JP2005319642A - Inkjet image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet image forming method capable of forming a fine and clear image by utilizing an undercoat layer of UV ink under not yet cured state when an image of UV ink is formed on the undercoat layer of UV ink by inkjet. <P>SOLUTION: The inkjet image forming method comprises a step for providing an undercoat layer 3 of UV-curing ink on the print surface of an optical disc, or the like, a step for forming an inkjet image 4 of UV-curing ink on the undercoat layer under not yet cured state, and an exposure step for irradiating the inkjet image 4 and the undercoat layer 3 simultaneously with UV-rays. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming method by ink jet using ultraviolet curable ink (hereinafter referred to as UV ink) having good adhesion to printed materials such as resin, glass, and metal other than paper.

  In recent years, many image forming methods using an ink jet printer have been used as image forming methods capable of forming images easily and inexpensively.

  In order to form a clear image without blur using an ink jet printer, an undercoat layer (receiving layer, image receiving layer) for accurately receiving fine ink ejected from the nozzles of the ink head (printer head) on the printing surface Layer) must be provided. Further, when clear printing is performed on a printed material whose printing surface is not white (especially when color printing is performed), it is necessary to provide a white or light single color undercoat layer.

  Water-based dye inks, water-based pigment inks, solvent inks, oil-based inks, and UV inks are known as ink types used in ink-jet printers. When water-based dye inks, water-based pigment inks, and oil-based inks are used, ink jet printers are used. An undercoat layer is essential for accurately receiving fine ink ejected from the ink.

  On the other hand, UV ink adheres well to printed materials such as resin other than paper, metal, glass, etc., and has the feature of good durability of printed images. Various industrial products other than paper (resin products such as optical disks) It is also effective for printing on glass products and metal products). An undercoat layer is not essential to ensure adhesion, but it is necessary to perform clear color printing on printed materials whose printed surface is not white. It is necessary to provide a white or light single color undercoat layer.

The quality of the image quality in the ink jet printer is determined by how accurately the fine ink ejected from the ink head is fixed (received) to the printing surface. Ink jet printers that are generally used at present are capable of clear printing because they are printed on special paper having a layer that accurately receives the ejected fine ink. When a color image is formed by UV ink inkjet on a printed material other than paper, it is desirable to provide a UV ink primer layer, but the UV ink after exposure and curing was ejected from an inkjet printer. There is a problem that it does not have a function of accurately receiving fine UV ink. That is, after UV ink as an undercoat layer is provided on a surface to be printed by a method such as printing or painting, the surface is cured by UV curing. When UV ink is printed on the cured UV ink by an ink jet printer, the discharged fine UV ink has fluidity, so the area becomes wider as shown in FIG. As shown in (C), the fine ink moves and overlaps with the fine inks of other colors, so that a fine image cannot be formed. One of the causes is a difference between the surface tension (surface energy) of the surface of the undercoat layer and the surface tension of the discharged fine UV ink. In other words, the following conditions: surface tension of surface to be printed (surface energy)> printing quality is improved when the surface tension of fine ink by ink jet is satisfied, but when UV ink primer layer is cured, It can be considered that the condition cannot be satisfied.

When the present inventors use UV ink as an undercoat layer, if it is in an uncured state, it becomes an appropriate wet surface, and a difference in surface tension occurs between the fine UV ink by inkjet and the above-mentioned conditions In other words, the surface tension of the printing surface (surface energy)> the surface tension of the fine ink by the ink jet can be sufficiently satisfied, and the fine UV ink for forming the ink jet image is held while maintaining the ejection shape without spreading to the periphery. I found what I could do.

  Therefore, in view of the above points, the present invention uses an uncured UV ink primer layer to form a fine image when an image is formed on the UV ink primer layer by inkjet ink. An object of the present invention is to provide an ink jet image forming method capable of forming a clear image.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

  In order to achieve the above object, an inkjet image forming method according to the present invention includes an undercoating step in which UV ink is provided as an undercoat layer on a printing surface, and an inkjet image with UV ink on the uncured undercoat layer. And an exposure step of simultaneously irradiating the inkjet image and the undercoat layer with ultraviolet rays.

  In the undercoating step, white, light monochromatic or transparent ultraviolet curable ink may be applied as an undercoat layer.

  In the image forming step, a color image using at least three primary color inks and a black ink or an image using a special color ink can be formed.

  In the exposure step, it is preferable to irradiate ultraviolet rays in parallel with the UV ink particles being ejected onto the printing surface in the image forming step.

The image forming method by ink jet according to the present invention uses an uncured UV ink primer layer, and the surface of the primer layer is wet and has appropriate flexibility. Then, a difference in surface tension occurs between the undercoat layer and the fine-grain UV ink by inkjet, the following conditions:
The surface tension of the printing surface (surface energy)> The surface tension of the fine ink by ink jet can be sufficiently satisfied, and the fine ink constituting the ink jet image discharged by the ink jet does not spread to the periphery, so that the discharged shape is maintained. Can be added. The UV ink of the uncured undercoat layer and the UV ink for image formation printed by inkjet can be cured simultaneously by irradiating with strong ultraviolet rays.

  By using the inkjet image forming method of the present invention, a clear and durable print can be made on the surface of a printed material other than paper such as resin products such as optical disks, glass products, and metal products. Furthermore, the primer layer and the image on it need only be cured simultaneously by UV irradiation, the number of exposure processes can be reduced, fewer lamps are required for UV curing, and the equipment installation area can be saved and power consumption can be reduced. There is also an effect of saving the amount.

  Hereinafter, as the best mode for carrying out the present invention, an embodiment of an image forming method using ink jet will be described with reference to the drawings.

  FIG. 1 shows an embodiment of an image forming method by ink jet according to the present invention, and an image forming on an optical disk will be described as an example.

  Optical discs (CD, DVD, CD-R, DVD-R, etc.) have a high appearance on the label surface (printed surface) due to the influence of the metal film processing (evaporation or sputtering) layer necessary for the function of the optical disc. Yes. Conventionally, offset printing or screen printing has been used for label printing of optical discs. However, even if an image such as a photograph is printed in color with the label surface left unprocessed, the image can be printed clearly on white media. Must not. For this reason, normally, white ink is printed by screen printing before color printing. The same applies to color printing on the label surface by an inkjet printer, and it is necessary to print white ink as an undercoat layer.

  For this reason, first, in the undercoating step of FIG. 1A, white UV ink is screen-printed, offset printed, and printed by an inkjet printer as an undercoat layer 3 on the image forming area of the label surface 2 that is the printing surface of the optical disc 1 Etc. to provide a uniform thickness (printing and coating).

  Next, in the image forming step of FIG. 1B, a color image is formed on the surface of the undercoat layer 3 from the ink head of the ink jet printer while the white UV ink as the undercoat layer 3 is not cured with ultraviolet rays. A fine UV ink for forming is ejected. The surface of the primer layer 3 in the uncured UV ink is a wet surface having moderate flexibility, and the fine UV ink constituting the inkjet image 4 ejected by inkjet is the periphery as shown in FIG. Therefore, the discharged shape can be maintained. For example, when a color image is formed by ejecting three primary color inks of yellow (yellow), magenta (red), and cyan (blue) and a black ink from an ink head, a fine particle of each color as shown in FIG. Since it is possible to prevent ink from spreading and mixing, a clear color image can be formed. In order to improve the image quality, in addition to the three primary color inks and the black ink, a light indigo ink and a light red ink may be used.

  Following the inkjet image formation in FIG. 1B, the inkjet image 4 and the undercoat layer 3 are simultaneously irradiated with ultraviolet rays by an ultraviolet lamp in the exposure step of FIG. At that time, in order to simultaneously cure the inkjet image 4 and the undercoat layer 3, a slightly stronger ultraviolet ray is irradiated. This exposure step may be performed after completion of color image formation by ink jetting on the image forming area of the label surface 2 in FIG. 1B, but an ultraviolet irradiation lamp is provided adjacent to the ink head of the ink jet printer. Alternatively, ultraviolet irradiation may be performed immediately after ejection of the fine UV ink by the ink head (in parallel with the image forming operation by the ink head).

  The UV ink that can be used in the present embodiment is, for example, prepared and manufactured with the following composition. The main materials (corresponding to ordinary solvent-based ink vehicles) are as follows.

a. Acrylic monomer
Acrylic compound that is not polymerized. The viscosity is low.
b. Acrylic oligomer An oligomer having an acryloyl group in the molecule and a molecular weight of up to about 10,000. Viscosity is high.
(A and b are mixed and adjusted to a viscosity suitable for the purpose. All are transparent. Occupies almost 50% by weight or more of UV ink.)
c. In the case of pigment ink, in the case of paint, an appropriate pigment (inorganic pigment such as black or white) or an organic pigment such as red, blue or green is used, and several kinds of pigments are usually mixed in order to obtain a desired color tone. It accounts for about 3 to 30% by weight. In the case of white ink, it may occupy around 50% by weight.
d. Photopolymerization initiator Upon receiving the energy of UV light or thermal energy, the molecule breaks and binds to a peripheral substance (in the case of ink or paint, the above-mentioned acrylic monomer or oligomer) and crosslinks. This cures (hardens).
e. Photopolymerization initiator glazes / sensitizers The above initiators are generally expensive chemicals, and are substances intended to assist and enhance the action of the chemicals. d and e are mixed amounts of several percent or less by weight.
f. Stabilizers Since UV inks and UV paints are generally more expensive than solvent-based inks and paints, stabilizers are added so as not to cause gluing during transportation and storage.
g. Additives Various substances that improve the physical properties of ink or paint (adhesiveness, cohesiveness, viscosity, etc. on printed materials and coated materials).

  According to this embodiment, the following effects can be obtained.

(1) When UV ink is used as the undercoat layer 3, if it is in an uncured state, an appropriate wet surface is formed, and a difference in surface tension occurs between the undercoat layer 3 and the fine-grain UV ink by inkjet. , The following conditions,
Surface tension of surface to be printed (surface energy)> The surface tension of fine-grain ink by ink jet can be sufficiently satisfied, and the fine UV ink for ink-jet image formation ejected by ink-jet can be formed without spreading to the periphery. You can keep it. Using this, yellow (yellow), magenta (red), and cyan (blue) three primary color inks and black ink are ejected from the ink head of the inkjet printer onto the uncured UV ink undercoat layer 3 to provide a clear image by inkjet. A color image can be formed.

(2) In the exposure process, the inkjet image 4 and the undercoat layer 3 can be simultaneously cured by simultaneously irradiating the inkjet image 4 and the undercoat layer 3 with an ultraviolet lamp, and each layer is exposed. Compared with the case of curing, the number of exposure processes can be reduced, the number of lamps necessary for ultraviolet curing can be reduced, the installation area of the apparatus can be saved, and the power consumption can be saved.

(3) Both the undercoat layer 3 and the inkjet image 4 are formed using UV ink and have high durability against water, light, and the like.

(4) Since the image formation by inkjet is performed on the uncured undercoat layer 3, the surface of the print image is flat (there is no swell due to inkjet image formation), and the finish is close to offset printing. Moreover, the gloss of the surface of the printed image is good and the feeling of roughness can be eliminated.

  The undercoat layer 3 is usually white, but if it has a special effect, it is possible to use a light single color (light yellow, etc.) other than white.

  In the present embodiment, the optical disk has been described as an example. However, the method of the present invention can be applied to the printing surface of various printed materials such as resin products, glass products, and metal products. In addition, it is possible to form a durable inkjet image with good adhesion.

  In the above embodiment, white or a light single color other than white (that is, an opaque undercoat layer) can be used as the undercoat layer, but it is also possible to use a transparent undercoat layer of UV ink. . For example, a transparent resin or transparent film backprint is often used for automobile meters, home appliances, audio products, mobile phone keypads, and the like. In these cases, if a transparent UV ink is used as the undercoat layer, the effect can be exerted also on the above-mentioned products having high quality requirements. In the case of the above product, an inkjet image (for example, a single color image of the special color ink) can be formed by using special color inks other than the three primary color inks and the black ink.

  Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

It is explanatory drawing which shows embodiment of the image forming method by the inkjet which concerns on this invention. It is explanatory drawing which shows typically the adhesion condition of the fine particle UV ink for inkjet image formation about the case of the undercoat layer of uncured UV ink, and the case of the undercoat layer of UV ink after hardening processing.

Explanation of symbols

1 Optical disc 2 Label surface 3 Undercoat layer 4 Inkjet image

Claims (4)

  An undercoating step of providing an ultraviolet curable ink as an undercoat layer on a printing surface; an image forming step of forming an inkjet image with an ultraviolet curable ink on the uncured undercoat layer; and the inkjet image and the undercoat layer And an exposure step of simultaneously irradiating with ultraviolet rays.   2. The ink jet image forming method according to claim 1, wherein in the undercoating step, white, light monochromatic or transparent ultraviolet curable ink is applied as an undercoat layer.   3. The image forming method by inkjet according to claim 1, wherein in the image forming step, a color image using at least three primary color inks and a black ink or an image using a special color ink is formed.   4. The ink jet image forming method according to claim 1, wherein in the exposure step, ultraviolet rays are irradiated in parallel with the ultraviolet ray curable ink particles being ejected onto the printing surface in the image forming step.

Images