JPH03261941A - Photosensitive sheet - Google Patents

Abstract

PURPOSE:To obtain the photosensitive sheet for which reversible color changes by light are utilized and which is repetitively reusable by incorporating a specific diaryl ethene photochromic compd. into this sheet. CONSTITUTION:This photosensitive sheet contains the diaryl ethene photochromic compd. expressed by formula I. In the formula I, (n) denotes 2 to 5 integer; A<1>, A<2> denote formula II, etc. In the formula II, R<1> denotes an alkyl group, fluorine substd. alkyl group, etc.; R<2>, R<5> denote a hydrogen atom, fluorine atom, etc.; A<1> and A<2> may be the same or different. Since this photosensitive material is repetitively reusable in this way, resources are saved or the burden of a waste treatment is decreased. The characters and figures copied in specific environment disappear of themselves. The photosensitive sheet helpful for preservation of secrecy is thus obtd.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a photosensitive sheet that can be used repeatedly, and more specifically, it relates to a photosensitive sheet that can be used repeatedly by utilizing the reversible color change of photochromic compounds caused by light. This relates to photosensitive sheets that can be produced.

(Prior Art) Conventionally, copying machines capable of copying characters and figures using light, such as so-called blue copies using diazonium salts or electrophotographic copying machines using electrostatic transfer, have been widely used.

In particular, electrophotographic copying machines can make copies very easily, so people tend to make large quantities of copies, even if they are only temporarily needed. However, since the copy paper cannot be reused in conventional copying machines, a large amount of copy paper is discarded as paper waste.

The destruction of nature due to wasteful use of valve resources and the increase in the incineration of paper waste have become serious problems, and improvements are desired.

In addition, the large number of copies makes it difficult to maintain confidentiality, and secrets are frequently leaked due to accidental forgetting or dropping, so effective countermeasures are required.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and its purpose is to save resources or reduce the burden of disposal because it can be reused repeatedly. Another object of the present invention is to provide a photosensitive sheet in which characters and figures copied under certain circumstances naturally disappear, thereby helping to maintain confidentiality.

(Means for Solving the Problems) The above object is achieved by formula (1) % formula % [where n represents an integer from 2 to 5]. AI, AI 1
This can be achieved by a photosensitive sheet containing a diarylethene-based tochromic compound represented by:

Next, the present invention will be explained in detail.

The diarylethene-based photochromic compound used in the present invention can be obtained by the method described in the patent application filed and pending by the inventors of the present application. And the above-
In formula (1), Ht and R4 are an alkyl group, a fluorine-substituted alkyl group, an aryl group, a cyano group, and an alkoxy group, but especially a lower alkyl group having 1 to 3 carbon atoms, a trifluoromethyl group, a cyano group, and a methoxy group. The group is preferable because it has good photochromic properties.

R1I RI and RI to R8 each represent a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an aryl group, an acyl group, a cyano group, or an alkoxy group, which may be appropriately selected in consideration of the hue of characters and figures.

The diarylethene-based photochromic compound used in the present invention is, for example, in the case of 1,2-bis(2゜4,5-trimethyl-3-thienyl)i3,4゜4.5.5-hexafluorocyclopentene: As shown in formula (2) below, when irradiated with ultraviolet light, it assumes a cyclic structure and changes from colorless to deep yellow. Next, when the colored material is irradiated with visible light, it returns to its original colorless closed-ring form.

The photosensitive sheet of the present invention is made of paper or a plastic sheet such as polyethylene, polyvinyl chloride, polyethylene terephthalate, cellulose acetate, etc., and the photochromic compound can be incorporated into these sheets by methods such as coating, impregnation, and kneading.

To make a copy, all you need is a light source that can irradiate appropriate ultraviolet or visible light. For example, if you overlap an original written on a transparent film with the photosensitive sheet of the present invention and irradiate ultraviolet light from the original side, the original can be irradiated with ultraviolet light or visible light. The photochromic compound in the photosensitive sheet corresponding to the self-other parts is colored, and a blank copy is obtained. Conversely, if you use a photosensitive sheet whose entire surface has been previously colored with ultraviolet light, overlap it with the original, and irradiate it with visible light, a copy with colored characters and figures can be obtained. Furthermore, if reflected light is utilized like an electrophotographic copying machine, it is possible to use opaque originals.

The characters and graphics copied onto the photosensitive sheet of the present invention will not disappear for a long time under light-shielding conditions, but will gradually fade under indoor light or sunlight, and the characters and graphics will normally disappear completely within several tens of minutes to several hours. disappears.

Therefore, even if you forget or drop it, your secrets will not be leaked.

The fading time depends on the intensity of visible light hitting the photosensitive sheet, but if a polymeric binder, scattering particles, etc. are used,
It is also possible to extend the length by about twice as long.

In addition, the photosensitive sheet that has returned to its original colorless state can be used again and can be copied several hundred times or several times, which saves storage space for documents and eliminates wasteful resource consumption and disposal. You don't have to do it.

(Effects of the Invention) As described above, the photosensitive sheet of the present invention can be used repeatedly many times, helping to save resources and reduce waste disposal. Since it can be stored away, it is also useful for maintaining confidentiality.

Next, the present invention will be specifically explained using examples, but the present invention is not limited to these examples.

Example 1 Diarylethene-based photochromic compound shown below 1.2-bis(2-methylbenzothienyl)-5゜3.
4.4.5.1 g of 5-hexafluorocyclopentene and 10 g of polyvinyl acetate were dissolved in 600 ml of ethyl acetate. PPC paper was immersed in this solution, squeezed with Marguru, and then dried.

Draw letters and figures on OHP transparent film with an oil-based pen, use it as base paper, layer it with the photosensitive sheet mentioned above, and heat it with a 500W high pressure mercury lamp (
When the photochromic compound was irradiated with ultraviolet light for 5 seconds using a UV light source (manufactured by Jitsunesha), the photochromic compound was colored red, and white letters and figures could be copied on a red background. Three copies were made in the same manner, one in a photosensitive paper storage bag, one indoors under a normal fluorescent light, and the remaining one outdoors in the sunlight on a clear day.

After two minutes of exposing the photosensitive sheet to sunlight, the entire surface turned pale pink and the text and drawings became illegible. Also, when the paper was left under a fluorescent light, the entire surface became colorless and unreadable after 50 minutes. On the other hand, the items placed in photosensitive paper storage bags remained unchanged even after a month, with clear letters and drawings remaining.

Example 2 Diarylethene-based photochromic compound shown below -1,2-bis(2,
4-dimethyl-5-cya-3-thienyl)-5,5
,4,4,5,5-hexafluorocyclopentene 1'
and 2 aag of cellulose acetate in 1! ! A photosensitive sheet with a thickness of 6 G am was prepared by dissolving the mixture in tetrahydrofuran and casting.

When three of these photosensitive sheets were irradiated with ultraviolet light using the high-pressure mercury lamp used in Example 1, the entire surface was colored blue.

Layer this blue photosensitive sheet over the base paper used in Example 1.
500W photoreflector lamp (manufactured by iK Shiba)
When irradiated for a second, the pond part of the base paper became colorless, leaving behind blue letters and figures.

As in Example 1, it was left outdoors, indoors, and in a photosensitive paper storage bag.

After about 5 minutes under sunlight outside the layer, the entire surface became almost colorless, and the letters and figures disappeared. Also, the items placed indoors are 4
After 0 minutes, it became colorless and the letters and figures became illegible.

On the other hand, the samples placed in photosensitive paper storage bags remained clearly readable even after one month had passed.

Claims (1)

[Claims] General formula (1) ▲There are numerical formulas, chemical formulas, tables, etc.▼... (1) [In the formula, n represents an integer from 2 to 5. A^1 and A^2 represent ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and R^1 and R^4 are alkyl groups, fluorine-substituted alkyl groups, and aryl groups. , represents a cyano group, or an alkoxy group, and R^2, R^3, R^5 to R^6 represent a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an aryl group, an acyl group, or a cyano alkoxy group. represent. Also, A^
1 and A^2 may be the same or different. ] A photosensitive sheet containing a diarylethene-based photochromic compound represented by the following.