TWI899505B - Inkjet ink for forming partition wall, inkjet ink set for forming partition wall, method for manufacturing light-emitting diode device, and light-emitting diode device - Google Patents

Abstract

This invention provides a partition wall inkjet ink for forming partition walls between LED chips, which can enhance the high-temperature durability of LED devices. It also provides a partition wall inkjet ink set, a method for manufacturing LED devices using the inkjet ink, and an LED device with enhanced high-temperature durability. The partition wall inkjet ink of this invention, used to form partition walls between LED chips in an LED device, contains a photopolymerizable component, a colorant, and a gelling agent, and is characterized by undergoing a sol-gel phase transition via temperature.

Description

Inkjet ink for forming partition wall, inkjet ink set for forming partition wall, method for manufacturing light-emitting diode device, and light-emitting diode device

The present invention relates to an inkjet ink for forming partition walls, an inkjet ink set for forming partition walls, a method for manufacturing a light-emitting diode (LED) device, and a light-emitting diode (LED) device. More specifically, the invention relates to an inkjet ink for forming partition walls, which is formed between LED chips and can improve the high-temperature durability of LED devices.

In LED devices such as LED (light-emitting diode) displays, partition walls are used to prevent color mixing between adjacent LED chips. Traditionally, these partition walls have been formed using photolithography, coating, or screen printing. However, photolithography poses a risk of damage to the LED chips caused by the developer. Furthermore, coating is inefficient, and screen printing presents difficulties in achieving fine processing.

As a technology to solve these problems, Patent Documents 1 and 2, for example, disclose a method for forming partition walls using an inkjet method. Inkjet partition walls can be formed without contact with the LED chip, preventing damage to the chip. Furthermore, compared to coating methods, partition walls can be formed more efficiently and can be processed in a micro-fabricated manner.

On the other hand, LED devices are required to have durability to withstand long-term use, especially in high-temperature environments. The LED devices disclosed in Patent Documents 1 and 2, which use ink to form partition walls, lack sufficient high-temperature durability. Therefore, there is a need for inks that enhance the high-temperature durability of LED devices using inkjet-based partition wall formation. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2019-210438 [Patent Document 2] Japanese Patent Application Publication No. 2021-046528

[Problem to be solved by the invention]

The present invention is made in view of the above-mentioned problems and circumstances, and aims to provide a partition wall that can improve the high-temperature durability of an LED device, an inkjet ink for forming a partition wall between LED chips, an inkjet ink set for forming a partition wall, a method for manufacturing an LED device using the same, and an LED device with improved high-temperature durability. [Means for Solving the Problem]

To address the aforementioned issues, the inventors have examined the causes of these issues and have discovered that they can provide an inkjet ink for forming partition walls between LED chips, which can enhance the high-temperature durability of LED devices by creating an ink containing a photopolymerizable composition, a colorant, and a gelling agent that undergoes a sol-gel phase transition depending on temperature. This has led to the present invention. The aforementioned issues of the present invention are addressed by the following means.

1. This inkjet ink for forming partition walls, used to form partition walls between LED chips in LED devices, contains a photopolymerizable composition, a colorant, and a gelling agent. This inkjet ink for forming partition walls is characterized by undergoing a sol-gel phase transition under temperature.

2. The inkjet ink for forming a partition wall described in item 1, characterized by containing a (meth)acrylate compound as a component of the aforementioned photopolymerizable composition.

3. The aforementioned colorant contains a white colorant or a black colorant. The inkjet ink for forming partition walls characterized by being described in item 1 or 2.

4. Inkjet inks for forming partition walls having a viscosity within the range of 1 to 1×10 ⁴ Pa·s at 25°C and a sol-gel phase transition point within the range of 40°C to 100°C as described in any of the preceding items.

5. The inkjet ink for forming a partition wall described in any one of Items 1 to 4, characterized in that the gelling agent comprises at least one compound 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 a linear chain having 12 or more carbon atoms, and may also have a branched alkyl chain.]

6. The aforementioned gelling agent is contained in an amount within the range of 0.5-5% by mass based on the total ink mass. This is a partition wall forming inkjet ink characterized by any of the items 1 to 5.

7. A partition wall forming inkjet ink set for forming partition walls between LED chips in an LED device, comprising: a first partition wall forming inkjet ink and a second partition wall forming inkjet ink; the first partition wall forming inkjet ink contains a photopolymerizable composition, a white colorant, and a gelling agent, and undergoes a sol-gel phase transition upon temperature; the second partition wall forming inkjet ink contains a photopolymerizable composition, a black colorant, and a gelling agent, and undergoes a sol-gel phase transition upon temperature.

8. A method for manufacturing an LED device having partition walls between LED chips, comprising: a partition wall formation step in which the partition walls are patterned by an inkjet method; a partition wall formation step in which an inkjet ink containing a photopolymerizable composition, a colorant, and a gelling agent is used, and wherein the inkjet ink undergoes a sol-gel phase transition under temperature.

9. The aforementioned partition wall formation process is a method for manufacturing an LED device described in Item 8, characterized by at least a white partition wall formation process.

10. The aforementioned partition wall formation process is a method for manufacturing an LED device described in Item 8 or Item 9, characterized by at least a black partition wall formation process.

11. The method for manufacturing an LED device according to any one of items 8 to 10, characterized in that the barrier rib formation step comprises at least a white barrier rib formation step and a black barrier rib formation step of forming black barrier ribs on the white barrier ribs formed in the white barrier rib formation step.

12. An LED device having partition walls between LED chips, wherein the partition walls comprise a cured photopolymerizable composition, a colorant, and a gelling agent.

13. The LED device described in item 12, characterized in that the aforementioned partition walls are composed of at least white partition walls.

14. The LED device described in item 12 or 13, characterized in that the partition walls are composed of at least black partition walls.

15. An LED device according to any one of items 12 to 14, wherein the partition wall is composed of at least a white partition wall and a black partition wall located thereon. [Effect of the Invention]

Through the above-mentioned means of the present invention, a partition wall that can improve the high-temperature durability of an LED device is provided, an inkjet ink for forming a partition wall between LED chips, an inkjet ink set for forming a partition wall, a manufacturing method of an LED device using the same, and an LED device with improved high-temperature durability are provided.

Although the discovery mechanism or mechanism of action of the effects of the present invention is not clear, it can be inferred as follows.

The inkjet ink used to form partition walls of the present invention is characterized by containing a gelling agent. The inclusion of a gelling agent makes the surface of the partition walls formed using this ink rougher than when the ink does not contain a gelling agent. In LED devices, transparent encapsulants are often used to protect the LED chips. However, the roughened surface of the partition walls formed using the ink of this invention increases the contact area between the partition walls and the transparent encapsulant, improving adhesion. This reduces the formation of gaps between the partition walls and the transparent encapsulant, enhancing the sealing performance and improving the high-temperature durability of the LED device.

Through these discovery mechanisms or working mechanisms, 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.

The inkjet ink for forming partition walls of the present invention is characterized by containing a photopolymerizable composition, a colorant, and a gelling agent, and undergoing a sol-gel phase transition under temperature. This feature is common to or corresponds to the technical features of the following embodiments.

In an embodiment of the inkjet ink for forming the partition wall of the present invention, it is preferred that the photopolymerizable composition contain a (meth)acrylate compound from the viewpoints of polymerization rate and polymerization degree.

In an embodiment of the inkjet ink for forming partition walls of the present invention, the colorant preferably includes a white colorant or a black colorant. This allows for the formation of white partition walls that enhance brightness or black partition walls that enhance contrast.

In embodiments of the inkjet ink for forming partition walls of the present invention, a viscosity within the range of 1 to 1× ^10⁴ Pa·s at 25°C is preferred, as it allows for sufficient gelation upon landing and cooling to room temperature, resulting in excellent fixability. Furthermore, a sol-gel phase transition point within the range of 40°C to 100°C is preferred. A sol-gel phase transition point of 40°C or higher allows for rapid gelation after landing, resulting in improved fixability. Furthermore, a sol-gel phase transition point below 100°C provides improved usability and enhanced injection stability.

In an embodiment of the inkjet ink for forming the spacer walls of the present invention, the gelling agent preferably comprises at least one compound having a structure represented by the aforementioned general formula (G1) or (G2). Since the compound having a structure represented by the aforementioned general formula (G1) or the compound having a structure represented by the aforementioned general formula (G2) has a carbon number of 12 or more in a linear or branched chain carbide (alkyl) group, the gelling agent exhibits enhanced crystallinity and creates sufficient space within the box structure. Consequently, the ink medium, such as a polymerizable compound, is easily enclosed within the aforementioned space, further enhancing the ink's fixability.

In the inkjet ink for forming partition walls of the present invention, the gelling agent preferably contains 0.5-5% by mass of the ink as a whole. When the gelling agent content is within this range, the solubility and fixation properties of the gelling agent are improved.

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

The present invention provides a method for manufacturing an LED device having partition walls between LED chips, including a partition wall formation step in which the partition walls are patterned by an inkjet method. The partition wall formation step is characterized by using a partition wall forming inkjet ink containing a photopolymerizable composition, a colorant, and a gelling agent, and undergoing a sol-gel phase transition under temperature.

In an embodiment of the LED device manufacturing method of the present invention, the partition wall forming step preferably includes at least a white partition wall forming step, thereby forming white partition walls that enhance brightness.

In an embodiment of the LED device manufacturing method of the present invention, the partition wall forming step preferably includes at least a black partition wall forming step, thereby forming black partition walls that enhance contrast.

In an embodiment of the LED device manufacturing method of the present invention, the barrier rib formation step preferably includes at least a white barrier rib formation step and a black barrier rib formation step in which black barrier ribs are formed on top of the white barrier ribs formed in the white barrier rib formation step. This allows for barrier ribs to be formed with a black top surface, which improves contrast, and a partially white side surface, which improves brightness.

The LED device of the present invention has partition walls between LED chips. The partition walls are characterized by containing a cured photopolymerizable composition, a colorant, and a gelling agent.

In an embodiment of the LED device of the present invention, it is preferred that the partition walls are at least white partition walls, thereby increasing brightness.

In an embodiment of the LED device of the present invention, it is preferred that the partition walls are at least black partition walls, thereby improving contrast.

In an embodiment of the LED device of the present invention, the partition walls preferably comprise at least white partition walls and black partition walls positioned thereon. This allows the top surface, which improves contrast, to be black, while the side surface, which improves brightness, is partially white, thereby simultaneously improving brightness and contrast.

The present invention, its components, and the configurations and aspects for implementing the present invention are described in detail below. However, in this case, "~" is inclusive and means that the numerical values described before and after it are used as lower and upper limits.

<1. Inkjet Ink for Partition Wall Formation> The inkjet ink for partition wall formation of the present invention (hereinafter simply referred to as "ink") is used to form partition walls between LED chips in an LED device. The inkjet ink contains a photopolymerizable component, a colorant, and a gelling agent, and is characterized by undergoing a sol-gel phase transition under temperature.

<1.1 Application of Ink> The ink of this invention is an inkjet ink for forming partition walls between LED chips in LED devices.

In the present invention, a "partition wall" is a wall formed between LED chips in an LED device to prevent color mixing between adjacent pixels or adjacent LED chips, and has a height of at least 25% of the height of the LED chips.

Figures 1A-C and 2A-C are schematic cross-sectional views of a portion of an LED device, illustrating the appearance of partition walls formed using the ink of the present invention. In LED device 1, red LED chips 3R, green LED chips 3G, and blue LED chips 3B are arranged on substrate 2. The partition walls 4 (black partition walls 4B1 and white partition walls 4Wh) can be formed to cover the periphery of each LED chip, as shown in Figures 1A-C, or to cover the periphery of the pixels formed by the three-color LED chips, as shown in Figures 2A-C. Figures 1A-C and 2A-C also illustrate a transparent sealing agent 5 and a cover glass 6 used to enclose the LED chips.

While the height of the LED chips on the partition walls should be at least 25%, to prevent color mixing, it's preferably at least 50%, and even more preferably at least 75%. Furthermore, since excessively high partition walls reduce brightness, the ideal height should be no more than 200% of the LED chip height.

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

Figure 4 shows an LED device without partition walls, while Figures 5-7 show LED devices with partition walls formed in different patterns. Figures 4-7 are schematic diagrams of a portion of the LED device viewed from above, showing a four-pixel area, with the red LED chip 3R, green LED chip 3G, and blue LED chip 3B forming a single pixel.

FIG5 shows a state equivalent to that seen from above in FIG1A-C and FIG3A-C (the transparent sealing agent 5 and the cover glass 6 are not shown, and the number of LED chips is also different), in which partition walls 4 are formed around the respective LED chips.

FIG6 shows a state equivalent to that seen from above in FIG2A-C (transparent sealing agent 5 and cover glass 6 are not shown), in which a partition wall 4 is formed around a pixel formed by three-color LED chips.

FIG7 is the same as FIG5, showing that although the partition wall 4 is formed around each LED chip, the partition wall is formed with a certain width, and there is also a pattern in which there is no partition wall between pixels.

However, Figures 1 to 7 illustrate exemplary embodiments and do not limit the pattern of 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 with a roughly constant width at the lower and upper portions, a shape with a wider lower portion, or a shape with a reversed-pushing width at the upper portion. The width of the partition wall is not particularly limited.

While the color of the partition walls is not particularly limited, white is preferred from the perspective of reflecting light emitted by the LED chips and improving brightness. Furthermore, black is preferred from the perspective of improving contrast. Figures 1A and 2A illustrate an LED device with white partition walls 4Wh, while Figures 1B and 2B illustrate an LED device with black partition walls 4Bl. Furthermore, the partition wall color is preferably gray to control reflectivity and contrast.

In this disclosure, "white" refers to a color with a lightness of 8.0 or greater and a chroma of 2.0 or less in the Munsell color system (JIS Z 8721). Furthermore, "black" refers to a color with a lightness of 2.0 or less and a chroma of 2.0 or less in the Munsell color system (JIS Z 8721). "Gray" refers to a mixture of white and black.

The ink barrier walls of the present invention can be formed by stacking two or more different colored barrier walls. For example, as shown in Figures 1C, 2C, and 3C, a barrier wall 4 formed by a white barrier wall 4Wh and a black barrier wall 4Bl positioned thereon can achieve both enhanced brightness and contrast by having a black top surface that improves contrast and a partially white side surface that improves brightness. However, when stacking two or more different colored barrier walls, the height and width dimensions described above refer to the overall dimensions of the barrier wall.

The ink of the present invention is used to form the above-mentioned partition walls.

<1.2 Ink Composition> The ink of this invention is characterized by containing a photopolymerizable component, a colorant, and a gelling agent. The following describes these components in detail.

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

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

The polymerizable compound is not particularly limited, and compounds that initiate polymerization and cure by polymerization and crosslinking upon exposure to active energy rays (electron beams, ultraviolet rays, α rays, γ rays, and X-rays, etc.) in the presence or absence of a photopolymerization initiator can be used. However, the polymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, and mixtures thereof.

Examples of the polymerizable compound include cationic polymerizable compounds, radical polymerizable compounds, and mixtures thereof. From the viewpoint of polymerization rate and polymerization degree, radical polymerizable compounds are preferred, and (meth)acrylate compounds are more preferred.

"Free radical polymerizable compounds" refer to compounds having ethylenically unsaturated double bonds in their molecules. Free radical polymerizable compounds can be monofunctional or polyfunctional.

Examples of free-radically polymerizable compounds include unsaturated carboxylic acid ester compounds, such as (meth)acrylate compounds. However, in the present invention, "(meth)acrylate" refers to either acrylate or methacrylate. Furthermore, in the present invention, "(meth)acrylate compounds" include compounds containing (meth)acryloyl groups in the main chain, compounds containing (meth)acryloyl groups as side chains, and compounds containing (meth)acryloyl groups as substituent groups in side chains.

Examples of (meth)acrylate compounds having no acidic group include isoamyl (meth)acrylate, octadecyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isooctadecyl (meth)acrylate, 2-ethylhexyl-diethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiglycol (meth)acrylate, and methoxydiglycol (meth)acrylate. Monofunctional acrylates such as methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, and t-butylcyclohexyl (meth)acrylate, and monofunctional acrylates including 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, Acrylates, polypropylene glycol 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, tricyclodecane di(meth)acrylate hydroxymethyl ester, PO addition of bisphenol A di(meth)acrylate, hydroxy pivalate neopentyl glycol di(meth)acrylate, polytetraethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate Bifunctional acrylates such as triol diacrylate and tricyclodecyl dimethanol diacrylate, and polyfunctional acrylates such as trihydroxymethylpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexyl(meth)acrylate, trihydroxymethylpropyl tetra(meth)acrylate, glycerol tri(meth)acrylate, and pentaerythritol isoethoxy tetra(meth)acrylate.

Examples of (meth)acrylate compounds having a carboxyl group include (meth)acrylate compounds having a hydroxyl group, or (meth)acrylates obtained by adding an acid anhydride to oligomers thereof. Examples of such acid anhydrides include anhydrous phthalic acid, isophthalic acid, terephthalic acid, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, nadic anhydride, maleic anhydride, trimellitic anhydride, methylcyclohexenetricarboxylic anhydride, and pyromellitic dianhydride. Specific examples of the (meth)acrylate compound having a carboxyl group include (meth)acryloyloxyalkoxycarbonylphthalic acid such as 2-carboxyethyl acrylate, 4-(meth)acryloyloxyethoxycarbonylphthalic acid, 4-(meth)acryloyloxybutoxycarbonylphthalic acid, 4-(meth)acryloyloxyhexyloxycarbonylphthalic acid, 4-(meth)acryloyloxydecyloxycarbonylphthalic acid, and 4-(meth)acryloyloxy (Meth)acryloyloxyalkoxyalkylphthalic acids such as acryloyloxyethoxyethoxyphthalic acid, mono-2-(acryloyloxy)ethyl succinate, 2,2-bis(acrylamido)acetic acid, 2-(meth)acryloylethyl ether succinic acid, 2-(meth)acryloylethyl ether phthalic acid, 2-(meth)acryloylethyl ether-2-hydroxyethyl-phthalic acid, and 2-(meth)acryloylethyl ether hexahydrophthalic acid.

Examples of the (meth)acrylate compound having phosphoric acid include bis(2-(meth)acryloyloxyethyl)phosphate, 2-hydroxyethyl (meth)acrylate, ethyl (meth)acrylate phosphate, 3-chloro-2-phosphinopropyl (meth)acrylate, polyoxyethylene glycol (meth)acrylate phosphate, 2-(meth)acryloyloxyhexanoic acid ethyl phosphate, and mono-2-(methacryloyloxy)ethyl phosphate. Furthermore, 2-(meth)acryloyloxyethyl phosphate (meaning 2-acryloyloxyethyl phosphate or 2-methacryloyloxyethyl phosphate, hereinafter referred to as such), 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, 1 (Meth)acryloyloxyalkyl phosphates such as 8-(meth)acryloyloxystearyl phosphate and 20-(meth)acryloyloxyeicosyl phosphate; di(meth)acryloyloxyalkyl phosphates such as 1,3-di(meth)acryloyloxypropyl-2-phosphate; (meth)acryloyloxyalkylaryl phosphates such as 2-(meth)acryloyloxyethylphenyl phosphate, 2-(meth)acryloyloxyethylanisyl phosphate, and 2-(meth)acryloyloxyethyltolyl phosphate; (meth)acryloyloxyalkylaryl phosphates such as 2-(meth)acryloyloxyethylphenylphosphonic acid; Phosphonic acids; 2-(meth)acryloyloxyethyl thiophosphate, 2-(meth)acryloyloxypropyl thiophosphate, 3-(meth)acryloyloxypropyl thiophosphate, 4-(meth)acryloyloxybutyl thiophosphate, 6-(meth)acryloyloxyhexyl thiophosphate, 8-(meth)acryloyloxyoctyl thiophosphate, 10-(meth)acryloyloxydecyl thiophosphate, 12-(meth)acryloyloxylauryl thiophosphate, 16-(meth)acryloyloxycetyl thiophosphate, 18-(meth)acryloyloxystearyl thiophosphate, 2 ...decyl thiophosphate, 16-(meth)acryloyloxycetyl thiophosphate, 18-(meth)acryloyloxystearyl thiophosphate, 20-(meth)acryloyloxydecyl thiophosphate, 12-(meth)acryloyloxydecyl thiophosphate, 12-(meth)acryloyloxydecyl thiophosphate, 16-(meth)acryloyloxycetyl thiophosphate, 18-(meth)acryloyloxydecyl thiophosphate, 18-(meth)acryloyloxydecyl thiophosphate, 18-(meth)acryloyloxydecyl thiophosphate, 18-(meth)acryloyloxydecyl thiophosphate, 18-(meth)acrylo (Meth)acryloyloxyalkyl thiophosphates such as (meth)acryloyloxyeicosyl thiophosphate; di(meth)acryloyloxyalkyl thiophosphates such as 1,3-di(meth)acryloyloxypropyl-2-thiophosphate; (meth)acryloyloxyalkylaryl thiophosphates such as 2-(meth)acryloyloxyethylphenyl thiophosphate, 2-(meth)acryloyloxyethylanisilyl thiophosphate, and 2-(meth)acryloyloxyethyltolyl thiophosphate; (meth)acryloyloxyalkylaryl thiophosphates such as 2-(meth)acryloyloxyethylphenylphosphonic acid.

Examples of the (meth)acrylate compound having a sulfonic acid group include methacrylic acid, bis(3-sulfopropyl)itaconic acid, 2-(sulfo)ethyl methacrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-sulfopropyl methacrylic acid, 3-sulfopropyl methacrylate, and 2-acrylamido-2-methylpropanesulfonic acid.

Examples of the monofunctional (meth)acrylate compound having a hydroxyl 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, p-hydroxymethylphenylmethyl (meth)acrylate, and 1-hydroxybutyl (meth)acrylate. acrylate, 2-(hydroxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, methyl α-hydroxymethacrylate, ethyl α-hydroxymethacrylate, hydroxyalkyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate.

Examples of the (meth)acrylate compound having a multifunctional hydroxyl group include 2-hydroxy-3-acryloyloxypropyl methyl acrylate, dipentaerythritol pentyl (meth)acrylate, ethylene oxide-added pentaerythritol tetra(meth)acrylate, trihydroxymethylpropane diacrylate, glycerol di(meth)acrylate, glycerol acrylate methacrylate, pentaerythritol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionate dipentaerythritol tri(meth)acrylate, hydroxypivalaldehyde-modified dihydroxymethylpropane tri(meth)acrylate, sorbitol tri(meth)acrylate, sorbitol tetra(meth)acrylate, sorbitol pentyl (meth)acrylate, sorbitol hexyl (meth)acrylate, and pentaerythritol tri(meth)acrylate.

The (meth)acrylate may be a modified product. Examples of the modified (meth)acrylate include ethylene oxide-modified trihydroxymethylpropane tri(meth)acrylate, ethylene oxide-modified (meth)acrylates such as ethylene oxide-modified pentaerythritol tetraacrylate, caprolactone-modified (meth)acrylates such as caprolactone-modified trihydroxymethylpropane tri(meth)acrylate, and caprolactamide-modified (meth)acrylates such as caprolactamide-modified dipentaerythritol hexa(meth)acrylate.

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

"Cationically polymerizable compounds" refer to compounds containing a cationically polymerizable group in their molecules. Examples of cationically polymerizable compounds include epoxy compounds, vinyl ether compounds, and oxazoline compounds.

Examples of epoxy compounds include aliphatic epoxy compounds (3,4-epoxyepoxyhexylmethyl-3',4'-epoxyepoxyhexylcarboxylate, bis(3,4-epoxyepoxyhexylmethyl)adipate, vinyl cyclohexene epoxide, ε-caprolactone-modified 3,4-epoxyepoxyhexylmethyl-3',4'-epoxyepoxyhexylcarboxylate, 1-methyl-4-(2-methylepoxyethyl)-7-oxobiscyclo[4,1,0]heptane, 2-(3,4-epoxyepoxyhexyl-5,5-spiro-3,4-epoxy)cyclohexanone-methyl-dioxane, and bis(2,3-epoxycyclopentyl)ether, etc.), aliphatic epoxy compounds (1,4-butanediol diglycidyl ether , diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerol, triglycidyl ether of trihydroxymethylpropane, diglycidyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, polyglycidyl ether of polyether polyols, etc.) and aromatic epoxy compounds (diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol A with alkylene oxide appendages oily ether, diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of hydrogenated bisphenol A with alkylene oxide appendages, polyglycidyl ether of bisphenol A, polyglycidyl ether of bisphenol A with alkylene oxide appendages, polyglycidyl ether of hydrogenated bisphenol A, polyglycidyl ether of hydrogenated bisphenol A with alkylene oxide appendages, and phenolic epoxy resins, etc.

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, cyclohexyl dimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl 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, cyclohexyl dimethanol divinyl ether, and trihydroxymethylpropane 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-diphenylethanedioneoxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, 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-oxocyclobutyl)methoxy]methyl}benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and di[1-ethyl(3-oxocyclobutyl)]methyl ether.

The photopolymerizable composition of the present invention preferably further comprises a photopolymerization initiator as needed.

The amount of photopolymerization initiator can be arbitrarily set within a range that allows the ink to be sufficiently cured by irradiation with active energy rays without compromising the ink jetting stability. For example, the amount of photopolymerization initiator is preferably within the range of 0.1-20% by mass, and more preferably within the range of 1.0-12% by mass, relative to the total ink.

The photopolymerization initiator may be any agent capable of initiating polymerization of the aforementioned polymerizable compounds. For example, when the ink contains a free radical polymerizable compound, the photopolymerization initiator may be a free radical photopolymerization initiator; when the ink contains a cationic polymerizable compound, the photopolymerization initiator may be a cationic photopolymerization initiator.

A single type of photopolymerization initiator may be used alone, or two or more types may be used in combination. Furthermore, a combination of a free radical photopolymerization initiator and a cationic photopolymerization initiator may also be used.

As free radical photopolymerization initiators, there are two types: intramolecular bond cleavage type and intramolecular dehydrogenation type.

Examples of intramolecular bond cleavage type free radical photopolymerization initiators include acetophenone-based photopolymerization initiators (diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropyl-1-ketone, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropyl-1-ketone, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-oxolinyl (4-methylthiophenyl)propyl-1-ketone, and 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butanone, etc.), benzoin-based photopolymerization initiators (benzoin, benzoin methyl ether, and benzoin isopropyl ether, etc.), acylphosphine oxide-based photopolymerization initiators (2,4,6-trimethylbenzyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzyl)-phenylphosphine oxide, bis-(2,6-dimethylbenzyl)-2,4,4-trimethylpentylphosphine oxide, etc.), diphenylethanedione, and methylphenylglyoxylate, etc.

Among these, acylphosphine oxide-based photopolymerization initiators are preferred from the perspective of further enhancing the curability of polymerizable compounds, especially the curability caused by the UV-LED light curing process.

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

Examples of intramolecular dehydrogenation-type free radical photopolymerization initiators include phenyl ketone-based photopolymerization initiators (phenyl ketone, methyl o-benzoylbenzoate, 4-phenyl phenyl ketone, 4,4'-dichloro phenyl ketone, hydroxy phenyl ketone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated phenyl ketone, 3,3',4,4'-tetrakis(t-butylperoxycarbonyl) phenyl ketone, and 3 , 3'-dimethyl-4-methoxydiphenyl ketone, etc.), thioxanthone-based photopolymerization initiators (2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, etc.), aminodiphenyl ketone-based photopolymerization initiators (Michler's ketone, 4,4'-diethylaminodiphenyl ketone, etc.), 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone, etc.

Examples of cationic photopolymerization initiators include photoacid generators. Examples of photoacid generators include diazonium salts, aromatic onium compounds containing ammonium, iodonium, coronium, and phosphonium, such _{as B} ( _C6F5 ) _4- ^, _PF6- , ^{AsF6- ,} _SbF6- ^, and _CF3SO3- salts; sulfonates that generate sulfonic acids; halides that generate photohydrohalides; ^and iron diolefin complexes _.

(Colorant) The ink of the present invention is characterized by containing a colorant. The colorant can be a pigment or a dye.

The color of the colorant is not particularly limited; a colorant corresponding to the color of the partition walls to be formed can be used. However, when the color of the partition walls is to increase brightness, white is preferred to increase reflectivity, and black is preferred to increase contrast, so the colorant is preferably white or black. As a black colorant, a black colorant can be used alone, or a black colorant can be formed by mixing red, green, and blue colorants. Furthermore, since gray is preferred to control reflectivity and contrast, a gray colorant can be used as the colorant contained in the ink. A gray colorant can be prepared, for example, by mixing a white colorant and a black colorant.

While the colorant content is not particularly limited, for white colorants, it is preferably within the range of 2-30 mass%, more preferably 5-20 mass%, and even more preferably 6-15 mass%. For black colorants, it is preferably within the range of 1-20 mass%, more preferably 1.5-15 mass%, and even more preferably 2-10 mass%.

The following specifically describes pigments that can be suitably used 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. Among the above white pigments, titanium oxide and zirconium oxide are preferred, and titanium oxide is more preferred.

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

Examples of zirconium oxide that can be used as the white pigment include the commercially available Zirconeo (manufactured by Aitec, "Zirconeo" is a registered trademark of the company).

In the example of black pigment, it contains pigments selected from Pigment Black 7, 28, 26 or a mixture thereof.

Examples of commercially available black pigments include Black Pigment (manufactured by Mikuni Co., Ltd.), CHROMOFINE BLACK A-1103 (manufactured by Dainichi Seika Co., Ltd.), Colortex Black 702, U905 (manufactured by Sanyo Pigment 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).

In the example of red or magenta pigment, it contains 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 Orange 13, 16, 20, and 36 pigments 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.

In the case of green pigments, pigments selected from Pigment Green 7, 26, 36, and 50, or mixtures thereof, are included.

In the example of yellow pigment, it contains 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 a mixture thereof.

Examples of commercially available pigments, in addition to those listed above, include CHROMOFINE YELLOW 2080, 5900, 5930, AF-1300, 2700L, CHROMOFINE ORANGE 3700L, 6730, CHROMOFINE SCARLET 6750, CHROMOFINE MAGEBTA 6880, 6886, 6891N, 6790, 6887, CHROMOFINE VIOLET RE, CHROMOFINE RED 6820, 6830, and CHROMOFINE BLUE. HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, CHROMOFINE GREEN2GN, 2GO, 2G-550D, 5310, 5370, 6830, SEIKAFAST YELLOW 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, SEIKAFAST RED 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, SEIKALIGHT ROSE R40, SEIKALIGHT VIOLET B800, 7805, SEIKAFAST MAROON 460N, SEIKAFAST ORANGE 900, 2900, SEIKALIGHT SEIKALIGHT BLUE C718、A612、CYANINE BLUE 4933M, 4933GN-EP, 4940, 4973 (Dainichi Seika 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 (DIC Corporation); 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, ColortexBlue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403; Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo INKI Co., Ltd.); Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostaperm Blue B2G (manufactured by Hoechst Industries); Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant Co., Ltd.), etc.

The pigment can be dispersed, for example, by a ball mill, sand mill, grinding mill, drum mill, blender, Henschel mixer, colloid mill, ultrasonic homogenizer, bead mill, wet jet mill, or paint mixer.

When using pigments as colorants, to improve inkjet head ejection performance, the average dispersed particle size of the pigment particles is preferably within the range of 50-150nm, with a maximum particle size within the range of 300-1000nm. The most preferred average dispersed particle size is within the range of 80-130nm.

The average dispersed particle size of pigment particles is determined by dynamic light scattering using a ZETASIZER NANO ZSP (manufactured by Malvern). However, since the ink containing the pigment is highly concentrated, the measurement light cannot penetrate it. Therefore, the ink was diluted 200-fold for measurement. Measurements were performed at room temperature (25°C).

The dispersion of pigments is adjusted through pigments, dispersants, dispersion media, dispersion conditions, and filtering conditions.

When the ink of the present invention uses a pigment as a colorant, it may further contain a dispersant to improve the dispersibility of the pigment. Examples of dispersants include carboxylates with hydroxyl 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, polyetherester-type anionic surfactants, naphthalene formaldehyde sulfonic acid condensate salts, aromatic formaldehyde sulfonic acid condensate salts, polyoxyethylene alkyl phosphates, nonylphenol polyoxyethylene ethers, and octadecylamine acetate salts. Examples of commercially available dispersants include the Solsperse series from Avecia and the PB series from Ajinomoto Fine-Techno.

When the ink of the present invention uses a pigment as a colorant, it may contain a dispersing agent as needed. The dispersing agent can be selected according to the pigment.

The total amount of dispersant and dispersing aid is preferably in the range of 1-50% by mass of the pigment.

When the ink of the present invention uses a pigment as a colorant, it may optionally contain a dispersion medium for dispersing the pigment. While solvents are acceptable as the dispersion medium, to minimize damage to the LED chip, a polymerizable compound (especially a low-viscosity monomer) such as the one described above is preferred.

(Gelling Agent) The ink of this invention contains a gelling agent, which improves the adhesion between the partition wall and the transparent sealing agent, thereby enhancing the high-temperature durability of the LED device.

Furthermore, by containing a gelling agent, the ejected and impacted ink droplets can be turned into a gel state and temporarily fixed (fixed), making it easy to form fine-shaped partition walls or partition walls with a high aspect ratio.

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, thereby reducing the reflectivity 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 the gelling agent of the present invention include dialkyl ketones, fatty acid esters, fatty acid amides, and oil gelling agents.

Furthermore, the gelling agent of the present invention preferably comprises at least one compound 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 a linear chain having 12 or more carbon atoms, and may also have a branched alkyl chain.]

Since the ketone wax having the structure represented by the general formula (G1) or the ester wax having the structure represented by the general formula (G2) has a linear or branched carbonyl group (alkyl group) with 12 or more carbon atoms, the crystallinity of the gelling agent is further improved, and sufficient space is generated in the box structure described below. As a result, the ink medium such as the polymerizable compound is easily enclosed within the above space, further improving the ink's fixability.

Furthermore, the carbon number of R ₁ to R ₄ is preferably 26 or less. When the carbon number is 26 or less, the melting point of the gelling agent is not excessively increased, and the ink does not need to be excessively heated when ejecting the ink.

From the above viewpoints, _R1 and _R2 , or _R3 and _R4 are preferably linear alkyl groups having 12 or more and 23 or less carbon atoms.

Furthermore, from the viewpoint of increasing the gelation temperature of the ink and rapidly gelling the ink after impact, it is preferred that either _R1 or _R2 , or either _R3 or _R4 , be a saturated alkyl group having 12 to 23 carbon atoms.

From the above viewpoints, both _R1 and _R2 , or both _R3 and _R4, are more preferably saturated alkyl groups having 11 or more and less than 23 carbon atoms.

Examples of ketone waxes having the structure represented by the general formula (G1) include dioctyl ketone (C24-C24), dibehenol (C22-C22), distearyl ketone (C18-C18), diaramidone (C20-C20), disalanol (C16-C16), dimyristone (C14-C14), dilauryl ketone (C12-C12), lauryl ketone (C16-C16), and dioctyl ketone (C14-C14). Cardone (C12-C14), lauryl palmitone (C12-C16), myristyl palmitone (C14-C16), myristyl stearone (C14-C18), myristyl behenone (C14-C22), palmitostearone (C16-C18), palmitostearone (C16-C22), and stearyl behenone (C18-C22). However, the carbon number in parentheses above refers to the number of carbon atoms in each of the two hydrogen carbonyl groups separated by the carbonyl group.

Examples of commercially available ketone waxes having a structure represented by general formula (G1) include Stearonne (manufactured by Alfa Aeser Co., Ltd.; Stearonne), 18-Pentatriacontanon (manufactured by Alfa Aeser Co., Ltd.), Hentriacontan-16-on (manufactured by Alfa Aeser Co., Ltd.), and KAO WAX 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), arachidyl arachidate (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C1 8), 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). However, the carbon number in parentheses above refers to the number of carbon atoms in each of the two hydrogen carbonyl groups separated by the ester group.

Examples of commercially available ester waxes having a structure represented by general formula (G2) include UNISTER M-2222SL and Spermaceti (both manufactured by NOF Corporation, "UNISTER" is a registered trademark of the company), EXCEPARL SS and EXCEPARL MY-M (both manufactured by Kao Corporation, "EXCEPARL" 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 AMREPS PC (manufactured by Advanced Alcohol Industries, Ltd., "AMREPS" is a registered trademark of the company).

Since most commercially available products are mixtures of two or more types, they can be separated and purified as needed and then incorporated into the ink. Among these gels, ketone waxes, ester waxes, higher fatty acids, higher alcohols, and fatty acid amides are preferred for enhancing fixation.

The gelling agent content is preferably within the range of 0.5-5.0% by mass of the total ink. Within this range, the gelling agent's solubility and fixation properties are excellent. Furthermore, from this perspective, the gelling agent content in the ink is more preferably within the range of 0.5-2.5% by mass.

Furthermore, from the following perspective, it is best for the gelling agent to crystallize within the ink at a temperature below the gelling temperature of the ink. The gelling temperature refers to the temperature at which the gelling agent transitions from the sol phase to the gel phase when the sol or liquefied ink is heated or cooled, causing the ink's viscosity to change dramatically. Specifically, the gelling temperature is determined by measuring the viscosity of the sol or liquefied ink using a viscoelasticity tester (e.g., MCR300, manufactured by Physica) while cooling it. The temperature at which the viscosity increases dramatically is considered the gelling temperature of the ink.

When the gelling agent crystallizes within the ink, a structure may form within the three-dimensional space formed by the plate-like crystallization of the gelling agent, enclosing the ink medium, such as a polymerizable compound (hereinafter referred to as a "box structure"). When the box structure is formed, the liquid ink medium is retained within the aforementioned space, making it more difficult for ink droplets to spread and wet, and thus improving the ink's fixability.

The best way to form a cassette structure is when the ink medium (e.g., polymerizable compound) and the gelling agent in the ink are miscible. In contrast, if the ink medium (e.g., polymerizable compound) and the gelling agent in the ink are phase-separated, it may be difficult to form a cassette structure.

(Solvents with a standard boiling point of 250°C or less) The ink of this invention preferably contains no more than 25% solvents with a standard boiling point (boiling point at 1 atmosphere) of 250°C or less. This prevents damage to the LED chip and reduces environmental impact. The content of solvents with a standard boiling point of 250°C or less is preferably no more than 15%, and more preferably no more than 5%.

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

(Other Ingredients) The ink of the present invention may further contain other ingredients such as polymerization inhibitors and surfactants, within the range necessary to achieve the desired effects of the present invention. The ink of the present invention may contain only one of these ingredients, or two or more of these ingredients.

Examples of polymerization inhibitors include (alkyl)phenol, hydroquinone, o-catechol, resorcinol, p-methoxyphenol, t-butyl o-catechol, t-butylhydroquinone, pyrogallol, 1,1-trinitrophenylhydrazine, phenanthridine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, copper iron reagent, N-nitrosophenyl hydroxylamine aluminum, tris-p-nitrobenzyl, N-(3-oxyanilino-1,3-dimethylbutylene)aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-propofol, butyraldehyde oxime, methyl ethyl ketone oxime, and cyclohexanone oxime.

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

The amount of the polymerization inhibitor can be arbitrarily set within a range that can achieve the effects of the present invention. The amount of the polymerization inhibitor is, for example, 0.001% by mass or more and less than 1.0% by mass based on the total ink.

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

Examples of polysilicone-based surfactants include polyether-modified polysiloxane compounds, specifically Tegorad 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, "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 of the hydrophobic groups of conventional surfactants are replaced with fluorine atoms. Examples of fluorine-based surfactants include Megafac F (manufactured by DIC Corporation, "Megafac" is a registered trademark of the company), Surflon (manufactured by AGC Seimi Chemical, "Surflon" is a registered trademark of the company), Fluorad FC (manufactured by 3M, "Fluorad" is a registered trademark of the company), Monflor (manufactured by Imperial Chemical Industries), Zonyls (manufactured by E. I. du Pont de Nemours and Company), Licowet VPF (manufactured by Hoechst AG), and FTERGENT (manufactured by NEOS, "FTERGENT" is a registered trademark of the company).

The amount of surfactant can be arbitrarily set within a range that can achieve the effects of the present invention. The amount of surfactant is, for example, 0.001% by mass to less than 1.0% by mass relative to the entire 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, "sol-gel phase transition" refers to a reversible change from a fluid sol at high temperatures to a non-fluid gel at low temperatures, with the sol-gel phase transition point as the boundary.

When the viscosity of the ink of the present invention at 25°C is within the range of 1~1×10 ⁴ Pa·s, it is preferable that the ink can be fully gelled when the ink is cooled to room temperature after being ejected, and the fixation is good.

Furthermore, from the perspective of further improving the ejection performance of the 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, 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 between 40°C and 100°C. When the sol-gel phase transition point is above 40°C, the ink gels quickly after impact, resulting in improved fixability. Furthermore, when the sol-gel phase transition point is below 100°C, the ink's usability improves and injection stability is enhanced. To enable ink ejection at lower temperatures and reduce the load on the inkjet device, the sol-gel phase transition point of the ink of the present invention is more preferably between 40°C and 60°C.

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

<1.4 Ink Color> The ink color of the present invention is not particularly limited; a colorant corresponding to the color of the partition walls to be formed can be used. However, if the partition walls are to be brighter, white is preferred to increase reflectivity, while black is preferred to increase contrast. Therefore, the ink color is preferably white or black. Furthermore, if the partition walls are to be gray to control reflectivity and contrast, gray ink may be used. The ink color is adjusted by adjusting the content of each colorant.

<1.5 Ink Preparation Method> The ink of the present invention can be prepared by mixing the aforementioned photopolymerizable composition, colorant, and gelling agent while heating them using conventional methods.

<1.6 Inkjet Ink Set for Partition Wall Formation> The inkjet ink set for partition wall formation of the present invention (hereinafter simply referred to as the "ink set") is used to form partition walls between LED chips in an LED device. The inkjet ink set comprises a first inkjet ink for partition wall formation and a second inkjet ink for partition wall formation. 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 under temperature. 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 under temperature.

The components of the first and second inkjet inks for forming partition walls are as described above. By using such an ink set, partition walls consisting of white partition walls and black partition walls described below can be formed.

The inkjet ink used to form the first partition walls is preferably white or gray, with white being particularly preferred. Furthermore, the inkjet ink used to form the second partition walls is preferably black. Using this ink set, partition walls consisting of white partition walls or gray and black partition walls, as described below, can be formed. The ink color is adjusted by adjusting the content of each colorant.

<2 LED Device Manufacturing Method> The present invention's LED device manufacturing method comprises a partition wall formation step in which the partition walls are patterned using an inkjet method. This partition wall formation step is characterized by using a partition wall forming inkjet ink containing a photopolymerizable composition, a colorant, and a gelling agent, and undergoing a sol-gel phase transition under temperature.

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

During the partition wall formation process, inkjet printing is used to pattern the partition walls. Specifically, ink droplets ejected from an inkjet head land on the substrate where the partition walls are to be formed, creating a pattern. The landed ink is then irradiated with active energy rays, which hardens the ink and forms the partition walls. By patterning the partition walls using inkjet printing, similar to photolithography, the process avoids damaging the LED chip and allows for the formation of fine partition walls that are difficult to achieve using screen printing or coating methods.

The inkjet head can be ejected either on-demand or continuously. Inkjet heads for on-demand use may be single-chamber, dual-chamber, supply-type, piston-type, shared-mode, or shared-wall types, employing electro-mechanical conversion methods, as well as thermal jet and bubble jet (bubble jet is a registered trademark of Canon Inc.) types employing electro-thermal conversion methods.

By heating the ink droplets before discharging them from the inkjet head, discharging stability can be improved. The ink temperature during discharging is preferably between 40 and 100°C, and more preferably between 40 and 90°C for even greater stability. Discharging is particularly effective when the ink viscosity is between 7 and 15 mPa·s, and more preferably between 8 and 13 mPa·s.

The method for heating the ink is not particularly limited. For example, at least one of the ink supply system, including the ink tank of the printhead cartridge, the supply pipe, the ink tank in the front chamber of the printhead, the piping with the filter, and the piezo head, can be heated using a plate heater, a strip heater, or warm water.

The ideal ink droplet size is 2-20 pL.

The active energy rays can be selected from electron rays, ultraviolet rays, α rays, γ rays, and X rays, for example, but ultraviolet rays are preferred.

The hardening of the ink formed by irradiation with active energy rays is performed simultaneously after all necessary ink has been deposited during partition wall formation. Alternatively, the hardening can be performed in multiple steps by repeating the ejection of ink and irradiation with active energy rays. This is preferably performed in multiple steps when forming high partition walls or highly detailed partition walls.

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

The peak illuminance when irradiating ultraviolet rays as active energy rays can be appropriately adjusted by the material or amount of the hardened ink, for example, it can be within the range of 0.1~4.0W/ ^cm2 .

The amount of ultraviolet light used as active energy ray can be appropriately adjusted according to the material or amount of the ink to be cured, and can be within the range of 100-5000 mJ/ ^cm2 , for example.

The partition wall formation process can form partition walls of any color. For example, in one embodiment, if the partition wall formation process includes at least a white partition wall formation process, white partition walls can be formed to enhance brightness. Alternatively, in one embodiment, if the partition wall formation process includes at least a black partition wall formation process, black partition walls can be formed to enhance contrast. Furthermore, in one embodiment, if the partition wall formation process includes at least a gray partition wall formation process, gray partition walls can be formed to control reflectivity and contrast.

Furthermore, to simultaneously enhance brightness and contrast, one embodiment includes a white partition wall formation process and a black partition wall formation process, in which black partition walls are formed on top of the white partition walls formed in the white partition wall formation process. In this case, irradiation with active energy rays can be performed separately for the white partition wall formation process and the black partition wall formation process, or both processes can be performed together after the black partition wall formation process. Furthermore, in this embodiment, a gray partition wall formation process can be added between the white partition wall formation process and the black partition wall formation process, replacing 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. The partition walls are characterized by containing a cured photopolymerizable composition, a colorant, and a gelling agent.

The size, color, and pattern of the partition walls are as described above.

The method of forming the partition wall is not limited to the aforementioned inkjet method, and can be formed by photolithography, coating, screen printing, etc.

The gelling agent contained in the partition walls is the same as that in the aforementioned ink. The partition walls of this LED device have a roughened surface due to the inclusion of the gelling agent, which improves adhesion with the transparent sealing agent filling the LED chip and enhances the high-temperature durability of the LED device. Furthermore, the roughened surface of the partition walls creates a matte effect, reducing the reflectivity of light from the viewing side.

The cured product of the photopolymerizable composition contained in the partition wall is the same photopolymerizable composition as that contained in the aforementioned ink, and is a resin that cures upon exposure to active energy rays. Furthermore, the colorant contained in the partition wall is the same as that contained in the aforementioned ink.

The LED device of the present invention preferably includes a transparent sealing agent on the LED chip. This prevents moisture from degrading the LED chip. Resins such as polyvinyl carbazole or epoxy resins can be used as the transparent sealing agent.

The LED chip may be a known one, and a MINI LED chip or a MICRO LED chip may also be used.

The substrate, cover glass, electrodes, circuits, wiring, and other components of the LED device of the present invention are not particularly limited and may be any known component. Furthermore, the device may include a wavelength conversion layer or a color filter layer as needed.

However, since the color of the substrate without partition walls affects contrast, black is preferred. In particular, as shown in Figure 7, in a pattern where there are areas between pixels without partition walls, contrast can be further enhanced by using a black substrate when partition walls are formed. For example, a black substrate can be used, made of a black material or treated with a blackening process such as sputtering. [Example]

Hereinafter, although the present invention is specifically described with reference to the following examples, the present invention is not limited thereto. However, in the examples, although "parts" or "%" are used, unless otherwise specified, they represent "parts by mass" or "% by mass".

<Preparing Pigment Dispersions> Prepare black pigment dispersion, white pigment dispersion A, and white pigment dispersion B using 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 (Ajisper PB824, manufactured by Ajinomoto Fine Techno Co., Ltd.) 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 cooling the resulting liquid to room temperature, 20.0 parts by weight of Pigment Black 7 (MA77, manufactured by Mitsubishi Chemical Corporation) were added as a black pigment to form a mixed liquid. The resulting mixture, along with 200 g of zirconium oxide balls (0.5 mm diameter), was placed in a sealed glass bottle and dispersed in a paint mixer for 5 hours. The zirconium oxide balls were then removed from the mixture to obtain a black pigment dispersion.

Preparation of White Pigment Dispersion A 70.7 parts by weight of tripropylene glycol diacrylate (Miramer M200, manufactured by Miwon Co., Ltd., "Miramer" is a registered trademark of the company) and 8 parts by weight of a dispersant (BYKJET-9151, manufactured by BYK Co., Ltd., "BYKJET" is a registered trademark of the company) were placed in a stainless steel beaker and heated on a hot plate at 65°C while stirring for 1 hour to dissolve the dispersant. After cooling the resulting liquid to room temperature, 21.3 parts by weight of titanium oxide (TCR-52, manufactured by Sakai Chemical Industry Co., Ltd.) was added as a white pigment to obtain a mixed solution. The resulting mixture, along with 220g of zirconium oxide balls (0.5mm diameter), was placed in a tightly closed glass bottle and dispersed in a paint blender for 5 hours. The zirconium oxide balls were then removed from the mixture to obtain white pigment dispersion A.

Preparation of White Pigment Dispersion B 70.7 parts by weight of tripropylene glycol diacrylate (Miramer M200, manufactured by Miwon Co., Ltd., "Miramer" is a registered trademark of the company) and 8 parts by weight of a dispersant (BYKJET-9151, manufactured by BYK, "BYKJET" is a registered trademark of the company) were placed in a stainless steel beaker and heated on a hot plate at 65°C while stirring for 1 hour to dissolve the dispersant. After cooling the resulting liquid to room temperature, 21.3 parts by weight of zirconium oxide (Zirconeo, manufactured by ITEC) was added as a white pigment to obtain a mixed solution. The resulting mixture, along with 220g of zirconium oxide balls (0.5mm diameter), was placed in a tightly closed glass bottle and dispersed in a paint blender for 5 hours. The zirconium oxide balls were then removed from the mixture to obtain white pigment dispersion B.

<Ink Preparation> Use the following procedure to prepare the black and white pigment inks.

(Preparation of Black Pigment Inks 1-7) Place the materials shown in Table I in a stainless steel beaker and heat to 80°C on a hot plate while stirring for 1 hour. While heating, filter the resulting solution through a 3μm Teflon (registered trademark) membrane filter manufactured by ADVATEC to obtain Black Pigment Inks 1-7.

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 trihydroxymethylpropane triacrylate 9EO-TMPTA: 9EO-modified trihydroxymethylpropane triacrylate PEGDA(600): Polyethylene glycol #600 diacrylate 4EO-PETA: 4EO-modified pentaerythritol tetraacrylate DAROCURE TPO: 2,4,6-Trimethylbenzyldiphenylphosphine, 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 KAO WAX T1: A compound having the structure represented by the general formula (G1), distearyl ketone, manufactured by Kao Corporation UNISTER M-2222SL: Compound having the structure represented by the general formula (G2) above, behenyl behenate, manufactured by NOF Corporation

(Preparation of White Pigment Inks 1-7) Place the materials shown in Table II in a stainless steel beaker and heat to 80°C on a hot plate while stirring for 1 hour. While heating, filter the resulting solution through a 3μm Teflon (registered trademark) membrane filter manufactured by ADVATEC to obtain White Pigment Inks 1-7.

The details of the materials shown in Table II are as follows. 6EO-TMPTA: 6EO-modified trihydroxymethylpropane triacrylate 4EO-HDDA: 4EO-modified hexanediol diacrylate TPGDA: tripropylene glycol diacrylate DAROCURE TPO: 2,4,6-trimethylbenzyldiphenylphosphine 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: White Pigment Dispersion A prepared above White Pigment Dispersion B: White Pigment Dispersion B prepared above KAO WAX T1: Compound having the structure represented by general formula (G1) above, distearyl ketone, manufactured by Kao Corporation UNISTER M-2222SL: Compound having the structure represented by general formula (G2) above, behenyl behenate, manufactured by NOF Corporation

(Viscosity and Sol-Gel Phase Transition Point) The viscosity at 25°C and 80°C, as well as the sol-gel phase transition point, of the prepared ink were determined using the following method. The ink was heated to 100°C and measured using a fatigue-controlled rheometer (Physica MCR301, Anton Paar, Inc., with a cone diameter of 75 mm and a cone angle of 1.0°). The viscosity temperature curve was then obtained while the ink was cooled to 20°C at a shear rate of 11.7 (1/s) and a cooling rate of 0.1°C/s. The viscosity at 25°C and 80°C was determined by reading the viscosity at 25°C and 80°C, respectively, from the viscosity temperature curve. The sol-gel phase transition point is the temperature at which the viscosity reaches 200 mPa·s, as determined from the temperature-dependent viscosity curve. The viscosity at 25°C, 80°C, and the sol-gel phase transition point of each ink are shown in Tables I and II.

<LED Device Production> Use the following steps to produce an LED device.

(Fabrication of LED Devices 1-16) Referring to the method described in paragraphs [0091]-[0106] of Japanese Patent Application Laid-Open No. 2021-110875, red, green, and blue LED chips were arranged on a substrate using the following procedure to form an LED device without partition walls.

The LED chips used are 100μm × 100μm × 100μm microLED chips. The three-color microLED chips form an 80×80 pixel, using a total of 80×80×3 microLED chips. The microLED chips are arranged within a pixel as shown in Figures 4 and 7, with the three-color microLED chips arranged horizontally. The spacing between adjacent microLED chips within the same pixel is 250μm. Furthermore, the pixel gap is 1300μm.

The driver substrate is constructed on a 200mm x 200mm alkali-free glass substrate, with a number of Cu electrode pads corresponding to the number of TFTs (thin-film transistors), wiring, and micro-LED chips. Except for the bonding area with the micro-LED chips on the driver substrate, the substrate is blackened by sputtering.

The intermediate substrate is the same size as the driver substrate and is made of 0.7mm thick, alkali-free glass. PDMS (polydimethylsiloxane) resin is deposited on the intermediate substrate to a thickness of 10μm.

PDMS resin is formed by applying a uniform film thickness to the substrate surface in layers. The PDMS resin is then heated in a 100°C oven for one hour to thermally crosslink the PDMS resin. The PDMS resin is manufactured by Shin-Etsu Chemical Co., Ltd., using Shin-Etsu SLICONES SIM360 and CAT360, and the final hardness is adjusted. The final hardness (after thermal crosslinking) is Shore A60 rubber.

The micro-LED chip is cut from the sapphire substrate on which the semiconductor layer is formed, transferred to a holding substrate, and then to an intermediate substrate. Chip-side electrodes are formed on the micro-LED chip, and micro-bumps with a height of 5μm are formed on these chip-side electrodes. The solder is made of SAC (SnAgCu).

The transfer of the intermediate substrate is done by stamping, arranging the MICRO LED chips on the intermediate substrate.

Next, the resin residue remaining on the micro-LED chip and the chip-side electrodes on the intermediate substrate is removed by oxygen ashing and then treated with Ar plasma.

Next, after aligning the driver substrate and the intermediate substrate, they are joined together at a temperature below the melting point of the solder at the location where the electrodes overlap. This creates a temporary bond between the chip-side electrode and the driver substrate-side electrode through soldering.

Next, the intermediate substrate is peeled off and removed.

Next, flux is applied to the surface of the MICRO LED chip on the driver substrate, which is then heated in a reflow oven to a temperature above the melting point of the solder. After this reflow process, the MICRO LED chip is mounted.

Through the above process, red, green, and blue MICRO LED chips are arranged on the substrate to form an LED device without partition walls.

Next, the prepared black ink 1 was used to coat the perimeter of each micro-LED chip in the previously formed LED device without partition walls, using the pattern shown in Figure 7, to form partition walls with a width of 200 μm and a total height of 100 μm. The specific steps are as follows.

An inkjet device was used to eject droplets of black pigment ink 1, patterning the area while simultaneously forming uncured partition walls with a height of 20 μm after curing. The ink temperature during ejection was maintained at 80°C. The droplet volume during ejection was 5 pL. Ultraviolet light was then irradiated onto the uncured partition walls at a dose of 1000 mJ/ ^cm² , forming partition walls with a height of 20 μm.

Next, droplets of the same black ink 1 as above were ejected onto the partition walls, forming uncured partition walls with a height of 20 μm after curing. The uncured partition walls were then irradiated with ultraviolet light at a dose of 1000 mJ/ ^cm² , resulting in a partition wall height of 40 μm.

Repeat the above process to form partition walls with a width of 200 μm and a total height of 100 μm.

After the above steps, the partition wall patterning process is carried out by inkjet printing.

Next, a dispenser is used to fill the MICRO LED chip with polyvinyl carbazole as a transparent sealing agent and bond it to the cover glass.

Through the above steps, the LED device 1 is manufactured.

In the fabrication of the aforementioned LED device 1, the ink and transparent sealing agent were modified as shown in Table III to fabricate LED devices 2 to 16.

(Fabrication of LED Devices 17-24) Using the same method as above, red, green, and blue micro LED chips are placed on the substrate to form an LED device without partition walls.

Next, using the prepared white ink 1 and black ink 1, the pattern shown in Figure 7 was used to coat the perimeter of each micro-LED chip in the previously formed LED device without partition walls, forming partition walls with a width of 200 μm and a total height of 100 μm. The specific steps are as follows.

Using an inkjet device, droplets of white pigment ink 1 were ejected, patterning the ink while forming uncured partition walls with a height of 20 μm after curing. The ink temperature during ejection was maintained at 80°C. The droplet volume during ejection was 5 pL. Ultraviolet light was then irradiated onto the uncured partition walls at a dose of 1000 mJ/ ^cm² , forming partition walls with a height of 20 μm.

Next, droplets of the same white ink 1 as above were ejected onto the partition walls, forming uncured partition walls with a height of 20 μm after curing. The uncured partition walls were then irradiated with ultraviolet light at a dose of 1000 mJ/ ^cm² , resulting in a partition wall height of 40 μm.

Repeat the above process to form white partitions with a width of 200 μm and a total height of 80 μm.

Next, droplets of black ink 1 were ejected onto the white partitions formed above, forming uncured partitions with a height of 20 μm after curing. These uncured partitions were then irradiated with ultraviolet light at a dose of 1000 mJ/ ^cm² , forming black partitions with a height of 20 μm. This resulted in partitions with a width of 200 μm and a total height of 100 μm.

Through the above steps, a partition wall forming process including a white partition wall forming process and a black partition wall forming process of forming black partition walls on the white partition walls formed in the white partition wall forming process is performed.

Next, a dispenser is used to fill the LED chip with polyvinyl carbazole as a transparent sealing agent and bond it to the cover glass.

Through the above steps, the LED device 17 is manufactured.

In the production of the aforementioned LED device 17, the ink and transparent sealing agent were changed as shown in Table III to produce LED devices 18-24.

<Evaluation> The LED devices fabricated above were used to conduct the following evaluations.

(Brightness) Light up the LED devices and measure their brightness. For LED devices 1-8, set the brightness of LED device 1 to 100 and calculate the relative brightness compared to this value. Similarly, for LED devices 9-16, set the brightness of LED device 9 to 100, and for LED devices 17-24, set the brightness of LED device 17 to 100 to calculate the relative brightness.

Based on the calculated relative brightness, the brightness was evaluated using the following criteria. The evaluation results are shown in Table III. ○: Relative brightness 80 or higher ×: Relative brightness less than 80

(High-Temperature Durability) The LED device was placed in a hot machine at 85°C and 85% relative humidity for 1500 hours. The brightness maintenance rate [%] was calculated using the following formula from the brightness before and after the 1500-hour storage period. Brightness maintenance rate [%] = brightness after storage / brightness before storage × 100

Based on the calculated brightness maintenance rate [%], high-temperature durability was evaluated using the following evaluation criteria. The evaluation results are shown in Table III. ○: Brightness maintenance rate is 95% or higher ×: Brightness maintenance rate is less than 95%

(Transparent Sealant Adhesion) A 20μm-thick flat coating was prepared on glass using ink used in LED device manufacturing. The coating was then cured by UV irradiation at 1000mJ/ ^cm² . The cured coating was then repeatedly coated with ink and irradiated with UV light at 1000mJ/ ^cm² , creating a total 100μm-thick flat coating. A transparent sealing agent (polyvinyl carbazole or epoxy resin) used in LED device manufacturing was applied on top of this coating to create a 100μm-thick flat coating. This sample was subjected to a cross-section test according to JIS K 5600-5-6, and evaluated using the following six-step scale (0-5). The evaluation results are shown in Table III.

0: The cut edge is completely smooth, with no peeling at any mesh. 1: Minor peeling of the coating at the cut intersections. The effect of the cross-cuts is clearly no more than 5%. 2: The coating peels along the cut edge and/or at the intersections. The effect of the cross-cuts is clearly more than 5% but less than 15%. 3: Major peeling of the coating occurs partially or completely along the cut edge and/or partially or completely in various areas of the mesh. The effect of the cross-cuts is clearly more than 15% but less than 35%. 4: Major peeling of the coating occurs partially or completely along the cut edge and/or partially or completely in several meshes. The impact of the cross-section is clearly not more than 35%. 5: Any degree of peeling that cannot be classified in Category 4.

These results demonstrate that the inkjet ink for forming partition walls of the present invention, by containing a gelling agent, improves the adhesion between the partition walls and the transparent sealing agent, thereby enabling the formation of partition walls that enhance the high-temperature durability of LED devices. [Industrial Applicability]

The present invention provides an inkjet ink for forming partition walls between LED chips, an inkjet ink set for forming partition walls, a method for manufacturing an LED device using the inkjet ink, and an LED device 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 sealing agent 6: Cover glass

[Figure 1A] A cross-sectional view of a portion of an LED device showing the shape of a partition wall formed by the ink of the present invention. Figure 1A [Figure 1B] A cross-sectional view of a portion of an LED device showing the shape of a partition wall formed by the ink of the present invention. Figure 1B [Figure 1C] A cross-sectional view of a portion of an LED device showing the shape of a partition wall formed by the ink of the present invention. Figure 1C [Figure 2A] A cross-sectional view of a portion of an LED device showing the shape of a partition wall formed by the ink of the present invention. Figure 2A [Figure 2B] A cross-sectional view of a portion of an LED device showing the shape of a partition wall formed by the ink of the present invention. Figure 2B [Figure 2C] A cross-sectional view of a portion of an LED device showing the shape of a partition wall formed by the ink of the present invention. Figure 2C [Figure 3A] Schematic diagram showing a portion of an LED device with partition walls formed using the ink of the present invention. [Figure 3B] Schematic diagram showing a portion of an LED device with partition walls formed using the ink of the present invention. [Figure 3C] Schematic diagram showing a portion of an LED device with partition walls formed using the ink of the present invention. [Figure 4] Schematic diagram showing an LED device without partition walls formed. [Figure 5] Schematic diagram showing a pattern in which partition walls are formed around individual LED chips. [Figure 6] Schematic diagram showing a pattern in which partition walls are formed around pixels composed of three-color LED chips. [Figure 7] shows a pattern where partition walls are formed around each LED chip, but the partition walls are formed with a certain width, and there are areas between pixels where no partition walls are formed.

1: LED device

2:Substrate

3R: Red LED chip

3G: Green LED chip

3B: Blue LED chip

4: Next door

4Wh: White partition

4Bl: Black partition wall

5: Transparent sealant

6: Cover glass

Claims (11)

A partition wall forming inkjet ink is used to form partition walls between LED chips of an LED device by an inkjet method. The partition wall forming inkjet ink is characterized by comprising a photopolymerizable composition, a colorant, and a gelling agent, and undergoing a sol-gel phase transition depending on the temperature. The photopolymerizable composition comprises a (meth)acrylate compound having a viscosity within the range of 1 to 1×10 ⁴ Pa·s at 25°C and a sol-gel phase transition point within the range of 40°C to less than 100°C. The gelling agent comprises at least one compound 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 [wherein, R ₁ to R ₄ each independently have a linear chain portion having 12 or more carbon atoms, and may also have a branched alkyl chain. The height of the partition wall is not less than 75% and not more than 200% of the height of the LED chip. The colorant includes a white colorant and a black colorant. The content of the white colorant is in the range of 2 to 6 mass % relative to the total ink, and the content of the black colorant is in the range of 1 to 1.5 mass % relative to the total ink. The inkjet ink for forming a partition wall as recited in claim 1, wherein the gelling agent is contained in an amount within a range of 0.5 to 5 mass % relative to the entire ink. A partition wall forming ink jet ink set is used to form partition walls between LED chips of an LED device. The partition wall forming ink jet ink set is characterized by comprising a first partition wall forming ink jet ink and a second partition wall forming ink jet ink. The first partition wall forming ink jet ink contains a photopolymerizable composition, a white colorant, and a gelling agent, and is subjected to sol-gel phase transition by temperature. The second partition wall forming ink jet ink is The inkjet ink contains a photopolymerizable composition, a black colorant, and a gelling agent, and undergoes a sol-gel phase transition due to temperature. The height of the partition wall is not less than 75% and not more than 200% of the height of the LED chip. The content of the white colorant is within the range of 2-6% by mass relative to the total ink, and the content of the black colorant is within the range of 1-1.5% by mass relative to the total ink. A method for manufacturing a light-emitting diode device having partitions between LED chips is characterized by a partition wall formation step in which the partition walls are patterned by an inkjet method. In the partition wall formation step, a partition wall-forming inkjet ink containing a photopolymerizable composition, a colorant, and a gelling agent, which undergoes a sol-gel phase transition at a temperature, is used. The height of the partition walls is not less than 75% and not more than 200% of the height of the LED chips. The colorants include a white colorant and a black colorant, with the white colorant content ranging from 2% to 6% by mass relative to the total ink, and the black colorant content ranging from 1% to 1.5% by mass relative to the total ink. In the method for manufacturing a light-emitting diode device as recited in claim 4, the partition wall forming step includes at least a white partition wall forming step. In the method for manufacturing a light-emitting diode device as recited in claim 4 or 5, the partition wall forming step includes at least a black partition wall forming step. The method for manufacturing a light-emitting diode device as recited in claim 4 or 5, wherein the partition wall forming step comprises at least a white partition wall forming step and a black partition wall forming step of forming black partition walls on the white partition walls formed in the white partition wall forming step. A light-emitting diode device having partitions between LED chips, wherein the partitions comprise a cured photopolymerizable composition, a colorant, and a gelling agent, wherein the height of the partitions is not less than 75% and not more than 200% of the height of the LED chips, and wherein the colorants comprise white and black colorants, wherein the content of the white colorant is within a range of 2-6 mass % relative to the total ink, and the content of the black colorant is within a range of 1-1.5 mass % relative to the total ink. In the light-emitting diode device of claim 8, the partition walls are at least composed of white partition walls. In the light-emitting diode device of claim 8 or 9, the partition walls are at least composed of black partition walls. The light-emitting diode device according to claim 8 or 9, wherein the partition walls are composed of at least white partition walls and black partition walls located thereon.