer having a thickness of 2.0 m, and a conductive single-sided adhesive tape was obtained.

(2) Measurement of degree of crosslinking W1 (g) of the acrylic pressure-sensitive adhesive layer was collected, this acrylic pressure-sensitive adhesive layer was immersed in ethyl acetate at 23 ° C. for 24 hours, and the insoluble matter was filtered through a 200-mesh wire mesh. The residue on the wire mesh was vacuum-dried, the weight W2 (g) of the dried residue was measured, and the crosslinking degree of the acrylic pressure-sensitive adhesive layer was calculated by the following formula (1).
Crosslinking degree (% by weight) = 100 × W2 / W1 (1)

(3) Measurement of storage elastic modulus G ′ at 25 ° C. Dynamic viscoelasticity measurement of an acrylic pressure-sensitive adhesive layer under the condition of a measurement frequency of 10 Hz by shear deformation using a dynamic viscoelasticity measuring device (DVA-200, manufactured by IT Corporation). The elastic spectrum was measured, and the storage elastic modulus G ′ at 25 ° C. of the acrylic pressure-sensitive adhesive layer was determined.

(4) Measurement of probe tack Size 1.0 mm × 1.0 mm × 1. Of SUS with respect to the acrylic adhesive layer of the conductive single-sided adhesive tape fixed on the support plate so that the acrylic adhesive layer is exposed. A 0 mm probe was contacted at a speed of 300 mm / min, left for 3 seconds with the probe in contact with the acrylic adhesive layer, and then the peeling force when peeling the probe from the acrylic adhesive layer at a speed of 300 mm / min was measured. Measurement was made to determine the probe tack of the conductive single-sided adhesive tape.

(5) Measurement of low-speed peeling force in the vertical direction A test piece was prepared by cutting a conductive single-sided adhesive tape into 30 mm square. A 30 mm × 30 mm × 2 mm PC plate was affixed to the back of the conductive single-sided adhesive tape using a commercially available double-sided tape. A 20 mm square hole was made in the center of a stainless steel plate (SUS plate), and a conductive single-sided adhesive tape with a PC plate was attached by hand to the periphery so that the application width was constant. Tensilon (manufactured by Shimadzu Corporation) was used to determine the low-speed peel force in the vertical direction of the conductive single-sided adhesive tape.

(6) Measurement of shear deviation length at 85 ° C. An acrylic pressure-sensitive adhesive having the same composition and thickness on both sides in the same manner as in the examples and comparative examples except that an acrylic pressure-sensitive adhesive layer was further formed on the surface of the light-shielding layer. A conductive double-sided pressure-sensitive adhesive tape having a layer was separately produced. The shear deviation length at 85 ° C. of the conductive double-sided pressure-sensitive adhesive tape was measured by the measuring method shown in FIG.

(Examples 2-14, Comparative Examples 1-6)
As shown in Tables 1 and 2, except that the conductive substrate and the acrylic pressure-sensitive adhesive layer were changed, a conductive single-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, and each physical property was determined.

<Evaluation>
The following evaluation was performed about the electroconductive single-sided adhesive tape obtained by the Example and the comparative example.
The results are shown in Tables 1 and 2.

(1) Step following property at the time of bonding A conductive single-sided adhesive tape was bonded to a glass plate having a step of 20 μm under a condition of one reciprocating pressure bonding with a 2 kg roller in a room temperature environment. The bubbles caught in the step boundary were observed using an optical microscope, and the distance from the step boundary to the end of the bubble was measured.

(2) Floating off (flip up)
A test piece was prepared by cutting the conductive single-sided adhesive tape into a flat rectangular shape of 0.8 mm × 20 mm. After pasting the test piece on the SUS plate in a normal temperature environment, the test piece was left in an environment of 60 ° C. and a humidity of 90% for 120 hours. After standing, the test piece was peeled off from the SUS plate by visual observation. The case where there was no lift-off was evaluated as “◯”, and the case where there was a lift-off was evaluated as “x”.

(3) Electrical characteristics (3-1) Resistance value A test piece was prepared by cutting a conductive single-sided adhesive tape into a 20 mm × 50 mm flat rectangular shape. The test piece was affixed on each SUS board so that two SUS boards might be bridged. At this time, the adhesion area to each SUS plate was set to 20 mm × 20 mm.
In this state, the resistance value between the two SUS plates was measured using a resistance value measuring device (manufactured by HIOKI).

(3-2) A test piece was prepared by cutting an electromagnetic wave shielding conductive single-sided adhesive tape into a 120 mm × 120 mm flat square shape. After bonding the test piece to a predetermined location of the measuring machine, the measurement was performed with a KEC apparatus (TSJ).

According to the present invention, it is suitably used for static electricity removal and electromagnetic wave shielding in a display device, has excellent step followability at the time of bonding, and does not easily float off for a long period of time and can maintain excellent electrical characteristics. A conductive adhesive tape can be provided.

DESCRIPTION OF SYMBOLS 1 Conductive adhesive tape 2 for display apparatuses Plastic film 3 Metal thin film 4 Acrylic adhesive layer 5 Light-shielding layer B Test piece C PET film D Metal base E Weight L Shearing deviation length (PET film with one end of acrylic adhesive layer on top (Distance shifted in the pulling direction of C)

Claims (4)

A conductive pressure-sensitive adhesive tape for a display device having an acrylic pressure-sensitive adhesive layer on at least one surface of a conductive substrate having a plastic film and a metal thin film,
The acrylic pressure-sensitive adhesive layer contains an acrylic copolymer and a metal filler,
The acrylic adhesive layer has a crosslinking degree of 20 to 45% by weight and a storage elastic modulus G ′ at 25 ° C. of 1.8 × 10 ^{5 to} 4.0 × 10 ⁵ Gpa,
The display is characterized in that the probe tack of the conductive adhesive tape for display device is 10 N / mm ² or more, the low-speed peel force in the vertical direction is 20 N / cm ² or more, and the shear deviation length at 85 ° C. is 2 mm or less. Conductive adhesive tape for equipment. The conductive adhesive tape for a display device according to claim 1, wherein the acrylic adhesive layer has a thickness of 20 to 60 µm. 3. The conductive adhesive tape for a display device according to claim 1, further comprising a light shielding layer on the plastic film side of the conductive substrate. The conductive adhesive tape for a display device according to claim 1, 2 or 3, which is used for removing static electricity and shielding an electromagnetic wave in the display device.

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