JP2000178488A - Ink composition and printer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink composition sufficiently curing even in the case of using titanium oxide having a high reflectance of light as a pigment and providing excellent printing qualities by mixing a pigment, a photocuring resin and a photocuring initiator having specific absorption characteristics into the ink composition. SOLUTION: This composition comprises (A) a pigment (e.g. white pigment titanium oxide, etc.), (B) a photocuring resin (e.g. polyester acrylate) and (C) a photocuring initiator having absorption characteristics at a wavelength of light to make roughly 40-70% reflectance based on the component A. In the case of using titanium oxide as the component A, a component C having absorption characteristics at 400-450 nm wavelength to make roughly 40-70% reflectance to ultraviolet rays of titanium oxide is preferable as the component C. For example, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide is cited as the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink composition for printing on an object to be printed such as glass or plastics, and a printer using the ink composition.

[0002]

2. Description of the Related Art Printers, such as ink jet printers, are used to print (or draw) on industrial parts such as glass and plastics.

As an ink composition for printing used in this ink jet printer, for example, an ink composition for ink jet recording is used. Specifically, this ink composition is prepared by dissolving, for example, a white pigment of a water-soluble dye, such as titanium oxide, a photocurable resin, and a photocurable initiator (initiator) in water or a mixture of water and an organic solvent. It was made.

[0004] Such an ink composition is used as an ink composition for ink-jet recording of an ink-jet printer when printing on industrial parts such as glass and plastics, for example. It is sprayed on the surface of industrial parts such as glass or plastic as a printing object.

[0005] Light, for example, ultraviolet rays (UV) is irradiated to the ink composition in a state of being sprayed on the surface of industrial parts such as glass or plastic. When the ultraviolet ray is irradiated in this way, the photocurable resin and the photocuring initiator arranged so as to cover the particles of the titanium oxide as the pigment are irradiated with the ultraviolet ray.
The photocurable resin is cured by the action of the photocuring initiator or the like by the irradiation of the ultraviolet rays, and the entire ink composition is also fixed to the surface of glass or plastic as a printing object.
Thus, the ink jet printer prints on the surface of glass or plastic with the ink composition for ink jet recording. If a white pigment is contained in the ink composition for inkjet recording, white printing can be performed on the surface of glass or plastic.

[0006]

In the case where white printing is performed on the surface of glass or plastic with such an ink jet printer, the ink composition for ink jet recording contains titanium oxide as a white pigment. An ink composition will be used. However, when such an ink composition is sprayed on the surface of glass or plastic to be printed, a state as shown in FIG. 6 is obtained.

In FIG. 6, an ink composition 10 for ink jet recording is sprayed on the surface of a glass 13. Then, the ink composition for inkjet recording 1
0 itself has particles of titanium oxide 11 therein, and has a structure in which a photocurable resin 12 having a liquid photocuring initiator is disposed around the particles.

In this state, when, for example, ultraviolet rays are irradiated from the direction of the arrow in FIG. 6, the portions of the photocurable resins 12a, 12a to which the ultraviolet rays are directly irradiated are cured by the action of a photocuring initiator or the like. However, the portion 12 of the photocurable resin 12 sandwiched between the particles of the titanium oxide 11 and the glass 13
b, 12b, and 12b are titanium oxide particles 11
Because of this, the light is hardly irradiated with ultraviolet rays.

In particular, when the light reflectance of titanium oxide is high, the ultraviolet rays are reflected to a considerable extent by the titanium oxide particles 11, so that it is difficult for the ultraviolet rays to enter the ink composition 10 for ink jet recording. As a result, the ink composition 10 for inkjet recording does not sufficiently cure.

As described above, if the ink composition 10 for ink-jet recording is insufficiently cured, there is a problem that printing on the glass 13 becomes insufficient and causes printing defects.

It is an object of the present invention to provide an ink composition which can solve the above-mentioned problems and can obtain good print quality and the like, and a printer using the same.

[0012]

According to a first aspect of the present invention, there is provided an ink composition containing a pigment, a photo-curable resin, and a photo-curing initiator, wherein the photo-curing initiator is approximately 4 parts of the pigment.
At a wavelength of light having a reflectance of about 0% to 70%,
An ink composition characterized by having absorption characteristics.

According to the first aspect of the present invention, the photo-curing initiator of the ink composition has an absorption characteristic at a wavelength of light having a reflectance of about 40% to 70% with respect to the pigment. Because, when this ink composition is irradiated with light, without being reflected at a high rate by the pigment,
This light reaches the inside of the ink composition, and the photocurable resin can be uniformly cured.

According to a second aspect of the present invention, there is provided an ink composition according to the first aspect, wherein the pigment is titanium oxide or zinc oxide.

In the invention of claim 2, since the pigment of the ink composition is titanium oxide or zinc oxide, even when titanium oxide or zinc oxide is used as the pigment,
The light reaches the inside of the ink composition without being reflected by the titanium oxide or the zinc oxide at a high rate, and the photocurable resin can be uniformly cured.

According to a third aspect of the present invention, in the constitution of the first aspect, the photo-curing initiator is bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylbentylphosphine oxide, bis (2 4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η
2,4-cyclopentadien-1-yl) -bis [2,
6-difluoro-3 (1H-pyrrol-1-yl) phenyl] titanium.

In the invention according to claim 3, the photo-curing initiator is bis (2,6-dimethoxybenzoyl) -2,4,4.
4-trimethylbentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η2,4-cyclopentadien-1-yl) -bis [2,6-difluoro-3 (1
H-pyrrol-1-yl) phenyl] titanium, these photocuring initiators exhibit an absorption characteristic at a wavelength of light at which the pigment has a reflectance of about 40% to 70%. Have. Therefore, the light curing resin is sufficiently cured by light irradiation.

According to a fourth aspect of the present invention, there is provided a printing object mounting means for mounting a printing object, and an ink composition is supplied to the printing object mounted on the printing object mounting means to perform printing. A printing unit, a moving unit that relatively changes the positions of the printing unit and the printing target when the printing unit prints on the printing target, and an ultraviolet light for irradiating the printing target with ultraviolet light. Irradiating means, wherein the photo-curing initiator contained in the ink composition is approximately 40% of the pigment contained in the ink composition.
The printer is characterized in that it has an absorption characteristic at the wavelength of the ultraviolet light having a reflectance of about% to 70%.

According to the fourth aspect of the present invention, the photo-curing initiator contained in the ink composition used in the printer is about 40% to 70% of the pigment contained in the ink composition.
%, The ink composition has an absorption characteristic at the wavelength of the ultraviolet light having a reflectance of about%, so that when the ink composition is irradiated with the ultraviolet light, the ultraviolet light is not reflected by the pigment at a high rate, and the ultraviolet light is absorbed by the ink. Reaches the interior of the composition,
This photocurable resin can be cured uniformly.

According to a fifth aspect of the present invention, there is provided a printer according to the fourth aspect, wherein the pigment is titanium oxide or zinc oxide.

According to the fifth aspect of the present invention, since the pigment contained in the ink composition used in the printer is titanium oxide or zinc oxide, even if titanium oxide or zinc oxide is used as the pigment, The ultraviolet rays reach the inside of the ink composition without being reflected by the titanium oxide or the zinc oxide at a high rate, and the photocurable resin can be uniformly cured.

According to a sixth aspect of the present invention, in the constitution of the fourth aspect, the photocuring initiator is bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylbentylphosphine oxide, bis (2 4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η
2,4-cyclopentadien-1-yl) -bis [2,
6-difluoro-3 (1H-pyrrol-1-yl) phenyl] titanium.

In the invention of claim 6, the photo-curing initiator contained in the ink composition used in the printer is bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylbentylphosphine oxide, Screw (2,
4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η 2,4-cyclopentadien-1-yl) -bis [2,6-difluoro-3 (1H-
(Pyrrol-1-yl) phenyl] titanium, these photo-curing initiators are generally 4
It has an absorption characteristic at a wavelength of ultraviolet light having a reflectance of about 0% to 70%. Therefore, the photocurable resin is sufficiently cured by irradiation with ultraviolet rays.

[0024]

DETAILED DESCRIPTION OF THE INVENTION The ink composition according to the embodiment of the present invention, for example, an ink composition for ink-jet recording, is basically made up of a pigment, a photo-curable resin, a photo-curing initiator (initiator) and the like. The composition comprises:

The pigment, photo-curable resin and photo-curing initiator according to this embodiment are specifically as follows.

As the pigment, for example, titanium oxide or zinc oxide which is a white pigment is used. These titanium oxides and zinc oxides are inorganic pigments having high light-shielding properties. Further, as shown in FIG. 1, the reflectance of the titanium oxide with respect to light, for example, ultraviolet light, is approximately 40% to 70% when the wavelength of the ultraviolet light is approximately 400 nm to 450 nm.

The titanium oxide is incorporated, for example, in an amount of about 0.5 to 20% by weight in the ink composition.

As the photocurable resin, a resin generally used for a photocurable ink for inkjet recording can be used.

As described above, the reflectance of titanium oxide with respect to ultraviolet rays is approximately 40% to 70%,
As shown in FIG. 2, ultraviolet rays can be taken into the ink composition.

That is, in the figure, the ink composition 100 according to the present embodiment has a titanium oxide 110 having a high light-shielding property.
Is made of a photocurable resin 120 containing a photocuring initiator having particles inside. The ink composition 100 is placed on the surface of, for example, a glass 130 that is a printing target.

In this state, as shown in FIG. 2, when ultraviolet rays 140, which are light, are irradiated downward in the figure, the ultraviolet rays 140 impinge on the titanium oxide 110 particles. At this time, the reflectance of the titanium oxide 110 with respect to ultraviolet rays is approximately 40% to 70%, and therefore, as shown by an arrow 140a in FIG.
Without total reflection toward the outside of the ultraviolet ray 140,
The light is diffusely reflected as indicated by an arrow 140b in FIG. Due to the irregular reflection of the ultraviolet rays, the entirety of the photo-curable resin 120 including the photo-curing initiator constituting the ink composition 100 is uniformly irradiated with the ultraviolet rays 140.

The photocurable resin 120 contained in the ink composition 100 may be any resin that is generally used in photocurable inks for ink jet recording.

For example, a radical polymerization type is composed of an acrylic oligomer having an acroyl group at a terminal or a side chain of a molecule and a monomer, and the acrylic oligomer includes polyester acrylate, epoxy acrylate And polyol acrylate.

The monomers include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, methyl acrylate, ethyl acrylate and propyl acrylate.
, Isopropyl acrylate, butyl acrylate,
Monofunctional acrylates such as amyl acrylate, isobutyl acrylate, pentyl acrylate, t-butyl acrylate and isoamyl acrylate;
Tripropanol triacrylate, trimethylolpropane ethylene oxide adduct triacrylate, pentaerythritol tetraacrylate, ethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4
And photopolymerizable monomers such as polyfunctional acrylates such as butanediol acrylate and 1,6-hexanediol acrylate.

The photocurable resin 120 is mixed, for example, in an amount of about 2 to 90% by weight in the ink composition 100.

These photocurable resins 120 are cured by irradiation with ultraviolet rays 140 due to the action of a photocuring initiator described later. At this time, a pigment such as titanium oxide 110 contained in the photocurable resin 120 is fixed on the surface of the glass 130 to be printed.

On the other hand, the photo-curing initiator is a pigment used in the same composition, for example, ultraviolet rays of titanium oxide 110.
Those having absorption characteristics in the wavelength range of 400 to 450 nm, which is a wavelength at which the reflectance with respect to 40 is approximately 40% to 70%, are preferable.

That is, the wavelength of the ultraviolet light 140 is set to 400
This is because, even when the ink composition 100 is irradiated with the light having a wavelength of about 450 nm, the ink composition 100 has an absorption property and acts to accelerate the curing of the photocurable resin 120. Therefore, even when the ink composition 100 is irradiated with the ultraviolet light 140 using the wavelength of the ultraviolet light 140 having no absorption property of the photocuring initiator, the photocuring initiator does not sufficiently exert its action. The curing failure of the photocurable resin 120 is caused.

Examples of the photo-curing initiator considered to be suitable in this embodiment include the following.

That is, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylbentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η
2,4-cyclopentadien-1-yl) -bis [2,
6-difluoro-3 (1H-pyrrol-1-yl) phenyl] titanium and the like.

Pigments such as titanium oxide 110 as described above,
The ink composition 100 according to the present embodiment is prepared by suspending the photocurable resin 120, the photocuring initiator, and the like in an aqueous solvent such as water.

Further, the above-mentioned pigment is dispersed, and
0, the ink composition 100
Will be prepared. As this solvent, for example,
Examples thereof include aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, alcohols, ketones, esters, ethers and the like.

(Examples) One example of the ink composition 100 according to the present embodiment described above is shown below.

Photopolymerizable oligomer: epoxy acrylate 50 parts by weight Photopolymerizable monomer: methyl acrylate 10 parts by weight pentaerythritol tetraacrylate 10 parts by weight Photocuring initiator: bis (2,6-dimethoxy) Benzoyl) -2,4,4-trimethylbentylphosphine oxide 5 parts by weight Pigment: titanium oxide 10 parts by weight As described above, the ink composition 100 according to the present embodiment is placed on the surface of a glass 130 or the like, 400-4 from above
By irradiating with ultraviolet rays 140 having a wavelength of 50 nm, it is possible to uniformly cure the photo-curable resin 120 while exhibiting the properties of a pigment such as titanium oxide 110. It can be fixed in a state.

Next, an ink jet printer 200 which is a printer using the ink composition 100 according to the above embodiment will be described below.

FIG. 3 is a perspective view showing an inkjet printer 200 according to the embodiment of the present invention.

Referring to FIG.
Has a base 220, a moving means 250, a table 460 as a printing object mounting means, an ink jet 300 as a printing means, an ultraviolet irradiation generating means 400 and the like.

The base 200 supports the first driving means 240 and the second driving means 260 of the moving means 250.

The moving means 250 has the first driving means 240 and the second driving means 260, and the first driving means 240 is directly mounted on the base 220. The first driving means 240 moves the table 460 in the Y-axis (first direction).
Direction) for positioning.

The first drive means 240 has a table 460, a slider 420, and a guide 410. Rails 411 and 411 of the guide 410 guide the slider 420 in the Y-axis direction. On the slider 420, a table 460 is provided with a motor 440 having a θ axis.
Mounted through.

When the θ-axis motor 440 operates, the table 460 can be indexed with respect to the slider 420 in the θ direction (rotation direction about the vertical axis).

The table 460 includes the positioning member 46.
By using OB, the glass 130 to be printed can be accurately positioned. Also, the suction holding means 500
Through the hole 460A of the table 460 and the glass 13
0 is sucked and held on the table 460 by vacuum suction.

The slider 420 has a motor 44 on the θ axis.
By the operation of “0”, it is moved and positioned in the Y-axis direction. The θ-axis motor 440 is, for example, a linear motor.

The second driving means 260 of the moving means 250 comprises supports 260A, 260A and columns 260A.
B, a slider 600 and the like. Column 260B
Are horizontally supported by the supports 260A, 260A at an interval with respect to the base 220.

The slider 600 is connected to the motor 700
By operating, the rails 620A, 620A move along the X axis (second direction) for positioning. The motor 700 is, for example, a linear motor.
It is.

The slider 600 has, for example, motors 620, 640, 660, 680 for moving and positioning the ink jet head 300 in various directions. By operating the motor 620, the ink jet head 300 can be positioned by moving up and down along the Z-axis direction (vertical direction). The Z axis is a direction orthogonal to the X axis with respect to the Y axis.

When the motor 640 is operated, the ink jet head 300 swings along the β direction and can be positioned. Then, when the motor 660 is operated,
The ink jet head 300 swings in the γ direction and can be positioned. Further, when the motor 680 is operated, the ink jet head 300 swings in the α direction and can be positioned.

As described above, the ink jet head 300
Can be positioned by linearly moving the slider 600 in the Z-axis direction, and can be positioned by swinging along α, β, and γ. From this, the ink composition ejection surface 300p of the inkjet head 300 is
The position or posture can be controlled accurately in response to a change in the shape or height of the glass 130 of the bull 460.

The ink jet printer 20 as described above
The above-described ink composition 100 is accommodated in the inkjet head 300 of the inkjet head 300.
The ink composition 100 is ejected onto the surface of the glass 130 from the ink composition ejection surface 300P provided in the printer.

FIG. 4 shows an example of an object controlled by the control unit 800. The control unit 800 is the motor 4 described above.
40, 620, 640, 660, 680, 690, 70
0 various controls are performed.

The control section 800 supplies a piezo element drive signal S3 to the piezo element drive circuit 1000. The piezo element drive signal S3 drives the piezo element of the ink jet head 300 based on ink management information sent from the ink management controller 980 via the computer 340, and outputs an appropriate amount of ink. Is supplied from the ink jet head 300 to the surface of the glass 130.

The ink supply unit 9 filled with the ink composition 100 described above is provided in the ink jet head 300.
70, and the ink supply unit 970 is connected to the viscometer 9
The viscosity and the temperature are controlled by 50 and a thermometer 960.

The feedback signal S is output from the viscometer 950.
2 is sent to the ink management controller 980 and the thermometer 9
From 60, a feedback signal S1 of the state of the ink composition 100 is sent to the ink management controller 980.

Thus, the ink management controller 98
0 determines the status of the ink in the ink supply unit 970,
The piezo element drive signal S3 corresponding to the state is sent to the piezo element drive circuit 1000 via the computer.
The piezo element driving circuit 1000 operates the ink jet head 300 according to the state of the ink composition 100 to supply an appropriate amount of the ink composition 100 to the glass 13.
0 surface.

Incidentally, the ultraviolet ray generating means 400 shown in FIG.
Are the operation unit 520, the AC power supply 521, and the ultraviolet lamp 5.
22. The AC power supply 521 is electrically connected between the ultraviolet lamp 522 and the table 460. Thus, the ultraviolet lamp 522 can irradiate the surface of the printing object 48 placed on the table 460.

The ultraviolet lamp 522 is, for example, a rod-shaped member, and is preferably set to be larger than the width of the glass 130. The reason for this is that the ultraviolet irradiation can be performed without leakage over the entire width of the glass 130.

FIG. 5 shows the ultraviolet lamp 522 in FIG.
FIG. 2 is an enlarged view of a structure in the vicinity thereof.

In FIG. 5, an ultraviolet irradiation lamp 522 for irradiating ultraviolet light is arranged in the power supply 521 near the ink jet head 300. The power supply from the power supply 521 is performed on the ultraviolet irradiation lamp 522, and the operation unit 520 brings the ultraviolet irradiation lamp 522 closer to the vicinity of the glass 130, so that the printing ink at the printing expected position of the glass 130 is printed. Composition 100
Can be subjected to a curing treatment.

At this time, the ink composition 100 is irradiated with ultraviolet rays 140 from an ultraviolet irradiation lamp 522. The ultraviolet light 140 is applied to the titanium oxide 110
UV rays having a reflectance of about 40% to 70%, for example, about 400 nm to 450 nm with respect to pigments such as, for example, irregularly reflected in the ink composition 100 and uniformly curing the ink composition 100. Can be done.

As described above, according to the ink jet printer 200 according to the present embodiment, the ink composition 100 can be uniformly cured by the ultraviolet light 140 of the ultraviolet lamp 522, and therefore, has excellent fixability to the glass 130. Good printing quality can be obtained.

In this embodiment, the glass 130 is shown as an object to be printed. However, the present invention is not limited to this, and it is apparent that the present invention can be applied to other objects such as plastics.

[0072]

As described above, according to the first aspect of the present invention, the ink composition can be uniformly cured, and good print quality can be obtained.

Further, according to the second aspect of the present invention, an ink composition using titanium oxide or zinc oxide as a pigment can be cured uniformly, thereby obtaining good printing quality and the like.

According to the third aspect of the present invention, bis (2,6-dimethoxybenzoyl)-is used as a photo-curing initiator.
2,4,4-trimethylbentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η 2,4-cyclopentadien-1-yl) -bis [2,6-difluoro The ink composition using [-3 (1H-pyrrol-1-yl) phenyl] titanium can be sufficiently cured to obtain good print quality and the like.

According to the fourth aspect of the present invention, there is provided a printer which is capable of uniformly curing an ink composition with ultraviolet rays, so that the printer has excellent fixability to a printing target and can obtain high quality printing. Can be.

According to the fifth aspect of the present invention, the ink composition using titanium oxide or zinc oxide as a pigment is uniformly cured by ultraviolet rays, so that the fixability to a printing object is excellent and high quality printing is performed. Can be provided.

According to the invention of claim 6, bis (2,6-dimethoxybenzoyl)-is used as a photo-curing initiator.
2,4,4-trimethylbentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or bis (η 2,4-cyclopentadien-1-yl) -bis [2,6-difluoro Since the ink composition using [-3 (1H-pyrrol-1-yl) phenyl] titanium can be sufficiently cured with ultraviolet light, excellent fixability to a printing target and high quality printing can be obtained. A printer can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the reflectance of titanium oxide (pigment) with respect to ultraviolet rays and the like.

FIG. 2 is an explanatory diagram of an ink composition according to an embodiment of the present invention.

FIG. 3 is a perspective view showing an inkjet print according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a control unit and the like of the inkjet printer in FIG. 3;

FIG. 5 is an enlarged view showing an ultraviolet lamp and the like in FIG. 3;

FIG. 6 is an explanatory diagram of a conventional ink composition.

[Explanation of symbols]

 100 ink composition 110 titanium oxide 120 photocurable resin 130 glass 140 ultraviolet 200 inkjet printer 220 Base 240 First driving unit 250 Moving unit 260 Second driving unit 340 Computer 460 Table 300 ··············································································· Operation unit 521 AC power supply 522 Ultraviolet lamp 800 Control unit 950 Viscometer 970 Ink supply unit 980 ·ink Management controller 1000 .... piezoelectric element drive circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 FC01 2H086 BA55 BA59 BA60 4J039 AD21 AE05 AE06 AE07 AF03 BA13 BA31 BA35 BC05 BC16 BC56 BE01 BE27 CA07 EA05 EA06 EA42 EA43 FA02 FA04 GA24

Claims (6)

[Claims] 1. An ink composition comprising a pigment, a photocurable resin, and a photocuring initiator, wherein a wavelength of light at which the photocuring initiator has a reflectance of about 40% to 70% with respect to the pigment. 3. The ink composition according to claim 1, wherein the ink composition has absorption characteristics. 2. The ink composition according to claim 1, wherein the pigment is titanium oxide or zinc oxide. 3. The photo-curing initiator according to claim 1, wherein the photo-curing initiator is bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylbentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or Bis (η 2,4-cyclopentadien-1-yl)-
Bis [2,6-difluoro-3 (1H-pyrrol-1-
2. The ink composition according to claim 1, wherein the composition is (I) phenyl) titanium. 4. A printing object mounting means for mounting a printing object, a printing means mounted on the printing object mounting means and supplying an ink composition to the printing object to perform printing. When the printing unit prints on the printing target, the printing unit includes a moving unit that relatively changes the positions of the printing unit and the printing target, and an ultraviolet irradiation unit that irradiates the printing target with ultraviolet light. A printer, wherein the photo-curing initiator contained in the ink composition is about 40% to 70% with respect to the pigment contained in the ink composition.
A printer characterized in that the printer has absorption characteristics at the wavelength of the ultraviolet light having a degree of reflectance. 5. The printer according to claim 4, wherein the pigment is titanium oxide or zinc oxide. 6. The photo-curing initiator according to claim 1, wherein bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylbentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or Bis (η 2,4-cyclopentadien-1-yl)-
Bis [2,6-difluoro-3 (1H-pyrrol-1-
5. The printer according to claim 4, wherein [Il) phenyl] titanium.