JP4604923B2 - Inkjet printing method and apparatus - Google Patents

Description

  The present invention relates to an inkjet printing method and apparatus using ultraviolet curable ink (UV ink).

Ink-jet printing using a conventional UV ink is performed by depositing ink of a predetermined color as particles in order and adhering to the printing surface, and curing the adhering ink by ultraviolet (UV) irradiation.
At this time, as shown in FIG. 6A, there is a problem that fine color density difference is seen due to an ink ejection direction error, a printing material feed error, and the like, and printing spots (unevenness) occur.

  In order to solve this problem, an error dispersion method has been adopted in the printing method using the conventional inkjet printing apparatus shown in FIG. That is, in the conventional inkjet printing apparatus 1, the UV ink discharge unit 2 and the UV irradiation unit 4 are linearly reciprocated in one direction by the first driving unit 5, while holding the printed material 10. 3 is configured to be linearly reciprocated by the second drive unit 6 in a direction perpendicular to the one direction. Therefore, in the conventional printing method based on the error dispersion method, as shown in FIG. 8, the ink ejection unit 2 or the holding unit 3 of the substrate 10 is moved by a predetermined distance in the direction perpendicular to one direction, and the same. The image is not completed by the same ink discharge unit, and the image is superimposed by repeating printing in one direction and movement in a direction perpendicular to one direction a predetermined number of times.

  However, in the above conventional ink jet printing method, as shown in FIGS. 6B and 6C, when the printed surface of the printing object 10 is viewed with reflected light, it looks without problems, but printing with transmitted light is performed. There is still a problem that printed spots are still visible when looking at the surface.

In order to suppress this printing unevenness, it is known that the printing unevenness can be reduced by sufficiently repeating the printing process and sufficiently performing error dispersion.
However, in this case, since it is necessary to supply abundantly the energy generated when the UV irradiation is performed from the UV irradiation unit 4, the characteristics of the printing material such as abnormal hardening, cracks, cracks, and deformation of the ink itself are hindered. It was not realistic.
In addition, a decrease in productivity of the printing material due to abundantly repeating the printing process has also been a problem.

  The present invention has been made in view of the above problems, and the object of the present invention is conventionally also in a printing apparatus in which there is an ink ejection direction error or a substrate feeding error between the ink ejection unit and the substrate holding unit. It is an object to provide an ink jet printing method and apparatus capable of performing ink jet printing with few printing spots with the same number of times of printing.

The present invention provides an ink-jet printing method and apparatus according to each of the claims as means for solving the above-mentioned problems.
The inkjet printing method according to claim 1, wherein an ultraviolet curable ink is ejected while moving the holding portion of the printing material relative to the ink ejection portion in one direction, and printing is performed by irradiating ultraviolet rays. A first printing process in which the movement of one pitch perpendicular to the one direction is alternately repeated on the surface of the substrate to be printed, and a direction change in which the holding portion is at an angle not parallel to the first printing process. A process, an operation of ejecting the ink while moving the printed material in one direction with respect to the direction-changed angle and irradiating with ultraviolet rays, and printing, and one pitch perpendicular to the direction-changed direction. And a second printing step in which the moving operation is alternately and repeatedly printed on the surface of the substrate. Thereby, by printing again from the direction in which the angle of the once printed surface is changed, the left and right positioning accuracy errors of the printing apparatus are averaged, and high-speed inkjet printing with less influence of printing spots becomes possible.

In the printing method according to claim 2, the reference position is printed in the first printing step, and the reference position is measured and positioned in the second printing step. By printing the start position and the end position which are the reference in the second printing process in the printing process, the first printing process and the print image of the second printing process can be superimposed with high accuracy. .
In the printing method according to claim 3, the reference position is printed in the first printing step, and the reference position is measured and positioned. In the second printing step, the print information of the printing object is arbitrarily set with respect to the reference position. Printing is performed with information converted into an angle, and by this, an arbitrary angle with respect to the reference position printed in the first printing process is converted into information on the image information of the printing material, In the second printing step, an ink ejection position different from that in the first printing step is given, and printing spots can be reduced.

In the printing method according to claim 4, the print information of the second printing step is converted in advance including rotation, and the operation is performed in the same manner as the rotation reference position and rotation angle in practice. The second printing step is performed, whereby the reference position printed in the first printing step is read and positioned in the second printing step of claim 2, or the second step of claim 3. The printing information is not converted into the positional information including the rotation on the spot, the positional accuracy is ensured, and the alignment time between the first printing process and the second printing process is shortened to increase the productivity. I can do it.
The printing method according to claim 5 uses a translucent resin base material as an object to be printed, and thereby allows the printed surface to be viewed with transmitted light in which printing spots (unevenness) are more strongly recognized. This is particularly effective for printing using a light-sensitive resin substrate.

The printing method according to claim 6 is a printing method paying attention to the fact that there is a correlation between the integrated light amount received by the base material from the ultraviolet lamp and the temperature rise of the base material, and the printed light image is reduced by reducing the integrated light amount received by the base material. By suppressing the shrinkage of the image, it is possible to suppress the misalignment of the printed image between printings to a level that does not cause a problem. Specifically, for example, there is a method of suppressing the integrated light quantity received by the base material by, for example, reducing the output of the ultraviolet lamp or increasing the printing speed.
It is also effective to reduce the temperature difference between each part of the base material from the start of printing to the end of printing instead of suppressing the above-described temperature rise.
The printing method according to claim 7 is a method of controlling the temperature of the holding unit that holds the base material and printing so that the temperature difference between each part of the base material is 10 ° C. or less, and suppresses the temperature difference. Thus, it is possible to suppress a print image shift between printings to a level where there is no problem.

The printing method according to claim 8 is a method of performing correction such as expanding each part on the print information in advance by the amount of contraction of the print image of each part, thereby obtaining a predetermined print image. And printing misalignment between printings can be suppressed to the extent that there is no problem. If the substrate size, thickness, and printing information are the same, the temperature rise in each part of the substrate is almost constant, and the shrinkage of the printed image is reproducible, so productivity is improved even during mass production. Printing deviation can be suppressed without lowering.
The printing method according to claim 9 is a method in which the printing end portion of the printing information in the second printing step is shifted to the printing area side to allow escape (trapping), thereby printing by converting the angle. Therefore, it is possible to suppress the protrusion from the printing end against the printing misalignment.

The ink jet printing apparatus according to claim 10 is an apparatus for carrying out the ink jet printing method described above, and includes a first drive unit that linearly moves the ink discharge unit and the ultraviolet irradiation unit, and a holding unit that holds the printed material. In addition to the second driving unit that linearly moves the ink ejection unit and the ultraviolet irradiation unit in a direction orthogonal to the moving direction of the ink ejection unit, a rotation driving unit that rotates the holding unit is provided. The ink jet printing apparatus according to claim 10 has substantially the same function and effect as the above ink jet printing method.
The ink jet printing apparatus according to claim 11 is provided with a temperature control mechanism in the holding portion, thereby suppressing a temperature difference between each part of the base material when the printing material is a resin base material. Deviation can be suppressed.

  Hereinafter, an inkjet printing method and apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a schematic overall configuration of an inkjet printing apparatus for carrying out an inkjet printing method according to an embodiment of the present invention. The ink jet printing apparatus 1 of the present invention includes an ink ejection unit 2 having a plurality of nozzle rows (not shown) that eject different color inks. Examples of the plurality of ink colors ejected from the nozzle row include four colors of magenta (red) M, cyan (blue) C, yellow (yellow) Y, and black (black) B, or a plurality of colors selected from them. can do. Further, in addition to or in place of the basic color, another specially prepared different color may be employed. An ink tank filled with each color ink is detachably arranged in parallel in the ink ejection unit 2. The ink discharge unit 2 is fixed to the carriage 21. Each of these color inks is an ultraviolet curable ink (UV ink).

  An ultraviolet irradiation unit 4 that radiates ultraviolet rays (UV), which is arranged side by side with the ink discharge unit 2, is also fixed to the carriage 21. Further, the carriage 21 is configured to be linearly reciprocable as indicated by an arrow A in FIG. Accordingly, the ink ejection unit 2 and the UV irradiation unit 4 linearly reciprocate in the direction indicated by the arrow A, and the ink applied to the surface of the printing material 10 by the ink ejection unit 2 is behind the movement direction of the ink ejection unit 2. The ink is cured by UV from the arranged UV irradiation unit 4.

  The substrate 10 is placed and held on the holding unit 3. The holding unit 3 is a kind of table, and is linear in a direction orthogonal to the direction A in which the ink discharge unit 2 and the UV irradiation unit 4 move by the second driving unit 6 as indicated by an arrow B in FIG. At the same time as being reciprocally movable, the rotational drive unit 7 is configured to be rotatable as indicated by an arrow C in FIG. That is, the rotation drive unit 7 is attached on the second drive unit 6, and the holding unit 3 is provided on the rotation drive unit 7. As these linear reciprocating mechanisms and rotating mechanisms, known mechanisms can be appropriately employed.

  The holding unit 3 is provided with a temperature control mechanism (not shown). As the temperature control mechanism, for example, a heater is installed inside the holding unit 3 or a water circulation path is installed inside the holding unit 3 to control the temperature of the holding unit 3, and the temperature of the substrate 10. It is possible to suppress a change in printing between printing processes by suppressing the change.

  That is, in ink jet printing using an ultraviolet lamp as the ultraviolet irradiation unit 4, the temperature of the printed material 10 rises due to the heat generated by the ultraviolet lamp. As the operation of ejecting ultraviolet curable ink and irradiating with ultraviolet rays is repeated, heat is gradually accumulated in the substrate 10 and the temperature gradually rises. When the substrate 10 is a resin base material, it expands by an amount corresponding to the thermal expansion coefficient as the temperature rises. Therefore, when printing is performed in this state, the temperature of the base material decreases after printing is finished, and the base material contracts. As a result, the printed image of the printed material is reduced more than the set image. When the first printing step and the second printing step, which will be described later in detail, are printed without changing the angle, the temperature rise at each part of the base material is almost the same, and thus printing misalignment between printed images occurs. However, when printing is performed while changing the angle, the thermal history received by the base material is different, which causes a problem of print misalignment between printed images. Therefore, suppressing the temperature rise of the substrate is a very important point in suppressing printing misalignment in the method of printing by changing the angle.

As a method for suppressing the temperature rise of the printing material 10, for example, in the UV irradiation unit 4, the output of the ultraviolet lamp is lowered, or for example, the ink discharge unit 2 and the UV irradiation unit 4 are in the direction indicated by the arrow A in FIG. linear reciprocating by increasing the moving speed when the moving subject integrated light quantity at 3000 mJ / cm ² or less of the substrate 10, even more preferably by printing with 2000 mJ / cm ² or less, the thermal expansion of the substrate 10 in Printing misalignment between printing processes can be suppressed.
Moreover, the UV irradiation part 4 may suppress the temperature rise of the to-be-printed material 10 using the ultraviolet light emitting diode (UVLED) which does not generate | occur | produce a lot of heat in the first place.

  Furthermore, instead of suppressing the above-described temperature rise, the temperature difference of the substrate 10 from the start of printing to the end of printing may be reduced (for example, 10 ° C. or less). Specifically, for example, the holding unit 3 is formed of aluminum or copper plate having good heat conduction, and a temperature control mechanism such as a heater is built in. The temperature of the holding unit 3 is set at about 45 ° C., the resin base material that is the substrate 10 is set, and the base material temperature immediately after the start of printing is increased in advance, from the start of printing to the end of printing. It is possible to suppress the substrate temperature difference. Further, for example, a water cooling or air cooling mechanism may be provided in the holding unit 3 instead of the heater. Thereby, the temperature rise can be suppressed by allowing the heat of the base material in the printing process to escape through the holding unit 3.

Reference numeral 8 denotes an information conversion unit for converting the print information of the substrate 10 to an arbitrary angle, and converts the print information of the substrate 10 on the holding unit 3 rotated by an arbitrary angle by the rotation driving unit 7. The print information includes the color type of the ejected ink, the moving distance of the ink ejecting unit 2, and the like.
Reference numeral 9 denotes a measuring unit for measuring and positioning a reference position, and positions a reference print start position and end position. The measuring unit 9 positions a reference position (print start position) before a first printing process described later, and positions the reference position again before the second printing process. This is because the reference position is shifted by rotating the holding unit 3.

The operation (ink jet printing method) of the ink jet printing apparatus of the present invention having the above configuration will be described. FIG. 2 is a diagram for explaining an inkjet printing method (procedure) according to the embodiment of the present invention. First, the substrate 10 is attached on the holding unit 3.
Next, ink of a predetermined color is ejected from the ink ejection unit 2, the ink is adhered to the substrate 10, and the ink ejection unit 2 and the UV irradiation unit 4 are connected while irradiating the ink with ultraviolet rays from the UV irradiation unit 4. It is moved by the first drive unit 5 in the width direction of the substrate 10 (the direction indicated by the arrow A in FIG. 2).

Next, the ink discharge unit 2 is returned to the initial position which is the reference position, and at the same time, the holding unit 3 is moved by a predetermined amount (one pitch) in the height direction of the substrate 10 (direction B orthogonal to the arrow A in FIG. 2). . Thereafter, as described above, the ink is adhered to the printing material 10 while moving the ink ejection unit 2 and the UV irradiation unit 4 in the width direction of the printing material 10.
In addition, while returning the ink ejection unit 2 to the initial position, the holding unit 3 is moved by a predetermined amount in the height direction of the printing material 10, and the ink ejection unit 2 is allowed to adhere the ink from the ink ejection unit 2 to the printing material 10. Printing may be performed to return to the initial position. However, in this case, it is necessary to provide the UV irradiation unit 4 on both sides of the ink discharge unit 2.
In this way, printing is performed on the surface of the substrate 10 while alternately repeating the movement of the ink ejection unit 2 and the UV irradiation unit 4 by the first driving unit 5 and the movement of the holding unit 3 by the second driving unit 6. A first printing process is performed.

  Next, while returning the holding unit 3 of the substrate 10 to the initial position at the start of printing, the measuring unit 9 measures the reference position of the substrate 10 that has finished the first printing process again, and positions the holding unit 3. The rotation drive unit 7 is rotated at an arbitrary angle. The information conversion unit 8 converts the printing information of the printing material 10 rotated along with the rotation of the holding unit 3 into the arbitrary angle.

Next, again, the linear movement of the ink ejection unit 2 and the UV irradiation unit 4 by the first driving unit 5 and the linear movement of the holding unit 3 by the second driving unit 6 are repeated again and again to be printed. A second printing step for printing on the surface of 10 is performed.
As described above, in the present embodiment, the printing object 10 is printed with an arbitrary angle between the first printing step and the second printing step, thereby causing printing spots of the printed image due to insufficient positioning accuracy of the printing apparatus. Can be eliminated.

Further, in the embodiment of the present invention, the printing information instruction unit 11 that instructs the printing information to the first printing process and the second printing process is provided. 3, 4, and 5 are diagrams illustrating the function of the print information instruction unit 11.
That is, as shown in FIG. 3, the print information instruction unit 11 instructs the print information of the first printing process and performs the first printing process as described above. Next, in a state where the rotation center point of the holding unit 3 coincides with the rotation reference point of the print information, the print information of the second printing process in which the print information is rotated is instructed, and the hold unit 3 performs the same operation as the print information. Then, the second printing process is performed. Thereby, it is possible to eliminate printing misalignment between printing processes without requiring reading of position information or positioning process between the first printing process and the second printing process.

  Further, as shown in FIG. 4, in the print information instruction unit 11, after printing in each printing process, correction such as enlargement of the print information in advance by the size contracted by the thermal expansion of the substrate 10 is performed. By doing so, a predetermined print image can be obtained, so that a printing shift between printing processes can be eliminated.

  Further, as shown in FIG. 5, in the print information instruction unit 11, the print end of the print information in the second print process is shifted from the end of the print information in the first print process to the print area side, thereby printing. Edge protrusion due to printing misalignment between processes can be eliminated.

  In the present embodiment, the ink discharge unit 2 and the UV irradiation unit 4 are attached to the first drive unit 5 via the carriage 21. However, the ink discharge unit 2 and the UV irradiation unit 4 are fixed, It is good also as a structure which attaches the 1st drive part 5 to the 2nd drive part 6. FIG. In this case, the holding unit 3 that holds the substrate 10 moves in addition to the B direction of the linear movement and the C direction of the rotational movement in FIG. 1 and also in the A direction, which is a linear direction orthogonal to the B direction. be able to.

  As described above, in the present invention, the surface that has been printed once is printed by changing the angle, the starting position and the ending position that are the reference in the second printing process in the first printing process, By converting the print information of the printed material into an angle by the information conversion unit, even in a printing apparatus in which there is an ink ejection direction error between the ink ejection unit and the holding unit and a feeding error of the printing material, the number of times of printing is the same as the conventional number of times. Inkjet printing without print spots is possible.

1 is a perspective view showing a schematic overall configuration of an inkjet printing apparatus according to an embodiment of the present invention. It is a figure explaining the inkjet printing method of embodiment of this invention. It is a figure explaining the method of eliminating the printing gap between printing processes in the inkjet printing method according to the embodiment of the present invention. It is a figure explaining the method of eliminating the printing shift between the printing processes by the influence of heat in the inkjet printing method of embodiment of this invention. In the ink jet printing method according to the embodiment of the present invention, it is a diagram for explaining a method of eliminating the end protrusion due to printing misalignment between printing steps. It is figure (a), (b), (c) explaining the problem of the conventional inkjet printing method. It is a perspective view which shows the general whole structure of the conventional inkjet printing apparatus. It is a figure explaining the conventional inkjet printing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2 Ink discharge part 21 Carriage 3 Holding part 4 Ultraviolet (UV) irradiation part 5 1st drive part 6 2nd drive part 7 Rotation drive part 8 Information conversion part 9 Measurement part 10 Printed material (resin base material) )
11 Print information instruction section

Claims (11)

Using an inkjet printing apparatus that includes at least an ink discharge unit that discharges ink, a holding unit that holds a printed material, and an ultraviolet irradiation unit that irradiates ultraviolet rays on the surface of the printed material, ultraviolet curable ink is printed In the ink jet printing method of performing ink jet printing by discharging the ink, and then curing and fixing the ink on the printing material by irradiating with ultraviolet rays,
An operation of ejecting UV curable ink while moving the holding portion relative to the ink ejecting portion in one direction, and irradiating with UV rays, and moving by one pitch perpendicular to the one direction. A first printing step in which the operation is alternately and repeatedly printed on the surface of the substrate,
A direction changing step in which the holding portion is at an angle not parallel to the first printing step;
An operation of ejecting the ink and irradiating it with ultraviolet rays while moving the printing material in one direction with respect to the direction-changed angle, and moving by one pitch perpendicular to the direction-changed direction. A second printing step of alternately and repeatedly printing on the surface of the substrate,
An ink-jet printing method comprising:   The inkjet printing method according to claim 1, wherein a reference position is printed in the first printing step, and the reference position is measured and positioned in the second printing step.   In the first printing step, a reference position is printed, and the reference position is measured and positioned. In the second printing step, the print information of the printing object is converted into an arbitrary angle with respect to the reference position. The inkjet printing method according to claim 1, wherein printing is performed. The printing information origins of the first printing process and the second printing process coincide with each other,
The rotation reference point set at an arbitrary position from the print information origin of the second printing step is matched with the rotation center point of the holding unit,
The printing is performed by matching an arbitrary rotation angle centered on the rotation reference point of the print information in the second printing step with a rotation angle centered on the rotation center point of the holding unit. Item 10. The inkjet printing method according to Item 1.   The inkjet printing method according to claim 1, wherein the substrate is a translucent resin substrate. The integrated light quantity per unit area received from the ultraviolet irradiation part of each of the first printing step and the second printing step is printed on the surface of the substrate at 3000 mJ / cm ² or less. Item 6. The inkjet printing method according to Item 5.   6. The ink jet printing method according to claim 5, wherein the temperature of the holding part is controlled so that a temperature change ΔT of the printing material in a printing process is 10 ° C. or less.   6. The ink jet printing method according to claim 5, wherein the printing information is printed by information obtained by correcting a printing deformation amount of the printing information due to thermal distortion of the printing material generated in the printing step.   In the first printing step and the second printing step, when printing the same printing region end, the printing in the second printing step is performed on the printing end of the printing information in the first printing step. The inkjet printing method according to claim 5, wherein printing is performed by shifting a printing end portion of information toward a printing region side. An inkjet printing apparatus for carrying out the inkjet printing method according to any one of claims 1 to 9,
A first drive unit that linearly moves the ink discharge unit and the ultraviolet irradiation unit;
Outside the second drive unit that linearly moves the holding unit that holds the printed material in a direction orthogonal to the moving direction of the ink discharge unit and the ultraviolet irradiation unit,
An ink jet printing apparatus comprising: a rotation driving unit that rotates the holding unit.   The inkjet printing apparatus according to claim 10, wherein the holding unit further includes a temperature control mechanism.

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