# US 5,710,856 A · Light reflective sheet and light reflector using it > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,856 A - Document ID: US5710856A - Status: Granted - Kind: A - Application number: 08/590,113 - Filed: 1996-01-23 - Granted: 1998-01-20 - Earliest claimed: 1995-01-27 - Assignees: Mitsui Toatsu Chemicals, Inc. - Inventors: Toshiyuki Ishii; Katsumi Senba; Takayuki Kajihara; Naoko Takemura - Web page: https://patentgrep.com/patent/US5710856A ## CPC - B32B 27/20: using fillers, pigments, thixotroping agents - B32B 27/08: of synthetic resin - B32B 27/308: {comprising acrylic (co)polymers} - B32B 27/32: comprising polyolefins {(comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30)} - B32B 27/36: comprising polyesters - F21V 7/22: characterised by materials, surface treatments or coatings, e.g. dichroic reflectors - G02B 6/0055: {Reflecting element, sheet or layer} - B32B 2305/026: Porous - B32B 2307/416: Reflective - B32B 2307/71: Resistive to light or to UV - B32B 2309/105: Thickness - B32B 2323/043: HDPE, i.e. high density polyethylene - B32B 2323/046: LDPE, i.e. low density polyethylene - G02B 6/0065: {Manufacturing aspects; Material aspects} - Y10S 385/901: Illuminating or display apparatus - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A light reflective sheet is here disclosed which comprises a porous resin sheet and a protective layer laminated on at least one surface of the porous resin sheet; the porous resin sheet comprises a polyolefin resin and 100 to 300 parts by weight of a finely powdery inorganic filler with respect to 100 parts by weight of a polyolefin resin; the porous resin sheet is stretched at an area stretch magnification of 1.5 to 20 times; the light reflectance of the porous resin sheet at a wave length of 550 nm is 95% or more; and the stiffness of the light reflective sheet is at least 50 mm. A light reflector using the light reflective sheet is also disclosed. Preferably, the protective layer has a function as a UV light protective layer and/or a light leakage preventing auxiliary layer. The light reflective sheet is excellent in light resistant to ultraviolet light and the like, structure holding properties and light reflectivity, and so it is useful as a light reflective sheet for back light units of liquid crystal displays of word processors, personal computers, televisions and the like as well as lights, copying machines, projector system displays, facsimiles, electronic blackboards and the like. ## Claims ### Claim 1 A light reflective sheet which comprises a porous resin sheet and a protective layer laminated on at least one surface of the porous resin sheet; the porous resin sheet comprising a polyolefin resin and 100 to 300 parts by weight of a finely powdery inorganic filler with respect to 100 parts by weight of a polyolefin resin; the porous resin sheet being stretched at an area stretch magnification of 1.5 to 20 times; the light reflectance of the porous resin sheet at a wave length of 550 nm being 95% or more; the stiffness of the light reflective sheet being at least 50 mm. ### Claim 2 (depends on 1) The light reflective sheet according to claim 1 wherein the protective layer is a UV light protective layer which increases the stiffness of the light reflective sheet up to 50 to 150 mm and which has a function as the UV light protective layer; the total light transmittance of the UV light protective layer is 80% or more; the total reflectance of a light beam having a wave length of 550 nm irradiated on the surface of the UV light protective layer of the light reflective sheet is 95% or more; and after the surface of the UV light protective layer of the light reflective sheet has been irradiated with an ultraviolet light of 400 MJ/m.sup.2 at 80.degree. C., deterioration ratios of the total reflectances of light beams having wave lengths of 450 nm and 550 nm in the light reflective sheet are both less than 10%. ### Claim 3 (depends on 1) The light reflective sheet according to claim 1 wherein the protective layer is a light leakage preventing auxiliary layer which increases the stiffness of the light reflective sheet comprising a porous resin sheet and the light leakage preventing auxiliary layer laminated only on the back surface of the porous resin sheet up to at least 100 mm and which has a light leakage preventing function; the total light transmittance of the light leakage preventing auxiliary layer is less than 20%; and the total reflectance of a light beam having a wave length of 550 nm irradiated on the surface of the porous resin sheet of the light reflective sheet is 95% or more. ### Claim 4 (depends on 1) The light reflective sheet according to claim 1 which is a laminate comprising the porous resin sheet and the protective layers laminated on both the surfaces of the porous resin sheet; the protective layer on the surface of the porous resin sheet is a UV light protective layer having a function as the UV light protective layer and a total light transmittance of 80% or more; the protective layer on the back surface of the porous resin sheet is a light leakage preventing auxiliary layer having a light leakage preventing function; the total reflectance of a light beam having a wave length of 550 nm irradiated on the surface of the UV light protective layer of the laminate is 95% or more; after the surface of the UV light protective layer of the laminate has been irradiated with an ultraviolet light of 400 MJ/m.sup.2 at 80.degree. C., the deterioration ratios of the total reflectances of light beams having wave lengths of 450 nm and 550 nm in the light reflective sheet are both less than 10%; and the stiffness of the light reflective sheet is at least 50 mm. ### Claim 5 (depends on 1) The light reflective sheet according to claim 1 wherein the polyolefin resin is at least one resin selected from the group consisting of high-density polyethylenes, low-density polyethylenes, polypropylenes, ethylene-.alpha.-olefin copolymers and ethylene-propylene copolymers. ### Claim 6 (depends on 1) The light reflective sheet according to claim 1 wherein the finely powdery inorganic filler is at least one filler selected from the group consisting of barium sulfate, calcium carbonate, titanium oxide, magnesium carbonate, alumina, magnesium hydroxide and zinc oxide. ### Claim 7 (depends on 1) The light reflective sheet according to claim 1 wherein the porous resin sheet contains, as another additive, 0.01 to 5 parts by weight of an ultraviolet absorber with respect to 100 parts by weight of the polyolefin resin. ### Claim 8 (depends on 1) The light reflective sheet according to claim 1 wherein the porosity of the porous resin sheet is in the range of from 40 to 70%. ### Claim 9 (depends on 1) The light reflective sheet according to claim 1 wherein the thickness of the porous resin sheet is in the range of from 50 to 500 .mu.m. ### Claim 10 (depends on 4) The light reflective sheet according to claim 4 wherein the protective layer having a function of protecting the porous resin sheet from UV is a resin film having a thickness of 1 to 100 .mu.m selected from the group consisting of a polyester resin film, a polyacrylic resin film and a silicone resin film. ### Claim 11 (depends on 4) The light reflective sheet according to claim 4 wherein the protective layer having a light leakage preventing function is a resin film having a thickness of 30 to 150 .mu.m which comprises a resin selected from the group consisting of a polyester resin, a polyacrylic resin and a silicone resin containing 5 to 70% by weight of an inorganic filler. ### Claim 12 (depends on 11) The light reflective sheet according to claim 11 wherein the inorganic filler is at least one filler selected from the group consisting of barium sulfate, calcium carbonate, titanium oxide, magnesium carbonate, alumina, magnesium hydroxide and zinc oxide. ### Claim 13 (depends on 4) The light reflective sheet according to claim 4 which can be used as a light reflective sheet for a device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards. ### Claim 14 (depends on 4) A device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards in which the light reflective sheet described in claim 4 is used. ### Claim 15 (depends on 4) The light reflective sheet according to claim 4 which can be used as a lamp holder constituting a back light unit of a liquid crystal display. ### Claim 16 (depends on 4) The light reflective sheet according to claim 4 which can be used as a light reflecting layer under a transparent light guide plate constituting a back light unit of a liquid crystal display. ### Claim 17 A light reflector which comprises a transparent light guide plate 4, a light reflecting layer under the transparent light guide plate 3 placed on one surface of the transparent light guide plate 4, a light diffusion sheet 5 placed on the other surface of the transparent light guide plate 4, a lens sheet 6 placed on the surface 150 .mu.m which comprises a resin selected from the group consisting of a polyester resin, a polyacrylic resin and a silicone resin containing 5 to 70% weight of an inorganic filler. ### Claim 18 (depends on 17) A device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards in which the light reflector described in claim 17 is used. ### Claim 19 (depends on 2) The light reflective sheet according to claim 2 wherein the protective layer having a function of protecting the porous resin sheet from UV is a resin film having a thickness of 1 to 100 .mu.m selected from the group consisting of a polyester resin film, a polyacrylic resin film and a silicone resin film. ### Claim 20 (depends on 3) The light reflective sheet according to claim 3 wherein the protective layer having a light leakage preventing function is a resin film having a thickness of 3- to of the light diffusion sheet 5, a light source 1 installed on at least one side of a laminate of these members 3, 4, 5 and 6, and a curved lamp holder 2 for covering the light source 1, a light reflective sheet comprising a porous resin sheet and a UV light protective layer having a function as the UV light protective layer laminated on the porous resin sheet being used as the lamp holder 2; and/or a light reflective sheet comprising the porous resin sheet and a light leakage preventing auxiliary layer having a light leakage preventing function laminated on the porous resin sheet being used as the light reflecting layer under the transparent light guide plate 3. ### Claim 21 (depends on 20) The light reflective sheet according to claim 20 wherein the inorganic filler is at least one filler selected from the group consisting of barium sulfate, calcium carbonate, titanium oxide, magnesium carbonate, alumina, magnesium hydroxide and zinc oxide. ### Claim 22 (depends on 3) The light reflective sheet according to claim 3 which can be used as a light reflective sheet for a device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards. ### Claim 23 (depends on 2) The light reflective sheet according to claim 2 which can be used as a light reflective sheet for a device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards. ### Claim 24 (depends on 1) The light reflective sheet according to claim 1 which can be used as a light reflective sheet for a device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards. ### Claim 25 (depends on 3) A device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards in which the light reflective sheet described in claim 3 is used. ### Claim 26 (depends on 2) A device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards in which the light reflective sheet described in claim 2 is used. ### Claim 27 (depends on 1) A device selected from the group consisting of back light units of liquid crystal displays, lights, copying machines, projector system displays, facsimiles and electronic blackboards in which the light reflective sheet described in claim 1 is used. ### Claim 28 (depends on 2) The light reflective sheet according to claim 2 which can be used as a lamp holder constituting a back light unit of a liquid crystal display. ### Claim 29 (depends on 1) The light reflective sheet according to claim 1 which can be used as a lamp holder constituting a back light unit of a liquid crystal display. ### Claim 30 (depends on 3) The light reflective sheet according to claim 3 which can be used as a light reflecting layer under a transparent light guide plate constituting a back light unit of a liquid crystal display. ### Claim 31 (depends on 1) The light reflective sheet according to claim 1 which can be used as a light reflecting layer under a transparent light guide plate constituting a back light unit of a liquid crystal display.