JPH01160689A - Ohp film - Google Patents

Abstract

PURPOSE:To obtain a satisfactory image with a sufficient contrast even it if transferred on an OHP film in a sublimating-migration type transfer method, by providing dyeing resin layers to be subjected to the transfer of a sublimating dye from a thermal transfer recording sheet on the both surfaces of a transparent plastic film. CONSTITUTION:An OHP film has a three layer construction wherein dyeing resin layers (a), (a') to be subjected to the transfer of a sublimating dye are provided on the both surfaces of a substrate film (b). Then, the dyeing resin layers (a) and (a') are provided on the both surfaces of the transparent plastic substrate (b), whereby a printing is carried out separately on the both surfaces. Therefore, an image with a remarkably high color density and a high contrast can be obtained on the OHP film without the occurrence of reverse-sublimation.

Description

[Detailed description of the invention] [Industrial application field] The present invention is an OHP (overhead projector)
More specifically, it is an OHP film for performing color recording by overlaying a thermal transfer recording sheet having a coloring material layer made of a sublimable dye and transferring the sublimable dye from the thermal transfer recording sheet by heating with a thermal head or the like. The object of the present invention is to provide an OHP film suitable for obtaining particularly good color density.

[Conventional technology]

In recent years, with the spread of personal computers, televisions, VTRs, video disks, etc. as information terminals and the use of color displays, there has been an increasing demand for printers that output these still images as color images. The recording method for this color printer is electrophotography,
There are inkjet methods, thermal transfer methods, etc., but the thermal transfer method is often used because it is noiseless and easy to maintain. This thermal transfer method uses a thermal transfer recording sheet in which pigments or dyes are bound with heat-melting wax, and a method that applies conventional sublimation transfer printing technology, using disperse dyes that are relatively easy to sublimate as a binder. There is a sublimation transfer type that uses a thermal transfer recording sheet bound with resin.

Thermal melt transfer type transfers pigments or dyes to the image receptor along with wax melted by thermal energy from a thermal head, etc., so it is difficult to obtain the necessary halftones for image quality, and it is difficult to obtain good hue due to the transferred wax. The disadvantage is that it is difficult to On the other hand, with the sublimation transfer type, only the sublimable dye is sublimated and transferred by the thermal energy of a thermal head, etc., and excellent hues and intermediate tones can be easily obtained because the sublimable dye sublimes in response to the thermal energy. , and has the advantage of being able to control the gradation at will, making it the most suitable method for full-color printers.As an image-receiving paper for this sublimation transfer type thermal transfer method, Japanese Patent Laid-Open No. 15446/1983 describes As mentioned above, just as it is possible to use plain paper, it is basically possible to use various transparent plastic films as OHP films, but plastic films alone do not have sufficient color. It is not possible to obtain a high density, and due to the poor fixability of the sublimable dye, the color fading phenomenon over time is also significant. For this reason, a dyeing resin layer made of a thermoplastic resin that can be effectively dyed with sublimable dyes such as saturated polyester resin, polyamide resin, and epoxy resin is generally provided on one side of the plastic film.

However, since the sublimation transfer type thermal transfer method uses a sublimable dye as a coloring material, it lacks hiding properties compared to a heat melt transfer type using pigments, and it is difficult to obtain sufficient contrast when enlarged and projected by OHP.

Furthermore, even if the energization time in the thermal head is increased, the sublimable dye will reach an equilibrium state between the ink layer on the thermal transfer recording sheet and the dyed resin layer on the OHP film, and will transfer reversibly.
It is generally difficult to increase the absolute amount of sublimable dyes on OHP films, so color density cannot be obtained and O
When enlarged and projected using HP, the image is generally pale and it is difficult to obtain sufficient color density. In addition, increasing the dye ratio in the ink layer on the thermal transfer recording sheet may be considered as a means to obtain sufficient color density on the OHP film, but increasing the dye ratio reduces the adhesion of the ink layer to the substrate. However, not only abnormal transcription occurs, but also storage stability is extremely reduced. Therefore, the problem of not being able to sufficiently increase the dye ratio and obtaining sufficient color density on the OHP film remains unsolved.

[Problems to be Solved by the Invention] The problems to be solved by the present invention are to overcome the drawbacks of the above-mentioned prior art, namely, that sufficient color density cannot be obtained in this type of OHP film. More specifically, it is an object of the present invention to provide an OHP film that has sufficient contrast and can produce good images even when transferred by OHP using a sublimation transfer type transfer method.

[Means for solving problems]

This problem is solved by transferring the dyed resin layer to both the front and back sides of a transparent plastic sheet, which selectively transfers the dye by heating with a thermal head etc. This can be solved by providing

[Function and structure of the invention]

As shown in FIG. 1, which is a cross-sectional view, the OHP film of the present invention has a 3N structure in which the dyeing resin layer (a) is provided on both the front and back surfaces of the base film (b). In this point, it is clearly distinguished from the conventional one in which the dyed resin layer (a) is simply provided on one side of the base film (b) shown in the cross-sectional view.

As explained above, with the conventional OHP film shown in Figure 2, sufficient color density and contrast cannot be obtained, and even if the dye ratio in the ink layer is increased to avoid this, abnormal transfer and This causes problems in storage stability. Furthermore, in order to obtain sufficient color density, even if printing is done twice on conventional OHP film, in this case the sublimable dye transferred in the first printing will be transferred to the thermal transfer recording system in the second printing. , - to the ink layer and desublimation), making it difficult to achieve the desired purpose.

On the other hand, in the OHP film of the present invention shown in FIG. 1, dyeing resin layers (a) and (a') are provided on both the front and back sides of a transparent plastic base material (b), and printing is performed separately on the front and back sides. Therefore, no desublimation occurs, and an image with extremely high color density and strong contrast can be obtained on the OHP film.

To explain the OHP film of the present invention in more detail, the OHP film of the present invention is first printed on the dyeing resin layer (a) on the front side, and then printed on the dyeing resin layer (ao) on the back side (a). The color density can be increased by printing a mirror image of the image. For this reason, it is particularly desirable to provide a detection marker that can optically detect the position so that no deviation occurs between the image on (a) and the image on (a'').The detection marker should not affect the image. It may be provided on any of the frames that do not have a frame, for example - as an example in FIG.
Figure 4 can be shown. However, in FIGS. 3 and 4, (C) shows the frame portion, and (d) shows the detection marker. The detection marker is provided to identify the OHP film, which is almost colorless and transparent, making it difficult to optically distinguish it from the color of the lining, making it difficult to cue accurately. In the present invention, any color may be used as long as it has the function of being optically distinguishable from the color of the lining. Examples include applying an ink liquid containing a pigment or pasting an adhesive tape with concealment properties.

As the dyeing resin N (a) (a'') used in the present invention, various thermoplastic resins having dyeability to sublimable dyes can be used, such as polyester resin. Some of these dyeing resins are heat-cured or
Alternatively, it may be photocured, and if necessary, a removable material such as silicone resin may be provided. The thickness of the dyeing resin layer may be any conventional thickness, for example 2 μm.
~30 μm is sufficient.

Next, as the base film (b) used in the present invention, any transparent plastic film can be used, but a polyester film having excellent heat resistance, transparency, and surface smoothness is particularly preferred. The thickness of these base films (b) is preferably 15 μm to 2.08 m1, particularly preferably 2.0 μm to 2.08 m1.
If the base film is 15 μm or less, handling becomes a national problem, and if the base film is 200 μm or less,
m or more, resulting in high costs.

When forming the dyed resin layer (a) of the present invention on the base film (b), the resin is dissolved or dispersed in a suitable organic solvent and coated with a suitable coating method using a reverse coater, kiss coater, fountain coater, etc. The base film (b
) is coated on both sides and dried. Furthermore, if the dyeable resin (with) is thermoplastic, it may be extruded and coated without a solvent.

The thermal transfer recording sheet used in the present invention is made by dispersing or dissolving a sublimable dye together with an appropriate binder and coating it on a substrate such as a polyester film or condenser paper. The above-mentioned sublimable dyes are widely used as long as they sublimate and migrate when heated.

〔Example〕

The present invention will be explained in more detail with reference to Examples below. However, parts indicate parts by weight.

(Example 1) Sublimable disperse dye (Kayacera) B-136: Nippon Kayakutan)
An ink liquid consisting of 10 parts of polyamide, 15 parts of toluene, and 60 parts of isopropyl alcohol was dispersed in a ball mill for 48 hours to prepare an ink liquid. This was coated on a 6μm polyester film with a silicone resin coated on the back side with a thickness of 0°2μm using a bar coater to a dry coating amount of 2g/2μm.
A thermal transfer recording sheet was prepared by coating and drying so as to obtain rd.

On the other hand, a dyeing resin solution consisting of 20 parts of saturated linear polyester resin and 80 parts of methyl ethyl ketone was applied onto a 100μ transparent polyester film at a dry coating amount of 5 g/rrf, and after drying, an ultraviolet curable silicone resin was applied. A 1% hexane solution of was applied onto the above polyester resin using a bar coater so that the dry coating amount was 1.5 g/rrr, and after drying, it was coated with a high pressure mercury lamp (80W) for 30 minutes.
It was irradiated for 00 seconds to cure and form a dyed resin layer. Further, a dyed resin layer was similarly provided on the back side of the polyester film. At this time, the coating was applied so as to provide a border as shown in FIG. A piece of high-quality paper was attached to this border using double-sided tape to serve as a detection marker, and an OHP-like film of the present invention was prepared.

Using the thus prepared thermal transfer recording sheet and OHP film, a gradation pattern was printed with a printer under thermal head recording conditions of 6 dots/mm and an applied power of 0.4 W/dot, varying the pulse width, and then printed on the back side. When a mirror image was printed under the same conditions, the color density shown in FIG. 5(a) was obtained. However, this measurement depended on the following method.

1 fixed vertical wide thermal head recording conditions: 6 dots/mm, applied power: 0.
4 The OHP film printed with a gradation pattern by changing the applied pulse width at W/dot was placed on a standard white plate (D =
0.05), and the reflection density at each tone was measured using a color reflection densitometer (Cosar 61J).

(Comparative number of layers) In Example 1, an OHP film was prepared by providing a dyeing resin layer only on one side of a 100 μm polyester film, and similarly printed using a printer, as shown in Figure 5 (b).
The color density shown was obtained.

(Comparative Example 2) When the print obtained in Comparative Example 1 was similarly printed using a printer, the color density shown in FIG. 5(C) was obtained.

[Effects of the Invention] As explained in detail above, the OHP film of the present invention enables printing on both sides of the OHP film, and provides sufficient color density and contrast even when enlarged and projected using an overhead projector. This is extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an OHP film of the present invention, and FIG. 2 is a sectional view of a conventional OHP film. Further, FIGS. 3 and 4 are both examples of plan views showing the positions of detection markers in the present invention. FIG. 5 is a graph showing the relationship between pulse duration and reflection density of a pattern-printed DHP film. (a) (a')...Dyeing resin layer (b)...
・・・・・・・・・Base film (C)・・・・・・・・・
...Edging part (d) ......Detection marker (more than) Pulse width (msec)

Claims (2)

[Claims] (1) An OHP film characterized in that a dyed resin layer that undergoes transfer of sublimable dye from a thermal transfer recording sheet is provided on both the front and back sides of a transparent plastic film. (2) The OHP film according to claim 1, wherein an optical detection marker is provided in at least one portion of the border portion where the dye is not transferred.