JP5754909B2 - Inkjet printing method - Google Patents

Description

  The present invention relates to an inkjet printing method in which printing is performed by directly spraying micronized ink onto a printing medium such as paper or plastic, without the need to prepare a printing plate like gravure printing or offset printing, More specifically, the present invention relates to an ink jet printing method capable of effectively preventing printing adhesion and peeling of printing ink without causing bleeding even when printing on a plastic film.

  For example, among printing techniques, the inkjet method is characterized in that the manufacturing cost is low because it is not necessary to prepare a plate, unlike gravure printing, offset printing, flexographic printing, and the like. Since this ink jet method is a method in which ink is directly sprayed, it is not required that the medium to be printed is flat. For example, printing can be performed on a plastic film other than paper or a metal foil such as aluminum.

  On the other hand, the ink jet system usually has problems such as occurrence of bleeding and lack of water resistance because water-soluble liquid ink is used. Furthermore, when printing on a plastic film by an ink jet method, it is difficult to adhere the ink unless a primer layer is formed on the printed portion, and if a overcoat layer is not formed after printing, a roll-shaped recording medium is wound up. At this time, there is a problem in that the ink receiving layer is missing and printing peeling easily occurs.

Therefore, various proposals have been made in the case of printing by the inkjet method.
For example, Patent Document 1 describes an inkjet recording medium that is particularly excellent in ink absorbability and has high primer layer strength.

Patent Document 2 describes an example in which primer treatment is performed in order to obtain high image quality and high storage stability, and overcoating is performed on the ejected ink.
Patent document 3 is applied to the food field, and in this document 3, a method of forming an image on an oily confectionery by ink jet printing is disclosed, and an oily overcoat is applied on the printed image and then cooled and cured. Thus, there is disclosed a technology that makes it possible to give sufficient adhesion strength, gloss, scratch resistance, and a texture that is not different from that of an oil-based substrate without causing bleeding even when new moisture is attached. Yes.

Patent Document 4 discloses an undercoat agent for preventing bleeding that can be applied using an ink jet printer.
Patent Document 5 discloses a method and apparatus for coating an ink overcoat liquid with a plurality of coating liquid discharge nozzles.

  In addition, when providing a primer layer or overcoat layer in gravure printing, offset printing, or flexographic printing, these layers must be set to have a considerably larger area and shape than the printing part due to the mechanism of the printing press. I must.

Usually, the primer layer and the overcoat layer are often formed on the entire recording medium, but in this case, there is a problem that it is technically easy but expensive.
Further, when trying to match a transparent primer or overcoat with the position of a printed pattern such as a character or an image, the alignment is also difficult.

  In particular, the overcoat layer is generally provided, but the size of the overcoat layer has not been developed and there is no literature. However, in inkjet printing, the appearance of the printed product has a great influence in addition to the influence on the printing speed. To prevent the overcoat layer or primer layer from appearing as much as possible from the printed image or characters, and to improve the appearance, the overcoat layer or primer layer is several dots from the printed image or characters. In the case of inkjet printing, however, the present invention was found to be in demand.

Japanese Patent No. 4111530 Japanese Patent No. 4114608 JP 2009-95 A JP 2003-227095 A JP 2003-53942 A

  In view of such circumstances, the present invention is not limited to paper, for example, and can be printed on plastic fills and metal foils. In any case where a primer layer or an overcoat layer is provided, printing is possible. Ink-jet printing that can form a primer layer or an overcoat layer in an appropriate position in an area as small as possible with respect to information such as printed characters and images, and has a good printed appearance and is inexpensive. It aims to provide a method.

In order to achieve the above object, an inkjet printing method according to the present invention comprises:
In an inkjet printing method for printing information such as characters or images on the surface of a recording medium by an inkjet method,
The recording medium is a multilayer coextruded plastic film,
When forming a primer layer on the upper layer of the recording medium, the primer liquid is jetted onto the recording medium so as to cover a range wider than the planned printing range of the information by inkjet ,
When an overcoat layer is formed on the upper layer of the recording medium, the overcoat liquid is jetted onto the recording medium by ink jet so as to cover a wider range than the printed image of the information .

  Such a method contributes to downsizing of the apparatus, and the position or area of the primer or overcoat layer can be provided at the same position and the same area as the picture, but the printing accuracy of the ink jet, etc. Therefore, in any case, it is possible to carry out an area that is slightly larger than the pattern and larger by several dots.

Furthermore, in the present invention, it is preferable that the primer layer and / or the overcoat layer has a shape substantially similar to the information and is 1 to 9 dots larger.
In the present invention, it is preferable that the primer layer and / or the overcoat layer has a shape surrounding the information formation region and is larger by 1 to 9 dots.

As described above, the present invention can be preferably applied to a roll-shaped plastic film, and is particularly effective for printing a multilayer coextruded plastic film. By providing the primer layer, information such as characters and images can be brought into close contact with the recording medium, and when an overcoat layer is provided, gloss can be obtained.

  In addition, since the primer layer and the overcoat layer are formed using inkjet, it is possible to contribute to cost reduction as compared with the case where the entire surface is coated.

  In the present invention, the primer and overcoat are formed only in necessary locations by aligning with information such as characters and images, so that it is inexpensive and has excellent ink adhesion and surface protection for ink-jet printed matter. Can be given.

FIG. 1A is a schematic diagram of a dot pattern per unit area in a case where, for example, an image is formed by directly spraying ink with an ink jet by a method generally used on a recording medium such as paper. 1B shows a case where the resolution is 1200 DPI, and FIG. 1B shows a unit area when an image is formed by spraying ink with a resolution of 2400 DPI by increasing the number of dots in the horizontal direction compared to FIG. 1A. It is the schematic of a hit dot pattern. FIG. 2 (A) is a schematic diagram of the dot pattern of the primer layer when the primer layer is printed on the surface of the recording medium by inkjet using the inkjet printing method of the present invention. FIG. 2 (B) is a schematic diagram of FIG. ) Is a schematic view when ink is sprayed on the upper surface where the primer layer is formed. FIG. 3A is a schematic diagram showing a dot pattern of ink per unit area when information such as an image is formed with ink with a resolution of 2400 DPI, and FIG. It is the schematic at the time of forming an overcoat layer on a dot pattern.

Hereinafter, the ink jet printing method according to the present invention will be described.
In the present invention, when forming the upper layer in the overcoat layer of a primer layer or printed image, the upper layer of the recording medium (multi-layer co-extruded printed substrate such as a plastic film), ink jet Both the layers It is formed by discharge from the nozzle by the method.

  When forming a primer layer and an overcoat layer, those liquids are discharged from different discharge nozzles. Each discharge nozzle is preferably mounted on a dedicated jet unit provided separately from the ink jet head on which the ink discharge nozzle is mounted. However, similarly to the case of Patent Document 5, each discharge nozzle may be mounted on the same ink jet head. good.

The diameter of the discharge nozzle that discharges the primer liquid or the overcoat liquid may be the same as or larger than the diameter of the ink discharge nozzle that discharges the ink.
When the recording medium is paper, it is preferable to provide a transparent primer layer before ejecting ink. Thereby, in addition to improving the adhesiveness of the ink to the recording medium, the occurrence of bleeding can be prevented. On the other hand, when the recording medium is a plastic film such as PET or nylon film, the primer layer may not be provided by corona treatment of the surface. However, in order to give stronger ink adhesion, it is preferable to provide a primer layer.

  The primer layer preferably has a shape approximately similar to information such as characters or images to be printed from now on and is larger by several dots. Specifically, when printing information such as characters and graphics by a collection of ink particles, it is preferable to provide a primer layer in a range larger by 1 to 9 dots on the outer peripheral side than the collection. Here, for example, when the information is a character such as “A” or “A”, the substantially similar shape means that the character is written in bold and is slightly larger like “A” or “A”. Refers to the shape. In addition, when the information is an image, the substantially similar shape refers to the entire outline of the outline of a collection of points on which the image is drawn.

  However, this primer layer formation region may not have a shape substantially complementary to the information to be printed. For example, it may be an area such as a square frame in which an image is accommodated. In short, it is only necessary that the primer layer is formed so as to cover not the entire printable area of the recording medium but a wider area than the upper surface of the actually printed image. The range in which the primer layer is widely formed is preferably 1 to 9 dots larger than characters and printed images, more preferably 2 to 7 dots, and most preferably 3 to 5 dots.

  If the primer layer is formed in such a range, the occurrence of bleeding can be prevented. Moreover, the usage-amount of primer liquid can be decreased and it can contribute to cost reduction. Also, the appearance of the printed product is good.

  On the other hand, when the recording medium is paper, PET, nylon film or the like, after information such as characters or images is printed by inkjet, an overcoat layer can be further provided thereon by an inkjet method. The overcoat layer is mainly used for the purpose of preventing scratches on information and printing effects that give gloss. However, in the case of forming the overcoat layer, as in the case of providing a primer layer, information such as characters or images is used. It is preferable to form an overcoat layer in a range larger by several dots. Specifically, this overcoat layer is preferably larger by 1 to 9 dots as in the case of the primer layer. More preferably, it is for 2 to 7 dots, and most preferably for 3 to 5 dots.

  If the overcoat layer is formed in such a range by the inkjet method, the printing effect is not greatly affected. If a large overcoat is applied as in the prior art, the design effect may be greatly impaired, such being undesirable.

  Further, the overcoat layer may not have a substantially phase shape that traces the upper surface of the printed information in bold. For example, a range and shape like a square frame surrounding the information may be used. In short, it is preferable that it is 1 to 9 dots, more preferably 2 to 7 dots, and most preferably 3 to 5 dots larger than the printing range with ink.

  The position and area of the primer layer and the overcoat layer may be the same. In this case, exactly both sides of the information are sandwiched between the primer layer and the overcoat layer. Preferably, the primer layer is in a slightly larger range than the overcoat layer.

  Conversely, if the area of the overcoat layer is larger than the area of the primer layer, the overcoat layer exceeds the area of the primer layer and comes into direct contact with the recording medium. In this case, there is no problem if the overcoat layer can be sufficiently adhered to the recording medium, but if the adhesion is weak, problems such as peeling off of the overcoat layer occur and the suitability as a printed matter is lost.

  It is not limited that both the primer layer and the overcoat layer are formed as a set, and only one of them may be formed. For example, it may be unnecessary to newly form a primer layer by surface treatment of a recording medium film or the like. Similarly, the overcoat layer may be unnecessary if the printing durability of the ink describing information such as characters and images is sufficient.

  There are cases where the primer layer is not necessary, as in the case where the object to be ink-jet printed is a confectionery or a PET film. In such a case, it is not necessary to provide a primer layer. Further, the overcoat layer does not always need to be transparent, and can be lightly colored as a design effect.

  On the other hand, the primer layer is basically transparent, but may be lightly colored from the viewpoint of design and the like. The agent for forming the primer layer or the overcoat layer is not limited at all. That is, the recording medium, the primer solution, and the overcoat solution can be variously changed in order to obtain optimum adhesion.

  Hereinafter, it demonstrates more concretely with reference to drawings. FIG. 1A and FIG. 1B show, for example, an ink dot pattern by ink-jet per unit area when an image is formed with ink. A collection of white circles 2 in FIG. For example, 1200 DPI with a small number of dots is shown, and a white circle 2 in FIG. 1B shows 2400 DPI with a large number of dots. Note that the printer DPI generally differs vertically and horizontally, and the resolution in the head movement direction (horizontal direction) is high.

  The collection of white circles 2 in FIG. 2A exemplifies a print pattern planned area by ink when a primer is applied to a recording medium by inkjet before printing the ink. A black circle 2 in FIG. 2B shows the dot pattern of the ink actually applied to the predetermined area, and a white circle 4 in FIG. 2B shows the lower layer primer applied before printing the ink. The dot pattern of the layer is shown.

  As shown in FIG. 2B, the region of the primer layer of the white circle 4 is formed in a range larger by one dot than the region of characters and images formed by the collection of black circles 2. The white circle 4 primer layer is formed one dot larger than the black circle 2 ink, but it can be formed in the same manner even if it is several dots larger. A discharge nozzle for discharging such a primer layer can be mounted on a jet unit dedicated to the primer.

  3A and 3B show the case where an overcoat layer is provided. When the overcoat layer is provided, an overcoat discharge nozzle can be mounted on another jet unit as in the case where the primer layer shown in FIGS. 2A and 2B is provided. A white circle 6 in FIG. 3A is an ink dot pattern for displaying information such as characters and images. A black circle 6 in FIG. 3B is a dot pattern of ink for displaying information such as characters and images, and a white circle 8 in FIG. 3B indicates a dot pattern of the overcoat layer. The dot pattern of the overcoat layer indicated by the white circle 8 in FIG. 3B is also formed to be one dot larger than the dot pattern of the ink indicated by the black circle 6.

  As described above, according to the present invention, the overcoat layer or the primer layer has an area that spreads outward with respect to the printed product with ink as much as possible, so that the appearance of the printed product such as characters and images is improved. Can do.

As described above, according to the ink jet printing method of the present invention, the primer layer and the overcoat layer are formed by the ink jet method, so that these layers can be formed in a necessary range. Therefore, the cost is low. Further, since the primer layer and the overcoat layer are formed so as to cover a range that is several dots wider than the printed image using ink, it is good in appearance.
In order to confirm the effect of the present invention, an experiment for printing an image was performed.

  As an example of the present invention, an acrylic radical polymerization type was prototyped as a UV inkjet ink for image formation, and a urethane solvent type was used as a primer inkjet ink. As an ink-jet ink for the overcoat layer, the same radical polymerization type without an acrylic pigment as in the case of an image was made as a prototype. As a printing substrate, a nylon / PE (polyethylene) multilayer coextruded bag was prepared. First, a primer layer is applied to the nylon side of a nylon / PE multilayer coextrusion bag with urethane solvent type primer inkjet ink, and in the next process, an acrylic radical polymerization type pattern is printed. An ink-jet ink for a polymerization type acrylic overcoat layer from which the pigment was removed was provided. Sample 1 was designated.

Sample 2 was prepared by printing a polymerized acrylic ink directly on the nylon surface of a nylon / PE (polyethylene) multilayer coextrusion bag without providing a primer layer, and curing it with UV. As a result of confirming the adhesiveness of the ink with the adhesive tape, it was determined that the ink was partially transferred onto the adhesive tape surface and the adhesiveness of the ink was slightly weak.
In the case of Sample 1, the adhesive strength of the primer layer was confirmed with cello tape (registered trademark), and sufficient adhesive strength was shown. Further, the adhesive strength of the polymerization type acrylic ink printed on the primer layer was also confirmed with cello tape (registered trademark), and sufficient adhesive strength and adhesion were confirmed. Ink adhesion and adhesion are better than those of sample 2.

The nylon / PE (polyethylene) multilayer coextrusion nylon surface treatment degree was 48 dynes.
In the experiment, the primer layer and the overcoat layer were larger by one dot, but there was no problem with the appearance of the print design.

  The method of providing the primer and overcoat layer of the present invention several dots larger than the pattern / characters by inkjet can be preferably applied to inkjet printing for packages. Further, it can be preferably applied to a plastic film extruded with multiple layers.

2 Ink dot pattern 4 Primer dot pattern 6 Ink dot pattern 8 Overcoat dot pattern

Claims (3)

In an inkjet printing method for printing information such as characters or images on the surface of a recording medium by an inkjet method,
The recording medium is a multilayer coextruded plastic film,
When forming a primer layer on the upper layer of the recording medium, the primer liquid is jetted onto the recording medium so as to cover a range wider than the planned printing range of the information by inkjet ,
When an overcoat layer is formed on an upper layer of the recording medium, the overcoat liquid is jetted onto the recording medium so as to cover a wider range than the printed image of the information by inkjet. .   The inkjet printing method according to claim 1, wherein the primer layer and / or the overcoat layer has a shape substantially similar to the information and is 1 to 9 dots larger.   The inkjet printing method according to claim 1, wherein the primer layer and / or the overcoat layer has a shape surrounding the information formation region and is 1 to 9 dots larger.

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