JPH065368B2 - Method for modifying photochromic recording layer and information recording method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method for modifying a photochromic recording layer and a method for repeatedly recording / erasing information such as characters, symbols and figures on the photochromic recording layer. It is a thing.

[Problems to be Solved by the Related Art and Invention] Various photochromic substances have been developed, which undergo reversible coloring and decoloring which develops color upon irradiation with ultraviolet rays or short-wavelength visible light and decolorizes upon heating or irradiation with visible light. Are known. Then, as one of the important usages thereof, the photochromic substance is dissolved in a suitable solvent together with a suitable binder, and this solution is coated on a suitable support or formed into a film without a support. There is a method in which a photochromic recording layer is formed and characters, symbols, figures, etc. (hereinafter referred to as characters) on this photochromic recording layer are repeatedly recorded and erased many times, and used for various purposes. Is expected.

However, the above-mentioned photochromic recording layer itself has a delay in performance improvement such as color density, color development life, storability, and number of times of repeated use, and further, information recording method on the photochromic recording layer has been substantially improved. The fact is that it has not been practically used yet due to the fact that it has not been done. For example, conventionally, the following photochromic recording layer and its information recording method have been adopted, so that there have been various problems.

(1) The unrecorded photochromic recording layer formed as described above can be processed without any special treatment,
Ultraviolet rays are radiated through a negative original drawing (or a blurred original drawing in which characters etc. are colored) in which characters etc. are transparently extracted from an ultraviolet ray source, and a portion corresponding to the characters exposed to the ultraviolet rays (other than characters etc. in case of positive original drawing) Portion) to record a positive image (a negative image in the case of a positive original image) (JP-A-50-7).
3626, JP-A-51-21819, JP-A-58-37078, etc.).

Although this information recording method is the most general, it has the following problems.

The color density of the photochromic recording layer is generally low,
Since the difference in brightness between characters and other parts was small, it was difficult to read the characters.

The photochromic recording layer generally has a coloring life of several minutes
Since it is only a few hours, it is difficult to read characters immediately.

The storage stability of the photochromic recording layer is poor.For example, when the photochromic recording layer is exposed to the sun or an ultraviolet ray source such as a strong fluorescent lamp after color development, the previously uncolored part is also colored and the difference in brightness from the already colored part is almost It disappears and you cannot read characters. Therefore, it is necessary to pay attention to the preservation method after color development.

Since it is not possible to use the information recording means such as an existing printer, it is necessary to prepare a different negative original image or positive original image for each different recorded content.

(2) The unrecorded photochromic recording layer is suddenly irradiated with ultraviolet rays that constitute letters and the like from the phosphor segment provided in the print head without any special treatment, and the letters and the like are colored to form a positive image. Method of recording
-16434 and JP-A-50-16435).

(3) The unrecorded photochromic recording layer was suddenly irradiated with ultraviolet rays over the entire surface without any special treatment, and then the laser light was scanned in the form of letters,
A method for recording a negative image by erasing the characters and the like (Japanese Patent Laid-Open No. Sho 58-58)
-37078, JP-A-59-122577, etc.).

According to these recording methods (2) and (3), the problems in the above-mentioned recording method (1) can be improved.
There was nothing that could be improved.

An object of the present invention is to eliminate the above-mentioned problems, have a high color density of information, have a long color development life, and have good storability after color development.Also, an information recording apparatus can be easily used by using an existing thermal printer or the like. An object of the present invention is to provide an epoch-making method of modifying a photochromic recording layer and an information recording method which can be configured.

[Means for Solving the Problem and Its Action] In order to achieve the above-mentioned object, the present inventor has conducted extensive studies on improvement of the photochromic recording layer and its information recording method, and as a result, the unrecorded photochromic recording layer was heated to an appropriate temperature. The above problems are remarkably ameliorated by heating and reforming, and instead of suddenly applying ultraviolet light to the photochromic recording layer, by heating and printing information first and then irradiating it with ultraviolet light. After finding out that, the present invention has been completed.

Until now, "heating" the photochromic recording layer was considered to be a means for decoloring after color development, but this "heating" was performed by heat modification or heat printing before color development. It is an epoch-making result that the color development is enhanced by carrying out, and the present invention is based on this reversal idea.

That is, in the method for modifying a photochromic recording layer according to claim 1, the unrecorded photochromic recording layer is 90-150.
The point is to heat to ℃.

Further, the method of recording information on the photochromic recording layer according to claim 2 comprises a step of heating and printing information on the photochromic recording layer, and thereafter ultraviolet rays or short wavelength visible light (hereinafter,
It is called ultraviolet rays. ) Is applied to develop the color of the information, and thereafter, the photochromic recording layer is heated to erase the color of the information.

These methods for modifying the photochromic recording layer or the information recording method are of course effective even if they are carried out individually, but the effect is further synergistically enhanced by using both methods together.

First, the photochromic recording layer used in the present invention will be briefly described. This photochromic recording layer is not limited to a specific component and manufacturing method, but the most commonly used one is to dissolve or finely disperse a photochromic substance in a solvent together with a binder, and apply this solution or fine dispersion to a support. It is formed by drying and drying. It also includes a film-like material having no support.

Examples of the photochromic substance include 1,3,3-trimethylindolino-6′-nitrobenzopyrrirospirane, 1,3,3-trimethylindolino-8′-methoxybenzopyrrirospirane and 1,3,3- Examples thereof include trimethylindolino-benzopyrrolospirane, 6'-hydroxyspirobenzopyran, 2- (2,4-dinitrobenzyl) pyridine and the like. The proportion of the photochromic substance used is appropriately 2 to 50% by weight, preferably 5 to 20% by weight, based on the binder. If it is less than 2% by weight, the color developability and the number of times that it can be used repeatedly are deteriorated. If it exceeds 50% by weight, not only the characters described later but also the surrounding parts are strongly colored, and the difference in brightness between them is small. This is because, on the contrary, it becomes difficult to read characters and the like, and the cost becomes high.

As the binder, a polymer having a good light-transmitting property is suitable, and more preferable is a polymer which is less likely to be melted by the heat at the time of heating printing, which is a feature of the present invention, and is less likely to be depressed by the pressing force. For example, polyester, polyamide,
Urethane, polymethylmethacrylate, polystyrene, polyethylene, polypropylene, polyacrylonitrile, polymethylmethacrylate, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyvinylidene chloride, cellulose acetate, nitrocellulose, phenol,
Examples thereof include epoxies and copolymers thereof. Among these polymers, the polyester copolymer is particularly suitable in terms of good light transmittance and high melting point, and the polyamide copolymer is particularly suitable in terms of good light transmittance and hardness.

Examples of the solvent include methyl ethyl ketone, cyclohexanone, tetrahydrofuran, methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl ether, dioxane, ethyl acetate, n-butyl acetate, toluene, xylene, ethylbenzene, acetone, n-hexane, cyclohexane, chloroform, methyl. Cellulsolve, dimethylsulfoxide, acetonitrile, dimethylformamide, dimethylsulfoxide and the like can be mentioned.

The photochromic substance-binder-a method of preparing a solution or fine dispersion of a solvent, a method of dissolving a photochromic substance and a binder in a common solvent in which both can be dissolved, or while dissolving the photochromic substance in a dedicated solvent A method in which the binder is dissolved in another dedicated solvent, the both are mixed and finely dispersed in each other, and the like can be mentioned.

Examples of the support include plastic, metal, glass, ceramics, paper, and composite materials thereof, and the plastic includes polyester,
Examples thereof include polyamide, polyimide, polycarbonate, polymethylmethacrylate, vinyl chloride, polyacetal, polyethylene terephthalate, and cellulose acetate.

Examples of the method for applying the solution or fine dispersion to the support include brushing, rollers, spraying, dipping, spin coating, and flow coating.

Now, the modification method and the information recording method of the present invention for the above photochromic recording layer will be described in more detail.

(1) First, the unrecorded photochromic recording layer 90-
A method of heating at 150 ° C. for reforming will be described.

This modification method is not for developing the color of the photochromic recording layer by itself, but for improving the color developability when it is subsequently irradiated with ultraviolet rays.

The heating temperature varies depending on the type of photochromic recording layer, but in most types, the range of 90 to 150 ° C. is suitable. When the temperature is lower than 90 ° C, the coloring property described later is hardly improved as compared with the case where it is not heated, and when the temperature exceeds 150 ° C, the photochromic substance is oxidized and decomposed and deteriorated, or the requirement for the melting point of the binder becomes strict. is there. For example, in the recording layer using a spiropyran compound and a polyester copolymer, 100 to 13
0 ° C is preferred.

The heating time differs depending on the type of photochromic recording layer and the heating temperature. For example, in a recording layer using a spiropyran compound and a polyester copolymer, 60 to 180 seconds are suitable when the heating temperature is 100 ° C, and 10 to 60 seconds are suitable when the heating temperature is 130 ° C.

Further, as the heating means, a constant temperature bath, a hot air dryer, an infrared drying oven, etc. can be exemplified.

Now, the method for modifying the photochromic recording layer by this preheating has the effect of improving the color developability in multiple ways as follows.

(A) Change the hue when the photochromic recording layer develops color upon irradiation with ultraviolet rays.

For example, in a photochromic recording layer formed by using a solution of 1,3,3-trimethylindolino-6′-nitrobenzopyrrirospirane, a polyester copolymer and methyl ethyl ketone, the coloring hue upon irradiation with ultraviolet rays is It was red when it was not subjected to the modification method, but it was bluish purple when it was subjected to the modification method.

(B) The color density of the photochromic recording layer is increased.

For example, in the example given in (A) above, the color density upon irradiation with ultraviolet rays, etc. was low in the case where the modification method was not used, whereas in the case where the modification method was used, a visual sensory test was conducted. More than 50% thicker.

(C) Extends the coloring life of the photochromic recording layer.

For example, in the example given in (A) above, the color development life is extended by at least 20% or more under the same conditions after the modification method, as compared with the case where the modification method is not performed.

Although the details of the above-mentioned modification mechanism are unknown, it is considered that one of them is that the compatibility state between the photochromic substance and the binder is changed by heating, which affects the working relationship between the two.

This modification method is effective for most types of photochromic recording layers, but the degree of the effect depends on the types of photochromic recording layer and binder. It is also possible to carry out only the information recording method of the present invention described in detail below without going through this reforming method.

(2) Next, an information recording method for the photochromic recording layer that has or has not undergone the above-described modification method will be described in the order of steps.

First, information composed of characters and the like is printed by heating on the photochromic recording layer (heating printing step).

This heating and printing step is not for developing the color of the photochromic recording layer by itself, but it is for making the characters and the like clearly appear by strongly coloring the heating and printing portion at the time of irradiation with ultraviolet rays, which will be described later. It's just like a sketch in the beginning.

Examples of the method of heat printing include a method of using a known thermal printer to directly perform heat printing on the photochromic recording layer with the thermal head, or a method of scanning the photochromic recording layer with a heat beam.

It is suitable that the temperature of the heat printing is 90 to 150 ° C, preferably around 105 ° C. If the temperature is less than 90 ° C, the degree of improvement in color developability described below is less than that in the case where heat printing is not performed.
This is because when the temperature exceeds 150 ° C., the requirement for the melting point of the binder becomes strict.

This heating and printing step has the effect of multi-facetedly improving the color developability of characters and the like as follows.

(a) The color density of the heat-printed portion when the photochromic recording layer is colored by irradiation with ultraviolet rays or the like is increased so that characters and the like can be clearly highlighted without using a negative original image as in the past.

For example, in a photochromic recording layer formed by using a solution of 1,3,3-trimethylindolino-6'-nitrobenzopyrrilospirane, a polyester copolymer and methyl ethyl ketone, the heat-printed portion of the heat-printed portion when irradiated with ultraviolet rays or the like is used. The color-developed density is three times or more darker than that of the portion not printed by heating by a visual sensory test.

(b) The color development life of the heat-printed portion of the photochromic recording layer is extended.

For example, in the example given in (a) above, the color development life of the heat-printed portion after irradiation with ultraviolet rays or the like is 50 times or more longer under the same conditions as compared with the non-heat-printed portion.

(c) To improve the storage stability of the photochromic recording layer.

For example, in the example given in (a) above, when the photochromic recording layer after color development is further exposed to a source of ultraviolet rays such as the sun or a strong fluorescent lamp, the color not printed by heating becomes dark, Since the color of the part becomes darker,
The difference in brightness between the two is maintained as it is, and characters and the like can be easily read. Therefore, it is not necessary to pay attention to the preservation method of the photochromic recording layer as in the conventional case.

The details of the mechanism for improving the color developability are unknown, but it is considered that one of them is that the compatibility state between the photochromic substance and the binder is changed by heating, which affects the working relationship between the two.

Then, at least the heat-printed portion of the photochromic recording layer is irradiated with ultraviolet rays or the like to develop the information (coloring step).

Examples of the irradiation light source include a constant light source such as the sun and a mercury lamp, and a pulse light source such as a flash and a xenon discharge tube strobe.

As the irradiation method, it is general to irradiate the surface over the heat-printed portion and its surroundings to darkly color the characters and the like and lightly color the surroundings as described above, but adjust the light beam to the characters and the like. It is also possible to irradiate only the heat-printed portion by scanning by scanning so that only the characters and the like are deeply colored.

The irradiation light intensity and the irradiation time are preferably such that the characters and the like on the heat-printed portion are sufficiently darkly colored, while the surrounding color is not so darkly colored. The specific value varies depending on the type of photochromic recording layer and the irradiation light source, and will be exemplified in Examples described later.

When the information is no longer needed, the photochromic recording layer is heated to erase the information (erasing step).

The heating temperature is appropriately 50 to 150 ° C., preferably 6
It is 0 to 130 ° C. This is because if the temperature is lower than 50 ° C, the color cannot be erased or it takes too long, and if the temperature exceeds 150 ° C, the photochromic dye tends to be oxidized and decomposed to deteriorate.

The heating time differs depending on the type of the photochromic recording layer. For example, a photochromic layer formed by using a solution of the above 1,3,3-trimethylindolino-6'-nitrobenzopyrrirospirane, a polyester copolymer and methyl ethyl ketone. In the recording layer, 60 ℃ in a warm water bath
If heated to 3 to 10 minutes, hot air dryer to 130
When heating to ℃, about 10 to 60 seconds is appropriate.

As the heating means, a constant temperature bath, a hot air dryer, an infrared drying furnace, a hot water bath, etc. can be exemplified. In particular, the use of a warm water bath has the advantage that oxidative deterioration of the photochromic substance can be prevented.

By repeating the above steps, the information can be rewritten many times.

However, the coloring property of the photochromic recording layer gradually decreases due to this repetition.The maximum number of times that the photochromic recording layer can be used repeatedly varies depending on the type of the photochromic recording layer, the coloring and decoloring conditions, the storage method, etc. The coloring property of the photochromic recording layer is improved by the quality method and / or the heating printing step, and the characters and the like can be clearly read even if the printing is repeated more times than in the conventional example which does not go through these, and thus the substantial repetition is possible. The number of times it can be used can be increased.

[Examples] (Example 1A) 1,3,3-Trimethylindolino-6'-nitrobenzopyrrilospirane was dissolved in methyl ethyl ketone, and a polyester copolymer (manufactured by Toyobo Co., Ltd .: trade name Byron-200) was added. It was dissolved in methyl ethyl ketone and both were mixed to prepare a recording layer forming solution. 1,3,3-Trimethylindolino to polyester copolymer
The proportion of 6'-nitrobenzopyrrilospirane used is 5% by weight.

As shown in FIG. 1, this recording layer forming solution was applied to the surface of a polyester resin substrate 1 by a bar coater No. It was applied at 20 and air-dried to form a photochromic recording layer 2 having a thickness of about 10 μm, which was left for another 2 days to evaporate methyl ethyl ketone almost completely. The background color of the photochromic recording layer 2 was pale yellow.

Next, as shown in FIG. 2, the substrate 1 was placed in the hot air dryer 3 and the photochromic recording layer 2 was heated at 100 ° C. for 60 seconds to be reformed (reforming step).

Next, as shown in FIG. 3, the substrate 1 was set in a commercially available general thermal printer, and characters 5 and the like were directly printed on the photochromic recording layer 2 by the thermal head 4 set at about 100 ° C. (heating). Printing process). The heat-printed portion was physically slightly recessed by the pressing force of the thermal head 4, but color development and discoloration were extremely slight.

Next, as shown in FIG. 4, a commercially available EP-ROM is provided on the heat-printed portion of the photochromic recording layer 2 and its peripheral portion.
The eraser 6 was used to irradiate the surface with ultraviolet rays or the like (coloring step). The EP-ROM eraser 6 emits ultraviolet rays as intermittent pulses. The pulse emission interval is about 0.2 seconds, the irradiation time is about 2 seconds, and the amount of ultraviolet rays (wavelength 253).
7Å) was 1.2 W · sec / cm ² . As a result, the characters 5 and the like on the heat-printed portion of the photochromic layer developed a deep bluish purple color, and the surrounding portion 7 developed a light bluish purple color.
The difference in brightness between the two was high, and the character 5 was clear and could be easily read.

Substrate 1 with photochromic recording layer 2 that develops this color
Was stored by the following two methods (storing step).

I: When stored at room temperature in a dark place without being exposed to other light rays, the color of the peripheral portion 7 was almost completely erased in about 10 hours, but the color of the character 5 was erased very slowly. Even after 960 hours, it was still readable.

II; When the product was exposed to sunlight for 3 minutes after color development, the color of the surrounding part 7 changed to a more bluish color and became darker, but the color of the character 5 did not change and became darker, Almost the difference in brightness between the two was maintained, and the character 5 and the like could be easily read. After that, when it was stored at room temperature and in a dark place, the color of the peripheral portion 7 was slightly left after 960 hours or more, but the color of the character 5 was 960.
Even after a lapse of time, it was still clear and easy to read.

Then, as shown in FIG. 5, when the substrate 1 was immersed in a warm water bath 8 at 60 ° C. for about 5 minutes, the color development of the characters 5 and the like on the photochromic recording layer 2 was completely erased (erasing step).

After that, when the heating printing step, the coloring step, the storing step and the erasing step were repeated, the background color of the photochromic recording layer 2 gradually turned yellow and the coloring density and the coloring life were shortened. It was possible to use it repeatedly 15 times, and when the preservation method II was taken, it could be used repeatedly 10 times.

The test results are shown in Table 1.

(Example 1B) In Example 1B, the modification step of Example 1A was not performed, and the other heating printing step, coloring step, storage step and decoloring step were performed in the same manner as in Example 1. It is a thing. The test results are also shown in Table 1.

(Example 2A) This example 2A is different from the example 1A only in the type of the photochromic recording layer, and the modifying step, the coloring step, the storing step and the erasing step are the same as those of the example 1A. .

In this example, 1,3,3-trimethylindolino-6 '
-Nitrobenzopyrrilospirane was dissolved in methyl ethyl ketone, a polyamide copolymer (manufactured by BASF: trade name Ultramid 1C) was dissolved in ethyl alcohol, and both were mixed to prepare a fine dispersion for recording layer formation. 1,3,3-Trimethylindolino for polyamide copolymer
The proportion of 6'-nitrobenzopyrrilospirane used is 5% by weight. This fine dispersion for recording layer formation was applied to the surface of the substrate with a bar coater No. 20 and then naturally dried to form a photochromic recording layer having a thickness of about 10 μm.
Methyl ethyl ketone and ethyl alcohol were almost completely volatilized in the sun.

The test results of this Example 2A are also shown in Table 1.

(Example 2B) In Example 2B, the modification step of Example 2A was not performed, and the other heating and printing steps, the coloring step, the storing step and the erasing step were performed in the same manner as in Example 2A. It is a thing.
The test results are also shown in Table 1.

(Example 3A) In this Example 3A, only the type of the photochromic recording layer and the irradiation time of the ultraviolet rays in the color development step are used.
Different from A, the other modification process, color development process, storage process and decolorization process were performed in the same manner as in Example 1A.

In this example, 1,3,3-trimethylindolino-8 '
-Methoxybenzopyrrillospirane was dissolved in methyl ethyl ketone, a polyester copolymer (manufactured by Toyobo Co., Ltd .: trade name Byron-200) was dissolved in methyl ethyl ketone, and both were mixed to prepare a recording layer forming solution. The ratio of 1,3,3-trimethylindolino-8'-methoxybenzopyrrillospirane to the polyester copolymer is 2
It is 0% by weight. This recording layer forming solution was applied to the surface of the substrate by a bar coater No. The photochromic recording layer having a thickness of about 10 μm was formed by coating at 20 and air-drying, and the mixture was left for another 2 days to evaporate methyl ethyl ketone almost completely.

Further, since this photochromic recording layer has a lower UV sensitivity than that of Example 1A and the like, the irradiation time of UV in the coloring step was set to about 5 seconds.

The test results of Example 3A are also shown in Table 1.

(Example 3B) In this Example 3B, the modification step of Example 3A was not performed, and the other heating printing step, coloring step, storage step and decoloring step were performed in the same manner as in Example 3A. It is a thing.
The test results are also shown in Table 1.

(Comparative Examples 1 to 3) These Comparative Examples 1, 2 and 3 are Examples 1A, 2A and 3A, respectively.
Information is directly recorded by the conventional recording method on the same photochromic recording layer as the above, without performing the modification step and the heating printing step. That is, the unrecorded photochromic recording layer is irradiated with ultraviolet rays from the EP-ROM erasing device through a negative original image in which characters and the like are transparently removed and other portions are colored so as to prevent ultraviolet rays from passing therethrough. Colored. The subsequent storage step and decoloring step are the same as in Example 1A and the like.

The test results of Comparative Examples 1 to 3 are also shown in Table 1. As is clear from the table, in each of the examples, the color density is higher than that of the corresponding comparative example, and the color development life is long, so that the readable time of characters and the like is long, and the severe storage as in the preservation method II is performed. It turns out that they are strong against the law. Furthermore, most of these properties are similar to those of Examples 1A and 2 which have undergone the modification process.
Examples 1B and 2 in which A and 3A do not undergo the reforming process
It turns out that it is superior to B and 3B.

[Effects of the Invention] Since the present invention is configured as described above, it has the following excellent effects.

According to the method of modifying the photochromic recording layer of the first aspect, it is possible to increase the color-developing density of information and extend the color-developing life.

According to the method of recording information on the photochromic recording layer of claim 2, the color density of information can be increased, the color development life can be extended, and the storability after color development can be improved, and the existing thermal printer or the like can be used easily. It is possible to configure the information recording device.

[Brief description of drawings]

FIG. 1 is a perspective view showing a substrate with a photochromic recording layer used in an embodiment of the present invention, FIG. 2 is a perspective view of a modification process of the same embodiment, and FIG. 3 is a perspective view of a heating printing process,
FIG. 4 is a perspective view of the same coloring step, and FIG. 5 is a perspective view of the same erasing step. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Photochromic recording layer, 3 ... Hot air dryer, 4 ... Thermal head, 5 ... Letters, etc. 6 ... EP-ROM eraser, 7 ... Surrounding part.

Claims (2)

[Claims] 1. An unrecorded photochromic recording layer having a thickness of 90 to
A method for modifying a photochromic recording layer, which comprises heating to 150 ° C. 2. A step of heating and printing information on the photochromic recording layer, followed by a step of irradiating at least a heating and printing portion of the photochromic recording layer with ultraviolet rays or short wavelength visible light to develop the information, and thereafter, A method for recording information on a photochromic recording layer, comprising the step of heating the photochromic recording layer to erase the information.