JPH03240064A - Recording medium for transfer type electrostatic thermal recording - Google Patents

Abstract

PURPOSE:To allow the recording of digital information on plain paper in a relatively simple process by specifying the specific volume resistance of an electrostatic thermal recording layer to a specific value at room temp. and to a prescribed resistance value at 120 deg.C. CONSTITUTION:The electrostatic thermal recording layer is electrified by a corona electrifier 3, an electrofying roller or electrifying brush. A thermal head 4 is brought into pressurized contact with a recording medium on a platen roller existing on the opposite surface to input the signals to be recorded and to form the latent image from which the load of the input part is eliminated. This latent image is subjected to reversal development by an electrifying toner 5 in a liquid developer or dry developer. Paper 7 to be formed with the image is electrified by a corona electrifier 6 to the charge opposite from the charge of the toner 5 to transfer the developed image onto the paper 7. The specific volume resistance of the recording layer is 1X10<12>OMEGAcm at room temp. and <=1X10<15>OMEGAcm at 120 deg.C. The specific volume resistance of the electrostatic thermal recording layer at 120 deg.C is <=1/50 the specific volume resistance at room temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording medium used in a transfer type electrostatic thermal recording method (electrothermography).

[Prior Art] A resin layer that reduces electrical resistance by heating, such as a resin layer made of polyvinyl chloride, polyethylene, polyester, polystyrene, styrene-maleic acid copolymer, etc., is provided on an electrically conductive substrate, and this layer is A method of forming an electrostatic latent image by electrostatically charging and irradiating with heat rays according to the original image (Japanese Patent Publication No. 35-14722), or using polyester, chlorinated polyvinyl chloride, vinyl chloride, etc. A copying method in which an electrothermographic material that is sufficiently transparent to heat rays is placed on the original image to be copied, an electrostatic charge is applied, and then an electrostatic latent image is created by the action of heat rays, which is then reversely developed and fixed using dry toner. Kosho 38-14347) is known.

In these techniques, infrared rays are irradiated while the document is in close contact with the document, resulting in poor image resolution and the required recording energy. Another problem is that the chargeable material directly serves as the recording material for images, resulting in high material costs.

[Problems to be Solved by the Invention] The present invention provides a method that allows the process to be performed at a higher volume rate than the conventional technology and can record digital information on plain paper, as well as at a low cost.
Moreover, it is an object of the present invention to provide a durable transfer type electrostatic thermal recording medium.

[Means for Solving the Problems] The structure of the present invention for solving the above problems is as follows: (1) The volume resistivity of the electrostatic thermal recording layer is IX at room temperature (25°C).
It is more than 1012Ω mark, and at 120℃ IXI (1”
A recording medium for transfer type electrostatic thermal recording having a resistance of Ω0 or less.

(2) The recording medium for transfer-type electrostatic thermal recording according to item (1) above, wherein the volume resistivity of the electrostatic thermal recording layer at 120° C. is 1/50 or less of its volume resistivity at room temperature.

An example of the structure of the recording medium of the present invention is shown in FIG. 1, which consists of an electrostatic thermal recording layer 1 and a conductive layer 2.

An example of a recording method using this recording medium is shown in FIGS. 2a to 2d and consists of the following steps. Charging process As shown in FIG. 2a, the electrostatic thermal recording layer (hereinafter simply referred to as recording layer) is charged by a corona charging device 3, a charging roller, a charging brush, or the like.

Thermal writing process As shown in Figure 2, the thermal head 4 is brought into pressure contact with the recording medium on the platen roller on the opposing surface, and the signal to be recorded is input (thermal writing), thereby eliminating the charge on the input section. Form a latent image. Developing Step As shown in FIG. 2C, the latent image is reversely developed using the charged toner 5 in a liquid developer or dry developer.

Transfer Step As shown in FIG. 2d, the paper 7 on which the image is to be formed is charged by the corona charging device 6 to a charge opposite to that of the toner 5, and the developed image is transferred onto the paper 7.

Fixing process The transferred image on the paper 7 is fixed using a hot plate, a hot roller, or the like.

After the initialization transfer, the recording medium is cleaned of residual toner and discharged of residual charge, initialized, and can be used repeatedly from the above-mentioned charging step.

If the recording medium is inexpensive, it can be used only once and then thrown away.

In the thermal writing step, the thermal head 4 may be pressed from the conductive layer 2 side for input.

The present invention is based on the discovery of a range of volume resistivity [,/'V] suitable for use as the recording layer of the recording medium.

That is, [/V] at room temperature (25°C) is I
If it is less than 1012 Ω mark, sufficient surface potential cannot be given in the charging process, and if [,f'V] at 120°C exceeds 1 × 1015 Ω (1), the charge will not be sufficiently dissipated in the thermal writing process, and development will fail. The image formed in the process may have low density or no image at all.

The time constant of the decay of the surface potential at 120°C is the C of the recording layer.
Since it was found through experiment that R−εε−J■,
In order to set this time constant to the recording time (1 ms to 1 oIls), assuming that the actual temperature of the recording medium is 150 to 200[deg.] C., a value of lXl0'' to lXl0I5Ω(1) or less is required.

A preferable range of the volume resistivity Jv of the recording layer at room temperature is 1XlO12ΩcI11 to 1×10I7Ω■.

Further, it is necessary that the ratio between the volume resistivity at room temperature and the volume resistivity at 120° C. be large, and specifically, it is preferable that the following conditions are satisfied.

[Example] EXAMPLES The present invention will be specifically described below with reference to Examples.

Examples 1 to 3 Recording media having the following configurations were produced, their volume resistivity was measured, and images were recorded to evaluate their quality. The results are shown in Table 1 below.

The recording conditions are 0.5 from a thermal head of 8 dot/mm.
It was manually written (written) with a recording energy of mJ/dat and developed using a liquid developer manufactured by Ricoh.

Configuration of recording medium Example 1: A recording layer made of a polyethylene film having a thickness of 25 μm and aluminum vapor-deposited as a conductive layer.

Example 2: A recording layer made of a polypropylene film having a thickness of 25 μm and aluminum vapor-deposited as a conductive layer.

Example 3: A recording layer made of a polyethylene terephthalate film having a thickness of 12 .mu.m was coated with aluminum as a conductive layer.

Comparative Examples A-B Structure of Recording Medium Comparative Example A: Consisting only of a vinyl chloride film (containing an antistatic agent) having a thickness of 10 μm.

Comparative Example B: A recording layer made of a Teflon film having a thickness of 25 .mu.m and aluminum vapor-deposited as a conductive layer.

From the above results, the recording medium of Comparative Example A has a low charging potential;
It can be seen that the image ID was small, the clarity was poor, and background stains occurred.

The recording medium of Comparative Example B has a sufficiently high volume resistivity [Jv] at room temperature and a high charging potential, but because the volume resistivity at 120°C is high, the ID of the image after development is insufficient and the sharpness is also low. I know it wasn't good.

[Effects of the Invention] As explained above, the recording medium of the present invention allows digital information to be recorded on plain paper through a relatively simple process.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the structure of the recording medium of the present invention, FIGS. 3 is a graph showing temperature characteristics of recording media of Examples and Comparative Examples. DESCRIPTION OF SYMBOLS 1... Electrostatic thermal recording layer, 2... Conductive layer, 3... Charging means. 4...Thermal head, 5...Toner 6...Transfer means, 7...Paper.

Claims (2)

[Claims] (1) The volume resistivity of the electrostatic thermal recording layer is at room temperature (25°C)
A recording medium for transfer-type electrostatic thermal recording, characterized in that it is 1×10^1^2 Ωcm or more at 1×10^1^2 Ωcm, and 1×10^1^5 Ωcm or less at 120°C. (2) The recording medium for transfer electrostatic thermal recording according to claim (1), wherein the volume resistivity of the electrostatic thermal recording layer at 120° C. is 1/50 or less of the volume resistivity at room temperature.