JP2002350907A - Display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a display medium which is capable of easily rewriting and erasing display contents, is good in visible and is high in contrast. SOLUTION: This display medium 1 is formed by providing at least one surface of a base material 2 with a display layer 3 consisting of a structure confined with spherical particles 5 which are colored to different colors and can be rotated by impressing magnetic fields thereto and a dispersion medium 4 which is liquid under specific conditions. In such a case, the display medium preferably consists of the constitution obtained by incorporating plural pieces of the spherical particles 5 into the smallest regions confined with the spherical particles 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display medium which can easily rewrite and erase display contents and has good visibility.

[0002]

2. Description of the Related Art In recent years, with the rapid development of information networks, various types of information have been digitized and used in business and daily life. As a result, it was thought that the society would become electronic and information-less, but paper consumption itself did not decrease. This is not preferable from the viewpoint of global environmental protection. Against this background, the development of display media, so-called electronic paper, which has both the ease of rewriting display contents, which is the advantage of electronic documents, and the shape variability, which is the advantage of paper documents, has been actively performed. .

At present, as a candidate technology for electronic paper, a method of displaying an image by changing the optical characteristics of the liquid crystal by electrically controlling the arrangement of liquid crystal molecules, a method of confining fine particles in an insulating liquid, and performing electrophoresis by electrophoresis. A method of moving the particles to display according to the contrast between the color of the liquid and the color of the particles,
N. K. There is known a method of performing display by rotation of a minute ball by electric field driving proposed by Sheridon et al.

Further, there is also known a display element in which a substrate has a multi-cell structure and a spherical magnet painted in a different color is sealed in each cell.

[0005]

However, the above-described display techniques known in the related art have 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 content over time due to aggregation and precipitation of particles in a sealed liquid. According to the method of rotating micro balls by electric field driving, it is difficult to produce a flexible display device using a polymer film for a substrate, as described in JP-A-11-85066. Furthermore, in a display element in which a substrate has a multi-cell structure and in which spherical magnets painted in different colors are sealed in each cell, it is difficult to control magnetic interaction between adjacent spherical particles.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of the prior art, to facilitate the rewriting and erasing of display contents, to have good visibility, to have excellent display stability over time, and to provide a display with a high contrast ratio. To provide a medium.

[0007]

As a result of diligent studies to achieve the object of the present invention, for example, as schematically shown in FIGS.
A display layer 3 having a structure in which spherical particles 5 which are colored in different colors (for example, one is black and the other is white) and which can be rotated by applying a magnetic field and a dispersion medium 4 which is a liquid under specific conditions, is enclosed. By providing the display medium, it has been found that the display medium 1 is capable of rewriting and erasing display contents, has good visibility, and is flexible. Display medium 1 of the present invention
Can apply a magnetic field to rotate a spherical particle 5 at a desired position, the surface of which is colored in a different color, to perform display. Therefore, a light-receiving display device that displays image information, paper It can be applied to a paper-like display that can be moved like paper, can write an image, can copy an image, can read an image, and can erase an image. 1 and 2 are used to hold the spherical particles 5 in a state of being encapsulated in the dispersion medium 4 (in a microencapsulated state). Will be described later.

Further, the minimum area of a structure containing spherical particles which are colored in different colors and can be rotated by applying a magnetic field and a dispersion medium which is a liquid under specific conditions (FIG. 1)
In each example of FIG. 2, one microcapsule is shown, and in each example of FIGS. 3 and 4, the divided minimum section is shown). For example, as shown in FIGS. 2 and 4, two or more spherical particles 5 are contained. By doing so, it has been found that a display medium having a higher contrast ratio can be produced. The ratio of the number of the minimum regions containing two or more spherical particles may be 70% or more, preferably 80% or more, more preferably 90% or more, and most preferably the total number of the minimum regions. Is 100%. This is because the higher this ratio, the higher the contrast ratio.

As described above, when two or more spherical particles are contained in 70% or more of the minimum region, the gap in the minimum region is reduced by that amount, so that the dispersion medium which is a liquid under specific conditions is reduced. And the background color hardly affect the color displayed by the rotation of the spherical particles. In this way, only the display color of the spherical particles can be relatively emphasized, and the contrast ratio itself can be increased.

By using the above method, it is possible to manufacture the above-described display medium in which the display contents can be easily rewritten and erased, the visibility is good, the display contents are stable over time, and the contrast ratio is high. In addition, even when a microcapsule or a film-like microcell structure is adopted as the minimum area, the method itself of containing spherical particles that can be rotated by applying a magnetic field becomes simpler, and as a result, the production cost itself can be reduced. Become.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The spherical particles used in the present invention are not limited as long as they have magnetic properties, such as nonmagnetic organic spherical particles or inorganic spherical particles obtained by coating a hemispherical surface with a magnetic paint. Incidentally, as spherical particles, dodecahedron,
It does not exclude polyhedrons such as icosahedrons, and substantially spherical particles in a range that does not hinder the rotation of granular materials.

[0012] Nonmagnetic organic spherical particles or inorganic spherical particles obtained by coating a semi-spherical particle with a magnetic paint can magnetize only one surface colored in a different color when magnetized. Are preferred because it is relatively easy to make the orientations of them the same.

In the case where the semi-spherical particles of the non-magnetic organic resin particles are coated with a magnetic paint and magnetized, the direction of the magnetic poles of only one surface colored differently as described above is made uniform. This has the advantage that, even if two or more spherical particles are confined in the minimum area, the magnetic interaction between adjacent spherical particles is weakened, and under specific conditions for confinement. This is particularly preferable because it has the advantages that the specific gravity can be made about the same as that of the liquid dispersion medium, so that it can be easily rotated when a magnetic field is applied and the display content can be held stably.

The size of the spherical particles used can be appropriately selected according to the application. For example, if the image resolution requires 250 dpi in A4 size, the size of the spherical particles is preferably 100 μm or less, and if used for large display or signage, the particle size should be large enough to not impair flexibility. It doesn't matter. The practical lower limit of the size of the spherical particles is 1 μm.

On the other hand, in forming the above-mentioned display layer, any manufacturing method may be used, but a typical method is as follows. (1) Spherical particles colored in different colors that can be rotated by applying a magnetic field are microencapsulated together with a water-insoluble dispersion medium which is a liquid under specific conditions, and are fixed together with a binder. . (2) Spherical particles colored in different colors that can be rotated by applying a magnetic field, a dispersion medium that is a liquid under specific conditions, and a binder are directly applied, and droplets are formed based on differences in solubility. Is prepared. (3) A large number of cells can be formed by processing a flexible film, pasting a partition material to the film, or molding or stamping, and rotating the cells by applying a magnetic field to these cells. The spherical particles colored in different colors and a dispersion medium that is a liquid under specific conditions are sealed and sealed.

As the dispersion medium which is liquid under the above-mentioned specific conditions, a dispersion medium which is liquid at ordinary temperature, a solid which is solid at ordinary temperature, and which becomes a liquid by melting at a certain temperature (for example, by applying a magnetic field at 50 ° C.) When printing or erasing is performed by melting at 50 ° C. or lower and becoming a liquid at 50 ° C.), or a dispersion medium having a viscosity that increases at room temperature, or a dispersion medium comprising a thixotropic dispersion (eg, A dispersion medium to which fine silica is added is used. By appropriately selecting these dispersion media, it is possible to further improve the holding stability of display contents.

As a binder for producing microcapsules and droplets, a resin that does not destroy microcapsules or a resin that can produce droplets can be used.
Various resins can be used regardless of whether they are aqueous or non-aqueous.

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

When the display layer is formed using microcapsules or droplets, the thickness of the display layer is about the same as the size of the microcapsules or droplets.
A thickness up to about twice is preferred. If the film thickness is smaller than the size of the microcapsules or droplets, the self-holding property is not sufficient and the strength of the film is weakened. If the film size is 5 times or more, the cost is unnecessarily increased. Further, in the case of manufacturing by processing a flexible film, the depth of the groove of the film portion divided into the minimum area,
It is preferably up to about 5 times the average particle diameter of the spherical particles, more preferably up to about 2 times. The size of the minimum area is
It is preferably about 2 to 10 times the size of the spherical particles.

The display medium of the present invention may have a layer 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 employed, there is no problem as long as the display contents can be rewritten and erased by applying a magnetic field. For example, the display layer is a lower layer, a transparent protective layer on the upper layer, an antistatic layer, a coloring layer,
An evaporation layer, an anti-curl layer, a layer for controlling slippage, a decoration layer, an anti-blocking layer, an anti-reflection layer, and the like may be provided. Conversely, the display layer may be an upper layer, and an antistatic layer, an ITO transparent electrode layer, a colored layer, and the like may be provided as a lower layer.

The display layer may be provided on at least one surface of the base material as a layer different from the base material layer, particularly when a microcapsule or droplet structure is formed (for example, FIGS. 1 and 2). 2).

The substrate may be in any form, such as a sheet or a cube, and its surface may be in any shape such as a plane or a curved surface. In particular, in applications such as the above-described electronic paper, it is preferable that the sheet is a flexible sheet, and any sheet having a flexible shape such as paper, a resin film, or a cloth can be used. It is. Various layers may be provided between these base materials and the display layer as needed. For example, in addition to the layer exemplified as the lower layer, an easy adhesion layer and the like are included.

In the present invention, the display layer may be provided on one side or both sides of the base material, or the display layer may be provided on a transparent base material so that the display layer can be observed from either side. Good. 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 slip, a decoration layer, a layer that can be provided for another use, and the like. They may be provided as needed.

In the production of the display medium of the present invention, if microcapsules or droplets are used to form the minimum area for enclosing the spherical particles, it is possible to produce the final product form by a coating method. It is easy, inexpensive and can be mass-produced. 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 base material, and then a generally known coating machine such as a blade coater, an air knife coater, or a reverse coater is applied thereon. With a bar coater, a gravure coater, a die coater, etc., apply and dry a coating composition containing a display layer and other necessary components.
Such a method is mentioned.

[0025]

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

Embodiment 1 FIG. 1 schematically shows a cross-sectional structure of a display medium according to Embodiment 1 of the present invention. This display medium 1 is one side of a substrate 2 made of a polyethylene terephthalate film. Has a display layer 3 provided on the surface of.
The display layer 3 is colored with a dispersion medium 4 which is a liquid under specific conditions and a magnetic paint such that a part of the surface has a different color from the other part (in the illustrated example, the former is black and the latter is white). And a binder 6 that holds the spherical particles 5 in a state of being encapsulated in the dispersion medium 4 (in a state of microencapsulation). Then, by applying a magnetic field from the outside and rotating the spherical particles 5 in the dispersion medium 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 contents. You can do it.

The above-described display medium 1 was manufactured as follows. First, cross-linked acrylic fine particles (Tuftic AR65)
A metal iron magnetic powder (DM-96, manufactured by Dowa Mining Co., Ltd.) and a vinyl chloride copolymer (MR-110, manufactured by Nippon Zeon Co., Ltd.) were placed on a hemispherical surface of 0LX-W, Toyobo Co., Ltd., average particle diameter 130 μm. By applying a magnetic paint in which is dispersed, spherical particles colored in different colors were produced. Next, the microcapsules in which the spherical particles colored in different colors and dodecylbenzene are included, and the periphery of which is sealed with a wall of gelatin and gum arabic, the average particle diameter of the microcapsules is determined by a complex coacervation method. 200 μm
It was adjusted to be.

The prepared microcapsules and a coating liquid in which polyvinyl alcohol was dispersed were coated on a polyethylene terephthalate film (substrate) so that the coating film thickness after drying was 250 μm. The display medium 1 having the flexibility as shown was obtained.

Embodiment 2 FIG. 2 schematically shows a cross-sectional structure of a display medium according to Embodiment 2 of the present invention. This display medium 1 has one side of a substrate 2 made of a polyethylene terephthalate film. Has a display layer 3 provided on the surface of.
The display layer 3 is colored with a dispersion medium 4 which is a liquid under specific conditions and a magnetic paint such that a part of the surface has a different color from the other part (in the illustrated example, the former is black and the latter is white). And a binder 6 that holds the two or more spherical particles 5 in a state of being encapsulated in the dispersion medium 4 (in a state of microencapsulation). Then, by applying a magnetic field from the outside and rotating the spherical particles 5 in the dispersion medium 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 contents. You can do it.

The above-mentioned spherical particles 5 were produced as follows. That is, crosslinked acrylic fine particles (Tuftic AR
650LX-W, manufactured by Toyobo, average particle diameter 130 μm)
Metallic iron magnetic powder (DM-96, manufactured by Dowa Mining Co., Ltd.)
And a vinyl chloride copolymer (MR-110, manufactured by Nippon Zeon Co., Ltd.) were dispersed therein to produce spherical particles colored in different colors. Next, a microcapsule in which the spherical particles colored in different colors and isoparaffin (Isopor M, manufactured by Esso Corporation) are included and microcapsules surrounded by a wall of polyvinyl alcohol and CMC (carboxymethylcellulose) is used as a composite core. The average particle size of the microcapsules is 300μ by the cervation method.
m. By microscopic observation of these, it was confirmed that a plurality of spherical particles colored in different colors were enclosed in the capsule. In addition, capsule 1
When the number of capsules in which a plurality of spherical particles colored in different colors were enclosed was examined for 00 pieces, the number was 70 or more.

A coating liquid in which the prepared microcapsules and polyvinyl alcohol (binder) are dispersed is prepared, and this is coated with a polyethylene terephthalate film (substrate) so that the coating thickness after drying is 350 μm. Coating was performed thereon to obtain a flexible display medium 1 as shown in FIG.

Example 3 A 0.5 mm thick polyethylene terephthalate film (substrate) was honeycomb-shaped with a distance between opposite sides of 0.5 mm and subjected to a dent process of 0.3 mm in depth, and isoparaffin (Isopar M, Esso Co., Ltd.) A liquid having fine silica (Aerosil A200, manufactured by Nippon Aerosil Co., Ltd.) dispersed therein and the spherical particles prepared in Example 2 are encapsulated into a flexible display medium 1 as shown in FIG. I got In FIG. 3 (similarly in FIG. 4), a portion indicated by reference numeral 7 is a transparent portion provided after the above-described sealing in order to close the opening side of the recess (cell) 8 in which the spherical particles 5 and the like are sealed. It is a protective layer. In the illustrated example, a polyethylene terephthalate film (thickness: 10 μm) is used for the protective layer.

Example 4 The same procedure as in Example 3 was carried out except that the distance between the opposite sides of the honeycomb shape of the polyethylene terephthalate film was 1.0 mm and the number of spherical particles to be enclosed in the minimum area was two or more. Thus, a display medium 1 having flexibility as shown in FIG.

The display characteristics of each of the display media of Examples 1 to 4 were examined by applying a magnetic field from the display surface side (the upper surface side in FIGS. 1 to 4). And the writing speed is 30msec
Met. The contrast ratio between the display part and the non-display part (linear scale) was 5 to 6 for the display media of Examples 1 and 3, and was 6 to 7 for the display media of Examples 2 and 4. Further, in all the display media, the retention of the display contents after removing the magnetic field was good.

[0035]

As described above, according to the present invention, it is possible to provide a display medium which is easy to rewrite and erase display contents, has good visibility, is excellent in stability of display contents over time, and has a high contrast ratio. can get.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a cross-sectional structure of a display medium according to a first embodiment.

FIG. 2 is a cross-sectional view schematically illustrating a cross-sectional structure of a display medium of Example 2.

FIG. 3 is a cross-sectional view schematically illustrating a cross-sectional structure of a display medium according to a third embodiment.

FIG. 4 is a cross-sectional view schematically illustrating a cross-sectional structure of a display medium according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Display medium 2 Base material 3 Display layer 4 Dispersion medium 5 Spherical particle 6 Binder 7 Protective layer 8 Depression

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Kono 1-1-88 Ushitora, Ibaraki-shi, Osaka Inside Hitachi Maxell Co., Ltd. (72) Inventor Shin Shinya 2-28-4 Tomigaya, Shibuya-ku, Tokyo School corporation Tokai University

Claims (4)

[Claims] 1. A display layer comprising a structure in which spherical particles colored in different colors and capable of being rotated by applying a magnetic field and a dispersion medium which is a liquid under specific conditions are sealed on at least one surface of a substrate. And a flexible display medium capable of rewriting and erasing display contents. 2. The minimum area of a structure containing spherical particles colored in different colors and capable of being rotated by applying a magnetic field and a dispersion medium which is a liquid under a specific condition is a microcapsule, a droplet or a multicell. The display medium according to claim 1, wherein the display medium is at least one of the smallest divided sections of the structure. 3. The display medium according to claim 1, wherein the minimum area contains two or more spherical particles. 4. The display medium according to claim 1, wherein energy for maintaining display is not required.