Inkjet resin composition and display device

Abstract

To provide an inkjet resin composition having reduced volatility, enhanced ejectability, and reduced spreadability, and a display device made from the inkjet resin composition.SOLUTION: An inkjet resin composition according to an embodiment includes 20-30 wt.% of 2-ethylhexyl acrylate, 20-30 wt.% of 4-hydroxybutyl acrylate, 40-50 wt.% of isodecyl acrylate, 1-10 wt.% of urethane acrylate, 1-5 wt.% of an initiator, 1-5 wt.% of a silane coupling agent, and 0.05-1 wt.% of a surface flow control additive.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to inkjet resin compositions and displays made from such inkjet resin compositions. [Background technology]

[0002] 2. Description of the Related Art As information technology advances, the importance of display devices, which are a medium connecting users with information, is increasing.

[0003] In recent years, research and development of foldable display devices, bendable display devices, rollable display devices, etc., utilizing the advantages of flexible display panels that can be bent or folded, has been underway. Such display devices can be applied to various fields such as portable electronic devices, wearable devices, televisions, monitors, etc.

[0004] In recent years, portable electronic devices such as smartphones and tablet PCs have become lighter and thinner for portability and have been developed in many areas for convenience of use. In particular, foldable electronic devices with flexible displays provide a relatively larger screen than typical bar-type electronic devices, but when the electronic device is folded, its size becomes smaller, making it convenient to carry, and are therefore attracting attention as electronic devices that satisfy consumer preferences.

[0005] In the case of such a foldable display device, each layer to be laminated must satisfy folding characteristics to be foldable. Each layer of the foldable display device can have an adhesive layer disposed therebetween. Summary of the Invention [Problem to be solved by the invention]

[0006] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to inkjet resin compositions having reduced volatility, improved jetting properties, and reduced diffusivity, and displays made from such inkjet resin compositions. [Means for solving the problem]

[0007] An inkjet resin composition according to one embodiment includes 20% to 30% by weight of 2-ethylhexyl acrylate, 20% to 30% by weight of 4-hydroxybutyl acrylate, 40% to 50% by weight of isodecyl acrylate, 1% to 10% by weight of urethane acrylate, 1% to 5% by weight of an initiator, 1% to 5% by weight of a silane coupling agent, and 0.05% to 1% by weight of a surface fluidity control additive.

[0008] The initiator can include one or more of 2,2-Dimethoxy-1,2-diphenylethan-1-one or Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide.

[0009] The surface fluidity adjusting additive may include PDMS (Polydimethylsiloxan).

[0010] The surface fluidity control additive may include a compound represented by the following Formula 2:

[0011] [ka] (Chemical formula 2)

[0012] In this case, in the above Chemical Formula 2, A and B are each independently an alkyl group or an acrylate group having 1 to 10 carbon atoms, and x is an integer of 1 to 10,000.

[0013] The content ratio of 2-ethylhexyl acrylate / 4-hydroxybutyl acrylate may be 0.5 to 1.5.

[0014] The content ratio of 2-ethylhexyl acrylate / (isodecyl acrylate+urethane acrylate) may be 0.6-1.

[0015] The inkjet resin composition may have a viscosity of 50 cp or less at room temperature (25° C.).

[0016] The surface tension of the inkjet resin composition may be 25 dyne / cm to 31 dyne / cm.

[0017] The inkjet resin composition may have a modulus (G') of 0.3 MPa or less at -20°C after UV curing.

[0018] The inkjet resin composition may have a modulus (G') of 0.01 MPa or more at 60° C. after UV curing.

[0019] A foldable device according to one embodiment includes a display panel, a cover window located on one side of the display panel, a battery located on the other side of the display panel, and an adhesive layer located between the display panel and the cover window, the adhesive layer including a cured inkjet resin composition, the inkjet resin composition including 20% ​​to 30% by weight of an acrylate having 3 to 10 carbon atoms, 20% to 30% by weight of 4-hydroxybutyl acrylate, 40% to 50% by weight of isodecyl acrylate, 1% to 10% by weight of a urethane acrylate, 1% to 5% by weight of an initiator, 1% to 5% by weight of a silane coupling agent, and 0.05% to 1% by weight of a surface fluidity control additive.

[0020] The glass transition temperature of the acrylate having 3 to 10 carbon atoms may be −40° C. or lower.

[0021] The surface fluidity adjusting additive may include PDMS (Polydimethylsiloxan).

[0022] A display device according to one embodiment includes a display panel, a cover window located on one side of the display panel, and an adhesive layer located between the display panel and the cover window, the adhesive layer including a cured inkjet resin composition, the inkjet resin composition including 20% ​​to 30% by weight of 2-ethylhexyl acrylate, 20% to 30% by weight of 4-hydroxybutyl acrylate, 40% to 50% by weight of isodecyl acrylate, 1% to 10% by weight of urethane acrylate, 1% to 5% by weight of an initiator, 1% to 5% by weight of a silane coupling agent, and 0.05% to 1% by weight of a surface fluidity control additive.

[0023] The edges of the adhesive layer may be curved.

[0024] The adhesive layer may have a modulus (G') of 0.3 MPa or less at -20°C.

[0025] The adhesive layer may have a modulus (G') at 60° C. of 0.01 MPa or more.

[0026] The display device may be foldable.

[0027] The cover window may have a thickness of 100 μm or less.

[0028] The adhesive layer may be in direct contact with the cover window. Effect of the Invention

[0029] According to an embodiment, there is provided an inkjet resin composition having reduced volatility, improved jetting properties, and reduced diffusivity, and a display device manufactured from such an inkjet resin composition. [Brief description of the drawings]

[0030] [Figure 1] 1 is a diagram simply illustrating a cross section of a display device according to an embodiment of the present invention. [Diagram 2]When the surface fluidity adjusting additive is not included, after the ink-jet resin composition is discharged and cured, a defect occurs in which craters are formed on the surface. [Diagram 3] FIG. 1 shows the crater in unfilled form. [Figure 4] FIG. 1 shows a half-filled crater. [Diagram 5] FIG. 1 is a graph showing glass transition temperatures depending on the carbon number of acrylic ester monomers. [Figure 6] FIG. 13 is a cross-sectional view of a display device according to another embodiment. [Figure 7] FIG. 13 is a simplified diagram illustrating a foldable display device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may, however, be embodied in various different forms and is not limited to the embodiments set forth herein.

[0032] In order to clearly explain the present invention, parts that are not necessary for the explanation will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0033] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited to those shown in the drawings. In the drawings, the thicknesses of various layers and regions are exaggerated to clearly express the layers and regions. In the drawings, the thicknesses of some layers and regions are exaggerated to facilitate explanation.

[0034] In addition, when a part such as a layer, film, region, or plate is said to be "on" or "above" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly on" another part, it means that there is no other part in between. In addition, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the direction against gravity.

[0035] In addition, throughout the specification, when a part "comprises" a certain element, this means that it may further include other elements, but not excluding other elements, unless specifically stated to the contrary.

[0036] Also, throughout the specification, "in a plane" means when the subject part is viewed from above, and "in cross section" means when the subject part is cut vertically and viewed from the side.

[0037] Hereinafter, an inkjet resin composition and a display device including the same according to the present embodiment will be described in detail with reference to the drawings.

[0038] 1 is a diagram showing a simplified cross section of a display device according to an embodiment of the present invention. Referring to FIG. 1, the display device according to the embodiment of the present invention includes a display panel DP, a cover window CW located on the display panel DP, and a resin adhesive layer 300 located between the display panel DP and the cover window CW. The resin adhesive layer 300 may be formed by applying an inkjet resin by an inkjet process and then curing it with UV light. The inkjet resin composition according to the embodiment of the present invention may be a composition for forming the resin adhesive layer 300 between the window CW and the display panel DP as shown in FIG. 1.

[0039] The display device according to the present embodiment may be a foldable display device that can be folded and unfolded. In the foldable display device, each layer can be bonded with a pressure sensitive adhesive film. However, the pressure sensitive adhesive film is expensive, and there is a problem that liquid is generated during the processing and punching process for bonding. Therefore, in the display device according to the present embodiment, a part of the adhesive layer of the foldable display device is formed with Inkjet OCR (Optically clear resin) using an inkjet resin composition.

[0040] However, in order to use an inkjet resin composition as an adhesive layer, the inkjet resin composition must have low viscosity to enable a jetting process, and must have high adhesive strength and low modulus after curing. That is, since slippage occurs during folding in a foldable display device, an inkjet resin composition for forming an adhesive layer is required to have low modulus to enable folding and excellent dischargeability to enable a jetting process. The present invention relates to an inkjet resin composition that satisfies such characteristics and a display device including the same.

[0041] The inkjet resin composition according to this embodiment can contain 20% by weight to 30% by weight of 2-ethylhexyl acrylate, 20% by weight to 30% by weight of 4-hydroxybutyl acrylate, 40% by weight to 50% by weight of isodecyl acrylate, 1% by weight to 10% by weight of urethane acrylate, 1% by weight to 5% by weight of an initiator, 1% by weight to 5% by weight of a silane coupling agent, and 0.05% by weight to 1% by weight of a surface fluidity control additive.

[0042] In this case, the initiator may include one or more of 2,2-Dimethoxy-1,2-diphenylethan-1-one (Irgacure 651) or Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819).

[0043] In addition, the surface fluidity control additive may include PDMS (Polydimethylsiloxan). In this case, PDMS may be a compound represented by the following formula 1, or may have a structure in which the methyl group is replaced with another compound, such as a compound represented by the following formula 2.

[0044] [ka] (chemical formula 1)

[0045] [ka] (Chemical formula 2)

[0046] In this case, in the above Chemical Formula 2, A and B may each independently be an alkyl or acrylate having 1 to 10 carbon atoms. The above x and n may be 1 to 10,000.

[0047] In the inkjet resin composition according to this embodiment, the content ratio of 2-ethylhexyl acrylate to 4-hydroxybutyl acrylate (2-EHA / 4-HBA) may be 0.5 to 1.5. If the content ratio of 2-EHA / 4-HBA is less than 0.5, the low temperature reliability may decrease, and if the content ratio is more than 1.5, the volatility may not be sufficiently reduced.

[0048] Furthermore, in the inkjet resin composition according to this embodiment, the content ratio of 2-ethylhexyl acrylate / (isodecyl acrylate+urethane acrylate) may be 0.6 to 1. When the content ratio of 2-ethylhexyl acrylate / (isodecyl acrylate+urethane acrylate) is 0.6 or less, low-temperature reliability may decrease, and when the content ratio is 1 or more, volatility may not decrease sufficiently.

[0049] The inkjet resin composition according to this embodiment may have a viscosity of 50 cp or less at room temperature, which is a viscosity that allows for good ejection.

[0050] In addition, the inkjet resin composition according to the present embodiment may have a modulus (G') of 0.3 MPa or less at -20°C after UV curing, and a modulus (G') of 0.01 MPa or more at 60°C. This is within the range in which folding is performed well at low and high temperatures when the inkjet resin composition is cured to form a resin adhesive layer.

[0051] The surface tension of the inkjet resin composition according to the present embodiment may be 25 dyne / cm to 31 dyne / cm. As will be described later, such a surface tension is achieved by including a surface fluidity control additive, which can prevent the occurrence of craters during application.

[0052] It is important for the inkjet resin composition to maintain its dischargeability. If the volatility is high, it is not preferable because the discharge is not performed well as time passes, and the resin volatilizes and diffuses after discharge, making it difficult to maintain the shape. However, the inkjet resin composition according to the present embodiment reduces the content of 2-ethylhexyl acrylate, which is highly volatile, to induce a mixed vapor pressure drop phenomenon and reduce the amount of volatilization at the discharge temperature. In addition, in order to prevent the low-temperature folding characteristic from decreasing due to the reduction in the content of 2-ethylhexyl acrylate, the content of isodecyl acrylate is increased to 40% by weight to 50% by weight, thereby maintaining the low-temperature folding characteristic. In addition, by including a surface fluidity control additive such as PDMS, the surface tension of the inkjet resin composition is reduced, thereby suppressing the occurrence of surface defects.

[0053] FIG. 2 is an image of a defect in which a crater is formed on the surface after the inkjet resin composition is discharged and cured when the surface fluidity control additive is not included. As shown in the circled portion in FIG. 2, the inkjet resin composition is not uniformly filled, and a crater may be formed in an unfilled or half-filled form. FIG. 3 shows a crater in an unfilled form, and FIG. 4 shows a crater in a half-filled form. In FIG. 3 and FIG. 4, the inkjet resin composition 310 is located on the substrate 110, and the inkjet resin composition 310 is not uniformly spread, and a crater in an unfilled form (FIG. 3) or half-filled form (FIG. 4) is formed. However, since the inkjet resin composition according to the present embodiment includes a surface fluidity control additive, the surface tension of the inkjet resin composition is reduced, and the formation of a crater on the surface can be prevented.

[0054] At this time, the content of the surface fluidity control additive may be 0.05% by weight to 1% by weight. If the content of the surface fluidity control additive is less than 0.05% by weight, the effect of reducing surface tension may decrease, and craters may be formed on the coated surface. Also, if the content of the surface fluidity control additive is more than 1% by weight, the adhesive strength of the inkjet resin composition may decrease.

[0055] The following Table 1 shows the degree of crater formation when the content of the surface fluidity control additive is changed. A total of 20 applications were performed, and the number of applications in which craters were formed was counted and recorded in Table 1.

[0056] [Table 1]

[0057] Referring to Table 1 above, it can be seen that when the content of the surface fluidity control additive (surface modifier) ​​is less than 0.05%, a crater hole is formed during application. Similarly, when the content of the surface fluidity control additive is 0.05 wt% or more, it can be seen that a crater hole is not formed during application. Table 2 below shows the adhesion of the inkjet resin composition measured while changing the content of the surface fluidity control additive.

[0058] [Table 2]

[0059] Referring to Table 2, it was confirmed that when the content of the surface fluidity control additive exceeds 1 wt%, the adhesive strength is rapidly reduced. Therefore, it was confirmed that when the content of the surface fluidity control additive is 0.05 wt% to 1 wt%, the adhesive strength can be maintained while preventing the formation of craters. As described above, the inkjet resin composition according to the present embodiment reduces the content of 2-ethylhexyl acrylate, which is a highly volatile material, and increases the content of 4-hydroxybutyl acrylate and isodecyl acrylate, which are less volatile, to reduce the amount of volatilization. In addition, since the surface fluidity control additive is included, the formation of surface craters can be prevented, and the physical properties can be maintained at low temperatures by selecting an appropriate compounding ratio between monomers.

[0060] An inkjet resin composition according to another embodiment may contain an acrylate having 3 to 10 carbon atoms instead of 2-ethylhexyl acrylate. The glass transition temperature of such an acrylate having 3 to 10 carbon atoms is preferably -40°C or lower. Fig. 5 is a diagram showing the glass transition temperature according to the carbon number of an acrylic ester monomer. As shown in Fig. 5, when the carbon number is 3 to 10, it can be confirmed that the glass transition temperature is -40°C or lower.

[0061] The effects of the inkjet resin composition according to this embodiment will be described below in comparison with comparative examples.

[0062] Table 3 below shows the compositions of the inkjet resin composition according to this embodiment (composition A) and the inkjet resin composition according to another embodiment (composition B).

[0063] [Table 3]

[0064] As shown in Table 3, composition A according to the present embodiment has a lower content of 2-ethylhexyl acrylate and a higher content of 4-hydroxybutyl acrylate and isodecyl acrylate than composition B. Composition A also contains a surface flow control additive (PDMS). The volatility characteristics of compositions A and B according to temperature were measured and are shown in Table 4.

[0065] [Table 4]

[0066] Referring to Table 4 above, it can be seen that composition A according to the present embodiment has a lower volatility than composition B. In other words, it can be seen that composition A according to the present embodiment has a lower volatility and has excellent ejection characteristics. Table 5 below shows the results of the dormancy evaluation during ejection and the volatility evaluation after ejection for composition B.

[0067] [Table 5]

[0068] Referring to Table 5 above, in the case of composition B, it was confirmed that discharge failure occurred after 3 minutes, and the discharged resin diffused while volatilizing. The following Table 6 shows the results of the dormancy evaluation during discharge and the volatility evaluation after discharge for composition A.

[0069] [Table 6]

[0070] Referring to Table 6, it was confirmed that in the case of composition A according to the present embodiment, no discharge failure occurred even after 15 minutes of discharge, and the discharged resin did not volatilize or diffuse even after 10 minutes. In other words, by comparing the results of Table 5 with the results of Table 6, it can be confirmed that composition A according to the present embodiment has excellent discharge characteristics and low diffusibility even after the passage of time. The occurrence rate of nozzle failure during discharge was measured for composition A and composition B, and the results are shown in Table 7.

[0071] [Table 7]

[0072] As can be seen from Table 7, no craters were formed even once in 100 tests for composition A according to the present embodiment, while craters were formed 10 times in 150 tests for composition B, resulting in a defective rate of 6.7%. That is, the inkjet resin composition according to the present embodiment has low volatility, and therefore has excellent discharge characteristics, and is less susceptible to resin diffusion caused by volatilization after discharge, and contains a surface property modifier, which can prevent the formation of craters during application.

[0073] The display device according to the present embodiment will now be described. The display device according to the present embodiment may include an adhesive layer formed by applying and curing the inkjet resin composition between a display panel and a window. Referring again to FIG. 1, the resin adhesive layer 300 according to the present embodiment may be formed with a curved edge. This is because the inkjet resin composition is prepared in a liquid state through a process of application and curing, and a curved slope is formed at the edge as shown in FIG. 1. However, in the case of an adhesive layer not prepared from such an inkjet resin composition, a curved slope is not formed at the edge, which is different.

[0074] FIG. 1 shows a simplified cross-sectional structure of a display device, and FIG. 6 shows a more detailed view of the same.

[0075] 6 is a cross-sectional view of a display device according to another embodiment. Referring to FIG. 6, the display device according to this embodiment includes a display panel DP, a first lower film 510 located at the lower part of the display panel DP, a second lower film 520, a first upper film 530 located at the upper part of the display panel DP, a second upper film 540, a cover window CW, and a protective film (PL). An adhesive layer PSA may be disposed between these layers. In addition, a resin adhesive layer 300 according to this embodiment may be disposed between the cover window CW and the first upper film 530. The resin adhesive layer 300 according to this embodiment is formed through a coating and curing process of an inkjet resin composition according to this embodiment, and may have a curved edge as described in FIG. 1.

[0076] The display device shown in Fig. 1 and Fig. 6 may be a foldable display device. In this case, the thickness of the cover window CW may be 100 μm or less. In Fig. 1 and Fig. 6, the modulus (G') of the resin adhesive layer 300 at -20°C may be 0.3 MPa or less, and the modulus (G') at 60°C may be 0.01 MPa or more. Such physical properties can be derived by the resin adhesive layer 300 having the above-mentioned composition.

[0077] 7 is a diagram illustrating a foldable display device according to another embodiment. Referring to FIG. 7, the foldable display device according to this embodiment may further include a battery 800 located under the display panel DP. That is, the foldable display device according to this embodiment may be a mobile device including the battery 800, and the description of the other components is the same as that described above and will not be provided.

[0078] Although the preferred embodiment of the present invention has been described above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims also fall within the scope of the present invention.

Claims

1. 20% to 30% by weight of 2-ethylhexyl acrylate, 20% to 30% by weight of 4-hydroxybutyl acrylate, 40% to 50% by weight of isodecyl acrylate, 1% by weight to 10% by weight of urethane acrylate, 1% to 5% by weight of an initiator; 1% to 5% by weight of a silane coupling agent, An inkjet resin composition comprising 0.05% to 1% by weight of a surface flow control additive.

2. 2. The inkjet resin composition of claim 1, wherein the initiator comprises at least one of 2,2-Dimethoxy-1,2-diphenylethane-1-one and Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

3. The inkjet resin composition according to claim 1 , wherein the surface fluidity control additive comprises PDMS (Polydimethylsiloxan).

4. The inkjet resin composition according to claim 1 , wherein the surface fluidity control additive comprises a compound represented by the following Formula 2: 【Chemistry 1】 (Chemical formula 2) In this case, in Formula 2, A and B are each independently an alkyl group or an acrylate group having 1 to 10 carbon atoms, and x is an integer of 1 to 10,000.

5. 2. The inkjet resin composition according to claim 1, wherein the content ratio of 2-ethylhexyl acrylate / 4-hydroxybutyl acrylate is 0.5 to 1.

5.

6. 2. The inkjet resin composition according to claim 1, wherein the content ratio of 2-ethylhexyl acrylate / (isodecyl acrylate+urethane acrylate) is 0.6 to 1.

7. The inkjet resin composition according to claim 1 , wherein the inkjet resin composition has a viscosity of 50 cp or less at room temperature (25° C.).

8. 2. The ink-jet resin composition according to claim 1, wherein the ink-jet resin composition has a surface tension of 25 dyne / cm to 31 dyne / cm.

9. The inkjet resin composition according to claim 1, wherein the inkjet resin composition has a modulus (G') of 0.3 MPa or less at -20°C after UV curing.

10. The inkjet resin composition according to claim 1 , wherein the inkjet resin composition has a modulus (G′) of 0.01 MPa or more at 60° C. after UV curing.

11. Display panel; a cover window located on one side of the display panel; a battery located on the other side of the display panel; an adhesive layer disposed between the display panel and the cover window; the adhesive layer comprises a cured inkjet resin composition; The inkjet resin composition 20% by weight to 30% by weight of an acrylate having 3 to 10 carbon atoms, 20% to 30% by weight of 4-hydroxybutyl acrylate, 40% to 50% by weight of isodecyl acrylate, 1% by weight to 10% by weight of urethane acrylate, 1% to 5% by weight of an initiator; 1% to 5% by weight of a silane coupling agent, A foldable device comprising 0.05% to 1% by weight of a surface flow control additive.

12. The foldable device according to claim 11, wherein the acrylate having 3 to 10 carbon atoms has a glass transition temperature of −40° C. or lower.

13. The foldable device of claim 11 , wherein the surface fluidity control additive comprises PDMS (Polydimethylsiloxan).

14. Display panel, a cover window located on one side of the display panel; an adhesive layer disposed between the display panel and the cover window; the adhesive layer comprises a cured inkjet resin composition; The inkjet resin composition 20% to 30% by weight of 2-ethylhexyl acrylate, 20% to 30% by weight of 4-hydroxybutyl acrylate, 40% to 50% by weight of isodecyl acrylate, 1% by weight to 10% by weight of urethane acrylate, 1% to 5% by weight of an initiator; 1% to 5% by weight of a silane coupling agent, A display device comprising 0.05% to 1% by weight of a surface flow control additive.

15. The display device of claim 14 , wherein the edge of the adhesive layer is curved.

16. The display device according to claim 14, wherein the adhesive layer has a modulus (G') of 0.3 MPa or less at -20°C.

17. The display device according to claim 14 , wherein the adhesive layer has a modulus (G′) of 0.01 MPa or more at 60° C.

18. The display device of claim 14 , wherein the display device is foldable.

19. The display device according to claim 14, wherein the cover window has a thickness of 100 μm or less.

20. 15. The display device of claim 14, wherein the adhesive layer is in direct contact with the cover window.

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