RESIN GLASS SHEET AND METHOD FOR MANUFACTURING SAME

Abstract

The present invention provides a resin glass plate, the surface of which is modified to be glass-like, and a method for manufacturing the same, whereby transparency, scratch resistance, abrasion resistance, and durability with respect to temperature change can be enhanced. In the present invention, a hard coat layer (6) comprising a thermosetting material of a silicone polymer containing cellulose nanofibers is formed on a transparent resin substrate (4), and a modification layer (7) having a film thickness of more than 0.2 m and less than 0.6 m is also formed thereon by irradiating the surface of the hard coat layer with vacuum ultraviolet rays having a wavelength of 200 nm or less.

Claims

1. A resin glass plate comprising: a transparent resin plate, and a hard coat layer formed on the transparent resin plate, wherein the hard coat layer is formed of a thermosetting material of a silicone polymer containing cellulose nanofibers of 0.4 to 4.0 pts. wt. based on 100 pts. wt. of silicone polymer, and wherein the hard coat layer has a surface formed into a modification layer having a film thickness of more than 0.2 m and less than 0.6 m, and said modification layer is composed mainly of silicon dioxide by selectively cutting and recombining SiOSi bonds.

2. (canceled)

3. The resin glass plate according to claim 1, further comprising: a primer layer formed on the transparent resin plate, and wherein the hard coat layer is formed on the primer layer.

4. A method for manufacturing a resin glass plate, comprising: applying a silicone polymer hard coating liquid containing 0.4 to 4.0 pts. wt. of cellulose nanofibers based on 100 pts. wt. of the silicone polymer to a transparent resin plate, forming a hard coat layer containing cellulose nanofibers by heat-drying the silicone polymer hard coating liquid, thereafter, irradiating with vacuum ultraviolet rays having a wavelength of 200 nm or less the hard coat layer, and forming a surface of the hard coat layer into a modification layer having a film thickness of more than 0.2 m and less than 0.6 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic diagram showing an embodiment of a method for manufacturing a resin glass plate of the present invention.

[0020] FIG. 2 is a schematic diagram showing a comparative embodiment different from the method for manufacturing the resin glass plate of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0021] The present invention will be explained bellow.

[0022] The resin glass plate is configured so as to form a hard coat layer containing cellulose nanofibers, the surface of which is formed into a modification layer due to photo-modification, on a transparent resin substrate.

[0023] In the present invention, the photo-modification is to modify a part of the hard coat layer into a hard thin film layer, namely, wherein chemical bonds of the surface layer of the hard coat layer are cut by irradiating vacuum ultraviolet rays of 200 nm or less wavelength on the hard coat layer and reactive oxygens separated from ozone generated from the vacuum ultraviolet rays and molecules of the cut surface layer are recombined.

[0024] Although the transparent resin substrate used in the present invention is not particularly limited, flat plates formed of transparent resin material such as polycarbonate, acrylic resin, polyarylate, polystyrene, polyethylene-terephthalate or styrene-based polymer, or various olefin resin material can be used. Above all, polycarbonate is preferably excellent in impact resistance and heat resistance, and able to be inexpensively obtained. The transparent resin plate having a thickness of 0.5 to 10.0 mm is preferable for window glass.

[0025] The hard coat layer in the present invention is formed by applying and curing a silicone-based hard coating liquid containing cellulose nanofibers composed mainly of silicone polymer on the transparent resin plate. Solvent having siloxane structure, which is obtained by hydrolyzing siloxane sol obtained through condensation reaction using alkoxysilane as a base, is used as the silicone-based hard coating liquid. Although the thickness of the hard coat layer is not particularly limited, the average film thickness is preferably 4.0 to 30.0 m.

[0026] The cellulose nanofibers incorporated in the hard coat layer are composed of fibers each having an average fiber diameter of 3 to 30 nm and an average fiber length of 200 to 1500 nm. When the fiber diameter is over 30 nm or the fiber length is over 1500 nm, the hard coat layer is easily damaged in transparency. Besides, in this case, a specified network structure based on the cellulose nanofibers is hardly formed in the hard coat layer, and the vacuum ultraviolet rays hardly reach the deep section of the hard coat layer, and because of those, the photo-modification cannot be sufficiently carried out.

[0027] There is no restriction on materials and manufacturing methods, but, for the cellulose nanofibers used in the present invention, they only need to have -1, 4-glucan structure, and may be cellulose chemically synthesized/modified (for example, cellulose derivatives). These cellulose nanofibers can be added into the silicone-based hard coating liquid directly or as dispersing liquid. However, in using the dispersing liquid, components other than cellulose such as hemicellulose or lignin derived from plant or excess chemical agents used in the chemical synthesis, which are incorporated in a manufacturing process of cellulose nanofibers, are preferably removed to maintain transparency of the hard coat layer.

[0028] The cellulose nanofiber content in the hard coat layer is preferably 0.4 to 4.0 wt. % to the silicone polymer of the main component. In case the cellulose nanofiber content is less than 0.4 wt. %, the hard coat layer cannot be sufficiently protected from thermal expansion, and therefore, the occurrence of cracks due to temperature change cannot be suppressed. In case the cellulose nanofiber content is over 4.0 wt. %, the vacuum ultraviolet rays are prevented from reaching the deep section of the hard coat layer, and therefore, a modification layer having the thickness enough to exhibit superior scratch resistance and abrasion resistance cannot be formed. In addition, it is also not preferable in point that the transparency is consequently lowered by high haze because the film thickness is increased because viscosity of the hard coat layer becomes higher and the coating property is reduced.

[0029] The hard coat layer containing the cellulose nanofibers, as shown in FIG. 1, is formed by heat-drying for the predetermined time after applying the silicone type hard coating liquid mixed with the cellulose nanofibers on the substrate by a dip coating method. Further, as shown in FIG. 2, it may be formed by once drying for the predetermined time after applying a cellulose nanofiber dispersion liquid on the substrate, and thereafter, by heat-drying for the predetermined time again after applying the silicone type hard coating liquid by the dip coating method.

[0030] In mixing the cellulose nanofibers into the hard coating liquid, the cellulose nanofibers are added into the hard coating liquid and homogeneously dispersed in the silicone type hard coating liquid by stirring and mixing by a magnet stirrer. The thickness of the hard coat layer containing cellulose nanofibers is adjusted by adjusting a drawing speed of the dip coating.

[0031] In forming the cellulose nanofiber layer on the substrate previously, for example, the cellulose nanofiber layer is formed by applying 1.0 wt. % cellulose nanofiber dispersion liquid on the substrate and drying for the predetermined time, and then, the silicone type hard coating liquid is applied thereon by the dip coating method, and in the same manner as mentioned above, the whole thickness of the hard coat layer containing cellulose nanofibers is adjusted.

[0032] The hard coating layer containing cellulose nanofibers in the present invention may be formed by applying the hard coating liquid mixed with the cellulose nanofibers by a spin coating method or a flow coating method.

[0033] In the present invention, in forming the hard coat layer containing cellulose nanofibers on the substrate, a primer layer may be provided therebetween to improve adhesion between the substrate and the hard coat layer. The primer layer is formed by heat-drying for the predetermined time after applying each resin such as polyester resin, acrylic resin, polyurethane resin, epoxy resin, melamine resin, polyolefin resin, or urethane acrylate resin by the dip coating method.

[0034] The hard coat layer containing cellulose nanofibers in the present invention is irradiated with the vacuum ultraviolet rays having a wavelength of 200 nm or less to be photo-modify the surface portion into a modification layer having a fixed thickness.

[0035] The modification layer in the present invention is formed into a hard thin layer composed mainly of silicon dioxide by selectively cutting CH bonds, SiC bonds and SiOSi bonds, which constitute a side-chain functional group of the silicone polymer of the hard coat layer, with the vacuum ultraviolet rays in order, and then recombining these cleft oxygen atoms and silicon atoms.

[0036] As a light source for the vacuum ultraviolet rays having a wavelength of 200 nm or less, for example, an excimer lamp, a low pressure mercury vapor lamp and an excimer laser can be used. When using any of these lamps, photo-modification can be efficiently performed because light can be widely irradiated. Irradiation energy differs depending on the thickness of the hard coat layer. For example, in case of an excimer lamp having a wavelength of 200 nm, the accumulative dose of the vacuum ultraviolet rays should be about 100 mJ/cm.sup.2, and an irradiation distance to the substrate should be about 3 mm.

[0037] In using the excimer lamp as a light source of the vacuum ultraviolet rays, light penetrating the hard coat layer sometimes reaches and decomposes the substrate under the hard coat layer, and also, the thickness of the modification layer is sometimes hard to be adjusted because the light penetrates the hard coat layer as high energy. In this case, for example, the modification layer can be adjusted so as to have the desired thickness by adjusting quantity of light of the penetrating vacuum ultraviolet rays by dispersing ultraviolet absorber on the hard coat layer.

[0038] The thickness of the modification layer in the present invention differs depending on the thickness of the hard coat layer, and also depending on the fiber diameter, the fiber length or the content of the included cellulose nanofibers. The modification layer having the thickness of more than 0.2 m and less than 0.6 m can preferably further improve durability due to temperature change (heat residence, weather residence) on exhibiting superior scratch residence and abrasion residence as window glass.

[0039] In the hard coat layer containing the cellulose nanofibers in the present invention, a thermal contraction force of the modification layer is dispersed by fine network structure due to the dispersed cellulose nanofibers, as a result, the occurrence of visible cracks is suppressed. Therefore, it is considered that the heat resistant can be improved. Further, a tensile stress due to thermal expansion of the substrate is moderated by the cellulose nanofibers with low thermal expansion coefficient contained in the non-modification layer, as a result, a difference in thermal expansion coefficient is reduced between the substrate and the modification layer. Therefore, it is considered that the occurrence of cracks is suppressed.

[0040] Resin glass and a method for manufacturing that is related to the present invention will be explained by using examples in detail. However, the present invention is not limited by these examples. The resin glasses obtained by the examples and comparative examples have been evaluated from the following items.

[0041] (Transparency, Scratch Resistance, Abrasion Resistance)

[0042] A friction test was performed in accordance with Taber Friction Test. The Taber Friction Test was performed under an abrasion condition of 500 g load and 1000 rotations conforming to JISK7204 according to Japanese Industrial Standards Committee (JISC) to evaluate these functions by measuring the haze value. In Table 1, a circle (o) is marked to examples wherein an increase in haze in before and after the Taber Friction Test is not more than 2.0%, and a cross (x) is marked in case of more than 2.0%.

[0043] (Heat Resistance)

[0044] Occurrence of cracks was visually confirmed after heating at 110 C. for 16 hours. In Table 1, a circle (o) is marked to examples wherein cracks were not confirmed, and a cross (x) is marked to examples wherein cracks were confirmed.

Example 1

[0045] The present example will be explained with reference to drawings.

[0046] As shown in FIG. 1, a cellulose nanofiber-containing hard coat liquid 3 was made by adding a cellulose nanofiber dispersion 2 (3-10 nm average fiber diameter, 200-800 nm average fiber length, 1 pts. Wt. aqueous dispersion) into a silicone hard coat liquid 1 (Momentive-made AS4700F: 27% silicone solid content) so that the cellulose nanofiber ratio is 0.4 wt. % to the silicone solid content, and then, by stirring them with a magnet stirrer.

[0047] A primer layer 5 having a thickness of 4 m was formed by applying a primer solution on a polycarbonate substrate 4 according to a dip coating method, and by heat-drying at 130 C. for 15 minutes. Then, a cellulose nanofiber-containing hard coat layer 6 having a thickness of 10 m was formed by applying the cellulose nanofiber-containing hard coat liquid 3 on the substrate according to the dip coating method, and by drying at 130 C. for 30 minutes. Then, a surface of the hard coat layer was modified by irradiating with an excimer lamp of 172 nm of a cumulative exposure dose of 2,100 mJ/cm.sup.2. The thickness of a modification layer 7 was 0.4 m.

Example 2

[0048] A hard coat layer was produced similarly to Example 1 except for using a hard coat liquid containing the cellulose nanofibers at the rate of 2.0 wt. % to the silicone solid content, and its surface was photo-modified. The thickness of a modification layer was 0.3 m.

Example 3

[0049] A hard coat layer was produced similarly to Example 1 except for using a hard coat liquid containing the cellulose nanofibers at the rate of 4.0 wt. % to the silicone solid content, and its surface was photo-modified. The thickness of a modification layer was 0.4 m.

Example 4

[0050] A hard coat layer was produced similarly to Example 1 except for using a dispersion containing cellulose nanofibers each having 10-30 nm average fiber diameter and 500-1500 nm average fiber length, and its surface was photo-modified. The thickness of a modification layer was 0.3 m.

Comparative Example 1

[0051] A hard coat layer containing no cellulose nanofibers was similarly produced, and the photo-modification was performed. The thickness of a modification layer was 0.5 m.

Comparative Example 2

[0052] A hard coat layer containing the cellulose nanofibers at the rate of 6.0 wt. % was similarly produced, and the photo-modification was performed. The thickness of a modification layer was 0.2 m.

Comparative Example 3

[0053] This is an example wherein a cellulose nanofiber layer is formed on a substrate in advance. As shown in FIG. 2, similarly to the above-mentioned Example 1, a primer layer 5 was formed on a polycarbonate substrate 4 by the dip coating, and thereafter, it was dried at 130 C. for 15 minutes. A cellulose nanofiber layer 8 was formed by putting a 10 wt. % cellulose nanofiber dispersion 2 on the substrate, and by drying at 40 C. for one day. Then, a hard coat layer 9 containing cellulose nanofibers was formed by applying a silicone hard coat liquid 1 by the dip coating similarly to the above-mentioned example, and by drying at 130 C. for 30 minutes after an entire night under decompression. The solid content concentration of cellulose nanofibers was 50%. Next, although the excimer lamp of 172 nm was irradiated on the surface of the hard coat layer containing cellulose nanofibers by the cumulative exposure dose of 2,100 mJ/cm.sup.2, a modification layer was not obtained. Numeral 10 is a hard coat layer having no cellulose nanofibers.

[0054] The scratch resistance and the heat resistance of each resin glass plate produced by Examples 1 to 4 and Comparative examples 1 to 3 were evaluated. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Evaluation Thickness of Haze value Modification (before Layer the exam.) Heat Scratch (%) (m) (%) resistance resistance Example 1 0.4 0.4 0.3 Example 2 2.0 0.4 0.3 Example 3 4.0 0.3 0.5 Example 4 0.4 0.3 0.5 Comparative 0.0 0.5 0.3 X example 1 Comparative 6.0 0.2 2.2 X example 2 Comparative 50 6.0 X example 3 indicates data missing or illegible when filed

[0055] As is clear from the evaluation of Table 1, the resin glass plates of the examples have respectively excellent scratch resistance and heat resistance as well as high transparency of a haze value of 1.0% or less. On the other hand, these characteristics cannot be made compatible in the resin glass plates of the comparative examples. When the content of cellulose nanofiber is less than 0.4 wt. %, the modification layer is produced in sufficient scratch resistance but inferior heat resistance. When it is more than 4.0 wt. %, the modification layer can be improved in heat resistance but insufficient scratch resistance.

INDUSTRIAL APPLICABILITY

[0056] The resin glass plate regarding the present invention can lengthen the service life of various resin windows for a vehicle, a ship, an aircraft and a building material.

EXPLANATION OF REFERENCED NUMERALS

[0057] 1 silicone-based hard coating liquid [0058] 2 cellulose nanofiber dispersion [0059] 3 cellulose nanofiber-containing hard coat liquid [0060] 4 polycarbonate substrate [0061] 5 primer layer [0062] 6, 9 cellulose nanofiber-containing hard coat layer [0063] 7 modification layer [0064] 8 cellulose nanofiber layer [0065] 10 hard coat layer having no cellulose nanofibers