A color resist dispersion liquid and its application

Abstract

The present invention relates to the field of display panel preparation, and particularly relates to a color resist dispersion liquid and its application. The dispersion resin modified on the surface of pigment particles has charged groups and polymerization groups, and combines polymerization technology and charged selective electrophoretic deposition technology (SEPD) to realize the production of a full-color CF substrate, achieving the purposes of high reliability, process saving, cost reduction, and environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the field of display panel preparation, and particularly to a color resist dispersion liquid and its application. Background Art

[0002] As the upper substrate of the TFT-LCD panel, the full-color CF substrate combines with the TFT substrate to form a liquid crystal cell, and decomposes the backlight white light into three primary colors of red, green, and blue through the principle of light filtration to achieve full-color display. The preparation process of the full-color CF substrate generally includes the following steps:

[0003] 1 Substrate treatment

[0004] Using high-purity glass as the substrate, cleaning and surface activation treatment are carried out to ensure the uniformity and adhesion of subsequent coatings.

[0005] 2 Black matrix (BM) formation

[0006] Coating a photoresist containing carbon black, and forming a grid-shaped light-shielding structure through exposure and development processes, which is used to separate pixels and enhance contrast.

[0007] 3 Coating of color layers (R / G / B color resists)

[0008] Using the pigment dispersion method or the dyeing method, successively coating red, green, and blue color resist materials (such as acrylic resin-based photoresists), and forming an accurate pixel array through photolithography processes. The color resist materials need to meet the requirements of high color purity, heat resistance, and chemical stability.

[0009] 4 Covering of protective layer (Over Coat)

[0010] Coating a transparent resin layer (such as acrylic, silicone resin, or polyimide), which is used to flatten the surface, protect the color resist layer, and enhance mechanical strength.

[0011] However, due to the diffraction of UV light in the mask exposure process of the CF film layer of the LCD, the line width and accuracy of the color resist are often limited. The minimum resolution of a conventional CF exposure machine is ~10 μm, which is difficult to meet the requirements of high-resolution products such as AR / VR. Therefore, currently, to manufacture a high-PPI color resist layer, it is generally achieved by developing a high-standard color resist + a high-resolution exposure machine, which makes its manufacturing cost relatively high.

[0012] The charged selective electrophoretic deposition technology (SEPD) has shown potential in the preparation process of colloidal quantum dot (QD) displays. By combining photolithography technology with SEPD technology, quantum dot patterns are selectively deposited only on the patterned electrodes, and uniform and rapid manufacturing of low-cost QD patterns is achieved on a large area of more than 1000 pixels per inch. However, for the colloidal quantum dots deposited in this way, they are only stacked into a film by physical action, and the film layer is prone to peeling, and the reliability is poor. Summary of the Invention

[0013] In view of the above-mentioned deficiencies such as the high difficulty and high cost in preparing the color resist layer with high PPI, the present invention provides a color resist dispersion liquid and its application.

[0014] Provide a reliable photosensitive electrodeposition material solution to solve the curing process problem in the later stage of the electrodeposition material and improve the optical performance and reliability of the color resist layer.

[0015] The technical solution of the present invention is realized as follows: Provide a color resist dispersion liquid, including a polar solvent, a monomer dissolved in the polar solvent, and a modified pigment;

[0016] The modified pigment is a pigment with a dispersion resin surface-modified and connected thereto, and the dispersion resin has a charged group and a polymerization group; the charged group dissociates and becomes charged in the polar solvent, and the polymerization group can undergo a cross-linking polymerization reaction with the monomer under initiation conditions.

[0017] In a preferred embodiment of the present invention, the polar solvent is selected from one of diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), cyclohexanone, isophorone;

[0018] The charged group is selected from at least one of -OH, -COOH, -NH2, -NHR.

[0019] In a preferred embodiment of the present invention, the initiation condition is photoinitiation, and the photosensitive reaction group on the polymerization group undergoes a photocuring reaction with the monomer. The photosensitive group of the photoresist needs to be a monomer containing an unsaturated group (alkenyl, alkynyl), so that the deposited pigments (polymers) cross-link with each other and solidify. According to the different exposure light sources and radiation sources, it is further divided into ultraviolet photoresist (including ultraviolet positive and negative photoresists), deep ultraviolet photoresist, X-ray resist, electron beam resist, ion beam resist, etc.

[0020] In a preferred embodiment of the present invention, the initiation condition is thermal initiation, and the thermosensitive reaction group on the polymerization group undergoes a thermal curing reaction with the monomer.

[0021] In a preferred embodiment of the present invention, the thermosensitive reaction group is the silicon-oxygen bond in the silicon-oxygen chain, and this silicon-oxygen bond can undergo an organosilicon thermal polymerization reaction with a silane monomer under thermal initiation conditions.

[0022] In a preferred embodiment of the present invention, the thermosensitive reaction group is an epoxy group, and this epoxy group can undergo an epoxy thermal polymerization reaction with the monomer under thermal initiation conditions.

[0023] The present invention also provides a method for preparing a color resist layer, which includes the following steps:

[0024] S1. Engrave the entire surface of R, G, and B electrodes on the CF substrate by photolithography technology;

[0025] S2. For the aforementioned color resist dispersion liquid, apply electric control to enable the modified pigment to be directionally deposited on the three electrodes; a polymer material (dispersion resin) containing charged groups and polymer groups is directly grafted onto R, G, and B pigment molecules, so that the pigment particles carry a single electric charge and are evenly dispersed in the solvent, thereby obtaining the corresponding color resist dispersion liquid;

[0026] S3. Under the initiation conditions, the polymer groups on the modified pigment undergo a cross-linking polymerization reaction with the monomers, and cross-linking and curing form a color resist layer.

[0027] In a preferred embodiment of the present invention, the electrodes of each color are connected to facilitate subsequent power supply. The required R, G, and B electrode shapes are engraved on the substrate, which can be circular, square, rectangular, etc. (the shape can be adjusted arbitrarily according to the requirements of the model), and this will determine the final shape of the color resist layer after electrophoretic deposition.

[0028] In a preferred embodiment of the present invention, the color resist dispersion liquids of R, G, and B are used one by one to respectively form color resist layers of corresponding colors.

[0029] In a preferred embodiment of the present invention, after curing the color resist of one color, it is cleaned and then the color resist process of another color is carried out. Where there is no pigment, cross-linking and curing cannot occur due to the absence of pigment, and no color resist residue will be generated.

[0030] The beneficial effects are as follows:

[0031] The production of a full-color CF substrate is achieved through the combination of initiation polymerization technology and pigment charged selective electrophoretic deposition (SEPD), achieving the purposes of high reliability, process saving, cost reduction, and environmental friendliness.

[0032] (1) High reliability. Different from the traditional one-step curing (after two power supply depositions, then full-surface curing), this patent adopts one-by-one curing (electrophoretic deposition of R → curing of R → cleaning → electrophoretic deposition of G →...). After curing one color resist, other color resist processes are carried out, effectively avoiding color mixing between different color resists.

[0033] (2) High resolution. Modifying the charge of the pigment molecules and grafting polymer groups can enable the pigment particles to be accurately deposited on the electrodes after power supply, and the minimum resolution can reach 2 μm.

[0034] (3) Simple process. After the pigment is deposited, the entire surface is cured. The polymer groups can polymerize with the free monomers in the solvent to solidify the pigment molecules, and the remaining sites can be released directly through a single cleaning process at the positions without pigment.

[0035] (4) Good optical performance. The pre-grafted polymer can ensure the uniform dispersion of the pigment in the color resist layer, thus making the light emission more uniform.

[0036] (5) Eliminate the BM process and improve penetration. After different pigments are accurately deposited on their respective electrodes, there is no longer film layer overlap, so the BM between the overlaps can be omitted, and at the same time, it can also bring an increase in the panel penetration rate. Description of the Drawings

[0037] Figure 1(a) is a schematic diagram of the process of modifying and decorating the reaction sites of the pigment in Example 1, and Figure 1(b) is a schematic diagram of the process of modifying and decorating the pigment and connecting the dispersion resin in Example 1.

[0038] Figure 2(a) is a schematic diagram of the process of modifying and decorating the reaction sites of the pigment in Example 2, and Figure 2(b) is a schematic diagram of the process of modifying and decorating the pigment and connecting the dispersion resin in Example 2.

[0039] Figure 3 It is the infrared spectrogram of the modified R and G pigments in the examples.

[0040] Figure 4 It is a schematic diagram of the structures of the R, G, and B electrodes on the substrate. Specific Embodiments

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0042] The present invention will be further described in detail below in conjunction with the drawings and embodiments.

[0043] Solution 1:

[0044] Modify the photosensitive polymer (resin) on the surface of the pigment particles. The groups such as -COOH (or -NH2) carried on the polymer can dissociate and become charged in a polar solvent, and then the pigment is selectively deposited by applying an electric drive, so that the pigment can be deposited at the corresponding positions. The photosensitive reaction groups carried on the polymer can provide crosslinking sites for subsequent photocuring.

[0045] The key to this invention lies in pigment modification, and its specific steps are as follows:

[0046] (1) Modify active groups on the surfaces of R, G, and B pigment molecules to provide reaction sites for subsequent polymer coating. These can be further reactive groups such as -OH, vinyl, ethynyl, halogen, etc.

[0047] (2) Coat the pigment particles with a polymer to increase the steric hindrance of the pigment. These can be one or more combinations of vinylpyrrolidone, styrene, carboxystyrene, aminostyrene, hydroxyethyl acrylate, methacrylate, acrylate, etc.

[0048] (3) Modify photosensitive reaction groups on the polymer chain for subsequent photocuring reactions. These can be functional groups such as vinyl and ethynyl that can undergo further crosslinking.

[0049] (4) Mix the obtained modified pigment with solvents, monomers, additives, initiators, etc. to prepare a photoresist for use.

[0050] Example 1: (Pigment Modification I):

[0051] (1) Modify the reaction sites. First, hydroxylate the pigment surface with concentrated HI, and then react with allyl bromide to modify vinyl unsaturated groups.

[0052] (2) Conduct polymer coating. The polymerization monomers include hydroxyethyl acrylate and isooctyl acrylate. Under the catalysis of the polymerization initiator AIBN, free radical polymerization is carried out to coat the pigment, thereby improving the dispersibility of the pigment in the solvent.

[0053] (3) Graft photosensitive groups. Compound 1 with photosensitive groups is obtained through isophorone diisocyanate and hydroxyethyl acrylate, and then Compound 1 is grafted onto the pigment molecules to obtain G pigment with uniform positive charge (-NH-R dissociates to be positively charged in the solvent) and photosensitive groups. The specific preparation process is shown in Figures 1(a) and 1(b), and the infrared spectrum is as Figure 3 shown. Modified G colorant: 3404 cm -1 is for N-H, 2942 cm -1 is the stretching vibration absorption peak of C-H on alkyl or cyclohexyl, 1726 cm -1 is the stretching vibration absorption peak in the ester group, 1640 cm -1 is the stretching vibration absorption peak of C=C, 1508 cm -1 and 1460 cm -1 are the vibration absorption peaks of the benzene ring skeleton C=C, 1158 cm -1 is the stretching vibration absorption peak of the ester group C-O-C.

[0054] Example 2 (Pigment Modification II):

[0055] (1) Modify the reaction sites. First, coat the surface of the pigment with SiO2, and then graft a silane coupling agent (such as KH570).

[0056] (2) Conduct polymer coating. The polymerization monomers include 2-hydroxyethyl acrylate, isooctyl acrylate, and 4-carboxystyrene. Free radical polymerization is carried out under the catalysis of the polymerization initiator AIBN to coat the pigment, thereby improving the dispersibility of the pigment in the solvent.

[0057] (3) Graft the photosensitive group. Graft the compound 1 with the photosensitive group obtained in Example 1 onto the pigment molecule to obtain the R pigment with uniform negative charge (-COOH dissociates to be negatively charged in the solvent) and with a photosensitive group. The specific preparation process is shown in Figures 2(a) and 2(b), and the infrared spectrum is as Figure 3 shown. Modified R color material: 3399 cm -1 is the stretching vibration absorption peak of the NH or OH group on the carboxyl group in the molecule, 2955 cm -1 , 2933 cm -1 are the stretching vibration absorption peaks of C-H on the alkyl or cyclohexyl group, 1733 cm -1 is the stretching vibration absorption peak of C=O in the ester group, 1645 cm -1 is the stretching vibration absorption peak of C=C, 1605 cm-1, 1500 cm -1 , 1449 cm -1 are the vibration absorption peaks of the benzene ring skeleton C=C, 1147 cm -1 is the stretching vibration absorption peak of C-O-C in the ester group.

[0058] Example 3 (Photoresist mixing):

[0059] (1) Weigh 0.1 - 1 wt% of the additive, 0.1 - 2 wt% of the initiator, and 5 - 15 wt% of the monomer and dissolve them in 60 - 80 wt% of the solvent, and stir to make the solution uniform;

[0060] (2) Add 5 - 15 wt% of the modified pigment and stir at room temperature for 0.5 - 12 h;

[0061] (3) Filter to obtain the target photoresist.

[0062] Example 4 (Preparation of the color resist layer on the CF substrate)

[0063] Product manufacturing process, forming the color resist layers of each color one by one:

[0064] (1) First, engrave the entire surface of the R, G, and B electrodes (the electrodes of a single color should be connected to facilitate later power supply) by mask lithography technology. The schematic structure is as Figure 4 ;

[0065] (2) A photoresist obtained by modifying and mixing to obtain pigment particles containing a single positive (or negative) charge R, G, B and having a photosensitive group;

[0066] (3) Coating the R photoresist and applying an electric charge to the pre-lithographed R pattern position. Among them, a positive potential is applied to the R color resist position, and a negative potential is applied to the G and B color resist positions. The applied voltage can range from 0.5 V / um to 5 V / um. The particle migration action can usually be completed within a few seconds or dozens of seconds;

[0067] (4) Then, drying the solvent, performing full-surface exposure, and post-drying can obtain the R single-channel color resist layer.

[0068] (5) Repeat 3 times to obtain a full-color CF layer containing R, G, B. The relevant results are shown in the following table.

[0069]

[0070] The above embodiment combines the principle of particle electrophoresis with the production of photoresist, and develops a photoresist with high-selectivity electrodeposition. It can use a one-step electrodeposition curing method to accurately deposit the photoresist onto the pre-etched electrode pattern. This can provide a cost-effective alternative solution for manufacturing high-PPI color resists. Its resolution can reach a minimum of 2 μm, and it has the advantages of high material utilization rate, saving the lithography process, and being environmentally friendly. It is of great significance to the improvement of the existing color resist process.

[0071] The photoresist electrodeposition technology has great technical advantages, but the process difficulty of its implementation is very high. One is that it is difficult to control the surface charge of the particles and their response threshold to the electric field. The second is that after a single electric charge application is completed, the particles need to be fixed (because different from quantum dots, after curing, the pigment dispersion and reliability in the liquid crystal panel need to be considered). Therefore, how to solve the particle charge regulation and the curing of the deposited pigment particles has become a problem worthy of discussion. Based on this, in this embodiment, a polymer material (dispersion resin) containing charged groups and photosensitive reaction groups is directly grafted onto the R, G, B pigment molecules, so that the pigment particles carry a single electric charge and are uniformly dispersed in the solvent, thereby obtaining the corresponding color photoresist material and solving the curing problem after the deposition of the electrodeposited photoresist.

[0072] Combined with the entire surface R, G, and B electrodes pre-sculpted by mask lithography technology, an electro-control system is used to control the directional deposition of pigment particles. Then, the entire substrate is exposed to light to crosslink and cure the photosensitive reactive groups on the pigments. Finally, a cleaning process is carried out to complete one or two color resist processes. Repeating one or two processes can produce a full-color CF substrate (where there is no pigment, no crosslinking and curing can occur due to the absence of pigment and photosensitive resin, and no color resist residue will be generated). The electro-deposited color resist layer produced in this way not only has controllable dimensions and high resolution, but also greatly improves the color uniformity and reliability of the color resist layer.

[0073] The optional methods in the specific implementation process are as follows:

[0074] ① Pigments include: Pigment Red 9, 19, 38, 43, 97, 122, 123, 144, 149, 166, 168, 177, 179, 180, 192, 208, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 240, 252, 254, 255, 264, 270, 291. Among them, the most common pigments in photoresist are 177, 254, 291; Pigment Green 7, 36, 56, 58, 59, G Dye (zinc phthalocyanine); Pigment Blue 15, 15:6, 16, 22, 23, 29, 60, 64; Pigment Green 7, 36, 56. Pigment Yellow 20, 23, 24, 86, 81, 83, 93, 108, 109, 110, 117, 125, 137, 138, 139, 147, 148, 150, 153, 154, 166, 168, 185, 231.

[0075] ② The unsaturated carboxylic acids used for pigment modification are selected from one or a combination of several of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, vinyl benzoic acid, etc.; the unsaturated amines are selected from one or a combination of several of vinyl aniline, vinylamine, etc.; the compounds containing unsaturated double bonds are selected from one or more of acrylate, methacrylate, styrene, a-methylstyrene, acrylonitrile.

[0076] ③ The solvent is usually a single polar solvent, and -COOH (-NH2) on the pigment polymer can be directly dissociated in the solution to promote particle charging. Most are ketones, ethers and ketone solvents with medium to high boiling points and low evaporation rates, such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), cyclohexanone, isophorone, etc.

[0077] ④ Monomers: The common polymerizable monomers (crosslinking agents) are acrylates of polyhydric alcohols.

[0078] ⑤ Initiator: including one or a mixture of more than one of 2,2 - azobisisobutyronitrile, benzoin, benzophenone, anthraquinone, acetophenone, bisimidazole, etc.

[0079] Scheme Two:

[0080] Modify the thermosensitive polymer (resin) on the surface of the pigment particles. The groups such as -COOH (or -NH2) carried on the polymer can be dissociated and charged in a polar solvent, and then the pigment is selectively deposited by applying an electric drive, so that the pigment can be deposited at the corresponding position. The thermosensitive reaction groups carried on the polymer can provide cross - linking sites for subsequent photocuring.

[0081] Similar to Scheme One, the polymerization groups will undergo a curing reaction with the monomers in the solution. The difference lies in that the reaction type is a thermal curing reaction, and the initiation condition is not photo - initiation but thermal initiation.

[0082] For example, the thermal curing reaction is an organosilicon thermal polymerization reaction. The oxygen atoms in the multifunctional silane monomers replace the silicon atoms in the silicon - oxygen chain to form silicon - oxygen - silicon bonds. The result of the cross - linking reaction is to form a three - dimensional network structure of organosilicon resin. The degree of cross - linking depends on the molar ratio of the multifunctional silane monomers and the conditions of the cross - linking reaction. The more cross - linking, the higher the hardness and strength of the resin.

[0083] Another example, the thermal curing reaction is an epoxy thermal polymerization, and the thermosensitive reaction group is an epoxy group. This epoxy group can undergo an epoxy thermal polymerization reaction with the monomers under thermal initiation conditions. Although the epoxy group has extremely high reactivity, it is very stable by itself without a curing agent, catalyst or harmful impurities. Under the catalytic action of Lewis bases such as tertiary amines or Lewis acids such as boron trifluoride, the epoxy group will undergo ring - opening homopolymerization according to the ionic polymerization reaction mechanism. If there is a tertiary amine present, the epoxy group will undergo ring - opening reaction according to the anionic polymerization process, causing the molecular chain to grow or cross - link continuously.

[0084] Optionally, the charging of the R, G, B pigment particles in the above - mentioned embodiments can be regulated by adjusting the monomers used in polymerization and their dosages.

[0085] The modified pigment structures listed above are only partial representatives. Other color - resistance dispersion liquids and related applications with the same concept are all within the scope of this patent protection.

[0086] Although the embodiments of the present invention have been shown and described above, it can be understood that the above - mentioned embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above - mentioned embodiments within the scope of the present invention.

Claims

1. A method for preparing a color resist layer, characterized in that, It includes the following steps: S1. Engrave the entire surface of R, G, and B electrodes on the CF substrate by lithography technology; S2. Apply electric control to the color resist dispersion liquid to enable the modified pigment to be directionally deposited on the three electrodes; S3. Under the initiation condition, the polymerization group on the modified pigment undergoes a cross-linking polymerization reaction with the monomer, and cross-linking and curing form a color resist layer; Among them, the color resist dispersion liquid includes a polar solvent, a monomer dissolved in the polar solvent, and a modified pigment; The modified pigment is a pigment with a dispersion resin surface-modified and connected, and the dispersion resin has a charged group and a polymerization group; the charged group dissociates and becomes charged in the polar solvent, and the polymerization group can undergo a cross-linking polymerization reaction with the monomer under the initiation condition.

2. The method for preparing the color resist layer according to claim 1, wherein The polar solvent is selected from one of diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, cyclohexanone, and isophorone; The charged group is selected from at least one of -OH, -COOH, -NH2, and -NHR.

3. The method for preparing the color resist layer according to claim 1, wherein The initiation condition is photoinitiation, and the photosensitive reaction group on the polymerization group undergoes a photocuring reaction with the monomer.

4. The method for preparing the color resist layer according to claim 1, characterized in that, The initiation condition is thermal initiation, and the thermosensitive reaction group on the polymerization group undergoes a thermal curing reaction with the monomer.

5. The method for preparing the color resist layer according to claim 4, wherein, The thermosensitive reaction group is the silicon-oxygen bond in the silicon-oxygen chain, and this silicon-oxygen bond can undergo an organosilicon thermal polymerization reaction with the silane monomer under the thermal initiation condition.

6. The method for preparing the color resist layer according to claim 4, characterized in that The thermosensitive reaction group is an epoxy group, and this epoxy group can undergo an epoxy thermal polymerization reaction with the monomer under the thermal initiation condition.

7. The method for preparing the color resistance layer according to claim 1, wherein, The electrodes of the same color are connected.

8. The preparation method of the color resist layer according to claim 1, characterized in that, The color resist dispersion liquids of the three colors of R, G, and B are used one by one to respectively form color resist layers of corresponding colors.

9. The method for preparing a color resist layer according to claim 8, wherein, After curing the color resist of one color, perform cleaning and then carry out the color resist process of another color.

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