JP7772081B2 - Inkjet ink for forming partition walls and LED devices - Google Patents

Description

The present invention relates to an ink-jet ink for forming partition walls and an LED device.
More particularly, the present invention relates to an inkjet ink for forming partition walls, which can form partition walls between LED chips and can improve the high-temperature durability of LED devices.

In LED devices such as LED (light emitting diode) displays, a technique for providing partitions between LED chips is used to prevent color mixing between adjacent LED chips. Conventional methods for forming such partitions include photolithography, coating, or screen printing. However, photolithography can pose a problem of damage to the LED chips caused by the developer. Furthermore, coating methods are inefficient, and screen printing methods make fine processing difficult.

As a technology that can solve these problems, Patent Documents 1 and 2, for example, disclose a technique for forming partition walls using an inkjet method. When forming partition walls using the inkjet method, the partition walls can be formed without contacting the LED chip, which does not damage the LED chip. Furthermore, the partition walls can be formed more efficiently than with coating methods, and microfabrication is also possible.

On the other hand, LED devices also require durability to withstand long-term use, particularly durability in high-temperature environments. LED devices in which partition walls are formed using the inks disclosed in Patent Documents 1 and 2 do not have sufficient high-temperature durability, so there has been a demand for an ink for forming partition walls using the inkjet method that can also improve the high-temperature durability of LED devices.

JP 2019-210438 A Japanese Patent Application Laid-Open No. 2021-046528

The present invention was made in consideration of the above problems and circumstances, and its objective is to provide an inkjet ink for forming partition walls that can form partition walls between LED chips and that can improve the high-temperature durability of LED devices, an inkjet ink set for forming partition walls, a method for manufacturing an LED device using the same, and an LED device with improved high-temperature durability.

The present inventors have investigated the causes of the above problems in order to solve them, and have found that by incorporating a photopolymerizable composition, a colorant, and a gelling agent to form an ink that undergoes a sol-gel phase transition depending on temperature, it is possible to provide an inkjet ink for forming partition walls that can form partition walls between LED chips and that can improve the high-temperature durability of LED devices, and have arrived at the present invention.
That is, the above-mentioned problems of the present invention are solved by the following means.

1. An ink-jet ink for forming partition walls between LED chips of an LED device, comprising:
A photopolymerizable composition (excluding a case where the composition contains a photopolymerizable compound having no acidic group and a photopolymerizable compound having an acidic group), a colorant, and a gelling agent,
Sol-gel phase transition occurs depending on the temperature.
The ink-jet ink for forming partition walls, characterized in that the color material contains a white color material or a black color material.

2. The ink-jet ink for forming partition walls according to item 1, wherein the photopolymerizable composition contains a (meth)acrylate compound.

3. The viscosity at 25°C is in the range of 1 to 1 x 10 ⁴ Pa·s, and
3. The ink-jet ink for forming partition walls according to item 1 or 2, which has a sol-gel phase transition point in the range of 40°C or higher but lower than 100°C.

4. The ink-jet ink for partition wall formation according to item 1 or 2, wherein the gelling agent contains at least one compound selected from compounds having a structure represented by the following general formula (G1) or (G2):
General formula (G1): R ₁ -CO-R ₂
General formula (G2): R ₃ -COO-R ₄
[In the formula, R ₁ to R ₄ each independently represent an alkyl chain having 12 or more carbon atoms and a linear portion, which may be branched.]

5. The ink-jet ink for forming partition walls according to item 1 or 2, wherein the gelling agent is contained in an amount within the range of 0.5 to 5% by mass based on the total mass of the ink.

6. An LED device having a partition between LED chips,
the partition wall contains a cured product of a photopolymerizable composition (excluding a case where the composition contains a photopolymerizable compound having no acidic group and a photopolymerizable compound having an acidic group), a colorant, and a gelling agent;
The LED device, wherein the partition walls are composed of at least white partition walls or black partition walls.

According to the above-described means of the present invention, it is possible to provide an ink-jet ink for forming partition walls, which can form partition walls between LED chips and can improve the high-temperature durability of LED devices, and an LED device.

The mechanism by which the effects of this invention are manifested or the mechanism of action is not clear, but is speculated as follows.

The inkjet ink for partition wall formation of the present invention is characterized by containing a gelling agent. By containing a gelling agent, the surface of the partition wall formed using the ink is rougher than when the ink does not contain a gelling agent. In LED devices, a transparent encapsulant is used to protect the LED chip, and because the partition wall formed using the ink of the present invention has a rough surface, the area of the contact interface between the partition wall and the transparent encapsulant is increased, improving adhesion. As a result, gaps are less likely to occur between the partition wall and the transparent encapsulant, improving sealing and the high-temperature durability of the LED device.

It is believed that due to these mechanisms of expression or action, the inkjet ink for forming partition walls of the present invention can form partition walls between LED chips that can improve the high-temperature durability of LED devices.

FIG. 1A is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 1B is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 1C is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 2A is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 2B is a cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 2C is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. 3A is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 3B is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. FIG. 3C is a schematic cross-sectional view of a portion of an LED device illustrating the appearance of partition walls formed by the ink of the present invention. Schematic diagram showing an LED device in which no partition wall is formed. Schematic diagram showing a pattern in which partition walls are formed to cover the periphery of each LED chip. Schematic diagram showing a pattern in which partition walls are formed to surround pixels each made up of three-color LED chips. A schematic diagram showing a pattern in which partition walls are formed to cover the periphery of each LED chip, but the partition walls are formed with a certain width, and there are also areas between pixels where no partition wall is formed.

The inkjet ink for partition wall formation of the present invention is an inkjet ink for partition wall formation used to form partition walls between LED chips of an LED device, and is characterized by containing a photopolymerizable composition, a colorant, and a gelling agent, and undergoing a sol-gel phase transition depending on temperature.
This feature is a technical feature common to or corresponding to the following embodiments.

In an embodiment of the inkjet ink for partition wall formation of the present invention, it is preferable that the photopolymerizable composition contains a (meth)acrylate compound as a component, from the viewpoints of polymerization rate, degree of polymerization, etc.

In an embodiment of the inkjet ink for forming partition walls of the present invention, it is preferable that the colorant contains a white colorant or a black colorant. This makes it possible to form white partition walls that can improve brightness or black partition walls that can improve contrast.

In an embodiment of the inkjet ink for partition wall formation of the present invention, it is preferable that the viscosity at 25°C is in the range of 1 to 1 x 10 ⁴ Pa·s, as this allows the ink to gel sufficiently when it lands and is cooled to room temperature, thereby improving pinning properties. It is also preferable that the ink has a sol-gel phase transition point in the range of 40°C or higher but lower than 100°C. If the sol-gel phase transition point is 40°C or higher, the ink will gel quickly after landing, thereby improving pinning properties. If the sol-gel phase transition point is lower than 100°C, the ink will be easy to handle and have high ejection stability.

In an embodiment of the inkjet ink for partition wall formation of the present invention, the gelling agent preferably contains at least one compound selected from compounds having a structure represented by the above general formula (G1) or (G2). The compound having a structure represented by the above general formula (G1) or the compound having a structure represented by the above general formula (G2) has a linear or branched hydrocarbon group (alkyl chain) with 12 or more carbon atoms, which enhances the crystallinity of the gelling agent and creates more sufficient spaces in the house-of-card structure. This makes it easier for the ink medium, such as the polymerizable compound, to be fully enclosed within the spaces, thereby improving the pinning ability of the ink.

In an embodiment of the inkjet ink for partition wall formation of the present invention, the gelling agent is preferably contained in an amount of 0.5 to 5% by mass relative to the total ink. By keeping the gelling agent content within this range, the solubility and pinning effect of the gelling agent are improved.

The inkjet ink set for partition wall formation of the present invention is an inkjet ink set for forming partition walls between LED chips in an LED device, and comprises a first inkjet ink for partition wall formation and a second inkjet ink for partition wall formation, wherein the first inkjet ink for partition wall formation contains a photopolymerizable composition, a white colorant, and a gelling agent, and undergoes a sol-gel phase transition in response to temperature, and the second inkjet ink for partition wall formation contains a photopolymerizable composition, a black colorant, and a gelling agent, and undergoes a sol-gel phase transition in response to temperature.

The method for manufacturing an LED device of the present invention is a method for manufacturing an LED device having partitions between LED chips, and includes a partition formation process in which the partitions are patterned by an inkjet method. The partition formation process is characterized by using an inkjet ink for forming partitions that contains a photopolymerizable composition, a colorant, and a gelling agent and that undergoes a sol-gel phase transition depending on the temperature.

In an embodiment of the LED device manufacturing method of the present invention, it is preferable that the partition wall formation process includes at least a white partition wall formation process. This makes it possible to form white partition walls that can improve brightness.

In an embodiment of the LED device manufacturing method of the present invention, it is preferable that the partition wall formation process includes at least a black partition wall formation process. This makes it possible to form black partition walls that can improve contrast.

In an embodiment of the LED device manufacturing method of the present invention, the partition wall forming process preferably includes at least a white partition wall forming process and a black partition wall forming process in which black partition walls are formed on the white partition walls formed in the white partition wall forming process. This allows the formation of partition walls whose top surfaces, which contribute to improving contrast, are black and whose side surfaces, which contribute to improving brightness, are partially white.

The LED device of the present invention is an LED device having partitions between LED chips, characterized in that the partitions contain a cured product of a photopolymerizable composition, a colorant, and a gelling agent.

In an embodiment of the LED device of the present invention, it is preferable that the partition walls are composed of at least white partition walls. This can improve brightness.

In an embodiment of the LED device of the present invention, it is preferable that the partition walls are at least composed of black partition walls. This can improve contrast.

In an embodiment of the LED device of the present invention, the partition wall preferably comprises at least a white partition wall and a black partition wall positioned above it. This allows the top surface, which contributes to improving contrast, to be black, while the side surface, which contributes to improving brightness, can be partially white, thereby simultaneously improving brightness and contrast.

The present invention, its components, and modes and aspects for implementing the invention are described in detail below. Note that in this application, the symbol "to" is used to mean that the numerical values before and after it are included as both the lower limit and upper limit.

<1. Inkjet ink for partition formation>
The ink-jet ink for partition wall formation (hereinafter also simply referred to as "ink") of the present invention is an ink-jet ink for partition wall formation for forming partition walls between LED chips of an LED device, and is characterized by containing a photopolymerizable composition, a colorant, and a gelling agent, and undergoing a sol-gel phase transition depending on temperature.

1.1 Ink applications
The ink of the present invention is an ink-jet ink for forming partition walls between LED chips in an LED device.

In this invention, a "partition wall" refers to a wall formed between LED chips in an LED device to prevent color mixing between adjacent pixels or adjacent LED chips, and having a height of 25% or more of the height of the LED chip.

Figures 1A-C and 2A-C are schematic cross-sectional views of a portion of an LED device to illustrate the appearance of partition walls formed using the ink of the present invention. In an LED device 1 in which red LED chips 3R, green LED chips 3G, and blue LED chips 3B are arranged on a substrate 2, the partition walls 4 (black partition walls 4Bl and white partition walls 4Wh) may be formed to cover the periphery of each LED chip, as shown in Figures 1A-C, or may be formed to cover the periphery of a pixel consisting of LED chips of three colors, as shown in Figures 2A-C. Figures 1A-C and 2A-C also show a transparent encapsulant 5 and a cover glass 6 for sealing the LED chips.

The height of the partition wall relative to the height of the LED chip must be at least 25%. To prevent color mixing, it is preferable that it be at least 50%, and more preferably at least 75%. Furthermore, because a partition wall that is too high reduces brightness, it is preferable that the height of the partition wall relative to the height of the LED chip be no more than 200%.

Figures 1A-C and 2A-C show LED devices in which partition walls are formed with a height that is approximately 150% of the height of the LED chip, and Figures 3A-C show LED devices in which partition walls are formed with a height that is approximately 50% of the height of the LED chip.

Figure 4 shows an LED device without partitions, while Figures 5 to 7 show LED devices with partitions formed in different patterns. All of Figures 4 to 7 are schematic top views of a portion of an LED device, showing an area equivalent to four pixels, where one pixel is a set consisting of a red LED chip 3R, a green LED chip 3G, and a blue LED chip 3B.

Figure 5 corresponds to a top view of Figures 1A-C and Figures 3A-C (the transparent sealant 5 and cover glass 6 are not shown, and the number of LED chips is different), and shows a pattern in which partition walls 4 are formed to cover the periphery of each LED chip.

Figure 6 corresponds to a top view of Figures 2A to 2C (the transparent sealant 5 and cover glass 6 are not shown), and shows a pattern in which a partition 4 is formed to cover the periphery of a pixel consisting of three color LED chips.

Figure 7 shows a pattern in which partitions 4 are formed to cover the periphery of each LED chip, as in Figure 5, but the partitions are formed to a certain width and there are also areas between pixels where no partitions are formed.

Note that Figures 1 to 7 illustrate embodiments and do not limit the pattern of the partition walls formed by the ink of the present invention or the arrangement of LED chips in an LED device using the ink of the present invention.

The cross-sectional shape of the partition wall in the width direction may be a shape in which the widths at the bottom and top are approximately constant, or may be a tapered shape in which the bottom is wider, or a reverse tapered shape in which the top is wider. The width of the partition wall is not particularly limited.

The color of the partition is not particularly limited, but is preferably white from the viewpoint of reflecting light emitted by the LED chip and improving brightness. Furthermore, from the viewpoint of improving contrast, it is preferably black. Figures 1A and 2A show an LED device in which white partition walls 4Wh are formed, while Figures 1B and 2B show an LED device in which black partition walls 4Bl are formed. It is also preferable that the color of the partition walls be gray in order to control reflectance and contrast.

In this invention, "white" refers to a color having a lightness of 8.0 or more and a saturation of 2.0 or less in the Munsell color system (JIS Z 8721). "Black" refers to a color having a lightness of 2.0 or less and a saturation of 2.0 or less in the Munsell color system (JIS Z 8721). "Gray" refers to a mixture of white and black.

The partition walls formed by the ink of the present invention may be composed of two or more overlapping partition walls of different colors. For example, as shown in Figures 1C, 2C, and 3C, by forming a partition wall 4 composed of a white partition wall 4Wh and a black partition wall 4Bl positioned above it, the top surface, which contributes to improving contrast, can be made black, while the side surface, which contributes to improving brightness, can be made partially white, thereby simultaneously improving brightness and contrast. Note that in the case of a partition wall composed of overlapping partition walls of two or more different colors, the dimensions such as height and width described above refer to the dimensions of the entire partition wall.

The ink of the present invention is an ink used to form the partition walls described above.

1.2 Ink components
The ink of the present invention is characterized by containing a photopolymerizable composition, a coloring material, and a gelling agent. The components will be described in detail below.

(Photopolymerizable composition)
The photopolymerizable composition according to the present invention preferably contains at least a polymerizable compound as a component, and further contains a photopolymerization initiator as needed.

The content of the polymerizable compound is preferably within the range of 1 to 97% by mass of the total ink, and more preferably within the range of 30 to 90% by mass.

The polymerizable compound is not particularly limited, and can be any compound that initiates a polymerization reaction upon irradiation with active energy rays (electron beams, ultraviolet rays, alpha rays, gamma rays, X-rays, etc.) in the presence or absence of a photopolymerization initiator, and hardens through polymerization and crosslinking. The polymerizable compound may be a monomer, polymerizable oligomer, prepolymer, or a mixture thereof.

Examples of polymerizable compounds include cationically polymerizable compounds, radically polymerizable compounds, and mixtures thereof. From the standpoint of polymerization rate and degree of polymerization, radically polymerizable compounds are preferred, and (meth)acrylate compounds are more preferred.

The term "radically polymerizable compound" refers to a compound having an ethylenically unsaturated double bond in the molecule. The radically polymerizable compound may be either a monofunctional or polyfunctional compound.

Radically polymerizable compounds include (meth)acrylate compounds, which are unsaturated carboxylic acid ester compounds. In the present invention, "(meth)acrylate" refers to acrylate or methacrylate. In the present invention, "(meth)acrylate compounds" include compounds containing a (meth)acryloyl group in the main chain, compounds having a (meth)acryloyl group as a side chain, and compounds having a (meth)acryloyl group as a substituent on the side chain.

Examples of (meth)acrylate compounds that do not have an acidic group include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyryl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate. monofunctional acrylates including acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, and t-butylcyclohexyl (meth)acrylate, as well as triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol Cole di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate and polyfunctional acrylates including tri- or higher functional acrylates such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate.

Examples of (meth)acrylate compounds having a carboxy group include (meth)acrylate compounds having a hydroxy group and (meth)acrylates obtained by adding an acid anhydride to an oligomer of these compounds. Examples of such acid anhydrides include phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, himic anhydride, maleic anhydride, trimellitic anhydride, methylcyclohexene tricarboxylic anhydride, and pyromellitic anhydride. Specific examples of the (meth)acrylate compound having a carboxy group include (meth)acryloyloxyalkoxycarbonylphthalates such as 2-carboxyethyl acrylate, 4-(meth)acryloyloxyethoxycarbonylphthalic acid, 4-(meth)acryloyloxybutoxycarbonylphthalic acid, 4-(meth)acryloyloxyhexyloxycarbonylphthalic acid, and 4-(meth)acryloyloxydecyloxycarbonylphthalic acid; Examples of the acryloyloxyalkyl phthalates include (meth)acryloyloxyalkoxyalkoxycarbonylphthalic acids such as bisethoxyethoxycarbonylphthalic acid, mono-2-(acryloyloxy)ethyl succinate, 2,2-bis(acryloylamido)acetic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, and 2-(meth)acryloyloxyethyl hexahydrophthalic acid.

Examples of (meth)acrylate compounds having a phosphate group include bis(2-(meth)acryloyloxyethyl)phosphate ester, 2-hydroxyethyl (meth)acrylate acid phosphate, ethyl (meth)acrylate acid phosphate, 3-chloro-2-acidphosphooxypropyl (meth)acrylate, polyoxyethylene glycol (meth)acrylate acid phosphate, 2-(meth)acryloyloxyethyl caproate acid phosphate, and mono-2-(methacryloyloxy)ethyl phosphate. Further, 2-(meth)acryloyloxyethyl phosphate (meaning 2-acryloyloxyethyl phosphate or 2-methacryloyloxyethyl phosphate, hereinafter this abbreviation will be used), 2-(meth)acryloyloxypropyl phosphate, 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, 6-(meth)acryloyloxyhexyl phosphate, 8-(meth)acryloyloxyoctyl phosphate, 10-(meth)acryloyloxydecyl phosphate, 12-(meth)acryloyloxylauryl phosphate, 16-(meth)acryloyloxycetyl phosphate, 18-(meth)acryloyloxyethyl phosphate, 19-(meth)acryloyloxyethyl phosphate, 20-(meth)acryloyloxyethyl phosphate, 21-(meth)acryloyloxyethyl phosphate, 22-(meth)acryloyloxyethyl phosphate, 23-(meth)acryloyloxyethyl phosphate, 24-(meth)acryloyloxyethyl phosphate, 25-(meth)acryloyloxyethyl phosphate, 26-(meth)acryloyloxyethyl phosphate, 27-(meth)acryloyloxyethyl phosphate, 28-(meth)acryloyloxyethyl phosphate, 29-(meth)acryloyloxyethyl phosphate, 30-(meth)acryloyloxyethyl phosphate, 31-(meth)acryloyloxyethyl phosphate, 32-(meth)acryloyloxyethyl phosphate, 33-(meth)acryloyloxyethyl phosphate, 34-(meth)acryloyloxyethyl phosphate, 35-(meth)acryloyloxyethyl phosphate, 36-(meth)acryloyloxyethyl phosphate, 37-(meth)acryloyloxyethyl phosphate, 38-( p) (meth)acryloyloxyalkyl phosphate esters such as acryloyloxystearyl phosphate ester and 20-(meth)acryloyloxyeicosyl phosphate ester; di(meth)acryloyloxyalkyl phosphate esters such as 1,3-di(meth)acryloyloxypropyl-2-phosphate ester; (meth)acryloyloxyalkylaryl phosphate esters such as 2-(meth)acryloyloxyethylphenyl phosphate ester, 2-(meth)acryloyloxyethyl anisyl phosphate ester and 2-(meth)acryloyloxyethyl tolyl phosphate ester; (meth)acryloyloxyalkylaryl phosphate esters such as 2-(meth)acryloyloxyethylphenylphosphonic acid phosphonic acids; 2-(meth)acryloyloxyethyl thiophosphate ester, 2-(meth)acryloyloxypropyl thiophosphate ester, 3-(meth)acryloyloxypropyl thiophosphate ester, 4-(meth)acryloyloxybutyl thiophosphate ester, 6-(meth)acryloyloxyhexyl thiophosphate ester, 8-(meth)acryloyloxyoctyl thiophosphate ester, 10-(meth)acryloyloxydecyl thiophosphate ester, 12-(meth)acryloyloxylauryl thiophosphate ester, 16-(meth)acryloyloxycetyl thiophosphate ester, 18-(meth)acryloyloxystearyl thiophosphate ester, 20-(meth)acryloyloxy Examples thereof include (meth)acryloyloxyalkyl thiophosphates such as ciaicosyl thiophosphate; di(meth)acryloyloxyalkyl thiophosphates such as 1,3-di(meth)acryloyloxypropyl-2-thiophosphate; (meth)acryloyloxyalkylaryl thiophosphates such as 2-(meth)acryloyloxyethyl phenyl thiophosphate, 2-(meth)acryloyloxyethyl anisyl thiophosphate, and 2-(meth)acryloyloxyethyl tolyl thiophosphate; and (meth)acryloyloxyalkylaryl thiophosphonic acids such as 2-(meth)acryloyloxyethyl phenyl thiophosphonic acid.

Examples of (meth)acrylate compounds having a sulfonic acid group include methallylsulfonic acid, bis(3-sulfopropyl)itaconic acid, 2-(sulfoxy)ethyl methacrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-sulfopropylacrylic acid, 3-sulfopropylmethacrylic acid, and acrylamido-2-methyl-2-propanesulfonic acid.

Examples of (meth)acrylate compounds having a monofunctional hydroxy group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxymethylcyclohexylmethyl (meth)acrylate, and p-hydroxymethylphenylmethyl (meth)acrylate. , 2-(hydroxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, methyl α-hydroxymethylacrylate, ethyl α-hydroxymethylacrylate, hydroxyalkyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate.

Examples of (meth)acrylate compounds having polyfunctional hydroxy groups include 2-hydroxy-3-acryloyloxypropyl methacrylate, dipentaerythritol penta(meth)acrylate, ethylene oxide-added pentaerythritol tetra(meth)acrylate, trimethylolpropane diacrylate, glycerin di(meth)acrylate, glycerin acrylate methacrylate, pentaerythritol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol propionate tri(meth)acrylate, hydroxypivalaldehyde-modified dimethylolpropane tri(meth)acrylate, sorbitol tri(meth)acrylate, sorbitol tetra(meth)acrylate, sorbitol penta(meth)acrylate, sorbitol hexa(meth)acrylate, and pentaerythritol tri(meth)acrylate.

The (meth)acrylate may be modified. Examples of modified (meth)acrylates include ethylene oxide-modified (meth)acrylates such as ethylene oxide-modified trimethylolpropane tri(meth)acrylate and ethylene oxide-modified pentaerythritol tetraacrylate, caprolactone-modified (meth)acrylates such as caprolactone-modified trimethylolpropane tri(meth)acrylate, and caprolactam-modified (meth)acrylates such as caprolactam-modified dipentaerythritol hexa(meth)acrylate.

The (meth)acrylate may be a polymerizable oligomer. Examples of (meth)acrylate polymerizable oligomers include epoxy (meth)acrylate oligomers, aliphatic urethane (meth)acrylate oligomers, aromatic urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and linear (meth)acrylic oligomers.

"Cationically polymerizable compound" refers to a compound that has a cationically polymerizable group in the molecule. Examples of cationically polymerizable compounds include epoxy compounds, vinyl ether compounds, and oxetane compounds.

Examples of epoxy compounds include alicyclic epoxy compounds (3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene monoepoxide, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 1-methyl-4-(2-methyloxiranyl)-7-oxabicyclo[4,1,0]heptane, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanone-meta-dioxane, and bis(2,3-epoxycyclopentyl)ether, etc.), aliphatic epoxy compounds (diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerin, etc.), and and aromatic epoxy compounds (diglycidyl ether of bisphenol A, diglycidyl ether of an alkylene oxide adduct of bisphenol A, diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of an alkylene oxide adduct of hydrogenated bisphenol A, polyglycidyl ether of bisphenol A, polyglycidyl ether of an alkylene oxide adduct of bisphenol A, polyglycidyl ether of hydrogenated bisphenol A, polyglycidyl ether of an alkylene oxide adduct of bisphenol A, polyglycidyl ether of hydrogenated bisphenol A, polyglycidyl ether of an alkylene oxide adduct of hydrogenated bisphenol A, and novolac-type epoxy resins).

Examples of vinyl ether compounds include ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether.

Examples of oxetane compounds include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-n-butyloxetane, 3-hydroxymethyl-3-phenyloxetane, 3-hydroxymethyl-3-benzyloxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, and 3-hydroxyethyl 3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxetane, 3-hydroxybutyl-3-methyloxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and di[1-ethyl(3-oxetanyl)]methyl ether.

The photopolymerizable composition of the present invention preferably contains a photopolymerization initiator, if necessary.

The content of the photopolymerization initiator can be set as desired, as long as the ink is sufficiently cured by irradiation with active energy rays and the ink's inkjet ejection stability is not reduced. For example, the content of the photopolymerization initiator is preferably within the range of 0.1 to 20% by mass, and more preferably within the range of 1.0 to 12% by mass, of the total ink.

The photopolymerization initiator may be any that can initiate polymerization of the polymerizable compound. For example, if the ink contains a radically polymerizable compound, the photopolymerization initiator should be a radical photopolymerization initiator; if the ink contains a cationic polymerizable compound, the photopolymerization initiator should be a cationic photopolymerization initiator.

One type of photopolymerization initiator may be used alone, or two or more types may be used in combination. Furthermore, both a radical photopolymerization initiator and a cationic photopolymerization initiator may be used in combination.

Radical photopolymerization initiators include intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

Examples of intramolecular bond cleavage type radical photopolymerization initiators include acetophenone-based photopolymerization initiators (diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propan-1-one, and 2-benzyl-2-dimethyl benzoin-based photopolymerization initiators (benzoin, benzoin methyl ether, benzoin isopropyl ether, etc.), acylphosphine oxide-based photopolymerization initiators (2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, etc.), benzyl and methylphenyl glyoxyesters, etc.

Of these, acylphosphine oxide-based photopolymerization initiators are preferred, as they further improve the curing properties of the polymerizable compound, particularly in the curing process using UV-LED light.

Commercially available acylphosphine oxide photopolymerization initiators include, for example, IRGACURE (registered trademark) 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide), IRGACURE (registered trademark) 1800 (a mixture of bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 25:75), and IRGACURE (registered trademark) TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).

Examples of the intramolecular hydrogen abstraction type radical photopolymerization initiator include benzophenone-based photopolymerization initiators (benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone), thioxanthone-based photopolymerization initiators (2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone), aminobenzophenone-based photopolymerization initiators (Michler's ketone, 4,4'-diethylaminobenzophenone), 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

Examples of the cationic photopolymerization initiator include photoacid generators, such as B(C 6 F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , and CF ₃ SO _{3 −} salts of aromatic onium compounds including diazonium, ammonium, iodonium ^, sulfonium, and phosphonium, sulfonates that generate sulfonic acid, halides that photogenerate hydrogen halide, and iron-allene complexes.

(Colorant)
The ink of the present invention is characterized by containing a coloring material, which may be a pigment or a dye.

The color of the colorant is not particularly limited, and a colorant that matches the color of the partition walls to be formed may be used. The color of the partition walls is preferably white to improve reflectance and brightness, and black to improve contrast; therefore, the colorant is preferably white or black. A black colorant may be used alone, or may be a mixture of red, green, and blue colorants. Furthermore, since the color of the partition walls is preferably gray to control reflectance and contrast, it is also preferable to use a gray colorant as the colorant to be contained in the ink. A gray colorant can be prepared, for example, by mixing a white colorant with a black colorant.

The content of the colorant is not particularly limited, but for white colorants, it is preferably in the range of 2 to 30% by mass, more preferably in the range of 5 to 20% by mass, and even more preferably in the range of 6 to 15% by mass, relative to the total ink. For black colorants, it is preferably in the range of 1 to 20% by mass, more preferably in the range of 1.5 to 15% by mass, and even more preferably in the range of 2 to 10% by mass, relative to the total ink.

Below, we will specifically explain the pigments that are suitable for use as colorants contained in the ink of the present invention.

Examples of white pigments include calcium carbonate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, antimony oxide, zirconium oxide, white hollow resin particles, and polymer particles. Of the above white pigments, titanium oxide and zirconium oxide are preferred, with titanium oxide being more preferred.

Examples of commercially available titanium oxides that can be used in the present invention include CR-EL, CR-50, CR-80, CR-90, R-780, R-930 (all manufactured by Ishihara Sangyo Kaisha), TCR-52, R-25, R-32, R-310 (all manufactured by Sakai Chemical Industry Co., Ltd.), KR-310, KR-380, and KR-380N (all manufactured by Titanium Industries Co., Ltd.), etc.

An example of zirconium oxide that can be used as the above-mentioned white pigment is the commercially available product Zirconeo (manufactured by ITEC Corporation, "Zirconeo" is a registered trademark of the company).

Examples of black pigments include pigments selected from Pigment Black 7, 28, 26, or mixtures thereof.

Examples of commercially available black pigments include Black Pigment (Mikuni), Chromofine Black A-1103 (Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and Colortex Black. 702, U905 (manufactured by Sanyo Dye Co., Ltd.), carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, and CF9 (all manufactured by Mitsubishi Chemical Corporation).

Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment and pigments selected from Orange 13, 16, 20, and 36, or mixtures thereof.

Examples of blue or cyan pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50 or mixtures thereof.

Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

In addition to the pigments listed above, commercially available examples of pigments include: Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5 000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Yellow 8040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seikafast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seikafast Bordeaux 10B-430, Seikalite Rose R40, Seikalite Violet B800, 7805, Seikafast Maroon 460N, Seikafast Orange 900, 2900, Seikalite Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (manufactured by DIC); Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, ColortexBlue516, 517, 518, 519, A818, P-908, 510, Colortex Green402, 403, Lionol Yellow1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink Co., Ltd.), Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapeam Blue B2G (manufactured by Hoechst Industrie); Novoperm P-HG, and Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant).

Pigments can be dispersed using, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, and paint shaker.

When using a pigment as the colorant, from the perspective of improving ejection performance from an inkjet head, it is preferable that the average dispersed particle diameter of the pigment particles be in the range of 50 to 150 nm and the maximum particle diameter be in the range of 300 to 1000 nm. An even more preferable average dispersed particle diameter is in the range of 80 to 130 nm.

The average dispersed particle size of pigment particles refers to the value determined by dynamic light scattering using a Datasizer Nano ZSP (manufactured by Malvern). Note that inks containing colorants are highly concentrated, and light does not pass through this measuring device, so the ink is diluted 200 times before measurement. Measurement temperature is room temperature (25°C).

Pigment dispersion is adjusted by the pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions, etc.

When a pigment is used as the colorant, the ink of the present invention may further contain a dispersant to improve the dispersibility of the pigment. Examples of dispersants include carboxylic acid esters with hydroxy groups, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high-molecular-weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalene sulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available dispersants include the Solsperse series from Avecia and the PB series from Ajinomoto Fine-Techno Co., Ltd.

When a pigment is used as the colorant, the ink of the present invention may contain a dispersing aid as needed. The dispersing aid may be selected depending on the pigment.

The total amount of dispersant and dispersing aid is preferably within the range of 1 to 50% by mass relative to the pigment.

When a pigment is used as the colorant, the ink of the present invention may optionally contain a dispersion medium for dispersing the pigment. The dispersion medium may be a solvent, but in order to minimize damage to the LED chip, it is preferable to use a polymerizable compound (especially a low-viscosity monomer) as described above as the dispersion medium.

(Gelling Agent)
By containing a gelling agent, the ink of the present invention can improve the adhesion between the partition walls and the transparent sealant, and can improve the high-temperature durability of the LED device.

In addition, by including a gelling agent, the ink droplets that are ejected and land can be gelled and temporarily fixed (pinned), making it easier to form partition walls with fine shapes or high aspect ratios.

Furthermore, the partition walls formed using the ink of the present invention containing a gelling agent have a matte effect due to the roughness of the partition wall surface, which can reduce the reflectance of light from the viewing side.

The ink of the present invention may contain only one type of gelling agent, or two or more types.

Examples of gelling agents of the present invention include dialkyl ketones, fatty acid esters, fatty acid amides, and oil gelling agents.

Furthermore, the gelling agent according to the present invention preferably contains at least one compound selected from compounds having a structure represented by the following general formula (G1) or (G2):
General formula (G1): R ₁ -CO-R ₂
General formula (G2): R ₃ -COO-R ₄
[In the formula, R ₁ to R ₄ each independently represent an alkyl chain having 12 or more carbon atoms and a linear portion, which may be branched.]

Ketone waxes having a structure represented by the above general formula (G1) or ester waxes having a structure represented by the above general formula (G2) have linear or branched hydrocarbon groups (alkyl chains) with 12 or more carbon atoms, which increases the crystallinity of the gelling agent and creates more space in the house-of-card structure described below. This makes it easier for ink media such as polymerizable compounds to be fully enclosed within the space, improving the ink's pinning ability.

Furthermore, the number of carbon atoms in R ₁ to R ₄ is preferably 26 or less. When the number of carbon atoms is 26 or less, the melting point of the gelling agent does not become excessively high, and therefore it is not necessary to heat the ink excessively when ejecting the ink.

From the above viewpoint, it is particularly preferable that R ₁ and R ₂ or R ₃ and R ₄ are linear hydrocarbon groups having 12 to 23 carbon atoms.

From the viewpoint of increasing the gelling temperature of the ink and causing the ink to gel more rapidly after landing, it is preferable that either _R1 or _R2 , or either _R3 or _R4, is a saturated hydrocarbon group having from 12 to 23 carbon atoms.

From the above viewpoint, it is more preferable that both R ₁ and R ₂ , or both R ₃ and R ₄ , are saturated hydrocarbon groups having 11 or more but less than 23 carbon atoms.

Examples of ketone waxes having the structure represented by the above general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), dieicosyl ketone (C20-C20), dipalmityl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), and lauryl myristyl ketone. Examples of ketones include ketone (C12-C14), lauryl palmityl ketone (C12-C16), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), palmityl behenyl ketone (C16-C22), and stearyl behenyl ketone (C18-C22). The number of carbon atoms in the parentheses indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the carbonyl group.

Commercially available examples of ketone waxes having the structure represented by general formula (G1) include Stearonne (manufactured by Alfa Aeser; Stearon), 18-Pentatriacontanon (manufactured by Alfa Aeser), Hentriacontan-16-on (manufactured by Alfa Aeser), and Kaowax T-1 (manufactured by Kao Corporation).

Examples of fatty acids or ester waxes having a structure represented by general formula (G2) include behenyl behenate (C21-C22), icosanoic acid icosyl (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C Myristate (C18-C18), myristyl myristate (C13-C14), cetyl myristate (C13-C16), octyldodecyl myristate (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22), and arachidyl linoleate (C17-C20). The number of carbon atoms in the parentheses indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the ester group.

Commercially available examples of ester waxes having the structure represented by general formula (G2) include Unistar M-2222SL and Sperm Acetate (both manufactured by NOF Corporation, "Unistar" is a registered trademark of the company), Exsepar SS and Exsepar MY-M (both manufactured by Kao Corporation, "Exsepar" is a registered trademark of the company), EMALEX CC-18 and EMALEX CC-10 (both manufactured by Nippon Emulsion Co., Ltd., "EMALEX" is a registered trademark of the company), and Amleps PC (manufactured by Kokyu Alcohol Kogyo Co., Ltd., "Amleps" is a registered trademark of the company).

Since these commercially available products are often mixtures of two or more types, they may be separated and purified as necessary before being incorporated into the ink. Of these gelling agents, ketone wax, ester wax, higher fatty acid, higher alcohol, and fatty acid amide are preferred from the perspective of further enhancing pinning properties.

The gelling agent content is preferably within the range of 0.5 to 5.0% by mass of the total ink. By keeping the gelling agent content within this range, the solubility and pinning effect of the gelling agent are improved. From the above perspective, it is more preferable that the gelling agent content in the ink be within the range of 0.5 to 2.5% by mass.

Furthermore, from the following viewpoint, it is preferable that the gelling agent crystallizes in the ink at a temperature below the gelling temperature of the ink. The gelling temperature is the temperature at which the gelling agent undergoes a phase transition from sol to gel when ink that has been solated or liquefied by heating is cooled, causing a sudden change in the viscosity of the ink. Specifically, the solated or liquefied ink is cooled while its viscosity is measured using a viscoelasticity measuring device (e.g., MCR300, manufactured by Physica), and the temperature at which the viscosity suddenly increases can be determined to be the gelling temperature of the ink.

When a gelling agent crystallizes in the ink, a structure may be formed in which the ink medium, such as a polymerizable compound, is enclosed in a three-dimensional space formed by the gelling agent that has crystallized into plates (such a structure will be referred to as a "house of cards structure" hereafter). When a house of cards structure is formed, the liquid ink medium is retained within the space, making it more difficult for ink droplets to wet and spread, and improving the ink's pinning ability.

To form a house-of-cards structure, it is preferable that the ink medium, such as the polymerizable compound in the ink, and the gelling agent are compatible. On the other hand, if the ink medium, such as the polymerizable compound in the ink, and the gelling agent are phase-separated, it may be difficult to form a house-of-cards structure.

(Solvents with a normal boiling point of 250°C or less)
The ink of the present invention preferably contains 25% or less of solvents with a normal boiling point (boiling point under 1 atmosphere) of 250°C or less. This can suppress damage to the LED chip and also reduce the environmental impact. The content of solvents with a normal boiling point of 250°C or less is more preferably 15% or less, and even more preferably 5% or less.

Examples of solvents with a standard boiling point of 250°C or less include alcohol-based solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, and i-propyl alcohol; cellosolve-based solvents such as methoxy alcohol and ethoxy alcohol; carbitol-based solvents such as methoxyethoxyethanol and ethoxyethoxyethanol; ester-based solvents such as ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, and ethyl lactate; ketone-based solvents such as acetone, methyl isobutyl ketone, and cyclohexanone; methoxyethyl acetate, propylene glycol monomethyl ether acetate, 3-methoxy-3-methyl-1-butyl acetate, 3-methoxybutyl acetate, methoxybutyl acetate, ethoxyethyl acetate, and ethyl cellosolve acetate; carbitol acetate solvents such as methoxyethoxyethyl acetate, ethoxyethoxyethyl acetate, and butyl carbitol acetate (BCA); ether solvents such as diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, and tetrahydrofuran; aprotic amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; lactone solvents such as γ-butyrolactone; unsaturated hydrocarbon solvents such as benzene, toluene, xylene, and naphthalene; and saturated hydrocarbon solvents such as N-heptane, N-hexane, and N-octane.

(Other ingredients)
The ink of the present invention may further contain other components including a polymerization inhibitor and a surfactant, as long as the effects of the present invention are obtained. Only one type of these components may be contained in the ink of the present invention, or two or more types may be contained.

Examples of polymerization inhibitors include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxyamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime.

Examples of commercially available polymerization inhibitors include Irgastab UV10 (manufactured by BASF) and Genorad 18 (manufactured by Rahn A.G.).

The amount of polymerization inhibitor can be set as desired as long as the effects of the present invention are achieved. The amount of polymerization inhibitor can be, for example, 0.001% by mass or more and less than 1.0% by mass of the total ink.

Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorine-based surfactants.

Examples of silicone surfactants include polyether-modified polysiloxane compounds, specifically Tego Rad 2250 (manufactured by Evonik), KF-351A, KF-352A, KF-642 and X-22-4272 (all manufactured by Shin-Etsu Chemical Co., Ltd.), BYK307, BYK345, BYK347 and BYK348 (all manufactured by BYK-Chemie, "BYK" is a registered trademark of the company), and TSF4452 (manufactured by Momentive Performance Materials).

Fluorine-based surfactants are surfactants in which some or all of the hydrogen atoms bonded to the carbon atoms in the hydrophobic groups of ordinary surfactants have been replaced with fluorine. Examples of fluorine-based surfactants include Megafac F (manufactured by DIC Corporation; "Megafac" is a registered trademark of DIC), Surflon (manufactured by AGC Sei Chemical Co., Ltd.; "Surflon" is a registered trademark of AGC Sei Chemical Co., Ltd.), Fluorad FC (manufactured by 3M Corporation; "Fluorad" is a registered trademark of 3M), Monflor (manufactured by Imperial Chemical Industries, Ltd.), Zonyls (manufactured by E.I. duPont Nemelas & Company), Licowet VPF (manufactured by Lubbewerke-Hoechst), and FTERGENT (manufactured by Neos Corporation; "FTERGENT" is a registered trademark of 3M).

The amount of surfactant can be set as desired as long as the effects of the present invention are achieved. The amount of surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass of the total ink.

1.3 Sol-gel phase transition of ink
The ink of the present invention is characterized by undergoing a sol-gel phase transition depending on temperature. In the present invention, the term "sol-gel phase transition" refers to a reversible change from a fluid sol state at a high temperature to a non-fluid gel state at a low temperature, with the sol-gel phase transition point as the boundary.

The viscosity of the ink of the present invention at 25° C. is preferably in the range of 1 to 1×10 ⁴ Pa·s, since this allows the ink to gel sufficiently when it lands and is cooled to room temperature, resulting in good pinning properties.

In addition, from the viewpoint of further improving ejection properties from an inkjet head, the viscosity of the ink of the present invention at 80°C is preferably in the range of 3 to 20 mPa·s, and more preferably in the range of 7 to 9 mPa·s.

The ink of the present invention preferably has a sol-gel phase transition point in the range of 40°C or higher but less than 100°C. If the sol-gel phase transition point is 40°C or higher, the ink will gel quickly after landing, resulting in higher pinning properties. Furthermore, if the sol-gel phase transition point is less than 100°C, the ink will be easier to handle and have higher ejection stability. From the perspective of enabling the ink to be ejected at lower temperatures and reducing the load on the inkjet device, it is more preferable that the sol-gel phase transition point of the ink of the present invention be in the range of 40 to 60°C.

The viscosity at 80°C, viscosity at 25°C and sol-gel phase transition point of the ink of the present invention can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink using a rheometer.

In the present invention, the ink viscosity and sol-gel phase transition point are values obtained by the following method. The ink is heated to 100°C and the viscosity is measured using a stress-controlled rheometer, Physica MCR301 (cone-plate diameter: 75 mm, cone angle: 1.0°) manufactured by Anton Paar. The ink is then cooled to 20°C at a shear rate of 11.7 (1/s) and a cooling rate of 0.1°C/s to obtain a viscosity temperature curve. The viscosities at 80°C and 25°C can be determined by reading the viscosities at 80°C and 25°C, respectively, on the viscosity temperature curve. The sol-gel phase transition point can be determined as the temperature at which the viscosity reaches 200 mPa·s on the viscosity temperature curve.

1.4 Ink Color
The color of the ink of the present invention is not particularly limited, and a coloring material corresponding to the color of the partition walls to be formed may be used. The color of the partition walls is preferably white to improve reflectance and brightness, and black to improve contrast, so the ink color is preferably white or black. Gray is also preferable for the color of the partition walls to control reflectance and contrast, so gray ink can also be used. The ink color can be adjusted by the content of each coloring material.

1.5 Ink Preparation Method
The ink of the present invention can be prepared by mixing the above-mentioned photopolymerizable composition, coloring material, gelling agent, etc., while heating using a known method.

<1.6 Inkjet ink set for partition wall formation>
The inkjet ink set for partition wall formation (hereinafter also simply referred to as "ink set") of the present invention is an inkjet ink set for forming partition walls between LED chips of an LED device, and comprises a first inkjet ink for partition wall formation and a second inkjet ink for partition wall formation, wherein the first inkjet ink for partition wall formation contains a photopolymerizable composition, a white colorant, and a gelling agent, and undergoes a sol-gel phase transition depending on the temperature, and the second inkjet ink for partition wall formation contains a photopolymerizable composition, a black colorant, and a gelling agent, and also undergoes a sol-gel phase transition depending on the temperature.

The components contained in the first partition wall forming inkjet ink and the second partition wall forming inkjet ink are as described above. By using such an ink set, it is possible to form partition walls composed of white partition walls and black partition walls, as described below.

The color of the inkjet ink for forming the first partition wall is preferably white or gray, and white is particularly preferred. The color of the inkjet ink for forming the second partition wall is preferably black. By using such an ink set, it is possible to form partition walls composed of white or gray partition walls and black partition walls, as described below. The color of the ink can be adjusted by the content of the colorant of each color.

<2. LED Device Manufacturing Method>
The method for manufacturing an LED device of the present invention is a method for manufacturing an LED device having partitions between LED chips, and includes a partition-forming step of patterning the partitions by an inkjet method, and is characterized in that the partition-forming step uses an inkjet ink for forming partitions, which contains a photopolymerizable composition, a colorant, and a gelling agent, and which undergoes a sol-gel phase transition depending on temperature.

The inkjet ink for forming partition walls used in the manufacturing method of the LED device is as described above.

In the partition wall formation process, the partition walls are patterned using the inkjet method. Specifically, ink droplets are ejected from an inkjet head and land on the substrate at the positions where the partition walls are to be formed, creating a pattern. The landed ink is irradiated with active energy rays to harden the ink, forming the partition walls. Patterning the partition walls using the inkjet method does not damage the LED chip as occurs with photolithography, and also makes it possible to form partition walls with fine shapes that are difficult to achieve using screen printing or coating methods.

The ejection method from the inkjet head may be either an on-demand method or a continuous method. On-demand inkjet heads may be electro-mechanical conversion types such as single-cavity, double-cavity, bender, piston, shear-mode, and shared-wall types, or electro-thermal conversion types such as thermal inkjet and bubble jet (Bubble Jet is a registered trademark of Canon Inc.).

Ejection stability can be improved by ejecting ink droplets from the inkjet head in a heated state. The ink temperature when ejected is preferably in the range of 40 to 100°C, and more preferably in the range of 40 to 90°C to further improve ejection stability. In particular, it is preferable to eject the ink at a temperature that results in a viscosity of 7 to 15 mPa·s, more preferably 8 to 13 mPa·s.

There are no particular restrictions on the method for heating the ink. For example, at least one of the ink supply system, such as the ink tank that makes up the head carriage, the supply pipe, and the anterior ink tank immediately before the head, the filtered piping, and the piezo head, can be heated using a panel heater, ribbon heater, or heated water.

It is preferable that the volume of ink droplets ejected be in the range of 2 to 20 pL.

The active energy rays can be selected from, for example, electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays, but ultraviolet rays are preferred.

The ink can be cured by irradiation with active energy rays all at once after all the ink required to form the partition walls has landed, or it can be cured in multiple steps by repeatedly ejecting the ink and irradiating it with active energy rays. When forming high or highly precise partition walls, it is preferable to cure the ink in multiple steps.

When ultraviolet light is used as the active energy ray, it can be irradiated at a wavelength of 395 nm using, for example, a water-cooled LED manufactured by Phoseon Technology. Using an LED as the light source can prevent poor ink curing caused by the ink melting due to the radiant heat from the light source.

When ultraviolet rays are used as active energy rays, the peak irradiance can be adjusted appropriately depending on the material and amount of the ink to be cured, but can be set within the range of 0.1 to 4.0 W/cm ² , for example.

When ultraviolet rays are used as active energy rays, the amount of light can be adjusted appropriately depending on the material and amount of ink to be cured, but can be set within the range of 100 to 5000 mJ/cm ² , for example.

In this partition wall formation process, partition walls of any color can be formed. For example, in one embodiment, when the partition wall formation process includes at least a white partition wall formation process, white partition walls can be formed to improve brightness. In another embodiment, when the partition wall formation process includes at least a black partition wall formation process, black partition walls can be formed to improve contrast. In yet another embodiment, when the partition wall formation process includes at least a gray partition wall formation process, gray partition walls can be formed to control reflectance and contrast.

In order to simultaneously improve brightness and contrast by forming partition walls composed of white partition walls and black partition walls positioned thereon, one embodiment may include a white partition wall formation process and a black partition wall formation process in which black partition walls are formed on the white partition walls formed in the white partition wall formation process. In this case, irradiation with active energy rays may be performed in both the white partition wall formation process and the black partition wall formation process, or may be performed together after the black partition wall formation process. Furthermore, in this embodiment, a gray partition wall formation process may be added between the white partition wall formation process and the black partition wall formation process, or the gray partition wall formation process may be performed instead of the white partition wall formation process.

<3 LED Device>
The LED device of the present invention is an LED device having partition walls between LED chips, characterized in that the partition walls contain a cured product of a photopolymerizable composition, a coloring material, and a gelling agent.

The dimensions, color, and pattern of the partitions shall be as described above.

The method for forming the partition walls is not limited to the inkjet method described above, but can also be formed by photolithography, coating, screen printing, etc.

The gelling agent contained in the partition walls is the same as that contained in the ink described above. By containing a gelling agent, the partition walls of the LED device have a rough surface, improving adhesion with the transparent encapsulant filled on the LED chip and improving the high-temperature durability of the LED device. Furthermore, the rough surface of the partition walls has a matte finish, which can reduce the reflectance of light from the viewing side.

The cured product of the photopolymerizable composition contained in the partition walls is a resin formed by curing a photopolymerizable composition similar to the photopolymerizable composition contained in the ink described above through irradiation with active energy rays. The colorant contained in the partition walls is the same as the colorant contained in the ink described above.

The LED device of the present invention preferably has a transparent encapsulant filled on the LED chip. This prevents the LED chip from deteriorating due to moisture. Resins such as polyvinyl carbazole and epoxy resins can be used as the transparent encapsulant.

The LED chip can be a known one, or a mini LED chip or a micro LED chip can also be used.

The substrate, cover glass, electrodes, circuits, wiring, and other components that may be included in the LED device of the present invention are not particularly limited, and known components can be used. Furthermore, if necessary, the LED device may also be configured to include a wavelength conversion layer or a color filter.

The color of the substrate is preferably black, since areas where no partitions or the like are formed can affect contrast. In particular, when partitions are formed in a pattern in which there are areas between pixels where no partitions are formed, as shown in Figure 7, a black substrate can further improve contrast. Examples of black substrates that can be used include substrates made of black material and substrates that have been blackened by sputtering or the like.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

<Preparation of Pigment Dispersion>
A black pigment dispersion, a white pigment dispersion A, and a white pigment dispersion B were prepared according to the following procedure.

(Preparation of Black Pigment Dispersion)
71.0 parts by weight of dipropylene glycol diacrylate and 9.0 parts by weight of a dispersant (Ajinomoto Fine-Techno Co., Ltd., Ajisper PB824) were placed in a stainless steel beaker and stirred for 1 hour while heating on a hot plate at 65 °C to dissolve the dispersant. After the resulting liquid was cooled to room temperature, 20.0 parts by weight of Pigment Black 7 (Mitsubishi Chemical Corporation, MA77) was added as a black pigment to obtain a mixed liquid. The resulting mixed liquid was placed in a glass bottle together with 200 g of zirconia beads (diameter: 0.5 mm), sealed, and dispersed for 5 hours using a paint shaker. The zirconia beads were then removed from the mixed liquid to obtain a black pigment dispersion.

(Preparation of White Pigment Dispersion A)
70.7 parts by mass of tripropylene glycol diacrylate (Miramer M200, manufactured by Miwon Corporation; "Miramer" is a registered trademark of the company) and 8 parts by mass of a dispersant (BYKJET-9151, manufactured by BYK Corporation; "BYKJET" is a registered trademark of the company) were placed in a stainless steel beaker and stirred for 1 hour while heating on a hot plate at 65°C to dissolve the dispersant. The resulting liquid was cooled to room temperature, and 21.3 parts by mass of titanium oxide (TCR-52, manufactured by Sakai Chemical Industry Co., Ltd.) was added as a white pigment to obtain a mixed liquid. The resulting mixed liquid was placed in a glass bottle together with 220 g of zirconia beads (diameter: 0.5 mm), sealed, and dispersed for 5 hours using a paint shaker. The zirconia beads were then removed from the mixed liquid to obtain White Pigment Dispersion A.

(Preparation of White Pigment Dispersion B)
70.7 parts by mass of tripropylene glycol diacrylate (Miramer M200, manufactured by Miwon Corporation; "Miramer" is a registered trademark of the company) and 8 parts by mass of a dispersant (BYKJET-9151, manufactured by BYK Corporation; "BYKJET" is a registered trademark of the company) were placed in a stainless steel beaker and stirred for 1 hour while heating on a hot plate at 65°C to dissolve the dispersant. The resulting liquid was cooled to room temperature, and then 21.3 parts by mass of zirconium oxide (Zirconeo, manufactured by ITEC Corporation) was added as a white pigment to obtain a mixed liquid. The resulting mixed liquid was placed in a glass bottle together with 220 g of zirconia beads (diameter: 0.5 mm), sealed, and dispersed for 5 hours using a paint shaker. The zirconia beads were then removed from the mixed liquid to obtain White Pigment Dispersion B.

<Ink Preparation>
Black pigment ink and white pigment ink were prepared according to the following procedure.

(Preparation of Black Pigment Inks 1 to 7)
The materials shown in Table I were placed in a stainless steel beaker and stirred for 1 hour while being heated to 80° C. on a hot plate. The resulting solution was filtered with a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVATEC while still being heated, to obtain black pigment inks 1 to 7.

The details of the materials shown in Table I are as follows:
DPGDA: dipropylene glycol diacrylate HDDA: 1,6-hexanediol diacrylate 3PO-TMPTA: 3PO-modified trimethylolpropane triacrylate 9EO-TMPTA: 9EO-modified trimethylolpropane triacrylate PEGDA (600): polyethylene glycol #600 diacrylate 4EO-PETA: 4EO-modified pentaerythritol tetraacrylate DAROCURE TPO: 2,4,6-trimethylbenzoin diphenylphosphine oxide, manufactured by BASF Speedcure ITX: 2-isopropylthioxanthone, manufactured by Lambson Irgastab UV-10: manufactured by BASF Black pigment dispersion: the black pigment dispersion prepared above Kaowax T1: a compound having a structure represented by the above general formula (G1), distearyl ketone, manufactured by Kao Corporation Unistar M-2222SL: a compound having a structure represented by the above general formula (G2), behenyl behenate, manufactured by NOF Corporation

(Preparation of White Pigment Inks 1 to 7)
The materials shown in Table II were placed in a stainless steel beaker and stirred for 1 hour while being heated to 80°C on a hot plate. The resulting solution was filtered with a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVATEC while still being heated, to obtain white pigment inks 1 to 7.

The details of the materials shown in Table II are as follows:
6EO-TMPTA: 6EO-modified trimethylolpropane triacrylate 4EO-HDDA: 4EO-modified hexanediol diacrylate TPGDA: tripropylene glycol diacrylate DAROCURE TPO: 2,4,6-trimethylbenzoin diphenylphosphine oxide, manufactured by BASF Irgacure 819: manufactured by BASF Irgastab UV-10: manufactured by BASF KF-352: manufactured by Shin-Etsu Chemical Co., Ltd. White pigment dispersion A: the white pigment dispersion A prepared above
White pigment dispersion B: the white pigment dispersion B prepared above
Kaowax T1: a compound having a structure represented by the above general formula (G1), distearyl ketone, manufactured by Kao Corporation Unistar M-2222SL: a compound having a structure represented by the above general formula (G2), behenyl behenate, manufactured by NOF Corporation

(Viscosity and sol-gel phase transition point)
The viscosities at 25°C, 80°C, and sol-gel phase transition points of the inks prepared above were determined by the following method. The inks were heated to 100°C and cooled to 20°C at a shear rate of 11.7 (1/s) and a cooling rate of 0.1°C/s while measuring the viscosity using a stress-controlled rheometer, Physica MCR301 (cone-plate diameter: 75 mm, cone angle: 1.0°), manufactured by Anton Paar. A viscosity temperature curve was then obtained. The viscosities at 25°C and 80°C were determined by reading the viscosities at 25°C and 80°C from the viscosity temperature curve. The sol-gel phase transition point was determined as the temperature at which the viscosity reached 200 mPa·s from the viscosity temperature curve. The viscosities at 25°C, 80°C, and sol-gel phase transition point of each ink are shown in Tables I and II.

<Fabrication of LED Device>
An LED device was fabricated in the following manner.

(Fabrication of LED Devices 1 to 16)
With reference to the method described in paragraphs [0091] to [0106] of the specification of JP-A-2021-110875, red, green, and blue LED chips were arranged on a substrate in the following procedure to form an LED device without a partition.

The LED chips used were micro LED chips measuring 100 μm x 100 μm x 100 μm. The number of pixels consisting of three-color micro LED chips was 80 x 80, for a total of 80 x 80 x 3 micro LED chips. The micro LED chips within a pixel were arranged horizontally, as shown in Figures 4 and 7. The spacing between adjacent micro LED chips within the same pixel was 250 μm. The pixel pitch was 1300 μm.

The drive substrate was a 200mm x 200mm alkali-free glass substrate with thin film transistors (TFTs), wiring, and Cu electrode pads corresponding to the number of micro-LED chips formed on it. The drive substrate was blackened by sputtering except for the area where it was bonded to the micro-LED chip.

The relay substrate was a non-alkali glass substrate of the same size as the drive substrate and 0.7 mm thick. PDMS (dimethylpolysiloxane) resin was formed on the relay substrate to a thickness of 10 μm.

The PDMS resin was formed by applying a uniform thickness of PDMS resin to the substrate surface using a laminating method, and then heating it in an oven at 100°C for 1 hour to thermally crosslink the PDMS resin. The PDMS resin was blended with Shin-Etsu Silicone SIM360 and CAT360 manufactured by Shin-Etsu Chemical Co., Ltd. to adjust the hardness of the finished product. The hardness of the finished product (after thermal crosslinking) was Shore A 60.

The micro LED chip was diced from the sapphire substrate on which the semiconductor layer was formed, transferred to a holding substrate, and then transferred to an intermediate substrate. Chip-side electrodes were formed on the micro LED chip, and 5 μm-high solder microbumps were formed on the chip-side electrodes. SAC (SnAgCu) solder was used.

To transfer the micro LED chips to the intermediate substrate, a stamp was used to arrange them on the intermediate substrate.

Next, any resin residue remaining on the micro LED chip and chip-side electrodes on the relay substrate was removed using an oxygen asher, and then the chip was treated with Ar plasma.

Next, after aligning the drive board and relay board, they were mass-bonded at the positions where their respective electrodes overlapped at a temperature below the solder melting point. This temporarily joined the chip-side electrodes and drive board-side electrodes via solder.

Next, the relay board was peeled off and removed.

Next, flux was applied to the surface of the drive board where the micro LED chip was temporarily attached, and the surface was heated in a reflow furnace to a temperature above the solder melting point. This reflow process mounted the micro LED chip.

Using the above procedure, red, green, and blue micro LED chips were placed on the substrate to form an LED device without a partition.

Next, using the black pigment ink 1 prepared above, partition walls with a width of 200 μm and a total height of 100 μm were formed in the pattern shown in Figure 7, covering the periphery of each micro LED chip of the LED device without partition walls formed above. The specific procedure is as follows.

Droplets of black pigment ink 1 were ejected using an inkjet device, and while patterning, uncured partition walls with a height of 20 μm after curing were formed. The temperature of the ink when ejected was adjusted to 80°C. The volume of the ink droplets when ejected was 5 pL. The uncured partition walls were irradiated with ultraviolet light at a light intensity of 1000 mJ/ ^cm2 , forming partition walls with a height of 20 μm.

Next, droplets of black pigment ink 1 were ejected onto the formed partition walls in the same manner as above to form uncured partition walls with a height of 20 μm after curing. The uncured partition walls were irradiated with ultraviolet light at a light intensity of 1000 mJ/ ^cm2 to form partition walls with a height of 40 μm.

The above process was repeated to form a partition wall with a width of 200 μm and a total height of 100 μm.

The above steps were used to perform the partition wall formation process, in which the partition walls were patterned using the inkjet method.

Next, polyvinylcarbazole was filled onto the micro LED chip as a transparent encapsulant using a dispenser, and the chip was then laminated with a cover glass.

LED device 1 was fabricated using the above steps.

In the preparation of LED device 1 above, the ink and transparent encapsulant were changed as shown in Table III to prepare LED devices 2 to 16.

(Fabrication of LED Devices 17 to 24)
Red, green, and blue micro LED chips were arranged on the substrate in the same manner as above to form an LED device without a partition formed thereon.

Next, using the white pigment ink 1 and black pigment ink 1 prepared above, partition walls with a width of 200 μm and a total height of 100 μm were formed in the pattern shown in Figure 7 to cover the periphery of each micro LED chip of the LED device without partition walls formed above. The specific procedure is as follows.

Droplets of white pigment ink 1 were ejected using an inkjet device, and while patterning, uncured partition walls with a height of 20 μm after curing were formed. The temperature of the ink when ejected was adjusted to 80°C. The volume of the ink droplets when ejected was 5 pL. The uncured partition walls were irradiated with ultraviolet light at a light intensity of 1000 mJ/ ^cm2 , forming partition walls with a height of 20 μm.

Next, droplets of white pigment ink 1 were ejected onto the formed partition walls in the same manner as above to form uncured partition walls with a height of 20 μm after curing. The uncured partition walls were irradiated with ultraviolet light at a light intensity of 1000 mJ/ ^cm2 to form partition walls with a height of 40 μm.

The above process was repeated to form white partition walls with a width of 200 μm and a total height of 80 μm.

Next, droplets of black pigment ink 1 were ejected onto the white partition walls formed above to form uncured partition walls with a height of 20 μm after curing. The uncured partition walls were irradiated with ultraviolet light at a light intensity of 1000 mJ/ ^cm2 to form black partition walls with a height of 20 μm. This resulted in the formation of partition walls with a width of 200 μm and a total height of 100 μm.

By following the above steps, a partition wall formation process was carried out, which included a white partition wall formation process and a black partition wall formation process in which black partition walls were formed on top of the white partition walls formed in the white partition wall formation process.

Next, polyvinylcarbazole was filled onto the LED chip as a transparent encapsulant using a dispenser, and the chip was then attached to a cover glass.

LED device 17 was fabricated using the above steps.

In the preparation of LED device 17 above, the ink and transparent sealant were changed as shown in Table III to prepare LED devices 18 to 24.

<Evaluation>
The LED device fabricated as described above was evaluated as follows.

(brightness)
The LED devices were turned on and their luminance was measured. For LED devices 1 to 8, the luminance of LED device 1 was set to 100, and the relative luminance value compared to this was calculated to obtain the relative luminance. Similarly, for LED devices 9 to 16, the luminance of LED device 9 was set to 100, and for LED devices 17 to 24, the luminance of LED device 17 was set to 100 to calculate the relative luminance.

The calculated relative luminance was evaluated according to the following criteria, and the evaluation results are shown in Table III.
○: Relative luminance is 80 or more ×: Relative luminance is less than 80

(High temperature durability)
The LED device was placed in a thermostat at a temperature of 85°C and a relative humidity of 85% and stored for 1500 hours. The luminance maintenance rate [%] was calculated from the luminance before and after 1500 hours of storage using the following formula.
Luminance maintenance rate [%] = luminance after storage / luminance before storage × 100

The high temperature durability was evaluated based on the calculated luminance maintenance rate [%] according to the following evaluation criteria. The evaluation results are shown in Table III.
○: Brightness maintenance rate is 95% or more ×: Brightness maintenance rate is less than 95%

(Transparent sealant adhesion)
The ink used in the fabrication of the LED device was applied to glass to create a 20 μm thick solid film, which was then cured by irradiating with UV light at a light intensity of 1000 mJ/ ^cm² . The process of applying ink to the cured solid film and irradiating with UV light at a light intensity of 1000 mJ/ ^cm² was repeated to create a total 100 μm solid film. The transparent encapsulant (polyvinyl carbazole or epoxy resin) used in the fabrication of the LED device was applied to the top layer of the solid film to create a 100 μm thick solid film. The sample was subjected to a cross-cut test in accordance with JIS K 5600-5-6 and evaluated using the following six-level classification (0 to 5). The evaluation results are shown in Table III.

0: The edges of the cut are completely smooth and there is no peeling on any of the grid cells.
1: Small peeling of the coating at the intersection of the cuts. The cross-cut area affected is not significantly more than 5%.
2: The coating is peeling along the edges of the cuts and/or at the intersections. Clearly more than 5% but not more than 15% of the cross-cut area is affected.
3: The coating has partially or completely peeled off significantly along the edges of the cuts and/or partially or completely peeled off in various areas of the mesh. The cross-cut area is clearly more than 15% affected but not more than 35%.
4: The coating is partially or completely peeled off in large areas along the edges of the cuts and/or partially or completely peeled off in several places. Not more than 35% of the cross-cut area is affected.
5: Any degree of peeling that cannot be classified even in classification 4.

From these results, it was confirmed that the inkjet ink for partition wall formation of the present invention, by containing a gelling agent, can improve the adhesion between the partition wall and the transparent encapsulant, thereby forming partition walls that can improve the high-temperature durability of LED devices.

The present invention can be used in an inkjet ink for forming partition walls, an inkjet ink set for forming partition walls, which can form partition walls between LED chips and improve the high-temperature durability of LED devices, a method for manufacturing LED devices using the same, and LED devices with improved high-temperature durability.

1 LED device 2 Substrate 3R Red LED chip 3G Green LED chip 3B Blue LED chip 4 Partition wall 4Wh White partition wall 4Bl Black partition wall 5 Transparent sealant 6 Cover glass

Claims (6)

1. An ink-jet ink for forming partition walls, for forming partition walls between LED chips of an LED device, comprising:
A photopolymerizable composition (excluding a case where the composition contains a photopolymerizable compound having no acidic group and a photopolymerizable compound having an acidic group), a colorant, and a gelling agent,
Sol-gel phase transition occurs depending on the temperature.
The ink-jet ink for forming partition walls, characterized in that the color material contains a white color material or a black color material. The ink-jet ink for forming partition walls according to claim 1 , wherein the photopolymerizable composition contains a (meth)acrylate compound as a component thereof. The viscosity at 25°C is in the range of 1 to 1 x 10 ⁴ Pa·s, and
The ink-jet ink for forming partition walls according to claim 1 or 2, which has a sol-gel phase transition point in the range of 40°C or higher and lower than 100°C. 3. The inkjet ink for forming partition walls according to claim 1, wherein the gelling agent contains at least one compound selected from compounds having a structure represented by the following general formula (G1) or (G2):
General formula (G1): R ₁ -CO-R ₂
General formula (G2): R ₃ -COO-R ₄
[In the formula, R ₁ to R ₄ each independently represent an alkyl chain having 12 or more carbon atoms and a linear portion, which may be branched.] 3. The ink-jet ink for forming partition walls according to claim 1, wherein the gelling agent is contained in an amount within a range of 0.5 to 5% by mass based on the total mass of the ink. An LED device having a partition between LED chips,
the partition wall contains a cured product of a photopolymerizable composition (excluding a case where the composition contains a photopolymerizable compound having no acidic group and a photopolymerizable compound having an acidic group), a colorant, and a gelling agent;
The LED device, wherein the partition walls are composed of at least white partition walls or black partition walls.