JPH0453759A - Thermal head - Google Patents

Abstract

PURPOSE:To improve a recording dot form at a block border part and thereby obtain a thermal head free from image quality deterioration due to the generation of a clearance by providing a cross-linking resistor which connects two thermal resistors together holding the border of two adjacent blocks. CONSTITUTION:A thermal head is divided into blocks A, B and a total of 512 thermal resistors consisting of each 256 thermal resistors RA, l to RA and RB, l to RB are provided in each block. The 256 thermal resistors RA l to RB is rectangular resistors with 140mum width arranged at every equal interval of 180mum. The thermal resistors RA 256 and RB l holding the block border are connected to each other by cross-linking resistors with l5mum width RA, B. The cross-linking resistors RA, B are of the same quality as the thermal resistors RA1 to RB 256 and are formed in one piece with thermal resistors RA 256 and RB1 when a sputtered resistor is pattern-etched into the form of a heat generating resistor.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a thermal head for thermal recording.In particular, it relates to a line thermal head that performs thermal recording by dividing a plurality of heating resistors into blocks. In the thermal head of equipment, etc., -
If you control the power supply to all heating elements at once, as the number of heating elements increases, a large amount of electric power will be required instantaneously, and a power source with large capacity and good responsiveness will be required. Although block division recording is generally performed for this purpose, block division recording (i) divides the heating element in the thermal head into a plurality of blocks and controls the energization of the heating element in each block at once. X is a method of sequentially switching the blocks to be energized. Figure 4 is a plan view of an example of a conventional thermal head. The head has four blocks A, & C.

Each block is divided into 128 heating resistors RA11~RA, 12&RB, 1~RB, 12g,
RC, 1-RC112 & RD, 1-RD, 12
Even if 8 is provided, heating resistors RA, 1 to RD, 12
8 has a width of 140 mm arranged at a pitch of 180 μm. um resistor 711O3A, 1-8A, 12g, SB
, 1-8B, 12 Kuma SC, 1~SC, 12&SD
, 1 to SD, 128 is a heating resistor RAXl-RD,
KA, 1 to KA are control electrodes with a width of 120 μm connected to the lower end of 128 and arranged at an equal pitch of 180 μm.
, 12 & KB, l ~ KB, 12 & KCXl
-KC112 turtle KD, 1~KD, 12g is heating resistor RA, 1~RD,! Connect to the upper end of 28 and connect to 180μ
Common electrodes KA, 1 to KD, 128 with a width of 120 μm arranged at equal pitches of m and control electrodes S A,
1-S D, 128 are opposed to each other with an interval of 300 μm, but when sublimation thermal transfer recording is performed at a recording speed of 16m5/1ine, each block is assigned an energizing time of 4IllS, and A-+B-C-4D You can also switch blocks sequentially with
The problem to be solved by the present invention is to give each heating resistor a block current-carrying time of up to 4 tns and a current-carrying time according to the input data. There was a major problem in that the recorded image quality was significantly impaired due to the occurrence of gaps.I will explain this in a little more detail.Figure 5 is an explanatory diagram illustrating the dot shape of recorded pixels recorded with a conventional thermal head. For the boundary between two blocks A and B, DA.

126 to D A1128 are dots in block A,
DB, 1 to DB, 3 are dots in block B a
Recording dots DA, 12 in the block DA, 127,
DB, 2. The dot shape of DB, 3 is stable and uniform, whereas the recording dots DA, 3 that sandwich the block boundary are
In the 12th order and DB, 1, the dot shape is different from other dots and is asymmetrical, and even though the side closer to the block boundary is thinner, the thinning of the dot DA, 128 is particularly remarkable, and this is due to the way the blocks are switched. This is because the order is A-B.The cause of this is the temperature distribution of the heating elements.The heating elements on both sides of the block generate heat in the same way, so heat flows in from both sides. When a heating element at the boundary of a block generates heat, the neighboring block is at rest, so heat only flows in from one side of the heating element. , the shape of the recording dot also becomes thinner on one side.In this way, at the block boundary, the shape of the recording dot becomes thinner on one side.The gap that is created looks like a white line.
In view of the above problem, the present invention provides a thermal head that improves the shape of recording dots at block boundaries and does not cause deterioration in image quality due to the occurrence of L-gaps. In the present invention, in order to solve the above-mentioned problems, - In a thermal head that performs block division recording, two heating resistors sandwiching a boundary between two adjacent blocks are connected to each other. The present invention operates even if a bridging resistor is provided, so that when electricity is applied to one of the two heat-generating resistors sandwiching the block boundary, part of the current flows to the bridging resistor, causing it to generate heat. Embodiment 1 FIG. 1 shows an embodiment of the present invention, which compensates for the temperature drop at the boundary due to divided driving, reduces the difference in recording density between other recording pixels, and eliminates the deterioration of the recorded image. This is a plan view of the main parts of the thin film thermal head in the example.The head has two blocks A,
Each block has 256 heating resistors RA, 1-RA, 25a, RB, t-RB, 25a.
(7) Even if a total of 512 pieces are provided, the heating resistors RA, 1-RB, and 256 are rectangular resistors with a width of 140 μm arranged at equal pitches of 180 μm.Heating resistors RA sandwiching the block boundary , 256 and RB, 1 are connected by bridging resistors RA, B with a width of 15 μm. The bridging resistors RA, B are connected to heating resistors RA11 to RB, 2.
The control electrode SA, 1 is the same resistor as the heating resistor RA, 256 and RB, 1 when the shape of the heating resistor is created by pattern etching the sputter-formed resistor. ~SA, 25a, 5B11-
8B, 256 are connected to the lower ends of heating resistors RA, 1 to RB, 256, and are arranged with a width of 120 μm at an equal pitch of 180 μm.
μm electrodes, 256 in each block, 512 in total
In this case, 256 control electrodes SA, 1 to SB, 256 are in a state where voltage can be applied simultaneously in block units.
A voltage is applied to the individual control electrodes in this block for a time determined based on input data.Common electrode KA
, 1~KA, 25 modified KB, 1~KB, 256 are connected to the upper ends of heating resistors RA, 1~RB, 256 with a thickness of 180 μm.
These are electrodes with a width of 120 μm arranged at equal pitches, and each block has 256 terminals, a total of 512 common electrodes KA,
Even if I~KB, 256 are connected to each other and have the same potential, the common electrode KAXl-KB, 256 and the control electrode S A
, 1-SB, 256 are opposed to each other with an interval of 300/J m. When performing block division driving at a recording speed of 16 m5/1 in. using the thermal head configured as described above, each of A and B. Assign 8ms of energization time to each block and switch blocks sequentially from A to B4A to B.a Each heating resistor in the selected block has a block energization time of 8I.
The heating resistor RA sandwiching the boundary between block A and block B is
, 256. The explanation will be given using RB,1 and bridging resistors RA,B as examples. When an applied voltage is applied to the control electrode in block A, approximately 9 of the current flowing from control electrode SA, 256
0% is common electrode K A through heating resistor RA, 256
, 256, but about 10% of the current flows through the bridging resistor RA
, B to reach the common electrode KB, 1 90% of the former
The current of 10% generates heat in the entire heating resistor RA, 256. Most of the heat generated by the latter 10% current is generated in the bridging resistors RA, B. The path of the 10% current is the heating resistor RA, 256. 256. It also passes through RB and 1, but their resistance values are much smaller than those of the bridge resistors RA and B. However, these resistance values hardly contribute to heat generation.
Electrical energy given from the control electrode S A, 256 (90% of the air generated around the heating resistor RA, 256)
It is also used for 10% of heat generation mainly in bridge resistors RA and B.
As already explained, in the heating resistor RA, 256, there is no inflow of heat from the adjacent heating resistors RB, 1, which causes a temperature drop on the block boundary side.According to the present invention, the heating resistor RA , 256, there are bridge resistors RA and B adjacent to the block boundary side, which generate heat.
Prevents temperature drop on the block boundary side of the heating resistor R^, 256. Therefore, the recording dot shape method using the heating resistor RA, 256 is preferable, with no narrowing on one side and no gaps.The same applies when energizing the block B. Approximately 90% of the current flowing from the control electrode SB, 1 is the heating resistor. Body R
The common electrode KB,1 is reached through B,1, but about 10%
The current flows through the bridging resistors RA, B to the common electrodes KA, 2.
56 is reached. The bridging resistors RA and B generate heat to prevent the temperature drop on the block boundary side of the heat generating resistors RB and l. Therefore, the recording dot shape L block boundary side is prevented from becoming thinner due to the heating resistors RB and 1, and as described above, according to this embodiment, a bridging resistor is provided to connect the heating resistors at the block boundaries, and this generates heat. By doing so, it is possible to compensate for the temperature drop at the block boundary due to divided driving and reduce the difference in recording density between other recording pixels. FIG. The head is divided into 4 blocks ASB, C, and D, and each block has 128 heating resistors R^, 1-RA,! 28.
RB, I~RB1128. RC11~RC1128
, RD, 1-RD, 12 512 heating resistors RA, 1-RD, 128 are provided along the axis X direction.
is a width of 140 μm arranged at equal pitch every 180 μm.
The bridging resistors R'A and B have one end e.
1 connects to the heating resistor RA, 128, and the other end e2
Even if it is connected to the heating resistor RB,1 at the connection point e
l is located 60 μm away from control electrode SA, 128, and connection point e2 is located 240 μm away from control electrode SB, 1. Heating resistor RA, 128 and RB
1 and the bridging resistors R'A and B when viewed as one body have an inverted N shape, and are asymmetrical with respect to an arbitrary axis y perpendicular to the axis X. B, C, R
' C1D has the same shape as bridging resistor R' A and B,
The resistance between the heating resistors RB, 128 and RC, l, respectively, is
Even if the control electrodes SA, 1 to S A112 & SB, 1 to 5 are connected between 128 and RD, 1,
BX12&SC, ] ~SC, +2a, SD, I
~SD, 128c heating resistor RA.

1-RD, 128 electrodes with a width of 120 μm connected to the lower end of 128 and arranged at an equal pitch of 180 μm, 128 in each block, total 512 control electrodes S A,, l~S
D, 128 is in a state in which 128 voltages can be applied simultaneously in a block unit. Voltage is applied to the individual control electrodes in this block for a time determined based on input data, but the common electrodes KA, 1-KA, 12 & KB, 1
-KB, 12 & KC, 1~KC, 128, K D,
1 to KD, 128 are heating resistors RA, l to RD, 1
The electrodes are 120 μm wide and are connected to the upper end of 28 and arranged at an equal pitch of 180 μm, and each block has 128 electrodes, totaling 512 electrodes.Common electrodes KA, 1 to KD, and 128 are connected to each other to have an equal potential. There is. Common electrode KA,]~K
D, 128 and the control electrodes SA, 1 to SD, 128 face each other with an interval of 300 μm. When performing block division driving at a recording speed of 16 ns/line using the thermal head configured as described above, A. , B, C, D multiple blocks can be assigned a 4+ns energization time, and the blocks can be switched sequentially as A+B-C-D.Each heating resistor in the selected block will respond to the input data with a block energization time of 4ms as a limit. The heating resistor RA sandwiching the boundary between block A and block B
, 12 &, RB, 1, and bridging resistors R'A, B will be explained as an example. First, when energizing block A,
About 90% of the current flowing from the control electrode SA, 128 reaches the common electrode KA, 128 through the heating resistor RA1128, while about 10% of the current flows through the bridging resistor R'A.

It passes through B and reaches the common electrode KB, 1. Therefore, 90% of the heat generation is generated in the heating resistor RA, 128 L. 10% is generated in the bridging resistors R'A and B. 4 Next, energize block B. (Top) Approximately 97% of the current flowing from the control electrode SB, 1 flows through the heating resistor RB, 1 to the common electrode K.
Approximately 3% of the current reaches the bridging resistor R' A, B
It passes through the common electrode K A and reaches the common electrode 128. Therefore, 97% of the heat generation is generated in the heating resistor RB, 1. 3% is generated in the bridging resistor R'A, B. 4 In this way, when block 8 is energized, Even though the amount of current passing through the bridging resistors RA, B is different between the current flow and when block B is energized, this is because the current path is asymmetrical with respect to the control electrodes SA, 128 and SB, 1, and the bridging resistors R'A, This is because the resistance values of the current paths including B are different.The above explanation took the boundary between blocks AB as an example, but the same is true between blocks BCl'ACD.Here, for example, when energizing block B Considering the temperature distribution at both ends of the block, the block is A -B-C-+D
Since the switching is performed in the order of
The temperature does not drop that much (at the right end on the tX block B side, there is no heat inflow because block C is not energized, so the temperature drop is large).

Therefore, the bridging resistors R'A and B do not need to generate much heat, but the bridging resistors R'B and C have a large need to generate heat - according to this embodiment, as already explained, the bridging resistor R
'A and B did not generate much heat, while bridge resistors R'B and C generated a lot of heat.Heating resistors RB, I and RB, 128
The same goes for blocks A, C, and D.As explained above, in this example, the bridge resistor is connected to the two heating resistors. The feature is that when integrated, the integrated shape is asymmetrical with respect to the axis y perpendicular to the direction in which the heating resistors are arranged. It is possible to compensate for the difference in temperature distribution at both ends of the block due to the block switching order.
This is particularly effective when multiple blocks of three or more blocks are divided. Divided into A and B RA, 1-RA, 256,
RB11-RB, 256. is the heating resistor a provided in each block SA, 1-3A, 25a, SB
, 1~SB, 256LL control electric maple KA, l~KA, 2
5th generation KB11 to KB, 256 are common electrodes, and the above structure is similar to that of FIG. 17). R''A, B are bridging resistors with a width of 50 μm and a length of 320 μm, and heating resistors RA, 25a, which sandwich the boundary between blocks A and B,
Connected to RB, l Bridge resistor R”A, BLt
Heating resistor RA, 25a, RB, 1 (7) Lower layer varnish formed, heating resistor RA, 1 to RB, 256
By using a material with lower conductivity than that of the heating resistor of the same shape or by forming the layer thinner than the heating resistor of about 10 to 20
Even if the sheet resistance value is about twice as high, if block division recording is performed using a thermal head configured in this way, some portions of the bridging resistors R''A and H will appear as explained in Fig. 1. Current flows and generates heat, compensating for the temperature drop at the block boundary and keeping the recording dot shape uniform.Here, the actual heat generating area of the bridging resistors R''A,H is the heating resistors RA, 256 and RB,1. This is the effect of increasing the sheet resistance of the bridging resistors R''A and B. Although the area of the bridging resistor can be increased while keeping the resistance value of the resistor the same, it is also possible to reduce the amount of current and heat generated per area of the bridging resistors R''A and B. Although it is possible to significantly extend the life of the bridging resistors R''A and B due to their current conduction history and thermal cycle, the present invention has more than the effects of the invention. By providing a bridging resistor that connects the pixels and generating heat, it compensates for the temperature drop at the block boundary during split drive, reduces the difference in recording density between other recording pixels, and eliminates the deterioration of recorded images. can also

[Brief explanation of the drawing]

Figure 1 shows the plane of the thermal head in the first embodiment of the present invention @ Figure 2 shows the plane of the thermal head in the second embodiment of the invention Figure 3 shows the plane of the thermal head in the third embodiment of the invention Figure 4 is a planar view of a conventional thermal head. Figure 5 is an explanatory diagram illustrating the dot shape of recording pixels recorded with the thermal head of Figure 4. ...Block, RX, N (
X=A, B, CXI), N=1 to 256)--Heating resistor. SX, N (X-A, B, C, D, N-1~256)
...Control electrode. KX, N (X-A, B, C, D, N-1~256
)-=common electrode, RA, R, R' A, B, R'
B, C, R' C, I), R"A, B... Bridge resistor. Name of agent: Patent attorney Shigetaka Awano Haga 1 person. Fig. 1 LOCK 8LOC, Fig. LQCK L Ck Fig. LOCK BLOCk' ○○○○○○

Claims (4)

[Claims] (1) In a thermal head in which a plurality of heat generating resistors arranged in a line are divided into a plurality of sets of blocks, and the heat generating resistors in each block are provided so as to be able to simultaneously conduct electricity and generate heat, two adjacent blocks A thermal head characterized in that a bridging resistor is provided to connect the two heating resistors with a boundary between them. (2) The shape formed by connecting the two heat generating resistors and the bridging resistor is a shape that is asymmetrical with respect to an arbitrary axis orthogonal to the direction in which the heat generating resistors are arranged. thermal head. (3) The thermal head according to claim 1, wherein the electrical conductivity of the bridging resistor is lower than that of the heating resistor. (4) The thermal head according to claim 1, wherein the thickness of the bridging resistor is smaller than the thickness of the heating resistor.