JP2003341021A - Ink jet printer and image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet printer and an image recording method in which an image can be formed on a large size recording medium with high image quality and high efficiency. <P>SOLUTION: Mounting weight of a carriage 3 reciprocating while mounting ink ejecting or radiation irradiating components, e.g. ink jet heads 2, 2,..., irradiating means 4, 4,..., and the like, is set in the range of 1-10 kg. Driving force for moving the carriage 3 during scanning operation of the ink jet heads 2, 2,..., is set not higher than 40 N. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ultraviolet (UV) ray,
An inkjet printer that forms a high-quality image by ejecting an ink that has the property of being cured by the irradiation of radiation such as an electron beam toward the recording medium, and a high-quality image on a recording medium that is non-absorptive of ink. The present invention relates to an image recording method for forming an image.

[0002]

2. Description of the Related Art An ink jet recording method is an image recording method applicable to on-demand printing premised on image formation for each small number of copies, and has recently attracted attention because it requires no special paper. The radiation-curing inkjet system is a method in which an ink containing a radiation-curable compound that is cured by irradiation with radiation such as ultraviolet rays (UV) is ejected from an inkjet head to land on a recording medium, and then the recording medium is irradiated with radiation. This is an image recording method in which the ink is cured by.

The UV ink jet system, which is one of the radiation curing ink jet systems, is an image recording system which uses as a ink a UV ink having a UV curable compound that is cured by irradiation of ultraviolet rays, which is one type of radiation.

In the image formation by the UV ink jet system, in order to form a high quality image on the recording medium, UV is used.
It is necessary to control the dot diameter by irradiating ultraviolet rays immediately after the ink has landed on the recording medium to cure the UV ink. Therefore, for example, as in the technique disclosed in JP-A-60-132767, a carriage is equipped with a light source such as an ultraviolet lamp together with an inkjet head, and when the inkjet head scans a recording medium, the light source is used together with the inkjet head. A method of moving the optical system such as an optical system such as an optical fiber, a collimator, and a mirror is mounted on the carriage as in the technology disclosed in US Pat. No. 6,145,979. Methods for inducing ultraviolet rays to the side of the inkjet head have been developed so far.

[0005]

However, in an ink jet printer for forming an image on a large-sized recording medium such as A0 or B0, if a heavy light source or an optical system is mounted on the carriage, the speed of the carriage will decrease. , Causing a drop in productivity. Further, when the driving force for moving the carriage is increased in order to increase the productivity, it is difficult to stop the carriage at a predetermined position to control the ink ejection position, and the image quality of the image deteriorates. It was happening.

Further, since the weight of the carriage increases the size of the ink jet printer as a whole, there is also a problem that the ink jet printer is restricted in terms of installation location.

An object of the present invention is to provide an ink jet printer and an image recording method capable of forming a high quality image with little bleeding on a large format recording medium with high efficiency.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 is to discharge and land an ink containing at least one radiation-curable compound which is cured by irradiation of radiation. An inkjet printer for irradiating a recording medium on which ink dots are formed with radiation to form an image, comprising: a carriage that reciprocates on the recording medium; a carriage driving unit that reciprocates the carriage; and a carriage mounted on the carriage. An inkjet head that ejects ink toward the recording medium, and an irradiation unit that has a generation unit that generates radiation and that irradiates the recording medium onto which the ink has been ejected with radiation. A total weight of the carriage and an object mounted on the carriage is 1 to 10 kg, and the carriage is Driving force for di driving means reciprocating the carriage equal to or less than 40N.

According to the first aspect of the present invention, by setting the mounting weight, which is the total weight of the carriage and the object mounted on the carriage, to 10 kg or less, the driving force for moving the carriage is 40 N or less. Even in such a case, it is possible to move the carriage at a high initial speed and perform scanning by the inkjet head with high responsiveness. Therefore, a high quality image can be formed with high efficiency.

Even when the mounted weight exceeds 10 kg, the ink jet head can be scanned with high response by setting the driving force to a value exceeding 40 N. However, in this case, it becomes difficult to control the speed and position of the inkjet head, and the quality of the image formed is deteriorated.

Further, when the weight of the carriage mounted exceeds 10 kg and the driving force is 40 N or less, the initial speed of the carriage when the carriage is moved at a high speed is lowered, so that the responsiveness at the time of scanning the ink jet head is low. As a result, the productivity at the time of forming an image at high speed becomes low. Therefore, there is a problem that the efficiency at the time of image formation becomes low when the weight of the carriage mounted exceeds 10 kg and the driving force is 40 N or less.

On the other hand, when the weight of the carriage is less than 1 kg, for example, in an inkjet printer that forms an image on a large-sized recording medium such as A0 size and B0 size, an inkjet head for ejecting ink onto the recording medium is used. The problem arises that the number, size, and weight are limited.

When the number of ink jet heads that can be mounted on the carriage is limited, a color image is formed with a gradation that matches the user's intention, and white ink is opaque white on a transparent recording medium so that the image does not pass through. However, there is a problem that it is difficult to discharge the ink. Further, when the size or weight of the inkjet head that can be mounted on the carriage is restricted, there is a problem that, for example, by mounting an inkjet head having a wide printing width, high-speed image formation cannot be performed.

From these things, the carriage weight is set to 1 to 10 kg and the driving force of the carriage is set to 40 N or less, whereby an ink jet head for forming a high quality image on a large-sized recording medium with high efficiency is produced. can do.

By setting the weight of the carriage to be 10 kg or less, the components such as the carriage driving means for moving the carriage can be made compact. Therefore, it is possible to provide the inkjet printer in a compact form that is not restricted by the installation location.

A second aspect of the present invention is the ink jet printer according to the first aspect, wherein the ink ejected by the ink jet head is yellow, magenta, or
It is characterized by including four colors of cyan and black.

According to the second aspect of the present invention, by setting the mounting weight, which is the total weight of the carriage and the objects mounted on the carriage, to be 1 to 10 kg, the ink jet head mounted on the carriage can be changed to a yellow color. Even when the process color inks of magenta, cyan, and black are ejected, the inkjet head can be scanned with high accuracy and high responsiveness. As a result, a color image can be formed with high image quality and high efficiency in an inkjet printer that forms an image on a large-sized recording medium.

According to a third aspect of the invention, there is provided the ink jet printer according to the second aspect, wherein the color of the ink ejected by the ink jet head includes white.

According to the third aspect of the present invention, by setting the weight of the carriage to be 1 to 10 kg, the special color is added to the process colors of yellow, magenta, cyan, and black from the ink jet head mounted on the carriage. Even when the white ink is ejected as described above, the inkjet head can be scanned with high accuracy and high responsiveness.

By thus allowing the white ink to be ejected as opaque white from the ink jet head, it is possible to form an image after white printing is performed on a large-sized transparent recording medium. Therefore, a color image can be formed with high image quality and high efficiency in an inkjet printer that forms an image on a large-sized transparent recording medium.

According to a fourth aspect of the present invention, there is provided the ink jet printer according to any one of the first to third aspects, wherein the generating unit is mounted on the carriage.

According to the fourth aspect of the present invention, the irradiation means can have a simple structure by mounting the generator on the carriage such that the weight of the mounted carriage is 10 kg or less. This facilitates the control of the irradiation means and enhances the durability of the irradiation means. Therefore, an inkjet printer capable of forming an image with high image quality and high efficiency can be easily controlled and provided at low cost.

According to a fifth aspect of the present invention, there is provided the ink jet printer according to the fourth aspect, wherein the generating unit has a fluorescent lamp.

According to the fifth aspect of the present invention, since the generating unit has the fluorescent lamp, the carriage mounting weight is 10 k.
It becomes easy to be g or less. Therefore, it is possible to produce an inkjet printer with less restrictions on the number, size, and weight of inkjet heads. Further, the irradiation means can be manufactured at low cost. As a result, an inkjet printer capable of forming images with high image quality and high efficiency can be provided at low cost.

The invention according to claim 6 is the ink jet printer according to claim 4, wherein the generating unit is an LD.
Alternatively, it is characterized by having an LED.

According to the sixth aspect of the invention, since the generating portion has the LD or the LED, the weight of the carriage mounted can be reduced. Therefore, it is possible to produce an inkjet printer with less restrictions on the number, size, and weight of inkjet heads. Further, it is possible to suppress the generation of ozone during irradiation of radiation. As a result, it is possible to inexpensively provide an inkjet printer capable of forming an image with high image quality and high efficiency without producing a bad odor.

According to a seventh aspect of the invention, there is provided the ink jet printer according to any one of the first to sixth aspects, which comprises temperature adjusting means for adjusting the temperature of the ink ejected from the ink jet head. At the same time, the temperature adjusting means maintains the temperature of the ink in the range of 30 to 80 ° C.

According to the seventh aspect of the present invention, by setting the weight of the carriage to be 10 kg or less, it is possible to mount the temperature adjusting means on the carriage which can efficiently adjust the temperature of the ink ejected from the ink jet head. it can. Then, by keeping the temperature of the ink ejected from the inkjet head in the range of 30 to 80 ° C., even if the viscosity of the ink is high at a low temperature near room temperature, the viscosity of the ink is kept optimal and the ink is stably ejected from the inkjet head. Ink can be ejected. Therefore, it is possible to provide an inkjet printer capable of forming an image with high image quality and high efficiency.

An eighth aspect of the present invention is an image recording method using the ink jet printer according to any one of the first to seventh aspects, wherein the surface layer on which the ink lands has a space for absorbing the ink. It is characterized in that an image is formed by irradiating radiation after ejecting ink onto a recording medium which is in a substantially homogeneous state.

According to the invention described in claim 8, the ink is ejected onto a cheap material having no voids for absorbing ink on the surface layer, and the radiation is applied to form an image, thereby improving durability, A printed matter having weather resistance can be produced at low cost with high image quality and high efficiency.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, according to the embodiments of the present invention, a UV ink having a property of being cured by irradiation of ultraviolet rays (UV) is ejected onto a recording medium P as one kind of ink which is cured by irradiation of radiation to form an image. An inkjet printer 1 of the type that performs the above will be described as an example with reference to the drawings.

In this specification, an inkjet printer 1 of the type that irradiates UV ink with ultraviolet rays will be described as a preferable example in terms of high curability of ink and low cost of a radiation source. However, the inkjet printer according to the present invention is not limited to the one using UV ink.

In addition to this embodiment, an ink having a property of being cured by irradiation with radiation such as infrared rays, visible rays, electron beams and X-rays may be used. The term "radiation" as used herein refers to radiation in a broad sense, and not only refers to those having the ability to ionize air, but also includes electromagnetic waves such as infrared rays, visible rays, ultraviolet rays, and electron beams as described above.

The ink jet printer 1 is a printer for forming a color image on a large-sized recording medium P such as A0 size or B0 size, which has a very low absorbency for UV ink such as a plastic sheet. The inkjet printer 1 performs image formation by a capstan system in which an image is formed on the recording medium P by ejecting UV ink from the inkjet head 2 while moving both the inkjet head 2 and the recording medium P. As shown in FIGS. 1 and 2, the inkjet printer 1 includes an inkjet head 2, a carriage 3, an irradiation unit 4, a guide rail 5, a conveyance unit, a temperature adjusting unit, a carriage driving unit, a control unit (not shown), and the like. Consists of

The control means (not shown) is a CPU (Central Proc
essing Unit), ROM (Read Only Memory), RAM (Random Ac)
cess Memory), an interface, etc.
Each component of the inkjet printer 1 is controlled based on the data of the image formed on the recording medium P, the data of the recording medium P, and the like. The guide rail 5 guides the carriage 3 when the carriage 3 moves in the X direction in FIG. 1 by the operation of the carriage driving means.

The carriage 3 is an ink jet head 2,
2, ..., Irradiation means 4, 4, .., etc., and a housing for mounting the irradiation means 4, 4 ,. The carriage 3 has an inkjet head 2,
2, ..., Irradiation means 4, 4, ..., Intermediate tanks 6, 6 ,.
A secondary irradiation unit 8, a temperature adjusting unit (not shown), an inkjet head drive circuit, etc. are mounted.

The carriage driving means comprises an electric motor (not shown) and the like, and applies a driving force to the carriage 3 for reciprocating the carriage 3 in the X direction. Here, the condition of the driving force will be described later.

Each of the ink jet heads 2, 2, ... Is provided with a plurality of ejection parts and ejection ports (not shown). The ejection unit is provided with, for example, a piezo element, and when a voltage is applied from the inkjet head drive circuit, U
V ink is ejected from the ejection port to form an ink dot on the recording medium P. A plurality of inkjet heads 2, 2, ... Are arranged in a line in the X direction according to the color of the ink used in the inkjet printer 1, and the ejection ports face downward so as to face the recording medium P. It is mounted on the carriage 3.

In FIG. 2, four color inks of magenta (M), cyan (C), yellow (Y) and black (B) are used, and one ink jet head 2 is used for each color. Drawing is done by taking the case as an example. As described above, the inkjet printer 1 uses the inkjet head 2 to apply the four color UV inks of magenta (M), cyan (C), yellow (Y), and black (K).
A color image can be formed on the recording medium P by allowing ejection from 2 ,.

Further, in addition to the above-described inkjet heads 2, 2 for ejecting the four color inks, inkjet heads 2, 2 for ejecting a white (W) ink are mounted on the carriage 3, so that the carriage 3 is transparent. It is possible to improve the image quality of an image by whitening a recording medium P made of a film so that an image formed thereafter or before is not transmitted. As for the arrangement of the white ink inkjet heads 2, 2, for example, as shown in FIG. 3A, the inkjet heads 2, 2, ... For the color inks Y, M, C, K are sandwiched in the X direction. 3B, or a configuration in which one Y, M, C, K inkjet head 2, 2, ... Is installed on the upstream side and the downstream side in the Y direction, as shown in FIG. 3B. Is mentioned.
It should be noted that two white inkjet heads 2 are not necessarily installed, and for example, a configuration in which one of the left and right white inkjet heads 2 is omitted in FIG.
It is also possible to adopt a configuration in which one white inkjet head 2 is installed on one of the upstream side and the downstream side in the Y direction with respect to the inkjet heads 2, 2, ... Of M, C, K.

The color of the UV ink ejected by the ink jet printer 1 is a design item. Depending on the user's intention, the inkjet printer 1 may eject a color such as light magenta (LM) or light cyan (LC) in addition to the above-described colors depending on the characteristics of the image formed on the recording medium P.

The ink jet head drive circuit generates an applied voltage based on the control of the control means, and applies the voltage to each ejection portion of the ink jet heads 2, 2, ....

The intermediate tanks 6, 6, ... Are provided one for each inkjet head 2 and one for the inkjet head 2.
It is installed in the form of being connected to the upper part of. The intermediate tank 6 stores the UV ink supplied from a main tank (not shown) and supplies it to the inkjet head 2. The intermediate tank 6 and the inkjet head 2 are provided with a temperature adjusting means (not shown) so that the UV ink supplied to the inkjet head 2 has an optimum viscosity for ejection.
The temperature of the inkjet head 2 is adjusted and kept optimal.

Here, in the intermediate tank 6 and the ink jet head 2, the temperature of the UV ink is preferably maintained in the range of 30 to 80 ° C. When the temperature is lower than 30 ° C., the viscosity of the UV ink becomes high, so that the UV ink cannot be stably ejected from the ejection port. On the other hand, when the temperature exceeds 80 ° C., the electric power required to adjust the temperature of the UV ink increases, and the inkjet printer 1
There is a problem that the total power consumption is increased.

The irradiating means 4 comprises a generator for generating ultraviolet rays, and irradiates the area of the recording medium P where the UV ink is ejected with ultraviolet rays. By irradiating the ink dots on the recording medium P in this manner, the surface layer portion of the ink dots is hardened to prevent bleeding and excessive spread on the recording medium P. The irradiation units 4, 4, ... Have a form in which the generation unit and other components are integrated, and are mounted on the carriage so as to face the recording medium P.

The arrangement of the irradiation means 4, 4, ... Is, for example, as shown in FIG. 2 (a), the X of the carriage 3 in such a manner that the ink jet heads 2, 2 ,.
In the form of arranging two in accordance with both ends in the direction,
As shown in (b), the inkjet heads 2, 2, ... Are alternately arranged in the X direction. Also, FIG.
When the white inkjet heads 2, 2 are arranged on the upstream side and the downstream side in the Y direction with respect to the inkjet heads 2, 2, ... For color inks such as Y, M, C, K as shown in FIG. Irradiation means 4 and 4 are further installed so as to sandwich the inkjet head 2.

Here, the irradiation means 4, 4, ... Is preferably installed so that the time from the landing of the UV ink on the recording medium P to the irradiation of ultraviolet rays is 0.02 to 500 ms. .

When the above time is less than 0.02 ms,
Since the UV ink that has landed on the recording medium P hardens without sufficiently leveling as ink dots, the dot diameter becomes extremely small, the image quality of the image formed on the recording medium P deteriorates, and the recording of these ink dots is performed. There is a problem that the adhesiveness to the medium P becomes low and the image strength becomes low. On the other hand, when the above time exceeds 500 ms, the UV ink bleeds on the recording medium P and deteriorates the image quality of the image.

The light source emits ultraviolet rays to irradiate the UV ink on the recording medium P. The light source applied to the generating unit is, for example, a mercury lamp, a metal halide lamp, an excimer lamp, a fluorescent lamp, an LD (Laser Diode), an LED (Lig).
ht Emitting Diode) or the like can be applied, and a light emitting material that emits light having a wavelength at which UV ink is rapidly cured by irradiation is appropriately selected.

As the light source applied to the generator, for example, a fluorescent lamp is preferable. By applying a fluorescent lamp as the light source, it is possible to make the generation unit lightweight. By making the generating portion lightweight in this way, the carriage 3 can be used for the purpose described later.
It becomes easy to keep the loading weight of 10kg or less,
It is possible to reduce restrictions on the number, size, and weight of the inkjet heads 2, 2, .... Further, by applying the fluorescent lamp as the light source, the issuing unit can be manufactured at low cost.

As a light source other than the fluorescent lamp, an LD (Laser
Diode) and LED (Light Emitting Diode) are preferable.
By applying the LD or the LED to the generation unit, the generation unit can be made lighter and the same effect as that of the fluorescent lamp can be obtained. Further, by applying the LD or the LED, it is possible to suppress the generation of ozone accompanying the irradiation of ultraviolet rays and prevent the generation of a bad odor.

Further, in the irradiation means 4, the method of mounting the generating portion on the carriage 3 as in the present embodiment is preferable in terms of durability and controllability of the irradiation means 4. By providing the irradiation means 4 with durability in this manner, the labor and cost related to the maintenance of the inkjet printer 1 can be reduced. Further, by increasing the controllability of the irradiation means 4, the operation of the inkjet printer 1 can be facilitated.

.., irradiation means 4, 4, intermediate tanks 6, 6, ..., Temperature adjusting means, inkjet head drive circuit, and the like. The weight of the carriage 3, which is the total weight of the components related to ultraviolet irradiation, is preferably 1 to 10 kg, and more preferably 1 to 7 kg. Further, it is preferable that the driving force for moving the carriage 3 when performing the scanning by the inkjet heads 2, 2, ... Is 40 N or less.

When the loaded weight is less than 1 kg,
In order to reduce the mounting weight, the number, size, and weight of the inkjet heads 2, 2, ... That can be mounted on the carriage 3 are significantly limited.

The ink jet heads 2, 2, ... Which eject the process color inks of Y, M, C, K are restricted by the number of the ink jet heads 2, 2 ,.
In addition, the inkjet heads 2, 2, ..., which eject special colors according to the characteristics of the image, are mounted on the cartridge 3 so as to form a color image having a gradation suitable for the user's intention or to transmit the image. When a white image is formed on the recording medium P having high property by opaque color and then an image is formed, it becomes difficult to form a clear image without transmission.

Further, by restricting the size and weight of the ink jet heads 2, 2, ..., A wide print width can be applied to the ink jet heads 2, 2 ,. There are restrictions on expanding the area. This causes a problem that high-speed image formation becomes difficult.

When the loaded weight exceeds 10 kg and the driving force is 40 N or less, when the carriage 3 is reciprocated in the X direction to scan the ink jet heads 2, 2, ... Noticeably lower. If the initial speed of the carriage 3 is reduced in this way, the response when the inkjet heads 2, 2, ... Is scanned at high speed becomes slower, and as a result, the productivity of the image forming operation on the recording medium P is reduced, so that the image forming operation is performed. The problem arises that efficiency cannot be improved.

On the other hand, in order to enhance the responsiveness of the carriage 3, the carriage 3 having a loading weight of more than 10 kg has a load of 40N.
When a high driving force exceeding 100 is applied, it becomes difficult to control the speed and position of the carriage 3 with high accuracy, and the accuracy of the position and shape of the ink dots formed on the recording medium P decreases, resulting in printing. There is a problem that the image quality of the image formed on the medium P deteriorates.

Furthermore, the weight of the carriage 3 mounted is 10 k.
If it exceeds g, the inkjet heads 2, 2, ...
It is necessary to form a component having a large volume and weight such as a carriage driving unit for reciprocating the carriage 3 during scanning and a chassis for accommodating and protecting each component of the inkjet printer 1. Therefore, the entire inkjet printer 1 becomes large in volume and weight,
The problem arises that the installation location is restricted.

By setting the weight of the carriage 3 to be 10 kg or less, the carriage 3 can be reciprocated in the X direction with high responsiveness even when the driving force is 40 N or less. Therefore, an image can be formed on the large-sized recording medium P with high image quality and high efficiency.

In order to enable high productivity image formation on the recording medium P, the ink jet heads 2, 2,
The weight of the carriage 3 mounted on the carriage 3 is reduced by reducing the weight of each component mounted on the carriage 3, such as the irradiation means 4, 4 ,.
Keep it below kg. It should be noted that the specific means for suppressing the mounting weight of the carriage 3 is a design matter, and is appropriately determined on the condition that the image quality of the image formed on the recording medium P is not deteriorated.

The secondary irradiating means 8 is provided with a generating portion for emitting ultraviolet rays in a wavelength region different from that of the irradiating means 4, and is arranged on the downstream side of the carriage 3 in the Y direction over the entire width of the recording medium P. It is installed so that it can be irradiated with ultraviolet rays.

Irradiation means 4, which is formed on the recording medium P,
The ink dots whose surface layer portion has been cured by being irradiated with ultraviolet rays from 4, ... Are cured to the inside by being irradiated with the secondary irradiation means 8 and firmly adhered to the recording medium P.

A mercury lamp, a metal halide lamp, a flash light source, a fluorescent lamp, or the like can be applied as a light source applied to the generation portion of the secondary irradiation means 8, and one capable of effectively curing the ink dots to the inside is used. It is selected appropriately.

Next, the UV ink applied to the ink jet printer 1 according to the present invention will be described.

U applied to the inkjet printer 1
The V ink has a temperature of 25 ° C. so that the dots are appropriately leveled and have adhesion on the recording medium P after landing.
Has a viscosity of 6 to 500 mPa · s and a surface tension of 20.
It is preferable to mix it so as to be about 35 dyn / cm. Further, at the time of ejection from the inkjet head 2, temperature control such that the viscosity of the UV ink is 6 to 20 mPa · s is used to control the dot diameter on the recording medium P and to prevent ink clogging at the nozzles. It is preferable in terms of prevention.

Further, it is preferable that the UV ink is filtered with a filter size of at least 2 μm or less, preferably 1 μm or less, and is supplied to the ink jet head 2 in a state where coarse particles are removed.

The UV ink has the above-mentioned physical properties and at least one or more kinds of coloring materials other than the coloring material for coloring so that the UV ink is irradiated with ultraviolet rays from the light irradiation means X to cause a polymerization reaction to be cured. The composition is composed of a polymerizable composition (radiation-curable compound) and an initiator. Furthermore, UV
The ink optionally contains a starting aid, a surfactant, a polymerization inhibitor, an antistatic agent, and the like. Furthermore, it is preferable to add a sensitizing dye to the UV ink as an initiation aid depending on the wavelength of the ultraviolet rays to be irradiated. Hereinafter, the specific composition of the UV ink will be described.

The polymerizable composition is a substance that cures UV ink by polymerizing by irradiation of ultraviolet rays to form a polymer. As the polymerizable composition, a photoradical polymerizable composition which is polymerized by a radical reaction upon irradiation with light, and a cationic polymerization type cationic polymerizable composition in which a cationic chemical species becomes a reactive species and is polymerized are known. ,
These are disclosed, for example, in JP-A-7-159983 and JP-B-7-
No. 31399, JP-A-8-224982, JP-A-10
-863, Japanese Patent Application No. 7-231444 and the like. Further, recently, a cationic photopolymerizable polymerizable composition sensitized to a long wavelength region of visible light or more is also disclosed in, for example, JP-A-6-43633 and JP-A-8-324137.
It is open to the public.

The radical-polymerizable composition is a compound having a radical-polymerizable ethylenically unsaturated bond, and may be any compound as long as it has at least one radical-polymerizable ethylenically unsaturated bond in the molecule. But well,
Those having chemical forms such as monomers, oligomers and polymers are included. Only one type of radically polymerizable composition may be used. Further, in the case where the irradiation means 4, 4, ... And the secondary irradiation means 8 are used to irradiate the ultraviolet rays in two stages as in the present embodiment, two or more kinds of radically polymerizable compositions are used at an arbitrary ratio. You may use together more than one kind.

Examples of the radically polymerizable compound having an ethylenically unsaturated bond include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid and maleic acid, and salts and esters thereof.
Radical polymerizable compositions such as urethane, amides and anhydrides, acrylonitrile, styrene, and various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides and unsaturated urethanes can be mentioned.

Specific examples of the above-mentioned radical polymerization type composition having an ethylenically unsaturated bond include the following methacryl derivatives. The methacryl derivative is 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate,
Carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate. , Triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,
Acrylic acid derivatives such as dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylol acrylamide, diacetone acrylamide, epoxy acrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl Methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, Trimethylol ethane trimethacrylate, trimethylol propane trimethacrylate, 2,2-bis (4-methacryloxy polyethoxy phenyl) methacrylamide derivatives such as propane.

Other radical polymerization compounds include
Examples thereof include derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate and triallyl trimellitate. More specifically, Shinzo Yamashita, "Crosslinking Agent Handbook," (Taiseisha, 1981); Kiyomi Kato, "UV.
・ EB Curing Handbook (raw materials) "(1985, Kobunshi Kogyokai); RadTech Study Group," Applications and Markets of UV / EB Curing Technology ", p. 79, (1989, CMC); Eiichiro Takiyama Commercially available products described in "Polyester Resin Handbook" (1988, Nikkan Kogyo Shimbun) and the like, or well-known radically polymerizable or crosslinkable monomers, oligomers and polymers can be used.

The amount of the radically polymerizable composition added to the UV ink is preferably 1 to 97% by mass. When the amount of the radically polymerizable composition added is less than 1% by mass, the UV ink is not rapidly cured by the irradiation of ultraviolet rays, which hinders the control of dot systems and the like. Further, when the amount of the radically polymerizable composition added exceeds 97% by mass, the coloring by the coloring material is not sufficiently performed, and the color reproducibility in the image on the recording medium P is deteriorated. In addition, U of the radically polymerizable composition
It is more preferable that the amount of addition to the V ink is 30 to 95% by mass.

As the cationically polymerizable polymerizable composition,
For example, an ultraviolet curable prepolymer of an epoxy type, which is a type of which polymerization is caused by cationic polymerization, or a monomer having two or more epoxy groups in one molecule can be applied. Examples of such prepolymers include alicyclic polyepoxides, polyglycidyl esters of polybasic acids, polyglycidyl ethers of polyhydric alcohols, polyglycidyl ethers of polyoxyalkylene glycols, and polyglycidyl aromatic polyols. Examples thereof include ethers, hydrogenated compounds of polyglycidyl ethers of aromatic polyols, urethane polyepoxy compounds and epoxidized polybutadienes. One of these polymerizable compositions may be used alone, or two or more thereof may be mixed and used.

Examples of the cationically polymerizable composition contained in the cationically polymerizable photocurable resin include, for example, the following (1) styrene derivative, (2) vinylnaphthalene derivative, (3) vinyl ethers and (4) N. -Vinyl compounds may be mentioned. (1) Styrene derivative For example, styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, p-methoxy-β-
Methylstyrene etc. (2) Vinylnaphthalene derivative, for example, 2-vinylnaphthalene, α-methyl-2-vinylnaphthalene, β-methyl-2-vinylnaphthalene, 4
-Methyl-2-vinylnaphthalene, 4-methoxy-2-
(3) Vinyl ethers such as vinyl naphthalene, for example, isobutyl vinyl ether, ethyl vinyl ether, phenyl vinyl ether, p-methylphenyl vinyl ether, p-methoxyphenyl vinyl ether,
α-Methylphenyl vinyl ether, β-methyl isobutyl vinyl ether, β-chloroisobutyl vinyl ether, etc. (4) N-vinyl compounds such as N-vinylcarbazole, N-vinylpyrrolidone, N-vinylindole, N-vinylpyrrole, N-
Vinylphenothiazine, N-vinylacetanilide, N
-Vinylethylacetamide, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, N-vinylimidazole, etc.

The content of the cationic polymerization type polymerizable composition is preferably 1 to 97% by mass. When the amount of the cationically polymerizable composition added is less than 1% by mass, the UV ink is not rapidly cured by irradiation with ultraviolet rays, which hinders control of dot systems and the like. On the other hand, the amount of the cationic polymerization composition added is 9
If it exceeds 7% by mass, coloring by the coloring material is not sufficiently performed and the color reproducibility in the image on the recording medium P is deteriorated. Further, the amount of the cationically polymerizable composition added to the UV ink is more preferably 30 to 95% by mass.

An initiator for initiating the polymerization reaction of the polymerizable composition upon irradiation with ultraviolet rays is added to the UV ink. As the initiator, those suitable for the radically polymerizable composition and the cationically polymerizable composition are applied.

In the case of a UV ink containing a radically polymerizable composition, aryl alkyl ketone, oxime ketone, acylphosphine oxide, acylphosphonate,
Well-known initiators such as S-phenyl thiobenzoate, titanocene, aromatic ketones, thioxanthone, benzyl and quinone derivatives or ketocoumarins can be applied.

Of the above initiators, acylphosphine oxide and acylphosphonate are preferable as the radical polymerization initiator. These initiators have characteristics that they have high sensitivity to ultraviolet rays and that the active species generated by irradiation with ultraviolet rays have a remarkably lower absorbance than the initiator before irradiation. Usually, the UV ink ejected from the inkjet head 2 and landed on the recording medium P has a thickness of 5 to 15 μm, so that an initiator such as an acylphosphine oxide or an acylphosphonate is deposited on the recording medium P.
It is preferable because the inside of the V ink is efficiently cured.

For the above-mentioned reasons, the radical polymerization initiators are specifically bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and bis (2,2).
6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide and the like are preferable.

Further, in the case of selecting an initiator which is highly sensitive to ultraviolet rays and whose polymerization is hardly inhibited by oxygen in the air, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone is selected. -1 and 1
-Hydroxy-cyclohexyl-phenyl-ketone, 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropane-1- On or 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropane-1-
A combination of one and diethylthioxanthone or isopropylthioxanthone, a combination of benzophenone and an acrylic acid derivative having a tertiary amino group, and addition of a tertiary amine are preferable.

The initiator is preferably added in an amount of 1 to 10% by mass. If the amount of the initiator added is less than 1% by mass, the UV ink that has landed on the recording medium will not cure rapidly, and the problem of difficulty in controlling the dot diameter and dot shape arises. Moreover, the addition amount is 10% by mass.
When it exceeds the above range, the concentration of the reactive species generated during the polymerization reaction becomes extremely high, so that the number of polymerization nuclei increases, and as a result, the polymerizable composition cannot polymerize at a high degree of polymerization, and the cured UV ink And the adhesiveness to the recording medium P are significantly reduced. Further, the addition amount of the initiator is more preferably 1 to 6% by mass.

In addition to the above-mentioned compounds, the initiator is well known in the literature such as "Application and Market of UV / EB Curing Technology" (CMC Publishing, edited by Yoneho Tabata / edited by Radtech Research Association). The compound may be applied.

On the other hand, when the cationically polymerizable composition is applied to the UV ink, a photo acid generator can be applied as an initiator. As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used. As these compounds, those described in "Organic Materials for Imaging" (edited by Research Committee on Organic Electronics Materials, Bushin Publishing Co., pp. 187-192, 1993) are applicable.

When a cationically polymerizable composition is applied to UV ink, for example, it is applied to chemically amplified photoresists and photocationic polymerization, "organic material for imaging" (Bushin Publishing Co., Ltd., 1993, pp. 187-192). Compounds known in the literature such as are applicable. The compounds suitable as the initiator can be classified into the following four groups.

The first group is cations exemplified in the formulas (1) to (14) such as diazonium, ammonium, iodonium, sulfonium and phosphonium, and B (C
₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ^{− and an} anion such as CF ₃ SO ₃ ⁻ . As the initiator belonging to the first group, those having borate as a counter anion are particularly preferable in that they have a high acid generating ability.

[Chemical 1]

The second group is the sulfonated compounds exemplified in formulas (15) to (25). These compounds generate sulfonate ions upon irradiation with ultraviolet rays.

[Chemical 2]

The third group is equations (26) to (32).
Is a halide exemplified in. These compounds generate hydrogen halide upon irradiation with ultraviolet rays.

[Chemical 3]

The fourth group is equations (33) and (34).
Is an iron allene complex.

[Chemical 4]

The fifth group is the titanocenes. Here, titanocene is a general term for compounds having a skeleton in which one or two cyclopentadienyl ligands are coordinated to a titanium atom, and specifically, bis-cyclopentadienyl-Ti. -Di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, di-cyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-cyclo Pentadienyl-T
i-bis-2,3,5,6-tetrafluorophenyl-1
-Yl, di-cyclopentadienyl-Ti-bis-2,
4,6-Trifluorophenyl-1-yl, di-cyclopentadienyl-Ti-bis-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-
2,4-difluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-
Pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2, 4-difluorophen-1-yl, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyrid-1-yl) phenyl) titanium (IRUGACURE784: manufactured by Ciba Specialty Chemicals) and the like can be mentioned. However, the present invention is not limited to this.

The initiator aid is a sensitizing dye which improves the efficiency of radical or acid generation of the initiator by donating energy to the initiator by irradiation of ultraviolet rays, electron donation, electron attraction, heat generation, etc. A substance that acts and is applied in combination with an initiator.

Examples of the combination of the initiator and the initiation aid applied to the radical-polymerizable composition include a peracid ester which is the initiator and an initiation aid, xanthene, a thioxanthone dye, ketocoumarin, and thiopyrylium salt. Combinations such as a combination of an onium salt such as a diphenyliodonium salt that is an initiator and a thioxanthene dye that is an initiation aid are well known.

When titanocenes are applied as the initiator, for example, cyanine, phthalocyanine, merocyanine, or porphyrin can be used as an initiation aid for sensitizing the titanocenes in the wavelength range from visible light to near-infrared light corresponding to laser or LED. , Spiro compound, ferrocene, fluorene, flugide, imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrylium compound, pyrromethene compound,
Pyrazolotriazole compounds, benzothiazole compounds, barbituric acid derivatives, thiobarbituric acid derivatives and the like can be applied.

As the initiation aid to be used in combination with titanocene, European Patent 568,993, US Pat. Nos. 4,508,811, 5,227,227, 2001-125255 and 11-125 271969
The compounds described in No. etc. are also applicable. Specific examples of such a combination of a photopolymerization initiator of titanocene and an initiation aid include JP-A-2001-125255 and JP-A-11-125255.
Certain combinations described in -271969 can be mentioned.

The initiation aid is applied when the initiator applied to the UV ink does not absorb the ultraviolet light emitted from the irradiation means 4, 4, ... Or the secondary irradiation means 8 with sufficient absorbance. That is, although the initiator is selected due to factors such as the strength of the ink dots when cured and the adhesiveness to the recording medium P, if the initiator does not absorb the ultraviolet rays that can be emitted at the generating portion, the start aid The ink dots can be cured by applying the agent. In this way, by making it possible to apply the initiation aid to the UV ink,
It is possible to form high-quality and high-strength images corresponding to many types of recording media and applications.

As the initiation aid, in addition to the above-mentioned compounds, "polymer additive development technology" (CMC Publishing,
A substance known to act as a sensitizing dye in the literature (such as supervised by Yasuichi Ohkatsu) may be applied.
The initiation aid can also be regarded as a component forming a part of the initiator.

To color the UV ink, the coloring material is dispersed and added as described above. As the coloring material, a coloring material that can be dissolved or dispersed in the main component of the polymerizable composition can be applied, and a pigment is preferable from the viewpoint of light resistance. As a pigment,
For example, those listed below are applicable, but the pigment applied to the present invention is not limited thereto. C. I Pigment Yellow-1,3,1
2, 13, 14, 17, 81, 83, 87, 95, 10
9, 42, 74, 128, 185, C.I. I Pigment Orange-16, 36,
38, C.I. I Pigment Red-5, 22, 38, 4
8: 1, 48: 2, 48: 4, 49: 1, 53: 1, 5
7: 1, 63: 1, 144, 146, 185, 101, 2, 12, 9, 122, 184, 188, C.I. I Pigment Violet-19, 23, C.I. I Pigment Blue-15: 1, 15:
3,15: 4,18,60,27,29, C.I. I Pigment Green-7, 36, C.I. I Pigment White-6, 18, 2
1, other organic white pigments C.I. I Pigment Black-7

The addition amount of the coloring material to be added to the UV ink is determined by the coloring property after dispersion and the like, but is preferably 0.1 to 15% by mass. Addition amount of coloring material is 0.1% by mass
If it is less than the above range, the color material does not sufficiently develop color, which causes a problem that the color reproducibility of the image formed on the recording medium P is deteriorated. Further, when the coloring material is added in an amount of more than 15% by mass, the ink dots are not rapidly cured by the irradiation of ultraviolet rays, and the ink dots are bleeding on the recording medium P to deteriorate the image quality of the image. Occurs.

To disperse the pigment in the UV ink,
Ball mill, sand mill, attritor, roll mill,
Agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill,
A paint shaker or the like can be used.

It is also possible to add a dispersant to disperse the pigment. A polymer dispersant is preferably used as the dispersant. As the polymer dispersant, for example, A
Vesia's Solsperse series may be mentioned. Further, it is possible to add synergists corresponding to various pigments to the UV ink as a dispersion aid.

These dispersants and dispersion aids are used as pigment 1
It is preferable to add 1 to 50 parts by mass to 00 parts by mass. When the addition amount of the dispersant and the dispersion aid is less than 1 part by mass with respect to 100 parts by mass of the pigment, the pigment is not uniformly dispersed in the UV ink and the image quality of the image on the recording medium P is remarkably deteriorated. The problem arises. On the other hand, when the addition amount of the dispersant and the dispersion aid exceeds 1 part by mass with respect to 100 parts by mass of the pigment, the coloring material does not sufficiently develop the color or the UV ink landed on the recording medium P is rapidly cured. The problem of not doing it occurs.

A solvent or a polymerizable composition is applied as a dispersion medium for dispersing the above pigment in the UV ink. Here, it is preferable that the UV ink applied to the present invention is rapidly cured by irradiation of ultraviolet rays and that the pigment is dispersed only by the polymerizable composition in order to prevent deterioration and odor of the UV ink after curing. Further, since the pigment is dispersed without using a solvent, it is preferable to apply a monomer having low viscosity to the polymerizable composition.

Upon dispersion of the pigment, the average particle diameter of the pigment is 0.
The thickness is preferably 08 to 0.5 μm. Here, the particle size of the pigment is measured by the light scattering method, and the average particle size is defined by the histogram average (D ₅₀ ). If the average particle size of the pigment is less than 0.08 μm, U
There is a problem that the cost of V ink is high.
Further, when the average particle diameter of the pigment exceeds 0.5 μm, the transparency of the UV ink landed on the recording medium P is impaired, or the UV ink is not rapidly cured by the irradiation of ultraviolet rays, so that the image However, there is a problem that the image quality of is deteriorated.

Further, the maximum particle size of the pigment is 0.3 to 10 μm.
It is preferably m. Maximum particle size of pigment is 0.3 μm
If it is less than this, there is a problem that the cost of UV ink is high. Further, when the maximum particle size of the pigment exceeds 10 μm, there is a problem that the UV ink is likely to be clogged in the nozzle. From the above reason, the maximum particle diameter of the pigment is more preferably 0.3 to 3 μm.

The components contained in the UV ink are not limited to those mentioned above. For example, in order to prevent the UV ink from being hardened before being ejected, a polymerization inhibitor of 200 to
It is also possible to add 20000 ppm. Especially U
When the V ink is made highly viscous, heated and made to have a low viscosity before being ejected, it is preferable to add a polymerization inhibitor to the UV ink in order to prevent clogging of the inkjet head due to thermal polymerization.

In addition to these, a surfactant, a leveling additive, a matting agent, a polyester resin for adjusting the physical properties of the film, a polyurethane resin, a vinyl resin, if necessary.
Acrylic resins, rubber resins, and waxes can be added. Further, in order to improve the adhesion between the recording medium P and the UV ink, it is also effective to add an extremely small amount of organic solvent. In this case, it is effective to add it in a range that does not cause problems of solvent resistance and odor, and the amount is 0.1 to 5% by mass, preferably 0.1 to 3% by mass.

As a means for preventing the sensitivity from being lowered due to the shielding effect of the ink coloring material, an initiator having a long life and a cationically polymerizable monomer are combined to prepare a UV ink, or a radically polymerizable composition and a cationically polymerizable composition are used. A hybrid type UV ink may be blended in combination with the composition.

Next, the recording medium P on which an image is formed by the ink jet printer 1 according to the present invention will be described. The recording medium P is a sheet-shaped medium made of a material that does not absorb ink. Here, the ink non-absorbent material is
It is a material in which the surface layer on which the ink lands is in a substantially homogeneous state without voids for absorbing the ink. here,
The ink-absorbing voids are formed by, for example, voids between fibers forming paper or the like, voids between polymers forming a resin having a property of absorbing ink and swelling, and fillers and resin particles. For example, voids in the layer.

The recording medium having voids for absorbing ink in the surface layer is expensive and has the problems of low durability and weather resistance. On the other hand, many recording media P made of a non-ink-absorbent material are inexpensive and have a constitution and durability. Therefore, by allowing the inkjet printer 1 according to the present invention to form an image on a material that does not absorb ink, it is possible to inexpensively produce a printed material suitable for an advertising medium, a packaging material, or the like.

Specific examples of the non-ink-absorbent material having no void for absorbing ink in the surface layer include metal, glass, plastic having no absorption layer, paper coated with resin on the surface, and the like. . Of the above materials, paper coated with a resin on the surface and plastic films for flexible packaging materials are preferable because they are inexpensive, have durability and weather resistance, and can be easily applied to advertising media and packaging materials.

Specific materials for the plastic film for the soft packaging material include polyester, polyolefin, polyamide, polyesteramide, polyether, polyimide, polyamideimide, polystyrene, polycarbonate, poly-p-phenylene sulfide, polyether ester, and polyester. Vinyl chloride, poly (meth) acrylic acid ester, polyethylene, polypropylene and nylon are preferable, and copolymers and mixtures of the above materials and materials formed by crosslinking the above polymers with each other are also applicable. Among the above materials, polyethylene terephthalate, polystyrene, polypropylene and nylon are preferable in terms of transparency, dimensional stability, rigidity, environmental load and cost.

The plastic film has a thickness of 2 to 10
A material having a thickness of 0 μm is applicable as a packaging material. Also,
The plastic film preferably has a thickness of 6 to 80 μm. The thickness of the plastic film is 2
When the thickness is less than μm, there is a problem that the strength is so low that it is easily broken and the contents cannot be stored and protected. Further, if the thickness exceeds 100 μm, the equipment for packaging the contents becomes special and the cost increases. Further, the plastic film preferably has a thickness of 10 to 70 μm.

Next, the procedure for forming an image on the non-ink-absorbing recording medium P having no void where the surface layer on which the ink is deposited absorbs the ink using the ink jet printer 1 according to this embodiment will be described.

Image formation is carried out by the inkjet head 2,
The process proceeds by the discharge of UV ink by 2, .... At this time, the inkjet heads 2, 2, ... Scan the recording medium P in the X direction in FIG. UV ink is ejected from ejection ports of the inkjet heads 2, 2, ... Simultaneously with this scanning. The UV ink is ejected by applying a voltage from the inkjet head drive circuit to the ejection portion under the control of the control unit based on the data of the image formed on the recording medium P. The temperature of the UV ink supplied to the inkjet head 2 is adjusted so that the UV ink has a viscosity suitable for ejection.

The UV ink ejected from the ink jet heads 2, 2, ... Lands on the recording medium P one after another to form ink dots. The ink dots spread on the recording medium P by leveling.

U from the ink jet heads 2, 2, ...
Subsequent to the ejection of the V ink, the region of the recording medium P where the ink dots are formed is irradiated with ultraviolet rays.

The scanning of the ink jet heads 2, 2, ... Is carried out concurrently with the ejection of UV ink. Therefore, the UV ink is ejected from the inkjet head 2,
The V ink lands on the recording medium P to form ink dots, and after being appropriately spread by leveling, the irradiation means 4
Moves to just above this ink dot and is irradiated with ultraviolet rays. In this way, the ink dots are hardened at the surface layer so as not to bleed.

The inkjet heads 2, 2, ... Perform scanning in the X direction over the entire width of the recording medium P to eject UV ink, and then the recording medium P is appropriately conveyed in the Y direction by the conveying means. After the recording medium P is conveyed in the Y direction, the inkjet heads 2, 2, ...
V ink is ejected, and the ink dots formed by the ejection are cured by the irradiation means 4, 4, ...

By the conveyance in the Y direction by the conveyance means, the area of the recording medium P on which the ink dots are formed moves to the area directly below the secondary irradiation means 8. The ink dots are cured to the inside by being irradiated with ultraviolet rays by the secondary irradiation means 8 and firmly adhered to the recording medium P.

An image is formed on the recording medium P by repeating the above operation. Here, when the recording medium P is made of a transparent material, the above operation is performed on the white ink to apply the white ink as opaque white to the area of the recording medium P where the image is to be formed, and after whitening is performed. , Y, M, C, K, and the like, the image forming is performed by repeating the above-described operations for the color inks including the process colors. Further, when the recording medium P is made of a non-transparent material, the above-described operation is repeated only for the color inks to form an image.

Next, an example of the ink jet printer 1 according to the above embodiment will be described.

[Examples Using Ink Set 1] In this example, an ink set 1 including black ink, yellow ink, magenta ink, light magenta ink, cyan ink, light cyan ink, and white ink was prepared as described below. After that, it was applied as a UV ink. To prepare the ink set 1, first, a pigment, a dispersant, etc. are blended in the following composition to prepare a white pigment dispersion W1, a yellow pigment dispersion Y1, a magenta pigment dispersion M1, a cyan pigment dispersion C1 and a black pigment dispersion. I got K1.

The compounding was carried out by first pre-dispersing a small amount of phenoxyethyl acrylate together with a predetermined amount of pigment, dispersant, and acrylic resin by a pressure kneader, sufficiently wetting the surface of the pigment, and then kneading with three roll mills. Was carried out, followed by adding the remaining phenoxyethyl acrylate and performing dispersion with a bead mill. <White pigment dispersion W1> Organic white pigment (Shigenox OWP: manufactured by Hakkol Chemical Co., Ltd.) 15.0 parts by mass Nonionic dispersant (dispersant) 1.5 parts by mass Phenoxyethyl acrylate (polymerizable composition) 80.0 parts by mass Parts Acrylic resin (acid value 0) 3.5 parts by mass <Yellow pigment dispersion Y1> Pigment Yellow 180 (pigment) 15.0 parts by mass Nonionic dispersant (dispersant) 1.5 parts by mass Phenoxyethyl acrylate (polymerization Functional composition) 80.0 parts by mass Acrylic resin (acid value 0) 3.5 parts by mass <Magenta pigment dispersion M1> Pigment Violet 19 (pigment) 15.0 parts by mass Nonionic dispersant (dispersant) 1. 5 parts by mass Phenoxyethyl acrylate (polymerizable composition) 80.0 parts by mass Acrylic resin (acid value 0) 3.5 parts by mass <Cyan face Dispersion C1> Pigment Blue 15: 3 (pigment) 15.0 parts by mass Nonionic dispersant (dispersant) 1.5 parts by mass Phenoxyethyl acrylate (polymerizable composition) 80.0 parts by mass Acrylic resin (acid value 0) 3.5 parts by mass <Black pigment dispersion M1> Pigment Violet 19 (pigment) 15.0 parts by mass Nonionic dispersant (dispersant) 1.5 parts by mass Phenoxyethyl acrylate (polymerizable composition) 80.0 Parts by mass Acrylic resin (acid value 0) 3.5 parts by mass

The above pigment dispersions W1, Y1, M1 and C
Ink set 1 as shown in Table 1 using No. 1 and K1
Was compounded. The UV ink is prepared by first mixing all the materials shown in Table 1 except the pigment dispersion and confirming that they are sufficiently dissolved, and then adding the above pigment dispersion little by little and using a dissolver sufficiently. It was carried out by stirring. After blending, pre-filtration was performed with a 10 μm filter, and then filtration was performed with a 0.8 μm filter.

[Table 1] Here, the abbreviations shown in Table 1 are as follows. DPCA60: Nippon Kayaku, KAYARAD DPCA (caprolactam modified dipentaerythritol hexaacrylate) TEGDA: Osaka Organic, viscoat # 335HP (tetraethylene glycol diacrylate) PO-A: Kyoeisha Chemical, light acrylate PO-A (phenoxyethyl acrylate) ) I369: Initiator, Ciba Specialty Chemicals, Ir
gacure369 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1)

In the above-mentioned filtration process, the occurrence of pressure loss is small,
Sufficient filtration rate was obtained. Next, the filtered UV ink was heated to 50 ° C. and stirred while being decompressed to remove the dissolved air and water, and then subjected to image formation. 25 of UV ink created in this way
The viscosity at 25 ° C is 25 to 35 mPa · s, and the surface tension is 3
0-40 dyn / cm, viscosity at 60 ° C is 10-2
It was 0 mPa · s. The average particle size of the pigment is 0.0
The water content was 8 to 0.3 μm and the water content was 0.7 to 1.2%.

An image was formed on the recording medium P by the ink jet printer 1 using the ink set 1 produced by the above procedure. Recording medium P for image formation
An OPP film (“Pyrene” film-OT manufactured by Toyobo Co., Ltd .: thickness of 40 μm) made of a material having no surface for absorbing ink was used as the material.

The carriage driving means for generating the driving force for moving the carriage 3 in the X direction is
Drive company UGMFD-B5L (rated voltage: DC3
0V, rated torque: 0.0529N · m, rated speed:
4200 rpm, rated output: 23 W, rated current: 1.1
A, stall torque: 0.392 N · m or more, no-load rotation speed: 4635 rpm ± 10%) were used as power sources.

The ink jet head 2 has a nozzle diameter 23.
A piezo-type inkjet head with 128 μm and 128 nozzles was used. At the generation part of the irradiation means 4, 4, ...
A Vzero85 manufactured by Integrated Technology was used, and a microminiature cold cathode black lamp (TBB30 series) manufactured by Hibeck was used for the generation part of the secondary irradiation means 8.

The ink supply system for supplying the UV ink to the ink jet head 2 is provided with a supply pipe and a pipe with a filter in addition to the main tank and the intermediate tank 6, and the intermediate tank 6 and the ink jet head 2 are insulated and shielded from light. A temperature sensor was installed in the intermediate tank 6 and the inkjet head 2, and temperature control was performed so that the temperature of the nozzle portion was maintained at 60 ± 2 ° C. based on the temperature detected by this temperature sensor.

The amount of UV ink ejected at one time is 7 pl.
Set to. The drive frequency is 720 × 720 dpi (dpi: dot per in
It was set to 10 kHz so that images could be formed with the resolution of ch). Further, at the time of evaluation of suitability for high-speed printing, which will be described later, the frequency was set to 40 kHz so that image formation could be performed at a resolution of 360 × 360 dpi. Further, the illuminance of the ultraviolet light emitted from the irradiation means 4, 4, ... And the secondary irradiation means 8 was adjusted to be 30 mW / cm ^{2 on the} recording medium P.

With respect to the above-mentioned inkjet printer 1, recording medium P, and ink set 1, image formation in each of the examples and comparative examples was performed under the following conditions.

In Example 1, image formation was carried out by using one ink jet head 2 for each of the five colors W, Y, M, C and K. The irradiation means 4, 4, ... Uses the TCG30 series for the generating portion and is arranged alternately with the inkjet heads 2, 2, ... As shown in FIG.

In Example 2, two W ink jet heads were used only for W, and other conditions were the same as in Example 1 to form an image.

In the third embodiment, W, Y, M, LM, C, L
Images were formed using one inkjet head 2 for each of the seven colors C and K. Irradiation means 4, 4,
, TCG30 series was used for the generation part, and they were arranged alternately with the inkjet heads 2, 2, ... As shown in FIG.

In Example 4, two W ink jet heads were used only for W, and other conditions were the same as in Example 3 to form an image.

In the fifth embodiment, the irradiating means 4 and 4 are arranged in the generating part.
As shown in FIG. 2A, two Vjets 85 are mounted on the carriage 3 so that the inkjet heads 2, 2, ... Are sandwiched in the X direction.

In Comparative Examples 1 to 4, Vz is applied to the generation part of the irradiation means 4.
Using ero85, the conditions other than the type of light source used for the generation unit are Comparative Example 1-Example 1, Comparative Example 2-Example 2, and Comparative Example 3-.
A combination of Example 3, Comparative Example 4 and Example 4 was prepared.

Under the conditions of Examples 1 to 5 and Comparative Examples 1 to 4, the mounting weights of the carriage 3 were as shown in Table 2. Under these conditions, a driving force of 30 is applied to the carriage 3.
By imparting N, the carriage 3 was reciprocally moved, an image was formed on the recording medium P, and the image quality of the formed image was evaluated.

Further, the driving force of the carriage 3 was set to 45 N, an image was formed on the recording medium P, and the image quality of the formed image was evaluated. The conditions of the inkjet heads 2, 2, ..., Which are mounted on the carriage 3 are as follows: Comparative Example 5-Example 1, Comparative Example 6-Example 2, Comparative Example 7-Example 3, Comparative Example 8-Example 4, I prepared with the combination.

The results of image formation under the conditions of Examples 1 to 4 and Comparative Examples 1 to 8 are summarized in Table 2.

[Table 2]

Here, the “image quality” is the image quality of the image formed on the recording medium P. ◎ means "almost uniform"
◯ means “slightly unevenness” and × means “visually noticeable unevenness”.

As shown in Table 2, when the driving force for moving the carriage 3 is set to 30 N, the third embodiment
Almost no unevenness was observed, and in other cases, slight unevenness was observed in the formed image.
On the other hand, when the driving force was set to 45 N, the formed image was so inferior that the unevenness was visually noticeable.

"High-speed printability" means a resolution of 360 × 3.
The printing speed is set to 60 dpi and the driving frequency is set to 40 kHz, and the main scanning speed, which is the scanning speed of the inkjet heads 2, 2, ..., Is changed to 1.0 m / s, 1.5 m / s, and 2.0 m / s for printing. The results are obtained by evaluating the productivity of image formation. ◎: "Stable printing is possible even at a main scanning speed of 2.0 m / s", ○: "Stable printing is possible up to a main scanning speed of 1.5 m / s", ×: "Main scanning speed of 1.0 m / s" Up to stable printing is possible ".

As shown in Table 2, when the weight of the carriage 3 mounted is 5 kg or less or the driving force is 45 N, the first and second embodiments are stable even at the main scanning speed of 2.0 m / s. Printable, otherwise main scanning speed is 1.5m
Stable printing was possible up to / s. On the other hand, when the weight of the carriage 3 exceeds 10 kg and the driving force of the carriage 3 is 30 N, stable printing can be performed only up to the main scanning speed of 1.0 m / s.

The "dot quality" is the result of evaluation of the bleeding of two adjacent ink dots and the bleeding at the edge portion of the image in the image formed on the recording medium P. ◯ means “without blurring of each color”, Δ means “blurring in some colors”, and × means “blurring in each color”.

As shown in Table 2, bleeding was not observed in all the colors in any of the examples except bleeding in some colors in Example 5.

As described above, in the embodiment of the ink set 1,
By setting the weight of the carriage 3 to be set to 5 kg or less, it was possible to form an image with stable image quality with very little unevenness. Further, by setting the driving force for reciprocating the carriage 3 to 30 N, it was possible to efficiently form an image with high productivity even when the main scanning speed was set to 1.5 m / s or more.

[Examples Using Ink Set 2] In Examples using Ink Set 2, an ink set 2 including black ink, yellow ink, magenta ink, light magenta ink, cyan ink, light cyan ink and white ink will be described below. After making it, UV
It was applied as an ink. To create ink set 2,
First, a pigment, a dispersant and the like were blended in the following composition to obtain a white pigment dispersion W2, a yellow pigment dispersion Y2, a magenta pigment dispersion M2, a cyan pigment dispersion C2 and a black pigment dispersion K2.

The compounding was carried out by first pre-dispersing a small amount of the oxetane compound together with a predetermined amount of pigment and a dispersant by a pressure kneader, sufficiently wetting the surface of the pigment, and then kneading the mixture with a three-roll mill, followed by the remaining residue. Oxetane compound was added and dispersed by a bead mill. After blending, pre-filtration was performed with a 10 μm filter, and then filtration was performed with a 0.8 μm filter. <White pigment dispersion W2> Titanium oxide (average particle diameter 0.15 μm, refractive index 2.52) 15.0 parts by mass Polymer dispersant 1.0 parts by mass Oxetane compound (polymerizable composition) 84.0 parts by mass <Yellow Pigment Dispersion Y2> Pigment Yellow 180 (Pigment) 15.0 parts by mass Polymer Dispersant 1.0 parts by mass Oxetane compound (polymerizable composition) 84.0 parts by mass <Magenta Pigment Dispersion M2> Pigment Violet 19 (Pigment) 15.0 parts by mass Polymer dispersant 1.0 parts by mass Oxetane compound (polymerizable composition) 84.0 parts by mass <Cyan pigment dispersion C2> Pigment Blue 15: 3 (pigment) 15.0 parts by mass Polymer dispersant 1.0 part by mass Oxetane compound (polymerizable composition) 84.0 parts by mass <Black Pigment Dispersion M2> Pigment Violet 19 (Pigment) 15.0 Parts by mass Polymer dispersant 1.0 parts by mass Oxetane compound (polymerizable composition) 84.0 parts by mass

Using the pigment dispersion thus obtained, Table 3
Ink sets 2 were prepared by mixing the inks of the respective colors as shown in FIG.

[Table 3] Here, what the abbreviations in Table 3 indicate are as follows. OXT: Oxetane compound OXT-221 (di [1-
Ethyl (3-oxetanyl)] methyl ether) 2021P: manufactured by Daicel, epoxy compound Celoxide 2021P (3,4-epoxycyclohexylmethyl-3,4-
Epoxycyclohexanecarboxylate) BBI102: Midori Kagaku, photoacid generator (4,4-tert-butyldiphenyliodonium hexafluorophosphate) DETX: Nippon Kayaku, sensitizer (2,4-diethylthioxanthone)

In the above-mentioned filtration step, the occurrence of pressure loss is small,
Sufficient filtration rate was obtained. Next, the filtered UV ink was heated to 50 ° C. and stirred while being decompressed to remove the dissolved air and water, and then subjected to image formation. 25 of UV ink created in this way
The viscosity at 25 ° C is 25-40 mPa · s, and the surface tension is 3
0-35 dyn / cm, viscosity at 60 ° C is 10-2
It was 0 mPa · s. The average particle size of the pigment is 0.0
The water content was 8 to 0.3 μm and the water content was 0.7 to 1.2%.

The ink set 2 shown in Table 3 is used as the UV ink, and the constituent elements mounted on the carriage 3 and the driving force for moving the carriage 3 are set under the conditions of Examples 1 to 1.
Image formation was performed in the same manner as in Example of Ink Set 1 in accordance with Example 5 and Examples 1 to 8, and the image formed on the recording medium P was evaluated. As a result, the glossiness of the surface of the image was improved, and although the difference between the example and the comparative example in terms of image quality was slightly reduced, the ink set 1 of the example in ink set 1 was appropriate in terms of high-speed printing suitability and spotting. Similar results were obtained.

As described above, the weight of the carriage 3 mounted with the inkjet heads 2, 2, ... And the irradiation means 4, 4 ,. By setting the driving force for moving the carriage 3 to 40 N, the initial speed when the carriage 3 moves is increased, and even when the inkjet heads 2, 2, ... An image can be formed on the large-sized recording medium P by controlling the speed and position of 2, ... With high accuracy. Therefore, an image can be formed on the large-sized recording medium P with high image quality and high efficiency.

Further, the weight of the carriage 3 mounted is 10 kg.
By the following, other components such as the carriage driving unit can be made compact. Therefore, the inkjet printer 1 can be made compact without being restricted by the installation location.

Further, when the total weight of the carriage 3 is set to 1 kg or more, the inkjet heads 2, 2, ... For ejecting the process color ink and the inkjet heads 2, 2 ,. Can be installed. Therefore, it is possible to form a color image with a gradation that suits the user's intention and to whiten the transparent recording medium P. Further, it is also possible to form an image at high speed by applying the inkjet heads 2, 2, ...

Further, the ink jet printer 1 according to the present invention is capable of producing high quality and high quality images on a large-sized recording medium P made of a material such as resin-coated paper or plastic film which does not have voids for absorbing ink in its surface layer. It can be formed efficiently. By providing an image with high image quality and high efficiency on an inexpensive material having weather resistance and durability, an inexpensive printed material having weather resistance and durability can be provided with high image quality and high efficiency. be able to.

In the ink jet printer 1 according to the present invention, the weight of the carriage 3 mounted is 1 to 10 kg.
The means that does not necessarily reduce the weight of the light source applied to the generation unit as in the above-described embodiment.

In order to keep the mounted weight within the above range, there are methods such as reducing the weight of the components such as the intermediate tanks 6, 6, ... And the ink jet head drive circuit, or installing them outside the carriage 3.

Further, it is also possible to adopt a structure in which the generating portions of the irradiation means 4, 4, ... Are not mounted on the carriage 3 but are installed separately from the carriage 3. In this case, an optical system such as a mirror or a prism is mounted on the carriage 3, and radiation such as ultraviolet rays generated by the generation unit is guided onto the recording medium P by this optical system, so that the ink dots can be promptly formed. The ink dots may be irradiated with radiation. Further, the irradiation unit 4 may be installed directly above the region where the carriage 3 reciprocates, in a form capable of irradiating radiation over the entire width of the recording medium P.

The means for setting the weight of the carriage 3 to be 1 to 10 kg is a design matter, and is appropriately determined on the condition that an image can be formed on the recording medium P with high image quality and high efficiency.

The ink jet printer and the image recording method according to the present invention are not limited to those described above. Radiation emitted by scanning the ink dots is not limited to ultraviolet rays. In the inkjet printer 1 and the image recording method according to the present invention, the ink dots may be cured using radiation such as visible light, infrared rays, electron beams, and X-rays.

For example, the ink jet printer 1 and the image recording method according to the present invention may be configured to irradiate the ink dots on the recording medium P with the electron beam. By applying the electron beam as the radiation, the ink dots can be quickly cured even when an inexpensive ink containing no polymerization initiator is applied. Therefore, a high-quality image can be formed on the recording medium P with high productivity and at low cost.

In addition, when an electron beam is applied as radiation, heat generated by generation and irradiation is less than in the case of ultraviolet rays, so that the cost required for cooling the ink jet printer 1 can be reduced. .

As the irradiation means 4 of the type that irradiates an electron beam as radiation, for example, "Development of UV / EB curing technology" (edited by Radtech Co., 1999 edition, page 95) and "Painting technology", October 2001 No. 90 page, known in the literature can be applied.

As an electron accelerator for electron beam irradiation applied to the irradiation means 4, a curtain beam type electron accelerator is preferable in that a large output can be realized at a relatively low cost.

Also, the acceleration voltage at the time of electron beam irradiation is 100
It is preferably ˜300 kV. The acceleration voltage is 1
When the voltage is below 00 kV, sufficient energy is not applied to the electron beam with which the ink dots are irradiated, and there is a problem that the ink dots cannot be sufficiently cured. On the other hand, when the accelerating voltage exceeds 300 kV, there arises a problem that costs for producing the irradiation means 4, electron beam irradiation, and maintenance are increased.

Further, it is preferable that the absorbed dose at which the ink dot absorbs the electron beam is 0.5 to 10 Mrad. When the absorbed dose is less than 0.5 Mrad, the ink dots are not sufficiently cured on the recording medium P, causing problems such as ink bleeding and low image strength. Further, if the absorbed dose exceeds 10 Mrad, the recording medium P may deteriorate.

As another type of radiation, infrared rays having a wavelength of 800 nm or more may be applied as energy rays. In this case, an energy ray curable ink having a property of being cured by a thermal reaction can be applied. As the energy ray curing ink, a peroxide compound such as benzoyl peroxide as a thermal reaction initiator, a diazo compound (thermal radical generator) such as AIBN, or a compound common to the photo-acid generator exemplified in the above-mentioned examples is used. Those applied can be applied. Also, as a starting aid,
Cyanine dye, squarylium dye, polymethine dye,
A substance having a strong tendency to radiate heat by absorbing near infrared rays, such as carbon black or titanium black, may be used.

Further, the ink jet printer 1 according to the present invention is not necessarily provided with the secondary irradiation means 8. When the ink dots are cured only by the irradiation of the irradiation means 4, 4, ..., The ink dots are cured with sufficient strength, and at the same time, the ink dots are adhered to the recording medium P with high adhesiveness, which is sufficient for an image. If high strength is imparted to the inkjet printer 1, the inkjet printer 1 may not have the secondary irradiation unit 8.

[0171]

According to the present invention, when the inkjet head is scanned, the inkjet head can be controlled with high responsiveness and high accuracy, so that an image can be formed on a large-sized recording medium with high image quality and high efficiency. can do. Also,
Printed matter with durability and weather resistance can be produced at low cost with high image quality and high efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of an inkjet printer 1 according to the present invention.

FIG. 2 is a perspective view of a main part showing an example of arrangement of components mounted on a carriage 3 applied to the present invention.

FIG. 3 is an inkjet head 2 applied to the present invention;
It is a principal part top view which shows the example of arrangement | positioning of 2, ....

[Explanation of symbols]

1 inkjet printer 2 inkjet head 3 carriage 4 irradiation means 6 Intermediate tank 8 Secondary irradiation means P recording medium

Claims (8)

[Claims] 1. An ink jet printer for forming an image by irradiating a recording medium on which ink dots are formed with an ink by ejecting an ink containing at least one kind of a radiation curable compound which is cured by irradiation of the radiation and landing the ink. A carriage that reciprocates on the recording medium; a carriage driving unit that reciprocates the carriage; an inkjet head that is installed on the carriage and that ejects ink toward the recording medium; And a radiation unit that radiates radiation toward a recording medium on which ink is ejected, and a total weight of the carriage and an object mounted on the carriage is 1 to 10 kg. In addition, the driving force for the carriage driving means to reciprocate the carriage is 40N. Inkjet printer, which is a bottom. 2. The ink jet printer according to claim 1, wherein ink colors ejected by the ink jet head include four colors of yellow, magenta, cyan and black. 3. The ink jet printer according to claim 2, wherein the color of the ink ejected by the ink jet head includes white. 4. The ink jet printer according to claim 1, wherein the generating unit is mounted on the carriage. 5. The ink jet printer according to claim 4, wherein the generating unit has a fluorescent lamp. 6. The ink jet printer according to claim 4, wherein the generating unit has an LD or an LED. 7. A temperature adjusting means for adjusting the temperature of the ink ejected from the ink jet head is provided, and the temperature adjusting means keeps the temperature of the ink within a range of 30 to 80 ° C. The inkjet printer according to any one of claims 1 to 6. 8. An image recording method using the ink jet printer according to any one of claims 1 to 7, wherein the surface layer on which the ink lands is in a substantially homogeneous state without voids for absorbing the ink. After ejecting ink to the recording medium,
An image recording method characterized by forming an image by irradiating radiation.