Pretreatment liquid and printing method

Abstract

To remove a deposit on a surface of a matter to be printed, and to improve adhesion between the surface of the matter to be printed and an ultraviolet curable ink.SOLUTION: The pretreatment liquid 30 is applied to the surface of the material to be printed 10 before the ink 50 is applied, and contains a volatile solvent and benzyl alcohol, and the content of benzyl alcohol is 1 to 50 [vol%].SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pretreatment liquid that is applied to the surface of a printing substrate, and a printing method that uses the pretreatment liquid. [Background technology]

[0002] It has been known for some time that a primer layer is formed on the surface of a substrate to improve adhesion between the substrate and the ink (see, for example, Patent Document 1). In this method, after a primer layer is formed on the surface of the substrate, ultraviolet-curable ink (hereinafter referred to as UV ink) is ejected onto the surface by an inkjet method, and the ink is irradiated with ultraviolet light to cure the ink. This improves adhesion between the substrate and the ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-9392 Summary of the Invention [Problem to be solved by the invention]

[0004] The surface of the substrate may be contaminated with oil or other contaminants. In this case, the printing method disclosed in Patent Document 1 requires wiping the surface of the substrate with alcohol or the like to remove the contaminants before forming a primer layer on the surface of the substrate, which is time-consuming and requires subsequent application of a primer or the like. Furthermore, when the substrate is acrylic, adhesion is often poor after direct printing with an inkjet printer and curing of the ink.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a pretreatment liquid and a printing method that can improve the adhesion between the surface of a substrate and ultraviolet-curable ink (UV ink), and can also remove deposits from the surface of the substrate. [Means for solving the problem]

[0006] A pretreatment liquid according to one embodiment of the present invention is a pretreatment liquid that is applied to the surface of a substrate before ink is applied, and contains a volatile solvent and benzyl alcohol, with the benzyl alcohol content being 1 [vol%] or more and 50 [vol%] or less.

[0007] In one embodiment of the present invention, the content of the benzyl alcohol is 1 [vol %] or more and less than 10 [vol %].

[0008] In one embodiment of the present invention, the content of the benzyl alcohol is 1 [vol %] or more and less than 5 [vol %].

[0009] In one embodiment of the present invention, in addition to the volatile solvent and the benzyl alcohol, water is contained.

[0010] In another embodiment of the present invention, the substrate is acrylic. The target acrylic can be any acrylic, regardless of the manufacturing method.

[0011] In yet another embodiment of the present invention, the volatile solvent is C X H Y It is a lower alcohol represented by -OH, where X is 2 or 3 carbon atoms.

[0012] In yet another embodiment of the present invention, the ink is an ultraviolet curable ink.

[0013] A printing method according to one aspect of the present invention includes the steps of: applying the pretreatment liquid to the surface of the substrate to modify and clean the surface of the substrate; ejecting the ultraviolet-curable ink onto the modified and cleaned surface of the substrate; and irradiating the ultraviolet-curable ink with ultraviolet light. [Effects of the Invention]

[0014] According to the present invention, it is possible to remove deposits from the surface of the substrate and improve the adhesion between the surface of the substrate and the ink. In particular, when the substrate is acrylic, the improvement of ink adhesion by modifying the surface and the improvement of adhesion by cleaning the surface can be achieved simultaneously, which has the effect of reducing the number of work steps before printing. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 10 is an explanatory diagram for explaining a pre-processing step in the printing method according to the embodiment of the present invention. [Figure 2] 3A to 3C are explanatory diagrams for explaining printing steps in a printing method according to an embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing experimental results regarding a pretreatment liquid according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] A pretreatment liquid and a printing method according to embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solutions of the invention. In the following embodiments, identical or corresponding components are designated by the same reference numerals, and redundant description will be omitted. Furthermore, in the embodiments, the arrangement, scale, dimensions, etc. of each component may be exaggerated or minimized and may not correspond to the actual components, and some components may be omitted.

[0017] [Printing method process] Fig. 1 is an explanatory diagram for explaining a pretreatment step in a printing method according to an embodiment of the present invention. Fig. 2 is an explanatory diagram for explaining a printing step in a printing method according to an embodiment of the present invention. The acrylic plate in Figs. 1 and 2 shows its cross section.

[0018] The pretreatment liquid and printing method according to this embodiment are applied to, for example, an inkjet printer (printing device) that uses ultraviolet-curable ink. However, the pretreatment liquid and printing method are not limited to ultraviolet light and can be applied to printing devices that use ink that is cured by irradiation with light.

[0019] The printing substrate shown in Figures 1 and 2 is, for example, an acrylic plate 10. There are two main methods for manufacturing the acrylic plate 10: extrusion and casting. The differences in the manufacturing methods result in acrylic plates 10 with different properties. One of the differences in properties is manifested in the difference in molecular weight; acrylic plates 10 made by the extrusion method tend to have higher adhesion to ultraviolet-curable ink (hereinafter referred to as UV ink 50) compared to acrylic plates 10 made by the casting method, while acrylic plates 10 made by the casting method tend to have lower adhesion to UV ink 50 due to their larger molecular weight and stronger chemical resistance. In general, the extrusion method is easier to apply than the casting method to direct printing with an inkjet printer using UV ink 50.

[0020] Furthermore, even in the case of acrylic sheets 10 manufactured by the extrusion method, adhesion of the UV ink 50 may be poor, and although it is possible to directly print the UV ink 50 onto the acrylic sheet 10, it is difficult to ensure adhesion. However, because the acrylic sheet 10 is transparent and has a wide range of uses, there is a demand for printing with UV ink using an inkjet printer.

[0021] Furthermore, the acrylic plate 10 is a highly transparent material and is provided with a protective film attached to prevent the surface from being scratched. Therefore, oil used to attach the protective film may remain on the surface of the acrylic plate 10 after the protective film is peeled off. If oil remains on the surface, the adhesion of the UV ink 50 to the acrylic plate 10 will be poor, even if the UV ink 50 is cured by irradiating it with ultraviolet light after printing. Therefore, before printing on the acrylic plate 10, the oil on the surface of the acrylic plate 10 is thoroughly removed using an alcohol-based solvent, and then printing is performed.

[0022] The pretreatment step shown in FIG. 1 is a step of applying a pretreatment liquid 30 to a surface 10A of a printing substrate (acrylic plate 10) to modify and clean the surface 10A of the printing substrate (acrylic plate 10).

[0023] As shown in Fig. 1(A), a deposit 20 such as oil is attached to a surface 10A of an acrylic plate 10. As shown in Fig. 1(B), a pre-treatment liquid 30 is applied to the surface 10A of the acrylic plate 10. The pre-treatment liquid 30 contains a volatile solvent and benzyl alcohol. The contents of the volatile solvent and benzyl alcohol will be described later (see Fig. 3).

[0024] Possible methods for applying the pretreatment liquid 30 to the surface 10A of the acrylic sheet 10 include, for example, a method in which an operator wipes the surface 10A of the acrylic sheet 10 with a cloth moistened with the pretreatment liquid 30, or a method in which an operator applies the pretreatment liquid 30 to the surface 10A of the acrylic sheet 10 and then wipes off excess pretreatment liquid 30 with a cloth. By applying the pretreatment liquid 30 to the surface 10A of the acrylic sheet 10 and wiping it off, the deposits 20 adhering to the surface 10A of the acrylic sheet 10 are removed. Note that, in order to avoid applying an excessive amount of the pretreatment liquid 30 to the acrylic sheet, it is preferable to use a method in which the pretreatment liquid 30 is moistened with a cloth and then wiped off.

[0025] 1(C), the surface 10A of the acrylic plate 10 is modified by the pretreatment liquid 30 to have high adhesive properties due to changes in density caused by changes in molecular arrangement, thereby improving the adhesiveness of the UV ink 50. Furthermore, the pretreatment liquid 30 is mainly composed of a volatile solvent, and therefore evaporates within a predetermined time.

[0026] The printing process shown in FIG. 2 is a process of ejecting UV ink 50 onto a surface 10A of a modified and cleaned printing substrate (acrylic plate 10), and a process of irradiating the UV ink 50 with ultraviolet light UV.

[0027] The print head 40 is configured to be movable by a drive mechanism in the printing direction indicated by the arrow in the drawing. The print head 40 includes an inkjet recording head unit 41 and an ultraviolet irradiation device 42.

[0028] As shown in FIG. 2A, the inkjet recording head unit 41 ejects UV ink 50 while moving in the printing direction. The UV ink 50 may be a single color or a plurality of different colors. Various inks, such as clear ink and white ink, may also be used. Because the surface 10A of the acrylic plate 10 has been modified with the pretreatment liquid 30, the UV ink 50 adheres closely to the surface 10A of the acrylic plate 10 after printing and curing.

[0029] The ultraviolet irradiation device 42 is mounted on the rear side in the printing direction of the inkjet recording head unit 41. As shown in Fig. 2(B), the ultraviolet irradiation device 42 irradiates ultraviolet rays UV onto the UV ink 50 ejected onto the surface 10A of the acrylic plate 10. This causes the UV ink 50 to harden.

[0030] [Experimental results for pretreatment solution 30] Next, experimental results regarding the pretreatment liquid 30 will be described. Fig. 3 is a diagram showing experimental results regarding the pretreatment liquid 30 according to an embodiment of the present invention. In Fig. 3, "CAS No." refers to the CAS Registry Number (registered trademark), which is a number used to identify a chemical substance. Furthermore, "bp" refers to the boiling point of each chemical substance.

[0031] The experiment was carried out using a solvent containing at least one of ethanol, 2-propanol, 1-propanol, water, and benzyl alcohol as the pretreatment liquid 30.

[0032] Ethanol is, for example, a compound represented by the following formula (1).

[0033] [ka]

[0034] 2-Propanol is, for example, a compound represented by the following formula (2).

[0035] [ka]

[0036] 1-Propanol is, for example, a compound represented by the following formula (3).

[0037] [ka]

[0038] Benzyl alcohol is, for example, a compound represented by the following formula (4).

[0039] [ka]

[0040] In this embodiment, ethanol, 2-propanol, 1-propanol, and combinations thereof may be referred to as volatile solvents or alcohol-based solvents. In addition, in Figure 3, the unit of the content of the compound is [vol%].

[0041] In Figure 3, "adhesion" represents the degree of adhesion between the surface 10A of the acrylic plate 10 after modification with the pretreatment liquid 30 and the UV ink 50 after curing. This adhesion is measured, for example, based on the "JIS K5600 4-6 cross-cut method." High adhesion is marked with "◯," low adhesion with "×," and intermediate adhesion with "△."

[0042] Furthermore, "transparency" refers to the transparency of the surface 10A of the acrylic sheet 10 after modification with the pretreatment liquid 30. High transparency (i.e., the acrylic sheet 10 does not become cloudy) is marked with "Good," and low transparency (i.e., the acrylic sheet 10 becomes cloudy) is marked with "Poor."

[0043] Furthermore, "drying property" indicates whether all of the pretreatment liquid 30 dries and the time it takes for the pretreatment liquid 30 to dry. When the drying property is high, i.e., when all of the pretreatment liquid 30 dries within 10 seconds (sec), it is marked "Good." When the drying property is medium, i.e., when the pretreatment liquid 30 dries within 10 seconds but some of the pretreatment liquid 30 remains undried, it is marked "Good." When the drying property is low, i.e., when the pretreatment liquid 30 dries in more than 10 seconds but some of the pretreatment liquid 30 remains undried, it is marked "Poor."

[0044] The "overall rating" is a comprehensive assessment of all the items of "adhesion," "transparency," and "drying speed." If all items are "good," the overall rating is "good." If only adhesion is "good" and the other items are "good," the overall rating is "good." If even one item is "bad," the overall rating is "bad."

[0045] Experiments were carried out in Examples 1 to 12 for pretreatment liquids 30 with different contents of volatile solvent and benzyl alcohol. Examples 1 to 14 will now be described.

[0046] [Example 1] This is an example for a pretreatment liquid 30 containing 100% ethanol. In this case, the adhesion was rated "x", the transparency was rated "good", and the drying property was rated "good", resulting in an overall rating of "x".

[0047] [Example 2] This is an example for a pretreatment liquid 30 containing 99% ethanol and 1% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "good", and the drying property was rated "good", resulting in an overall rating of "good".

[0048] [Example 3] This is an example for a pretreatment liquid 30 containing 98% ethanol and 2% benzyl alcohol. In this case as well, the adhesion was rated "good", the transparency was rated "good", and the drying property was rated "good", resulting in an overall rating of "good".

[0049] [Example 4] This is an example for a pretreatment liquid 30 containing 95% ethanol and 5% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "good", the drying property was rated "fair", and the overall evaluation was rated "fair".

[0050] [Example 5] This is an example for a pretreatment liquid 30 containing 91% ethanol and 9% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "good", the drying property was rated "fair", and the overall evaluation was rated "fair".

[0051] [Example 6] This is an example for a pretreatment liquid 30 containing 90% ethanol and 10% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "good", the drying property was rated "poor", and the overall evaluation was rated "poor".

[0052] [Example 7] This is an example for a pretreatment liquid 30 containing 75% ethanol and 25% benzyl alcohol. In this case as well, the adhesion was rated "good", the transparency was rated "good", the drying property was rated "poor", and the overall evaluation was rated "poor".

[0053] [Example 8] This is an example for a pretreatment liquid 30 containing 50% ethanol and 50% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "fair", and the drying property was rated "poor", resulting in an overall rating of "poor".

[0054] [Example 9] This is an example for a pretreatment liquid 30 containing 25% ethanol and 75% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "poor", and the drying property was rated "poor", resulting in an overall rating of "poor".

[0055] [Example 10] This is an example for a pretreatment liquid 30 containing 0% ethanol and 100% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "poor", and the drying property was rated "poor", resulting in an overall rating of "poor".

[0056] [Example 11] This is an example for a pretreatment liquid 30 containing 98% 2-propanol and 2% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "good", and the drying property was rated "good", resulting in an overall rating of "good".

[0057] [Example 12] This is an example for a pretreatment liquid 30 containing 49% ethanol, 49% 2-propanol, and 2% benzyl alcohol. In this case, the adhesion was rated "good", the transparency was rated "good", and the drying property was rated "good", resulting in an overall rating of "good".

[0058] [Example 13] This is an example of a pretreatment liquid 30 containing 86.3% ethanol, 3.9% 2-propanol, 7.8% 1-propanol, and 2% benzyl alcohol. In this case, the adhesion is rated "good," the transparency is rated "good," and the drying property is rated "good," resulting in an overall rating of "good." The solvent in Example 13 is sometimes called denatured alcohol. As the denatured alcohol, neoethanol PIP, for example, is used.

[0059] [Example 14] This is an example for a pretreatment liquid 30 having an ethanol content of 88%, a water content of 10%, and a benzyl alcohol content of 2%. In this case, the adhesion was rated "good", the transparency was rated "good", and the drying property was rated "good", resulting in an overall rating of "good".

[0060] As shown in FIG. 3, when the benzyl alcohol content in the pre-treatment liquid 30 is 1% or more, the adhesion is improved. When the benzyl alcohol content in the pre-treatment liquid 30 is 5% or more, the drying property is slightly deteriorated, and when the benzyl alcohol content is 10% or more, the drying property is deteriorated. Furthermore, when the benzyl alcohol content in the pre-treatment liquid 30 is more than 50%, the transparency is deteriorated. For these reasons, the benzyl alcohol content in the pre-treatment liquid 30 is preferably 1 vol% or more and 50 vol% or less. Furthermore, the benzyl alcohol content in the pre-treatment liquid 30 is more preferably 1 vol% or more and less than 10 vol%. Furthermore, the benzyl alcohol content in the pre-treatment liquid 30 is more preferably 1 vol% or more and less than 5 vol%.

[0061] The volatile solvent (alcohol-based solvent) is not limited to the solvents shown in FIG. 3, as long as it has a fast evaporation rate at room temperature.

[0062] The main solvent of the volatile solvent (alcohol-based solvent) may be a lower alcohol (alcohols are represented by the general formula R-OH (R is a saturated or unsaturated hydrocarbon chain), but the hydrocarbon chain has a small number of carbon atoms). For example, the main solvent of the volatile solvent may be C X H Y It may also be a lower alcohol represented by —OH, where X is 2 or 3 carbon atoms.

[0063] As described above, according to this embodiment, before printing, the pretreatment liquid 30 is applied to the surface 10A of the acrylic plate 10 using a cloth or the like to which it has been applied, and at the same time, dirt is wiped away, thereby modifying and cleaning the surface of the acrylic plate 10. This improves the adhesion of the UV ink 50 to the acrylic plate 10 after printing and curing, making it possible to perform direct printing, and also cleans the surface 10A of the acrylic plate 10 at the same time, further improving the adhesion of the UV ink 50.

[0064] The total content of the volatile solvent and benzyl alcohol does not have to be 100%. That is, the pre-treatment liquid 30 may contain water or a solvent (compound) other than the volatile solvent and benzyl alcohol. For example, the pre-treatment liquid 30 of Example 14 contains water in addition to the volatile solvent and benzyl alcohol.

[0065] Furthermore, although the printing substrate is an acrylic plate 10 in the above embodiment, it does not have to be plate-shaped. Furthermore, the printing substrate may be an object other than an acrylic product, as long as the effects of the pretreatment liquid 30 (adhesion, transparency, and drying properties) are not impaired. Furthermore, the printing substrate may be an acrylic plate manufactured by a method other than the extrusion method or the casting method, and the printing method is not limited to the inkjet method. Furthermore, the ink does not have to be UV-curable ink, as long as it can be printed on the printing substrate.

[0066] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0067] 10 Acrylic board (printing material, acrylic) 10A surface 30 Pre-treatment liquid 40 print heads 41 Inkjet recording head unit 42 Ultraviolet irradiation device 50 UV-curable ink (UV ink, ink)

Claims

1. A pretreatment liquid that is applied to a surface of a printing substrate before ink is applied, Contains a volatile solvent and benzyl alcohol, The content of the benzyl alcohol is 1 [vol %] or more and 50 [vol %] or less. Pretreatment solution.

2. The content of the benzyl alcohol is 1 [vol %] or more and less than 10 [vol %]. The pretreatment liquid according to claim 1.

3. The content of the benzyl alcohol is 1 [vol %] or more and less than 5 [vol %]. The pretreatment liquid according to claim 1.

4. In addition to the volatile solvent and the benzyl alcohol, water is contained The pretreatment liquid according to claim 1.

5. The substrate is acrylic The pretreatment liquid according to claim 1.

6. The volatile solvent is C Ｘ H Ｙ A lower alcohol represented by -OH, where X is 2 or 3 carbon atoms. The pretreatment liquid according to claim 1.

7. The ink is an ultraviolet curable ink. The pretreatment liquid according to claim 1.

8. a step of applying the pretreatment liquid according to any one of claims 1 to 7 to the surface of the printing substrate to modify and clean the surface of the printing substrate; A step of ejecting the ultraviolet curable ink onto the surface of the printing substrate that has been modified and cleaned; irradiating the ultraviolet curable ink with ultraviolet light; A printing method comprising:

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