JPH0585046A - Thermally reversible recording material, production thereof and thermal recording medium - Google Patents

Abstract

PURPOSE:To improve the contrast of transparency and opacity or sensitivity by forming a thermally reversible recording material by dispersing a low-molecular org. compound having a molecule generating a reversible change from a dimer to a monomer in a polymeric resin. CONSTITUTION:When a low-molecular org. compound is melted at its m.p., the moecules thereof form a dimer by a hydrogen bond. At this time, by using a polymeric resin whose meltability is near to that of the low molecular org. compound, the low molecular org. compound is melted to penetrate in the interstices between the molecular chains of the polymeric resin to become transparent apparently and, even when the recording material consisting of the polymeric resin and the low-molecular org. compound returns to room temp., the transparent state is held. When the recording material is heated to higher temp., the movement of the low-molecular org. compound becomes active and the hydrogen bond forming the dimer is cut to change the dimer to a monomer and the recording material changes in meltability to become hydrophilic. The low-molecular org. compound is detached from the meltability of the polymeric resin to generate phase separation to become a fine particulate state and the recording material becomes opaque when it is returned to room temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoreversible recording material, a method for producing the same and a heat-sensitive recording medium, and more particularly to a thermoreversible recording material capable of reversibly making transparent and opaque by heating and the production thereof. A method and a thermal recording medium.

Although there are still few practical examples of such thermoreversible recording materials, in the future, from the standpoints of resource saving, environmental measures, cleanliness and automation, in the fields of "display", "recording", "dimming", etc.
Usage is expected to increase rapidly.

[0003]

2. Description of the Related Art As an example of a conventional thermoreversible recording material,
There is a method in which a fatty acid or the like is dispersed in a vinyl chloride resin matrix and the crystal state of the fatty acid reversibly changes with a change in temperature.

The structure and manufacturing method of this thermoreversible recording material are described, for example, in JP-A-57-82086 and 57.
-82087, 57-82088, 63-1320
No. 89, etc. Hereinafter, a method for producing the thermoreversible recording material will be described.

Tetrahydrofuran, which is a solvent, is a mixture of docosanoic acid (behenic acid) 0.25 g (14% by weight), polyvinylidene chloride / acrylonitrile copolymer 1.5 g (86% by weight) (Asahi Kasei Saran Resin R-200). 8.0
After fully dissolving in g (450% by weight), the above solution is applied on a 120 μm thick Mylar film (polyester film) by a casting method, and the solvent is evaporated at 50 ° C. to form a 15 μm thick thermoreversible film. Forming a sexual recording material.

[0006]

FIG. 14 is a schematic view and a graph showing states of the conventional thermoreversible recording material under various conditions. In these figures, docosanoic acid and polyvinylidene chloride / acrylonitrile are shown. The state in which the copolymer is dispersed in tetrahydrofuran, is the state of the thermoreversible recording material at room temperature T, is the state of the thermoreversible recording at a temperature of 90 ° C. which is higher than the melting point of the low molecular weight organic compound in the thermoreversible recording material. The state of the material indicates the state of the thermoreversible recording material when the state is returned to room temperature T, and the state of the material indicates the state of the thermoreversible recording material when the state is changed to 110 ° C.

However, the thermoreversible recording material according to the conventional example as described above is white translucent, and when this is handwritten with a hot pen (not shown) having a tip of 90 ° C., that portion changes to transparent. Although transparent characters could be drawn thinly on a white background (states shown in FIGS. 1 and 14), the contrast between transparent and opaque was insufficient, resulting in poor clarity and difficulty in reading. The light transmittance of the white background was 78%, the light transmittance of the transparent portion was 84%, and the difference in light transmittance between the transparent and opaque areas was only about 6%. Next, when this conventional thermoreversible recording material was put into a hot air oven (not shown) at 110 ° C., the transparent portion became cloudy and the whole was returned to the original translucent state (FIGS. 1 and 14). Condition). However, when this was repeated several times, the contrast was further reduced.

According to the conventional example, when a white translucent state and a transparent state sample of the thermoreversible recording material were observed with an electron microscope, it was found that the particles of docosanoic acid were very fine and almost dissolved. That is, since the conventional manufacturing method uses a solvent such as tetrahydrofuran in which a low molecular weight organic compound such as docosanoic acid is easily dissolved, the low molecular weight organic compound is not in a dispersed state in which fine particles are formed. For this reason, the docosanoic acid molecules already exist in the polymer chain of the polyvinylidene chloride / acrylonitrile copolymer in a monomolecular state in the film-forming state and do not form fine particles. There is a problem that it is hard to generate enough and sufficient opacity cannot be realized.

Therefore, by increasing the thickness of the thermoreversible recording layer, the contrast between transparent and opaque is improved to some extent, but this method has a problem that the sensitivity is lowered, and the thermoreversible recording medium and the support of the magnetic card are reversible. When applied to a magnetic card that has a magnetic recording layer between it and a magnetic recording layer and is capable of printing on both sides of a magnetic card, the magnetic reading will become easier if the distance between the magnetic head and the thermoreversible recording layer is increased. Since it becomes impossible, it is necessary to further reduce the thickness of the thermoreversible recording layer.

Therefore, conventionally, there has been no thermoreversible recording material having a good contrast of transparency and opaqueness and a high sensitivity even if the film thickness is thin. SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoreversible recording material having a transparent and opaque contrast and a good sensitivity even if the film thickness is thin, and a manufacturing method for supplying the thermoreversible recording material.

[0011]

The above problems can be solved by the thermoreversible recording material shown below. That is, in a thermoreversible recording material in which a low molecular weight organic compound is dispersed in a polymer resin and a transparent state and an opaque state can be reversibly repeated depending on a temperature history, the low molecular weight organic compound is a proton-donating group in one molecule. (A) and proton accepting group (B)
T1 which has both the above and the melting point of the low molecular weight organic compound or more.
In the thermoreversible recording material, a dimer is formed and the monomer is separated into a monomer at a temperature T2 higher than the temperature T1. The present invention can be realized in the following three modes.

First of all, at a temperature T1 above the melting point of the low molecular weight organic compound (a), two molecules of the low molecular weight organic compound (a) form a dimer by hydrogen bonding, and a polymer resin (b) is formed. Dissolves in. Furthermore, the thermoreversible recording material is characterized in that it undergoes phase separation from the polymer resin (b) at a temperature T2 higher than the temperature T1.

The second is a structure in which the low molecular weight organic compound (c) is dispersed in the polymer resin (d) in a dot shape,
Thermoreversible property, characterized in that the polymer resin (d) is not compatible with the low molecular weight organic compound (c) and maintains a dot shape at a temperature T1 higher than the melting point of the low molecular weight organic compound (c). It is a recording material.

Finally, thirdly, the polymer resin (f) forms a three-dimensional network structure, and the low molecular weight organic compound (e) is present in the polymer resin (f) in a continuous phase. And at a temperature T1 above the melting point of the low molecular weight organic compound (e),
The polymer resin (f) is a thermoreversible recording material which is incompatible with the low molecular weight organic compound (c) and maintains a three-dimensional network.

[0015]

The basic principle of the thermoreversible recording material of the present invention is that a molecule of a low molecular weight organic compound, which is a component of the thermoreversible recording material, undergoes a reversible change from a dimer to a monomer. , To use. FIG. 13 shows the structural formula of the low molecular weight organic compound forming the dimer of the present invention. That is, at a temperature T1 higher than the melting point of the low molecular weight organic compound, the molecule of the low molecular weight organic compound is
And possesses both a proton acceptor group (B),
The hydrogen bonding of these causes the molecules of the low molecular weight organic compound to dimerize and share the polar groups, so that the polar groups have no effect on the outside. On the other hand, when the temperature is further increased, the activity of the molecule is activated, so that the molecule can no longer exist as a dimer and is separated into a monomer. At this time, since the polar group directly acts on the outside, the apparent polarities of the dimer and the monomer are different.
Therefore, the solubility of the low molecular weight organic compound in the polymer resin changes, and the refractive index when it crystallizes also changes. Utilizing this fact, by uniformly dispersing such a low molecular weight organic compound in a transparent polymer resin,
Reversible dissolution and phase separation phenomenon due to change in solubility and change in refractive index are performed to reversibly change from a transparent state to an opaque state.

Utilizing the above, the above-mentioned three aspects of the thermoreversible recording material of the present invention produce the following actions. First, in the first aspect, as shown in FIG.
When the low-molecular-weight organic compound melts at the melting point, the molecules of the low-molecular-weight organic compound form dimers due to hydrogen bonds, and a polymer resin with a solubility close to that of the low-molecular-weight organic compound at this time is used. By using it, the low molecular weight organic compound dissolves and permeates between the molecular chains of the polymer, making it apparently transparent (),
This state is maintained even after returning to room temperature (). Then, when the temperature is further raised, the movement of the low molecular weight organic compound is activated, the hydrogen bond forming the dimer is broken and converted into a monomer, and thus the solubility is changed (becomes more hydrophilic). , The low molecular weight organic compound becomes fine particles due to phase separation, which is out of the solubility of the polymer (), and becomes opaque when it is returned to room temperature ().

Next, in the second embodiment, as shown in FIG. 2, when the low molecular weight organic compound is melted at the melting point, the polymer resin is incompatible with the low molecular weight organic compound, and the fine particles are Melts inside without changing its shape. At this time, the low-molecular-weight organic compound forms a dimer with the adjacent molecule, and the non-polar groups are arranged so that they face outward (),
This state is maintained even when the temperature is returned to room temperature. When the refractive index n1 at this time is set, the polymer resin becomes transparent when the refractive index n0 is close to this, and becomes opaque when the refractive index n0 is opposite ().
Next, at higher temperature, the movement of the low molecular weight organic compound is activated, the bond of the dimer is cleaved and converted into a monomer, and the molecular arrangement is changed (). When this is returned to room temperature, the monomer is crystallized as it is, and the refractive index becomes n3. This time, conversely, the refractive index n0 of the polymer resin deviates from the value of opacity, and conversely, it becomes transparent ().

Finally, in the third mode, as shown in FIG. 3, the polymer resin forms a three-dimensional network (sponge-like) structure, in which the low molecular weight organic compound is in dot form. It exists as a continuous phase rather than (). When the low molecular weight organic compound melts at the melting point, the polymer resin is incompatible with the low molecular weight organic compound, and the continuous phase low molecular weight organic compound dissolves while the shape of the network remains unchanged. At this time, the low-molecular-weight organic compound forms a dimer with the adjacent molecule, and the nonpolar groups are arranged with the non-polar group facing outward (), and this state is maintained even when the temperature is returned to room temperature. Therefore, when the refractive index n1 at this time is set, when the refractive index n0 of the polymer resin is close to this, it becomes transparent, and in the opposite case, it becomes opaque. Next, at higher temperature, the movement of the low molecular weight organic compound is activated, the bond of the dimer is cleaved and converted into a monomer, and the molecular arrangement is changed (). When this is returned to room temperature, the monomer crystallizes as it is, and the refractive index becomes n2. This time, conversely, the refractive index n0 of the polymer resin deviates from the value of opacity, and conversely, it becomes transparent ().

[0019]

Embodiments of the present invention will be specifically described below with reference to the drawings. 1, 2, 3, and 4 are schematic diagrams and graphs showing states of the thermoreversible recording material of the present invention under various conditions. In these figures,
Is a state in which a low molecular weight organic compound and a polymer resin are uniformly dispersed in a solvent, is a state of a thermoreversible recording material at room temperature T, is a temperature equal to or higher than the melting point of the low molecular weight organic compound in the thermoreversible recording material. State of the thermoreversible recording material at temperature T1,
Indicates the state of the thermoreversible recording material when the state is returned to room temperature T, and indicates the state of the thermoreversible recording material when the state is changed to a temperature T2 higher than the temperature T1.

[First Embodiment] A first embodiment of the present invention is one in which the present invention is applied to a display board, and the embodiment shown in FIGS. 1 and 4 is utilized. The sectional view of a display board is shown.

Stearamide a 15% by weight Polymethylmethacrylate b 85% by weight Toluene / MEK = 7/3 400% by weight are uniformly dispersed in a sand mill. At this time, polymethylmethacrylate b was dissolved in the solvent toluene / MEK = 7/3, but stearic acid amide a which was not dissolved in toluene / MEK = 7/3 was uniformly dissolved in toluene / MEK = 7/3. To be dispersed (state of FIG. 1). Then, the above-mentioned solution is applied to a polyester film 12 having a thickness of 100 μm by a casting method, and toluene / MEK = 7/3 which is a solvent is evaporated at 60 ° C. to obtain a first embodiment of the present invention having a thickness of 10 μm. A thermoreversible recording layer 1 made of a white opaque thermoreversible recording material (structure of FIG. 1).
1 is obtained (states of FIGS. 1 and 4).

In FIG. 5A, the surface of the thermoreversible recording layer 11 obtained above was coated with Aronix UV-3333 (Toa Gosei, one-pack type UV curable acrylic resin) in a thickness of 5 μm,
The protective film 13 was formed by UV (ultraviolet) curing.

Next, the above-mentioned polyester film 12
Was pasted on a steel plate 14 whose surface was colored black to form a display plate. In FIG. 5 (b), when this is handwritten with the hot pen 15 having a tip of 100 ° C., the hot pen 1
The molecule of stearic acid amide a (low molecular weight organic compound) in the portion contacted with 5 forms a dimer by hydrogen bonding, and polymethacrylic acid having a solubility close to that of stearic acid amide a at this time is formed. By using methyl b (polymer resin), stearic acid amide a is dissolved and permeated between the molecular chains of the polymer (states shown in FIGS. 1 and 4).

After that, when the hot pen is separated from the display plate, the stearic acid amide a is dissolved and permeated between the polymer molecular chains to be solidified, so that the thermoreversible recording material changes to a transparent state (see FIGS. 1 and 1). 4)), black characters were clearly printed on a white background, and it was as if writing with a black marker on a whiteboard. Despite the black plate behind the white part, it was hardly affected by it, and the whiteness was high, so the black and white contrast was very good.

In FIG. 5 (c), when this is contacted with an iron-type erasing hot plate 16 at 120 ° C., the movement of stearic acid amide a is activated and the hydrogen bond forming the dimer is broken. Since it changes to a monomer, the solubility changes,
The stearic acid amide a is made into fine particles by phase separation which is deviated from the solubility of the polymethylmethacrylate b (see FIG. 1).
When the thermoreversible recording material was returned to room temperature, the transparent portion became cloudy and the whole was returned to the original white background, and the characters disappeared (return to the states of FIGS. 1 and 4). Then, even if this was repeated 500 times, printing could be performed without problems.

FIG. 5D shows an example in which the sheet heating element 17 is provided on the steel plate 14 in FIG. 5A and is used for erasing. Next, when a white (opaque) state sample and a transparent state sample of the thermoreversible recording material are observed with an electron microscope, when the sample is in a white state, the stearic acid amide a is about 0.2.
In the case of a transparent state, fine particles of ˜1.0 μm are distributed, and stearic acid amide a is dissolved and permeated between the molecular chains of polymethylmethacrylate b, so the particles do not exist in a clear state. I knew that. The light transmittance was 80% in the transparent state and 60% in the opaque state.

[Second Embodiment] Two kinds of thermoreversible recording materials were obtained in the same manner as in the first embodiment except that the ratio of stearic acid amide a and polymethyl methacrylate b was changed. Table 1 shows these ratios and characteristics of these two types of thermoreversible recording materials as the second example.

[0028]

[Table 1]

As a result, the contrast was best in the first example in which the ratio of stearic acid amide a to polymethylmethacrylate b was 15:85. The ratio of stearic acid amide a to polymethylmethacrylate b is 5: 9.
It is considered that 5 to 40:60 is suitable, and if the low molecular weight organic compound is contained in an amount of 5 to 40% by volume of the whole, even better contrast can be obtained.

The relationship between the light transmittances of the transparent state and the opaque state for obtaining a sufficient contrast is that the light transmittance of the opaque state is 75% or less, and the difference between the light transmittances of the transparent state and the opaque state is the following. It should be 5% or more. This is because when the light transmittance when opaque is 75% or more, the color of the colored support that is usually placed on the background is transparent and the contrast is insufficient, and the difference in light transmittance when transparent is less than 5%. In this case, the difference in change is too small to obtain sufficient contrast.

The method for producing the thermoreversible recording material according to the first aspect of the present invention (structure of FIG. 1) is such that the low molecular weight organic compound a is not dissolved but the high molecular weight resin b is dissolved in the solvent. It is obtained by uniformly finely dispersing the compound a, forming a film by a casting method, and drying the solvent. In the film after drying, the low molecular weight organic compound a is finely dispersed in the polymer resin b,
It is in an opaque state.

The particle size of the low molecular weight organic compound a is 0.1
5 μm is optimal for obtaining high contrast. If the particle size is smaller than this, the light scattering power is insufficient because the wavelength is close to the wavelength of light, and if the particle size is larger than this, a large number of particles in a unit volume cannot be maintained, so that the light scattering is reduced.

As the polymer resin b used in the first embodiment of the present invention (structure of FIG. 1), polyacrylic acid ester, polymethacrylic acid ester, polystyrene, methyl methacrylate / styrene copolymer, acrylonitrile /
Styrene copolymer, styrene / butadiene copolymer,
Acrylonitrile / acrylic ester / styrene copolymer, polymethylpentene, transparent ABS resin, polycarbonate, silicone resin, polyvinyl butyral, polyvinyl formal, ethyl cellulose, methyl cellulose, cellulose acetate, nitrocellulose, polyvinyl alcohol, polyacrylic acid, polyacrylamide, Examples thereof include starch, gum arabic, styrene-maleic acid copolymer, gelatin, polyvinyl acetate, ethylene vinyl acetate copolymer, ethylene vinyl acetate partially saponified product and the like.

As a method for further improving the contrast, it is effective to make it difficult for the color of the background colored layer to pass through when it is made opaque. Therefore, a thermoreversible recording material is preliminarily provided on the transparent support to make it transparent. Thermoreversible recording is performed from the colored support by bonding the back side of the support to the colored support through a spacer such as inorganic or organic particles having a particle diameter of 1 to 500 μm or fibers or resin printed dot patterns. The color of the colored layer is transmitted by separating the layers and not directly collecting the reflected light from the colored support into the thermoreversible recording layer, but by once scattering the light on the back side of the thermoreversible recording layer to reduce the transmittance. It is difficult to do so, and as a result, the contrast can be improved.

Next, a third embodiment in which a spacer is provided on the display plate of the first embodiment will be described. [Third Embodiment] A third embodiment of the present invention is one in which the present invention is applied to a display panel having a spacer and is shown in FIG.

In FIG. 6A, between the polyester film 12 having the thermoreversible recording layer 11 and the protective layer 13 obtained in the first embodiment and the steel plate 14 whose surface is colored black. , Urea resin particles 1 with a particle size of about 500 μm
8 as a spacer, and a film 12 with a sealant.
And the steel plate 14 were bonded together to form a display plate similar to that of the first embodiment.

When the tip of this is handwritten with a hot pen (not shown) having a temperature of 100 ° C., that portion changes to transparent, black characters are clearly printed on a white background, and the whiteness of the white background is further improved as compared with the first embodiment. However, the contrast became good. Table 2
6 is a table comparing the reflection densities of the first embodiment and the third embodiment.

[0038]

[Table 2]

In the third embodiment, as shown in FIG. 6B, a space is provided between the thermoreversible recording material and the black background behind the recording material.
Since the reflected light from the back is once scattered and then made incident on the recording layer, it is less affected by the back and the whiteness is improved.

The display boards described in the first and third embodiments are used for blackboards, whiteboards, OA boards, information boards, advertising boards, etc., and can achieve cleanliness, labor saving, etc., and personal computers etc. By combining with, self-portraits are also possible, which is extremely convenient.

As the support under the thermoreversible recording material, a polyester film and a steel plate were used, but various other materials such as a film, a resin plate, paper, a metal plate, glass and a composite material can be used. It can also be used. Then, it is necessary to color these in a color other than white. A colored layer may be provided on the surface, or the support itself may be colored, and in the case of a transparent support, the back surface may be colored. In order to obtain contrast, black or silver is preferable.

[Fourth Embodiment] The fourth embodiment of the present invention is one in which the present invention is applied to an OHP sheet.
And the embodiment shown in FIG. 4 is used.
The sectional view of a P sheet is shown.

First, although not shown, octadecyl monoisocyanate ethyl alcohol condensate c 25% by weight acrylic oligomer (tetraethylene glycol diacrylate) 71% by weight benzophenone d 4% by weight toluene 300% by weight were uniformly dispersed in a sand mill ( (State of FIG. 2), a polyester film 2 having a thickness of 120 μm by a casting method.
2 is coated with the above solution to evaporate toluene as a solvent at 60 ° C., and then is irradiated with UV light (ultraviolet light) to be cured,
A thermoreversible recording layer 21 composed of a white opaque thermoreversible recording material according to the second aspect of the present invention (structure of FIG. 2) having a thickness of 15 μm is obtained (states of FIGS. 2 and 4).

In FIG. 7 (a), a film of polyethylene naphthalate having a thickness of 20 μm is laminated on the surface of the thermoreversible recording layer 21 obtained above to form a protective film 23,
An OHP (overhead projector) sheet was formed.

In FIG. 7 (b), the tip of this is 90.degree.
When printing is performed using the hot pen 24 or a thermal printer (not shown), the molecules of the low molecular weight organic compound c in the thermoreversible recording material in the printed portion form a dimer (see FIGS. 2 and 4). Condition). After that, when the temperature of the printed part returns to room temperature, the molecules that formed the dimer solidify as they are,
The low molecular weight organic compound c and the acrylic resin d have almost the same refractive index, and the thermoreversible recording material in the printed portion changes to transparent (states of FIGS. 2 and 4), and clear characters are clearly visible on a white background. I was able to draw. When this was projected by OHP, a very clear negative image was projected.

Next, when this is erased, it is passed through a hot roller (not shown) at a higher temperature of 110 ° C., and the molecule c forming the dimer returns to the monomer (see FIG. 2 and FIG. 4
State), since the monomer solidifies as it is when returned to room temperature, the transparent part becomes cloudy due to the difference in refractive index between the low molecular weight organic compound c and the acrylic resin d, and the whole returns to the original white background. Disappeared (states of FIGS. 2 and 4). Then, this OHP sheet could be used without any problem even if rewriting was repeated 500 times.

In this way, the thermal printer directly
A P-sheet can be created and can be erased and used again after proofreading, so there is no waste. For the transparent support such as polyester film, general polyethylene terephthalate, acetyl cellulose, etc. can be used.

Next, the white color of the thermoreversible recording material (opaque)
When the sample in the transparent state and the sample in the transparent state are observed with an electron microscope, in the case of the white state, the condensation product c has a concentration of about 0.2 to 4.0 μm
It was found that even in the transparent state, the particles were present in a clear shape, and only the transparency was increased. The light transmittance was 87% in the transparent state and 60% in the opaque state.

In the same manner as in Example 4, except that acetone was used in place of toluene as a solvent, Table 3
A thermoreversible recording material of Comparative Example 1 shown in Table 1 was obtained.

[0050]

[Table 3]

As a result, the low molecular weight organic compound c is easily dissolved in acetone, and is not dispersed into an appropriate particle size during the film formation process.
Since it existed in a dissolved state of 0.1 μm or less, the light transmittance at the time of opaqueness was too large, and contrast could not be obtained.

As the polymer resin used in the second embodiment (configuration of FIG. 2) of the present invention, those not compatible with the low molecular weight organic compound are preferable, and a curable resin is used. When a thermoplastic resin is used, a resin that is incompatible with the low molecular weight organic compound is used. Alternatively, a microcapsule made of a resin that is not compatible with the low molecular weight organic compound may be dispersed in the thermoplastic resin.

As the curable resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, urethane resin, acrylic resin, etc. are used. A low molecular weight organic compound, an oligomer or a monomer, and a polymerization initiator are added and uniformly dispersed, and the resultant is coated on a support and polymerized by heat, light or electron beam.

The conditions of light transmittance for obtaining a high contrast, and the particle size and the compounding ratio when the low molecular weight organic compound forms fine particles are the same as those in the first aspect of the present invention (configuration of FIG. 1). Is.

[Fifth Embodiment] The fifth embodiment of the present invention is one in which the present invention is applied to a heat-sensitive sheet and is shown in FIG.

In FIG. 8, the thermoreversible recording layer 21 and the protective film 23 of the fourth embodiment are colored black and have a thickness of 80 μm.
m coated paper 24 to form a heat sensitive sheet. When printed on a 90 ° C. thermal printer (not shown) of Fujitsu word processor OASYS 30 ms (trademark), black characters were clearly printed on a white background. Then, when this was sandwiched between 110 ° C. hot rolls (not shown) and passed, the characters disappeared.

Despite the black paper behind the white portion, it was hardly affected by it, and the whiteness was high, so that the black and white contrast was very good. This replaces the field in which thermal paper has been used in the past with the rewritable thermal sheet of the present invention, thereby eliminating waste of disposable paper, and not only thermal paper, but also handwritten memo paper and disposable application paper at once. By replacing it with this, it becomes possible to use it again and again, which contributes to reduction of paper consumption.

In the present invention, a sheet made of a film, paper or other composite material colored in a color other than white is used as a support, and a thermoreversible recording material is provided thereon, and a heat-resistant protective layer or It has a protective film and can be used in either roll or cut paper form.

If this is set and used in an output thermal printer of a personal computer, a word processor, etc., it can be repeatedly used by erasing it for calibration first and erasing it when not needed, which is extremely convenient. is there. Also,
If it is used for a facsimile, it is possible to save the waste that the original was always copied for preservation and the original was discarded.

With respect to the spacer, the same technique as in the third embodiment can be applied. [Sixth Embodiment] The sixth embodiment of the present invention is one in which the present invention is applied to a magnetic card, and the embodiment shown in FIGS. 2 and 4 is utilized. A cross-sectional view is shown.

Stearic acid 20% by weight Gelatin 5% by weight Ethylcellulose 75% by weight Ethyl alcohol 400% by weight Stearic acid is microencapsulated with an aqueous gelatin solution, and this is added to an ethyl alcohol solution of ethylcellulose to prepare a dispersion liquid (see FIG. 2). State), and coating this on the magnetic recording surface 32 of the magnetic card by the cast method,
By drying at 5 ° C., a thermoreversible recording layer 31 made of a white opaque thermoreversible recording material according to the second aspect (configuration of FIG. 2) of the present invention by the microcapsule method is obtained (state of FIG. 2). ..

In FIG. 9, on the surface of the thermoreversible recording layer 31 obtained above, Aronix UV-3333 (Toa Gosei,
1-component UV curable acrylic resin) is applied to 5 μm and UV
(UV) curing was performed to form the protective film 33.

In addition to this, 80 of Fujitsu card reader / writer
When printing is performed with a thermal printer (not shown) at ℃, the molecules of the low molecular weight organic compound stearic acid in the thermoreversible recording material in the printed portion form a dimer (states of FIGS. 2 and 4). After that, when the temperature of the printed part returns to room temperature, the dimer-forming molecules solidify as they are, so that the refractive indices of stearic acid and ethyl cellulose become almost equal, and the thermoreversible recording material in the printed part changes to transparent. (Figs. 2 and 4
(State of), black characters were clearly printed on a white background. Although the white portion has a black magnetic recording layer behind it, it is hardly affected by it and has a high whiteness, so that the contrast of black and white is extremely good.

Next, this was sandwiched between 110 ° C. hot rolls (not shown) and passed through, and the molecules forming the dimer returned to the monomers (states of FIGS. 2 and 4), When the temperature is returned to room temperature, the monomer solidifies as it is, and due to the difference in the refractive index between stearic acid and ethyl cellulose, the transparent part becomes cloudy and the whole character returns to the original white background, and the characters disappear (Figs. 2 and 4). Condition). Then, even if this was repeated 500 times, printing could be performed without problems.

In the sixth embodiment, it is possible to print on the front surface of the magnetic card and display it on the back surface with the thermoreversible recording layer.
However, since the thermoreversible recording layer is provided on the magnetic surface, it is necessary to keep the film thickness within 10 μm from the problem of magnetic reading.

Next, the white color (opaque) of the thermoreversible recording material
When the sample in the transparent state and the transparent state is observed with an electron microscope, it is about 0.4 to 0.8 of stearic acid in the case of the white state.
The fine particles of μm had an extremely narrow particle size distribution width. It was found that in the transparent state, the particles were present in a very clear form and were completely protected by the microcapsules. Light transmittance is 88% in transparent state, 5 in opaque state
It was 8%.

A known method is used for the microencapsulation, and the material for encapsulating the low molecular weight organic compound needs to be insoluble with the low molecular weight organic compound.
Polyvinyl alcohol or the like is used. As the polymer resin holding the microcapsules, any of the above-mentioned thermoplastic resins is used. However, it is necessary to match the refractive index of the microcapsule and the polymer.

[Seventh Embodiment] A seventh embodiment of the present invention is applied to a magnetic card obtained by modifying the sixth embodiment, and is shown in FIG.

In FIG. 10, the thermoreversible recording layer 31 and the protective film 33 of the sixth embodiment are provided, and the blue colored layer 34 is provided on the surface opposite to the magnetic recording surface of the magnetic card 32, and is provided thereon. .. When printed with a thermal printer (not shown) at 80 ° C. of a card reader / writer manufactured by Fujitsu, blue letters were clearly printed on a white background. Then, when this was sandwiched between 110 ° C. hot rolls (not shown) and passed, the characters disappeared.

Although the white portion had a blue colored layer behind it, it was hardly affected by it, and the whiteness was high, resulting in extremely good contrast. By making rewriting on the magnetic card, there are advantages such as correction of erroneous entry, countermeasures when there are a large number of entry items, rewriting information, and new services such as advertising services.

With respect to the spacer, the same technique as in the third embodiment can be applied. [Eighth Embodiment] The eighth embodiment of the present invention is an application of the present invention to a light control film, which utilizes the mode shown in FIGS. 3 and 4, and the light control shown in FIG. The cross section of the film is shown.

Erucamide amide e 50% by weight Polyester polyol (Takeda Chemicals, Takelac U-53) 35% by weight Polyisocyanate (Takeda Chemicals, Takenate D-160N) f 15% by weight Toluene 100% by weight is uniformly dispersed in a sand mill ( (State of FIG. 3), coating on a polyester film 42 having a thickness of 120 μm,
The solvent, toluene, is evaporated at 0 ° C., and is then cured by irradiation with UV light (ultraviolet light) to obtain a white opaque thermoreversible recording material having a thickness of 7 μm according to the third aspect of the present invention (configuration of FIG. 3). A thermoreversible recording layer 41 consisting of is obtained (state of FIG. 3).

In FIG. 11, a 20 μm film of polyethylene naphthalate was laminated on the surface of the thermoreversible recording layer 41 obtained above to form a protective film 43. Then, between the polyester film 42 and the heat-resistant protective film 44, a transparent heating sheet 45 (made by Gunze, made of 100 μm-thick polyester film with a transparent resistor pattern)
A transparent film heater) was superposed and integrated, and an electric wire was attached so that an electric current could be applied, and the voltage was switched so that the heat generation temperature could be switched in two steps to prepare a light control film of the present invention. ..

An electric current is applied to this to heat the heat generating sheet at 90 ° C.
When heat is generated, the molecules of erucamide amide e in the thermoreversible recording material form a dimer (states in FIGS. 3 and 4). After that, when the temperature of the heated part returns to room temperature,
Since the molecules forming the dimer solidify as they are, the refractive indices of the erucamide amide e and the polyester polyol / polyisocyanate cured product f become approximately the same, and the heat-reversible recording material in the heated portion changes to transparent. (The state of FIG. 3 and FIG. 4) The light control film became transparent.

Next, when the switch is switched to generate heat at 110 ° C., the molecule e forming the dimer returns to the monomer (states of FIGS. 3 and 4), the switch is turned off and the temperature is returned to room temperature. And the monomer solidifies as it is, erucic acid amide e
Due to the difference in refractive index between the polyester polyol / polyisocyanate cured product f, the transparent portion became cloudy and the whole became opaque (states of FIGS. 3 and 4). Then, there was no problem even if this was repeated 500 times.

Next, the white color of the thermoreversible recording material (opaque)
When the sample in the transparent state and the sample in the transparent state are observed by an electron microscope, the continuous phase fine structure of the erucic acid amide e is complicatedly distributed in the case of the white state, and the polymer urethane f has a three-dimensional network ( Sponge-like),
It was found that even in the transparent state, it was still present and only the transparency was increased. Light transmittance is 90 in transparent state
% And 55% in the opaque state.

The above-mentioned second aspect of the present invention (configuration of FIG. 2)
The difference is that the low molecular weight organic compound is in a dot form or a continuous phase. That is, in the present invention (first aspect) and (second aspect), in the constitution of the thermoreversible recording material, the low molecular weight organic compound occupies about 5 to 40% by volume of the whole, and the particle diameter thereof is 0.1 to 5 μm was optimum. In the present invention (third aspect), in the constitution of the thermoreversible recording material, the low molecular weight organic compound occupies 30 to 80% by volume of the whole and forms a continuous phase. In the case of a continuous phase, the principles of transparency and opacity are similar and have similar functions, but the difference is that the continuous phase has a larger light scattering ability, and thus a larger contrast can be obtained. .. This has the advantage that it is possible to achieve the same contrast with a thinner film thickness.

[Ninth Embodiment] The ninth embodiment of the present invention is one in which the present invention is applied to light control glass.
Shown in.

In FIG. 12, the light control film obtained in the eighth embodiment was sandwiched between two glass plates 46 via polyvinyl butyral to produce a light control glass. If you attach this to transparent glass, you only have to turn on the switch when you want to switch between transparent and opaque, like the conventional liquid crystal type, you do not need to constantly turn on electricity when making it transparent,
It was convenient.

The light control film or the light control glass can be used in place of the curtain or the frosted glass and can be returned to the original condition when necessary. However, it has been very expensive since the conventional liquid crystal is used. According to the present invention, it can be manufactured at a very low cost. Further, there is an advantage that it is not necessary to constantly apply a voltage to make it transparent.

Here, the following compounds may be mentioned as examples of low molecular weight organic compounds usable in the present invention. First, since the first condition is to apply heat when changing from opaque to transparent, the melting point of the low molecular weight organic compound must be higher than room temperature. Therefore, in the case of a low molecular weight organic compound having a melting point of 40 ° C. or higher, higher fatty acid amide, higher alcohol,
Examples include saturated / unsaturated higher fatty acids, higher fatty acid glycerin esters, higher fatty acid esters, amino acids, and low molecular weight urethane.

Examples of the higher fatty acid amide include lauric acid amide, myristic acid amide, palmitic acid amide,
Stearic acid amide, docosanoic acid amide, arachidic acid amide, oleic acid amide, erucic acid amide, erucic acid amide, elaidic acid amide, linoleic acid amide, linolenic acid amide, ricinoleic acid amide, stearyl stearic acid amide, distearyl stearic acid amide Etc.

Examples of higher alcohols include stearyl alcohol and lauryl alcohol. Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, docosanoic acid, and arachidic acid.

As the higher fatty acid glycerin ester,
Examples include stearic acid monoglycerin ester, lauric acid monoglycerin ester, and lauric acid polyglycerin ester.

As the higher fatty acid ester, stearyl behenate, stearyl stearate, lanolinate, trimethylolpropane tetrastearate, methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, octadecyl palmitate, Examples include docosyl behenate.

Examples of amino acids include glutamic acid. Examples of the low molecular weight urethane include an alcohol condensate of hexamethylene diisocyanate, an alcohol condensate of xylylene diisocyanate, and octyl monoisocyanate.

Finally, Table 4 shows a comparison of contrast under various conditions between the first, fourth, sixth and eighth embodiments and the above-mentioned conventional example.

[0088]

[Table 4]

As described above, in the present embodiment, in the thermoreversible recording material in which transparent and opaque are repeated due to a temperature change, the solubility of the low molecular weight organic compound at the melting point is used by using a solvent in which the low molecular weight organic compound is insoluble. When using a polymer resin that has a solubility close to that of the low molecular weight organic compound, or when the low molecular weight organic compound melts at the melting point, use a polymer resin that is not compatible with the low molecular weight organic compound, or microcapsulate the low molecular weight organic compound. Or, depending on the ratio of low molecular weight organic compound and polymer resin,
It is possible to make the particle size of the low molecular weight organic compound into a dot shape having a particle size of 0.1 to 5 μm or to make the low molecular weight organic compound a continuous phase. Therefore, high contrast can be obtained.

In the embodiment, by using the protective film on the thermoreversible recording material, the thermoreversible recording material is free from scratches, stains and fusion with the heating pen, and the life is greatly improved. As the protective film, a resin having no softening point or a temperature of 150 ° C. or higher and a light transmittance of 65% or higher is used. That is, a cross-linking resin such as a thermosetting resin, a photo-curing resin, an electron beam-curing resin or the like is surface-coated and cured, or the softening point 15
This can be achieved by coating a thermoplastic resin at 0 ° C. or higher or laminating a film. Examples of the thermoplastic resin film include polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, polycarbonate, polyimide and the like.

[0091]

As described above, according to the present invention, since the opacity is large and the base cannot be seen through, the whiteness is large, the display is easy to see from a distance, and the film thickness can be reduced. Therefore, it is possible to perform recording with excellent sensitivity and responsiveness as compared with the conventional case.

The product to which this is applied largely eliminates the waste of disposable items and contributes to the automation and labor saving of the display.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a thermoreversible recording material, which is a principle diagram of the present invention (1).

FIG. 2 is a schematic diagram of a thermoreversible recording material, which is a principle diagram of the present invention (2).

FIG. 3 is a schematic diagram of a thermoreversible recording material, which is a principle diagram of the present invention (3).

FIG. 4 is a graph showing transparency according to temperature of the thermoreversible recording material of the present invention.

FIG. 5 is a sectional view of a display panel according to the first embodiment of the present invention.

FIG. 6 is a sectional view of a display panel according to a second embodiment of the present invention.

FIG. 7 is a sectional view of an OHP sheet according to a third embodiment of the present invention.

FIG. 8 is a sectional view of a heat-sensitive sheet according to a fourth embodiment of the present invention.

FIG. 9 is a sectional view of a magnetic card according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view of a magnetic card according to a sixth embodiment of the present invention.

FIG. 11 is a sectional view of a light control film according to a seventh embodiment of the present invention.

FIG. 12 is a sectional view of a light control glass in an eighth embodiment of the present invention.

FIG. 13 is a structural formula of a low molecular weight organic compound forming a dimer of the present invention.

FIG. 14 is a schematic diagram of a thermoreversible recording material, which is a principle diagram of a conventional example.

[Explanation of symbols]

 A Proton donating group for forming a dimer B Proton accepting group for forming a dimer C Dimer formed by hydrogen bond

Front page continuation (72) Inventor Narisei Tanji 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited

Claims (11)

[Claims] 1. A thermoreversible recording material in which a low-molecular weight organic compound is dispersed in a polymer resin and which can reversibly repeat a transparent state and an opaque state depending on a temperature history, wherein the low-molecular weight organic compound is within one molecule. Has both a proton donating group (A) and a proton accepting group (B), forms a dimer (C) at a temperature T1 above the melting point of the low molecular weight organic compound, and A thermoreversible recording material, characterized in that it separates into a monomer at a high temperature T2. 2. The low molecular weight organic compound (a) is dissolved in the polymer resin (b) at a temperature T1 which is equal to or higher than the melting point, and further,
The thermoreversible recording material according to claim 1, wherein the thermoreversible recording material undergoes phase separation from the polymer resin (b) at a temperature T2 higher than the temperature T1. 3. A structure in which the low-molecular weight organic compound (c) is dispersed in the polymer resin (d) in a dot shape, and at a temperature T1 above the melting point of the low-molecular weight organic compound (c), The polymer resin (d) is incompatible with the low molecular weight organic compound (c),
The thermoreversible recording material according to claim 1, wherein the thermoreversible recording material maintains a dot shape. 4. A structure in which the polymer resin (f) forms a three-dimensional network structure, and the low molecular weight organic compound (e) exists in the polymer resin (f) in a continuous phase state. That is, at a temperature T1 which is equal to or higher than the melting point of the low molecular weight organic compound (e), the high molecular weight resin (f) is not compatible with the low molecular weight organic compound (c) and maintains a three-dimensional network. 2. The thermoreversible recording material according to claim 1. 5. The thermoreversible recording material according to claim 3, wherein the low-molecular weight organic compound is dispersed in the polymer resin in a microencapsulated state. 6. A mixture of the low molecular weight organic compound (a) having both a proton donating group (A) and a proton accepting group (B) in one molecule, the polymer resin (b) and a solvent. A step of forming a solution, a step of dispersing the low molecular weight organic compound in a solvent, a step of applying the solution on a support (12), and a step of subsequently drying the solution, 4. The thermoreversible recording material according to claim 2, wherein the solvent is a non-solvent or a poor solvent for the low molecular weight organic compound (a) and is soluble in the polymer resin (b). Production method. 7. A step of dispersing a solution containing the low molecular weight organic compound, an oligomer or a monomer or an oligomer and a monomer, and a polymerization initiator, a step of applying the solution on a support, and thereafter, 5. The method for producing a thermoreversible recording material according to claim 3, further comprising: a step of polymerizing the oligomer or the monomer or the oligomer and the monomer to form a film. 8. The method of producing a thermoreversible recording material according to claim 3, wherein the step of microencapsulating the low-molecular weight organic compound and the low-molecular weight organic compound dispersed in the polymer resin. Method. 9. A heat-generating means (1) having a recording layer (11) made of the thermoreversible recording material according to claim 1 on a support.
According to 5), the rewritable thermosensitive recording medium is characterized in that the recording layer (11) reversibly changes between transparent and opaque. 10. The thermosensitive recording medium according to claim 9, wherein a protective layer (13) is provided on the surface of the thermoreversible recording material. 11. The thermosensitive recording medium according to claim 9, wherein a distance (18) is provided between the thermoreversible recording layer (11) and the colored layer (14).