JP2001117122A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a bright image showing high contrast without depending on the viewing angle. SOLUTION: The image display device 10 of this invention is equipped with a surface substrate 12, a back substrate 14, electrodes 16, 18 disposed on the inner sides of the substrates, respectively, and display layer 26 formed between the surface substrate 12 and the back substrate 14. The display layer 26 contains a binder resin 20, polymer gel particles 22 dispersed in the binder, and color fine particles 24 electrified into negative charges and included in the polymer gel particles 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel image display device.

[0002]

2. Description of the Related Art Conventionally, as a display device of information equipment,
CRT (cathode ray tube) display monitor, liquid crystal display, plasma display, EL
(Electroluminescent) displays, field emission displays, and the like have been put to practical use.

[0003] Of these display devices, display monitors of desktop computers and notebook computers and display devices of personal digital assistants (PDAs) are required to be thinner, lighter and more diversified. Is used as a display device most suitable for such specifications.

[0004]

However, the liquid crystal display is
Due to its structure, it has drawbacks related to the viewing angle, such as a change in contrast depending on the viewing angle and color reversal, as well as drawbacks such as darkness of display, complexity of the manufacturing process, and high cost. .

As a display device which does not use liquid crystal having such a drawback, Japanese Patent Application Laid-Open No. 5-173190 discloses a display device using a gel polymer. This device is a non-light-emitting device in which a gel polymer that swells or shrinks in response to an electric field is arranged between a pair of substrates on which electrodes are arranged, and swells the gel polymer to transmit light. Alternatively, a voltage is applied to the gel to cause the gel to shrink, to generate irregularities on the surface, and to scatter light to perform light modulation. However, the light modulation is not sufficient, and the production process is complicated because a gel is polymerized in the cell after the cell is formed on the electrode in advance, and the gel is sealed in the cell together with the electrolytic solution.

As another display device using a gel-like polymer, Japanese Patent Application Laid-Open No. 5-188354 discloses a gel-like polymer particle which swells or shrinks in response to an electric field between a pair of substrates on which electrodes are arranged. A disposed non-emissive device is disclosed. In this device, light modulation is performed by changing the size of gel-like polymer particles to change the state of light transmission or scattering. However, the light modulation is not sufficient.

Further, Japanese Patent Application Laid-Open No. Hei 9-160081 discloses a pair of substrates, an electrode provided between the pair of substrates,
A light modulating layer including a functional gel that is deformed by an electric field applied between the electrodes, and the amount of light incident on the light modulating layer is adjusted by the deformation of the functional gel, thereby depending on the viewing angle. A novel display device suitable for a portable display device that achieves high contrast, high reflectance, and high light use efficiency without using the same is disclosed. However, light modulation is not sufficient, and after a cell is formed on an electrode in advance, a gel is polymerized in the cell, and the cell is sealed in the cell together with an electrolytic solution, so that the manufacturing process is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a display device which has good contrast, is bright, and can be easily manufactured without depending on the viewing angle.

[0009]

The present invention comprises a pair of substrates, a pair of electrodes respectively disposed inside the pair of substrates, and a display layer provided between the pair of substrates. The display layer is a binder resin, dispersed in the binder resin, polymer gel particles whose volume is reversibly changed in response to an electric field, and contained in the polymer gel particles, and the color of the polymer gel particles. Provided is an image display device including colorant fine particles having different colors.

In this image display device, when the polymer gel is swollen, the color of the polymer gel is displayed. On the other hand, when the polymer gel contracts, the coloring material fine particles contained in the polymer gel are released from the polymer gel,
The color of the color material particles is displayed. An image is displayed by this contrast. The polymer gel particles and the coloring material fine particles can be colored in an arbitrary color, and various colors can be displayed. Accordingly, a bright image with good contrast can be displayed without depending on the viewing angle.

In the case where the coloring material fine particles migrate on the electrode side on the side where the polymer gel contracts, when the polymer gel contracts on the electrode side transmitting visible light, the coloring material released This is preferable because the fine particles migrate to the electrode side and the color of the coloring material fine particles is more easily displayed.

The particle size of the polymer gel particles is preferably smaller than the range of the pixels of the pair of electrodes, and the binder resin may be a stimulus-curable resin. A filter layer can be formed on the display layer as needed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The present invention includes a pair of substrates, a pair of electrodes disposed inside the pair of substrates, respectively, and a display layer provided between the pair of substrates.

One of the substrates needs to transmit visible light, and glass, polyethylene terephthalate resin, polycarbonate resin, polyester resin, epoxy resin, polyurethane resin and the like can be used. The other side of the substrate may or may not transmit visible light, and a polyester resin, an epoxy resin, a polyurethane resin, a polyimide resin, a polyamide resin, a phenol resin, a polyolefin resin, a polyether resin, a silicone resin, or the like can be used. When both substrates are formed of plastic, a flexible display device can be obtained.

An electrode on a substrate (surface substrate) that transmits visible light also needs to transmit visible light, so that ITO (Ind
oxide semiconductors such as SnO ₂ -based, SnO ₂ -based, ZnO-based Cd ₂ SnO ₄ -based, Au, Ag, Cu
Such metals as can be used. For the other substrate (back substrate), Cu, Ni, Au, or Pt can be used in addition to the above materials. The electrode can be formed by a sputtering method or the like.

The display layer includes a binder resin, polymer gel particles dispersed in the binder resin and whose volume is reversibly changed in response to an electric field, and the polymer gel encapsulated in the polymer gel particles. Color material fine particles having a color different from the color of the particles are included.

Examples of the binder resin include a fluorine resin, an acrylic resin, a polyester resin, a vinyl acetate resin, a vinyl chloride resin, a styrene-butadiene copolymer, a polyurethane resin, a polystyrene resin, a vinyl acetate-acryl copolymer, and vinyl acetate. -Acrylamide copolymers, ethylene-vinyl acetate copolymers, epoxy resins, polyamide resins, silicone resins and the like. Also, a stimulus-curing resin such as an ultraviolet-curing resin can be used. These binder resins can be used alone or in combination.

The polymer gel reversibly changes in volume in response to an electric field, and swells or contracts reversibly in response to the polarity of an applied electric field to change its shape. In order to respond to an electric field, conjugate electrification is necessary, and the polymer electrolyte has it. However, a dielectric gel having a large dielectric constant without electrification responds to an electric field, and a polymer having a zwitterion responds similarly. In the case of a polymer electrolyte gel, when an electric field is applied, cations and anions move in the gel toward the corresponding electrodes, and the resulting distortion occurs in the gel. For example, an acrylic acid-acrylamide copolymer gel swollen with a protic solvent, under a DC electric field of about 10 V, in an aqueous solution of a salt, when the acrylamide content is small, the anode side shrinks, and when the acrylamide content is large, The cathode side swells. Aprotic solvents such as D
PVA (polyvinyl alcohol) swollen with MSO (dimethyl sulfoxide) is distorted under a DC electric field of about 250V. The driving mechanism in this case is DMS
O is oriented in an electric field, the structure and properties of the solvent change, and PVA
It is considered that gel distortion was induced as a result of the interaction between DMSO and DMSO. As the material of the polymer gel acting in this way, polyacrylic acid-polyacrylamide type,
Copolymers such as polyvinyl alcohol-polyacrylamide, starch, cellulose, hyaluronic acid,
It is possible to use copolymers such as polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyoxyethylene, polystyrenesulfonic acid, polyacrylamide-2-methylpropanesulfonic acid acrylic, polyurethane resin and various oreganogels. it can. Examples of the method for producing these polymer gel particles include an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, and a precipitation polymerization method. In order to obtain large gel particles, a suspension polymerization method is suitable, and a crosslinking agent, a polymerization initiator, an accelerator, and a solvent that is a good solvent for the monomer and a poor solvent for the polymer are added to the droplets of the monomer. And polymerize.

The particle size of the polymer gel particles is preferably smaller than one pixel range of the electrode, more preferably not more than half, more preferably 10 to 50 μm. This eliminates the need for a difficult step of aligning the pixels with the polymer gel particles, and allows an image to be displayed with higher resolution.

Pigments can be suitably used as the coloring material fine particles. Titanium oxide (rutile or atanase type) and zinc sulfide are used for the white type, and yellow iron oxide, cadmium yellow, and titanium are used for the yellow type. Inorganic pigments such as yellow and graphite, and organic pigments such as Hansa Yellow and Pigment Yellow are red-based inorganic pigments such as Bengala and Cadmiumium Red, and Shinkasia Red Y, Permanent Red, and First Slow Red. Aji pigment-based organic pigments such as
Organic pigments such as ultramarine, navy blue, cobalt blue, and cerulean blue, and organic pigments such as phthalocyanine blue and phthalocyanine pigments such as Fast Sky Blue, and indanthrene pigments such as indanthrene blue are green. Inorganic pigments such as chrome green, chromium oxide, and viridian; and organic pigments such as nitroso pigments such as pigment green and naphthol green; and phthalocyanine pigments such as phthalocyanine green. These pigments can be used alone or in combination of two or more. It is preferable that these coloring material fine particles migrate according to an electric field formed between the front substrate and the rear substrate. In other words, it is preferable that the coloring material fine particles migrate on the electrode side on the side where the polymer gel is contracted. This allows
When the polymer gel shrinks on the electrode side on the surface substrate side, the released color material fine particles migrate to the electrode side, and the color of the color material fine particles is more easily displayed.

The inclusion of these fine particles in the polymer gel can be achieved by repeatedly swelling and shrinking the polymer gel particles in a dispersion medium in which the prepared polymer gel particles and the fine particles are dispersed.

The method for producing the display layer includes a method in which a dispersion in which polymer gel particles containing coloring material fine particles are dispersed in a solution in which a binder resin is dissolved is sealed between substrates and dried, and a surfactant, etc. Using a stimulus-curable resin precursor, a dispersion liquid in which polymer gel particles containing coloring material particles are dispersed is sealed between the substrates, and the polymer gel particles are tightly packed between the substrates using ultrasonic vibration or the like. To reduce the distance between the substrates to about 4/5 of the particle size of the polymer gel particles, increase the contact area between the polymer gel particles and the electrodes, and apply stimuli such as ultraviolet rays, electron beams, visible rays, and heat. To cure the resin precursor. Of these, a method using a stimulus-curing resin is preferred because it is simple. As the resin derivative, ester-based, epoxy-based, urethane-based, alkyd-based, silicone-based oligomers and monomers can be used.

As a solvent for dissolving the binder resin,
For example, ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate, lactic acid Examples include ethyl, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethylsulfoxide, sulfolane, γ-butyrolactone, toluene and the like.

The thickness of the display layer is preferably from 10 to 100 μm, more preferably from 10 to 50 μm. The polymer gel particles are preferably monodispersed. Further, the weight ratio of the binder resin, the polymer gel particles and the coloring material fine particles in the display layer is preferably from 15: 10: 1 to 30: 10: 1.

The display layer can be provided with a filter for preventing scratches and dirt, and a filter for preventing reflection. In addition, the polymer gel particles are black, the coloring material particles are white, or vice versa, and an arbitrary color is displayed by forming a light transmitting color filter of an arbitrary color on the surface substrate side of the display layer. Is also good.

FIG. 4 shows an image display device 10 according to the present invention. The front substrate 12 and the rear substrate 14 are arranged so as to face each other, and electrodes 16 and 18 are provided inside the front substrate 12 and the rear substrate 14, respectively. A display layer 26 in which polymer gel particles 22 are dispersed in a binder resin 20 is disposed between the front substrate 12 and the rear substrate 14. The polymer gel particles 22 contain coloring material fine particles 24 that are negatively charged.
In the image display device 10, two polymer gel particles 22 correspond to one pixel.

In this image display device 10, when no voltage is applied, the polymer gel particles swell as shown in FIG. For example, as shown in FIG. 2, when a positive voltage is applied to the electrode 16 and a negative electrode is applied to the electrode 18, the electrode 16 side of the polymer gel particles 22 contracts, and a part of the coloring material fine particles 24 is released. . The released coloring material fine particles 24 are electrophoresed toward the electrode 16 as an anode by Coulomb force, and the coloring material fine particles 24 adhere to the electrode 16,
The color of the color material particles is displayed.

On the other hand, as shown in FIG. 3, when the applied electric field is reversed, that is, when a negative voltage is applied to the electrode 16 and a positive electrode is applied to the electrode 18, the surface substrate of the polymer gel particles 22 Since the side 12 is swollen, the color of the polymer gel particles 22 is displayed.

If the polarity of the voltage applied to the electrode 16 on the surface substrate 12 is changed for each pixel, an image is formed by the contrast between the color of the polymer gel particles 22 and the color of the color material fine particles 24 as shown in FIG. Is displayed.

[0031]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. Example 1 A pregel solution was prepared by mixing acrylamide, acrylic acid, vinyl alcohol, ammonium persulfate as an initiator, and sorbitan monolaurate as a surfactant at a molar ratio of 40: 659: 1: 2: 10. Then, dry nitrogen was passed through this pregel solution for 20 minutes to sufficiently dissolve dissolved oxygen. This pregel solution was polymerized at 50 ° C. for 4 hours while gently stirring under a nitrogen atmosphere, and then exposed to ion exchanged water for 2 days to sufficiently diffuse unreacted substances. The obtained polymer gel particles were centrifuged with a centrifugal force of 1.5 * 10 ³ g for 30 minutes using a centrifuge manufactured by Shimadzu Corporation to remove large aggregates, and acrylic acid having an average particle size of about 50 μm was used. -An acrylamide-vinyl alcohol copolymer gel particle was obtained.

The copolymer gel particles and titanium oxide (T
A voltage was applied in a dispersion medium in which white fine particles of iO ₂ ) were dispersed, and swelling and shrinking of the copolymer gel particles were repeated, whereby the white fine particles were included in the copolymer gel particles.

The particles were dispersed at 70% by weight in an epoxy ultraviolet curing resin (Nippon Synthetic Rubber Co., Ltd., Desolite SCR-700) to prepare a dispersion.

On the other hand, ITO was deposited on each of the two ITO substrates by a vacuum deposition method to form electrodes having a thickness of 0.5 μm. The ITO substrate was arranged so that the electrodes were on the inside, the dispersion liquid was sealed therebetween, and ultrasonic vibration was applied to arrange the polymer gel particles densely. Next, the interval between the ITO substrates was reduced from about 50 μm to 40 μm, and then 10 mW using an ultraviolet light irradiation device manufactured by Ushio Electric.
An ultraviolet ray having an intensity of cm ⁻² was irradiated for about 60 seconds to cure the ultraviolet curable resin, thereby producing an image display device.

When a voltage of 10 V is applied between the electrodes of the obtained image display device (a negative voltage to the electrode on the front substrate side and a positive voltage to the electrode on the rear substrate side), the surface substrate side of the polymer gel particles contracts, The white fine particles were released, and the released white fine particles were electrophoresed and adhered to the electrode on the front substrate side, and a bright white image was obtained on the front substrate. When the polarity of the applied voltage was reversed, the white fine particles adhered to the surface electrode were separated and electrophoresed, the polymer gel particles swelled on the surface substrate side, contained white fine particles, and a black image was obtained on the surface substrate. . (Comparative Example 1) Acrylamide, acrylic acid, vinyl alcohol and ammonium persulfate as an initiator were mixed at a molar ratio of 659: 40: 1: 2 on the ITO substrate having electrodes formed on the surface used in Example 1. Thus, a pregel solution was prepared, and dry nitrogen was passed through the pregel solution for 20 minutes to sufficiently dissolve dissolved oxygen. The pregel solution was applied to an ITO substrate with a thickness of about 1 μm by spin coating, heated and polymerized at 50 ° C. for 4 hours to form an acrylic acid-acrylamide copolymer gel. Further, a non-conductive particle of 40 μm is interposed as a spacer between the ITO substrate on which the gel is formed and the ITO substrate on which the gel is not formed, and the periphery is sealed with an epoxy-based adhesive. A liquid in which water and acetone were mixed at a volume ratio of 1: 1 was sealed in the gap, to produce an image display device. Comparative Example 2 N-acryloxysuccinimide, N-isopropylpyracrylamide, ammonium persulfate as an initiator, and sorbitan monolaurate as a surfactant were ion-exchanged at a molar ratio of 1: 1: 0.005: 0.01. A pregel solution was prepared by dissolving in water, and dry nitrogen was passed through the pregel solution for 20 minutes to sufficiently dissolve dissolved oxygen. The pregel solution was polymerized at 50 ° C. for 4 hours while being gently stirred under a nitrogen atmosphere, exposed to ion-exchanged water, and allowed to sufficiently diffuse unreacted substances for one day, thereby selecting gel fine particles. An ITO substrate having an electrode formed on the surface used in Example 1 was arranged so that the electrode was on the inside, 40 μm of non-conductive particles were interposed therebetween as a spacer, and the periphery was sealed with an epoxy adhesive. Thereafter, ethanol in which the Kell microparticles were dispersed at 30% by weight was sealed in the gap between the electrodes, thereby producing an image display device.

Display and non-display were switched for the display devices manufactured in the example and the comparative example, and two points of brightness and contrast were evaluated. Table 1 shows the results.

[0037]

[Table 1]

In Table 1, the brightness was evaluated based on the reflectance at the time of white display, and ○ indicates 60% or more, Δ indicates 30% or more and less than 60%, and × indicates 30% or less. Contrast is evaluated by (reflected light intensity at white display−reflected light intensity at black display) / (reflected light intensity at white display + reflected light intensity at black display) with respect to incident light at white and black display. 0.6 or more was rated as ○, less than 0.6 was rated as Δ, and less than 0.4 was rated as x.

From Table 1, it can be seen that in Example 1, a fairly bright display was obtained due to the white fine particles adhering to the surface electrode. The display brightness was 62%, the contrast was 0.6, and both of them were good. Results were obtained. In Comparative Example 1, the brightness of the display was 60%, but the contrast of 0.5 was not sufficient. In Comparative Example 2, the brightness of the display was slightly dark at 55, and the contrast was not enough at 0.4.

[0040]

The image display device of the present invention comprises a polymer gel particle whose volume is reversibly changed in response to an electric field, by enclosing or releasing a coloring material fine particle by swelling or shrinking. In addition, since the color of the polymer gel particles and the color of the coloring material fine particles are displayed, a high-contrast and bright image can be displayed regardless of the viewing angle.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state where a voltage is not applied to an image display device of the present invention.

FIG. 2 is a cross-sectional view showing a state where a voltage is applied to the image display device of FIG.

FIG. 3 is a cross-sectional view illustrating a state where a voltage is applied to the image display device of FIG. 1;

FIG. 4 is a sectional view showing the image display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image display apparatus 12 Front substrate 14 Back substrate 16 Electrode 18 Electrode 20 Binder resin 22 Polymer gel particle 24 Color material fine particle 26 Display layer

Claims (5)

[Claims] 1. A display device comprising: a pair of substrates; a pair of electrodes respectively disposed inside the pair of substrates; and a display layer provided between the pair of substrates. Polymer gel particles which are dispersed in a resin and whose volume is reversibly changed in response to an electric field, and contained in the polymer gel particles, coloring material fine particles having a color different from the color of the polymer gel particles. Image display device including. 2. The image display device according to claim 1, wherein the coloring material fine particles migrate on the electrode side on the side where the polymer gel shrinks. 3. The image display device according to claim 1, wherein a particle diameter of the polymer gel particles is smaller than a range of a pixel of the pair of electrodes. 4. The image display device according to claim 1, wherein the binder resin is a stimulus-curable resin. 5. The image display device according to claim 1, further comprising a filter layer on the display layer.