Mar resistance, non-glare transparent acrylic sheet with consistent optical properties at various sheet thicknesses

1. A mar resistant transparent co-extruded sheet, comprised of:

a cap layer containing particles having a mean particle size of about 1 to 60 microns wherein 90% of the particles are less than 70 microns, at a loading of 0.1 to 18%, melt blended with an acrylic matrix, wherein the particle and matrix have refractive indices within 0.020 units when measured in conformance with ASTM D 542; and

a clear substrate layer comprised of an acrylic composition, wherein the substrate has a refractive index within 0.020 units of the refractive index of the cap layer matrix when measured in conformance with ASTM D 542; and

wherein the co-extruded product has

(i) a luminous transmission (CIE tristimulus Y value) of greater than 90% when measuring spectral transmission data using a spectrophotometer and the 2° standard observer, and calculating the CIE tristimulus Y value in conformance with ASTM E 308, and

(i) a haze of less than 16% when measured in conformance with ASTM D 1003;

 and at least one properly selected from (iii) or (iv),

(ii) 60° gloss values measured on two different sheet thicknesses within the range of 0.04 to 0.5 inches thick which are within 15 units of each other when measured using a micro-TRI-gloss meter in conformance with ASTM D 523 using a black felt backing, and

(iii) a change in haze as measured in conformance with ASTM D 1044, after 500 revolutions using a 500 g load and CS10F wheel, of less than 25%.

2. The sheet of claim 1 wherein the particles of the capcoat are cross-linked and are comprised of alkyl methacrylate homo polymers, or copolymers of alkyl methacrylates with other alkyl methacrylates or alkyl acrylates or other ethylenically unsaturated monomers.

3. The sheet of claim 2 wherein the particles are comprised of a polymer or copolymer of methyl methacrylate and a (C1-C10) alkyl acrylates.

4. The sheet of claim 3 wherein the particles are comprised of a copolymer of 80-99% methyl methacrylate, and 1-20% ethyl acrylate.

5. The sheet of claim 3 wherein the particles are comprised of a copolymer of 90-98% methyl methacrylate and 2-10% ethyl acrylate.

6. The sheet of claim 1 wherein the acrylic matrix of the cap layer is selected from the group comprising;

i) alkyl methacrylate homo polymers,

ii) copolymers of alkyl methacrylates with other alkyl methacrylates or alkyl acrylates or other ethylenically unsaturated monomers,

iii) alkyl acrylate homo polymers, and

iv) copolymers of alkyl acrylates with other alkyl acrylates or alkyl methacrylates or other ethylenically unsaturated monomers.

7. The sheet of claim 1 wherein clear substrate is comprised of a composition selected from the group comprising:

i) alkyl methacrylate homo polymers,

ii) copolymers of alkyl methacrylates with other alkyl methacrylates or alkyl acrylates or other ethylenically unsaturated monomers,

iii) alkyl acrylate homo polymers, and

iv) copolymers of alkyl acrylates with other alkyl acrylates or alkyl methacrylates or other ethylenically unsaturated monomers.

8. The sheet of claim 1 having an overall thickness of 0.05 to 0.18 inches thick, comprised of:

(a) a cap layer, 0.001 to 0.025 inches thick, containing

(i) spherical particles, having a mean particle size of at 20-35 microns, wherein 90% of the particles are less then 40 microns, at a loading of 0.5 to 12%, with an acrylic matrix, the particles are comprised of a polymer or copolymer of 80-99% methyl methacrylate, 1-5% methyl acrylate or ethyl acrylate with a crosslinking agent; melt blended with

(ii) an acrylic matrix,

wherein the particle and matrix have refractive indices within 0.020 units, preferably within 0.005 units, when measured in conformance with ASTM D 542; and

(b) a clear substrate layer comprised of an acrylic composition, wherein the substrate has a refractive index within 0.010 units, of the refractive index of the cap layer matrix when measured in conformance with ASTM D 542; and

wherein the co-extruded product has

(i) luminous transmission (CIE tristimulus Y value) of greater than 91%, when measuring spectral transmission data using a spectrophotometer and the 2° standard observer, and calculating the CIE tristimulus Y value in conformance with ASTM E 308;

2. haze of less than 12%, when measured in conformance with ASTM D 1003;

and at least one of

(iii) 60° gloss values measured on two different sheet thicknesses within the range of 0.04 to 0.25 inches thick which are within 15 units of each other when measured using a micro-TRI-gloss meter in conformance with ASTM D 523 using a black felt backing; and

(iv) change in haze as measured in conformance with ASTM D 1044, after 500 revolutions using a 500 g load and CS10F wheel, of less than 22%.

9. The sheet of claim 8 wherein the acrylic matrix of the cap layer is selected from the group comprising:

i) alkyl methacrylate homo polymers.

ii) copolymers of alkyl methacrylates with other alkyl methacrylates or alkyl acrylates or other ethylenically unsaturated monomers,

iii) alkyl acrylate homo polymers, and

iv) copolymers of alkyl acrylates with other alkyl acrylates or alkyl methacrylates or other ethylenically unsaturated monomers.

10. The sheet of claim 9 wherein clear substrate is comprised of a composition selected from the group comprising:

i) alkyl methacrylate homo polymers,

ii) copolymers of alkyl methacrylates with other alkyl methacrylates or alkyl acrylates or other ethylenically unsaturated monomers,

iii) alkyl acrylate homo polymers, and

iv) copolymers of alkyl acrylates with other alkyl acrylates or alkyl methacrylates or other ethylenically unsaturated monomers.

11. A polished transparent co-extruded sheet, 0.04 to 0.25 inches thick, comprised of:

a cap layer, 0.001 to 0.025 inches thick containing particles having a mean particle size of about 10 to 32 microns wherein 90% of the particles are less than 40 microns, at a loading of 0.1 to 18% melt blended with an MMA/EA acrylic matrix, wherein the particle and matrix have refractive indices within 0.005 units of each other when measured in conformance with ASTM D 542; and

a clear layer of an acrylic substrate of MMA/EA, wherein the substrate has a refractive index within 0.005 units of the refractive index of the cap layer matrix when measured in conformance with ASTM D 542;

wherein the co-extruded product

1. a luminous transmission (CIE tristimulus Y value) of greater than 90% when measuring spectral transmission data spectrophotometer and the 2° standard observer, and calculating the CIE tristimulus Y value in conformance with ASTM E 308, and

(ii) a haze of less than 16% when measured in conformance with ASTM D 1003;

and at least one property selected from (iii) or (iv),

a 60° gloss value measured on a 0.118 inch thick sample within 15 units of the 60° gloss value measured on a 0.080 inch thick sample when measured using a micro-TRI-gloss meter in conformance with ASTM D 523 using a black felt backing, and

(iv) a change in haze as measured in conformance with ASTM D 1044, after 500 revolutions using a 500 g load and CS10F wheel, of less than 25%.