JPH0577467A - Thermla head and thermal printer - Google Patents

Abstract

PURPOSE:To reduce the irregularity of printing density due to the gaps between printed adjacent dots by providing gaps between many heating elements constituting a thermal head and continuously arranging the respective heating elements at angles to a paper moving direction. CONSTITUTION:In a thermal head consisting of many heating elements Rn, the respective heating elements Rn are obliquely provided with respect to a paper moving direction Y. Gaps delta are provided between the heating elements Rn and the heating elements Rn are continuously arranged so as to provide an angle theta with respect to the paper moving direction Y and, further, parts OB overlapped with respect to the paper moving direction Y are provided to many heating elements Rn adjacent to each other. In a thermal printer, a printing head applying printing to paper is constituted of the above mentioned thermal head. By this constitution, the irregularity of printing density due to the gaps between adjacent dots in a printed bar code is reduced and the reading of bar code data is accurately performed.

Description

Detailed Description of the Invention

[Table of Contents] Industrial Application Field of the Prior Art (FIG. 6) Problem to be Solved by the Invention (FIG. 7) Means for Solving the Problem (FIG. 1) Action Example (FIGS. 2 to 5) ) The invention's effect

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head and a thermal printer, and more particularly to a printer for printing a bar code to be printed and its head structure.

In recent years, in the distribution process of fresh foods and the like, a bar code is printed on the label of which the surface of the thermal paper is processed to be waterproof so as to show the price and the product display. For this bar code printing, a thermal printer is used, which has a better printing resolution than the wire dot type printer.

According to this, a thermal head composed of a plurality of heating resistors is arranged in a direction perpendicular to the moving direction of the thermal paper. Further, the heat generation amount of each heat generating resistor has a normal distribution in which the central portion is large and both side portions are small.

For this reason, the amount of heat generated at the boundary between adjacent heating elements in the head is smaller than the amount of heat generated at the center. Therefore, the print density unevenness may occur in the bar code subjected to the thermal printing process by the head.

Further, in a thermal printer incorporating the head, a black bar and a white pattern can be accurately discriminated by a bar code reader based on variations in print density due to gaps between the dots of a bar code which is thermally printed (black bar portion). It may be difficult to perform, and the barcode printing information may be erroneously read.

Therefore, the plurality of heating resistors are not arranged at right angles to the moving direction of the thermal paper, but the arrangement thereof is devised to reduce the print density variation due to the clearance between the adjacent dots as much as possible. There is a demand for a thermal head and a thermal printer that can accurately read barcode information that is a print target.

[0008]

2. Description of the Related Art FIGS. 6 and 7 are explanatory views according to a conventional example. 6 (a) and 6 (b) show a layout and a configuration diagram of a thermal head according to a conventional example.

In FIG. 6A, for example, thermal paper 15
The line dot type thermal head 1 for bar code printing is composed of a plurality of heating resistors R1 to Rn, which are attached in a direction perpendicular to the moving direction Y of the thermal paper 15. The head 1 is pressed and fixed to the platen 2 by a leaf spring or the like.

The function of the thermal head is that the head 1
When the thermal paper 15 is sequentially fed between the platen 2 and the platen 2, the plurality of heating resistors R1 to Rn are energized and controlled. As a result, heat is supplied to the thermal paper 15 between the thermal head 1 and the platen 2, and the barcode 3 is printed on that portion. For example, as shown in FIG. 7A, the bar code 3 that has been subjected to the thermal printing processing is composed of black print bar portions 3A and 3C and a white pattern portion 3B, and the black print bar portions 3A and 3C.
C is composed of a printing portion for one dot of the heating resistor and a continuous printing portion for several dots.

FIG. 6B is a structural view of a thermal head according to a conventional example, showing a plan view thereof. Figure 6
In (b), for example, each rectangular heating resistor R1
Rn are arranged in a line in the X direction with respect to the moving direction Y of the thermal paper 15. The plurality of heating resistors R1 to Rn are formed by connecting the conductor pattern 1A to a resistor layer provided on the ceramic substrate.

[0012]

By the way, according to the conventional thermal head 1, a plurality of rectangular heating resistors R1 are provided.
Rn are parallel to one side of the moving direction Y of the thermal paper 15 and are arranged in a line in the X direction. Further, the heat generation amount of each heating resistor Rn has a normal distribution in which the central portion is large and both side portions are small.

Therefore, the following problems may occur. In the head 1, the heat generation amount at the boundary between the adjacent heat generating elements Ri and Rj is smaller than the heat generation amount at the central portion. That is, both side portions of each heating resistor Rn are remarkably deteriorated as compared with the heat distribution in the central portion.

From the above, as shown in the problem of FIG. 7B, in the bar code 3 which is thermally printed by the head 1, the heating resistor Rn is continuously printed over several dots in black. Print density unevenness (print unevenness due to gaps between black-printed dots) may occur in the bar printing portion.

In order to prevent this, there is also a method of setting the drive voltage of the thermal head 1 with high accuracy to make the print density uniform. However, in order to ensure a stable and sufficient reading process of the barcode reader, when the upper limit of the head resistance value is used as a reference, it is not necessary to set the voltage value higher than the drive voltage during normal use. Inevitably, the capacity of the power supply itself must be increased.

Further, in this situation, when the thermal head 1 is used in a thermal printer based on the lower limit value of the head resistance value, the life of the thermal printer becomes extremely short. As a result, the head resistance value increases and the print density decreases, which may make it impossible to read the bar code information.

Further, in the thermal printer having the thermal head 1 built-in, since the heat distribution at the boundary portion between the heating element Ri and Rj is remarkably reduced, the print unevenness due to the gap between the black printed dots is noticeable. Unable to perform reliable barcode printing.

As a result, it becomes difficult for the bar code reader to accurately discriminate between the black bar and the white pattern due to the variation in the print density due to the clearance between the adjacent dots.
The bar code print information may be erroneously read.

For example, in FIG. 7B, the ambient temperature is 0
When the bar code 3 thermally printed at [° C.] and 25 [° C.] is read by a bar code reader for comparison, the bar code 3 (broken line portion) 3 thermally printed at a low temperature is shown in FIG. As shown in c), the barcode reader may cause a count error.

Here, as shown in FIG. 7 (c), the count error is that the "L" (low) level is erroneously detected during the "H" (high) level period of the waveform-shaped code read signal. It is something. The code read signal is obtained by shaping the reference voltage (threshold value), which is the comparison reference voltage set to 1/2 of the output waveform peak voltage value, with respect to the detection voltage of the bar code reader light receiving portion.

As a result, the barcode reader causes a count error in the distribution process of fresh food and the like, and the price code and the like are erroneously recognized. The present invention was created in view of the problems of the conventional example, and the plurality of heating resistors are not arranged at right angles to the moving direction of the thermal paper, but their arrangement is devised so that they are adjacent to each other. It is an object of the present invention to provide a thermal head and a thermal printer that can minimize the variation in printing density due to the gap between dots and can accurately read barcode information.

[0022]

[Means for Solving the Problems] FIGS. 1 (a) and 1 (b) are
It is a principle view of a thermal head and a thermal printer according to the present invention.

As shown in FIG. 1A, the thermal head of the present invention has a plurality of heating element elements Rn, n = 1, 2, i, j.
In the thermal head including the above, the plurality of heat generating elements Rn are provided obliquely with respect to the sheet moving direction Y.

In the thermal head, a gap δ is provided between each of the plurality of heating element elements Ri and Rj, and each heating element element Rn has a sheet moving direction Y.
It is characterized in that they are continuously arranged at an angle [θ] with respect to.

In the thermal head, when the plurality of heat generating elements Rn are continuously arranged, two heat generating elements Ri and Rj adjacent to each other are arranged in the sheet moving direction Y.
Is provided with an overlapping portion OB.

Further, the thermal printer of the present invention, as shown in FIG. 1B, is a paper moving means 11 for moving and supplying the paper 15, and a print head 12 for printing on the paper 15.
The print head 12 comprises: a head drive control means 13 for controlling the drive of the print head 12; and a control means 14 for controlling the input / output of the paper moving means 11 and the head drive control means 13. The above-mentioned object is achieved by comprising the thermal head described in 1.

[0027]

[Operation] According to the thermal head of the present invention, FIG.
As shown in (a), a plurality of heating element Rn, n = 1,
2, i, j are provided obliquely with respect to the paper movement direction Y.

For example, a gap δ is provided between each of the plurality of heating element Ri, Rj, and each heating element R
n are continuously arranged at an angle [θ] with respect to the sheet moving direction Y (see FIG. 1A).

For this reason, the heat generation distributions of the heat generating elements Ri and Rj adjacent to each other in the head overlap each other, and the heat generation amount at the boundary between the heat generating elements Ri and Rj becomes larger than that in the conventional example.

Further, two heat generating elements Ri and Rj adjacent to each other are continuously arranged in the head in the paper moving direction Y by providing an overlapping portion OB in advance. For this reason, the heat distribution at the boundary between the heating elements Ri and Rj becomes larger than that in the conventional example. Therefore, in the bar code which is thermally printed by the head, the heating resistor Rn is spread over several dots. It is possible to reduce uneven printing density (unevenness of printing due to gaps between black-printed dots) in the black bar printing portion that has been continuously printed.

As a result, it becomes possible to perform bar code printing with higher reliability than in the conventional example. Further, according to the thermal printer of the present invention, as shown in FIG. 1B, a paper moving means 11, a print head 12, a head drive control means 13 and a control means 14 are provided.
2 comprises the thermal head of the present invention.

For example, when the paper 15 is moved and supplied by the paper moving means 11, the print head 12 comprising the thermal head of the present invention is driven and controlled by the head drive control means 13 via the control means 14. As a result, the paper 15 is thermally printed by the print head 12.

Therefore, even when the ambient temperature is low or the output of the head drive power source varies, the heat distribution at the boundary between the heating elements Ri and Rj of the print head 12 is higher than that in the conventional example. Since the number is increased, it is possible to perform reliable barcode printing in which print unevenness due to gaps between black printed dots is reduced as much as possible.

As a result, it becomes possible to accurately discriminate between the black bar and the white pattern in the bar code reader.

[0035]

Embodiments of the present invention will now be described with reference to the drawings. 2 to 5 are diagrams illustrating a thermal head and a thermal printer according to an embodiment of the present invention. 2 (a) and 2 (b) are configuration diagrams of a thermal head according to an embodiment of the present invention, FIG. 2 (a) is a plan view thereof, and FIG. 2 (b) is a sectional view thereof. ing.

For example, the thermal head 20 with n = 640 has 640 heating element elements R1 in FIG. 2 (a).
.About.R640 are provided obliquely to the paper movement direction Y.
That is, the heating element R1, R2 or R2, R3 ... Rn-
A gap δ is provided between the R1 and R640, and all the heat generating elements R1 to R640 are continuously arranged at an angle θ = 30 ° with respect to the sheet moving direction Y.

In the continuous arrangement state of the heating element elements R1 to R640, OB is an overlapping portion, and two heating element elements R1 and R2 adjacent to each other in the head 20 are provided.
And R2, R3 ... Rn-1, R640 are portions that overlap in the sheet moving direction Y.

Further, the thermal head 20 is shown in FIG.
In the cross-sectional view, the heat-resistant glass layer 20B, the resistor layer 20C, the conductor pattern 20D and the protective film 20E are laminated on the ceramic substrate 20A, for example.

The method of forming the thermal head 20 is as follows.
First, the heat-resistant glass layer 20B is formed on the ceramic substrate 20A, and then the resistor layer 20C such as tantalum nitride is formed on the heat-resistant glass layer 20B. The heat-resistant glass layer 20B
Is used to keep the resistor layer 20C provided on the ceramic substrate 20A in close contact.

Then, a conductor pattern 20D is formed on the entire surface of the ceramic substrate 20A on which the resistor layer 20C is formed. Then, the conductor pattern 20D is exposed to light using a resist as a mask and cured by UV (ultraviolet) light.

In the mask pattern at this time, 640 openings are provided obliquely to one side of the ceramic substrate 20A. That is, a gap δ is provided between the openings, and all the openings are continuously opened at an angle θ = 30 ° with respect to one side of the substrate 20A.

Further, the conductor pattern 20D is opened by wet etching, ion etching or the like to form a resistor layer.
A conductor pattern 20D where 20C is exposed is formed. afterwards,
A heat-resistant protective film 20 is formed on the entire surface of the patterned substrate 20A.
Form E.

As a result, 640 heating elements R1 to R
It is possible to manufacture the thermal head 20 in which 640 is provided obliquely to the paper movement direction Y. The principle of heat generation of the head 20 is that when a voltage having a predetermined energization period is applied to the heating element R1 via the conductor pattern 20D, the resistance layer 20C corresponding to the heating element number exposed in the opening causes Joule heat is generated.

In this way, according to the thermal head 20 according to the embodiment of the present invention, as shown in FIGS. 2A and 2B, the heat generating elements R1, R2 and R2, R3 ... Rn-1,
A gap δ is provided between each R640, and all the heating elements R1 to R640 form an angle θ = with respect to the sheet moving direction Y.
They are continuously arranged at an angle of 30 °, and an overlap portion OB is provided on them.

Therefore, the heat generation distributions of the heat generating elements R1, R2 and R2, R3 ... Rn-1, R640 which are adjacent to each other in the head 20 overlap each other, and each heat generating element R1, R2 or R2, R3 ... Rn. The heat generation amount at the boundary between -1, R640 is larger than that of the conventional example.

From the above, in the bar code which is thermally printed by the head 20, particularly the heating resistors R1 to R are used.
It is possible to reduce uneven printing density (unevenness of printing due to a gap between black-printed dots) in a black bar printing portion in which 640 dots are continuously printed over several dots.

As a result, it becomes possible to perform bar code printing with higher reliability than in the conventional example. FIG. 3 is a block diagram of a thermal printer according to an embodiment of the present invention, and FIG. 4 is an operation explanatory diagram thereof. In FIG. 3, a thermal printer that performs thermal printing on thermal paper, which is an example of paper 15, is
The thermal paper movement control circuit 21, the thermal head 22, the head drive control circuit 23, the MPU 24, the motor 25, the platen 26 and the leaf spring 27.

That is, the thermal paper movement control circuit 21 is an embodiment of the thermal paper moving means 11 and moves and supplies the thermal paper 15. For example, the output control of the motor 25 is performed based on the movement control data D2 from the MPU 24.

The thermal head 22 is an embodiment of the print head 12 and is used to perform thermal printing on the thermal paper 15.
The thermal head 22 comprises the thermal head 20 according to the embodiment of the present invention, which is pressed against the platen 26 by a pressing force F via a leaf spring 27.

The head drive control circuit 23 is an embodiment of the head drive control means 13 and controls the drive of the thermal head 22. For example, the head drive control circuit 2
3 is “ON” and “OF” of 640 heating resistors R1 to R640.
The "H" level energization period of the voltage applied to each base of the 640 transistors based on the print data D1 from the MPU 24, that is, 640 print driving transistors that individually control the energization of "F", that is, The printing drive time is controlled by the optimally calibrated energization period.

The MPU 24 is an embodiment of the control means 14, and controls the input / output of the thermal paper movement control circuit 21 and the head drive control circuit 23 based on the external input data DIN.

The platen 26 is the thermal head 22.
The heat-sensitive paper 15 is made to roll at a predetermined position in order to make the head 22 and a predetermined print-target area of the heat-sensitive paper 15 face each other. Further, the motor 25 is the platen 2
6 is driven.

Next, the operation of the thermal printer will be described. 4A to 4C are operation explanatory diagrams of the thermal printer according to the embodiment of the present invention.
(A) is the control flow chart, FIG. 4 (b), (c)
Shows respective supplementary explanatory views thereof.

For example, when printing a bar code 15A for displaying a price, a product code, etc. in the distribution process of fresh food, etc., first, in FIG. 4 (a), the thermal printer is initialized at step P1. At this time, the MPU 24 is initialized based on the external input data DIN.

Next, in step P2, an input preparation (READY) process for the print data D1 is performed. At this time, for example,
The thermal paper movement control circuit 21 is controlled based on the movement control data D2 from the MPU 24, whereby the motor 25
Is controlled to move and supply the thermal paper 15. In addition,
The platen 26 rolls the thermal paper 15 at a predetermined position of the thermal head 22 so that the head 22 and a predetermined print area of the thermal paper 15 are opposed to each other.

Further, in step P3, it is determined whether or not data has been input. At this time, if there is no data input (NO)
Wait for it in step P3. If there is data input (YES), the process proceeds to step P4.

Therefore, in step P4, the data input (B
USY) process, and the print data D1 is stored in step P5. At this time, the print data D1 is stored in the RAM or the like of the head drive control circuit 23 from the MPU 24.

Then, in step P6, it is determined whether or not there is a print command. At this time, if there is no print command (NO), the process returns to step P2 and the input preparation (READY) process of the print data D1 is performed. If there is a print command (YES), the process proceeds to step P7.

Therefore, in step P7, the thermal head 2
2 drive control. At this time, the head drive control circuit 2
The thermal head 22 is drive-controlled by 3. For example, the head drive control circuit 23 is controlled based on the print data D1 from the MPU 24, which optimally controls the "H" level energization period of the voltage applied to each base of the 640 transistors. Heating resistors R1 to
R640 "ON" and "OFF" are head drive control circuit 23
The energization is controlled individually by.

Then, in step P8, it is determined whether the printing is completed. At this time, if printing is not completed (N
In (O), the process returns to step P7 and the drive control of the thermal head is continued. Further, the printer control is ended by the end of printing (YES).

As a result, the bar code 15A as shown in FIG. 4B can be printed. Note that FIG. 4 (c)
As shown in the enlarged view of the bar code 15A, the drive control of the thermal head 22 may be performed so that the print position of the front row and the print position of the next row overlap the print area. ..

Next, the bar code reading characteristic according to the embodiment of the present invention will be described with supplementing the bar code. 5A to 5E are explanatory views of the bar code reading characteristic according to the embodiment of the present invention, FIG. 5A is an explanatory view of the bar code reader, and FIG. Configuration diagram for explaining the barcode reading principle, FIG.
(E) shows the respective characteristic diagrams.

In FIG. 5A, the bar code reader 2
Reference numeral 8 is for reading a bar code printed on a label having the surface of the thermal paper 15 processed to be water resistant, and deciphering its price, product display, etc., in the distribution process of, for example, fresh food.

In FIG. 5B, the principle of reading the bar code is that the laser beam emitted from the light emitting section 28A provided inside the bar code reader 28 is the white pattern of the bar code or the black bar printing section. The reflected light is detected by the light receiving portion 28B by being scanned. As a result, by performing signal processing on the reflected light, the price, product display, etc. can be decoded.

FIG. 5C shows the drive time characteristics of the thermal head. For example, 3 bits of the heating element R1 to R3 of the head 22 and 1 bit of the element R5 are energized. The drive time is shown. Here, P is the applied energy, which is proportional to the amount of heat generation.

As a result, in the bar code 15A that is thermally printed by the head 22, for example, the heating resistor R
In the black bar printing portion in which the three dots of 1 to R3 are continuously printed, the print density unevenness as in the conventional example is suppressed as much as possible. This is because the heating resistors R1 to R3 are provided obliquely with respect to the moving and supplying direction of the thermal paper 15, so that the heat generation amount at the boundary portion between the adjacent heating element elements R1, R2 and R2, R3 is the same as the conventional example. It depends on what is more.

FIG. 5D shows a light reception signal waveform of the bar code reader. For example, heat generated by 3 bits of the heating element R1 to R3 of the head 22 and 1 bit of the element R5. It is a signal waveform obtained by receiving the reflected light of the printed barcode.

Ambient temperature 0 [° C], 25 [° C]
When a bar code reader 15A is printed by means of a bar code reader and compared, a bar code reader such as the conventional example does not count even if it is a bar code (a broken line part) that is heat printed in a low temperature state. Will not occur.

Further, FIG. 5E shows a code read signal waveform whose waveform has been shaped. During the "H" (high) level period, the "L" (low) level is erroneously detected as in the conventional example. Never be done. The code read signal is obtained by shaping the reference voltage (threshold value), which is the comparison reference voltage set to 1/2 of the output waveform peak voltage value, with respect to the detection voltage of the bar code reader light receiving portion.

As a result, in the distribution process of fresh food and the like, the counting error due to the barcode reader as in the conventional example is suppressed as much as possible, and the price code and the like are not erroneously recognized.

As described above, the thermal printer according to the embodiment of the present invention is provided with the thermal paper movement control circuit 21, the thermal head 22, the head drive control circuit 23 and the MPU 24 as shown in FIG. The head 22 is a thermal head according to an embodiment of the present invention.

Therefore, when the thermal paper 15 is moved and supplied by the thermal paper movement control circuit 21, the thermal head 22 of the embodiment of the present invention is driven and controlled by the head drive control circuit 23 via the MPU 24. Thereby, the head 2
2, the thermal paper 15 is thermally printed.

From this fact, a gap δ is provided between the heating elements R1, R2 and R2, R3 ... Rn-1, R640 of the thermal head 22 and all the heating elements R are provided.
Since the heat distribution at the boundary portion of 1 to R640 is larger than that of the conventional example, it is possible to perform reliable barcode printing in which uneven printing due to the gap between the black printed dots is reduced as much as possible. ..

As a result, it becomes possible to accurately discriminate between the black bar and the white pattern in the bar code reader.

[0075]

As described above, according to the thermal head of the present invention, a gap is provided between each of the plurality of heating elements, and each heating element has an angle [θ] with respect to the sheet moving direction. Are arranged continuously.

Therefore, the heat generation distributions of the heat generating elements adjacent to each other in the head overlap each other, and the heat generation amount at the boundary portion of each heat generating element becomes larger than that in the conventional example. From this, in the bar code subjected to the thermal printing process by the head, it is possible to particularly reduce the print density unevenness in the black bar printing portion where the heating resistor is continuously printed over several dots.

Further, according to the thermal printer of the present invention, a paper moving means, a print head, a head drive control means and a control means are provided, and the print head comprises the thermal head of the present invention.

Therefore, even if the ambient temperature is low or the output of the head drive power source varies, the heat distribution at the boundary between the heating elements of the print head is improved as compared with the conventional example. As a result, it is possible to perform reliable barcode printing in which print unevenness due to gaps between black printed dots is reduced as much as possible. As a result, the bar code reader can more accurately discriminate the black bar and the white pattern as compared with the conventional example.

This greatly contributes to the provision of a thermal printer or the like which performs bar code printing with high printing quality and high reliability.

[Brief description of drawings]

FIG. 1 is a principle diagram of a thermal head and a thermal printer according to the present invention.

FIG. 2 is a configuration diagram of a thermal head according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a thermal printer according to an embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the thermal printer according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of bar code reading characteristics according to the embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a thermal head according to a conventional example.

FIG. 7 is a bar code reading characteristic diagram for explaining the problems in the conventional example.

[Explanation of symbols]

 11 ... Paper moving means, 12 ... Print head, 13 ... Head drive control means, 14 ... Control means, Rn ... Plural heat generating element (n = 1, 2, i, j ...), D1 ... Print data, D2 ... Movement control data, DIN ... External input data, δ ... Gap, OB ... Overlap portion, θ ... Angle, Y ... Paper movement direction.

Claims (4)

[Claims] 1. A plurality of heating elements (Rn, n = 1, 2,
A thermal head comprising i, j), wherein the plurality of heating element elements (Rn) are provided obliquely with respect to the sheet moving direction (Y). 2. The thermal head according to claim 1, wherein a gap (δ) is provided between each of the plurality of heating element (Ri, Rj), and each heating element (R).
n) are continuously arranged at an angle [θ] with respect to the sheet moving direction (Y). 3. The thermal head according to claim 1, wherein two heating element elements (Ri, Rj) adjacent to each other in a state where the plurality of heating element elements (Rn) are continuously arranged.
Has an overlapping portion (OB) in the sheet moving direction (Y). 4. A paper moving means (11) for moving and supplying a paper (15), a print head (12) for printing on the paper (15), and a head drive for controlling the drive of the print head (12). The print head (12) according to claim 1, further comprising a control means (13) and a control means (14) for controlling input / output of the paper moving means (11) and the head drive control means (13). A thermal printer comprising a thermal head.