JPH0535188A - Electrophorectic display device - Google Patents

Abstract

PURPOSE:To provide the electrophoretic display device which can maintain display quality excellent over a long period of time. CONSTITUTION:A transparent substrate 1 is a glass plate and a transparent conductive film 2 is formed over the entire surface thereof. A polyethylene terephthalate film having 100mum thickness is used as a rear substrate 4 and is disposed to face the transparent substrate 1 by adhering and fixing via a spacer 3, by which a space is formed. A film-like migrating body 5 contg. fine particles and liquid varying in color from the color of the fine particles are packed in this space and thereafter, the space is hermetically sealed by an adhesive 6, by which the electrophoretic display device is constituted. The film formed of a dispersion prepd. by dispersing the fine particles treated with a coupling agent having a vinyl group into a vinyl compd. having a vinyl group at its terminal or the film formed from a dispersion prepd. by dispersing the fine particles treated with a coupling agent having an amino group or glycidy group into an epoxy resin is used as the film-like migrating body 5 contg. the fine particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophoretic display device.

[0002]

2. Description of the Related Art In an electrophoretic display device, two transparent substrates, at least one of which is transparent, are arranged facing each other with a spacer interposed therebetween to form a sealed space. The display liquid (electrophoretic display system) dispersed in a different dispersion medium is filled, and a means for applying an electric field to the display liquid is provided, and a transparent plate is provided on the surface. The display liquid filled in the sealed space includes a dispersion medium such as xylene and isoparaffin, fine particles such as titanium dioxide, a dye for providing color contrast with the fine particles, a dispersant such as a surfactant and a charge-imparting agent. Composed of additives. By applying an electric field to the display liquid, the fine particles in the display liquid move to the transparent plate side, and the color of the fine particles appears on the surface. By applying an electric field in the opposite direction, the fine particles move to the back side and the color of the dispersion medium appears on the surface.

As described above, the electrophoretic display device can obtain a desired display by controlling the direction of the electric field.
Since the display liquid is made of a low-cost material which is relatively easily available, the viewing angle is as wide as that of a normal printed matter, the power consumption is small, and the memory property is provided, and therefore, it is attracting attention as an inexpensive display device.

As the electric field applying means of the electrophoretic display device, a method of applying a voltage between electrodes formed on a pair of substrate surfaces, a corona ion generator as disclosed in JP-A-62-34187, and A method of forming an electrostatic latent image on the surface of one substrate by a write electrode including a control electrode that controls the flow of ions, and generating an electric field between the electrostatic latent image and the transparent electrode on the surface of the other substrate. Etc. are used.

[0005]

As the fine particles in the display liquid for an electrophoretic display device, an inorganic pigment having a high refractive index such as titanium dioxide is generally used. These inorganic pigments have a very large difference in specific gravity from the dispersion medium in the display liquid and are separated by sedimentation, so that the uniformity or contrast of the display is deteriorated by the sedimentation and aggregation of fine particles, and the display quality is deteriorated. There was a problem. The present invention provides an electrophoretic display device capable of preventing sedimentation and aggregation of fine particles and maintaining excellent display quality for a long period of time.

[0006]

SUMMARY OF THE INVENTION According to the present invention, at least one of two transparent substrates is opposed to each other with a spacer provided therebetween at a required interval to form a sealed space, and the sealed space contains fine particles containing fine particles. What is claimed is: 1. An electrophoretic display device, comprising: a display panel in which an electrophoretic display system composed of electrophoretic particles and fine particles and a liquid of a different color is enclosed; and a means for applying an electric field to the electrophoretic display system, which is in the form of a film containing fine particles. The electrophoretic material is one obtained by forming a dispersion liquid in which fine particles treated with a coupling agent having a vinyl group are dispersed in a vinyl compound having a vinyl group at the terminal, or a coupling having an amino group or a glycidyl group. The electrophoretic display device is characterized in that a dispersion liquid in which fine particles treated with an agent are dispersed in an epoxy resin is formed into a film.

As fine particles used in the present invention, inorganic pigments such as titanium dioxide and zinc oxide exhibiting white color, inorganic pigments such as chrome yellow and cadmium yellow exhibiting yellow color, and insoluble azo compounds such as fast yellow Organic pigments such as azo compounds, condensed azo compounds such as chromophthal yellow, azo complex salts such as benzimidazolone azo yellow, condensed polycyclic compounds such as flavans yellow, and nitro compounds such as naphthol yellow show orange color As inorganic pigments such as molybdate orange, azo complex salts such as benzimidazolone azo orange, and condensed polycyclic compounds such as perinone orange, red pigments such as red iron oxide, cadmium red, etc. Dyed rakes, such as
Organic pigments such as soluble azo compounds such as lake red, insoluble azo compounds such as naphthol red, condensed azo compounds such as chromophthal scarlet, condensed polycycles such as thioindigo bordeaux, and manganese as purple. Inorganic pigments such as violet, dyeing lakes such as rhodamine lake, and organic pigments such as condensed polycyclics such as dioxazine violet are blue as inorganic pigments such as navy blue and ultramarine blue, phthalocyanines such as phthalocyanine blue, and alkali. Organic pigments such as blue show inorganic colors such as inorganic pigments such as emerald green, azo complex salts such as nickel azo yellow, phthalocyanines such as phthalocyanine green, and nitroso compounds such as pigment green.
Inorganic pigments such as carbon black and iron black, and organic pigments such as aniline black can be used to show black. These pigments can be used alone or in admixture of two or more. The fine particles may be opaque. The average particle size of the fine particles is preferably 0.1 to 100 μm.

As the coupling agent having a vinyl group, alkoxysilanes such as vinyltrimethoxysilane and dimethylvinylmethoxysilane, chlorosilanes such as vinyltrichlorosilane and dimethylchlorosilane,
γ-methacryloxypropyltrimethoxysilane, γ-
Methacryloxysilanes such as methacryloxypropylmethyldimethoxysilane, quaternary ammonium salts such as N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, isopropyldimethacrylisostearoyl titanate, isopropyldimethan Titanates such as acrylic isostearoyl titanate can be used. These coupling agents may be used alone or in admixture of two or more.

Examples of the coupling agent having an amino group or a glycidyl group include silane coupling agents such as γ-aminopropyltriethoxysilane and γ-methacryloxypropyltriethoxysilane, and isopropyltri (N-aminoethyl-aminoethyl). A titanate coupling agent such as titanate is used. These coupling agents may be used alone or in admixture of two or more.

By treating the fine particles with the coupling agent, a coating layer of the coupling agent is formed on the surface of the fine particles. It is desirable that the amount of the coupling agent treated be equal to or larger than the specific surface area of the fine particles. When the treatment amount of the coupling agent is less than the specific surface area of the fine particles, the improvement in dispersibility of the fine particles treated with the coupling agent is small.

As the method for treating the fine particles with the coupling agent, a dry method in which the coupling agent solution is sprayed with dry air or nitrogen gas while forcibly stirring the particles with a V blender, or the particles are dispersed in water or a solvent. A wet method in which a coupling agent solution is added to a slurry state or a spray method in which a coupling agent solution is sprayed while vigorously stirring preheated particles is used.

As the compound having a vinyl group at the terminal,
Acrylic acid, methacrylic acid, acrylic acid derivatives such as alkyl acrylate, methacrylic acid derivatives such as alkyl methacrylate, vinyl pyridine, vinylpyrrolidone, vinyl acetate, acrylonitrile, vinyl monomers such as styrene derivatives such as α-methylstyrene, poly Polyacrylic acid metal salts such as sodium acrylate, polymethacrylic acid metal salts such as potassium polymethacrylate,
Vinyl-based polymers such as vinyl group-terminated polyisobutylene, methacryloyl group-terminated polystyrene, methacryloyl group-terminated polystyrene-polyacrylonitrile copolymer, methacryloyl group-terminated polyacrylate, methacryloyl group-terminated polymethacrylate, and methacryloyl group-terminated silicone are used. These vinyl compounds may be used alone or in admixture of two or more.

As the epoxy resin, phenol type glycidyl ether type, alcohol type glycidyl ether type, glycidyl ester type, glycidyl amine type, alicyclic type and the like are used. These epoxy resins may be used alone or in combination of two or more.

A dispersion liquid in which fine particles treated with a coupling agent having a vinyl group are dispersed in a vinyl compound having a vinyl group at the terminal, or fine particles treated with a coupling agent having an amino group or a glycidyl group are contained in an epoxy resin. The dispersion liquid dispersed in is formed into a film to form a film-shaped migration body containing fine particles. The thickness of the film electrophoretic material is 5 to 1
It is preferably 50 μm.

When a fine particle treated with a coupling agent having a vinyl group is dispersed in a vinyl compound having a vinyl group at a terminal to form a film, a fine particle-containing electrophoretic material is treated. The coupling agent having a vinyl group is reacted with the vinyl compound. For this reaction, a usual vinyl monomer polymerization method can be used. As the polymerization initiator used at that time, ketone peroxides such as methyl ethyl ketone peroxide, 1,1-bis (t-butylperoxy) 3,3,3
Peroxyketals such as 5-trimethylcyclohexane, hydroperoxides such as cumene hydroperoxide, dialkyl peroxides such as di-t-butyl peroxide, diacyl peroxides such as benzoyl peroxide, diisopropylperoxydiene Peroxydicarbonates such as carbonates, organic peroxides such as peroxyesters such as t-butylperoxy-2-ethylhexanate, azo compounds such as azoisobutyronitrile, organics such as n-butyllithium A metal compound or the like is used. These polymerization initiators may be used alone or in admixture of two or more.

When a dispersion liquid in which fine particles treated with a coupling agent having an amino group or a glycidyl group are dispersed in an epoxy resin is formed into a film to form a film-shaped migration body containing the fine particles, the amino group treated with the fine particles is used. Alternatively, a coupling agent having a glycidyl group is reacted with an epoxy resin. This reaction can be carried out by using a usual epoxy resin curing method, and as a curing agent used at that time, an aliphatic polyamine such as triethylenetetramine,
Amide amines such as vegetable oil fatty acids, aromatic polyamines such as 4,4′-diaminodiphenylmethane, acid anhydrides such as tetrahydrophthalic anhydride, catalytic curing agents such as boron trifluoride monoethylamine, and other polymercaptans, polysulfides, etc. To be These curing agents can be used alone or in admixture of two or more.

As the liquid having a color different from that of the fine particles, a highly insulating organic solvent in which a dye having a color different from that of the fine particles is dissolved is used. Here, as the dye, an oil-soluble dye which is soluble in an organic solvent is preferable, and as the one showing yellow, an azo compound such as Oil Yellow 3G (trade name, manufactured by Orient Chemical Co., Ltd.) and the one showing orange is Fast Orange G. (BASF Corporation, trade name) and other azo compounds show red, and Oil Red 5B (Orient Chemical Co., trade name) and other azo compounds show purple and oil violet # 730 (Orient Chemistry) Anthraquinones such as products manufactured by the company, anthraquinones such as Macrolex Blue RR (product name manufactured by Bayer, Inc.) as a blue color, and Sumiplast Green G (a product of Sumitomo Chemical Co., Ltd.) as a green color Anthraquinones such as those manufactured by Brand name Oil Brown GR (Orient Chemistry) Ltd., azo compounds such as trade name), Sudan Black X60 (BASF Corporation as indicating black, and product name) azo compounds such as can be used.

Examples of highly insulating organic solvents having low electric conductivity include aromatic hydrocarbons such as benzene, toluene, xylene and naphthene hydrocarbons, and aliphatic hydrocarbons such as hexane, cyclohexane, kerosene and paraffin hydrocarbons. And halogenated hydrocarbons such as chloroform, trichloroethylene, trichlorotrifluoroethylene, ethyl bromide, etc. are used. These organic solvents may be used alone or in admixture of two or more.

FIG. 1 shows a cross-sectional view of an electrophoretic display device using the charging of corona ions as an example of the electrophoretic display device using such a film-like electrophoretic material. Transparent substrate 1
Is a glass plate having a length and width of 500 mm and a thickness of 3 mm, and a transparent conductive film 2 is formed on one surface of the glass plate.
A polyethylene terephthalate film having a thickness of 100 μm is used as the rear substrate 4, and the transparent substrate 1 and the transparent substrate 1 are arranged so as to face each other with a spacer 3 interposed therebetween to form a space.
An electrophoretic display device can be obtained by filling this space with a film-like electrophoretic body 5 containing the particles of the present invention and a liquid having a color different from that of the particles, and sealing with an adhesive 6.

On the other hand, corona ions generated by applying a positive or negative voltage of about 3 to 10 KV to the gold-plated tungsten wire (corona wire) 7 are controlled by the control electrode 8 and the rear substrate 4 of this electrophoretic display device is controlled. Ions are selectively charged on the surface to form an electrostatic latent image 9. An electric field is generated between the ion-charged portion and the transparent electrode 2, whereby the film-like electrophoretic material in the liquid moves to the transparent substrate side, and the color of fine particles appears on the surface. Since no electric field is generated in the non-charged portion of the ions, the liquid color appears on the surface. Thus, the electrostatic latent image 9 formed on the rear substrate 4
An image corresponding to is formed on the transparent substrate. When an electric field in the opposite direction is applied, the film-shaped electrophoretic material that has moved to the transparent substrate side moves to the back substrate side, so the image formed on the transparent substrate disappears and the entire surface becomes a liquid color. Become. Thus, the electrophoretic display device can obtain a desired display by controlling the direction of the electric field. To form such an electrostatic latent image, a corona ion generator disclosed in JP-A-62-34187 and a writing electrode composed of a control electrode for controlling the flow of this ion can be used.

[0021]

【Example】

Example 1 34 g of titanium tetraisobutoxide was weighed out in a 1 liter beaker containing 500 ml of isopropyl alcohol, and sufficiently dissolved and mixed using a magnetic stirrer. Distilled water (5.4 g) was added to this mixed solution, and the mixture was stirred at room temperature for 1 hour.
A suspension containing a hydrolyzate having a particle diameter of about 400 nm was obtained by continuing the stirring for 24 hours. This suspension was 3,000 using a tabletop centrifuge (CT5DL type, manufactured by Hitachi Ltd.).
Solid-liquid separation was carried out for 15 minutes at rpm, and the precipitate was heated to 100 ° C.
By vacuum drying for 1 hour, about 8 g of a hydrolyzed product was obtained. 5 g of this hydrolyzed product was placed in a vat made of aluminum oxide and placed in a muffle furnace (EP-31 type, Yamato Chemical Co., Ltd.).
Was used to produce titanium dioxide fine particles having an average particle size of 1 μm.

In a 1 liter beaker, 500 ml of isopropyl alcohol, 0.26 g of γ-methacryloxypropyltrimethoxysilane (trade name: TSL8370, manufactured by Toshiba Silicone Co., Ltd.) and 0.06 g of distilled water were weighed and magnetically measured. After stirring with a stirrer for about 15 minutes, 10 g of the above titanium dioxide fine particles were added and stirring was continued at room temperature for 1 hour. This solution is a tabletop centrifuge (CT5DL
Type, manufactured by Hitachi, Ltd.), solid-liquid separation was performed at 3000 rpm for 15 minutes, and the precipitate was vacuum dried at 100 ° C. for 1 hour to obtain about 1 g of surface-treated titanium dioxide fine particles. When performing solid-liquid separation with a tabletop centrifuge, 0.2
The supernatant was collected through a μm filter, the unreacted amount of the coupling agent was measured using a gas chromatograph (Model G-3000, manufactured by Hitachi, Ltd.), and the ratio with the initial treated amount was calculated as the reaction rate. As a result, the reaction rate was 99% or more.

2 g of surface-treated titanium dioxide fine particles was added to 10 g of methyl methacrylate and mixed for 10 minutes with an ultrasonic homogenizer (US-300 type, manufactured by Nippon Seiki Seisakusho), and then 0.5 g of azoisobutyronitrile was added. Then, they were thoroughly mixed to prepare a dispersion liquid of fine particles. This dispersion is dropped on a glass plate, and the glass plate is placed on the glass plate and placed in a dryer and heated at 80 ° C. for 1 hour.
The 0 μm film-like electrophoretic material was peeled off.

100 ml of isoparaffin hydrocarbon (trade name: Isopa G, manufactured by Exxon Chemical Co., Ltd.) is mixed with anthraquinone blue dye (trade name: Macrolex Blue R).
R, manufactured by Bayer Co., Ltd.) and sufficiently dissolved and mixed to prepare a liquid having a different color from the titanium dioxide fine particles. On the other hand, a Pyrex glass plate having a thickness of 3 mm was used as a transparent substrate, and a transparent conductive film (ITO film) was formed on one surface thereof. A 100 μm-thick polyethylene terephthalate film is used as the back substrate, the film-shaped electrophoretic material prepared above is placed thereon, and nylon beads (trade name: SP-500, manufactured by Toray Industries, Inc.) are used as spacers. The above transparent substrate and epoxy resin adhesive (trade name:
Araldite rapid, manufactured by Ciba-Geigy Co., Ltd., were opposed to each other to form spaces at intervals of about 100 μm.
The space between the transparent substrate and the back substrate is filled with an epoxy resin adhesive (trade name: DP-110, Sumitomo) An electrophoretic display device was produced by sealing with 3M Co., Ltd. A corona ion generator using a gold-plated tungsten wire and a writing electrode composed of a control electrode for controlling the flow of the ions are selectively charged on the rear substrate of the electrophoretic display device to form an electrostatic latent image. When formed, the electrophoretic migration of the film-shaped electrophoretic material in the corresponding portion onto the transparent substrate causes the same display as the electrostatic latent image formed on the rear substrate to produce a clear and clear white display on the transparent substrate. Was obtained. Also,
The number of rewritable times has also been greatly improved, and the titanium dioxide fine particles are not desorbed from the film-shaped electrophoretic material even after long-term use, and the life can be extended.

Example 2 34 g of titanium tetraisobutoxide was weighed out in a 1 liter beaker containing 500 ml of isopropyl alcohol, and sufficiently dissolved and mixed using a magnetic stirrer. Distilled water (5.4 g) was added to this mixed solution, and the mixture was stirred at room temperature for 1 hour.
A suspension containing a hydrolyzate having a particle diameter of about 400 nm was obtained by continuing the stirring for 24 hours. This suspension was 3,000 using a tabletop centrifuge (CT5DL type, manufactured by Hitachi Ltd.).
Solid-liquid separation was carried out for 15 minutes at rpm, and the precipitate was heated to 100 ° C.
By vacuum drying for 1 hour, about 8 g of a hydrolyzed product was obtained. 5 g of this hydrolyzed product was placed in a vat made of aluminum oxide and placed in a muffle furnace (EP-31 type, Yamato Chemical Co., Ltd.).
Was used to produce titanium dioxide fine particles having an average particle size of 1 μm.

In a 1-liter beaker, 500 ml of isopropyl alcohol and γ-glycidoxypropyltrimethoxysilane (trade name: TSL8350, Toshiba Silicone)
0.26 g and 0.06 g of distilled water are weighed out,
After stirring for about 15 minutes using a magnetic stirrer, 10 g of the above titanium dioxide fine particles were added and stirring was continued at room temperature for 1 hour. This solution is a tabletop centrifuge (CT5DL type,
(Manufactured by Hitachi, Ltd.) was used for solid-liquid separation at 3000 rpm for 15 minutes, and the precipitate was vacuum dried at 100 ° C. for 1 hour to obtain about 1 g of surface-treated titanium dioxide fine particles. 0.2 μm for solid-liquid separation using a tabletop centrifuge
The supernatant was collected through the filter of No. 3, and the unreacted amount of the coupling agent was measured using a gas chromatograph (Model G-3000, manufactured by Hitachi Ltd.), and the ratio with the initial treated amount was calculated as the reaction rate. As a result, the reaction rate was 99% or more.

Bisphenol A type epoxy resin (trade name: Epicoat 828, manufactured by Yuka Shell Epoxy Co., Ltd.) 1
0 g of surface-treated titanium dioxide fine particles was added, and the mixture was mixed with an ultrasonic homogenizer (US-300 type, manufactured by Nippon Seiki Seisakusho Ltd.) for 10 minutes, and triethylenetetramine was added.
5 g was added and mixed well to prepare a dispersion liquid of fine particles. This dispersion was dropped on a glass plate, and the glass plate was placed on the glass plate and allowed to stand at room temperature for 24 hours, and then a film-shaped electrophoretic material having a thickness of about 20 μm was peeled off from the glass plate.

100 ml of isoparaffin hydrocarbon (trade name: Isopa G, manufactured by Exxon Chemical Co., Ltd.) is mixed with anthraquinone blue dye (trade name: Macrolex Blue RR,
1 g (manufactured by Bayer) was added and sufficiently dissolved and mixed to prepare a liquid having a color different from that of the titanium dioxide fine particles. On the other hand, a Pyrex glass plate having a thickness of 3 mm was used as a transparent substrate, and a transparent conductive film (ITO film) was formed on one surface thereof. A 100 μm-thick polyethylene terephthalate film is used as the back substrate, the film-shaped electrophoretic material prepared above is placed on this, and nylon beads (trade name: SP-500, manufactured by Toray Industries, Inc.) used as a spacer are inserted. The transparent substrate and an epoxy resin adhesive (trade name: Araldite Rapid, manufactured by Ciba-Geigy) were arranged to face each other, and spaces were formed at intervals of about 100 μm. The space between the transparent substrate and the back substrate is filled with an epoxy resin adhesive (trade name: D
An electrophoretic display device was produced by sealing with P-110, manufactured by Sumitomo 3M Limited. A corona ion generator using a gold-plated tungsten wire and a writing electrode composed of a control electrode for controlling the flow of the ions are selectively charged on the rear substrate of the electrophoretic display device to form an electrostatic latent image. When formed, the electrophoretic migration of the film-shaped electrophoretic material in the corresponding portion onto the transparent substrate causes the same display as the electrostatic latent image formed on the rear substrate to produce a clear and clear white display on the transparent substrate. Was obtained. In addition, the number of rewritable times was significantly improved, and the titanium dioxide fine particles were not desorbed from the film-like electrophoretic material even after long-term use, and the life could be extended.

[0029]

According to the present invention, it is possible to prevent the fine particles from settling and aggregating in a liquid, and since the fine particles do not detach from the film-like electrophoretic material, the electrophoretic display device is stable for a long period of time. The display can be obtained, and the number of rewritable times can be greatly improved to be highly reliable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrophoretic display device of the present invention.

[Explanation of symbols]

1 transparent substrate 2 transparent conductive film 3 Spacer 4 Rear substrate 5 Film-like migration material 6 Adhesive 7 Corona wire 8 Control electrode 9 electrostatic latent image

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuko Suzuki             48, Wadai, Tsukuba-shi, Ibaraki Hitachi Chemical Co., Ltd.             Ceremony Company Tsukuba Development Laboratory (72) Inventor Masanori Yamaguchi             48, Wadai, Tsukuba-shi, Ibaraki Hitachi Chemical Co., Ltd.             Ceremony Company Tsukuba Development Laboratory

Claims (4)

[Claims] 1. At least one of two transparent substrates is opposed to each other with a spacer provided therebetween at a required interval to form a sealed space, and the film-shaped electrophoretic material containing fine particles in the sealed space and the particles have different colors. What is claimed is: 1. An electrophoretic display device comprising: a display panel enclosing an electrophoretic display system made of a liquid; and means for applying an electric field to the electrophoretic display system, wherein the film-like electrophoretic body containing fine particles has a vinyl group. An electrophoretic display device comprising: a dispersion liquid in which fine particles treated with a ring agent are dispersed in a vinyl compound having a vinyl group at a terminal, and a film is formed. 2. The electrophoretic display device according to claim 1, wherein the coupling agent having a vinyl group is a silane coupling agent or a titanate coupling agent. 3. At least one of the two transparent substrates is opposed to each other with a spacer interposed therebetween at a predetermined interval to form a sealed space, and the film-shaped electrophoretic body containing particles and the particles have different colors from each other in the sealed space. What is claimed is: 1. An electrophoretic display device comprising: a display panel enclosing an electrophoretic display system made of a liquid; and means for applying an electric field to the electrophoretic display system, wherein a film-like electrophoretic material containing fine particles has an amino group or a glycidyl group. An electrophoretic display device, comprising: a dispersion liquid obtained by dispersing fine particles treated with a coupling agent having: in an epoxy resin to form a film. 4. The electrophoretic display device according to claim 3, wherein the coupling agent having an amino group or a glycidyl group is a silane coupling agent or a titanate coupling agent.