JPS583837B2 - thermal printing head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermoelectric printing press, and in particular to a thermoelectric printhead for non-impact printing and a method for positioning and locking such a head relative to a movable carriage of the printing press. Regarding the mechanism for

Such heads are adapted to produce visible printing on an electrically insulated and heat-sensitive recording medium in response to incoming electrical impulses.

In order to take advantage of the speed of modern electronic information processing systems, it is essential to have efficient peripheral high-speed printing units and to ensure that such printing units do not emit noise. It is desirable to do so.

This is because, in installation locations such as offices, these printing units are usually placed near the user.

When using a printing device that performs printing by striking a type carrier elastically against an ink ribbon in contact with a recording medium, there is an inherent operating speed limit for the mechanical actuation system of the type carrier reservoir. Moreover, sometimes the noise becomes more than I can bear.

By using a non-impact printing device, such disadvantages such as noise and limited operating speed can be eliminated.

Non-impact printing devices using thermoelectric printing methods are known.

For example, US Pat. No. 3,596,055 discloses a thermoelectric printing unit with a print head having a matrix of printing elements (i.e., a dot matrix) for generating the characters to be printed.

This matrix usually consists of 35 elements, in particular 5 columns spaced equally apart from each other over the width of the character and each containing 7 elements, with 7 elements in each column. The elements are also equally spaced from each other over the height of the character to be printed.

These elements are heated by the resistors incorporated within these elements when the resistors are subjected to a potential difference.

Printing is done character by character, and a selection and control circuit is provided to electrically energize and heat only those elements (points) of the point matrix necessary to form the character to be printed. It is being

According to the above-mentioned US patent, the printing operation is carried out by a head fixed with respect to the recording medium, which printing operation comprises the step of pressing the head onto the heat-sensitive recording medium while heating the elements (spots) to be printed. Consists of.

This printing operation is thus similar to a heated (high temperature) printing operation, and the printing of each element (dot) on the recording medium is substantially the same size as the printing element (dot).

The movement of the head along the print line is therefore intermittent, with a number of pauses equal to the number of characters making up the print line.

Although these pauses are short, they are interleaved with extremely rapid movements from one printing position to the next, causing a substantial reduction in printing speed.

For example, another known thermoelectric point matrix printing method disclosed in U.S. Pat. A thermoelectric head is used that has a single column of elements.

The height of each printing element is equal to the height of the paint to be obtained on the recording medium, and the width of each printing element is less than the width of the paint to be printed.

Instead, the head can be moved continuously along the printing line, and the points to be printed are provided by the combined effect of heating of the printing elements and movement of the printing elements.

If we now consider a character shape of the kind obtained with a 7 x 5 element matrix as described above, this latter print head produces each character by means of five basic printing actions and controls and sensing circuitry energizes the necessary elements to print the desired character, with the necessary delays.

Compared to the method disclosed in the aforementioned U.S. Pat. It moves along the line without interruption, allowing for high-speed printing.

Furthermore, the arrangement for moving the head is fairly simple, as no step movements are required.

However, the method of US Pat. No. 3,777,116 has drawbacks with respect to individual printing elements and their mounting within a single head.

The printing element is made of graphite and is fabricated within a rectangular body connected to control and monitoring circuitry.

A printing surface is formed on the tapered portion.

The printing elements are mounted within a single head with the printing surface in contact with a ribbon of metallic material supported by the head.

The ribbon constitutes a common return line for the operating circuits of all printing elements.

The head is positioned such that the metal ribbon is in contact with the heat sensitive recording medium.

The contact resistance between the printing surface of each element and the metal ribbon, the particular dimensions of the printing elements and the materials used all contribute to significantly increasing the power required to operate the printing elements.

It is therefore an object of the present invention to provide a thermoelectric printhead having a single column of multiple printing points (elements) adapted to print continuously while sliding along the recording medium. and the size and shape of the printing dots are such that these printing elements allow high printing speeds and give good sharpness of the printing dots and therefore good sharpness of the printed characters;
At the same time, the power required to energize the print points is reduced.

To achieve the above object, the present invention provides a thick film resistor selectively energized to print corresponding dots and covering the opposite ends of two opposing electrodes and the gap between the electrodes. In a thermal printing head constructed of a flat insulating substrate carrying a plurality of heating elements having a convex outer surface and having a resistive region formed of a material, the opposing electrodes are connected to a substrate having a thickness of 7 to 10 μm. It is formed from a conductive thick film, the two electrodes are arranged in the same direction, and the width is at least 1
00μ, and the interelectrode gap is 50μ along the above direction.
The resistive material film has a maximum thickness of about 60 μm, its representative surface is partially cylindrical, its generatrix is oriented to intersect the direction, and the resistive film is oriented between the electrodes. A thermal printing head is provided, characterized in that the thermal printing head covers each end of the corresponding electrodes over a region longer than the length of the gap.

To explain using the drawings, one embodiment of the thermoelectric print head according to the present invention is shown in the second embodiment. 3. 4 and 5.

The head consists of a support 10 (FIG. 2) in the form of a rectangular plate, on the plane 11 of which are located adjacent to its sides 12 7
resistive elements 13 are arranged, and the resistive elements 13 are arranged on the side part 12.
, each resistive element having a base in contact with the plane 11.

Each base is substantially rectangular (FIG. 4) with its short sides 14 parallel to the sides 12.

The surface of the resistive element 13 facing the base in contact with the plane 11 assumes a partial cylindrical shape, its generatrix parallel to the short side 14 and its concave surface facing towards the base in contact with the plane 11. (Figure 5).

Seven feed conductors 15 (FIG. 2) deposited on plane 11 are each associated with a corresponding resistive element 13 and extend substantially parallel to each other; adjacent side 12 and away from side 16 until contacting resistive element 13 along the dimension of short side 14 (FIG. 4) and extending partially below the base.

Seven return conductors 17 deposited on the plane 11
extends perpendicularly to the side 12 and at one end:
It is in contact with the resistive element 13 along a contact line parallel to the short side 14 and, at the other end, with a common conductor 18 deposited on the plane 11.

A common conductor 18 extends parallel to side 12 and
6 (Figure 2).

The return conductor 17 is located partially below the base of the resistive element.

The technique for depositing these resistive elements and conductors on the plane 11 may be any one of the techniques known in the art.

A suitable example is thick film technology.

Second. 4. When using this technique to form the pattern shown in Figure 5, a conductive layer (conductor) 1
5.17, leaving a gap of several tens of microns between each feed conductor 15 and the corresponding return conductor 17, and according to the shape shown in FIG. A thick film of paste is first deposited.

In this way, seven rectangular areas 20 are formed on the plane 11 that are not covered with conductive material and are interposed between the feed conductor 15 and the corresponding return conductor 17; The zone 20 is aligned parallel to the side 12 of the plane 11 and has dimensions equal to the width of the feed and return conductors of the zone and equal to the width of the gap a (tens of microns).

Another thick layer of resistive paste, such as bismuth oxide, ruthenium oxide, precious metal, is then deposited within each zone 20 using thick film techniques, so that the required thickness and requirements are met. A resistor element 13 having a cross section is obtained.

By suitably controlling the deposition operation of these resistive thick film layers, it is possible to obtain curved external surfaces of the resistive element as described above.

The resistive layer is an extension of the resistive glue above the conductive layer 15, 17. The layers 15, 17, 18 form parts of the resistive element 13 that are completely short-circuited.

This portion of the electrically active resistive element 13 is located within the area 20 mentioned above and is delimited in FIG. 5 by hatched lines.

Within the ranges mentioned above, the dimensions of the area 20 and the conductive layer 1
The dimensions of 5, 17, and 18 can be changed arbitrarily.

In practice, a conductive layer thickness of 7 to 10 μm and a conductive layer width of 200 μm and a gap width of 50 μm in the vicinity of the area 20 result in the lowest electrical loss, good clarity of the printed characters. Good results were obtained, including faster print speeds and faster print speeds.

The distance between one resistive element and another resistive element is
It depends on the height of the characters to be printed and the need to maintain good electrical isolation between each resistive element 13 and the next resistive element.

When printing characters with a height of 2.54 mm, a satisfactory result can be obtained by setting the distance to 200 μ.

The function of the resistive element 13 is to generate heat in the area 20 when current is passed through it, thereby creating a "hot spot" having the dimensions of the area 20.

Therefore, the resistance of these resistive elements must be at least greater than the resistance of the corresponding conductor.

In practice, it has been found that an element resistance of 60-100 ohms is sufficient to heat the element to a temperature of 150-200 DEG C. by passing a current of 150-200 mA.

6 and 7 show a second embodiment of a resistive element for a thermoelectric printhead according to the invention.

FIG. 6 shows the plane 11 of the support plate 10 adjacent to the side 12.
It is an enlarged view of the area.

The shape of the conductor 15 in the remaining part of the plane 11 is the same as in the first embodiment.

On the other hand, in this area, the difference from the first embodiment is that
The conductors 15 have a first portion 30 which is reduced in width to have a larger relative distance than in the first embodiment, and the width of each conductor is increased compared to the width of the first portion. The connecting end portion 31 is increased in width compared to the width of the corresponding portion of the connecting end portion 31 .

In fact, the width of this part is approximately 300μ, while the corresponding distance between the conductors 15 is approximately 100μ in their end portions.

The end portion 31 of the conductor 15 faces a conductor 18 placed on the plane 11 , the conductor 18 being spaced apart from the end portion 31 by a gap b and extending parallel to the side 12 . It has reached 16.

A strip 35 consisting of several layers of thick film of resistant glue
It lies parallel to the side 12 over the end portion 31 and the conductor 18 and over the entire area associated with the conductor 15 .

The strip 35 has a surface which does not touch the plane 11, which surface has a partial cylindrical shape (i.e. an arcuate shape) with a concave surface facing towards the plane 11 (FIG. 7), the generatrix of which lies on the side 12. is parallel to

When a suitable value of potential difference is applied between one of the conductors 15 and the conductor 18, these conductors 15.
A current flows in a circuit consisting of 18 and the resistive area between these conductors, causing this energized conductor 15 to
and the common conductor 18, thereby heating the area comprised between the end portion 31 and the common conductor 18, whereby, as in the first embodiment, a substantially Limit the "hot points" of the rectangle.

The arrangement of conductor 15 is such as to prevent undue heating of the portion of the resistive strip adjacent to the thermally energized portion.

Compared to the first embodiment, such an arrangement of the conductors 15 avoids physical separation of the resistive elements 13 while ensuring the required thermal insulation between the parts of the strip included between each conductor 15. .

As mentioned above, the print head is designed to print characters using a matrix of points with the basic printing action(s), and during each printing action, a column of characters is Printing is performed on the recording medium in successive relative movements with respect to the medium head.

The heat-sensitive recording medium 25 (FIG. 3) may be made of treated paper, for example consisting of an ordinary paper sheet acting as a support, covered with a layer of heat-sensitive material; Heat-sensitive materials have the characteristic of changing color when the material is heated above a certain threshold characteristic of the material.

The initial and final colors (ie, the colors before and after the change) depend on the paper support and the heat-sensitive material coating it.

Generally, these colors should be very light at the beginning and very dark at the end to provide good contrast in printing.

Another recording medium may be the known thermally conductive ink ribbon interposed between the head and a regular paper sheet, onto which ink is transferred by selectively heating the ink ribbon.

For printing, the head is mounted, for example with a heat sensitive sensor of the type described above, in such a way that the column of resistive elements 13 or resistive strips 35 is in contact with the paper and perpendicular to the line to be printed (FIG. 3). The paper sheet 25 is placed on a sheet of paper 25.

Thus, the total length of the column of seven resistive elements 13 or strips 35 determines the height of the characters to be printed.

By using a support 10 in the form of a rectangular plate as shown in FIGS.
The 11,000-sided surface of the paper is at an angle of several degrees α (0.5°
~2.5°).

This slanted position is caused by the fact that the thickness of the resistive layer separating 1,000 planes 11 from the paper sheet 25 is very thin (usually 60μ), which is effective in preventing the head from getting caught on the paper.

However, the tilting of the head relative to the heat-sensitive paper sheet is not essential.

The reason is that such a slope depends on the type of support used as conductive and resistive elements.

8th. 9. Figure 10 shows two embodiments of a thermoelectric printhead in which the support is such as to prevent the possibility of the head getting stuck in the recording medium, and in which the printhead is It can slide over the recording medium and print in two directions on the recording medium without tilting the support with respect to the medium.

In FIGS. 8 and 9, the support 10 has a short side and an oblique side.
It has an isosceles trapezoidal cross section that intersects at an obtuse angle β of 80° or less (Fig. 9).

The end portions of the resistive element 13 or resistive strip 35 and the conductors 15, 18 correspond to the short sides and are connected to the resistive element 13.
surface 37. having a width slightly greater than the width of . Above, fifth,
6, while the conductor 15.18B extends on a surface 39.40 corresponding to the hypotenuse of the cross-sectional shape of the support.

The head is positioned with respect to the recording medium 25 in the relationship shown in FIG. 9 (ie, with surface 37 parallel to the recording medium).

In FIG. 10, the support 10 has a partially cylindrical surface 28 with a generatrix perpendicular to the plane of the page of FIG.

In this case, a resistive element is placed on top of the surface 28 along the busbar.

Conductors 15,18 are suitably spaced on surface 28.

The head is arranged in a relationship with respect to the recording medium as shown in FIG. ) is located.

Whatever type of support is used, the resistive element 13 or resistive strip 35 and the recording medium (heat-sensitive paper sheet) 2
Contact occurs between 5 and 5.

This is because the curved surface of the element 13 follows a tangential line (theoretically only one line) perpendicular to the direction of movement of the head along the paper sheet following perpendicular to the print line.

In practice, this tangential line has a finite width of more than 50 μ, ie less than the width of the area 20 (gap a) of the resistive element 13 or less than the gap b of the strip 35.

Feed conductor 15 and common return conductor 18
is connected to a selection and control circuit which, during the movement of the head relative to the paper sheet, electrically and therefore thermally controls the resistive elements in the column of resistive elements 13 necessary for the formation of the characters to be printed. It is becoming more and more popular.

This circuit is similar to the known type disclosed in the above-mentioned US Pat. No. 3,777,116 and will not be described in detail herein.

Using "hot spots" of the type described above, the sliding speed of the head across the paper sheet can be significantly increased without resorting to very short firing times that are difficult to control.

The width of the printing "hot spot" and the resulting printed spot (usually this printed spot is square and its width is equal to the width of the printing "hot spot")
In fact, if we determine the width of
An increase in the sliding speed of the head across the paper sheet will correspondingly reduce the thermal energization time of the "hot spots" during the sliding movement of the head to obtain printed spots of the desired size. it is obvious.

However, the time required to change the temperature of a resistive element below a certain value corresponding to the thermal inertia of each resistive element 13 (i.e., from a value above the threshold to a value below the threshold or from a value below the threshold to a value above the threshold) ) is impossible to limit the activation time.

Thermal inertia is generally a function of the dimensions of the body to be heated, and therefore the fact that the resistive element 13 has been configured with the characteristics described above (i.e. so that the dimensions of the heated part are minimized) and The fact that the resistive element is in tangential contact with the recording medium has the advantage of reducing thermal inertia and of good sharpness and coloration of the printed dots even at high sliding speeds. This provides the advantage that relatively long energization times can be used, resulting in higher energization times.

In terms of resistance and current values, the power required to energize the resistive element can be reduced to very small values (such as 2 to 4 watts), small enough to allow power supply from a battery. .

Figures 11.12.13 show another embodiment of a thermoelectric printhead according to the invention.

In this example. In this case, the same precision of the placement of the conductor and resistive layer is maintained, and the different geometries of the electrodes and conductors give approximately twice as good a definition as obtained in the previous embodiment.

In particular, for letters of the same height, there are columns of 13 "hot spots" or printing spots that can be individually energized.

However, this kind of arrangement has 1 instead of 7 hot points.
It is clear that a selection and control circuit designed to selectively energize the three points is required.

See Figure 12. A first set of seven conductors 61 to 67 and a second set of seven conductors are formed by thick film technology on a support 10 of the type shown in FIG.
Conductors 68 to 74 are placed, respectively, and these conductors are arranged at equal intervals on the two hypotenuses 39.40, and have enlarged end portions 61a to 63a, etc. on the surface (short side) 37. 68a to 70a, etc., and the end portions of each set are opposite to each other.
As shown in Figure 2, they are arranged alternately.

Each conductor of the first set and a corresponding (opposed) conductor of the second set
The distance c between the conductor and the conductor is approximately 50μ.

The width d of the end portion is the same for each set and is about 350μ.

The distance e between two consecutive end parts of the same set is 30-50
μ.

The width f of the conductor near the end portion is approximately 100μ.

On the opposite end portions 61a-63a, etc. and 68a-70a, etc., a strip 75 consisting of several layers of resistive glue in the form of a thick film is placed by thick film technology, which strip extends perpendicular to the direction of the conductor over the entire area in question.

This strip has a cylindrical curved surface that is not in contact with surface 37, the concave side of this curved surface facing toward surface 37 (FIG. 13).

As shown, each set of conductors is connected to a switch 6lb~
It is electrically connected via 67b and 68b-74b to opposite poles of a generator 76 with an appropriate value of potential.

For example, if switches 61b and 69b are closed at the same time,
Area 81 of resistive strip 75 included between conductors 61, 69 and facing portions of end portions 61a and 69a
A current flows in the circuit configured by.

This current heats the resistive glue located in area 81, thereby defining a "hot spot" measuring approximately 50μ x 150μ.

The placement of the conductors and the selection of the conductor dimensions are such that portions of the resistive strip adjacent to the selected resistive strip are prevented from heating.

Because there are 13 zones where the end portions of the first set of conductors are opposite the end portions of the second set of conductors, a plurality of hot points (areas) 80-8 are present in the resistive strip 75.
4, etc., and these hot spots can be selectively energized individually and, if desired, physically isolated by lateral grooves 96 in the strip 75. sell.

By using the dimensions shown, the placement technique of this embodiment requires less precision than in the two previously described embodiments.

It is also unnecessary to consider the positioning of the head with respect to the recording medium and the printing method as described above.

The two sets of conductors are of a general type designed to energize points 80-84, etc. of the resistive strip necessary to print the desired character during each basic printing operation, with the necessary delays. must be connected to a control and selection circuit of a type known in the art.

FIG. 1 is a partially exploded perspective view of a printing press for in-line printing using a thermoelectric head according to the present invention and equipped with a carriage 47 for moving the head along a printing line.

The head is fixed, for example by adhesive, to the surface 43 of a support block 44, which is arranged at the desired angle of inclination α and in such a manner that the resistive elements 13 are perpendicular to the printing line (described in detail later). and engages a positioning and locking device 46 secured to the carriage 47 for the purpose of positioning the support block 44 and thus the head secured to the block such that the head is in contact with the heat-sensitive paper sheet 25. It is now possible to do so.

Still, eight electrically conductive elastic foils 48 fixed to the carriage 47 are connected via cables 49 to a selection and control circuit (not shown), these foils are connected to the support block 4.
4 is positioned on the carriage 47, it contacts the end portions of the seven conductors 15 and the conductor 18 closest to the side 16 of the support plate 10, thereby establishing an electrical connection between the conductors and the selection and control circuit described above. Guarantee.

The carriage 47 is slidably mounted on guides 50 extending laterally to the heat-sensitive paper sheet 25 and fixed to the body 42 at both ends.

The carriage is still able to pivot around this guide 50, and for this purpose cooperates with a vertically movable rod 51 which is fixed to the body 42.

Means for continuously moving the carriage along the guide are known and are not shown.

A heat-sensitive paper sheet is fed off a reel 52 and pulled stepwise by rollers 53, 54, moving the paper sheet to a new printing line for each printing step.

The paper sheet 25 is in contact with a flat plate 55 fixed to the main body 42 along the printing line.

During the movement of the carriage from left to right in FIG. 1, rod 51 is in the position shown so that the head contacts heat-sensitive paper sheet 25 along the printing line and the printing operation Characters 56 are formed on the sheet.

When the carriage completes its movement stroke to the right (FIG. 1), the rod 51 moves vertically downward, causing the carriage to pivot clockwise and move the head away from the heat-sensitive paper sheet, causing the head to move away from the paper sheet. Return the carriage to the left without touching it.

During the movement of the carriage to the left, the paper sheet 25 is pulled by rollers 53, 54 and moved to a new printing line.

The use of 7 or 13 resistive elements or printing dots 13 aligned and arranged perpendicularly to the printing line along the height of the character is dependent on the arrangement of the resistive elements with respect to the recording medium and the number of resistive elements used. is not limited.

For example, the column of resistive elements 13 may have the same length as a printed line on the recording medium and may include a number of resistive elements equal to a multiple n (for example, 5 times) of the number of characters that can be printed on the printed line. .

The head is in this case positioned such that the column of resistive elements is parallel to the printing line and perpendicular to the direction of movement of the paper sheet.

In this case, printing is done in a "parallel" manner,
For each basic printing operation, if we consider characters to be printed in a matrix of m columns and n columns, one column out of m columns of all characters in one printing line is printed. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a partially exploded perspective view of a printing press having a thermoelectric printhead embodying the invention and apparatus for positioning and locking the head; FIG. FIG. 2 is a front view of a first embodiment of a thermoelectric print head according to the present invention. FIG. 3 is a plan view of the head of FIG. 2. FIG. 4 is an enlarged detailed view of FIG. 2. Figure 5 shows the ■ of Figure 4.
A sectional view taken along the line 1. FIG. 6 is an enlarged detailed front view of a second embodiment of a thermoelectric print head according to the present invention. FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6. FIG. 8 is a front view of a third embodiment of the head according to the present invention. FIG. 9 is a plan view of the head of FIG. 8. FIG. 10 is a plan view of a fourth embodiment of the head according to the present invention. FIG. 11 is a front view of a fifth embodiment of a thermoelectric print head according to the present invention. FIG. 12 is an enlarged detailed view of FIG. 11. FIG. 13 is a sectional view taken along line 1-2 in FIG. 12. 10: Support (plate), 13: Resistive element, 15: Feed conductor, 18: Common conductor, 20: Area of resistive material, 35: Resistive strip, 25: Recording medium,
61-67. 68-74: Conductor, 75: Resistive strip, 81: Area of the strip, 44: Support block, 46: Positioning and locking device, 47: Carriage, 48: Elastic foil, 56: Letters.

Claims (1)

Claims: 1. A resistor formed by a thick film of resistive material selectively energized to print corresponding dots and covering the opposing ends of two opposing electrodes and the gap between the electrodes. In a thermal printing head having a flat insulating substrate structure carrying a plurality of heat generating elements having a convex outer surface and forming a conductive region, the opposing electrodes are formed of a conductive thick film with a thickness of 7 to 10 μm. The electrodes are arranged in the same direction, the width thereof is at least 100μ, the gap between the electrodes is about 50μ along the above direction, the maximum thickness of the film of the resistive material is about 60μ, and the outer surface thereof is Partially cylindrical,
Thermal printing characterized in that the generatrix is oriented to intersect with the direction, and the resistive film covers each end of the corresponding electrodes over an area longer than the length of the inter-electrode gap. head. 2. In the thermal printing head according to claim 1, each of the electrodes has a trapezoidal end region, the electrode width near the end region is approximately 100 μm, and the width of the end region is approximately 2 μm.
00μ to 350μ, and the resistive regions are aligned along a direction intersecting the direction, each having a substantially rectangular shape. 3. The thermal printing head according to claim 1, wherein the conductive material is selected from the group of materials including gold, silver, palladium and gold palladium, and the resistive material is selected from the group of materials including gold, silver, palladium and gold palladium, and the resistive material is selected from the group of materials including gold, silver, palladium and gold palladium. A thermal printing head characterized in that the material is selected from a group of materials including precious metals and has a resistance value of 60 to 100 ohms. 4. The thermal printing head according to claim 1, wherein the conductive material is selected from the group of materials including gold, silver, palladium and gold-palladium, and the resistive material is selected from the group of materials including gold, silver, palladium and gold palladium, and the resistive material is selected from the group of materials including bismuth oxide, ruthenium oxide and noble metal oxide. the substrate is rectangular in shape, the heating element is aligned near the edge of the substrate, and the printed area is a single strip of resistive material. What is claimed is: 1. A thermal printing head comprising each part of the head, and having a pattern of a conductive material layer as a common control electrode.