JPS59159391A - Thermal recording method - Google Patents

Abstract

PURPOSE:To enable to record at a high speed irrespectively of the kind of a sheet or temperature and prevent ground fogging from occurring, by a method wherein when printing on a thermal recording sheet by heating from the face of a recording surface, the sheet is heated from the back side for a period from the moment immediately before recording to the time of recording. CONSTITUTION:When printing on a thermal recording sheet by heating form the side of a recording surface of the sheet by a thermal head or the like, the sheet is heated from the back side for the period from the moment immediately before recording to the time of recording, whereby the sheet is heated to a temperature required for high-speed recording. Heating may be effected by a heated roll method, an infrared ray irradiating method, a hot air blowing method or the like, among which a method of using a platen roll for pressing the thermal head as a heated roll is simple and preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording method. The term "thermal recording method" as used herein refers to a recording method in which printing is performed by heating a thermosensitive recording sheet (hereinafter abbreviated as "sheet") that develops color when heated.

The biggest problem with thermal recording methods is that high-speed recording is difficult. High-speed recording is particularly difficult under low temperature conditions. To solve this problem, attempts have been made to improve heat-sensitive recording methods in areas other than sheet improvements and sheet heating methods for printing. For example, in the case of a thermal recording method in which a thermal head is used to heat a sheet and print, according to Japanese Patent Publication No. 57-156281, the thermal head is energized for a short time at predetermined time intervals so that the sheet hardly develops color. A method of preheating the temperature has been used.

However, the method of the present invention has the following drawbacks because it does not take into account the type of sheet whose heat capacity is usually much larger than that of a thermal head or the temperature of the sheet before recording. In other words, if the preheating conditions of the thermal head are set so that high-speed recording is possible at room temperature (15 to 20°C) and there is almost no background fogging using the method of the present invention, the background will change when recording at high temperature (30°C or higher). If fog is recorded at low temperatures (below 5° C.), recording density is likely to be insufficient. This is because at high temperatures, the amount of heat required to develop color on the sheet is small, which tends to cause background fogging due to the heat given to the sheet from the preheated thermal head, and at low temperatures, the amount of heat required to develop color on the sheet is large, resulting in high-speed recording. At this time, it is difficult to obtain sufficient recording density due to the heat applied to the sheet from the thermal head.

The above-mentioned disadvantages of the thermal recording method of Japanese Patent Publication No. 57-156281 are that the thermal recording method of 156281/1983 is not particularly effective when the thermal head is not preheated, or when a printing method other than the thermal head is used, such as a thermal recording method using infrared rays or laser beam radiation. That applies.

In order to solve this problem, the inventors of the present invention have developed a heat-sensitive recording method that heats the sheet immediately before and during recording, allowing high-speed recording regardless of the type of sheet or the temperature of the sheet.

The thermal recording method of the present invention is a method in which printing is performed by coloring a sheet by heating it from its recording surface, and is characterized in that the sheet is heated from its back surface from immediately before recording to during recording.

As a method of heating the sheet from the back side, preferably a heating roll in contact with the back side of the sheet is used.

In the heat-sensitive recording method of the present invention, the sheet is heated from the back side to bring the sheet to a temperature necessary for high-speed recording by the time of recording. At that time, depending on the heating conditions from the back side, it is possible to almost prevent background fogging. Heating methods include using a hot roll, shining infrared light onto the back of the sheet, and blowing warm air onto the back of the sheet. Among these methods, the method of heating the sheet with a hot roll is simple and good. Although there are various methods of heating the sheet recording portion of the printing reservoir in thermal recording methods, in the present invention, a printing method using a thermal head is preferable. This is because the sheet is brought into pressure contact with the thermal head of the printing reservoir by the heat roll on the back side of the sheet, and the sheet is effectively heated by the heat roll.

If the heat-sensitive recording method of the present invention is used, high-speed recording is possible regardless of the type of sheet or the temperature of the sheet. Furthermore, by controlling the heating conditions of the sheet from the back side, it is possible to perform six-shot recording with almost no background fogging on the sheet.

Next, the present invention will be explained in more detail with reference to Examples.

(Example) The model used for the test was Fujitsu's Fa com Fax 621-0 model (G-: III), which is known as a thermal recording device with high-speed recording. A commercially available thermal HI recording paper for G-I (trade name: 1i'200-2, H) manufactured by Mitsubishi Paper Mills, Ltd. was used. As a method of heating the back side of the sheet, there is a method of heating the sheet from just before recording to during recording using a roll (platen roll) that is preheated to 70°C for bringing the sheet and the thermal head into pressure contact. Using. The test results are shown when the lower clothing has a sheet and the room temperature is set to a low temperature (0°C) and a high temperature (32°C). In each case, a test was conducted under the same conditions using an unheated platen roll without heating from the back side in order to reduce the drawing ratio, and the results are shown in the table below.

As is clear from the table below, if the sheet is not heated from the back side, sufficient recording immersion cannot be obtained even if high-speed recording is performed at low temperatures, whereas high-speed recording is achieved when the sheet is heated from the back side with a hot roll. When this was done, sufficient recording density was obtained. In addition, when recording at high speed at high temperatures, a more satisfactory density can be obtained when using a heat roll than when one of the four is not used.
Furthermore, there was no background fogging even when a hot roll was used.

From this, it was found that the thermal recording method using the thermal roll of this experiment allows high-speed recording regardless of the temperature of the sheet, and does not cause background fog on the sheet.

(table) (B) When using a heat roll at low temperatures (b) When not using a heat roll at low temperatures (c) When using a heat roll at high temperatures (d) When not using a heat roll at high temperatures (Here, low temperature refers to 0℃ and high temperature refers to 32℃.

) The facsimile manuscript for this test was the Institute of Image Electronics Engineers of Japan standard chart A2, and the high-speed mode was used as the recording mode. The recording density and background density were measured immediately after recording using a Macbeth densitometer RD514 (filter: Ratten J11i106). This n? As a result of concentration measurement using a hygrometer, it was 7. % (If there is a low difference, it can be sufficiently identified as a difference in shading under normal lighting.

7-

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording method in which printing is performed by coloring a heat-sensitive recording sheet by heating it from its recording surface, which is characterized in that the heat-sensitive recording sheet is heated from the back side from immediately before recording to during recording. . 2. Claim 1 uses a heat roll in contact with the m-side of the sheet as a method for heating the heat-sensitive recording sheet from the back side.
Thermosensitive recording method described in section.