JPH0333118B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a heat-sensitive transfer film that has excellent heat transferability, excellent surface properties of the transferred object after transfer, and is easy to handle. (Prior art) Conventionally, as a thermal transfer film suitable for a thermal transfer recording method using a thermal head, a transfer layer mainly composed of wax containing a colorant is formed on a thin base material such as a polyester film or condenser paper. something is known. However, since conventionally used thermal transfer films are composed of a single transfer layer, the main properties required for thermal transfer films are thermal transferability and surface performance of the transferred object after transfer. It is difficult to satisfy all of the requirements such as easiness of use and operability of a transfer film, and there has been a demand for a transfer film that solves these problems. From the viewpoint of the composition of the transfer layer, the main efforts that have been made in the past have been to lower the melting point and melt viscosity to improve thermal transferability, improve the operability and storage stability of the transfer film, and improve the surface of the transferred material. In order to balance the two directions of high melting point and high melt viscosity to improve performance and printing quality, and to achieve both, it is important to reduce the sensitivity to heating during transfer, that is, the sudden change in melt viscosity within an extremely narrow temperature range. It was about pursuing change. Although these efforts have yielded many results in the basic study of the composition of thermal transfer layers, the results have not yet reached a point of complete satisfaction. (Purpose) As a result of various studies, the present inventors have
In order to satisfy the above requirements, the inventors came to the conclusion that a composite transfer layer rather than a single transfer layer is preferable, leading to the completion of the present invention. Hereinafter, the progress leading to the present invention will be explained in detail. (Structure) In the present invention, the base material is a thin film, paper, etc. that has good thermal conductivity, heat resistance, and strength.
Typically, condenser paper or polyester film is used. Further, as the binder, waxes such as natural waxes and synthetic waxes, and if necessary, other thermoplastic resins are used, and as the colorant, generally known organic pigments, inorganic pigments, and dyes are used. A solvent-dispersed resin composition is a composition in which the binder and colorant are dispersed in a liquid dispersion medium that volatilizes or evaporates during the transfer film manufacturing process. is a mixture of the above-mentioned binder and colorant that becomes part of the transfer layer as it is, and therefore refers to a mixture that is solid at room temperature and becomes liquid when it is melted by heat during coating. Initially, the present inventors used two methods to form a composite transfer layer: a method in which hot-melt resin compositions were applied in layers, and a method in which solvent-dispersed resin compositions were applied in layers. However, in the first method, if the melting points of the resin composition to be applied first and the resin composition to be applied next are close to each other, the two will mix during coating, making it difficult to form a uniform coating layer. could not be formed. In the second method, the transfer energy was high and satisfactory results could not be obtained in terms of transferability. The problem common to both is that the melting point and melt viscosity of the first coating layer to improve transferability must be significantly lowered compared to the first coating layer to improve the surface performance of Hiko transfers. First, this caused blocking and set-off of the transfer film. As a result of examining this process in detail, the present inventors noticed the following remarkable results. That is, between a transfer layer formed of a solvent-dispersed resin composition and a transfer layer formed of a hot-melt resin composition, which have essentially the same composition, the former is clearly more necessary. The results show that the transfer energy is high and the adhesion to the base material is good. The reasons for this include the thermal history during the process, the tension of the base material,
Various factors can be considered, such as wetting of the composition onto the base material, but this is still within the realm of speculation. Based on the above results, the present inventors have provided a layer formed of a solvent-dispersed resin composition as a transfer layer in contact with a substrate, and a layer formed of a hot-melt resin composition as a transfer layer in contact with an object to be transferred. We became convinced that we could obtain a transfer film that satisfies the three points mentioned above: transferability, surface performance of the transferred object after transfer, and ease of handling of the transfer film, so we conducted further research. As a result, the present invention was completed. That is, the gist of the present invention is to coat one side of a base material with a solvent-dispersed resin composition in which a resin composition that melts when heated and a colorant are dispersed in a solvent, and then dry to remove the solvent. The first transfer layer is formed by volatilization, and then a hot-melt resin composition containing a colorant in a resin composition that melts when heated is applied in a heated molten state, and then cooled to form a first transfer layer. This is a method for producing a heat-sensitive transfer film, which is characterized by forming a second transfer layer. (Effects) As described above, the present invention achieves (1) adhesion to the substrate by forming a transfer layer by applying two types of compositions that have almost the same composition but different states at the time of coating. Improves the quality of the product and prevents it from rubbing off and peeling off from the base material. (2) Lower melting point and lower melt viscosity without causing blocking of the layer in contact with the transferred material, thus improving transferability for the same applied energy. However, in addition, when applying a hot-melt resin composition over a resin layer with improved adhesion to the base material, it is better to apply a transfer formed with a hot-melt resin composition. Compared to coating from the top of the layer,
An advantage is that less reduction in coating temperature is required. These are intended to further expand the range of selection of each resin composition, and therefore, a transfer layer formed with a solvent-dispersed resin composition and a transfer layer formed with a hot-melt resin composition are compositionally the same. There is no need for it to exist, and it goes without saying that changing the composition of each transfer layer depending on the purpose is not excluded. Example 1 1.5 g/m ² of the following resin composition was applied onto a 6μ thick polyester film using a gravure coater.
After applying dry and drying for 30 seconds at 60°C, further coat the following resin composition at 2.0g/m ² dry using a gravure coater at 85°C, and then cool it.
A transfer film was produced. [Resin composition] Synthetic wax (melting point 71°C) 22 parts by weight Carbon black (colorant) 25 Toluene (solvent) 75 Dispersant 0.2 [Resin composition] Synthetic wax (melting point 71°C) 110 parts by weight Carbon black (Colorant) 12.5 Dispersant 1 part by weight As a comparative example, a transfer film was prepared by applying only the resin composition to the same polyester film at a rate of 3.5 g/m ² dry at 85°C. This was measured using a Beck smoothness meter for 200 seconds using a thermal head of 8 dots/mm, a pulse width of 1 ms, and an applied energy.
When transferring at 0.2W/dot, the following results were obtained.

[Resin composition]

Synthetic wax (melting point 73℃) 22 parts by weight Carbon black (coloring agent) 2.5 〃 Toluene (solvent) 75 〃 Dispersant 0.2 〃 [Resin composition] Synthetic wax (melting point 64℃) 106 parts by weight Carbon black (colorant) 12.5 〃 Dispersant 1 Oil 4 〃

【table】

Claims (1)

[Claims] 1. A solvent-dispersed resin composition in which a resin composition that melts when heated and a colorant are dispersed in a solvent is applied to one side of the base material, and dried to volatilize the solvent to form a first transfer layer. Then, a hot-melt type resin composition in which a coloring agent is blended into a resin composition that melts when heated is applied thereon in a heated molten state, and then cooled to form a second transfer layer. A method for producing a thermal transfer film.