JP6608300B2 - Image forming method - Google Patents

Description

  The present invention relates to an image forming method in which a plurality of ink layers are stacked.

  The thermal transfer image receptor described in Patent Document 1 is obtained by heating a thermal transfer paper {thermal transfer ribbon} in which a heat-meltable color material layer is provided on a substrate with a thermal head, so that a color can be applied to a substrate such as a plastic film. The material layer is selectively thermally transferred to form a color image. In this thermal transfer image receptor, since the adhesive layer is provided on the back surface not subjected to the transfer of the color material layer, the smoothness of the surface to which the color material layer is transferred can be ensured. An image can be formed.

JP-A 63-307989

  Digital on-demand printing such as hot melt transfer technology does not require the preparation of a master plate like ordinary screen printing or gravure printing, and can respond to high-volume and low-volume printing at high speed and low cost. The number of cases used for various decorative printing on articles is increasing.

  In recent years, decorative printing has been applied to smartphones, mobile phones and other small portable electronic devices, and further, the demand for high design by decorative printing has increased, so in addition to conventional full-color printing, For example, there is a demand for high-quality decoration using a combination of various printing methods such as metallic printing and concealing printing for hiding the background. When performing such decorative printing by hot melt transfer, in addition to ink ribbons for the three primary colors of cyan, magenta, and yellow, there are many types such as ink ribbons for metallic printing and ink ribbons for concealment printing. In order to overlap the ink layers with the ink ribbon, it is necessary to further cleanly superimpose the ink layer on the ink layer having a thickness that has not been conventionally achieved.

  For example, in printing on an infrared transmission / reception window part of a smartphone, an ink layer is not formed on the infrared window part, but a number of ink layers are laminated on the peripheral part of the infrared window part by thermal melt transfer printing. On the ink layer laminated in this way, an ink layer having infrared transparency is formed by hot melt transfer printing so as to cover the infrared window portion.

  However, when a plurality of ink layers are laminated like the peripheral portion of the infrared window portion, a step is generated between the ink layers or within the ink layers due to the difference in the dot pattern of each ink layer. When an ink layer having infrared transparency is further formed on the laminated ink layer by thermal melt transfer, when a thin ink ribbon of about several μm is used, the ink cannot be transferred following the step. Will be insufficient, and printing will be lost. On the other hand, if the printing energy given to the ink ribbon is increased so as to follow the step, the printing energy given to the non-step region becomes excessive, and the ink on the ink ribbon melts excessively. The surface of the layer is matte, that is, the surface is not glossy with a large surface roughness, and the appearance quality is degraded.

  On the other hand, when a thick ink ribbon is used to make it easier to follow the level difference, the transfer property of the ink ribbon deteriorates, and it becomes difficult to clearly separate the area to be printed and the non-printing area, and the edges of the printing area are clearly displayed. There is an adverse effect such as a decrease in the sharpness of the image due to the disappearance.

  Therefore, the present invention provides a further ink layer on the laminated ink layer so that there is no printing omission and maintains high definition even when a step is generated by laminating a plurality of ink layers. An object of the present invention is to provide an image forming method that can be formed.

In order to solve the above problems, an image forming method of the present invention is an image forming method in which a functional ink layer is laminated on a plurality of base ink layers laminated on a substrate as a pattern of ink dots. layer is laminated on the plurality of underlying ink layer by providing a printing energy to the ink medium, and have your to each of the plurality of base ink layer, a set of regions and ink dot exists a set of ink dots based on the pattern The printing energy applied to the ink medium is controlled according to the level difference between the area where the body does not exist and the area where the ink dot aggregate exists and the ink dot aggregate does not exist due to the functional ink layer. The region and the step are covered .
As a result, even when there is a level difference in the underlying ink layer, the functional ink layer can be formed without causing printing loss or deterioration in appearance when the functional ink layer is laminated from above the underlying ink layer. Can be formed.

In the image forming method of the present invention, the history acquisition step of acquiring print history for a plurality of underlying ink layer, on the basis of the obtained result by history acquisition step, a step difference occurs Te each layer smell of the plurality of base ink layer It is preferable to have a step area calculation step for calculating the area. Each of the plurality of base ink layers is printed on the base material or another base ink layer by applying printing energy to the ink medium, and the print history includes the number of layers of the plurality of base ink layers and the plurality of base ink layers. The ink dot pattern in each layer of the underlying ink layer, the ink composition of each ink medium used to form the plurality of underlying ink layers, and each of the ink media when forming each of the plurality of underlying ink layers And the printing energy applied to the region.
Since the stepped area is calculated based on the printing history of the underlying ink layer, it is possible to accurately estimate the position, range, shape, etc. of the step, thereby accurately controlling the printing energy applied to the ink medium. It is possible to perform well.

The image forming method of the present invention preferably includes a print pattern correction step for correcting a print pattern for forming the functional ink layer based on the calculation result of the step region calculation step. In this print pattern correction step, the number of layers of the base ink layer is compared with the sum of the stacked ink dots for each region in the plane direction of the base material, and the functional ink layer is formed based on the comparison result. It is preferable to correct the printing pattern for
Thereby, it is possible to perform highly accurate correction with simple arithmetic processing.

In the image forming method of the present invention, for the area where the comparison result is smaller than the threshold value, the printing energy given for forming the ink dots in the corresponding area in the functional ink layer with respect to the area where the comparison result is equal to or larger than the threshold value. It is preferable to enlarge it.
As a result, the functional ink layer can be formed so as to follow the step and cover the step in the stepped region, and the functional ink layer maintaining a high texture can be formed in the region without the step. .

In the image forming method of the present invention, the ink medium is transfer sheet ink having a thermally fusible are laminated, printed energy is preferably a thermal energy generated by the power supply to the heater.
Thereby, the functional ink layer which does not have a printing omission or a deterioration of a texture can be laminated | stacked on the base ink layer in which the level | step difference produced by hot-melt transfer printing.

  According to the present invention, even when a step is generated by stacking a plurality of base ink layers, further ink is maintained on the stacked base ink layers so that there is no printing omission and high sharpness is maintained. A layer can be formed.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. (A) is a cross-sectional view showing a process of transferring ink from the top of the three underlying ink layers by the image forming apparatus shown in FIG. 1, and (B) is a functional ink layer formed on the three underlying ink layers. It is sectional drawing which shows the structure of the image-formed product made. It is a flowchart which shows the correction | amendment procedure of the data of the printing pattern of a functional ink layer. (A) is a photomicrograph of a cross-sectional view of an image formed product produced by the image forming method according to the embodiment of the present invention, (B) is an enlarged view of the 4B portion of (A), and (C) is conventional image formation. The micrograph of the cross-sectional view of the image formation produced by the method, (D) is an enlarged view of the 4D portion of (C).

  Hereinafter, an image forming apparatus used in an image forming method according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus 10 according to the present embodiment. As illustrated in FIG. 1, the image forming apparatus 10 includes a heater 11, a drive unit 12, a control unit 13, a calculation unit 14, and a memory 15. FIG. 2A is a cross-sectional view showing a process of transferring ink from above the three underlying ink layers 31, 32, 33 by the image forming apparatus 10, and FIG. , 32, 33 are cross-sectional views showing a configuration of an image formed product 40 in which a functional ink layer 34 is formed. 2A and 2B are cross-sectional views along a direction L in which three base ink layers 31, 32, and 33 and a functional ink layer 34 are sequentially laminated on the substrate 22. The upper side of the stacking direction L shown in FIGS. 2A and 2B may be referred to as the upper direction, and the lower side may be referred to as the lower direction. The plane direction P of the substrate 22 is a direction orthogonal to the stacking direction L. Here, as the base ink layer, for example, color ink layers such as three primary colors of cyan, magenta, and yellow for decoration, a metallic ink layer for giving a metallic luster, and the back side of the image formed product are made invisible. For example, a concealing ink layer made of a light-impermeable ink or a black ink can be used. Examples of the functional ink layer include an ink layer that transmits only light having a specific wavelength and a protective ink layer that protects the base ink layer.

  As shown in FIG. 2A, the heater 11 is arranged so as to face a predetermined position in the plane direction P with respect to the base material 22, and an ink medium is provided between the heater 11 and the base material 22. The transfer sheet 21 is arranged. The transfer sheet 21 has a configuration in which an ink layer 21b having heat melting properties is laminated on a base film 21a made of PET (polyethylene terephthalate) or other flexible material. The heater 11 is biased toward the base material 22 by a biasing member (not shown) such as a spring so as to come into contact with a predetermined position on the upper surface 21c of the base film 21a. The lower surface 21d of 21b is in contact with the substrate 22 or the surface of the ink layer laminated on the substrate 22.

  Metal wiring is formed on the heater 11 in a predetermined pattern, and the heater 11 generates heat when the wiring is energized. The thermal energy generated by the heat generated by the heater 11 is applied to the transfer sheet 21 that contacts the heater 11, whereby the ink in the ink layer 21 b of the transfer sheet 21 is melted. The melted ink is transferred onto the substrate 22 or a base ink layer laminated on the substrate 22. Energization of the heater 11 is controlled by the control unit 13 and energized to a part or all of the wirings so as to correspond to the print pattern of the ink layer to be formed. Here, the print pattern is an energization pattern for forming ink dots corresponding to the image pattern of the ink layer to be formed. As a result, the ink in the region corresponding to the heated wiring is melted and transferred from the transfer sheet 21 onto the substrate 22 or the laminated base ink layer, and a preset ink dot pattern is formed.

  The drive unit 12 is a mechanism that moves the transfer sheet 21 and the base material 22 in synchronization. The control unit 13 moves the transfer sheet 21 and the base material 22 in accordance with the timing of energization of the heater 11. Be controlled.

  The control unit 13 controls the operation of the heater 11 and the drive unit 12, instructs the calculation unit 14 to perform calculation, and controls the printing energy applied to the transfer sheet 21. This printing energy is thermal energy generated by the heat generated by the heater 11.

As the thermal energy control, in forming a plurality of base ink layers to be stacked on the substrate 22, the heater 11 is formed so that an ink dot pattern is formed according to a print pattern set in advance for each base ink layer. In FIG. 5, the wirings at positions corresponding to the ink dot patterns are energized. The energization pattern for each underlying ink layer is stored in the memory 15.
In this embodiment, an example in which the base ink layer is formed by hot melt transfer printing is described. However, if it is possible to acquire the print history of the base ink layer, a method other than hot melt transfer, for example, heat The base ink layer may be formed by sublimation printing or ink jet printing.

  On the other hand, in the functional ink layer that is laminated on the plurality of already formed base ink layers, the control unit 13 prints the printing energy given to the transfer sheet 21 in accordance with the steps of the ink dots in each of the plurality of base ink layers. To control. Regarding the step, the calculation unit 14 calculates a region where the step is generated in the plane direction P of the base material 22 based on the print history regarding the plurality of base ink layers. Here, the area | region in the plane direction P of the base material 22 is an area | region divided | segmented so that it might correspond to the ink dot or the aggregate | assembly of an ink dot in each ink layer, for example. In addition, for example, as shown in FIG. 2A, the region where the step is generated in the present embodiment is (1) a step in the plane direction P between the substrate 22 and the lowermost first base ink layer 31. (2) Regions A2 and A3 in which the second second base ink layer 32 and the third third base ink 33 from the bottom generate a step in the plane direction P of the substrate 22. Is mentioned.

The print history includes the number of layers of the plurality of base ink layers, the print pattern in each layer of the plurality of base ink layers, the ink composition of the transfer sheet 21, and the printing energy applied to each region of the transfer sheet 21. These are stored in the memory 15. Based on the number of layers of the plurality of base ink layers and the printing pattern, it is possible to know the distribution of the ink dots or the ink dot aggregates laminated on the base material 22 or the ink layer already laminated on the base material 22. Based on the data, the calculation unit 14 calculates the sum of the stacked ink dots for each region in the plane direction P of the base material 22.
Further, the calculation unit 14 uses the ink composition of the transfer sheet 21 and the ink layered on the base material 22 or the ink layer that has already been stacked on the base material 22 based on the printing energy applied to each region of the transfer sheet 21. The amount or thickness of the dots can be calculated for each region in the plane direction P of the base material 22.

  The memory 15 stores a print pattern of the functional ink layer 34. The control unit 13 corrects the print pattern of the functional ink layer 34 in accordance with the ink dot level difference in each of the plurality of base ink layers 31, 32, and 33. That is, the print pattern is corrected based on the sum of the ink dots stacked for each region in the plane direction P of the base material 22. The correction of the print pattern is performed by the calculation unit 14, and this correction is performed by, for example, comparing the number of base ink layers with the sum of ink dots stacked when a plurality of base ink layers are formed. . In this comparison, first, for each region in the planar direction P of the base material 22, the ratio between the number of base ink layers and the sum of the stacked ink dots is calculated as a comparison result. As a comparison result, the difference between the number of base ink layers and the sum of the stacked ink dots may be used.

  Next, in a region where the ratio is less than the threshold value, that is, a region where there is a base ink layer to which no ink dots are transferred, the energization amount is increased so that the thermal energy applied to the transfer sheet 21 is increased. The region where the ratio is equal to or greater than the threshold value, that is, the region where the ink dots are transferred in all the underlying ink layers and the ink is continuous in the stacking direction of the ink layers is not corrected. Therefore, in the region where the ratio is smaller than the threshold value, the thermal energy applied for forming the ink dots is increased with respect to the region where the ratio is equal to or greater than the threshold value.

  Here, the correction for the print pattern is adjusted for the change in the energization amount near the boundary between the region where the energization amount is increased and the region where the correction is not performed so that the change in the energization amount in the planar direction P of the base material 22 becomes gentle. It is preferable to do. In the region where the ratio is less than the threshold value, if the number of underlying ink layers to which ink dots are not transferred and the thickness of the underlying ink layer are different, the correction amount can be adjusted according to the number of layers and the thickness. preferable. Furthermore, it is preferable to change the correction rate according to the type of ink and physical properties of the transfer sheet.

  In the correction of the print pattern, an ink dot may be added to an area where no ink dot is formed in the print pattern before correction according to the level difference of the base ink layer. Thereby, for example, ink dots can be formed in the peripheral portion of the stepped portion of the base ink layer, and the ink dots of the functional ink layer 34 can be prevented from being interrupted.

  Next, referring to FIG. 3, the functional ink layer 34 is formed on the plurality of base ink layers 31, 32, 33 already formed on the substrate 22 by the image forming method using the image forming apparatus 10 of the present embodiment. The process of forming the will be described. FIG. 3 is a flowchart showing a procedure for correcting the print pattern data (print data) of the functional ink layer 34.

  First, the control unit 13 clears the step information map acquired in the past ink layer formation and stored in the memory 15 (step S1). Subsequently, the control unit 13 reads from the memory 15 the print data of the functional ink layer 34 formed in this step, that is, the layer that is the target of the step correction (step S2).

  Next, from the memory 15, “3” as the number of layers of the background ink layers 31, 32, 33 formed so far, and the print pattern in each layer of the plurality of background ink layers 31, 32, 33 are recorded as print history. Then, the ink composition of the transfer sheet 21 and the printing energy applied to each area of the transfer sheet 21 are read (history acquisition step). Based on these printing histories, the control unit 13 (1) a region where a level difference has occurred in the background ink layers 31, 32, 33 formed so far, and (2) a background ink layer 31, 32 in this region. , 33 is caused to calculate the ratio between the number of layers 33 and the sum of the stacked ink dots (step area calculation step).

  Further, the control unit 13 sends an instruction signal to the calculation unit 14 so as to perform a calculation for correcting the print data for forming the functional ink layer 34 for an area where the calculated ratio is less than the threshold, and the calculation is performed according to the instruction signal. The unit 14 generates print data corrected corresponding to the print history (step S3, print pattern correction step).

  The control unit 13 sends an instruction signal to the heater 11 and the drive unit 12 so as to form the functional ink layer 34 on the already formed base ink layers 31, 32, 33 according to the corrected print data. As a result, according to the corrected print data, the heater 11 is energized larger than the pre-correction condition in the region where the step is generated, and is energized under the condition without correction in the region where the step is not generated. The As shown in FIG. 2 (B), the functional ink layer 34 formed by such a process has regions B1, B2 (FIG. 2) having no step with respect to the already formed base ink layers 31, 32, 33. (B)) is laminated as a flat layer along the upper surface 33a of 33, and is formed so as to cover the steps in the stepped regions A1, A2, and A3, thereby forming the image-formed product 40. .

  Subsequently, the control unit 13 adds the corrected print data generated in step S3 to the print history, and based on this, the calculation unit 14 calculates a new step region, and the step information map reflecting this result. Is stored in the memory 15, and the step information map is updated (step S4). The control unit 13 also stores the corrected print data generated in step S3 in the memory 15 (step S5).

  Next, the control unit 13 determines whether or not the functional ink layer 34 formed based on the corrected print data generated in step S3 is an ink layer (final print plane) to be finally formed (step). S6). When an ink layer is further laminated on the functional ink layer 34 (No in step S6), the processes of steps S2 to S6 are performed again for the newly formed ink layer. On the other hand, when the functional ink layer 34 which is the current uppermost layer is the final print plane (Yes in step S6), the process is terminated.

  Next, with reference to FIGS. 4A, 4 </ b> B, 4 </ b> C, and 4 </ b> D, an image formed product created by the image forming method of the present embodiment will be described. 4A is a photomicrograph of a cross-sectional view of an image formed product produced by the image forming method of the present embodiment, FIG. 4B is an enlarged view of a portion 4B of FIG. 4A, and FIG. FIG. 4D is a micrograph of a cross-sectional view of an image formed product produced by a conventional image forming method, and FIG. 4D is an enlarged view of a 4D portion of FIG. 4C. 4A to 4D are photographs taken by a scanning electron microscope. The magnifications are 1000 times in FIG. 4A, 1500 times in FIG. 4B, and FIGS. 4C and 4D. Is 5000 times.

  In the example shown in FIGS. 4A, 4B, 4C, and 4D, a white ink layer W is formed as a base ink layer in a partial region of PET as the substrate S, and the white ink A black ink layer is laminated as a functional ink layer on the entire substrate S from above the layer W. As shown in FIGS. 4A, 4 </ b> B, 4 </ b> C, and 4 </ b> D, a step is generated between the white ink layer W and the substrate S in the region A <b> 11 on the substrate S.

  In the example shown in FIGS. 4A and 4B, the print data is generated by correcting the print data of the black ink layer based on the print data as the print history of the white ink layer W. . That is, in the step area A11 corresponding to the outer edge portion of the image by the white ink layer W, the print data is corrected so as to increase the energization amount to the heater 11 compared to the other areas. On the other hand, in the example shown in FIGS. 4C and 4D, the print data of the black ink layer is used without being corrected based on the print history of the white ink layer W.

  When the black ink layer is formed based on the above print data, in the example shown in FIGS. 4A and 4B, the black ink layers C1 and C2 are formed on the substrate S and the white ink layer W, respectively. In the step region A11, a black ink layer C3 is formed so as to cover the step, and these black ink layers C1, C2, and C3 are continuous ink layers without interruption. Further, the surface roughness of the black ink layers C1, C2, and C3 was within a certain range, and there was no region that was recognized as a mat shape.

  On the other hand, in the example shown in FIGS. 4C and 4D, the black ink layer C3 is formed on the white ink layer W, and the black ink is formed on the step region A11 so as to be continuous with the black ink layer C3. Layer C4 is formed. The black ink layer C4 is formed so as to protrude from the black ink layer C3 while being separated from the substrate S. Further, the black ink layer C4 has a surface roughness that increases with distance from the black ink layer C3, is interrupted without contacting the substrate S, and is not transferred in the region A12.

With the configuration described above, the following effects are achieved according to the above embodiment.
(1) According to the image forming method of the present embodiment, the thermal energy given to the transfer sheet 21 by the control unit 13 is controlled according to the level difference of the ink dots in each of the three underlying ink layers 31, 32, 33. Therefore, even if there are steps in the three underlying ink layers 31, 32, 33, the functional ink layer 34 can be formed so as to follow the steps and cover the steps in the stepped region. In addition, since the functional ink layer 34 that maintains a high texture can be formed in an area without a step, it is possible to form the image formed product 40 that is free from printing omission and appearance quality degradation.

(2) The position, range, shape, etc. of the step are accurately determined by calculating the region where the step is generated in the plane direction P of the base material 22 based on the printing history regarding the three underlying ink layers 31, 32, 33. This makes it possible to accurately control the heat energy applied to the transfer sheet 21.

(3) Sum of ink dots stacked for each region in the plane direction P of the base material 22 based on the number of base ink layers and the print pattern in each of the three base ink layers 31, 32, and 33 Is calculated, and the print pattern for forming the functional ink layer 34 is corrected based on this sum. Therefore, high-accuracy correction can be performed with a simple and less burdensome calculation process.
Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the above embodiment, and can be improved or changed within the scope of the purpose of the improvement or the idea of the present invention.

  As described above, the image forming method according to the present invention is useful for manufacturing an image formed product in which a multi-layer ink layer is laminated for decoration.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Heater 12 Drive part 13 Control part 14 Calculation part 15 Memory 21 Transfer sheet (ink medium)
21a Substrate film 21b Ink layer 22 Substrate 31, 32, 33 Underlying ink layer 34 Functional ink layer 40 Image formed product

Claims (7)

An image forming method of laminating a functional ink layer on a plurality of base ink layers laminated on a substrate as an ink dot pattern,
The functional ink layer is laminated on the plurality of base ink layers by applying printing energy to an ink medium,
Wherein the plurality of have you to each of the underlying ink layer, depending on the level difference generated between the regions in which the aggregate is not present in the ink dots and area aggregate is present in the ink dots based on the pattern, the ink The printing energy applied to the medium is controlled, and the functional ink layer covers the area where the ink dot aggregate exists, the area where the ink dot aggregate does not exist, and the step. Forming method. A history acquisition step of acquiring a print history relating to the plurality of base ink layers;
Based on the obtained result by the history acquisition step, according to claim 1, characterized in that it comprises a step region calculating step before Kidan difference to calculate the area generated in each layer of the plurality of underlying ink layer Image forming method. Each of the plurality of base ink layers is printed on the substrate or another base ink layer by applying printing energy to an ink medium,
The printing history includes the number of layers of the plurality of base ink layers, the pattern of the ink dots in each layer of the plurality of base ink layers, and the ink of each ink medium used to form the plurality of base ink layers. The image forming method according to claim 2, further comprising: a composition; and printing energy applied to each region of each ink medium when each of the plurality of base ink layers is formed .   4. The image forming method according to claim 2, further comprising a print pattern correction step of correcting a print pattern for forming the functional ink layer based on a calculation result obtained by the step region calculation step. 5. .   In the printing pattern correction step, for each region in the planar direction of the base material, the number of layers of the base ink layer is compared with the sum of the stacked ink dots, and the function is determined based on the comparison result. The image forming method according to claim 4, wherein a printing pattern for forming the ink layer is corrected.   For an area where the comparison result is smaller than a threshold value, the printing energy applied for forming ink dots in the corresponding area in the functional ink layer is increased with respect to an area where the comparison result is equal to or greater than the threshold value. The image forming method according to claim 5. The ink vehicle is a transfer sheet in which the ink having a thermally fusible are stacked, pre SL printing energy is one of claims 1, characterized in that the thermal energy generated by the power supply to the heater according to claim 6 The image forming method according to claim 1.