JPS6079976A - Thick film type thermal recording head - Google Patents

Abstract

PURPOSE:To provide the titled head in which resistance is made to be uniform by a method wherein a low-resistance part of a linear form heating resistor is previously supplied with an amount of electric power to previously increase the resistance of that part. CONSTITUTION:For example, in a thick film type thermal head for recording on an A4 size paper and having a resolution of 8 dots/mm. and 1,728 dots/line, the heating resistor 2 is divided into 54 groups each of which consists of 32 dots, and of 54 electrodes provided at each boundary of the groups and at both ends of the resistor 2, those electrodes 4 on the other side are provided with resistance-correcting electrodes 11. When the resistance of the resistor 2 is lower at a part 13 thereof, an electric power (e.g., 1.1W) somewhat higher than a normal printing power (0.6W) is impressed on the resistance-correcting electrodes 11 at both ends of the group corresponding to the part 13, for example, through probe pins, to increase the resistance of the part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thick film type thermal recording head used in thermal recording devices such as printers and facsimiles.

[Prior art]

2. Description of the Related Art A thermal recording device such as a printer or a facsimile uses a thermal recording head to perform thermal recording on thermal paper or plain paper overlaid with an ink donor sheet.

There are two types of thermal recording heads: thick film type and thin film type.

FIG. 1 shows an example of a thick film type thermal recording head. In this 17-film type thermal recording head, a heating resistor 2 is provided on the upper surface of a substrate 1 in a straight line 1J3. A plurality of one electrodes 3 are provided on the negative side of the heating resistor 2 in the width direction.
are provided at intervals. Furthermore, on the other widthwise side of the heating resistor 2, a plurality of electrodes 4 are provided at intervals. These electric wires 4.1 and 3.4 are arranged alternately, and one end of each of them is embedded in the heating resistor 2. One end of each of the heating resistor 2 and both electrodes 3.4 is covered with a wear-resistant layer (not shown).

In this thick-film type thermal recording head, when a voltage is applied to one electrode and the other electrode 4 adjacent to it, the heating resistor 2 between them generates heat. The ink donor notebook and the recessed paper superimposed thereon are brought into pressure contact with the heat generating resistor 2, and the heat generating resistor 2 between the two electrodes is selectively sold off according to the image information.
- Then, image information is recorded.

By the way, the thick-film type thermal recording head No. 2 has the advantage of being strong against overload due to the mechanical strength of the heating resistor 2, compared to the one using I.G11Vj4%1. There was a problem in that there was considerable variation in resistance values. For this reason, this thick film type thermal recording head has the disadvantage that the power consumption in the portions with low resistance increases, resulting in an increase in the overall power consumption. Further, although this thick film type thermal recording head can perform halftone recording by controlling the applied voltage, it has a drawback in that good halftone recording cannot be performed due to variations in resistance values.

[Purpose of the invention]

The present invention was developed in view of the above circumstances, and the object is to provide a thick film type thermal recording head that can make the resistance value of the heat generating resistor even more uniform.

[Structure of the invention]

The present invention focuses on the characteristic that when a certain amount of power is applied to a heating resistor, the mechanical and electrical strength itself does not change, but the resistance value increases and is maintained in that state, and the resistance value of the heating resistor is low. A certain amount of power is applied to the portion in advance to increase the resistance value of the portion.

〔Example〕

The present invention will be described in detail with reference to Examples below.

FIG. 2, in which parts that are the same as those in FIG. 1 are designated by the same number E1, shows the main parts of a thick-film type thermal recording head according to an embodiment of the present invention.

This thick film type thermal recording head is, for example, for Δ4 size and has a resolution of 8 dots/mmS and 1728 dots/line. In this thick film type thermal recording head, the heating resistor 2 is divided into 54 groups of 32 dots each, and the other 55 electrodes 4 located at the boundaries of each of these groups and at both ends of the heating resistor 2 are connected to each other. An electrode II for value correction is provided.

By the way, what about the heating resistor of a thick-film thermal recording head? If we look at the resistance values of each heating element, for example, they are scattered in the shaded ranges in Figures '83 and 4, respectively, and there is considerable variation. However, in the example shown in FIG. 3, the resistance value of one end portion 12 of the heating resistor 2 is considerably lower than that of the other portions. In the example shown in FIG. 4, the resistance value of a portion 13 appropriately distant from one end of the heating resistor 2 is considerably lower than that of other portions.

Therefore, normal printing power (0, (approximately 6 W). Then, as is clear from the results of the well-known step stress test, the relevant group of the heating resistor 2,
- The resistance value of the loop increases to a certain extent and is maintained in that state.

For example 1. When IW power was applied for about 3 minutes, the resistance value increased by about 20% and was maintained in this state. At this time, the mechanical and electrical strength of the heating resistor 2 did not change at all. If, as a result of measuring the resistance value of the relevant group of the heat generating resistor 2, it is still lower than other parts, then applying -C power of 1.1 W again to the resistance value at that point will cause the resistance value of the relevant group to The resistance value increases further. In this way, the resistance value of the heating resistor 2 can be made substantially uniform throughout.

Here, the step stress test will be briefly explained.

A step stress test is a test that is widely used to estimate the life characteristics of a heating resistor with respect to applied power. FIG. 5 shows the results of a step stress test on a 32-dot heating resistor with a resolution of 8 dots/llll11.

As is clear from this figure, the applied power is 1. When it is about IW, the resistance value increases by about 20% and is maintained in this state.

Alternatively, the resistance value of each 32 dots, that is, each group, may be checked via the resistance value correction electrode 11, and the resistance value may be corrected based on the results. In this way, it is not necessary to check the resistance value of each heating element of the heating resistor 2, making it easy to measure the resistance value, and also significantly shortening the measurement time.

〔Effect of the invention〕

As explained above, according to the present invention, the resistance value of the heat generating resistor can be made even more uniform over the whole, so there is no part where the resistance value is extremely low, and therefore power consumption can be reduced. It is also possible to perform good halftone recording.

[Brief explanation of the drawing]

FIG. 1 is a partial plan view showing an example of a conventional thick-film type thermal recording head, FIG. 2 is a plan view showing the main parts of a thick-film type thermal recording head according to an embodiment of the present invention, and FIG. 4 is a diagram showing each side of the variation in the resistance value of the heating resistor, and FIG. 5 is a diagram showing the results of a step stress test. 2... Heat generating resistor, 3.4... Electrode, 11... Electrode for correcting resistance value. Representative Fuji Xerox Co., Ltd. Patent Attorney Ume Yu Yamauchi 1 Figure 111 Figure 3 Figure 4 Other locations ← JM paper price closed → One end

Claims (1)

[Claims] It is characterized by comprising a linear heating resistor, and increasing the resistance value of a portion whose resistance value is lower than a predetermined resistance value based on the resistance value characteristics by applying a certain amount of electric power to the portion in advance. Thick film type thermal recording head.