WO2013012206A2

WO2013012206A2 - Alkali-soluble silicone resin, silicone resin composition comprising the same and preparation method thereof

Info

Publication number: WO2013012206A2
Application number: PCT/KR2012/005560
Authority: WO
Inventors: Jin Hyuk Lee; Seung Hyun Kang; Ji Yoon Park; Jung Mo An; Ji Hwan Park; Jang Hyun Yoo
Original assignee: Kcc Corporation
Priority date: 2011-07-15
Filing date: 2012-07-13
Publication date: 2013-01-24
Also published as: WO2013012206A3; TW201311770A; TWI557157B; KR20130009429A; KR101290260B1

Abstract

The present invention relates to an alkali-soluble silicone resin, a silicone resin composition comprising the same and preparation a method thereof. More specifically, the present invention relates to an alkali-soluble silicone resin which comprises 60 to 95 mol% of trifunctional structure and has a weight average molecular weight of 5,000 to 20,000, a silicone resin composition comprising the same and a preparation method thereof. The silicone resin composition of the present invention can provide excellent coating property, hardness, heat resistance and crack resistance.

Description

ALKALI-SOLUBLE SILICONE RESIN, SILICONE RESIN COMPOSITION COMPRISING THE SAME AND PREPARATION METHOD THEREOF

The present invention relates to an alkali-soluble silicone resin, a silicone resin composition comprising the same and a preparation method thereof. More specifically, the present invention relates to an alkali-soluble silicone resin which comprises 60 to 95 mol% of trifunctional structure and has a weight average molecular weight of 5,000 to 20,000, a silicone resin composition comprising the same and a preparation method thereof. The silicone resin composition of the present invention can provide excellent coating property, hardness, heat resistance and crack resistance.

Organic materials have been widely used in electronic industries such as display. Organic materials are advantageous in terms of low cost and good line conformity. However, as display devices have recently become large-scale, high resolution, and slim, the requirement for properties of coating materials to be applied thereto has become stricter. In light of this, conventional organic materials that are poor in properties such as heat resistance are limited in their application scope.

Accordingly, as a coating material having good properties in developing property (property of photoresist), transmittance, heat resistance, etc., silicone resins have received attention. Silicone resins are applied as semiconductor insulation films (for example, hydrogen polysiloxane), solvent-type coating agents (for example, a silicone resin diluted with aromatic organic solvent), solvent-free conformal coating agents, sealants and adhesives for electronics, and molding materials for LED chips.

Silicone resin manufacturers have produced various products such as silicone resin for paint, MQ resin, silsesquioxane, coating resin, etc. on the basis of conventional preparation technologies. Such preparation technologies would be known to a person skilled in the art. For example, a silicone resin can be prepared by condensing a hydrolysis product of chlorosilane or alkoxysilane. However, when a silicone coating material of an electronic grade for display is prepared by such a conventional method, defects in the coating surface may be caused by the strong catalyst used, ion species contained in the raw materials, gel particles generated during the preparation, etc. Furthermore, such a silicone coating material of display-applicable level cannot be produced in large scale with low cost, and thus the economic feasibility becomes low.

Korean Laid-open Patent Publication No. 10-2009-0072835 A relates to a water-soluble photosensitive silicone resin having good heat resistance and electrical insulation for liquid crystal display devices, and discloses a method for preparing the resin by a sol-gel reaction wherein a silicone compound is synthesized by a hydrosilation reaction of 4-pentenoic acid or 2-allylphenol with trimethoxysilane, and hydrochloric acid catalyst is added thereto. However, this method requires expensive starting materials, and the platinum catalyst used in the hydrosilation reaction and/or hydrochloric acid used as the reaction catalyst remain in the prepared resin and may chemically change the terminal carboxyl group and hydroxyphenyl group. A procedure for removing the residual catalyst such as hydrochloric acid may be further employed, but in this case the time and cost for production increase, and thus the productivity decreases.

Korean Laid-open Patent Publication No. 10-2009-0040079 A relates to a photosensitive polysilsesquioxane resin composition having good alkali-developing property and pattern resolution, and discloses a method for synthesizing the resin with a molecular weight of 1,800 to 4,500 by reacting acrylic silane and another alkoxysilane in an organic solvent by hydrochloric acid and diluting the prepared resin. However, this method uses trifunctional raw materials only, without mentioning the use of bifunctional groups or the like. Thus, after the prepared resin is coated and prebaked, cracks or pin-holes may occur in the coating layer. Furthermore, gelation by hydrochloric acid may occur during the procedure of polymerizing the acrylic silane.

Accordingly, there is a need to develop a silicone coating material which satisfies the principally required properties such as alkali-developing property, transmittance, coating property, heat resistance, hardness and crack resistance, and can be prepared on a large scale with low cost.

[Prior art publications]

Korean Laid-open Patent Publication No. 10-2009-0072835 A

Korean Laid-open Patent Publication No. 10-2009-0040079 A

The present invention is intended to solve the problems involved in the prior arts as stated above. The technical purpose of the present invention is to provide an alkali-soluble silicone resin that can be used as a coating agent for thin film transistor liquid crystal display device, etc. and has good alkali-developing property, coating property, heat resistance, hardness, crack resistance and productivity, and a composition comprising the same.

In order to achieve the above technical purpose, the present invention provides an alkali-soluble silicone resin comprising: (A) at least one thermally curable functional group selected from the group consisting of hydroxy, alkoxy and epoxy, (B) at least one alkali-developable functional group selected from the group consisting of hydroxy and alkoxy, (C) at least one functional group selected from the group consisting of C₁-C₂₀ alkyl groups and aromatic groups, and (D) 60 to 95 mol% of trifunctional structure derived from organotrialkoxysilane, wherein the resin has a weight average molecular weight of 5,000 to 20,000.

In another aspect, the present invention provides a silicone resin composition comprising said alkali-soluble silicone resin and solvent, and a method for preparing said silicone resin composition, the method comprising the steps of: (a) mixing an alkoxysilane raw material with dilution solvent, organic acid and water for hydrolysis; (b) distilling the obtained product under normal pressure to remove the organic acid and water; (c) adding further organic acid and water to the obtained product to hydrolyze the remaining raw material; (d) distilling the obtained product under reduced pressure at low temperature to further remove the organic acid and water; and (e) adding further dilution solvent and conducting an aging procedure to control the weight average molecular weight of the silicone resin to 5,000 to 20,000.

In another aspect, the present invention provides a coating layer formed by the application of said silicone resin composition.

The alkali-soluble silicone resin composition of the present invention has good coating property, heat resistance, hardness and crack resistance, and can be produced on a large scale with using raw materials cheaper than conventional raw materials, by which the application scope of silicone coating materials in electronic industries can be expanded. Specifically, the silicone resin composition of the present invention is alkali-developable with a level of 15 microns to the coating surface and can secure a transmittance of 95% or more (400nm, t = 3μm), heat resistance having a weight loss of 1% or less (280 to 350°C * 10 minutes) and hardness of about 6H pencil hardness.

Hereinafter, the present invention will be described more specifically.

The alkali-soluble silicone resin of the present invention comprises (A) at least one thermally curable functional group selected from the group consisting of hydroxy, alkoxy and epoxy, (B) at least one alkali-developable functional group selected from the group consisting of hydroxy and alkoxy, (C) at least one functional group selected from the group consisting of C₁-C₂₀ alkyl groups and aromatic groups, and (D) 60 to 95 mol% of trifunctional structure derived from organotrialkoxysilane, wherein the resin has a weight average molecular weight of 5,000 to 20,000. In another aspect, the silicone resin composition of the present invention comprises said alkali-soluble silicone resin and solvent (a solvent-dilution type silicone polymer).

The thermally curable functional group means a structure causing a curing reaction of the resin by heat source or radiation of light source, and this stems from the functionality of raw materials used in the resin synthesis. Examples of the thermally curable functional group may include hydroxy, alkoxy, epoxy, etc., and hydroxy group is preferred. In an embodiment, when a thin film of the resin composition is coated and heated, the solvent is evaporated by heat and at the same time the -OH groups in the resin rapidly react with each other to cause the curing.

Alkali-developing property means, for example, the dissolution of the coating layer when the coating surface is contacted with 0.4% to 2.38% aqueous solution of tetramethylammonium hydroxide (TMAH) which is generally used in electronic industries. Principally, as the alkali-developable functional group, hydrophilic groups are more preferred than hydrophobic groups. Concretely, hydroxy group (Si-OH) and alkoxy group (for example, Si-OCH₃) may be used. In terms of improvement in heat resistance, alkoxy group may be preferably replaced with silanol group as much as possible through the process. In light of this, the preferred one of the alkali-developable functional group may be Si-OH which is also mentioned above as a preferred thermally curable functional group. That is, the alkali-developable functional group and the thermally curable functional group are different in terms of the purpose of use but may be the same in terms of the structure.

Examples of C₁-C₂₀ alkyl groups and aromatic groups (preferably C₆-C₂₀ aromatic groups) may include methyl, phenyl, 3-glycidoxypropyl, 2-(3,4-epoxycyclohexyl)ethyl and the like, without limitation thereto.

Such organic groups are irregularly incorporated into the resin generated through the hydrolysis of raw materials, and in this case the curing rate and hardness of the coating layer may vary according to the functionality type of the used raw materials. If many trifunctional groups exist, the curing rate is high and the coating layer becomes hard but there is a disadvantage of brittleness. If many bifunctional groups exist, the storage stability of the resin is improved but there are the disadvantages of softness of the coating layer and low curing rate. Accordingly, the proper combination of bifunctional group and trifunctional group is important. In general, the proper combination of methyl and phenyl groups is an important factor in improving the coating property, and epoxy ring plays a role in complementing heat curability and adhesion.

In the alkali-soluble silicone resin of the present invention, the trifunctional structure derived from organotrialkoxysilane is incorporated in an amount of 60 to 95 mol% and more preferably 70 to 95 mol%, partially imparting the property of polysilsesquioxane to the resin. That is, 100% polysilsesquioxane is excluded from the present invention. This is a result of considering the provision of the optimized coating property, curing rate, storage stability, etc. as explained above. If the amount of the trifunctional structure contained in the resin is less than 60 mol%, the storage stability is improved but the coating layer becomes soft and the curing rate becomes low. If the amount of the trifunctional structure contained in the resin is greater than 95 mol%, the curing rate is high and the coating layer becomes hard, but there is a problem of brittleness.

Preferably, the alkali-soluble silicone resin further comprises 5 to 40 mol% of bifunctional structure in addition to the trifunctional structure. In order to coat silicone materials, it is principally necessary to incorporate a lot of trifunctional structure which has good coating property. However, if the bifunctional structure is further incorporated properly in addition to the trifunctional structure, the required properties other than coating property can also be obtained. A person skilled in the art may incorporate the bifunctional structure with a proper amount in consideration of the required properties (for example, coating property, hardness and high heat resistance) according to the use of the resin composition.

In the present invention, the alkali-soluble silicone resin has a weight average molecular weight of 5,000 to 20,000 and more preferably 5,500 to 15,000. The present inventors confirmed that when the weight average molecular weight of the resin was controlled within the scope of 5,000 to 20,000, the optimum properties of the coating surface were provided.

If the weight average molecular weight of the resin is less than 5,000, the dilution viscosity becomes low and thus the coating becomes non-uniform and sticking after prebaking occurs, and it is hard to obtain the desired coating hardness even though hardbaking has been conducted. To the contrary, if the weight average molecular weight of the resin is greater than 20,000, the lack of terminal alkali-developable groups deteriorates the function as a photoresist, and the phenomenon of brittleness may occur on the coating surface. If the molecular weight becomes extremely large and thus uncontrollable, gelation may occur during the resin-production process, and thus the production itself may be impossible.

The present invention uses alkoxysilane material as a raw material of the alkali-soluble silicone resin. Examples of the alkoxysilane may include methoxysilane, ethoxysilane and the like, without limitation thereto. Preferably, methoxysilane is used since it is cheap and easily available.

In an embodiment, if methoxysilane is used as a raw material, the hydrolysis of the terminal methoxy group under acid atmosphere results in replacement with silanol group and formation of siloxane bond at the same time. In this case, by adjusting the acidity of the used catalyst or the condensation method, many terminal silanol groups may remain or almost of them may be removed. Although the remaining -OH is condensed with other -OH in the same or adjacent molecules, the activity may be suppressed by excessive use of solvent and storage at low temperature. On the contrary, if the resin composition is coated as a thin film and heated, as explained above, the solvent is evaporated by heat, and simultaneously the rapid reaction between -OH participates in the curing.

Examples of the raw materials useful in preparing the alkali-soluble silicone resin composition of the present invention are shown in the following Table 1.

Table 1

In an embodiment, the alkali-soluble silicone resin may be represented by the following chemical formula 1 (the combination order of each unit may be changed).

[Chemical formula 1]

In the above chemical formula 1, R₁ is independently methyl, 3-glycidoxypropyl or hydroxy; R₂ is independently hydroxy; R₃ is independently methyl, phenyl, 3-glycidoxypropyl or 2-(3,4-epoxycyclohexyl)ethyl, preferably 2-(3,4-epoxycyclohexyl)ethyl; and a, b and c are mole fractions satisfying a + b + c = 1.

The properties of the coating surface vary according to the concrete kinds of R₁, R₂ and R₃, and the adjustment of a, b and c. The matters regarding this will be mentioned concretely in the examples described below.

In the above chemical formula 1, the relationship between the concrete kinds of R₁, R₂ and R₃ and the raw materials (Table 1) is shown in the following Table 2.

Table 2

In a preferred embodiment, the alkali-soluble silicone resin has a structure of the following chemical formula 2 after curing (the combination order of each unit may be changed).

[Chemical formula 2]

In the above chemical formula 2, n1 to n6 are mole fractions satisfying n1 + n2 + n3 + n4 + n5 + n6 = 1, and 0≤n1≤0.4, 0≤n2≤0.4, 0≤(n1+n2)≤0.4, 0≤n3≤0.95, 0≤n4≤0.95, 0≤n5≤0.95, 0≤n6≤0.95 and 0≤(n3+n4+n5+n6)≤0.95.

The silicone resin composition of the present invention comprises solvent in addition to the alkali-soluble silicone resin. There is no special limitation to the kind of solvent that can be used, and solvents conventionally used for silicone coating materials such as propyleneglycol monomethylether acetate (PGMEA) can be used alone or in combination of two or more. In a preferred embodiment, PGMEA is used as a solvent for the reaction (synthesis) and dilution in aging. There is no special limitation to the use amount of solvent, and it is preferably used in such an amount that the viscosity of the composition is in the range of 10 to 200cP.

There is no special limitation to the method for preparing the silicone resin composition of the present invention, and it can be prepared by using a general method in this field of art.

Preferably, the silicone resin composition of the present invention can be prepared by the method comprising the steps of: (a) mixing an alkoxysilane raw material with dilution solvent, organic acid and water for hydrolysis; (b) distilling the obtained product under normal pressure to remove the organic acid and water; (c) adding further organic acid and water to the obtained product to hydrolyze the remaining raw material; (d) distilling the obtained product under reduced pressure at low temperature to further remove the organic acid and water; and (e) adding further dilution solvent and conducting an aging procedure to control the weight average molecular weight of the silicone resin to 5,000 to 20,000.

First, an alkoxysilane material as the starting material is added dropwise to an aqueous mixture solution of dilution solvent (for example, PGMEA) and organic acid and hydrolyzed therein. In the present invention, the useful catalyst is organic acid, preferably acetic acid and/or oxalic acid, and more preferably acetic acid. If strong acid such as hydrochloric acid or sulfuric acid is used, additional procedures such as neutralization procedure or water-washing procedure, etc. is required separately and chloro group or the like may remain in the resin, resulting in deterioration of the properties of the final product. To the contrary, since organic acid (for example, acetic acid) has a low boiling point and high water solubility, it can be removed as much as possible by distillation after use, and even if it remains in the resin in an amount that does not affect the storage stability, it can be evaporated during the prebaking and hardbaking procedures thereafter. Accordingly, organic acid is very advantageous as a catalyst.

Next, the hydrolyzed product is refluxed to make the bonding solid and then distilled under normal pressure to remove the organic acid, water and byproducts (for example, methanol).

Again, the hydrolysis using an aqueous solution of organic acid is repeated, which seeks to remove the remaining alkoxy group in the resin as much as possible and is generally conducted 2 to 3 times. In this case, if the distillation is done under normal pressure with heating to high temperature to remove the organic acid and water, the molecular weight may increase rapidly as the temperature rises. Thus, the distillation is conducted under reduced pressure at room temperature and the temperature may then increase slowly. By the distillation under reduced pressure at room temperature, the cloudy appearance inside becomes clear as water is removed. The distillation under reduced pressure may be stopped at this point, or a heating procedure may be accompanied in order to remove the remaining organic acid (for example, acetic acid) in the resin as much as possible. In this case, it is preferable to maintain the inner temperature as 90°C or lower (for example, 20 to 90°C) in terms of the prevention of rapid increase of molecular weight and gelation. Such a distillation under reduced pressure is not a general method and is herein referred to as “distillation under reduced pressure at low temperature.”

To the prepared silicone resin, a given amount of dilution solvent (for example, PGMEA) is added to adjust the concentration to the desired level. Although PGMEA is preferably used as a dilution solvent for the reaction, any solvent conventionally used in electronic industries may be used as the further dilution solvent which is added after the distillation under reduced pressure at low temperature.

Next, the obtained product is stirred slowly at medium temperature such as 50 to 80°C (for example, about 50°C) for aging until the desired molecular weight distribution―i.e., Mw of 5,000 to 20,000―is achieved.

Additionally, the silicone resin having a completely controlled molecular weight distribution through the aging procedure is treated with the synthetic magnesium silicate (2MgO·6SiO₂·xH₂O; for example, KYOWAAD-600 as commercial name)―which is an ion treatment agent (ion adsorbing agent)―in an amount of 1 to 2% based on solid content, and then filtered with diatomite (for example, Dicalite Speed-plus as commercial name) to remove impurities completely.

Lastly, the obtained composition is filtered finally through 0.1 micron cartridge filter (KAREI), and packed and stored. At this time, in order to minimize the activity of the catalyst and secure the storage stability, the prepared composition is tightly sealed and kept in a glass bottle under nitrogen atmosphere at low temperature, preferably 5°C or lower and more preferably 3°C or lower, by which the storage stability for a maximum of six (6) months can be secured.

According to the present invention, the silicone resin composition can be prepared stably and easily by a standardized process using general alkoxysilane raw material which is not a specialty raw material. Furthermore, since the silicone resin composition can be prepared with good productivity and economic feasibility, it is anticipated to greatly contribute to the popularization of silicone coating materials.

According to another aspect of the present invention, a coating layer formed by the application of the silicone resin composition as explained above is provided. There is no special limitation to the method for applying the silicone resin composition of the present invention to a substrate and forming its coating layer thereon. Any conventional method used in this field of art such as spin coating, dip coating, etc. may be used to form the coating layer. Also, there is no special limitation to the curing method and curing condition after the coating. For example, the coating layer may be thermally cured with conditions of 150°C, 30 minutes and t = 1 to 3μm. In addition, the curing may be conducted by dual means―i.e., by heat (thermal curing) and UV radiation (photocuring).

The coating layer formed from the composition of the present invention has, after prebaking, solubility to TMAH aqueous solution of 0.4% to 2.38%, and thus it is suitably applicable to a photoresist process and can provide a coating surface with high hardness, high transparency and high heat resistance. In particular, the composition of the present invention is usefully applicable as a level coating agent, overcoating agent, etc. for thin film transistor liquid crystal display devices and the like.

Hereinafter, the present invention will be illustrated more specifically through Examples. However, they are provided only to facilitate the understanding of the present invention, and the scope of the present invention is by no means limited thereto.

Examples 1 to 4 and Comparative Examples 1 and 2: Preparation of Resins 1 to 6

In a 3000ml round-bottom flask, PGMEA (712.01g), acetic acid (7.12g) and water (487.74g) were added and stirred. With maintaining the mixture at 40°C, a liquid mixture of PTMS (364.29g), MTMS (850g), GPTMS (108.54g) and GPMDMS (101.19g) was added thereto dropwise for 1 hour. Then, the temperature was slowly elevated to the refluxing point and maintained for 2 to 5 hours, and distillation under normal pressure was conducted up to 110°C to remove low-boiling point materials. Again, water (487.74g) and acetic acid (2.14g) were added thereto, refluxing was conducted for 3 to 6 hours, and the resulting mixture was cooled to room temperature. By a low temperature-reduced pressure method, the cooled mixture was subjected to 80°C stripping, the pressure was released, PGMEA was added thereto for diluting to solid content of 40 to 50%, and then stirring was continued at 50°C until the desired molecular weight (molecular weight shown in Table 5 below) was obtained. The resin for silicone coating with the controlled molecular weight was filtered through a diatomite filter and a 0.1 micron filter. The final resin composition was tightly sealed and kept at 5°C or lower, avoiding contact with air. As for Resins 1 to 5, the added amounts of the raw materials were the same but the aging procedures (aging times) were different, by which the prepared resins had different weight average molecular weights from one another. As for Resin 6, the gelation proceeded due to excessive aging and thus the resin could not be prepared substantially.

Examples 5 and 6, and Comparative Example 3: Preparation of Resins 7 to 9

With the components and amounts shown in Table 3 below, the resin composition was prepared through the same process as above. As for Resins 7 to 9, the added amounts of the raw materials were the same but the aging procedures were different, by which the prepared resins had different weight average molecular weights from one another.

Comparative Example 4 and Example 7: Preparation of Resins 10 and 11

With the components and amounts shown in Table 3 below, the resin composition was prepared through the same process as above.

Comparative Examples 5 and 6: Preparation of Resins 12 and 13

With the components and amounts shown in Table 3 below, the resin composition was prepared through the same process as above. As for Comparative Example 6, the gelation proceeded during the synthesis, and thus Resin 13 could not be prepared.

Table 3

The molar ratios of bifunctionality and trifunctionality of the prepared Resins 1 to 13 are shown in Table 4 below, which relates to the structure of chemical formula 1. Chemical formula 1 is a schematization in consideration of -OH group. Table 4 shows the molar ratios of bifunctionality and trifunctionality, based on the coating layer wherein all -OH groups participated in the curing.

Table 4

The following chemical formulas 3 to 8 show the functionalities in the above Table 4 structurally.

[Chemical formula 3] (D^Me2)

[Chemical formula 4] (D^MeEp)

[Chemical formula 5] (T^Me)

[Chemical formula 6] (T^Ph)

[Chemical formula 7] (T^Ep)

[Chemical formula 8] (T^CEp)

As can be seen from Table 4 above, Resins 1 to 6 had D/T of 5/95 (5% of bifunctionality and 95% of trifunctionality). Resins 7 to 9 and 10 had D/T of 15/85, Resin 11 had D/T of 10/90, and Resin 12 had D/T of 50/50. Resin 13 only had T of 100. As such, the ratio of bifunctionality (D) and trifunctionality (T) is a factor to be considered preferentially in preparation of silicone resins, and by this the properties of the coating surface can be predicted to some extent.

Property Evaluation

For Resins (compositions) 1 to 13 prepared in the Examples and Comparative Examples, the properties of each coating layer were measured/evaluated by the following methods, and the results are shown in Table 5.

1) Coating method: PGMEA was added to make the solid content 30% (weight basis), and stirred and diluted by using a vortex mixer for 1 minute. The resulting mixture was coated on a glass substrate (150×300×2mm) by using a bar coater (RDS3, wet coating layer of 6.86 micron thick) and kept at room temperature for 1 minute.

2) Prebaking: The coating layer of 1) above was placed in an electric oven set to 110°C, kept therein for 90 seconds, taken out therefrom and cooled to room temperature.

3) Alkali solubility: On the coating surface prepared in 2) above, 2 drops of 0.4% TMAH aqueous solution were dropped and kept for 60 seconds. After washing with water, the appearance of the coating layer was observed.

4) Coating property: By touching the coating surface prepared in 2) above by hand, the stickiness was evaluated.

5) Hardbaking: After the prebaking, the coated glass substrate was placed in an electric oven set to 150°C, kept therein for 30 minutes, taken out therefrom and cooled to room temperature.

6) Pencil hardness: to the coated glass substrate prepared in 5) above, the coating surface was scratched by using YOSHIMITSU 221-D type equipped with a Mitsubishi pencil and the degree of scratch was measured by using Peak Lupe of 22 magnifications.

7) Heat resistance: On a preweighed aluminum dish (Ace Sciences, Co. Ltd.), 1.0 to 1.2 g of the coating composition was placed and weighed precisely, the prebaking and hardbaking were conducted, and then the weight of the coated layer was calculated. After keeping the sample in an electric oven at 280°C for 10 minutes and cooling to room temperature, the ratio of weight loss was calculated.

Table 5

As can be seen from Table 5 above, the compositions of the present invention comprising the silicone resin having T unit of 60 to 95 mol% and molecular weight of 5,000 to 20,000 showed good properties overall. To the contrary, Comparative Examples 1 and 4 remained sticky after coating and showed poor heat resistance. In Comparative Example 3, cracking occurred. Comparative Example 5 remained sticky after coating and was in an uncured state, by which the coating test could not be conducted. In Comparative Examples 2 and 6, gelation occurred during the synthesis and thus the resins could not be prepared substantially.

Claims

An alkali-soluble silicone resin comprising:

(A) at least one thermally curable functional group selected from the group consisting of hydroxy, alkoxy and epoxy,

(B) at least one alkali-developable functional group selected from the group consisting of hydroxy and alkoxy,

(C) at least one functional group selected from the group consisting of C₁-C₂₀ alkyl groups and aromatic groups, and

(D) 60 to 95 mol% of trifunctional structure derived from organotrialkoxysilane,

wherein the resin has a weight average molecular weight of 5,000 to 20,000.
The alkali-soluble silicone resin according to claim 1, which is represented by the following chemical formula 1:

[Chemical formula 1]

wherein in the above chemical formula 1,

R₁ is independently methyl, 3-glycidoxypropyl or hydroxy,

R₂ is independently hydroxy,

R₃ is independently methyl, phenyl, 3-glycidoxypropyl or 2-(3,4-epoxycyclohexyl)ethyl, and

a, b and c are mole fractions satisfying a + b + c = 1.
The alkali-soluble silicone resin according to claim 2, which has a structure of the following chemical formula 2 after curing:

[Chemical formula 2]

wherein in the above chemical formula 2,

n1 to n6 are mole fractions satisfying n1 + n2 + n3 + n4 + n5 + n6 = 1, and

0≤n1≤0.4, 0≤n2≤0.4, 0≤(n1+n2)≤0.4, 0≤n3≤0.95, 0≤n4≤0.95, 0≤n5≤0.95, 0≤n6≤0.95 and 0≤(n3+n4+n5+n6)≤0.95.
The alkali-soluble silicone resin according to claim 1, further comprising 5 to 40 mol% of bifunctional structure.
A silicone resin composition comprising the alkali-soluble silicone resin according to any one of claims 1 to 4, and solvent.
A method for preparing the silicone resin composition of claim 5, the method comprising the steps of:

(a) mixing an alkoxysilane raw material with dilution solvent, organic acid and water for hydrolysis;

(b) distilling the obtained product under normal pressure to remove the organic acid and water;

(c) adding further organic acid and water to the obtained product to hydrolyze the remaining raw material;

(d) distilling the obtained product under reduced pressure at low temperature to further remove the organic acid and water; and

(e) adding further dilution solvent and conducting an aging procedure to control the weight average molecular weight of the silicone resin to 5,000 to 20,000.
The method for preparing the silicone resin composition according to claim 6, wherein said dilution solvent in said step (a) is propyleneglycol monomethyl ether acetate (PGMEA).
The method for preparing the silicone resin composition according to claim 6, wherein said organic acid is at least one selected from acetic acid and oxalic acid.
The method for preparing the silicone resin composition according to claim 6, wherein said step (d) is conducted at a temperature of 90°C or lower.
A coating layer formed by the application of the silicone resin composition according to claim 5.