WO2013129691A1

WO2013129691A1 - Process for producing article having fluorine-containing silane-based coating

Info

Publication number: WO2013129691A1
Application number: PCT/JP2013/056054
Authority: WO
Inventors: Yoshiaki Honda; Teruyuki Fukuda; Yasuhiro Nakai
Original assignee: Daikin Industries, Ltd.
Priority date: 2012-02-28
Filing date: 2013-02-27
Publication date: 2013-09-06
Also published as: CN104321393A; JP2015511174A; KR20140116540A; TW201343817A

Abstract

The present invention provides a process for producing an article comprising a base material and a perfluoropolyether group-containing silane-based coating which coats a surface of the base material, wherein the process can form the perfluoropolyether group-containing silane-based coating having increased friction durability. The process comprises the steps of; (a) forming a precursor coating which comprises a perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si on the surface of the base material; (b) supplying water to the precursor coating; and then (c) heating the precursor coating on the surface of the base material under a dry atmosphere at over 60oC to form the perfluoropolyether group-containing silane-based coating derived from the precursor coating on the surface of the base material.

Description

DESCRIPTION

PROCESS FOR PRODUCING ARTICLE HAVING FLUORINE-CONTAINING

SILANE-BASED COATING [0001]

This application claims priority to and the benefit of U.S. provisional application No. 61/604,431, filed February 28, 2012, the entire contents of which are incorporated herein by reference.

Technical Field

[0002]

The present invention relates to a process for producing an article having a perfluoropolyether group- containing silane-based coating and an article produced by the process.

Background Art

[0003]

A certain fluorine-containing silane-based compound is known to be able to provide excellent water-repellency, oil -repellency, antifouling property, surface slip property, and the like when it is used in a surface treatment of a base material. A coating formed from the fluorine- containing silane-based compound, i.e. a fluorine- containing silane-based coating is applied to various base materials such as a glass, a plastic, a fiber and a building material as a so-called a functional thin coating (see Patent Literatures 1 and 2) .

[0004]

The fluorine-containing silane-based coating can be formed on a surface of the base material by a wet coating method such as dipping and spray, a dry coating method such as vacuum deposition and sputtering, or an atmospheric pressure plasma method, or the like (see Patent Literature 2) .

[0005]

It is known to supply water to the formed coating to facilitate a reaction after coating the surface of the base material with a composition comprising a silane compound, because the fluorine-containing silane-based coating takes a long time to sufficiently exert the above functions (see Patent Literature 1) . Further, it is known to supply a superheated water vapor to a high-temperature firing furnace during water-repellent treatment of a surface of glass to increase the alkali resistance (see Patent Literature 3 ) .

Citation List

[0006] Patent Literature

Patent Literature 1 : JP 3570134 B

Patent Literature 2 : JP 2008-534696 A

Patent Literature 3 : JP 2010-227883 A

Summary of Invention

[0007]

The fluorine-containing silane-based coating is required to have high durability in order to provide the base material with the above functions for a long time. Since the fluorine-containing silane-based coating can exert such functions even in form of a thin coating, it is suitably used in an optical member such as glasses and a touch panel which are required to have optical transparency or transparency. In particular, in these uses, it is required to further increase friction durability. However, the conventional process for forming a fluorine-containing silane-based coating is no longer sufficient to meet increasing requirement for increased friction durability.

[0008]

Furthermore, because excellent surface slip property is also required in the above use, a perfluoropolyether group-containing silane-based coating which is able to provide the excellent surface slip property is suitable. However, it was found that the perfluoropolyether group- containing silnae-based coating which is subjected to heat- drying during formation of coating has lesser friction durability than that which is subjected to natural drying.

[0009]

An object of the present invention is to provide a process for producing an article comprising a base material and a perfluoropolyether group-containing silane-based coating which coats a surface of the base material, wherein the process can form the perfluoropolyether group- containing silane-based coating having increased friction durability.

[0010]

According to the first aspect of the present invention, there is provided a process for producing an article comprising a base material and a perfluoropolyether group- containing silane-based coating which coats a surface of the base material, wherein the process comprises the steps of ;

(a) forming a precursor coating on the surface of the base material, wherein the precursor coating comprises a perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si;

(b) supplying water to the precursor coating; and then

(c) heating the precursor coating on the surface of the base material under a dry atmosphere at over 60°C to form the perfluoropolyether group-containing silane-based coating derived from the precursor coating on the surface of the base material.

[0011]

According to the above process for producing an article of the present invention, the perfluoropolyether group-containing silane-based coating can be formed, which has higher friction durability compared to the conventional process for producing an article (more specifically, the process for forming a perfluoropolyether group-containing silane-based coating) . Although the present invention is not bound to any theory, the reason for increasing friction durability can be considered as follows. According to the process for producing an article of the present invention, a precursor coating comprising a perfluoropolyether group- containing silane compound having a hydrolyzable group bonded to Si is formed on the surface of the base material in the step (a) , and then water is supplied to the precursor coating in the step (b) . Therefore, water acts on the hydrolyzable group bonded to Si present in the perfluoropolyether group-containing silane compound, thereby enabling rapid hydrolysis of the perfluoropolyether group-containing silane compound. Then, this precursor coating is heated under a dry atmosphere at over 60°C on the surface of the base material in the step (c) , thereby enabling rapid dehydration-condensation of hydrolyzed groups bonded to Si between the perfluoropolyether group- containing silane compounds, and enabling rapid reaction (for example, dehydration-condensation) between the hydrolyzed group bonded to Si in the perfluoropolyether grou -containing silane compound and a reactive group (for example, a hydroxyl group, or the like) present on the surface of the base material. As a result, in the perfluoropolyether group-containing silane-based coating formed on the surface of the base material, the perfluoropolyether group-containing silane compounds bind to each other, as well as the perfluoropolyether group- containing silane compound binds to the base material. Therefore, coating strength of the perfluoropolyether group-containing silane-based coating itself and adherence strength between the perfluoropolyether group-containing silane-based coating and the surface of the base material are increased, thereby obtaining high friction durability.

[0012]

The perfluoropolyether group-containing silane-based coating which is formed by the process for producing an article of the present invention may have water-repellency, oil-repellency, antifouling property (for example, preventing from adhering a fouling such as fingerprints) , surface slip property (or lubricity, for example, wiping property of a fouling such as fingerprints) , and the like in addition to high friction durability, therefore, it may be suitably used as a functional thin coating.

[0013]

In the present invention, supplying of water in the step (b) may be performed under an atmosphere at a temperature from 0 to 500°C. By supplying water at such temperature range, hydrolysis is enabled to proceed.

[0014]

In an embodiment of the present invention, the step

(b) and the step (c) can sequentially performed by exposing the base material on which the precursor coating is formed in the step (a) to a superheated water vapor. The "superheated water vapor" is also called "superheated steam", and represents that which is obtained by heating a saturated water vapor to a temperature over the boiling point (100°C under ambient pressure) . By exposing the base material on which the precursor coating is formed to the superheated water vapor, firstly, a dew condensation occurs on the surface of the precursor coating, thereby, supplying water to the precursor coating. Presently, an amount of water on the surface of the precursor coating is gradually decreased under a dry atmosphere due to the superheated water vapor. Furthermore, during the precursor coating is under the dry atmosphere, the precursor coating on the surface of the base material is heated by contacting with the superheated water vapor. Therefore, by using the superheated water vapor, water supplying and dry heating are enabled to be sequentially carried out simply by exposing the base material on which the precursor coating is formed to the superheated water vapor.

[0015]

As the perfluoropolyether group-containing silane compound used in the present invention, a compound having a perfluoropolyether group in addition to the hydrolyzable group bonded to Si may be used.

[0016]

Examples of the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si include one or more compounds of any of the following general formulae (la) and (lb) :

Y

Rf¹- (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂C)_m-X ^■•• ( 1 a)

Z (CH₂) _e-SiT_nRY_n

Y Y

X-(CCH₂),-(CF₂)_fCF- (OC₄F₈)_s- (OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂C)_m-X

W W , Z Z (CH₂) _e-SiT_nR _n

^■■■ ( 1 b)

wherein : Rf¹ is an alkyl group having 1 to 16 carbon atoms which may or may not be substituted by one or more fluorine atoms ;

a, b, c and s are each independently an integer from 0 to 200, wherein the sum of a, b, c and s is at least 1, and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c, or s is not limited in the formulae;

d and f are each independently 0 or 1;

e and g are each independently an integer from 0 to 2; m and 1 are each independently an integer from 1 to

10;

X is a hydrogen atom or a halogen atom;

Y is a hydrogen atom or a lower alkyl group;

Z is a fluorine atom or a lower fluoroalkyl group;

T is a hydrolyzable group;

R¹ is a hydrogen atom or an alkyl group having 1 to 22 carbon atoms; and

n is an integer from 1 to 3.

[0017]

Other examples of the perfluoropolyether group- containing silane compound having a hydrolyzable group bonded to Si include one or more compounds of any of the following general formulae (2a) and (2b) : RP- (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂)_h-0-(CH₂) -SiT_nR _n ^■ -^■ (2a)

Z

R²3-_nT_nSi-(CH₂)_k-0-(CH₂)_r(CF₂)_fCF- *

z

* - (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂)_h-0-(CH₂)_rSiT_nR _n

¹ - " (2b) wherein :

Rf² is an alkyl group having 1 to 16 carbon atoms which may or may not be substituted by one or more fluorine atoms ;

a, b, c and s are each independently an integer from 0 to 200, wherein the sum of a, b, c and s is at least 1, and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c or s is not limited in the formulae;

d and f are each independently 0 or 1 ,- h and j are each independently 1 or 2;

i and k are each independently an integer from 2 to 20;

Z is a fluorine atom or a lower fluoroalkyl group;

T is a hydrolyzable group;

R² is a hydrogen atom or an alkyl group having 1 to 22 carbon atoms ; and

n is an integer from 1 to 3..

[0018] - ^{^"}~ ^{"": " ■}-— Further other examples of the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si include one or more compounds of the following general formula (3) :

Rf³ [-L³ _p-X-R³¹-Si (OR³²)₃]_q (3) wherein :

Rf³ is a perfluoropolyether group, provided that all or part of the fluorine atoms attached to the terminal carbon atom may or may not be a hydrogen atom;

p is 0 or 1;

q is 1 or 2 ;

R³¹ is an alkylene group;

R³² is an alkyl group;

L³ is -CO-;

X is a group selected from the group consisting of -0-, -NR³³-, -S-, -S0₂-, -S0₂NR³³- and -NR³³CO- ; wherein R³³ is a hydrogen atom or an alkyl group having 3 or less carbon atoms.

[0019]

According to other aspect of the present invention, there is also provided an article which is produced by the above process for producing of the present invention. The perfluoropolyether group-containing silane-based coating in the article has higher friction durability compared to the perfluoropolyether group-containing silane-based coating in an article which is produced by the conventional process for producing as mentioned above.

[0020]

In an embodiment of the present invention, the material constituting the surface of the base material may have a hydroxyl group. By the existence of the hydroxyl group on the surface of the base material, a group which is bonded to Si in the perfluoropolyether group-containing silane compound after hydrolysis can bind to the hydroxyl group on the surface of the base material by dehydration- condensation.

[0021]

For example, the material constituting the surface of the base material may be selected from the group consisting of a glass, a resin, a metal and a ceramic. The hydroxyl group may originally exist in the material constituting the surface of the base material or become to exist on the surface of the base material by any treatment.

[0022]

The article produced by the present invention may be, for example, an optical member, but not particularly limited thereto. The present invention may be suitably applied to the optical member because it is highly demanded to have improved friction durability.

[0023]

According to the present invention, a perfluoropolyether group-containing silane-based coating having high friction durability can be formed by supplying water to a precursor coating comprising a perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si, and then heating it under a dry atmosphere at over 60°C.

Brief Description of Drawings

[0024]

Fig. 1 is a graph showing friction durability of the perfluoropolyether group-containing silane-based coatings which were produced in Examples 1-4 and Comparative Examples 1-4.

Fig. 2 is a graph showing friction durability of the perfluoropolyether group-containing silane-based coatings which were produced in Examples 5-9.

Description of Embodiments

[0025]

Hereinafter, the process for producing an article of the present invention and an article produced by the process will be described in detail through an embodiment of the present invention, although the present invention is not limited thereto.

[0026]

The process for producing an article of the present invention may be also generally understood as a method wherein a coating comprising a perfluoropolyether group- containing silane compound is formed on a surface of a base material as a precursor coating, and then this precursor coating is posttreated to form a perfluoropolyether group- containing silane-based coating. As this posttreatment , water supplying and dry heating are sequentially performed.

[0027]

Firstly, the base material is provided. The base material usable in the present invention may be composed of any suitable material such as a glass, a resin (may be a natural or synthetic resin such as a common plastic material, and may be in form of a plate, a film, or others), a metal (may be a simple substance of a metal such as aluminum, copper, or iron, or a complex such as alloy or the like) , a ceramic, a semiconductor (silicon, germanium, or the like) , a fiber (a fabric, a non-woven fabric, or the like) , a fur, a leather, a wood, a pottery, a stone, or the like. The base material is not specifically limited as long as the surface of the base material is made of a material which has a reactive group (a group which is able to react with a group bonded to Si in the perfluoropolyether group-containing silane compound after hydrolysis) at least just prior to forming the precursor coating.

[0028]

For example, when an article to be produced is an optical member, any layer (or coating) such as a hard coating layer or an antireflection layer may be formed on the surface (outermost layer) of the base material. As the antireflection layer, either a single antireflection layer or a multi antireflection layer may be used. Examples of an inorganic material usable in the antireflection layer include Si0₂, SiO, Zr0₂, Ti0₂, TiO, Ti₂0₃, Ti₂0₅, A1₂0₃, Ta₂0_5> Ce0_2/ MgO, Y₂0₃, Sn0₂, MgF₂ , W0₃ , and the like. These inorganic materials may be used alone or in combination with two or more (for example, as a mixture) . When using the multi antireflection layer, preferably, Si0₂ and/or SiO are used in the outermost layer. When an article to be produced is an optical glass part for a touch panel, it may have a transparent electrode, for example, a thin layer comprising indium tin oxide (ITO) , indium zinc oxide, or the like on a part of the surface of the base material (glass) . Furthermore, the base material may have an antistatic layer, an insulating layer, an adhesive layer, a protecting layer, a decorated frame layer (I-CON) , an atomizing layer, a hard coating layer, a polarizing film, a phase difference film, a liquid crystal display module, and the like, according to its specific specification.

[0029]

The shape of the base material is not specifically limited. The region of the surface of the base material on which the perfluoropolyether group-containing silane-based coating should be formed may be at least a part of the surface of the base material, and may be appropriately determined depending on use, the specific specification, and the like of the article to be produced.

[0030]

The base material may be that of which at least the surface consist of a material originally having a hydroxyl group. Examples of the material include a glass, in addition, a metal on which a natural oxidized membrane or a thermal oxidized membrane is formed (in particular, a base metal), a ceramic, a semiconductor, and the like. Alternatively, as in a resin, when the hydroxyl groups are present but not sufficient, or when the hydroxyl group is originally absent, the hydroxyl group can be introduced on the surface of the base material, or the number of the hydroxyl group can be increased by subjecting the base material to any pretreatment . Examples of the pretreatment include a plasma treatment (for example, corona discharge) or an ion beam irradiation. The plasma treatment may be suitably used to introduce or increase the hydroxyl group on the surface of the base material, further, to clarify the surface of the base material (remove foreign materials, and the like) . Alternatively, other examples of the pretreatment include a method wherein a monolayer of a surface adsorbent having a carbon-carbon unsaturated bond group is formed on the surface of the base material by using a LB method (Langmuir-Blodgett method) or a chemical adsorption method beforehand, and then, cleaving the unsaturated bond under an atmosphere of oxygen and nitrogen [0031]

Alternatively, the base material may be that of which at least the surface consist of a material comprising other reactive group such as a silicon compound having one or more Si-H groups or alkoxysilane .

[0032]

Next, a precursor coating comprising the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si is formed on the surface of the base material .

[0033]

Examples of the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si include a compound of any of the following general formulae (la) and (lb) (may be one compound or a mixture of two or more compounds) .

Y

Rfⁱ- (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂C)_m-X ^■■■ ( 1 a)

Z (CH₂) _e-SiT_nRV_n

Y Y

X-(CCH₂),-(CF₂)_fCF- (OC,F₈)_s- (OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂C)_m-X

WA) . Z Z ( H₂) e-SiT_n „

^■■■ ( 1 b)

In these formulae:

Rf¹ is an alkyl group having 1-16 carbon atoms which may or may not be substituted by one or more fluorine atoms, preferably an alkyl group having 1-3 carbon atoms which may or may not be substituted by one or more fluorine atoms. Preferably, the above alkyl group which may or may not be substituted by one or more fluorine atoms is a perfluoroalkyl group.

Subscripts a, b, c and s represent the repeating number of each of three repeating units of perfluoropolyether which constitute a main backbone of the polymer, and are each independently an integer from 0 to 200 wherein the sum of a, b, c and s is at least 1, preferably 1-100. The occurrence order of the respective repeating units in parentheses with the subscript a, b, c or s is not limited in the formulae. Among these repeating units, the - (OC₄F₈) - group may be any of - (OCF₂CF₂CF₂CF₂) - , - (OCF(CF₃)CF₂CF₂) - (OCF₂CF(CF₃)CF₂) -, - (OCF₂CF₂CF (CF₃) ) - , - (OC(CF₃)₂CF₂) -, - (OCF₂C(CF₃)₂) -, - (OCF (CF₃) CF (CF₃) ) - , (OCF (C₂F₅) CF₂) - and - (OCF₂CF (C₂F₅) ) - , preferably

(OCF₂CF₂CF₂CF₂) . The - (OC₃F₆) - group may be any of (OCF₂CF₂CF₂) -, - (OCF(CF₃)CF₂) - and - (OCF₂CF (CF₃) ) - , preferably - (OCF₂CF₂CF₂) - . The - (OC₂F₄) - group may be any of - ( OCF₂CF₂ ) - and - (OCF(CF₃) ) -, preferably - (OCF₂CF₂) - .

Subscripts d and f are each independently 0 or 1.

Subscripts e and g are each independently an integer from 0 to 2.

Subscripts m and 1 are each independently an integer from 1 to 10.

X is a hydrogen atom or a halogen atom. The halogen atom is preferably an iodine atom, a chlorine atom, or a fluorine atom.

Y is a hydrogen atom or a lower alkyl group. The lower alkyl group is preferably an alkyl group having 1-20 carbon atoms.

Z is a fluorine atom or a lower fluoroalkyl group. The lower fluoroalkyl group is, for example, a fluoroalkyl group having 1-3 carbon atoms, preferably a perfluoroalkyl group having 1-3 carbon atoms, more preferably a trifluoromethyl group or a pentafluoroethyl group, further preferably a trifluoromethyl group. Representatively, Z is a fluorine atom, and d and f is 1.

T and R¹ are a group bonded to Si.

T is a hydrolyzable group. Examples of the hydrolyzable group include -OA, -OCOA, -0-N=C(A)₂, -N(A)₂, -NHA, halogen (wherein, A is a substituted or unsubstituted alkyl group having 1-3 carbon atoms), and the like.

R¹ is a hydrogen atom or an alkyl group having 1-22 carbon atoms, preferably an alkyl group having 1-22 carbon atoms, more preferably an alkyl group having 1-3 carbon atoms .

Subscript n is an integer from 1 to 3.

[0034]

Other examples of the perfluoropolyether group- containing silane compound having a hydrolyzable group bonded to Si include a compound of any of the following general formulae (2a) and (2b) (may be one compound or a mixture of two or more compounds) .

Rf²- (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂)_h-0-(CH₂)_i-SiT_nR² ₃„_n ^■ '^■ (2a)

Z

R²3-_nT_nSi-(CH₂)_k-0-(CH₂)_r(CF₂)_fCF- *

z

* - (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂)_h-0-(CH₂)_rSiT_nR2₃._n

¹ "-(2b) In these formulae :

Rf² is an alkyl group having 1-16 carbon atoms which may or may not be substituted by one or more fluorine atoms, preferably an alkyl group having 1-3 carbon atoms which may or may not be substituted by one or more fluorine atoms. Preferably, the above alkyl group which may or may not be substituted by one or more fluorine atoms is a perfluoroalkyl group

Subscripts a, b, c and s represent the repeating number of each of three repeating units of perfluoropolyether which constitute a main backbone of the polymer, and are each independently an integer from 0 to 200 wherein the sum of a, b, c and s is at least 1, preferably 1-100. The occurrence order of the respective repeating units in parentheses with the subscript a, b, c or s is not limited in the formulae. Among these repeating units, the - (OC₄F₈) - group may be any of - (OCF₂CF₂CF₂CF₂) - , - (OCF(CF₃)CF₂CF₂) -, - (OCF₂CF(CF₃)CF₂) - (OCF₂CF₂CF (CF₃) ) - , - (OC(CF₃)₂CF₂) -, - (OCF₂C(CF₃) ₂) -, - (OCF (CF₃ ) CF (CF₃ ) ) - , (OCF(C₂F₅) CF₂) - and - (OCF₂CF (C₂F₅) ) - , preferably

(OCF₂CF₂CF₂CF₂) . The - (OC₃F₆) - group may be any of (OCF₂CF₂CF₂) - , - (OCF(CF₃)CF₂) - and - (OCF₂CF (CF₃) ) - , preferably - (OCF₂CF₂CF₂) - . The - (OC₂F₄) - group may be any of -(OCF₂CF₂)- and - (OCF (CF₃) ) - , preferably - (OCF₂CF₂) - .

Subscripts d and f are each independently 0 or 1. Subscripts h and j are each independently 1 or 2.

Subscripts i and k are each independently an integer from 2 to 20.

Z is a fluorine atom or a lower fluoroalkyl group. The lower fluoroalkyl group is, for example, a fluoroalkyl group having 1-3 carbon atoms, preferably a perfluoroalkyl group having 1-3 carbon atoms, more preferably a trifluoromethyl group or a pentafluoroethyl group, further preferably a trifluoromethyl group. Representatively, Z is a fluorine atom, and d and f are 1.

T and R² are a group bonded to Si.

R² is a hydrogen atom or an alkyl group having 1-22 carbon atoms, preferably an alkyl group having 1-22 carbon atoms, more preferably an alkyl group having 1-3 carbon atoms .

Subscript n is an integer from 1 to 3.

[0035]

Further other examples of the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si and a perfluoropolyether group include a compound of the following general formula (3) (may be one compound or a mixture of two or more compounds) .

Rf³ [-L³ _p-X-R³¹-Si (OR³²)₃J _q (3) In the formula:

Rf³ is a perfluoropolyether group, provided that all or part of the fluorine atoms attached to the terminal carbon atom may or may not be a hydrogen atom, preferably a perfluoropolyether group having 1-300 carbon atoms .

Subscript p is 0 or 1.

Subscript q is 1 or 2.

R³¹ is an alkylene group, preferably an alkylene group having 1-3 carbon atoms.

The -OR³² group is an alkoxy group bonded to Si, R³² is an alkyl group, preferably an alkyl group having 1-3 carbon atoms .

L³ is -CO- .

X is a group selected from the group consisting of -O- , -NR³³-, -S-, -SO₂-, -SO₂NR³³- and -NR³³CO-, preferably -0- . R³³ is a hydrogen atom or an alkyl group having 3 or less carbon atoms .

[0036]

The perfluoropolyether group-containing silane compound used may be appropriately selected depending on the functions required in the perfluoropolyether group- containing silane-based coating, specifically, water- repellency, oil-repellency, antifduling property, surface slip property (or lubricity), or the like.

[0037]

The formation of the precursor coating can be performed by applying the above perfluoropolyether group- containing silane compound having a hydrolyzable group bonded to Si alone or as a composition comprising the compound to the surface of the base material so that the surface is coated.

[0038]

The above composition may comprise a fluoropolyether compound which may be also understood as a perfluoropolyether group-containing oil (hereinafter referred to as "a fluorine-containing oil" for the purpose of distinguishing from a perfluoropolyether group- containing silane compound) , preferably a perfluoropolyether compound in addition to the perfluoropolyether group-containing silane compound. The fluorine-containing oil contributes to increasing of surface slip property of the perfluoropolyether group- containing silane-based coating.

[0039]

The fluorine-containing oil may be contained in the composition, for example, at 0-300 parts by weight, preferably 50-200 parts by weight with respect to 100 parts by weight of the fluorine-containing silane compound (as the total weight when two or more compounds are used; hereinafter the same shall apply) .

[0040]

Examples of the fluorine-containing oil include a compound of the following general formula (5) (a perfluoropolyether compound) . R²¹- (OC₄F₈)_S'- (OC₃F₆)_a-- (OC₂F₄)_b'- (OCF₂)_c--R²² (5)

In the formula:

R²¹ is an alkyl group having 1-16 carbon atoms which may or may not be substituted by one or more fluorine atoms, preferably an alkyl group having 1-3 carbon atoms which may or may not be substituted by one or more fluorine atoms. Preferably, the above alkyl group which may or may not be substituted by one or more fluorine atoms is a perfluoroalkyl group.

R²² is a hydrogen atom, a fluorine atom or an alkyl group having 1-16 carbon atoms which may or may not be substituted by one or more fluorine atoms, preferably an alkyl group having 1-3 carbon atoms which may or may not be substituted by one or more fluorine atoms. Preferably, the above alkyl group which may or may not be substituted by one or more fluorine atoms is a perfluoroalkyl group.

Subscripts a', b', c' and s' represent the repeating number of each of three repeating units of perfluoropolyether which constitute a main backbone of the polymer, and are each independently an integer from 0 to 300 wherein the sum of a', b', c' and s' is at least 1, preferably 1-100. The occurrence order of the respective repeating units in parentheses with the subscript a¹, b'₍ c' or s ' is not limited in the formulae. Among these repeating units, the - (OC₄F₈) - group may be any of

(OCF₂CF₂CF₂CF₂) -, - (OCF(CF₃)CF₂CF₂) -, - (OCF₂CF (CF₃) CF₂) - , - (OCF₂CF₂CF(CF₃) ) -, - (OC(CF₃)₂CF₂) -, - (OCF₂C (CF₃) ₂) - ,

(OCF(CF₃)CF(CF₃) ) -, - (OCF(C₂F₅)CF₂) - and - (OCF₂CF (C₂F₅) ) - , preferably - (OCF₂CF₂CF₂CF₂) . The - (OC₃F₆) - group may be any of - (OCF₂CF₂CF₂) - , - (OCF (CF₃) CF₂) - and - (OCF₂CF (CF₃ ) ) - , preferably - (OCF₂CF₂CF₂) - . The - (OC₂F₄) - group may be any of -(OCF₂CF₂)- and - (OCF (CF₃) ) - , preferably -(OCF₂CF₂)-.

[0041]

Examples of the perfluoropolyether compound of the above general formula (5) include a compound of any of the following general formulae (5a) and (5b) (may be one compound or a mixture of two or more compounds) .

R - (OCF₂CF₂CF₂ ) ' -R (5a)

R²¹- (OCF₂CF₂CF₂CF₂)_a..- (OCF₂CF₂CF₂)_a - (OCF₂CF₂)_b-- (0CF₂)_c - R²² (5b)

In these formulae:

R²¹ and R²² are as defined above; in the formula (5a) , a" is an integer from 1 to 100; and in the formula (5b), s" and a" are each independently an integer from 1 to 30, and b" and c" are each independently an integer from 1 to 300. The occurrence order of the respective repeating units in parentheses with the subscript a", b", c" or s" is not limited in the formulae.

[0042]

The compound of the general formula (5a) and the compound of the general formula (5b) may be used alone or in combination. When they are used in combination, preferably, the ratio of the compound of the general formula (5a) to the compound of the general formula (5b) is 1:1 to 1:30 by weight. By applying such ratio, a perfluoropolyether group-containing silane-based coating which has a good balance of surface slip property and friction durability can be obtained.

[0043]

From the other point of view, the fluorine-containing oil may be a compound of the general formula: Rf¹-F (wherein, Rf¹ is as defined above) . The compound of Rf^F is preferable because the compound has high affinity for the compound of any of the above general formulae (la) and

(lb) .

[0044]

The fluorine-containing oil may have 1,000-30,000 of average molecular weight. By having this average molecular weight, high surface slip property can be obtained. Representatively, for the compound of the general formula (5a), the average molecular weight is preferably 2,000- 6,000. For the compound of the general formula (5b), the average molecular weight is preferably 8,000-30,000. Within this range of average molecular weight, high surface slip property can be obtained.

[0045]

Furthermore, the composition may comprise a silicone compound which may be also understood as a silicone oil (hereinafter referred to as "a silicone oil") in addition to the perfluoropolyether group-containing silane compound. The silicone oil contributes to increasing of surface slip property of the perfluoropolyether group-containing silane- based coating.

[0046]

The silicone oil may be contained in the composition, for example, at 0-300 parts by weight, preferably 50-200 parts by weight with respect to 100 parts by weight of the perfluoropolyether group-containing silane compound. [0047]

Examples of the silicone oil include, for example, a liner or cyclic silicone oil having 2,000 or less siloxane bonds. The liner silicone oil may be so-called a straight silicone oil and a modified silicon oil. Examples of the straight silicone oil include dimethylsilicone oil, methylphenylsilicone oil, and methylhydrogensilicone oil. Examples of the modified silicone oil include that which is obtained by modifying a straight silicone oil with alkyl, aralkyl, polyether, higher fatty acid ester, fluoroalkyl , amino, epoxy, carboxyl, alcohol, or the like. Examples of the cyclic silicone oil include, for example, cyclic dimethylsiloxane oil.

[0048]

The method of coating is not specifically limited.

For example, a wet coating method or a dry coating method can be used.

[0049]

Examples of the wet coating method include dip coating, spin coating, flow coating, spray coating, roll coating, gravure coating, and a similar method.

[0050]

Examples of the dry coating method include vacuum deposition, sputtering, CVD and a similar method. The specific examples of the vacuum deposition method include resistance heating, electron beam, high-frequency heating, ion beam, and a similar method. The specific examples of the CVD method include plasma-CVD, optical CVD, thermal CVD and a similar method.

[0051]

Additionally, coating can be performed by an atmospheric pressure plasma method.

[0052]

When the wet coating method is used, the perfluoropolyether group-containing silane compound (may be alone or in form of a composition comprising the compound) is diluted with a solvent, and then it is applied to the surface of the base material. In view of stability of the perfluoropolyether group-containing silane compound or the composition and volatile property of the solvent, the following solvents are preferably used: an aliphatic perfluorohydrocarbon having 5-12 carbon atoms (for example, perfluorohexane , perfluoromethylcyclohexane and perfluoro- 1 , 3 -dimethylcyclohexane) ; an aromatic polyfluorohydrocarbon (for example, bis (trifluoromethyl) enzene) ; an aliphatic polyfluorohydrocarbon; a hydrofluoroether (HFE) (for example, an alkyl perfluoroalkyl ether such as perfluoropropyl methyl ether (C₃F₇OCH₃) , perfluorobutyl methyl ether (C₄F₉OCH₃) , perfluorobutyl ethyl ether (C₄F₉OC₂H₅) , and perfluorohexyl methyl ether (C₂F₅CF (OCH₃) C₃F₇) (the perfluoroalkyl group and the alkyl group may be liner or branched)), and the like. These solvents may are used alone or as a mixture of two or more. Among them, the hydrofluoroether is preferable, perfluorobutyl methyl ether (CF₉OCH₃) and/or perfluorobutyl ethyl ether (C₄F₉OC₂H₅) are particularly preferable.

[0053]

The formation of the precursor coating is preferably performed so that the perfluoropolyether group-containing silane compound is present together with a catalyst for hydrolysis and dehydration-condensation in the precursor coating. Simply, when the wet coating method is used, after the perfluoropolyether group-containing silane compound (may be alone or in form of a composition comprising the compound) is diluted with a solvent, and just prior to be applied to the surface of the base material, the catalyst may be added to the diluted solution of the perfluoropolyether group-containing silane compound. When the dry coating method is used, the perfluoropolyether group-containing silane compound to which a catalyst has been added itself is used in vacuum deposition, or pellets may be used in vacuum deposition, wherein the pellets is obtained by impregnating a porous metal such as iron or copper with the perfluoropolyether group-containing silane compound to which the catalyst has been added. [0054]

As the catalyst, any suitable acid or base can be used. As the acid catalyst, for example, acetic acid, formic acid, trifluoroacetic acid, or the like can be used. As the base catalyst, for example, ammonia, an organic amine, or the like can be used.

[0055]

After the precursor coating is formed on the surface of the base material as mentioned above, water is supplied to this precursor coating. The method of supplying water may be, for example, a method using dew condensation due to the temperature difference between the precursor coating (and the base material) and ambient atmosphere or spraying of water vapor (steam) , but not specifically limited thereto.

[0056]

It is considered that, when water is supplied to the precursor coating, water acts on the hydrolyzable group bonded to Si present in the perfluoropolyether group- containing silane compound, thereby enabling rapid hydrolysis of the perfluoropolyether group-containing silane compound.

[0057]

The supplying of water may be performed under an atmosphere, for example, at a temperature between 0 and 500°C, preferably between 100°C and 300°C. By supplying water at such temperature range, hydrolysis can proceed. The pressure at this time is not specifically limited but simply may be ambient pressure.

[0058]

Then, the precursor coating is heated on the surface of the base material under a dry atmosphere over 60°C. The method of dry heating may be to place the precursor coating together with the base material in an atmosphere at a temperature over 60°C, preferably over 100°C, and for example, of 500°C or less, preferably of 300°C or less, and at unsaturated water vapor pressure, but not specifically limited thereto. The pressure at this time is not specifically limited but simply may be ambient pressure.

[0059]

Under such atmosphere, between the perfluoropolyether group-containing silane compounds, the groups being bonded to Si after hydrolysis are rapidly dehydration-condensed with each other. Furthermore, between the perfluoropolyether group-containing silane compound and the base material, the group being bonded to Si in the compound after hydrolysis and a reactive group present on the surface of the base material are rapidly reacted, in particular, when the reactive group present on the surface of the base material is a hydroxyl group, dehydration- condensation is caused. As the result, the bond between the perfluoropolyether group-containing silane compounds is formed, and the bond between the perfluoropolyether group- containing silane compound and the base material is formed.

[0060]

Preferably, the above supplying of water and dry heating are sequentially performed by using a superheated water vapor.

[0061]

The superheated water vapor is a gas which is obtained by heating a saturated water vapor to a temperature over the boiling point, wherein the gas, under an ambient pressure, has become to have a unsaturated water vapor pressure by heating to a temperature over 100°C, generally of 500°C or less, for example, of 300°C or less, and over the boiling point. When the base material on which the precursor coating is formed is exposed to a superheated water vapor, firstly, due to the temperature difference between the superheated water vapor and the precursor coating of a relatively low temperature, dew condensation is generated on the surface of the precursor coating, thereby supplying water to the precursor coating. Presently, as the temperature difference between the superheated water vapor and the precursor coating decreases, water on the surface of the precursor coating is evaporated under the dry atmosphere due to the superheated water vapor, and an amount of water on the surface of the precursor coating gradually decreases. During the amount of water on the surface of the precursor coating is decreasing, that is, during the precursor coating is under the dry atmosphere, the precursor coating on the surface of the base material contacts with the superheated water vapor, as a result, the precursor coating is heated to the temperature of the superheated water vapor (temperature over 100°C under ambient pressure) . Therefore, by using a superheated water vapor, supplying of water and dry heating are enabled to be sequentially carried out simply by exposing the base material on which the precursor coating is formed to a superheated water vapor.

[0062]

By the above, the perfluoropolyether group-containing silane-based coating derived from the precursor coating is formed on the surface of the base material . The perfluoropolyether group-containing silane-based coating thus obtained has high friction durability. Furthermore, this perfluoropolyether group-containing silane-based coating may have, depending on the perfluoropolyether group-containing silane compound used, water-repellency, oil-repellency, antifouling property (for example, preventing from adhering a fouling such as fingerprints) , surface slip property (or lubricity, for example, wiping property of a fouling such as fingerprints) , in addition to high friction durability, thus may be suitably used as a functional thin coating.

[0063]

An article having the perfluoropolyether group- containing silane-based coating thus obtained is not specifically limited to, but may be an optical member. Examples of the optical member include the followings: lens of glasses, or the like; a front surface protective plate, an antireflection plate, a polarizing plate, or an antiglare plate on a display such as PDP and LCD; a touch panel sheet of an instrument such as a mobile phone or a personal digital assistance; a disk surface of an optical disk such as Blu-ray disk, DVD disk, CD-R or MO; an optical fiber, and the like.

[0064]

The thickness of the perfluoropolyether group- containing silane-based coating is not specifically limited. For the optical member, the thickness of the perfluoropolyether group-containing silane-based coating is within the range of 1-30 nm, preferably 1-15 nm, in view of optical performance, friction durability and antifouling property. Examples

[0065]

Hereinafter, the process for producing an article of the present invention will be described in detail through Examples, although the present invention is not limited to Examples .

[0066]

Example 1

- Preparation of a composition for forming a coating A composition (0.1 part by weight) comprising a compound of the following formula (molecular weight: about 4,000) as a main component and hydrofluoroether (99.9 parts by weight) (Novec HFE 7200 (perfluorobutyl ethyl ether) manufactured by Sumitomo 3M Limited) were mixed to prepare Coating Composition A.

CF₃CF₂CF₂0(CF₂CF₂CF₂0)_nCF₂CF₂(CH₂CH)_mH

Si(OCH₃)₃ wherein: n is an integer from 20 to 30, and m is an integer from 1 to 5.

[0067]

- Base material and Pretreatment

A chemical strengthening glass (Gorilla glass manufactured by Corning Incorporated; thickness: 0.55 mm, flat dimension: 55 mm x 100 mm) was used as a base material No pretreatment of the base material was carried out.

[0068]

- Formation of a precursor coating

Coating Composition A prepared above was uniformly spray-coated on the surface of the base material by using the commercial spray coating equipment equipped with a two- fluid nozzle (head speed: 70. mm/sec) . A coating amount of Coating Composition A was 1 ml per sheet of the base material (strengthening glass) (flow rate of the coating composition: 4 ml/min) . Thus, the precursor coating was formed on the surface of the base material .

[0069]

- Posttreatment

Next, pure water was added to the bottom of a container with a cover made of heat-resistant resin, and the base material on which the precursor coating was formed above was located above water in this container and fixed (keep from contacting with water) . This container was covered and heated in an electric furnace. The base material on which the precursor coating was formed above was maintained for 1 hour under a condition that the temperature of the gas phase inside the container was 130°C, thereby exposing the base material on which the precursor coating was formed to a superheated water vapor at 130°C and at an ambient pressure. Then, the base material was taken out from the container, and stood under a condition of 22°C room temperature and 50% humidity.

Thus, the perfluoropolyether group-containing silane- based coating derived from the precursor coating was formed on the surface of the base material .

[0070]

Example 2

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that the coating amount of the coating composition was 2 ml per sheet of the base material (strengthening glass) (flow rate of the coating composition: 8 ml/min) .

[0071]

Example 3

A perfluoropolyether grou -containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that the surface of the base material was washed and activated by a plasma treatment using an atmospheric pressure plasma generator (manufactured by Enercon Industries Corporation, Dyne-A-Mite IT) as a pretreatment of formation of the precursor coating just prior to spray coating, and that 900 ppm by weight of acetic acid was added to Coating Composition A, then performed spray- coating.

[0072]

Example 4

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 3 except that the coating amount of the coating composition was 2 ml per sheet of the base material (strengthening glass) (flow rate of the coating composition: 8 ml/min) .

[0073]

Conditions of Examples 1-4 are shown in Table 1.

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Examples 1-4, respectively, except that the base material on which the precursor coating was formed was located in the container with a cover made of heat-resistant resin without adding water to the bottom of the container, and the base material on which the precursor coating was formed was exposed to dry air at 150°C and at an ambient pressure.

[0076]

Conditions of Comparative Examples 1-4 are shown in Table 2.

[0078]

Example 5

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that the base material on which the precursor coating was formed was maintained in the container for 30 minutes .

[0079]

Example 6

A perfluoropolyether grou -containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that Coating Composition B was prepared by mixing a composition (0.1 part by weight) comprising a compound of the following formula (molecular weight: about 4,000) as a main component, and hydrofluoroether (99.9 parts by weight) (Novec HFE 7200 (perfluorobutyl ethyl ether) manufactured by Sumitomo 3M Limited) and used.

(CH₃0)₃SiCH₂CH₂CH₂OCH₂CF₂- *

* -0(CF₂CF₂0)_p(CF₂0)_qCF₂CH₂OCH₂CH₂CH₂Si(OCH₃)₃ wherein, p is an integer from 10 to 30, and q is an integer from 10 to 50.

[0080] Example 7

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that Coating Composition C was prepared by mixing a composition (0.1 part by weight) comprising a compound of the following formula (molecular weight: about 4,000) as a main component, and hydrofluoroether (99.9 parts by weight) (Novec HFE 7200 (perfluorobutyl ethyl ether) manufactured by Sumitomo 3M Limited) and used.

CF₃CF₂CF₂0(CF₂CF₂CF₂0)_nCF₂CF₂CH₂OCH₂CH₂CH₂Si(OCH₃)₃ wherein, n is an integer from 20 to 30.

[0081]

Example 8

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that the precursor coating was formed by impregnating with Coating Composition to Kimwipe and coating the surface of the base material by shuttling this Kimwipe on the surface of the horizontally-arranged base material in its longitudinal direction ten times (hand- coating) .

[0082] Example 9

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 1 except that, as a posttreatment after the formation of the precursor coating, the base material on which the precursor coating was formed was exposed to a superheated water vapor at 200°C under an ambient pressure by spraying the superheated water vapor at 200°C generated by a superheated water vapor generator (DPH manufactured by Seta Kousan Chemical Industry Co., LTD.) to the base material on which the precursor coating was formed for five minutes.

[0083]

Conditions of Examples 5-9 are shown in Table 3.

[0085]

Comparative Examples 5-6

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Comparative Example 1 except that Coating Composition B and C which were prepared in Examples 6 and 7 were used, respectively.

[0086]

Conditions of Comparative Examples 5-6 are shown in Table 4.

[0087]

Table 4

[0088]

Evaluation

A static water contact angle of the perf luoropolyethe group-containing silane-based coatings which were formed on the surface of the base material in the above Examples and Comparative Examples was measured. The static water contact angle was measured for 1 yL of water by using a contact angle measuring instrument (manufactured by KYO A INTERFACE SCIENCE Co., LTD.).

[0089]

Firstly, as an initial evaluation, the static water contact angle of the perfluoropolyether group-containing silane-based coating of which the surface had not still contacted with anything after formation thereof was measured (the friction number of times is zero) .

[0090]

Then, as an evaluation of the friction durability, a steel wool friction durability evaluation was performed. Specifically, the base material on which the perfluoropolyether group-containing silane-based coating was formed was horizontally arranged, and then, a steel wool (grade No. 0000, dimensions: 10 mm x 10 mm x 5 mm) was contacted with the exposed surface of the perfluoropolyether group-containing silane-based coating and a load of 1000 gf was applied thereon. Then, the steel wool was shuttled at a rate of 140 mm/second while applying the load. The static water contact angle (degree) was measured per 1,000 shuttling. However, in Example 9, the static water contact angle (degree) was measured per 2,000 shuttling after being measured at 1,000 shuttling. The evaluation was stopped when the measured value of the contact angle became to be less than 100.

[0091]

The results are shown in Tables 5-6 and Figs. 1-2. The symbol "-" represents "not measured".

[0094]

Example 10

- Formation of a precursor coating

A compound of the following formula (molecular weight: about 4,000) (80 mg) was added to a copper container in an upper open state (diameter: 10 mm) and vacuum deposition was conducted in a vacuum deposition equipment (manufactured by Shincron Co., Ltd.; diameter: 1,900 mm) to form a precursor coating on the surface of the base material .

CF₃CF₂CF₂0(CF₂CF₂CF₂0)_nCF₂CF₂(CH₂CH)_mH

[0095]

- Posttreatment

The posttreatment was conducted similarly to Example 9 to form the perfluoropolyether group-containing silane- based coating derived from the precursor coating on the surface of the base material .

[0096]

Comparative Examples 7-8

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 10, except that the base material on which the precursor coating was formed was exposed to dry air at 100°C and 200 °C, respectively, and at an ambient pressure as the posttreatment .

[0097]

Comparative Examples 9-10

A perfluoropolyether group-containing silane-based coating derived from the precursor coating was formed on the surface of the base material similarly to Example 10, except that the posttreatment was not conducted, and the base material on which the precursor coating was formed was stood at a room temperature and at an ambient pressure for 1 hour or 18 hours, respectively.

[0098]

Conditions of Example 10 and Comparative Examples 7-10 are shown in Table 7.

[0100]

Evaluation

A static water contact angle of the perfluoropolyether group-containing silane-based coatings which were formed on the surface of the base material in Example 10 and Comparative Examples 7-10 was measured similarly to the above. The results are shown in Table 8. The symbol "-" represents "not measured" .

[0102]

As understood from Table 5 and Fig. 1, Examples 1-4 using a superheated water vapor at 130°C showed considerably increased friction durability compared to Comparative Examples 1-4 using dry air at 150°C. Furthermore, as understood from Table 6 and Fig. 2, the time required to posttreatment can be reduced by using a superheated water vapor than when dry air was used to heat (from comparison between Examples 5 and 9 and Comparative Example 1) . The similar increased friction durability can be obtained even when the perfluoropolyether group- containing silane compound in each of Coating Compositions B and C was used. Furthermore, the high friction durability can be obtained by using a superheated water vapor even when coating was performed by hand coating in Example 8 (generally, though hand coating provides less uniformity of thickness of the coating than when coating machine is used, hand coating is suitably used when simplicity is desired) . Furthermore, as understood from Table 8, the time required to posttreatment can be reduced by using a superheated water vapor than when dry air was used to heat, and the high friction durability can be obtained even when the precursor coating was formed by vacuum deposition. Furthermore, by using a superheated water vapor, the friction durability over that obtained in natural drying for a long time (18 hours) can be obtained in a short time (5 minutes) .

Industrial Applicability

[0103]

The present invention is suitably applied for forming a perf luoropolyether group-containing silane-based coating on a surface of various base materials, in particular, an optical member in which transparency is required.

Claims

1. A process for producing an article comprising a base material and a perfluoropolyether group-containing silane- based coating which coats a surface of the base material, wherein the process comprises the steps of;

(b) supplying water to the precursor coating; and then

(c) heating the precursor coating on the surface of the base material under a dry atmosphere at a temperature more than 60°C to form the perfluoropolyether group- containing silane-based coating derived from the precursor coating on the surface of the base material.

2. The process for producing an article according to claim 1, wherein supplying of water in the step (b) is performed under an atmosphere at a temperature from 0 to 500°C.

3. The process for producing an article according to claim 1 or 2, wherein the steps (b) and (c) are sequentially performed by exposing the base material on which the precursor coating is formed in the step (a) to a superheated water vapor.

4. The process for producing an article according to claim 1, wherein the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si comprises one or more compounds of any of the following general formulae (la) and (lb) :

Rf¹- (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂C)_m-X ^■■■ ( 1 a)

Z (CH₂) _e-SiT_nRi₃._n

Y Y

X-(CCH₂)_f(CF₂)_fCF- (OC₄F₈)_s- (OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂C)_m-X

RV_nT_nSi-(CH₂) _g Z Z ( H₂) _e-SiT_nRi₃,

^■■■ ( 1 b)

wherein :

Rf¹ is an alkyl group having 1 to 16 carbon atoms which may or may not be substituted by one or more fluorine atoms ;

a, b, c and s are each independently an integer from 0 to 200, wherein the sum of a, b, c and s is at least 1, and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c or s is not limited in the formulae; d and f are each independently 0 or 1;

10;

X is a hydrogen atom or a halogen atom;

Y is a hydrogen atom or a lower alkyl group;

Z is a fluorine atom or a lower fluoroalkyl group;

T is a hydrolyzable group;

R¹ is a hydrogen atom or an alkyl group having 1 to 22 carbon atoms,- and

n is an integer from 1 to 3.

5. The process for producing an article according to claim 1, wherein the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si comprises one or more compounds of any of the following general formulae (2a) and (2b) :

Rf²- (OC₄F₈)_s-(OC₃F₆)_a-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂)_h-0-(CH₂)_i-SiT_nR^_n ^■ ·^■ (2a)

Z

R² ₃-nTnSi-(CH₂)_k-0-(CH₂)_r(CF₂)_fCF- *

z

* - (OC₄F₈)_s-(OC3F₆)₃-(OC₂F₄)_b-(OCF₂)_c-OCF(CF₂)_d-(CH₂)_h-0-(CH₂) -SiT_nR² _3.n

^Z ---(2b)

wherein: Rf is an alkyl group having 1 to 16 carbon atoms which may or may not be substituted by one or more fluorine atoms ;

d and f are each independently 0 or 1 ;

h and j are 1 or 2 ;

i and k are each independently an integer from 2 to

20;

Z is a fluorine atom or a lower fluoroalkyl group;

T is a hydrolyzable group;

R² is a hydrogen atom or an alkyl group having 1 to 22 carbon atoms ; and

n is an integer from 1 to 3.

6. The process for producing an article according to claiml, wherein the perfluoropolyether group-containing silane compound having a hydrolyzable group bonded to Si comprises one or more compounds of the following general formula (3) :

Rf³ [-L³ _p-X-R³¹-Si (OR^: (3) wherein:

p is 0 or 1;

q is 1 or 2;

R³¹ is an alkylene group;

R³² is an alkyl group;

L³ is -CO-;

X is a group selected from the group consisting of -0-, -NR³³- , -S-, -S0₂-, -S0₂NR³³- and -NR³³CO-_; wherein R³³ is a hydrogen atom or an alkyl group having 3 or less carbon atoms .

7. An article which is produced by the process according to any one of claims 1-6.

8. The article according to claim 7, wherein the surface of the base material is made of a material which has a hydroxyl group .

9. The article according to claim 7 or 8, wherein the surface of the base material is made of a material selected from the group consisting of a glass, a resin, a metal and a ceramic

The article according to any one of claims 7-9 which . optical member.