JPS595249A - Transparent film for overhead projector - Google Patents

Abstract

PURPOSE:To obtain the entitled transparent film superior in copying aptitude and heat resistance, by coating one or both sides of a film with a specified photopolymerizable acrylic cation type water-soluble resin, and hardening it by irradiation of electron beams. CONSTITUTION:A coating soln. contains a photopolymerizable acrylic cation type water-soluble resin having quaternary ammonium salts added, such as glycidyl trimethy ammonium chloride; when needed, 1.0-5wt% nonpolymerizable water- soluble polymer, such as gelatin; 1.0-99.0wt% photopolymerizable water-soluble polymer, such as polyvinylpyrrolidone; and/or a photopolymerization initiator, and the total solids are dissolved in water-alcohol solvents in 1.0-30.0wt% of the total soln. One or both sides of a transparent film base 1 are coated with said coating soln. by the medium of an anchor coat agent 2 so as to amount to 0.5-5.0g/m<2>, dried at temp. up to 100 deg.C, and hardened by irradiation of UV rays or electron beams to obtain a resin layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transparent film for an overhead projector (hereinafter abbreviated as OHP) which has excellent copying suitability for electronic copying machines. The present invention relates to a transparent film for OHP which has not only copying suitability but also OHI suitability by providing a coating layer of a resin composition that can be cured by radiation.

Recently, OHPs have been widely used for lectures and educational purposes. The teaching materials used for OHP are semi-transparent or transparent base materials,
For example, handwritten or photocopied materials are used on transparent paper, film, etc., but from the perspective of the clarity of the projected image, it is preferable that the base material be as transparent as possible, and plastic films are generally preferred. . On the other hand, depending on the teaching material, there may be cases where it is desired to copy the content of a single character, such as a drawing, as is from a book, literature, document, or the like. This copying is usually carried out by an electronic copying machine such as a Xerox, and in the case of a plastic film base material, various troublesome problems arise during copying, unlike in the case of paper. That is, if the surface resistivity of the film is not within a suitable range, the transfer of the latent image from the medium will be inaccurate, making it impossible to faithfully reproduce the characters or Figure 1m. There is also a problem with the adhesion of the toner to the film after the toner is removed, and it is not practical if the toner peels off due to simple friction.

In addition, in the case of an electronic copying machine that heats and fuses toner, there is a problem in that the film surface becomes wavy and uneven due to the heat, and this imposes restrictions on the type and thickness of the film.

Furthermore, when a large number of films are stacked and stored in a tray and one film is continuously fed into the copying section, the film is not introduced into the one-sheet copying section, but two or six films are introduced at the same time. The so-called "double feed" problem is also likely to occur in the case of film.

In order to avoid various troubles such as these, it is essential to select the base film and treat the surface.
In the invention of No. 34, a plastic film with a heat-resistant temperature of 100°C or higher is used as the base material, and polyester resin,
A resin composition whose main component is an acrylic acid ester resin, a methacrylic acid ester resin, or a copolymer of a resin monomer such as these and styrene is coated. In addition, in order to adjust the surface resistivity of the coating layer of the resin composition to 109 to 1015 Ω, an antistatic agent is added to prevent the generation of static electricity, and at the same time, matt AIJ made of inorganic or organic fine particles is added. A method has been proposed in which double feeding is prevented by blending to reduce frictional resistance. Although this method is successful as a film surface modification technique, as a result of investigation, it was found that it still has a few critical deficiencies that make it unsuitable for use as an OHP film.

That is, first, after coating a film with a resin composition, when drying the film, waving occurs due to thermal deformation of the film. As the film becomes thinner, this tendency becomes particularly severe, resulting in not only a loss of commercial value but also an unsatisfactory practicality. Second, toner correctability may be poor.

Toner correctability is a property necessary to dissolve and remove toner once fused using a solvent-based correction fluid.

It is often necessary to erase parts of characters or drawings after copying, and this is a property that this type of film should definitely have.

Lastly, the writing quality is poor. Writability is a property that allows characters, lines, etc. to be written on the film after copying or correction, and is a desired property along with correctability. Writing may be done with oil-based ink such as marker ink, but water-based ink may also be used, and if possible, it is desirable to have the ability to write with both types of ink.

As is clear from the above description, the known OHP films have many drawbacks that should be improved, and it is difficult to call them a completed technology.

As a result of intensive research into the surface coating layer of transparent films used for OHP after electronic copying, the present inventors discovered that the main component is a photopolymerizable acrylic type water-soluble resin with a quaternary ammonium base added. A transparent film obtained by coating a transparent plastic film with a resin composition and then curing it by irradiating it with ultraviolet rays or electron beams to form a coating layer on one or both sides has good copyability with an electronic copying machine. Furthermore, he discovered that copies have excellent writing and correcting properties, leading to the invention of a completely new OHP film.

In the present invention, the advantages of the method of developing a -C radical polymerization or crosslinking reaction using ultraviolet rays or electron beams to form a coating layer are as follows.

That is, the conventional 01. (In contrast to the production method for P film, the ultraviolet or electron beam curing of the present invention enables low-temperature processing, completely prevents film deformation and shrinkage observed during heat drying, and provides excellent flatness without waving. Therefore, it is possible to use films with relatively low heat resistance, which could not be used with conventional heat drying methods, and the selection range of base films has been expanded, and it is also possible to use films with high heat resistance. Even thin films can be processed.

Furthermore, the six-dimensional cross-linked structure of the coating film cured with ultraviolet rays or electron beams has increased heat resistance, which protects the base film from the heat generated during toner fusing in the copying machine, and improves the flatness of the film. Effective for maintenance.

Next, the advantages of using a photopolymerizable acrylic cation type resin to which a quaternary ammonium base is added will be explained. As mentioned above, this resin is water-soluble and easily forms a crosslinked structure and cures by irradiation with ultraviolet rays or electron beams. Furthermore, a major feature of this resin is that by adjusting the amount of quaternary ammonium base added, the electrical conductivity of the resin, which is caused by the hydrophilicity and ionic conductivity of the coating layer, can be changed arbitrarily. The surface resistivity value of the coating layer mainly composed of resin is 1.0x10 to 1.0x10. [lxl[If it is set within the range of 1Ω, the transfer of the latent image from the medium by the electronic copying machine will be good, and it will not only be possible to obtain sufficient developability and density of the image after development, but also to prevent dust caused by static electricity. It is also possible to prevent adhesion. In addition, this resin can be made to have sufficient adhesion to profiteer films by using anchor coating or other suitable means, and is a (meth)acrylic acid ester resin commonly used as a binder for toner for electronic copying machines. Also, since it has good affinity with copolymer resins of styrene and styrene, the adhesion of the toner during heat fixing or wet fixing is good.

Furthermore, the coating film cured by ultraviolet rays or electron beams of this resin has excellent water resistance, heat resistance, and solvent resistance, and is compatible with oil-based inks,
It has sufficient writability with water-based ink and correctability of the writing portion with solvent or water, and of course also has rewriting ability of the corrected portion. The good writability of water-based inks is mainly due to the hydrophilicity resulting from the quaternary ammonium base.

The fact that writing properties are imparted to the surface coating layer in this way means that the film can be used simply through electronic copying. This also means that it is an OHP film that can be used by handwriting.

As the photopolymerizable acrylic cation type resin to which a quaternary ammonium base has been added according to the present invention, for example, quaternary ammonium salts such as glycidyltrimethylammonium chloride, chlorohydroxypropyltrimethylammonium chloride, chlorohydroxypropyltrihydroxyethylammonium chloride, etc. The acrylate resin is reacted with a photopolymerizable acrylic V monomer or comonomer, or oligomer such as aminoethyl (meth)acrylate or diethylaminoethyl (meth)acrylate, to add the acrylate resin in the form of a quaternary ammonium base tependant. Degenerate further if necessary.

Photopolymerizable water-soluble acrylates such as hydroxyethyl (meth)acrylate, ethylene glycol di(meth)acrylate, and acrylamide are also copolymerized or mixed.

The water-soluble polymer that can be blended into the photopolymerizable acrylic cation type water-soluble resin of the present invention includes photopolymerizable water-soluble nylon (for example, a water-sensitive polymer made of dimethylamino group-added nylon and a photopolymerizable unsaturated compound). Photopolymerizable special water-based oligomers such as polyamide resin (manufactured by Toshi Co., Ltd.), urethane type, urethane-acrylic type, acrylic copolymer (e.g., manufactured by PoIymerics Co., Ltd.), polyvinylpyrrolidone, or tertiary polymers. There are methacrylic acid ester mono Y-(dimethylaminoethyl methacrylate) having an amine group, hydroxyethyl (meth)acrylate, polyethylene glycol dimethacrylate, etc. Non-photopolymerizable CD water YJ povmers include:
Examples include water-soluble polyester, water-soluble polyamide, PVA, casein, gelatin, shellac, and CMC.

Since the resin coating film blended with these resins generally has a surface resistivity of 1o15Ω or more, by blending it with the acrylic cation resin of the present invention, the surface resistivity of the coating film can be adjusted to between 108 and 1o16Ω. The surface paperiness can be adjusted by making small adjustments as desired.

However, when blending non-photopolymerizable polymers,
If the amount is increased, the ultraviolet or electron beam curability deteriorates, and the strength, water resistance, toner adhesion, hydrophilicity, etc. of the cured coating film are impaired.

The blending amount is within the range of 1.0 to 50% by weight (based on the total resin number),
The optimum amount is desirably 5.0 to 20.0% by weight.

In addition, among the resins blended, resins such as casein and water-soluble nylon promote adhesion between the surface coating layer and the base film, simplifying the process by omitting anchor coating treatment etc. The effect is significant.

The photopolymerizable acrylic cationic resin of the present invention has antistatic properties and can be extremely effective in preventing double feeding and aligning films. The slipperiness can also be adjusted by blending to an extent that does not impair the transparency of the base film. Inorganic matting agents include silicon dioxide, calcium carbonate, talc, calcined alumina, and titanium dioxide.

There are kaolin, etc., and organic types such as polyethylene,
Examples include fine particles of polypropylene, polyester, polystyrene, polycarbonate, epoxy, and the like. These matting agents have a ratio of 0.01 to 10.
It is suitable to mix it in the range of 0% by weight.

Although the present invention has advantages in low-temperature processing during coating film formation and heat resistance of the coating film, it is preferable to use polyester, polysulfone, cellulose ester, polyamide, polyimide, etc. as a base film for dry type electronic copying machines. It is desirable to use a material with high heat resistance.

In the present invention, when forming a surface coating layer on a transparent film, all film pretreatments such as corona discharge treatment or anchor coating treatment are carried out as necessary. When using polyester film, which is the most common base film, as the anchor coating agent, polyvinylidene chloride resin, polyester resin, polyamide resin, casein, etc. are suitable, and it is about 0.5 to 1.5.9/n12. Sufficient adhesion can be obtained by coating.

In order to cure the photopolymerizable acrylic cation type resin to which the quaternary ammonium base of the present invention has been added by ultraviolet light, a water-alcohol solution containing a photoradical polymerization initiator and a sensitizer is used in a total solid content of Adjust the coating viscosity within the range of 1.0 to 30.0 = s, and coat the transparent base film with a coating viscosity of 0.5 to 30.0 s using the Mayer barcode method or knife coating method.
5.0g Ao2 (solid content) was applied and the solvent was heated at a relatively low temperature (
After drying and removing at <<too°C), a cured coating film is formed by test irradiation with ultraviolet rays. As a photo-radical polymerization initiator, 0.1 to 10.0% by weight of known initiators such as benzophenones, henzine ethers, I\rogenated acetophenones, and biacetyls (based on the acrylic cation resin).
.

Desirably, the amount is 2.0 to 5.0% by weight, and if necessary, 0.1 to 3.0% by weight of an amine type or ketone type sensitizer is added. When using the electron beam irradiation method, it is not necessary to add such photopolymerization initiators and sensitizers.

The resin composition forming the surface coating layer may further contain dyes, anti-aging agents, wetting improvers, etc., if necessary.

In the present invention, the resin coating layer is provided on one or both sides of the base film. Coating on one side is sufficient for the purpose of copying and projection on OHP, but it is difficult to identify the coated side.
It is a hassle to have to check the front and back sides when copying. In such cases, it is necessary to clearly identify the front and back sides by appropriate means such as marking or cutting the edges. Coating both sides will solve this problem.

The figure shows a cross section of the OH film according to the present invention, and Figure 1 shows an anchor coat layer on one side of the base film and a surface mainly composed of a photopolymerizable acrylic cation type resin to which a quaternary ammonium base is added. A cross-sectional view when a coating layer is provided. Figure 2 is a cross-sectional view when a similar anchor coat layer and a surface coating layer are provided on both sides of the base film. Figure 3 is a cross-sectional view when a similar anchor coat layer and surface coating layer are provided on both sides of the base film. This is a cross-sectional view of the case where a blended composition of a photopolymerizable acrylic cation type resin with a quaternary ammonium base added and an adhesion-imparting polymer is directly applied. Various other combinations are possible, but it would be complicated. Therefore, illustration is omitted.

It goes without saying that a transparent film having such a structure can be used not only for OHP purposes, but also as a second original image when, for example, a plurality of diazo copies are made.

Examples will be described below. Various tests in the examples were conducted as follows. The degree of curing of the coating film was determined from the water resistance of the coating film developed by irradiation with ultraviolet rays or electron beams.

That is, when a predetermined amount of water droplets were dropped on the coating layer and rubbed 100 times with bleached cotton, the coating layer was rated ○ if there was no change such as damage, and the coating layer was rated × if there was damage. The adhesion between the base film and the coating layer was 5 in a peel test using cellophane tape.
Evaluate on a graded basis, and 5. indicates good adhesion and no peeling at all. 3. Items that can be peeled off about half of the time. A sample that completely peeled off due to poor adhesion was rated 1. Transparency and haze were each measured using a Toyo Seiki Transparency Meter Model 162 (wavelength λ = 450 nm) S haze meter (JIS K 6717). The coefficient of friction was measured using a friction coefficient measuring device manufactured by Toyo Tester Co., Ltd., at a load of 1.0 kg, a sample speed of 150 mm, and 7%, and measured the static friction coefficient and dynamic friction coefficient between the coated surfaces. The surface resistivity of the coated surface was measured using a terra ohmmeter R- manufactured by Kawaguchi Electric Co., Ltd.
Measurement was performed using Model 503 at a temperature of 20° C. and a humidity of 65% RH. In the attachment test for evaluating chargeability, the coated surface was rubbed with dry bleached cotton 10 times, and then placed at a height of 10 mm from cigarette ash. If the ash did not adhere, it was rated ○, and if it did, it was rated x. Copy density and wax transferability were tested using an actual electronic copying machine, and good results were evaluated as ○,
Defective items were also marked as ×.

Poor runnability means occurrence of double feeding and poor alignment on the storage tray. Toner adhesion was determined by cellophane tape.
I11# Test: The toner correctability was determined by an erasing test using a correction liquid (a mixture of cellosolve acetate 40 fa/x cellosolve 60). Good results were evaluated as ○, and poor results were evaluated as poor. Writing is also done with magic ink,
Perform a writing test with water-based ink and mark the one that is good as ○.
Bad items were marked as ×.

In the examples, all amounts shown are parts by weight.

Example 1 A polyester film (with a thickness of 10,100p as the base material,
Polyvinylidene chloride resin: Fullhalon 5OA (manufactured by Kureha Chemical Co., Ltd.) was coated using the Niemeyer bar coating method so that the coating amount was 1.0gA♂, and an anchor coat treatment was performed on this film. Acrylic cation type 11N resin A (Mitsubishi Yuka Co., Ltd.) to which an ammonium base has been added and polyvinorure to the resin.

A 10% by weight water-alcohol solution of a photopolymerizable resin composition containing alcohol (PVA) After drying at a temperature of 90°C for 2 minutes, the resin was cured by irradiating it with ultraviolet rays at a conveyor speed of 10 m/min using an ultraviolet irradiation device (Unicure-4000 manufactured by Ushio Inc., 160'/cm standard lamp). An OHP film with a coating weight of 1 and 5'An of 2 was produced.

(2J P
VA-117 (produced 1010% aqueous solution manufactured by Kura L' Co., Ltd.)
3) Chlorinated acetophenone (Sandoz, photopolymerization initiator)
Prepare a 10% methanol solution (4) Prepare a 10% methanol solution using fine silica powder (manufactured by Mizusawa Chemical Co., Ltd.). I tested it from different angles and got the results shown in Table 2.

As is clear from Table 2, sample numbers 4 and 5, in which the PVA content was 60 parts or 80 m, had appropriate surface resistivity and good copy density, but the curability with ultraviolet rays decreased and the cured coating film The water resistance was poor, and the adhesion of the toner was also reduced. When the amount of PVA is 40 parts or less, both water resistance and toner adhesion are good, and film running properties in copying machines, toner correctability, oiliness, writing properties of water-based inks, and other properties are improved.
All in all, I was satisfied.

The comparative example (sample number 6) in the right column of Table 2 is a conventional type OHP film with a surface coating consisting of a thermosetting acrylic resin as a main component and containing an antistatic agent and a matting agent. It had various properties necessary for copying, and had good toner correctability and good writing properties with oil-based inks, but had no writing properties with water-based inks.

On the other hand, when other commercially available OHP films were tested, it was found that the toner correctability was poor, and the surface coating was eroded by the correction fluid, and when writing with marker ink, the surface coating was immersed in the ink solvent, making it difficult to write. The effect was impaired. Of course, water-based ink □□□□-1" Example 2 Instead of PVA in Example 1, photosensitive water-soluble nylon (photosensitive nylon 6° modified with dimethylamino group, manufactured by Toshi Co., Ltd.)
was blended. Resin compositions in Table 6 (NO.

A 10% by weight water-alcohol solution of 7 to NO, 9) was prepared, and an untreated polyester film (100 μml was coated with Mayer barcode so that the coating amount was 1.5.9/rr12) as in Example 1. A cured coating film was formed by irradiating ultraviolet rays under the same conditions.

Table 6 Made by r8 tff Table 4 shows the physical properties of the obtained coated film.

As shown in Table 4, Sample No. 7, in which photopolymerizable acrylic cationic resin A alone was coated on an untreated film, had poor adhesion between the surface layer and the base film and was unusable. This defect was improved by adding 5 to 10 parts of water-soluble nylon, and sample numbers 8 and 9 had good copyability on Xerox 3207 (dry type), no double feeding trouble, good single image density, and toner The OHP film had excellent adhesion and good writing properties with oil-based and water-based inks.

Downstream margin Table 4 Example 3 As is clear from the results in Table 6 that the amount of quaternary ammonium base added is lower than that of the acrylic cationic IL resin A used in Example 1, the film was subjected to corona discharge treatment. Even if acrylic cationic resin B is used alone (sample no. 10), the one in which 5 parts of casein is added (sample no. 11) has poor adhesion between the coating layer and the film, and is therefore impractical. Contains 10 to 30 parts of casein (
Sample numbers 12 to 14) had sufficient adhesion, clearly demonstrating the effect of the casein formulation. However, even if 200 parts of casein were distributed as in Sample No. 15, if the corona treatment of the film was omitted, the adhesion was poor, indicating that corona treatment is an essential condition.

Further, when the amount of casein added is 30 parts, a problem arises in the adhesion of the toner as shown in sample number 14.

Therefore, when blending casein, it is important to keep the blending amount within the range of 10 to 20 parts, and to subject the base film to corona treatment.The OHP films obtained in this way (sample numbers 12 and 13) are extremely excellent. It showed good copying aptitude and 0HPJ property.

Male side 4 Water of acrylic cation type resin in which the quaternary ammonium base of Example 6 was added to a polyester film (100IIm) anchor-coated on both sides with polyvinylidene chloride resin (Kurehalon SOA manufactured by Kureha Chemical Co., Ltd.) Ituburobanol solution (solid content 60%, manufactured by Mitsubishi Yuka Co., Ltd.) 33
A resin composition consisting of 6 parts (solid equivalent: 100 parts), 0.5 parts of Mizuka Seal, 10,005 m of Sunray, and an appropriate amount of methanol was applied to two 1.5 l linings and cured with UV rays to provide a surface coating layer on both sides of the film. An OHP film was produced (sample number 16).

When this film was used for copying with a Xerox 3207 (dry type) and a Copier LD11 (wet type), there was no double feeding trouble, and both image density and toner adhesion were good. Furthermore, this film has excellent toner correction and writing properties, and since it is coated on both sides, there is no need to worry about confusing the front and back sides, and it can be used for both dry and wet OHP.
Example 5 The resin composition of Example 4 except for the photopolymerization initiator Sunray 1000 was applied to a polyester film (100 μm) which had been anchor-coated in advance to give a coating weight of 1.511/, ♂. After coating by the Mayer bar method and drying (80°C, 2 minutes), it was coated with an electron beam irradiation device (CB-150, manufactured by Energy Sciences) at an irradiation speed of 30 m/min at an irradiation rate of 5 Mrad in an oxygen-substituted atmosphere with N2. Electron beam irradiation was performed. The coating layer showed good curability.

One case of water resistance, good adhesion to the base film, and one surface specific resistance value was 5.5 x 1012Ω.

When I copied this film using a Xerox 3207, the image density was sufficient, the toner correctability, solvent-based ink and water-based ink marking properties were good, and the OH film did not attract dust.
A film for P was obtained.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a film for 001) in which an anchor coat layer is provided on one side of the film and an ultraviolet curable resin composition is coated thereon, and Figure 2 is an anchor coat Al and an ultraviolet curable resin on both sides of the film. FIG. 6 shows a cross-sectional view of an OHP film in which a coating layer of an ultraviolet curable resin composition is directly provided on one side of an untreated film. In the figure, 1 is a base film, and 2 is an anchor coat layer. 3 indicates an ultraviolet curing resin layer. Figure 1 Figure 2 Figure 3 Procedural amendment July 23, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office 1. Patent application for indication of the case No. 113993/1982 2. Name of the invention Transparent film for overhead projector 6. Relationship with the case of the person making the amendment Patent applicant address 1-4-5 Marunouchi, Chiyoda-ku, Tokyo Name (23
4) Sanyo Kokusaku Pulp Co., Ltd. President Osamu Nasu 4, Agent 100 Address 23 Eiraku Building, 1-4-5 Marunouchi, Chiyoda-ku, Tokyo
Room 4Telephone: 214-2861■6. Column Z for detailed explanation of the invention in the specification subject to amendment.Contents of amendmentThe following points in the specification will be amended. (1) In the 7th line from the bottom of page 19, the text "isopanol" will be corrected to "isopropatool." (2) On the 4th line from the bottom of page 25, "Isopanol" will be corrected to "Impropa Tool." (3) The text "(Document number 16)" on page 28, lines 11-12 will be deleted. Procedural amendment dated October 22, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1, Special application for indication of the case No. 113993/1982 2, Title of invention Transparent film for overhead projector 6, Person making the amendment Related Patent Applicant Address 1-4-5 Marunouchi, Chiyoda-ku, Tokyo Name (2)
34) Nasu, President and Director of Sanyo Kokusaku Pulp Co., Ltd.
Tadaki 4, Agent 100 Address: 1-4-56 Marunouchi, Chiyoda-ku, Tokyo, I am correcting the point in the middle of the detailed description of the invention in the specification subject to amendment, iE. . (1) On page 19, line 20, the phrase [-preparation of all solutions] will be corrected to [preparation of dispersion liquid].

Claims (1)

[Scope of Claims] 1. A transparent film for an overhead projector, in which a photopolymerizable acrylic cation type water-soluble resin to which a quaternary ammonium base has been added is coated on one or both sides of the film and cured with an electron beam. 2. Claim 1, in which 1.0 to 50% by weight of a non-photopolymerizable water-soluble polymer is blended with the photopolymerizable acrylic cationic water-soluble resin to which a quaternary ammonium base has been added, based on the total amount of the resin. Transparent film for overhead projector as described in Section 1. 3. Claim No. 3, in which a photopolymerizable water-soluble polymer is blended in a photopolymerizable cationic water-soluble resin to which a quaternary ammonium base has been added in an amount of 1.0 to 99.0% by weight based on the total resin amount. The transparent film for overhead projector according to item 1. 4 A photopolymerizable acrylic cation type water-soluble resin to which a quaternary ammonium base has been added and a photopolymerization initiator added is coated on one or both sides of the film and cured by ultraviolet 7 rays. Transparent film for overhead projectors. 5 A non-photopolymerizable water-soluble poly-
5. The transparent film for an overhead projector according to claim 4, wherein 1.0 to 50% by weight of the total resin is blended. 6. Claim No. 6, wherein the photopolymerizable water-soluble polymer is blended in the photopolymerizable acrylic cation type water-soluble resin to which a quaternary ammonium base has been added in an amount of 1.0 to 99.0% by weight based on the total resin amount. The transparent film for overhead projector according to item 4.