JP2021123679A - ink - Google Patents

Abstract

To provide ink capable of improving scratch resistance and hardness after fixing.SOLUTION: Ink 10 has first particles 11 having average particle diameters that are first particle diameters, second particles 12 having average particle diameters that are second particle diameters smaller than the first particle diameters, and an ink vehicle 13 to which the first particles 11 and the second particles 12 are added. The ink vehicle 13 contains a binder resin for binding between the plurality of first particles 11, between the plurality of second particles 12, and between the first particles 11 and the second particles 12 when the ink 10 is fixed thereto, and the first particles 11 are an inorganic pigment.SELECTED DRAWING: Figure 1

Description

The present invention relates to inks used for printing on a printing medium.

As conventional inks, particles of a first binder resin that is emulsion or suspended in a dispersion solvent and a colorant, and particles of a first binder resin that are emulsion or suspended in a dispersion solvent and have an average particle diameter of the first binder resin. It is known that the particles contain particles of the second binder resin smaller than the average particle size of (see, for example, Patent Document 1).

In the conventional ink, in the ink film formed on the printing medium by being fixed on the printing medium, the particles of the second binder resin having a small average particle size are the particles of the first binder resin having a large average particle size. Since the gaps generated between them are filled, the density of the ink film can be improved, and as a result, the strength of the ink film and the adhesion of the ink film to the printing medium can be improved.

Japanese Unexamined Patent Publication No. 2014-129497

However, in the conventional ink, since the main component of the ink film formed on the print medium by being fixed on the print medium is resin, the ink film comes into contact with minerals and metals harder than the resin. , There is a problem that the ink film is scratched. That is, the conventional ink has a problem that it does not have sufficient scratch resistance and hardness after being fixed on the printing medium.

Therefore, an object of the present invention is to provide an ink capable of improving scratch resistance and hardness after fixing.

The ink of the present invention comprises a first particle having an average particle size of a first particle size, a second particle having an average particle size smaller than the first particle size, and a second particle having an average particle size smaller than the first particle size. An ink comprising one particle and an ink vehicle to which the second particle is added and having a solvent, wherein the ink vehicle is a plurality of the first particles when the ink is fixed. The first particle and the second particle contain a binder resin that binds between the space, between the plurality of the second particles, and between the first particle and the second particle. It is characterized in that it has a higher hardness than the binder resin when cured, and is an extender pigment for hardening the ink film.

With this configuration, in the ink of the present invention, since the second particles fill the gaps formed between the first particles, the volume of the binder resin can be reduced, and as a result, the scratch resistance after fixing and the scratch resistance and the scratch resistance after fixing can be reduced. Hardness can be improved.

In the ink of the present invention, the first particles may have higher light transmittance than the binder resin.

With this configuration, the ink of the present invention can form an ink film having excellent light transmission.

In the ink of the present invention, the first particles may be inorganic pigments.

With this configuration, in the ink of the present invention, since the first particle whose average particle size is larger than the average particle size of the second particle is an inorganic pigment, the ink film formed by fixing is harder than the resin. Ink pigments with a high particle size are included, and as a result, scratch resistance and hardness after fixing can be improved.

In the ink of the present invention, the volume of the first particles in the ink after fixing may be 0.3 times or more the volume of the ink after fixing by drying the solvent.

With this configuration, in the ink of the present invention, the volume of the first particles in the ink film formed by fixing is 0.3 times or more the volume of the ink film, so that the hardness of the main component of the ink film is hard. Is higher than the resin, and as a result, the scratch resistance and hardness after fixing can be improved.

In the ink of the present invention, the volume of the first particles in the ink after fixing may be 0.7 times or less the volume of the ink after fixing by drying the solvent.

With this configuration, in the ink of the present invention, the volume of the first particles in the ink film formed by fixing is 0.7 times or less the volume of the ink film, so that the volume of the binder resin in the ink film is The ratio can be secured sufficiently high, and as a result, the adhesive strength of the ink film can be sufficiently obtained by the binder resin.

In the ink of the present invention, the second particles may have a size that fits into a gap formed by contacting at least three of the first particles.

With this configuration, in the ink of the present invention, instead of the binder resin entering the gap formed by contacting at least three first particles with each other, the gap is filled with the second particle having a hardness higher than that of the binder resin. Therefore, the volume of the binder resin can be reduced, and as a result, the scratch resistance and hardness after fixing can be improved.

In the ink of the present invention, the second particle size may be 0.155 times or less the first particle size.

With this configuration, the ink of the present invention has an average particle size of the second particles of 0.155 times or less the average particle size of the first particles, and thus is formed on the surface of the ink film formed by fixing. The second particle having a small average particle size fills the groove formed between the first particle having a large average particle size, and as a result, the surface of the ink film can be flattened. Therefore, the ink of the present invention can improve the glossiness of the ink film.

In the ink of the present invention, the first particle size may be 500 nm or less.

With this configuration, in the ink of the present invention, the average particle size of the first particles is 500 nm or less, and the average particle size of the second particles is 0.155 times or less the average particle size of the first particles. In the ink film formed by fixing, the second particles having an average particle diameter smaller than the wavelength of visible light fill the gaps formed between the first particles having a large average particle diameter, and as a result, the first particle. Diffuse reflection of light at the boundary of the particles can be reduced. Therefore, the ink of the present invention can improve the transparency of the ink film.

The ink of the present invention can improve scratch resistance and hardness after fixing.

It is a side view of the ink which concerns on one Embodiment of this invention before being fixed on the printing medium. It is a side view of the ink shown in FIG. 1 after being fixed on a printing medium. It is a figure which shows an example of the arrangement of the 1st particle and the 2nd particle of the ink shown in FIG. 1 after being fixed on the printing medium.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the composition of the ink according to the present embodiment will be described.

The ink according to this embodiment is ejected toward a printing medium by an inkjet printer (not shown) and then fixed on the printing medium. As the print medium, various media can be adopted. For example, the medium to be printed may be a medium such as a plastic film, paper, cloth, metal, or glass. Further, the print medium may be a medium having an image receiving layer. Further, the printing medium may be one in which the ink film is transferred to another printing medium by heat or pressure after the ink film is formed by the ink.

FIG. 1 is a side view of the ink 10 according to the present embodiment before being fixed on the printing medium.

Ink 10 shown in Figure 1, the first particles 11 having an average particle diameter of _{D 1,} the second particles 12 having an average particle diameter of _{D 1} is smaller than _{D 2,} the first particle 11 and the second It is provided with an ink vehicle 13 to which the particles 12 of the above are added.

The first particle 11 is, for example, an inorganic pigment such as an extender pigment. The first particle 11 has a higher hardness than the binder resin when cured, and is an extender pigment for hardening the ink film. The first particle 11 is not an organic pigment, but may be an organic particle other than the organic pigment. D ₁ is, for example, 30 nm to 500 nm, and 50 nm to 500 nm is optimal. The first particle 11 has a substantially spherical shape with a ratio of the major axis to the minor axis smaller than 2. The first particle 11 is made of an inorganic colorless transparent, white, or colored material having a Mohs hardness of 3 or more. The first particle 11 is, for example, silicon dioxide (SiO ₂ ), titanium dioxide, zinc phosphate, potassium phosphate, aluminum phosphate, ZnO, diamond, calcium carbonate, barium sulfate, talc, white carbon, gypsum, aluminum oxide. , Kaolin (clay), red pigment (bengara red, etc.), yellow pigment (cadmium, yellow lead, ocher, cadmium yellow, etc.), green pigment (emerald green, chromium oxide green, etc.), blue pigment (dark blue, cobalt blue, etc.) ), Purple pigments (manganese violet, mars violet, etc.), black pigments (carbon black, graphite, iron black, etc.), metallic (SUS powder, titanium alloy, chromium molybdenum steel powder, platinum powder, aluminum alloy powder, etc.), It is composed of ceramic pigments and the like.

The second particle 12 may be, for example, an inorganic pigment such as an extender pigment, or a resin particle such as a latex particle which is a resin such as an elastic rubber-like synthetic resin or a dispersed particle of various thermoplastic resins. good. The second particle 12 has a higher hardness than the binder resin when cured, and is an extender pigment for hardening the ink film. The second particle 12 is not an organic pigment, but may be an organic particle other than the organic pigment. D ₂ is, for example, 5 nm to 8 nm. The second particle 12 has a substantially spherical shape with a ratio of the major axis to the minor axis smaller than 2. When the second particle 12 is an inorganic pigment, it is made of a colorless transparent, white, or colored color material of an inorganic substance having a Mohs hardness of 3 or more. When the second particle 12 is an inorganic pigment, for example, silicon dioxide (SiO ₂ ), titanium dioxide, zinc phosphate, potassium phosphate, aluminum phosphate, ZnO, diamond, calcium carbonate, barium sulfate, talc, white Carbon, gypsum, aluminum oxide, kaolin (clay), etc., red pigments (bengara red, etc.), yellow pigments (cadmium, yellow lead, ocher, cadmium yellow, etc.), green pigments (emerald green, chromium oxide green, etc.), blue pigments (Navy blue, cobalt blue, etc.), purple pigments (manganese violet, mars violet, etc.), black pigments (carbon black, graphite, iron black, etc.), metallic (SUS powder, titanium alloy, chromium molybdenum steel powder, platinum powder, etc.) It is composed of aluminum alloy powder, etc.) and ceramic pigments.

The ink vehicle 13 contains a solvent as a main component, between a plurality of first particles 11 when the ink 10 is fixed on a printing medium, between a plurality of second particles 12, and a second. It contains a binder resin that binds between the first particle 11 and the second particle 12. The ink vehicle 13 may contain a dispersant composed of a monomer or an oligomer. The ink vehicle 13 may contain a surfactant. The ink vehicle 13 may contain various additives for purposes such as low temperature bleeding prevention, viscosity adjustment, and adhesive strength improvement.

The solvent of the ink vehicle 13 may be an evaporation-drying type solvent. The solvent may be, for example, water, a solvent, or a mixture of water and a solvent. When the ink 10 is fixed on the printing medium 90, the solvent moves the first particles 11 and the second particles 12 to high-density and stable positions by the time the ink 10 is fixed on the printing medium 90. It is preferable that the ink 10 is 10% by volume or more, preferably 30 to 85% by volume or more, based on the ink 10 in a state before being fixed on the printing medium 90 so as not to prevent the ink 10.

The main component of the binder resin of the ink vehicle 13 may be a thermoplastic resin or a UV curable resin such as a monomer or an oligomer that cures by causing a polymerization reaction when irradiated with ultraviolet rays. As the binder resin, for example, alkyd resin, fluororesin, polyester resin, urethane tree finger, acrylic tree finger, epoxy resin, silicone resin, melamine resin, phenol resin, vinyl chloride thermoplastic resin and the like are adopted alone or in combination. You may.

The ink 10 may further contain an inorganic pigment or an organic color material. The average particle size of this color material is, for example, 5 nm to 8 nm.

FIG. 2 is a side view of the ink 10 after being fixed on the printing medium 90.

The ink 10 shown in FIG. 1 is fixed on the printing medium 90 to be formed as an ink film 14 on the printing medium 90 as shown in FIG. When the solvent of the ink vehicle 13 (see FIG. 1) is an evaporation-drying type, the ink 10 is fixed to the printing medium 90 by evaporating-drying the solvent. Further, in the ink 10, when the ink vehicle 13 is a UV curable type, the ink vehicle 13 is cured by irradiation with ultraviolet rays and is fixed on the printing medium 90.

The main components of the ink film 14, which is the ink 10 after being fixed on the printing medium 90, are the first particles 11 and the binder resin.

Assuming that the volume of the ink film 14 is V ₀ and the volume of the first particle 11 is V ₁ , _{it is preferable that V 1} satisfies the following equation (1).
0.3V ₀ ≤ V ₁ ≤ 0.7V ₀ ... (1)

Hereinafter, "0.3" and "0.7" in the formula (1) will be described.

Assuming that the volume of a cube having a side length of 2R is V ₁₀ , V ₁₀ can be expressed using R as follows.
V ₁₀ = (2R) ³ = 8R ³

Assuming that the volume of a sphere having a radius R that falls into a cube having a side length of 2R is V ₁₁ , V ₁₁ can be expressed using R as follows.
V ₁₁ = (4/3) πR ³

Therefore, V ₁₁ can be expressed using V _{10 as follows.
V 11 = (4/3) π (} V 10 /8)≒0.523V 10

The values obtained by giving a margin of about ± 25% to this “0.523” are “0.3” and “0.7” in the formula (1). The reasons why the margin is necessary are, for example, when the first particle 11 is an inorganic pigment, the particles of the inorganic pigment have variations in particle size, and the shape of the particles of the inorganic pigment is not completely spherical. In addition, there are cases where the arrangement of the particles of the inorganic pigment deviates from the ideal densely packed or sparsely packed arrangement in the process of evaporation and drying of the solvent of the ink vehicle 13.

_{The reason why "0.3V 0} ", which is the lower limit _{of V 1} , is required in the equation (1) will be described. The strength of the ink film 14 is determined by the strength of the principal component in the ink film 14. Therefore, in order to increase the scratch resistance and hardness of the ink film 14, the volume of the first particles 11 in the ink film 14 is increased so that the main component of the ink film 14 is the first particles 11. It is preferably 0.3 times or more the volume of 14. That is, it is preferable _{that the ink film 14 is provided with a lower limit value "0.3V 0} " indicating that the volume ratio of the first particles 11 does not fall below 30%.

The reason why the upper limit value _{of V 1 “0.7V 0} ” is required in the equation (1) will be described. By fixing the ink 10 to the printing medium 90, the film property and flexibility of the ink coating 14 formed on the printing medium 90 are maintained, and the ink coating 14 is strongly adhered to the printing medium 90. In order to obtain the force, when it is considered that only the first particles 11 and the binder resin are present in the ink film 14, the volume ratio of the binder resin in the ink film 14 does not fall below 30%, that is, the ink film 14 The volume of the first particle 11 in the above is preferably 0.7 times or less the volume of the ink film 14. That is, it is preferable _{that the ink film 14 is provided with an upper limit value "0.7V 0} " indicating that the volume ratio of the first particles 11 does not exceed 70%.

_{It is preferable that D 1} which is the average particle size of the first particle 11 _{and D 2} which is the average particle size of the second particle 12 satisfy the relationship of the following formula (2).
D ₂ ≤ 0.155 _{D 1} ... (2)

FIG. 3 is a diagram showing an example of arrangement of the first particle 11 and the second particle 12 of the ink 10 after being fixed on the printing medium 90.

As shown in FIG. 3, when the arrangement of the first particles 11 is a close-packed arrangement and only one second particle 12 fits snugly in the gap of the first particles 11, the first The following relationship is established between _{R 1} which is the radius of the particle 11 _{and R 2} which is the radius of the second particle 12.
R ₁ = (R ₁ + R ₂ ) cos 30 °

Therefore, R ₂ can be expressed using R _{2 as follows.}
R ₂ = R ₁ / cos30 ° -R ₁ = (1 / cos30 ° -1) R ₁ ≒ 0.155R ₁

Equation (2) is derived using this "0.155".

Next, a printing method using the ink 10 will be described.

First, an ink-adhesion step of adhering the ink 10 to the printing medium 90 is executed by an inkjet printer (not shown). As the inkjet printing method in the ink adhesion process, various methods can be adopted. For example, the inkjet printing method in the ink adhesion step may be a multi-pass (serial) printing method or a line (one-pass) printing method.

When the solvent of the ink vehicle 13 is of the evaporation drying type, the solvent evaporation drying step of evaporating and drying the solvent is executed after the ink adhesion step. Examples of the method of evaporating and drying the solvent in the solvent evaporative drying step include a method of evaporating and drying the solvent by heating with a heater, a method of evaporating and drying the solvent by heating with infrared rays, and a method of heating the ink by irradiation with ultraviolet rays. There is a method such as a UV instant drying method in which the solvent is vaporized and dried.

As shown in FIG. 2, in the ink film 14 formed on the printing medium 90 by evaporating and drying the solvent in the solvent evaporation drying step, the second particles 12 fill the gaps between the first particles 11 to each other. It will be buried.

As described above, when the first particle 11 having an average particle diameter larger than the average particle diameter of the second particle 12 is an inorganic pigment, the ink 10 is fixed on the printing medium 90 to be printed. The ink film 14 formed on the medium 90 contains an inorganic pigment having a hardness higher than that of the resin, and as a result, scratch resistance and hardness after fixing to the medium 90 to be printed can be improved.

When the ink film 14 formed on the printing medium 90 by being fixed on the printing medium 90 contains the first particles 11 of the inorganic pigment having higher weather resistance and light resistance than the resin, the ink 10 is formed. It is possible to improve the weather resistance and light resistance after fixing to the print medium 90.

The printed matter using the ink 10 may be used indoors. However, since the ink 10 can improve scratch resistance, hardness, weather resistance, and light resistance after fixing to the print medium 90, the printed matter using the ink 10 may be used outdoors. ..

_{In the ink 10, the volume V 1} of the first particles 11 in the ink film 14 formed on the print medium 90 by being fixed on the print medium 90 is 0.3 times _{the volume V 0} of the ink film 14. As described above, the hardness of the main component of the ink film 14 is higher than that of the resin, and as a result, the scratch resistance and hardness after fixing to the printing medium 90 can be improved.

_{In the ink 10, the volume V 1} of the first particles 11 in the ink film 14 formed on the print medium 90 by being fixed on the print medium 90 is 0.7 times _{the volume V 0} of the ink film 14. Therefore, the volume ratio of the binder resin in the ink film 14 can be sufficiently high, and as a result, the binder resin sufficiently obtains an adhesive force for strongly adhering the ink film 14 to the printing medium 90. be able to.

_{Since the average particle diameter D 2} of the second particles 12 of the ink 10 is 0.155 times or less the average particle diameter D ₁ of the first particles 11, the ink 10 is fixed on the printing medium 90 to be printed on the printing medium. the surface of the ink coating 14 formed on the 90, the second particles 12 smaller the average particle diameter D ₂ is, fill the grooves generated between the first particle 11 is greater average particle diameter D _1, the As a result, the surface of the ink film 14 can be flattened. Therefore, the ink 10 can improve the glossiness of the ink film 14. It is more preferable that the average particle size D ₂ of the second particles 12 of the ink 10 is 0.1 times or less the average particle size D _{1 of the first particles 11.}

In the ink 10, the average particle diameter D ₁ of the first particles 11 is 500 nm or less, and the average particle diameter D ₂ of the second particles 12 is 0.155 times or less the average particle diameter D _{1 of the first particles 11.} Therefore, in the ink film 14 formed on the print medium 90 by being fixed on the print medium 90, _{the second particles 12 having an average particle diameter D 2} smaller than the visible light wavelength are the average particle diameter. It is possible to fill the gap generated between the large first particles 11 which are D ₁ , and as a result, the diffused reflection of light at the boundary of the first particles 11 can be reduced. Therefore, the ink 10 can improve the transparency of the ink film 14. Since the ink 10 can improve the transparency of the ink film 14, for example, by forming the ink film 14 on the glass as the printing medium 90, a stained glass-like clear color image can be produced on the glass. Can be formed.

In the ink 10, instead of the binder resin entering the gap formed by the first particles 11 coming into contact with each other in the ink film 14, the gap is filled with the second particle 12 having a hardness higher than that of the binder resin. Therefore, the volume of the binder resin in the ink film 14 can be reduced, and as a result, the scratch resistance and hardness of the ink film 14 can be improved.

When the binder resin of the ink vehicle 13 is heat-melted and fixed, the ink 10 reduces air bubbles in the binder resin after fixing because air is released from the binder resin by heat-melting and fixing the binder resin. be able to. When the ink 10 reduces air bubbles in the binder resin after fixing, the binding force of the binder resin can be improved. Further, when the ink 10 reduces the bubbles in the binder resin after fixing, the density of the first particles 11 and the second particles 12 in the ink film 14 can be improved, and as a result, the resistance of the ink film 14 can be improved. Abrasionability, hardness, glossiness and transparency can be improved.

When the first particles 11 have higher light transmission than the binder resin, the ink 10 can form an ink film 14 having excellent light transmission. Therefore, for example, the image quality can be improved by overcoating the printed image with an ink film 14 having excellent light transmission. It is preferable that the second particle 12 also has a higher light transmittance than the binder resin.

In the ink 10, when the first particles 11 are inorganic pigments, the main component of the ink film 14 formed on the printing medium 90 by being fixed on the printing medium 90 is an inorganic pigment that does not easily shrink during fixing. In addition, since the thickness of the ink film 14 can be made thinner than that of the conventional UV-curable ink, residual distortion is less likely to occur in the ink film 14 as compared with the conventional UV-curable ink, and as a result, with the passage of time. It is possible to reduce the possibility that the ink film 14 is cracked or the ink film 14 is peeled off from the printing medium 90 over time.

When the solvent of the ink 10 is an evaporation-drying type, the first particles 11 and the second particles 12 are concentrated at the time of evaporation-drying, so that the color density of the printed image can be increased.

By changing the composition of the ink vehicle 13, the ink 10 may be, for example, a solvent ink, a latex ink, an SUV (solvent UV) ink, a UV curable ink diluted with a solvent, a water-based UV curable ink, a UV instant drying ink, or the like. Can be changed to. The SUV ink is a UV curable ink containing a solvent as a solvent, and is cured by being irradiated with ultraviolet rays after the surface is flattened by evaporating and drying the solvent which is a solvent by heating with a print heater or the like. It is an instantly dried ink that can be fixed. The UV-curable ink diluted with a solvent is a water-based pigment ink which is an ink which is dispersed (emulsified) as liquid particles without being dissolved in a solvent such as water. The water-based UV-curable ink is a water-based curable ink that is a UV-curable ink dissolved in water.

As the color of the ink 10, various colors can be adopted. For example, the color of the ink 10 may be not only colorless and transparent, but also a color such as yellow, magenta, cyan, red, green, or blue, or a special color such as white, pearl, metallic, fluorescence, or phosphorescence.

The ink 10 can be used for printing a clear coat, for example, when it is colorless and transparent. That is, the ink 10 is printed on a printed image with inks such as solvent ink, latex ink, UV curable ink, SUV ink, water-based pigment ink, and UV instant drying ink to improve the scratch resistance of the printed image. It can be improved, the surface gloss can be given to the printed image, and a raised transparent pattern can be added on the printed image. However, the ink 10 may be used for printing other than clear coat printing.

10 Ink 11 First particle 12 Second particle 13 Ink vehicle

Claims (8)

The first particle whose average particle size is the first particle size,
A second particle having an average particle size smaller than the first particle size and a second particle size,
An ink comprising the first particle and an ink vehicle to which the second particle is added and having a solvent.
The ink vehicle is formed between a plurality of the first particles, between a plurality of the second particles, and between the first particles and the second particles when the ink is fixed. Contains a binder resin that binds the particles together
An ink characterized in that the first particles and the second particles have higher hardness than the binder resin when cured, and are extender pigments for hardening the ink film. The ink according to claim 1, wherein the first particles have higher light transmittance than the binder resin. The ink according to claim 1 or 2, wherein the first particle is an inorganic pigment. Any of claims 1 to 3, wherein the volume of the first particles in the ink after fixing is 0.3 times or more the volume of the ink after fixing by drying the solvent. Ink described in Crab. Any of claims 1 to 4, wherein the volume of the first particles in the ink after fixing is 0.7 times or less the volume of the ink after fixing by drying the solvent. Ink described in Crab. The ink according to any one of claims 1 to 5, wherein the second particles have a size that allows the first particles to enter a gap formed by contacting at least three of the first particles. .. The ink according to any one of claims 1 to 6, wherein the second particle size is 0.155 times or less the first particle size. The ink according to claim 7, wherein the first particle size is 500 nm or less.

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