Low Reflectance Transparent Material Having Antisoiling Properties

Now, the present invention will be described in further detail with reference to Examples. However, the present invention is by no means restricted by these specific Examples. In the Examples, the low reflectance material having antisoiling properties was evaluated by the following methods.

Reflectance:

An average reflectance was measured at an angle of incidence of 5.degree. of a wavelength of from 400 to 700 n.mu.m by means of an automatic recording spectrophtometer with a specular reflection measuring device (323 Model, manufactured by Hitachi, Ltd.).

Layer thickness:

The thickness was obtained by the measurement of needle pressure by means of "Talystep" (manufactured by Rank Taylor Hobson Co.).

Pencil Hardness:

The pencil hardness was measured by means of a pencil scratching tester (JIS-K5401).

Water repellency:

The contact angle of a water drop was measured.

Oil repellency:

The contact angle of hexadecane was measured.

Preparation of condensation products containing metal oxides for the undercoating layer

The starting materials identified in Table 1 were mixed in the respective amounts (g) as identified in Table 1. The respective mixtures were reacted for one week under stirring at room temperature, and then filtered to obtain Treating Solutions No. A to No. P, i.e. treating solutions of TiO.sub.2 -containing condensation products, SiO.sub.2 -containing condensation products, SiO.sub.2 -TiO.sub.2 -containing condensation products and SiO.sub.2 -ZrO.sub.2 -containing condensation products.

Preparation of condensation products of fluorine-containing silicon compounds for the top coating layer

The starting materials identified in Table 2 were mixed in the respective amounts (g) as identified in Table 2. The respective mixtures were reacted for 24 hours under stirring at room temperature, and then filtered to obtain Treating Solutions No. Q to No. U, i.e. treating solutions of condensation products containing fluorine-containing silicon compounds.

Preparation of condensation products of fluorine-containing silicon compounds for the top coating layer

The starting materials identified in Table 3 were mixed in the respective amounts (g) as identified in Table 3. The respective mixtures were reacted for 24 hours under stirring at room temperature, and then filtered to obtain Treating Solutions No. V to No. Y, i.e. treating solutions of condensation products of fluorine-containing silicon compounds.

Preparation of a condensation product of a fluorine-containing silicon compound for the top coating layer

For a Comparative Example, the starting materials identified in Table 4 were mixed in the respective amounts (g) as identified in Table 4, and reacted in the same manner as in Preparation Example 2 to obtain a Treating Solution No. Z.

Preparation of treating solutions for a primer coating to be optionally formed on a plastic surface

Into an autoclave reactor, 70 g of methyl methacrylate, 15 g of 2-hdyroxyethyl methacrylate, 15 g of N,N-dimethylaminoethyl methacrylate, 397 g of 2-propanol and 3 g of azobisisobutyronitrile were charged, and after replacing the internal atmosphere of the reactor with nitrogen gas, reacted at 65.degree. C. for 10 hours under stirring to obtain a polymer. To this polymer, 500 g of isopropyl alcohol and 1000 g of ethyl cellusolve were added to obtain Treating Solution No. .alpha..

Separately, 30 g of methyltrimethoxysilane, 20 g of .gamma.-glycidoxypropyltrimethoxysilane, 10 g of 3-methacryloxy propyltrimethoxysilane, 40 g of tetramethoxysilane, 3 g of aluminum acetylacetonate and 400 g of ethanol were mixed, and after an addition of 37.6 g of a 1% hydrochloric acid aqueous solution under stirring, reacted at room temperature for 10 hours to obtain Treating Solution No. .beta..

A glass plate having a refractive index of 1.52 (soda lime glass 5.times.10 cm) was cleaned with a cleaning agent, washed with distilled water and then dried in air. This glass plate was dipped in Treating Solution No. A of the metal oxide-containing condensation product for the undercoating layer as identified in Table 1, withdrawn at a speed of 11 cm/min., then dried at room temperature for 30 minutes, and maintained at 540.degree. C. for 30 minutes for thermal curing, whereby an undercoating layer having a thickness of 0.14 .mu.m and a refractive index of 1.80 was formed. Then, the glass plate formed with this undercoating layer, was dipped in a 2% hydrofluoric acid aqueous solution for 1 minute, then withdrawn, washed with distilled water, dried in air, dipped in Treating Solution No. Q of the condensation product of the fluorine-containing silicon compound for the top coating layer as identified in Table 2, then withdrawn at a speed of 4 cm/min., and maintained at 160.degree. C. for 2 hours, whereby a top coating layer having a thickness of 0.09 .mu.m and a refractive index of 1.40 was formed.

With respect to the low reflectance glass having a thin coating of a two layer structure thus obtained, the reflectance was measured, and was found to be 0.8% per one surface, and the pencil hardness was H. The contact angles of water and hexadecane were 117.5.degree. and 67.6.degree. respectively.

Low reflectance glasses formed with coatings of a double layer structure were obtained by the same treatment as in Example 1 except that the metal oxide-containing condensation product for the undercoating layer in Example 1 was selected to be Treating Solutions No. A to No. D in Table 1, the withdrawing speed from dipping and the thermal curing time were changed, further the condensation product of the fluorine-containing silicon compound for the top coating layer was selected to be Treating Solutions No. Q to No. S as shown in Table 2, and the withdrawing speed was changed.

With respect to the low reflectance glasses thus obtained, the thickness, refractive indices, reflectance, pencil hardness and contact angles were measured. The results are shown in Table 5.

Treating Solution No. Q of the condensation product of a fluorine-containing silicon compound for the top coating layer was applied onto the same glass plate as in Example 1 to form a single layer coating in the same manner as in Example 1. With respect to the glass plate thus obtained, the layer thickness, refractive index, reflectance, pencil hardness and contact angles were measured. Further, with respect to the same glass plate as in Example 1, the reflectance and contact angles in non-treated conditions were measured. The results of the measurements are shown in Table 5.

As the metal oxide-containing condensation product for the undercoating layer in Example 1, Treating Solution No. E identified in Table 1 was used, and a glass plate was dipped therein, withdrawn at a speed of 10 cm/min., then dried at 160.degree. C. for 10 minutes, thereafter dipped in Treating Solution No. F, withdrawn at a speed of 20 cm/min., again dried at 160.degree. C. for 10 minutes, and maintained at 540.degree. C. for 30 minutes for curing, whereby a multi-layer coating comprising two layers i.e. the first undercoating layer having a thickness of 0.07 .mu.m and a refractive index of 1.7 and a second undercoating layer having a thickness of 0.115 .mu.m and a refractive index of 2.10, was formed.

Then, the glass plate formed with these metal oxide layers, was dipped in a 2% hydrofluoric acid aqueous solution for 1 minute, then withdrawn, washed with distilled water, dried in air, then dipped in Treating Solution No. Q i.e. the condensation product containing a fluorine-containing silicon compound for the top coating layer as shown in Table 2, withdrawn at a speed of 6 cm/min., and maintained at 160.degree. C. for 2 hours for thermal curing, whereby a top coating layer having a thickness of 0.09 .mu.m and a refractive index of 1.40 was formed.

With respect to the low reflectance glass formed with a thin coating having the three layer structure thus obtained, the reflectance was measured, and found to be 0.25% per one surface, and the pencil hardness was H. Further, the contact angles of water and hexadecane were 117.2.degree. and 67.5.degree., respectively.

In the same manner as in Example 8, the metal oxide-containing condensation product for the undercoating layer was selected to be Treating Solutions No. E to No. L as identified in Table 1, and a multi-layer coating comprising two layers was formed on the glass surface, and further, by using Treating Solutions No. Q to No. S shown in Table 2 as the condensation products of fluorine-containing silicon compounds for the top coating layer, low reflectance glasses formed with thin coatings having a three layer structure were obtained.

In Examples 14 and 15, the undercoating layers having a two layer structure were maintained at 200.degree. C. for 60 minutes for thermal curing. With respect to the low reflectance glasses thus obtained, the thickness, refractive indices, reflectance, pencil hardness and contact angles were measured. The results are shown in Table 6.

In the same manner as in Example 9, Treating Solutions No. E and No. I identified in Table 1 were used as the metal oxide-containing condensation products for the undercoating layer, and a multi-layer coating comprising two layers was formed on the glass surface, and further by using Treating Solution No. Z identified in Table 4 as the condensation product of a fluorine-containing silicon compound for the top coating layer, a low reflectance glass formed with a thin coating having a three layer structure, was obtained. The properties were measured, and the results are shown in Table 6.

In the same manner as in Example 8, Treating Solutions No. E to No. J identified in Table 1 were used as the metal oxide-containing condensation products for the undercoating layer, and multi-layer coatings comprising two layers, were formed on glass surfaces, and further by using Treating Solutions No. V to No. Y identified in Table 3 as the condensation products of fluorine-containing silicon compounds for the top coating layer, low reflectance glasses formed with thin layers having a three layer structure were obtained. The properties of the low reflectance glasses were measured. The results are shown in Table 7.

A glass plate having a refractive index of 1.52 (soda lime glass 5.times.10 cm) was cleaned with a cleaning agent, washed with distilled water and then dried in air. This glass plate was dipped in Treating Solution No. M of the metal oxide-containing condensation product for the undercoating layer as identified in Table 1, then withdrawn at a speed of 5 cm/min., and dried at 160.degree. C. for 10 minutes. After cooling, the coated plate was dipped in Treating Solution No. E, withdrawn at a speed of 7 cm/min., dried at 160.degree. C. for 10 minutes, then cooled, and further dipped in Treating Solution No. I, withdrawn at a speed of 16 cm/min., dried at 160.degree. C. for 10 minutes, then maintained at a temperature of 540.degree. C. for 30 minutes for thermal curing, whereby a first layer having a thickness of 0.05 .mu.m and a refractive index of 1.46, a second layer having a thickness of 0.06 .mu. m and a refractive index of 1.70, and a third layer having a thickness of 0.11 .mu.m and a refractive index of 2.10, were formed. Then, the glass plate formed with the undercoating layer comprising these three layers, was dipped in a 15% sodium hydroxide aqueous solution for 5 minutes, then withdrawn, washed with distilled water, dried in air, then dipped in Treating Solution No. S of the condensation product of a fluorine-containing silicon compound for the top coating layer as shown in Table 2, withdrawn at a speed of 5 cm/min., and maintained at 160.degree. C. for 2 hours for thermal curing, whereby a top coating layer having a thickness of 0.085 .mu.m and a refractive index of 1.43, was formed. With respect to the low reflectance glass formed with a thin coating having a four layer structure thus obtained, the reflectance was measured and found to be 0.35% per one surface, and the pencil hardness was at least 5H. Further, the contact angles of water and hexadecane were 100.5.degree. and 61.5.degree., respectively.

A quick drying type black ink (for felt-pens) was applied to the surface of each of the low reflectance glasses obtained in Examples 1 to 24 to stain the surface. One hour later, the surface was wiped with a cotton cloth, whereby the black ink on each low reflectance glass was readily removed.

A quick drying type black ink was applied on the surface of each of the glasses treated in Comparative Examples 2 and 3, and then wiped in the same manner as in Example 25, it was impossible to completely remove the ink, and scratch marks appeared on the coating layer.

A flat plate (5.times.5 cm) of poly(diethylene glycol bis-allylcarbonate) was dipped in a 10% sodium hydroxide solution heated to 50.degree. for 1 minute, and immediately washed with water and dried. This flat plate was dipped in Treating Solution NO. N of the metal oxide-containing condensation product identified in Table 1 of Preparation Example 1, withdrawn at a speed of 10 cm/min., dried at 120.degree. C. for 10 minutes to form a undercoating layer, then, again dipped in Treating Solution No. N, withdrawn at a speed of 10 cm/min., and dried at 120.degree. C. for 10 minutes to form a undercoating layer composed of two layers having a refractive index of 1.90 and a thickness of 0.13 .mu.m.

Then, the flat plate formed with the above-mentioned undercoating layer was dipped in Treating Solution No. T of a fluorine-containing silicon condesation product as identified in Table 2 of Preparation Example 2, withdrawn at a speed of 7.5 cm/min., thermally treated at 120.degree. C. for 90 minutes, to form a top coating layer having a refractive index of 1.40 and a thickness of 0.09 .mu.m.

The reflectance of the flat plate formed with a thin coating layer thus obtained, was 0.7% per one surface. Further, the contact angles of water and hexadecane were 110.5.degree. and 70.5.degree., respectively.

The treatments were conducted in the same manner as in Example 26 except that the treating solution of the metal oxide-containing condensation product for the undercoating layer in Example 26 was selected to be Treating Solutions No. N to No. P identified in Table 1, and further the treating solution of the condensation product containing a fluorine-containing silicon compound for the top coating layer, was selected to be Treating Solutions No. T and No. U as identified in Table 2, whereby flat plates formed with thin coatings were obtained. The properties of the flat plates formed with the thin layers thus obtained, were measured. The results are shown in Table 8.

Instead of the dipping treatment of the flat plate in the 10% sodium hydroxide solution in Example 28, flat paltes were, respectively, dipped in Treating Solutions No. .alpha. and No. .beta. for primer coatings of Preparation Example 5, withdrawn at a speed of 7 cm/min., and then heat treated at 120.degree. C. for 30 minutes to form the primer layer. The flat plates thus formed with the primer layers, were treated in the same manner as in Example 26, whereby thin coatings were formed on the respective primer layers, and flat plates formed with the thin layer was obtained.

The properties of the flat plates formed with the thin layers thus obtained, were measured. The results are shown in Table 8.

The treatment was conducted in the same manner as in Example 26 except that the treating solution for the top coating layer comprising a fluorine-silicon condensation product in Example 26 was changed to Treating Solution No. Z, to obtain a flat plate formed with a thin coating.

The properties of the flat plate formed with the thin coating thus prepared and the flat plate to which no treatment for the formation of the thin coating was applied in Example 26, were measured. The results are shown in Table 8.

The treatment was conducted in the same manner as in Example 32 except that a flat plate (5.times.5 cm) of polycarbonate was used, whereby a flat plate formed with a thin coating was obtained.

The properties of the flat plate thus obtained were measured. The results are shown in Table 9.

The treatment was conducted in the same manner as in Example 33 except that a flat plate (5.times.5 cm) of polymethyl methacrylate was used, whereby a flat plate formed with a thin coating was obtained.

The properties of the flat plate thus prepared were measured. The results are shown in Table 9.

In Example 32, after the formation of the undercoating layer of the metal oxide-containing condensation product, the activating treatment of the thin coating as identified in Table 10 was conducted, followed by washing with water and drying. Then, a top coating layer was formed on the thin layer in the same manner as in Example 32.

As the properties of the flat plates formed with the thin layers thus obtained, the respective antisoiling properties were tested by the removal of the black ink in the same manner as in Example 25. The results are shown in Table 10.