Invalidity dossier
US 4673254
Added 9/23/2026, 3:25:50 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US4673254A
Title: Back-reflection type light diffusing apparatus
Patent number: US4673254A
Application number: US06/886,892
Inventors: Kuniaki Kato; Mutsumi Takahashi
Original assignee: Tokyo Keiki Co., Ltd. (listed current assignee: Tokyo Keiki Inc)
Prior art date: 1985-07-30
Filing date: 1986-07-18
Publication/grant date: 1987-06-16
Legal status: Expired – Fee Related (anticipated expiration 2006-07-18)
Source: https://patents.google.com/patent/[US4673254](/patent/US4673254)/en
Purpose. The apparatus is a back-reflection type light diffusing apparatus, stated to be suitable for liquid crystal displays or for seeing through drawings. It addresses a stated problem of conventional back-reflection apparatuses: more light is radiated near the light-emitting portions and less from distant areas, so light cannot be radiated uniformly over the entire radiating surface. The stated object is to radiate substantially uniform light over the whole light radiating surface regardless of its shape.
Plain-language scope. A light guiding plate has one surface forming a first (light-radiating) surface and another surface forming a second (light-reflecting) surface. Light from a source near the lateral end of the plate enters the plate, is diffused three-dimensionally, and propagates by repeated reflection between the two surfaces before being radiated. The distinguishing feature is that the light reflecting surface is distributed so that its area decreases the closer it becomes to the light source; light is then reflected with similar intensity over the entire second surface, producing substantially uniform radiation. In the described embodiment the plate is transparent plastic, rectangular, with pairs of notches at both lateral ends, each notch housing a light source; a light reflecting plate carrying the reflecting surface is mounted on the second surface.
What the excerpt does not establish. The supplied text is an excerpt: the claims text, full description, drawing contents, and any express claim language are omitted, so the exact metes and bounds of the claimed invention cannot be confirmed from it. The excerpt also does not establish the numbers of claims, the precise reflecting/non-reflecting distribution of FIGS. 5–10, or any legal conclusion about validity, enforceability, or scope.
Generated 10/1/2026, 9:51:37 PM
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Litigation summary
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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