JPH01285363A - Thermal head resistance adjustment device for high image quality - Google Patents

Abstract

PURPOSE:To obtain a high image quality, by a method wherein, a relation between a coloring density and a correction resistance value is previously identified in one head system and, thereafter, a resistance value is corrected to be a correction amount. CONSTITUTION:For adjusting the resistance values of heating elements, a thick-film head is temporarily assembled, and the distribution of resistance values Ri of the head is previously measured. A recording with all the resistors is carried out by a predetermined coloring evaluation device, and the distribution of average densities Di according to the respective elements is obtained. A correction is performed to make the resistance values constant, a trial printing is conducted by the head having the corrected resistor group, and the distribution of densities Di' at this time is obtained. Here, a resistance value correction amount DELTARi is further determined correspondingly to a density fluctuation amount DELTADi', and the resistance value Ri is adjusted to reach a predetermined resistance value Ri'. In this resistance value correction method, by using a remarkably thin thick-film material as an electrode material the dispersion of resistance values due to the printing and burning of the resistors can be controlled to be within + or -10%, and a postprocess can be reduced. As a result, an image quality as high as a 32-step or 64-step gradation can accomplished, and a density unevenness DELTADi can be also remarkably reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a final manufacturing method for a thermal recording head, which is a main device of an image printer, and particularly relates to a method for adjusting the final resistance value of a thick film type thermal recording head. .

[Conventional technology]

A thermal recording head is generally mounted on a ceramic substrate.
It has heating resistors arranged in a row and a drive circuit that selectively applies recording signals and voltages to the heating resistors, and records by giving heat to the recording medium according to the Joule heat of the heating resistors. It is something to do.

Conventionally, there are two types of heads, thin-film type and thick-film type, depending on the manufacturing process, but the former is suitable for high definition and high image quality. However, due to cost issues, there is a desire to somehow support high image quality with a thick film head. Therefore, a laser is used to make multiple micro-perforations to eliminate the resistance value distribution, which originally has a large variation, so that it becomes a constant value.

The resistance value was adjusted by the number of holes.
Publication No. 2102). In this case, since the resistance value was constant, it was possible to adjust the resistance value variation to about ±1%.

In addition, resistance adjustment using voltage pulses is possible using the
As seen in Japanese Patent No. 9 and Japanese Patent Application Laid-open No. 62-278061, various positive and negative shifts have been considered, but in all cases the target is a constant resistance value, and a sequence is established.

[Problem to be solved by the invention]

The above-mentioned conventional technology is a technology developed based on the control concept of keeping the resistance value constant, and does not directly link the output image and the resistance value. The amount of heat generated is V2, where the applied voltage is v1 and the resistance value is R.
Since it is proportional to /R, this variation in resistance value is considered to be the primary cause of uneven color density. However, Fig. 2(a)
, As shown in (b), the surface of a thermal recording head (particularly a thick-film thermal recording head) has unevenness of the electrodes and unevenness of the surface due to printing accuracy, etc., resulting in uneven color density independent of resistance value variations. This will result in 1 is a ceramic substrate, 2 is a glass glaze, 3 is an electrode, 4
is a resistor, and 5 is a protective glass.

FIG. 3 shows the analysis results of the cause of density unevenness in sublimation thermal transfer when the conventional laser perforation method is used. As is clear from this figure, the conventional method of improving image quality is an indirect method that focuses only on resistance value variations.

An object of the present invention is to perform resistance adjustment including various influencing factors from a direct connection with the image, and to finally obtain high image quality.

[Means to solve the problem]

The above purpose is to directly link one image and the resistance value.

It is necessary to set the resistance value according to each heating element, and by using the temporarily assembled thick film head to output the specified evaluation butter / and obtain the average color density distribution according to each element,
achieved.

To put it simply, after clarifying the relationship between one color density and the amount of corrected resistance value in one head system,
The resistance value is corrected up to the correction amount. By adopting this method, higher image quality can be achieved than in the conventional case where the resistance value is adjusted to a constant value.

It is preferable that the minute density measurement system has an optical sensor capable of step feeding in the main scanning direction in order to obtain the average color density distribution corresponding to the heating element. The adjustment system also includes a positioning device to adjust the resistance value of the heating element.

Preferably, a device capable of applying high voltage short-time pulses is provided.

[Effect]

The concentration distribution can be measured using a temporarily assembled head using a sensor equipped with a light receiving element such as a CCD. On the other hand, it is well known that the resistance value of a thick film resistance element shifts due to the application of a voltage with an extremely short pulse width, and the present method involves artificially controlling the amount of this shift.

For example, a resistance value shift due to static electricity can be said to be an extreme example of this.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall flowchart of the invention.

The thick film head is pre-assembled using standard processes. Therefore, unlike the conventional laser perforation method, the formation of the protective film is advantageous in terms of reliability because stable firing conditions of around 5ooC can be ensured. The resistance value; R3 distribution of this temporarily assembled head is measured in advance. Next, all the resistive elements are recorded using a specified color development evaluation device, and the average density according to each resistive element is determined.
Find the D1 distribution. Usually, concentration characteristics can be determined by a photoelectric converter such as a COD (charge-coupled device). This system is shown in FIG. First, an image sample 8 is placed on an XY table 7 driven by a pulse motor, measurement positions are selected at a predetermined pitch, and the average density is determined by a density detector 9.

Data processing and position control are performed by the MPU 6.

The color density of thermal transfer; Dl has various influencing factors as shown in FIG. 3, but it can be divided into resistance value and other factors. For heads manufactured using normal manufacturing methods, it is sufficient to consider the influence of contacts and the influence of resistance value.

In the next step, corrections are made to keep the resistance constant. For this purpose, a system as shown in FIG. 5 is used. First, place the head on the position control table. This head is constructed with resistance elements 14a, and the resistance is adjusted by applying an extremely short pulse voltage to each of these elements.

At this time, the voltage is applied and the resistance value is monitored, and the process is stopped when a predetermined resistance value is reached.

Usually, in the case of an extremely short pulse, as shown in FIG. 6(a).

With thick film resistor materials, the resistance value often shifts to the negative side, and in the pulse input range of the normal usage level, it seems to shift from a -temporal negative side shift to a positive side shift. , arbitrary resistance value adjustment is possible. In this way, another trial print was made using the head with the resistance group modified to be approximately constant, and the density distribution D
Find +'.

Here, a resistance value correction amount ΔR1 is further determined for the concentration fluctuation amount ΔD+', and the resistance value is brought to a predetermined resistance value: R+1'.

Since the resistance value modification is normally completed within several seconds per resistive element, the process does not require much time even if it is repeated.

In fact, if an extremely thin thick film material (for example, organic gold, etc.) is used as the electrode material, variations in resistance value due to printing and firing of resistors can be suppressed to less than ±10%, and subsequent steps can also be shortened. As a result, high image quality such as 32 gradations and 64 gradations can be achieved, and density unevenness ΔD+ can be extremely reduced.

〔Effect of the invention〕

According to the present invention, no scalpel is inserted into the surface shape of the head;
By setting the resistance value lower for areas with lower density and higher value for darker areas, the amount of heat transferred from each resistance element to the media can be maintained at a constant pressure, resulting in unprecedentedly high image quality and uneven density. We can supply thick film heads without

In this regard, conventional techniques have been used to achieve high image quality. Since the microboring process can be omitted, this process is very suitable for mass production. In other words, lower prices can be achieved.

Secondly, since the resistance value correction of this head does not involve the conventional laser drilling method, it is possible to first use a high-temperature fired protective film, which greatly improves reliability in terms of running and static electricity.

In addition, since the correction method can be configured in an extremely systematic manner, it is easy to automate, and it is suitable for mass production.

It has the above effects.

[Brief explanation of the drawing]

Figure 1 is a flow diagram of the high image quality system by modifying resistance values based on concentration distribution according to the present invention, Figure 2 is a plan view and cross-sectional view of a thick film head with a comb-teeth electrode structure, and Figure 3 is an image of the current state. A flow diagram showing the causes and countermeasures for density unevenness in printers. Figure 4 is a system block diagram for measuring color density distribution corresponding to each resistance element. Figure 5 is a system block diagram for adjusting resistance values by applying pulsed voltage. The block diagram and FIG. 6 are characteristic diagrams showing how the resistance value changes due to pulse application. 1... Ceramic substrate, 2... Glass glaze,
3... Electrode, 4... Resistor, 5... Protective glass,
6... Control computer, 7... Pulse motor drive X
Y table. 8... Image sample, 9... Color density detector, 10
...Pulse generation power supply, 11...Digital multimeter. 1st Concave 2 Figure (2L) 3rd I! 1 <Source, Figure><FengEast> Mine 4 Figure 5I21 Otsu / 14 Drifting Ridge

Claims (1)

[Claims] 1. In a thermal recording head for an image printer, the resistance value of each heating element is determined based on the evaluation image output by the head formed by a normal process, and the resistance is corrected by applying a voltage pulse. A thermal head resistance adjustment device that supports high image quality.