TOUCH SCREEN PANEL AND METHOD OF PREPARING THE SAME

A method for preparing a touch screen panel includes forming a non-conductive pattern on a non-display part on one face of a window plate, so that the thickness of the non-conductive pattern is decreased to produce a thin touch screen panel. In addition, this will prevent leakage of ink through the holes of the window plate, and improve the reliability of a conductive electrode pattern layer at a lateral side of the non-conductive pattern, thereby reducing failure rates.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention discloses a method for preparing a touch screen panel and, in particular, a method for preparing a touch screen panel, which includes forming a non-conductive pattern on a non-display part on one face of a window plate by offset printing, so that the thickness of the non-conductive pattern may be decreased producing a thin touch screen panel. In addition, it is possible to prevent leakage of ink through the holes of the window plate, and improve reliability of a conductive electrode pattern layer at a lateral side of the non-conductive pattern, thereby reducing failure rates.

Conventionally, a non-conductive pattern can be formed by screen printing. In this regard, in order to attain shielding effects through the non-conductive pattern, printing must be repeatedly executed to increase the thickness of the pattern. Accordingly, due to a step height caused by the thickness, there are problems associated with difficulty in forming a conductive electrode pattern layer, an increase in overall thickness of a touch screen panel, and ink leakage through the holes of a window plate.

Conversely, the method for preparing a touch screen panel of the present invention includes forming a non-conductive pattern by offset printing, thereby preventing ink leakage through the holes of a window plate and improving the reliability of an electrode pattern layer, which in turn reduces failure rates.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

The method for preparing a touch screen panel of the present invention may include forming a non-conductive pattern on a non-display part on one face of a window plate by offset printing.

Offset printing is a process of transferring ink images on a rubber blanket and printing the same on a subject to be printed. Non-limiting types of offset printing include, for example, gravure offset printing, reverse offset printing, or the like. Preferably, reverse offset printing is used.FIG. 1schematically illustrates one embodiment of the reverse offset printing mode. More particularly, this method may be executed by applying an ink composition for forming a non-conductive pattern to a blanket, contacting the blanket with an embossed cliché to form a desired pattern, and transferring the formed pattern to one face of a window plate.

A conventional non-conductive pattern was formed by a general screen printing process, wherein an ink composition for forming a non-conductive pattern is placed on a patterned screen, and the ink composition for forming a non-conductive pattern is directly provided on a window plate through a screen having an empty inner-space using a squeegee.

In screen printing, since a pigment typically includes large particles and has a rough surface, printing must be repeatedly conducted two to eight times in order to attain the desired shielding effects through the non-conductive pattern. Accordingly, by repeatedly printing four times, the thickness of the non-conductive pattern increased to about 20 μm, hence causing problems associated with increasing the overall thickness of the touch screen panel.

The conductive electrode pattern layer, typically included in the touch screen panel, is formed to cover the non-conductive pattern and window plate. However, since the non-conductive pattern was thickened, the reliability of the conductive electrode pattern layer at a lateral side of the non-conductive pattern is diminished. Furthermore, there are problems with ink leakage through the holes of the window plate.

However, the method for forming a touch screen panel of the present invention may form a non-conductive pattern by offset printing, wherein a pigment having a small particle size is used, and a process of coating a blanket with the pigment and transferring the pigment on the same is employed, so that the touch screen panel has a uniform surface flatness, and the smaller pigment particles ensure uniform packing effects, thus accomplishing the desired shielding effects by the non-conductive pattern, even if printing is executed only once.

Accordingly, the non-conductive pattern formed, as described above, may have a thickness of 1.5 to 2 μm, thus producing a thin touch screen panel and improving the reliability of a conductive electrode pattern formed on the non-conductive pattern.

Further, according to the design of the cliché, the transferring is executed in one-to-one, thus not causing problems of ink leakage through the holes of a window plate.

FIG. 2schematically illustrates one example of the method for preparing a touch screen panel according to the present invention. Hereinafter, the present invention will be described in detail with reference toFIG. 2.

A window plate311is a part receiving contact input from a specific object such as the human fingers of a user or a stylus pen, etc., in order to secure the outer appearance of a touch screen panel.

The window plate311may be prepared from any material, without limitation, so long as the material has the durability to sufficiently protect the touch screen panel from external forces, and allow a user to adequately view the display. The material may include, for example, glass, polyethersulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene napthalate (PEN), polyethylene terepthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate (CAP), or the like, which can be used alone or in combination with two or more thereof.

A non-conductive pattern312is formed on a non-display part on one face of the window plate311.

In order to hide an inner board and/or wiring of a device, the non-conductive pattern312has an opaque ornamental layer formed on a display part along the periphery of the window plate311, in such a way that the display part as a touch area is defined as the center of the window plate311.

The non-conductive pattern312according to the present invention may be a non-conductive color pattern or non-conductive shielding pattern.

The non-conductive color pattern may be formed using an ink composition for forming a non-conductive color pattern, generally used in offset printing, which includes a binder resin, coloring agent, polymerization initiator, solvent and the like.

Coloring agents are without limitation, so long as the coloring agents can express a color required by a user, and may include, for example: red, green, or blue dyes or pigments; yellow, orange, violet, or brown dyes or pigments for combinations of colors; black pigments; carbon black, and the like, which can be used alone or in combination with two or more thereof.

The coloring agents may further include metal powder, white pigments, fluorescent pigments, etc., as necessary.

The pigments may be inorganic pigments or organic pigments.

Inorganic pigments are without limitation, and may include, for example, barium sulfate, lead sulfate, titanium oxide, yellow lead, Bengal lead, calcium carbonate, chromium oxide, carbon black, or the like.

Organic pigments are without limitation, and may include pigments listed by the Color Index (C.I.) numbers below.

Phthalocyanine dyes are without limitation, and may include, for example, C.I. pad blue 5, or the like.

Quinonimine dyes are without limitation, and may include, for example, C.I. basic blue 3, C.I. basic blue 9, or the like.

Quinoline dyes are without limitation, and may include, for example, C.I. solvent yellow 33, C.I. acid yellow 3, C.I. disperse yellow 64, or the like.

Nitro dyes are without limitation, and may include, for example, C.I. acid yellow 1, C.I. acid orange 3, C.I. disperse yellow 42, or the like.

The binder resin plays a role of supporting the pattern and may be a copolymer of a monomer having a carboxyl group, and another monomer having an unsaturated bond.

The monomer having a carboxyl group is an unsaturated carboxylic acid having at least one carboxyl group in the molecule and may include, for example: a monocarboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, etc.; dicarboxylic acids such as fumaric acid, metaconic acid, itaconic acid, etc.; and anhydrides thereof, and the like.

Monomers having an unsaturated bond are without limitation so long as any monomer having an unsaturated double bond is copolymerizable with the monomer having a carboxyl group. Particular examples thereof may include: unsaturated carboxylic acid ester compounds such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, etc.; unsubstituted or substituted alkylester compounds of unsaturated carboxylic acids such as aminoethyl(meth)acrylate; unsaturated carboxylic acid ester compounds having alicyclic substituents such as cyclopentyl(meth)acrylate, cyclohexyl(meth)acrylate, methylcyclohexyl(meth)acrylate, cycloheptyl(meth)acrylate, cyclooctyl(meth)acrylate, cyclopentenyl(meth)acrylate, cyclohexenyl(meth)acrylate, cycloheptenyl(meth)acrylate, cyclooctenyl(meth)acrylate, isobornyl(meth)acrylate, adamantly(meth)acrylate, norbornyl(meth)acrylate, etc.; unsaturated carboxylic acid ester compounds having thermo-curable substituents such as 3-methyl-3-(meth)acryloxymethyloxetane, 3-ethyl-3-(meth)acryloxymethyloxetane, 3-methyl-3-(meth)acryloxyethyloxetane, etc.; unsaturated glycidyl carboxylic acid ester compounds such as glycidyl(meth)acrylate, etc.; unsaturated carboxylic acid ester compounds having aromatic ring-containing substituents such as benzyl(meth)acrylate, phenoxy(meth)acrylate, etc.; aromatic vinyl compounds such as styrene, vinyl toluene, α-methyl styrene, etc.; carboxylic acid vinylesters such as vinyl acetate, vinyl propionate, etc.; acrylonitrile derivatives such as (meth)acrylonitrile, α-chloroacrylonitrile, etc., which can used alone or in combination with two or more thereof.

Polymerizable compounds are without limitation, and may be any compound generally known or used in the art, for example, a compound having an epoxy group hardened by heat.

Compounds having an epoxy group are without limitation, and may include, for example, a curable monomer having an epoxy(meth)acrylate functional group structure.

Curable monomers having an epoxy(meth)acrylate functional group may be any epoxy(meth)acrylate selected from commercially available compounds, including for example, compounds having two epoxy acrylate groups or four epoxy acrylate groups within the same molecule.

Polymerization initiators used herein are without limitation, and may include any polymerization initiator known or used in the art, for example, triazines, acetophenones, xanthones, benzoins, imidazoles, etc., which can be used alone or in combination with two or more thereof.

The non-conductive shielding pattern may be formed using an ink composition for forming the non-conductive shielding pattern generally used in offset printing, which includes a binder resin, shielding agent, polymerizable compound, polymerization initiator, solvent, and the like.

The shielding agent is without limitation so long as it has insulating properties and shielding effects, and may include, for example: black or white achromatic color pigments; and pigments expressing black or white by mixing the same, which can be used alone or in combination with two or more thereof.

Optionally, the shielding agent may further include carbon black, aniline black, chromium oxide, iron oxide, titanium black, or mixtures thereof.

Other components except for the shielding agent may be the same components as those included in an ink composition for forming a non-conductive color pattern.

The inventive non-conductive pattern formed using the above ink composition may play a role in providing an external color for a device or the hiding and shielding of an inner board and wiring of the device.

The ink composition for forming a non-conductive pattern may have a viscosity ranging from 1 cps to 30 cps, preferably, 5 cps to 10 cps. If the viscosity of the ink composition for forming a non-conductive pattern is within the above range, the ink stability (a process maintaining the ability of the ink) is maintained during the appropriate ink coating, thereby enabling uniform coating and printing.

After formation of the non-conductive pattern312, the resulting product is subjected to further typical processes associated with preparing a touch screen panel to thus produce a complete touch screen panel.

According to one embodiment of the method for preparing a touch screen panel, after formation of the non-conductive pattern, a conductive electrode pattern layer313is formed on a window plate311having the non-conductive pattern312formed thereon.

The conductive electrode pattern layer313may play a role in detecting static electricity generated from the body of a human when his or her finger contacts the display part as a touch area of an image sensor, thereby converting it to electric signals.

A conductive material used for forming the conductive electrode pattern layer313is without limitation, and may include, for example, indium-tin oxide (ITO), indium-zinc oxide (IZO), zinc oxide (ZnO), indium-zinc-tin oxide (IZTO), cadmium-tin oxide (CTO), poly(3,4-ethylenedioxythiopene) (PEDOT), carbon nanotube (CNT), metal wire, etc., which can be used alone or in combination with two or more thereof.

Metals used in the metal wire are without limitation, and may include, for example, silver, gold, aluminum, copper, iron, nickel, titanium, tellurium, chromium, etc., which can be used alone or in combination with two or more thereof.

The method for forming the conductive electrode pattern layer313is without limitation. The conductive electrode pattern layer may be formed by, for example, photolithography using an etching paste, inkjet printing, screen printing, pad printing, gravure printing, flexography printing, offset printing, stencil printing, imprinting, or the like.

Next, an electrode pattern314may be formed on an area corresponding to the non-display part in the conductive electrode pattern layer313.

The electrode pattern314plays a role in delivering the electrical signal generated from the conductive electrode pattern layer313to flexible printed circuit board (FPCB), IC chips, or the like, by touching the display part of the window plate311.

The electrode pattern314may be formed from the same material by the same method as used for the conductive electrode pattern layer313.

Thereafter, a scattering preventative film315may be formed on the window plate311having the conductive transparent electrode pattern layer313and electrode pattern314formed thereon.

The scattering preventative film315may play a role in protecting both the patterns313and314, and preventing the same from being scattered when the window is broken.

Materials of the scattering preventative film315are without limitation so long as the materials are transparent and provide durability, and may include, for example, polyethylene terephthalate (PET).

A method for forming the scattering preventative film315is without limitation, and may include, for example, spin coating, roll coating, spray coating, dip coating, flow coating, doctor blade and dispensing, inkjet printing, screen printing, pad printing, gravure printing, offset printing, flexography printing, stencil printing, imprinting, and the like.

Next, a terminal316of a printed circuit board is connected to the electrode pattern314.

With respect to the printed circuit board, various types of printed circuit boards may be used, for example, a flexible printed circuit board (FPCB) may be used.

The method for preparing a touch screen panel according to present invention, which includes the above described steps, may decrease the thickness of a non-conductive pattern to produce a thin touch screen panel, prevent ink leakage through the holes of a window plate311, and improve the reliability of a conductive electrode pattern layer313at a lateral side of the non-conductive pattern, thereby reducing failure rates.