JP7813620B2 - Decorative inks and their uses - Google Patents

Description

This disclosure relates to decorative inks and their uses.

In recent years, technologies have been developed for drawing images on inorganic substrates such as glass substrates, ceramic substrates (e.g., porcelain, ceramic tile), and metal substrates. Various colored inks can be used when drawing such images. For example, Patent Document 1 below discloses technology related to colored ink (red ink). It is stated that such colored ink contains an inorganic pigment as a coloring material.

Japanese Patent Application Laid-Open No. 2020-007384

The present inventors have discovered that glass frit containing gold particles (hereinafter simply referred to as "gold-containing glass") can be preferably used as a coloring material for magenta (reddish-purple) ink. Here, magenta ink containing gold-containing glass contains a relatively high amount of glass components. On the other hand, other color inks, particularly when used to print images on glass substrates, tend to contain a high amount of inorganic pigments (in other words, have a relatively low content of glass components) to ensure the hiding power of the coating film. Furthermore, the inventors' research has revealed that, for example, when printing an image on a glass substrate, using such magenta ink in combination with other color inks (i.e., multicolor printing) can result in differences in shrinkage rates during firing. This is undesirable because it can cause cracks to form in the image (hereinafter also referred to as "decorative portion") after firing.

This disclosure was made in light of these circumstances, and its main purpose is to provide technology that can form decorative features on a glass substrate that optimally combine crack suppression with excellent color development.

To achieve this objective, the present disclosure provides a decorative ink used to depict images on a glass substrate. This decorative ink includes a glass frit containing gold particles and an inorganic filler that does not constitute an amorphous matrix in the glass frit. Furthermore, when the total volume of inorganic solid components including the glass frit and the inorganic filler is taken as 100 volume %, the inorganic filler accounts for 5 volume % or more and less than 80 volume %. As will be described in more detail below, a decorative ink (magenta ink) with this configuration can be used to form a decorative portion on a glass substrate that effectively suppresses cracking and provides excellent color development.

In one preferred embodiment of the decorative ink disclosed herein, the inorganic filler is contained in an amount of 20% by volume or more and less than 60% by volume, assuming the total volume of the inorganic solid components to be 100% by volume. A decorative ink containing an inorganic filler within this range is preferred because it more suitably improves the adhesion of the decorative portion to the glass substrate.

In one embodiment of the decorative ink disclosed herein, the inorganic filler is at least one selected from the group consisting of silica, alumina, inorganic pigments, and high-temperature glass. With this configuration, a decorative portion can be formed on the glass substrate with cracks suitably suppressed.

In one embodiment of the decorative ink disclosed herein, the decorative ink is an inkjet ink, and when the total volume of the inkjet ink is taken as 100% by volume, the inorganic solid components are contained in an amount of 35% by volume or less. When the decorative ink is an inkjet ink, it is preferable that the inorganic solid components be contained in an amount of 35% by volume or less, from the perspective of ensuring an appropriate viscosity of the inkjet ink.

In one preferred embodiment, the decorative ink disclosed herein further contains a photocurable monomer component. Using a decorative ink that exhibits good curing properties when irradiated with ultraviolet light is preferable because it allows for clearer images to be drawn on water-repellent transfer paper coated with a water-soluble adhesive, for example.

In another aspect, the present disclosure provides a printed matter bearing an image depicting the decorative ink of any one of the decorative inks disclosed herein. Such a printed matter is preferable because it has an image (decorative portion) that favorably combines crack suppression with excellent color development.

In another aspect, the present disclosure provides transfer paper bearing an image formed from any of the decorative inks disclosed herein. Such transfer paper is preferable because it has an image (decorative portion) that favorably combines crack suppression with excellent color development.

In another aspect, the present disclosure provides a method for manufacturing a glass product. The method for manufacturing such a glass product includes a step of decorating the surface of a glass substrate using any of the decorative inks disclosed herein. This manufacturing method is preferable because it allows for the production of a glass product having an image (decorative portion) that optimally achieves both crack suppression and excellent color development.

In one embodiment of the glass product manufacturing method disclosed herein, the decorating step includes the following steps: depositing a cured product of any of the decorative inks disclosed herein on the surface of a glass substrate; and firing the glass substrate under conditions in which the maximum firing temperature is set within the range of 350°C to 1000°C.

FIG. 1 is a diagram schematically illustrating an agitator/pulverizer used in the production of inkjet ink. FIG. 1 is a diagram schematically illustrating an example of an inkjet device. FIG. 3 is a cross-sectional view schematically showing an inkjet head of the inkjet device in FIG. 2.

Preferred embodiments of the present disclosure are described below. Matters necessary for implementing the present disclosure, other than those specifically mentioned in this specification, can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. The following embodiments are not intended to limit the technology disclosed herein. In the drawings shown in this specification, components and parts that perform the same function are denoted by the same reference numerals. Dimensional relationships (length, width, thickness, etc.) in each figure do not reflect actual dimensional relationships. In this specification and claims, when a specified numerical range is expressed as A to B (A and B are arbitrary numbers), it means A or greater and B or less. Therefore, it includes cases where the range is greater than A and less than B. In this specification and claims, "decorative ink" typically refers to a composition in which inorganic solid components such as glass frit and inorganic filler are dispersed (or dissolved) in a medium, and is a concept that can encompass paste-like compositions and slurry-like compositions.

1. Decorative Ink The decorative ink (magenta ink) disclosed herein is a decorative ink used to draw images on glass substrates. This decorative ink contains glass frit containing gold particles (i.e., gold-containing glass) and an inorganic filler that does not constitute an amorphous matrix in the glass frit. When the total volume of the inorganic solid components including the glass frit and the inorganic filler is taken as 100 volume %, the inorganic filler accounts for 5 volume % or more and less than 80 volume %.

The reasons for achieving the effects of the technology disclosed herein by using the above configuration are believed to be, but are not limited to, the following: Specifically, by including a predetermined amount of inorganic filler in addition to the metal-containing glass in the decorative ink (magenta ink), the proportion of glass components in the decorative ink can be reduced. This allows the decorative ink composition to be closer to the composition of other colored inks with relatively low glass component contents. Furthermore, for example, when the decorative ink is used in combination with other colored inks (i.e., multicolor printing), the difference in shrinkage rate during firing can be suitably reduced, thereby suitably suppressing cracks in the image (i.e., the decorative portion) after firing. Furthermore, because the metal-containing glass has excellent magenta color development, it can impart excellent color development to the magenta portion of the decorative portion. Therefore, the decorative ink disclosed herein can form a decorative portion on a glass substrate that suitably achieves both crack suppression and excellent color development. Please note that the above explanation is the inventor's speculation based on experimental results, and the technology disclosed herein should not be interpreted as being limited to the above mechanism. Each component will be explained below.

(1) Inorganic Solid Components The inorganic solid components are components that constitute the base material of the image after firing, and include glass frit and inorganic filler.

(a) Glass Frit The glass frit disclosed herein contains gold particles. Specifically, gold particles are dispersed in an amorphous matrix of the glass frit (hereinafter simply referred to as "glass matrix"). The glass component and the gold particles are typically sintered together to form a sintered body.

The glass matrix is a component that typically functions as an inorganic binder and serves to enhance the bonding between the gold particles and the glass substrate. The linear thermal expansion coefficient of the glass constituting the glass matrix (specifically, the average linear thermal expansion coefficient measured using a thermomechanical analyzer in a temperature range from 25°C to 500°C; the same applies hereinafter) is not particularly limited as long as the effects of the technology disclosed herein are exhibited, but may be the same as that of the glass substrate. In one example, the thermal expansion coefficient of the glass may be approximately ±2×10 ⁻⁶ K ⁻¹ of the thermal expansion coefficient of the glass substrate. For example, it may be approximately 4.0×10 ⁻⁶ K ⁻¹ to 10.0×10 ⁻⁶ K ⁻¹ . This reduces the difference in shrinkage rate between the glass substrate and the glass frit during firing, making cracks less likely to occur in the decorative portion.

The glass transition point (Tg value based on differential scanning calorimetry; the same applies hereinafter) of the glass that constitutes the glass matrix is not particularly limited, as long as the effects of the technology disclosed herein are achieved. For example, in relation to the sintering temperature described below, a glass transition point of approximately 400 to 1500°C is preferable. In particular, for underglaze and sink-in applications, a glass transition point of approximately 900 to 1300°C is preferable, and for overglaze applications, a glass transition point of approximately 500 to 900°C is preferable.

Examples of glasses that can have such properties (thermal expansion coefficient and glass transition point) include SiO ₂ -RO (RO represents an oxide of a Group 2 element, such as MgO, CaO, SrO, or BaO; the same applies hereinafter)-based glasses, SiO ₂ -RO-R ₂ O (R ₂ O represents an oxide of an alkali metal element, such as Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, or Fr ₂ O; particularly Li ₂ O; the same applies hereinafter)-based glasses, SiO ₂ -RO-ZnO-based glasses, SiO ₂ -RO-ZrO _2- based glasses, SiO ₂ -RO-Al ₂ O _3- based glasses, SiO ₂ -RO-Bi ₂ O ₃ -based glasses, SiO ₂ -R ₂ O-based glasses, and SiO ₂ Examples of such glasses include SiO-ZnO _- based glasses, SiO-ZrO _- based glasses, SiO _{- ZnO -} ZrO- _{TiO -} based glasses, _{SiO -} Al-based glasses, RO-R-based glasses, and RO-ZnO-based glasses. These glasses may contain one or more components in addition to the main components indicated by the names above. Furthermore, the glass may be a typical amorphous glass or a crystallized glass containing crystals.

In a preferred embodiment, when the entire glass is taken as 100 mol %, SiO ₂ accounts for more than half (50 mol %) in terms of the molar ratio of oxide. Generally, the higher the SiO ₂ ratio, the higher the glass transition temperature tends to be. Therefore, for example, when the sintering temperature is set low, it is advisable to keep the SiO ₂ ratio to approximately 80 mol % or less. Furthermore, from the viewpoint of lowering the glass transition temperature and improving the meltability of the glass, it is effective to add components such as RO, R ₂ O, and B ₂ O _3. On the other hand, the greater the content of these components, the higher the thermal expansion coefficient of the glass tends to be. In a preferred embodiment, when the entire glass is taken as 100 mol %, RO accounts for 15 to 35 mol % in terms of the molar ratio of oxide. In a preferred embodiment, when the entire glass is taken as 100 mol %, R ₂ O accounts for 0 to 5 mol % in terms of the molar ratio of oxide.

In a preferred embodiment, the glass is composed of a multi-component system of four or more components (e.g., five or more components). This improves physical stability. For example, when used to decorate tableware, the decorative portion must also have sufficient acid resistance against acidic foods and sufficient alkali resistance against alkaline detergents. In such cases, it is effective to add components such as _Al2O3 , ZnO, and CaO, for example, in a proportion of 100% by mole _or more. This improves the chemical durability of the decorative portion. Preferably, it also improves wear resistance.

The proportion of glass matrix in the decorative ink is not particularly limited, as long as the effects of the technology disclosed herein are achieved. From the perspective of improving bonding with the glass substrate, it is preferable that the proportion be approximately 1% by volume or more, typically 5% by volume or more, for example 10% by volume or more, when the decorative ink as a whole is taken as 100% by volume. Furthermore, from the perspective of more effectively suppressing cracks in the decorative portion, it is preferable that the proportion of glass matrix be approximately 30% by volume or less, typically 20% by volume or less, for example 14% by volume or less, when the decorative ink as a whole is taken as 100% by volume.

In a preferred embodiment, the glass matrix is substantially free of components that may be harmful to the human body or the environment, such as arsenic, lead, and cadmium. In particular, for applications such as decorative tableware, it is preferable not to actively add these components (although their inclusion as unavoidable impurities may be tolerated).

As described above, the glass frit disclosed herein contains gold particles. Metal particles have unique optical characteristics (e.g., strong light absorption bands) in the ultraviolet to visible range due to surface plasmon resonance (SPR). Gold (Au) particles, in particular, absorb light with a wavelength around 530 nm (green to light blue light) and exhibit a bluish-red (reddish-purple) color known as "magenta." Therefore, glass frit containing gold particles can produce a vivid magenta color.

In this specification and claims, "gold particles" can refer to particles composed primarily of gold (Au). "Composed primarily of gold" means that of the components constituting the particles, gold (Au) is the component that is contained in the greatest amount by weight. When the total weight of the particles is taken as 100% by weight, gold particles can be particles that preferably contain 90% by weight or more, 95% by weight or more, or 99% by weight or more of gold (Au). Components other than gold include various metallic elements and non-metallic elements that are unavoidable impurities.

The shape of the gold particles is not particularly limited and may be spherical or aspherical. Furthermore, the average particle size (D50 particle size) of the gold particles is not particularly limited as long as the effects of the technology disclosed herein are achieved. However, taking into account the above-mentioned surface plasmon resonance, a particle size of nanometer size is preferable. The effect of surface plasmon resonance of gold particles can vary depending on the particle size. Therefore, by appropriately adjusting the particle size, the effect of surface plasmon resonance can be more effectively achieved. In a preferred embodiment, the average particle size of the gold particles is approximately 1 nm or more, 5 nm or more, typically 10 nm or more, for example, 15 nm or more. In a preferred embodiment, the average particle size of the gold particles is, for example, 100 nm or less, 80 nm or less, typically 50 nm or less, for example, 30 nm or less. By setting the average particle size within the above range, the absorbance of the gold particles at a specific wavelength is increased, allowing for good magenta color development with a small amount of addition. Furthermore, detailed decoration with minimal color unevenness can be achieved.

The shape of the glass frit is not particularly limited and may be spherical or aspherical. The average particle diameter (D50 particle diameter) of the glass frit is not particularly limited as long as the effects of the technology disclosed herein are achieved, but can be approximately 0.1 μm to 10 μm (e.g., approximately 0.5 μm to 5 μm). When the decorative ink is used as an inkjet ink, the particle diameter of the glass frit can affect the viscosity of the ink, so it is preferable to adjust it appropriately taking into account the ejection properties from the inkjet device. Specifically, if the ink contains glass frit with a large particle diameter, the ejection orifices may be easily clogged, which may reduce the ejection properties. Therefore, it is preferable to control the particle diameter of the glass frit so that the average particle diameter is, for example, 1 μm or less (preferably 0.85 μm or less).

In this specification, "average particle size" (D50 particle size) can refer to the particle size corresponding to the cumulative 50% smallest particle size in a volume-based particle size distribution based on laser diffraction/scattering. Such measurements can be performed using, for example, a commercially available device, the Microtrac MT3000II manufactured by Microtrac Bell Corporation.

The proportion of gold particles in the decorative ink is not particularly limited, as long as the effects of the technology disclosed herein are achieved. From the perspective of improving magenta color development and cost considerations, when the decorative ink as a whole is taken as 100% by volume, it is desirable that the proportion be approximately 0.01% by volume or more, for example 0.05% by volume or more, 0.1% by volume or more, and approximately 0.5% by volume or less, typically 0.3% by volume or less, for example 0.2% by volume or less.

In a preferred embodiment, the proportion of gold particles is approximately 0.1 parts by volume or more, preferably 0.5 parts by volume or more, for example, 1 part by volume or more, relative to 100 parts by volume of the glass matrix. By setting the proportion of gold particles at a predetermined value or more, the a ^* value in the red direction in the L ^* a ^* b ^* color system can be improved, thereby enhancing red color development. Furthermore, the lightness L ^* value can be improved, resulting in a brighter, more vivid color. In a preferred embodiment, the proportion of gold particles is approximately 5 parts by volume or less, typically 3 parts by volume or less, and preferably 2 parts by volume or less, relative to 100 parts by volume of the glass matrix. By setting the proportion of gold particles at a predetermined value or less, the lightness L ^* value can be improved in the L ^* a ^* b ^* color system, thereby enhancing a brighter, more vivid color. Furthermore, costs can be kept low.

(b) Inorganic Filler As described above, the decorative ink (magenta ink) disclosed herein contains an inorganic filler in addition to the metal-containing glass. Such inorganic filler includes an inorganic filler that does not constitute a glass matrix (in other words, has a higher melting point than the glass matrix). That is, the decorative ink disclosed herein may contain only an inorganic filler that does not constitute a glass matrix, or it may contain an inorganic filler that does not constitute a glass matrix and an inorganic filler integrated with the above-mentioned glass frit.

Examples of inorganic fillers include ceramic particles such as silica, alumina, zirconia, and titania, inorganic pigments, and high-temperature glass. Among these, it is preferable to use at least one selected from the group consisting of silica, alumina, inorganic pigments, and high-temperature glass. Here, the inorganic pigment can reduce the difference in shrinkage rate during firing as described above and improve the color development of the decorative portion. Such inorganic pigments contain, for example, metal compounds (typically metal oxides) and have excellent heat resistance. Therefore, discoloration (or fading) of the inorganic pigment can be suppressed when the glass substrate to which the ink is applied is fired at 350°C or higher (e.g., 350°C to 1000°C). Specific examples of such inorganic pigments include composite metal compounds containing at least one metal element selected from the group consisting of Cu, Mn, Zr, Ti, Pr, Cr, Sb, Ni, Co, Al, and Cd. Examples of such inorganic pigments include tin-sphene-based, zinc ferrite-based, and zircon-based pigments. The a ^* value of such inorganic pigments in the L ^* a ^* b ^* color system based on JIS Z8729 (2004) is not particularly limited, but can be approximately 5 to 60. Furthermore, high-temperature glass can refer to glass having a melting point of 1000°C or higher. The composition of such high-temperature glass is not particularly limited, and examples include silicate glass used in glazes. The inorganic filler may be used alone or in combination of two or more types. Commercially available inorganic fillers can be used without particular limitations.

The shape of the inorganic filler is not particularly limited and may be spherical or non-spherical. From the perspective of ease of handling, it is typically preferable that the inorganic filler be spherical. Furthermore, the average particle size (D50 particle size) of the inorganic filler is not particularly limited as long as the effects of the technology disclosed herein are achieved. The D50 particle size of the inorganic filler can typically be approximately 0.001 μm to 4 μm (e.g., approximately 0.005 μm to 2 μm). Furthermore, the inorganic filler may typically be particulate. When using the decorative ink as an inkjet ink, for example, it is preferable to appropriately adjust the particle size of such particulate inorganic filler, taking into account the diameter of the nozzle of the inkjet device described below. If the particle size of the inorganic filler is too large, the inorganic filler may clog the nozzle, reducing the ink's ejection performance. Because the diameter of the ejection ports of typical inkjet devices is approximately 15 μm to 60 μm (e.g., 25 μm), it is preferable to microparticulate the inorganic filler so that the D100 particle size (maximum particle size), which corresponds to a cumulative 100% number of particles from the smallest particle size side, is 5 μm or less (preferably 1 μm or less). The D100 particle size can be a value measured based on particle size distribution measurement using dynamic light scattering.

The proportion of inorganic filler in the decorative ink is not particularly limited, but it is preferable that it be approximately 0.5% by volume or more, 1% by volume or more, for example 3% by volume or more, when the decorative ink as a whole is taken as 100% by volume. Furthermore, from the perspective of enhancing gloss and shine, it is preferable that the proportion of inorganic filler be approximately 20% by volume or less, for example 15% by volume or less, 12% by volume or less, when the decorative ink as a whole is taken as 100% by volume.

In a preferred embodiment, the inorganic filler is substantially free of components that may be harmful to the human body or the environment, such as arsenic, lead, and cadmium (though their inclusion as unavoidable impurities may be tolerated). It is particularly preferable for the filler to be free of these components when used to decorate tableware.

(2) Other Components The decorative ink disclosed herein may contain other components as appropriate, as long as the effects of the technology disclosed herein are achieved. Examples of other components include dispersants, monomer components, photopolymerization initiators, polymerization inhibitors, organic binders, reaction accelerators, surfactants, thickeners, pH adjusters, preservatives, antifoaming agents, plasticizers, stabilizers, and oxidation inhibitors. For example, the monomer components and dispersants can serve as liquid components that disperse (or dissolve) inorganic solid components such as glass frit and inorganic fillers.

(a) Monomer Component The decorative ink disclosed herein may contain a monomer component. Examples of such monomer components include thermosetting monomers and photocurable monomers. As long as the effects of the present disclosure are not significantly impaired, any monomer that can be used in general decorative inks can be used without particular limitation. Furthermore, monomer components that are liquid at room temperature (typically, about 25°C) are preferably used. The weight-average molecular weight of the monomer component is not particularly limited as long as the effects of the technology disclosed herein are exhibited, but can be approximately 500 to 5,000 (e.g., about 1,000 to 3,000). In this specification, "weight-average molecular weight" refers to the weight-average molecular weight measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve. The monomer component may be used alone or in combination of two or more types. Commercially available products can be used as the monomer component without particular limitation.

Here, it is preferable to include a photocurable monomer as a monomer component, as this allows for clearer images to be depicted on, for example, water-repellent transfer paper coated with a water-soluble adhesive. Here, "photocurable monomer component" in this specification refers to a material containing at least one resin monomer that polymerizes (or crosslinks) and hardens when irradiated with light (e.g., ultraviolet light).

Suitable examples of photocurable monomer components include (a1) monofunctional acrylate monomers, (a2) monofunctional N-vinyl compound monomers, and (a3) polyfunctional vinyl ether monomers. Photocurable monomer components containing at least one of the monomers (a1) to (a3) above have excellent fixability (photocurability) to the printing target, making them suitable for use on a variety of printing targets. Furthermore, photocurable monomer components containing at least one of the monomers (a1) to (a3) above also have the advantage of excellent flexibility after photocuring, making them particularly suitable for use on printing targets that need to be curved during use (e.g., transfer paper).

(a1) Monofunctional Acrylate Monomer The monofunctional acrylate monomer is a compound containing one acryloyl group ( _CH2 =CHCOO-) or one methacryloyl group ( _CH2 = _CCH3COO- ) in the molecule. Such monofunctional acrylate monomers have excellent dispersibility of inorganic solid components and can suppress an increase in ink viscosity, thereby contributing to the preparation of ink with favorable jetting properties. Furthermore, among photocurable monomers, monofunctional acrylate monomers also have the property of having relatively low rigidity after photocuring (high flexibility). From the viewpoint of further improving jetting properties and flexibility, the volume ratio of the monofunctional acrylate monomer when the total volume of the photocurable monomer components is taken as 100 volume% is preferably 40 volume% or more, more preferably 45 volume% or more, even more preferably 50 volume% or more, and particularly preferably 55 volume% or more, for example 60 volume% or more. On the other hand, since monofunctional acrylate monomers tend to have relatively low photocurability, from the viewpoint of ensuring the content of monomers with excellent photocurability, which will be described later, the content is preferably 96% by volume or less, more preferably 90% by volume or less, even more preferably 85% by volume or less, and particularly preferably 80% by volume or less, for example, 78% by volume or less.

Specific examples of monofunctional acrylate monomers include benzyl acrylate, cyclic trimethylolpropane formal acrylate, phenoxyethyl acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, methoxyethyl acrylate, cyclohexyl acrylate, ethyl carbitol acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, methyl (meth)acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, n-stearyl acrylate, butoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate. acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, isoamyl acrylate, lauryl (meth)acrylate, octyl acrylate, isooctyl (meth)acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, tridecyl (meth)acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl-diglycol acrylate, 4-hydroxybutyl acrylate, methoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, ethoxydiethylene glycol acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, 2-ethylhexyl carbitol acrylate, phenoxyethoxyethyl acrylate, etc. The above-mentioned (meth)acrylate compounds can be used alone or in combination of two or more. Among these, benzyl acrylate, phenoxyethyl acrylate, and cyclic trimethylolpropane formal acrylate have particularly excellent flexibility after photocuring, making them ideal for preventing cracks from occurring when the transfer paper is bent.

(a2) Monofunctional N-vinyl Compound Monomer A monofunctional N-vinyl compound monomer is a compound in which one vinyl group is bonded to the nitrogen (N) atom of a nitrogen-containing compound. Here, "vinyl group" refers to CH ₂ ═CR ¹ — (where R ¹ is a hydrogen atom or an organic group). Such monofunctional N-vinyl compound monomers have high extensibility, thereby preventing cracks from occurring in the drawn image. Furthermore, monofunctional N-vinyl compound monomers have excellent photocurability and function to improve fixation to the surface of the printed object. From the perspective of further improving fixation, the volume ratio of the monofunctional N-vinyl compound monomer, when the total volume of the photocurable monomer components is taken as 100% by volume, is preferably 2% by volume or more, more preferably 3% by volume or more, even more preferably 4% by volume or more, and particularly preferably 5% by volume or more. On the other hand, the addition of a monofunctional N-vinyl compound monomer tends to reduce the flexibility of the ink after curing. For this reason, it is preferable to reduce the content of the monofunctional N-vinyl compound monomer when printing on transfer paper, etc. From this viewpoint, the volume ratio of the monofunctional N-vinyl compound monomer is preferably 20% by volume or less, more preferably 17% by volume or less, even more preferably 15% by volume or less, particularly preferably 13% by volume or less, for example, 10% by volume or less.

The N-vinyl compound monomer is represented by, for example, the following general formula (I):
CH ₂ =CR ¹ -NR ² R ³ (I)
In the general formula (I), R ¹ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a benzyl group, or a halogen group. Among these, a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is preferred, with a hydrogen atom being particularly preferred. ^{R 2} and R ³ may be selected from a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group, an alkynyl group, an aralkyl group, an alkoxy group, an alkoxyalkyl group, an alkylol group, an acetyl group (CH ₃ CO—), and an aromatic group. R ² and R ³ may be the same or different. The total number of carbon atoms in the alkyl group, alkenyl group, alkynyl group, aralkyl group, alkoxy group, alkoxyalkyl group, alkylol group, and acetyl group which may have a substituent may be 1 to 20. The alkyl group, alkenyl group, alkynyl group, aralkyl group, alkoxy group, alkoxyalkyl group, alkylol group, and acetyl group which may have a substituent may be linear or cyclic, with linear being preferred. The aromatic group is an aryl group which may have a substituent. The total number of carbon atoms in the aromatic group is 6 to 36. Substituents that the alkyl group, alkenyl group, alkynyl group, aralkyl group, alkoxy group, alkoxyalkyl group, alkylol group, acetyl group, and aromatic group may have include, for example, a hydroxyl group and a halogen atom such as a fluorine atom or a chlorine atom. In the general formula (I), ^R2 and ^R3 may be bonded to each other to form a cyclic structure.

Suitable examples of the monofunctional N-vinyl compound monomer include N-vinyl-2-caprolactam, N-vinyl-2-pyrrolidone, N-vinyl-3-morpholinone, N-vinylpiperidine, N-vinylpyrrolidine, N-vinylaziridine, N-vinylazetidine, N-vinylimidazole, N-vinylmorpholine, N-vinylpyrazole, N-vinylvalerolactam, N-vinylcarbazole, N-vinylphthalimide, N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylformamide, and N-methyl-N-vinylacetamide. Among these, N-vinyl-2-caprolactam has high photocurability among monofunctional N-vinyl compound monomers, and can further improve fixation to the surface of the printed object.

(a3) Polyfunctional Vinyl Ether Monomer A polyfunctional vinyl ether monomer is a compound containing at least two vinyl ether groups in the molecule. The term "vinyl ether group" as used herein refers to -O-CH=CHR ¹ (where R ¹ is a hydrogen atom or an organic group). Such polyfunctional vinyl ether monomers containing at least two vinyl ether groups have a fast photocuring rate upon UV irradiation and excellent photocurability, thereby improving fixation to the surface of a printed object. Furthermore, among monomers with excellent photocurability, polyfunctional vinyl ether monomers have the properties of low rigidity after curing and excellent flexibility. From the perspective of achieving both fixation to a printed object and flexibility after photocuring, the volume ratio of the polyfunctional vinyl ether monomer, when the total volume of the photocurable monomer components is taken as 100% by volume, is preferably 2% by volume or more, more preferably 5% by volume or more, even more preferably 7% by volume or more, and particularly preferably 10% by volume or more, for example, 15% by volume or more. On the other hand, if too much polyfunctional vinyl ether monomer is added, the amount of monofunctional acrylate monomer added tends to be reduced, resulting in reduced flexibility after photocuring. Therefore, the upper limit of the volume ratio of the polyfunctional vinyl ether monomer is preferably 40% by volume or less, more preferably 35% by volume or less, even more preferably 30% by volume or less, and particularly preferably 25% by volume or less, for example, 20% by volume or less.

Suitable examples of the above-mentioned polyfunctional vinyl ether monomers include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, tripropylene glycol divinyl ether, polypropylene glycol divinyl ether, butanediol divinyl ether, neopentyl glycol divinyl ether, hexanediol divinyl ether, nonanediol divinyl ether, and 1,4-cyclohexanedimethanol divinyl ether. Among these, diethylene glycol divinyl ether, triethylene glycol divinyl ether, and 1,4-cyclohexanedimethanol divinyl ether are particularly preferred because they achieve both high levels of adhesion to the substrate surface and flexibility after photocuring.

(a4) Other Photocurable Monomers As mentioned above, the photocurable monomer component in the decorative ink disclosed herein can be any photocurable monomer component that can be used in general decorative inks, and is not limited to the monomers (a1) to (a3) described above.
An example of a monomer (other monomer) other than the above (a1) to (a3) is a polyfunctional acrylate monomer containing at least two acryloyl groups or methacryloyl groups in the molecule. Suitable examples of this polyfunctional acrylate monomer include 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, tricyclodecane dimethanol diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, triethylene glycol di(meth)acrylate, tetramethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,3-but ...hydroxypivalic acid neopentyl glycol diacrylate, hydroxy acrylate, neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, cyclohexane-1,4-dimethanol di(meth)acrylate, cyclohexane-1,3-dimethanol di(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, dipentaerythritol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, bisphenol Trimethylol AEO 3.8 mol adduct diacrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol propionate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, sorbitol tri(meth)acrylate, ditrimethylol Examples of the acrylate include methylpropane tetra(meth)acrylate, pentaerythritol polyethoxy tetra(meth)acrylate, pentaerythritol polyproxy tetra(meth)acrylate, sorbitol tetra(meth)acrylate, dipentaerythritol propionate tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, sorbitol penta(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and sorbitol hexa(meth)acrylate.
Furthermore, examples of other monomers other than the polyfunctional acrylate monomers include butyl vinyl ether, butyl propenyl ether, butyl butenyl ether, hexyl vinyl ether, ethylhexyl vinyl ether, phenyl vinyl ether, benzyl vinyl ether, phenyl allyl ether, vinyl acetate, acrylamide, methacrylamide, trimethylolpropane tri((meth)acryloyloxypropyl)ether, tri((meth)acryloyloxyethyl)isocyanurate, and bisphenol A diglycidyl ether acrylic acid adduct.

In order to achieve both fixation to the printing surface and flexibility after photocuring, the volume ratio of the other photocurable monomers, when the total volume of the photocurable monomer components is taken as 100% by volume, is preferably 2% by volume or more, more preferably 5% by volume or more, even more preferably 7% by volume or more, and particularly preferably 10% by volume or more, for example 15% by volume or more. The upper limit of the volume ratio of the other photocurable monomers is preferably 40% by volume or less, more preferably 35% by volume or less, even more preferably 30% by volume or less, and particularly preferably 25% by volume or less, for example 20% by volume or less.

When using a photocurable monomer component containing the monomers (a1) to (a4) described above, the volume ratio of the photocurable monomer component, when the total volume of the decorative ink is taken as 100 volume %, is preferably 30 volume % or more, more preferably 40 volume % or more, and even more preferably 50 volume % or more. This allows for a high level of both fixation to the surface of the printing object and flexibility after fixation. Furthermore, from the perspective of ensuring a sufficient content of inorganic solid components and forming an image with excellent gloss and color development, the volume ratio of the photocurable monomer component is preferably 65 volume % or less, more preferably 60 volume % or less. Furthermore, it is preferable that the blending ratio of (a1) to (a4) be determined appropriately depending on the intended use, etc.

(b) Dispersant The decorative ink disclosed herein may contain a dispersant. Examples of dispersants include cationic dispersants. Such cationic dispersants efficiently adhere to the surface of inorganic fillers (e.g., inorganic pigments) through an acid-base reaction. Therefore, unlike other dispersants such as phosphate-based dispersants, they can suppress the aggregation of the inorganic fillers and effectively disperse them. An example of such a cationic dispersant is an amine-based dispersant. Such an amine-based dispersant can suppress the aggregation of inorganic fillers due to steric hindrance and stabilize the inorganic filler. Furthermore, by imparting the same charge to inorganic filler particles, they can also effectively suppress the aggregation of inorganic fillers. This effectively reduces the viscosity of the ink and significantly improves printability. Examples of such amine-based dispersants include fatty acid amine-based dispersants and polyester amine-based dispersants. The content of the dispersant is not particularly limited and can be approximately 10 to 50% by volume, assuming the entire decorative ink to be 100% by volume. Furthermore, commercially available dispersants can be used without any particular restrictions.

(c) Photopolymerization Initiator: When the decorative ink disclosed herein contains, for example, a photocurable monomer component, it may further contain a photopolymerization initiator. The photopolymerization initiator absorbs light and becomes activated, generating reaction initiators such as radical molecules and hydrogen ions. These reaction initiators act on the photocurable monomer, accelerating the polymerization and crosslinking reactions of the photocurable monomer. In other words, by increasing the content of the photopolymerization initiator, it is possible to prepare an ink that cures easily even with a small amount of light. Conventional photopolymerization initiators can be used as the photopolymerization initiator without any particular restrictions. Examples include radical photopolymerization initiators such as alkylphenone-based photopolymerization initiators and acylphosphine oxide-based photopolymerization initiators. As such alkylphenone-based photopolymerization initiators, for example, α-aminoalkylphenone-based photopolymerization initiators (e.g., 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, etc.) are preferably used. Further, as other examples of alkylphenone-based photopolymerization initiators, α-hydroxyalkylphenone-based photopolymerization initiators (1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, etc.) can be used. Among the various photopolymerization initiators described above, α-aminoalkylphenone-based photopolymerization initiators such as 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one are particularly preferred because they exhibit high reactivity, can improve the ink curing speed, and have excellent thin film curing properties and surface curing properties. The content of the photopolymerization initiator is not particularly limited, and can be approximately 1 to 5% by volume when the entire decorative ink is taken as 100% by volume. Furthermore, commercially available photopolymerization initiators can be used without any particular restrictions.

(d) Polymerization Inhibitor: When the decorative ink disclosed herein contains a photocurable monomer component, it may further contain a polymerization inhibitor. Adding such a polymerization inhibitor can prevent the photocurable monomer component from polymerizing and curing before use, thereby facilitating ink storage. Any polymerization inhibitor conventionally used in the field of photocurable inkjet inks can be used without particular limitation, as long as it does not significantly reduce the photocurability of the photocurable monomer component and thus the effects of the technology disclosed herein. Examples of such polymerization inhibitors include hydroquinone, methoquinone, di-t-butylhydroquinone, p-methoxyphenol, butylhydroxytoluene, and nitrosamine salts. Among these compounds, N-nitroso-N-phenylhydroxylamine aluminum salt is particularly suitable due to its excellent long-term storage stability. The content of the polymerization inhibitor is not particularly limited, and can be approximately 0.1 to 5% by volume, based on 100% by volume of the entire decorative ink. Furthermore, commercially available polymerization inhibitors can be used without particular limitation.

(3) Content of Each Component The decorative ink disclosed herein is characterized by (a) the volume ratio of the inorganic filler to the total amount of inorganic solid components being controlled within a predetermined range. The decorative ink disclosed herein may also have (b) the volume ratio of the inorganic filler to the total amount of metal-containing glass being controlled within a predetermined range. When the decorative ink is used as an inkjet ink, it is preferable that (c) the volume ratio of the inorganic solid components to the total amount of ink be controlled within a predetermined range, in order to maintain the viscosity of the ink within an appropriate range.

(a) Volume Ratio of Inorganic Filler to the Total Amount of Inorganic Solid Components In the decorative ink disclosed herein, the volume of the inorganic filler is adjusted to 5% by volume or more when the total volume of the inorganic solid components is 100% by volume. Here, the "total volume of inorganic solid components" refers to the combined volume of the inorganic filler and the glass frit. From the viewpoint of obtaining the effects of the inorganic filler, the lower limit of the volume ratio of the inorganic filler is set to 5% by volume or more. Note that, from the viewpoints of suppressing cracks in the decorative portion and improving adhesion to the glass substrate, the lower limit of the inorganic filler is preferably 20% by volume or more. On the other hand, if the volume ratio of the inorganic filler to the total amount of inorganic solid components is increased too much, the color development of the decorative portion may be reduced, and the adhesion of the decorative portion may be reduced due to a decrease in the glass frit content. From these viewpoints, the upper limit of the volume ratio of the inorganic filler is set to less than 80% by volume. From the viewpoint of improving the fixation of the decorative portion, the upper limit of the volume of the inorganic filler is preferably 70% by volume or less (for example, 60% by volume or less), and more preferably 40% by volume or less.

(b) Volume ratio of inorganic filler to the total amount of metal-containing glass In the decorative ink disclosed herein, the volume ratio of the inorganic filler relative to the total volume of the metal-containing glass, taken as 100 parts by volume, is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The lower limit of the volume ratio of the inorganic filler is generally 1 part by volume or more, for example, 5 parts by volume or more, or 15 parts by volume or more. From the viewpoint of more effectively suppressing cracks in the decorative portion, 20 parts by volume or more is preferable. The upper limit of the volume of the inorganic filler is generally 300 parts by volume or less (e.g., 250 parts by volume or less). From the viewpoint of improving the color development of the decorative portion, 200 parts by volume or less (e.g., 150 parts by volume or less) is preferable. Furthermore, from the viewpoint of improving the fixation property of the decorative portion, 100 parts by volume or less (e.g., 70 parts by volume or less) is even more preferable.

(c) Volume Ratio of Inorganic Solid Components to the Total Amount of Decorative Ink When the decorative ink disclosed herein is used as an inkjet ink, the volume ratio of the inorganic solid components is set to 35% by volume or less when the total volume of the inkjet ink is taken as 100% by volume, in order to maintain an appropriate viscosity range. Here, the "total volume of inorganic solid components" refers to the combined volume of the inorganic filler and glass frit. Increasing the volume of the inorganic solid components tends to increase the ink viscosity. Note that there are many types of inorganic filler and glass frit contained in the inorganic solid components, and their specific gravities vary. Therefore, in this embodiment, the "volume" of the inorganic solid components is adjusted rather than the "weight." By setting the volume ratio of the inorganic solid components to the total amount of ink to 35% by volume or less, a low ink viscosity suitable for inkjet printing (typically between 20 mPa·s and 110 mPa·s, preferably between 30 mPa·s and 70 mPa·s) can be obtained. From the viewpoint of more suitably reducing the ink viscosity, the volume ratio of the inorganic solid component is preferably 30% by volume or less, and more preferably 20% by volume or less. On the other hand, from the viewpoint of ensuring sufficient hiding power and fixation power of the decorative portion, the lower limit of the volume ratio of the inorganic solid component is preferably 10% by volume or more, and more preferably 15% by volume or more (for example, 16% by volume or more).

2. Preparation of Decorative Inks The decorative inks disclosed herein can be used as various inks. The decorative inks disclosed herein can be used, for example, as screen printing inks, painting inks, inkjet inks, etc. These inks can be prepared by conventionally known methods. Furthermore, the viscosity of each ink can be adjusted, for example, according to the viscosity of each conventionally known ink. Below, as an example, a method for preparing an inkjet ink as the decorative ink will be described.

First, we will explain a suitable method for preparing glass frit. First, the gold particles and glass components described above are wet mixed to prepare a liquid mixture (mixture preparation step). Next, this mixture is heat-treated to obtain a sintered body in which the gold particles are dispersed in a glass matrix (heat treatment step). This sintered body is then pulverized (pulverization step). This manufacturing method makes it possible to obtain glass frit through the simple steps of mixing and heat treatment.

In the mixture preparation process, gold particles and glass components are mixed in a predetermined ratio. Because such gold particles have a high tendency to aggregate, they are typically sold commercially as a stabilized dispersion in a dispersion solvent. The mixing process can be performed using, for example, a magnetic stirrer or ultrasound. In this embodiment, a highly homogeneous mixture can be obtained by mixing gold particles and glass frit using a wet method. In this manner, a liquid mixture is prepared.

In the heat treatment process, the mixture is heat-treated. For example, it is first dried at a temperature below 100°C to remove some of the dispersant, and then heated to a temperature above the glass transition point of the glass component to sinter it into a cohesive body. The sintering temperature should generally be set to about 0 to 300°C above the glass transition point. For example, in the production of overglaze paint, if the glass transition point of the glass component is 600 to 800°C, the sintering temperature should be set to about 800 to 900°C. The sintering time is usually about 0.1 to several hours. The sintering atmosphere can be air, an oxidizing atmosphere, or an inert gas atmosphere. By heat treating in this manner, a cohesive sintered body is obtained in which gold particles are dispersed in a glass matrix.

In the pulverization process, the sintered body is pulverized (which may be crushed) and/or classified to adjust it to the desired size. The pulverization operation can be carried out using, for example, a vibrating mill, a planetary mill, or a stirring mill.

In this way, the glass frit disclosed herein can be obtained.

The inkjet ink disclosed herein can be prepared by mixing the above-mentioned materials in the specified ratios, followed by crushing and dispersing the inorganic solid components. Figure 1 is a cross-sectional view that schematically shows an agitator/pulverizer used in the production of inkjet ink. Note that the following description is not intended to limit the inkjet ink disclosed herein.

To manufacture the inkjet ink disclosed herein, the above-described materials are first weighed and mixed to prepare a slurry, which is a precursor of the ink. Next, using an agitator/miller 100 such as that shown in FIG. 1, the slurry is agitated and the inorganic solid components (glass frit and inorganic filler) are pulverized. Specifically, milling beads (e.g., zirconia beads with a diameter of 0.5 mm) are added to the slurry, and the slurry is then supplied from the supply port 110 into the agitator vessel 120. The agitator vessel 120 contains a shaft 134 with multiple agitator blades 132. One end of the shaft 134 is attached to a motor (not shown). Operating the motor rotates the shaft 134, stirring the slurry with the multiple agitator blades 132 while sending it downstream in the liquid feed direction A. During this agitation, the inorganic solid components are pulverized by the milling beads added to the slurry, and the finely divided inorganic solid components are dispersed throughout the slurry.

The slurry sent downstream in the liquid feed direction A then passes through the filter 140. As a result, the grinding beads and unatomized inorganic solid components are collected by the filter 140, and the inkjet ink with the atomized inorganic solid components sufficiently dispersed is discharged from the outlet 150. By adjusting the pore size of the filter 140 at this time, the maximum particle size of the inorganic solid components in the inkjet ink can be controlled.

3. Uses of Decorative Ink Next, uses of the decorative ink disclosed herein will be described. The following description will be given, as an example, of a case where the decorative ink is an inkjet ink. As described above, the inkjet ink disclosed herein can be suitably used to draw images on a colorless, transparent glass substrate. In this specification, the phrase "used to draw an image on a glass substrate" refers not only to a case where the ink is directly applied to the surface of the glass substrate, but also to a case where the ink is indirectly applied to the surface of the glass substrate via transfer paper or the like. In other words, the decorative ink disclosed herein can be used for printing on transfer paper (transfer paper manufacturing) or printing on the surface of a glass substrate (glass product manufacturing). A product printed directly on the surface of a glass substrate will be referred to as a "printed matter."

(1) Production of Transfer Paper A method for producing transfer paper for glass substrates (a printing method for drawing an image on the surface of transfer paper) using the inkjet ink disclosed herein will be described. Figure 2 is a general view showing a typical example of an inkjet device. Figure 3 is a cross-sectional view showing a typical inkjet head of the inkjet device shown in Figure 2.

The inkjet ink disclosed herein is stored in the inkjet head 10 of the inkjet device 1 shown in Figure 2. This inkjet device 1 is equipped with four inkjet heads 10. Each inkjet head 10 stores four different colors of ink: black (K), cyan (C), yellow (Y), and magenta (M). The inkjet ink disclosed herein is stored in the magenta (M) inkjet head 10. Each inkjet head 10 is housed inside a print cartridge 40. This print cartridge 40 is inserted into a guide shaft 20 and is configured to move back and forth along the axial direction X of the guide shaft 20. Although not shown, this inkjet device 1 also includes a moving means for moving the guide shaft 20 in the vertical direction Y. This allows ink to be ejected from the inkjet head 10 toward a desired position on the transfer paper backing W.

As mentioned above, the decorative ink (magenta ink) disclosed herein, when used in combination with other colored inks (in other words, when printed in multiple colors), can reduce the difference in shrinkage rate after firing, thereby effectively suppressing the occurrence of cracks in the decorative portion. Examples of other colored inks include inks containing inorganic pigments and glass components. In such other colored inks, the volume ratio of inorganic pigment to glass component can be approximately 30:70 to 90:10 (for example, approximately 40:60 to 80:20). However, this composition is not limited to this.

The inkjet head 10 shown in Figure 2 is, for example, a piezoelectric inkjet head such as that shown in Figure 3. This piezoelectric inkjet head 10 has a storage section 13 for storing ink within a case 12, and the storage section 13 is connected to a discharge section 16 via a liquid supply path 15. This discharge section 16 has a discharge port 17 that opens to the outside of the case 12, and a piezoelectric element 18 is arranged opposite the discharge port 17. In this inkjet head 10, the piezoelectric element 18 is vibrated to discharge the ink in the discharge section 16 from the discharge port 17 toward the backing paper W (see Figure 2).

A UV irradiation means 30 is attached to the guide shaft 20 of the inkjet device 1 shown in Figure 2. This UV irradiation means 30 is positioned adjacent to the print cartridge 40 and moves as the print cartridge 40 reciprocates, irradiating the ink-adhered backing paper W with ultraviolet light. This causes the ink to harden immediately after adhering to the surface of the backing paper W, allowing a sufficient thickness of ink to be fixed to the surface of the transfer paper (backing paper W).

As mentioned above, in the inkjet ink disclosed herein, the volume of inorganic solid components relative to the total volume of the inkjet ink is adjusted to 35% by volume or less. This allows the ink viscosity to be maintained at a low level, enabling the ink to be ejected from the ejection port 17 with high precision and a precise image to be drawn on the surface of the printing target (in this case, transfer paper).

In addition, it is preferable to use a photocurable monomer component containing the monomers (a1) to (a4) described above when manufacturing this transfer paper. This allows for the printing of an image (cured ink) with sufficient flexibility, which effectively prevents cracks from occurring in the image when the transfer paper is bent.

(2) Production of Printed Material Next, a method for producing a printed material using the inkjet ink disclosed herein will be described. A printed material can be produced by drawing an image on the surface of a glass substrate using an inkjet device. For the method for drawing an image using an inkjet device, see the above-mentioned "Production of Transfer Paper."

(3) Method for Manufacturing Glass Products Next, a method for manufacturing a glass product using the inkjet ink disclosed herein will be described. The method for manufacturing a glass product includes a step of decorating the surface of a glass substrate using a decorative ink (here, an inkjet ink). In a preferred embodiment of the method for manufacturing a glass product, the decorating step includes the following steps: a step of depositing a cured product of any of the decorative inks disclosed herein on the surface of the glass substrate (a deposition step); and a step of firing the glass substrate under conditions in which the maximum firing temperature is set within the range of 350°C to 1000°C (a firing step).

The glass products produced using this manufacturing method are not particularly limited, as long as they have a decorative portion formed on the surface of a glass substrate. For example, glass products are not limited to everyday items such as tableware, window glass, and cooking equipment, but may also be industrial products such as electronic devices and displays. Furthermore, the glass substrate to be printed on is not particularly limited, and commonly used glass components can be used without any particular restrictions. Considering the firing process described below, it is preferable to use a glass substrate with a softening point of 500°C or higher (more preferably 600°C or higher, and even more preferably 700°C or higher). Meanwhile, there are no particular restrictions on the upper limit of the softening point of the glass substrate. For example, the upper limit of the softening point of the glass substrate may be 1600°C or lower, 1200°C or lower, or 1000°C or lower.

The color tone of the magenta color portion of the decorative portion formed on the glass substrate is determined, for example, in the L ^* a ^* b ^* color system based on JIS Z8729 (2004) according to the following conditions:
- an L ^* value of 10 to 80 (preferably 15 to 75);
a ^* value is 5 or more (preferably 6 or more);
The b ^* value is -15 or more and 15 or less (preferably -10 or more and 10 or less, for example -8 or more and 8 or less);
can be preferably satisfied. By setting the lightness L ^* value to a predetermined value or more, a bright and vivid color can be realized. Furthermore, by setting the lightness L ^* value to a predetermined value or less, a color with depth and warmth can be realized. Furthermore, by setting the a ^* value in the red direction to a predetermined value or more, the red coloring can be enhanced, and a sharp and clear color can be realized. Furthermore, by setting the b ^* value in the yellow direction to a predetermined value or less, in other words, by keeping the b ^* value in the yellow direction small, a purple to bluish color like "magenta" can be developed, and a vivid magenta color can be realized. Note that such measurements can be performed using, for example, a commercially available device.

Furthermore, the hue angle (h ^* value) of the magenta portion of the decorative portion formed on the glass substrate can be calculated from a ^* and b ^* based on the L ^* a ^* b ^* color system, for example, as specified in JIS Z8729 (2004). The h ^* value can refer to the angle shifted counterclockwise from the a ^* -red axis, with the axis at 0°. By setting the h ^* value within a predetermined range, the magenta color development can be enhanced, resulting in a sharp and distinct hue. In a preferred embodiment, the h ^* value is -45° or more and 45° or less, for example, -45° or more and 40° or less, or -40° or more and 45° or less, preferably -40° or more and 40° or less. Such measurements can be performed, for example, using a commercially available device.

In the deposition process, the inkjet ink is applied (deposited) onto the surface of the glass substrate. The means for applying the ink to the glass substrate is not particularly limited, and the ink may be applied directly to the surface of the glass substrate using an inkjet device, or the ink may be applied indirectly via the transfer paper described above. When using an inkjet device to apply the ink directly to the surface of the glass substrate, it is preferable to eject the ink toward the surface of the glass substrate according to the same procedure as in the "Manufacturing the Transfer Paper" described above.

In the firing process, the glass substrate with the ink attached is fired at a maximum firing temperature within the range of 350°C to 1000°C (preferably 500°C to 1000°C, more preferably 550°C to 850°C). This burns off the resin component, which is the hardened monomer, and melts the glass frit in the inorganic solid component. The melted glass frit then solidifies upon cooling after firing, and the fired film is fixed to the surface of the substrate. The manufacturing method disclosed herein uses ink in which the volume of inorganic filler relative to the total volume of inorganic solid components is adjusted to 5% by volume or more, thereby forming a beautiful decorative portion with excellent hiding power. Furthermore, the volume of inorganic filler relative to the total volume of inorganic solid components is adjusted to less than 80% by volume, allowing the fired film to be properly fixed to the surface of the glass substrate.

Test examples relating to the decorative ink disclosed herein are described below, but the present disclosure is not intended to be limited to these test examples. Furthermore, the following describes the use of the decorative ink disclosed herein as an inkjet ink.

[Test Example 1]
<Preparation of Inkjet Ink>
In this test, five types of inkjet inks (Examples 1 to 5) containing an inorganic solid component, a photocurable compound, and a photopolymerization initiator were prepared. Specifically, the raw materials were mixed in the volume ratios shown in Table 1 to prepare slurries, and the inks of Examples 1 to 5 were obtained by performing a pulverization and dispersion process using pulverization beads (zirconia beads with a diameter of 0.5 mm). The volume ratios in the table are values assuming the total volume of the ink as 100% by volume, unless otherwise specified. In this test example, an inorganic pigment (M-81, tin-sphene type, a ^* value: 20.5, manufactured by Nitto Pigment Co., Ltd.) and a metal-containing glass manufactured in-house were used as the inorganic solid component. Here, the gold-containing glass used was in the form of gold particles (specifically, gold particles with an average particle size of about 20 nm) dispersed in a glass matrix (specifically, SiO ₂ -ZnO-ZrO ₂ -TiO ₂ glass (67-11-4-5 mol %), Tg: 500°C, thermal expansion coefficient: 9×10 ⁻⁶ K ⁻¹ ). The average particle size of the gold-containing glass was about 3 μm, and 0.1 parts by volume of gold particles were contained per 100 parts by volume of the glass matrix. The average particle size (D50 particle size) of the gold-containing glass after pulverization (dispersion) was 1 μm or less. Then, an amine-based dispersant (BYK-2013 manufactured by BYK Japan K.K.) was added as a dispersant, an acylphosphine oxide-based photopolymerization initiator (Omnirad 819 manufactured by IGM RESINS) was added as a photopolymerization initiator, and N-nitroso-N-phenylhydroxylamine aluminum (Q-1301 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a polymerization inhibitor.

The "photocurable monomer component" in Table 1 is a mixture of a monofunctional acrylate monomer, a monofunctional N-vinyl compound monomer, a bifunctional acrylate monomer, and a bifunctional vinyl ether monomer in a specified volume ratio. The monofunctional acrylate monomers used were a mixture of isobornyl acrylate (IBXA, manufactured by Osaka Organic Chemical Industry Ltd.), benzyl acrylate (BZA, manufactured by Osaka Organic Chemical Industry Ltd.), phenoxyethyl acrylate (PHEA, manufactured by Osaka Organic Chemical Industry Ltd.), and cyclic trimethylolpropane formal acrylate (CTFA, manufactured by Osaka Organic Chemical Industry Ltd.). The monofunctional N-vinyl compound monomer used was N-vinyl-ε-caprolactam (NVC, manufactured by Tokyo Chemical Industry Co., Ltd.). The bifunctional acrylate monomer used was 1,9-nonanediol diacrylate (NDDA, manufactured by Osaka Organic Chemical Industry Ltd.). The bifunctional vinyl ether monomer used was a mixture of triethylene glycol divinyl ether (manufactured by Nippon Carbide Corporation: TEGDVE), diethylene glycol divinyl ether (manufactured by Nippon Carbide Corporation: DEGDVE), and 1,4-cyclohexanedimethanol divinyl ether (manufactured by Nippon Carbide Corporation: CHDVE).

In this test example, the "volume ratio of inorganic solid components to the total amount of ink" and the "volume ratio of inorganic filler to inorganic solid components" were calculated for each example. Note that the "volume ratio of inorganic solid components to the total amount of ink" is a value when the total amount of ink is 100% by volume, and the "volume ratio of inorganic filler to inorganic solid components" is a value when the total amount of inorganic solid components is 100% by volume. The same applies to Table 2, which will be described later.

<Evaluation test>
Evaluation of Ink Viscosity The viscosity of the ink prepared in each example was measured using a Brookfield viscometer (Programmable Rheometer LVDV-III Ultra, manufactured by S.T. Johnson & Co., Japan). The ink temperature during measurement was set to 25°C, and the spindle rotation speed was set to 5 rpm. Inks with a viscosity of less than 70 mPa·s were evaluated as having an ink viscosity of "◎", inks with a viscosity of 70 mPa·s or more but less than 110 mPa·s were evaluated as having an ink viscosity of "◯", and inks with a viscosity of 110 mPa·s or more were evaluated as having an ink viscosity of "×". The evaluation results are shown in the corresponding columns in Table 1.

As shown in Table 1, when the total volume of the decorative ink (here, inkjet ink) is taken as 100% by volume, it was confirmed that the ink viscosity could be appropriately adjusted in Examples 1 to 4, which contain 35% or less by volume of inorganic solid components (here, inorganic filler and metal-containing glass). On the other hand, it was confirmed that the ink viscosity could not be appropriately adjusted in Example 5, which contains inorganic solid components outside the above range. Furthermore, it was confirmed that the ink viscosity could be more appropriately adjusted in Examples 1 to 3, which contain inorganic solid components less than 30% (e.g., 20% or less).

[Test Example 2]
In this test example, the hardness, color development, fixability, and cracking of the image (i.e., decorative part) after baking were evaluated for cases where the inorganic solid component was less than 30%, which was confirmed to be able to adjust the ink viscosity particularly favorably in Test Example 1.

<Preparation of Inkjet Ink>
In this test, 13 types of inkjet inks (Examples 6 to 18) containing inorganic solid components, photocurable compounds, and photopolymerization initiators were prepared. Specifically, the inks of Examples 6 to 18 were obtained by preparing slurries by mixing the raw materials in the volume ratios shown in Table 2, and then performing a pulverization and dispersion process using pulverization beads (zirconia beads with a diameter of 0.5 mm). The volume ratios in the table are values assuming the total volume of the ink as 100% by volume, unless otherwise specified. The raw materials in Table 2 were the same as those used in Test Example 1. In addition to the inorganic pigment (M-81) described above, the inorganic fillers used in Table 2 included silica (SO-C2 manufactured by Admattex Co., Ltd.), alumina (AKP-20 manufactured by Sumitomo Chemical Co., Ltd.), and high-fired glass (690N manufactured by Noritake Co., Ltd.).

<Printing images>
Using inkjet printing, the ink of each example was printed on the surface of a 5 mm thick glass substrate (softening point: 820°C). Specifically, an ink was ejected onto the surface of the glass substrate using an inkjet device (Fujifilm Corporation: Material Printer DMP-2831), and then an image with a thickness of 5 μm to 50 μm was drawn on the surface of the glass substrate by irradiating it with UV light (wavelength: 395 nm) for 1 second. Then, this glass substrate was fired at 700°C to produce a test piece having an image (decorative portion).

Hardness of decorative part The hardness of the image (decorative part) on the glass substrate of the test piece prepared as described above was measured by scratch hardness (pencil method) (JIS K5600-5-4), and a pencil hardness of 3H or more was rated as "◎", a pencil hardness of 1H or more but less than 3H was rated as "○", and a pencil hardness of less than 1H was rated as "×". The evaluation results are shown in the corresponding columns in Table 2.

<Preparation of Laminate>
Using inkjet printing, the ink of each example was printed on the surface of a 5 mm thick glass substrate (softening point: 820°C). Specifically, an ink was ejected onto the surface of the glass substrate using an inkjet device (Fujifilm Corporation: Material Printer (DMP-2831)), and then UV light (wavelength: 395 nm) was irradiated for 1 second to draw an image 5 μm to 50 μm thick on the surface of the glass substrate. A white layer having a volume ratio of inorganic pigment to glass of 60:40 was then laminated on top of this, and fired at 700°C to produce a laminate with a decorative portion.

- Color development evaluation The chromaticity (a ^* value) and hue angle (h ^* value) of the magenta color part of the decorative part in the laminate prepared as described above were measured using a spectrophotometer (Konica Minolta, Inc.: CM-600) according to JIS Z8729 (2004) in terms of a ^* and h ^* of the L ^* a ^* b ^* color system. Then, if a ^* ≧ 6 and -35 ° ≦ h ^* ≦ 35 °, the color development was evaluated as "◎", if a ^* ≧ 6 and 35 ° < h ^* ≦ 45 ° and -45 ° ≦ h ^* < 35 °, the color development was evaluated as "○", and if a ^* < 6 or 45 ° < h ^* < 315 °, the color development was evaluated as "×". The evaluation results are shown in the corresponding columns in Table 2.

- Evaluation of Fixation Ability In a tape pull test (Nichiban No. 405) for the laminates prepared as described above, the fixation was evaluated as "◎" when peeling was less than 10%, "○" when peeling was 10% or more but less than 80%, and "×" when peeling was 80% or more. The evaluation results are shown in the corresponding columns in Table 2.

Crack evaluation The presence or absence of cracks in the decorative portion of the laminate prepared as described above was observed from the glass side using a digital microscope (Leica DVM6). Those in which no cracks were observed at a magnification of 500x were marked with a "Crack" symbol, those in which cracks were observed using the digital microscope but not visually were marked with a "Crack" symbol, and those in which cracks were observed visually were marked with a "Crack" symbol. The evaluation results are shown in the corresponding columns in Table 2.

As shown in Table 2, in Examples 6 to 16, which contain glass frit containing gold particles and inorganic filler that does not form an amorphous matrix in the glass frit, and in which the inorganic filler is contained in an amount of 5% by volume or more and less than 80% by volume when the total volume of the inorganic solid components (here, the inorganic filler and gold-containing glass) is taken as 100% by volume, it was confirmed that crack suppression and excellent color development were both achieved in the decorative portion. Furthermore, it was confirmed that the decorative portion had excellent hardness and fixation. On the other hand, in Examples 17 and 18, in which the inorganic filler content was outside the above range, it was confirmed that crack suppression and excellent color development were both not achieved in the decorative portion.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above.

REFERENCE SIGNS LIST 1 Inkjet device 10 Inkjet head 12 Case 13 Storage section 15 Liquid supply path 16 Discharge section 17 Discharge port 18 Piezo element 20 Guide shaft 30 UV irradiation means 40 Print cartridge 100 Stirring and grinding machine 110 Supply port 120 Stirring container 132 Stirring blade 134 Shaft 140 Filter 150 Discharge port A Liquid supply direction X Axial direction of guide shaft Y Vertical direction of guide shaft

Claims (8)

1. A decorative ink used to render images on a glass substrate, comprising:
a glass frit containing gold particles;
an inorganic filler that does not constitute an amorphous matrix in the glass frit;
Including,
The decorative ink contains the inorganic filler in an amount of 20 % by volume or more and less than 60 % by volume when the total volume of the inorganic solid components including the glass frit and the inorganic filler is taken as 100% by volume. 2. The decorative ink according to claim 1 , wherein the inorganic filler is at least one selected from the group consisting of silica, alumina, inorganic pigments, and high-fired glass. The decorative ink is an inkjet ink,
3. The decorative ink according to claim 1, wherein the inorganic solid component accounts for 35% by volume or less when the total volume of the inkjet ink is taken as 100% by volume. The decorative ink according to any one of claims 1 to 3 , further comprising a photocurable monomer component. A printed matter bearing an image depiction made from the decorative ink of any one of claims 1 to 4 . A transfer paper bearing an image formed from the decorative ink of any one of claims 1 to 4 . A method for manufacturing a glass product, comprising:
A method for manufacturing a glass product, comprising a decorating step of decorating the surface of a glass substrate using the decorative ink according to any one of claims 1 to 4 . The decoration process includes the following steps:
A step of depositing a cured product of the decorative ink according to any one of claims 1 to 4 on the surface of a glass substrate; and
Firing the glass substrate under conditions in which a maximum firing temperature is set within a range of 350°C to 1000°C;
The method of claim 7 , comprising: