Hard coating, preparation method thereof and flexible OLED touch display screen

Abstract

The invention relates to the technical field of touch display screens, in particular to a hard coating, a preparation method of the hard coating and a flexible OLED touch display screen. The invention discloses a hard coating. The hard coating comprises the following raw materials: POSS resin, a solvent and a first initiator, the weight ratio of the POSS resin to the solvent to the initiator is 100: 100: 4. The hard coating provided by the invention has good pencil hardness, scratch resistance, wear resistance, adhesive force, light transmittance, bending resistance, impact resistance and the like; when the hard coating is applied to the OLED touch display screen, the water and oxygen resistance stability, the bending resistance, the scratch and wear resistance and the impact resistance of the flexible OLED touch display screen are improved.

Description

Technical Field

[0001] The present application relates to the technical field of touch display screens, and in particular to a hard coating and a preparation method thereof, and a flexible OLED touch display screen. Background Art

[0002] Display screens used for high-definition display generally come in two forms: LCD and OLED. LCD is a transmissive light-emitting form, which realizes display by converting the light emitted by the backlight source through liquid crystal. Its contrast, color gamut, viewing angle, power consumption and response time are not as good as those of self-luminous OLED. Rigid OLED touch screens are generally encapsulated in glass and used as display panels in mobile phones and computers. Flexible OLED touch screens are generally encapsulated in thin films or ultra-thin glass (UTG) and are used in wearable electronic products or curved screens. Current OLED touch screens have the following disadvantages:

[0003] (1) Since the self-luminous layer of the OLED touch display is made of organic materials, its environmental stability such as temperature resistance, water vapor resistance, and humidity resistance is poor;

[0004] (2) Existing flexible OLED touch screens are encapsulated with thin films or ultra-thin glass (UTG), which have poor scratch resistance, wear resistance, bending resistance, and impact resistance.

[0005] In addition, frequent bending of OLED touch screens can cause fatigue problems. After being subjected to multiple compression and tensile stresses, creases and damage may appear in the middle of the screen. Although CPI film or UTG can be bent, they cannot meet the hardness requirements.

[0006] To this end, the present application provides a hard coating and a preparation method thereof, and a flexible OLED touch display screen. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present application provides a hard coating and a preparation method thereof, and a flexible OLED touch display screen. The hard coating has good pencil hardness, scratch resistance, wear resistance, adhesion, light transmittance, bending resistance, impact resistance and other properties; when the hard coating is applied to the flexible OLED touch display screen, the water and oxygen stability, bending resistance, scratch resistance, wear resistance and impact resistance of the flexible OLED touch display screen are improved.

[0008] The technical solution adopted by this application to solve its technical problem is:

[0009] In a first aspect, the present application provides a hard coating, comprising the following raw materials: a POSS resin, a solvent and a first initiator; the weight ratio of the POSS resin, the solvent and the initiator is 100:100:4.

[0010] In some embodiments, the first initiator is any one or more of 4-phenylbenzophenone, methyl o-benzoylbenzoate, and dimethyl benzoate.

[0011] In some embodiments, the preparation method of the POSS resin comprises the following steps:

[0012] S1. The silane coupling agent and the solvent are mixed, and a catalyst is added to react at 50-60°C for 20-60 minutes. After the reaction is completed, an inorganic acid is added and the mixture is kept warm;

[0013] The weight ratio of the silane coupling agent to the catalyst is 8:1;

[0014] S2. After the insulation is completed, water is added and the pressure is reduced; after the pressure is reduced, ethyl acetate is added and the liquid is separated to obtain an upper liquid;

[0015] S3. Washing the upper liquid with a metal chloride solution; adding sulfate to the washed upper liquid, and then decompressing to obtain a crude resin;

[0016] S4. The crude resin is purified to obtain POSS resin.

[0017] In some embodiments, the silane coupling agent is any one of an epoxy resin-based silane coupling agent, γ-aminopropyltriethoxysilane (KH-550) and vinyltrimethoxysilane; and the catalyst is any one of P2O5 and Mn2O7.

[0018] In some embodiments, in step S1, an acrylate compound and a second initiator are added together with the catalyst, and the reaction is carried out at 50-60° C. for 20-60 minutes. After the reaction is completed, an inorganic acid is added and the reaction is kept warm.

[0019] The acrylate compound is any one of methyl methacrylate, ethyl acrylate and butyl crotonate; the second initiator is any one of peroxybenzoylacetic acid and dibutyl peroxybenzoylformate.

[0020] In some embodiments, the preparation method of the POSS resin comprises the following steps:

[0021] S1. Mix the RSiX3 compound, polyurethane, water and solvent, add a catalyst to react at 50-60°C for 20-60 minutes, add an inorganic acid after the reaction, and keep warm;

[0022] The weight ratio of the RSiX3 compound to the catalyst is 20:1, and the molar ratio to water is 1:1.5;

[0023] In the RSiX3 compound, R is H or other organic functional groups, X is Cl or alkoxy; the catalyst is any one of acetic acid and adipic acid;

[0024] S2. After the insulation is completed, water is added and the pressure is reduced; after the pressure is reduced, ethyl acetate is added and the liquid is separated to obtain an upper liquid;

[0025] S3. Washing the upper liquid with a metal chloride solution; adding sulfate to the washed upper liquid, and then decompressing to obtain a crude resin;

[0026] S4. The crude resin is purified to obtain POSS resin.

[0027] In some embodiments, in step S1, hexafluorodianhydride is further added to carry out a catalytic reaction; the weight ratio of the silane coupling agent, the catalyst, and the hexafluorodianhydride is 60:7.5:5.

[0028] In some embodiments, in step S1, SiO2 nanoparticles are further added for catalytic reaction, and the weight ratio of silane coupling agent, catalyst, and SiO2 nanoparticles is 60:7.5:5.

[0029] In a second aspect, the present application provides a method for preparing the above-mentioned hard coating, comprising the following steps:

[0030] The material is taken according to the weight ratio of POSS resin: solvent: first initiator = 100:100:4, the POSS resin is added with the solvent and stirred to dissolve, and then the first initiator is added and stirred evenly; the sample is scraped on the carrier, dried and cured to obtain a hard coating.

[0031] In a third aspect, the present application provides a flexible OLED touch display screen, comprising the hard coating layer, and a carrier coated with the hard coating layer;

[0032] The flexible OLED touch display screen includes an In Cell structure or an On Cell structure;

[0033] In the In Cell structure, the carrier is a CPI film or a UTG cover layer, an encapsulation film, or a protective film;

[0034] In the On Cell structure, the carrier is a CPI film or a UTG cover layer, an OLED device layer, and a protective film.

[0035] The beneficial effects of this application are:

[0036] 1. The hard coating in the present invention is mainly a POSS resin hard coating, which has good pencil hardness, scratch resistance, wear resistance, adhesion, light transmittance, bending resistance, impact resistance and other properties.

[0037] Adding acrylate compounds to the synthesis of POSS resin can improve its adhesion, high-temperature adhesion and bending resistance; the yield of POSS resin synthesized using RSiX3 as raw material is low, but the yield can be improved by adding polyurethane and carboxyl-containing organic acid, and the bending resistance is improved; adding hexafluorodianhydride (6FDA) to the synthesis of POSS resin can improve its light transmittance, bending resistance and high-temperature resistance; adding SiO2 nano-ions to the synthesis of POSS resin can improve its transparency, hardness, wear resistance and thermal stability.

[0038] 2. The POSS hard coating in the present invention is coated on a carrier in a flexible OLED touch display screen, thereby improving the water and oxygen resistance, stability, bending resistance, scratch resistance, wear resistance and impact resistance of the flexible OLED touch display screen. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0040] Figure 1 This is a schematic diagram of the In Cell structure of the flexible OLED touch display screen described in this application;

[0041] Figure 2 This is a schematic diagram of the On Cell structure of the flexible OLED touch display screen described in this application;

[0042] Figure 3 This is a schematic diagram of the manufacturing process of the flexible OLED touch display screen described in this application. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the concept, specific structure and technical effects of the present application in combination with the embodiments and drawings, so as to fully understand the purpose, characteristics and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present application. In addition, all the connection / connection relationships involved in the patent do not simply refer to the direct connection of components, but refer to the formation of a better connection structure by adding or reducing connection accessories according to the specific implementation situation. The various technical features created in this application can be combined interactively without conflicting with each other.

[0044] Terminology explanation:

[0045] Coating: It is a solid continuous film layer of paint applied on the surface of an object, which plays a role in protection, waterproofing, insulation, decoration, etc.

[0046] OLED: Organic light-emitting diode, mainly used for display.

[0047] CPI: Traditional polyimide (PI) film has strong absorption in the visible light range due to the action of intermolecular and intramolecular charge transfer complex (CTC), and presents a dark brown-yellow color. CPI film refers to transparent polyimide film.

[0048] UTG: Ultra-Thin Glass, which means "ultra-thin glass", usually has a thickness between 1.2 mm and 0.1 mm. Ultra-thin glass with a thickness between 0.2 and 1 mm can be bent, while that with a thickness of less than 0.2 mm can be foldable.

[0049] In this application, the hard coating is composed of POSS resin, which is used to provide adhesion, improve scratch resistance, wear resistance, bending resistance and impact resistance. Frequent bending of flexible display screens can cause fatigue problems. After multiple compression and tensile stresses, crease damage may occur in the middle of the screen. Although CPI film or UTG can be bent, it cannot meet the hardness requirements. Therefore, in this application, a POSS transparent hard coating is added to the surface of CPI film or UTG, the side of the encapsulation film away from the touch layer, and the surface of the protective film to enhance the bending resistance, scratch resistance, wear resistance and impact resistance of the OLED flexible display screen.

[0050] The main component of the hard coating is POSS resin, and the general chemical structure is: (RSiO 3 / 2 ) n , R is a group connected by n vertices of Si atoms, 6≤n≤12. In the present application, the R group is one of epoxy resin group, aminopropyl triethoxy group and vinyl trimethoxy group, and the properties of the hard coating described in the present application are:

[0051] (1) Highly transparent: <1% light loss;

[0052] (2) Anti-scratch: 250g / cm 2 , >2500 times;

[0053] (3) Flexibility: R1.5, bending > 500,000 times;

[0054] (4) Impact resistance: 15cm drop resistance;

[0055] (5) Anti-fouling: water drop angle > 110 degrees;

[0056] (6) Good adhesion: high temperature resistant adhesion>3B.

[0057] Preparation Example 1

[0058] The preparation method of crude POSS resin is:

[0059] A1. In a 1000 ml three-necked flask equipped with a thermometer, a stirring device and a reflux cooler, 60 g of a silane coupling agent and 250 g of acetone were added, the stirring speed was adjusted to 100 rpm, and the temperature was raised to 50° C., wherein the silane coupling agent was one of an epoxy resin-based silane coupling agent, γ-aminopropyltriethoxysilane (KH-550) and vinyltrimethoxysilane;

[0060] A2, when the temperature reaches 50°C, keep warm for 10 minutes, add 7.5g of acidic solid catalyst to the above mixture within five minutes, and react at 50°C for 20-60 minutes, wherein the acidic solid catalyst is an acidic metal oxide such as P2O5 and Mn2O7;

[0061] A3, then add 45g hydrochloric acid (saturated concentrated hydrochloric acid), stir at 50°C, keep warm for 5-8h, and obtain a colorless and transparent reaction solution;

[0062] A4. After the reaction is complete, stop heating, add 360 g of deionized water, and stir for 10 minutes;

[0063] A5, distill under reduced pressure at 40°C for 0.5-1h by oil vacuum pump, add 300g ethyl acetate, stir for 20 minutes, then transfer the mixture to a 1000ml separatory funnel, separate the liquid, release the lower layer, retain the upper layer, and test the pH;

[0064] A6, weigh 500g of deionized water, add 5g of metal chloride, stir to dissolve, add to the separatory funnel in A5, cover with lid and shake manually for 5 minutes, separate the liquid, release the lower layer of liquid, and test the pH;

[0065] A7, pour the upper liquid after separation in A6 into a 1000ml beaker, slowly add 25g of sulfate, and the solution becomes clear and transparent;

[0066] A8. The clear liquid was transferred to a 1000 ml three-necked flask and distilled under reduced pressure at 40° C. for about 1-2 hours using an oil vacuum pump to obtain a product. The product was transferred to a black sealed container and stored in a refrigerator to obtain a crude POSS resin.

[0067] Preparation Example 2

[0068] In order to improve the properties of crude POSS resin, the following method was used to modify the crude POSS resin to prepare modified POSS resin.

[0069] Method 1: Increase the viscosity of crude POSS resin

[0070] In the reaction process of step A2, in addition to adding the solid catalyst, 10 g of an acrylate compound (CH2=CHCOOR) and 1 g of an initiator are added, wherein R represents a hydrocarbon group. The initiator is one of peroxybenzoylacetic acid and dibutyl peroxybenzoylformate, which is used for free radical polymerization. The remaining steps are consistent with steps A1, A3-A8 of Preparation Example 1.

[0071] By free radical polymerization, that is, the CH2=CHCOO- group in the acrylate compound and the vinyl, alkyl, epoxy and hydroxyl groups in the silane coupling agent undergo addition reaction, the acrylate compound-modified POSS is obtained, which can improve the viscosity, that is, the adhesion, of the POSS resin.

[0072] Method 2: Synthesize POSS using RSiX3 as raw material

[0073] RSiX3 generates new Si-O-Si bonds through hydrolysis, and then establishes a polyhedral cage-type three-dimensional skeleton structure with Si-O-Si bonds as edges, where R is H or other organic functional groups, and X=Cl or alkoxy.

[0074]

[0075] The reaction cycle of synthesizing POSS by this method is long, the synthesis yield is low, and the requirements for synthesis conditions are very high. In order to improve the synthesis yield and the hydrolysis reaction efficiency, a high molecular material polyurethane (mass is 10% of RSiX3) containing an ester group (-COO-) is added to the raw materials, and an organic acid (acetic acid, adipic acid, etc.) containing a carboxyl group is used as a catalyst (mass is 5% of RSiX3). The hydroxyl group and the silicon-oxygen bond on the POSS skeleton form an ester bond or other covalent bonds with the ester group and the carboxyl group of the organic acid, thereby improving the efficiency of the hydrolysis reaction and improving the yield of the POSS resin.

[0076] The specific preparation method is:

[0077] A1. In a 1000ml three-necked flask equipped with a thermometer, a stirring device and a reflux cooler, 60g of RSiX3 compound, 6g of polyurethane, 1.5 times the molar number of RSiX3 of water and 60g of n-hexane were added, the stirring speed was adjusted to 100 rpm and the temperature was raised to 50°C;

[0078] A2, when the temperature reaches 50°C, keep warm for 10 minutes, add 3g of organic acid catalyst to the above mixture within five minutes, and react at 50°C for 20-60 minutes, wherein the organic acid catalyst is acetic acid or adipic acid;

[0079] The remaining steps are consistent with steps A4-A8 of Preparation Example 1, except for step A3 of Preparation Example 1.

[0080] Method 3: Improving the transparency of POSS synthetic resin

[0081] In optoelectronic displays or optical applications, the transparency of the coating is extremely important. Therefore, when POSS resin is used as a transparent coating, its transparency is an important performance indicator.

[0082] In the reaction process of step A2, except adding solid catalyst, 5g hexafluorodianhydride (6FDA) is added as catalyst, because fluorine atom has the highest electronegativity, therefore hexafluorodianhydride (6FDA) has extremely strong electronegativity, can attract electron density, so can form stronger electronegativity center in molecule interior. The remaining steps are consistent with steps A1, A3-A8 of preparation example 1. The redistribution of this electron cloud helps to reduce the intermolecular π-π stacking effect, increases the spatial free volume of molecular chain, interrupts the conjugation between molecular chains, reduces the formation of charge transfer complex (CTC), thereby reduces the absorption of material in visible light region, thereby improves the light transmittance of film. In addition, the introduction of hexafluorodianhydride can also enhance the thermal stability of POSS, because it can stabilize molecular chain, reduces heat-induced structural changes. Therefore add hexafluorodianhydride (6FDA) as catalyst, its extremely strong electronegativity can reduce the accumulation and conjugation of molecular chain, reduces light absorption, thereby improves the transparency of POSS.

[0083] Method 4: Use inorganic nano-SiO2 to improve the transparency, hardness, wear resistance and thermal stability of POSS synthetic resin.

[0084] Another method for improving the transparency of POSS synthetic resin is in the reaction process of step A2, except adding solid catalyst, then add 5g size SiO2 nanoparticle below 10nm, less SiO2 nanoparticle can be more evenly dispersed in matrix, reduces light scattering, also reduces reunion, therefore can improve the transparency of POSS resin.In addition, SiO2 the refractive index of nanoparticle and the refractive index of POSS matrix are all about 1.5, and difference is less, can avoid causing light to have strong reflection and refraction at interface too much because of refractive index difference, causes the problem of transparency decline.All the other steps are consistent with steps A1, A3-A8 of preparation example 1.

[0085] Inorganic nano-SiO2 has good wear resistance, hardness and high temperature resistance. Its high rigidity and large specific surface area help to enhance the interfacial adhesion of the material and reduce the generation of defects. Therefore, the addition of SiO2 inorganic nanoparticle filler can improve the hardness, wear resistance and thermal stability of POSS synthetic resin.

[0086] Preparation Example 3

[0087] The prepared modified POSS resin can be purified, and the specific steps are as follows:

[0088] 1. Weigh 100 g of modified POSS resin, add 300 g of acetonitrile and stir to dissolve, transfer to a 1000 mL separatory funnel, and add 300 g of cyclohexane.

[0089] 2. Shake the separatory funnel vigorously and release the air for three times in a row, which takes about 2-3 minutes in total. After shaking, let it stand for 30 minutes. Observe the inner wall of the funnel. If there are small oil droplets between the lower layer of liquid and the inner wall, quickly tap the outer wall of the funnel with an ear bulb. After 30 minutes, collect the lower layer, discard the upper layer and rinse the separatory funnel. Pour the collected lower layer into the separatory funnel and add 300g of cyclohexane. Shake the separatory funnel vigorously and release the air for three times in a row, and let it stand for 1 hour.

[0090] 3. After standing for about 1 hour, the lower layer of liquid becomes clear from turbid, and the lower layer of liquid begins to be released. When the liquid is almost reaching the separation interface, close the knob and pour out the rest.

[0091] 4. Collect the lower layer of POSS-acetonitrile solution and filter it with a suction filter. Use a 0.22μm PTFE filter membrane for filtration. Both the upper and lower surfaces of the filter membrane need to be wetted and cannot dry out during filtration.

[0092] 5. Collect the filtrate and rotate it at 40°C and 120 rpm to obtain clear and transparent purified modified POSS resin after about 30-60 minutes.

[0093] Preparation Example 4

[0094] POSS coating preparation process:

[0095] The purified modified POSS resin: butanone: photoinitiator are added in a ratio of 100:100:4; the purified POSS resin is added with butanone and stirred to be evenly dissolved, then the photoinitiator is added and stirred evenly, filtered with a 0.1 μm double-sided hydrophobic PTFE filter membrane at positive pressure for 4 times, then scraped on a carrier, baked at 60°C for 3-5 minutes, and finally cured under a weak UV lamp for 2 times, each time for 3-5 seconds.

[0096] Example 1

[0097] The hard coating preparation comprises the following steps:

[0098] S1. Prepare crude POSS resin by steps A1-A8 of Preparation Example 1;

[0099] Adopt the purification process of Preparation Example 3, the crude resin is purified (i.e. in step 1 of Preparation Example 3, 100g of crude POSS resin is weighed);

[0100] S2. Prepare a hard coating by curing according to Preparation Example 4, wherein the carrier of the hard coating is UTG ultra-thin glass.

[0101] In the preparation example 1, the silane coupling agent in step A1 is an epoxy resin-based silane coupling agent.

[0102] The acidic solid catalyst in step A2 is P2O5,

[0103] The metal chloride in step A6 is CaCl2,

[0104] The sulfate in step A7 is magnesium sulfate.

[0105] Example 2

[0106] The hard coating preparation comprises the following steps:

[0107] S1. Prepare a modified POSS resin by using steps A1, A3-A8 of Preparation Example 1 and method 1 of Preparation Example 2, and purify the modified POSS resin by using the purification process of Preparation Example 3;

[0108] S2. Prepare a hard coating by curing according to Preparation Example 4, wherein the carrier of the hard coating is UTG ultra-thin glass.

[0109] Example 3

[0110] The hard coating preparation comprises the following steps:

[0111] S1. Prepare modified POSS resin by using steps A4-A8 of Preparation Example 1 and method 2 of Preparation Example 2,

[0112] The modified POSS resin was purified by the purification process of Preparation Example 3;

[0113] S2. Prepare a hard coating by curing according to Preparation Example 4, wherein the carrier of the hard coating is UTG ultra-thin glass.

[0114] Example 4

[0115] The hard coating preparation comprises the following steps:

[0116] S1. Prepare a modified POSS resin by using steps A1, A3-A8 of Preparation Example 1 and method 3 of Preparation Example 2, and purify the modified POSS resin by using the purification process of Preparation Example 3;

[0117] S2. Prepare a hard coating by curing according to Preparation Example 4, wherein the carrier of the hard coating is UTG ultra-thin glass.

[0118] Example 5

[0119] The hard coating preparation comprises the following steps:

[0120] S1. Using steps A1, A3-A8 of Preparation Example 1 and method 4 of Preparation Example 2, a modified POSS resin is prepared, and the purification process of Preparation Example 3 is used to purify the modified POSS resin;

[0121] S2. Prepare a hard coating by curing according to Preparation Example 4, wherein the carrier of the hard coating is UTG ultra-thin glass.

[0122] Comparative Example 1

[0123] The hard coating preparation comprises the following steps:

[0124] The other steps are the same as those in Example 1, except that: in step A2 of Preparation Example 1, the acidic solid catalyst is replaced by the alkaline solid catalyst NaOH, and in step A3 of Preparation Example 1, the hydrochloric acid is replaced by tetrabutylammonium fluoride to synthesize the crude POSS resin; and the purification process of Preparation Example 3 is adopted for purification.

[0125] Comparative Example 2

[0126] The other steps are the same as those in Example 1, except that the sulfate in Step A7 is removed in Preparation Example 1 to synthesize a crude POSS resin; and the crude POSS resin is purified using the purification process of Preparation Example 3.

[0127] Comparative Example 3

[0128] The other steps are the same as those in Example 1, except that in the reaction process of Step A2 of Preparation Example 1, in addition to adding the solid catalyst, 10 g of ethanol and 1 g of initiator are added to synthesize the crude POSS resin; and the crude POSS resin is purified by the purification process of Preparation Example 3.

[0129] Comparative Example 4

[0130] The other steps are the same as those in Example 1, except that: in the reaction process of step A2 of Preparation Example 1, in addition to adding the solid catalyst, 5 g of graphene with a size of less than 10 nm is added to synthesize the crude POSS resin; and the purification process of Preparation Example 3 is used for purification.

[0131] The POSS resins and coatings prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to the following performance tests, and the test results are summarized in Table 1.

[0132] The appearance was tested by visual inspection, and the thickness of the substrate and coating was tested by micrometer according to ASTM D 3652;

[0133] The transmittance is tested by photoelectric haze meter according to ASTM-D1003 standard;

[0134] The surface hardness is tested using the pencil hardness ASTM D3363 standard;

[0135] The scratch test is carried out using a multifunctional scratch tester according to ASTM D5178 standard.

[0136] Flexibility, i.e. the number of bending resistance, is tested using an MIT folding strength tester according to ASTM-D2176 standard;

[0137] The impact resistance was tested using a M&G pencil (K35, 12g, G5 tube);

[0138] The water drop angle test is conducted using a water drop angle tester in accordance with GB / T 30447-2013 standard;

[0139] The adhesion is tested using the 100-grid method (0B, 1B, 2B, 3B, 4B, 5B) according to GB / T 9286-2021 standard; the high-temperature adhesion test is carried out after the sample is boiled in water at 95°C for 30 minutes.

[0140] Table 1 Performance of POSS resin and coating (on UTG glass) of embodiments and comparative examples

[0141]

[0142] As shown in Table 1, during the synthesis of POSS, the addition of acrylate groups (CH2=CHCOOR) can improve its adhesion, high temperature adhesion and bending resistance;

[0143] The yield of POSS synthesized with RSiX3 as raw material is low, but it can be improved by adding polyurethane and carboxyl-containing organic acid, and the bending resistance is improved;

[0144] Adding hexafluorodianhydride (6FDA) to the synthesis of POSS can improve its light transmittance, bending resistance and high temperature resistance.

[0145] Adding SiO2 nanoparticles in POSS synthesis can improve its transparency, hardness, wear resistance and thermal stability;

[0146] The performance of POSS resins synthesized by alkaline catalysts and acidic catalysts is slightly different. When POSS is synthesized by alkaline catalysts, the yield is slightly reduced.

[0147] Removing inorganic salts during POSS synthesis will reduce the yield of POSS resin; adding graphene during POSS synthesis can improve its hardness, wear resistance and thermal stability, but will significantly reduce the transmittance.

[0148] The present application provides a flexible OLED touch display screen, comprising the above-mentioned hard coating and a carrier;

[0149] The specific OLED touch display screen is divided into two structures: In Cell and On Cell according to the location of the touch layer.

[0150] like Figure 1 As shown in the In Cell structure, the OLED display screen is composed of an optical film, a hard coating 1, a CPI film (transparent polyimide film) or UTG (ultra-thin glass), an OCA optical glue, a polarizer, a hard coating 2, an encapsulation film, a touch layer, an OLED device layer, a TFT (thin film transistor) film, a protective film, a hard coating 3, a flexible circuit board (FPC) and a control chip bound and connected to the touch layer. The optical film is one or more of AG (anti-glare), AR (anti-reflection), and AF (anti-fingerprint), which is used for the anti-glare, anti-reflection and anti-fingerprint protection functions of the display surface, and enhances the anti-reflection, viewing angle, light transmittance, anti-oil and fingerprint capabilities of the screen surface. CPI film or UTG are both flexible and bendable materials, belonging to hard ultra-thin films or glass materials, which are used to provide surface protection and touch and display support for the screen, replacing the glass cover in non-flexible display screens. OCA glue is used to bond CPI film or UTG and polarizer, and polarizer is used to effectively resist the interference of ambient light on the brightness and contrast of OLED display. The encapsulation film is a transparent BOPET (biaxially oriented polyester film) film with good rigidity and light transmittance, which is used to encapsulate OLED devices. The OLED device layer is an organic light-emitting device, which consists of a cathode, an electron injection layer, an electron transport layer, an organic light-emitting layer, a hole transport layer, a hole injection layer, an anode and a flexible substrate. The TFT film consists of a flexible film, a TFT thin-film transistor array etched thereon, and electrodes, which are used to control the light emission of OLED pixels. The protective film is also made of BOPET film and is pasted on the bottom of the OLED panel to further prevent damage and bending during the bending process of the OLED screen.

[0151] like Figure 2 As shown, in the On Cell structure, the OLED display screen is composed of an optical film, a hard coating 1, a CPI film or UTG, an OCA optical adhesive, a polarizer, a touch layer, an encapsulation film, a hard coating 2, an OLED device layer, a TFT film, a protective film, a hard coating 3, a flexible circuit board (FPC) bonded and connected to the touch layer, and a control chip.

[0152] It can be seen that in the In Cell structure, the carrier of the hard coating is the CPI film or UTG surface, encapsulation film, and protective film; in the On Cell structure, the carrier of the hard coating is the CPI film or UTG surface, OLED device layer, and protective film; the hard coating is used to provide adhesion, improve scratch resistance, wear resistance, bending resistance, and impact resistance.

[0153] The preparation process of OLED touch display is as follows: Figure 3 As shown, the specific steps are as follows:

[0154] T1. After cleaning the CPI film or UTG glass, a POSS coating is applied on the upper surface of the CPI or UTG. Specifically, the POSS coating process is as follows: POSS and butanone are weighed in a mass ratio of 1:1, mixed and stirred to dissolve evenly, a photoinitiator of 4% by mass of the POSS is added and stirred evenly, and a 0.1 μm double-sided hydrophobic PTFE filter membrane is used for positive pressure filtration 4 times to obtain a POSS solution to be coated, and then a POSS coating is applied on the upper surface of the CPI or UTG, and a weak UV lamp is used for irradiation for 3-5 seconds;

[0155] T2. Laminating or coating different optical films. The optical film may be one or more of the optical films or coatings with anti-fingerprint (AF), anti-glare (AG), and anti-reflection (AR) functions;

[0156] T3. Attach the polarizer on top of the OLED module to the lower surface of CPI or UTG using OCA optical adhesive;

[0157] T4, attach the encapsulation film (In Cell or OnCell) with touch layer and POSS hard coating under the polarizer.

[0158] Specifically, the manufacturing process of the encapsulation film with a touch layer and a POSS hard coating is as follows:

[0159] (1) The encapsulation film is a nano silver wire conductive film formed by coating nano silver wire ink on a BOPET film (biaxially oriented polyester film).

[0160] (2) Photolithography of the required pattern on one side of the nano silver wire conductive film to produce X-axis and Y-axis electrode matrices to form a touch sensor, and then plating metal circuits or screen-printing silver paste circuits to form a touch layer.

[0161] (3) Apply a POSS coating on the other side of the nano silver wire conductive film and irradiate with a weak UV lamp for 3-5 seconds.

[0162] (4) In the In Cell structure, the POSS coating is bonded to the polarizer above the encapsulation film, and the touch layer is bonded to the OLED device layer below the encapsulation film.

[0163] (5) In the On Cell structure, the touch layer is laminated to the polarizer above the encapsulation film, and the POSS coating is laminated to the OLED device layer below the encapsulation film;

[0164] T5. Use ACF glue to bind the FPC flexible circuit board to the packaging glass with the touch layer, bind the control chip to the FPC, apply protective glue to each binding position, and UV cure;

[0165] T6. After appearance inspection and functional testing, glue is dispensed and the OLED device with TFT thin film obtained by evaporation process is bonded. The interior of the OLED device is generally composed of an anode, a hole injection / transport layer, an organic light-emitting layer, an electron transport / injection layer, and a cathode.

[0166] T7. Apply a POSS coating on the protective film, adhere the protective film with the POSS coating to the TFT film, and then UV cure it, perform functional testing and appearance inspection, and obtain an OLED touch display screen.

[0167] The comparison of various performance parameters of UTG with and without POSS hard coating is shown in Table 2.

[0168] Table 2 Performance comparison of UTG with POSS coating and pure UTG

[0169]

[0170] It can be seen from Table 2 that the POSS hard coating has almost no effect on the transmittance, color difference and bendability of UTG (ultra-thin glass), where ΔE<1 means that the color difference is almost imperceptible and the color difference is very small, and 1≤ΔE<2 means that the color difference is weak and can only be detected upon careful observation; the POSS hard coating can significantly improve the surface hardness, impact resistance, water contact angle, scratch resistance and wear resistance and high temperature adhesion performance of UTG.

[0171] Therefore, the POSS hard coating has almost no effect on the transmittance, chromatic aberration and bendability of UTG (ultra-thin glass). The POSS coating can significantly improve the surface hardness, impact resistance, water contact angle, scratch resistance and wear resistance and high-temperature adhesion performance of UTG.

[0172] The above is a specific description of the preferred implementation of the present application, but the invention of the present application is not limited to the described embodiments. Technical personnel familiar with the field can also make various equivalent modifications or substitutions without violating the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A hard coating, characterized in that: The invention comprises the following raw materials: POSS resin, solvent and a first initiator; the weight ratio of the POSS resin, solvent and initiator is 100:100:

4.

2. The hard coating according to claim 1, characterized in that The first initiator is any one or more of 4-phenylbenzophenone, methyl o-benzoylbenzoate, and benzoin dimethyl ether.

3. The hard coating according to claim 1, characterized in that The preparation method of the POSS resin comprises the following steps: S1. The silane coupling agent and the solvent are mixed, and a catalyst is added to react at 50-60°C for 20-60 minutes. After the reaction is completed, an inorganic acid is added and the mixture is kept warm; The weight ratio of the silane coupling agent to the catalyst is 8:1; S2. After the insulation is completed, water is added and the pressure is reduced; after the pressure is reduced, ethyl acetate is added and the liquid is separated to obtain an upper liquid; S3. Washing the upper liquid with a metal chloride solution; adding sulfate to the washed upper liquid, and then decompressing to obtain a crude resin; S4. The crude resin is purified to obtain POSS resin.

4. The hard coating according to claim 3, characterized in that In step S1, the silane coupling agent is any one of epoxy resin-based silane coupling agent, γ-aminopropyltriethoxysilane (KH-550) and vinyltrimethoxysilane; the catalyst is any one of P2O5 and Mn2O7.

5. The hard coating according to claim 4, characterized in that In step S1, an acrylate compound and a second initiator are added together with a catalyst, and the reaction is carried out at 50-60° C. for 20-60 minutes. After the reaction is completed, an inorganic acid is added and the reaction is kept warm. The acrylate compound is any one of methyl methacrylate, ethyl acrylate and butyl crotonate; the second initiator is any one of peroxybenzoylacetic acid and dibutyl peroxybenzoylformate.

6. The hard coating according to claim 1, characterized in that The preparation method of the POSS resin comprises the following steps: S1. Mixing the RSiX3 compound, polyurethane, water and solvent, adding an organic acid catalyst at 50-60°C to react for 20-60 minutes; The weight ratio of the RSiX3 compound to the catalyst is 20:1; In the RSiX3 compound, R is H or other organic functional groups, X is Cl or alkoxy; the organic acid catalyst is any one of acetic acid and adipic acid; S2. After the reaction is completed, water is added and the reaction is decompressed; after the decompression is completed, ethyl acetate is added and the liquid is separated to obtain an upper liquid; S3. Washing the upper liquid with a metal chloride solution; adding sulfate to the washed upper liquid, and then decompressing to obtain a crude resin; S4. The crude resin is purified to obtain POSS resin.

7. The hard coating according to claim 4, characterized in that In step S1, hexafluorodianhydride is also added for catalytic reaction; the weight ratio of silane coupling agent, catalyst and hexafluorodianhydride is 60:7.5:

5.

8. The hard coating according to claim 4, characterized in that In step S1, SiO2 nanoparticles are also added for catalytic reaction, and the weight ratio of silane coupling agent, catalyst and SiO2 nanoparticles is 60:7.5:

5.

9. A method for preparing a hard coating according to any one of claims 1 to 8, characterized in that: The following steps are involved: The material is taken according to the weight ratio of POSS resin: solvent: first initiator = 100:100:4, the POSS resin is added with the solvent and stirred to dissolve, and then the first initiator is added and stirred evenly; the sample is scraped on the carrier, dried and cured to obtain a hard coating.

10. Flexible OLED touch display screen, characterized in that: A hard coating comprising the hard coating according to any one of claims 1 to 8 or the hard coating prepared by the preparation method according to claim 9, and a carrier coated with the hard coating; The flexible OLED touch display screen includes an In Cell structure or an On Cell structure; In the In Cell structure, the carrier is a CPI film or a UTG cover layer, an encapsulation film, or a protective film; In the On Cell structure, the carrier is a CPI film or a UTG cover layer, an OLED device layer, and a protective film.

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