JPH02295792A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer sheet stable to the heat energy of a thermal printing head and having excellent runnability by constituting the main component of the material of a heat-resistant slip layer of gel microparticles composed of a styrenic polymer or a styrene/acrylic copolymer and polyvinyl alcohol having a specific saponification degree. CONSTITUTION:Gel microparticles mainly composed of a styrenic polymer or a styrene/acrylic copolymer used in a heat-resistant slip layer have good lubricating effect, because long-time dispersion is unnecessary and the particle size thereof can be made uniform. Further, since the interior of particles is crosslinked three-dimensionally, said particles are rich in heat resistance. Furthermore, polyvinyl alcohol having high Tg, excellent in heat resistance and having a saponification degree of 90% or more is pref. used and the MW thereof is pref. 20000-400000. Glyoxal can be added for the sake of applying the heat resistance and water resistance of polyvinyl alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-sensitive transfer sheet having a heat-sensitive transfer layer on one side of a base material and a heat-resistant slip layer on the other side.

[Prior Art] In recent years, heat-melting ink layers containing pigments and dyes, sublimation ink layers containing sublimable dyes in binders, or heat-reactive coloring components have been developed on base materials such as plastic films. Using a heat-sensitive transfer sheet with a heat-sensitive transfer layer that
A widely used method is to perform thermal printing according to image information using a heating means such as a thermal head to form an image on a receiving sheet.

Conventionally, plastic films such as polyester films, polyimide films, polypropylene films, aromatic polyamide films, cellulose acetate films, and cellophane films with a thickness of 2 to 15 μm have been used as substrates for such heat-sensitive transfer sheets. Among these, polyester film is preferably used because it is easy to form a uniform thickness, has excellent surface smoothness, and is easy to operate in a printer.

However, thermal transfer sheets using this polyester film as a base material require high energy to obtain sufficient print density, so a so-called sticking phenomenon occurs in which the polyester film itself fuses with the thermal head. In addition, in order to maintain the thermal head pressure and the heat-sensitive transfer sheet, the butt pressure in the cassette or the contact resistance with the roll in the printer, etc.
The runnability is poor, resulting in disturbances in print density, scumming, etc., and in severe cases, the substrate may break.

In order to prevent these phenomena, for example, there is a method of providing a heat-resistant layer or a friction-resistant layer made of silicon oxide on the base material (Japanese Unexamined Patent Publication No.
4-1 4 3 1 5 2, JP-A-57-741
95), a method of providing a heat-resistant resin layer such as silicone resin or epoxy resin (JP-A-55-7467), a method of providing a resin layer containing a surfactant, etc. that is solid or semi-solid at room temperature (JP-A-55-7467), A method of providing a heat-sensitive resin layer containing an active inorganic pigment (Japanese Patent Application Laid-Open No. 56-155794) has been proposed.

However, these methods require expensive processes such as vapor deposition, use a large amount of thermal energy for curing, and require long aging to provide sufficient heat resistance. Furthermore, there was a problem that the activity was insufficient, and there was also a drawback that dirt adhered to the thermal head.

Furthermore, since the heat-sensitive transfer sheet used in the above conventional method is generally stored rolled up, the heat-resistant layer and the transfer layer come into contact with each other during storage, causing a blocking phenomenon, resulting in background smudges and image fading when printed. There was a problem that occurred.

Furthermore, methods using waxes that exhibit lubricity as a lubricant by being fused by the heat from the thermal head, such as the method of JP-A-58-187396, may cause sticking phenomena during heat absorption, non-feeding of the thermal transfer sheet, etc. There was a drawback that this occurred.

[Problems to be Solved by the Invention] The present invention provides a thermal transfer sheet that is stable against the thermal energy of a thermal head during printing and has excellent feeding properties, and also has high heat resistance and high lubricity. Therefore,
The present invention aims to provide a thermal transfer sheet that reduces the occurrence of wrinkles in printers using line thermal heads, particularly facsimiles, bar code printers, and the like.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a heat-sensitive transfer sheet having a heat-sensitive transfer layer on one side of a base material and a heat-resistant slip layer on the other side of the base material. , a heat-sensitive transfer sheet made of microgel particles mainly made of a styrene polymer or a styrene-acrylic copolymer and polyvinyl alcohol with a saponification degree of 90% or more as the main components of the material of the heat-resistant slip layer; A heat-sensitive transfer sheet containing glyoxal as a main component of the material of the slip layer is provided.

In the present invention, the microgel particles mainly made of a styrene polymer or styrene-acrylic copolymer used in the heat-resistant slip layer are atomized from the time of preparation of the microgel, so when an inorganic filler or the like is used as a lubricant, It has the advantage that it does not require long-term dispersion. In addition, this microgel has the advantage that the particle size can be adjusted arbitrarily, and since the particle size is uniform, the lubricity effect is very good. Its particle size is 0.1
0-1.0 μm, preferably 0.2-0.6 μm. Furthermore, this microgel has a property of being highly heat resistant because the inside of the particle is three-dimensionally crosslinked. Styrenic polymers or styrene-acrylic copolymers, especially styrene-methyl methacrylate, can be thermally decomposed by DTA.
The 5% weight loss temperature is 300°C to 350°C.

Microgels can be produced by conventionally known methods. One example of these is described in detail in Shinsuke Yamazaki, Shigeru Hattori, et al.'s review, 25.2.86 (1987). Alternatively, commercially available products may be used.

Furthermore, polyvinyl alcohol has a high Tg and is excellent in terms of high heat resistance, and polyvinyl alcohol with a degree of saponification of 90% or more is preferably used. Further, their molecular weight is preferably from 20,000 to 400,000. Bobal 117 manufactured by Kuraray Co., Ltd. is a commercially available product that is most suitable for the above characteristics.

Furthermore, in order to utilize the heat resistance and water resistance of this polyvinyl alcohol, glyoxal can be added. This glyoxal is crosslinked and cured by heating and drying after application.

The amounts of the above microgels, polyvinyl alcohol, and glyoxal to be used can be determined arbitrarily, but usually the total amount of the heat-resistant slip layer is 100 parts (the thickness of these films varies depending on the feedability of the printer, applied energy, etc., but it is usually 0 parts). A suitable range is 0.05 to 10 μm, preferably 0.2 to 5 μm.

As the plastic film used as the base material in the present invention, those formed from various conventionally known thermoplastic resins can be used, such as polyester film, polyamide film, polyolefin film,
Examples include polycarbonate films and cellulose films, and the thickness thereof is usually about 0.5 to 50 μm, preferably about 3 to 10 μm.

In the present invention, the type of the heat-sensitive transfer layer formed on the base material is not limited, and a non-reactive type or a reactive type can be arbitrarily used. Examples of transfer layers include a transfer layer made of meltable ink or a transfer layer made of sublimable dye. Examples of reactive type transfer layers include transfer layers containing one of the reactive components of a color-forming reaction system in the combination shown below. layers can be mentioned.

(1) Combination of leuco dye and color developer (electron-accepting substance).

(2) Combinations of long-chain aliphatic iron salts such as ferric stearate and ferric myristate with phenols such as tannic acid, gallic acid, and ammonium salicylate.

(3) Heavy metal sulfates such as silver, lead, mercury, 1.lium sulfates and Na-tetrathionate, sodium thiosulfate,
In combination with sulfur compounds such as thiourea.

(4) A combination of a noble metal salt of an organic acid such as silver behenate or silver stearate and an aromatic organic reducing agent such as protocatechuic acid, spiroindane or hydroquinone.

(5) Combinations of organic acid lead salts such as lead cabroate, lead pelargonate, and lead behenate with thiourea derivatives such as ethylenethiourea and N-dodecylthiourea.

Taking a non-reactive heat-sensitive transfer layer as an example, the formation method is explained below.A composition consisting of a coloring agent, a binder agent, etc. is hot-melt coated onto a film substrate, or the composition is dispersed in an appropriate solvent. The coating solution can be solvent coated to form a layer of about 1 to 20 μm. As the colorant, any of various dyes or pigments such as carbon black, which have been conventionally used in the field of copying paper, can be used, and as the binder, waxes such as carnauba wax, book wax, and beeswax can be used. I can do it.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Note that the amounts (parts) of each component described in the Examples are parts by weight.

Example 1 A heat-resistant slip layer coating solution having the following composition was prepared.

Solid content weight ratio Styrene microgel emulsion (particle size 0.40 μm 1 DTA 5% weight loss temperature 300°C) = 30 parts Polyvinyl alcohol aqueous solution (Kuraray Poval 117 completely saponified): 70 parts Coating liquid with the above composition was coated with 4.5 μm polyethylene gel. A heat-resistant slip layer was obtained by coating and drying the mixture onto a lactate film so that the film thickness after drying was 0.5 μm.

Next, a hot-melt ink coating liquid having the following composition was prepared.

Carbon black: 15 parts Paraffin wax 155'F: 33 parts Carnauba wax No. l: 25 parts polyethylene wax: 25 parts mineral oil
: 2 parts The above composition was hot-melt coated to form an ink layer with a thickness of 3.0 μm on the surface opposite to the heat-resistant slip layer to obtain a heat-sensitive transfer sheet.

Example 2 A heat-resistant slip layer coating liquid having the following composition was prepared.

Solid content weight ratio styrene-methyl methacrylate copolymer microgel emulsion (particle size 0.50, czm, DTA 5% weight loss temperature
350°C) 225 parts Polyvinyl alcohol aqueous solution (same as Example 1) 265 parts Glyoxal aqueous solution = 10 parts The coating liquid of the above composition was applied onto a 4.5 μm polyethylene terethalate film so that the film thickness after drying was 1.0 μm. Apply as follows, 11
Curing was performed at 0° C. for 2 minutes to obtain a heat-resistant slip layer.

The ink layer was formed in the same manner as in Example 1.

Comparative Example 1 In Example 1, a 2% toluene solution of silicone oil was coated to a thickness of 0.05 μm as a heat-resistant slip layer forming material.

The rest was prepared in the same manner as in Example 1.

Comparative Evaluation The heat-sensitive transfer sheets obtained in each of the above examples were mounted on a line printer, and comparative evaluation was performed.

・Printing conditions Thermal head: Line type thin film partial blaze Platen pressure: 230 gf'/am Peeling angle: 45° (relative to the transferred paper) Printing speed = 2 inches/see Transferred paper: Bec smooth 200sec high quality paper stamp processing energy: 15-35IIJ/III12・Evaluation item ■. Heat Resistance 2 Solid printing is performed under the above printing conditions, and the timing of occurrence of wrinkles when solid printing is repeated using the appropriate energy of the evaluated ink (20 mJ/am2) using the energy that caused the substrate to break.3. Abnormal image: presence/absence of dirt, voids, etc./evaluation results 2. Wrinkles: [Effects of the Invention] As explained above, the thermal transfer sheet of the present invention (1) is stable against the thermal energy of the thermal head and does not cause sticking, so it runs stably in the printer.

2. No sticking occurs even when excessive heat energy is applied, and no wrinkles occur on the ink sheet.
This has the effect of being suitable for multi-printing.

Claims (2)

[Claims] (1) In a heat-sensitive transfer sheet that has a heat-sensitive transfer layer on one side of the base material and a heat-resistant slip layer on the other side of the base material, the main component of the material of the heat-resistant slip layer is mainly a styrene polymer or styrene. - A heat-sensitive transfer sheet comprising microgel particles made of an acrylic copolymer and polyvinyl alcohol having a degree of saponification of 90% or more. (2) A claim characterized in that the main components of the heat-resistant slip layer are microgel particles mainly made of a styrene copolymer or a styrene-acrylic copolymer, polyvinyl alcohol with a degree of saponification of 90% or more, and glyoxal. The thermal transfer sheet described in item (1).