ES2198300T3 - PROCEDURE THAT ALLOWS TO PRINT A PRINTING CLICHE WITH THE HELP OF THERMOPLASTIC INKS AND INK DEPOSITS USED FOR THE PERFORMANCE OF SUCH PROCEDURE. - Google Patents

Abstract

The invention relates to a process for inking a printing plate attached to a holder, with a thermoplastic ink, to be used in pad printing, whereby a relative movement is maintained between the holder and an ink tank filled with thermoplastic ink, characterised in that the holder or the ink tank, or both these components are heated at the temperature required for the thermoplastic ink. The invention also relates to the ink tanks to be used in this process. <IMAGE>

Description

Procedure that allows inking a cliché of printing with the help of thermoplastic inks and deposits ink used for performing said procedure.

This invention relates to a process that it allows inking a cliché fixed on a support by means of a thermoplastic ink intended to be used for printing with buffer called pad printing in which a movement is maintained relative between the support and an ink-filled ink tank thermoplastic

To print substrates such as glass, ceramics and porcelain, what is usually called a thermoplastic ink This ink has the viscosity of a paste thick at room temperature. In printing, this ink is heats to about 80 ° C, temperature at which it becomes very fluid. After printing, the very fluid ink on the printed substrate cools to room temperature and therefore coagulates again. The printing on the substrate is fixed by firing the printed product for a certain period of time at elevated temperature (approximately 800 ° C). Proceeding in this way, the ink will vitrifies and melts towards the substrate. The result is an impression strongly adherent that does not erase or wear out, even in case of frequent washing in the dishwasher.

Screen printing is currently the procedure commonly used to print the glass by means of thermoplastic inks to obtain acceptable quality.

In the existing screen printing technique, it is used a screen that is composed of a plastic material or a metal, but which must withstand a maximum temperature of 100ºC, and which is attached to a wooden or metal frame. The screen is covered by a waterproof layer, with the exception of sites whereby the ink must be able to cross the screen to form the  Image to be printed on the substrate.

Thermoplastic paste inks are placed in the screen. The screen is heated so that the ink Thermoplastic become fluid.

The thermoplastic ink is pushed through the screen by means of a scraper of plastic or metallic material, only through the openings that show the image directly on the product: glass, ceramic or porcelain. East Procedure has the following limitations:

limited in resolution by the use of a screen, in which the density of the threads that form the screen is physically limited;

can only be used for printing flat and cylindrical objects;

The quality is markedly reduced by how much the surface of the object to be printed is folded inward or outward.

In addition to screen printing, it also You can use the technique known as pad printing.

Pad printing with thermoplastic ink it has had little success so far seen the lack of reliability and the lack of consistency in quality.

In the technique known as `` printing pad printing '', an engraved cliché is used, which is inked in its entire surface in a first phase, after which it remove the excess ink through the scraper and collect it in a ink duct or similar system. In this way the ink remains exclusively on recorded parts.

The different operations related to In this regard they can be summarized as follows:

one)

the support of scraper with tray is removed from the cliché and kept separate from the cliché during the inking phase.

two)

the support of scraper with tray moves with respect to the cliché during the inking phase in its longitudinal direction.

3)

after the phase inking, the scraper is put back in contact with the cliche.

4)

the scraper is displaces with respect to cliché; the ink is removed with the scraper except for recorded parts and collected in a deposit of ink.

It is clear that the relative movements of scraper stand with tray with respect to the cliché are the result of a displacement of these pieces with respect to stationary cliché, as well as vice versa, and that consequently both the cliché and the scraper with the tray can move in the opposite direction.

The scraper is always adjusted with respect to the cliché so that it forms an acute angle with this cliché, with the part of the cliché that has been inked and in which there is still pass the scraper.

The techniques that are generally applied, and briefly described, show a series of drawbacks that They can summarize as follows:

to)

the cliché is exposed to high wear, given the pressure exerted by the scraper on the cliché. The correct application of the scraper on ink is indeed an absolute requirement, which requires, during the installation of the scraper as described more above, a high pressure of the scraper on the cliché.

b)

on each occasion, it They require two movements that can be summarized as follows: up and down movement of the scraper blade during the relative movements of the scraper with respect to the cliche.

Since thermoplastic inks are used that they must keep at a constant and regulated temperature, there are numerous inconveniences associated with this system. These are summarized from the Following way:

-

strong wear of the cliché and the blade of the scraper due to the high pressure required of the scraper blade on the cliché, with very negative repercussions on the quality of Print.

-

trouble keep the temperature at a constant level during movements up and down the blade of the scraper, which heats and cools continuously, with the result that the blade of the scraper is loaded and `` dirty '' quickly with ink hardened.

The combination of the inconveniences above indicated is the reason why it is almost impossible to perform a Production with constant print quality.

Japan's patent compendiums, `` ABREGES OF BREVETS DU JAPON '', Volume 15, No. 491 (M-1190), of December 12, 1991 (1991-12-12) and JP 03213341 A (THINK LAB KK) of September 18, 1991 (1991-09-18) disclose a procedure for inking a print cylinder engraved with a ink whose viscosity is reduced by heating, maintaining a relative movement between the etched surface and a deposit of ink filled with the aforementioned ink, in which the reservoir of ink is heated to the temperature required for this ink. However, these teachings are not directly applicable with a thermoplastic ink

The invention is intended to remedy the drawbacks of this known technique and prescribe a procedure and a device that ensures, with some means technically reliable, an extension of the life of the cliché and that allows reliable use of thermoplastic inks.

To make this possible, according to the invention, the support or the ink tank or each of these components is heats to the temperature required for thermoplastic ink.

In a first possible embodiment, a heated ink tank is used as an ink tank electrically provided with a circular or oval scraper made of a hard material such as a hard metal or a material plastic shaped monolithic piece of a non-deformable material, in the contour of which a circular or oval channel is made for fix the scraper mentioned above in enclosure, as well as to fix the scraper mentioned above to this piece, by gluing.

According to another possible embodiment, use a device consisting of the combination of a heated ink tank and at least one scraper, of which at least the bottom edge, which is in contact with the cliché, is regulated with respect to cliché with a negative angle measured with regarding the inked part of the cliché over which the scraper, and a relative movement of the scraper is generated with with respect to the cliché, without changing the position of the scraper, in a direction to ink the cliché, on the one hand, and on the other direction to remove the ink from the cliché with the scraper, by other.

The invention also relates to some closed ink tanks that will be used within the framework of the invention.

Other details and advantages of the invention will arise from the inking procedure of a cliché attached to a support, by means of thermoplastic ink and ink tank used here according to the invention. Reference numbers are They refer to the drawings attached.

Figures 1 to 4 schematically illustrate a Classic pad printing procedure.

Figure 5 schematically illustrates a deposit closed ink with a heated cliché holder.

Figure 6 schematically shows a deposit of ink closed with a heated cliché.

Figure 7 schematically shows a deposit of ink closed with a heated support.

Figure 8 schematically shows a deposit closed ink with a heated tank.

Figure 9 schematically illustrates a camera of closed scraper with a heated cliché support.

Figure 10 schematically illustrates a camera of closed scraper with a heated cliché.

Figure 11 schematically illustrates a camera of closed and heated scraper.

The procedure shown by figures 1 to 4 illustrates schematically but clearly the different stages of inked in the pad printing technique.

Reference 1 refers to the cliché that is fixed in a holder 2, whose deep part forms the ink chamber 3, in the one that collects the ink after the passage of scraper through cliché 1. In principle, a cliché inking device includes always an ink tray 4 and a scraper 5. These pieces are move up and down separately by means that don't They will be described here in detail.

It is clear that the relative movements of scraper stand with tray with respect to the cliché are the result of a displacement of these pieces with respect to stationary cliché, as well as vice versa, and that consequently both the cliché and the scraper with tray can move in opposite direction.

The techniques that are generally applied and that are briefly describe show a number of drawbacks that are They can summarize as follows:

to)

the scraper is always regulates in such a way that with respect to the cliché that forms a acute angle with this cliché, with the part of the cliché that has been inked and through which the scraper must still be passed.

b)

the cliché is exposed to high wear due to the pressure exerted by the scraper on the cliché. A good scratch of the ink is indeed an absolute requirement and this requires, during the scraper installation as described above, a pressure raised from the scraper on the cliché.

c)

every time, it they require two movements that can be summarized as follows way: up and down movement of the blade of the scraper during relative movements of the scraper with Regarding the cliche.

Since thermoplastic inks must kept at a constant and regulated temperature, they are associated numerous inconveniences to the procedure just described. These drawbacks are in particular:

-

strong wear of the cliché and the blade of the scraper due to the high pressure required of the scraper blade on the cliché, with very negative repercussions on the quality of Print.

-

trouble keep the temperature at a constant level during movements up and down the blade of the scraper, which heats and cools continuously, with the result that the blade of the scraper is loaded and `` dirty '' quickly with ink hardened.

The combination of the inconveniences above indicated is the reason why it is almost impossible to perform a Production with constant print quality.

According to the invention indicated herein, a heated cliché holder 4 or a closed ink tank and heated due to the use of thermoplastic inks, but it will be directly evident that these two pieces could get warm.

The different modalities of realization of procedure and the media or ink tanks used in This will be discussed below.

In the embodiment indicated in the Figure 5, a cliché 6 will be used, fixed to the cliché support 7. In 8, reference is made to an inking chamber by 8 with support 9. Thus, in this embodiment, only heats the cliché holder 7.

Figure 6 refers to an alternative of the invention according to which cliché 6 is heated, while not heat neither the cliché holder 7, nor the inking chamber 8. As previously stated, a combination can be designed of the embodiments that have just been described.

In the embodiment according to figure 7, only the inking chamber holder 9 is heated while that according to figure 8, only the inking chamber 8 is heated. In the sense of the invention, the embodiments according to Figures 5 to 8 can be combined with each other.

The closed chambers 10 according to figures 9 to 11 they refer to a very remarkable embodiment of the camera inking to use with this application. The cameras of closed inks are combined here according to the modality of embodiment described below, namely

to)

(Figure 9) in this case, the inking chamber 10 is used in combination with a heated cliché holder 7;

b)

(Figure 10) in this case, only cliché 6 is heated;

c)

(Figure 11) in this embodiment, only the inking chamber is heated 10.

In the spirit of the invention, the modalities according to figures 9 to 11 can be combined mutually.

The inking chamber 10 is a mode of especially attractive realization. It consists of a box 11 that form, in combination with two scrapers 12, an inking chamber completely closed 13.

The ink 14 that is present in the chamber of inked is extended and scratched the cliché simultaneously with the two scrapers 8.

Given the special angle at which the scrapers 8 with respect to cliché 6, an `` interstitium of inking '' of the closed inking chamber, which results especially useful in case of use of inks thermoplastics

The instrumentation of an inking chamber closed of the type illustrated by figures 9, 10 and 11 creates some ideal conditions for the use of inks thermoplastics

The remarkable advantages of the procedure according to the invention and of the closed inking chambers used in this can be summarized as follows:

to)

Since there is no up and down movement of the inking chamber closed nor of the mechanism of the scraper chamber, these do not They can cool.

b)

Given the amount Limited thermoplastic ink used to be used according to the procedure, constant temperature maintenance is more simple.

c)

Minimum wear of cliché since the pressure of the scraper chamber or the Inkwell on cliché is scarce.

d)

The clichés and the Ink are easily interchangeable, with very changing times short

and)

Ink consumption It is very economical since ink losses during Cleaning are very low.

F)

Given the amount Limited thermoplastic ink used and the absence of a ink tank, the machine reaches temperatures faster operating after switching on, at the time of commissioning March at room temperature.

Claims (17)

1. Inking procedure of a cliché fixed on a support, for a thermoplastic ink intended to be used for printing with buffer, in which a relative movement is maintained between the support and a reservoir of ink filled with thermoplastic ink, characterized in that the support or the ink tank or each of these pieces is heated to the temperature required for the thermoplastic ink, the ink being heated to about 80 ° C. 2. Method according to claim 1, characterized in that a heated ink tank provided with a circular or oval scraper is used as an ink tank, made of a hard material such as a hard metal or a plastic material in the form of monolithic piece of a non-deformable material, in the contour of which a circular or oval channel is made to fix the aforementioned scraper by encyclizing, as well as to fix to this piece the aforementioned scraper, by gluing. 3. A method according to claim 1, characterized in that a device consisting of the combination of a heated ink tank and at least one scraper, of which at least the bottom edge, which is at the bottom, is used as an ink tank in contact with the cliché, it is regulated with respect to the cliché with a negative angle measured with respect to the inked part of the cliché on which the scraper is passed, and a relative movement of the scraper is generated with respect to the cliché, without changing the position of the scraper, in one direction to inking the cliché, on the one hand, and in the other direction to remove the ink from the cliché with the scraper, on the other. 4. Ink tank intended to be used for the instrumentation of the method according to claim 2, characterized in that it can be heated and is provided with a circular or oval scraper of a hard material, such as a hard metal or a plastic material, and in that it is made in the form of a monolithic piece in a non-deformable material, on the contour of which a circular or oval channel is made to fix the aforementioned scraper by a binding by encliquetado, as well as to fix to this piece the scraper mentioned above, by pasting. 5. Ink tank according to claim 4, characterized in that the aforementioned hard material is a synthetic material. 6. Ink tank according to claim 5, characterized in that the aforementioned synthetic material is polyacetate. 7. Ink tank according to any one of claims 5 and 6, characterized in that the aforementioned scraper of said synthetic material is fixed by means of an adhesive. 8. Ink tank according to claim 4, characterized in that the aforementioned scraper, of said synthetic material, is fixed to the piece by a union of the encycled type. 9. Ink tank according to any one of claims 4 or 5, characterized in that, during the vaporization or molding of said synthetic material in which said ink tank is made, the said scraper was mounted therein. 10. Heater ink tank for the instrumentation of the method according to claim 3, characterized in that it consists of the combination of

to)

a deposit of ink to ink the cliché during a relative movement of the cliché regarding this ink tank, and

b)

at least one scraper whose bottom edge, which is in contact with the cliché is regulates with respect to the cliché with a negative angle, namely a angle measured with respect to the inked part of the cliché in which The scraper has already been passed.

11. Ink tank according to claim 10, characterized in that said scraper is adjusted with a negative angle included between approximately 90 and 180 °. 12. Ink tank according to any one of claims 10 and 11, characterized in that it is elongated and in which it forms an elongated ink space with the said scraper. 13. Ink tank according to claim 12, characterized in that the said scraper and the ink tank are mounted in a common elongated box. 14. Ink tank according to claim 13, characterized in that the said scraper and said elongate box form a whole. 15. Ink tank according to any one of claims 10 to 14, characterized in that two scrapers are positioned opposite each other. 16. Ink tank according to any one of claims 10 to 15, characterized in that the said scraper forms a closed circle and in which a part of the scraper extends according to the mentioned negative angle. 17. Ink tank according to any one of claims 13 to 16, characterized in that a heating resistance is located above the aforementioned box.