JP2000290408A - Active energy ray irradiation method and irradiated object - Google Patents

Abstract

(57) Abstract: The present invention provides a method for irradiating a coating agent or the like with an active energy ray including an electron beam to cure, crosslink, or modify the coating agent or the like. SOLUTION: An active energy ray irradiation method characterized by irradiating an object to be irradiated with ultraviolet rays in an inert gas atmosphere and then irradiating an electron beam with an acceleration voltage of 100 Kv or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a coating material such as a paint, a printing ink, an adhesive or the like provided on a substrate with an active energy ray including an electron beam to cure, crosslink or modify the coating material. On how to do it. Furthermore, it relates to an irradiation object.

[0002]

2. Description of the Related Art Electron beam curing has been proposed as a method for curing, crosslinking or modifying coating materials such as paints, printing inks and adhesives applied to substrates, and many studies have been made so far. The method of curing with an electron beam is called "Radiation which reacts and cures instantaneously with active energy rays"
(1) "solvent-free inks and paints" that do not contain volatile components such as solvents, so there is no release to the environment because of (2) curing and drying with lower energy than thermal drying. It is expected to be an "environmentally friendly system" because of its excellent energy efficiency. Recently, VOC (Vola
As global environmental considerations such as the reduction of tile organic compounds) and the regulation of carbon dioxide emissions increase, the role to be played is increasing, and materials and equipment are being actively developed.

At present, ultraviolet (UV) curing systems are widely used in various fields such as printing and coating, taking advantage of the characteristics that the apparatus is small and can be cured even in the air. However, the UV system also has some problems mainly due to the limitation of the curing performance as described below, and the solution is strongly desired. (1) It cannot meet the needs for high speed printing and coating. (2) Multicolor, thick film,
When the concentration is increased, the transmission of ultraviolet rays is hindered, so that the curing becomes insufficient, and it is impossible to cope with the improvement of the print quality.
(3) Heat is generated together with ultraviolet rays, and the energy efficiency (electric conversion) has not been improved as expected. (4) It is difficult to use for applications that dislike heat, such as films.

[0004] On the other hand, from the past, ink by electron beam (EB) having much larger energy than ultraviolet (UV) ink,
It has been known that the method of curing a paint is an ideal method for solving the problems of UV. This method
In this method, electrons are accelerated by a voltage in a vacuum, the accelerated electrons are taken out into an atmospheric pressure atmosphere such as air, and an object is irradiated with an electron beam. Advantages of curing, cross-linking or modifying by electron beam irradiation include the following. (1) It is environmentally friendly because it does not need to contain an organic solvent as a diluent. (2) Fast curing, cross-linking or modification speed (high productivity). (3) Heat is not applied to the substrate. (4) Even a colored film or a thick film having a high concealing property can be cured. (5) Since an initiator and a sensitizer are not required, a stable film having high purity can be obtained.

Conventional EB irradiators have the following disadvantages. (1) The apparatus itself is large and the initial cost is high. (2) It takes time and effort to start up and maintain. (3) The EB acceleration voltage is 175 Kv (kilovolt) or more. Therefore, the depth of arrival was deep, and the film and the base material were degraded. Therefore, the spread of the EB system was slower than that of the UV system. Recently, in order to solve these problems, a relatively small-sized low acceleration voltage type of about 150 Kv has been introduced to some markets, but the fundamental solution has not yet been reached. In addition, it has been pointed out that the electron beam curing method requires inerting with nitrogen gas or the like. This is an electron beam curing method.
Radicals generated by irradiating an object to be treated with an electron beam cause a polymerization reaction, whereby a polymer film is formed and curing proceeds. In this case, if oxygen is present in the irradiation chamber, oxygen radicals generated by the electron beam will react with the growing radicals in the irradiation object, and the radical polymerization required for curing will be inhibited. The rate of generation of oxygen radicals is proportional to the accelerating voltage and the like. At about 200 Kv, which is generally used, irradiation is performed at an oxygen concentration of 500 ppm or less using an inert gas such as nitrogen. Further, the following are also mentioned as disadvantages of the high acceleration voltage. -It passes through the treatment layer which is reacted and cured by the electron beam, and the treatment efficiency decreases. -Use is limited because it causes damage and deterioration of the base material such as a film, and impairs the commercial value. -In order to generate strong secondary X-rays, a large shield such as a lead plate is required, resulting in an increase in the size of the apparatus. -It is necessary to evacuate the entire system including the chamber with the electron source over a long period of time using a vacuum pump. -These make the whole system large and expensive.

In addition, in the actual printing process, multi-color printing of four or more colors is often performed. In this case, the adhesion of ink overprinting is ensured, and the adhesion of ink to the guide rollers is prevented. To prevent this, it is necessary to provide a dryer between the printing cylinders (stations) of the respective colors to dry the ink. In the case of UV, since the lamp size is small, it can be provided between the printing cylinders and drying between the colors can be performed. However, in the case of EB, it is difficult to provide it between the printing cylinders due to the large size of the apparatus. This has also been one of the causes of EB not being widely used in the printing process and the like. As described above, the curing or cross-linking technology by electron beam irradiation has attracted attention as an energy-saving and environmentally friendly process that does not release solvents, but the equipment is large, the process flexibility is low, the initial investment is high, and inert gas There are many cases in which practical use is not achieved due to the high running cost due to the use of (nitrogen) and the like.

For this reason, there is a strong demand for the development of a new apparatus or a curing method for putting the electron beam curing method having many excellent characteristics into practical use in the printing and coating fields.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an active energy ray irradiating method and an irradiating object having high practical value and having both high curing performance and excellent cost performance. The purpose is to do. More specifically, an object of the present invention is to provide an active energy ray irradiation method and an irradiation object having excellent curing performance and capable of reducing the degree of inertization by an inert gas.

[0009]

In order to solve the above problems, the present invention firstly irradiates an object to be irradiated with ultraviolet rays in an inert gas atmosphere, and then applies an electron beam having an acceleration voltage of 100 Kv or less. The present invention provides an active energy ray irradiation method and an irradiation object, characterized by irradiating an active energy ray. Secondly, in an inert gas atmosphere, an object to be irradiated is irradiated with an electron beam having an acceleration voltage of 50 Kv or less, preferably 40 Kv or less, and then irradiated with ultraviolet rays, and an irradiation method of the active energy beam is provided. I will provide a. Third, in an inert gas atmosphere, an object to be irradiated is irradiated with an electron beam having an acceleration voltage of 50 Kv or less, preferably 40 Kv or less, and then irradiated with an electron beam having a higher acceleration voltage. An energy beam irradiation method and an irradiation object are provided.

[0010] In the present invention, the term "inert gas atmosphere" refers to a state in which a gas such as nitrogen gas, carbon dioxide gas or exhaust gas is contained at a concentration higher than the concentration of nitrogen gas in air. In the present invention, the inert gas need not be 100% (volume)% by volume, and the inert gas can be carried out at a concentration closer to air than in an inert gas atmosphere performed by ordinary electron beam irradiation. In the present invention, irradiation is preferably performed in an inert gas atmosphere having an oxygen concentration of more than 0.05% and 18% or less, preferably 0.1 to 16%. Hereinafter, embodiments of the present invention will be specifically described. FIG. 1 is a schematic view showing an irradiation tube as an electron beam generator used in an electron beam irradiation apparatus for carrying out the present invention. The apparatus comprises a cylindrical vacuum vessel 1 made of glass or ceramic, an electron beam generating section 2 provided in the vessel 1 for taking out electrons emitted from a cathode as an electron beam and accelerating the electron beam, An electron beam emitting unit 3 that is provided at an end of the container 1 and emits an electron beam, and a pin unit 4 for supplying power from a power supply unit (not shown). The electron beam emitting section 3 is provided with a thin-film irradiation window 5. Irradiation window 5 of electron beam emitting unit 3
Has a function of transmitting an electron beam without transmitting a gas, and has a flat shape as shown in FIG. And
An electron beam emitted from the irradiation window 5 is irradiated on the irradiation object arranged in the irradiation chamber.

That is, this device is a vacuum tube type electron beam irradiation device, and is fundamentally different from a conventional drum type electron beam irradiation device. 2. Description of the Related Art A conventional drum-type electron beam irradiation apparatus is of a type that irradiates an electron beam while constantly evacuating the inside of a drum. An apparatus having an irradiation tube having such a structure is disclosed in U.S. Pat. No. 5,414,267, and is described in American International Technologies (AI).
This is being considered as a Min-EB device by T).
In this apparatus, even at a low accelerating voltage of 100 kV or less, a decrease in the transmission power of the electron beam is small, and the electron beam can be extracted effectively. This makes it possible to cause the electron beam to act on the coating material on the base material at a low depth, thereby reducing the adverse effect on the base material and the generation amount of secondary X-rays, and providing a large shield. Is not necessarily required.

Further, since the energy of the electron beam is low, it is possible to reduce the inhibition of the reaction on the surface of the coating agent due to the oxygen radicals, and the necessity of inerting is reduced. Irradiating an electron beam by inerting with a low inert gas concentration has merits such as lowering running costs. In the present invention, in consideration of this, in order to prevent polymerization inhibition due to oxygen radicals which are problematic in electron beam irradiation in the presence of air, first, only the surface layer portion is cross-linked, cured or modified with respect to the irradiated object. Is irradiated, followed by electron beam irradiation. Thereby, a more complete crosslinked product, cured product or modified product can be obtained without causing polymerization inhibition by oxygen. In particular, in high-speed printing and high-speed coating at 300 m / min or more, even if inertizing, an increase in oxygen concentration due to entrainment of air is inevitable.
Even in this case, according to the present invention, sufficient curing can be performed at low cost. The fact that a more complete cured product can be obtained even with a low inert gas concentration means that a cured product with a low extraction rate can be obtained with high productivity / low cost / low energy,
Industrial and practical benefits are great. Merits of performing the irradiation in an inert gas atmosphere also in the ultraviolet irradiation include the following points. That is, by promoting the desorption of oxygen previously adsorbed on the surface layer, a cured film having higher hardness can be obtained even at a lower inert gas concentration in the next step of electron beam irradiation.

Also, by irradiating an object to be irradiated with an electron beam having an accelerating voltage of 40 Kv or less in an inert gas atmosphere and then irradiating an ultraviolet ray, similarly, polymerization inhibition by oxygen does not occur, and more complete curing is achieved. You can get things. further,
A similar effect can be obtained by irradiating an object to be irradiated with an electron beam having an acceleration voltage of 40 Kv or less in an inert gas atmosphere and then performing an electron beam irradiation at an acceleration voltage higher than that. In this case, it is more preferable to first irradiate an electron beam with an acceleration voltage of 30 Kv or less and then irradiate the electron beam with a higher acceleration voltage. As a typical embodiment of the present invention, as shown in FIG. 3, an array 11 is configured by combining a plurality of electron beam irradiation devices 10 having the above-described configuration, and in an irradiation room 12 below the array 11, A method of irradiating the irradiation object 13 conveyed at a predetermined speed with an electron beam from each of the electron beam irradiation devices 10 constituting the array 11 is exemplified. In the drawings, reference numeral 14 denotes an X-ray shield, and 15 denotes a conveyor shield.

As described above, since the shield can be reduced in size and inertia can be reduced, and the electron beam generating portion can be reduced in size due to the low accelerating voltage. It becomes possible, and the above-mentioned device is expected to be applied to various fields. Incidentally, the crosslinking and curing in the present invention also include graft polymerization, and the modification is a crosslinking,
Means other than polymerization, such as chemical bond breaking and orientation. Irradiated objects to which the present invention can be applied include printing inks, paints,
In addition to adhesives, pressure-sensitive adhesives, and the like that are formed relatively thinly on a substrate, a sustained-release material that gradually releases an active ingredient such as a poultice, a golf ball, and the like can be given.

Among these, the printing ink and paint formed on the base material are formed by crosslinking, hardening or modifying only the surface portion, thereby suppressing the curing shrinkage of the portion in contact with the base material and forming a coating with the base material. Can be obtained. In the case of an adhesive or a pressure-sensitive adhesive, it can be applied to various uses by crosslinking and curing only the surface portion and keeping the inside soft and maintaining the adhesive effect. Illuminated objects to which the present invention can be applied include coatings applied to substrates such as printing inks, paints, and adhesives. Among them, examples of the printing ink include a relief ink, an offset ink, a gravure ink, a flexographic ink, an active energy ray cross-linking / curing ink such as an electron beam such as a screen ink, and the like.

[0016] The paint may be an acrylic resin, an epoxy resin, a urethane resin, a polyester resin or the like, or an ultraviolet or electron beam using various photosensitive monomers, oligomers and / or prepolymers. An energy beam crosslinking / curing type coating material is exemplified. Further, as the adhesive, a vinyl polymerization type (cyanoacrylate type, diacrylate type, unsaturated polyester resin type), a condensation type (phenol resin type, urea resin type, melamine resin type), a polyaddition type (epoxy resin type, Reaction-curing type (monomer type, oligomer type, urethane resin type)
(Prepolymer type) adhesives. As an application example of the adhesive, in addition to a conventional one, it can be applied to a substrate which is weak to heat, such as adhesion of a lens and adhesion of a glass sheet.

Examples of the substrate on which these are applied include metals such as stainless steel (SUS) and aluminum, plastics such as polyethylene, polypropylene, polyethylene terephthalate and polyethylene naphthalate, paper and fibers, regardless of whether they are treated or not. Can be In the above coating agent, various additives conventionally used can be used. Examples of various additives include pigments, dyes, stabilizers, solvents, preservatives, antibacterial agents, lubricants, activators, and the like.

[0018]

Embodiments of the present invention will be described below. In the following description, "parts" and "%" are parts by weight and% by weight, respectively. (Example 1) An example in which an offset ink was used as a curable coating composition will be described. The adjustment of the offset ink was performed in the following procedure. [Preparation of varnish] 69.9% of dipentaerythritol hexaacrylate and 0.1% of hydroquinone were charged.
The temperature was raised to 100 ° C., and then 30 parts of DT (diallyl phthalate resin manufactured by Toto Kasei) was gradually charged and discharged at the time of dissolution. At this time, the year is 2100 poise (25
° C). [Preparation of Printing Ink] An ink for offset printing was mixed according to the following formulation and dispersed with three rolls.

Indigo pigment (LIONOL BLUE FG7330) 15 parts The above-mentioned varnish 50 parts Dipentaerythritol hexaacrylate 25 parts Pentaerythritol tetraacrylate 10 parts Photopolymerization initiator 2 parts Printing was performed with a thickness of about 2 μm using a generally used simple printing machine. After printing, UV irradiation was performed at an exposure amount of 16 mJ using an UV irradiation device manufactured by Ushio Inc.
Then, EB irradiation was performed using a Min-EB device manufactured by AIT. EB
Irradiation conditions were as follows: an acceleration voltage of 50 Kv and an irradiation dose of 0.5 Mrad were used. Inerting used nitrogen gas, and the oxygen concentration was changed by adjusting the nitrogen flow rate. As shown in Table 1, 0.
The oxygen concentrations were 5% and 10%.

After the irradiation, the curability was evaluated by evaluating the dryness with a touch finger. The evaluation standard is 5 for complete curing,
The evaluation was a five-point scale with uncured as 1. Table 1 shows the obtained results. As comparative examples, (1) conventional electron beam irradiation (acceleration voltage 200 Kv) without UV irradiation,
(2) The same electron beam irradiation apparatus as in Example 1 (acceleration voltage 50K
v), (3) After irradiating ultraviolet rays with an exposure amount of 16 mJ using an ultraviolet irradiator manufactured by Ushio Inc. in the air, the ink was cured with the same electron beam irradiator (acceleration voltage of 50 Kv) as in Example 1. The curability at the time of this was evaluated. Table 1 shows the results.

[0021]

[Table 1] Example 2 An ink was prepared by removing the photopolymerization initiator from the printing ink used in Example 1, and printing was performed to a thickness of about 2 μm in the same manner as in Example 1.

Using an AIT Min-EB device, an oxygen concentration of 15
% Electron gas irradiation at an acceleration voltage of 30 Kv, and then an electron beam irradiation at an acceleration voltage of 60 Kv. After the irradiation, the evaluation of the curability was performed based on the dryness by a touch finger and the adhesion by peeling off a cellophane tape. The evaluation criteria of the adhesion were evaluated as good 5 to poor 1. Table 2 shows the results. In addition, as a comparative example, electron beam irradiation of only 30 Kv and electron beam irradiation of only 60 Kv were performed using the same apparatus.

[0023]

[Table 2] (Example 3) After printing was performed in the same manner as in Example 1, electron beam irradiation was performed at an acceleration voltage of 30 KV in a nitrogen gas atmosphere with an oxygen concentration of 15% using a Min-EB device manufactured by AIT.
Next, ultraviolet irradiation of 16 mJ was performed. The curability of the obtained printed film was as good as in Example 1.

As is clear from the examples and comparative examples,
ADVANTAGE OF THE INVENTION According to this invention, compared with the case of irradiation only with an electron beam, a hardening performance equivalent or more is obtained under a lower dose and a high oxygen concentration, and it is advantageous also in terms of energy efficiency and cost.

[0025]

As described above, according to the present invention,
It is possible to provide an active energy ray irradiating method and an irradiating object having high practical value and having both high curing performance and excellent cost performance. More specifically, an active energy ray irradiating method and an irradiating object which have excellent curing performance, and are capable of suppressing running costs by reducing the degree of inertization by an inert gas, which is a bottleneck of electron beam irradiation. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an electron beam irradiation apparatus for carrying out the present invention.

FIG. 2 is a diagram showing an electron beam emitting unit of the apparatus of FIG.

FIG. 3 is a diagram for explaining one embodiment when implementing the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Electron beam generation part 3 ... Electron beam emission part 4 ... Pin part 5 ... Irradiation window 10 ... Electron beam irradiation device 11 ... Array 12 ... Irradiation room 13. ..Irradiated object 14 ... X-ray shield 15 ... Conveyor shield

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F073 AA05 BA02 BA07 BA08 BA18 BA22 BA23 BA24 BA28 CA01 CA45 CA62 CA65 DA01 GA07 HA12

Claims (6)

[Claims] 1. An active energy ray irradiation method comprising irradiating an object to be irradiated with ultraviolet rays in an inert gas atmosphere, and then irradiating an electron beam with an acceleration voltage of 100 Kv or less. 2. The active energy ray irradiation method according to claim 1, wherein the inert gas atmosphere has an oxygen concentration of more than 0.05 and not more than 18 (volume)%. 3. An active energy beam irradiation method, comprising irradiating an object to be irradiated with an electron beam having an acceleration voltage of 50 Kv or less and then irradiating an ultraviolet ray in an inert gas atmosphere. 4. An active energy beam irradiation method, comprising: irradiating an object to be irradiated with an electron beam having an acceleration voltage of 50 Kv or less in an inert gas atmosphere, and then irradiating the object with an electron beam at a higher acceleration voltage. . 5. An active energy beam, wherein an irradiation object having a coating material formed on a substrate is cured, cross-linked or modified by the method according to any one of claims 1 to 4. Irradiation method. 6. An active energy ray-irradiated substance obtained by irradiation by the method according to claim 1.