Durable glass articles for use as writable erasable marker boards

Patent metadata

Field	Value
Publication number	US-9604492-B2
Application number	US-201414282570-A
Country	US
Kind code	B2
Filing date	May 20, 2014
Priority date	Nov 30, 2012
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

The invention relates to glass articles suitable for use as writable erasable marker boards. More particularly, disclosed is a strengthened glass article suitable for use as a writable erasable marker boards, wherein the glass sheet exhibits an ion exchanged glass having a front surface and a back surface and exhibiting a thickness of less than 2.0 mm and having a depth of layer (DOL) greater than 20 microns and a surface compressive strength of at least 300 MPa. The strengthened glass article exhibits certain optical properties which render it particularly suitable for use as a writable erasable marker boards electronic including: (1) shadow parallax to thickness ratio of less than 1 measured at a 60 degree incident light angle and for an index of refraction n; and, (2) a haze of less than 50%. Further disclosed is a markerboard with improved magnetic force attributes; sufficient to hold weak magnets in place.

First claim

We claim:

1. A writable erasable marker board comprising:
a strengthened glass sheet having a front surface and a back surface wherein the glass sheet exhibits a thickness of less than 2.0 mm, a shadow parallax to thickness ratio of less than 1 measured at a 60 degree incident light angle, an index of refraction of 1.5, a transmission haze of less than 40%, an RMS roughness in a range from about 50 nm up to about 500 nm, and a distinctness of image (DOI) of less than about 85.

2. The writable erasable marker board of claim 1 , wherein the strengthened glass article further exhibits a fracture toughness of greater than 0.75 MPa·m 1/2 , an abraded MOR of greater than 350 MPa, a Vickers hardness of at least 600 kgf/mm 2 , a Young's Modulus of greater than 60 GPa, and a surface compressive stress of greater than 300 MPa.

3. The writable erasable marker board of claim 1 , wherein the strengthened glass sheet has a surface compressive strength of at least 300 MPa.

4. The writable erasable marker board of claim 1 , wherein the strengthened glass sheet has at least one compressively-stressed region near the front surface or the back surface, and wherein the compressively-stressed region has a layer depth of at least 20 microns.

5. The writable erasable marker board of claim 1 , wherein the strengthened glass article exhibits an MOR of greater than 475 MPa.

6. The writable erasable marker board of claim 1 further comprising a mounting means, wherein the mounting means is selected from the group consisting of (i) a magnetic layer on the back surface of the strengthened glass sheet, (ii) an adhesive layer on the back surface of the strengthened glass sheet, and (iii) a static cling layer on the back surface of the strengthened glass sheet.

7. The writable erasable marker board of claim 1 further comprising a mounting means, wherein the mounting means is selected from the group consisting of (i) one or more mounting holes formed in the strengthened glass sheet, (ii) one or more glass sheet hanging elements attached to the strengthened glass sheet, and (iii) one or more glass sheet framing elements attached to the strengthened glass sheet.

8. The writable erasable marker board of claim 1 wherein the glass is an ion-exchanged alkali-aluminosilicate glass.

9. The writable erasable marker board of claim 1 , wherein the glass is an ion-exchanged alkali-aluminosilicate glass comprising, in weight percent as oxides on a batched basis, of 40-80% SiO 2 , 0-28% Al 2 O 3 , 0-8% B 2 O 3 ,0-18% Li 2 O, 0-10% Na 2 O, 0-11% K 2 O, 0-16MgO, 0-18% CaO, 0-15% CaF 2 , 0-20% SrO, 0-12% BaO, 0-8% ZnO, 0-4% P 2 O 5 , 0-8% TiO 2 , 0-5% ZrO 2 , 0-1% Sn 0 2 , 0-1 Sb 2 O 3 , and 0-1% As 2 O 3 .

10. The writable erasable marker board of claim 1 , wherein the glass is an ion-exchanged alkali-aluminosilicate glass comprising: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-8 mol % MgO; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol % ≦Li 2 O+Na 2 O+K 2 O≦20 mol % and 0 mol % ≦MgO+CaO≦10 mol %.

11. The writable erasable marker board of claim 1 , wherein the glass is an ion-exchanged alkali-aluminosilicate glass comprising at least 50 mol % SiO 2 , less than 10 mol % B 2 O 3 , and at least 8 mol % Na 2 O, wherein the aluminoborosilicate glass is ion exchangeable, wherein a ratio

Al
2

⁢

O
3

⁡

(

mol
⁢

⁢
%

)

+

B
2

⁢

O
3

⁡

(

mol
⁢

⁢
%

)

Σ
⁢

⁢

modifiers
⁡

(

mol
⁢

⁢
%

)

>
1

,

wherein Al 2 O 3 (mol %) >B 2 O 3 (mol %) and the modifiers are Na 2 O and, optionally, at least one oxide selected from the group consisting of alkali metal oxides R 2 O other than Na 2 O and alkaline earth oxides RO, wherein the aluminoborosilicate glass has a Young's modulus of less than about 69 GPa, and wherein −6 mol % <Σmodifiers−Al 2 O 3 <3 mol %.

12. The writable erasable marker board of claim 1 wherein the marker board further comprises an organic film structure which is laminated to at least one side of the glass sheet which provides anti-splinter functionality.

13. The writable erasable marker board of claim 1 , wherein the marker board further comprises a decorative layer attached to at least one side of the glass sheet.

14. The writable erasable marker board of claim 1 , wherein the shadow parallax to thickness ratio is less than about 0.75 measured at a 60 degree incident light angle.

15. A writable erasable marker board comprising:
a strengthened glass sheet having a front surface and a back surface wherein the glass sheet exhibits a thickness of less than 2.0 mm, a shadow parallax to thickness ratio of less than 1 when measured at a 60 degree incident light angle, an index of refraction of 1.5, a transmission haze of less than 40%, an RMS roughness in a range from about 50 nm up to about 500 nm, and a distinctness of image (DOI) of less than about 85; and
a magnetic or ferrous steel backing plate positioned on at least one side of the glass sheet such that when the marker board is vertical, a permanent magnet with maximum energy product of less than 10 MGOe will remain attached to the glass sheet through magnetic force only.

16. The writable erasable marker board of claim 15 , wherein a permanent

Assignees

• Corning Inc

Inventors

• Bookbinder Dana Craig
• Domey Jeffrey John
• Fenton Matthew Wade
• Weidman David Lee

Classifications

• C03C3/093

  containing zinc or zirconium · CPC title

• B43L1/12 Primary

  having translucent writing surfaces producing visual impressions by co-operation with backing members {(B43L1/008 takes precedence)} · CPC title

• C03C3/087

  containing calcium oxide, e.g. common sheet or container glass · CPC title

• B43L1/002

  chemical details · CPC title

• B43L1/00 Primary

  Repeatedly-usable boards or tablets for writing or drawing (drawing-boards B43L5/00) · CPC title