JPH0466197B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an overhead projector (hereinafter referred to as OHP) sheet that can be used in a thermal transfer printer to obtain clear print quality. be. (Prior art) The heat melt transfer method, which is one of the heat transfer recording methods, involves superimposing an ink ribbon having a heat melt ink layer on a recording material, and heating patterns such as letters and figures from above the ink ribbon. This method involves heating the ink ribbon in a pattern and attempting to transfer the hot-melt ink from the ink ribbon onto the recording material. On the other hand, the characters, figures, etc. on the sheet are projected onto the screen by transmitting light through the created sheet.
In OHP, the above-mentioned hot-melt ink transfer method is used to create sheets. In this case, conventional recording materials that become OHP sheets include transparent films coated with rubber adhesive layers or acrylic adhesive layers, or coated layers containing solid solders that are highly compatible with hot melt ink (especially 1986-
No. 154096) etc. have been used and proposed. (Problems to be Solved by the Invention) On the other hand, there are two types of thermal transfer printers: serial type and line type, but line type is superior in printing speed. To obtain a full color image using this line type color thermal transfer printer, it takes 1
A drum type, a swing type, a multi-head type, etc. are used, which use an ink ribbon to which ink materials of multiple colors are sequentially applied along the longitudinal direction of one screen. In order to print colored inks on the same recording material, the recording material needs to reciprocate three to four times between the thermal head and the platen or rotating drum. However, when the OHP sheet described above is moved back and forth between the thermal head and the platen or rotating drum multiple times for thermal transfer, a large amount of static electricity is generated on the surface of the OHP sheet, and this static electricity causes the ink ribbon to The drawback is that the ink material such as wax ink applied to the OHP sheet is transferred to the printing surface of the OHP sheet more than necessary, making it impossible to obtain a clear image. Also, since belts, rollers, etc. are used to move the recording material back and forth in the printer, the back side of the recording material comes into contact with the belt, rollers, and other parts when the recording material moves back and forth. In this case, OHP made of transparent film is used as recording material.
When using sheets, feed scratches occur especially on the back of the OHP sheet while driving, causing overhead and
When using a projector to project the image, it has the disadvantage that it is projected as a clear black line, making the image difficult to see. Furthermore, when the OHP sheet is run between the thermal head and the platen or rotating drum multiple times as described above, there is a drawback that the dots are misaligned and the image is therefore likely to smear. In addition, in the coating layer provided on the transparent film of an OHP sheet, heat is not necessarily transferred uniformly, so when ink material is transferred using a thermal head etc., color unevenness occurs.
There are drawbacks such as not being able to obtain high-quality printing performance. Furthermore, since the OHP sheets themselves are transparent, if they are stacked one on top of the other when organizing them, they become difficult to see due to the reflected light, making it difficult to distinguish one sheet from another. (Means for solving the problem) In order to solve the above problems, a thermal transfer ink receiving layer is formed on the printing surface side of the transparent base material.
The receiving layer is an OHP sheet, and the receiving layer contains 0.1 to 25 parts by weight of a hydrophobic fine powder, 0.1 to 10 parts by weight of a conductive cationic polymer, or 0.01 to 1 part by weight of a fine metal powder, based on 10 parts by weight of a polyester resin. It is made by coating a composition made of a dispersion medium that can uniformly disperse each of the above components, and furthermore, the opposite side of the transparent base material to the printing side is coated with paper,
For thermal transfer, a backing sheet made of synthetic paper or plastic sheet is attached to a transparent substrate in a polymeric manner so that only one end surface is adhesively bonded.
An OHP sheet was constructed. In this invention, the polyester resin is a thermoplastic polymer saturated polyester resin, and has a molecular weight of 5,000 to 500,000, preferably 10,000 to 50,000. On the other hand, in this invention, hydrophobic fine powders include silica, clay, quartz, light calcium carbonate, colloidal calcium carbonate, precipitated barium sulfate, mica, talc, aluminum hydroxide, magnesium carbonate, colloidal hydrated aluminum silicate, Any hydrophobically treated inorganic powder such as diatom, quartz, or glass beads can be used as long as it does not adversely affect transparency and surface roughness. Hydrophobic treatment is generally carried out by treating the hydrophilic groups on the surface of the powder with treatment agents such as dimethyldichlorosilane, trimethylchlorosilane, hexamethyldisilazane, octylmethoxysilane, silicone oil, aminosilane, and methacryloxylan, as well as silane monomers. , silane coupling agents, polysiloxanes,
Powders treated with modified polysiloxanes or organic polymer materials can also be used. Furthermore, as antistatic agents, cationic polymers,
A conductive agent such as fine metal powder can be used. Here, the cationic polymer is a known polymer having ionic cationic properties, and any polymer can be used as long as it has conductivity. Among these, preferred are cationic polymers having a quaternary ammonium group, but particularly preferred are compounds of the following general formula () and polypolymers having monomers represented by the following general formulas () to () as constituent units. It is an alamine derivative. R ₁ , R ₂ , R ₃ in the formula are hydrogen or alkyl groups,
m represents 1 to 7, n represents 2 to 20, and Y represents an acid group. R ₁ and R ₂ in formulas () to () are −CH ₃ , −CH _2
CH3 , _-CH2CH2OH , Y represents _an acid group. Examples of the compound represented by the general formula () include Nalpoly 607 (manufactured by Nalco Chemical Co., Ltd.) and Polyfix 601 (manufactured by Showa Kobunshi Co., Ltd.). The compounds represented by general formulas () to () are polydiallylamine derivatives, obtained by cyclopolymerization of diallylamine compounds, and Percoll 1697
(manufactured by Allied Colloid), Cat Flowe (manufactured by Calgon Corp.), PAS (manufactured by Nittobo Co., Ltd.),
Neofix RPD (manufactured by NICCA Chemical Co., Ltd.) can be mentioned. In addition, any fine metal powder can be used as long as it does not affect transparency, but fine metal powder such as Fe, Cu, Zn, Al, etc.
Any material that can be crushed to a size of about 1 to 0.01 μm may be used. The conductive agent such as the cationic polymer or fine metal powder is mixed into the coating material so that the surface resistance of the OHP sheet is, for example, 10 ⁷ to 10 ¹² Ω at a temperature of 20° C. and a humidity of 65%. If the amount of conductive agent blended is small and the surface resistance of the OHP sheet is higher than 10 ¹² Ω, problems may occur during thermal transfer printing.
Static electricity is generated on the surface of the OHP sheet, reducing printing performance. In addition, even if a large amount of conductive agent is added to the OHP sheet so that the surface resistance is 10 ⁷ Ω or less, printing performance cannot be significantly improved. In the case of metal powder, the transparency of the OHP sheet will decrease. On the other hand, if the amount of hydrophobic fine powder added is large, powder drop-off is likely to occur, and if the amount is small, printing performance may deteriorate. Based on the above-mentioned trends of each component, the blending ratio of these components is in the range of 0.1 to 25 parts by weight of hydrophobic fine powder, 0.1 to 10 parts by weight of cationic polymer, or 0.01 to 1 part by weight of metal fine powder to 10 parts by weight of polyester resin. They may be blended together, and a dispersion medium may be added thereto as appropriate to obtain a coating material in the form of a solution. The dispersion medium used here may be one that can uniformly disperse polyester resin, hydrophobic fine powder, cationic polymer, metal powder, etc., such as petroleum solvents such as toluene and xylene, methyl ethyl ketone (MEK), dimethyl formamide, etc. (DMF)
polar solvents such as 1.1.1-trichloroethane, trichlorethylene, perchloroethylene, alcohol solvents such as methanol, ethanol, isopropyl alcohol, butyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc. A system solvent can be used. The transparent base material used in the OHP sheet for thermal transfer of the present invention is, for example, a transparent film made of polyethylene terephthalate, polycarbonate, polyacetal, etc., and biaxially oriented polyethylene terephthalate having a film thickness of 25 to 100 μm is particularly suitable. The thickness is appropriately selected depending on the characteristics and purpose of the printer. The film thickness when coating the above-mentioned coating material on a substrate may be a dry thickness of 0.01 .mu.m or more, and preferably 0.05 to 3 .mu.m in consideration of performance, economy, etc. As a coating method, air knife coater, bar coater, reverse coater, gravure coater, hot melt coater, etc. can be used. The back sheet that can be used in the present invention includes paper, synthetic paper, and plastic sheets, with synthetic paper and plastic sheets being particularly suitable. The paper that can be used here needs only to be flexible and thick enough to run inside the printer. For example, coated paper, MC paper, medium-quality paper, high-quality paper, resin-treated paper,
Examples include glassine paper, oil-proof paper, white napkin paper, super calendar, roll paper, clay art paper, casein art paper, kraft paper, carton paper, imitation paper, pure white roll paper, Indian paper, and the like. As the synthetic paper, for example, synthetic paper manufactured by a film method is used. Synthetic paper manufactured using the film method involves mixing synthetic resin with fillers and additives, melting and kneading it in an extruder, and then extruding it into a film, or stretching it further to create micropores. Those manufactured using the so-called extrusion method, those manufactured using the surface coating method in which a coating layer containing facial fillers and fillers is applied to the surface of the plastic film, and those manufactured using the surface coating method, in which the surface of the plastic film is subjected to chemical treatment, sandblasting, etc. Any synthetic paper can be used as a suitable material, although some are manufactured using surface treatment methods that involve physical and chemical treatments. Note that a synthetic paper with a thickness of about 80 μm is suitable in terms of productivity, cost, and handling. The plastic sheet that can be used in the present invention has any composition, structure, or configuration as long as it is flexible, has a smooth surface, and has a thickness that allows it to run inside the printer. Examples include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, fluorine resin, polycarbonate, cellulose acetate, polyester, polyamide,
Sheets of polyimide, polyphenylene oxide, polysulfone, methylpentene (TPX) polymer, polyparaxylene, hydrochloric acid rubber, polyurethane, ionomer, etc. can be used. Plastic sheets that have been surface-treated by lamination, lamination, vapor deposition, coating, antistatic treatment, etc. can also be used. Preferred materials for the back sheet to eliminate misalignment of the dots include synthetic paper manufactured by the film method, plastic sheet, etc. among the above-mentioned materials. In addition, in order to eliminate color unevenness and improve the printing performance of OHP sheets, among the above-mentioned materials for the back sheet, coated paper, MC paper, medium-quality paper, wood-free paper, resin-treated paper, glassine paper, Papers such as oil-proof paper, white napkin paper, super calendar, roll paper, clay art paper, casein art paper, kraft paper, carton paper, imitation paper, pure white roll paper, Indian paper, synthetic paper manufactured by the film method,
Plastic sheet is the preferred material. Furthermore, in order to prevent the stacked OHP sheets from becoming difficult to see due to reflected light, it is preferable to use a colored or opaque sheet, especially a white sheet, as the back sheet, rather than a colorless transparent sheet, and synthetic paper or white plastic sheets are preferable. Both are suitable materials because they are opaque. In addition, in order to prevent the superimposed OHP sheet and back sheet from peeling off during printing, both sheets may be pasted together.In particular, it is effective to paste both sheets in order to prevent dots from misaligning during printing. There is. In addition, it is best to glue the back sheet to the OHP sheet in the transverse direction.
The preferred location for bonding is within 25 m/m from the leading edge of the OHP sheet and back sheet. (Effects of the Invention) In summary, the thermal transfer OHP sheet of the present invention has a polyester resin, a hydrophobic fine powder, and an antistatic agent, especially a cationic polymer and a fine metal powder mixed as an antistatic agent on the printing surface side of a transparent base material. Since the thermal transfer ink-receiving layer is formed by coating a coating material, the OHP sheet can be easily attached to the head, platen, or rotating, as when printing in full color using a drum-type or swing-type color thermal transfer printer. Even if the drum is run back and forth multiple times,
No static electricity is generated on the surface of the OHP sheet. Therefore, signals from the thermal head can be faithfully transmitted to the OHP sheet without transferring more ink material than necessary from the ink ribbon to the printing surface of the OHP sheet. Furthermore, according to the present invention, since the back side of the OHP sheet is protected by the back sheet, it is protected from feed scratches on the back side that occur while running inside the printer, and the printed OHP sheet is not scratched.
Therefore, clear images can be obtained. In addition, by using an opaque or white sheet such as a colored sheet, synthetic paper, or plastic sheet as the back sheet, it is possible to prevent the overlapped OHP sheets from becoming difficult to see due to reflected light. . Furthermore, by using the above-mentioned paper, synthetic paper produced by the film method, plastic sheet, etc. as the back sheet, color unevenness is eliminated.
Printing performance can be improved. Although there are many unknowns about the mechanism by which color unevenness is eliminated and printing performance is improved in the present invention, when a dense material such as the one mentioned above is used as the back sheet, the ink ribbon is pressed against the printing surface of the OHP sheet. When the thermal head is heated, the ink material from the ink ribbon is melted and transferred to the printing surface of the OHP sheet, and at the same time, heat flows uniformly to the back sheet. Therefore, the ink transferred to the OHP sheet is cooled uniformly, and the printed surface of the ink ribbon and the OHP sheet are evenly peeled off.
Therefore, it is considered that color unevenness does not occur. Furthermore, by providing a back sheet on the side opposite to the printing surface of the OHP sheet, it is possible to
Thermal conductivity to the OHP sheet is improved, so even if the ink ribbon is heated by the thermal head, the ink material will not melt excessively and be transferred to the printing surface of the OHP sheet, thus preventing color unevenness. It is conceivable that this will not occur. In addition, in the present invention, the back sheet is provided on the opposite side of the printing surface of the OHP sheet, and only one end surface is adhesively bonded, so when printing by wrapping the tip around a rotating drum, etc., the OHP sheet is attached to the back sheet. It slides (closely contacts and shifts), and does not suffer from distortion even if it is moved back and forth multiple times between the platen and the rotating drum in color copying, etc., and provides sufficient contact and accurate positioning (dots). (no misalignment occurs). (Example) Examples of the present invention will be shown below. Example 1 50 μm of polyethylene terephthalate (manufactured by Toyobo Co., Ltd., trade name: Ester Film 5001) was used as a base material.
A coating material with the following composition is applied to a film with a thickness of , haze, powder shedding, runnability, and transportability were evaluated. The evaluation criteria were as follows, and the coating materials and evaluation results are shown in Table 1. Note that the surface resistance in Table 1 was measured based on JIS K 6911. Evaluation criteria (1) Printing performance: Using Sharp's Color Scanner Printer CX-5000, those with clear prints were rated ○, those with fair clarity were rated △, and those with poor quality were rated ×. . Clear printing means (a) no color shift, (b) color gradation, (c) clear printing of magenta, yellow, cyan, and black, and (d) no color unevenness. I decided based on that. (2) Travelability and transportability: Set 50 OHP sheets in the paper feed cassette of the printer used in (1),
Three-color overlapping solid printing of magenta M, cyan C, and yellow Y was performed, and when all 50 sheets were fed and discharged, it was marked as ◯, when 25 to 49 sheets were fed and discharged as △, and when 25 or less sheets were rated as ×. (3) Scratches on the back: After printing, prints were hung on an OHP, and those with no scratches on the back were rated ○, and those with scratches were rated ×. 【table】

Claims (1)

[Claims] 1. An OHP sheet for thermal transfer in which a thermal transfer ink receiving layer is formed on the printing surface side of a transparent base material, wherein the receiving layer is composed of 0.1 to 25 parts by weight of hydrophobic fine powder based on 10 parts by weight of polyester resin. parts by weight, 0.1 to 10 parts by weight of a conductive cationic polymer or 0.01 to 1 part by weight of fine metal powder, and a dispersion medium capable of uniformly dispersing each of the above components. , paper on the opposite side of the transparent substrate to the printing side,
An OHP sheet for thermal transfer, characterized in that a back sheet made of synthetic paper or plastic sheet is attached to a transparent base material in a polymeric manner so that only one end surface thereof is adhesively bonded. 2 The surface resistance of the OHP sheet is at a temperature of 20℃ and a humidity of 65℃.
The OHP sheet for thermal transfer according to claim 1, which has a resistance of 10 ⁷ to 10 ¹² Ω in terms of %.