JP2005091442A - Image display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device which can obtain excellent reflectivity and contrast without any limitation on an aperture ratio, and to provide its manufacturing method. <P>SOLUTION: The image display device equipped with a panel for image display that is constituted by charging a particle group or powder liquid between two opposite substrates 1 and 2 at least one of which is transparent and displays an image by applying an electric field to the particle group or powder liquid or moving particles or powder liquid is characterized in that spacers 11 are provided between the two opposite substrates 1 and 2 of the panel for image display. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display device including an image display panel capable of repeatedly displaying and erasing an image with movement of particles or powder fluid using static electricity, and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, image display devices using techniques such as an electrophoresis method, an electrochromic method, a thermal method, and a two-color particle rotation method have been proposed as image display devices that can replace liquid crystal (LCD).

  Compared to LCDs, these conventional technologies have advantages such as a wide viewing angle close to that of ordinary printed materials, low power consumption, and a memory function. It is considered as a technology that can be used for mobile phones, and is expected to expand to image display for mobile terminals, electronic paper, and the like. Particularly recently, an electrophoretic method in which a dispersion liquid composed of dispersed particles and a colored solution is encapsulated and disposed between opposing substrates has been proposed and is expected.

  However, the electrophoresis method has a problem that the response speed becomes slow due to the viscous resistance of the liquid because the particles migrate in the liquid. Furthermore, since particles with high specific gravity such as titanium oxide are dispersed in a solution with low specific gravity, it is easy to settle, and it is difficult to maintain the stability of the dispersed state, and there is a problem of lack of image repetition stability. . Even when microencapsulation is performed, the cell size is set to the microcapsule level, and the above-described drawbacks are hardly made to appear, and the essential problems are not solved at all.

On the other hand, a method in which conductive particles and a charge transport layer are incorporated into a part of a substrate without using a solution is proposed instead of an electrophoresis method using behavior in a solution (see, for example, Non-Patent Document 1). ). However, the structure is complicated because the charge transport layer and further the charge generation layer are arranged, and it is difficult to inject the charges into the conductive particles.
趙 Kuniori and three others, “New Toner Display Device (I)”, July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcopy'99” Proceedings, p.249-252

  In order to solve the above-described problems and the like, in recent years, a particle group or a powder fluid is sealed between two opposing substrates, at least one of which is transparent, and an electric field is applied to the particle group or the powder fluid. There is known an image display device including an image display panel that displays an image by moving the.

  In an image display panel used in this type of image display device, as shown in FIGS. 8A and 8B, a lattice pattern is formed between two opposing substrates (only one substrate 51 is shown here). A (or honeycomb-shaped) partition wall 52 is provided to adjust the gap between the substrates and prevent aggregation of particles or powder fluid. The partition 52 does not only adjust the gap between the substrates and prevents aggregation of particles or powder fluid, but it is necessary to form the lattice-like partition 52 on the entire image display panel. The rate was limited. As a result, there is a problem that the reflectance, contrast, and the like are limited.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to provide an image display device capable of obtaining good reflectivity and contrast without the limitation of the aperture ratio and a method for manufacturing the same.

  The image display device of the present invention encloses a particle group or powder fluid between two opposing substrates, at least one of which is transparent, applies an electric field to the particle group or powder fluid, and moves the particles or powder fluid. An image display device including an image display panel for displaying an image is characterized in that a spacer is provided between two opposing substrates of the image display panel.

  Further, as a preferable example of the image display device of the present invention, the spacer is columnar or spherical, and the ratio of the projected area of the portion without the spacer is 85% or more, more preferably 95% or more.

  The manufacturing method of the image display device of the present invention is the manufacturing method of the image display device having the above-described configuration. (1) A spherical spacer particle having a predetermined size is provided between two opposing substrates of the image display panel. A spherical spacer is provided by spraying or (2) a columnar spacer is formed by forming a columnar spacer by a photoresist method, a printing method or a molding method.

  According to the image display device of the present invention and the manufacturing method thereof, by providing a spacer between two opposing substrates of the image display panel, the aperture ratio is not limited and good reflectance and contrast can be obtained. Can do.

  First, the basic configuration of the image display panel used in the image display device of the present invention will be described. FIGS. 1A to 1C are explanatory views showing an example of an image display panel used in the image display device of the present invention and its display operation principle. FIG. 1A shows an image display panel used in the image display device of the present invention, between a front substrate 1 (preferably transparent) and a back substrate 2 (transparent or not transparent) facing each other. Shows a state where the negatively charged particles 5 and the positively charged particles 6 are arranged. When a voltage is applied to this state so that the display electrode 3 side is at a low potential and the counter electrode 4 side is at a high potential, the positively chargeable particles 6 are displayed on the display electrode by Coulomb force as shown in FIG. The negatively chargeable particles 5 move to the counter electrode 4 side. In this case, the display surface viewed from the front substrate 1 side looks like the color of the positively chargeable particles 6. Next, when the potential of the power source is switched and a voltage is applied so that the display electrode 3 side is at a high potential and the counter electrode 4 is at a low potential, the negatively charged particles 5 are caused by Coulomb force as shown in FIG. It moves to the display electrode 3 and the positively chargeable particles 6 move to the counter electrode 4 side. In this case, the display surface viewed from the front substrate 1 side looks like the color of the negatively charged particles 5. In addition, 7 is a partition and 8 is an insulator.

  Between FIG. 1 (b) and FIG. 1 (c), it is possible to repeatedly display only by reversing the potential of the power supply, and the color can be reversibly changed by reversing the potential of the power supply in this way. . The color of the particles can be selected at will. For example, when the negatively charged particles 5 are white and the positively charged particles 6 are black, or the negatively charged particles 5 are black and the positively charged particles 6 are white, the display is a reversible display between white and black. It becomes. In this method, once the display is performed, each particle is attached to the electrode due to a mirror image force. Therefore, the display image is retained for a long time even after the voltage application is stopped, and the memory retainability is good. In the above description, the particle group including the negatively chargeable particles 5 and the positively chargeable particles 6 has been described as an example. However, the same applies to the powder fluid including the negatively chargeable powder fluid and the positively chargeable powder fluid. .

  The image display device according to the present invention is characterized in that it is not a grid-like (or honeycomb-like) partition wall between two opposing substrates, that is, between the opposing front substrate 1 and rear substrate 2, and is preferably columnar or spherical. It is in the point which provided the spacer. Hereinafter, features of the image display device of the present invention will be described in detail.

  2 (a), 2 (b), 3 (a), and 3 (b) are diagrams for explaining an example of an image display panel provided in the image display device of the present invention. 2A and 2B show an example in which columnar spacers 11 are provided on the back substrate 2 in the same manner as FIGS. 8A and 8B showing the conventional example. 3A and 3B also show an example in which a spherical spacer 12 is provided on the back substrate 2. FIG.

  In the present invention, it is difficult to agglomerate the particle group and the powder fluid described in detail below, so it is only necessary to adjust the gap between the substrates among the roles of the conventional grid-like (or honeycomb-like) partition walls, By providing the spacers 11 and 12, the same function as that of the conventional partition can be achieved. In addition, the spacers 11 and 12 are arranged as shown in FIGS. 2A and 2B and FIGS. 3A and 3B, so that the conventional lattice-shaped (or honeycomb-shaped) partition wall is formed. As compared with the above, the aperture ratio can be greatly improved, and the reflectance and contrast when configured as an image display panel can be improved.

  The spacers 11 and 12 are not particularly limited in configuration, but the gap between the front substrate 1 and the rear substrate 2 is adjusted so that the substrates come into contact with the display electrode 3 provided on the substrate. It is necessary to arrange a sufficient number of spacers so that the electrode 4 is not short-circuited. On the other hand, since the ratio of the projected areas of the portions without the spacers 11 and 12 is the aperture ratio, the ratio of the projected areas is 85% or more, more preferably 95% or more within the range satisfying the above conditions. preferable.

  Next, a manufacturing method of the spacers 11 and 12 which are characteristic among the manufacturing methods of the image display device of the present invention will be described. First, in the case of the columnar spacer 11 shown in FIGS. 2A and 2B, any one of a photoresist method, various printing methods, and a molding method can be employed. Here, as an example of manufacturing the columnar spacer 11 by the photoresist method, it is formed by exposing through a mask having a predetermined negative pattern using a negative dry film having a thickness of 50 μm for photoresist, developing, and washing. You can take a method. As an example of manufacturing the columnar spacers 11 by a printing method, a method of forming by repeating the screen printing method several times using a predetermined plate can be taken. As an example of manufacturing the columnar spacers 11 by a molding method, a method can be used in which a spacer material is uniformly applied on a substrate and a finely processed die is pressed into a predetermined pattern prepared in advance.

  In the case of the spherical spacer 12 shown in FIGS. 3A and 3B, spacer particles having a predetermined size (made of plastic, silica, or glass fiber) are manufactured and used as the spacer 12. . Then, by dispersing the produced spacer particles as the spacers 12 between the front substrate 1 and the rear substrate 2, an image display panel included in the image display device can be manufactured.

Hereafter, each member which comprises the image display apparatus of this invention is demonstrated in detail.
As for the substrate, at least one substrate is the transparent front substrate 1 from which the color of particles or powder fluid can be confirmed from the outside of the apparatus, and a material having high visible light transmittance and good heat resistance is suitable. The back substrate 2 may be transparent or opaque. Whether the substrate is flexible or not is appropriately selected depending on the application. For example, a flexible material for applications such as electronic paper, and flexibility for applications such as mobile phones, PDAs, and notebook PCs. A material with no is preferred. Examples of the substrate material include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, and inorganic sheets such as glass and quartz. The thickness of the substrate is preferably 2 to 5000 μm, and particularly preferably 5 to 1000 μm. If it is too thin, it will be difficult to maintain the strength and the uniformity of the distance between the substrates, and if it is too thick, the display function will have sharpness and contrast. Decrease occurs, and in particular in the case of electronic paper use, flexibility is lacking.

  As for the electrodes, the display electrode 3 and the counter electrode 4 which are two kinds of electrodes having different potentials in the example shown in FIG. 1 are both provided on the side of the back substrate 2 facing the front substrate 1. As another electrode arrangement method, there is a method in which the display electrode 3 is arranged on the front substrate 1 and the counter electrode 4 is arranged on the rear substrate 2 as shown in FIG. 4, but in this case, the display electrode 3 is transparent. An electrode is required. In the example shown in FIG. 1, since both the display electrode 3 and the counter electrode 4 may be opaque electrodes, a metal electrode that is inexpensive and low in resistance, such as copper or aluminum, can be used. The external voltage application may be a direct current or an alternating current superimposed thereon. Each electrode is preferably formed with an insulating coating layer so that the charge of the charged particles does not escape. In this coating layer, it is particularly preferable to use a positively chargeable resin for the negatively chargeable particles and a negatively chargeable resin for the positively chargeable particles because the charge of the particles is difficult to escape. Moreover, what is necessary is just to provide an electrode as needed.

Next, the particle group used for display in the image display apparatus of the present invention will be described.
The particle group for display in the image display device of the present invention may be any negatively or positively charged colored particle group that can be moved by Coulomb force. In particular, it is composed of spherical particles having a small specific gravity. The particle group is suitable. The particle group is of a single color, and white or black particle groups are preferably used. The average particle diameter of the particles constituting the particle group is preferably from 0.1 to 50 μm, particularly preferably from 1 to 30 μm. If the particle diameter is smaller than this range, the charge density of the particles is too large and the mirror image force on the electrode or substrate is too strong, and the memory property is good, but the followability when the electric field is reversed is poor. On the other hand, if the particle diameter is larger than this range, the followability is good, but the memory property is poor.

  A method of charging the particles negatively or positively is not particularly limited, and a method of charging the particles such as a corona discharge method, an electrode injection method, and a friction method is used. The charge amount of particles naturally depends on the measurement conditions, but the charge amount of particles in the image display device is almost dependent on the initial charge amount, contact with the substrate, contact with different types of particles, and charge decay with elapsed time. In particular, it has been found that the “contact with different types of particles”, that is, the saturation value of the charging behavior associated with the contact between two particles is the dominant factor. Therefore, it is important to know the difference in charging characteristics between the two particles, that is, the difference in work function, in terms of the charge amount, but this is difficult by simple measurement.

  As a result of intensive studies, the present inventors have found that the same carrier can be used in the blow-off method to perform relative evaluation by measuring the charge amount of each particle. By defining this by the surface charge density, the image can be obtained. It has been found that the charge amount of particles suitable as a display device can be predicted.

  Although the measurement method will be described later in detail, the charge amount per unit weight of the particle can be measured by sufficiently bringing the particle and the carrier into contact with each other by the blow-off method and measuring the saturated charge amount. Then, the surface charge density of the particles can be calculated by separately obtaining the particle diameter and specific gravity of the particles.

In the image display device, the particle diameter of the particles used is small and the influence of gravity is so small that it can be ignored. Therefore, the specific gravity of the particles does not affect the movement of the particles. However, regarding the charge amount of the particles, even if the average charge amount per unit weight is the same for the particles having the same particle diameter, the charge amount to be held when the specific gravity of the particles is two times different will be two times different. Therefore, it was found that the charging characteristics of the particles used in the image display device are preferably evaluated by the surface charge density (unit: μC / m ² ) that is independent of the specific gravity of the particles.

  When there is a sufficient difference in surface charge density between the particles, the two kinds of particles retain different amounts of charge due to contact with each other and retain the function of moving by an electric field.

  Here, the surface charge density needs to have a certain difference in order to make the charging characteristics of the two particles different, but the larger the surface charge density, the better. In image display devices based on particle movement, when the particle size of the particle is large, the electric image force tends to be a factor that mainly determines the flying electric field (voltage) of the particle, so this particle is moved with a low electric field (voltage). For this purpose, a lower charge amount is better. In addition, when the particle size of the particle is small, non-electric forces such as intermolecular force and liquid crosslinking force are often determinants of the flying electric field (voltage), so this particle is moved with a low electric field (voltage). Therefore, a higher charge amount is better. However, since this greatly depends on the surface properties (material / shape) of the particles, it cannot be generally defined by the particle diameter and the charge amount.

In the case of particles having an average particle diameter of 0.1 to 50 μm, the present inventors have an absolute value of the difference in surface charge density between two types of particles measured by the blow-off method using the same type of carrier is 5 to 150 μC / It has been found that when m ² , the particles can be used as an image display device.

  The blow-off method measurement principle and method are as follows. In the blow-off method, a mixture of powder and carrier is placed in a cylindrical container with nets at both ends, high pressure gas is blown from one end to separate the powder and carrier, and only the powder is removed from the mesh opening. Blow off. At this time, the charge amount equal to the charge amount taken away from the container by the powder remains on the carrier. All of the electric flux due to this charge is collected by the Faraday cage, and the capacitor is charged by this amount. Therefore, by measuring the potential across the capacitor, the charge amount Q of the powder can be obtained as Q = CV (C: capacitor capacity, V: voltage across the capacitor).

  TB-200 manufactured by Toshiba Chemical Co. was used as a blow-off powder charge measuring device. In the present invention, F963-2535 manufactured by Powdertech Co. was used as a carrier. The particle charge amount was measured from these, and the surface charge density of the particle was calculated from the particle diameter and particle specific gravity separately obtained.

  The particle diameter was measured by the method described below, and the specific gravity was measured using a hydrometer (trade name: Multi-Volume Density Meter H 1305) manufactured by Shimadzu Corporation.

  Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring device, the particle size was charged into a nitrogen stream and the attached analysis software (based on the volume reference distribution using Mie theory) Distribution, particle diameter calculation software), and the average particle diameter d (0.5) (number of particles expressed in μm as 50% of particles larger than this and 50% smaller than this) μm).

Since the particles need to retain their charged charges, insulating particles having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more are preferable, and in particular, insulating particles having 1 × 10 ¹² Ω · cm or more are preferable. Further, particles having slow charge decay evaluated by the method described below are more preferable.

  That is, the particles are separately formed into a film having a thickness of 5 to 100 μm by pressing, heat melting, casting, or the like. Then, a voltage of 8 KV is applied to a corona discharger disposed at a distance of 1 mm from the film surface to generate a corona discharge to charge the surface, and a change in the surface potential is measured and determined. In this case, it is important to select and prepare the particle constituent material so that the maximum value of the surface potential after 0.3 seconds is greater than 300V, preferably greater than 400V.

  In addition, the measurement of the said surface potential can be performed, for example with the apparatus (CRT2000 by QEA) shown in FIG. In the case of this apparatus, the above-mentioned measuring unit is provided with both ends of the shaft of the roll on which the above-mentioned film is arranged held by the chuck 21 and the small scorotron discharger 22 and the surface potential meter 23 are separated from each other by a predetermined distance. The surface potential is applied while giving a surface charge by moving the measuring unit at a constant speed from one end to the other end of the film while the film is placed in a stationary state with a distance of 1 mm from the surface of the film. The method of measuring is preferably employed. The measurement environment is a temperature of 25 ± 3 ° C. and a humidity of 55 ± 5 RH%.

The particles may be composed of any material as long as charging performance and the like are satisfied. For example, it can be formed from a resin, a charge control agent, a colorant, an inorganic additive, or the like, or a colorant alone.
Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin and the like can be mentioned, and two or more kinds can be mixed. In particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are suitable from the viewpoint of controlling the adhesive force with the substrate.

  The charge control agent is not particularly limited. Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, metal-containing oil-soluble dyes (including metal ions and metal atoms), and quaternary ammonium salt systems. Examples thereof include compounds, calixarene compounds, boron-containing compounds (benzyl acid boron complexes), and nitroimidazole derivatives. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and the like. In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide, ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives and salts thereof, various organic pigments, resins containing fluorine, chlorine, nitrogen, etc. are also charged. It can also be used as a control agent.

  As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.

  Examples of black pigments include carbon black, copper oxide, manganese dioxide, aniline black, and activated carbon. Yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline There are yellow rake, permanent yellow NCG, tartrage rake and so on. Examples of the orange pigment include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK. Red pigments include Bengala, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin. Rake, Brilliant Carmine 3B, etc.

  Examples of purple pigments include manganese purple, first violet B, and methyl violet lake. Examples of blue pigments include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and induslen blue BC. Examples of the green pigment include chrome green, chromium oxide, pigment green B, malachite green lake, final yellow green G, and the like. Examples of white pigments include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Examples of various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue. These colorants can be used alone or in combination. In particular, carbon black is preferable as the black colorant, and titanium oxide is preferable as the white colorant.

  The method for producing the particles is not particularly limited, and for example, a pulverization method and a polymerization method according to the case of producing an electrophotographic toner can be used. In addition, a method of coating a resin, a charge control agent, or the like on the surface of an inorganic or organic pigment powder is also used.

  The distance between the two opposing substrates may be adjusted to 10 to 5000 μm, preferably 30 to 500 μm, as long as the particles can fly and move and maintain the contrast. The particle filling amount may be 3 to 70%, preferably 5 to 60% of the space volume between the substrates.

Further, in order to further improve the repeated durability here, it is effective to manage the stability of the resin constituting the particles, particularly the water absorption rate and the solvent insolubility rate.
The water absorption of the resin constituting the particles to be sealed between the substrates is preferably 3% by weight or less, particularly preferably 2% by weight or less. The water absorption is measured according to ASTM-D570, and the measurement condition is 23 ° C. for 24 hours.
Regarding the solvent insolubility of the resin constituting the particles, the solvent insolubility of the particles represented by the following relational formula is preferably 50% or more, particularly 70% or more.
Solvent insolubility (%) = (B / A) × 100
(However, A represents the weight of the resin before dipping in the solvent, and B represents the weight after dipping the resin in a good solvent at 25 ° C. for 24 hours.)
If the solvent insolubility is less than 50%, bleeding may occur on the particle surface during long-term storage, affecting the adhesion with the particle and hindering the movement of the particle, which may impair the image display durability.
The solvent (good solvent) for measuring the solvent insolubility is methyl ethyl ketone, etc. for fluororesins, methanol, etc. for polyamide resins, methyl ethyl ketone, toluene, etc. for acrylic urethane resins, acetone, isopropanol, etc. for melamine resins, silicone As the resin, toluene or the like is preferable.

Next, the powder fluid used for display in the image display device of the present invention will be described.
The “powder fluid” in the present invention is a substance in an intermediate state of both fluid and particle characteristics that exhibits fluidity by itself without borrowing the force of gas or liquid. For example, liquid crystal is defined as an intermediate phase between a liquid and a solid, and has fluidity that is a characteristic of liquid and anisotropy (optical properties) that is a characteristic of solid (Heibonsha: Encyclopedia) . On the other hand, the definition of particle is an object with a finite mass even if it is negligible, and is said to be affected by gravity (Maruzen: Physics Encyclopedia). Here, even in the case of particles, there are special states of gas-solid fluidized bed and liquid-solid fluids. When gas is flowed from the bottom plate to the particles, upward force is applied to the particles according to the velocity of the gas. Is a gas-solid fluidized bed that is in a state where it can easily flow when it balances with gravity, and it is also called a liquid-solid fluidized state that is fluidized by a fluid (ordinary) Company: Encyclopedia). As described above, the gas-solid fluidized bed body and the liquid-solid fluid are in a state of using a gas or liquid flow. In the present invention, it has been found that a substance in a state of fluidity can be produced specifically without borrowing the force of such gas and liquid, and this is defined as powder fluid.

  That is, the pulverulent fluid in the present invention is in an intermediate state having both the characteristics of particles and liquid, as in the definition of liquid crystal (liquid and solid intermediate phase), and is the characteristic of the above-mentioned particles. It is a substance that is extremely unaffected and exhibits a unique state with high fluidity. Such a substance can be obtained in an aerosol state, that is, a dispersion system in which a solid or liquid substance is stably suspended as a dispersoid in a gas, and the solid substance is used as a dispersoid in the image display device of the present invention. Is.

  The image display panel of the present invention encloses a powder fluid that exhibits high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid in a gas between two opposing substrates, at least one of which is transparent. Such a powder fluid can be easily and stably moved by a Coulomb force or the like by applying a low voltage.

  As described above, the powdered fluid is a substance in an intermediate state between the fluid and the particle, which exhibits fluidity by itself without borrowing the force of gas or liquid. This powder fluid can be in an aerosol state in particular, and in the image display device of the present invention, a solid substance is used in a state of relatively stably floating as a dispersoid in the gas.

The range of the aerosol state is preferably such that the apparent volume of the pulverized fluid when it is floated is twice or more that when it is not suspended, more preferably 2.5 times or more, and particularly preferably 3 times or more. Although an upper limit is not specifically limited, It is preferable that it is 12 times or less.
If the apparent volume of the pulverized fluid is less than twice that of the unfloating state, it is difficult to control the display, and if it is more than 12 times, the powder fluid will be overloaded when sealed in the device. Inconvenience in handling occurs. The apparent volume at the maximum floating time is measured as follows. That is, the powdered fluid is put into a closed container that allows the powdered fluid to permeate, and the container itself is vibrated or dropped to create a maximum floating state, and the apparent volume at that time is measured from the outside of the container. Specifically, in a container with a lid (trade name: iBoy: manufactured by ASONE Co., Ltd.) having a diameter (inner diameter) of 6 cm and a height of 10 cm, a powder fluid equivalent to 1/5 of the volume as a powder fluid when not floating. And set the container on a shaker, and shake at a distance of 6 cm at 3 reciprocations / sec for 3 hours. The apparent volume immediately after stopping shaking is the apparent volume at the maximum floating time.

In addition, the image display panel of the present invention preferably has a temporal change in the apparent volume of the powder fluid satisfying the following formula.
V ₁₀ / V ₅ > 0.8
Here, V ₅ represents an apparent volume (cm ³ ) 5 minutes after the maximum floating time, and V ₁₀ represents an apparent volume (cm ³ ) 10 minutes after the maximum floating time. In the image display device of the present invention, the apparent volumetric change V ₁₀ / V ₅ of the powder fluid is preferably larger than 0.85, and more preferably larger than 0.9. When V ₁₀ / V ₅ is 0.8 or less, it becomes the same as when ordinary so-called particles are used, and it becomes impossible to ensure the effect of high-speed response and durability as in the present invention.

  The average particle diameter (d (0.5)) of the particulate material constituting the powder fluid is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and particularly preferably 0.9 to 8 μm. is there. If it is smaller than 0.1 μm, it is difficult to control the display, and if it is larger than 20 μm, it is possible to display but the concealment rate is lowered and it is difficult to make the device thin. The average particle diameter (d (0.5)) of the particulate material constituting the powder fluid is the same as d (0.5) in the next particle diameter distribution Span.

The particle substance constituting the powder fluid preferably has a particle size distribution Span represented by the following formula of less than 5, more preferably less than 3.
Particle size distribution Span = (d (0.9) -d (0.1)) / d (0.5)
Here, d (0.5) is a numerical value expressed in μm of the particle diameter that 50% of the particulate material constituting the powder fluid is larger than this and 50% is smaller than this, and d (0.1) is less than this. A numerical value in which the ratio of the particle substance constituting the powder fluid is 10%, expressed in μm, and d (0.9) is the particle diameter in which the particulate substance constituting the powder fluid is 90% μm It is a numerical value expressed by By setting the particle size distribution Span of the particulate material constituting the powder fluid to 5 or less, the sizes are uniform and uniform powder fluid movement becomes possible.

  The above particle size distribution and particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated to the powder fluid to be measured, a light intensity distribution pattern of diffracted / scattered light is generated spatially, and this light intensity pattern has a corresponding relationship with the particle diameter, so the particle diameter and particle diameter distribution are measured. it can. This particle size and particle size distribution are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring machine, the powdered fluid was introduced into the nitrogen stream, and the attached analysis software (software based on volume reference distribution using Mie theory) Measurements can be made.

  Preparation of powder fluid can be done by kneading and pulverizing the necessary resin, charge control agent, colorant, and other additives, or by polymerization from monomers, and adding existing particles to resin, charge control agent, colorant, and other It may be coated with an agent. Hereinafter, the resin, charge control agent, colorant, and other additives constituting the powder fluid will be exemplified.

  Examples of the resin include urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, silicone resin, nylon resin, epoxy resin, styrene resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluorine resin, etc. Two or more types can also be mixed. In particular, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, urethane resin, and fluororesin are preferable from the viewpoint of controlling the adhesive force with the substrate.

  Examples of charge control agents include quaternary ammonium salt compounds, nigrosine dyes, triphenylmethane compounds, imidazole derivatives and the like in the case of imparting positive charges, and metal-containing azo compounds in the case of imparting negative charges. Examples thereof include dyes, salicylic acid metal complexes, and nitroimidazole derivatives.

  Examples of the coloring agent include basic and acidic dyes such as nigrosine, methylene blue, quinoline yellow, and rose bengal.

  Examples of inorganic additives include titanium oxide, zinc white, zinc sulfide, antimony oxide, calcium carbonate, lead white, talc, silica, calcium silicate, alumina white, cadmium yellow, cadmium red, cadmium orange, titanium yellow, Examples include bitumen, ultramarine blue, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.

  However, even if such a material is kneaded and coated without any ingenuity, a powder fluid that shows an aerosol state cannot be produced. The production method of the powder fluid showing the aerosol state is not clear, but is exemplified as follows.

  First, it is appropriate to fix inorganic fine particles having an average particle diameter of 20 to 100 nm, preferably 20 to 80 nm, to the surface of a substance constituting the powder fluid. Furthermore, it is appropriate that the inorganic fine particles are treated with silicone oil. Here, examples of the inorganic fine particles include silicon dioxide (silica), zinc oxide, aluminum oxide, magnesium oxide, cerium oxide, iron oxide, and copper oxide. The method of fixing the inorganic fine particles is important. For example, using a hybridizer (manufactured by Nara Machinery Co., Ltd.) or mechanofusion (manufactured by Hosokawa Micron Co., Ltd.) or the like, under certain limited conditions (for example, processing time) ), A powder fluid showing an aerosol state can be produced.

Here, in order to further improve the repeated durability, it is effective to manage the stability of the resin constituting the powder fluid, particularly the water absorption rate and the solvent insolubility rate. It is preferable that the water absorption rate of the resin constituting the powdered fluid enclosed in the cells partitioned by the partition walls is 3% by weight or less, particularly 2% by weight or less. The water absorption is measured according to ASTM-D570, and the measurement condition is 23 ° C. for 24 hours. Regarding the solvent insolubility of the resin constituting the powder fluid, the solvent insolubility of the powder fluid represented by the following relational expression is preferably 50% or more, particularly 70% or more.
Solvent insolubility (%) = (B / A) × 100
(However, A represents the weight of the resin before dipping in the solvent, and B represents the weight after dipping the resin in a good solvent at 25 ° C. for 24 hours.)

  If this solvent insolubility is less than 50%, bleeding occurs on the surface of the particulate material that constitutes the powder fluid during long-term storage, which affects the adhesion with the powder fluid and hinders the movement of the powder fluid, resulting in improved image display durability. May cause problems. The solvent (good solvent) for measuring the solvent insolubility is methyl ethyl ketone, etc. for fluororesins, methanol, etc. for polyamide resins, methyl ethyl ketone, toluene, etc. for acrylic urethane resins, acetone, isopropanol, etc. for melamine resins, silicone resins, etc. In this case, toluene or the like is preferable.

Furthermore, in the present invention, it is important to manage the gas in the voids surrounding the particle group or the powder fluid between the substrates, which contributes to the improvement of display stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less, more preferably 35% RH or less with respect to the humidity of the gas in the gap.
In FIG. 1, this void portion refers to the portion occupied by the electrodes 3 and 4, the particle group (or powder fluid) 5 and 6, the partition 7 and the insulator 8 from the portion sandwiched between the opposing substrate 1 and substrate 2. The gas part where the so-called particle group (or powder fluid) contacts, excluding the part and the device seal part.
The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas needs to be sealed in the apparatus so that the humidity is maintained. For example, filling of particles or powder fluid, assembly of the substrate, etc. are performed in a predetermined humidity environment, It is important to apply a sealing material and a sealing method to prevent moisture intrusion.

  In the image display panel of the present invention, a plurality of the above cells are used and arranged in a matrix to perform display. When displaying an arbitrary color other than black and white, a combination of particles or powder fluid colors may be appropriately performed. In the case of a full color, there are three types, ie, R (red), G (green), and B (blue) color plates, and each cell has black particles or powder fluid, and a plurality of them are arranged. Thus, an image display panel is preferable.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Test method>
(1) Production of Back Substrate with Spacer A spacer was formed with a photoresist in a pattern shape to be described later on a glass substrate (back substrate) having an ITO electrode and adjusted to 30Ω / □.
(2) Filling of particles White particles and black particles were dispersed on the back substrate with a spacer by a free fall method. Thereafter, unnecessary particles on the spacer were removed using a slightly adhesive sheet or a slightly adhesive roll. The spreading amount was black particles: 8 g / m ² and white particles: 8 g / m ² .

  As white particles, thermoplastic polyetherester elastomer: Hytrel 6377 (manufactured by Toray DuPont), CB 4phr and charge control agent Bontron N07 (manufactured by Orient Chemical) 2phr are added, kneaded and then pulverized and classified in a jet mill. It was used. Also, as black particles, add 10 phr of titanium oxide and 2 phr of charge control agent Bontron E89 (manufactured by Orient Chemical) to the thermoplastic polyetherester elastomer: Hytrel 6377 (manufactured by Toray DuPont). What was pulverized and classified was used.

(3) Bonding of front substrate A PET film having a thickness of 100 μm adjusted to 30Ω / □ by vapor deposition of ITO electrode was used as a front substrate and bonded to a rear substrate with a spacer filled with the above particle group.
(4) Inversion test A voltage of 150 V was applied between the electrodes, the display color was inverted, and the white reflectance and the black reflectance were measured using a Minolta reflective liquid crystal system. The results are shown in Table 1 below. In Table 1, the evaluation of each example shows that the contrast is 8.0 or higher, the contrast is 7.0 or higher, the contrast is 6.0 or higher, and the gap can be maintained. Those that were short-circuited between the electrodes and could not be reversed were marked with x.

<Pattern shape>
Example 1
As shown in FIG. 6, columnar spacers having a height of 50 μm and a diameter of 50 μm were arranged at a pitch of 120 μm. At this time, the number of spacers per unit area was 69.4 / mm ² , and the ratio to the projected area of the portion without the spacers was 86.4%.
Example 2
As shown in FIG. 6, columnar spacers having a height of 50 μm and a diameter of 50 μm were arranged at a pitch of 160 μm. At this time, the number of spacers per unit area was 39.1 / mm ² , and the ratio of the projected area of the portion without spacers was 92.3%.
Example 3
As shown in FIG. 6, columnar spacers having a height of 50 μm and a diameter of 50 μm were arranged at a pitch of 100 μm. At this time, the number of spacers per unit area was 20.7 / mm ² , and the ratio of the projected area of the portion without spacers was 95.9%.
Example 4
A spherical spacer made of acrylic resin having a diameter of 50 μm and a span of 0.5 was arranged at 50 pieces / mm ² by a free fall method. At this time, the ratio of the projected area of the inner portion of the spacer was 90.2%.

Comparative Example 1
As shown in FIG. 7, partition walls having a height of 50 μm and a width of 50 μm were arranged in a lattice shape at a pitch of 500 μm. At this time, the ratio of the projected area of the portion without the partition (opening) was 81.0%.
Comparative Example 2
As shown in FIG. 7, partition walls having a height of 50 μm and a width of 50 μm were arranged in a lattice shape at a pitch of 1400 μm. At this time, the ratio of the projected area of the portion without the partition (opening) was 93.0%.
Comparative Example 3
As shown in FIG. 7, partition walls having a height of 50 μm and a width of 50 μm were arranged in a lattice shape at a pitch of 2200 μm. At this time, the ratio of the projected area of the portion without the partition (opening) was 95.5%.

  From the results in Table 1, Examples 1 to 3 using columnar spacers and Example 4 using spherical spacers are superior in both reflectance and contrast compared to Comparative Examples 1 to 3 using conventional partition walls. It was found that high evaluation was obtained.

  An image display device using the spacer of the present invention and a manufacturing method thereof include image display units of mobile devices such as notebook computers, PDAs, and mobile phones, electronic papers such as electronic books and electronic newspapers, bulletin boards such as signboards, posters, and blackboards. It is used for image display units such as calculators, home appliances, and automobile products, electronic advertisements, electronic POPs, and the like.

(A)-(c) is explanatory drawing which shows an example of the panel for an image display used with the image display apparatus of this invention, respectively, and its display operation principle. (A), (b) is a figure for demonstrating the other example of the image display panel with which the image display apparatus of this invention is provided, respectively. (A), (b) is a figure for demonstrating an example of the image display panel with which the image display apparatus of this invention is provided, respectively. It is a figure which shows the structure of the other example of the image display panel used with the image display apparatus of this invention. It is explanatory drawing of the measuring apparatus for measuring the surface potential of the particle | grains in this invention. It is a figure which shows the arrangement | positioning state of the spacer in an Example. It is a figure which shows the arrangement | positioning state of the partition in a comparative example. (A), (b) is a figure for demonstrating an example of the image display panel with which the conventional image display apparatus is provided, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front substrate 2 Back substrate 3 Display electrode 4 Counter electrode 5 Negatively charged particle 6 Positively charged particle 7 Bulkhead 8 Insulator 11 Columnar spacer 12 Spherical spacer 21 Chuck 22 Scorotron discharger 23 Surface potential meter

Claims (5)

  An image display panel that encloses a particle group or powder fluid between two opposing substrates, at least one of which is transparent, applies an electric field to the particle group or powder fluid, and moves the particles or powder fluid to display an image. An image display device comprising a spacer provided between two opposing substrates of an image display panel.   The image display device according to claim 1, wherein the spacer is columnar or spherical.   The image display device according to claim 1 or 2, wherein a ratio of a projected area of a portion having no spacer is 85% or more, more preferably 95% or more.   In the manufacturing method of the image display device according to any one of claims 1 to 3, by dispersing spherical spacer particles with a predetermined size between two opposing substrates of the image display panel, A method for manufacturing an image display device, comprising a spherical spacer.   4. The method for manufacturing an image display device according to claim 1, wherein a columnar spacer is formed between two opposing substrates of the image display panel by a photoresist method, a printing method, or a molding method. Thus, a method for manufacturing an image display device, characterized in that a columnar spacer is provided.

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