JP6631033B2 - Coated and recorded materials - Google Patents

Description

  The present invention relates to a coated article and a recorded article.

  2. Description of the Related Art Conventionally, as an image formation using an active energy curable ink, it has been known that an ultraviolet curable ink is irradiated with ultraviolet rays to cure the ink, thereby fixing an image on a recording medium. It is known that an ink-jet recording apparatus using an on-demand type ultraviolet curable ink can form an image regardless of a recording medium. With widespread use, many ink jet recording apparatuses using ultraviolet curable inks are used in various applications.

  In an ink jet recording apparatus using an ultraviolet curable ink, a head mounted on a carriage scans along a recording medium by moving the carriage, and discharges and lands the ultraviolet curable ink on the recording medium. The recording medium on which the ink has landed is irradiated with ultraviolet light by an ultraviolet light source, and an image is formed by curing the ultraviolet curable ink on the recording medium.

Here, a screen printing method may be used as the ultraviolet curing type printing method in addition to the ink jet method. In particular, in the case of image formation where transmission density is required, since the image thickness is usually required, the image is formed by a screen printing method capable of thick film coating.
However, in the screen printing method, an ink jet method has been attracting attention because it is difficult to express a gradation (gradation) of a fine image and it is relatively difficult to perform multicolor printing. The ink jet method can freely control the characteristics of the coating film (adhesion between the substrate and the film, hardness of the film, etc.) by an image forming process, and is expected to be applied to various fields.

  In the case of the ink-jet method, since an image is formed by dots, by using an ultraviolet curable ink as the type of ink to be ejected, the leveling state and physical properties of the ink droplets can be controlled by the irradiation conditions of the ultraviolet light. In addition, it is fundamental to form a dot image using digital data. However, since there are many parameters that can be changed by adjusting the drop volume based on the image and the drop configuration procedure (changing the ejection order), the finish depends on the image forming process. Image quality and film characteristics can be changed.

  However, in the current single-layer printing using an ultraviolet curable inkjet method, when a film function such as hardness and ease of secondary processing is required, it is very difficult to control the coating film performance with a single-layer configuration. Difficult. Even when multi-layer printing is performed, it is difficult to control the state and shape of the ink droplets after landing if the layers are formed by the same image forming method.

  Patent Literature 1 discloses a method for manufacturing a printed material having a light-shielding layer formed by an inkjet method. The method for manufacturing a printed matter described in Patent Document 1 discloses that a light-shielding layer and a light-shielding layer are formed by repeating a step of discharging ink droplets of radiation-curable ink for forming a light-shielding layer onto a resin substrate and a step of irradiating radiation to cure the ink. A light-shielding correction layer is formed.

  However, in the film production according to Patent Literature 1, radiation irradiation conditions after image formation are not changed between printing processes, and it is difficult to make a difference in coating film characteristics for each layer. In addition, since all the layers are printed in multi-layers with high definition image quality, productivity is expected to decrease even when high image quality is not required. In addition, it is difficult to provide a film function such as hardness and ease of secondary processing.

  As described above, when forming a film having a function on an image by multi-layer printing, a coated film which does not decrease productivity, is a good image, and satisfies hardness and ease of secondary processing. Was desired.

  In view of the above problems, an object of the present invention is to provide a coated film that can be manufactured without lowering productivity, that is, a good image, and that satisfies hardness and ease of secondary processing. I do.

In order to solve the above-mentioned problem, the coating material of the present invention has a multilayer structure of two or more layers formed by an active energy curable ink, and the active energy curable ink forming each layer of the multilayer film is: The ink components other than the pigment component are the same, the difference in the component ratio of the ink components is ± 5% by weight or less, and the pigment component may or may not be contained. among them, at least two layers film hardness Ri Do different, and wherein the most film hardness uppermost layer is large.

  ADVANTAGE OF THE INVENTION According to this invention, it can manufacture without deteriorating productivity, can provide a favorable image, and can provide the coating material which can satisfy hardness and ease of secondary processing.

FIG. 2 is a schematic diagram illustrating an example of an image forming apparatus. FIG. 3 is another schematic diagram illustrating an example of an image forming apparatus. FIG. 2 is a schematic diagram of a main part of an example of an image forming apparatus. FIG. 2 is a schematic diagram for explaining an example of a case where an image is formed by an image forming apparatus. FIG. 4 is a diagram for explaining the behavior of the dot diameter of a landing droplet on each base material. FIG. 4 is a diagram for explaining the behavior of the dot height of a landing droplet on each base material. FIG. 4 is a schematic diagram for explaining a state of coalescence of dots forming a layer with adjacent dots. FIG. 4 is a schematic diagram for explaining a difference in dot diameter between dots forming a multilayer film. FIG. 9 is another schematic diagram for explaining a difference in dot diameter between dots forming a multilayer film. FIG. 9 is a diagram illustrating an example of a dot formation pattern using a normal printing order mask. FIG. 9 is a diagram illustrating an example of a dot formation pattern using a random order mask. It is a figure which shows an example of film | membrane formation by changing the order mask of each layer. It is a figure which shows an example of the irradiation intensity of the irradiation surface in the presence or absence of a slit. It is sectional drawing which shows an example of a coating material typically. It is a mimetic diagram for explaining a crack at the time of processing a press hole. It is a figure showing an example of the relation between hardness and press nature. It is a figure showing an example of the relation between a reaction rate and an integrated light quantity.

  Hereinafter, the coated film and the recorded matter according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments described below, and can be changed in other embodiments, additions, modifications, deletions, and the like within a range that can be conceived by those skilled in the art. The present invention is also included in the scope of the present invention as long as the functions and effects of the present invention are exhibited.

  The coating material of the present invention has a multilayer structure of two or more layers formed by an active energy curable ink, and the active energy curable ink forming each layer of the multilayer film has the same components other than the pigment component. Yes, the pigment component may or may not be contained, and at least two or more of the multilayer films have different film hardness.

Hereinafter, a preferred configuration of the coating film according to the present invention will be described with reference to the drawings.
The term "active energy" refers to general energy light such as ultraviolet rays in addition to electron beams and infrared rays. In the following embodiments, an ultraviolet ray will be described as an example.

The active energy-curable ink forming each layer of the multilayer film in this embodiment has the same components other than the pigment component, and may or may not include the pigment component.
The active energy curable ink is not particularly limited and can be appropriately changed. For example, known pigments, dispersions, polymerization initiators, surfactants, solvents, resins and the like can be used.

Further, “the components other than the pigment component are the same” means that the ink constituent materials other than the components that determine the ink color, such as the dispersion, the polymerization initiator, and the monomer component, are the same. Therefore, the pigment component (the component that determines the ink color) in each layer forming the multilayer film may be different from each other.
Although there is no particular limitation for being “identical”, it is preferable that the difference between the component ratios of certain inks A and B be ± 5% by weight or less when compared.
Further, the active energy curable ink in the present embodiment may or may not include the pigment component. When the ink contains a pigment component, it is a color ink. When the ink contains a pigment component, it is a clear ink. The two types of inks may be present in the same layer, or may be a layer containing only the clear ink.

  In the present embodiment, since the active energy-curable ink forming each layer of the multilayer film has the same components other than the pigment component, a coated film can be produced without reducing productivity. Although details will be described later, if the components of the ink are changed for the purpose of changing the characteristics of the film such as changing the film hardness of each layer in the multilayer film, the equipment cost increases and the productivity decreases.

  Generally, the surface of the coated film is required to have high film hardness in terms of film hardness represented by pencil hardness or the like, and is required to be a hard film. On the other hand, in the case of performing secondary processing such as making a hole in a coated film, it is required that the film be somewhat soft. However, since the film hardness and the secondary workability (pressability) are in a trade-off relationship, it is very difficult to satisfy both coating properties simultaneously.

For example, the following method can be considered for imparting coating film properties.
(1) Hardening the whole film By applying a large amount of ultraviolet light, the hardness of the film itself can be increased and the film hardness can be secured. However, because of the hard film, the workability is very poor.
(2) Softening the whole film The hardness of the film itself can be reduced and softened by weakly applying the amount of ultraviolet light. However, it is naturally difficult to secure the hardness of the surface.

  Therefore, the present embodiment is characterized in that at least two or more of the multilayer films have different film hardness. By adopting a multilayer structure and forming a film having different characteristics for each layer, for example, a coating film structure of a multilayer film having a hard surface and a soft inside can be realized, and film hardness and pressability (secondary workability) can be realized. Both characteristics can be satisfied.

  In addition, if the inside of the coating film is left in a soft state (internal curing failure), the components of the coating film may evaporate over time. When such a coating film is placed in an enclosed space and used, for example, a clouding phenomenon may occur inside the enclosed space.

  On the other hand, in the present embodiment, the uppermost layer of the multilayer film can be completely cured to cover the lower layer portion, and problems such as the clouding phenomenon can be solved. Further, according to the present embodiment, it is possible to secure necessary functions (for example, substrate adhesion, workability, and hardness) for each layer, and a specific function can be given to a specific layer.

For the production of a multilayer film having different functions and specifications for each layer, film formation by changing the image forming process for each layer is effective. As an example, as a method of changing the image forming process in the ink jet system, for example, the following method can be used.
(1) Change of scan direction (that is, one-way printing or two-way printing)
(2) Image order image mask (change of arrangement order of dot drops)
(3) Change in the number of scans (4) Change in print resolution (5) Change in the amount of ejected droplets (landing droplet diameter)

Further, in the case where an image is formed using a UV curable ink among the above-described ink jet systems, the coating film characteristics of a finally obtained image can be freely changed by performing the following method.
(6) Change of UV irradiation timing (7) Change of process linear speed (change of scanning speed of carriage, etc.)

  The change of the image forming process for each layer needs to be selected according to the function required for each layer. The image forming process used in the present embodiment is an example in which a carriage on which a print head is mounted moves and scans in a direction perpendicular to a scanning direction of a transport stage that transports a recording medium (substrate) to form an image. I will explain it.

  FIG. 1 shows a schematic diagram of an example of the image forming apparatus. FIG. 1 shows a carriage 10, a head unit 12, a UV irradiation device 14, a light source 16, a transport stage 18, and a recording medium 20. As shown in the figure, image formation is performed by moving and scanning the carriage 10 in the vertical direction (forward path (a), return path (b)) with respect to the scanning direction of the transport stage that transports the recording medium.

  As shown in FIG. 1, the image forming apparatus includes a head unit 12 in which ink jet heads for discharging droplets are arranged, a transport stage 18, and a UV irradiating device as an irradiating unit that cures ink on a recording medium 20 to form an image. It has 14. One UV irradiation device 14 is mounted in each of the head unit forward and backward scanning directions.

  FIG. 2 is a schematic diagram of a main part of a plan view of the inkjet head in FIG. FIG. 2 shows inkjet heads (12B, 12C, 12M, 12Y, 12Cl, 12W) of each color, and UV irradiation devices A and B (reference numerals 14a and 14b).

The inkjet head mounted in the head unit 12 uses black (Bk), cyan (Cy), magenta (Ma), yellow (Ye), clear (Cl), and white (Wh) inks of a total of six colors. Further, two heads of each color are connected in the longitudinal direction. Each head of this embodiment has a resolution of 600 dpi in four rows (150 dpi per row).
The recording medium 20 set on the transport stage 18 is transported on the stage, and an image is formed by the head unit 12 as an image forming unit. In the present embodiment, an ultraviolet curable ink, which is one of the active energy curable inks, is used as the ink ejected at that time.

The recording medium (base material) used in the present embodiment is not particularly limited, and a known medium can be used. It may be a permeable recording medium such as a paper medium or a non-permeable recording medium such as a plastic material (eg, polypropylene, polyethylene). Although a plastic material is preferable in consideration of workability, a material such as a metal and a ceramic can be used.
When an active energy-curable ink is printed on a non-permeable recording medium and an image is formed, the material of the recording medium is not selected as compared with a normal aqueous ink or the like. Having. In the following description of the embodiments, a plastic material will be described as an example.

  As the light source 16 of the UV irradiation device 14, for example, a light source that outputs each ultraviolet region such as UV-A, UV-B, and UV-C as an emission spectrum can be used. For example, a high-pressure mercury lamp, a metal halide lamp, an electrodeless UV lamp, a UV laser, a xenon lamp, an LED lamp, a germicidal lamp, or the like can be used.

Also, in recent years, LED-type ultraviolet irradiation has the advantage of narrowing down the emission wavelength to a certain narrow wavelength region, further obtaining high illuminance with good emission efficiency at the peak wavelength, low power consumption, and long life. Apparatus is often used. While the peak illuminance at 365 nm of a typical electrode lamp is several W / cm ² , the peak illuminance of a 395 nm LED or a 405 nm LED irradiator is several tens of W / cm ^2, which is several times that of a normal electrode lamp. Shows the strength of

Ideally, the lamps used in these ultraviolet irradiation sections are selected according to the photopolymerization initiator in the ink composition and matched as the emission peak wavelength by the absorption characteristics of the photopolymerization initiator. As an example, if the reaction peak wavelength of the photopolymerization initiator in the ink composition is 365 nm, a lamp having a strong wavelength range of 300 to 450 nm is selected. Specifically, if the reaction peak wavelength of the photopolymerization initiator in the ink composition is 240 nm, it is appropriate to select a metal halide lamp or a high-pressure mercury lamp.
As described above, it can be said that a normal electrodeed lamp shows an emission spectrum in a wide wavelength range, but an LED lamp shows a narrow emission spectrum around each central wavelength as described above.

  In addition to performing image formation using two or more types of ultraviolet lamps having different emission wavelengths and a common ink containing a polymerization initiator that reacts to the emission wavelength of each lamp, irradiation conditions (emission wavelength, leveling time, By controlling the irradiation intensity, it is possible to partially secure an arbitrary image quality.

  In the case of performing bidirectional printing, there is a repetition accuracy of the conveying device in addition to the characteristic of the ejection bending of the nozzle itself, and a finished image is largely influenced by the accuracy of the dot landing position. In the case of bidirectional printing, as shown in FIG. 2, in the case of printing of the same color, for example, Bk color, the time from printing and landing of the ejected droplets on the recording medium to irradiation of UV light, (Arrow (a)) and the return path (arrow (b)). The level difference of the ink droplet changes due to the time difference between the printing and the impact of the ink droplet on the recording medium and the irradiation of the UV light, and a large difference occurs in the finished image.

The scan direction can be selected by the user on software set at the time of printing, and one-way printing or two-way printing can be selected.
When creating images with the same resolution, there is an advantage that the printing speed can be increased (productivity can be increased) by performing the bidirectional printing. On the other hand, there is a concern that a weak point of the ink-jet method, that is, a bidirectional color difference or the like due to the influence of the accuracy of the landing position in the bidirectional printing occurs, thereby deteriorating the image quality.

However, in an image forming system using an ultraviolet curable ink whose main medium is a non-penetrable recording medium, the ink curing process is performed after each color ink is mixed on the base material, so that the influence of the bidirectional color difference can be suppressed. Therefore, it does not greatly affect the final image quality.
However, when forming a multilayer film in consideration of higher image quality and productivity, the lower layer is formed by bidirectional printing, and the uppermost layer is formed by unidirectional printing, so that overall productivity is maximized. Good image quality can be obtained.

FIGS. 3 and 4 are views for explaining the Scan method in the present embodiment. In the present embodiment, an example will be described in which one-way 16 Scan printing is performed.
FIG. 3 is a schematic diagram of a main part of an example of the image forming apparatus, and is a diagram illustrating a nozzle row used by the head in 16-scan printing. It should be noted that one of the Bk inkjet heads 12B shown in FIG. 2 is shown as an example.
In the case of setting of 16-scan printing, printing is performed by dividing all nozzle rows of the head into 16 in the longitudinal direction. The first scan is performed using the right 1/16 nozzle row group in the head division view of FIG. 3, and then the second scan is performed using the right 2/16 nozzle row group in the head division view, and the processing is performed up to the 16th scan. . Here, multi-pass printing using a random printing order mask is performed. FIG. 4 shows these temporal prints in a diagram.

FIG. 4 is a schematic diagram for explaining an example in which an image is formed by the image forming apparatus, and is a diagram schematically illustrating an example of a forming process in the case of forming a coating material on a base material. As shown by the arrow in FIG. 4, the base material 22 is transported in the base material feed direction, and the carriage 10 scans in a direction perpendicular to the base material feed direction to form an image. As shown in FIG. 2, there are two ink jet heads in the longitudinal direction, and FIG. 4 shows the position of a specific color head at a certain moment.
FIG. 4 shows an example of 16 scans, but the present embodiment is not limited to this, and can be changed as appropriate. For example, by increasing the number of scans, high image quality is aimed at. be able to. Therefore, 16 scans (scan the same place 16 times to form a target image) are an example of a printing method that can be set by the system used in the present invention, and FIG. It shows a depiction example.

  Usually, this is dealt with by changing the ink components according to the desired image quality and coating film characteristics. For example, if it is desired to improve the adhesion to the substrate, measures such as adding a surfactant are taken. However, mounting multiple types of inks means increasing the number of print heads, which is expensive as equipment, including not only the heads but also a drive system for driving the heads, resulting in an increase in equipment costs. Is inevitable. Specifically, the number of ink jet heads as shown in FIG. 2 increases, the system cost increases, and the size of the apparatus also increases.

The ink used in the present embodiment does not need to change the type of ink used for each desired image quality and coating film characteristic, and can be handled by the image forming process.
The emission wavelength [nm], irradiation intensity (peak illuminance) [mW / cm ² ], and integrated light amount [mJ / cm ² ] of the ultraviolet light used for curing the ink are determined based on the adhesion to the substrate or the adhesion between the ink layers. Not only has a great effect, but also has a great effect on the characteristics of the film to be formed. Specifically, the film strength, glossiness, and surface state of the film can be controlled by changing the above irradiation conditions. Determining the irradiation conditions is considered to require precise conditions in order to determine the image quality of the final product.

The ultraviolet irradiation device (UV irradiation device 14) shown in FIG. 1 has a control function for changing the power of the total output of the emission spectrum in each region output from the irradiation device. Thus, from 0% output to 100% output, the irradiation intensity (peak illuminance) [mW / cm ² ] and the integrated light amount [mJ / cm ² ] necessary for ink curing and for obtaining the target film characteristics are obtained. Can be changed arbitrarily. In the case of curing with the same control output, when the ink composition is the same, there is no difference in the finished film characteristics.

In addition to the above-described mechanical and electrical irradiation control, control of the timing of ultraviolet irradiation after forming an image with ink ejected from the ejection head is also an important parameter in determining image quality. Optimal irradiation can be performed by arbitrarily changing the peak illuminance [mW / cm ² ] and the integrated light amount [mJ / cm ² ] under irradiation conditions suitable for each purpose for each printing. On the other hand, when the integrated light amount [mJ / cm ² ] is desired to be constant, both means for irradiating strong light [mW / cm ² ] for a short time and means for irradiating weak light [mW / cm ² ] for a long time Conceivable. However, if it is desired to secure the integrated light quantity, it is necessary to change the transport speed, which affects the productivity. Therefore, it is difficult to secure the target film characteristics only by these measures.

  On the other hand, although the lower layer does not need to have high image quality, the lowermost layer needs to satisfy the adhesiveness with the base material. Therefore, by promoting coalescence with the adjacent dots, a solid image with a small gap is formed, and as a result, the adhesion can be improved. Compared with unidirectional printing, bidirectional printing, which is inferior in landing position accuracy, has an effect of promoting coalescence with adjacent dots.

  Note that a simple printing process may be used to complete one layer, but a printing process in which two or three layers are further stacked, for example, a case where transmission density is required as image quality, may be mentioned.

As described above, in the inkjet method, dots are stacked in multiple directions to form a film. Therefore, it is necessary to stack the same image on an already formed image. In this case, the lowermost layer is formed on the surface of the recording medium, but the layer above this is the already formed layer itself. Therefore, even if an image is formed on each layer by the same image forming process, the quality becomes completely different, which is inconvenient. For example, in the case of a three-layer configuration, the characteristics required for each layer are as follows.
(1) First layer: adhesion to base material (2) Second layer: adhesion to lower ink layer (first layer) (3) Third layer: formation of ideal dots for high image quality (user Visible part of
By satisfying all of these, the functions and specifications of the product will be satisfied.

  In the present invention, it is preferable that the multilayer film includes at least two or more layers having different dot diameters of dots forming the layers. By changing the dot diameter for each layer, it is possible to achieve individual functions (particularly coating film characteristics) required for each formed film.

The method of changing the dot diameter in each formed film is not particularly limited, but may be, for example, as follows.
First, after the ink droplet lands on the base material, the ink droplet is cured while keeping the dot shape on the base material. As a result, an image with high image quality and low gloss can be obtained. Other examples include landing ink droplets on a base material, leveling saturation on the base material, and then curing the ink droplets. Thereby, the adhesiveness can be improved. As described above, by controlling at which stage after the ink droplets have landed on the base material, the individual functions required for each forming layer can be achieved.

  Generally, when the recording medium is a plastic material (polypropylene, polyethylene, or the like), no functional groups are present on the surface of the recording medium. For this reason, when forming an image on these materials, measures must be taken to obtain adhesion. Many plastics contain substances to promote the adhesive action, but in some cases there are product-derived catalysts, and these substances diffuse to the substrate-ink interface, which can weaken the adhesion . Therefore, measures such as cleaning the surface of a plastic material with a solvent have been taken. However, this makes it extremely difficult to go online.

  On the other hand, in the present embodiment, it is possible to cope by performing leveling control of ink droplets. This is a leveling control of landed ink droplets (hereinafter, may be referred to as landed droplets). In the case of an image forming apparatus using UV curable ink, UV irradiation is performed after ink droplets land on a base material. It is possible to control the time up to as a parameter.

FIG. 5 shows an example of the relationship between the time from the ink droplet landing on each base material to the irradiation of ultraviolet rays and the size (dot radius) of the landing droplet. According to FIG. 5, it can be confirmed from the landing droplet behavior evaluation that the leveling state of the landing droplet changes depending on the type of the base material, and it can be seen that the leveling of the landing droplet is saturated after about 0.5 seconds ( Arrow (a)). This state is the state in which the landed droplets are in contact with the surface of the base material in the largest area. By irradiating the active light in this state, it is possible to improve the adhesion.
When activating light is applied after 0.5 seconds, the leveling state of the landed droplets does not change, so there is no problem if attention is paid only to the adhesion, but it is saturated as much as possible considering the productivity of the recorded matter. It is desirable to irradiate active light immediately after the state.

  As described above, if the time from when the ink droplet lands on the base material until the UV irradiation is shortened, the landed droplet can be cured while standing (small leveling). Leveling proceeds. In the case of the lowermost layer, it is preferable to provide a long leveling time to secure adhesion to the base material. On the other hand, since the image quality deteriorates due to the spread of the landing droplets, it is preferable not to level the landing droplets in the uppermost layer. This makes it possible to improve the adhesion to the substrate.

  As means for promoting leveling, in addition to increasing the droplet size, it is also effective to employ a hitting order mask, which will be described later, where landing droplets are easy to unite. These controls are important in controlling various image quality and various coating film characteristics of a target completed image.

  In the present invention, it is preferable that the multilayer film includes at least two or more layers having different dot heights of dots forming the layer. By changing the height of dots forming a film for each layer, it is possible to achieve individual functions (especially image quality) required for each formed film. In the present embodiment, the height of the formed dots can also be freely controlled, and the dot height greatly affects the image quality, particularly the surface glossiness.

  As a method of increasing the height of the dots, there is a method of shortening the time from when the ink droplet lands to when the ink droplet is irradiated with ultraviolet rays, whereby the ink droplet can be cured with the dots standing up. As a result, unevenness can be formed on the surface, and a matte image can be provided as image quality. On the other hand, by increasing the time from when the ink droplet lands to when the ink droplet is irradiated with ultraviolet rays, the dot height can be reduced, and glossiness can be imparted to the image surface.

  FIG. 6 shows an example of the relationship between the time from the landing of ink droplets on each base material to the irradiation of ultraviolet rays and the height of landing droplets. According to FIG. 6, it can be confirmed from the landing droplet behavior evaluation that the height of the landing droplet changes depending on the type of the base material, and it can be seen that the height of the landing droplet is saturated after about 0.5 seconds. (Arrow (a)). In the present embodiment, if it is desired to obtain a matte feeling on the surface of the recorded matter, the active droplet is irradiated within 0.5 seconds after the ink droplet lands on the base material, so that the image is formed in a state where the landed droplet stands. Are formed, and an image having a matte feeling is obtained. At this time, the shorter the time from when the ink droplet lands on the substrate to when the active energy is irradiated, the higher the height of the landed droplet.

  Further, in the present invention, it is preferable that the multilayer film includes at least two or more layers having different bonding states between adjacent dots in the dots forming the layer. The difference in the union of the dots causes, for example, a change in the adhesiveness and a change in the solid density due to a change in the gap between the dots. By changing the bonding state of the dots forming the film for each layer, it becomes possible to achieve individual functions required for each formed film.

  FIG. 7 is a schematic cross-sectional view for explaining a union state with adjacent dots. FIG. 7A is an example of a case where the impacted droplets are cured by irradiating active energy while the adjacent dots are not united and the shape of the impacted droplet is maintained. As shown in the figure, since the contact area with the substrate is small, the adhesion is weakened, which is not preferable as the lowermost layer in the multilayer film. On the other hand, since the curing is performed by irradiating the activated light while maintaining the shape of the landing droplet, the uppermost layer is effective as a landing droplet for improving image quality (high image quality).

  On the other hand, FIG. 7B shows a coating film formed by an image forming process in which coalescence with adjacent dots is promoted. This is an example of a case where a landing droplet is cured by irradiation. As shown in the figure, the contact area with the base material is large, so that the adhesiveness becomes strong and is effective as the lowermost layer in the multilayer film.

The method of controlling the union of the adjacent dots is not particularly limited, and examples thereof include a change in the dot arrangement pattern and a change in the scan direction.
FIG. 7A shows a schematic cross section of an ink droplet formed by one-way printing, and FIG. 7B shows a schematic cross section of an ink droplet formed by bidirectional printing.
As shown in FIG. 7A, in one-way printing, since the accuracy of the landing position of the ink droplet is good, there is little dot coalescence with the adjacent ink droplet, and the ink droplet can be cured in a standing state. Therefore, it is possible to form an image with high image quality unique to the inkjet method.
On the other hand, as shown in FIG. 7B, in the bidirectional printing, since the accuracy of the landing position of the ink droplet is poor, the number of dots and the number of adjacent ink droplets increase, and the leveling of the ink droplet progresses. . As a result, for example, bleeding occurs at the edge portion of the image, and the image quality of the image is likely to deteriorate.
Taking into account the properties of the above-mentioned impacted droplets, it is extremely important to produce the desired recordings by changing the imaging process for each layer for the coating film necessary to fulfill the function of each layer. Become.

  In the present invention, it is preferable that the dot diameter of the dot forming the lowermost layer is larger than the dot diameter of the dot forming the layer above the lowermost layer. Thereby, the adhesiveness between the base material and the lowermost layer and the adhesiveness between the formed films can be improved.

For example, when distinguishing the uppermost layer, the intermediate layer, and the lowermost layer in the multilayer film, each layer is required to have the following functions.
(1) The uppermost layer is required to have high image quality in order to secure image quality in addition to scratch resistance as a coating film characteristic.
(2) In addition to ensuring adhesion to the lowermost layer, the intermediate layer is required to ensure smoothness for landing of ink droplets and to secure a film thickness for other thick-film products.
(3) The lowermost layer is required to ensure adhesion to the base material.

  Particularly, the function required for the lowermost layer is adhesion, which greatly contributes to the improvement of product quality. The method of increasing the diameter of the dot forming the lowermost layer is not particularly limited, but includes, for example, a method of controlling the time from when an ink droplet lands to when it is irradiated as described above. . For example, by increasing the time from when an ink droplet lands to the time when ultraviolet rays are radiated, the landed droplet on the base material can spread on the base material (promoting leveling) and increase the dot diameter. it can. As a result, the contact area between the substrate and the landing droplets increases, and a formed film with improved adhesion to the substrate can be obtained.

  That is, in the case of an image forming apparatus using an ultraviolet-curable ink, the leveling control of the landing droplets can be controlled using the time from the landing of the ink droplets on the base material to the irradiation of ultraviolet rays as a parameter.

  FIG. 8 is a schematic diagram for explaining the dot diameter of each layer in a two-layer configuration. FIG. 8 shows an example in which a lowermost layer (reference numeral 26) having a large dot diameter is formed on a base material, and an uppermost layer (reference numeral 28) having a small dot diameter is formed on the lowermost layer. . In this case, the lowermost layer having a large dot diameter comes into contact with the surface of the base material with a large area, and by irradiating the active light in this state, the adhesion can be improved. On the other hand, the uppermost layer preferably has a small dot diameter for higher image quality.

  In the present invention, it is preferable that the volume of the dot forming the lowermost layer is larger than the volume of the dot forming the layer above the lowermost layer. By forming the lowermost layer by increasing the droplet volume per droplet ejected from the inkjet head under the same resolution ejection conditions, that is, by increasing the dot volume and forming the lowermost layer, adjacent dots are formed. The two will unite. Thus, in the lowermost layer, the landing droplets unite with each other to form a large ink droplet, thereby filling the gap and increasing the contact area between the base material and the landing droplet. Therefore, it is possible to obtain a coated film having improved adhesion to the substrate.

FIG. 9 is a schematic diagram illustrating an example of a multilayer film when an image is formed by changing the amount of ink droplets ejected from the inkjet head. FIG. 9 shows, as an example, three layers: a lowermost layer (reference numeral 30), an intermediate layer (reference numeral 32), and an uppermost layer (reference numeral 34).
In the example illustrated in FIG. 9, the amount of the lowermost ink droplet (dot) formed on the base material is, for example, 14 pl, and the amount of the uppermost ink droplet is, for example, 7 pl. That is, the amount of ink droplets in the uppermost layer is controlled to half (1/2) the amount of ink droplets in the lowermost layer.
Controlling the amount of ink drops also controls the size of the ink drops. In this example, since the amount of ink droplets in the uppermost layer is small, the size of the ink droplets is also small, and the diameter of the dots forming the image is small. Thereby, the image quality of the image formed by the ink droplet film of the uppermost layer is improved, and the image quality can be improved.

In the example shown in FIG. 9, since the amount of ink droplets (14 pl) is large (the size of ink droplets is large) in the lowermost layer, the number of scans is, for example, eight. In the uppermost layer, since the amount of ink droplets (7 pl) is small (the size of ink droplets is small), the number of scans is, for example, 16 scans. The lowermost layer performs bidirectional printing, and the uppermost layer is formed by unidirectional printing.
As described above, by combining the control of the amount of ink droplets (the size of ink droplets), the control of the scan direction, the control of the number of scans, and the control of the resolution, a multilayer thick film having the film characteristics required for each layer can be formed. Obtainable.

  It is also effective to properly use the dot arrangement pattern to be used depending on the function of each layer. In the present invention, it is preferable that at least two or more types of dot arrangement patterns are used for the multilayer film. Even in the same image data, the film characteristics and image quality can be changed by controlling the landing pattern of ink droplets. By changing the dot arrangement pattern, the likelihood of landing of coalesced droplets changes. The coalescing state of the landing droplets greatly contributes to image quality, in particular, to characteristics that influence image quality such as banding, in addition to the coating film characteristics of the product.

As the dot arrangement pattern, for example, pattern formation using a normal hitting order mask or a random hitting order mask can be mentioned. By changing the printing order mask for each layer and changing the order in which the dots are arranged, it is possible to control the union status of the dots.
FIG. 10 and FIG. 11 are diagrams showing a hitting order mask used in the present embodiment and images of landing droplets formed by each hitting order mask as viewed from above. FIG. 10 shows an example of a dot formation pattern using a normal printing order mask, and FIG. 11 shows an example of a dot formation pattern using a random printing order mask. In order to effectively utilize the individual resolution of the inkjet head to be used and to increase the printing speed by forming a minimum image, a normal printing order mask that does not perform complicated image processing is effective.

However, when an image is formed using a normal shot order mask, characteristics of each nozzle of each ink jet head (ejection bending, speed fluctuation, and the like) appear as they are in a completed image. As a result, the image appears as banding, which causes an image defect.
Therefore, particularly in the uppermost layer, a good image can be obtained by using a random order mask instead of using a normal order mask.

  Although the random hitting order mask is used, the image quality can be changed by changing the number of scans even when the same random hitting order mask is used. By changing the nozzles used for each pass as compared with the normal shot order mask, it is difficult to be affected by the ejection characteristics such as individual ejection bends unique to each nozzle, and these characteristics can be scattered throughout the image. By changing the number of scans, the number of divisions of the head row is changed. Naturally, if the number of scans is increased, the influence of the ejection bend becomes less likely. However, the printing speed decreases.

Therefore, the number of scans is increased in the uppermost layer which directly affects the image quality, and the number of scans is reduced in the lower layers below the uppermost layer. It is possible to obtain necessary functions for each.
Further effects can be obtained by changing the image forming process for each layer by combining the above-described change of the scan direction, change of the printing order mask, change of the number of scans, and change of the discharge droplets by changing the resolution and the drive waveform. Can be

  In the present invention, the lowermost layer is formed by an array pattern of dots that maximizes coalescence with adjacent dots, and the uppermost layer is formed by an array pattern of dots that minimizes coalescence with adjacent dots. Is preferred. Even in the same image data, by controlling the ink droplet landing order, that is, by controlling the dot arrangement pattern, it is possible to change the film characteristics and the image quality. In particular, a banding reduction effect can be expected.

  In order to reduce banding, it is preferable to use a random order mask, but since banding reduction is required only on the top layer that can be seen by the user, banding in the lower layer will not significantly affect the product . Therefore, productivity and image quality can be made compatible with each other by using a normal mask in the lower layer than the uppermost layer.

FIG. 12 is a schematic diagram illustrating an example of a film configuration when the dot array pattern is changed. FIG. 12 illustrates a two-layer structure of the A layer and the B layer, in which the lowermost A layer is formed in contact with the base material, and the uppermost B layer is formed on the outermost surface.
The layer A shown in FIG. 12 appears to be two layers, but is one layer because the landing positions of the ink droplets 24 are different. The B layer is composed of a portion a and a portion b when viewed in detail. The portion a of the layer B has a different landing position of the ink droplet 24 as in the case of the layer A. The b portion of the B layer is formed for expressing a matte feeling, and here, the portion a and the portion b are considered as one layer.

For example, in the case of a 16-scan image formation with a two-layer configuration, in the image formation process from the first scan to the 16th scan of the first layer, image formation is not performed at the same position, and after the first layer is completed, The first to 16 scan images of the second layer are formed in exactly the same landing order of the droplets, and a total of two layers are formed.
On the other hand, in the example shown in FIG. 12, in the normal two-layer image formation, for example, the first scan of the first layer, the first scan of the second layer, and the second scan of the first layer, Then, the second scan of the second layer is performed. The 16th scan of the second layer is performed next to the 16th scan of the first layer. The total amount of ink constituting the layer at the time of finishing does not change in either order, but a completely different coating film is completed due to the different order.
In the example shown in FIG. 12, the A layer and the B layer are each formed by 16 scans, and the layer formed by 16 scans is considered as one layer.

  In the example shown in FIG. 12, the layer A is formed by bidirectional printing with 14 pl per drop, the portion a of the layer B is formed by bidirectional printing with 7 pl per drop, and the portion b of layer B is formed by 1 bidirectional printing. It is formed by unidirectional printing with 7 pl of drops. The lowermost layer has little effect on image quality, but it is necessary to ensure adhesion to the base material, so high-speed printing and bidirectional printing with large ink droplets using a normal printing order mask that promotes dot coalescence Is preferably performed.

In the uppermost layer, image quality is greatly affected.However, since it is not necessary to secure the adhesion to the substrate, it is necessary to perform low-speed printing and reduce dot coalescence to improve image quality. It is preferable to use a random hitting order mask for the purpose of reducing banding that has a large effect. Further, it is preferable to form an image by unidirectional printing of small ink droplets.
As in the above-described image forming process, by controlling the image formation of the multilayer film having the required image quality and coating film function as required, it is possible to obtain the desired coated film.

  In the above description, the ultraviolet ray is taken as an example of the active energy. However, the present invention is not limited to this, and an electron beam, an infrared ray, or the like can be used. Among these, it is preferable that the active energy used for curing the ink is ultraviolet light.

  When stretchability is required as a function of a film forming a multilayer film, film characteristics can be controlled by changing the elastic modulus of the coating film by an image forming process. Here, the controllable parameters include the peak illuminance and the integrated light amount. These can be controlled by various means, and can be controlled not only by changing the output of the irradiator itself (peak illuminance) but also by changing the line linear velocity (integrated light amount).

  Another means is to adjust the opening range of the irradiation surface under the same condition (the same peak illuminance) for the output setting from the irradiation machine lamp. The adjustment of the opening range of the irradiation surface can be performed, for example, by adjusting the slit width of the opening of the irradiation surface in the irradiation machine.

  FIG. 13 shows an example of the irradiation intensity profile of the irradiation surface with and without the slit. The horizontal axis is the distance from the irradiation point (spot), and the vertical axis is the peak illuminance. As shown in FIG. 13, when a slit is provided, the area of the medium irradiated with ultraviolet light is reduced, whereas when there is no slit, the area of the medium irradiated with ultraviolet light is increased. Thereby, the total amount of light to be irradiated is controlled, and it is possible to control the elastic modulus and stretchability of the coated film.

  Normally, in order to obtain a target integrated light amount while keeping the peak illuminance at the same value, it is necessary to reduce the line linear velocity, and there is a concern that productivity may decrease at the same time. On the other hand, by performing the control as shown in FIG. 13, it is possible to obtain the required peak illuminance, and also to change the integrated light amount while keeping the line linear speed at the same speed.

  As described above, the presence or absence of the slit changes the elastic modulus of the film cured by the irradiation of ultraviolet rays. Even if the reaction rates are the same, since the film characteristics are different depending on how light is irradiated, the elastic modulus greatly contributes to the stretching of the film, and the elastic modulus when the slit is provided is larger than the elastic modulus when the slit is not provided. Utilizing this property, for a layer that needs to be stretched, a target stretched film can be secured by reducing the high peak illuminance and the total amount of light with a slit under the same peak illuminance. At this time, since the area irradiated with the ultraviolet light is reduced, a strong peak illuminance is irradiated to the film in a short time, and the three-dimensional network structure formed by the reaction becomes uniform, and shows a high elastic modulus. It is believed that a highly stretched film is formed.

On the other hand, by not providing a slit, the irradiation area is increased by increasing the high peak illuminance and the total light amount, and as a result, the change in the irradiation intensity of the ultraviolet light becomes gentler than the former (with the slit). Therefore, it is considered that a distribution also occurs in the polymerization reaction of the ink, and the three-dimensional network structure becomes non-uniform, so that the network is widened, and as a result, it is difficult to obtain a stretched film.
Thus, various kinds of coating film characteristics can be obtained by controlling the two important parameters (peak illuminance, integrated light amount) in detail.

  Next, the film hardness and pressability will be described. FIG. 14 is a schematic view of an example of a formed film aiming at compatibility between film hardness and pressability. FIG. 14 illustrates the substrate 22, the soft film 38, and the hard film 39.

  The coating film surface is generally required to have a film hardness represented by pencil hardness or the like, and a hard film is preferred. As means for securing the film hardness, for example, adjusting the irradiation amount to the coating film, such as increasing the ultraviolet irradiation intensity for curing the ink, or increasing the total integrated light amount, and thereby, the target film hardness Can be achieved.

  On the other hand, in the case of a coating film that requires secondary processing such as making a press hole in the coating film, a coating film having flexibility is required. In the case of a hard coating film, cracks and the like occur when pressing is performed, which is a factor that causes a defect.

  FIG. 15 shows a diagram for explaining a crack when a press hole is formed. In FIG. 15, it is determined whether there is a crack or a chip, and the rank is evaluated as 1 to 5. Ranks 1 to 3 do not satisfy the level that can withstand the implementation, and ranks 4 and 5 are the levels that can withstand the implementation. In ranks 1 to 3, the horizontal portion of the press hole has cracks or chips in the vertical direction, but not in ranks 4 and 5. In the case of rank 4, although cracks are observed on the press slope, it is at a level that can withstand the implementation.

  In general, as a means for forming a film having flexibility, a method of changing the ink formulation or reducing the ultraviolet intensity or the total irradiation amount used for curing the ink is used. However, it is very difficult to obtain a desired film because there is a trade-off relationship between film hardness and pressability (workability).

  FIG. 16 shows a diagram for explaining the relationship between hardness and pressability. The horizontal axis is the ultraviolet control output, the right vertical axis is the pencil hardness, and the left vertical axis is the press rank (rank in FIG. 15). As shown in the figure, as the UV control output is increased, the pressability (left vertical axis) deteriorates at a certain value, while the hardness (right vertical axis) satisfies a satisfactory level. That is, the region indicated by the arrow (a) has good pressability, and the region indicated by the arrow (b) has good hardness.

In order to harden the entire film, it is possible to increase the hardness of the film itself by applying a large amount of ultraviolet light. However, because of the hard film, the workability is very poor. On the other hand, in order to soften the entire film, it is possible to form the film in a soft state by applying a weak amount of ultraviolet light. However, it is difficult to secure the hardness of the surface.
For this reason, it is difficult to simultaneously satisfy the characteristics of both coating films in an image forming process that achieves either one of the characteristics of hardening or softening the entire coating film.

  Therefore, in the present embodiment, as shown in FIG. 14, the film hardness of the multilayer film is made different, the upper layer in the multilayer film is a hard film (hard film 39), the lower layer is a soft film (soft film 38), and the surface is hard. , The inside of which is soft. This makes it possible to obtain a coating film that satisfies both characteristics at the same time.

In addition, if the inside of the cured film is formed of a soft film to ensure pressability (secondary workability), internal curing failure may occur. May occur. When such a coated material is used in an enclosed space, a clouding phenomenon inside the enclosed space may occur.
Therefore, in the present embodiment, by forming a film that completely cures the uppermost layer and covers the lower layer portion, it is possible to suppress volatilization with time, and the above problem is solved.

  Further, in the present invention, the multilayer film is preferably made of a polymer, and preferably has at least two or more layers having different reaction rates of the monomers constituting the polymer. The film hardness of the film forming the multilayer film can be changed due to the difference in the reaction rate of the monomer. In the present invention, the polymer and monomer are not particularly limited, and known polymers and monomers can be used.

  FIG. 17 is a diagram for explaining the relationship between the integrated light amount and the reaction rate. In FIG. 17, the horizontal axis represents the integrated light amount, and the vertical axis represents the reaction rate. Plots were made for two different types of ink. In the figures, the term "reaction rate" indicates the reaction rate of the monomer.

In the present embodiment, when the monomer reaction rate is 90%, it is regarded as a fixed line ((a) in the figure), and when the monomer reaction rate falls below 90%, the ink is uncured. Therefore, when it is less than 90%, there is a concern that the ink will evaporate over time. In the example shown in FIG. 17, in order to make the monomer reaction rate 90% or more, it is preferable that the integrated light amount be 400 mJ / cm ² ((b) in the figure) or more.

Therefore, in the case of this embodiment, in the case of this embodiment, the uppermost layer (hard film 39) is formed with an integrated light amount of 400 mJ / cm ² or more, and the soft film 38 is formed with an integrated light amount of 400 mJ / cm ² or less. As a result, a coated film having both hardness and pressability can be obtained.

  Further, in the present invention, there is provided a recorded article formed by forming the above-mentioned coated article of the present invention on a recording medium. Note that, as described above, the recording medium used for the recorded matter is not particularly limited, and can be appropriately changed.

Reference Signs List 10 Carriage 12 Head unit 13a to 13p Scan mask 14, 14a, 14b UV irradiation device 16 Light source 18 Transport stage 20 Coating material 22 Base material 24 Ink droplet 26, 30 Lowermost layer 28, 34 Uppermost layer 32 Intermediate layer 38 Soft film 39 Dura

JP 2012-192721 A

Claims (10)

A multi-layer structure of two or more layers formed by an active energy curable ink,
The active energy-curable ink forming each layer of the multilayer film has the same ink constituent material other than the pigment component, the difference in the component ratio of the ink constituent material is ± 5% by weight or less, and contains the pigment component. May or may not be included
Wherein among the multi-layer film, coating material, wherein at least two layers Ri Do different film hardness, the most film hardness uppermost layer is large.   The coated article according to claim 1, wherein the multilayer film includes at least two or more layers having different dot diameters of dots forming the layer.   The coated article according to claim 1, wherein the multilayer film includes at least two or more layers having different dot heights of dots forming the layers.   The coated article according to any one of claims 1 to 3, wherein the multilayer film includes at least two or more layers having different bonding states with adjacent dots in dots forming the layer.   The multilayer film according to any one of claims 1 to 4, wherein a dot diameter of a dot forming a lowermost layer is larger than a dot diameter of a dot forming a layer above the lowermost layer. The coated film described in the above.   The volume of the dot which forms the lowermost layer of the said multilayer film is larger than the volume of the dot which forms the layer above the lowermost layer, The Claims any one of Claims 1-5 characterized by the above-mentioned. Coating material.   The coated film according to any one of claims 1 to 6, wherein at least two or more types of dot arrangement patterns are used for the multilayer film. The coated article according to any one of claims 1 to 7 , wherein the multilayer film is made of a polymer, and has at least two or more layers having different reaction rates of monomers constituting the polymer. The coated material according to any one of claims 1 to 8 , wherein the activation energy is ultraviolet light. A recorded matter, comprising a recording medium on which the coated matter according to any one of claims 1 to 9 is formed.