JPH01290490A - Thermal transfer recording method - Google Patents

Abstract

PURPOSE:To enable printing even on a recording medium having low smoothness and obtain a record with high quality by bringing a thin film into contact with an outer peripheral surface of an ink roll comprising a supercoolable thermal transfer ink, applying heat to the ink in a pattern so as to transfer an ink pattern to the film, and pressing a recording material against the film to trans fer the ink pattern onto the recording material. CONSTITUTION:A thermal head 3 is brought into contact with an outer peripheral surface of an ink roll 1 which surface is constituted of a supercoolable thermally transferable ink, with a thin film 2 therebetween, and heat according to a printing pattern is supplied to the ink constituting the outer peripheral surface. The ink is thermally melted or softened according to the heating pattern, and the melted or softened ink is transferred onto the thin film 2. While the tacky pattern of the ink is maintained, the film 2 is brought into contact with a recording material 6 at a transferring position, when a transfer recorded image 7 is formed under a pressure exerted by a pressing roll 5a and a roll 5d through the recording material 6. Thereafter, the ink roll 1 is further rotated, and the rugged outer peripheral surface of the ink roll is smoothened by a thermal head 4. These steps are repeated.

Description

[Detailed Description of the Invention] [Technical Field] The present invention reduces recording costs by eliminating the need for a thermal transfer material, and enables printing with excellent sharpness even on recording materials with low smoothness. The present invention relates to a thermal transfer recording method.

[Background Art] The thermal transfer recording method has been widely used recently because it can record on plain paper, and the apparatus used is compact and noiseless.

This heat-sensitive transfer recording method generally uses a heat-sensitive transfer material formed by coating a sheet-like support with a heat-transferable ink made of a heat-melting binder and a colorant dispersed therein. The conductive ink layer is superimposed on the recording medium so as to be in contact with the recording medium, and heat is supplied from the support side of the thermal transfer material using an external heating member such as a thermal head, or a voltage is applied to the conductive support or ink layer. is applied to cause the conductive support or the ink layer itself to generate heat using Joule heat (#Open and Close No. 58-220795, JP-A-58-12
No. 790, etc.), a transferred recorded image corresponding to the heat supply shape is formed on the recording medium by transferring molten ink onto the recording medium.

[Problems to be solved by the invention] However, in the conventional thermal transfer recording method, a thermal transfer material is used in which a thermal transferable ink layer is formed on a heat-resistant plastic film support by a complicated coating process. In addition, since this thermal transfer material is essentially disposable, it has the drawback of increasing the cost of thermal transfer recording. Furthermore, since the transferability of the thermal transfer ink is low even on a recording medium with low smoothness, there is also a drawback that the printing quality is poor.

In order to reduce the recording cost of thermal transfer recording method,
It is also possible to use an endless belt-shaped or drum-shaped support that can be used repeatedly, coat and form a thermal transfer ink layer on the spot to create a thermal transfer material, and use it as it is for thermal transfer recording. However, in this case, since it is necessary to incorporate the ink application mechanism into the thermal transfer device, there is a problem that the device becomes complicated and large.

[Objective of the Invention] The main object of the present invention is to eliminate the drawbacks of the conventional thermal transfer recording method described above, maintain various thermal transfer performances, use a compact device, reduce recording cost, and improve smoothness. It is an object of the present invention to provide a thermal transfer recording method capable of printing even on low-quality recording media and capable of high-quality recording.

[Means for Solving the Problems] The thermal transfer recording method of the present invention uses an ink roll made of thermal transfer ink having supercooling properties, and brings an 8i film into contact with the outer peripheral surface of the ink roll. applying patterned heat to the outer circumferential surface through the thin film to transfer the thermally transferable ink to the thin film; and superimposing the thin film to which the ink has been transferred and the recording medium to transfer the ink. The method includes a step of press-transferring the image onto a recording medium.

Hereinafter, the present invention will be described in further detail with reference to the drawings as necessary. “%” indicates quantitative ratio in the following descriptions.
"Parts" and "parts" are based on weight unless otherwise specified.

[Detailed Description of the Invention] Figure 1 shows an embodiment of the present invention in which a thermal head is used as a source of heat to melt or soften thermal transfer ink (hereinafter, this heat supply system is referred to as a "thermal head system"). FIG. 2 is a schematic cross-sectional view in the thickness direction.

Referring to FIG. 1, an ink roll 1 made of thermal transfer ink whose outer peripheral surface has supercooling properties rotates continuously or intermittently in the six directions of arrows.

An endless belt-shaped thin film 2 partially contacts the outer peripheral surface of the ink roll 1 and moves in the direction of arrow B at the same speed as the ink roll 1. The thin film 2 is rolled into rolls 5a and 5b.
and 5c.

On the other hand, a thermal head 3 is brought into contact with the right outer circumferential surface of the ink roll l rotating in this manner via a thin film 2, and heat corresponding to the desired printing pattern is supplied to the thermal transfer ink constituting the outer circumferential surface. do. The ink supplied with heat is thermally melted or thermally softened according to the heating pattern described above, becomes sticky, and is transferred to the thin film 2.

While the adhesive pattern of the thermal transfer ink transferred to the thin film 2 is maintained, F! At the transfer position, the membrane film 2 comes into contact with the recording medium 6 that is being transferred to the right in the figure, but at this time, the above-mentioned pressure is applied via the recording medium 6 from the pressure roll 5a and the roll 5d. The thermal transfer ink that maintains its patterned adhesive state is compressed and transferred onto the recording medium 6 to form a transferred recorded image 7 .

After the above transfer step, the ink roll 1 further rotates from the transfer position in the direction of arrow A, its uneven outer peripheral surface is smoothed by the thermal head 4, and the above steps are repeated again.

Next, the configuration of each part shown in the drawings will be explained.

The ink roll 1 is a member having a rotating body shape such as a cylinder or a truncated cone, and at least its outer peripheral surface is made of thermal transferable ink, and is capable of rotating around the center 11 of the ink roll 1. The ink roll 1 may be formed by molding only the thermal transferable ink into the above-mentioned rotating body shape, or the ink roll 1 may be formed by forming a layer of the above-mentioned ink around a core material made of a material such as metal or resin. It may also be l.

The ink that has been melted or softened in a pattern by the application of heat from the thermal head 3 needs to maintain its transferability up to the transfer position upon contact with the recording medium 6. For this purpose, it is better to use supercooled thermal transfer ink as the thermal transfer ink forming the outer peripheral surface of the ink roll l.

Here, supercooled thermal transferable ink refers to a molten or softened state that, when heated to melt or soften and then cooled, can be transferred to a recording medium even at the future melting point of the ink or at a temperature below its softening point. , refers to something that maintains a sticky state for a certain period of time.

The thermal transfer ink used in the present invention is made by dispersing colorants such as dyes and pigments in a binder having supercooling properties. A binder having supercooling properties refers to a binder that maintains the molten state for a certain period of time even at a temperature below the original melting point, when the binder is heated above the melting point and cooled from the molten state.

Such supercooled thermofusible binders include plasticizers such as N-cyclohexyl-p-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, dicyclohexyl phthalate, etc., which are known supercooled substances, Alternatively, benzotriazole, acetanilide, etc., or their derivatives may be used alone or in combination of two or more, and these supercooled substances may be used in polyamide resins, polyester resins, epoxy resins, etc., which are used in conventional thermal transfer inks. Thermoplastic resins such as polyurethane resin, polyacrylic resin, polyvinyl chloride resin, cellulose resin, polyvinyl alcohol resin, petroleum resin, phenolic resin, polystyrene resin, spermaceti, beeswax, lanolin, guaruna Natural waxes such as bawax, candelilla wax, montan wax, and ceresin wax, petroleum waxes such as paraffin wax and microcrystalline wax, oxidized waxes and ester waxes, low molecular weight polyethylene, synthetic waxes such as Fischer-Tropsch wax, lauric acid, and myristic wax. Waxes represented by acids, higher fatty acids such as palmitic acid, stearic acid, and behenic acid, higher alcohols such as stearyl alcohol and behenyl alcohol, esters such as sucrose fatty acid ester and sorbitan fatty acid ester, and amides such as oleylamide. or natural rubber, styrene-butadiene rubber, isoprene rubber,
Elastomers such as chloroprene rubber (preferably with a softening point of 40 to 230°C, more preferably 50 to 200°C)
"C").

In order to obtain the supercooled thermofusible binder as described above, for example, 20 to 90 parts of the above supercooled substance may be mixed into 10 to 90 parts of the conventional thermofusible binder.

As other supercooled thermofusible binders, resins or waxes that themselves have supercooling properties can be used.

For example, there are certain types of unsaturated polyester resins, polyamide resins, polyurethane resins, amide waxes, and oxidized waxes.

It is also possible to adjust the supercooling property by adding an oil or the like to the supercooled thermofusible binder, or to adjust the melt viscosity, adhesive strength, etc. by adding elastomers or the like.

As the coloring agent constituting the thermal transfer ink together with the binder, for example, all facial cleansers commonly used for printing or other recording methods such as carbon black can be used, and these facial cleansers may be used alone or in combination of two types. The content of the colorant mixed above is preferably 1 to 40% with respect to the above ink.

The supercooled thermal transfer ink used in the present invention is
It is preferable to have a melt viscosity range of 102 to 106 voids when the temperature range is 40 to 120°C, and more preferably 40 to 106 voids.
10' to 10' voids when the temperature range is 120°C, more preferably 1 when the temperature range is 60°C to 100°C.
It is preferable to have a melt viscosity range of 0' to io' voids. The melt viscosity and melting point in the present invention are measured using a Shimadzu flow tester CFT-500 with a load of 10 kg.
It is defined by the apparent viscosity and outflow start temperature when the thermal properties of the sample ink are measured under the condition of a heating rate of 2° C./2.

As the supercooled ink roll l rotates, it comes into contact with the thermal head 3 through the thin film 2, and heat is applied from the heating element. may be pushed out in a direction opposite to the direction of rotation of the ink roll. the result,
The recorded image after transfer may become trailing and unclear. Furthermore, when the melt viscosity is greater than 106 voids, the ink in the molten state has a high cohesive force, which reduces the amount of ink transferred to the recording medium during transfer.

As mentioned above, the supercooled thermal transfer ink composed of a supercooled binder, colorant, and other additives has a melting point or softening point of preferably about 40 to 180°C, more preferably about 50 to 150°C. and -
Once heated to above the melting point or softening point to melt or soften, the time required for solidification to start when left at room temperature (hereinafter referred to as "supercooling time") is preferably 0.1
It is set to about seconds to 100 seconds, more preferably about 0.1 seconds to 50 seconds. Most preferably it is 0.1 seconds or more and 10 seconds or less. The melting point or softening point of the ink is 40°C
If the melting point or softening point is higher than 180°C, the storage stability of the ink roll 1 will deteriorate and the non-printing area of the recording medium will be stained. On the other hand, if the melting point or softening point is higher than 180°C, a large amount of thermal energy is required to melt or soften the ink. This will require the following.

Furthermore, if the supercooling time is shorter than 0.1 seconds, it will be difficult to maintain the melted or softened state after the heat application process is completed until the transfer process to the recording medium.
If it is larger than seconds, the recorded image immediately after being transferred to the recording medium will lack stability.

In order to obtain the ink roll l used in the present invention, for example, the above-mentioned supercooled thermal transferable binder, colorant, and additives are melt-kneaded using a dispersion device such as an attritor to obtain a thermal transferable ink, and as needed. The core material is then used to form a desired rotating body shape using a mold or the like.

The Q membrane film 2 may be either an edge belt or an endless belt, and the endless belt is advantageous in terms of running costs. Materials for the thin film 2 include:
A plastic film such as polyester, polyolefin, polyamide, polyimide, etc. is suitable, and the surface to which the thermal transfer ink is transferred is subjected to release treatment as necessary so that the ink is transferred well to the recording medium. Alternatively, the surface that comes into contact with the thermal head may be subjected to heat-resistant treatment or lubricant treatment.

In addition, the thickness of this thin film 2 is determined by mechanical strength,
The amount may be selected in consideration of heat resistance, but it is preferably 1 to 20 g, more preferably 2 to 10 g. It is also possible to use ink rolls l having a plurality of different tones for color recording.

As the thermal head 3, a conventional thermal head can be used as is. The pressure applied by this heat head 3 is 2 K
g/cm" or less, and in order to prevent the ink from shifting, the smaller the applied pressure, the better, and the applied pulse width should be 0.5 g/cm" or less.
A condition of 5 to 5 m5ec is preferably adopted.

By changing the amount of heat applied by the heat head 3, s
It is also possible to obtain so-called halftone recording on the recording medium 6 by changing the amount of ink transferred to the Wi film.

As the pressure rolls 5a and 5d, either an elastic roll whose surface is made of various rubbers, resins, etc., or a rigid roll whose surface is made of metal, ceramics, etc. can be used.

The pressure by these pressure rolls 5a and 5d is a linear pressure of 0.
5 to 10 Kg/c■, more preferably 1 to 5 g/C■. From the viewpoint of sufficiently adhering the thermal transfer ink to the concave portions on the surface of the recording medium with poor surface smoothness, it is preferable that the pressure is large.

The thermal head 4 is a member that heats the outer circumferential surface of the ink roll 1, which has become uneven due to the transfer process, by heat through the RN membrane 2, and heats it in a negative direction.

This smoothing is performed by heating the outer circumferential surface to some extent to melt or soften the ink again.

The embodiments of the present invention have been described above in which a thermal head method is used, that is, a thermal head is used as a heat source in the heat application process, but the present invention can also be applied when a laser beam or other heat source is used instead of the thermal head. It is easy to understand that the same can be done.

[Effects of the Invention] As described above, according to the present invention, after applying heat in a pattern through a thin film to the smooth outer peripheral surface of an ink roll having an outer peripheral surface made of supercooled thermal transferable ink, the above-mentioned pattern is applied. Provided is a thermal transfer recording method in which the ink is transferred under pressure onto a recording medium that is in a melted or softened state depending on the temperature.

According to the recording method of the present invention, while using a compact thermal transfer device, there is no need for the conventionally used thermal transfer material coated with ink in a complicated manner, thereby reducing recording costs in terms of materials and energy costs. Costs can be significantly reduced.

Further, according to the present invention, it is possible to obtain high-quality printing even on a recording medium with low smoothness, and it is also possible to obtain halftone recording.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view in the thickness direction of a recording medium showing an embodiment of the thermal transfer recording method of the present invention. l... Ink roll 2... Thin film 3.4... Thermal head 6... Recorded object 7... Transfer recorded image

Claims (1)

[Scope of Claims] An ink roll made of thermal transfer ink having supercooling properties is used, a thin film is brought into contact with the outer peripheral surface of the ink roll, and a pattern of heat is applied to the outer peripheral surface of the ink roll through the thin film. The method is characterized by comprising the steps of: transferring the thermally transferable ink onto the thin film by applying a pressure; and superimposing the thin film to which the ink has been transferred and the recording object, and pressingly transferring the ink onto the recording object. A thermal transfer recording method.