DE4025613A1 - POLYESTER FILM FOR USE FOR HEAT TRANSFER RECORDING BLADES, AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

Polyester films (I) for thermal transfer recording sheets (II) is obtd. by applying an electron beam-curable resin (III) to one side of a polyester film before complete crystalline orientation of the film, stretching the coated film and curing the resin layer with an electron beam. The above process is claimed as such. Specifically (III) is a polyester-acrylate, epoxy-acrylate, polyurethane-acrylate, pllyetheracrylate, melamine-acrylate, alkyd-acrylate or silicone-acrylate resin. Substrate film is PET, PBT, etc. (III) is, e.g. adipic acid/1,6-hexanediol/acrylic acid copolymer, TMA/diethylene glycol/acrylic acid copolymer, Bisphenol A/epichlorhydrin/-acrylic acid copolymer, TD1/polyester/2-HEMA copolymer, or other types as above; (III) ca contain various fillers to increase its heat resistance further; pref. coating thickness is 0.4-1.0 micron and total thickness of (I) is 4-8 microns. (I) is coated with fusible or sublimable ink or dye on the opposite side to (III). USE/ADVANTAGE - (iii) are useful in thermal printers, thermal fax machines, etc. The invention provides a heat resistant film which does not "stick" (to thermal printer heads, etc.).

Description

This invention relates to a polyester film for Use for heat transfer recording sheets. In particular, the invention relates to a polyester film for use with heat transfer recording sheets, which is heat resistant.

For some time, the heat transfer record applied on a large scale when recording on usual sheets of paper, such as those for thermal printers, Thermofacsimilegeräte and the like can be used. This heat transfer record requires one simple mechanical arrangement, easy with low Cost can be maintained, sharp and fast Records with low energy consumption allows and which also enables color printing can be done relatively easily by that different sheets containing colored ink  be used. The comprehensive for some time Application of this type of recording is on it due. In particular, become monochrome Heat transfer recording sheets more and more used as the thermal printer for word processors and Thermo-facsimile machines and the like have become more popular are.

As base films for heat transfer recording sheets are known films made of polyester, polycarbonate, Polystyrene, polypropylene, polyvinylchloride, Polyvinylidene chloride, polyimide, polyamide and the like consist. In general, polyesters are used.

Heat transfer recording sheets containing a Polyester film contain, however, suffer from the fact that the Surface of the molten polyester film on a Thermal head adheres whose temperature is above the Melting point of the polyester film is when the Heat transfer is carried out for the pressure. This causes the thermal head to diminish one Leaf characteristic gets, which in turn causes that the transfer printing does not occur. This is called "sticking" designated; it was tried to generalize prevent by using polyester films that a heat-resistant layer on one side of the film formed by forming the film with a heat-resistant material is coated.

For example, JP-A-55-76767 describes sheets which a base film containing one side with a heat-resistant resin is coated, for example, with  a silicone resin, epoxy resin, nitrocellulose and like. JP-OS 56-15 579 describes leaves which contain a base film that is a highly polished, inorganic pigment and a thermosetting or heat-softening resin material with which the base surface of the base film is coated. The JP OS 57-74 195 describes sheets that have a base film containing a three-dimensional cross-linked layer Silicon oxides or multifunctional (meth) acrylates has, with the base surface of the base film is coated.

These documents illustrate techniques to provide a Heat resistant coating on a fast produced Base film by solvent coating, Hot melt coating, lamination and the like manufacture.

On the other hand, there are techniques in which used resins instead of the above materials which are curable by electron beams.

For example, JP-OS 62-2 49 793 describes that a heat-resistant substance, which is a major component Contains acrylic resins which are either heat fixable or are curable by UV or EB rays and the finely divided organic or inorganic particles included, layered on the base of a carrier becomes. The JP-OS 63-1 15 790 describes that a silicon modified electron beam curable Resin is coated on one side of a substrate.  

However, both publications, as well as describe the previously discussed publications, the use a ready-made base film, which subsequently is coated and irradiated with electron beams.

As discussed above, the Heat transfer recording sheets in general made by at least two steps. These exist in that a coating layer (heat-resistant Layer) of a heat resistant material on one Side of a base film is applied, and that the another side of the base film with one by heat coated meltable recording substance layer becomes. On the other hand, for example, a other type of heat transfer recording sheets, which can produce lusterless printers, three steps make necessary. These are that a heat-resistant layer on one side of a base film is applied and that a lackluster layer and a heat fusible layer of a marking substance in a laminate form on the other side of the base film can be generated, as disclosed in JP-A 60-1 01 083 is. This method therefore requires many steps and is complicated, so that increases the cost of the process are.

The aforementioned general techniques for the Application of the layer of heat-resistant material very often require the use of organic Solvents, what about the removal of the used solvents after the application step Poses problems. Therefore, it is desirable to have a to develop heat-resistant polyester film.  

An object of this task is to provide a polyester film to provide that is heat resistant. As well is a method for producing such Polyester film can be proposed.

Solutions of these objects are in claims 1 and 3 specified; advantageous developments are the subject of the subclaims 2 and 4.

According to the invention, a polyester film is used for Heat transfer recording sheets available provided, which is made by a through Electron beam curable resin on one side of a Polyester film before its complete crystalline Orientation is applied to that of the coated film is then stretched and that the applied resin layer cured by irradiation with an electron beam becomes.

According to the invention, a method for Preparation of a polyester film for use in Heat transfer recording sheets proposed which has the following steps:

• a) becomes an electron beam curable resin on one side of a polyester film in front of it full crystalline orientation applied;
• b) the coated film is stretched; and
• c) the coated and stretched film is with irradiated with an electron beam,  whereby a coating layer of by Electron beams of curable resin is formed.

The invention will be described in more detail below.

The polyester used in the invention provides a highly crystalline linear saturated polyester which from a dibasic aromatic acid or its ester-forming derivative and a diol is synthesized, including, specifically, polyethylene terephthalate, Polybutylene terephthalate, polyethylene-2,6-naphthalate and like. To improve the sliding of the film, can the polyester calcium carbonate, kaolin, silica, Aluminum hydroxide and the like may be added.

The electron beam curable resin which is used according to the invention is hereinafter shown.

The following connections can be considered: Polyesteracrylates, like Adipic acid / 1,6-hexanediol / acrylic acid copolymer, Phthalic anhydride / propylene oxide / acrylic acid copolymer and Trimellitic acid / diethylene glycol / acrylic acid copolymer; Epoxy acrylates, like Bisphenol A / epichlorohydrin / acrylic acid copolymer, Phenol novolac / epichlorohydrin / acrylic acid copolymer and Copolymers of alicyclic compounds and acrylic acid, Polyurethane acrylates, such as Tolylene diisocyanate / polyester / 2-hydroxyethyl acrylate copolymer; polyether; melamine; alkydacrylate; silicone acrylate; a combination of these and the like.  

Usually, ready-to-use polyester films are used are balanced in terms of orientation or the are reinforced by uniaxial stretching or by biaxial extension are reinforced, with heat-resistant Coated materials.

According to the invention, the above-described film is made of Polyester resin with the electron beam curable Resin coated, then stretched and with a Electron beam irradiated to the through Harden electron beam curable resin. The resulting film is already heat resistant. With the thus produced film can be Heat transfer recording sheets only by a make single step by one by heat fusible recording substance on the other side of the Filmes are applied, not the cured Resin layer contains.

The elimination of the step that is heat-resistant Materials applied, has a large Advantage in the production of Heat transfer recording sheets on.

The inventive method for producing a Polyester film for use for Heat transfer recording sheets, is a so-called co-rotating coating process, in which the polyester film before its complete crystalline Orientation (the film is unstretched or uniaxial stretched) with the electron beam curable resin is coated, then stretched  (longitudinal or transverse) and with electron beams is irradiated to cure the resin.

In practice, said polyester resin is using melt extruded in a conventional film making machine, to make a film that is cooled and then uniaxial is stretched to a 3- to 5-fold elongation. The longitudinally stretched film gets through with Electron beam curable resin coated. After that will the longitudinally stretched and coated film stretched transversally to a 3- to 5-fold stretch and then irradiated with electron beams to one biaxially stretched polyester film.

Because this method is achieved by coating the film with the by electron beam curable film and by immediately subsequent stretching of the coated Filmes performed is the coating even and thin.

Since the electron beam curable resin as a heat-resistant material is used, in addition any drying step is eliminated; thereby will not have problems regarding the removal of spent organic solvents.

The electron beam-curable resin can by any of the usual methods are applied. For example, a job machine can be used become, like a rod order machine, one Gravure coater, an opposite one Roller painting line, a direct roll coating line or a knife coater.  

To the heat resistance of by electron beams hardenable resin, the resin can be an organic Filler, such as benzoguanamine resin, melamine resin, silicone resin or similar; or an inorganic filler, such as Kaolin, calcium carbonate, aluminum hydroxide, titanium dioxide or the like may be added.

The amount of coating by electron beam hardenable resin can be varied depending on the extent of elongation achieved after coating becomes. The coating should be stretched after stretching Thickness in the range of 0.1 to 2.0μm, preferably 0.3 to 1.5 .mu.m, in particular 0.4 to 1.0 .mu.m.

The polyester film thus prepared for use with Heat transfer recording sheets should have a thickness from 3 to 18 μm, preferably 4 to 8 μm.

The irradiation by electron beams should desirably at a dose of 0.1 to 20 Mrad Electron beam irradiation be performed. A Irradiation dose below 0.1 Mrad does not result a sufficient radiation effect, and a dose above 20 Mrad may be a destruction of the Polyester film and the coating materials cause.

For example, the irradiation with electron beams using a system of scanning, Curtain beam or large field irradiation performed become.  

The acceleration voltage for the irradiation is preferably in the range of 100 to 300 kV.

The polyester film according to the invention for use for Heat transfer recording sheets comes with a Layer of a heat-transferable recording substance layered on the side of the film, the side opposite to that by electron beams hardenable resin is coated. As a heat transferable The recording substance can either be one by heat fusible or heat-sublimable ink or Color to be used.

The heat-fusible paint can mainly consist of a dye, wax and a resin.

The dye contains, for example, benzidine yellow G for Yellow, rhodamine varnish Y for magenta, phthalocyanine blue for Cyan and soot for black.

The wax contains, for example, paraffin wax, Carnauba wax, microcrystalline wax, a wax out Low molecular weight polyethylene, oxidized polyethylene wax and synthesized wax.

The resin contains, for example Ethylene / vinyl acetate copolymer, Ethylene / ethyl acrylate copolymer, aliphatic Hydrocarbon resin and aromatic Hydrocarbon resin.

Other additives, for example a  Pigment dispersants, oil and the like can, if necessary, to the heat fusible colors be added.

The heat sublimable color is mainly from a dye, a binder and a Solvent to dissolve or bind the binder disperse.

The dye should have a sublimation temperature in the range of preferably from 70 to 400 ° C, especially from 150 to 250 ° C. For example, disperse dyes such as Disperse Blue 20 (available under the trademark Duranol Blue 2G), Disperse Yellow 42 (available under the trademark Resulinn Yellow GR) and Disperse Red 1 (available under the trademark Celition Scarlet B); Quinalizarin dyes, monoazo dispersant dyes, anthraquinone dispersant dyes, nitrodiphenylamine dispersing dispersants, anthracene dyes, and the like.

The binder contains cellulose resins, such as Methyl cellulose, ethyl cellulose and hydroxyethyl cellulose, Acrylic resins such as polyacrylic acid, vinyl resins such as Polyvinyl alcohol, polyvinyl acetate; Resins on rosin; Polyamide resins, phenolic resins, alkyd resins, Polyurethane resins; and the same.

The solvent used to dissolve or disperse the Binder contains alcohols such as Methanol, ethanol, propanol and butanol; Cellosolven, like  Methyl cellosolve and ethyl cellosolve; aromatic Solvents such as benzene, toluene and xylene; Esters, like Ethyl acetate and butyl acetate; Ketones, such as acetone, Methyl ethyl ketone and cyclohexanone; Hydrocarbons, like Ligroin, cyclohexane and kerosene; dimethylformamide; and like.

The above, heat-meltable or through Heat sublimable color can be replaced by a Hot melt coating process or by a Solvent coating method with a Rod applicator, a gravure coater, a opposing Walzenlackieranlage, one Direct roll coater or the like be applied.

The polyester film according to the invention for use for Heat transfer recording sheets is heat resistant, and the process for its preparation is a so-called accompanying coating process. The Procedure can be performed by the Polyester resin using a film-making machine is melt extruded to form a film by the Film is uniaxially stretched by the uniaxial stretched film with the electron beam curable Resin is coated, which is a heat resistant Material represented by the coated film stretched and then the stretched film with electron beams is irradiated.

The polyester film according to the invention for use for Heat transfer recording sheets has a  heat-resistant layer due to the trailing Process is made evenly. The The method according to the invention requires only one step for coating the film with the paint to the Produce recording sheets. This leads to a Cost reduction for the production of Heat transfer recording sheets that finally to be obtained.

The invention will be described below with reference to FIGS Examples explained in more detail.

EXAMPLE 1

Polyethylene terephthalate having an intrinsic viscosity of 0.66 and 0.08 parts by weight of a flat Aluminum hydroxide with an average Diameter of 1.5μm, is at a Temperature of 285 ° C melted and on a cooling drum extruded at 60 ° C. Then it is at a temperature of 83 ° C longitudinally stretched to a 3.5-fold elongation.

The stretched film will go through with a Electron beam curable resin coated, made of a silicon-based acrylate (KJC-8000, available from Shinetzu Chemical Industries), and Immediately thereafter, the film is at a temperature of 110 ° C to a 3.5-fold stretched transversely. After stretching the film with a Electron radiation in a dose of 10 Mrad with help an electron beam irradiated to a  Polyester film for use with To obtain heat transfer recording sheets. The electron beam curable acrylate resin layer Silicon base has a thickness of after stretching 0.5μm and is even.

The thus-prepared polyester film for use for heat transfer recording sheets is coated with a heat-fusible paint comprising the following components by means of a hot-melt coating equipment to achieve a coating amount of 4 g / m ² , thereby preparing a heat transfer recording sheet:

soot 15 parts by weight black dye 5 parts by weight paraffin wax 40 parts by weight carnauba 30 parts by weight Ethylene / vinyl acetate 10 parts by weight

The above-prepared heat transfer recording sheet is recorded on a recording sheet (TTR-T, Heat transfer recording paper, available from Mitsubishi Paper Mills, Ltd.) and it becomes one Printing done by using a thermal printing machine (available from Matsushita Electronic Parts).

As a result, a good pressure was performed without an adhesion occurred.

The polyester film according to the invention for use for Heat transfer recording sheets can by  Use of a heat-resistant material, i. one by electron beam curable resin, while the Film production are produced. Therefore, the Production of heat transfer recording sheets, using a heat-fusible paint, simplified. Thus, the present invention is very great practical advantages.

Claims (4)

1. Polyester film for use for Heat transfer recording sheets that by available is that one by electron beams curable resin on one side of a polyester film before its complete crystalline orientation is applied, that the coated film then is stretched and that the applied resin layer cured by irradiation with electron beams becomes. 2. Polyester film according to claim 1, characterized characterized in that by Electron-beam curable resin from the group selected from polyester acrylate, Epoxy acrylate, polyurethane acrylate, polyether acrylate, Melamine acrylate, alkyd acrylate and silicone acrylate consists. A process for producing a polyester film for use in heat transfer recording sheets, comprising the steps of:

• a) an electron beam curable resin is applied to one side of a polyester film prior to its full crystalline orientation;
• b) the coated film is stretched; and
• c) the coated and stretched film is irradiated with an electron beam, thereby forming a coating layer of the electron beam curable resin.

4. The method according to claim 3, characterized characterized in that by Electron-beam curable resin from the group selected from polyester acrylate, Epoxy acrylate, polyurethane acrylate, polyether acrylate, Melamine acrylate, alkydacrylate and silicone acrylate, consists.