Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
2000-04-06
2001-11-06
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S161000, C428S172000, C428S212000, C362S026000, C362S035000, C362S331000, C385S901000
Reexamination Certificate
active
06312787
ABSTRACT:
TECHNICAL FIELD
The present invention relates to such a resin sheet applicable to various objects and uses as a light diffusing sheet and a light-guiding sheet suitable for an illuminator cover, a lighting window, a building material, a traffic sign, a sign board, a liquid crystal display device, etc., and an artistic design sheet having a deep appearance and/or a three-dimensional appearance, and an apparatus and a process for producing the resin sheet. Furthermore, the present invention relates to a surface light source element in which the resin sheet is used as a light guide, and a laminate in which such resin sheets are stacked.
BACKGROUND ART
Transparent resin sheets having a surface unevenness formed by a mold, transparent resin sheets coated with a light-diffusing agent or light-scattering agent on the back surface, and similar resin sheets, have been known as light diffusible resin sheets.
Transparent resin sheets subjected to shading printing, shadow printing, or the like printing, and transparent resin sheets having an unevenness in the interior have been known as artistic design sheets.
Japanese Examined Utility Model Publication (Kokoku) No. 7-36742 discloses a luminous decorative sheet prepared by successively laminating a transparent resin layer, a transparent embossed resin layer and a light reflective layer. However, the light reflective layer is laminated to the portion having an uneven pattern in the transparent embossed resin layer. As a result, the sheet is not suited to a light guide which is used by making light incident on the back surface or side of the sheet.
Japanese Unexamined Patent Publication (Kokai) No. 3-256735 discloses a cut-glass-like sheet which is a composite sheet prepared by forming V-shaped grooves on one side of a polyvinyl chloride sheet, and bonding a polyvinyl chloride sheet having a smooth surface to the V-shaped groove-formed surface and which has a closed air layer in the V-shaped groove portion. However, since such a sheet having a structure with an inner air layer shows a large difference in refractive indexes between the resin layer and the air layer, the light divisibility becomes too large. The sheet is, therefore, not suitable for a light guide.
On the other hand, as an instance of a back surface light source device used for a liquid crystal display device, a sign board, a traffic sign, etc., there is an edge-lit-type back surface light source device in which a linear light source is arranged on an end surface of a plate-like light guide. Such an edge-lit-type back surface light source device is one wherein a plate-like transparent material such as an acrylic resin plate is used as a light guide, light from a light source arranged on one side end thereof is made incident thereon, and light is allowed to exit in a plane form from the surface (light-exiting surface) thereof. The light guide used herein usually has a light-scattering portion and/or light-diffusing portion formed on the surface or on the back surface. Such a surface light source element is required to ensure the uniformity of the luminance of the exiting light regardless of the distance from the light source. The performance is particularly important to a large size surface light source element.
Japanese Unexamined Patent Publication (Kokai) No. 5-127159 discloses a surface light source element having a light guide the surface of which is printed with a light-diffusing material such as titanium white in a dot form, and a prism sheet is placed on the light-exiting surface. uniform luminance can be obtained from such a surface light source element by changing the covering ratio of the dots according to a distance from the light source. However, the dot-like pattern must be shielded with a light diffusible sheet. Consequently, the luminance is lowered, and the structure of the surface light source element becomes complicated.
Japanese Unexamined Patent Publication (Kokai) No. 2-84618 discloses a surface light source element having a light guide with a satin surface at least on one of the surface (light-exiting surface) and the back surface, and a prism sheet placed on the light-exiting surface. Although a very high luminance can be obtained from such a surface light source element, the uniformity of the luminance of the exiting light is not satisfactory.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a transparent resin sheet which can be used as a light guide, a light diffusible sheet, an artistic design sheet, etc.
Another object of the present invention is to provide an apparatus and a method capable of producing the resin sheet at low cost with high productivity.
A further object of the present invention is to provide a surface light source element in which the resin sheet is used as a light guide.
A still further object of the present invention is to provide a resin sheet laminate in which the resin sheets are laminated.
The above-mentioned objects of the present invention can be achieved by the present invention having the constitutions as described below.
1. A resin sheet having a laminate structure in which a transparent resin layer C is sandwiched between a transparent resin layer A and a transparent resin layer B, and having a smooth outer surface, any two adjacent resin layers of the three resin layers having refractive indexes which differ from each other,
in a cross-section represented by an xy plane wherein y is a thickness direction of the resin sheet, and x is a width direction thereof, at least one of two interfaces formed between the resin layers A and C and between the resin layers B and C having an uneven shape.
2. A resin sheet having a laminate structure of a transparent resin layer A and a transparent resin layer B, and having a smooth outer surface,
the adjacent resin layers having refractive indexes which differ from each other,
in a cross-section represented by an xy plane wherein y is a thickness direction of the resin sheet, and x is a width direction thereof, an interface formed between the resin layers A and B having an uneven shape.
3. An apparatus for producing the resin sheet in 1 above which comprises
a composite resin flow passage
21
having a predetermined width in the X direction, a predetermined thickness in the Y direction and a predetermined length in the Z direction, and comprising a composite flow formation portion
22
at one end in the Z direction, and a composite flow outlet
23
at the other end,
a slit-like flow passage
31
extending in the X direction, for allowing a resin c for the resin layer C to flow toward the Z direction in the composite flow formation portion
22
, and
two flow passages
41
,
42
for allowing a resin a for the resin layer A and a resin b for the resin layer B to flow into the composite flow formation portion
22
from both sides of an XZ plane including the flow passage
31
for the resin c,
at least one of the XZ cross-sections of the flow passages 41, 42 for the respective resins a and b having a shape in which a portion or portions (Ln and/or Rn) having a large height in the Z direction and a portion or portions (Lm and/or Rm) having a small height (including zero) in the Z direction are alternately arranged.
4. An apparatus for producing the resin sheet in 2 above which comprises
a composite resin flow passage
21
having a predetermined width in the X direction, a predetermined thickness in the Y direction and a predetermined length in the Z direction, and comprising a composite flow formation portion
22
at one end in the Z direction, and a composite flow outlet
23
at the other end, and
two flow passages
41
,
42
for allowing a resin a for the resin layer A and a resin b for the resin layer B to flow into the composite flow formation portion
22
from both sides of an XZ plane including the flow passage
21
,
at least one of XZ cross-sections of the flow passages
41
,
42
for the respective resins a and b having a shape in which a portion or portions (Ln and/or Rn) having a large height in the Z direction and a portion or portions (Lm and/or Rm) havin
Chiba Issei
Hayashi Yasuko
Oda Masaharu
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Mitsubishi Rayon Co. Ltd.
Thibodeau Paul
Zacharia Ramsey
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