JP7096656B2 - Coating composition, conductive film, touch panel and manufacturing method - Google Patents

Description

The present invention relates to a coating composition for forming a conductive film, and more particularly to a coating composition for forming a conductive film of a touch panel.

Conventionally, the majority of liquid crystal display panels used to be the vertical electric field method represented by the TN (twist nematic) type, but recently, the liquid crystal display panel called the horizontal electric field method has also become mainstream. It's coming. The horizontal electric field type liquid crystal display panel has an advantage that the viewing angle is wider than the vertical electric field type, but as a problem that does not occur in the vertical electric field type liquid crystal display panel, electrostatic from the outside or the inside of the liquid crystal display panel is electrostatic. There is a problem that the display quality is deteriorated, such as light omission when the display is black due to the influence or external electromagnetic interference. This is because the horizontal electric field type liquid crystal display panel has a structure in which a display electrode and a reference electrode are integrated on one transparent substrate, so that it has a conductive layer having a shielding function against static electricity from the outside. This is because it is not configured.

In order to solve such a panel configuration problem in the transverse electric field method, the surface of the transparent substrate of the liquid crystal display panel on the side opposite to the liquid crystal layer of the transparent substrate on the side far from the backlight unit is translucent. A technique has been proposed in which a conductive layer comprising the above is formed to have an electrostatic discharge (ESD) function, and specifically, a method of forming an antistatic film containing ITO or the like as a conductive layer has been put into practical use.

Further, as a type of touch panel, various methods have been proposed based on the principle of detecting the position on the touch panel sensor. Capacitance methods are often used in smart phones because they are optically bright and have a simple structure. In principle, when the outer conductor whose position should be detected comes into contact with the touch panel sensor layer via the dielectric, a new parasite capacitance is generated, and the change in this capacitive coupling is used to position the object. It is a mechanism to detect.

Recently, there is an increasing demand for a liquid crystal display device using a liquid crystal display panel having a touch panel function, as typified by a liquid crystal display device used for smart phones and the like. An example of a liquid crystal display panel with a built-in touch panel function is a so-called on-cell touch panel. The on-cell touch panel is a liquid crystal display panel with a built-in touch panel function, which has a layered structure in which touch detection electrodes are laminated between a color filter substrate and an upper polarizing plate.

Patent Document 1 describes the structure of a liquid crystal display panel with a built-in touch panel function. The touch panel shown in FIG. 6 of Patent Document 1 is a TFT array substrate 21, a touch panel drive electrode COML, a liquid crystal layer 6, a color filter 32, and a touch, which are sequentially laminated between two polarizing plates 4 and 54. It has a layer structure including a detection electrode CB1, a protective layer 33, an adhesive layer 51, a conductive layer 52, and a cover layer 53.

The conductive layer 52 has a conductive function and is conductive to the TFT array substrate. As a result, the conductive layer 52 reduces the distortion of the image display when static electricity is applied to the surface of the polarizing plate 5. Alternatively, the conductive layer 52 prevents or suppresses a decrease in the touch detection sensitivity when static electricity is applied to the surface of the polarizing plate 5.

Since the on-cell touch panel exhibits excellent sensitivity, it is used in liquid crystal display devices that require high quality.

Japanese Unexamined Patent Publication No. 2016-4183

As for the touch panel, as the display performance of the liquid crystal display panel is improved, it is required to further improve the touch panel performance such as touch detection sensitivity, operation reliability and stability.

The present invention is a coating composition containing chain conductive inorganic particles, a binder, a high boiling point solvent, and a low boiling point solvent.
The coating composition has a content of the chain conductive inorganic particles of 10 to 70% by mass with respect to the total amount of the chain conductive inorganic particles and the binder.
Used for forming a conductive film on the surface of a touch panel substrate having an electrode pattern in a touch panel having a TFT substrate, a liquid crystal layer, a color filter substrate, and a touch panel substrate, which are sequentially laminated between two polarizing plates. Provided is a coating composition that is to be used.

In one embodiment, the coating composition contains a solid content of the chain conductive inorganic particles and the binder in an amount of 0.1 to 5.0% by mass and a viscosity of 7.0 mPa · s or less. Has.

In one embodiment, the chain conductive inorganic particles are formed by connecting 2 to 50 primary particles having a particle size of 2 to 30 nm.

In one embodiment, the chain conductive inorganic particles include at least one particle selected from the group consisting of antimony-containing tin oxide particles, tin-containing indium oxide particles, and phosphorus-containing tin oxide particles.

In one embodiment, the touch panel is a touch panel having a second touch panel substrate laminated between a TFT substrate and a color filter substrate.

Further, in the present invention, any of the above coating compositions is used on the upper surface of a touch panel substrate of a touch panel having a TFT substrate, a liquid crystal layer, a color filter substrate, and a touch panel substrate, which are sequentially laminated between two polarizing plates. To provide a conductive film formed in the above.

In one embodiment, the conductive film has a film thickness of 2-100 nm.

In one embodiment, the conductive film has a surface electrical resistance of 1.0 × 10 ⁹ to 1.0 × 10 ¹⁴ Ω / square or more.

In one embodiment, the conductive film has a pencil hardness of 3H-9H.

In one embodiment, the touch panel is a touch panel having a second touch panel substrate laminated between a TFT substrate and a color filter substrate.

The present invention also provides a TFT substrate, a liquid crystal layer, a color filter substrate, a touch panel substrate, and a touch panel having any of the above-mentioned conductive films, which are sequentially laminated between two polarizing plates.

In one embodiment, the touch panel is a touch panel having a second touch panel substrate laminated between a TFT substrate and a color filter substrate.

Further, according to the present invention, in a touch panel having a TFT substrate, a liquid crystal layer, a color filter substrate, and a touch panel substrate, which are sequentially laminated between two polarizing plates, a coating composition is provided on the surface where the electrode pattern of the touch panel substrate is present. A method of forming a conductive film, which comprises a step of applying and drying.
The coating composition comprises chain conductive inorganic particles, a binder, a high boiling point solvent, and a low boiling point solvent.
The content of the chain conductive inorganic particles is 10 to 70% by mass with respect to the total amount of the chain conductive inorganic particles and the binder.
The coating provides a method performed using a spray coating method.

According to the present invention, there is provided a coating composition and a conductive film capable of improving touch panel performance such as touch detection sensitivity of a touch panel and stability over time of operation. Further, according to the present invention, there is provided a touch panel having improved touch panel performance such as touch detection sensitivity, operation reliability and stability.

It is sectional drawing which shows the structure of the on-cell type touch panel which is one Embodiment of this invention. It is sectional drawing which shows typically the layer structure of the on-cell type touch panel to which the coating composition of this invention can be applied. It is sectional drawing which shows typically the layer structure of the in-cell type touch panel to which the coating composition of this invention can be applied. 6 is a transmission electron micrograph of the tin oxide particles containing chain antimony used in Example 1. FIG. 4 is an enlarged transmission electron micrograph of FIG. 4.

The touch panel to which the coating composition of the present invention is applied is a capacitance type touch panel that detects a capacitance that changes according to the capacitance of an object that is close to or in contact with an electrode. Further, the liquid crystal display device with a touch detection function in which the touch panel is used is a horizontal electric field type liquid crystal display device in which a detection electrode for touch detection is provided on either one of the TFT substrate and the facing substrate forming the display device. ..

(Coating composition)
First, the coating composition of the present embodiment will be described.

The coating composition of the present embodiment contains chain conductive inorganic particles, a binder, a high boiling point solvent, and a low boiling point solvent. The content of the chain conductive inorganic particles is 10 to 70% by mass with respect to the total amount of the chain conductive inorganic particles and the binder.

By using the above coating composition, it is possible to provide a conductive film having a high ESD function, not lowering the touch sensitivity, and having excellent light transmittance and hardness.

<Chain-like conductive inorganic particles>
The coating composition of the present embodiment has an ESD function by setting the content of the chain conductive inorganic particles to 10 to 70% by mass with respect to the total amount of the chain conductive inorganic particles and the binder. It is possible to provide a conductive film which is high and does not reduce the touch sensitivity. When the content of the chain conductive inorganic particles is less than 10% by mass, the ESD function of the conductive film is lowered, and when the content of the chain conductive inorganic particles is more than 70% by mass, the touch sensitivity is lowered. The content of the chain conductive inorganic particles is preferably 12 to 62% by mass, more preferably 14 to 43% by mass, and further preferably 15 to 15 to the total amount of the chain conductive inorganic particles and the binder. It is 34% by mass.

Further, by using the above-mentioned chain-like conductive inorganic particles, the conductivity of the conductive film can be enhanced with a smaller amount as compared with the case of using the non-chain-like conductive inorganic particles. This is because the chain structure of the inorganic particles increases the conductive network between the inorganic particles as compared with the presence of the inorganic particles alone, and the conductivity of the entire conductive film is improved. Seem. Therefore, since the amount of inorganic particles for realizing the predetermined conductivity of the conductive film can be reduced, the light transmittance of the conductive film can also be improved.

The chain-shaped conductive inorganic particles refer to chain-shaped secondary particles in which primary particles are linked. The primary particle means a particle existing alone, and the secondary particle means a particle in which two or more primary particles exist. Specifically, as the chain conductive inorganic particles, it is preferable to use 2 to 50 primary particles having a particle size of 2 to 30 nm, and 3 to 20 primary particles are more likely to be connected. preferable. When the number of connected primary particles having a particle size exceeds 50, the haze value of the conductive film tends to increase due to the scattering of the particles. Further, when the number of connected primary particles having a particle size of less than two is less than two, the particles become non-chained, it becomes difficult to form a conductive network between the inorganic particles, and the conductivity of the conductive film is lowered.

The particle size and the number of connections are determined by, for example, a conductive film obtained by diluting the coating composition with a low boiling point solvent and thinly coating it on various substrates with a thickness of 2 to 10 nm by a transmission electron microscope (TEM). It can be obtained by observing and measuring the particle size and the number of connections of the individual particles constituting the chain conductive inorganic particles.

The chain conductive inorganic particles are not particularly limited as long as they are chain particles having both transparency and conductivity, and for example, metal particles, carbon particles, conductive metal oxide particles, conductive nitride particles and the like. Can be used. Of these, conductive metal oxide particles having both transparency and conductivity are preferable. Examples of the conductive metal oxide particles include tin oxide particles, antimony oxide particles, antimony-containing tin oxide (ATO) particles, tin-containing indium oxide (ITO) particles, phosphorus-containing tin oxide (PTO) particles, and aluminum-containing zinc oxide (. Examples thereof include metal oxide particles such as AZO) particles and gallium-containing zinc oxide (GZO) particles. The conductive metal oxide particles may be used alone or in combination of two or more. Further, the chain conductive inorganic particles preferably contain at least one selected from the group consisting of ATO particles, ITO particles and PTO particles. This is because these conductive inorganic particles are excellent in transparency, conductivity and chemical properties, and can realize high light transmittance and conductivity even when a conductive film is formed.

The method for producing the chain conductive inorganic particles is not particularly limited, and for example, JP-A-2000-196287, JP-A-2005-139026, JP-A-2006-339113, and JP-A-2012-25793 are not particularly limited. The manufacturing method described in the above can be adopted.

<Binder>
The binder is not particularly limited as long as it can disperse the chain conductive inorganic particles to form a coating film, and either an inorganic binder or an organic binder can be used. The content of the binder is preferably 20% by mass or more with respect to the total amount of the chain conductive inorganic particles and the binder. This is because if it is less than 20% by mass, the strength of the conductive thin film tends to decrease.

As the inorganic binder, for example, alkoxysilane can be used. More specifically, the alkoxysilane is a compound in which 3 to 4 alkoxy groups are bonded to silicon, and when dissolved in water, it polymerizes into ^two high molecular weight SiO bodies connected by -OSiO-. Can be used.

The alkoxysilane preferably contains at least one polyfunctional alkoxysilane selected from the group consisting of tetraalkoxysilane, trialkoxysilane, dialkoxysilane, and alkoxysilane oligomer. The alkoxysilane oligomer is a high molecular weight alkoxysilane formed by condensation of alkoxysilane monomers, and refers to an oligomer having two or more siloxane bonds (-OSiO-) in one molecule. .. The number of bonds is preferably 2 to 20.

Examples of the tetraalkoxysilane include silanes substituted with an alkoxy group having 1 to 4 carbon atoms such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraiso-propoxysilane, and tetrat-butoxysilane. Will be.

Examples of the above-mentioned trialkoxysilane are tri-substituted with an alkoxy group having 1 to 4 carbon atoms such as trimethoxysilane, triethoxysilane, tripropoxysilane, tributoxysilane, triiso-propoxysilane, and triL-butoxysilane. Examples thereof include silanes such as "KBM-13 (methyltrimethoxysilane)" and "KBE-13 (methyltriethoxysilane)" in which a part thereof is substituted with an alkyl group.

Examples of the dialkoxysilane include "KBM-22 (dimethyldimethoxy), which is a silane di-substituted with an alkoxy group having 1 to 4 carbon atoms such as dimethyldimethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, and diphenyldiethoxysilane. Examples thereof include silane in which a part of "silane)", "KBE-22 (dimethyldiethoxysilane)" and the like are substituted with an alkyl group.

Examples of the alkoxysilane oligomer include a relatively low molecular weight alkoxysilane oligomer having both an organic group and an alkoxysilyl group. As specific examples, "X-40-2308", "X-40-9238", "X-40-9247", "KR-401N", "KR-510", "KR-9218" manufactured by Shin-Etsu Chemical Co., Ltd. , "Ethyl silicate 40", "Ethyl silicate 48", "Methyl silicate 51", "Methyl silicate 53A" and the like manufactured by Corcote.

Among the specific examples of the above alkoxysilanes, in order to form a conductive thin film having a higher hardness, tetraalkoxylan, tetraalkoxysilane and trialkoxysilane may be used in combination, or trialkoxysilane in which a part is substituted with an alkyl group or the like. Alkoxysilane and an alkoxysilane oligomer having an alkoxysilyl group as a functional group are preferable. By using these, the hardness of the conductive film becomes stronger due to the three-dimensional cross-linking that promotes the siloxane bond between the binder molecules, the risk of cracking in the conductive thin film due to aging is further eliminated, and the substrate and the substrate are used. This is because the adhesiveness of the film can be further enhanced.

Further, in order to form a high-quality film with good reproducibility in a more stable state, it is preferable to promote the hydrolysis reaction of alkoxysilane in the coating composition and use it in a silanolized state. Examples of the adjusting method include a method of adding water and an acid catalyst to alkoxysilane diluted with a low boiling point solvent such as alcohol to silanolize in advance, and a method of adding water and an acid catalyst to a conductive coating composition to form silanol. The method can be mentioned. The theoretical value of the water content can be obtained by obtaining the hydrolysis rate from the structure of the alkoxysilane, but it is appropriately adjusted according to the pot life of the coating composition, the coating suitability, and the physical characteristics of the conductive film. The content of the water is preferably 50 to 1500% by mass with respect to the total amount of alkoxysilane. This is because if it is less than 50% by mass, the strength of the conductive thin film is lowered, and if it exceeds 1500% by mass, the drying speed is slowed down, which affects the coating suitability.

Examples of the organic binder include acrylic resin, polyester resin, polyamide resin, polycarbonate resin, polyurethane resin, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polyvinyl acetate resin, and light. A photopolymerizable resin containing a polymerizable monomer and a polymerization initiator can be used.

The photopolymerizable monomer preferably contains 50 to 90% of a trifunctional or higher functional (meth) acrylic monomer. Here, the content of the photopolymerizable monomer means the mass ratio of the photopolymerizable monomer to the total mass of the photopolymerizable monomer and the polymerization initiator. By polymerizing and curing a (meth) acrylic monomer having many reaction points to form a matrix resin, the strength of the conductive film can be further increased. When the mass ratio of the trifunctional or higher photopolymerizable monomer is less than 50%, the hardness of the coating film becomes weak and the durability is lowered. Further, since it is necessary to use a polymerization initiator together with the photopolymerizable monomer, it is practically difficult for the mass ratio of the photopolymerizable monomer to exceed 90%.

As the trifunctional (meth) acrylic monomer, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) acrylate; as a tetrafunctional or higher functional (meth) acrylic monomer, Examples thereof include pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate. Further, the photopolymerizable monomer may be a polyfunctional acrylic oligomer that is generally sold, and particularly preferably one having high curability and high hardness, for example, "AH-600" manufactured by Kyoeisha Chemical Co., Ltd., " Examples thereof include "UA-306H", "NK Oligo U-6HA" and "NK Oligo U-15HA" manufactured by Shin-Nakamura Chemical Co., Ltd.

Further, the photopolymerizable monomer may contain monofunctional and bifunctional photopolymerizable monomers, for example, 1,4-butanediol di (meth) acrylate and neopentyl glycol di (meth) acrylate. , 1,6-Hexanediol di (meth) acrylate, 1,9 nonanediol di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate and other bifunctional polymerizable monomers; Vinyl monomers such as vinylpyrrolidone and vinylformamide, alkyl (meth) acrylates such as butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, alicyclic (meth) such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate. Hydroxy (meth) acrylates such as acrylates, (meth) hydroxyethyl (meth) acrylates and hydroxypropyl (meth) acrylates, nitrogen-containing (meth) acrylates such as acryloylmorpholine and dimethylaminoethyl (meth) acrylates, benzyl (meth) Examples thereof include monofunctional polymerizable monomers such as aromatic (meth) acrylates such as acrylates, phenoxyethyl (meth) acrylates and tetrahydrofurfuryl acrylates.

Examples of the polymerization initiator include α-diketones such as benzyl and diacetyl, acyloins such as benzoin, acyloin ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether, thioxanthone and 2,4-diethyl. Thioxanthones such as thioxanthone, 2-chlorothioxanthone, thioxanthone-4-sulfonic acid, benzophenone, benzophenone such as 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, Michiller ketones, Acetphenone, 2- (4-toluenesulfonyloxy) -2-phenylacetophenone, p-dimethylaminoacetophenone, α, α'-dimethoxyacetoxybenzophenone, 2,2'-dimethoxy-2-phenylacetophenone, p-methoxyacetophenone, 2 -Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1-one, etc. Acetphenones, anthraquinones, quinones such as 1,4-naphthoquinone, halogen compounds such as phenacylloride, trihalomethylphenylsulfone, tris (trihalomethyl) -s-triazine, acylphosphine oxides, di-t-butyl peroxide Examples thereof include peroxides such as.

One type of each of the photopolymerizable monomer and the polymerization initiator may be used alone, or two or more types may be used in combination.

<High boiling point solvent>
The high boiling point solvent may be any solvent as long as it can dissolve the binder component and can be removed by a drying step after coating. For example, ethylene glycol, dimethyl sulfoxide, N-methylpyrrolidone, N-ethylpyrrolidone, N-methylformamide. , 1,2-Propanediol, N, N-dimethylaniline, cresol, nitrobenzene, ethylene glycol and the like can be used. The high boiling point solvent is preferably an organic or inorganic solvent having a boiling point of 120 ° C. or higher.

The content of the high boiling point solvent may be about 0.1 to 30.0% by mass with respect to the total amount of the conductive coating composition.

<Low boiling point solvent>
Examples of the low boiling point solvent include ethyl alcohol, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, acetone, dioxane, ethyl acetate, chloroform, acetonitrile, and the like. Ppyridine, acetic acid, water, etc. can be used. By using the low boiling point solvent, the dispersibility of the chain conductive inorganic particles is improved. The low boiling point solvent is preferably an organic or inorganic solvent having a boiling point of less than 120 ° C.

The content of the low boiling point solvent may be about 50.0 to 99.5% by mass with respect to the total amount of the conductive coating composition.

<Acid catalyst>
A commonly used acid catalyst (hydrochloric acid, sulfuric acid, acetic acid, phosphoric acid, etc.) can be further added to the coating composition of the present invention. This makes it possible to form a high-quality conductive film with more stable performance and good reproducibility. The content of the acid catalyst may be about 1.0 to 30.0% by mass with respect to the total amount of alkoxysilane.

<Leveling agent>
A leveling agent can be further added to the coating composition of the present invention. As a result, the surface smoothness of the conductive film can be ensured. As the leveling agent, for example, polyether-modified polydimethylsiloxane, dipropylene glycol monomethyl ether and the like can be used. The content of the leveling agent catalyst may be about 0.01 to 5.0% by mass with respect to the total amount of the conductive coating composition.

<Preparation method>
The method for preparing the coating composition of the present invention is not particularly limited as long as the above-mentioned components can be mixed and the above-mentioned chain conductive inorganic particles can be dispersed in the above-mentioned binder and the above-mentioned solvent. It can be mixed and dispersed by mechanical treatment using a medium such as a sand mill, pico mill, paint conditioner, or dispersion treatment using an ultrasonic disperser, homogenizer, disper, jet mill, or the like.

The coating composition of the present invention after the above preparation has a solid content concentration of 0.1 to 5.0% by mass with respect to the total amount. The solid content of the coating composition is typically the total amount of the chain conductive inorganic particles and the binder. When the solid content concentration of the coating composition is less than 0.1% by mass, the thickness of the conductive film is controlled within an appropriate range. It takes time and is not realistic as a manufacturing process. On the other hand, if it exceeds 5.0% by mass, the coating amount becomes small, so that the thickness of the wet film becomes insufficient, leveling performance is not exhibited, and deviation in the film characteristics such as surface electrical resistance occurs in the substrate. The solid content concentration of the coating composition is preferably 0.3 to 3.0% by mass, more preferably 0.5 to 2.0% by mass.

The coating composition of the present invention preferably has a viscosity of 50 mPa · s or less. If the viscosity of the coating composition exceeds 50 mPa · s, the composition is not properly atomized in the spray method, and the spray droplets become too large or the spray droplet particle size distribution becomes too uneven. As a result, characteristic deviations in the substrate may occur in the film characteristics such as surface electrical resistance, and the appearance of the film may deteriorate. The viscosity of the coating composition is preferably 25 mPa · s or less, more preferably 7.0 mPa · s or less.

(Conductive film)
Next, the conductive film of the present invention will be described.

The conductive film of the present invention is formed by applying the coating composition of the present invention to a touch panel substrate 9 described later to form a coating film, and then drying the coating film, if necessary, curing the coating film.

As a method for applying the coating composition, it is preferable to use a spray coating method. The object to be coated is the touch panel substrate 9, and the electrode pattern 92 is present on the upper surface thereof. That is, a patterned convex portion exists on the surface of the object to be coated. Therefore, by using the spray coating method, it is possible to form a film having a uniform thickness on the entire surface of the electrode substrate 91 and the electrode pattern 92.

As the application conditions using the spray coating method, the diameter of the spray gun is 0.5 to 3.0 mm, the needle opening is 0.05 to 0.30 mm, the discharge liquid amount is 0.10 to 3.00 g / min, and the spray. The shortest distance between the gun and the substrate is preferably 50 to 300 mm, the coating speed is preferably 100 to 2000 mm / sec, the stacking pitch is 2 to 30 mm, and the pressure of atomized air is preferably 0.05 to 0.50 MPa. As for the number of spray guns, in addition to operating with a single gun, a plurality of guns may be arranged according to the substrate size from the viewpoint of improving coating efficiency.

After the coating composition is applied to the upper surface of the electrode substrate 91, the solvent is removed by drying to form a film. If necessary, the coating film may be irradiated with UV light or EB light to cure the coating film. For example, a film formed by forming a coating film using the coating composition of the present invention and the spray coating method, drying the coating film, and if necessary, curing the coating film can be said to be a conductive spray film.

The conductive film of the present invention has a surface electrical resistance of 1.0 × 10 ⁹ to 1.0 × 10 ¹⁴ Ω / square. If the surface electrical resistance of the conductive film is less than 1.0 × 10 ⁹ Ω / square, the touch sensitivity is lowered, and if it exceeds 1.0 × 10 ¹⁴ Ω / square, the antistatic performance is lowered. The surface electrical resistance of the conductive film is preferably 1.0 × 10 ⁹ to 1.0 × 10 ¹³ Ω / square, and more preferably 7.0 × 10 ¹⁰ to 5.0 × 10 ¹² Ω / square. be.

The conductive film of the present invention has a surface electrical resistance of 1.0 × 10 ⁹ to 1.0 × 10 ¹⁴ Ω / square, preferably 1 after being held for 500 hours in an environment of a temperature of 65 ° C. and a relative humidity of 90%. It is 0.0 × 10 ⁹ to 1.0 × 10 ¹³ Ω / square, more preferably 7.0 × 10 ¹⁰ to 5.0 × 10 ¹² Ω / square. In addition, in order to provide a conductive film having a high ESD function even after the reliability test and not deteriorating the touch sensitivity, the change in surface electrical resistance before and after the reliability is 1 regardless of whether the surface electrical resistance changes to the descending side or the ascending side. A range of .0 Ω / square is preferred. More preferably, it is in the range of 0.5 Ω / square.

The conductive film of the present invention has a thickness of 2 to 100 nm. If the thickness of the conductive film is less than 2 nm, it is smaller than the size of the primary particles themselves, so that the smoothness of the film surface is impaired and the deviation of the surface electrical resistance is likely to occur. The rate gets worse. The thickness of the conductive film is preferably 5 to 80 nm, more preferably 10 to 60 nm.

The conductive film of the present invention has a pencil hardness of 3H to 9H, preferably 4H to 7H, and more preferably 5H to 6H.

The conductive film of the present invention has a total light transmittance (JIS K7105 compliant) of 95.0% or more, preferably 97.0 to 99.9%.

Further, in the panel manufacturing process, the touch panel is generally divided from a large-sized substrate into a small-sized substrate by a diamond cutter. Therefore, it is preferable that the conductive film of the present invention provides a smooth cut surface without generating deposits on the cutter when cut together with the glass substrate.

<Touch panel>
The touch panel to which the coating composition of the present invention is applied is a type of touch panel having a layered structure in which a touch panel substrate is laminated on a color filter substrate. As such a touch panel, an on-cell type touch panel is typically exemplified. The touch panel to which the coating composition of the present invention is applied may have a second touch panel substrate. The second touch panel substrate may be laminated at an appropriate position between the color filter substrate and the upper polarizing plate, or may be laminated at an appropriate position between the TFT substrate and the color filter substrate.

FIG. 1 is a cross-sectional view showing the structure of an on-cell touch panel according to an embodiment of the present invention. The display area of the on-cell touch panel 1 is displayed as Ad, and the non-display area is displayed as As. Generally, the peripheral region As is a region on the upper surface of the substrate 21, and is a region located on the outer peripheral side of the substrate 21 with respect to the display region Ad.

The on-cell touch panel 1 has the following elements laminated between the lower polarizing plate 2 and the upper polarizing plate 3. That is, a TFT substrate 4, a common electrode 5, an insulating film 6, a liquid crystal display panel 7 (composed of a pixel electrode 71, a liquid crystal layer 72, and a sealing portion 73), a color filter substrate 8, and a touch panel substrate 9 (electrode substrate). 91, the electrode pattern 92), the conductive film 10 and the pressure-sensitive adhesive layer 11. The adhesive layer 12 and the cover glass 13 are laminated on the upper polarizing plate 3.

In the specification of the present application, "laminated" means that the layered materials are in an overlapping state. The layers to be laminated may not be in contact with each other, for example, because another layer is present between them.

The electrode pattern 92 constituting the touch panel substrate 9 is composed of a conductive wire provided on the upper surface of the electrode substrate 91. The thickness of the conductive wire is generally several μm, for example, 5 μm. The pattern shape of the electrode pattern 92 is generally a zigzag shape or a mesh shape in a plan view. That is, a patterned convex portion exists on the upper surface of the touch panel substrate 9.

A conductive film 10 is provided on the upper surface of the touch panel substrate 9. When the conductive film 10 is not provided, the surface of the polarizing plate 5, for example, is charged by static electricity applied from the outside of the on-cell touch panel 1, and the electric field caused by the static electricity causes the liquid crystal molecules of the liquid crystal layer 6 to be charged. The orientation may be disturbed and the image display may be disturbed.

On the other hand, by providing the conductive film 10, static electricity applied from the outside of the on-cell touch panel 1 can be released to the outside, so that the image display is disturbed when static electricity is applied to the on-cell touch panel 1. Can be reduced.

Preferably, the conductive film 10 is arranged on the upper surface of the touch panel substrate 9 so as to cover the electrode pattern in the entire display region Ad. The conductive film 10 is formed by using the coating composition of the present invention. That is, the conductive film 10 is directly provided on the upper surface of the touch panel substrate without using an adhesive layer.

This provides an on-cell touch panel with improved touch panel performance such as touch detection sensitivity, operation reliability and stability. The reason is not clear, but it can be considered as follows. Generally, an adhesive is used for adhering components of a touch panel. This is because a strong adhesive force is not required, and a constant adhesive force can be obtained immediately after the adhesive is bonded.

For example, in the on-cell touch panel of Patent Documents 1 and 6, an adhesive layer 51 is provided between the conductive layer 52 and the conductive pattern CB1. Further, as another form of the antistatic conductive film, there is one in which conductive inorganic particles are dispersed in the pressure-sensitive adhesive layer.

On the other hand, the pressure-sensitive adhesive is flexible even after being bonded. Therefore, the elements laminated via the adhesive are not completely fixed in that position. For example, the pressure-sensitive adhesive may gradually flow when a lapse of time has passed since the bonding, or the pressure-sensitive adhesive may soften when the temperature of the ambient environment is high, and the position of the adherend may change.

The static electricity applied to the on-cell touch panel 1 is released to the TFT substrate through the antistatic conductive film and wiring, but when the antistatic conductive film is laminated via the adhesive, it is for antistatic. As a result of the change in the position of the conductive film, the distance between the antistatic conductive film and the TFT substrate also changes, so that the conductivity changes. Further, in the antistatic conductive film in which the conductive inorganic particles are dispersed in the pressure-sensitive adhesive layer, the position of the conductive inorganic particles changes in the pressure-sensitive adhesive layer, and the conductivity changes.

On the other hand, the conductive film of the present invention does not use an adhesive when it is formed on the upper surface of the touch panel substrate. The conductive film of the present invention has a high pencil hardness of 3H to 9H. Therefore, the conductive inorganic particles are fixed in the conductive film, and the distance between the conductive film and the TFT substrate does not change. Moreover, the distance between the conductive film and the TFT substrate is shortened by the amount that the adhesive layer is omitted, and the conductivity is increased.

As a result, the touch panel of the present invention is considered to improve touch panel performance such as touch detection sensitivity, operation reliability and stability.

FIG. 2 is a cross-sectional view schematically showing a layer structure of an on-cell touch panel to which the coating composition of the present invention can be applied. As shown in FIG. 2a, the on-cell touch panel may have a second touch panel substrate 9'stacked between the color filter substrate 8 and the touch panel substrate 9. As shown in FIG. 2b, the second touch panel substrate may be laminated between the liquid crystal layer 72 and the color filter substrate 8.

FIG. 3 is a cross-sectional view schematically showing a layer structure of an in-cell type touch panel to which the coating composition of the present invention can be applied. In the in-cell touch panel of FIG. 3, a common electrode having a touch detection function, that is, a common electrode and a touch electrode 5'is laminated on the TFT substrate 4. Further, the touch panel substrate 9 is laminated between the color filter substrate 8 and the upper polarizing plate. The common electrode and touch electrode 5'corresponds to the second touch panel substrate. Even if it is an in-cell type touch panel, if the touch panel substrate has a layered structure laminated on the color filter substrate, the coating composition of the present invention is on the pattern electrode of the touch panel substrate laminated on the color filter substrate. Things can be applied.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to the following examples. In the following, "part" and "%" are based on mass unless otherwise specified. Examples 1 and 2 and Examples 4, 5 and 6 are reference examples.

<Tin (ATO) particle dispersion containing chain antimony>
"ELCOM V-3560" manufactured by JGC Catalysts and Chemicals Co., Ltd. was prepared as a chain ATO particle dispersion. The chain ATO particle dispersion "ELCOM V-3560" is a mixed dispersion of chain ATO particles: 20.8 parts, ethyl alcohol: 70.0 parts, and isopropyl alcohol 9.2 parts.

3 and 4 are transmission electron microscope (TEM) photographs of the chain ATO particles used in the above chain ATO particle dispersion. With reference to FIGS. 2 and 3, the ATO particles are chain ATO particles (chain conductive inorganic particles) formed by connecting 2 to 50 primary particles having a particle size of 2 to 30 nm. I understand. The main materials used in the examples are shown in Table 1.

[Table 1]

(Manufacturing example)
<Manufacturing of dispersion A>
In a plastic bottle, 20.8 parts of conductive ATO particles "SN100P" (trade name) manufactured by Ishihara Sangyo Co., Ltd., 2.0 parts of dispersant "BYK180" (trade name) manufactured by Big Chemie Japan, and isobutyl 77.2 parts of alcohol (solvent) was charged, and the mixture was dispersed with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) for 2 hours using zirconia beads having a diameter of 0.3 mm, and then stirred to produce a dispersion liquid A.

(Examples 1 to 6 and Comparative Examples 1 to 3)
<Manufacturing of coating composition>
A coating composition was prepared by charging each component into a plastic bottle in an amount having a predetermined content and stirring the mixture. However, the alkoxysilane was diluted with a part of alcohol, and water and an acid catalyst were added to make silanol in advance before use.

The viscosity of the obtained coating composition was measured using a TV25 type viscometer manufactured by Toki Sangyo Co., Ltd. Tables 2 and 3 show the types of components, the blending amounts, the non-volatile solid content and the viscosities of the coating composition.

[Table 2]

[Table 3]

<Manufacturing of conductive film>
The above coating composition was applied to a non-alkali glass substrate having a size of 10 cm square and a thickness of 0.7 mm by a spray coating method to form a coating film. A spray gun (swirl nozzle, caliber: 1.0 mm) manufactured by Nordson was used as the spray coater. The application conditions were as follows. That is, needle opening: 0.10 mm, discharge amount: 0.60 g / min, shortest distance between spray gun and substrate: 100 mm, coating speed: 300 mm / sec, stacking pitch: 10 mm, atomizing air and swirl air pressure. : 0.25 MPa. The formed coating film was heated at 120 ° C. for 1 hour to prepare a conductive film.

In the case of Example 6, the coating liquid of Example 6 was applied onto a glass substrate with a spray coater in the same manner as above, dried at 80 ° C. for 5 minutes, and then irradiated with ultraviolet rays at 300 mJ / with a high-pressure mercury lamp. The conductive film of Example 6 was formed by irradiating with a light amount of cm ² and curing.

Next, the characteristics of the obtained conductive film were tested as follows. The results are shown in Tables 4 and 5.

<Film thickness>
The conductive film was cut together with the glass substrate, and the film thickness was measured by observing the cross section with a scanning electron microscope (SEM, "S-4500" manufactured by Hitachi, Ltd.).

<Surface electrical resistance>
The surface electrical resistance of the conductive film was measured using a surface resistance meter (“Highresta MCP-HT450” manufactured by Mitsubishi Chemical Corporation, applied voltage: 10V) and used as a normal surface electrical resistance.

Further, the surface electrical resistance of the conductive film after holding the glass substrate with the conductive film at a temperature of 65 ° C. and a relative humidity of 90% for 500 hours was measured in the same manner as above, and after the high temperature and high humidity test. The surface electrical resistance was used.

<Total light transmittance>
First, the total light transmittance of the glass substrate with a conductive film was measured using a photometer "Haze Meter NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd. The numerical value shows the value of only the coating film.

<Pencil hardness>
The pencil hardness of the conductive film was measured using a surface tester "HEIDON-14DR" manufactured by Shinto Kagaku Co., Ltd.

<Glass cutting property>
A glass substrate to which a conductive film was applied was cut using a simple slick bar "Linear Cutter LC200AHH" manufactured by Samsung Diamond Industry Co., Ltd. and a scribe wheel "APIO φ3 mm TYPE A", and the glass cutting property was evaluated.

The conditions for disconnection were set as follows. That is, it was repeated 100 times under the conditions of a load of 10 N, a depth of cut of 0.15 μm, and a scribe length of 100 mm. After that, the condition of the wheel deposits and the cut surface was visually confirmed. The evaluation criteria are specified as follows.

Glass cutability evaluation criteria ○: No deposits, good cut surface, △: There are some deposits, there are some chips on the cut surface, ×: There are deposits, there are chips on the cut surface

[Table 4]

[Table 5]

<Manufacturing of on-cell touch panel>
A liquid crystal display device having a configuration shown in FIG. 1 having a screen size of 4 inches and a total thickness of the liquid crystal display device of 1 mm was produced.

The conductive film was formed by applying the above coating liquid on the upper surface of the touch panel substrate using a spray coater under the same conditions as described above, and then drying the film in a dryer at 120 ° C. for 1 hour. Next, a ground wire was attached to the end of the conductive film with a silver paste (“Dotite D-362” manufactured by Fujikura Kasei Co., Ltd.), and then a polarizing plate was attached on the conductive film. In addition, a pixel electrode and a common electrode were provided, and a polarizing plate was also attached to the backlight side of the lower glass substrate.

Next, the touch sensitivity and electrostatic discharge (ESD) property of each of the above liquid crystal display devices were confirmed as follows.

<Touch sensitivity>
The touch sensitivity was confirmed by touching the liquid crystal display device with a finger. As a result, the case of responding to the touch of the finger was evaluated as ◯, and the case of not responding to the touch of the finger was evaluated as x.

Further, the touch sensitivity of the conductive film after holding the glass substrate with the conductive film at a temperature of 65 ° C. and a relative humidity of 90% for 500 hours is measured in the same manner as above, and the touch after the high temperature and high humidity test is performed. The sensitivity was set.

<ESD property>
After irradiating light from the lower glass substrate side with a backlight and confirming that the liquid crystal display device is black in the non-energized state, static electricity is applied to the upper glass substrate with an electrostatic application device at a voltage of ± 12 kV. Applied. Then, after grounding the ground wire of the conductive film, the display of the non-energized state was visually confirmed. As a result, the case where the liquid crystal display device maintained the black display was evaluated as ◯, and the case where whitening due to light leakage was observed was evaluated as x.

Further, the ESD property of the conductive film after holding the glass substrate with the conductive film at a temperature of 65 ° C. and a relative humidity of 90% for 500 hours is measured in the same manner as above, and the ESD after the high temperature and high humidity test is performed. I made it sex.

The above results are shown in Tables 6 and 7.

[Table 6]

[Table 7]

1 ... On-cell touch panel,
2 ... Lower polarizing plate,
3 ... Upper polarizing plate,
4 ... TFT substrate,
5 ... Common electrode,
5'... Common electrode and touch detection electrode,
6 ... Insulating film,
72 ... Liquid crystal layer,
8 ... Color filter board,
9 ... Touch panel board,
9'... Second touch panel board,
10 ... Conductive film,
11 ... Adhesive layer,
12 ... Adhesive layer,
13 ... Cover glass.

Claims (12)

A coating composition containing chain conductive inorganic particles, a binder, a high boiling point solvent, and a low boiling point solvent.
The coating composition has a content of the chain conductive inorganic particles of 10 to 30 % by mass with respect to the total amount of the chain conductive inorganic particles and the binder.
In a touch panel having a TFT substrate, a liquid crystal layer, a color filter substrate, and a touch panel substrate, which are sequentially laminated between two polarizing plates, the surface on which the electrode pattern of the touch panel substrate is present has a film thickness of 2 to 60 nm. It is used for the purpose of forming a conductive film, and is used.
The binder is a coating composition comprising alkoxysilane. The coating composition according to claim 1, which contains a solid content composed of the chain conductive inorganic particles and the binder in an amount of 0.1 to 5.0% by mass and has a viscosity of 7.0 mPa · s or less. The coating composition according to claim 1 or 2, wherein the chain conductive inorganic particles are formed by connecting 2 to 50 primary particles having a particle size of 2 to 30 nm. 13. The coating composition described. The coating composition according to any one of claims 1 to 4, wherein the touch panel is a touch panel having a second touch panel substrate laminated between a TFT substrate and a color filter substrate. The coating composition according to any one of claims 1 to 5 on the upper surface of a touch panel substrate of a touch panel having a TFT substrate, a liquid crystal layer, a color filter substrate, and a touch panel substrate, which are sequentially laminated between two polarizing plates. A conductive film having a film thickness of 2 to 60 nm , which is formed by using an object.
Conductive membrane. The conductive film according to claim 6 , wherein the surface electrical resistance after holding for 500 hours in an environment of a temperature of 65 ° C. and a relative humidity of 90% is 1.0 × 10 ⁹ or more and 8.5 × 10 ¹¹ Ω / square. .. The conductive film according to claim 6 or 7 , which has a pencil hardness of 5H to 9H. The conductive film according to any one of claims 6 to 8 , wherein the touch panel is a touch panel having a second touch panel substrate laminated between the TFT substrate and the color filter substrate. The touch panel having the TFT substrate, the liquid crystal layer, the color filter substrate, the touch panel substrate, and the conductive film according to any one of claims 6 to 9, which are sequentially laminated between two polarizing plates. The touch panel according to claim 10 , further comprising a second touch panel substrate laminated between the TFT substrate and the color filter substrate. In a touch panel having a TFT substrate, a liquid crystal layer, a color filter substrate, and a touch panel substrate, which are sequentially laminated between two polarizing plates, a step of applying a coating composition to the surface of the touch panel substrate on which an electrode pattern is present and drying the coating composition. A method for forming a conductive film having a film thickness of 2 to 60 nm, which comprises .
The coating composition comprises chain conductive inorganic particles, a binder, a high boiling point solvent, and a low boiling point solvent.
The content of the chain conductive inorganic particles is 10 to 30 % by mass with respect to the total amount of the chain conductive inorganic particles and the binder.
The application is made using the spray coat method and
A method in which the binder is made of alkoxysilane.

Images