# US 10,310,153 B2 · Polarizing plate, method for manufacturing polarizing plate, image display device, method for manufacturing image display device, and method for improving transmittance of polarizing plate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,310,153 B2 - Document ID: US10310153B2 - Status: Granted - Kind: B2 - Application number: 14/917,189 - Filed: 2014-08-06 - Published: 2016-07-21 - Granted: 2019-06-04 - Earliest claimed: 2013-09-10 - Assignees: Dai Nippon Printing Co., Ltd. - Applicants: Dai Nippon Printing Co., Ltd. - Inventors: Takashi Kuroda - Web page: https://patentgrep.com/patent/US10310153B2 ## CPC - G02B 5/305: {including organic materials, e.g. polymeric layers} - G02B 5/3025: {Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state (G02B5/3008, G02B5/3016 take precedence)} - G02B 5/3041: {comprising multiple thin layers, e.g. multilayer stacks} - G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)} - G02B 27/283: {used for beam splitting or combining} - G02F 1/133528: {Polarisers} - G02F 1/13362: {providing polarized light, e.g. by converting a polarisation component into another one} - G02F 1/133531: {characterised by the arrangement of polariser or analyser axes} - G02F 1/13355: {Polarising beam splitters [PBS]} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract The present invention provides a polarizer excellent in transmittance even if it includes a light-transmitting substrate having no in-plane phase difference. The present invention relates to a polarizer configured to be disposed on a backlight source side in an image display device, the polarizer including at least a light-transmitting substrate having in-plane birefringence and a polarizing element layered in said order from the backlight source side, the light-transmitting substrate receiving incidence of polarized light, the light-transmitting substrate and the polarizing element being layered such that a fast axis of the light-transmitting substrate along a direction in which the substrate shows a smaller refractive index and a transmission axis of the polarizing element form an angle of 0°±30° or 90°±30°. ## Claims ### Claim 1 An image display device comprising: an image display element; a backlight source emitting light to the image display element; and a polarizer disposed between the backlight source and the image display element and comprising at least a light-transmitting polyester substrate having in-plane birefringence and a polarizing element layered in said order from the backlight source side, the light-transmitting substrate having in-plane birefringence receiving incidence of polarized light, the light-transmitting substrate having in-plane birefringence and the polarizing element being layered such that a fast axis of the light-transmitting substrate having in-plane birefringence along a direction in which the substrate shows a smaller refractive index and a transmission axis of the polarizing element form an angle of 90°±30°, the light-transmitting substrate having in-plane birefringence exhibiting a difference (nx−ny) between the refractive indexes of 0.05 or greater, where nx represents a refractive index in the direction of the slow axis in which the substrate shows a greater refractive index, and ny represents a refractive index in the direction of the fast axis that is orthogonal to the slow axis, and the thickness of the substrate being 10 to 300 μm. ### Claim 2 (depends on 1) The image display device according to claim 1, wherein the light-transmitting substrate having in-plane birefringence and the polarizing element are layered such that the fast axis of the light-transmitting substrate having in-plane birefringence along a direction in which the substrate shows a smaller refractive index and the transmission axis of the polarizing element form an angle of 90°±15°. ### Claim 3 (depends on 1) The image display device according to claim 1, wherein the light-transmitting substrate having in-plane birefringence satisfies the relation of nx>N>ny, where N represents an average refractive index of the light-transmitting substrate. ### Claim 4 (depends on 1) The image display device according to claim 1, wherein a polarization separation film is provided between the backlight source and the light-transmitting substrate having in-plane birefringence. ### Claim 5 (depends on 1) The image display device of claim 1, wherein the image display element comprises a liquid crystal cell. ### Claim 6 (depends on 1) The image display device of claim 1, further comprising a second polarizer on a viewer side of the image display element. ### Claim 7 (depends on 6) The image display device according to claim 6, wherein the second polarizer comprises an upper light-transmitting substrate having in-plane birefringence and an upper polarizing element, the upper light-transmitting substrate being provided on the upper polarizing element, wherein the upper light-transmitting substrate having in-plane birefringence and the upper polarizing element are arranged such that a fast axis of the upper light-transmitting substrate having in-plane birefringence along a direction in which the upper light-transmitting substrate shows a smaller refractive index and a transmission axis of the upper polarizing element do not form an angle of 90°. ### Claim 8 A method for producing an image display device that comprises a polarizer disposed between a backlight source and an image display element in an image display device, the polarizer including a light-transmitting polyester substrate having in-plane birefringence and a polarizing element layered in said order, the method comprising the step of layering the light-transmitting substrate having in-plane birefringence and the polarizing element such that a fast axis of the light-transmitting substrate having in-plane birefringence along a direction in which the substrate shows a smaller refractive index and a transmission axis of the polarizing element form an angle of 90°±30°, the light-transmitting substrate having in-plane birefringence exhibiting a difference (nx−ny) between the refractive indexes of 0.05 or greater, where nx represents a refractive index in the direction of the slow axis in which the substrate shows a greater refractive index, and ny represents a refractive index in the direction of the fast axis that is orthogonal to the slow axis, and the thickness of the substrate being 10 to 300 μm. ### Claim 9 A method for improving the transmittance of a polarizer disposed between a backlight source and an image display element in an image display device, the polarizer comprising at least a light-transmitting polyester substrate having in-plane birefringence and a polarizing element layered in said order, the method comprising the step of layering the light-transmitting substrate having in-plane birefringence and the polarizing element such that a fast axis of the light-transmitting substrate having in-plane birefringence along a direction in which the substrate shows a smaller refractive index and a transmission axis of the polarizing element form an angle of 90°±30°, the light-transmitting substrate having in-plane birefringence exhibiting a difference (nx−ny) between the refractive indexes of 0.05 or greater, where nx represents a refractive index in the direction of the slow axis in which the substrate shows a greater refractive index, and ny represents a refractive index in the direction of the fast axis that is orthogonal to the slow axis, and the thickness of the substrate being 10 to 300 μm.