# US 7,746,434 B2 · Optical film assembly for a display device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,434 B2 - Document ID: US7746434B2 - Status: Granted - Kind: B2 - Application number: 11/011,215 - Filed: 2004-12-13 - Published: 2005-06-23 - Granted: 2010-06-29 - Earliest claimed: 2003-12-17 - Assignees: Samsung Electronics Co., Ltd. - Inventors: Won-Sang Park; Sang-Woo Kim; Jae-Young Lee; Sung-Eun Cha; Jae-Ik Lim; Jae-Hyun Kim - Web page: https://patentgrep.com/patent/US7746434B2 ## CPC - G02F 1/133555: {Transflectors} - G02F 1/1393: {the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells (G02F1/1396, G02F1/141 take precedence)} - G02F 1/133638: {Waveplates, i.e. plates with a retardation value of lambda/n} - G02F 2202/40: Materials having a particular birefringence, retardation - 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 An LCD apparatus including a first member, a second member, a liquid crystal layer and an optical film assembly is presented. A phase delay of the optical film assembly is about −α. In a normally white mode, the phase delay of the liquid crystal layer is about (λ/2)+α when no voltage is applied and about “α” when voltage is applied. In a normally black mode, the phase delay of the liquid crystal layer is about “α” when no voltage is applied, and about (λ/2)+α when voltage is applied. The phase delay between the liquid crystal layer when voltage is applied and the liquid crystal layer when voltage is not applied is about λ/2. “α” is a positive number. By manipulating the value of α, power consumption can be reduced. For example, the apparatus can be driven with a voltage below 2.5 V. ## Claims ### Claim 1 A liquid crystal display device comprising: a first member having a first surface and a second surface; a second member having a third surface and a fourth surface; a liquid crystal layer positioned between the first member and the second member, wherein the liquid crystal layer generates a phase delay for light passing therethrough; a voltage application structure for applying a voltage to the liquid crystal layer, wherein the phase delay generated by the liquid crystal layer is varied between (λ/2+α) and α, wherein α has a non-zero value, according to the voltage that is applied; and a compensation film coupled to at least one of the first member and the second member, wherein the compensation film generates a compensation phase delay of −α, wherein the device operates in a normally white mode, and wherein the phase delay generated by the liquid crystal layer is (λ/2+α) for a white image when no voltage is applied and α for a black image when the voltage is applied. ### Claim 2 (depends on 1) The device of claim 1, wherein the device has a transmissive region, and wherein the phase delay in the transmissive region is about (λ/2+α) for the white image when no voltage is applied and is about α for the black image when the voltage is applied. ### Claim 3 (depends on 1) The device of claim 1, wherein the device has a reflective region with a reflective region phase delay, and wherein the reflective region phase delay is about (λ/2+α)/2 for the white image when no voltage is applied and is about α/2 for the black image when the voltage is applied. ### Claim 4 A liquid crystal display device comprising: a first member having a first surface and a second surface; a second member having a third surface and a fourth surface; a liquid crystal layer positioned between the first member and the second member, wherein the liquid crystal layer generates a phase delay for light passing therethrough; a voltage application structure for applying a voltage to the liquid crystal layer, wherein the phase delay generated by the liquid crystal layer is varied between (λ/2+α) and α, wherein α has a non-zero value, according to the voltage that is applied; and a compensation film coupled to at least one of the first member and the second member, wherein the compensation film generates a compensation phase delay of −α, wherein the device operates in a normally black mode, and wherein the phase delay generated by the liquid crystal layer is α for a black image when no voltage is applied and is (λ/2+α) for a white image when the voltage is applied. ### Claim 5 (depends on 4) The device of claim 4, wherein the device has a reflective region with a reflective region phase delay, and wherein the reflective region phase delay is about α/2 for the black image when no voltage is applied and is about (λ/2+α)/2 for the white image when the voltage is applied. ### Claim 6 (depends on 4) The device of claim 4, wherein the device has a transmissive region, and wherein the phase delay generated by the liquid crystal layer is α for the black image when no voltage is applied and (λ/2+α) for the white image when the voltage is applied. ### Claim 7 A liquid crystal display device comprising: a first member having a first surface and a second surface; a second member having a third surface and a fourth surface; a liquid crystal layer positioned between the first member and the second member, wherein the liquid crystal layer generates a phase delay for light passing therethrough; a voltage application structure for applying a voltage to the liquid crystal layer, wherein the phase delay generated by the liquid crystal layer is varied between (λ/2+α) and α, wherein α has a non-zero value, according to the voltage that is applied; and a compensation film coupled to at least one of the first member and the second member, wherein the compensation film generates a compensation phase delay of −α, wherein the phase delay changes by about 10 nm to about 30 nm in response to a change in the voltage by about 0.1 V. ### Claim 8 (depends on 7) The device of claim 7, wherein λ is about 460 nm to about 550 nm. ### Claim 9 (depends on 7) The device of claim 7, wherein the value of α is such that: (Vsu−Vth)/(Vs−Vth)×0.3λ<α<(Vsu−Vth)/(Vs−Vth)×0.7λ, wherein Vsu is a target operating voltage of the liquid crystal display device; Vs is an intrinsic saturation voltage of a liquid crystal mixture; and Vth is an actual threshold voltage of the liquid crystal layer. ### Claim 10 (depends on 7) The device of claim 7, wherein the liquid crystal layer is homogeneously aligned. ### Claim 11 (depends on 7) The device of claim 7, wherein the voltage is applied to two electrodes sandwiching the liquid crystal layer. ### Claim 12 (depends on 7) The device of claim 7, wherein the voltage is applied to two electrodes on a same side of the liquid crystal layer. ### Claim 13 (depends on 7) The device of claim 7 further comprising an optical film assembly, wherein the optical film assembly includes a first film assembly coupled to the first member and a second film assembly coupled to the second member. ### Claim 14 (depends on 13) The device of claim 13, wherein the compensation film is positioned between the first member and the first film assembly. ### Claim 15 (depends on 13) The device of claim 13, wherein the compensation film is positioned between the second member and the second film assembly. ### Claim 16 (depends on 13) The device of claim 13, wherein the optical film assembly comprises: a polarizer; a first film for generating a phase shift of λ/2; and a second film for generating a phase shift of λ/4. ### Claim 17 (depends on 7) The device of claim 7, wherein the compensation film is a C-plate having a phase shift of α to generate a compensation phase delay of −α. ### Claim 18 (depends on 7) The device of claim 7, wherein the liquid crystal layer has a first cell gap in the reflective region and a second cell gap in the transmissive region, wherein the first cell gap generates a phase difference of about 140 nm to about 240 nm for λ of about 550 nm. ### Claim 19 (depends on 7) The device of claim 7, wherein the liquid crystal layer has a first cell gap in the reflective region and a second cell gap in the transmissive region, wherein the second cell gap generates a phase delay of about 280 nm to about 480 nm.