JPS62158073A - Image-recording method - Google Patents

Abstract

PURPOSE:To ensure that only an ink necessary for recording can be transfer recorded through rapidly solidifying a molten ink, prevent ground fogging or ghost from being generated and obtain clear images, by transferring a supercoolable ink onto a recording medium, thermally smoothening the surface of a transfer medium used for transfer, and maintaining the surface at a relatively high temperature which is not higher than the melting point of the ink. CONSTITUTION:An ink roller 1 has the shape of a body of rotation such as a cylinder, and at least the surface thereof is constituted of a supercoolable heat-fusible ink layer. The region ranging from a thermal smoothening member 5 to a recording head 3 is covered by a heat-insulating cover 6 along the surface of the ink roller 1, whereby the temperature of the surface of the ink roller 1 heated by the thermal smoothening member 5 which smoothens the surface of the ink roller 1 rugged due to a transferring operation by heating the surface to some extent is prevented from being considerably lowered. The surface of the ink roller melted by heating is maintained at a relatively high temperature which is lower than the melting point of the ink, whereby the molten surface of the ink roller is rapidly solidified.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image recording method using ink having supercooling characteristics.

<Prior art> Among image recording methods, the thermal recording method has been widely used in recent years because the device is small and lightweight and generates little noise, as well as being able to record on plain paper. .

The heat-sensitive recording method commonly used in the past uses an ink sheet in which a thin layer of heat-melting ink is coated on a heat-resistant base film. The ink layer is melted in an image pattern by heating with a recording head that generates heat according to image information, and the molten ink is transferred and recorded on a recording medium (Japanese Patent Laid-Open No. 58-220795).
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However, in the above recording method, hot-melt ink must be applied on a relatively expensive heat-resistant base film through a complicated process, and this ink sheet is disposable once the ink is transferred. There are drawbacks such as high running costs and poor thermal efficiency since the ink layer is heated through the base film.

Therefore, recently, a recording device has been proposed that uses ink that has supercooling characteristics, that is, ink that maintains a melted or softened state for a certain period of time even if it is heated and melted or softened and then cooled. No. 151375). In this apparatus, the ink having the above-mentioned supercooling characteristic is melted and applied onto the recording roller, and after the ink is solidified, heat is directly applied in the form of an image pattern by the recording head to cool the ink into one layer.
It melts the ink and transfers the molten ink to the recording medium.As mentioned above, the ink can be heated without going through a heat film, so it has good thermal efficiency, and the recording roller can be rotated to transfer the molten ink to the recording medium. Since recording can be performed repeatedly by consuming only ink, running costs can be effectively reduced.

<Problems to be Solved by the Invention> Although the recording method using an ink line having supercooling characteristics has the above-mentioned advantages, after the substance having supercooling characteristics reaches a temperature below the melting point from a molten or softened state, It does not solidify rapidly after a certain period of time, but gradually solidifies.

Therefore, for supercooled ink that can maintain a molten state with low viscosity to obtain a transferred image of sufficient density after being heated in an image pattern, it is necessary to melt and apply the ink onto the recording roller before applying it to the transfer process. It will not completely solidify until a very long time has passed.

If transfer recording is performed before the supercooled ink is completely solidified, ground force blur will occur. Therefore, in order to prevent the above-mentioned soil blurring, it is necessary to increase the diameter of the recording roller in a device that uses supercooled ink and to lengthen the time from melt application of the ink to transfer.As a result, the device becomes larger and There were also problems such as slow recording speed.

The present invention aims to solve the above-mentioned conventional problems and provide an image recording method that can increase the recording speed without increasing the size of the apparatus used.

<Means for Solving the Problems> The present invention solves the above-mentioned conventional problems by heating the surface of a rotating transfer medium that has supercooled thermofusible ink on its surface in accordance with image information. a step of transferring the transfer medium to a recording medium, a step of heating and smoothing the surface of the transfer medium after the transfer, and measuring the surface temperature of the transfer medium after the smoothing and before being heated according to the image information before the transfer. The ink is maintained at a temperature higher than the surface temperature of the ink and lower than the melting point of the ink.

<Function> According to the above means, the ink melted or softened in an image pattern is transferred to a predetermined recording medium, and the surface of the transfer medium after the transfer is heated to melt and smooth. Since the surface of the transfer medium after smoothing is kept at a relatively high temperature below the melting point, solidification of the supercooled thermofusible ink is promoted, and as a result, the surface of the transfer medium after melting and smoothing is heated again in an image pattern. This eliminates the need for a long period of time.

<Example> Next, an example of the present invention to which the above-mentioned means is applied will be described with reference to a schematic sectional view shown in FIG.

In the figure, an ink roller 1 is a transfer medium made of solidified ink having supercooling characteristics, and is configured to be rotatable about a shaft 1a.

A pressure roller 2 is disposed below the ink roller 1 and is in pressure contact with the surface of the ink roller 1, and the pressure roller 2 is moved continuously or intermittently in the direction of arrow a depending on the recording operation. When the ink roller 1 is driven to rotate in the direction indicated by the arrow, the ink roller 1 is driven to rotate in the direction indicated by the arrow.

Further, as the ink roller 1 rotates, the ink roller 1 is disposed on the upstream side in the rotational direction of the ink roller 1 with reference to the pressure contact portion between the ink roller 1 and the pressure roller 2 (hereinafter referred to as the “pressure contact portion”), and The recording head 3 in contact with the surface of the ink roller 1 generates heat according to image information, and the surface of the ink roller 1 is melted or softened in an image pattern due to the heat generation.

At this time, the recording medium 4 is conveyed in the direction of arrow C by a predetermined conveyance means in synchronization with the rotation of the ink roller 1, and reaches the pressure contact section, where the melted or softened ink is recorded. The image is transferred to the medium 4.

After the ink is transferred to the recording medium 4, minute irregularities occur on the surface of the ink roller; Thermal smooth member 5 in line contact with the surface of
The ink is heated and melted by the molten ink, and is smoothed by the surface tension of the molten ink.

The ink roller 1 whose surface has been heat-smoothed is covered with a heat-insulating cover 6 serving as a heat-insulating means, and the surface temperature of the ink roller 1 heated and melted by the heat-smoothing member 5 is maintained at a relatively high temperature below the melting point, as will be described later. The solidification of the molten ink roller surface is promoted.

Continuous recording is performed by repeating the above steps.

Although the diameter of the ink roller 1 decreases in accordance with the transfer recording, the ink roller 1 is held via the spring 1b and is always pressed against the pressure roller 2 even if the roller diameter decreases. Further, the recording head 3 and the thermal smoothing member 5 are also held via springs 3a and 5a, respectively, so that they are always in contact with the surface of the ink roller 1.

Next, the configuration of each part shown in FIG. 1 will be individually explained.

First, the ink roller 1 has a rotating body shape such as a cylinder or a truncated cone, and at least its surface is made of a heat-melting ink layer having supercooling characteristics. This ink roller 1 may be formed by molding only thermal transferable ink into the shape of the rotating body, or the ink layer may be formed around a core material made of a material such as metal or resin.

The supercooled thermofusible ink forming the ink roller 1 is composed of a coloring agent such as a dye or pigment dispersed in a thermofusible binder having supercooling properties. Here, the supercooled thermofusible binder refers to a binder that, once heated above its melting point and cooled from its molten state, maintains the molten state for a certain period of time even at a temperature below its original melting point. , itself is known. In addition, for binders that do not exhibit a constant melting point, r
The softening point J determined by the ring and ball method is used.

Examples of the binder having supercooling properties include plasticizers such as N-cyclohexyl-p-)luenesulfonamide, N-ethyl-p-)luenesulfonamide, dicyclohexyl phthalate, etc., which are known supercooling substances. , or hensitriazole, acetanilide, etc., or derivatives thereof, singly or in combination of two or more, to produce polyamide resins, polyacrylic resins, polyvinyl acetate resins, or combinations thereof, which have been used in conventional hot-melt inks. Thermoplastic resin such as a polymer (preferably a softening point of 40 to 230°C due to undetermined ring J, more preferably 50 to 200°C)
(°C), various natural or synthetic waxes, or other heat-melting binders.

To obtain the supercooled thermofusible binder used in the present invention,
For example, 20 to 90 parts by weight of the supercooled substance may be mixed with 10 to 90 parts by weight of the heat-melting binder.

Further, it is also possible to adjust the supercooling property by adding an oil or the like to the supercooled hot-melt binder, or to adjust the melt viscosity, adhesive force, etc. to trR by adding an elastomer g or the like.

As the coloring agent constituting the supercooled thermofusible ink together with the supercooled thermofusible binder, all dyes and pigments commonly used for printing carbon blanks or other recording methods can be used. Dyes and pigments may be used alone or in combination of two or more. The content of the colorant is preferably 1 to 40% by weight based on the ink.

As mentioned above, the supercooled thermofusible ink composed of the supercooled thermofusible binder, colorant, and other additives preferably has a melting point or softening point of about 40 to 200°C, more preferably 50 to 180'C. Once heated above the melting point or softening point and melted or softened,
When left at room temperature, the time until a solidification starts (hereinafter referred to as "cooling time j") is preferably 0.1 seconds to 100 seconds.
It is set to a certain degree, more preferably 0.1 seconds to 50 seconds, and even more preferably 0.1 seconds to 10 seconds.

When the melting point or softening point of the ink is lower than 40°C,
The storage stability of the thermal transfer material is deteriorated and the non-recording portion of the intermediate transfer member 2 is smeared. On the other hand, if the melting point or softening point is higher than 200° C., a large amount of thermal energy is required to heat the pattern.

Furthermore, if the supercooling time is shorter than 0.1 seconds, it will be inappropriate to maintain the molten state until the retransfer process to the recording medium 4 after the completion of the image pattern heating process, whereas the supercooling time is 10 seconds. If it is larger, the recorded image after being transferred to the recording medium 4 will lack stability.

To obtain the ink roller 1 used in the present invention, the above-mentioned supercooled thermofusible binder, colorant, and additives are melt-kneaded using a dispersion device such as an attritor to obtain a thermal transfer ink, and if necessary, The core material may be used to form a desired rotating body shape using a mold or the like. Furthermore, for color recording, supercooled thermofusible ink rollers of several different tones can be used.

Next, the pressure roller 2 has a surface made of nitrile rubber.
Either an elastic roller made of polyurethane rubber, natural rubber, ethylene propylene rubber, vinyl chloride resin, nylon resin, etc., or a rigid roller whose surface is made of metal, ceramics, etc. can be used.

In addition, the pressure between the ink roller 1 and the pressure roller 2 due to the spring 1b is set at a linear pressure of 50 to 500 g/c so that the hot-melt ink can sufficiently adhere to the concavities on the surface of the recording medium 4.
m is preferred.

The recording head 3 has a large number of heating elements arranged on a substrate, and is configured to generate heat according to image information, and heats and melts or softens the surface of the rotating ink roller 1 in an image pattern. It is something that makes you

As the recording head 3, a head made of needle-shaped recording electrodes is used instead of the heat-generating head as described above, and this head is combined with a conductive drum made of a resistive layer and a conductive layer. The structure may be such that Joule heat is generated in the resistance layer by applying a voltage to the recording electrode, or a heat source using laser light may be used.

The thermal smoothing member 5 is a member that heats the surface of the ink roller 1, which has become uneven due to the transfer process, to a certain extent to smooth it.The thermal smoothing member 5 is a member that heats the surface of the ink roller 1, which has become uneven due to the transfer process, to make it smooth. The heater contacts the surface of the ink roller 1 to heat and melt the surface of the ink roller 1, smoothing it by the surface tension of the molten ink.

Now, to explain the heat retaining means, a heat retaining cover 6 covers the area along the surface of the ink roller from the thermal smoothing member 5 to the recording head 3, and the surface temperature of the ink roller heated by the thermal smoothing member 5 is The insulating cover 6 retains heat and maintains the temperature higher than room temperature and lower than the melting point of the ink.

When the ink roller surface after heating and melting is maintained at a relatively high temperature lower than the melting point of the ink and within that range, the molten surface rapidly solidifies as shown in FIG. In other words, after an ink with supercooled thermofusibility melts, it will solidify in the shortest time when the temperature is slightly lower than the melting point of the ink, and if the temperature is lower than that, the time until solidification will be will take a long time.

Therefore, the surface of the ink roller l is maintained at a relatively low temperature to prevent the ink from solidifying after it is melted into an image pattern by the recording head 3 until it is transferred to the recording medium 4.
After being thermally melted by the thermal smoothing member 5 and reaching the recording head 3 again, it is desirable that the temperature be maintained at a relatively high temperature below the melting point of the ink so that the ink can solidify quickly.

If we consider the reason why supercooled thermofusible ink has the properties shown in Figure 2, when a substance with supercooling properties is melted and then cooled below its melting point, the molecules slowly crystallize. The molten state changes from the molten state to the solidified state. When the molten supercooled thermofusible ink is kept at a relatively high temperature below its melting point, the thermal motion of the molecules becomes active, and as a result, the probability of arranging them in a crystalline state increases,
It is thought that the transition to a solidified state is accelerated.

However, when the temperature of the ink reaches a temperature near the melting point or higher, crystallization due to thermal movement of molecules is prevented, so it is thought that the ink will not solidify.

Generally, in this type of recording method, ink having a melting point of 60° C. or higher is used in consideration of the storage stability of the transfer recording. Therefore, if the surface of the ink roller 1 smoothed by the thermal smoothing member 5 is heated to a temperature slightly higher than room temperature, it will take a long time to solidify. It is important to keep the temperature relatively high.

According to experiments conducted by the applicant, the ink having the above-mentioned supercooling characteristics was melted, and the melted ink was transferred to the chamber/IJL2.
When the temperature was maintained at a temperature 5 to 30 degrees Celsius higher than 5 degrees Celsius, the time it took for the ink to solidify was 11 times longer than when it was left at room temperature.
It was shortened to about 1/2 to 1/10.

Therefore, when the ink roller surface that has been thermally smoothed by the thermal smoothing member 5 is maintained at a relatively high temperature below the melting point of the ink, it solidifies rapidly. The time required to heat the image pattern can be shortened, and the recording speed can be increased.

In the above-mentioned embodiment, the surface of the ink roller after being melted by the thermal smoothing member 5 was simply covered with the heat-insulating cover 6, but the cover 6 has a built-in heater, and the heater is made to generate heat appropriately to melt the molten ink. It is more effective to always maintain the optimum temperature to solidify in the shortest possible time. In particular, since the internal temperature of the heat retaining cover 6 is not high when the device starts operating, it is effective to raise the temperature inside the heat retaining cover to the optimum temperature using a heater.

Furthermore, it is easy to understand that the same effect can be obtained even if the ink roller surface, which has been melted by the thermal smoothing member 5, is maintained at a relatively high temperature only by the heater, without using the heat insulating cover 6.

<Effects of the Invention> As described above, the present invention transfers ink having supercooling characteristics onto a recording medium, thermally smoothes the surface of the transfer medium after the transfer, and then smooths the surface at a temperature below the melting point of the ink for comparison. By maintaining the temperature at a target temperature, it became possible to rapidly solidify the molten ink. Therefore, it is possible to transfer and record only the ink necessary for recording without using expensive ink sheets as in the past, and it is also possible to increase the recording speed using a small device, and even if the recording speed is increased, the land resistance is Clear images can be recorded without blurring or ghosting.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional explanatory diagram of a configuration embodying a recording method according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the temperature of melted supercooled thermofusible ink and the time until it solidifies. It is. 2 is an ink roller, 1a is a shaft, 1b is a spring, 2 is a pressure roller, 3 is a recording head, 3a is a spring, 4 is a recording medium, 5 is a thermal smoothing member, 5a is a spring, and 6 is a heat insulation cover.

Claims (1)

[Claims] A step of heating the surface of a rotating transfer medium having supercooled thermofusible ink on its surface in accordance with image information to transfer the ink to a recording medium, and a step of heating and smoothing the surface of the transfer medium after the transfer. and a step of maintaining the surface temperature of the transfer medium after the smoothing and before being heated according to the image information to be higher than the surface temperature before the transfer and lower than the melting point of the ink. Recording method.