JP2007196614A - Relief printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relief printer which enables the cleaning of a relief printing plate without damage to the relief printing plate with the relief printing plate installed a plate cylinder, and which can do a proper printing immediately after the cleaning by improving the wettability of ink. <P>SOLUTION: The plate cylinder 1 is rotated in such a manner that the plate cylinder 1 and a plate cleaning device 4 face each other in a cleanable state; a jet of cleaning liquid, which is supplied from a cleaning liquid supply unit 5, is emitted onto the surface of the relief printing plate 11; subsequently, a jet of pressurized gas, which is supplied from a blowing unit 6, is emitted so that the cleaning liquid on the surface of the relief printing plate is blown off for the drying of the surface of the relief printing plate; and a droplet of the cleaning liquid, which is produced when the jet of the pressurized gas is emitted, is sucked in for recovery by a cleaning liquid recovery unit 7. After the completion of the cleaning of the relief printing plate, the cleaning liquid, which adheres to the relief printing plate 1, is wiped off by making the plate cylinder 1 and a plate wiping device 4 face each other in the readiness to be wiped off. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a relief printing apparatus suitable for forming a light emitting layer of a polymer organic EL display by printing an ink obtained by dissolving a polymer organic material in a solvent on a substrate to be printed.

  2. Description of the Related Art In recent years, organic EL elements having features such as thinness, low power, and high luminance display have attracted attention as display elements in mobile phones, PDAs (personal digital assistants), mobile personal computers, in-vehicle navigation systems, and the like. In this organic EL element, for example, an anode (transparent conductive film, ITO film), a light emitting layer containing an organic light emitter, and a cathode (metal electrode) are laminated on a transparent substrate.

The light emitting layer of the organic EL is usually formed by vacuum vapor deposition of a low molecular organic light emitter. In this case, there is a limit to increasing the size of the element from the viewpoint of the vapor deposition apparatus. Therefore, an attempt has been proposed to form a light-emitting layer by dissolving and dispersing a polymer organic light-emitting material in a solvent to form an ink, and using a known printing method (for example, see Patent Document 1).
Such a printing method is excellent in mass productivity and can reduce the manufacturing cost, and specific printing methods include offset printing and gravure printing.

On the other hand, flexographic printing is a printing method that uses a flexible relief printing plate made of rubber or resin, an inking roll called an anilox roll, and ink, and has been widely used for simple printed materials such as wrapping paper. This flexographic printing is particularly suitable for forming a thin and stable printing layer having a film thickness of about 0.01 to 0.2 μm.
In addition, flexographic printing has flexibility in the relief printing part where printing pressure is applied. Furthermore, because it is printing at a very low printing pressure called kiss touch, it is transparent so that characteristics can be destroyed by applying a glass substrate or high pressure. This is a printing method particularly suitable for forming a light emitting layer of an organic EL element because it is also suitable for printing on a substrate to be printed on which electrodes and the like are formed.
JP 2001-185352 A Special Table 2000-511835

By the way, when using an organic EL element for a full-color display application, it is necessary to separately coat the light emitting layer with RGB, and a fine pattern of about 150 to 200 ppi is formed by flexographic printing.
However, while the fine pattern printing is continuously performed, the dried ink accumulates on the surface of the relief printing plate and the depressions, and defects such as fluctuations in printing line width and film thickness occur. In particular, a polymer organic light-emitting material converted into an ink uses a volatile organic solvent, so that drying is fast and ink is likely to be deposited. For this reason, it is necessary to clean the relief printing between successive printings, but in order to maintain the alignment accuracy of the printing pattern, it is desirable to wash the relief printing without removing it from the printing press.

As a prior art for a printing machine loaded with a cleaning device that performs cleaning of the relief printing without removing it from the printing machine, for example, the one shown in Patent Document 2 is known.
However, this type of relief printing apparatus is considered to be used for maintenance at the end of printing, and has a fine pattern for printing a light emitting layer of an organic EL element because it is a method of rubbing the relief plate surface with a brush roll. If the relief printing plate is used for the purpose of regularly washing between printing operations, the relief printing plate is greatly damaged and good printing cannot be performed.
In addition, after washing the relief printing plate, the familiarity between the relief printing plate and the ink is poor, and sufficient inking cannot be performed. Therefore, the printed matter has a reduction in line width, a defect such as blurring, and the like. There is a problem that a large number of printed substrates are consumed by periodic discard printing in the case of mass production.

  The present invention has been made to solve the conventional problems as described above, and its object is a relief plate or other relief plate for forming a light emitting layer of a polymer organic EL device. Another object of the present invention is to provide a relief printing apparatus that can clean these letterpress plates without damaging the letterpress plates while improving the wettability of the ink and can perform good printing immediately after washing. .

  To achieve the above object, the present invention provides a relief printing apparatus using a relief plate as a printing plate, a rotary plate cylinder on which the relief plate is installed, a substrate surface plate on which a substrate to be printed is placed, An ink supply device for supplying ink to a relief printing plate, a relief printing washing device for washing the surface of the relief printing plate, and a plate wiping device for wiping the cleaning liquid on the surface of the relief printing plate, wherein the relief printing device is attached to the printing plate cylinder A cleaning liquid supply unit for supplying a cleaning liquid to the surface of the letterpress plate installed, a blower unit for injecting a pressurized gas to the letterpress plate supplied with the cleaning liquid, and a suction for sucking the cleaning liquid scattered by the blower unit It is characterized by comprising at least a unit and a cleaning liquid recovery unit that receives the cleaning liquid supplied to the surface of the relief printing plate.

  According to the relief printing apparatus of the present invention, the plate cylinder and the plate cleaning device are opposed to each other in a washable state, the plate cylinder is rotated, the cleaning liquid supplied from the cleaning liquid supply unit is sprayed onto the surface of the relief printing plate, and then the blower unit It is dried by spraying the pressurized gas supplied from and blowing off the cleaning liquid adhering to the relief plate surface, and the spray of the cleaning solution generated when jetting the pressurized gas is sucked and collected by the washing liquid recovery unit. After cleaning is completed, the plate cylinder and the plate wiping device are placed in a state where they can be wiped off, so that the cleaning liquid adhering to the relief plate is wiped off, so that the relief plate is left in the plate cylinder and the relief plate is damaged. In this way, the ink wettability is improved, and good printing can be performed immediately after washing.

The present invention relates to a relief printing apparatus comprising a rotary plate cylinder for installing a relief plate, a substrate surface plate on which a substrate to be printed is placed, and an ink supply device for applying ink to the relief plate, particularly a flexographic printing machine. Applies to As for the form of the printing machine, there are a system in which the rotary plate cylinder moves on the substrate surface plate and a method in which the substrate surface plate moves under the plate cylinder, but either form may be used.
As for the ink supply apparatus of the present invention, a flat anilox plate provided with a doctoring mechanism, an anilox roll, a capillary coater, etc. can be considered, but any system may be used.

  Moreover, the installation system of the plate cleaning apparatus of the present invention varies depending on the mechanism of the relief printing press. For example, a plate cleaning device of a relief printing press that moves the plate cylinder is installed in parallel with the substrate surface plate, and a method in which the plate cylinder moves to a position facing the plate cleaning device is suitable. In the plate cleaning device of a relief printing press of the type in which the position of the plate is fixed, a method in which the retracted plate cleaning device moves to a position facing the plate cylinder only during plate cleaning is suitable. However, the method of installing the plate cleaning apparatus according to the present invention is not limited to this, and a method in which a fixed type and a movable type are mixed for each unit is also conceivable.

The cleaning liquid supply unit constituting the plate cleaning apparatus of the present invention is a system in which a cleaning liquid composed of a mixture of water and a detergent or an organic solvent is sprayed on the surface of a relief plate installed in a plate cylinder with a nozzle. As the nozzle configuration in this case, a spray nozzle arranged in parallel in the width direction of the plate cylinder or a mechanism in which the spray nozzle moves in the width direction of the plate cylinder can be considered. Considering the influence on the slit nozzle, a slit nozzle that can supply the cleaning liquid in a uniform film shape in the width direction of the plate cylinder is desirable.
Moreover, in order to scrape out the ink residue accumulated in the concave portion of the relief printing plate, a two-fluid nozzle that ejects the cleaning liquid together with the pressurized gas may be used. The nozzle installation position is a position where the cleaning liquid can be poured from a uniform distance in the width direction of the plate cylinder. Further, the position where the incident angle is inclined downward with respect to the rotation direction of the plate cylinder, that is, the nozzle position of the cleaning liquid supply unit with respect to the surface of the relief plate, the relief plate installed in the plate cylinder is in the rotation direction of the plate cylinder. In this case, it is desirable that the nozzle is installed so that the cleaning liquid is supplied to the relief plate within a range of 180 degrees in the rotation direction of the plate cylinder from the position facing the bottom of the plate cylinder.

  Further, the blower unit of the present invention sprays pressurized gas composed of air or inert gas onto the relief plate surface from an air knife nozzle installed in parallel with the nozzle of the washing solution supply unit, and lowers the washing solution remaining on the relief plate surface. It is a method of blowing down in the direction. Further, it is desirable that the air knife nozzle is also installed so as to have an incident angle inclined downward with respect to the rotation direction of the plate cylinder, similarly to the nozzle of the cleaning liquid supply unit.

  In addition, a common slit nozzle is used for the nozzle of the cleaning liquid supply unit and the air knife nozzle of the blower unit in the present invention, and a mechanism for selectively ejecting the cleaning liquid and the pressurized gas by switching from this single slit nozzle. You can also. In this case, after spraying the cleaning liquid from the slit nozzle, when spraying the pressurized gas for drying, the cleaning liquid droplets remaining on the slit nozzle tip are simultaneously blown off. Prevents the occurrence of cleaning unevenness due to.

The cleaning liquid recovery unit according to the present invention is for receiving the cleaning liquid dripping from the nozzle of the cleaning liquid supply unit or the cleaning liquid dripping along the surface of the relief printing plate and the surface of the plate cylinder, and at least from directly below the nozzle of the cleaning liquid supply unit, It is necessary to arrange so as to cover the space up to the bottom of the lowermost part.
Further, it is further preferable that the cleaning liquid tray that constitutes the cleaning liquid recovery unit is directly connected to the suction port of the suction unit, and the cleaning liquid splashes collected on the tray are recovered by the suction unit.

  The nozzle of the cleaning liquid supply unit, the nozzle of the blower unit, the suction port of the suction unit and the cleaning liquid recovery unit in the present invention are accommodated in one cover, and only the surface of the cover facing the outer periphery of the plate cylinder is opened, and An opening having a curved surface following the outer shape of the plate cylinder is provided, and the clearance between the outer periphery of the plate cylinder and the cover when the plate cylinder is opposed to the cover is set to 5 mm or less. This prevents splashing of the cleaning liquid used during the operation of the plate cleaning apparatus from scattering outside the cover.

  Further, the plate wiping device according to the present invention, when operated, the wiping roller is pressed against the surface of the relief plate installed on the plate cylinder surface, and the wiping roller rotates with the rotation of the plate cylinder to wipe off the cleaning liquid adhering to the relief plate surface. It is a method. At this time, a method is also conceivable in which the wiping roller itself is composed of an adsorption roller or the like, and the cleaning liquid is adsorbed directly onto the wiping roller. In this case, however, the wiping roller itself needs to be cleaned. Therefore, a film-type wiping sheet wound around the surface of the wiping roll is sandwiched between and pressed between the wiping roll and the relief printing, and the cleaning liquid on the relief printing surface is transferred to the wiping sheet surface, and the wiping sheet is fed out from the supply roll. It is desirable to have a mechanism in which the wiping sheet is fed along with the rotation of the plate cylinder and the wiping roll and wound around the collecting roll so that a roll-like sheet is always brought into contact with the relief plate. The material of the wiping sheet may be a non-woven fabric, an adhesive sheet, etc., but a resin film such as PET is desirable in consideration of the influence of dust generation and adhesive residue.

Next, the operation of the plate cleaning apparatus according to the present invention will be described.
When the light emitting layer of an organic EL device is printed by flexographic printing, the ink of a polymer organic light emitter using a volatile organic solvent as a solvent dries and accumulates the ink residue on the surface of the relief printing plate. When the printing is repeated a number of times, the print pattern is printed larger than the desired dimension due to the influence of the ink residue accumulated in the concave portions of the relief printing, or the film thickness varies in an unstable manner, resulting in uneven printing. Therefore, the printing operation is temporarily interrupted to operate the plate cleaning apparatus.

In this case, first, the plate cylinder and the plate cleaning device are opposed to each other in a washable state, and the plate cylinder is rotated. From the state in which the front end (printing start side) of the pattern part of the relief printing reaches the vicinity of the nozzle of the washing liquid supply unit, the washing liquid is applied to the relief printing surface, and then the compressed air is sprayed from the nozzle of the drying unit to blow off the washing liquid on the relief printing surface. dry. At this time, from the time when the plate cylinder and the plate cleaning device are opposed to each other, the suction unit is operated to suck the droplets of the cleaning liquid. The suction amount of the suction unit is made larger than the discharge amount of the drying unit, the inside of the cover of the plate cleaning device is set to a negative pressure rather than the external pressure, and the cleaning machine splashes from the gap between the cover and the plate cylinder to the outside of the plate cleaning device. Make sure the atmosphere does not leak.
After the plate cleaning using the cleaning liquid is completed, the plate cylinder and the ink supply device are brought into contact with each other to supply ink onto the relief printing plate. However, the relief printing plate with the washing liquid component remaining unsuitable with the ink and the ink is not sufficiently supplied. . Therefore, the wiping roll of the plate wiping device is pressed against the plate cylinder to wipe off the ink supplied insufficiently on the relief plate. After that, repeat the ink supply and wiping as many times as desired until the cleaning liquid component remaining on the relief plate is reduced and the ink wettability is improved so that a sufficient amount of ink can be supplied. After that, the printing operation which has been temporarily suspended is resumed.

Hereinafter, Example 1 of a relief printing apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating the overall configuration of the relief printing apparatus according to the first embodiment, FIG. 2 is a schematic diagram illustrating the operation of the plate cleaning apparatus in the relief printing apparatus according to the first embodiment, and FIG. 3 is a relief printing according to the first embodiment. It is a schematic diagram at the time of operation | movement of the plate wiping apparatus in a printing apparatus.

  As shown in FIG. 1, the relief printing apparatus includes a movable plate cylinder 1, a substrate surface plate 2, an ink supply device 3, and a plate cleaning device arranged in parallel on the printing machine base 10 at a predetermined interval. 4 and a plate wiping device 9 having a lifting mechanism (not shown) at a position higher than the passage of the plate cylinder 1 above the ink supply device 3. This relief printing apparatus constitutes a flexographic printing machine and is applied to pattern printing of a light emitting layer of an organic EL element.

The plate cleaning device 4 cleans the surface of the relief plate 11 installed in the plate cylinder 1, and as shown in FIG. 2, a washing solution supply unit that supplies a washing solution to the surface of the relief plate 11 installed in the plate cylinder 1. 5, a blower unit 6 that jets pressurized gas to the surface of the relief plate 11 after the cleaning liquid is supplied, and a suction unit 7 that sucks the cleaning liquid scattered by the jetting of pressurized gas from the blower unit 6. And a receiving tray 8 for recovering the cleaning liquid that receives the cleaning liquid flowing down after being supplied to the surface of the relief plate 11 (corresponding to the cleaning liquid recovery unit described in the claims).
As shown in FIG. 2, the cleaning liquid supply unit 5 has a cleaning liquid injection nozzle 51 that injects the cleaning liquid onto the surface of the relief plate 11, and this cleaning liquid injection nozzle 51 is connected to the cleaning liquid supply unit 5 by a cleaning liquid supply hose 52. .
Further, as shown in FIG. 2, the blower unit 6 has a gas injection nozzle 61 that injects a pressurized gas onto the surface of the relief plate 1 supplied with the cleaning liquid. The gas injection nozzle 61 is a pressurized gas supply hose 62. To the blower unit 6.
As shown in FIG. 2, the suction unit 7 has a suction port 71 that communicates with the bottom of the cleaning liquid collection tray 8, and the suction port 71 is connected to the suction unit 7 by a suction hose 72.

As shown in FIG. 2, the plate cleaning device 4 has a cover 41 that houses a cleaning liquid injection nozzle 51, a gas injection nozzle 61, and a cleaning liquid collection tray 8, and corresponds to the outer peripheral curved surface of the plate cylinder 1 of this cover 41. The portion to be formed is formed in a curved surface shape corresponding to the outer peripheral curved surface of the plate cylinder 1, and the curved surface shape portion 42 of the cover 41 is opened, and further, a gap between the outer peripheral curved surface of the plate cylinder 1 and the curved surface shape portion 42. Is set to 5 mm or less.
Further, as shown in FIG. 2, the cleaning liquid supply nozzle 51 and the gas injection nozzle 61 are arranged back and forth in the rotational direction of the plate cylinder 1 so as to face the opening of the curved portion 42.
As shown in FIGS. 1 and 3, the plate wiping device 9 is a wiping sheet supply roll in which a long cleaning liquid wiping sheet 94 is wound in a roll shape (corresponding to a wiping sheet supply means described in the claims). ) 92, a wiping roll (corresponding to the wiping means described in claims) 91 for pressing the wiping sheet 94 fed from the supply roll 92 against the surface of the relief plate 11 installed in the plate cylinder 1, It is comprised from the collection | recovery roll (equivalent to the wiping sheet collection | recovery means described in the claim) 93 which winds up the wiping sheet | seat 94 after wiping off the cleaning liquid adhering to the surface.

  The ink supply device 3 supplies ink containing a polymer light emitter via the anilox roll 31 to the surface of the relief plate 11 having a desired convex pattern installed on the surface of the plate cylinder 1, and then the plate cylinder 1. The light-emitting layer is formed by pressing the relief plate 11 against the surface of the substrate 21 to be printed and rolling the ink in a pattern while rolling on the substrate 21 placed on the substrate surface plate 2. While this printing operation is repeated about 20 to 100 times, the ink residue remaining on the surface of the relief plate 11 is accumulated and clogged in the recesses of the relief plate 11, and the printing pattern is printed larger than the desired dimension, or printing unevenness occurs. Will come to do.

  Therefore, in the first embodiment, as shown in FIG. 2, the plate cylinder 1 is moved to a position where it abuts on the plate cleaning device 4, and the plate cylinder 1 is rotated while the plate cylinder 1 is rotated near the nozzle 51 of the cleaning liquid supply unit 5. From the position where the front end 11a of 11 has reached, while blowing toluene as the cleaning liquid from the nozzle 51 of the cleaning liquid supply unit 5 onto the surface of the relief plate 11, the compressed air is blown from the nozzle 61 of the drying unit 6 to the surface of the relief plate 11, and at the same time 7 is sucked in from the inlet 71 of the cleaning liquid, and the toluene dripping onto the cleaning liquid tray 8. This operation is continued until the plate cylinder 1 is rotated and the rear end 11b of the relief plate 11 is filled with toluene as a cleaning liquid and dried. Thereafter, the cleaning operation ends.

  Next, as shown in FIG. 3, the plate cylinder 1 is moved to a position where it abuts against the ink supply device 3, and ink is supplied to the surface of the relief plate 11 while rotating the plate cylinder 1. Thereafter, the plate cylinder 1 is raised and brought into contact with the wiping roll 91 of the wiping unit 9 via the wiping sheet 94. The plate cylinder 1 and the wiping roll 91 are rotated at the same peripheral speed, and the wiping sheet 94 is fed, and the ink attached to the surface of the relief plate 11 is transferred to the wiping sheet 94 to be wiped off. Thereafter, the supply of ink and the wiping of ink are alternately repeated about 1 to 5 times. Thereafter, the printer is returned to the normal operation, and the organic EL element is printed with the light emitting layer to form a light emitting layer having a pattern with a desired dimension.

  According to the relief printing apparatus shown in the first embodiment, it is possible to clean the relief plate 11 without damaging the relief plate 11 while the relief plate 11 is installed on the plate cylinder 1, thereby improving the wettability of the ink. In addition to being able to perform good printing immediately after washing, it is not necessary to perform discarded printing on the substrate to be printed as in the prior art, and wasteful consumption of the substrate to be printed can be prevented. Then, by applying the relief printing apparatus shown in Example 1 to pattern printing of the light emitting layer of the organic EL element, it becomes possible to inexpensively produce a polymer organic EL element capable of displaying a high-quality image. .

1 is a schematic diagram illustrating an overall configuration of a relief printing apparatus in Embodiment 1. FIG. It is a schematic diagram at the time of operation | movement of the plate washing | cleaning apparatus in the relief printing apparatus of the present Example 1. FIG. It is a schematic diagram at the time of operation | movement of the plate wiping apparatus in the relief printing apparatus of the present Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plate cylinder, 11 ... Letterpress, 2 ... Substrate surface plate, 21 ... Substrate to be printed, 3 ... Ink supply device, 31 ... Anilox roll, 4 ... Plate washing device, 41 ... Cover, 5 ... Cleaning liquid supply unit, 51 ... Cleaning liquid supply nozzle, 6 ... Blower unit, 61 ... Gas injection nozzle, 7 ... Suction unit, 71 ... Suction port, 8 ... Cleaning liquid tray, 9 ... Wiping plate Equipment: 91 ... Wiping roll, 92 ... Supply roll, 93 ... Recovery roll, 94 ... Wiping sheet, 10 ... Printing press base.

Claims (7)

A letterpress printing apparatus using a letterpress as a printing plate,
A rotary plate cylinder on which the relief plate is installed, a substrate surface plate on which a substrate to be printed is placed, an ink supply device that supplies ink to the relief plate, a relief plate cleaning device that cleans the surface of the relief plate, A plate wiping device for wiping off the cleaning solution on the surface of the relief printing plate after cleaning,
The relief cleaning apparatus includes a cleaning liquid supply unit that supplies a cleaning liquid to the surface of the relief plate installed in the plate cylinder, a blower unit that injects a pressurized gas to the relief after the cleaning liquid is supplied, A letterpress printing apparatus comprising at least a suction unit that sucks the cleaning liquid scattered by the blower unit and a cleaning liquid recovery unit that receives the cleaning liquid supplied to the surface of the letterpress.   2. The relief printing apparatus according to claim 1, wherein the cleaning liquid supply unit is configured to supply only the cleaning liquid to the surface of the relief printing plate without contacting the relief printing plate.   The cleaning liquid supply position from the cleaning liquid supply unit with respect to the surface of the relief printing plate is such that the relief printing plate installed in the printing cylinder is rotated from the position where the relief printing plate faces the bottom of the printing cylinder in the rotation direction of the printing cylinder. The relief printing apparatus according to claim 1, wherein the relief printing apparatus is in a range of 180 degrees.   The cleaning liquid supply unit has a cleaning liquid injection nozzle that injects a cleaning liquid onto the surface of the relief plate, and the blower unit has a gas injection nozzle that injects pressurized gas onto the relief plate after the cleaning liquid has been injected, The suction unit has a suction port for sucking the droplets of the cleaning liquid, the cleaning liquid injection nozzle, the gas injection nozzle, and the cleaning liquid recovery unit are accommodated in a cover, and a location corresponding to the outer peripheral curved surface of the plate cylinder of the cover Is formed in a curved surface shape corresponding to the outer peripheral curved surface of the plate cylinder, the cover is open only in the curved surface shape portion, and the gap between the outer peripheral curved surface of the plate cylinder and the curved surface shape portion is set to 5 mm or less. The letterpress printing apparatus according to any one of claims 1 to 3, wherein the letterpress printing apparatus is provided.   5. The relief printing apparatus according to claim 4, wherein the cleaning liquid supply nozzle and the gas injection nozzle are arranged back and forth in the rotation direction of the plate cylinder so as to face the opening of the curved surface portion.   The nozzle for injecting the cleaning liquid from the cleaning liquid supply unit to the surface of the relief plate and the nozzle for injecting the pressurized gas from the blower unit to the relief plate after the cleaning liquid is supplied are constituted by a single nozzle, The letterpress printing apparatus according to any one of claims 1 to 4, wherein a cleaning liquid and pressurized gas are switched from a nozzle and sprayed onto the letterpress. The plate wiping device comprises: a wiping sheet supply means for sending out a long cleaning liquid wiping sheet; and a wiping means for bringing the wiping sheet from the wiping sheet supply means into contact with the surface of the relief plate and wiping the cleaning liquid adhering to the relief plate surface; 2. The letterpress printing apparatus according to claim 1, further comprising a wiping sheet collecting means for winding the wiping sheet after wiping off the cleaning liquid adhering to the letterpress surface.

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