Coating composition having anti-reflective and anti-fogging properties

• US 5,753,373 A
• Filed: 12/21/1995
• Issued: 05/19/1998
• Est. Priority Date: 12/21/1995
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Scholz, Matthew T., Kausch, William L.
• Primary Examiner(s): TURNER, ARCHENE A
• Application Number:
  US08/576,255
• Time in Patent Office: 880 Days
• Field of Search: 428/412, 428/429, 428/404, 428/447, 428/451, 428/452, 428/454, 524/730, 524/731, 524/837, 524/786, 524/783, 524/780, 106/282.1, 106/287.11, 106/287.12, 106/287.13, 106/287.14, 106/287.16, 128/206.16, 128/206.27, 128/206.28, 128/201.12, 128/201.17, 128/206.23, 2/8, 2/9, 2/12, 2/13, 2/15
• US Class Current: 428/429
• CPC Class Codes: C09D 1/00 Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• CPC Class Codes: C09D 5/00 Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced electrically insulating plastics, resins or waxes H01B3/30; Filling pastes
• CPC Class Codes: C09K 3/18 for application to surfaces to minimize adherence of ice, mist or water thereto rendering particulate materials free flowing, in general, e.g. making them hydrophobic B01J2/30; Thawing or antifreeze materials for application to surfaces used in liquids for heat-transfer, heat-exchange or heat-storage or for the production of heat or cold other than by combustion, e.g. radiator liquids, C09K5/00
• CPC Class Codes: Y10T 428/31612 As silicone, silane or siloxane
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane
• CPC Class Codes: Y10T 428/31667 Next to addition polymer from unsaturated monomers, or aldehyde or ketone condensation product

Abstract

A coating composition which imparts anti-reflective and anti-fog properties to substrates coated therewith. The coating composition utilizes an inorganic metal oxide in combination with particular polyhydroxy surfactants. The coating compositions are particularly useful in the manufacture of disposable surgical masks and face shields.

Claims

1. A coating composition which imparts anti-reflection and anti-fogging properties to a substrate having at least one surface coated therewith, the coating composition comprising:

(a) inorganic metal oxide particles; and

(b) a nonionic surfactant comprised of at least one hydrophobic group and at least one hydrophilic group, wherein

(1) the hydrophilic group is selected from the group consisting of

(i) pyrrolidone, and

(ii) a polyhydroxyl group comprising at least two hydroxyl groups, wherein at least two of the hydroxyl groups are separated by no more than 5 atoms, and the number of said hydroxyl groups is greater than or equal to the total number of hydrophobic groups present within the surfactant molecule, and

(2) wherein the hydrophobic group is a hydrocarbon chain comprising at least 4 carbon atoms or a perfluorinated radical comprising at least 3 carbon atoms, and wherein the coating composition when coated on at least one side of a light transmissive substrate;

(1) provides a porous inorganic metal oxide network of uniform average thickness;

(2) provides said substrate with a drop diameter of at least 4 mm when tested in accordance with the Wetting Test described herein; and

(3) provides said substrate with a percent transmission at 550 nm which is at least 3 percent greater than that of the uncoated substrate.

2. The coating composition of claim 1 wherein the surfactant has the general formula:

##STR11## wherein R is an alkyl group having about 4 to 36 carbon atoms, an aralkyl group having about 7 to 36 carbon atoms, or a perfluorinated alkyl group having about 3 to 12 carbon atoms, and

a is between 0 and 20.

3. The coating composition of claim 1 wherein the surfactant has the general formula:

space="preserve" listing-type="equation">R--C(O)--O--CH.sub.2 CH(OH)--CH.sub.2 OH,

wherein

R is an alkyl group having about 4 to 36 carbon atoms, an aralkyl group having about 7 to 36 carbon atoms, or a perfluorinated alkyl group having about 3 to 12 carbon atoms.

4. The coating composition of claim 1 wherein the surfactant has the general formula:

space="preserve" listing-type="equation">Y--O--(CH.sub.2 CH(OY)--CH.sub.2 O).sub.n Y

wherein

Y is 11 or --C(O) R, where R is an alkyl group having about 8 to 36 carbon atoms, or an aralkyl group having about 7 to 36 carbon atoms, or a perfluorinated alkyl group having about 3 to 12 carbon atoms, with the proviso that there are at least two OH groups, and

n is between about 2 and 20.

5. The coating composition of claim 1 wherein the surfactant has the general formula:

space="preserve" listing-type="equation">R--C(O)--N(CH.sub.2 CH.sub.2 OH).sub.2

wherein

R is an alkyl group having about 4 to 36 carbon atoms, an aralkyl group having about 7 to 36 carbon atoms, or a perfluorinated alkyl group having about 3 to 12 carbon atoms.

6. The coating composition of claim 1 wherein the surfactant has the general formula:

##STR12## wherein R is an alkyl group having about 4 to 36 carbon atoms, an aralkyl group having about 7 to 36 carbon atoms, or a perfluorinated alkyl group having about 3 to 12 carbon atoms.

7. The coating composition of claim 1 wherein the surfactant has the general formula:

##STR13## where R is an alkyl group having about 4 to 36 carbon atoms, an aralkyl group having about 7 to 36 carbon atoms, or a perfluorinated alkyl group having about 3 to 12 carbon atoms.

8. The coating composition of claim 1 wherein the inorganic metal oxide is selected from the group consisting of aluminum oxide, tin oxide, titanium oxide, antimony oxide, silica, zirconium oxide and mixtures thereof.

9. A coating composition according to claim 1 wherein the inorganic metal oxide comprises silica.

10. A coating composition according to claim 1 wherein the inorganic metal oxide is provided as a colloidal solution of inorganic metal oxide particles.

11. The coating composition of claim 1 wherein the surfactant is present in a concentration of less than 0.15 percent by weight.

12. The coating composition of claim 1 wherein the surfactant is present in the coating composition in a concentration of less than 10 percent by weight of the metal oxide.

13. The coating composition of claim 1 further comprising:

a second surfactant comprised of at least one hydrophobic group and at least one hydrophilic anionic group, wherein;

(i) the hydrophilic anionic group comprises an anion selected from the group consisting of --OSO₂ O^-, --SO₂ O^-, --CO₂^-, (--O)₂ P(O)O^-, --OP(O)(O^-)₂, --P(O)(O^-)₂, --P(O^-)₂, --OP(O^-)₂, (--SO₂)₂ N^-, --SO₂ N(R")--, (--SO₂)₂ C^- H, and --N⁺ (R")₂ (CH₂)_x L'"'"', wherein R" is hydrogen, an alkyl group which is unsubstituted or substituted with atoms independently selected from the group consisting of oxygen, nitrogen and sulfur, or an alkylene carboxyl group, which alkyl or alkylene carboxyl group comprises about 1 to 10 carbon atoms;

x is 1 to 4; and

L'"'"' is selected from the group consisting of --OSO₂ O^-, --SO₂ O^-, (--O)₂ P(O)O^-, --OP(O)(O^-)₂, --P(O)(O^-)₂ and --CO^-₂ ; and

wherein each anionic group is associated with or covalently bound to at least one cation, which cation is selected from the group consisting of H⁺, Na⁺, K⁺, Li⁺, Ca⁺², Mg⁺², Sr⁺², Al⁺³, and R'"'"'"A⁺, wherein R'"'"'" is R⁴ or R⁵ wherein R⁴ is hydrogen or an alkyl or cycloalkyl group of about 1 to 10 carbon atoms, and R⁵ is covalently bonded to the surfactant molecule and is an alkyl bridging group of 1 to 10 carbon atoms, and A⁺ is N⁺ R⁴₃, a guanidinium ion optionally substituted with oxygen, nitrogen or sulfur atoms, or N⁺ B wherein B comprises 3 to 7 atoms selected from the group consisting of carbon, nitrogen, sulfur and oxygen atoms which complete the nitrogen containing heterocyclic ring; and

wherein any R⁴ or R⁵ group may be unsubstituted or substituted with atoms independently selected from the group consisting of oxygen, nitrogen or sulfur;

the cation selected such that the net charge of the surfactant molecule is neutral; and

(ii) wherein the hydrophobic group comprises a hydrocarbon chain comprising at least 4 carbon atoms, or a perfluorinated radical comprising at least 3 carbon atoms.

14. The coating composition of claim 13 wherein the second surfactant is a lithium, sodium or potassium salt of an anionic perfluoro group-containing compound.

15. The coating composition of claim 1 further comprising a silane coupling agent capable of covalently bonding the metal oxide to the surfactant or substrate.

16. The coating composition of claim 15 wherein the silane coupling agent has the general formula:

##STR14## wherein;

R⁹ is a divalent hydrocarbon bridging group of about 1 to 20 carbon atoms, optionally including in the backbone 1 to 5 moieties selected from the group consisting of --O--, --C(O)--, --S--, --SO₂ -- and --NR"-- groups, and optionally substituted on the backbone by --OH, --SH, or --NR"₂, wherein R" is hydrogen, acetyl, or a hydrocarbon group of 1 to 6 carbon atoms;

X is --OR¹² where R¹² is an alkyl, aryl, heteroaryl or aralkyl group of 1 to 8 carbon atoms, or --N═

C(R¹³)₂, wherein R¹³ is independently an alkyl, aryl or aralkyl group of 1 to 8 carbon atoms;

R¹⁰ is independently an alkyl, aryl, aralkyl or alkoxy group of 1 to 8 carbon atoms which is unsubstituted or independently substituted in available positions by oxygen, nitrogen and/or sulfur atoms;

f is 0, 1, or 2;

g is 2 or 3; and

Q is a reactive functional group having one moiety selected from the group consisting of amino;

hydroxyl;

mercaptan;

oxirane;

chloro-, iodo-, and bromo-alkyl;

aziridine;

cyclic carboxylic anhydride;

acrylate;

methacrylate;

acrylamide, azide, and isocyanato groups.

17. An article comprising a substrate having a surface and a layer of a coating composition according to claim 1 on at least one surface of the substrate which coating composition has been dried.

18. An article according to claim 17 wherein the surface is plastic or glass.

19. An article according to claim 17 wherein the substrate is transparent or translucent to visible light incident thereon.

20. An article according to claim 17 wherein the substrate is selected from the group consisting of polyester, polycarbonate, allyldiglycolcarbonate, polyacrylates, polystyrene, polysulfone, polyethersulfone, cellulose acetate butyrate, glass, blends and laminates thereof.

21. An article according to claim 17 wherein the layer of the coating composition has a thickness in the range of about 500 to 2500 Å

.

22. An article according to claim 17 wherein the layer of the coating composition provides a continuous network of inorganic metal oxide particles.

26. The article of claim 1 wherein at least one surface of the substrate is coated with the porous inorganic metal oxide network, the surfactant, or a combination thereof.

23. An eye shield comprising a substrate which is transparent or translucent to visible light coated with

(a) a porous inorganic metal oxide network of uniform average thickness which provides anti-reflection properties to the substrate;

and

(b) a nonionic surfactant comprised of at least one hydrophobic group and at least one hydrophilic group, wherein

(1) the hydrophilic group is selected from the group consisting of

(i) pyrrolidone, and

(ii) a polyhydroxyl group comprising at least two hydroxyl groups, wherein at least two of the hydroxyl groups are separated by no more than 5 atoms, and the number of said hydroxyl groups is greater than or equal to the total number of hydrophobic groups present within the surfactant molecule, and

(2) wherein the hydrophobic group is a hydrocarbon chain comprising at least 4 carbon atoms or a perfluorinated radical comprising at least 3 carbon atoms;

which coated substrate when coated on at least one surface exhibits;

(1) a drop diameter of at least 4 mm when tested in accordance with the Wetting Test described herein; and

(2) a percent transmission at 550 nm which is at least 3 percent greater than that of the uncoated substrate.

24. A surgical mask comprising a face mask and an eye shield according to claim 23.

25. The eye shield of claim 23 wherein at least one surface of the substrate is coated with the porous inorganic metal oxide network, the surfactant, or a combination thereof.

27. An article comprising a substrate which is transparent or translucent to visible light coated with

(a) a porous inorganic metal oxide network of uniform average thickness which provides anti-reflection properties to the substrate;

and

(b) a nonionic surfactant comprised of at least one hydrophobic group and at least one hydrophilic group, wherein

(1) the hydrophilic group is selected from the group consisting of

(i) pyrrolidone, and

(ii) a polyhydroxyl group comprising at least two hydroxyl groups, wherein at least two of the hydroxyl groups are separated by no more than 5 atoms, and the number of said hydroxyl groups is greater than or equal to the total number of hydrophobic groups present within the surfactant molecule, and

(2) wherein the hydrophobic group is a hydrocarbon chain comprising at least 4 carbon atoms or a perfluorinated radical comprising at least 3 carbon atoms;

which coated substrate when coated on at least one surface exhibits;

(1) a drop diameter of at least 4 mm when tested in accordance with the Wetting Test described herein; and

(2) a percent transmission at 550 nm which is at least 3 percent greater than that of the uncoated substrate.

28. The article of claim 27 wherein the coating comprises about 85 percent by weight to about 99.7 percent by weight of the inorganic metal oxide and about 0.2 percent by weight to about 5 percent by weight of surfactant.

29. A method of imparting anti-reflection and anti-fogging properties to a substrate, the method comprising the steps of:

(a) providing a substrate;

(b) preparing a composition comprising;

(1) inorganic metal oxide particles; and

(2) a nonionic surfactant comprised of at least one hydrophobic group and at least one hydrophilic group, wherein

(a) the hydrophilic group is selected from the group consisting of

(i) pyrrolidone, and

(ii) a polyhydroxyl group comprising at least two hydroxyl groups, wherein at least two of the hydroxyl groups are separated by no more than 5 atoms, and the number of said hydroxyl groups is greater than or equal to the total number of hydrophobic groups present within the surfactant molecule, and

(b) wherein the hydrophobic group is a hydrocarbon chain comprising at least 4 carbon atoms or a perfluorinated radical comprising at least 3 carbon atoms;

(c) applying the coating composition to at least one side of the substrate; and

(d) drying the coating composition to produce a coated substrate having a porous inorganic metal oxide network of uniform average thickness;

which coated substrate when coated on at least one surface exhibits;

(1) a drop diameter of at least 4 mm when tested in accordance with the Wetting Test described herein; and

(2) a percent transmission at 550 nm which is at least 3 percent greater than that of the uncoated substrate.

30. The method of claim 29 wherein the coating composition is applied to the substrate in a uniform average thickness which varies by less than about 200 Å

.

31. The method of claim 29 wherein the coating composition is applied to the substrate at a thickness of about 500 to 2500 Å

.

32. The method of claim 29 wherein the substrate is coated on both sides with the coating composition.

33. A method of imparting anti-reflection and anti-fogging properties to a substrate, the method comprising the steps of:

(a) providing a substrate;

(b) preparing a first coating composition comprising inorganic metal oxide particles;

(c) preparing a second coating composition comprising a nonionic surfactant comprised of at least one hydrophobic group and at least one hydrophilic group, wherein

(1) the hydrophilic group is selected from the group consisting of

(i) pyrrolidone, and

(ii) a polyhydroxyl group comprising at least two hydroxyl groups, wherein at least two of the hydroxyl groups are separated by no more than 5 atoms, and the number of said hydroxyl groups is greater than or equal to the total number of hydrophobic groups present within the surfactant molecule, and

(2) wherein the hydrophobic group is a hydrocarbon chain comprising at least 4 carbon atoms or a perfluorinated radical comprising at least 3 carbon atoms;

(d) applying either the first or second coating composition to at least one side of the substrate;

(e) allowing the coating applied in step (d) to dry;

(f) applying the coating composition not applied in step (d) to at least one side of the substrate;

(g) allowing the coating applied in step (f) to dry;

wherein the substrate is light transmissive and the amount of metal oxide and surfactant applied to the substrate is sufficient to provide the coated substrate with

(1 ) a porous inorganic metal oxide network of uniform average thickness;

(2 ) a drop diameter of at least about 4 mm when tested in accordance with the Wetting Test described herein; and

(3) a percent transmission at 550 nm which is at least 3 percent greater than that of the uncoated substrate.