JP6146084B2 - Printing method - Google Patents

Description

  The present invention relates to a printing method.

There has been developed a printing apparatus that forms an image by ejecting ultraviolet curable ink onto a medium and irradiating the ink that has landed on the medium with light. Since many ultraviolet curable inks have a relatively high viscosity, the viscosity of the ink is lowered by heating the ink before ejection.

Patent Document 1 discloses that a head that discharges heated ink and the temperature of a recording medium on which printing is performed by the head are controlled to a target set temperature.

Japanese Patent Laid-Open No. 2003-13692

When a difference in the temperature of the medium occurs during printing, a difference in the print quality occurs because the way in which the ink wets and spreads is different. For example, when the temperature of the medium fluctuates in one print job, the print quality in the print job fluctuates. Although there is a concept of thorough temperature control in order to maintain the highest print quality, there are many cases where it is only necessary to maintain the same print quality within a print unit such as a print job although it is not the highest print quality. In this case, there is also a demand for cost reduction because the highest print quality is not output. That is, it is desired to maintain the same print quality within one printing unit while suppressing the cost.

The present invention has been made in view of such circumstances, and an object of the present invention is to maintain the same level of print quality within one print unit while suppressing cost.

The main invention for achieving the above object is:
A head that ejects photocurable ink onto the medium, an irradiation unit that irradiates the medium with light, a transport unit that transports the medium, and a temperature measurement unit that measures a temperature associated with the medium,
A first step of conveying the medium, irradiating the medium with the light and measuring a temperature associated with the medium;
A second step of starting image printing by discharging the photocurable ink onto the medium after the temperature related to the medium becomes equal to or higher than the first temperature;
It is a printing method characterized by having.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is an overall configuration block diagram of a printer 1. FIG. 2 is a schematic side view of the printer 1. FIG. It is a graph showing the height of the measured ink. It is a flowchart of the printing operation in this embodiment. 5 is a flowchart of print processing in the present embodiment. It is explanatory drawing of a duty restriction | limiting. It is explanatory drawing of edge periphery thinning-out process. It is a graph showing the ink height when the edge periphery thinning process is performed.

At least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
A head that ejects photocurable ink onto the medium, an irradiation unit that irradiates the medium with light, a transport unit that transports the medium, and a temperature measurement unit that measures a temperature associated with the medium,
A first step of conveying the medium, irradiating the medium with the light and measuring a temperature associated with the medium;
A second step of starting image printing by discharging the photocurable ink onto the medium after the temperature related to the medium becomes equal to or higher than the first temperature;
It is a printing method characterized by having.
When the temperature associated with the medium is low and when the temperature is high, an image may be printed with different quality due to a change in the viscosity of the landing ink. For this reason, there is a case where it is desired to continuously print images while reducing temperature fluctuations related to the medium during printing, but with the above configuration, the irradiation unit can be used without providing a separate heating means. The printing of the image can be started after the temperature related to the medium is raised to the first temperature or higher. Then, it is possible to continuously print the image with the print quality when the temperature related to the medium is maintained above the first temperature. That is, since it is not necessary to separately provide a device for raising the temperature related to the medium, it is possible to maintain the same print quality within one printing unit while suppressing the cost.

In this liquid ejecting apparatus, it is preferable that the photocurable ink is ejected onto the medium in the first step.
Although the reaction heat is generated when the photocurable ink is cured, the temperature of the medium can be increased by the reaction heat by discharging the photocurable ink onto the medium even before the start of image printing.
And before the start of image printing, the temperature of the medium can be increased using not only the light from the irradiation section but also the reaction heat.

The image forming apparatus further includes a support member that supports the medium and a cooling unit that lowers a temperature related to the medium, and measures a temperature related to the medium after the printing of the image is started, and relates to the medium. It is desirable to operate the cooling unit when the temperature becomes a second temperature higher than the first temperature.
By doing in this way, the heat by the irradiated light is also transmitted to the support member. The transmitted heat is further transmitted to the medium to be transported. That is, the temperature of the conveyed medium can be increased using the heat capacity of the support member. Moreover, it can suppress that the temperature relevant to a medium rises too much by a cooling part. And the dispersion | variation in print quality by the temperature relevant to a medium rising too much can be suppressed.

The image forming apparatus further includes a support member that supports the medium and a cooling unit that lowers a temperature related to the medium, and measures a temperature related to the medium after printing of the image and relates to the medium. When the temperature is equal to or higher than the second temperature higher than the first temperature, the cooling strength of the cooling unit may be made stronger than before the temperature reaches the second temperature.
Also by doing in this way, the heat by the irradiated light is also transmitted to the support member. The transmitted heat is further transmitted to the medium to be transported. That is, the temperature of the conveyed medium can be increased using the heat capacity of the support member. Moreover, it can suppress that the temperature relevant to a medium rises too much by a cooling part. And the dispersion | variation in print quality by the temperature relevant to a medium rising too much can be suppressed.

The head is capable of discharging a plurality of color curable inks, and it is desirable to limit a maximum discharge amount per unit area of the specific color photocurable ink among the plurality of color curable inks. .
By doing in this way, the discharge amount of the photocurable ink of the color which is easy to cause the fall of print quality with a temperature rise can be reduced, and the fall of print quality can be suppressed.

In addition, it is preferable that the photocurable ink is ejected so that the ejection amount of the photocurable ink is reduced in a partial region of the image.
By doing so, for example, it is possible to suppress an increase in the ink height around the edge of the image and to suppress a decrease in print quality.

=== Embodiment ===
FIG. 1 is a block diagram of the overall configuration of the printer 1, and FIG. 2 is a schematic side view of the printer 1. The printer 1 that has received print data such as a print job from the computer 100, which is an external device, controls the units (conveyance unit 20, head unit 30, ultraviolet irradiation unit 80, cooling fan 90) by the controller 10, and the paper S Print an image on Further, the detector group 40 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

The controller 10 is a control unit for controlling the printer 1. The interface unit 11 is for transmitting and receiving data between the computer 100 as an external device and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit using the unit control circuit 14 in accordance with a program stored in the memory 13.

The transport unit 20 includes a feed roll 21, a take-up roll 22, and a platen 23. The feeding roll 21 supplies a medium such as paper S. The feeding roll 21 is connected to a motor (not shown), and its rotation is controlled by the controller 10. The take-up roll 22 takes up and collects a medium such as the paper S. The winding roll 22 is also connected to a motor (not shown), and its rotation is controlled by the controller 10. Further, the transport unit 20 includes a platen 23 (corresponding to a support member) for supporting the paper S between the feeding roll 21 and the take-up roll 22. In this way, the paper S supplied from the feeding roll 21 is supported by the platen 23,
An image can be formed by ejecting ink onto the paper S on the platen 23. Further, as will be described later, the heat of the sheet S that has been heated by the ultraviolet irradiation is transmitted to the platen 23, whereby the heat is stored in the platen 23 itself. The stored heat is transmitted to the succeeding paper S. Therefore, the temperature of the paper S conveyed using the heat capacity of the platen 23 can be increased.

In FIG. 2, the white ink head unit 30W, the yellow ink head unit 30Y, the magenta ink head unit 30M, the cyan ink head unit 30Cy, and the black ink head unit 30K are cleared from the upstream side in the transport direction of the paper S. An ink head unit 30Cl is disposed. In the case where the ink color is not specified, only the symbol “30” is given as the overall head unit.

These head units 30 are for ejecting ink droplets onto the paper S and have a plurality of heads. A plurality of nozzles that are ink discharge portions are provided on the lower surface of the head. By arranging a plurality of heads in a staggered manner in the head unit 30, it is possible to form a wide image in the width direction of the paper S. Each nozzle is provided with a pressure chamber (not shown) containing ink and a drive element (piezo element) for changing the volume of the pressure chamber to eject ink. In the present embodiment, the ink ejected from these head units 30 is ultraviolet curable ink (UV ink).

Further, the printer 1 includes ultraviolet irradiation units 80W, 80Y, 80M, 80Cy, 80K, and 80Cl corresponding to the downstream side of each head unit 30. These ultraviolet irradiation units are for temporarily curing ink landed on the paper S. Further, an ultraviolet irradiation unit 80last is provided on the most downstream side. UV irradiation unit 80last
Is for main-curing the ink landed on the paper S. Temporary curing is to cure the surface of the paper S to such an extent that the ink does not flow.
The ink is cured to the inside of the upper ink.

The detector group 40 includes a temperature measuring device 41. The temperature measuring device 41 employed in the present embodiment is a non-contact type temperature measuring device that receives infrared energy and measures temperature. The temperature measuring device 41 measures the temperature of the conveyed medium and sends the measurement result to the controller 10. In this case, the temperature of the medium is directly measured.
The temperature of the sheet S may be indirectly measured by measuring the temperature of the platen 23.

A cooling fan 90 that blows air to the platen 23 is provided below the platen 23. The operation of the cooling fan 90 is controlled by the controller 10. And
The temperature of the sheet S is indirectly decreased through the platen 23. Here, the temperature of the sheet S is decreased using the cooling fan 90, but the temperature may be decreased using a Peltier element or the like.

FIG. 3 is a graph showing the measured ink height. FIG. 3 shows the height of ink when so-called solid printing (printing by discharging ink with a discharge duty of 100%) is performed on a sheet. The horizontal axis represents the distance from the edge of the paper, and the vertical axis represents the amount of swelling due to ink.

Here, it is assumed that ink is not landed from the edge of the paper to 250 μm, and solid printing is performed on the inner area after 250 μm from the edge of the paper.

Referring to FIG. 3, the ink height increases after 250 μm where solid printing is performed, and 4
The ink height peaks in the range from 00 μm to 550 μm. However, the ink height decreases after the paper position is 500 μm and converges to a certain height.

In this way, even when solid printing is performed uniformly, a phenomenon in which ink swells at a specific position as shown in FIG. 3 occurs. This is considered to be caused by the ink flowing near the edge after the ink has landed on the paper S. When the ink is cured by irradiating with ultraviolet rays in this state, the ultraviolet rays do not reach the inside of the portion where the ink height is high, so that wrinkles are generated at that portion. That is, wrinkles are generated only in a specific area near the edge of the image.

As described above, the generation of wrinkles is considered to be related to the fluidity of ink, but the fluidity of ink is related to its viscosity. Since the viscosity of the ink changes according to the temperature, the degree of wrinkles generated according to the temperature of the medium also changes.

Although it is a wrinkle generated for such a reason, it is not preferable that the wrinkle is generated or not generated in one print job because the print quality is not constant. On the other hand, even if wrinkles occur, depending on the degree, the print quality may be determined to be within an allowable range.

In the present embodiment, fluctuations in print quality within one print job are suppressed by the following method.

FIG. 4 is a flowchart of the printing operation in the present embodiment.
First, the controller 10 of the printer 1 receives a print job transmitted from the computer 100 (S102).

When the print job is received, the controller 10 of the printer 1 causes the transport unit 20 to transport the medium. Further, the ultraviolet irradiation on the paper S is started by the ultraviolet irradiation device 80 (S104). At this time, the sheet S is irradiated with ultraviolet rays while being conveyed, but the conveying speed can be made slower than when printing an image.

Next, the temperature of the paper S is measured by the temperature measuring device 41. Then, it is determined whether or not the measured temperature of the sheet S is 30 ° C. (corresponding to the first temperature) or more (S106). And
When the temperature of the paper S is not 30 ° C. or higher, the ink is not ejected and the ultraviolet irradiation is continued.

On the other hand, if the measured temperature of the paper S is 30 ° C. or higher, the printing process is started (S108).

FIG. 5 is a flowchart of the printing process in this embodiment.
In the printing process (S108), ink is ejected based on the print job sent from the computer 100. Then, an image is formed on the paper S (S1081).

During the ejection of ink, the temperature of the paper S is measured by the temperature measuring device 41 at predetermined time intervals. Then, it is determined whether or not the measured temperature of the sheet S is 40 ° C. (corresponding to the second temperature) or higher (S1082).

When the temperature of the sheet S is 40 ° C. or higher, the cooling fan 90 is operated (S10).
83). On the other hand, when the temperature of the paper S is not 40 ° C. or higher, the cooling fan 90 is stopped (S1084).

Next, it is determined whether printing of the print job sent from the computer 100 is completed (S1085). If printing has not been completed, the process returns to step S1081 to perform printing. On the other hand, if printing has been completed, the printing process (S108) is terminated.

Since the viscosity of the ink changes depending on whether the temperature of the paper S is low or high, an image may be printed with different quality. For this reason, there is a demand for continuously printing images while reducing temperature fluctuations of the paper S being printed. In this embodiment, the temperature of the paper S is raised by the irradiated ultraviolet rays. Therefore, printing of an image can be started after the temperature of the paper S is raised to 30 ° C. or higher without providing a means for raising the temperature of the paper S separately. And 30 ° C
As described above, images can be continuously printed with the print quality when the temperature of the paper S is maintained. That is, since it is not necessary to separately provide a device for raising the temperature of the paper S, it is possible to make the print quality uniform within a print unit such as a print job while suppressing costs.

In step S1083 and step S1084, since the operation of the cooling fan 90 is controlled and stopped, it is possible to prevent the temperature of the paper S from rising excessively. And the change of the printing quality by the paper S rising too much can be suppressed.

In step S104, the paper is transported and the ultraviolet rays are irradiated without ejecting ink. However, ink can be ejected in step S104. In this case, reaction heat is generated when the ultraviolet curable ink is cured, and therefore the temperature of the medium can be increased by utilizing not only the ultraviolet irradiation heat but also the reaction heat of the ultraviolet curable ink.

Further, when ink is ejected in step S104, solid printing can be performed on the entire surface of the paper (that is, ink is ejected with a higher ejection duty than when printing an image). By doing so, the reaction heat when the ultraviolet curable ink is cured can be maximized, so that the temperature of the paper can be quickly increased before the start of printing.

In step S1083, the cooling fan 90 is operated, and in step 1084, the cooling fan 90 is stopped. In step S1083, the cooling fan 90 is operated weakly, and in step S1084, the cooling fan 90 is operated strongly. Also good. Also by doing this, it is possible to suppress the temperature of the paper from rising too much. In addition, it is possible to suppress variations in print quality due to an excessive increase in the paper temperature.

Even when the generation of some wrinkles is allowed as described above, the generation of wrinkles has never been suppressed. Therefore, the following processing can be performed while performing the above-described printing operation.

Wrinkles are likely to occur at the edge of an image when the ink ejection duty is high, such as so-called solid printing. Also, depending on the type of ink, there are cases where wrinkles are likely to occur at the edge of an image and are difficult to occur. Therefore, in particular, when there is an ink that is likely to be wrinkled at the end, the maximum discharge duty of the ink can be limited to less than 100%.

FIG. 6 is an explanatory diagram of duty limitation. In the ink employed in the present embodiment, for example, yellow ink is most likely to cause wrinkles at the edge of the image. In such a case, for example, the discharge duty of yellow ink is limited to 95% at the maximum. By doing so, it is possible to limit the discharge duty to such an extent that wrinkles are hardly generated at the edge of the ink image, thereby suppressing the deterioration of the print quality.

In addition, the following processing can be performed to suppress the occurrence of wrinkles at the end.
FIG. 7 is an explanatory diagram of edge peripheral thinning processing. In FIG. 7, a hatched place is a place where an image is formed, and a place where a gap is provided is a place where an image is not formed regardless of image data.

The cause of wrinkles at the edge of the image was the rise of ink near the edges. Therefore, FIG.
As shown in FIG. 4, a process of thinning out dot formation near the edge is performed. The dot is 200 from the edge of the image.
The height of the ink was high within a range of about μm. Therefore, no dot is formed at a position corresponding to this, that is, a position corresponding to several pixels from the edge of the image. Also by doing in this way, generation | occurrence | production of the wrinkle of an edge part can be suppressed.

FIG. 8 is a graph showing the ink height when the edge periphery thinning process is performed. As a result of performing the edge periphery thinning process in this way, it can be seen that the dot height in the vicinity of 200 μm from the image edge is suppressed. In this way, the generation of wrinkles at the end of the sheet can be suppressed.

=== Other Embodiments ===
In the above-described embodiment, the platen 23 has been described as a support member that supports the paper S, but the form of the support member is not limited thereto. For example, a drum form around which the paper S is wound may be used.

Moreover, in the said embodiment, although 1st temperature was 30 degreeC and 2nd temperature was 40 degreeC, these temperature can be changed according to the quality of printed matter.

In the above-described embodiment, the printer 1 has been described as a printing apparatus. However, the printer 1 is not limited to this, and other fluids (liquids and liquids in which particles of functional materials are dispersed, gels, and the like) are not limited thereto. It is also possible to embody the present invention in a liquid ejecting apparatus that ejects or ejects a fluid. For example, color filter manufacturing device, dyeing device, fine processing device, semiconductor manufacturing device, surface processing device, 3D modeling machine, gas vaporizer, organic EL manufacturing device (especially polymer EL)
The same technology as that of the above-described embodiment may be applied to various devices to which inkjet technology is applied such as a manufacturing device), a display manufacturing device, a film forming device, and a DNA chip manufacturing device. These methods and manufacturing methods are also within the scope of application.

The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About the head>
In the above-described embodiment, ink can be ejected using a piezoelectric element, and various ink ejection methods such as a method of generating bubbles in a nozzle by heat can be employed.

1 Printer, 10 Controller, 11 Interface section,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 21 feeding roll, 22 take-up roll,
23 platen,
30 head units, 31 heads,
40 detector groups, 41 temperature measuring device,
80 UV irradiation unit, 90 cooling fan,
100 computers

Claims (5)

Printing comprising: a head that ejects photocurable ink onto a medium; an irradiation unit that irradiates the medium with light; a conveyance unit that conveys the medium; and a temperature measurement unit that measures a temperature associated with the medium. A printing method in an apparatus ,
A first step of conveying the medium, irradiating the medium with the light and measuring a temperature associated with the medium;
A second step of starting image printing by discharging the photocurable ink onto the medium after the temperature related to the medium becomes equal to or higher than the first temperature;
I have a,
In the first step, the photocurable ink is ejected onto the medium . The printing method according to claim 1, comprising:
The printing apparatus further includes a support member that supports the medium, and a cooling unit that reduces a temperature related to the medium,
The temperature related to the medium is measured after the printing of the image is started, and the cooling unit is operated when the temperature related to the medium becomes a second temperature higher than the first temperature. Printing method. The printing method according to claim 1, comprising:
The printing apparatus further includes a support member that supports the medium, and a cooling unit that reduces a temperature related to the medium,
After the printing of the image is started, the temperature related to the medium is measured, and when the temperature related to the medium becomes equal to or higher than a second temperature higher than the first temperature, the cooling strength of the cooling unit is set to the first temperature. A printing method characterized in that the printing method is stronger than before two temperatures. A printing method according to any one of claims 1 to 3 ,
The head is capable of discharging a plurality of colors of photocurable ink,
A printing method characterized by limiting a maximum discharge amount per unit area of a photocurable ink of a specific color among the photocurable inks of a plurality of colors. A printing method according to any one of claims 1 to 4 ,
A printing method, wherein the photocurable ink is ejected so that a discharge amount of the photocurable ink is reduced in a partial region of the image.