JPS61286196A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer sheet free of transfer to the back side even when being preserved at a high temperature, by incorporating a specified releasing agent into an ink layer. CONSTITUTION:A releasing agent is incorporated into the ink layer of a thermal transfer sheet comprising a heat-fusible ink layer provided on one side of a film base. At least one compound in which a part or all of hydrogen atoms bonded to carbon atoms of a compound having a polar group are substituted by fluorine atoms or at least one fluorocarbon having no polar groups is preferably used singly or in combination, as the releasing agent. The releasing agent may be used in an amount of 0.5 times of the amount of the ink composition, preferably not more than 15 times. Even when a part of the ink is melted under preservation of the transfer sheet under a high temperature, the ink layer will not be transferred to the back side of the sheet, and the ink layer is prevented from being delaminated from the base.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a novel thermal transfer sheet used in thermal transfer type printers and facsimile machines.

<Prior Art> In recent years, thermal transfer printers have been widely used due to their advantages such as no noise during printing, easy handling, and low cost.

Thermal transfer sheets (hereinafter referred to as transfer sheets) used in such recording methods are made by blending a coloring agent into a heat-melting binder such as a low melting point resin or a softener on one side of a base material such as plastic, and applying transfer ink. It has a structure that forms a layer (hereinafter abbreviated as ink layer).9, usually medium 61!1m to 5001m
It has been commercialized with a 11ff+ slit and a rolled proboscis shape.

By the way, transfer sheets are sometimes exposed to various conditions during storage before use. For example, the ambient temperature is 6.
Temperatures can reach 0°C.

With conventional transfer sheets, when the ambient temperature during storage is high, part of the ink layer melts and transfers to the back of the inner layer of the scroll, a so-called back side adhesion phenomenon, which occurs when the temperature drops again. However, the ink layer does not completely return to the original base film side, resulting in missing characters and contaminating the thermal head. Such backside adhesion occurs because the wax or softener used as a binder contains a component with a low melting point that is easy to flow.

<Problems to be Solved by the Invention> The present invention has been made in view of the above situation and aims to provide a thermal transfer sheet free from back side transfer.

<Means for Solving the Problems> The present inventors have developed a new technology in which a transfer sheet with an ink layer containing a specific release agent does not cause backside adhesion even when stored at high temperatures. After discovering this fact, we have completed the present invention.

The transfer sheet according to the present invention prevents the ink layer from being transferred to the back surface even if a portion of the ink melts during high-temperature storage, and furthermore, prevents only the transfer of the ink to the back surface, and prevents transfer of the ink layer from the base material on which the ink layer is provided. There is no peeling of ink.

The present invention will be explained in detail below.

As the base material, commonly used plastic films such as polyester and polyimide, and papers such as condenser paper can be used.

Alternatively, a base material may be used in which a protective layer such as a silicone resin is provided on the side of the plastic film opposite to the side on which the ink layer is formed. The thickness of the base material can range from 1 to 20 μm. If the thickness is less than 1 .mu.m, the base material is likely to tear during handling, and if it is 20 .mu.m or more, high energy is required for printing, which is disadvantageous.

The ink composition is based on a low melting point resin, colorant, and release agent.
Additives such as softeners, petroleum resins, and surfactants may be added as necessary.

The low melting point resin is selected from paraffin wax, oxidized wax, carnauba wax, ester wax, other natural waxes, and synthetic waxes.

As the coloring agent, carbon black, various rice dyes, and pigments can be used.

In addition to silicone resins, the mold release agents used in the present invention include higher fatty acids, fatty acid salts, fatty acid esters, fatty acid amides, alcohols, ethers, higher alcohol esters of lower fatty acids, etc., but the above-mentioned ones are preferable. It is preferable to use a compound in which all or part of the hydrogen bonded to the carbon of a compound having a polar group is replaced with fluorine, or a fluorocarbon having no polar group as mentioned above, alone or in combination.

Combination of low melting point resin, coloring agent, and additives blended as needed in the ink.Assuming 100 parts by weight of Wakin (hereinafter referred to as "parts"), the low melting point resin is 40 to 90 parts, and the colorant is 10 to 60 parts by weight.
part, mold release agent [15 parts or more is sufficient, but preferably 15 parts
below.

If the low melting point resin is less than 40 parts, the thermal meltability is poor and transfer is difficult, and if it is more than 90 parts, the fixing performance is decreased. Also, the colorant is 1
If it is less than 0 copies, the print density will be low, and if it is more than 30 copies, the fixability to paper after transfer will be poor.

The amount of the release agent added to the above ink composition is 0.
The amount may be 5 parts or more, but preferably 15 parts or less.

Q: If the amount is less than 5 parts, there is no effect of preventing back side adhesion, and if it is more than 15 parts, the effect is saturated, and more than that is unnecessary.

Furthermore, additives that may be added as necessary will be mentioned.

Plasticizers, oils, liquid resins, etc. are used as softeners.
Petroleum resins include aliphatic, alicyclic, aromatic, alicyclic aromatic reactants, etc., and surfactants include nonionic, anionic, cationic, and amphoteric surfactants other than fluorine, each singly or Can be used in combination.

As a method for applying the above-described composition to a base material, there is a so-called normal hot-melt coating method in which the ink components are melted by heating and applied using a bar code, roll coating, or gravure coating method. Although preferred, a solvent may be used if necessary. The thickness of the ink islands provided as described above is 1 μm to 30 μm, preferably 2 μm to 10 μm. If the thickness is less than 1 μm, the printing density decreases, and if it is more than 30 μm, a large amount of printing energy is required, which is disadvantageous.

Next, the present invention will be explained with reference to Examples. Note that all parts are by weight.

Examples 1 to 5 and Comparative Example 1 A transfer ink was prepared according to the following formulation 1, and applied to a polyester film having a thickness of about 4 μm and a VCf11 cloth having a thickness of about 4 μm.
A transfer sheet was produced. This was subjected to an ink back transfer test under the test conditions described below. Table IK shows the results.
show.

Formulation 1 Paraffin wax 60 parts Oxidized wax 20 parts Carbon black 20 parts Fluorine compound (
perfluoroalkyl quaternary ammonium iodide)
(L2 to 15 parts (variable, see Table 1) Examples 4 to 6, Comparative Example 2 A transfer ink was prepared according to the following formulation 2, and applied to a 4 μm thick polyester film to a thickness of about 4 μm to form a transfer sheet. This was subjected to an ink back transfer test under the test conditions described below.The results are shown in Table 1.

Blend 2 Paraffin wax 60 parts Oxidized wax 10 parts Carbon black 20 parts Oil 10 parts Fluorine compound (half-fluoroalkyl boriether: Montefluos sea bream, Garde yLS) 0.2 to 15 parts (variable, Table 1
Reference Examples 7 to 9, Comparative Example 3 A transfer ink was prepared according to the following formulation 5 and applied to a 4 μm thick polyester film to a thickness of about 4 μm to prepare a transfer sheet. This was subjected to an ink back transfer test under the test conditions described below. The results are shown in Table 1.

Formulation 3 Paraffin wax 50 parts Microcrystalline wax 10 parts Carnauba wax 20 parts Carbon black 20 parts Silicone resin (Shin-Etsu Silicone: KS61) α2 to 15 parts (variable, see Table 1) Comparative Example 4 Transfer ink was prepared using the following Formulation 4 Then, a transfer sheet was prepared by applying the mixture to a thickness of 4 μm on a polyester film having a thickness of 4 μm. This was subjected to an ink back transfer test under the test conditions described below. The results are shown in Table IK.

Margin Table 1 below [Test conditions: After leaving the transfer film roll in the temperature atmosphere shown in the right column of Table 1 for 20 minutes, rewind the film at room temperature at 100 mm/sec and visually check whether the ink has transferred to the back side. confirmed.

Evaluation 20 Ink transfer area to the back side 0% △ Ink transfer area to the back side 5% or less × Ink transfer area to the back side 10% or more Here, the back side transfer is 55℃ and preferably 60℃. It is necessary that this does not occur at ℃.

As is clear from Table 1, no back side transfer occurred in the ink layer containing a release agent.

<Effects of the Invention> As described above, according to the present invention, it is possible to provide a friendly heat-sensitive transfer sheet that does not cause ink transfer to the back side even in a high-temperature atmosphere and has excellent storage stability.

Claims (1)

[Scope of Claims] 1. A heat-sensitive transfer sheet comprising a heat-melt ink layer provided on one side of a film base material, characterized in that a release agent is blended in the heat-melt ink layer. 2. The heat-sensitive transfer sheet according to claim 1, wherein the amount of the release agent is 0.5 to 15 parts by weight per 100 parts by weight of the heat-melting ink component. 3. Claim 1 in which the mold release agent is a fluorine compound
The heat-sensitive transfer sheet according to item 1 or 2.