JPS60199692A - Printer - Google Patents

Abstract

PURPOSE:To enhance dot reproducibility in low-density gradations, by a method wherein a heat-fusible ink comprising electrically charged particles is transferred to a printing material in an electric field. CONSTITUTION:A recording sheet 40 comprises a heat-fusible ink layer 44 and a base film 43, wherein the ink layer 44 comprises a coloring pigment or dye, a binder, electrically charged particles, a dispersant and a plasticizer. The direction of an electric field generated between a thermal head 42 and a conductive support base 47 is so set as to move the charged particles contained in the ink layer toward the recording paper, and an impressed voltage is determined by the thicknesses of the sheet 40, the recording paper 45 and an insulator 46. When an electric field is applied to electrets mixed in the ink layer to thereby transfer dots onto an ordinary paper, the ink adheres not only to fibrous parts exposed on the surface of the paper but also into gaps between fibers, so that gradation reproducibility at low density becomes favorable, and image quality is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a printing device that melts ink using heat and performs transfer.

[Prior art]

A printing device that melts ink using heat and performs transfer is
Heat-sensitive melting coloring material C A recording paper in which heat-sensitive melting ink is melted, softened, and bonded by selectively applying heat to a sheet (hereinafter referred to as recording sheet) coated with a base film (hereinafter referred to as heat-sensitive melting ink). It is a method of transferring and solidifying the image, and is broadly called a thermal transfer device.

This thermal transfer device can be roughly divided into two methods. One is a narrowly defined thermal transfer device that applies only heat to the recording sheet using a thermal head, as shown in Figure 1, and the other is a thermal transfer device in which a resistance layer is provided on the opposite side of the recording sheet from the heat-sensitive melting ink layer. This is an energization transfer device that energizes the resistance layer and generates heat.

The principle is shown in FIGS. 1 and 2.

FIG. 1 is a diagram showing the principle of a thermal transfer device in a narrow sense.

In the figure, 11 is the power supply for the thermal head, 12 is the thermal head, 13 is the base film of the recording sheet,
14 is a heat-sensitive melting ink layer; 15 is an ink transfer portion; 1
6 is recording paper. Further, a region 17 indicated by a dotted line is a simulated region where the heat applied by the thermal head 12 spreads through the base film 13 and the heat-sensitive melting ink layer 14.

In this method, the heat applied by the thermal head 12
The heat is transmitted to an area 17 indicated by a dotted line, melts and softens the heat-sensitive melting ink in that area, and transfers it to the recording paper.

Figure 2 shows the principle of the electrical transfer device,
1 is %, source, nα and 22b are the current-carrying heads, ta is the resistance layer of the recording sheet, Sae is the base film of the recording sheet, 25 is the heat-sensitive melting ink layer, part is the ink transfer part, sword is the recording paper,
28 is a region to which heat generated by the resistance layer is transmitted.

In the same figure, in order to show the principle, the current-carrying head has two needles〃α
Although I have only drawn 22b and 22b, the needles are actually lined up over 2] to 30 needles, with 3 to 5 needles per key. The current is
These needles are alternatively supplied with a power source and flow through a resistive layer. At this time, Joule heat is generated in the resistance layer, and the heat passes through the base film and heat-sensitive melting ink 7.
@25, the heat-sensitive melting ink is melted and softened, and transferred to recording paper.

The size of the transferred ink dot is controlled by the pulse width of the signal current, and the diameter of the large dot is 200 to 8
00 μm, and the diameter of the small dots is 20-30 μm. Gradation is displayed depending on the dot diameter. The dot spacing and gradation display method are the same for the thermal transfer device shown in FIG.

Except in special cases, plain paper is used as an inexpensive material for printing.

When using this plain paper, conventional thermal transfer devices, such as those shown in "Shashin Kogyo, June 1981 issue, Page 116" and the devices shown in Figures 1 and 2 of the main text, have problems with reproducibility when transferring small dots. It has the disadvantage that it is very bad.

When producing low-density gradation, dots with a diameter of 20 to 30 μm must be transferred. However, the surface of plain paper is uneven with intertwined fibers with a diameter of 10 to 20 μm. In order to transfer small ink dots onto this surface, the image seen with an electron microscope is as shown in FIG. 8.

FIG. 3 is a diagram showing the shape of a small dot of about 30 μm transferred onto the surface of plain paper. In the same figure, 3
1 is the paper fiber, 32 is the transferred ink, and 0 is the gap between the fibers. As shown in Fig. 3, the transferred ink sticks only to the portion of the fibers that are exposed on the surface, and does not stick to the inside through the gaps between the fibers. Therefore, the shape of the dot and the area covered by the ink depend on the shape of the fibers in the transfer area.

Therefore, when attempting to produce a low density gradation, even if the signal pulses are the same, the size of the dots will vary, and in some cases, untransferred areas called ``drops'' will appear.

When trying to produce halftones with a printer, one of the major causes of deterioration in image quality is the inability to transfer low-density tones well, as described above.

〔the purpose〕

The present invention is intended to solve these problems, and its purpose is to improve the reproducibility of dots at low density gradations.

[Summary] The printing device of the present invention is a printing device that performs transfer by melting an ink layer using heat, which transfers thermosensitive melting ink mixed with charged particles to a printing material in an electric field, and further transfers electrets as charged particles. It is characterized in that it further contains a dispersant for dispersing the electret in a heat-sensitive melting ink layer containing wax as a main component.

〔Example〕

(Embodiment 1) FIG. 4 shows a principle diagram of the present invention regarding thermal transfer in a narrow sense, that is, when ink is transferred by applying heat with a thermal head.

The recording sheet 40 consists of a heat-sensitive melting ink layer material and a base film 43.

The heat-sensitive melting ink layer 44 is composed of a known coloring pigment or dye, a binder, charged particles, a dispersant for dispersing the charged particles, and, if necessary, a plasticizer.

The binder is polyethylene or polyvinyl chloride or polyvinyl acetate or polybutyral or vinyl chloride acetate copolymer or nitrided wire or epoxy resin or modified wax such as paraffin wax or oxidized wax.

The charged particles are electrets made by injecting charges into highly insulating polymers such as polytetrafluoroethylene by corona charging or electron beam irradiation.

The dispersant is trichloromonofluoromethane or tetrachlorodifluoroethane or trichlorotrifluoroethane or methylene chloride or ethanol or perfluoroalkyl carboxylate or perfluoroalkyl amine compound or perfluoroalkyl quaternary ammonium salt or perfluoroalkyl. It contains at least one of betaine, a perfluoroalkyl ethylene oxide adduct, or a non-dissociable perfluoroalkyl compound.

Plasticizers include phthalate esters or glycol esters.

41 is the power supply for the thermal head, 42 is the thermal head,
45 is a recording paper, 46 is an insulating material such as silicone rubber, 47 is a conductive branch base, the area indicated by the dotted line 48 is a heat transfer area, and 49 is a power source for applying an electric field.

The direction of the electric field generated between the thermal head 42 and the conductive branch 47 by the electric field applying power source 49 is the direction in which charged particles in the heat-sensitive melting ink layer are moved toward the recording paper. The applied voltage is 40 ioμm'1)
'When the recording paper 45 was ωμm and the insulator 46 was 500μm, the DC voltage was set to 2KV. The applied voltage is the recording sheet) 40
, is determined by the thickness of the recording paper 45 and the insulator 46, and its value is 1 to 3 KV. The same applies when either the positive or negative electrode of the electric field applying power source 49 is grounded.

(Example 2) A diagram of the principle of the present invention regarding electrical transfer is shown in FIG.

The recording sheet 50 includes a heat-sensitive melting ink layer 55 made of the same material as in Example 1, a base film 54, and 1-10
and a resistance layer 58 having a resistance value of KΩ/sub2.

51 is a power source for the current-carrying head, 52α and 52b are the current-carrying head, 56 is recording paper, 57 is an insulating material such as silicone rubber, 5
8 is a conductive support base, and 59 is a power source for applying an electric field.

In the figure, in order to show the principle, the energizing head has two needles 52.
I drew only α and 52 b, but actually 8 to 5/+I
The needles are lined up over ~30 ann at intervals of Ia.

The direction of the electric field generated between the resistive layer 53 and the conductive support base 58 by the electric field applying power supply 59 is the direction in which the charged particles in the heat-sensitive melting ink layer are moved toward the recording paper. The applied voltage is 15μ for the recording sheet 50 and ωμ for the recording paper 56.
m, and the insulator 57 was set to 2 KV DC when the thickness of the insulator 57 was 500 μm. The applied voltage is the recording sheet 50. It depends on the thickness of the recording paper 56 and the insulator 57, and the value is 1 to 3 KV.

The same applies when either the positive or negative electrode of the electric field applying power source 59 is grounded.

〔effect〕

FIG. 6 is a diagram showing the shape of dots with a blade size of about .mu.m transferred onto the surface of plain paper by mixing electret into the heat-sensitive melting ink layer and applying an electric field.

In the figure, reference numeral 61 indicates paper fibers, 62 indicates transferred ink, and 68 indicates gaps between the fibers.

In the conventional thermal transfer device, as shown in FIG. 3, the transferred ink sticks only to the surface of the fibers and does not stick to the inside through the gaps between the fibers. On the other hand, when heat-sensitive melting ink mixed with electret is transferred onto recording paper in an electric field as in the present invention, as can be seen from Fig. Since it is attached even to the gaps between the layers, it has the effect of improving low-density gradation reproducibility and improving image quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of a conventional thermal transfer device in a narrow sense. FIG. 2 is a diagram showing the principle of a conventional electrical transfer device. Figure 8 shows the shape of a dot of about 30 μm in a conventional thermal transfer device. FIG. 4 shows an embodiment of the present invention. FIG. 5 shows an embodiment of the present invention. Figure 6 shows the shape of dots approximately 30 μm in size transferred to the surface of plain paper by mixing electret into the heat-sensitive melting ink layer and applying an electric field. 40, 50...Recording sheet 4], 51...Power source 42 Thermal head 43, 54...φ base film 44, 55...Thermosensitive melting ink layer 45 J56...Recording paper 52α, 52b1111 Current-carrying head 58...Resistance layer 46, 57...Insulator 47, 58...Conductive support base 49, 59...Power source for applying electric field 61...Paper fibers 62...Transferred ink 63...Gap between fibers or more Applications People Suwa Seikosha Co., Ltd. 5 1st/2nd figure 3rd figure 4th figure

Claims (4)

[Claims] (1) A printing device that performs transfer by melting an ink layer using heat, and is characterized in that a thermosensitive melting ink mixed with charged particles is transferred to a printing material in an electric field. (2) The printing device according to claim 1, characterized in that electrets are used as the charged particles. (3) The printing device according to claim 1, further comprising a dispersant for dispersing the electret in the heat-sensitive melting ink layer containing wax as a main component. (4) As the dispersant described in item 3, trichloromonofluoromethanoic acid, tetrachlorodifluoroethane, trichlorotrifluoroethane, methylene chloride, ethanol, perfluoroalkyl carboxylate, perfluoroalkylamine compound, or perfluoroalkyl Claim 1, wherein the quaternary ammonium salt or barfluoroalkylpetaine contains at least one of a perfluoroalkylethylene oxide adduct or a non-dissociable perfluoroalkyl compound. Printing device.