JP2003276332A - Reversible recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reversible recording medium which can realize retouching/erasing with a writing implement and, even when the retouched medium is put on top of another medium, does not have a fear of the retouched material on the surface of the recording medium being transferred onto the backside of the another medium. <P>SOLUTION: In this repeatedly rewritable and displayable reversible recording medium, the contact angle of the backside of the reversible recording medium with distilled water is not less than 90 degrees, and the dynamic swept-back contact angle of the surface of the medium to distilled water is in the range of 75 to 100 degrees. Lubricants and fillers such as silicone-modified polymers are incorporated in the surface layer of the medium and/or the backside layer to control surface properties such as contact angle and carriability. <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 reversible recording medium capable of forming and erasing an image.

[0002]

2. Description of the Related Art With the development and popularization of computer and network technology, it becomes possible to process a large amount of information and process at high speed, and the amount of paper used in offices continues to increase. Although most information is now digitized and processed electronically, it is often the case that viewing it on a display is not enough for people to think about it. It is printed on paper using a printer.

Paper has the advantages that it is easy to see and that it does not tire the eyes, that it can be viewed anywhere without the need for a power source, and that it is light and easy to handle. Moreover, many pieces of necessary information can be viewed side by side. Because it has a comprehensive list, it is an essential environment for thinking. However, on the other hand, the large consumption of paper causes environmental problems such as depletion of forest resources and social problems such as the large amount of paper waste. Recycling is in progress to collect and recycle used paper, but even recycled paper requires the same amount of electricity and water as the paper made from new pulp, and this alone cannot solve the problem. .

On the other hand, a reversible recording medium has been developed which can be repeatedly used by rewriting an image many times. First, a recording medium having a recording layer in which particles of a low molecular weight compound such as fatty acid are dispersed in a polymer film and reversibly in two states of transparent and cloudy was developed. However, this uses changes in the light scattering property, and because it prints white characters on the colored background, it cannot be handled as an ordinary document, and as a result, it is put to practical use as an information display unit such as a magnetic card. It was only done.

On the other hand, according to the patent publication, a recording medium capable of reversibly developing and erasing color has been proposed. For example, a medium using gallic acid and phloroglucinol in combination as a color developer (Japanese Patent Laid-Open Publication No. 1994-242242) JP-A-60-193691), using compounds such as phenolphthalein and thymolphthalein as color developers (JP-A-61-2376).
No. 84), a recording layer containing a homogeneous compatible solution of a color former, a developer and a carboxylic acid ester (JP-A-62-13).
No. 8556, JP-A-62-138568 and JP-A-62-140881), those using an ascorbic acid derivative as the developer (JP-A-63-173684), and the developer as bis ( Hydroxyphenyl) acetic acid or a salt of gallic acid with a higher aliphatic amine (JP-A-2-188293, JP-A-2-188294)
No. gazette) is proposed.

Furthermore, the present inventors have previously proposed that Japanese Patent Laid-Open No. 5-12
In JP 4360, an organic phosphoric acid compound having a long-chain aliphatic hydrocarbon group, an aliphatic carboxylic acid compound or a phenol compound is used as a color developer, and by combining this with a leuco dye which is a color developing agent, color development is achieved. Decoloring can be easily performed under heating / cooling conditions, and moreover, not only can the colored state and the decolored state be stably maintained at room temperature, but also reversible that can repeat the coloring and decoloring. We proposed a thermosensitive coloring composition and a reversible thermosensitive recording medium using the composition for a recording layer. Further, thereafter, use of a phenol compound having a long-chain aliphatic hydrocarbon group having a specific structure has been proposed (Japanese Patent Laid-Open Publication No. H6-6120).
-210954).

These reversible recording media can be used for temporary output of conference materials and mail documents in the office. In such applications, it is indispensable to be able to add content to add and confirm it. Further, the reversible recording medium needs to be repeatedly used, but when the writing is performed on the surface of the recording medium by using an ordinary writing tool, there is a problem that it becomes difficult to erase the added portion and the medium cannot be reused. In addition, when using a whiteboard marker, etc., it is easy to erase the added part, but the fixability of the added part is poor, and there is a problem that it can be easily removed when it comes into contact with other documents or clothes. Was.

As an erasable writing means for a reversible recording medium, a heat erasable pen using a heat erasable ink and the like have been proposed in Japanese Patent Laid-Open No. 7-113055. Since the ink composition remains on the surface of the recording medium even after the color is erased, there is a problem that a printing failure occurs during repeated printing with a thermal head.

Further, Japanese Patent Laid-Open Nos. 10-100536 and 5-286258 propose a display device in which a reversible thermosensitive recording layer is provided on a transparent support and additionally recorded on the opposite surface. The display medium of (1) is limited to one in which the support has transparency, and since the printed portion is viewed through the support from the opposite side, there is a problem of poor visibility.

In a reversible thermosensitive recording medium for recording and erasing by heat, a writing means such as a hot pen may be considered, but in the writing means using a hot pen, the color tone of the writing portion is limited to the same color tone as that of the medium. However, there is a problem in safety since it is necessary to generate heat at a high temperature.

It is also conceivable to use a writing composition which can be wiped and removed by a non-woven fabric or the like (hereinafter referred to as "additional material") to add or erase to these media. When used, there is a problem that when the mediums are overlaid, the added matter is easily transferred from the surface of the medium to the back surface of another medium.

Further, the present inventors have previously found that it is possible to perform writing / erasing by setting the receding contact angle of the surface of the recording medium within a specific range. However, it was added to such a reversible recording medium. When a plurality of sheets are stacked on top of each other, the added matter is transferred to the back surface of the recording medium and the recording medium is contaminated. However, up to now, almost no studies have been made on the back surface of these reversible recording media.

In addition, the reversible recording medium as described above is currently mainly used in the form of a card for a point card or the like.
When erased, it was difficult to remove the added matter, although it had the ability to add and fix.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is that it is possible to write with a writing instrument, and it has such a fixing property that the written matter cannot be easily removed even if the touched portion comes into contact with another document or the like. At the same time, the added matter can be easily removed without remaining on the recording medium by an eraser, etc., and the added matter on the surface does not transfer to the back side of another medium even when the written mediums are stacked. It is to provide a reversible recording medium.

[0015]

Means for Solving the Problems The present inventors have made various studies on the surface characteristics of a recording medium and the addition property, fixing property and removability, and the contact angle of the back surface of the recording medium has a great influence on these properties. It has been found that this problem can be solved when the contact angle with respect to distilled water is 90 degrees or more and the dynamic receding contact angle with respect to the distilled water on the medium surface is in the range of 75 degrees or more and 100 degrees or less. (Note that the front surface of the recording medium in the present invention is a surface on which reversible recording is performed, and the back surface of the recording medium is a surface on which reversible recording is performed or a surface opposite to a surface on which writing is performed.)

The present inventors have completed the present invention based on the above knowledge, and the present invention has a configuration as described below.

(1) In a reversible recording medium that can be repeatedly rewritten and displayed, the contact angle of distilled water on the back surface of the reversible recording medium is 90 degrees or more, and the dynamic receding contact angle of distilled water on the surface of the reversible recording medium. Is in the range of not less than 75 degrees and not more than 100 degrees, and a reversible recording medium. (2) The reversible recording medium according to (1) above, which has a laminated structure including at least a support layer, a front surface layer, and a back surface layer. (3) The reversible recording medium according to (2), wherein the surface layer is either a recording layer or a protective layer provided on the recording layer.

(4) The material constituting the surface of the reversible recording medium and / or the material constituting the back surface of the reversible recording medium contains a lubricant, in any one of the above (1) to (3). Reversible recording medium. (5) The reversible recording medium according to the above (4), wherein the lubricant is a silicone-modified polymer. (6) The reversible recording medium according to any one of claims 1 to 5, wherein the material forming the front surface of the reversible recording medium and / or the material forming the back surface of the reversible recording medium contains filler particles. .

(7) The average particle diameter of the filler particles in the material constituting the surface of the reversible recording medium is 0.2 to 2.0 μm.
The reversible recording medium according to the above (6), characterized in that (8) The reversible recording medium according to the above (6), wherein the filler particles in the material constituting the back surface of the reversible recording medium have an average particle size in the range of 0.5 to 5.0 μm. The reversible recording medium according to any one of (6) to (8), wherein the filler particles are coated with calcium.

(10) The reversible recording medium has a reversible recording section and an information storage section, and the above (1) to (1)
The reversible recording medium according to any one of (9). (11) The reversible recording material as described in (10) above, wherein the information storage section is a magnetic recording layer or an IC. (12) The reversible recording medium according to any one of (1) to (11) above, which has a printed portion.

(13) Reversibility according to any one of the above (1) to (12), wherein the reversible recording layer reversibly forms a colored image by heating and displays the image. recoding media. (14) The erasing device using the reversible thermosensitive recording medium according to the above (13), which erases color by heating to a temperature lower than the color development start temperature. (15) The erasing device as described in (14) above, which has a heater selected from a thermal head, a ceramic heater, a planar heater and a heat roller as a heating means.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the reversible recording medium of the present invention will be described in detail. Can be suppressed from being transferred to the back surface of another medium. If the contact angle on the back surface of the medium is less than 90 degrees, the ink is likely to adhere to the medium, and when the mediums are stacked, the writing object on the front surface is transferred.

In the present invention, the back surface of the reversible recording medium is
It suffices that the value of the contact angle be 90 degrees or more, and the material forming the back surface is not particularly limited. The back surface of the support may directly form the back surface of the recording medium, or one or more back layers may be formed on the support. In the case of providing, the surface of the outermost layer may constitute the back surface of the recording medium. That is, the contact angle may be within the above range depending on the properties of the material used for the back surface layer, the composition ratio, the shape of the surface, and the like.

Further, the surface layer of the recording medium can be rewritten with a marker and must be easily wiped off at the time of erasing, but the dynamic receding contact angle has a great influence on these characteristics. And the dynamic receding contact angle of the medium surface is 7
When the angle is 5 degrees or more and 100 degrees or less, the reversible recording medium of the present invention exhibits excellent rewriting characteristics.

When the dynamic receding contact angle of the surface of the recording medium is less than 75 degrees, the marker is excellent in the writing property and exhibits good fixing property, but it is difficult to remove and the writing object remains on the surface of the recording medium. If the surface exceeds the limit, the repellency will be so large that it will not be possible to retouch.

In the present invention, the value of the dynamic receding contact angle of the surface of the recording medium may be in the range of 75 degrees to 100 degrees, and the material used for the surface layer is not limited. That is, the dynamic receding contact angle may be within the above range depending on the properties of the material used for the surface layer, the composition ratio, the shape of the surface, and the like.

Further, in the present invention, the reversible recording medium surface may have a constitution in which only the recording layer is provided on the support,
If necessary, a protective layer may be formed, or an intermediate layer may be formed between the recording layer and the protective layer, and an under layer may be formed between the recording layer and the support. In the case of only the recording layer, the characteristics of the surface of the recording layer, or in the case of laminating a plurality of layers, the outermost layer thereof may be within the range of the dynamic receding contact angle.

From the viewpoint of repeated durability, light resistance and transportability, it is preferable to provide a protective layer on the surface of the recording layer and a back layer on the back side of the recording medium. Hereinafter, the present invention will be described by taking a recording medium provided with a protective layer and a back layer as an example. However, when the recording layer forms the outermost layer on the surface of the recording medium, the recording layer is a protective layer described below. If the back surface of the support forms the back surface of the recording medium, the back surface of the support may have the same characteristics as the back layer described below.

The contact angle and the dynamic receding contact angle are shown in the table /
It is influenced by the hydrophilic / hydrophobic property of the protective layer formed as the back surface layer and the shape of the front / back surface. Hydrophilicity /
The hydrophobicity may be a characteristic of the resin itself or a characteristic of a lubricant such as silicone oil or wax as an additive.

At this time, particularly on the surface of the recording medium, when the additive used has a low molecular weight, it is repeatedly used to precipitate from the surface or diffuse into the inside of the recording medium. Surface properties can change. According to one aspect of the present invention, the use of the silicone-modified polymer reduces the change when it is repeated, resulting in excellent durability.

Examples of the silicone-modified polymer include silicone graft polymers, silicone block polymers,
Silicone-modified acrylic polymers and silicone-modified polyvinyl alcohols are preferred, with silicone graft polymers being especially preferred. As the silicone graft polymer, silicone graft acrylic polymer, silicone graft modified polyvinyl alcohol, etc. are preferably used. Of these, polymers that can be crosslinked by heat, ultraviolet rays, electron beams, etc. are particularly preferably used.

These silicone-modified polymers can be used alone or in combination to form layers. As the polymer to be mixed and used, in addition to conventionally known thermoplastic resins such as vinyl chloride-vinyl acetate resin, polystyrene and polyester, thermosetting resin, ultraviolet curable resin, electron beam curable resin and the like from the viewpoint of repeated durability. A curable resin is preferably used.

Regarding the back surface of the medium as well, it is desired that the characteristics do not change when repeatedly used, and the above materials are preferably used similarly to the front surface, but the material constitutions of the front surface and the back surface may not be the same.

The shape of the front / back surface can be controlled by using a filler in the front / back surface layer, and the addition of this filler makes the back surface excellent in transportability and the surface excellent in writability. Will be things. As the filler to be used, conventionally known organic / inorganic fillers may be used alone or in combination. Preferably as the organic filler, for example, a silicone-based filler, a fluorine-based filler,
Examples thereof include acrylic fillers, polyamide fillers, epoxy resin fillers, thermosetting resin hollow spheres, polyethylene wax, shellac, wood powder, cork powder and the like.

As the inorganic filler, silica, alumina,
Zinc oxide, indium oxide, zirconia oxide, tin oxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calcium oxide, barium oxide, bismuth oxide,
Metal oxides such as nickel oxide, magnesium oxide, chromium oxide, manganese oxide, tantalum oxide, niobium oxide, thorium oxide, hafnium oxide, molybdenum oxide, iron ferrite, nickel ferrite, cobalt ferrite, barium titanate, potassium titanate; Carbonates such as calcium carbonate and magnesium carbonate; silicates such as anhydrous silicic acid, hydrous silicic acid, hydrous aluminum silicate and hydrous calcium silicate; hydroxides such as aluminum hydroxide and iron hydroxide; zinc sulfide , Metal sulfides or sulfate compounds such as barium sulfate; metal carbides such as titanium carbide, silicon carbide, molybdenum carbide, tungsten carbide, tantalum carbide; aluminum nitride, silicon nitride, boron nitride, Zirconium nitride, vanadium nitride , Titanium nitride, niobium nitride,
Metal nitrides such as gallium nitride; talc, kaolin,
Examples of the clay include an inorganic filler, which is preferably used from the viewpoint of durability. Particularly, on the surface of the recording medium, an inorganic filler coated or complexed with calcium is preferably used because of its influence on the coloring / decoloring characteristics.

Usually, the filler is dispersed and used, and the shape of the surface changes depending on the particle diameter. If the particle size is small, the effect of adding a filler does not appear, and if the particle size is coarse, the writing material tends to be unable to be removed because it enters the uneven portion when removing the writing material.
The filler particle size on the medium surface is preferably 0.2 to 2 μm, and particularly preferably 0.4 to 1 μm. On the back surface of the medium, a filler having a particle diameter of 0.5 to 5.0 μm is preferably used.

The surface of the reversible recording medium is required to be able to be rewritten in order to additionally record or confirm / correct the recorded contents, but the rewritten recording medium must be able to be erased in order to repeatedly use the recording medium. Furthermore, in order to eliminate the influence on writing and erasing on the recording medium itself, the additional matter should not remain on the surface of the recording medium after the additional matter is erased. Also,
Additives must not easily transfer to the backside of other media when the media are stacked. There has never been a reversible recording medium satisfying such requirements. The reversible recording medium of the present invention described above enables addition and erasure by a writing instrument on the reversible recording medium.

If the contact angle of the back surface is increased by adding a lubricant or the like in order to prevent the transfer of the added matter to the back surface, the transportability of the medium in the printing / erasing apparatus may be deteriorated. Good transportability can be obtained by adjusting the particle size of the above to a suitable value to obtain a medium having an appropriate friction coefficient.

The reversible recording medium of the present invention is provided with both a reversible recording section and an information recording section so that the information stored in the information storage section is displayed on the reversible recording section, so that a special device can be provided. You can check the information without it, which improves convenience. The storage unit used at that time is a magnetic recording layer or I
The C recording section and the like are preferably used.

Further, these can be processed into a shape according to the application, and when processed into a general document size such as A4 size, by using the printing / erasing device, not to mention test printing, It can be widely used for temporary output such as circulation documents and conference materials.

Further, the reversible recording medium of the present invention can be subjected to irreversible printing processing of images, characters, etc. on the front surface or the back surface thereof depending on the purpose, and the non-printed portion is recorded for printing / erasing. It can be used repeatedly as a part.

The reversible recording layer used in the present invention comprises heat, light,
It suffices if the image can be reversibly formed using energy such as electricity and magnetism, but especially if it is a method of recording and erasing by heat, the printing and erasing device can be simplified, downsizing and cost reduction. Is possible.

The reversible recording layer used in the present invention comprises heat, light,
Any layer can be used as long as it can reversibly form a visible image by using energy such as electricity and magnetism, and rewriting thereof, that is, erasing and printing of an image uses only one kind of energy, but two or more kinds The energy may be used in combination. Typical reversible recording layers and their materials are shown below, but the present invention is not limited thereto.

For the reversible recording layer that uses heat energy to develop and decolor, a reversible color development reaction of a leuco dye can be used. As the leuco dye, one or more compounds used in this type of reversible thermosensitive recording medium can be used. Examples of such a compound include known dye precursors such as phthalide compounds, azaphthalide compounds and fluorane compounds. is there.

Typical examples of the color developer used in the recording layer are, for example, JP-A-5-124360, JP-A-6-210954, and JP-A-10-9.
The color developer described in Japanese Patent No. 5175 can be used.

The color developer used here has a structure having a color-developing ability to develop a leuco dye in the molecule, such as a phenolic hydroxyl group, a carboxylic acid group or a phosphoric acid group, and has an intermolecular cohesive force. It is a compound having one or more structures for controlling, for example, structures in which long-chain hydrocarbon groups are linked. A divalent or higher valent linking group containing a hetero atom may be interposed in the linking moiety, and the same linking group and / or
Alternatively, it may contain an aromatic group. Specific examples of such a reversible developer are described in, for example, JP-A 9-290563 and JP-A 11-188969.

The reversible recording layer using these leuco dye and developer develops and decolors by the process shown in FIG.
When the initial decolored state (A) is heated, the leuco dye and the color developer are melt-mixed at the temperature T1 or higher to develop a color (B), and when this state is rapidly cooled, the colored state (c) is fixed. When the color-developed state (C) is heated, the color is erased at a temperature T2 lower than the color-developing temperature. In this way, the recording layer can be erased by controlling the heating temperature and the cooling rate after heating.

When a reversible recording medium containing the above-mentioned leuco dye and color developer in the recording layer is used, the erasing device is a device for erasing by heating to a temperature lower than the erasing temperature. It is preferable to use. That is, in order to erase the color-developed portion of the reversible recording layer, it is sufficient to heat it to a color-developing temperature or higher and then gradually cool it, or to heat it to a color-erasing temperature lower than the color-developing temperature, but the latter requires a shorter time. This is because stable erasing can be performed. As a heating means in this case, a heater selected from a thermal head, a ceramic heater, a planar heater, and a heat roller can be used.

Printing with this recording layer provides high contrast and excellent image quality. Further, it is excellent in storage stability and durability against repeated printing and erasing, and is particularly suitable as the rewritable recording medium for documents of the present invention. Printing on a reversible recording medium using this recording layer can be performed by a thermal head as in the case of ordinary thermal recording, and erasing can be performed by a temperature-controlled heat roller, a heating element such as a ceramic heater, or a thermal head. Can be used with a small and simple rewrite device.

In the reversible recording medium of the present invention, the leuco dye, the color developing agent and the color development / erasing control agent form the recording layer together with the resin. The resin used at this time is only required to be able to bind these materials to the support, and conventionally known resins are widely used. Among them, a resin curable by heat, ultraviolet rays, an electron beam, or the like is preferably used in order to improve durability during repetition, and a thermosetting resin using an isocyanate compound or the like as a crosslinking agent is preferably used.

The support of the reversible recording medium of the present invention may be any one capable of holding the recording layer, and preferably paper, synthetic paper, PET film or the like is used, but it is light, easy to read and has a long life. Paper is preferably used because of its ease. In addition, these supports on which the recording layer is formed are used for other papers,
You may stick and use it on a sheet etc.

Examples of the recording layer for rewriting by utilizing heat include the following recording layers in addition to those described above. For example, mention may be made of a recording layer utilizing the reversible change of the light scattering property of a composite film in which crystal particles of a low molecular compound are dispersed in a polymer, and a recording layer utilizing the reversible change of the light scattering property of a polymer liquid crystal layer. You can

The former usually makes the recording layer cloudy by printing above the melting point of the low molecular weight compound and prints, and when heated to a temperature lower than this it returns to transparent and erases. In the latter case, the recording layer is made transparent by printing by heating and quenching to an isotropic point or more, and then it is returned to white turbidity by erasing by making it into a white turbid state by heating and slow cooling. In addition to this, there is a recording layer in which a liquid crystal material or a polymer material is used alone or in combination, and recording and erasing are performed depending on the difference in heating temperature or cooling rate after heating.

A preferable recording layer of the reversible recording medium of the present invention is a memory type recording layer which can form an image electrically and which does not require electric power for holding an image. Above all, a recording layer that can be printed / erased by an electric field is particularly preferable because it can reduce power consumption. Some of such recording layers use a liquid crystal material.

For example, the ferroelectric polymer liquid crystal layer has a stable memory property and is preferable as a rewritable recording layer. Also, a smectic liquid crystal material having a memory property can be used. These liquid crystal materials can form an image by utilizing the change in the polarization characteristics of the recording layer, but a colored image can also be reversibly formed by containing a dichroic dye.

These recording layers generally form an image reversibly with an electric field, but a method that enables rewriting of an image not only by the electric field but also by combination with other energy such as heat or the like. , There is a method of improving the image holding property.

Further, an electrophoretic material can be used for the recording layer capable of electrically rewriting. In this method, for example, white fine particles such as titanium oxide are dispersed in a colored solvent, and the particles are moved by an electric field to reversibly form an image. In particular, a recording layer in which this electrophoretic system is enclosed in microcapsules and held on a support such as a polymer film is suitable as a rewritable rewritable recording medium for documents.

Further, particles which are spherical particles and whose hemisphere is colored and whose hemisphere is white are enclosed in a microcapsule together with a medium, and the microcapsule is held on a support and the sphere is rotated by an electric field to reversibly produce an image. The recording layer to be formed is also a preferable recording layer of the present invention.

In the image formation by the electric field of such a recording layer, an electrostatic stylus or a head in which the stylus is arranged in a line is used for writing, an ion flow is used for writing, or an electrophotographic photoreceptor is used to form an electrostatic latent image. A known writing method such as a method of transferring onto a recording medium can be used.

As the writing tool used for the reversible recording medium of the present invention, a writing tool such as a marker pen using an alcohol solvent ink is preferably used.

[0061]

The present invention will be described in more detail with reference to the following examples. In the examples, "parts" and "%" are based on weight.

[0062]

[Example 1] <Preparation of recording layer>   1) 2-anilino-3-methyl-6 dibutylaminofluorane 2 parts   2) 8 parts of color developer with the following structure

[0063]

[Chemical 1]

[0064]   3) Color development / decoloration control agent having the following structure 3 parts

[0065]

[Chemical 2]

[0066]   4) 15 parts of acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd.)   5) Tetrahydrofuran (THF) solution 130 parts

The above composition was pulverized and dispersed using a ball mill to an average particle size of about 1 μm. 20 parts of Coronate HL (75% ethyl acetate solution of adduct-type hexamethylene diisocyanate) manufactured by Nippon Polyurethane Industry Co., Ltd. was added to the obtained dispersion liquid and well stirred to prepare a recording layer coating liquid. The coating solution for the recording layer having the above composition was coated on Shiraioi coated paper manufactured by Daishowa Paper Co., Ltd. using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to have a film thickness of about 9.0 μm. A recording layer was provided.

[0068]   <Preparation of protective layer> 1) 10 parts of acrylic polyol resin (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 2) Silica (P-832 manufactured by Mizusawa Chemical Co., Ltd.) 4 parts   3) Silicone graft polymer (FS700 made by NOF CORPORATION) 1.2 parts   4) MEK 50 parts

The above composition was pulverized and dispersed by a ball mill to an average particle size of about 1.0 μm, and 4 parts of Coronate HX manufactured by Nippon Polyurethane Co., Ltd. was added to the obtained dispersion and well stirred to prepare a protective layer coating solution. did. The coating solution for the protective layer was applied onto the recording layer using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to give a film thickness of about 3.0.
A reversible recording medium of the present invention was produced by providing a recording layer of μm.

[0070] <Preparation of back layer>   1) Acrylic polyol resin (Mitsubishi Rayon LR327) 6 parts   2) 1 part of silica (P-526 manufactured by Mizusawa Chemical Co., Ltd.)   3) 1.2 parts of silicone graft polymer (FS700 made by NOF CORPORATION)   4) MEK 33 parts

The above composition was pulverized and dispersed using a ball mill to an average particle size of about 0.65 μm. To the obtained dispersion liquid, 4 parts of Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd. was added and well stirred to prepare a back layer coating liquid. The back layer coating solution is applied to the back surface of the support using a wire bar.
After drying at 0 ° C. for 2 minutes, it was heated at 60 ° C. for 24 hours to provide a back layer having a film thickness of about 3.0 μm, and the reversible recording medium of the present invention was produced.

[0072]

Example 2 A reversible recording medium was produced in the same manner as in Example 1 except that the back layer coating liquid in Example 1 was changed as follows. 1) Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd.) 6 parts 2) Silica (P-526 manufactured by Mizusawa Chemical Co., Ltd.) 1 part 3) Silicone graft polymer (X-22-161AS manufactured by Shin-Etsu Chemical Co., Ltd.) 1.2 parts 4 ) MEK 35 parts Using a ball mill, the average particle size of about 4.0 μm
It was pulverized and dispersed to m. To the obtained dispersion liquid, 4 parts of Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd. was added and well stirred to prepare a back layer coating liquid.

[0073]

Example 3 A reversible recording medium was prepared in the same manner as in Example 1 except that the back layer coating liquid in Example 1 was changed as follows. 1) Acrylic polyol resin (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 6 parts 2) Silica (P-526 manufactured by Mizusawa Chemical Co., Ltd.) 1 part 3) Silicone graft polymer (GS1015 manufactured by Toagosei Co., Ltd.) 1.5 parts 4) MEK 33 parts Above The composition was treated with a ball mill to give an average particle size of about 2.7μ.
It was pulverized and dispersed to m. To the obtained dispersion liquid, 4 parts of Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd. was added and well stirred to prepare a back layer coating liquid.

[0074]

Example 4 A reversible recording medium was prepared in the same manner as in Example 3 except that the liquid for the protective layer in Example 3 was changed as follows. 1) 40% solution of UV absorbing polymer (Nippon Shokubai Co., UV-A11) 25 parts 2) Silica (P-832 manufactured by Mizusawa Chemical Co., Ltd.) 4 parts 3) Silicone graft polymer (GS1015 manufactured by Toagosei Co., Ltd.) 1 part 4 ) MEK 30 parts Using a ball mill, the average particle size of about 1.0
It was pulverized and dispersed to m. To the obtained dispersion liquid, 4 parts of Coronate HX manufactured by Nippon Polyurethane Co., Ltd. was added and well stirred to prepare a protective layer coating liquid.

[0075]

Comparative Example 1 A reversible recording medium was prepared in the same manner as in Example 1 except that the back layer coating solution in Example 1 was changed as follows. 1) Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd.) 7 parts 2) Silica (P-526 manufactured by Mizusawa Chemical Co., Ltd.) 1 part 3) MEK 30 parts An average particle diameter of about 3.0 μm of the above composition using a ball mill
It was pulverized and dispersed to m. To the obtained dispersion liquid, 4 parts of Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd. was added and well stirred to prepare a back layer coating liquid.

[0076]

Comparative Example 2 A reversible thermosensitive recording medium was prepared in the same manner as in Example 4, except that the back layer was not coated.

[0077]

Comparative Example 3 A reversible recording medium was produced in the same manner as in Example 1 except that the coating solution for protective layer in Example 1 was changed as follows. 1) Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Talc (# 12 manufactured by Muramatsu Sangyo Co., Ltd.) 4 parts 3) MEK 50 parts An average particle size of about 1.0 μm of the above composition using a ball mill
Then, 4 parts of Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd. was added to the obtained dispersion liquid and well stirred to prepare a protective layer coating liquid.

[0078]

Comparative Example 4 A reversible recording medium was produced in the same manner as in Example 1 except that the coating solution for protective layer in Example 1 was changed as follows. 1) Acrylic polyol resin (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Silica (P-832 manufactured by Mizusawa Chemical Co., Ltd.) 1.5 parts 3) Silicone graft polymer (FS700, manufactured by NOF CORPORATION) 2.4 parts 4) MEK 50 Parts The above composition was used to form an average particle size of about 1.0 μ using a ball mill.
Then, 4 parts of Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd. was added to the obtained dispersion liquid and well stirred to prepare a protective layer coating liquid.

[0079]

[Comparative Example 5] A point card using a reversible thermosensitive recording medium was obtained from the market and designated as Comparative Example 5.

The recording medium manufactured as described above was subjected to a thermal printing device manufactured by Okura Electric Co., Ltd., voltage 13.3 V, pulse width 1.
When printed for 2 msec, all developed high density color. The color development image obtained is measured by a thermal tilt tester manufactured by Toyo Seiki Co., Ltd.
When the color was erased under the condition of 120 ° C for 1 second, almost all the samples could be erased.

Physical properties and evaluation tests were conducted on the recording media produced in Examples 1 to 4 and Comparative Examples 1 to 5. First, the test method will be described.

<Test 1> (Measurement of Contact Angle on Backside of Recording Medium) Distilled water was added to the surface of the thermosensitive coloring layer on the paper coated with the thermosensitive coloring layer using an automatic contact angle meter (Kyowa Interface Science Co., Ltd.). The contact angle was measured.

<Test 2> (Measurement of Dynamic Receding Contact Angle on Recording Medium Surface) The dynamic receding contact angle of distilled water on the recording medium prepared was
It was measured at a dipping speed of 100 mm / min using a dynamic receding contact angle measuring device DCA-20 manufactured by Orientec.

<Test 3> (Ink transfer test) Writing was performed on the surface of the recording medium prepared using an oil-based marker piece (black) manufactured by Mitsubishi Pencil Co., and the recording medium was overlaid, and the transferability of the ink to the back surface of the recording medium was evaluated. Was performed (Table-1)

<Test 4> (Addition / removal characteristic test) The added marker / removal characteristic of the produced recording medium was evaluated by carrying out the following marker test. [Writability test] An oil-based marker piece (black) manufactured by Mitsubishi Pencil Co., Ltd. was used for writing on the surface of the produced recording medium, and repellency was evaluated from the handwriting. [Fixability test] 188 against the handwriting of the above-mentioned writing test
The PET film having a thickness of μm was overlaid and rubbed to evaluate the fixability. [Removability] The handwriting of the above-mentioned writing test was rubbed with a cotton swab to evaluate the removability. The results of the above tests are shown in Table-1.
In addition, "-" in the table indicates that the ink could not be evaluated because the ink was repelled on the writing surface, and therefore the evaluation could not be performed.

[0086]

[Table 1]

From the results shown in the above table, the recording mediums of Examples 1 to 4 satisfying the numerical values of the contact angle and the dynamic alternating contact angle specified in the present invention are compared with the recording medium of the comparative example.
It can be seen that the ink is excellent in transfer of the ink to the back surface, writing property, fixing property and removability.

[0088]

INDUSTRIAL APPLICABILITY The reversible recording medium of the present invention is capable of being rewritten on a medium, and even when the retouched mediums are stacked, the writing member on the front surface does not transfer to the back surface of another medium. Produce an effect.

[Brief description of drawings]

FIG. 1 is a diagram showing color developing / decoloring characteristics of a reversible recording medium according to an example of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kyoji Tsutsui             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H026 AA07 AA09 DD01 DD32 DD48                       DD53 DD55 DD58 FF01 FF11                       FF17 FF24 FF25                 2H111 HA07 HA23 HA35                 5B035 BB02 BB09 BB12

Claims (15)

[Claims] 1. A reversible recording medium capable of being repeatedly rewritten and displayed, wherein the reversible recording medium has a back surface having a contact angle with distilled water of 90 degrees or more and a reversible recording medium surface with a dynamic receding contact angle with distilled water. A reversible recording medium, which is in the range of 75 degrees to 100 degrees. 2. The reversible recording medium according to claim 1, wherein the reversible recording medium has a laminated structure including at least a support layer, a front surface layer and a back surface layer. 3. The reversible recording medium according to claim 2, wherein the surface layer is either a recording layer or a protective layer provided on the recording layer. 4. The reversible recording according to claim 1, wherein the material constituting the reversible recording medium front surface and / or the material constituting the reversible recording medium back surface contains a lubricant. Medium. 5. The reversible recording medium according to claim 4, wherein the lubricant is a silicone-modified polymer. 6. The reversibility according to any one of claims 1 to 5, wherein the material forming the front surface of the reversible recording medium and / or the material forming the back surface of the reversible recording medium contains filler particles. recoding media. 7. The reversible recording medium according to claim 6, wherein the filler particles in the material forming the surface of the reversible recording medium have an average particle size in the range of 0.2 to 2.0 μm. . 8. The reversible recording medium according to claim 6, wherein the filler particles in the material forming the back surface of the reversible recording medium have an average particle size in the range of 0.5 to 5.0 μm. 9. The reversible recording medium according to claim 6, wherein the filler particles are coated with calcium. 10. The reversible recording medium according to claim 1, which has a reversible recording unit and an information storage unit. 11. The reversible recording material according to claim 10, wherein the information storage unit is a magnetic recording layer or an IC. 12. The reversible recording medium according to claim 1, wherein the reversible recording medium has a printed portion. 13. The reversible recording medium according to claim 1, wherein the reversible recording layer reversibly forms a colored image by heating and displays the colored image. 14. The erasing device using the reversible thermosensitive recording medium according to claim 13, wherein the erasing is performed by heating to a temperature lower than a color development starting temperature. 15. A heater selected from a thermal head, a ceramic heater, a sheet heater, and a heat roller is provided as a heating means.
Erase device described.