JPS6178670A - Thermal transfer gradation recorder - Google Patents

Abstract

PURPOSE:To express intermediate gradations while retaining resolution, by a method wherein a thermal transfer sheet obtained by coating a base with a mixture of a binder and a plurality of kinds of microcapsules having different particle diameters and comprising a color former covered by a heat-fusible resin is used, and images with a density according to thermal energy impressed are recorded on a recording paper. CONSTITUTION:A plurality of kinds of microcapsules 23 differing in thermal breakdown point are prepared each of which comprises a color former layer 24 covered by an outer shell 25 formed of a heat-fusible resin to that the microcapsules 23 have different particle diameters. The microcapsules 23 are mixed with each other, and the mixture is applied to the same base 21 together with a binder 22. To the thermal transfer sheet 11 thus obtained, heat 31 of certain energy is locally applied by a thermal head 14. As a result, only those microcapsules 23' which has the outer shell 25 having a thermal breakdown point not higher than the temperature reached in a heated region 32 are melted and broken to form a color. When the sheet 11 and the recording paper 12 are released from each other, only the microcapsules surrounded by the melted binder 22' are left on the paper 12, resulting in the performing of recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal transfer gradation recording device that records gradation images using a novel thermal transfer sheet.

[Technical background of the invention and its problems]

Thermal transfer recording has the advantages of low noise, high speed printing, use of plain paper as recording paper, no need for processing such as development and fixing, and easy maintenance, making it suitable for office automation systems. It is seen as having great promise as an electronic printer that will play a role in the future.

In conventional thermal transfer recording devices, a thermal transfer sheet is constructed by coating a support material with a coloring material dispersed in a binder made of a uniform heat-melting resin having a fixed melting point to a thickness of several microns. (also called an ink ribbon), and with such thermal transfer sheets, recording is done depending on whether or not the binder in the heated area melts and separates from the support and is transferred onto the recording paper. Actually, only 21ifl recording is possible. Therefore, when expressing halftones, area modulation methods such as the dither method and the 0 degree pattern method have been used, but these methods inherently have a problem in that they are accompanied by a decrease in resolution.

[Purpose of the invention]

An object of the present invention is to provide a thermal transfer gradation recording device that can express halftones without reducing resolution.

[Summary of the invention]

In this invention, a gradation image can be obtained by changing the thermal energy applied to a thermal transfer sheet.

That is, in the thermal transfer gradation recording device of the present invention, there is a difference in the thermal breakdown point due to the difference in particle size of the coloring material covered with the heat-melting resin. ! A thermal transfer sheet made by mixing several types of microcapsules with a binder containing a heat-melting resin and coating the mixture on the same support is used, and this thermal transfer sheet is heated from the support side with energy according to the image information to be recorded. is heated to record a gradation image having a density corresponding to the thermal energy applied to the thermal transfer sheet on a recording paper provided opposite the microcapsules and the binder-coated surface of the thermal transfer sheet. . here,
For example, if a binder containing an electron-accepting substance is used, the coloring material inside the microcapsules, which is melted and destroyed by the thermal energy applied to the thermal transfer sheet, and the electron-accepting substance in the binder can be used as a binder. An image is formed on the recording paper by the reaction.

〔Effect of the invention〕

According to this invention, only the microcapsules that are melted and destroyed by the thermal energy applied to the thermal transfer sheet develop color and form an image, so by changing this thermal energy according to the image information to be recorded, the image information can be An image having the Ill tonality specified by is obtained. That is, it is possible to record an image with gradation characteristics without using an area modulation method such as a dither method. Therefore, it is possible to produce 1q of extremely high-quality gradation images without the reduction in resolution that is unavoidable with the area modulation method.
.

Furthermore, when this invention is applied to the recording of color images and is used in conjunction with dithering, for example, it is possible to achieve 64 gradations, which is the minimum required to express full color, using the smallest size dither barcoon. This makes it possible to form images with outstanding resolution and color reproducibility even in color recording.

[Embodiments of the invention]

FIG. 1 shows a thermal transfer gradation recording device according to an embodiment of the present invention! This shows the rJ case structure. As shown in the figure, the thermal transfer sheet 11 and recording 112 are placed on the platen roller 1.
An image is recorded on the recording paper 12 by passing it between the recording paper 3 and the thermal head 14 as shown by an arrow 15.

As shown in FIG. 2(a), the thermal transfer sheet 11 includes microcapsules 23 and a binder 2 on a sheet-like support 21.
Microcapsule 2 is mixed with Microcapsule 2 and applied.
3 is, for example, phenoxazine H as shown in FIG. 2(b).
Heat-melting lit is applied around the Color Four 7 layer 24, which is made of a mixture of a coloring material such as m-type and a resin such as ethyl cellulose.
It is covered with an outer covering 25 made of fat. Here, the microcapsules 23 are prepared in a plurality of types with different thermal breakdown points and melting points due to the different particle sizes of the thermofusible resin constituting the jacket 25, and these plurality of types of microcapsules are They are mixed and applied together with the binder 22 onto the same support 21. The binder 22 is mainly composed of thermofusible B1 resin having a lower melting point than the thermofusible resin of the outer sheath 25 of the microcapsules 23, and preferably an active material that is an electron-accepting substance is further mixed into the binder 22. ing.

Next, the image recording process in this embodiment will be explained with reference to FIG. The arrow 31 in FIG. 3(a) is applied to the thermal transfer sheet 11 from the support 21 side by the thermal head 14.
When heat of a certain energy is locally applied as shown in the figure, among the microcapsules in the area 32 to which the heat is applied, thermally fused particles of different particle sizes have a thermal breakdown point below the temperature reached in this area 32. As a result of melting and destruction of only the microcapsules 23' having the outer covering 25 made of 1t a+ fat, the coloring material inside the microcapsules 23' reacts with the electron-accepting substance in the binder 22' to produce color. Also, in this region, the heat-fusible substance in the binder 22'! A also melts. On the other hand, the area where no heat was applied [33,34
In this case, the binder 22 does not melt, and of course the microcapsules 2
3 will not be destroyed.

Next, after the step of FIG. 3(a), when the thermal transfer sheet 11 and the recording paper 12 are separated as shown in FIG. 3(b), the melted binder 22' and binder in the heated area 32 are removed. Only the microcapsules surrounded by 22' remain on the recording paper 12 and are transferred, and an image is recorded.

The density of the image recorded on this recording paper 12 depends on the thermal energy applied to the thermal transfer sheet 11 by the thermal head 14. In other words, only the microcapsules in the area 32 whose outer sheath 25 is melted and destroyed by the thermal energy from the thermal head 14 react with the electron-accepting substance in the binder 22 and contribute to color development, so the applied heat is Depending on the energy, the outer sheath 25 melts and
The number of microcapsules destroyed increases, and the image density increases accordingly.

This situation is shown in FIG. In FIG. 4, the horizontal axis represents the thermal energy applied to the thermal transfer sheet 11, and the vertical axis represents the am degree. Thermal transfer recording using a conventional thermal transfer sheet exhibits the characteristics shown in FIG. 41, and almost no gradation can be obtained. Against this.

According to the embodiment of the present invention, a thermal energy pair image density characteristic as shown in characteristic 42 can be obtained, and sufficient gradation can be obtained.

As described above, according to the present invention, the image density can be controlled by changing the thermal energy applied to the thermal transfer sheet, and an image with gradation can be obtained. Therefore, if the device of the present invention is combined with, for example, a conventional dither method to record a color image, the 64 gradations necessary to record a full color image can be achieved using the minimum size (2×2) dither pattern. It is also possible to realize this. In that case,
The reduction in resolution variation due to the dithering method is minimized and (
↓You can record Hatake quality images for the first time.

It should be noted that the present invention is not limited to the above-described embodiments, but can be modified in various ways without departing from the spirit thereof. For example, in the above embodiment, an electron-accepting substance was included in the binder of the thermal transfer sheet, and this was reacted with la F, 2, and the coloring in the destroyed microcapsules (4, etc.). In that case, the coloring material in the microcapsules melted and destroyed in the outer cover is dispersed in the binder, coloring occurs, and an image is recorded.

In addition, in the above embodiment, it was explained that the number of gradations required in combination with the dither method is 1q, but the number of gradations required in combination with the dither method etc. is not combined, but by controlling only the heating energy of the thermal transfer sheet. The number of gradations may be realized.

[Brief explanation of drawings]

Figure 7A1 shows thermal transfer gradation recording 4 according to an embodiment of the present invention.
2(a) and 2(b) are cross-sectional views of the thermal transfer sheet and microcapsules in the same example, and FIGS. 3(a) and (b) are image recording diagrams in the same example. A diagram to explain the process, Figure 4 shows the thermal energy applied to the thermal transfer sheet and the recorded image! It is a figure showing the relationship with Ia degree. DESCRIPTION OF SYMBOLS 11... Thermal transfer...Recording paper, 13... Platen roller, 14... Thermal head, 21... Support, 22... Binder, 23... Microcapsule, 24... Color development Color former including material, 25...
・An outer covering made of a heat-fusible substance. Applicant's agent: Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) A thermal transfer sheet formed by mixing multiple types of microcapsules with different particle sizes in which a coloring material is covered with a heat-melting resin with a binder containing a heat-melting resin and coating the mixture on a support; means for heating from the support side with energy according to the image information to be recorded, and according to the thermal energy applied to the thermal transfer sheet on a recording paper provided facing the microcapsules and the binder coated surface of the thermal transfer sheet. 1. A thermal transfer gradation recording device characterized in that it records a gradation image having a density. (2) The binder contains an electron-accepting substance, and the coloring material inside the microcapsules, which is melted by the thermal energy applied to the thermal transfer sheet, reacts with the electron-accepting substance in the binder, so that the coloring material is transferred onto the recording paper. 2. A thermal transfer gradation recording device according to claim 1, wherein an image is recorded on a thermal transfer gradation recording device.