JP3106533B2 - Thermal head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head device used for a facsimile or a printer, and more particularly to a thermal head device capable of obtaining good image quality without density unevenness.

[0002]

2. Description of the Related Art A thermal head device, which is a type of recording element, has been widely used in facsimile printing units and various printers because it has low operating noise and does not require processing steps such as development and fixing. FIGS. 7 to 9 are explanatory views of one structural example of this type of thermal head device, in which a first substrate on which a thermal head unit is mounted and a second substrate on which a drive circuit unit such as a drive IC is mounted are mounted on a heat dissipation substrate. 2 shows a thermal head device of the type bonded to FIG. FIG. 7 is a sectional view of the head substrate.
Is an insulating substrate formed by coating an underglaze layer of a glass material on a substrate made of a ceramic material, 2 is a resistor layer (heating resistor) forming a heating section, 3 is a common electrode, 4 is an individual electrode, 5 is an individual electrode. A wear-resistant layer (overglaze layer)
Hereinafter, this is referred to as substrate A.

FIG. 8 is a side view of a thermal head device. Reference numeral 6 denotes a heat radiating substrate, on which a head substrate A and a driving circuit substrate (hereinafter, referred to as a B substrate) on which a driving IC is mounted are adhered. The individual electrodes 4 on the A board and the drive IC wiring on the B board are connected by bonding wires 8 such as gold wires.
A connector 9 for making an electrical connection to an external circuit is connected to the B board, and the external circuit and the driving IC wiring are connected via the connector 9. FIG. 9 is a top view of the thermal head. The A substrate on which the heat generating portion is formed extends in the main scanning direction X, and the driving IC 7 for supplying a driving current to the heat generating portion formed on the A substrate is mounted on the B substrate. A plurality of connectors 9 for connecting to an external circuit are arranged in a required number.

The heat generating portion of the A substrate generates heat by Joule heat generated by a current flowing between the selected individual electrode 4 and the common electrode 3 via the drive IC 7, and directly heats the heat-sensitive recording paper to form a color or to form an ink sheet. The recording is performed by melting the ink and transferring it to recording paper, or by heating the ink donor film to sublimate the dye on the sublimation recording paper to develop color.
By the way, if the resistance values of the resistors are not uniform over the entire area, there will be a difference in the temperature of the heating elements when heat is generated, and density unevenness will occur in the recorded result. In order to make the resistance of the resistor uniform for all dots, a so-called trimming process has been conventionally performed. This trimming utilizes the property that the resistance value of the resistor is reduced by an electric field, and pulse trimming in which the resistance value of the resistor is individually adjusted by applying a voltage pulse through a common electrode and an individual electrode,
The resistance value or current value is adjusted by partially processing the resistor or electrode by laser beam or changing the resistance value by heating, and as a result, the heating value of the resistor is uniformly adjusted between dots Laser trimming is known.

FIG. 10 is a view showing a conventional process for manufacturing a thermal head. First, metal organic deposition (MO) is performed on an insulating substrate 1 by screen printing or the like.
D) Resistor layer is formed by coating and drying a resistor material.
(P11), a step of forming a layer of a conductor (for example, gold (Au)) by screen printing on the resistor layer 2 (P12), and patterning of the conductor layer by photolithographic etching to form the common electrode 3 The step of forming the individual electrodes 4 (P13), the step of forming the required heat generating portion by etching the resistor layer 2 using the electrodes as a mask (P14), and the step of forming the overglaze layer 5 (P15) Obtain an A substrate having the formed thermal head, and
The resistance value of the thermal head formed on the A substrate is adjusted by laser trimming (P2). Next, the A substrate, the drive IC, and the B substrate, which is a wiring substrate on which the connector is mounted, are bonded on the heat dissipation substrate 1 (P3), and the drive IC is mounted on the B substrate (P4). The common electrode 4 is connected to the terminal of the driving IC (P5), and the mounting inspection of the driving IC is performed (P6). After the drive IC mounting inspection is completed, the exposed electrode portions including the drive IC and its terminal portion are sealed with resin (P7), the connector 9 is connected (P8), and then the thermal head cover is bonded. T (P
9) Complete.

FIG. 11 is a side sectional view of the completed thermal head device, 10 is the sealing resin layer, and 11 is a cover. The trimming of the resistance value of the resistor in the step P2 is performed by contacting a probe (measurement probe) of an ohmmeter with the common electrode 3 and the individual electrode 4 connected to each resistor (corresponding to one dot) constituting the heating section. Then, the resistance value is measured, and a laser trimming method of irradiating a laser beam to adjust the resistance value of the resistor portion is used. In conventional pulse trimming and laser trimming, the resistance value of the heating resistor bit of the thermal head is adjusted so as to be equal to a certain resistance value after trimming, and trimming is performed so that the wiring resistance value is also constant. Some have reduced the occurrence. Further, the laser trimming methods disclosed in JP-A-54-79457 and JP-A-54-132758 provide a method of adjusting the resistance value without damaging the protective film of the resistor.

[0007]

In the above-mentioned prior art, the unevenness in the density is caused by making the resistance of the thermal head and the resistance of the wiring formed on the substrate A constant and equalizing the heat capacities of the heating parts. However, no consideration is given to density unevenness caused by a cause on the B substrate side. FIG. 12 is an explanatory diagram of a positional relationship of terminals (here, referred to as pads) of a drive IC for driving a thermal head.
1 is an output pad, and 72 is a ground pad (GND pad). As shown in the figure, the output voltage of the drive IC is determined by the distance between the output pad 71 and the GND pad 72. FIG. 13 is an explanatory diagram of an example of a measured value of the output voltage drop (drive IC drop) of each output pad of the drive IC shown in FIG. 12, and as shown in FIG.
The voltage drop (drive IC drop) due to the internal resistance of each drive output terminal (output pad: bit terminal) has a variation in the internal resistance for each bit (for each drive bit corresponding to one dot heat generation). Since the drive IC drop amount of each bit is different due to the difference in resistance value, even if the resistance values on the thermal head side are precisely adjusted, the heat generation amount differs for each dot, and as a result, density unevenness occurs. There is a problem of doing. In FIG. 3, the horizontal axis represents the bit terminal numbers of the drive ICs having bit terminals 0 to 64, and the vertical axis represents the respective drive IC drop voltages (V). An object of the present invention is to solve the above-described problems of the conventional technology and to make the heat generation amounts of the respective print dots uniform by taking the drive IC drop into consideration and to make the dot shape uniform.
It is an object of the present invention to provide a thermal head device which has excellent print quality and can perform density gradation recording of more gradations than a conventional thermal head device.

[0008]

In order to achieve the above object, the present invention provides a plurality of heat generating sections each including a plurality of resistance elements, and a common electrode connected to one end of each of the plurality of heat generating sections. And a thermal head unit having a plurality of individual electrodes connected to the other ends of the plurality of heat generating units, and a drive IC having output terminals connected to the plurality of individual electrodes, respectively, on a heat dissipation substrate. In the mounted thermal head device, the heat generation amount of the heat generating portion of the thermal head portion is set according to a voltage drop amount existing for each output terminal of the drive IC, and the drive IC drop voltage is measured in advance. In advance, or by trimming the resistance value of the heating resistor and / or the resistance value of the electrode bridging the resistor in consideration of the internal resistance value during trimming, Adjust as heating value of the resistor for printing bets becomes uniform, characterized in that to obtain a thermal head apparatus without density unevenness. That is, by adjusting the resistance value of the resistor of the heating section to a constant value in accordance with the output voltage drop amount for each bit of the drive circuit such as the drive IC, or the voltage drop for each bit of the drive IC By adjusting the resistance value of the electrode of the corresponding heating part to a constant value according to the amount, or by adjusting the resistance value of both the resistor and the electrode to a constant value, the heating value of the heating part is fixed. Align to value. The resistance value of the resistor is adjusted by pulse trimming or laser trimming. The resistance value of the above resistor is adjusted by changing the resistance value by modifying the resistance characteristics by pulse trimming or laser trimming, or by changing the size and shape by laser trimming. The resistance value of the electrode is adjusted by laser. This is done by changing their size and shape by trimming.

[0009]

The amount of heat generated by the heat generating portion of the thermal head is set in accordance with the amount of voltage drop present at each output terminal of the drive IC, so that the density unevenness at each output voltage of the drive circuit and the drive circuit In the case where a plurality of drive ICs are used, it is possible to eliminate unevenness in the density of the heat generating portion driven for each drive IC. Adjustment of the resistance value of the resistor by pulse trimming or laser trimming (heating action)
The resistance value can be increased without changing the shape or size of the resistor, and the adjustment of the resistance value of the resistor or the electrode by laser trimming (processing) is performed by changing the shape of the resistor or the electrode. . By performing the above-described resistance value adjustments, the heat value (heat capacity) of each dot can be set uniformly, and the print density becomes uniform.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, a description will be given of a device using a drive IC as a drive circuit. FIG. 1 is a block diagram for explaining an example of a drive IC drop measuring device for obtaining a thermal head device according to the present invention. Reference numeral 20 denotes a thermal head having a resistor array having the same resistance value as an actual thermal head. Yes, r1, r2,... Rn
Is the resistance of each resistor, 70 is a drive IC, T1, T2, T3
,... Tn are the resistors r1, r2,.
And a driving circuit for driving each dot, and is involved in printing of each dot. Also, 80 is an oscilloscope, 90 is a pulse generation circuit, and 100 is a probe. A pulse voltage is applied from the pulse generation circuit 90 to the resistance array 20 having the same resistance value as the actual thermal head, and connected to each bit (each resistance r1, r2,... Rn constituting the resistance array). The probe 100 is applied to the output electrode pad of the IC, and the drive IC drop is read by observing the resistance value with an oscilloscope. The drive IC drop characteristic as shown in FIG. 13 can be obtained by the above-described measuring device. The adjustment amount of the resistance value is calculated as follows. That is, the applied voltage when the probe is applied is V, the minimum value of the drop voltage is Vn, and the difference between the drop voltage for each bit and Vn is ΔV.
(N). Next, the target resistance value of each bit is calculated as follows. Let R be the resistance value to be aligned, and let ΔR (n) be the adjustment amount for each bit for correcting the variation in the heat generation amount due to the variation in the drive IC drop. In order to keep the calorific value constant, (V−Vn−ΔV (n)) 2 / (R−ΔR (n)) = (V−Vn) 2 / R = const. ... (Equation 1) The amount of adjustment for each bit is obtained using the following equation.

FIG. 2 is a block diagram showing an example of the configuration of a pulse trimming device, wherein 201 is a control device (computer), 202 is a pulse generator for generating a trimming pulse, 203 is a resistance measuring device, and 204 is a resistance array. A multiplexer relay 205 for switching in order; a switch 205 for switching between resistance measurement and application of a trimming pulse;
Reference numeral 06 denotes a measuring device (prober), and reference numeral 207 denotes a thermal head device to be adjusted. Note that the laser trimming apparatus has a configuration including a laser oscillator instead of the pulse generator in FIG. Specifically, a thick film type lift-off thermal head having a resolution of 8 dots / mm was subjected to high-precision pulse trimming using the apparatus shown in FIG. 2 to obtain a result as shown in FIG. FIG. 3 is an explanatory diagram of the resistance value of the resistor array after pulse trimming, and shows that the maximum resistance of 12.8 Ω has been adjusted for the average resistance value of 1000 Ω.

FIG. 4 is a resistance characteristic diagram showing the result of adjusting the resistance value of the resistor by laser trimming using an 8 dot / mm thin film type thermal head. Was eliminated, and good image quality was obtained. Each of the above specific examples adjusts the resistance value of the resistor by trimming. Next, a specific example of adjusting the resistance value will be described. FIG. 5 is an explanatory view of a thermal head in which the resistance value is adjusted by changing the width (main scanning direction) of the resistor of the heat generating portion, and includes 2-1, 2-2, and 2
-3, ... 2-i, 2-j, ... 2-62,2-
63 and 2-64 are resistors. Here, 8dot
The width of the mask was designed so as to have the above-mentioned resistance value by adjusting the width of the resistor of the thin film thermal head of / mm. Specifically, the conventional line width of 100 μm is 100
Since it is 0 Ω, the resistor 2-i set to 987 Ω was designed to be 98.7 μm, and the resistor 2-63 set to 988 Ω was designed to be 98.8 μm. As a result, it was possible to substantially eliminate unevenness in each driving IC. Also, 8dot
/ Mm Adjust the width of the thin-film thermal head wiring,
The design was performed such that the thermal head of the wiring resistance was ΔR (n). The following equation was used as the basic equation for the calculation. Rw = (L / W) × ρ (Equation 2) where Rw is the wiring resistance, L is the wiring length, W is the wiring width,
ρ is a sheet resistance value. Specifically, since aluminum having a sheet resistance value of 5 mΩ / □ was used for wiring of about 12 mm, the maximum line width was 100 mm.
It had a resistance of 8Ω at μm. Therefore, by transforming the above equation, (Equation 3) W (n) = {Rw / (Rw + ΔR (n))} × W (Equation 3) where Rw = 8Ω W = 100 μm The wiring width was calculated and designed.

FIG. 6 is an explanatory view of a thermal head in which the width of the individual electrodes in the main scanning direction is trimmed to adjust the amount of heat generated by the heat generating section. 4-1, 4-2, 4-3,.・ 4-
i, 4-j ... 4-62, 4-63, 4-64 are individual electrodes. In this case, the width of the electrodes 4-i and 4-j was 38 [mu] m, the width of the electrodes 4-62 to 4-64 was 42 [mu] m, and the minimum line width was 38 [mu] m as shown in FIG.

[0014]

As described above, in the thermal head device according to the present invention, even if the internal resistance of the driving circuit (IC or the like) varies greatly, the heating value of each resistance element of the thermal head is kept constant, and the uniform dot shape is obtained. Can be printed. Incidentally, when the thermal head device of the present invention was installed in a sublimation printer and recorded, it was impossible to perform multi-gradation recording of 32 or more gradations with the conventional thermal head device due to unevenness in the internal resistance of the drive IC. 256
Good recording without unevenness up to the gradation was obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a drive IC drop measuring device for obtaining a thermal head device according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a pulse trimming device.

FIG. 3 is an explanatory diagram of a resistance value of a resistor array after pulse trimming is performed.

FIG. 4 is a resistance characteristic diagram showing a result of adjusting a resistance value of a resistor by laser trimming using an 8 dot / mm thin film type thermal head.

FIG. 5 is an explanatory diagram of a thermal head in which the resistance value is adjusted by changing the width (main scanning direction) of a resistor of a heating unit.

FIG. 6 is an explanatory diagram of a thermal head in which a width of an individual electrode in a main scanning direction is trimmed to adjust a heat generation amount of a heat generation unit.

FIG. 7 is a sectional view of a head substrate.

FIG. 8 is a side view of the thermal head device.

FIG. 9 is a top view of the thermal head.

FIG. 10 is a conventional process diagram for manufacturing a thermal head.

FIG. 11 is a side sectional view of the completed thermal head device.

FIG. 12 is an explanatory diagram of a positional relationship between terminals of a driving IC for driving a thermal head.

13 is an explanatory diagram of an example of a measured value of a drop of an output voltage of each output pad of the drive IC shown in FIG.

[Explanation of symbols]

1 ... insulating substrate, 2 ... resistor, 3 ... common electrode, 4 ... individual electrode, 5 ... overglaze layer, 6 ... heat dissipation substrate, 7 .... Drive IC, 8
.... Bonding wire, 9 ... Connector,
20 ··· thermal head, 70 ··· drive IC,
80 ... oscilloscope, 90 ... pulse generator, 100 ... probe.

Continuation of the front page (72) Inventor Yoshiyuki Shiratsuke 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Works (56) References JP-A-2-263666 (JP, A) JP-A-63-141765 (JP, A) JP-A-60-171178 (JP, A) JP-A-4-168058 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/35 H01C 17 / 242

Claims (1)

(57) [Claims] A plurality of heat generating portions each including a plurality of resistance elements; a common electrode connected to one end of each of the plurality of heat generating portions; and a common electrode connected to the other end of each of the plurality of heat generating portions. In a thermal head device in which a thermal head unit having a plurality of individual electrodes and a drive IC having an output terminal connected to each of the plurality of individual electrodes are mounted on a heat dissipation board, the thermal head unit of the thermal head unit A thermal head device wherein a heat generation amount is set according to a voltage drop amount present for each output terminal of the drive IC.