JP2969900B2 - Thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head in which heating elements are arranged in a line for use in an apparatus that performs thermal recording separately for each block of a plurality of heating elements.

2. Description of the Related Art In a thermal head such as a thermal printer,
When energization control is performed on all the heating elements in a lump, large power is required instantaneously as the number of heating elements increases, and a large-capacity and high-responsive power supply is required. Therefore, in order to suppress the instantaneous power and control the energization of all the heating elements, the heating elements in the thermal head are divided into a plurality of groups, and this group is hereinafter referred to as a "divided block". Method of performing energization control collectively and sequentially at different timings for each heating element (hereinafter referred to as “block division recording”).
That. ) Is generally known.

Here, the block division recording method will be described. As an example, a case will be described in which all the heating elements of the thermal head are divided into two blocks and time-division recording is performed by a sublimation type thermal transfer method. FIG. 3 is a block diagram of the above-described two-block divided recording unit in a printer apparatus using a conventional thermal head, and FIG. 4 is a timing chart. In FIG. 3, reference numeral 301 denotes a data transfer clock CLK and a strobe ST.
B, a head control signal generation circuit that generates each head control signal of enable ENB1 and ENB2, 302 is a data output circuit that stores print data and outputs serial data according to the data transfer clock CLK, and 303 and 304 are serial data 305, 306 are latches for latching the converted parallel data by a strobe STB, 307, 308 are heating element drive circuits, 30
Reference numerals 9 and 310 denote heating element groups divided into two and arranged in a line.

Hereinafter, the operation will be described. As shown in FIG. 3, the head control signal generation circuit 301 generates a head control signal for a data transfer clock CLK, a strobe STB, and enable ENB1 and ENB2. The print data of the first block is sent from the data output circuit 302 to the head in synchronization with the transfer clock CLK, and is converted into parallel data corresponding to the dots by the shift registers 303 and 304 by the data transfer clock CLK and latched by the strobe STB. Latched at 305 and 306. Here, the same data is latched in the latches 305 and 306. The latched data is sent to the heating element drive circuits 307 and 308. When the enable ENB1 is activated, a recording current flows through the heating element group 309, and the recording of the first block is performed. During the recording of the first block, the recording data of the second block is sent from the recording data output circuit 302 to the head this time, and the shift registers 303 and 30 are output.
The data is converted into parallel data corresponding to the dot by 4 and latched by the latches 305 and 306 by the strobe STB.
The latched data is sent to the heating element drive circuits 307 and 308. This time, by activating the enable ENB2, a recording current corresponding to the recording data sent to the second block flows through the heating element group 310, and the second Block recording is performed. As described above, the heating elements in the thermal head are divided into a plurality of groups, and the heating elements in this one group are
The energization control is sequentially and collectively performed at different timings.

Next, the heating elements r1,1 to r2, N during two-block division recording using a conventional thermal head, and the heating elements r1,1 to
The arrangement example of the electrode pairs p1,1 to p2, N for supplying current to r2, N
Shown in the figure. As shown in FIG. 5, the heating elements r1,1 to r2, N have a width L.
i, heating element interval is Lf, electrode pairs p1,1 to p2, N are width Le, electrode pair interval is Lf same as heating element interval, electrode spacing is Lg, heating element width in main scanning direction is Lh, each constant It is. FIG. 9 shows the recording density distribution of the recording pixels with respect to the position of the heating element and the electrode pair near the block boundary when the above-described sublimation type thermal transfer printer apparatus performs two-block division recording with the same data using this thermal head. . The positions of the heating element and the electrode pairs in FIG. 6 show a cross section of the thermal head in the main scanning direction (line-like direction) viewed from a direction perpendicular to the main scanning direction.

In this two-block division recording, as shown in FIG.
First, thermal transfer recording is performed by controlling the energization of the heating elements r1,1 to r1, N (N is a natural number) included in the divided block b1, and then,
The energization control is performed on the heating elements r2,1 to r2, N included in the divided block b2 to perform thermal transfer recording. Therefore, the heating elements r1, N are not affected by the heating elements r1,1-N among the heating elements r1,1-N, r2,1 on both sides. Heating element r2,1 divided block b1
Since the divided block b2 is driven immediately after driving, the heating element r
It is affected by the heat generated by 1, N, but not as much as the heat generated by the heating elements r2,2. As shown in FIG.
The recording density distribution of the recording pixels energized and recorded by the heating elements r1, N, r2, 1 sandwiching the boundary between b1 and b2 is compared with the recording density distribution of the recording pixels energized and recorded by the other heating elements. At the same time as the density peak is low, it is shifted away from the boundary, and the recording density (recording density at the boundary) between recording pixels that are energized and recorded by the heating elements r1, N, and r2, 1 and it has a concentration D _0. The decrease in the density of the recording pixels at the boundary, the increase in the density difference between the recording density at the boundary and the recording pixels outside the boundary, and the increase in the low-density area at the boundary cause gaps to occur at the boundaries of the divided blocks. I have. The gap formed at the boundary between the divided blocks appears to be recorded as a white line in the recorded image, and there is a great problem that the aesthetic elements of the recorded image are significantly impaired.

Therefore, by weighting the recording data corresponding to each of the heating elements r1, N and r2, 1 with a predetermined value, the heating elements r1, N
A method to make the recording density of the recording pixel corresponding to N, r2,1 the same as the recording density corresponding to the other heating elements, and to compensate for the decrease in the density at the boundary of the divided block (hereinafter referred to as a “division compensation method”). .) To reduce the interstitial gap. The recording density of the recording pixels for the heating elements r1, N, r2, 1 according to the division compensation method is represented by a broken line a in FIG.

Problems to be Solved by the Invention In the conventional example, the boundary gap is reduced only by the division compensation method. However, this conventional method alone is used to reduce the density difference between the recording density at the boundary and the recording pixels outside the boundary. increase,
The cause of the increase in the low-concentration region at the boundary and the gap at the boundary cannot be eliminated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a thermal head which can eliminate the gap even when recording is performed by the above-described conventional block division recording method.

Means for Solving the Problems A heating element group composed of a plurality of heating elements arranged in a line, and an electrode pair group composed of a plurality of electrode pairs arranged at equal intervals in the line direction for supplying power to the heating element. Wherein, among the divided heating element groups obtained by dividing the heating element group into a plurality of groups, at least one of the two heating elements sandwiching a boundary between two adjacent divided heating element groups, A thermal head enlarged in the boundary direction is used.

Effect of the Invention According to the present invention, while arranging a plurality of electrode pairs at equal intervals in the line direction of a thermal head, the area of at least one of the two heating elements sandwiching the boundary between two adjacent heating element groups is different. Since the heat generating element is wider in the boundary direction than the heat generating element, the heat generating temperature distribution of the heat generating element in contact with the boundary and the peak of the heat generating temperature are shifted toward the boundary. Therefore,
The recording density at the boundary due to the division drive increases, and the peak of the recording density distribution of the recording pixels shifts in the boundary direction, so that the density of the boundary and other densities are maintained without breaking the pixel interval recorded by all the heating elements. The difference from the recording density between the recording pixels and the gap width at the boundary can be reduced.

Embodiment FIG. 1 shows an arrangement of a heating element and an electrode pair for supplying power to the heating element during two-block division recording of a thermal head according to an embodiment of the present invention. In FIG. 1, R1,1 to R1, N,
R2,1 to R2, N (N is a natural number) are heating elements arranged in a line, and P1,1 to P1, N, P2,1 to P2, N (N is a natural number) are heating elements R
An electrode pair for supplying current to 1,1 to R1, N and R2,1 to R2, N. The electrode pairs P1,1 to P1, N and P2,1 to P2, N are constant in width La, the electrode pair interval is Lb, and the electrode interval is Lc. The heating elements R1,1 to R1, N are in the first block, and the heating elements R2,1 to R2, N are in the second block.
It is divided into two blocks, heating elements R1,1 to R1, N,
R2,1 to R2, N are constant at the heating element width Lb in the main scanning direction, and when the heating elements are arranged in an equal area, the heating element width is Ls, and the heating element interval is equal to the electrode pair interval Lb. The number of heating elements is 2N (N is a natural number).

In the embodiment of the first invention, as shown in FIG.
Except for the heating elements R1, N and the heating elements R2, 1, the heating elements are arranged with an equal area Sa, and the heating elements R1, N expand the heating elements by the shaded area Sb in the boundary direction, and the heating elements R2, 1 Indicates the heating element
Only Sc is set to expand in the boundary direction. Heating element
The heating element areas of R1, N and heating elements R2, 1 are (Sa + S
b), (Sa + Sc), and the enlarged area Sb of the heating elements R1, N and the enlarged area Sc of the heating elements R2,1 have a relationship of Sb> Sc.

Using the thermal head of the embodiment of the first aspect of the invention, the recording density distribution of the recording pixels with respect to the position of the heating element and the electrode pair near the block boundary in the case where the same data is divided into two blocks by the division compensation method. Shown in the figure. The position of the heating element and the pair of electrodes in FIG. 2 shows a cross section of the thermal head in the main scanning direction (linear direction) viewed from a direction perpendicular to the main scanning direction.

Here, since the heating elements R1,1 to R1, N of the first block are being driven while the heating elements R2,1 to R2, N of the second block are at rest during the driving of the first block, the recording of the first block is performed. Heating element R
1, N is only affected by the heat generated from the heating elements R1, N-1 among the heating elements R1, N-1, R2,1 on both sides of the heating elements R1, N. The heating elements R2 and 1 are almost the same as the heating elements R1 and N.
Since the heating elements R2,1 to R2, N of the second block are driven immediately after the heating elements R1,1 to R1, N of the block have been driven, the heating elements R2,1
Is not as large as the heating elements R2,2, but is also affected by the heat generated from the heating elements R1, N. Therefore, as described above, the enlarged area Sb of the heating elements R1 and N and the enlarged area Sc of the heating elements R2 and 1 are defined as Sb> Sc.
It is set to become a relationship.

Also, the density of the boundary is corrected by the division compensation method,
Since the areas of the heating elements R1, N, R2, 1 are enlarged in advance in the boundary direction of the divided blocks as compared with the conventional example, the heating elements R1, N, R2, 1
As shown in FIG. 2, the recording density distribution of the recording pixels is not much different from the conventional example in the density peak position, but the density gradient at the boundary (between the heating elements R1, N and the heating elements R2, 1) is small. It becomes gentle. Thus, the difference between the recording density of between recording pixels recorded by the recording density and other heating element is reduced, narrowed the range of the paper density D ₀ of the boundary portion, the gap of the boundary is reduced.

In the embodiment of the present invention, the thermal head for the two-part drive has been described. However, even for the three-part or more drive, as described above, the area of the heating element at the boundary between the divided blocks is enlarged in the boundary direction. Thereby, a similar effect can be obtained.

Effect of the Invention As described above, the present invention provides an electrode pair group including a plurality of electrode pairs for supplying power to the heating element while disposing a plurality of electrode pairs for supplying power to the heating element at equal intervals in the line direction of the thermal head. And at least one of the two heating elements sandwiching the boundary
By increasing the area of one heating element in the boundary direction, the difference between the density at the boundary and the recording density between other recording pixels is reduced without breaking the interval between the recording pixels, and the gap width at the boundary is reduced. Can be done. Therefore, a remarkable density difference between the boundary and another pixel is reduced, a low density region at the boundary, that is, a gap between the boundaries is narrowed, and image deterioration due to the gap between the boundaries can be eliminated.

As described above, by using the thermal head of the present invention, the gap at the boundary, which was a problem, can be reduced, and the degradation of the recorded image, which is a white line on the recorded image, can be eliminated.
Its practical effect is great.

[Brief description of the drawings]

FIG. 1 is a diagram showing the arrangement of heating elements and electrode pairs in two-block division recording of a thermal head according to an embodiment of the present invention, and FIG. 2 is a heating element near the boundary between divided blocks of the thermal head according to the embodiment of the present invention. FIG. 3 is a diagram showing a recording density distribution of a recording pixel with respect to an electrode pair position, FIG. 3 is a block diagram of a two-block divided recording unit in a sublimation type thermal transfer printer using a conventional thermal head, and FIG. FIG. 5 is a timing chart of two-block division printing in a sublimation type thermal transfer printer device using a printer. FIG. 5 shows an example of the arrangement of heating elements (r1, 1 to r2, N) in two-block division recording using a conventional thermal head. FIG. 6 is a diagram showing recording on the heating element and electrode pair positions near the block boundary when two blocks are dividedly recorded with the same data using a conventional thermal head. It is a diagram showing a recording density distribution of the unit. R1,1 to R2, N, r1,1 to r2, N, heating element, P1,1 to P2, N, p1,1 to p2, N, electrode pair, La, Le ... electrode pair width Lb, Lf: Electrode pair spacing and heating element spacing, Lc, Lg: Electrode spacing, Ld, Lh: Heating element width in the main scanning direction, Li: Heating element width, Ls: Heating element has the same area Heating element width when arrayed as follows: D ₀ … paper density.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideshi Ishihara 1006 Kazuma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-199466 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B41J 2/335

Claims (1)

(57) [Claims] 1. A heating element group comprising a plurality of heating elements arranged in a line, and an electrode pair group comprising a plurality of electrode pairs disposed at equal intervals in the line direction for supplying power to the heating elements. The heating element group is divided into a plurality of heating element groups, and at least one of the two heating elements sandwiching the boundary between two adjacent divided heating element groups is moved in the boundary direction. Thermal head characterized in that it has been enlarged.