Inkjet resin composition and display device

Abstract

An inkjet resin composition according to an embodiment and a display device prepared from the inkjet resin composition are provided. The inkjet resin composition includes 16 wt% to 24 wt% of a urethane oligomer, 56 wt% to 84 wt% of a monomer, 4 wt% to 6 wt% of a crosslinking agent, 4 wt% to 6 wt% of an additive, and 1 wt% to 3 wt% of a photoinitiator, and the content of the semi-crystalline polymer in the urethane oligomer is from 5% by weight to 50% by weight.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0096709 filed in the Korean Intellectual Property Office on July 25, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an inkjet resin composition and a display device using the inkjet resin composition. Background Art

[0004] With the development of information technology, the importance of display devices as a connecting medium between users and information is becoming more and more prominent.

[0005] Recently, research and development on a foldable display device, a bendable display device, a rollable display device, and the like, which take advantage of a flexible display panel that can be bent or folded, are underway.

[0006] Such a display device can be applied to various fields such as televisions and monitors as well as portable electronic devices and wearable devices.

[0007] Recently, portable electronic devices such as smartphones and tablet PCs are becoming lighter and thinner for ease of portability, and various studies are being conducted in various fields for ease of use.

[0008] Specifically, a "foldable" electronic device with a flexible display provides a relatively larger screen than a general bar-type electronic device, but when the electronic device is folded, the size is reduced, making it easy to carry. Therefore, it has attracted much attention as an electronic device that meets the tastes of consumers.

[0009] In the case of such a foldable display device, it is necessary to ensure the reliability of the folding or bending operation of each member used.

[0010] Furthermore, an adhesive resin for forming an adhesive resin layer applied to display devices of various shapes needs to have stability in terms of components of display devices of various shapes. Summary of the invention

[0011] Embodiments are directed to providing an inkjet resin composition having improved impact resistance and a display device including the inkjet resin composition.

[0012] The inkjet resin composition according to the embodiment includes 16 wt % to 24 wt % of a urethane oligomer, 56 wt % to 84 wt % of a monomer, 4 wt % to 6 wt % of a crosslinking agent, 4 wt % to 6 wt % of an additive, and 1 wt % to 3 wt % of a photoinitiator, and the urethane oligomer includes a semi-crystalline polymer, and the content of the semi-crystalline polymer in the urethane oligomer is 5 wt % to 50 wt %.

[0013] The urethane oligomer may have a molecular weight of 3,000 to 6,000.

[0014] The urethane oligomer may further include an amorphous polymer.

[0015] The amorphous polymer may be polyethylene oxide.

[0016] The semi-crystalline polymer may include polycaprolactone having a molecular weight of 1,000 to 5,000.

[0017] The semi-crystalline polymer may include at least one selected from the group consisting of polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyarylate, poly(DPAA), polyetherimide, and polyoxymethylene.

[0018] The monomers may include 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate, and exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acrylate.

[0019] The additives may include a silane coupling agent, an adhesion promoter, and an anti-yellowing agent.

[0020] The photoinitiator may include a short wavelength photoinitiator causing the inkjet resin composition to be cured at a wavelength of 320 nm to 365 nm and a long wavelength photoinitiator causing the inkjet resin composition to be cured at a wavelength of 370 nm to 420 nm.

[0021] The inkjet resin composition may have a viscosity of 30 cp or less.

[0022] A display device according to an embodiment includes a display panel, a cover window disposed on one surface of the display panel, and an adhesive resin layer disposed between the display panel and the cover window, wherein the adhesive resin layer contains a cured inkjet resin composition, the cured inkjet resin composition is a cured layer of an inkjet resin composition, the inkjet resin composition includes 16 wt % to 24 wt % of a urethane oligomer, 56 wt % to 84 wt % of a monomer, 4 wt % to 6 wt % of a cross-linking agent, 4 wt % to 6 wt % of an additive, and 1 wt % to 3 wt % of a photoinitiator, and the urethane oligomer includes a semi-crystalline polymer, and the content of the semi-crystalline polymer in the urethane oligomer may be 5 wt % to 50 wt %.

[0023] An edge of the adhesive resin layer may have a curved edge.

[0024] The urethane oligomer may have a molecular weight of 3,000 to 6,000.

[0025] The urethane oligomer may further include an amorphous polymer.

[0026] The amorphous polymer may be polyethylene oxide.

[0027] The semi-crystalline polymer may be polycaprolactone having a molecular weight of 1,000 to 5,000.

[0028] The semi-crystalline polymer may include at least one selected from the group consisting of polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyarylate, poly(DPAA), polyetherimide, and polyoxymethylene.

[0029] The monomers may include 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate, and exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acrylate.

[0030] The additives may include a silane coupling agent, an adhesion promoter, and an anti-yellowing agent.

[0031] The inkjet resin composition may have a viscosity of 30 cp or less.

[0032] According to an embodiment, an inkjet resin composition having improved impact resistance and a display device including the inkjet resin composition are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A cross section of a display device according to the embodiment is schematically shown. DETAILED DESCRIPTION

[0034] Hereinafter, various embodiments of the present inventive concept will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily realize the present inventive concept.

[0035] The inventive concept may be embodied in many different forms and is not limited to the embodiments set forth herein.

[0036] In order to clearly describe the present inventive concept, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

[0037] Furthermore, since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, the inventive concept is not necessarily limited to what is shown.

[0038] In the drawings, the thickness is shown exaggerated to clearly indicate each layer and region.

[0039] Also, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0040] Furthermore, when a part such as a layer, film, region, or plate is referred to as being “on” or “over” another part, this includes not only the case where it is “directly on” the other part but also the case where the other part exists therebetween.

[0041] In contrast, when a part is referred to as being "directly on" another part, it means that there is no other part between them.

[0042] Furthermore, “above” or “on” a reference portion means being located above or below the reference portion, and does not necessarily mean being located “above” or “on” the reference portion in an opposite direction of gravity.

[0043] In addition, throughout the specification, when a certain component is referred to as “comprising”, unless otherwise specified, it means that other components may be further included without excluding the other components.

[0044] Furthermore, throughout the specification, when a “planar image” is mentioned, it means when the target portion is observed from above; and when a “cross-sectional image” is mentioned, it means when a cross section of the target portion cut vertically is observed from the side.

[0045] Hereinafter, an inkjet resin composition according to the present embodiment and a display device including the inkjet resin composition will be described in detail with reference to the accompanying drawings.

[0046] Figure 1 Schematically shows a cross section of a display device according to an embodiment. Figure 1, the display device according to the present embodiment includes a display panel DP, a cover window CW disposed on the display panel DP, and an adhesive resin layer 300 disposed between the display panel DP and the cover window CW.

[0047] The adhesive resin layer 300 may be formed by UV curing after applying the inkjet resin composition through an inkjet process.

[0048] The adhesive resin layer 300 according to this embodiment may have a curved edge.

[0049] This is because the adhesive resin layer 300 is manufactured by a coating and curing process of a liquid forming the adhesive resin layer 300. Figure 1 As shown, the adhesive resin layer 300 may have rounded edges in a cross-sectional view.

[0050] However, the adhesive resin layer 300 formed by a process other than the inkjet process does not have a rounded edge in a cross-sectional view.

[0051] The inkjet resin composition according to the present embodiment may be a composition for forming the adhesive resin layer 300 disposed between the window CW and the display panel DP.

[0052] The following describes in detail the process for forming Figure 1 The adhesive resin layer 300 is composed of an inkjet resin composition.

[0053] Generally, a binder resin layer formed by curing an inkjet resin has brittleness due to a high glass transition temperature, and has a property of being easily broken by an applied external impact.

[0054] Therefore, when the cured inkjet resin composition is used to attach the cover window CW to the display panel DP, there may be a problem in that the cured adhesive resin layer 300 is broken due to low impact resistance.

[0055] The inkjet resin composition according to the embodiment has improved impact resistance due to improved properties of the inkjet resin composition.

[0056] The inkjet resin composition according to the present embodiment may include 16 to 24 wt % of a urethane oligomer, 56 to 84 wt % of a monomer, 4 to 6 wt % of a crosslinking agent, 4 to 6 wt % of an additive, and 1 to 3 wt % of a photoinitiator.

[0057] In the inkjet resin composition according to the present embodiment, the urethane oligomer may be urethane acrylate.

[0058] The urethane oligomer may have a molecular weight of 3,000 to 6,000.

[0059] The urethane oligomer may contain 5 to 50 weight percent of a semi-crystalline polymer.

[0060] Additionally, the urethane oligomer may include an amorphous polymer.

[0061] Amorphous polymers may include, for example, polyethylene oxide.

[0062] The inkjet resin composition according to the present embodiment is characterized in that a semi-crystalline polymer is included in a urethane oligomer, and the semi-crystalline polymer can form a partial segment cross-linked structure by serving as a cross-linking site in the urethane oligomer.

[0063] Therefore, the brittleness of the inkjet resin composition can be improved, and the impact resistance can be improved.

[0064] That is, the weight of the semi-crystalline polymer may be 5 wt % to 50 wt % based on the total weight of the urethane oligomer.

[0065] This content range is a range in which the inkjet resin composition has appropriate strength and a low glass transition temperature.

[0066] The semi-crystalline polymer may be polycaprolactone having a molecular weight of 1,000 to 5,000.

[0067] Alternatively, the semi-crystalline polymer may be at least one selected from the group consisting of polycarbonate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyarylate (PAR), poly(DPAA), polyetherimide (PEI), and polyoxymethylene (POM).

[0068] The monomers may include 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate, and exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acrylate.

[0069] The inkjet resin composition according to the present embodiment may include all of the above four types of monomers.

[0070] The additives may include silane coupling agents, adhesion promoters, and anti-yellowing agents.

[0071] The silane coupling agent is (3-glycidyloxypropyl) trimethoxysilane, (3-glycidyloxypropyl) triethoxysilane, (3-glycidyloxypropyl) methyl dimethoxysilane, (3-glycidyloxypropyl) methyl diethoxysilane, (3-glycidyloxypropyl) dimethylethoxysilane, 3,4-epoxybutyl trimethoxysilane, 3,4-epoxybutyl triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane, 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane,

[0063] As used herein, the term "silicon dioxide" refers to silane, which is a silane having a molecular weight of 400 μm, ...

[0072] However, these materials are examples, and the present inventive concept is not limited thereto.

[0073] The adhesion promoter may be a silane coupling agent having a reactive substituent such as a carboxyl group, a methacrylic group, an isocyanate group, or an epoxy group.

[0074] Specific examples of the silane coupling agent include γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane (γ-isocyanatepropyltriethoxysilane), γ-glycidyloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexylethyltrimethoxysilane) (β-3,4-epoxycyclohexylethyltrimethoxysilane), and the like.

[0075] These may be used alone or in combination.

[0076] However, these materials are examples, and the present inventive concept is not limited thereto.

[0077] The anti-yellowing agent is a linear or branched alkyl ester of 7 to 9 carbon atoms of 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxybenzene of propionic acid, 2-(benzotriazol-2-yl)-4-(2,4,4-trimethylpentane-2-yl)phenol, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(5[2, dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2,4-di Hydroxybenzophenone, 2,4-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxy-4-methoxybenzophenone-5-sulfonic acid, 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine or 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, etc.

[0078] However, these materials are examples, and the present inventive concept is not limited thereto.

[0079] The photoinitiator may include a short wavelength photoinitiator and a long wavelength photoinitiator, and the short wavelength photoinitiator and the long wavelength photoinitiator may be mixed before use.

[0080] The short wavelength photoinitiator may be a material that causes the inkjet resin composition to be cured at a wavelength of 320 nm to 365 nm, and the long wavelength photoinitiator may be a material that causes the inkjet resin composition to be cured at a wavelength of 370 nm to 420 nm.

[0081] When the inkjet resin composition is used to form the adhesive resin layer 300 for a display device, the adhesive resin layer 300 may be formed in various shapes such as circular / groove / hole shapes, and has an advantage in that it may be realized by preparing a coating pattern.

[0082] However, due to the brittleness of the cured inkjet resin composition, there is a problem that the cured inkjet resin composition is peeled off from the display panel or the resin is cracked inside the cured adhesive resin layer.

[0083] This is because the number of cross-linking sites between short chains of acrylic oligomers and acrylic monomers increases during curing of the inkjet resin composition.

[0084] Therefore, in order to improve the brittleness of the cured inkjet resin composition, it is necessary to form a partial segment crosslinking structure.

[0085] In this embodiment, the brittleness of the inkjet resin composition is improved by adding a semi-crystalline polymer that can serve as a cross-linking site to the urethane oligomer.

[0086] The inkjet resin composition according to the present embodiment may have a viscosity of 30 cp or less at room temperature.

[0087] An inkjet resin composition having a viscosity of 30 cp or less at room temperature can be easily ejected from an inkjet device.

[0088] When the viscosity at room temperature is 30 cp or more, the inkjet resin composition cannot be easily ejected from an inkjet device.

[0089] Next, the composition and composition differences between the inkjet resin composition according to this embodiment (embodiment 1), the slit resin composition according to another embodiment (embodiment 2), and the inkjet resin composition according to another embodiment (embodiment 3) will be described below. The resulting properties will be compared and explained.

[0090] Table 1 shows the compositions of the inkjet resin composition according to this embodiment (Embodiment 1) and inkjet resin compositions according to other embodiments (Embodiments 2 and 3).

[0091] The inkjet resin composition of Embodiment 1 includes a urethane acrylate oligomer, and the urethane acrylate oligomer includes 50 wt % of a semi-crystalline polymer, for example, polycaprolactone having a molecular weight of 1,000 to 5,000.

[0092] In the case of the inkjet resin composition of Embodiment 1, the oligomer content is reduced compared to Embodiment 2 to achieve low viscosity, and a separate flexible component is not included.

[0093] Embodiments 1 and 3 are inkjet resin compositions for an inkjet process, and Embodiment 2 is a slit resin composition for a slit process.

[0094] (Table 1)

[0095]

[0096]

[0097] The compounds listed in Table 1 are commercially available names or abbreviations, and their specific meanings are as follows.

[0098] TPO is 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0099] IRQ 819 is bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0100] Darocur MBF is methyl benzoylformate.

[0101] 2-HPMA means 2-hydroxypropyl methacrylate, 4-HBA means 4-hydroxybutyl acrylate, IBOA means isobornyl acrylate, and 2-EHA means 2-ethylhexyl acrylate.

[0102] Table 2 below shows measured physical properties of the compositions of Examples 1 to 3 according to the compositions of Table 1 above.

[0103] (Table 2)

[0104]

[0105]

[0106] In Table 1 and Table 2, the viscosity was analyzed using a viscometer.

[0107] The components and functional groups of the composition of each example were mass analyzed by FT-IR and PY-GC, and the molecular weight and molecular weight distribution of the oligomer were analyzed using GPC.

[0108] Furthermore, the storage elastic modulus (viscoelasticity) was analyzed using a rheometer, and the mechanical strength (hardness) was analyzed using a durometer (DMA, dynamic mechanical analyzer).

[0109] The glass transition temperature Tg is analyzed using differential scanning calorimetry (DSC) or thermomechanical analyzer (TMA).

[0110] Referring to Table 2, in the case of Embodiment 1 in which polycaprolactone (polycaprolactone is a semi-crystalline polymer) is included in the urethane acrylate monomer, the viscosity is lower than those of the compositions of Embodiments 2 and 3.

[0111] Therefore, it was confirmed that the inkjet process could be easily performed.

[0112] Furthermore, since the inkjet resin composition of Embodiment 1 has the lowest glass transition temperature, it is confirmed that brittleness is improved compared with other compositions.

[0113] Therefore, it was confirmed that the inkjet resin composition of Embodiment 1 had stronger impact resistance than other compositions.

[0114] Furthermore, the inkjet resin composition of Embodiment 1 showed a low storage elastic modulus of 0.24 at 25° C. and a high elongation of 500%, indicating that the inkjet resin composition according to Embodiment 1 has high elasticity and high elongation.

[0115] Therefore, it was confirmed that Embodiment 1 is not easily broken by impact.

[0116] Hereinafter, the effects of the inkjet resin composition according to the present embodiment will be described through specific dynamic impact strength evaluation test examples.

[0117] Experimental implementation 1: Evaluation of dynamic impact strength

[0118] In order to evaluate the dynamic impact strength, 30 g of four monomers (4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate and exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acrylate) were placed in a three-necked glass reaction vessel equipped with a thermometer and a dropping funnel and kept under a nitrogen atmosphere.

[0119] The temperature of the reactor was raised to 45° C. to 50° C., and 30 g of urethane acrylate oligomer, 20 g of flexible polymer binder, and 10 g of semi-crystalline polymer binder were added to the reactor.

[0120] While stirring the reactor, 3 parts per hundred parts of rubber (phr) of photoinitiator were slowly added.

[0121] When the photoinitiator dissociates under stirring for 1 hour, the additives and silane coupling agent are added and stirred.

[0122] For the dynamic impact strength evaluation, a 32 g steel ball with a diameter of 2 mm was used.

[0123] The display panel to which the inkjet resin composition was applied and cured was fixed, and the falling height of the ball was measured while varying from 1 cm to 50 cm, and the height of the generated bubbles was recorded.

[0124] Table 3 below shows the results of a dynamic impact strength test conducted on the cured inkjet resin composition.

[0125] 20 ball drops were performed for each of the four sections of the display panel.

[0126] (Table 3)

[0127]

[0128]

[0129] Referring to Table 3, it was confirmed that the inkjet resin composition according to Embodiment 1 did not generate bubbles at a drop height of 50 cm during a drop ball test after curing.

[0130] Table 4 below shows the results of the same dynamic impact strength test conducted on the inkjet resin composition of Embodiment 3 after curing.

[0131] (Table 4)

[0132]

[0133] In Table 4, the average height at which bubbles began to appear in the drop ball test was 6 cm to 9 cm, which is significantly lower than 50 cm in Table 3.

[0134] That is, it is confirmed that the inkjet resin composition according to the present embodiment including the semi-crystalline polymer in the urethane oligomer has higher impact resistance than the inkjet resin composition not including the semi-crystalline polymer.

[0135] Although the embodiments of the inventive concept have been described in detail above, the scope of the inventive concept is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the inventive concept defined in the appended claims are also included in the scope of the inventive concept.

Claims

1. An inkjet resin composition comprising: 16 to 24 wt % of a urethane oligomer; 56 to 84 wt% monomers; 4 to 6 wt % of a crosslinking agent; 4 to 6 wt% additives; as well as 1 to 3 wt % of a photoinitiator; The urethane oligomer comprises a semi-crystalline polymer, and the content of the semi-crystalline polymer in the urethane oligomer is 5 wt % to 50 wt %.

2. The inkjet resin composition according to claim 1, wherein: The urethane oligomer has a molecular weight of 3,000 to 6,000.

3. The inkjet resin composition according to claim 1, wherein: The urethane oligomer further comprises an amorphous polymer.

4. The inkjet resin composition according to claim 3, wherein: The amorphous polymer is polyethylene oxide.

5. The inkjet resin composition according to claim 1, wherein: The semi-crystalline polymer includes polycaprolactone having a molecular weight of 1,000 to 5,000.

6. The inkjet resin composition according to claim 1, wherein: The semi-crystalline polymer includes at least one selected from the group consisting of polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyarylate, poly(DPAA), polyetherimide, and polyoxymethylene.

7. The inkjet resin composition according to claim 1, wherein: The monomers include 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate and exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acrylate.

8. The inkjet resin composition according to claim 1, wherein: The additives include a silane coupling agent, an adhesion promoter, and an anti-yellowing agent.

9. The inkjet resin composition according to claim 1, wherein: The photoinitiator includes a short wavelength photoinitiator that causes the inkjet resin composition to be cured at a wavelength of 320 nm to 365 nm and a long wavelength photoinitiator that causes the inkjet resin composition to be cured at a wavelength of 370 nm to 420 nm.

10. The inkjet resin composition according to claim 1, wherein: The inkjet resin composition has a viscosity of 30 cp or less.

11. A display device comprising: Display panel; a cover window on one side of the display panel; as well as an adhesive resin layer disposed between the display panel and the cover window; wherein the binder resin layer comprises a cured inkjet resin composition, the cured inkjet resin composition is a cured layer of an inkjet resin composition, The inkjet resin composition comprises: 16 to 24 wt. % of a urethane oligomer, 56 to 84% by weight of monomers, 4 to 6 wt. % of a crosslinking agent, 4 to 6 wt% of additives, and 1 to 3 wt % of a photoinitiator, and The urethane oligomer comprises a semi-crystalline polymer, and the content of the semi-crystalline polymer in the urethane oligomer is 5 wt % to 50 wt %.

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