CN112708295A - Resin composition and flexible display screen - Google Patents

Abstract

The invention relates to a resin composition and a flexible display screen, wherein the resin composition comprises the following components: titanium dioxide-hybridized polymethyl methacrylate, urethane acrylate with cyclohexyl, acrylate with ethylene glycol group and photoinitiator; the urethane acrylate having a cyclohexyl group and the acrylate having an ethylene glycol group each independently contain at least two reactive functional groups. According to the invention, the synergistic effect of titanium dioxide hybridized polymethyl methacrylate, cyclohexyl carbamate acrylate and ethylene glycol acrylate is utilized to ensure that the obtained resin composition has good hardness and flexibility after curing, and can be applied to flexible display hard coatings.

Description

Resin composition and flexible display screen

Technical Field

The invention relates to the technical field of flexible display, in particular to a resin composition and a flexible display screen.

Background

Since 2018, flexible displays have entered the development climax. The flexible display is made of soft material and is a deformable and bendable display device. The conventional glass protective layer cannot be used because it does not have a bending characteristic.

Recently, active studies have been made on an optical plastic cover having strength and scratch resistance equivalent to a tempered glass while securing flexibility and impact resistance. Generally, as a material of a cover made of transparent plastic for optical use having flexibility compared to tempered glass, there are polyethylene terephthalate (PET), Polyethersulfone (PES), polyethylene naphthalate (PEN), Polyacrylate (PAR), Polycarbonate (PC), Polyimide (PI), and the like. However, these polymer plastic substrates have not only insufficient physical properties in terms of hardness and scratch resistance, but also insufficient impact resistance, as compared with tempered glass used as a window film for display protection.

CN108299899A discloses a hard coat composition, a hard coat film using the same, and an image display device having the hard coat film, the hard coat composition comprising: an alkoxysilane compound or a silicone resin having an epoxy group, an acrylate compound having an isocyanate group, a photopolymerization initiator, and a solvent. The hard coating film according to the present invention can minimize the occurrence of curling while having excellent hardness. But the maximum hardness can only reach 3H, and still needs to be further improved.

CN107402414A discloses a hard coat film and a flexible display having the same, the hard coat film comprising a substrate, a first hard coat layer formed on one surface of the substrate, and a second hard coat layer formed on the other surface of the substrate, wherein the first hard coat layer comprises a crosslinked polymer of an oligomer having an elongation of 50 to 350%, the second hard coat layer comprises a crosslinked polymer of an oligomer having an elongation of 0.1 to 50%, and the crosslinking density of the first hard coat layer is less than that of the second hard coat layer. The hard coat film of the present invention has excellent impact resistance and curling properties, and also has excellent bending resistance. However, the hardness and flexibility of the hard coating layer have been difficult to meet the requirements of the flexible display screen at present, and need to be further improved.

CN109627478A discloses a hard coating composition and a flexible cover plate, relating to the technical field of coatings. The hard coating composition includes: an acrylate oligomer having a functionality of not less than 6; and an acrylate monomer, the functionality of the acrylate monomer is not less than 3, and the molecular weight of the acrylate monomer is not more than 150 times the functionality of the acrylate monomer; wherein the mass ratio of the acrylate oligomer to the acrylate monomer is not less than 1: 1. According to the embodiment of the invention, the mass ratio of the acrylate oligomer to the acrylate monomer is set to be not less than 1:1, so that the formed hard coating can generate smaller curing shrinkage, and the condition that the hard coating is easy to warp is effectively improved. However, it is difficult to have both high hardness and flexibility in the hard coat layer.

Therefore, there is a need in the art to develop a resin composition having high hardness and flexibility after curing.

Disclosure of Invention

An object of the present invention is to provide a resin composition which has good hardness and flexibility after curing and can be used for a flexible display hard coating.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a resin composition, which comprises the following components: titanium dioxide-hybridized polymethyl methacrylate, urethane acrylate with cyclohexyl, acrylate with ethylene glycol group and photoinitiator;

the urethane acrylate having a cyclohexyl group and the acrylate having an ethylene glycol group each independently contain at least two reactive functional groups, for example, 3, 4, 5, 6, 7, 8, or 9, and the like.

The invention provides a novel resin composition, wherein titanium dioxide hybridized polymethyl methacrylate is introduced into the composition, an inorganic hybridized part is introduced into the resin with better hardness, so that the hardness can be better improved, and in addition, the obtained resin composition has good hardness and flexibility after being cured through the synergistic effect of the titanium dioxide hybridized polymethyl methacrylate, the urethane acrylate with cyclohexyl and the acrylate with ethylene glycol group, so that the resin composition can be applied to a flexible display hard coating.

Preferably, the preparation method of the titanium dioxide hybridized polymethyl methacrylate comprises the following steps: mixing TiCl₄Mixing the polymethyl methacrylate, the surfactant and the free radical initiator, and reacting to obtain the titanium dioxide hybridized polymethyl methacrylate.

Preferably, the surfactant comprises oleic acid.

Preferably, the free radical initiator comprises azobisisobutyronitrile.

The preparation method of the titanium dioxide hybridized polymethyl methacrylate includes, but is not limited to, the above-mentioned method.

Preferably, the urethane acrylate having a cyclohexyl group comprises a compound of formula I and/or a compound of formula II, preferably a combination of a compound of formula I and a compound of formula II;

in the formula I, A is

The dashed line marks represent the linking of groups;

the present invention preferably selects the two urethane acrylates having a cyclohexyl group of specific structures described above, and can further improve hardness and flexibility, and when they are used in combination, they can be matched with each other, and hardness and flexibility are optimized.

Preferably, the acrylate having an ethylene glycol group comprises a compound of formula III and/or a compound of formula IV, preferably a combination of a compound of formula III and a compound of formula IV;

in the formula III, m is an integer of 1-4, such as 2 or 3, preferably 1;

in formula IV, p and n are each independently an integer of 1 to 4, such as 2 or 3, preferably 2.

The present invention preferably selects the two types of acrylic esters having ethylene glycol groups of specific structures, and can further improve hardness and flexibility, and when they are used in combination, they can be matched with each other, and hardness and flexibility are optimized.

Preferably, the content of the titanium dioxide hybridized polymethylmethacrylate in the resin composition is 10-30 wt.%, such as 12 wt.%, 14 wt.%, 16 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, 24 wt.%, 26 wt.%, 28 wt.%, etc.

Preferably, the content of the urethane acrylate having a cyclohexyl group in the resin composition is 10 to 30 wt.%, for example 12 wt.%, 14 wt.%, 16 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, 24 wt.%, 26 wt.%, 28 wt.%, etc.

Preferably, the amount of the acrylate with ethylene glycol groups in the resin composition is 10 to 30 wt.%, such as 12 wt.%, 14 wt.%, 16 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, 24 wt.%, 26 wt.%, 28 wt.% and the like.

Preferably, the photoinitiator is present in the resin composition in an amount of 2 to 10 wt.%, e.g. 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, etc.

Preferably, the photoinitiator comprises a cleavage type radical initiator and/or a hydrogen abstraction type radical initiator.

Preferably, the resin composition further comprises a solvent.

Preferably, the solvent comprises any one or a combination of at least two of propylene glycol methyl ether acetate, methyl isobutyl ketone or methyl ethyl ketone.

Preferably, the amount of solvent in the resin composition is 30 to 70 wt.%, such as 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, etc.

Preferably, the resin composition further comprises an antioxidant and/or a leveling agent.

It is a second object of the present invention to provide a flexible display panel comprising a hard coat layer containing a cured product of the resin composition according to the first object.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a novel resin composition, which has good hardness (4H or above) and flexibility (bending radius is 4mm or below) after being cured through the synergistic action of titanium dioxide hybridized polymethyl methacrylate, cyclohexyl-containing urethane acrylate and ethylene glycol-containing acrylate, and can be applied to a flexible display hard coating.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Preparation example 1

The preparation example provides a titanium dioxide hybridized polymethyl methacrylate, and the preparation method comprises the following steps:

(1) preparation of titanium dioxide sols

Taking 25mL of absolute ethyl alcohol and a three-neck flask, adding 8.52mL of butyl titanate (TBOT) and 2.02mL of diethanol amine under stirring, after stirring for 2 hours, slowly adding 13.60mL of absolute ethyl alcohol and 0.90mL of secondary deionized water through a separating funnel, and stirring for 12 hours at room temperature to obtain yellow transparent titanium dioxide sol;

(2) synthesis of polymethyl methacrylate (PMMA)

A mixed solution of Methyl Methacrylate (MMA) and an initiator (azobisisobutyronitrile, AIBN) was added dropwise from a dropping funnel to a 100mL three-necked round-bottomed flask equipped with a thermometer, a stirrer and a cooling device over 1 hour, and after completion of the addition, the ratio of the amounts of MMA to AIBN was adjusted to 2:0.05, and the system was kept at 70 ℃ and stirred for 12 hours to form a colorless transparent PMMA solution.

(3) Preparation of titanium dioxide hybridized polymethyl methacrylate

And (3) dropwise adding the prepared titanium dioxide sol into the PMMA solution obtained in the step (2) through a dropping funnel, violently stirring for 12 hours, sampling, standing, and cooling to room temperature to obtain the titanium dioxide hybridized polymethyl methacrylate.

The above preparation method refers to the following prior art: university of Shanxi newspaper (Nature science edition) 32 (2): 244 to 247,2009, polymethyl methacrylate-acrylamide/SiO₂/TiO₂Preparation and characterization.

Examples 1 to 8 and comparative examples 1 to 3 each provide a resin composition, and the specific formulation is shown in table 1.

TABLE 1

The details of the components in table 1 are as follows:

titanium dioxide-hybridized polymethyl methacrylate: the product of preparation 1.

Urethane acrylate having cyclohexyl group (formula I): SOU-1700B, SHIN-AT & C.

Urethane acrylate having cyclohexyl group (formula II): SOU-1290, SHIN-AT & C.

An acrylate having an ethylene glycol group (formula III): m is 1, M4004, manufactured by Meiyuan specialty Chemicals Co.

An acrylate having an ethylene glycol group (formula IV): p and n are both 2, DPEA126, manufactured by Nippon chemical Co.

Solvent: propylene glycol methyl ether acetate.

Initiator: ingacure184, manufactured by basf.

Example 9

The difference from example 4 is that in the acrylate with ethylene glycol group of formula III, M is 2 (available from MIWON SPECIATY under the brand name M-4004), and in the acrylate with ethylene glycol group of formula IV, p and n are both 1 (available from Japan chemical company under the brand name DPEA-12).

And (3) performance testing:

the resin compositions of the above examples and comparative examples were uniformly mixed in proportion in a light-shielding container, then coated on the surface of a flexible substrate using a coating apparatus, dried at 100 ℃ for 2min, and then cured under Ultraviolet (UV) irradiation at a wavelength of 365nm for 2min to obtain a hard coating.

The test method comprises the following steps:

(1) surface hardness test: the pencil hardness was measured at a rate of 180mm/min under a load of 750gf using a pencil hardness meter;

(2) curling: testing the hard coating by using a bending machine to obtain the minimum curvature radius which does not generate cracks after being bent for 10000 times, namely the bending radius;

(3) wear resistance: the flexible substrate was fixed on a flat surface with the hard coat layer surface facing upward, and a rod wound with a nonwoven fabric was reciprocated 1000 times at a speed of 15rpm under a load of 1kgf to examine whether or not scratches were generated, and the evaluation criteria were as follows:

a: less than 10 scratches;

b: greater than 10 and no greater than 20 scratches;

c: greater than 20 and no greater than 30 scratches;

d: greater than 30 scratches.

The results of the above performance tests are shown in table 2.

TABLE 2

As can be seen from the data in Table 2, the resin composition provided by the invention forms a hard coating after being cured, which has good hardness and flexibility, and simultaneously has good wear resistance, the hardness grade is 4H or more, the highest can reach 5H, and the bending radius is 4mm or less, and the lowest can reach 2 mm.

Comparative examples 1 to 3 are different from example 4 only in that any one of titanium dioxide hybridized polymethylmethacrylate, urethane acrylate having cyclohexyl group and acrylate having ethylene glycol group is omitted, respectively, but the hardness and flexibility of comparative examples 1 to 3 are significantly reduced compared to example 4, thereby proving that there is a certain synergistic effect between the above three components in the present invention, resulting in an effect of 1+1 > 2, and the technical effect of the present invention cannot be achieved by omitting any one of them.

From comparative examples 4 and 5, it is understood that the use of both urethane acrylates having cyclohexyl groups of formula I and formula II (example 4) further improves the hardness and flexibility of the cured product as compared with the use of only one of formula I and formula II (example 5).

As is apparent from comparative examples 4 and 6, the use of both of the acrylates having ethylene glycol groups of the formulae III and IV (example 4) further improves the hardness and flexibility of the cured product as compared with the use of only one of the formulae III and IV (example 6).

The present invention is illustrated in detail by the examples described above, but the present invention is not limited to the details described above, i.e., it is not intended that the present invention be implemented by relying on the details described above. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. A resin composition, characterized in that the resin composition comprises the following components: titanium dioxide-hybridized polymethyl methacrylate, urethane acrylate with cyclohexyl, acrylate with ethylene glycol group and photoinitiator;

the urethane acrylate having a cyclohexyl group and the acrylate having an ethylene glycol group each independently contain at least two reactive functional groups.

2. The resin composition of claim 1, wherein the titanium dioxide hybridized polymethyl methacrylate is prepared by a method comprising: mixing the titanium dioxide sol and the polymethyl methacrylate, and reacting to obtain the titanium dioxide hybridized polymethyl methacrylate.

3. Resin composition according to claim 1 or 2, characterized in that the urethane acrylate with a cyclohexyl group comprises a compound of formula I and/or a compound of formula II, preferably a combination of a compound of formula I and a compound of formula II;

in the formula I, A is

The dashed line marks represent the linking of groups;

4. the resin composition according to any one of claims 1 to 3, wherein the acrylate having an ethylene glycol group comprises a compound of formula III and/or a compound of formula IV, preferably a combination of a compound of formula III and a compound of formula IV;

in the formula III, m is an integer of 1-4, preferably 1;

in formula IV, p and n are each independently an integer of 1 to 4, preferably 2.

5. The resin composition according to any one of claims 1 to 4, wherein the content of the titanium dioxide-hybridized polymethyl methacrylate in the resin composition is 10 to 30 wt.%.

6. The resin composition according to any one of claims 1 to 5, wherein the content of the urethane acrylate having a cyclohexyl group in the resin composition is 10 to 30 wt.%.

7. The resin composition according to any one of claims 1 to 6, wherein the content of the acrylate having an ethylene glycol group in the resin composition is 10 to 30 wt.%.

8. The resin composition according to any one of claims 1 to 7, wherein the photoinitiator is present in the resin composition in an amount of 2 to 10 wt.%;

preferably, the photoinitiator comprises a cleavage type radical initiator and/or a hydrogen abstraction type radical initiator.

9. The resin composition according to any one of claims 1 to 8, further comprising a solvent;

preferably, the solvent comprises any one or at least two of propylene glycol methyl ether acetate, methyl isobutyl ketone or methyl ethyl ketone;

preferably, the content of the solvent in the resin composition is 30-70 wt.%;

preferably, the resin composition further comprises an antioxidant and/or a leveling agent.

10. A flexible display panel comprising a hard coat layer containing a cured product of the resin composition according to any one of claims 1 to 9.