JPH0144516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal ink transfer element for a thermoelectric printing machine, which ink mixture can be transferred onto a display medium (recording medium) when the element is heated under pressure. The mixture contains a pigment or dye and a binder made of a thermally transferable resin.

Ribbons for thermal printing machines of the above-mentioned type are known; in such known ribbons, the pigment on the surface of the ribbon has no viscosity at room temperature and has a viscosity of 80 to 100
It is mixed with a resin that can be melted at a temperature of ℃. Such mixtures form relatively thick layers on the support film and are less viscous and therefore more susceptible to cracking.

The technical problem to be solved by the present invention is that the layer thickness of the mixture is small relative to the thickness of the basic support, the mixture has great adhesive and plastic properties, is flexible, and has a relatively low temperature. It is an object of the present invention to provide a thermal ink transfer element that can be transferred onto a recording medium in a manner similar to that described above.

This technical problem is solved by the thermal ink transfer element according to the invention. The present invention is a thermal ink transfer element for a thermoelectric printing machine, having a basic support made of plastic material, wherein one side of the basic support is heated when the thermal ink transfer element is heated under pressure. The thickness of the ink mixture that can be transferred to the display medium is 2~
coated with a 4 micron thin layer, said ink mixture containing a pigment or dye and a binder consisting of a heat transferable resin and a high melting plasticizer to increase its plasticizing and adhesion capabilities. wherein the plasticizer comprises a thermoplastic resin, the binder comprises a terpene resin, and the plasticizer comprises vinyl chloride having a 1:1 ratio to the binder. a thermal ink transfer element made of vinyl isobutyl ether copolymer, characterized in that the base support has a thickness of 7 to 12 microns and the ink mixture is meltable at a temperature of 60 to 80 °C; This is what we provide.

Referring to Figures 1 to 5, for example, the patent application
A thermal printing head of the type shown in Japanese Patent Publication No. 122332 (Japanese Unexamined Patent Publication No. 48-45137) is shown at 10.

The printing head 10 includes a support 11 made of insulating material, for example in the form of a prism and having an isosceles trapezoidal cross-section, the angle .beta. between the short side and the hypotenuse of the isosceles trapezoid being slightly less than 180 DEG. On the flat surface 12 corresponding to the short sides of the isosceles trapezoid, N thermal elements 13 are arranged parallel to the corners of the support 11 and arranged. Although seven elements are illustrated in the figure, it should be noted that the number is not limited to this number.

Each thermal element 13 has a supply lead 15 and a return lead 1
8 and the lead 18 is common to all thermal elements. Leads 15, 18 start from surface 12 and extend to surfaces 16, 17 corresponding to the hypotenuses;
It reaches the base 19 of the prismatic support 11.

The technique for placing these leads and thermal elements on the support may be thick film techniques well known in the art. In this example, a gap of several tens of microns (for example, 50 microns) is left between the end 15a of the lead 15 and the end 17 of the lead 18, which has a width equal to 150 to 200 microns. The conductive layers 15, 18 are first arranged as in the shape shown. Subsequently, several layers of resistive material are applied to each area 2 existing between the end 15a of the lead 15 and the return lead 18.
In this arrangement,
The surface of the resistive material that is not in contact with the support is
Make it curved as shown. This resistive material on leads 15, 18 is completely shorted from the underlying conductive material (leads 15, 18).

The only area that is not short-circuited is area 2, which has one base of a rectangular shape (dimensions a x b = 50 x 200 microns) and an outer curved surface in contact with the support.
0 (shown within the dotted line in FIG. 5). These areas constitute the thermal elements 13 of the printhead, each thermal element being heated by applying a suitable potential difference between the corresponding supply lead 15 and return lead 18.

FIG. 1 shows a printing unit using a printing head 10 of the type described above. The printing head 10 is fixed to a printing head support 30, which has positioning and guiding elements 33, these elements 33
can cooperate with a corresponding positioning and guiding element 34 located on the carriage 36 for moving the print head along the print line of the display medium 60.

For this purpose, the carriage is mounted on rods 39, 4 connected to the end plates 41, 42 of the frame of the printing press.
It is pivoted to 0. A guide rod 40 extends through corresponding holes 46, 45 in the right and left end plates and operates in conjunction with an arm 50 of a lever 51 pivotally mounted on the guide rod 39. The lever 51 is the second
It has an arm 53.

A spring 99 is tensioned between arm 53 and the frame of the printing press.

Lever 51 can assume two distinct positions, one of which is the position shown in FIG.
In the other position, the lever 51 is rotated clockwise relative to the position shown in FIG. In a similar manner, guide rod 40 is inserted into holes 45, 4.
6 or towards the bottom of the holes 45, 46 to rotate the carriage. The carriage is pivotally connected to guide rod 39, and when the guide rod is moved toward the bottom of holes 45, 46, the carriage is caused to rotate in a clockwise direction relative to the position of FIG.

A display medium 60, preferably consisting of plain paper, is typically fed from a spool 61 rotatably mounted on the end plates 41, 42 of the printing press frame. The paper 60 is moved by a drive roller 65 rotatably mounted to the end plates 41, 42 and by a lever 69, which is pivotally mounted to the end plates 41, 42 and connected thereto by springs 71, 72. It is fed out by pressure rollers 67, 68 rotatably mounted on 70. Springs 71 and 72 apply force to rollers 67 and 68 causing them to cooperate with drive roller 65.

Drive roller 65 is controlled by a step motor (not shown) of known type for controlling the vertical spacing of the display medium (print paper). A display medium 60 is maintained along the print line in contact with a platen 80, which includes a rigid support 100 mounted to the frame of the printing press;
The support is covered with a thin layer 101 of an elastoplastic, non-resistive material, such as a layer of hard rubber, and is further coated with a plastic material, such as polyvinyl chloride.

A ribbon 85 comprising a support carrying a layer of thermally transferable material on the display medium side is inserted between the carriage assembly containing the print head 10 and the display medium 60 along the platen. The ribbon is moved by a take-up reel 86 and a supply reel 85, which are mounted on the frame of the printing press and are controlled by a motor to keep the ribbon taut and properly fed.

The two illustrated ribbon guides 87 and 88 are attached to the end plate 4.
1 and 42, and is formed integrally with the end plate. By inserting the print head support 30 into the carriage assembly 36, the print head is positioned such that the thermal elements 13 are perpendicular to the print line and the ribbon 8 is aligned.
It is positioned so that it contacts 3. The eight electrical contacts present on the carriage consist of flexible thin plate leads 90 connected by flexible cables 91 to a known type of thermal element selection and electrical control circuitry (not shown). . This arrangement includes the circuit itself and the leads 15,1 of the thermal elements 13 of the print head 10.
8.

During printing, the carriage uses a motor of known type (not shown in Figure 1) to
It is moved from left to right in Figure 1 at a constant speed. During this period of movement, print head 10 is maintained in contact with ribbon 83 because lever 51 is in the position shown in FIG. 1, and lever 51 and guide rod 40 are used to provide the necessary force to print head 10.
Also, during and in synchronization with this movement, the control and selection circuitry energizes the thermal elements 13 to the extent necessary to print all points of the characters on the printing line.

Therefore, in the parts of the ribbon 83 that are simultaneously pressed by these printing points and heated by the thermal elements 13, the thermally transferable material of the ribbon is transferred onto the display medium, thus printing the characters 110. . This process will be detailed later.

At the end of the movement from left to right (Fig. 1),
That is, after printing is completed for one print line on the display medium 60, the lever 51 is rotated clockwise against the action of the spring 99, causing the guide rod 40 to engage with the bottoms of the holes 45, 46. and causes clockwise rotation of the carriage 36 about the guide rod 39, thereby drawing the print head away from the display medium. The carriage is then moved from right to left under the control of a motor of known type to
Return to the position shown in the figure. Meanwhile, a drive roller 65 controlled by a step motor moves the display medium one line (one line).
line) only. Ribbon 83 has been fed from supply reel 85 to take-up reel 86 by a length equal to the length of the print line. In this way, the printing press is ready for printing characters on the next printing line.

The construction and material of the ribbon, the shape and placement of the thermal elements, and the type of platen condition the transfer of thermally transferable material to the display medium and, therefore, the quality of the print.

The ribbon 83 coated with a layer of thermally transferable material used in a printing press must have very specific properties not possessed by ribbons of the type known in the art.

Firstly, the support carrying the layer of thermally transferable material must have very good thermal conductivity properties, which can be thermally transferred by selective activation of the thermal elements 13. The thermal image produced on the transferable layer must be uniform so that it is not distorted. Therefore, the ribbon support should be as thin as possible while providing the necessary properties of mechanical strength and resistance to distortion, which are essential for feeding and handling the ribbon, and operating the printing press at high speeds. Transfer of the thermal image must be acceptable with minimal blurring and smearing even when the image is exposed.

The need for low thermal inertia is such that when head 10 is moving along the printing line during printing operations,
It is very important, therefore, that the time required for each printing operation is kept strictly constant and depends on the speed of the print head. Therefore, in order to obtain good printing speeds, the heat provided by the energized thermal elements must be such that it softens the thermally transferable material in a short period of time.

From this point of view, theoretical considerations and experiments revealed that when using the same material, the support, which is a ribbon, behaves in the same manner as an RC transmission line, and the equivalent time constant of this RC transmission line is the same as that of the support. It has been found that the printing speed is therefore completely conditioned by this thickness.

The ribbon support may also be heated at a temperature above the temperature at which the coating of thermally transferable material begins to soften when the surface in contact with the printing head is subjected to a temperature above the temperature at which the coating of thermally transferable material begins to soften. It must be able to withstand high temperatures such as

The coating of ink material must soften above a certain threshold temperature value. This threshold temperature value must be very clear. The reason is that this threshold temperature helps in the selection of transfer and in such situations the coating of ink material adheres to the display medium with a force equal to or greater than that of the substrate but with as little contact pressure as possible. This is because it has to be attached.

Below the threshold temperature, the layer of material must not be even partially transferred, regardless of the applied pressure, so that the smearing and smearing phenomena described above do not occur.

Furthermore, the adhesion of the coating that has been softened and then transferred onto the display medium is such that the ribbon support is such that upon separation of the ribbon and the display medium, a complete transfer of material from the ribbon to the display medium occurs. It must be greater than the adhesive force to the body.

With this in mind, the ribbon and display medium must remain completely stationary until the layers of material have been completely transferred.

A description will now be given of a ribbon according to the invention carrying a layer of thermally transferable material which satisfies all the above requirements.

Experiments using various plastic materials as ribbon supports have yielded satisfactory results at thicknesses of 7 to 12 microns. Very good results were obtained with ``Mylar'' and ``Hostaphan'' (respectively from DuPont).
Ribbon lined with polyethylene glycol terephthalate (registered trade name for polyethylene glycol terephthalate film produced by Pont) and Hofchsty or polyethylene with a special thickness of 7 to 12 microns. Obtained by using a support.

Specifically, for polyethylene backings, above these values for layer thicknesses, which are included in the thicknesses used in conventional single-use ribbons, polyethylene backings It has been demonstrated that the thermal inertia is too large to transfer heat with sufficient strength and rate to the thermally transferable coating, while for values that are too small, the polyethylene backing It has been found that the ribbon becomes distorted under the action of heating by the element, thereby interfering with the regular feeding and handling of the ribbon.

Experiments with other plastic materials such as polyvinyl chloride, cellulose ester polyurethane, polycarbonate, and polypropylene have not yielded satisfactory results.

As far as thermally transferable coatings are concerned, it has been found that most of the required properties depend not only on the composition of this coating, but also on the thickness of the layers of the coating. especially,
With a thickness of 2 to 4 microns and with the composition detailed below, the ribbons of the present invention did not require the use of a primer to improve the adhesion properties of the coating. On the other hand, for conventionally known ribbons, such an undercoat is indispensable. On the other hand, it can be seen that the adhesive properties thus obtained have the required properties. That is, when subjected to heat in conjunction with pressure, the adhesion to the backing decreases and this adhesion remains strong even when the display medium is made of non-cellulosic materials such as polyethylene, wax paper, etc. The adhesion force is weaker than that of the coating, thus allowing any clear transfer of the heated part of the coating.

Furthermore, the thickness range described above may be utilized to prevent migration of portions of the coating adjacent to the heated portion.

The material of the thermally transferable coating (layer) consists of three basic components: pigments and/or dyes, binders and plasticizers.

The role of the pigments and/or dyes is to color the coating in the required color. This can be any pigment and/or dye commonly used in inks.

The role of the binder is to bind particles of the various components, especially pigments, together. This binder plays an important role in the thermal reaction of the coating and in the transfer of the coating to the display medium. The binder consists of a reversible thermoplastic resin that is stable over time and whose primary function is to determine the softening point of the coating. The plasticizer ensures adhesion to the backing and ensures that the coating remains intact during ribbon handling (i.e., during ribbon feeding, unwinding, and changing).
Avoid creating cracks.

A preferred binder is one comprised of a terpene resin.

The best terpene resin is Picolyte, manufactured and sold by Pennsylvania Industrial Company.

A preferred plasticizer is one consisting of vinyl chloride/vinyl isobutyl ether copolymer, manufactured by BASF
Vinoflex manufactured and sold by
The product with the product name MP400 is most suitable.

It has been found that the best results are obtained when the weight ratio of pigment to binder is between 1:4 and 1:8.

An example of a method for manufacturing a thermal ink transfer element of the present invention is shown.

Example 100 grams of Vinoflex as plasticizer
MP400, 50 grams of Picolite S as binder
-70 and 50 grams of Picolite S-55, 25 grams of Raven Carbon Black 1200 (manufactured and sold by Columbia Carbon Company) as pigments, 750 c.c. of toluene, 150 grams of
cc of methyl isobutyl ketone and 100 c.c. of methyl ethyl ketone in a steel jar, the mixture was stirred well for 48 hours, then filtered and then deposited on an 8 micron thick film of Hostphan. coated with. It is clear that the weight ratio of plasticizer (100 grams) to binder (50 grams + 50 grams) is 1.

After drying, the ink mixture on the finished ribbon is approx.
It has a softening point of 80°C and produces sharp black dots after heat transfer.

The heat-sensitive ribbon thus produced can only be used once and is first inspected visually by exposing it to light and as a copying negative or using another known system. It can be used to create documents of thermally transferred text that can be copied.

For specific uses, ribbons can also be made with two colored coatings.

When a ribbon of the type described above was used in a conventional typewriter with a typing pressure of 10 kg for the characters, no symbols remained on the printed paper.

Conversely, ribbon 83 was used in the above-mentioned printing machine with the operating temperature of the heating element being 120-180°C, the corresponding softening temperature of the coating being 65-70°C, and the acting force of spring 99 being 250-1200g, with satisfactory results. Excellent results were obtained, with clear and complete text transfer without smearing at maximum print speeds of 40 characters per second.

As already mentioned, the shape of the heating element primarily determines the quality of the transfer of the coating onto ordinary paper.

In fact, the surface of the coating of material facing the display medium is usually quite smooth, primarily due to the material of which it is constructed and also due to the coating operation.

Conversely, a display medium made of ordinary paper has an irregular, rough surface. Therefore, when the coating is being thermally transferred onto ordinary paper, it is necessary to create close contact between the surface of the coating and the paper to eliminate this roughness. .

This is accomplished by applying appropriate pressure to the rear of the ribbon; the shape and dimensions of the surface applying this pressure are also important. If this surface is flat and fairly wide, for example, it has the same number of heating elements as points in the matrix format and is stationary with respect to the ribbon and paper during each printing operation (if the matrix format has 5 points) It consists of seven columns, each with a character width of 2 mm and a height of
In the case of printing head thermal elements (considering 2.5 mm), these elements are typically square with sides of 0.3 mm or 300 microns. In this case, even when applying considerable pressure, it is extremely difficult to obtain intimate contact between the thermally transferable coating and the paper over all surfaces under pressure. It is. Such contact is ensured only on rough surface protrusions, and the coating is transferred only on such protrusions, as a result of which the sharpness and contrast of the printed dots and printed characters is impaired.

FIG. 6 is an enlarged view of the field of thermal elements 13 of print head 10, which includes a thermally transferable ink layer 111 in contact with a surface 113 of display medium 60 having a rough surface 112. In contact with the support 110 of the ribbon 83 according to the present invention,
Positioned during printing operation.

Display medium 60 is elastoplastic layer 10 of platen 80
1, a layer 115 of plastic material, such as polyvinyl chloride, and a layer 11 of hard rubber inside.
6 and in contact with the layer 101 consisting of 6 and 6.

Due to the pressure exerted on the printing head 10 by the spring 99, the thermal element 13 constituting the field indents the ribbon 83 and the display medium 60 in the contact area d and with the aid of the elastic-plastic properties of the platen 80. a thermally transferable coating 1 in the contact area;
11 and display medium 60 are pressed together to flatten the rough surface 112 in the contact area.

If the thermal element 13 is heated to a temperature such that the corresponding coating 111 melts in this contact area, the coating 111 will adhere to the surface 113;
Thus, ribbon 83 and display medium 60 will contact at these points.

Movement of the print head 10 moves these depressions to the next pressure point on the print head, thus creating a rough surface 1.
12 and ensure good contact over the entire width of the printed dot.

When the coating 111 is transferred, the separation of the ribbon 83 and the display medium 60 at the end of printing in the printing line leaves intact the portion of the coating that was previously softened and adhered to the display medium 60. to produce the necessary printing.

For good quality printing, the pressure on each heating element 13 is purely elastically proportional to the local penetration of each heating element 10.
It is necessary to prevent 1 from causing local reactions. Additionally, the flexibility of layer 101 ensures that the penetration of each thermal element is not conditional on the penetration of neighboring thermal elements in the same column, and the reaction remains substantially constant even for different penetrations. It is necessary to do so.

From this point of view, a layer 115 of plastic material, such as polyvinyl chloride, with a layer 116 of hard rubber on the inside, is useful because this layer 115 has considerable elastic hysteresis properties and therefore no rebound is added to the printing head. It gave satisfactory results only if the pressure time was longer than the given pressure time.

The above shows how a printing head of the above-mentioned type and a thermally transferable ribbon having the above-mentioned properties can be combined to move along the printing line during the printing operation without the disadvantage of contamination. We hope that you now understand that it is possible to provide a thermoelectric printing machine that uses a printing head to print on a display medium, preferably ordinary paper that is not heat sensitive.

[Brief explanation of drawings]

FIG. 1 is an enlarged perspective view of a thermoelectric printing machine that can utilize a thermal ink transfer element according to the present invention. Figure 2 shows
FIG. 2 is an enlarged front view of the printing head of the thermoelectric printing machine shown in FIG. 1; FIG. 3 is a side view of FIG. 2. Figure 4 shows
Enlarged detailed view of FIG. 2. Figure 5 shows - of Figure 4.
A cross-sectional view along the line. FIG. 6 is an enlarged partial view of the print head of FIG. 2, also illustrating the thermally transferable ink elements and display medium of the present invention. 10: Printing head, 13: Thermal element, 36: Carriage, 60: Display medium (recording medium), 80: Platen, 83: Ribbon, 111: Ink layer (coating).

Claims (1)

[Claims] 1 A thermal ink transfer element for a thermoelectric printing machine, having a basic support made of plastic material,
One side of the base support is coated with a thin 2-4 micron thick layer of an ink mixture transferable to the display medium when the thermal ink transfer element is heated under pressure, the ink mixture containing pigments or dyes. and a binder consisting of a heat transferable resin, and a high melting plasticizer for increasing its plasticizing and adhesion abilities, the plasticizer consisting of a thermoplastic resin. In the ink transfer element, the binder comprises a terpene resin and the plasticizer comprises:
consisting of vinyl chloride-vinyl isobutyl ether copolymer with a 1:1 ratio to the binder, the thickness of the base support is 7-12 microns, and the ink mixture is heated at a temperature of 60-80°C. A thermal ink transfer element characterized in that it is meltable at .