JP5586082B2 - Image transfer apparatus and image transfer method - Google Patents

Description

  The present invention relates to an image transfer apparatus and an image transfer method.

  Conventionally, as a method of printing on a curved surface or the like, a method of printing by pad printing (also referred to as tampo printing) is known (see, for example, Patent Document 1). In pad printing, ink (ink) placed on a flat plate (intaglio) on which a pattern has been formed by etching is transferred to a pad, and the image on the pad is once transferred to the pad. ) Is retransferred to print.

JP 2000-263755 A Japanese Patent Laid-Open No. 10-250052 JP 2005-161603 A JP 2008-44235 A JP 2007-112117 A

  In the conventional method, pad printing requires producing a printing plate by etching in accordance with an image to be printed. For this reason, for example, if printing is performed in a small amount and a wide variety, a problem such as an increase in cost occurs. On the other hand, the inventor of the present application forms an image to be transferred using an inkjet head on the surface of the pad or a flat plate corresponding to an intaglio so that, for example, it can easily and appropriately cope with printing of a small variety of products. Therefore, we examined pad printing with a configuration that does not require a printing plate.

  However, when printing a high-definition image with an inkjet head, in order to properly eject ink droplets, it is necessary to keep the viscosity of the ink under the ejection conditions low. For example, the viscosity of the ink needs to be kept at a low viscosity of about 8 to 10 mPa · sec, or about 3 to 5 mPa · sec, depending on the printing resolution.

  On the other hand, in consideration of image transfer, the surface of the pad or the like needs to be in a light lyophobic state. For this reason, even if an image is directly formed on these surfaces with a low-viscosity ink using an ink jet head, ink beading, repelling, blurring, etc. may occur, and the image may not be formed properly.

  Further, even if an image can be formed on the surface of the pad, for example, if the viscosity of the ink is low, the ink does not move properly to the transfer medium and remains on the pad when transferring to the transfer medium. There is a risk of poor transfer. As a result, printing defects such as unevenness are likely to occur.

  Therefore, conventionally, for example, a method of performing pad printing by a more appropriate method with a configuration that does not require a printing plate has been desired. Therefore, an object of the present invention is to provide an image transfer apparatus and an image transfer method that can solve the above-described problems.

  In addition, as a method for performing printing by transferring an image, there is conventionally known a configuration in which printing is performed on a transfer medium such as a transfer drum and then thermal transfer is performed on a transfer medium such as paper (for example, Patent Documents 2 to 2). 5). In such a transfer system, for example, after printing on a transfer medium using ultraviolet curable ink (UV ink), transfer to a medium such as paper is performed. However, these configurations are configurations for printing on plain paper or the like having a flat transfer surface, and are not related to pad printing. Therefore, it cannot be directly applied to the configuration for pad printing that prints on a curved surface or the like. In addition, if it is considered to apply to pad printing, for example, the following problems may occur.

  For example, in the configurations disclosed in Patent Documents 2 and 3, the transfer is performed after the ink on the transfer medium is cured. However, the ultraviolet curable ink is usually in a state where no adhesive force is generated when it is completely cured. For this reason, in these cases, the ink after transfer is in a state of only being applied to the surface with a weak adhesive force to the medium to be transferred. As a result, problems such as scratching may occur due to insufficient adhesive force. Furthermore, there is a possibility that a problem that the transfer itself cannot be performed stably is caused. In addition, the completely cured ink is difficult to flatten the surface of the ink after transfer even if pressure is applied during transfer. For this reason, for example, the dot size of the ink may be reduced, the dot gain characteristics may be deteriorated, and it may be difficult to gloss the printed surface.

  For example, in the configuration disclosed in Patent Document 4, a monofunctional polymerization compound component having thermoplasticity even after curing with ultraviolet rays is used as the main component of the ink, thereby maintaining the thermoplasticity after curing. After the ink on the transfer medium is cured, transfer is performed. Further, at the time of transfer, heat-pressure transfer to paper is performed by heating above the softening point of the polymerized compound in the ink after curing.

  However, in this method, heating up to the softening point showing the thermoplasticity is necessarily required, which may increase the cost of the apparatus required for transfer. In particular, in pad printing, unlike the case where thermal transfer is performed using a transfer drum or the like, transfer is usually performed in a non-heated room temperature state. For this reason, adding a configuration for heating may cause a significant cost increase.

  Further, since the thermoplasticity of the ink remains after being transferred to the paper, there is a possibility that the printed result is not sufficiently scratched. In addition, since the heating temperature at the time of transfer needs to be equal to or lower than the heat resistance temperature of the medium, for example, when using a medium such as plastic having a low heat resistance compared to paper or the like, the ink after curing is heat resistant such as plastic. It is only thermocompression-bonded to the medium at a relatively low temperature below the property. Therefore, in such a case, the adhesive force of the ink to the medium may be weakened.

  For these problems, for example, in the configuration disclosed in Patent Document 5, by using two types of light sources, a semi-curing light source and a main curing light source, the ink before transfer is made into a semi-cured state, and after the transfer, The ink is fully cured. In addition, when using a semi-curing light source, in order to prevent complete curing and maintain a semi-cured state, an ultraviolet curable ink containing two types of ultraviolet curing initiators having different spectral absorption characteristics is used. .

  However, for example, when the curing initiator exemplified in Patent Document 5 is used as the two types of ultraviolet curing initiators, the peak wavelength of the absorptance is close, so that the main curing is performed, for example, by irradiation with ultraviolet rays from a semi-curing light source. The reaction of the ultraviolet curing initiator for use also proceeds, and there is a possibility that it approaches the state of main curing. For this reason, it may be difficult to appropriately maintain the semi-cured state. Even if it is considered to use an ultraviolet curing initiator having a peak wavelength of absorption that is further away, it may be difficult to select an appropriate substance as an ink component for an inkjet printer.

  Furthermore, when such special ink is used, the cost of ink that is a consumable item increases. Further, due to cost and print quality requirements, it may be desirable to use a more general ink instead of using such a special ink.

  The inventor of the present application has conducted intensive research on a configuration in which pad printing is performed without using a printing plate by forming an image to be transferred using an inkjet head. And it discovered that an image could be appropriately transferred with good reproducibility by using an ultraviolet curable ink and curing the ink in two stages before and after transfer. More specifically, before transferring, the ink is not completely cured but is semi-cured, and after the transfer, the ink is completely cured, thereby performing appropriate transfer by the pad printing method. Found to get. In order to solve the above problems, the present invention has the following configuration.

(Configuration 1) An image in which a transferred image is transferred to a transfer medium by using a pad having a curved image forming surface on which the transferred image is formed, and contacting the image forming surface of the pad with the transferred medium. A transfer device that discharges ink droplets of ultraviolet curable ink to emit light to an image to be transferred in an ink jet head that forms an image to be transferred and a state before transfer from a pad to a transfer medium. In the state after the transfer from the pad to the transfer medium, and after the transfer, the post-transfer image that is an image formed on the transfer medium by transfer is irradiated with ultraviolet rays. The pre-transfer light irradiating unit irradiates the transferred image with light, thereby increasing the viscosity of the ink constituting the transferred image as compared with that before the light irradiation. The irradiation part As ultraviolet rays to be irradiated to Utsushigo image, and generates ultraviolet rays to cure the ultraviolet curable ink, the ultraviolet curable inks, as an initiator to initiate curing of the ultraviolet curable ink, one having sensitivity peak in the ultraviolet region And an ink that increases in viscosity in response to light generated by the pre-transfer light irradiating unit, and the pre-transfer light irradiating unit emits light as light irradiating the transferred image. Visible light having an intensity peak in the spectrum longer than 420 nm is generated. This pad is, for example, a curved pad with a flexible image forming surface. That the image forming surface is flexible means that the image forming surface has flexibility to deform flexibly according to the pressure received when it comes into contact with another object.

  The image transfer apparatus is a printing apparatus that performs printing by pad printing, for example. Further, this pad is, for example, a pad used in pad printing. To increase the viscosity of the ink more than before the light irradiation by the pre-transfer light irradiation unit is, for example, to make the ink semi-cured without completely curing it.

  When configured in this way, for example, even when the viscosity of the ink under the discharge conditions is low, it is possible to appropriately increase the viscosity of the ink in the transferred image in the state before transfer. Thereby, for example, it is possible to appropriately prevent ink from bleeding in the transferred image. Further, by increasing the viscosity of the ink, it is possible to appropriately prevent the occurrence of ink transfer failure.

  Therefore, if comprised in this way, in a pad printing, it becomes possible to form a to-be-transferred image appropriately with an inkjet head. Thereby, pad printing can be appropriately performed by the structure which does not require the printing plate for printing. Further, for example, pad printing can be appropriately performed by a method suitable for printing a small variety of products.

  (Configuration 2) The ultraviolet curable ink is an ink that increases in viscosity in response to light generated by the pre-transfer light irradiating unit. The pre-transfer light irradiating unit emits an emission spectrum as light that irradiates the image to be transferred. Visible light having an intensity peak at a wavelength longer than 420 nm is generated. Further, the pre-transfer light irradiating unit generates visible light having a wavelength range with a condition that the light absorption coefficient is small with respect to, for example, ultraviolet curable ink and can reach the inside of the ink uniformly as the visible light. It is preferable.

  The inventor of the present application has conducted intensive research on a method for making the ultraviolet curable ink before transfer not completely cured but semi-cured. Then, first, it was considered that the ultraviolet curable ink was made to be in a semi-cured state by irradiating ultraviolet rays having low strength.

  However, the inventor of the present application has found that in this method, it may be difficult to sufficiently transmit ultraviolet rays to the inside of the ink dots. As a result, for example, unevenness of the degree of curing occurs between the surface and the inside of the ink dots formed on the transfer medium, and it is difficult to appropriately semi-cure the entire dots. I found it.

  When such uneven curing occurs, for example, when the surface of the dot is in a semi-cured state, the viscosity of the ink remains low on the inner side of the dot. In this case, the shape of the dots is liable to collapse during transfer, so that the semi-cured state suitable for transfer is not achieved. Further, for example, when trying to make a semi-cured state deep inside the dot, the vicinity of the surface of the dot is completely cured. In this case, since the adhesive force between the recording medium and the ink is the same as when the ink is completely cured and then transferred, the adhesive force of the ink to the recording medium can be sufficiently increased after the transfer. It will not be. In addition, such a problem that unevenness of the degree of curing occurs between the surface of the dots and the inside is caused by, for example, two types of ultraviolet curing initiators having different spectral absorption characteristics as in the configuration of Patent Document 5. Even when using the ultraviolet curable ink containing, it is thought that it arises similarly.

  In contrast, the inventor of the present application has further studied earnestly, and by irradiating the ultraviolet curable ink with visible light whose wavelength corresponding to the intensity peak deviates from the ultraviolet region to the long wavelength side, It has been found that the degree of curing can be made more uniform between the surface and the interior. Further, it has been found that a semi-cured state that is more suitable for transfer can be realized.

  If comprised like the structure 2, the light which the light irradiation part for pre-transfer generate | occur | produces can be appropriately reached to the inner back | inner side with respect to the dot of the ink in a to-be-transferred image, for example. Therefore, for example, it is possible to appropriately prevent the curing of only the surface while the viscosity on the back side inside is low.

  Thereby, for example, the ink before transfer in the transferred image can be appropriately cured to a semi-cured state suitable for transfer. Furthermore, by appropriately setting the ink before transfer to a semi-cured state, the image can be transferred by a more appropriate method, for example, by the pad printing method.

  For example, the pre-transfer light irradiating unit generates visible light having a blue or green wavelength intensity peak. The pre-transfer light irradiation unit may generate white visible light. As the ultraviolet curable ink, for example, an ink that is semi-cured by light generated by the pre-transfer light irradiating portion among known ultraviolet curable inks used in known inkjet printers can be selected and used.

  In addition, the inventors of the present application have made extensive researches on the post-transfer ultraviolet irradiation part even when, for example, light in the near ultraviolet region is used as light deviating from the ultraviolet region for semi-curing the ink to the long wavelength side. It has been found that the degree of curing can be made uniform between the surface and the inside of the dots as compared with the case of irradiating the same ultraviolet rays. Therefore, the pre-transfer light irradiating unit may generate light in the visible to near-ultraviolet region, for example.

  (Structure 3) The inkjet head forms an image to be transferred on a planar member by ejecting ink droplets onto a planar member whose main surface is a planar member. The transferred image formed on the image forming surface of the pad is irradiated with light on the upper transferred image, and is an image transferred from a flat medium in a state after the light is irradiated on the pre-transfer light irradiation portion. is there.

  If comprised in this way, a to-be-transferred image can be formed appropriately using an inkjet head. Further, by increasing the viscosity of the ink in the transferred image on the flat member, for example, it is possible to appropriately prevent the ink from bleeding in the transferred image. Further, for example, transfer from the planar member to the pad and transfer from the pad to the transfer medium can be appropriately performed. Therefore, if constituted in this way, it becomes possible to perform pad printing by an appropriate method, for example by composition which does not require a printing plate.

  (Configuration 4) The inkjet head forms an image to be transferred on the image forming surface by ejecting ink droplets on the image forming surface of the pad, and the pre-transfer light irradiation unit is on the image forming surface of the pad. Light is applied to the image to be printed.

  If comprised in this way, a to-be-transferred image can be formed appropriately using an inkjet head. Further, by increasing the viscosity of the ink in the transferred image on the pad, for example, it is possible to appropriately prevent the ink from bleeding in the transferred image. Further, for example, transfer from the pad to the transfer medium can be performed appropriately. Therefore, if constituted in this way, it becomes possible to perform pad printing by an appropriate method, for example by composition which does not require a printing plate.

  Further, if configured in this manner, an image to be transferred can be appropriately formed directly on the pad. Thereby, for example, the number of times of transfer can be reduced as compared with a case where an image to be transferred is formed on the pad by transfer from another member. Further, by reducing the number of times of transfer, problems that may occur during transfer such as color shift and blurring can be made difficult to occur.

  (Configuration 5) The ultraviolet curable ink includes a thickener that increases the viscosity of the ultraviolet curable ink according to the ultraviolet light, and an initiator that initiates the curing of the ultraviolet curable ink according to the ultraviolet light. The wavelength of the intensity peak in the emission spectrum of the light generated by the irradiating part is 200 nm or more longer than the wavelength of the absorption wavelength peak of the thickener and the wavelength of the absorption wavelength peak of the initiator. is there.

  With this configuration, for example, the light generated by the pre-transfer light irradiation unit can be more appropriately reached to the inner back side of the ink dots. This also makes it possible to more appropriately semi-cure the entire ink dot.

  (Configuration 6) The intensity peak in the emission spectrum of visible light generated by the pre-transfer light irradiation section is 200 nm or more longer than the intensity peak in the emission spectrum of ultraviolet light generated by the post-transfer ultraviolet irradiation section. If comprised in this way, the light which the light irradiation part for pre-transfer generate | occur | produces can be more appropriately reached to the inner back | inner side with respect to the dot of an ink, for example. Note that the emission spectrum of the ultraviolet light generated by the post-transfer ultraviolet irradiation part is set in accordance with, for example, at least one of the peak absorption wavelength of the thickener and the peak absorption wavelength of the initiator. .

  (Configuration 7) The pre-transfer light irradiating unit includes an LED that generates visible light as a light source that generates light having an intensity peak wavelength. By using the LED, light having a target wavelength can be generated efficiently. In addition, when an LED is used, it becomes easier to control the light output. Therefore, if comprised in this way, it will become possible to semi-harden ink more appropriately, for example.

  (Configuration 8) The transfer medium is a non-planar medium. The non-planar medium is, for example, a medium whose transfer surface is a curved surface or a three-dimensional medium. The non-planar medium may be a medium other than the planar medium. The medium on a plane is a medium such as a sheet or a plate.

  As a method of transferring an image to a flat medium such as plain paper, a method such as thermocompression bonding is known as disclosed in Patent Documents 2 to 5, for example. In this method, for example, an image is transferred by applying pressure with a transfer medium sandwiched between a transfer drum and a transfer roller. However, in the case of a non-planar medium, it is difficult to apply pressure appropriately by sandwiching the medium to be transferred between the transfer drum and the transfer roller. For this reason, it is difficult to transfer appropriately with such a method.

  On the other hand, in pad printing, an image can be appropriately transferred even to a non-planar medium. Further, when configured as in configuration 7, for example, pad printing can be performed by an appropriate method using a configuration that does not require a printing plate. Therefore, if constituted in this way, printing can be appropriately performed at a low cost on, for example, a non-planar medium.

(Arrangement 9) An image in which a transfer image is transferred to a transfer medium by using a pad with a curved image formation surface on which the transfer image is formed, and contacting the image formation surface of the pad with the transfer medium. A transfer method in which an image to be transferred is formed by an inkjet head that discharges ink droplets of ultraviolet curable ink, and light is irradiated to the image to be transferred before being transferred from the pad to the transfer medium. Thus, the viscosity of the ink constituting the image to be transferred is made higher than that before light irradiation, and the image formed on the transfer medium by transfer in the state after the transfer from the pad to the transfer medium to transfer after the image is, the ultraviolet light to cure the ultraviolet curable ink by irradiating the ultraviolet curable inks, as an initiator to initiate curing of the ultraviolet curable ink, the sensitivity peak in the ultraviolet region Comprises one of the initiator having, and said an ink capable of reacting with increased viscosity in the light beam irradiation unit for pre-transfer occurs, the pre-transfer light irradiation portion, light irradiated the to be transferred image As a result, visible light having an intensity peak in the emission spectrum longer than 420 nm is generated. In this way, for example, the same effect as that of Configuration 1 can be obtained.

  According to the present invention, an image can be transferred by a more appropriate method, for example, by a pad printing method. In addition, this makes it possible to perform pad printing by an appropriate method, for example, with a configuration that does not require a printing plate.

It is a figure which shows the 1st example of a structure and operation | movement of the image transfer apparatus 10 which concerns on one Embodiment of this invention. FIG. 1A shows an example of the timing at which the transferred image 102 is formed by the inkjet head 12. FIG. 1B shows an example of the timing of transferring the transferred image 102 from the flat plate 40 to the pad 14. FIG. 1C shows an example of the timing of transferring the transferred image 102 from the pad 14 to the transferred medium 50. 2 is a diagram illustrating a first example of the configuration and operation of the image transfer apparatus 10. FIG. FIG. 2A shows an example of the timing of curing the ink after transfer. FIG. 2B shows an example of the timing of cleaning the pad 14. It is a figure explaining the semi-hardening of an ultraviolet curable ink. FIG. 3A shows an example of the state of the dots 202 of the ultraviolet curable ink formed on the flat plate 40. FIG. 3B is a graph showing an example of a change in the light absorption distribution according to the distance L from the surface of the ink dot 202. 6 is a diagram illustrating a second example of the configuration and operation of the image transfer apparatus 10. FIG. FIG. 4A shows an example of the timing of forming the transferred image 102 by the inkjet head 12. FIG. 4B shows an example of the timing of transferring the transferred image 102 from the pad 14 to the transferred medium 50. FIG. 4C shows an example of the timing of ink curing after transfer.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. 1 and 2 show a first example of the configuration and operation of an image transfer apparatus 10 according to an embodiment of the present invention. FIG. 1A, FIG. 1B, FIG. 1C, FIG. 2A, and FIG. 2B show an example of how the image transfer apparatus 10 operates at each timing. In these drawings, for convenience of illustration and explanation, only the configuration for performing the corresponding operation among the respective units of the image transfer apparatus 10 is shown. The image transfer apparatus 10 is a printing apparatus that performs printing by pad printing, and includes an inkjet head 12, a semi-curing light source 18, a pad 14, and a main curing light source 20.

  The semi-curing light source 18 is an example of a pre-transfer light irradiation unit. The main curing light source 20 is an example of a post-transfer ultraviolet irradiation unit. This pad printing is, for example, digital pad printing that performs pad printing based on print data of digital data. In this example, the image transfer apparatus 10 further uses the flat plate 40 and the cleaning sheet 60 in a series of operations for transferring an image. Each of these components will be described in more detail below together with the description of the operation of the image transfer apparatus 10.

  Although not shown, the image transfer apparatus 10 may further include various configurations necessary for printing. For example, the image transfer apparatus 10 may further include a maintenance mechanism for the inkjet head 12, a standby structure for maintenance, a scanning mechanism, and the like. Various known configurations can be used as these configurations.

  Hereinafter, the state at each timing of the operation of the image transfer apparatus 10 will be described. FIG. 1A shows an example of the timing at which the transferred image 102 is formed by the inkjet head 12. In this example, the inkjet head 12 is a print head that ejects ink droplets of ultraviolet curable ink, and forms an image to be transferred 102 on the flat plate 40 with the ultraviolet curable ink.

  The flat plate 40 is an example of a planar member whose main surface is a planar member. Further, the flat plate 40 is a member corresponding to, for example, an intaglio used in conventional pad printing. As the flat plate 40, for example, a resin or metal plate can be suitably used. The surface of the flat plate 40 is preferably surface-treated or coated so as to be lyophilic with respect to the ultraviolet curable ink as long as the transferred image 102 can be transferred to the pad 14. Producing lyophilicity with respect to the ultraviolet curable ink means, for example, producing lyophilicity with respect to the monomer or oligomer that is the composition of the ultraviolet curable ink. If comprised in this way, the beading phenomenon which an ink collects on the flat plate 40 by the surface tension of a white part can be prevented appropriately, for example. The surface of the flat plate 40 preferably exhibits a liquid repellency of, for example, a contact angle of 40 degrees or more, preferably 45 degrees or more, with respect to the liquid ink before curing starts.

  Further, the inkjet head 12 ejects ink droplets to each position of the flat plate 40 by scanning the flat plate 40, for example. This scanning can be performed by, for example, a known method. For example, the inkjet head 12 scans the flat plate 40 by a multi-scan method, as in a conventional inkjet printer that performs printing by a serial method. Further, for example, it is conceivable to use a line-type inkjet head 12 having a nozzle row having a length corresponding to the width of the flat plate 40 in order to increase printing speed.

  Further, in this example, the ultraviolet curable ink includes a thickening agent that increases the viscosity of the ultraviolet curable ink in response to ultraviolet rays, and an initiator that initiates curing of the ultraviolet curable ink in response to ultraviolet rays. The ultraviolet curable ink before curing, which is in a state before light irradiation, has a viscosity of, for example, 3 to 30 mPa · sec, preferably 3 to 20 mPa · sec at room temperature. The viscosity of the ink is preferably adjusted as appropriate according to the ink jet head used. The ultraviolet curable ink of this example is kept at a low viscosity of about 8 to 10 mPa · sec or about 3 to 5 mPa · sec depending on the printing resolution, for example, under the conditions at the time of ejection from the inkjet head 12.

  Further, after the transferred image 102 is formed by the inkjet head 12, the image transfer apparatus 10 irradiates the transferred image on the flat plate 40 with light by the semi-curing light source 18. Thus, the semi-curing light source 18 irradiates the transferred image 102 with light in a state before being transferred to the transferred medium 50. The semi-curing light source 18 increases the viscosity of the ink on the flat plate 40 by light irradiation. Thereby, the semi-curing light source 18 performs a semi-curing process for changing the ink to a semi-cured state before the transfer.

  In this example, the semi-curing process is to make the ink in a state of increasing the viscosity without completely curing the ink before performing the curing with the main curing light source 20 later. Further, the semi-cured state does not mean that the curing has progressed to half, but is not limited to half, for example, and is a state in which the polymerization reaction of components contained in the ink has partially progressed. The semi-cured state may be a state in which the viscosity of the ink is higher than that before light irradiation in a state where the ink is not completely cured. Further, for example, the semi-cured state may be a state of being cured to a hardness of about 10% (for example, 5 to 15%) as compared with a state in which the light is cured by the main curing light source 20 later. In the semi-cured state, the viscosity of the ultraviolet curable ink is increased to, for example, 30 to 300 mPa · sec. In the semi-cured state, the ultraviolet curable ink is, for example, a liquid or soft paste and has adhesiveness.

  According to this example, for example, even when the ink viscosity under the discharge conditions is low, the ink viscosity in the transferred image 102 can be appropriately increased in the state before transfer. Further, by making the ink on the flat plate 40 semi-cured, it is possible to appropriately prevent the ink from spreading on the flat plate 40. In addition, this makes it possible to appropriately prevent ink bleeding from occurring in the transferred image 102. Furthermore, by setting the ink to a semi-cured state, the viscosity of the ink can be increased, and the state of the ink can be made suitable for transfer and less likely to cause bleeding after transfer. Thereby, for example, it is possible to appropriately prevent the occurrence of ink transfer failure in later transfer.

  Here, in this example, the semi-curing light source 18 generates visible light having an intensity peak in the emission spectrum longer than 420 nm as light irradiated to the transferred image 102. The wavelength of the intensity peak in the emission spectrum of the light generated by the semi-curing light source 18 is, for example, the peak wavelength of the absorption wavelength of the thickener and the peak of the absorption wavelength of the initiator in the ultraviolet curable ink to be used. It is a wavelength on the longer wavelength side of 200 nm or more than any of the wavelengths. More specifically, for example, the semi-curing light source 18 generates visible light having a wavelength whose intensity peak is blue or green in accordance with the characteristics of the ultraviolet curable ink. The semi-curing light source 18 may generate white visible light.

  Further, the intensity peak in the emission spectrum of visible light generated by the semi-curing light source 18 may be 200 nm or more longer than the intensity peak in the emission spectrum of ultraviolet light generated by the main curing light source 20 described in detail later. preferable. In the modification of the present invention, the semi-curing light source 18 may generate, for example, near ultraviolet light.

  The semi-curing light source 18 includes an LED that generates visible light as a light source that generates light having an intensity peak wavelength. By using the LED, light having a target wavelength can be generated efficiently. In addition, when an LED is used, it becomes easier to control the light output. According to this example, for example, the ink in the transferred image 102 can be appropriately cured to a semi-cured state suitable for transfer.

  The semi-curing light source 18 is provided adjacent to the inkjet head 12, for example, and is driven integrally with the inkjet head 12. If comprised in this way, light can be appropriately irradiated with respect to the ink droplet immediately after landing on the flat plate 40, for example. The semi-curing light source 18 may be driven separately from the inkjet head 12. In addition, the semi-curing light source 18 may further irradiate visible light to ink droplets that are flying from the inkjet head 12 toward the flat plate 40, for example.

  The relationship between the characteristics of the ultraviolet curable ink and the light generated by the semi-curing light source 18 will be described in more detail later. Further, the semi-curing light source 18 may further generate ultraviolet rays having an intensity weaker than the intensity peak in addition to the visible light. In this case, the semi-curing light source 18 may further include, for example, a UV LED that generates ultraviolet rays in addition to the LED for visible light. For example, the UVLED generates ultraviolet rays with an intensity that does not completely cure the ink by generating ultraviolet rays with an intensity smaller than the visible light generated by the visible light LED. If comprised in this way, the surface of the dot of an ink can be semi-hardened in a shorter time, for example. In addition, this makes it possible to appropriately prevent the ink dots in the transferred image 102 from spreading before becoming a semi-cured state. This UV LED preferably generates ultraviolet rays having a relatively long wavelength of, for example, 350 to 420 nm.

  FIG. 1B shows an example of the timing of transferring the transferred image 102 from the flat plate 40 to the pad 14. At this timing, the transferred image 102 is transferred from the flat plate 40 to the pad 14 by bringing the image forming surface of the pad 14 into contact with the flat plate 40 and pressing the pad 14 against the flat plate 40. As a result, the transferred image 102 after being irradiated with the light to the semi-curing light source 18 is transferred from the flat plate 40 to the image forming surface of the pad 14. The image forming surface of the pad 14 is a surface on which the transferred image 102 is formed on the pad 14. In this example, the image forming surface of the pad 14 is curved.

  The material and shape of the pad 14 may be the same as or similar to a known pad used in conventional pad printing. For example, silicon rubber or the like can be suitably used as the material of the pad 14. In addition, for example, fluororubber, butyl rubber, chloroprene rubber, urethane rubber, butadiene rubber, neoprene, EPDM and other rubbers, various elastomer resins, and the like can be selected according to the purpose.

  FIG. 1C shows an example of the timing of transferring the transferred image 102 from the pad 14 to the transferred medium 50. At this timing, the transferred image 102 is transferred from the pad 14 to the transfer medium 50 by bringing the image forming surface of the pad 14 into contact with the transfer medium 50 and pressing the pad 14 against the transfer medium 50. As a result, a post-transfer image 104 is formed on the transfer medium 50.

  FIG. 2A shows an example of the timing of curing the ink after transfer. In this example, the image transfer apparatus 10 transfers ultraviolet light that cures ultraviolet curable ink by the main curing light source 20 after the transferred image 102 of the pad 14 is transferred to the transferred medium 50 as the post-transfer image 104. The rear image 104 is irradiated. As a result, the main curing light source 20 completely cures the semi-cured ink and fixes it to the transfer medium 50. Accordingly, the main curing light source 20 performs a main curing process for completely curing the ultraviolet curable ink on the transfer medium 50. To completely cure the ultraviolet curable ink is, for example, to cure the ink to a sufficient hardness as a state after printing.

  As the ultraviolet light source in the main curing light source 20, various light sources capable of generating ultraviolet light having sufficient intensity to cure the ultraviolet curable ink can be used. For example, the main curing light source 20 includes a UV LED as a light source that generates ultraviolet rays. Further, the main curing light source 20 may include, for example, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, or the like as a light source that generates ultraviolet rays, instead of the UV LED. Further, the emission spectrum of ultraviolet rays generated by the main curing light source 20 includes, for example, the peak wavelength of the absorption wavelength of the thickener and the peak wavelength of the absorption wavelength of the initiator contained in the ultraviolet curable ink used. It is set according to at least one.

  FIG. 2B shows an example of the timing of cleaning the pad 14. In this example, for example, when printing is performed continuously, the ink remaining on the pad 14 after the transfer is removed by the cleaning sheet 60. The cleaning sheet 60 is an example of a cleaning unit that removes ink. As the cleaning means, for example, a blade, cloth, or non-woven wiper may be used.

  In order to increase the cleaning efficiency, it is effective to solidify the ink on the pad 14 without leaving it in a semi-cured state. Therefore, the image transfer apparatus 10 may further include a residual ink curing light source that cures the ink remaining on the pad 14 as necessary. The residual ink curing light source irradiates the ink on the pad 14 with ultraviolet rays to cure the ink before removing the ink. The necessity of the residual ink curing light source is determined, for example, in relation to the performance of the cleaning means.

  Thus, the digital pad printing process by the image transfer apparatus 10 is completed. According to this example, for example, with respect to the ultraviolet curable ink, the transferred image 102 in which the ink is in a semi-cured state is obtained by using a change between two states of a semi-cured state having a high viscosity and a completely cured state. By transferring, it is possible to appropriately prevent bleeding on the pad 14 or after transfer, occurrence of transfer failure, and the like. Further, the adhesive force between the ink constituting the post-transfer image 104 and the transfer medium 50 can be sufficiently increased.

  Moreover, since the transfer is performed in a semi-cured state, the transfer can be performed efficiently. For this reason, for example, transfer can be appropriately performed without heating or the like. Thereby, it can transfer appropriately by the method of pad printing. Therefore, according to this example, it is possible to appropriately perform transfer even on a non-planar transfer medium 50 such as a curved surface or a three-dimensional shape. For example, as in the state shown in the drawing, it is possible to appropriately transfer the spherical transfer medium 50 as well.

  Further, in this example, since the transfer is performed in a semi-cured soft state, the surface of the ink is flattened by the pressure during transfer. Thereby, for example, it is possible to give gloss to the image after transfer. In addition, the problem of matting the surface, which is known as a problem that occurs when using an ultraviolet curable ink, can be solved appropriately. Furthermore, since the surface of the ink is flattened, for example, the problem of insufficient gain that the ink dot size is insufficient is less likely to occur. In the post-transfer image 104, when it is desired to leave the mat feeling in reverse, the surface of the pad 14 may be formed in a mat shape.

  Furthermore, by performing the transfer in a semi-cured state, it is possible to realize a strong adhesive force and difficulty in bleeding, so that it is possible to transfer to the transfer medium 50 of various materials. For example, when transfer is performed in a state where the ink is completely cured, transfer can be appropriately performed even to a material to be transferred 50 of a material for which sufficient adhesive force cannot be obtained. For example, according to this example, it is possible to appropriately perform transfer even to a transfer medium 50 formed of a plastic film, a plastic plate, a wooden board, cardboard, or the like. This also makes it possible to appropriately transfer the transfer medium 50 having various shapes such as a plastic three-dimensional object formed of these materials. Furthermore, in this example, since transfer is performed with a pressure contact force, unlike in the case of electrophotography or the like in which transfer is performed electrostatically, transfer defects due to a decrease in electric field do not occur. Therefore, even when the thick transfer medium 50 is used, transfer can be performed easily and appropriately.

  Further, for example, when direct printing is performed by the inkjet head 12, high-definition images can be appropriately formed even on a material to be transferred 50 that is difficult to achieve high-definition printing due to ink bleeding. . Further, the present invention is also applicable to the case where a transfer medium 50 made of a material that easily absorbs ink inside, such as plain paper or Japanese paper, and is difficult to print at high density when directly printed by the inkjet head 12 is used. In the example, since the ink is thickened, it is difficult for the ink to penetrate into the inside, and sufficient ink remains near the surface of the transfer medium 50. Therefore, according to this example, even when such a transfer medium 50 is used, a high-density image can be appropriately formed.

  In addition, as described above, in pad printing, the transferred image 102 can be appropriately formed by the inkjet head 12, and therefore pad printing is appropriately performed with a configuration that does not require a printing plate. Can do. For this reason, for example, pad printing can be appropriately performed by a method suitable for printing a small variety of products. In addition, for example, a small amount of various types of curved surface printing can be performed in a short time and at a low cost. Furthermore, high-gloss printing can be appropriately performed by applying pressure to the semi-cured ink during transfer.

  In the process described above, the transferred image 102 may be a color image formed with, for example, a plurality of colors of ink. In this case, the formation of the transferred image 102 by the inkjet head 12 and the subsequent transfer may be performed sequentially for each color or may be performed simultaneously for a plurality of colors. When a plurality of colors are collectively performed, for example, the ink jet head 12 may perform color printing of two colors, four colors, six colors, etc. on the flat plate 40 all at once. In this case, the transferred image 102 formed as a color image on the flat plate 40 is then transferred to the pad 14 and the transferred medium 50.

  Further, in the steps described above, the transfer of the transferred image 102 from the flat plate 40 to the pad 14 and from the pad 14 to the transferred medium 50 can be appropriately performed at room temperature as in normal pad printing. Further, for example, in order to stabilize the transfer conditions, these transfers may be performed under conditions of heating to a certain temperature.

  In the modification of the present invention, for example, the transfer of the transfer target image 102 from the pad 14 to the transfer target medium 50 using the medium heating unit that heats the transfer target medium 50, and then the main curing light source 20. It is also conceivable to heat the transfer medium 50 before the ultraviolet irradiation. With this configuration, for example, the viscosity of the ink on the transfer medium 50 can be once lowered before the ink is completely cured. This also makes it possible to more appropriately fix the ink on the transfer medium 50. For example, in the case of using a transfer medium 50 or the like formed of paper, the ink can be more firmly fixed on the transfer medium 50 by allowing the ink to permeate into the fibers of the paper.

  In this case, as the medium heating unit, a heat transfer heater, an induction heater, an infrared heater, a heating roller, or the like can be suitably used. Further, the medium heating unit heats the transfer medium 50 to a temperature higher than the temperature at the time when the transfer image 102 is transferred, for example.

  Next, the relationship between the characteristics of the ultraviolet curable ink and the light generated by the semi-curing light source 18 will be described in more detail. FIG. 3 is a diagram for explaining the semi-curing of the ultraviolet curable ink. FIG. 3A shows an example of the state of the dots 202 of the ultraviolet curable ink formed on the flat plate 40. In this example, the ink droplets ejected by the inkjet head 12 become ink dots 202 by landing on the flat plate 40.

  FIG. 3B is a graph showing an example of a change in the light absorption distribution according to the distance L from the surface of the ink dot 202. The distance L and the light absorption distribution immediately after the dot 202 starts to be irradiated with ultraviolet rays or visible light. An example of the relationship is shown. In the graph, the dot bottom surface position is the position of the surface of the flat plate 40 with which the bottom surface of the dot is in contact, and indicates the position where the distance L from the surface is maximum inside the dot 202.

  A dotted line shows an example of a change in the light absorption distribution according to the distance L from the surface when the dot 202 is irradiated with ultraviolet rays corresponding to the used ultraviolet curable ink. This ultraviolet ray is, for example, an ultraviolet ray in a wavelength range generated by the main curing light source 20, and is an ultraviolet ray in a wavelength range used for completely curing the ultraviolet curable ink.

  The alternate long and short dash line indicates an example of a change in the light absorption distribution depending on the distance L from the surface when the dot 202 is irradiated with visible light in a predetermined wavelength range. This visible light is, for example, light in a wavelength range generated by the semi-curing light source 18. This wavelength range is selected according to the characteristics of the ultraviolet curable ink, for example.

  When ultraviolet rays in the above wavelength range are irradiated to the ultraviolet curable ink, since the ink absorbs ultraviolet rays with high efficiency, the irradiated ultraviolet rays are mainly absorbed in the vicinity of the surface of the dots 202, and the inside of the dots 202 is absorbed. It becomes difficult to reach the back side of. In this case, for example, even if the vicinity of the surface of the dot 202 is in a semi-cured state, the inner back side remains in a low viscosity state. For this reason, for example, if transfer is performed in this state, the shape of the dots 202 may be lost during transfer, and appropriate transfer may not be performed.

  In addition, for example, when intense ultraviolet light is irradiated so that the inner back side of the dot 202 is in a semi-cured state, the vicinity of the surface of the dot 202 is completely cured. Therefore, in this case, the adhesive force with respect to the transfer medium 50 becomes weak, and there is a possibility that appropriate transfer cannot be performed.

  On the other hand, when the dot 202 is irradiated with visible light having a wavelength longer than that of ultraviolet rays as in the case of the semi-curing light source 18 in this example, the absorption near the surface is reduced, and thus the distance L from the surface is reduced. Even at a large position, the attenuation of light is small. Therefore, more light can be transmitted to the inner side of the dot 202. As a result, the relationship between the distance L from the surface of the dot 202 and the light absorption distribution has a smaller change in the light absorption distribution due to the distance L than ultraviolet light.

  Further, the ultraviolet curable ink usually undergoes a curing reaction to some extent even when irradiated with visible light such as blue and green. Therefore, as shown in this example, when the difference in the amount of light absorption between the vicinity of the surface of the dot 202 and the inner back side is reduced by irradiating visible light, curing by the position in the dot 202 is performed. It is possible to appropriately prevent the difference in the way of traveling from becoming large. This also makes it possible to more uniformly and appropriately semi-harden the surface and the inside of the dot 202.

  Further, by appropriately setting the surface of the dot 202 to a semi-cured state, the adhesion force to the transfer medium 50 can be sufficiently increased after the transfer. Also, the inside of the dot 202 can be appropriately semi-cured to a hardness that does not cause the shape of the dot 202 to be deformed after transfer.

  In this example, the semi-curing light source 18 generates visible light in a wavelength range that increases the viscosity of the ink, such as blue, green, or white, depending on the ultraviolet curable ink to be used. As the ultraviolet curable ink, various known ultraviolet curable inks can be used as long as the viscosity increases in response to visible light having a predetermined wavelength. As the ultraviolet curable ink, for example, an ink in which both the peak wavelength of the thickener contained and the peak wavelength of the initiator absorption wavelength are in the near ultraviolet (for example, wavelength 200 to 380 nm) is used. It is possible. Further, the peak wavelength of the absorption wavelength of the thickener and the initiator is more preferably in the range of 308 to 365 nm. If comprised in this way, ink can be semi-hardened more appropriately by irradiation of visible light, for example.

  More specifically, as the ultraviolet curable ink, for example, various inks for LED type UV curable inkjet printer UJV-160 manufactured by Mimaki Engineering Co., Ltd. can be used. As this ink, for example, model number LF-200 (four colors of Y, M, C, K) which is a flexible UV ink and model number LH-100 (Y, M, C, K, W) which is a hard UV ink are used. 5 colors) or the like can be considered.

  In this example, the color of the ultraviolet curable ink is not limited to a specific color or a combination thereof. The color of the ultraviolet curable ink may be, for example, each color of YMCK ink, or light color, white color, metallic color, or clear color of each color of YMCK ink. Further, the ultraviolet curable ink may be either a cationic polymerization type or a radical polymerization type, or an ink in which both are mixed. Further, the ultraviolet curable ink may contain, for example, a solvent for adjusting viscosity. In this case, the ultraviolet curable ink contains a viscosity adjusting solvent or the like in a range that does not inhibit the ultraviolet curing, for example, in a range of 30% by weight or less.

  As described above, according to the present example, for example, the ultraviolet curable ink is made to have a high viscosity by the light irradiation before transfer by the semi-curing light source 18 and the ultraviolet light irradiation after transfer by the main curing light source 20. It is possible to appropriately change between two states, a cured state and a completely cured state. Further, due to the change in the two states, for example, bleeding on the pad 14 or the like can be appropriately prevented. Further, since the adhesive force to the transfer medium 50 is increased and transfer efficiency is improved, ink transfer failure during transfer is appropriately prevented, and at the same time, the state after transfer to the transfer medium 50 is strong. A printed image can be appropriately formed. In addition, it is possible to fix ink to various transfer media 50.

  In the modified example of the present invention, it is conceivable to use a light source that emits ultraviolet light weaker than the light source 20 for curing, for example, without using a visible light source as the semi-curing light source 18. In this case, for example, it is preferable to use, for example, a UVLED as the ultraviolet light source. In this case, for example, it is preferable to use a UV LED that generates ultraviolet rays having a relatively long wavelength of 350 nm to 420 nm. Even in such a configuration, it is possible to make the ultraviolet rays reach the inner side of the ink as compared with the case where ultraviolet rays having a shorter wavelength are used, for example. This also allows the ink dots to be in a semi-cured state.

  Further, as the light source for generating ultraviolet rays in the semi-curing light source 18, for example, it is conceivable to use a metal halide lamp, a xenon lamp or the like after cutting ultraviolet rays having a short wavelength. It is also conceivable to use black light that generates UV-C light. Even in such a case, the ultraviolet rays can reach the inner side of the ink by cutting the short wavelength ultraviolet rays. This also allows the ink dots to be in a semi-cured state.

  FIG. 4 shows a second example of the configuration and operation of the image transfer apparatus 10. Except for the points described below, the configuration and operation of the image transfer apparatus 10 are the same as or similar to those of the image transfer apparatus 10 described with reference to FIGS. 1 and 2. In this example, the image transfer apparatus 10 forms the transferred image 102 directly on the pad 14 by the inkjet head 12 without using the flat plate 40.

  FIG. 4A shows an example of the timing of forming the transferred image 102 by the inkjet head 12. In this example, the image transfer apparatus 10 forms the transferred image 102 directly on the pad 14 by the inkjet head 12. Further, the formed image to be transferred 102 is irradiated with light by the semi-curing light source 18. As a result, the ink in the transferred image 102 is brought into a semi-cured state on the pad 14.

  In this example, as the pad 14, for example, it is preferable to use a pad having a curved shape of the image forming surface close to a flat plate. With this configuration, the transferred image 102 can be more appropriately formed by the inkjet head 12. The image transfer apparatus 10 preferably includes a configuration that performs position control for causing the inkjet head 12 to follow a curved surface.

  FIG. 4B shows an example of the timing of transferring the transferred image 102 from the pad 14 to the transferred medium 50. FIG. 4C shows an example of the timing of ink curing after transfer.

In this example, by setting the ink on the pad 14 to a semi-cured state, the subsequent steps can be performed in the same manner as described with reference to FIGS. Therefore, the transfer to the transfer medium 50 and the step of curing the ink after the transfer can be performed, for example, in the same or similar manner as the steps described with reference to FIGS. 1C and 2A.

  In FIG. 4, the flat plate-shaped transfer medium 50 is also illustrated as the transfer medium 50 in addition to the pad 14 having a curved surface shape of the image forming surface close to a flat plate. However, also in this example, similarly to the case described with reference to FIG. 1 and FIG. 2, it is possible to use a transfer medium 50 of various materials such as a curved surface or a three-dimensional shape.

  Also in this example, similarly to the case described with reference to FIGS. 1 and 2, by making the ink semi-cured, for example, the ink of the transferred image 102 is appropriately prevented from spreading on the pad 14. be able to. Further, for example, transfer from the pad 14 to the transfer medium 50 can be performed appropriately. Furthermore, this makes it possible to perform pad printing by an appropriate method, for example, with a configuration that does not require a printing plate.

  Further, for example, in the case described with reference to FIGS. 1 and 2, transfer is required twice, but in this example, the number of transfers is one. Therefore, according to this example, the number of times of transfer can be reduced as compared with the case where the transfer target image 102 is formed on the pad 14 by transfer from another member. Further, by reducing the number of times of transfer, problems that may occur during transfer, such as color shift and bleeding, can be made difficult to occur.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

  The present invention can be suitably used for an image transfer apparatus, for example.

DESCRIPTION OF SYMBOLS 10 ... Image transfer apparatus, 12 ... Inkjet head, 14 ... Pad, 18 ... Semi-curing light source (pre-transfer light irradiation part), 20 ... Main curing light source (after transfer) UV irradiation part), 40 ... flat plate, 50 ... transferred medium, 60 ... cleaning sheet, 102 ... transferred image, 104 ... transferred image, 202 ... dot

Claims (9)

An image on which the image to be transferred is transferred to the transfer medium by using a pad having a curved image forming surface and bringing the image formation surface of the pad into contact with the transfer medium A transfer device,
An inkjet head that forms the transferred image by ejecting ink droplets of ultraviolet curable ink; and
In a state before being transferred from the pad to the transfer medium, a pre-transfer light irradiating unit that irradiates light to the transferred image;
A post-transfer ultraviolet irradiation unit that irradiates the post-transfer image which is an image formed on the transfer medium by transfer in a state after being transferred from the pad to the transfer medium;
The pre-transfer light irradiation unit irradiates the transferred image with light, thereby increasing the viscosity of the ink constituting the transferred image than before the light irradiation,
The post-transfer ultraviolet irradiation unit generates ultraviolet rays that cure the ultraviolet curable ink as ultraviolet rays to be applied to the post-transfer image.
The ultraviolet curable ink contains, as an initiator for starting the curing of the ultraviolet curable ink, one kind of initiator having a sensitivity peak in the ultraviolet region, and the light generated by the pre-transfer light irradiation unit An ink that reacts to increase viscosity,
The image transfer apparatus according to claim 1, wherein the pre-transfer light irradiating unit generates visible light having an intensity peak in an emission spectrum longer than 420 nm as light applied to the transferred image. The pre-transfer light irradiating unit has a wavelength range with a condition that the visible light has a small light absorption coefficient with respect to the ultraviolet curable ink and can reach the inside of the ink constituting the transferred image uniformly. It generates visible light,
The ultraviolet curable ink has a reduced difference in the amount of light absorption between the vicinity of the surface of the ink constituting the transferred image and the inner back side when irradiated with visible light. The image transfer apparatus according to claim 1. The inkjet head forms the transferred image on the planar member by ejecting ink droplets onto a planar member whose main surface is a planar member,
The pre-transfer light irradiation unit irradiates the transferred image on the planar member with light,
The transferred image formed on the image forming surface of the pad is an image transferred from the planar medium in a state after the light is irradiated on the pre-transfer light irradiation unit. The image transfer apparatus according to claim 1. The inkjet head forms the transferred image on the image forming surface by ejecting ink droplets on the image forming surface of the pad,
The image transfer apparatus according to claim 1, wherein the pre-transfer light irradiating unit irradiates light to the image to be printed on the image forming surface of the pad. The ultraviolet curable ink includes a thickener that increases the viscosity of the ultraviolet curable ink according to ultraviolet rays, and an initiator that initiates curing of the ultraviolet curable ink according to ultraviolet rays,
The wavelength of the intensity peak in the light emission spectrum of the light generated by the pre-transfer light irradiation part is greater than the wavelength of the peak of the absorption wavelength of the thickener and the wavelength of the peak of the absorption wavelength of the initiator. 5. The image transfer apparatus according to claim 1, wherein the image transfer apparatus has a wavelength on the long wavelength side of 200 nm or more.   The intensity peak in the emission spectrum of visible light generated by the pre-transfer light irradiation part is 200 nm or more longer than the intensity peak in the emission spectrum of ultraviolet light generated by the post-transfer ultraviolet irradiation part, The image transfer apparatus according to claim 1.   The image transfer apparatus according to claim 1, wherein the pre-transfer light irradiation unit includes an LED that generates visible light as a light source that generates light having a wavelength of the intensity peak.   The image transfer apparatus according to claim 1, wherein the transfer medium is a non-planar medium. An image on which the image to be transferred is transferred to the transfer medium by using a pad having a curved image forming surface and bringing the image formation surface of the pad into contact with the transfer medium A transfer method,
The transferred image is formed by an inkjet head that ejects ink droplets of ultraviolet curable ink,
In a state before being transferred from the pad to the transfer medium, by irradiating the transferred image with light, the viscosity of the ink constituting the transferred image is made higher than before the light irradiation,
In a state after the transfer from the pad to the transfer medium, the post-transfer image, which is an image formed on the transfer medium by transfer, is irradiated with ultraviolet rays that cure the ultraviolet curable ink,
The ultraviolet curable ink contains, as an initiator for starting the curing of the ultraviolet curable ink, one kind of initiator having a sensitivity peak in the ultraviolet region, and the light generated by the pre-transfer light irradiation unit An ink that reacts to increase viscosity,
The image transfer method according to claim 1, wherein the pre-transfer light irradiating unit generates visible light having an intensity peak in an emission spectrum longer than 420 nm as light applied to the transferred image.

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