Display unit integral with touch panel bonded through an...

Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel

Reexamination Certificate

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Details

C178S018030

Reexamination Certificate

active

06310612

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an adhesive composition to be used in production of a display unit, such as CRT (cathode ray tube) and LCD (liquid crystal display), integral with a touch panel by bonding the touch panel to the display unit. The present invention also relates to an adhesive film, a display unit integral with a touch panel made with the adhesive composition or adhesive film, and a process for producing them.
In recent years, there has been seen a general use of the display unit integral with a touch panel (which is integrally composed of a touch panel and a display unit such as CRT and LCD) for ATMs and CDs in banks, ticket vending machines in stations, and portable information terminals.
The display unit integral with a touch panel is, as shown in
FIG. 2
, composed of a touch panel
1
, a display unit
2
(such as LCD), and a spacer
3
interposed between them. The touch panel
1
and the display unit
2
are separated from each other by a prescribed gap
4
(about 0.4 mm). Without this gap, the touch panel
1
under pressure by touching will come into direct contact with the display unit
2
, thereby blurring the images. This problem is likely to arise in the case of LCD display unit, because the layer of liquid crystal easily distorts to give blurred images.
Unfortunately, the gap between the touch panel and the display unit reflects, scatters, and absorbs light, thereby decreasing the contrast of display, an important factor as a display, by half. This lowers visibility and causes parallax and shade at the time of input.
Therefore, it is desirable to eliminate the gap by bonding the touch panel directly to the display unit. Unfortunately, there has been no adhesive available for this purpose. An adhesive such as epoxy resin adhesive is not suitable because it forms a hard adhesive layer which transmits pressure directly to the display unit when the touch panel is pressed. This results in blurred images. Moreover, an epoxy resin adhesive is poor in wetting properties and hence does not give a uniform adhesive layer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an adhesive composition to be used in production of a display unit integral with a touch panel, an adhesive film, a display unit integral with a touch panel, and a process for producing them. The adhesive composition, when used to bond a touch panel directly to a display unit, gives an adhesive layer which has an adequate elastic property or buffering action and is superior in clarity, adhesiveness, and durability, the clarity imparting good visibility to the display unit integral with a touch panel.
The present invention provides the following adhesive composition, adhesive film, display unit and process for producing the display unit.
[I] A heat- and/or photo-curing adhesive composition to be used in production of a display unit integral with a touch panel by bonding the touch panel to the display unit, the adhesive composition comprising as a main component of one or more than one kind of copolymer selected from
(1) ethylene-vinyl acetate copolymer;
(2) copolymer of ethylene, vinyl acetate, and acrylate and/or methacrylate monomer;
(3) copolymer of ethylene, vinyl acetate, and maleic acid and/or maleic anhydride; and
(4) copolymer of ethylene, acrylate and/or methacrylate monomer, and maleic acid and/or maleic anhydride.
The adhesive composition may be incorporated with an organic peroxide and/or photosensitizer to make it heat- and/or photo-curable through crosslinking. It may also be incorporated with additives such as silane coupling agent, acryloxy group-containing compound, methacryloxy group-containing compound, allyl group-containing compound, and hydrocarbon resin.
[II] An adhesive film for a display unit integral with a touch panel which is formed from the above-defined adhesive composition and has its one side or both sides embossed such that the average surface roughness Ra is 0.1-20 &mgr;m.
[III] A display unit integral with a touch panel which is characterized in that the touch panel and the display unit are bonded together by a heat- and/or photo-cured layer of the above-defined adhesive composition.
[IV] A process for producing a display unit integral with a touch panel, the process comprising interposing the above-defined adhesive composition between the touch panel and the display unit, and then curing the adhesive composition by heat and/or light.
[V] A process for producing a display unit integral with a touch panel, the process comprising interposing the adhesive film being made from the above-defined adhesive composition between the touch panel and the display unit, and then melting and curing simultaneously the adhesive film by heating under reduced pressure.
[VI] A process for producing a display unit integral with a touch panel, the process comprising interposing the adhesive film being made from the above-defined adhesive composition between the touch panel and the display unit, and then melting and curing simultaneously the adhesive film by heating under pressure.
According to the present invention, the adhesive composition and the adhesive film are heat- and/or photo-curable. The adhesive composition can be made into an adhesive film which can be used to bond the touch panel and the display unit together easily and accurately. Having autohesion properties (surface tackiness), the adhesive composition or adhesive film makes it possible to bond the touch panel to the display unit easily at comparatively low temperatures (room temperature to about 80° C.). Owing to its autohesion properties, the adhesive composition or adhesive film permits the bonded parts to be handled freely without displacement and/or peeling before it is cured. After curing, the adhesive composition or adhesive film exhibits good flexibility with a low modulus of elasticity.
When this adhesive composition or adhesive film is used to bond the touch panel directly to the display unit, the resulting display unit integral with a touch panel does not pose the above-mentioned problems (decreased contrast, decreased visibility, parallax at the time of input, display shade, and so on) because there is no gap between the touch panel and the display unit. Owing to adequate elastic properties and buffering action, the display unit integral with a touch panel poses no problem of blurring despite their direct bonding. The adhesion layer formed by the adhesive composition or adhesive film is superior in clarity, adhesiveness, and durability, which contributes to sturdy display units.
The above-mentioned adhesive film, particularly the embossed one, is easy to use in production of display units, because it has no surface tackiness and hence it can be easily moved for accurate positioning when it is interposed between the touch panel and the display unit. Moreover, the embossed adhesive film makes it easy to evacuate air between the touch panel and the display unit under reduced pressure or under pressure. The resulting adhesion layer is uniform freeing from a failure such as entrapped air bubbles and hence permits close adhesion between the touch panel and the display unit.


REFERENCES:
patent: 5731050 (1998-03-01), Kotsubo et al.
patent: 6016134 (2000-01-01), Ota
patent: 0 727 471 A2 (1996-02-01), None
patent: 7-105781 (1995-04-01), None
Patent Abstracts of Japan, vol. 098, No. 001, Jan. 30, 1998 & JP 09 25 1159 A Sep. 22, 1997 *abstract*.
Patent Abstracts of Japan, vol. 095, No. 010, Nov. 30, 1995 & JP 07 169367 A Jul. 4, 1995 *abstract*.
Patent Abstracts of Japan, vol. 010, No. 094 (C-338), Apr. 11, 1986 & JP 60 226589 A Nov. 11, 1985 *abstract*.

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