JP2003161968A - Rewritable and erasable display medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a display medium whose display contents can easily be rewritten and erased and which has satisfactory visibility and high contrast. <P>SOLUTION: A display layer 3 consisting of a structure, wherein spherical particles 5 constituted of two or more parts different in color and a substance 4 having fluidity under a specified condition are incorporated, is provided on at least one surface of a substrate 2. A substance having a function for concealing the shadow of the spherical particles 5 is used as the substance 4 having fluidity. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display medium in which display contents can be easily rewritten and erased, visibility is high, and contrast is high.

[0002]

2. Description of the Related Art In recent years, with the rapid development of information networks, various information has been digitized and used for business and daily life. As a result, it was thought that the electronic information society would become paperless, but the paper consumption itself did not decrease. This is not preferable from the viewpoint of protecting the global environment. Based on such a background, recently, a display medium so-called electronic paper (an analog paper, which is a conventional paper medium, has both an advantage of rewriting the display content, which is an advantage of an electronic document, and a shape variability, which is an advantage of a paper document. On the other hand, it is also called digital paper).

At present, as a candidate technology of electronic paper, a method of electrically controlling the arrangement of liquid crystal molecules to change the optical characteristics of liquid crystal to perform display, or electrophoretic by enclosing fine particles in an insulating liquid. The method of moving particles to display by the contrast between the color of liquid and the color of particles, or N. K. There is known a method proposed by Sheridon et al., In which display is performed by rotating a minute ball by electric field driving.

[0004]

However, each of the above-described display technologies known in the related art has the following problems. That is, in the method using liquid crystal, the contrast ratio is low and the visibility is not good. In the method of moving particles by electrophoresis, there is a problem in stability of display contents with time due to aggregation / precipitation of particles in a sealed liquid. With the method of rotating minute balls by electric field driving, it is difficult to manufacture a flexible display device using a polymer film as a substrate, as described in JP-A No. 11-85066.

An object of the present invention is to solve the above disadvantages of the prior art, to easily rewrite and erase display contents, to have good visibility, to be stable in display contents over time, and to display with a high contrast ratio. To provide the medium.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the object of the present invention, as shown in FIG.
At least one surface of the base material 2 is composed of at least two kinds of parts having different colors, and an external electric field, magnetic field,
Spherical particles 5 that can be rotated by applying energy such as heat or light and a substance 4 that has fluidity under specific conditions
In a rewritable and erasable display medium provided with a display layer 3 having a structure in which and are contained, by using a substance having a function of hiding the shadow of the spherical particles 5 as the substance 4 having fluidity, It has been found that a display medium 1 can be produced which is easy to rewrite and erase contents, has good visibility, has excellent stability of displayed contents over time, and has a high contrast ratio.

In the above display medium 1, the substance 4 is used.
Since the shadow of the spherical particles 5 is hidden by the above, when the display surface is observed in that state, the shadow generated by the adjacent spherical particles 5 becomes difficult to see, and it is difficult to affect the colors that can be displayed. As a result, the display color can be relatively emphasized, and the contrast ratio itself can be increased. The spherical particles 5 are dodecahedron,
It does not exclude polyhedral bodies such as icosahedrons, and substantially spherical particles within a range that does not hinder rotation such as granular bodies.

[0008]

The spherical particles used in the present invention, that is, the spherical particles composed of at least two kinds of portions having different colors can be appropriately adjusted according to the energy required for display. For example, if spherical particles are adjusted so as to impart partially different charges, they can be rotated by an electric field, and as a result, different colors can be displayed. Further, if it is adjusted so as to impart magnetization, different colors can be displayed depending on the magnetic field. In this way, the spherical particles can be appropriately adjusted according to the energy required for display. Among them, spherical particles colored in different colors so that writing / erasing can be performed by a magnetic field, and a part of which is magnetized are preferable because the dipoles are easily aligned. Also,
Spherical particles made of non-magnetic organic resin, partially colored differently, and magnetized in part of them can not only make the polarities of the spherical particles relatively easy, but also contain them. It is particularly preferable because it has the same specific gravity as that of a substance having fluidity under specific conditions, and thus has advantages such as easy rotation when a magnetic field is applied and stable display content retention. .

The size of the spherical particles used can be appropriately selected according to the application. For example, in the case of A4 size and image resolution of 250 dpi is required, the size of the spherical particles is preferably 100 μm or less, and when used for large-scale display or signboard, the particle size should be increased to the extent that flexibility is not impaired. It doesn't matter. Further, in practical use, the lower limit of the size of the spherical particles is 1 μm.

On the other hand, any manufacturing method may be used to form the display layer. The following methods can be given as typical methods. (1) Spherical particles composed of at least two different kinds of parts that can be rotated by applying energy from the outside are microencapsulated with a substance having fluidity under specific conditions, and a binder is used together. And fix it. (2) Direct coating of spherical particles composed of at least two different types of portions that can be rotated by applying energy from the outside, a substance having fluidity under specific conditions, and a binder, A droplet is produced from the difference in solubility. (3) A flexible film is processed, a partition material is attached to the film, or a large number of cells are produced by molding or stamping, and the cells are rotated by applying energy from the outside. Spherical particles composed of at least two types of portions having different colors and a substance having fluidity under specific conditions are contained and sealed.

The material having fluidity under the above-mentioned specific conditions is a liquid at room temperature, a solid at room temperature and melts at a certain temperature or more to be a liquid, for example, external energy at 50 ° C. In the case of applying and printing or erasing by applying, a substance that melts at 50 ° C. or lower and becomes a liquid at 50 ° C., or a substance whose viscosity increases at room temperature or a substance having thixotropic property, for example, fine particle silica A dispersion liquid or the like can be used. By appropriately selecting a substance having fluidity under specific conditions, it becomes possible to further improve the storage stability of the displayed content.

Further, as the substance which conceals the shadow of the spherical particles and has fluidity under specific conditions, only a solvent may be used as long as it can impart the concealing property, and the rotation of the spherical particles when energy is applied from the outside. A substance containing a pigment or a dye may be used as long as it does not inhibit the above. In this case, a dispersant or resin, an antifoaming agent, a coloring agent,
You may use together various additives, such as a charge control agent. Further, when performing a two-color display of white and black, it is preferable to use a dispersion containing an extender pigment such as titanium oxide, zinc oxide, or calcium carbonate, which has a strong hiding property, especially for imparting the hiding property. It is more preferable to use titanium oxide as a pigment.

The binder used when producing a display medium using microcapsules or droplets may be a resin that does not destroy the microcapsules or a resin that can produce droplets, regardless of whether it is aqueous or non-aqueous. Various resins can be used.

In addition to the above components, various additives may be used if necessary. For example, a cross-linking agent, an antistatic agent, a lubricant, a surfactant, a surface conditioner and the like can be used.

In order to conceal the shadow of the spherical particles, not only the concealing property of the substance having fluidity under the specific conditions is improved as described above, but also the concealing property is imparted to the wall portion itself of the microcapsule or the droplet. Alternatively, a flexible film may be used which is processed such that the partition part divided into the minimum area (cell) is colored to provide concealing property.

When the display layer is manufactured using microcapsules or droplets, the thickness of the display layer is preferably about the same as the size of the microcapsules or droplets up to about 5 times. .
When the film thickness of the display layer is smaller than the size of the microcapsule or droplet, the self-holding property is not sufficient and the strength of the film becomes weak, and when the film thickness becomes 5 times or more the size of the microcapsule or droplet, Unnecessarily increase the cost. When a flexible film is processed and produced, the groove depth of the film portion divided into the minimum regions is preferably about 5 times the average particle diameter of the spherical particles, and up to about 2 times. Is more preferable. Also,
When the film is processed and produced, the size of the minimum region is preferably about 2 to 10 times the average particle diameter of the spherical particles.

The display medium of the present invention may have a layered structure of two or more layers, and the above-mentioned display layer may be used as an upper layer or an intermediate layer. Even if such a laminated structure is adopted, there is no problem if the display contents can be rewritten and erased by applying energy from the outside. For example, the display layer is used as a lower layer, and a transparent protective layer, an antistatic layer, a coloring layer, a vapor deposition layer, an anti-curl layer, a slip adjusting layer, a decorative layer, an anti-blocking layer, an anti-reflection layer, etc. are provided on the upper layer. Good. On the contrary, the display layer may be an upper layer and an antistatic layer, an ITO transparent electrode layer, a coloring layer and the like may be provided as a lower layer.

The display layer is provided as, for example, the surface portion of the film which is the base material, or as a layer separate from the base material. At least one of the base materials is used particularly when a microcapsule or droplet structure is formed. On the surface of, it is easy to provide as a layer different from the substrate layer (in the structure of forming a cell that becomes the minimum area for containing spherical particles on the flexible film described above, It is convenient to form the display layer on, for example, the surface layer portion of the substrate film).

The base material may be a sheet or a cube.
It may be in any shape, and its surface shape may be any shape such as a flat surface or a curved surface. In particular, for applications such as the electronic paper described above, it is preferable that the sheet has flexibility, and any shape having flexibility such as paper, resin film, cloth, etc. can be used. Is. Various layers may be provided between the base material and the display layer as required. For example, in addition to the layers exemplified as the lower layer, an easy-adhesion layer and the like can be mentioned.

The display layer may be provided on one surface or both surfaces of the base material, or by providing the display layer on a transparent base material, the structure may be observed from both surfaces. Further, a display layer is provided on one side, and on the other side, an antistatic layer, a coloring layer, a vapor deposition layer, an anti-curl layer, a layer for adjusting slippage, a decorative layer, a layer that can be used for another purpose, and the like. You may provide as needed.

In manufacturing the display medium of the present invention, if microcapsules or droplets are used to form the minimum area for containing the spherical particles, the final product form can be manufactured by the coating method, so that the size of the display medium is increased. It is easy, cheap, and mass producible. As a typical example of the coating method, first, if necessary, a surface treatment or a treatment for forming a lower layer is performed on a substrate, and then a generally known coating machine, for example, a blade coater, an air knife coater, a reverse coater. A bar coater, a gravure coater, a die coater, etc., and a coating composition containing the display layer and other necessary components is applied and dried.
There is a method such as.

[0022]

EXAMPLES Examples of the present invention will be described below. However, the scope of the present invention is not limited to these.

[Embodiment 1] FIG. 1 shows a cross-sectional structure of a display medium according to an embodiment of the present invention. This display medium 1 is one of base materials 2 made of polyethylene terephthalate (PET) film. The display layer 3 is provided on the surface.
The display layer 3 is colored with a substance 4 having fluidity under a specific condition and a magnetic paint so that a part of the surface has a color different from other parts (black and white in the illustrated example). The spherical particles 5 and the binder 6 that holds the spherical particles 5 in the substance 4 in a state of enclosing the spherical particles 5 (in a microencapsulated state). Then, by applying a magnetic field from the outside to rotate the spherical particles 5 in the substance 4, the position of the colored portion on the surface of the spherical particles 5 is relatively changed, thereby easily rewriting and erasing the display content. It can be done.

The above spherical particles 5 were produced as follows. First, crosslinked acrylic fine particles (Toughtic AR65
0LX-W; Toyobo Co., Ltd., average particle diameter 130 μm),
It was evenly fixed on a pressure-sensitive adhesive sheet (Intelimer WS5030LD; manufactured by Nitta Co., Ltd.) whose adhesiveness changes with temperature. Then, while rotating the sheet, ferrite plating was performed while simultaneously spray-coating iron chloride and an oxidizing agent in an N ₂ atmosphere to fix Fe ₃ O ₄ (magnetite) on the surface of the spherical particles. And
After the spherical particles fixed to the sheet are magnetized, the spherical particles are peeled from the sheet and different colors (here, black of magnetite and white of crosslinked acrylic fine particles)
Spherical particles that were colored with and partially magnetized to the same magnetic pole were prepared.

Spherical particles colored in different colors as described above,
A dispersion liquid in which titanium oxide (Taipaque R-550; manufactured by Ishihara Sangyo Co., Ltd.) and isoparaffin (Isopar M; manufactured by Esso Co., Ltd.) were dispersed with a dispersant (Solspers S17000; manufactured by Avicia Co., Ltd.) was used as an inclusion, and its surroundings. Microcapsules containing poly (vinyl alcohol) and CMC (carboxymethyl cellulose) walls were adjusted by the complex coacervation method so that the average particle size of the microcapsules was 200 μm and one spherical particle was enclosed in each capsule. did. Microscopic observation of these revealed that 70% or more of all the microcapsules contained one spherical particle. Further observation of the microencapsulated particles with a magnifying glass dispersion (a substance that has fluidity under certain conditions and masks the shadow of spherical particles)
It was confirmed that the hiding property of No. 3 was good and that the shadow of the encapsulated spherical particles did not occur.

A coating liquid in which the prepared microcapsules and polyvinyl alcohol (binder) are dispersed is prepared, and the coating liquid is coated on a PET film so that the coating film thickness after drying is 250 μm. A flexible display medium was obtained.

[Example 2] A 0.5 mm thick PET film was dented to a depth of 0.3 mm in a honeycomb shape having a distance between opposite sides of 1 mm, and the spherical particles and the dispersion liquid of Example 1 were sealed therein. A display medium having flexibility was obtained.

When the display characteristics were examined by applying a magnetic field from the display surface side (upper surface side in FIG. 1) of the display media of Examples 1 and 2, it was easy to write and erase, and the writing speed was 30 msec. And the contrast ratio of the non-display portion (in linear scale) was about 6 to 7. Also, the retention of the display content after removing the magnetic field was good.

[0029]

As described above, according to the present invention, it is possible to obtain a display medium in which display contents can be easily rewritten and erased, the visibility is good, and the contrast ratio is high.

[Brief description of drawings]

FIG. 1 is a sectional view showing a sectional structure of a display medium according to an embodiment of the present invention.

[Explanation of symbols]

1 Display medium 2 base materials 3 display layers 4 Substances that have fluidity under specific conditions 5 spherical particles 6 Binder

Claims (3)

[Claims] 1. A display layer having a structure in which, on at least one surface of a base material, spherical particles composed of at least two kinds of portions having different colors and a substance having fluidity under specific conditions are contained. A rewritable and erasable display medium provided, wherein the fluid substance is composed of a substance that also has a function of hiding the shadow of spherical particles. . 2. A spherical particle composed of at least two kinds of parts having different colors is a non-magnetic organic spherical particle or inorganic spherical particle, and a magnetic substance is formed in the hemispherical part thereof. The rewritable and erasable display medium according to claim 1. 3. The rewritable and erasable display medium according to claim 1, which has flexibility.