JPS6212271A - Driving circuit for thermal recording head - Google Patents

Abstract

PURPOSE:To decrease the number of input data and to shorten a data transfer time and a printing time by providing shift registers for inputting the same input data to plural heat generating elements and selecting a shift register according to the definition of input information to be recorded. CONSTITUTION:When a signal is inputted and recorded by plural-dot units, i.e. 2-dot units, input data DA which are reduced in quantity to half are inputted to shift registers SR5, SR6... with a clock CK. Then, gate circuits G1, G2... are supplied with a select signal C2 and then only data B passes through gate circuits G1 and G2 from the SR5 and gate circuits G3 and G4 from the SR6, so that the same data of every two dots are inputted to latches L1 and L2, and L3 and L4 with latch pulses LA. For the purpose, driving pulses BE are supplied to drives D2-D4 and then heat generating elements H1 and H2, H3 and H4,... generate heat for every two dots in response to the same data, so recording is performed by two-dot units. Thus, the data input time is shortened.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a thermal recording device for recording images, characters, etc. on a recording medium, and is particularly applicable to high-speed recording of various input information on a large screen. The present invention relates to a drive circuit for a thermal recording head that is suitable for performing this purpose.

[Background of the invention]

As the field of use of communication equipment and image processing equipment expands, the information handled is also becoming more diverse. Various notebook copying devices have been proposed for a wide range of uses, including high-definition color images with fine halftones. Furthermore, there is an increasing need for a handy hard copy device that can handle any of these various types of input information. Among these, the thermal recording method has the advantage of being noiseless and requiring no maintenance.Among them, the thermal transfer method using sublimation dye ink paper can produce U-level gradations by controlling the time when electricity is applied to the thermal head. It is possible to record halftones and is a powerful method.

The thermal recording head and gradation recording method in the conventional thermal transfer method use a thermal line head in which heating elements are arranged in a line, as shown in, for example, Japanese Patent Laid-Open No. 56-130579. , a drive circuit (driving circuit), a latch, and a shift register. FIG. 2 shows an example of the configuration of a conventional thermal head.

In Fig. 2, H3~HN are heating elements, D1~D
I is a driver that drives each heating element, L1 to L are latches, and SR and SRN are shift registers that serially transfer input data. To perform gradation recording, first the heating elements H1 to IN of the recording cloth in one line of recording signal are
The recording presence 9 signal is input to the shift registers SR1 to SRN corresponding to the shift registers SR1 to SRN. Input data is shifted in the shift register every clock pulse, and by applying N clock pulses, data for N heating elements is input. When all data have been input to the shift register, a latch pulse is applied to move the data to latches L1 to L corresponding to each heating element.

Next, a heating element energizing pulse BE is applied to the drivers D1 to DI, and a voltage VB is applied to the heating element corresponding to the recording cloth for a time t1 necessary to obtain a density corresponding to gradation level 1 to generate heat. Next, apply a similar clock pulse to the shift register corresponding to the recording heating element of gradation level 2, input the recording signal, and latch it to obtain the density equivalent to gradation level 2 of the corresponding heating element. Generate heat for the required table additional time 6. By repeating this operation as many times as the number of maximum gradation levels, each heating element is made to generate heat for a time corresponding to the input gradation level, and one line is recorded.

According to this method, it is necessary to repeatedly input the input data for the number of heating elements as many times as the maximum number of gradations, so for line heads with a large number of heating elements, it takes a lot of time to input data. The disadvantage is that it takes a long time to print. By the way, the input information for one line to be recorded rarely differs from one dot to the next, and the same data is often input over several to tens of dots, which is difficult when recording figures or computer graphics. In extreme cases, the same data may be input to all dots for one line, and if the method of inputting corresponding data for each heating element as in the conventional head, the same data cannot be input. It had the disadvantage of being extremely inefficient as it required input and recording.

[Purpose of the invention]

An object of the present invention is to provide a drive circuit for a thermal recording head that can change the number of unit heating resistive elements of a thermal head according to the definition of input data such as printing information, and shorten the printing time of low-definition printing information. It is about providing.

C. Summary of the Invention] In the thermal head drive circuit according to the present invention, in addition to the shift register corresponding to one heating element, the same human power data can be applied to a plurality of heating elements such as for driving in units of 2 dots and driving in units of 3 dots. A shift register is provided to store the
By selecting the shift register to be used according to the definition of the input information to be recorded, the number of input data and data transfer time are reduced, thereby reducing the printing time.

[Embodiments of the invention]

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

FIG. 1 shows an example of the configuration of a drive circuit for a thermal recording line according to the present invention, and for simplicity, only four heating elements are shown.

In FIG. 1, H3~ku... are the heating elements of the thermal head, D8~... are the drivers that drive the heating elements,
L1 to L4... are latches, G1 to G,... are gate circuits for selecting inputs to the latches, and SR1 to SR.

... is a shift register for independent input one dot at a time, S
R, SR, . . . are shift registers for inputting two dots at a time, and l, . . . are shift registers for inputting four dots at a time. The output from the shift register SR is two gates) G1. G, IIC, shift register SR,
The output from the two gates G3. G4I/c are connected in parallel, respectively, and the output from shift register 5ILr is connected to four gates 01~. The gate circuits 01 to G, . It is composed of an OR gate 4, and can select the connection to the shift register and change the input data to the latch according to the selection signals C1 to C8. When recording high-definition data independent of 1 dot, shift registers SR, ~SR6...K independent data I)A is inputted to clock pulse cxixb, and selection signal C1 is given to the gate circuit to output only AND gate 1. are made conductive, and only data A from shift registers SR8 to SR,... is passed through to gate circuits 01 to..., and independent data is input to latch pulse LAK and silatch Lt-L,... do. Therefore, if a driving pulse EE is applied to the drivers D8 to D, . . . , the voltage VH is applied to the heating elements H, -H, .
is applied, and like a normal head, the heating elements I, ~ are also
can independently generate heat.

Next, a method for recording information that can be recorded in units of two or more dots will be described. For example, when inputting and recording in units of 2 dots, input data DA whose data number has been reduced to 1/2 in advance is inputted to shift registers SR5, SR6, . . . using clock CK. Since the number of data is 1/2, shift register s
The input time to R,,sR,... can be reduced to 1/2. At this time, shift register SR.

There is no problem even if data is input to horses ~l, , and S at the same time. (Only half of the data enters the shift registers SR1 to SR4, and SZ becomes data over.) Next, the selection signal C! is sent to the gate circuits G1, s'2, and so on.
, and only the data B from the shift registers SR, , l, . . . is passed through the gate circuits G, .about.G4 .

In other words, only the data from the shift register S is sent to the gate circuit GIm'! Then, only the data from the shift register 54 passes through the gate circuit GSmG, so that the same data is input into the latches L, .about.L, . . . two dots at a time. When the latch pulse LA is applied, the data stored in the shift register S is stored in the latch L1mLt, and the data stored in the shift register 5R6 is stored in the latch LlllL4.
The data entered in 1C is input. So driver D
If a driving pulse BE is applied to 8 to D4..., the heating element H1 and horse.

R3 and 14. Since the same data generates heat every two dots, it is possible to record in units of two dots. Similarly, if you want to record in units of 4 dots, reduce the number of data to 1/4, input the data DA for 9 people to the shift register, and give the selection signal C1, so that only the same data C will be recorded every 4 dots. The signals are inputted to latches L, -L4, etc. through gate circuits G, -G4, and so on, and can be recorded in units of four dots. Needless to say, the data input time at this time can be reduced to 1/4.

4 and 5 are block diagrams showing an example of a hexagonal signal processing system in the method for driving a thermal recording head according to the present invention.

In the example shown in Fig. 4, the switch is changed according to the type of long sword information to be recorded, and the recording method is specified, such as driving in 1-dot, 2-dot, or 4-dot units.For example, the recording mode set in the printer is By selecting a button, high-speed recording can be performed at a pixel density suitable for the recording information.

In FIG. 4, pixel data (for example, town, G1, . . . ) input from an image source 5 to a line memory 6.

αN (where 4 is the number of gradations of a pixel and N is the total number of dots of a thermal recording head) is, for example, in the case of information such as characters or computer graphics with little variation in definition or gradation.
The recording mode switch 7 is switched to a multiple dot unit drive mode, such as a 2 dot unit or 4 dot unit drive.

When the switch 7 is switched to the multiple dot unit drive mode, the addressing circuit 8 selects G1 . G3. G
5. ...or G1. G6. α,.

..., data thinned out every 2 dots, every 4 dots, etc. is selected, N/2 pieces, ! The data reduced to four pieces or the like is sent to the thermal recording head 9. At the same time, the gate selection circuit 10 operates in conjunction with the recording mode switch 5, and the selection signal C2 shown in FIG. The data is sent to the head 9, and one pixel data can be recorded in units of 2 dots, dots, or 4 dots. Note that the recording mode switch 7 and the address designation circuit 8 may be provided between the image source 5 and the line memory 60, and in this case, the line memory 6 has a number of
By inputting data reduced to /4 or the like and sending a gate selection signal at the same time as sending the data to the thermal recording head, similar printing can be performed in units of multiple dots.

In the example shown in FIG. 5, input data is automatically determined and a recording mode is selected. For example, a microcomputer is provided in the printer to perform the following operations.

In FIG. 5, pixel data (α1, α7, . . . , cLN) input from the image source 5 to the line memory 6 is first divided into groups of two dots by a gradation number comparison circuit l. The gradation numbers (α, 12α, and “4*”’#”#-11!:”N) of each two dots are compared. As a result, if there are more than a certain number (appropriate small number) of pairs in which the tone difference between two dots is, for example, two or more tone levels, then N
The pixel data is sent as is to the thermal recording head 9, and the gate selection circuit 10 selects the selection signal C8 for driving one dot at a time, and normal recording in which one data corresponds to one dot is performed. If the number of sets in which the difference in gradation between two dots is two or more gradations does not reach a certain number (it does not matter how many gradation differences there are between the sets), then the number of gradation comparators 11 , ~α,,α, ~α♂.

. . . e'N-3 to α are grouped into groups of four dots, and the number of gradations between each four dots is compared. As a result.

If there are more than a certain number of sets in which the gradation difference between the four dots is two or more gradations, the data creation circuit 12 (which has the same function as the addressing circuit in FIG. 4) performs α.

α8. α1. ... The data thinned out every 2 dots is selected, and the data reduced to N/2 pieces is sent to the thermal recording head 9, and the gate selection circuit 1
0 selects the selection signal C° for driving in units of 2 dots, and one data is recorded in units of 2 dots. If the number of sets in which the gradation difference between the four dots is two or more gradations does not reach a certain number, the data creation circuit 12 further uses α1. α1. α
0. . . . The data thinned out every 4 dots is selected, and the data reduced to V4 pieces is sent to the thermal recording head 9, and the gate selection circuit 10 generates a selection signal for driving in units of 4 dots. C1 is selected and one data is recorded in units of four dots. According to this method, even for an input source with many gradation changes such as a video image, recording of an image part where one line of input data is uniform, such as a blue sky, can be performed in units of multiple dots. , data transfer time can be efficiently shortened, and printing time can be shortened.

The embodiment shown in Fig. 1 shows an example in which input and drive are performed in units of 1 dot, 2 dots, and 4 dots, but if similar shift registers and gate circuits are provided, one input data can be inputted arbitrarily. The voltage can be applied to as many heating elements as possible, and it is possible to drive in units of multiple dots. For example, by using a thermal head with a 12 dots/MO heating element, you can freely select pixel densities such as 6 dots/fin, 4 dots/W, 3 dots/M, 2 dots/fin, and 1 dot/-. , if you reduce the number of input data according to the input information,
You can print quickly even on large screens.

Further, by using the method of driving a thermal recording head according to the present invention, it is possible to reduce or enlarge the screen. For example, in the case of reduced recording, the address designation circuit 8 shown in FIG. If you provide a reduced recording mode that allows you to select C8, 94 or V4 data can be reduced to 1.
Since it is driven in units of dots, it is possible to obtain a recording interval in which the screen is reduced to 1/2 or 1/4. vice versa,
By inputting dot-by-dot data without thinning and providing an enlarged recording mode in which drive circuits for multiple dots can be selected, partial enlarged recording of the screen is possible. However, it is necessary to change the paper feeding speed in accordance with the reduction/enlargement ratio.

〔Effect of the invention〕

As described above, according to the present invention, since a shift register and a selectable gate circuit for recording in units of multiple dots are provided in the thermal recording head, the number of input data can be adjusted according to the input information to be printed. The data transfer time and therefore the printing time can be significantly reduced. For example, 2560 dots (1
2 dots/simple), data transfer frequency 4MH2 (1 person power)
If you try to record one 24-size page in 6 gradations of pull color using this head, the data transfer time for one line will be 2.
560Xα25μzX64q41x, so if one page is 1500 lines, it is 0.041X1500X
5 colors #185 seconds of printing time is required, but 2 to 6 dots can be printed using the driving method of the present invention.

If the drive is performed in units of dots, the printing time is only 30 to 9 Q seconds, and the effect is remarkable.

Note that the drive circuit of the present invention, like the conventional drive circuit,
Since it can be converted into C and mounted on a thermal recording head,
The head configuration and manufacturing process are not complicated.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a driving circuit for a thermal recording head according to the present invention, FIG. 2 is a circuit diagram showing a driving circuit for a conventional thermal recording head, FIG. 3 is a partial explanatory diagram thereof, and FIGS.
FIG. 1 is a block diagram showing an input signal processing method for a thermal recording head according to the present invention. SR, -5R,...Shift register H8-H6...Heating resistance element D1-D4...Driver G, ~G4...Gate circuit 5...Image source 6
... Line memory 7 ... Switch 8 ... Address designation circuit 9 ... Thermal head 10 ... Gate selection circuit 1] ... Gradation comparison circuit 12 ... Data creation circuit Summer 2 Fig. Figure 3 Q.

Claims (1)

[Claims] (1) In a drive device for a thermal recording head that selectively supplies power to each heating resistance element of a thermal head having a plurality of heating resistance elements, the output end of each stage is connected to each heating element of the thermal head. a first shift register connected to the first shift register; a second shift register having an output end of each stage connected to at least two successively arranged heating resistive elements of the thermal head; The apparatus further comprises a gate means provided between the second shift register and the thermal head, which switches the output signals of the first and second shift registers according to the definition of print data and supplies the signal to the thermal head. A drive circuit for a thermal recording head.