JPH0281678A - Thermal transfer plastic film - Google Patents

Abstract

PURPOSE:To make printability good keeping mechanical strength capable of bearing high speed printing by a method wherein a plastic film of which a bubble content is under 20vol.% is laminated on one face or both faces of a plastic film of which the bubble content is a specific % by volume. CONSTITUTION:A film layer (a layer B) in which any bubble is hardly contained is laminated on one face or both faces of the film layer (a layer A) in which many fine independent bubbles are contained on a surface of or inside the film. Then, the layer made cushiony by containing an independent bubble and besides, surface roughness effective for film travelling is revealed. Further, the layer B is the layer for making up for decrease of mechanical strength of the layer A and besides, for controlling the film at a suitable surface roughness required for the film travelling. Therefore, a bubble content of the layer A is necessarily within a range of 20 to 60vol.% and further, the bubble content of the layer B is necessarily under 20vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a base film used as a transfer material for thermal transfer recording. Specifically, the present invention relates to a plastic film for transfer material that has excellent running properties and printing properties, has good mechanical strength, and is suitable for high-speed transfer.

[Problems to be solved by conventional technology and invention]

Conventionally, various methods have been known for recording various types of information in the form of notebook copies, but the most popular recording method for printers and facsimile machines is to use thermal heads, which are small, lightweight, low cost, and highly reliable. The thermal transfer method used is widely used. The base material of this transfer material for thermal transfer is used. In order to improve its runnability and staking resistance, an appropriate amount of inorganic particles of appropriate particle size, such as silicon dioxide or calcium carbonate, is blended into the film.

Now, in recent years, there has been a strong demand for faster recording, and along with this, there has been a trend to relatively increase the surface roughness of the base film and to make the film thinner in order to maintain high running performance. However, in this case, a new problem arises.

That is, in order to impart such surface roughness, it is necessary for K to increase the particle size and amount of inorganic particles contained in the film, and as a result, the number of coarse particles increases, resulting in poor printing performance by transfer. Become. This is thought to be due to the fact that when the part with coarse particles hits the thermal head, the touchability of the head deteriorates, and sufficient heat transfer is not achieved, resulting in uneven or missing prints. becomes. Furthermore, as the film thickness becomes thinner, the film becomes extremely stiff and wrinkles occur during running, which causes poor running and poor printing.

[Means for solving problems]

The present inventors have discovered that the present invention is useful as a base film for thermal transfer, which is suitable for high-speed recording and has excellent printability and mechanical strength while maintaining the following characteristics, and has completed the present invention.

In other words, the gist of the present invention is that a plastic film with a bubble content of 20 to 60 volume is coated on one side with a bubble content of 20 to 60 volume.
Less than 0 volume / Exists in a plastic film for thermal transfer formed by laminating plastic films.

The present invention will be explained in detail below.

The plastic film as used in the present invention refers to a thin film mainly composed of thermoplastic polymers such as polyester, polyolefin, polyamide, polyphenylene sulfide, polyurethane, polyvinyl chloride, polystyrene, and polyether ether ketone. Therefore, in the present invention, there are no particular limitations on the type of polymer, but polyester films are particularly preferably used from the viewpoint of the surface properties and physical properties of the film. Polyester here refers to polyethylene terephthalate, polyethylene 1-1, 6-naphthalate, polybutylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene bisphenoxycarboxylate, or modified products thereof, but among these, dimensional stability and Considering mechanical properties, price, etc., polyethylene terephthalate is particularly preferably used in the present invention.

In this proposal, a film is made using the above-mentioned polymer. The point is that film layers (hereinafter abbreviated as 8 layers) containing almost no air bubbles are laminated on both sides. That is, layer A is a film layer for cushioning the film itself by containing closed cells, and also for developing surface roughness that is effective for film running.
This layer is a layer for compensating for the decrease in mechanical strength of layer A and controlling the surface roughness to an appropriate level necessary for film running.

Therefore, the bubble content of layer A needs to be in the range of 20 to 60 volume cm, preferably 2! The range is from r to θ volume. Further, the bubble content of layer B needs to be less than 20 by volume, preferably less than /S volume, more preferably 10 by volume. If the bubble content of layer A is less than 20 vol., it is unfavorable because the thermal head touchability is poor and the surface roughness that maintains sufficient runnability cannot be imparted, whereas if it exceeds 60 vol. However, it is undesirable to be busy as it may break while driving. Furthermore, if the bubble content of layer B is 20 vol/cm or more, although the running properties are good, the surface smoothness becomes extremely poor, and the mechanical strength also decreases, which is not preferable.

In the present invention, it is necessary to satisfy the above requirements, and furthermore, the total thickness of the film of the present invention is preferably in the range of 1 to 25 μm, and at the same time, the thickness of layer A is greater than or equal to the thickness of layer B. It is preferable. If the thickness of the B layer is thicker than the thickness of the A layer, the cushioning properties of the entire film will be poor, and the contact properties with the thermal head will be poor, which is not preferable. Moreover, if the total thickness exceeds 23 μm, heat transfer will deteriorate, which is undesirable. On the other hand, if the total thickness exceeds 23 μm, it will not have sufficient mechanical strength, which is undesirable.

In the present invention, there are no particular limitations on the manufacturing method as long as the above gist is satisfied. That is, as for the method of manufacturing the A layer, for example,
A method of forming a foam by adding a gas or a vaporizable substance, as described in Japanese Patent Publication No. G765, Japanese Patent Publication No. 1976-1ItlIst, or Japanese Patent Application Laid-open No. 7-31193/, etc. Kaisho 52-4', 7g? / issue bulletin and special public show! A method of forming a foam by adding a substance that chemically decomposes to generate gas as described in RG-TA No. 0A25, etc.; Co276Al.

Examples include a method of forming a foam by impregnating it with a liquid after molding and extracting a substance soluble in a solvent, as described in Japanese Patent Publication No. 2003-100000, and any method may be used.

However, these methods are not necessarily easy methods because they involve special molding equipment and complicated manufacturing processes, and in the case of polyester films that are particularly preferably used in the present invention, Previously proposed Japanese Patent Application Laid-open No. 4.7-/6g Doug/No. 1 and patent application No. 63-75
Particularly preferred is the method described in No. 4da 95.

That is, it is a method in which polyester is blended with a specific different type of polymer, extrusion molded, and then the obtained sheet is stretched in at least one direction to form a film. If this method is adopted, the A layer of the present invention, that is, the bubble content will be 20-4.
Films with a volume in the range of -0 can be easily obtained. Moreover, in this case, the film can be formed within the range of normal stretching conditions without any special modifications to the equipment for producing normal polyester films, so the production cost can be kept low, and this is a great industrial advantage.

This method will be explained in more detail. The different polymers blended in this method are polymers that do not dissolve or immediately cause reactions such as transesterification with polyester, and when melt-mixed, the polyester (sea component)
It is a thermoplastic polymer that is dispersed in the form of fine particles to form island components. Moreover, it is necessary that the polymer easily forms voids, that is, voids at the interface with the polyester when the polyester is stretched. Examples of such polymers include polystyrene, polymethyl methacrylate, polyolefin, liquid crystalline polyester, and polyphenylene sulfide, among which polyolefin, particularly polypropylene, is preferably used, but the polymer is not limited to these.

Further, the blending amount of these different types of polymers is in the range of 3 to 10% by weight, preferably in the range of 5 to 30% by weight. If the blending amount is less than 3% by weight, it is extremely difficult to achieve a bubble content of more than 0% by weight, and if it exceeds 0% by weight, it is undesirable because stretching breaks occur frequently during film formation and productivity is extremely poor. . In this way, polyester is mixed with specific different polymers to form a film, but this method requires further stretching in at least one axis direction. This is done not only to give the film sufficient mechanical strength, but also to make the film have the bubble content necessary for the present invention only after the stretching process. As mentioned above, the stretching conditions themselves do not require any special operation and are carried out within the range of conditions for producing ordinary polyester films.

The manufacturing conditions will be explained in more detail. That is, in an extruder using a polyester raw material blended with different polymers, 23
0~. The mixture is melt-kneaded at a temperature of 320°C, extruded through a die into slits, and cooled to a temperature of about 70°C or less to form a substantially amorphous polyester sheet. Next, the obtained sheet is stretched in the longitudinal and/or transverse directions at an area magnification of 2 times or more, preferably 9 times or more, and further heat-treated at 710 to 250°C, so that the air bubble content is 20 to 60 vol. Manufactures polyester films that range from:

In this way, it is possible to obtain a film (layer A) having a bubble content of 20 to 60 volume cm according to the present invention by using a polyester blended with an appropriate amount of different polymers. It is not limited to only.

Now, as a method for manufacturing layer B, that is, a film layer containing almost no fine closed cells in the present invention, a conventionally known method is used, for example, in the case of polyester film, Japanese Patent Publication No. 30-1989-1. ; The method described in Japanese Patent No. 439 can be used. That is, using normal polyester raw materials, 2
Melt extrusion into a sheet at 0~320℃, 0~gθ℃
After cooling and solidifying the sheet into an amorphous sheet, it is stretched in the longitudinal and/or transverse directions at an area magnification of t or more times, preferably 2 times or more, and then /20 to . 2! ; A method of heat treatment at 0° C., etc. can be used.

In the present invention, the B layer is laminated on one or both sides of the A layer described above, but as long as the gist is satisfied, the polymers used for the A layer and the B layer may be the same or different types. When layer B is laminated on both sides, the polymers may be the same or different. Also, A layer and B layer
There are no particular limitations on the method of laminating the layers, and layers A and B, which have been separately manufactured in advance, may be laminated together via an adhesive layer, or layers B may be laminated in the process of manufacturing layer A. The layers may also be melt extrusion laminated.

However, in the present invention, when productivity and quality are highly considered, a lamination method using so-called coextrusion is particularly preferred. That is, the raw materials forming layer A and the raw materials forming layer B are each melted in separate extruders, then introduced into one die, and both are laminated in a molten state to obtain an extruded sheet in the form of slits. It's a method.

In the case of extrusion lamination, the flatness of the film was poor when layers A and B were previously produced separately and laminated together using an adhesive.

It is undesirable because there are many problems in terms of quality, such as poor thickness accuracy, and production, such as increasing the number of steps and increasing production cost if each is manufactured individually.

Thus, the film of the invention is obtained, but the line absorber,
Pigments, dyes, lubricants, matting agents, fluorescent brighteners, surfactants, etc. are included, and they must be added in the required amount by an appropriate method as necessary.The entire heat-sensitive transfer layer is formed on one side of the film. However, the transfer layer is preferably formed on the B layer surface.

This is because the cushioning properties of layer A efficiently contribute to the head touchability, and the uniform coating of the transfer layer is not particularly limited, and may be either non-reactive type or reactive type. Examples of the non-reactive type include a transfer layer made of a heat-melting ink or a transfer layer made of a sublimable ink, and examples of the reactive type include a combination of a leuco dye and a color developer. .

On the other hand, on the other side on which the transfer layer is not provided, a fusion prevention layer may be formed of silicone resin, melamine resin, 7-carbon resin, epoxy resin, phenol resin, etc. all having good heat resistance.

In addition, on at least one side of the base film of the present invention,
In order to improve the adhesion with the heat-sensitive transfer layer and the anti-fusing layer, various surface treatments such as various primer treatments and corona discharge treatments can be carried out at appropriate times and in appropriate amounts.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measurements and evaluations used in the present invention are as follows.

(1) Bubble content V (volume value) The thicknesses of layer A and layer B in the cross section of the film were measured using a microscope, and then the entire 8-layer film was cut using a microtome. The true density ρn (g/d) + was measured from the weight per unit volume of the film before and after all eight layers were cut, and the bubble content V (volume factor) was calculated using the following formula.

[2) Tensile breaking strength FB CkQ/d) Using a tensile tester 200/type manufactured by Intesco, 23°C jtORH
% temperature and humidity, a sample with a sample width is- is pulled at a strain rate of 100/-, the stress at sample breakage is measured, and the strength per unit cross-sectional area FB (k(7/-)
It was converted into

(3) Evaluation of film runnability 35 parts by weight of paraffin wax, 30 m by weight of carnauba wax, low molecular weight polyethylene/
! A heat-melting coloring material layer consisting of parts by weight and l-parts by weight of carbon black was applied so that the dry coating thickness was 2.58 m. Furthermore, a silicon-based heat-resistant protective layer having a thickness of 0.S.mu.m was provided on the opposite surface of the coloring material layer.

Such a thermal transfer film is manufactured by Fuji Xerox Co., Ltd.
Observe the running condition using a milli-telecopier cog 'S type,
Evaluated on the following three levels: O: The running condition is good and there are no problems at all.

Δ: The ribbon may be slightly wrinkled.

×; The ribbon is wrinkled and the feeding condition is often poor.

(4) Evaluation of Sticking Characteristics Sticking characteristics were evaluated in the following three stages using the same thermal transfer film and evaluation machine as in the evaluation in item (3) above.

○: Good with no problems at all Δ: Slight fusion is observed.

×: Fusion often occurs, and the ribbon may not be conveyed properly and may break.

(5) Evaluation of printability Using the same thermal transfer film and evaluation machine as in the evaluation in item (3) above, the printability was evaluated in the following three stages.

○: Good quality with no shading (unevenness) or missing prints.

Δ: Slight shading and missing parts of the print are observed.

×: The unevenness of the printing density is large, and the missing parts of the printing are clearly visible.

(6) Evaluation of base film film formability Observe the state of breakage when the extruded sheet is stretched in the longitudinal direction and laterally stretched in a tenter. If the sheet breaks frequently in the stretching or heat treatment area and the productivity is poor. ×1 Those with almost no breakage and good productivity were evaluated as ○.

Example 1 Raw material A', which was prepared by adding polypropylene chips + is weight xs to polyethylene terephthalate chips with an intrinsic viscosity of 0.67 and blending them to an even ratio of τ, and the raw material of only the polyethylene terephthalate chips were extruded into separate extruders.
The materials are melted at 0'C, guided through one die, melted and laminated so that raw material A' becomes layer A and raw material B' becomes layer B, extruded into a slit shape, and placed on a cooling drum at yo℃. A so-called two-layer co-extruded non-stretched sheet having a thickness of approximately 6 0 μm was obtained.

Then, the obtained sheet was multiplied by 3.5 times in the vertical direction and 3 times in the horizontal direction.
．． After stretching twice, it was heat-treated at 233° C. for 5 seconds to finally obtain a laminated film in which layer A had a thickness of 3 μm and layer B had a thickness of 7 μm. The bubble content of the A layer of the obtained film was 0% by volume, and the bubble content of the 98 layers was less than 1% by volume. Moreover, the tensile breaking strength of the obtained film is I'1kQ/-
, and showed good film-forming properties without breaking during film formation.

A transfer ink layer, A
A heat-resistant protective layer was coated on the layer side and evaluated as a heat-sensitive transfer material.

In Example/Example/, the amount of polypropylene of raw material A' was 25
A film was obtained in the same manner as in Example 1, except that the raw material B' was changed to polyethylene terephthalate with an intrinsic viscosity of 0.66 containing titanium dioxide fr with an average particle size θ and 3 μm, and then thermal transfer. We evaluated it as a material.

Example 3 A film was formed in the same manner as in Example 1, except that the raw material A', polypropylene, was changed to 20% by weight of a terephthalic acid-isophthalic acid-noxaoxybenzoic acid-ethylene glycol-based liquid crystal polyester. , finally A layer! A laminated film having a thickness of 15βm with an am%B layer was obtained and evaluated as a heat-sensitive transfer material.

Comparative Example 1 In Example 1, raw material A'? The process was repeated in the same manner as in Example 1 except that raw material B' was not coextruded as polyethylene terephthalate having an intrinsic viscosity of 0.66 and containing 2 parts by weight of calcium carbonate with an average particle size of 7 μm. A thick non-laminated film was obtained and evaluated as a heat-sensitive transfer material.

Comparative Example A non-laminated film having a thickness of 7 μm was finally obtained in the same manner as in Example 1, except that the raw material was not used and coextrusion was not performed, and it was evaluated as a thermal transfer material.

Comparative Example 3, q A film was obtained in the same manner as in Example 1 except that the amount of polypropylene in the raw material A' was changed to 3% by weight or xis weight ratio, and evaluated as a thermal transfer material.

Comparative Example S A film was obtained and evaluated as a heat-sensitive transfer material in the same manner as in Example 1 except that io weight of polypropylene was added to the raw material B'.

The results obtained above are summarized in Cloth-1 below.

〔Effect of the invention〕

As detailed above, the film of the present invention is a plastic film laminated with a film that has cushioning properties by containing a large number of fine closed cells, and a film that contains almost no closed cells, Such a film can be used as a thermal transfer material and can highly improve printability while maintaining mechanical strength that can withstand high-speed printing.
Its industrial value is high.

Claims (1)

[Claims] (1) A plastic film for thermal transfer made by laminating a plastic film with a bubble content of less than 20 volume % on one or both sides of a plastic film with a bubble content of 20 to 60 volume %.