WO1997027149A1 - Method of coating organic polymer onto glass surface, and organic polymer-coated glass - Google Patents

Abstract

This application relates to a glass having a porous layer which is coated by an organic polymer having excellent adhesive properties and peel resistance, and a method for coating glass with organic polymers whereby a porous layer is provided on one side of the glass, and a polymer solution composed of an organic polymer and a solvent capable of dissolving this polymer is applied onto the porous layer. A heat treatment is carried out at no less than the melting point or the glass transition temperature of this polymer.

Description

ΗTLE

METHODOFCOATINGORGANICPOLYMERONTOGLASSSURFACE,

ANDORGANICPOLYMER-COATEDGLASS

BACKGROUNDOFTHEINVENTION This invention relates to glass having a porous layer that has been coated with an organic polymer, and a method for coating said organic polymer.

In conducting research and development on methods for coating the surface of glass with an organic polymer, those conversant with the art refer to the polymer coating methods that have hitherto been carried out on metals and the like. A number ofattempts have hitherto been made to coat polymer onto the surface of a metal substrate, and fluoroplastic coating in particular has been carried out in order to prevent metal corrosion. A specific method that has been used consists of, after the enameling treatment of a metal base material surface, applying, then drying a fluoroplastic primer, then applying a fluoroplastic and baking. There is also a substrate treatment method in which, in order to enhance bonding properties and durability, one type or a combination of glass, enamel glass or porcelain glaze frit is used, and a mixture of this with a blowing agent is applied onto the surface ofthe base material and dried, then fired, in this way forming a porous substrate layer in which irregularities have been formed in the surface by the decomposition ofthe blowing agent (Japanese published unexamined patent application (Kokai) No. 58-70,867 (1983)).

However, even when a glass surface is treated and coated with a fluororesin by means of this method, the bonding strength is low and the durability is inadequate. At the same time, with regard to the polymer coating on the glass surface, polymers having hydrogen bonds, such as polyamides and polyvinyl alcohols, or polymers that have silanol groups (SiOH groups) and react with the SiOH groups on the glass surface, are capable of adhesion having a certain degree of strength, even in conventional plate glass that is not porous. However, it has been very difficult to bond other polymers (organic polymer) to plate glass.

The object ofthe present invention is to resolve the above problems, and to provide both glass coated with an excellent bonding strength, regardless ofthe type of organic polymer, this being done even with organic polymers that could not be coated onto the glass while maintaining strong adhesive properties by prior- art methods, as well as an organic polymer coating method.

SUMMARY OF THE INVENTION In order to resolve the above problems, the glass according to the present invention is a glass having a porous layer and an organic polymer layer coated onto the porous layer, and the organic polymer layer is a layer that has been coated by applying a solution containing the organic polymer onto the porous layer, then carrying out heat treatment at no less than the melting point or glass transition temperature ofthe organic polymer.

This porous layer is preferably a layer composed of a porous material obtained by firing an organic/glass hybrid fabricated by a sol-gel reaction. Moreover, the organic polymer coating method based on the present invention is a method for coating an organic polymer onto a glass surface, which method has a step in which a porous layer is provided on at least one side ofthe glass; a step in which an organic polymer solution composed of an organic polymer and a solvent capable of dissolving said organic polymer is coated onto said porous layer; and a step in which said porous layer on which said organic polymer has been coated is heat-treated at no less than the melting point or glass transition temperature of said organic polymer.

This porous layer is preferably obtained by firing an organic/glass hybrid that has been fabricated by a sol-gel reaction.

DETAILED DESCRIPTION According to the present invention, the method of coating an organic polymer onto the surface of a glass plate consists of providing a porous layer on the surface ofthe glass plate and applying a polymer solution to this porous layer, then heat-treating at no less than the melting point or glass transition temperature ofthe polymer, and thereby obtaining an organic polymer-coated glass.

Any known method may be used as the method for providing a porous layer on the surface ofthe glass plate. Specific examples that are known include a method whereby the surface ofthe glass plate is treated with a silica supersaturated aqueous solution of hexafluorosilicic acid (Kokai No. 57-166,337 (1982)), a method whereby a solution in which two types of precursor sols having different average molecular weights (of several thousands and several tens of thousands) have been mixed as the starting solutions for the silicon oxide are applied and fired (Kokai No. 5-147,976 (1993)), liquid-phase deposition (LPD) methods whereby a porous layer is obtained by forming a silicon dioxide film on the glass surface, and methods that use a glass hybrid.

The method of using the above-described glass-hybrid shall now be described. This method comprises a step in which a glass-hybrid is obtained by dissolving an organic polymer and a silicic acid compound in a sol-gel reaction solvent, and carrying out the sol-gel reaction with an acid catalyst; and a step in which the glass-hybrid obtained by means of this step is applied to the surface of the glass plate, and a porous layer is formed by firing this at a temperature at which Siθ₂ does ^{not me}^- When the porous layer is formed by means of this method, the porosity and depth can easily be changed as desired, and so the reflectance can be freely controlled. Kokai No. 6-509,131 cites a typical method for fabricating the glass-hybrid by means of a sol-gel reaction. The pores in the porous layer formed on the glass plate surface are from several tens to several thousands of nanometers, and preferably 10-100 nm, in size. The greater the number of pores in this porous layer, the better the bonding properties of the polymer.

The polymer solution applied to the porous layer is obtained by dissolving a polymer selected according to the intended purpose of coating and dissolving this in a solvent in which the polymer is capable of dissolving. A polar polymer that forms hydrogen bonds with the glass surface, such as a polyamide, can be coated onto the surface of conventional plate glass with good bonding strength without having to use the coating method ofthe present invention. However, in cases where a non-polar polymer or fluoropolymer that does not have hydrogen bonds or chemical bonds with glass surfaces is coated, by preparing a polymer solution using a solvent that has been selectively chosen based on the polymer used, then applying and heat-treating this, coating at a good bonding strength becomes possible. Windshield glass in cars, building glass, and polymer having hydrogen bond and chemical bonds with the glass surface have to be bonded even more strongly. In cases where transparency, stainability and antifogging properties are required, as in eyeglasses, for example, the use of fluoropolymers is preferable. In cases where the aim is to tint the glass or block ultraviolet radiation, colorants or ultraviolet light stabilizers can be included in the polymethyl methacrylate or polystyrene.

The polymer selected in accordance with the aim of coating is dissolved in a solvent capable of dissolving this polymer, and is applied to the glass having a porous layer. If this polymer is a polyamide, use may typically be made of formic acid as the solvent. Even in cases where a non-polar polymer or a fluoropolymer is coated, these may be dissolved with good results.

The organic polymer solution composed of an organic polymer and a solvent in which that polymer can be dissolved in applied by means of a known method, such as dipping, spraying or spin-coating. The heat treatment temperature after coating the polymer solution is determined according to the polymer used. In the case of crystalline polymers, heat treatment is carried out at no less than the melting point ofthe polymer, and in the case of non-crystalline polymers, at no less than the glass-transition temperature. Heat treatment may be carried out by any known method, such as with an oven, a vacuum oven or the like.

For example, in cases where a fluoropolymer, such as a copolymer derived from hexafluoropropylene and tetrafluoroethyiene, represented by the general formula (1) below (available from DuPont) is coated onto glass having a porous layer, this fluoropolymer is applied, as a polymer solution obtained by dissolution in a fluorine solvent, and preferably "Florinate" CF-75 (3M Company), onto the above-described porous layer, then is heat-treated at a temperature of at least 40°C.

-<CF₂CF_{2 ) m}- ₍CF₂-CF_{) n}-

CF₂ ( 1 )

In the case of porous glass which has been coated by another fluoropolymer represented by general formula (2) below (Teflon® AF 1600 or Teflon^® AF2400 amorphous fluoropolymers which are copolymers derived from tetrafluoroethyiene and 2,2-bis(trifluoromethyl)-4,5-difluoro-l,3-dioxole available from DuPont), after the polymer solution prepared using the above-mentioned solvent has been applied to glass having a porous layer, this is heat-treated at a temperature of at least 160°C for Teflon^® AF1600 and at least 240°C for Teflon® AF2400.

-<CF₂CF₂ ) _m- (CF-CF) _n- O 0

\ / c

/ \

CT{ CF₃ ( 2 )

Another fluoropolymer contemplated as useful in the present invention is a copolymer derived from tetrafluoroethyiene and a perfluoroalkylvinyl ether. Glass having a porous layer coated with polymethyl methacrylate or polystyrene is fabricated by applying the polymer solution prepared using tetrahydrofuran as the solvent, then firing this at a temperature of at least 100°C. As described above, when a polymer solution composed of an organic polymer and a solvent capable of dissolving this polymer has been applied onto the porous layer of glass having a porous layer, by carrying out heat treatment at no less than the melting point or glass transition point of this polymer, this has the effect that the adhesive properties and peel resistance ofthe coated film composed of the coated organic polymer becomes very high compared to that in prior art polymer-coated glass. Specific examples ofthe present invention, as well as comparative examples, are presented below.

EXAMPLES EXAMPLE 1 Organic polymer-coated glass in accordance with the present invention was fabricated as follows.

Using glass (AR Glass, manufactured by Nippon Sheet Glass Co., Ltd.) on the surface of which a porous layer had been formed by the LPD process, a polymer solution composed ofthe organic polymer shown in Table 1 below and a solvent capable of dissolving this polymer was applied onto the porous layer surface of this glass. Next, in this example, heat treatment was carried out at no less than the melting point or the glass transition temperature ofthe polymer. Application ofthe above-described polymer solution was carried out by a dipping method using a Film Lift manufactured by "Lauda" Co. The porous glass was drawn out ofthe polymer solution at three different speeds, and the influence of each drawing speed was examined.

In addition, the same operation was carried out using glass slides (manufactured by Matsunami Co.) as the conventional plate glass, and polymer coated glass was fabricated for the sake of comparison. EXAMPLE 2

The porous layer ofthe glass coated with an organic polymer based upon the present invention was fabricated by means ofthe following sol-gel method.

Next, using a polymer obtained from 37.3 mol% of 2-hydroxyethyl methacrylate, 36.3 mol% of butyl acrylate, 20 mol% of styrene, 2 mol% of methyl methacrylate, 2 mol% of isobutyl methacrylate and 2.4 mol% of methacrylate (manufactured by DuPont Automotive), and having a number-average molecular weight of approximately 11,000 and a glass transition point of 30°C, an acrylic polymer solution having a composition of 65 wt% of polymer, 30 wt% of xylene and 5 wt% of methyl ethyl ketone was prepared. Twenty grams ofthe acrylic polymer solution, 30 g of tetraethoxy silicate,

20 g of 2-butoxyethanol, and 10 g of 2-propanol were mixed and uniformly dissolved. To this was slowly added a mixture of 8 g of an aqueous solution of HCI (36%) and 6 g of pure water, and this was stirred for about 4^l/2 hours at room temperature. The liquid generated heat during this reaction. A glass substrate that had been successively washed in a neutral detergent, water, alcohol, acetone and the like, then dried, was immersed in this solution, after which it was drawn out at a drawing speed of 30 mm/min or 100 mm/min, and left to stand overnight at room temperature, whereupon the polymer solution that had deposited onto the glass substrate acquired an agar-like form This was dried at 120°C for one hour and fired at 600°C for 20 minutes, thereby forming a porous layer.

TABLE 1

Solution Organic Polymer Glass Transition

No. (Content) Solvent Temperature (°C)

1 HFP/TFE copolymer (5 wt%) "Florinate" FC-75 20

2 Viton AHV (5 wt%) Tetrahydrofuran -30

3 Teflon® AF1600 (2 wt%) "Florinate" FC-75 160

4 Teflon® AF2400 (2 wt%) "Florinate" FC-75 240

5 Polystyrene (5 wt%) Tetrahydrofuran 90

6 Polymethyl methacrylate (5 wt%) Tetrahydrofuran 105

In Table 1 , the organic polymer is a copolymer (available from DuPont) consisting of 43 mol% hexafluoropropylene (HFP) and 57 mol% tetrafluoro¬ ethyiene (TFE). The "Florinate" CF-75 is a fluorine-based solvent produced by the 3M Company. In addition, the polystyrene and the polymethyl methacrylate used were respectively PS666 and PMMA 560F, both made by Asahi Chemical Industry. The Viton AHV is an HFP TFE/vinylidene fluoride (VDF) terpolymer. The coated glasses obtained in this way in Examples 1 and 2 were subjected to a tape peeling test, and to a tape peeling test after cross-cuts had been made therein.

In the tape peel test, Cellotape (made by Nichiban Co.) and Scotch Tape 810 and Scotch Tape 898 (both made by 3M Company) were affixed to the glass, peeling was repeated ten times in each case, and the peeled state of each ofthe coated films was examined.

At the same time, in the cross-cut peel test, cuts that reached the glass surface were made with a utility knife in a cross-cut fashion (such as to give 100 squares measuring 1 mm x 1 mm) on the coating film surface ofthe coated glass. After making these cuts, forced peeling ofthe coated film surface was carried out ten times using the above-described adhesive tape, this being done ten times for each type of tape.

The results ofthe above-described tape peel test and the tape cross-cut peel test are presented in Tables 2-4 below. In the tables, the symbol "O" means that no peeling was observed, the symbol "Δ" means that peeling was observed in the corners of some ofthe 1-mm squares, and the symbol "X" means that at least one 1-m square was essentially completely peeled away. With regard to the transparency ofthe coated glass, a good transparency was indicated by the symbol "O", and a poor transparency was indicated by the symbol "X".

In addition, "slide" means a glass slide (manufactured by Matsunami Co.,), "AR" refers to glass on the surface of which a porous layer was formed by the LPD method (manufactured by Nippon Sheet Glass Co.), and "hybrid" refers to glass on the surface of which a porous layer was formed by the sol-gel method.

TABLE 2

Heat Treatment Drawing Peeling Solution Temperature Rate of Cross-cut Composition (°C) Glass (mm/min) Tape Tape Transparency

1 150 Slide 30 X - O

1 150 Slide 100 X - O

1 150 Slide 300 X - O

1 150 Slide 30 Δ - X

1 150 Slide 100 Δ - X

1 150 Slide 300 Δ - X

1 150 Hybrid 30 O O O

1 150 Hybrid 100 O O o

1 150 Hybrid 300 O 0 o

1 150 AR 30 O o o

1 150 AR 100 O 0 o

1 150 AR 300 O o 0

I 50 Slide 30 X - o

1 50 Slide 100 X - o

1 50 Slide 300 X - 0

1 150 Hybrid 30 Δ - o

1 150 Hybrid 100 X - o

1 150 Hybrid 300 X - 0

1 150 AR 30 Δ - o

1 150 AR 100 X - o

1 150 AR 300 X . 0

TABLE 4

Heat

Treatment Drawing Peeling

Solution Temperature Rate of Cross-cut

Composition (°C) Glass (mm/min) Tape Tape Transparency

5 200 Slide 30 X - O

5 200 Slide 100 X - O

5 200 Hybrid 30 O O O

5 200 Hybrid 100 O O O

5 200 AR 30 O 0 O

5 200 AR 100 O 0 O

6 200 Slide 30 X - O

6 200 Slide 100 X - O

6 200 Hybrid 30 O 0 O

6 200 Hybrid 100 O 0 O

6 200 AR 30 O 0 O

6 200 AR 100 O 0 O

As is apparent from above Tables 2-4, compared with prior-art (polymer coated glass), glass on which polymer coating has been carried out by a method according to the present invention exhibits excellent peel resistance without any loss in transparency.

Claims

WHAT IS CLAIMED IS:

1. A composition, comprising: a glass having a porous layer and an organic polymer layer coated onto the porous layer.

2. The composition of Claim 1 wherein the organic polymer layer has been coated by applying onto said porous layer a solution comprising an organic polymer, then carrying out heat treatment at no less than the melting point or glass transition temperature ofthe organic polymer.

3. The composition of Claim 2 wherein the porous layer is a layer composed of a porous body obtained by firing an organic/glass hybrid fabricated by means of a sol-gel reaction.

4. The composition of Claim 2 wherein the organic polymer is a fluoropolymer.

5. The composition of Claim 4 wherein the fluoropolymer is a copolymer derived from hexafluoropropylene and tetrafluoroethyiene represented by formula (1)

-(CF₂CF₂ ) _r-- (CF₂-CF) _n- CF₂

a copolymer derived from 2,2-bis(trifluoromethyl)-4,5-difluoro-l,3-dioxole and tetrafluoroethyiene represented by formula (2)

-(CF₂CF₂) _m- (CF-CF) _n-

0 o

\ / c

CF / \ CF,

(2) , or a copolymer derived from tetrafluoroethyiene and a perfluoroalkylvinyl ether.

6. A method for coating an organic polymer onto a glass surface, comprising the steps of: providing a porous layer on at least one side of a glass; coating the porous layer with an organic polymer solution composed of an organic polymer and a solvent capable of dissolving the organic polymer; and heat-treating the porous layer on which said organic polymer has been coated at no less than the melting point or glass transition temperature of said organic polymer.

7. The method of Claim 6 wherein the porous layer is obtained by firing an organic/glass hybrid fabricated by means of a sol-gel reaction.

8. The method of Claim 6 wherein the organic polymer is a fluoropolymer.

9. The method of Claim 8 wherein the fluoropolymer is a copolymer derived from hexafluoropropylene and tetrafluoroethyiene represented by formula (1)

-< CF₂CF₂ ) _m- ( CF₂-CF ) _n - CF₂ ( 1 )

a copolymer derived from 2,2-bis(trifluoromethyl)-4,5-difluoro-l,3-dioxole and tetrafluoroethyiene represented by formula (2)

-( CF₂CF₂ ) _m- ( CF-CF)

0 0

\ /

C

CFi CF ,

( 2 ) or

a copolymer derived from tetrafluoroethyiene and a perfluoroalkylvinyl ether.