KR100448042B1 - Reflective type liquid crystal display - Google Patents
Reflective type liquid crystal display Download PDFInfo
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- KR100448042B1 KR100448042B1 KR10-2000-0072284A KR20000072284A KR100448042B1 KR 100448042 B1 KR100448042 B1 KR 100448042B1 KR 20000072284 A KR20000072284 A KR 20000072284A KR 100448042 B1 KR100448042 B1 KR 100448042B1
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- G—PHYSICS
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- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133553—Reflecting elements
- G02F1/133555—Transflectors
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- G—PHYSICS
- G02—OPTICS
- 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
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
- G02F1/133707—Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes
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- G—PHYSICS
- G02—OPTICS
- 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
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1343—Electrodes
- G02F1/134309—Electrodes characterised by their geometrical arrangement
- G02F1/134372—Electrodes characterised by their geometrical arrangement for fringe field switching [FFS] where the common electrode is not patterned
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- G—PHYSICS
- G02—OPTICS
- 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
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
- G02F1/13787—Hybrid-alignment cells
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- G—PHYSICS
- G02—OPTICS
- 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
- G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
- G02F2201/12—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 electrode
- G02F2201/123—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 electrode pixel
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Abstract
본 발명은 암흑상태를 향상시킨 반사형 액정표시소자를 개시한다. 개시된 본 발명에 따른 반사형 액정표시소자는, 소정 간격으로 대향 배치된 하부기판 및 상부기판과, 상기 하부기판 상에 프린지 필드를 발생시키도록 전극간 간격이 전극 폭 및 셀 갭(cell gap) 보다 작거나 같도록 형성된 상대전극과 화소전극과, 상기 하부기판과 상부기판 사이에 개재된 수 개의 액정으로 구성된 액정층과, 상기 하부기판과 액정층 사이에 개재되며, 상기 액정층이 양의 유전율 이방성을 갖는 액정들로 구성된 경우는 수평방향에 대해 45∼90°로 수평 배향되고, 음의 유전율 이방성을 갖는 액정들로 구성되는 경우는 수평방향에 대해 0∼45°로 수평 배향된 하부 배향막과, 상기 상부기판과 액정층 사이에 개재되며, 하이브리드(hybrid) 배향을 이루도록 수직 배향된 상부 배향막과, 상기 상부기판의 외측면 상에 차례로 적층된 λ/2 위상차판과 편광판을 포함하며, 상기 상대전극은 반사판의 역할을 겸하는 것을 특징으로 한다.The present invention discloses a reflective liquid crystal display device having an improved dark state. Reflective liquid crystal display device according to the present invention, the lower substrate and the upper substrate facing each other at predetermined intervals, and the interval between the electrodes to generate a fringe field on the lower substrate is more than the electrode width and cell gap (cell gap) A liquid crystal layer comprising a counter electrode and a pixel electrode formed to be smaller or equal, and several liquid crystals interposed between the lower substrate and the upper substrate, and interposed between the lower substrate and the liquid crystal layer, wherein the liquid crystal layer is positive dielectric anisotropy. A lower alignment layer horizontally aligned at 45 to 90 ° with respect to the horizontal direction, and a lower alignment layer horizontally aligned at 0 to 45 ° with respect to the horizontal direction, when the liquid crystals have a liquid crystal having a negative dielectric anisotropy; An upper alignment layer interposed between the upper substrate and the liquid crystal layer and vertically aligned to form a hybrid alignment, and a λ / 2 phase difference plate sequentially stacked on an outer surface of the upper substrate; And a polarizing plate, wherein the counter electrode serves as a reflecting plate.
Description
본 발명은 반사형 액정표시소자에 관한 것으로, 보다 상세하게는, 암흑상태 (dark state)를 향상시킴으로써 콘트라스트비(constrast ratio)를 증가시킨 반사형 액정표시소자에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device, and more particularly, to a reflective liquid crystal display device in which a contrast ratio is increased by improving a dark state.
TFT(Thin Film Transistor)를 스위칭(Switching) 소자로 하는 액정표시소자는 평판 표시소자들 가운데에서 그 활용성에서 주목받고 있다. 이 중 반사형 액정표시소자는 종래 투과형 액정표시소자에 비해 백라이트(BackLight:B/L)를 사용하지 않기 때문에 저 소비전력을 사용하고, 무게가 가볍다는 장점이 있어서, 차세대 액정 디스플레이로 많은 연구의 대상이 되고 있다.그러나, 종래의 액정표시소자는 정규(Normally) TN(Twisted Nematic) 모드를 사용해왔기 때문에 시야각 등에서 많은 문제가 있어왔다. 따라서, 프린지 필드(Fringe Field)와 같은 광시야각 모드를 이용한 여러가지 반사형 액정표시소자를 제안하고 있다. 그 중 하나가 하부기판 측에서는 수평 배향을 하고, 상부기판 측에서는 수직 배향을 한 FFS-HAN(Fringe Field Switching-Hybrid Alignment Nematic) 모드를 반사형에 응용한 것이다. 이 모드는 투과형에서 액정의 위상지연값(dΔn)이 노말(Normal)의 경우 보다 큰 값에서 투과율이 최대가 되기 때문에 반사형으로 사용할 때 현재 사용되고 있는 공정 조건에 무리없이 적용할 수 있다는 장점을 가지고 있다.그러나 처음에 제안된 FFS-HAN 반사형 모드는 편광판(Polarizer)과 액정층, 그리고, 반사판을 사용한 것으로 액정의 투과율 파장 의존성 때문에 정규 암흑 모드(Normally Black Mode)로 사용시에 암흑상태(dark state)를 만들기가 어려운 문제점이 있었다.Liquid crystal display devices using TFTs (Thin Film Transistors) as switching devices have been attracting attention in their use among flat panel display devices. Among them, the reflective liquid crystal display device has a low power consumption and a light weight because it does not use a backlight (B / L) as compared to the conventional transmissive liquid crystal display device. However, since the conventional liquid crystal display device has used a normally twisted nematic (TN) mode, there have been many problems in viewing angles and the like. Accordingly, various reflection type liquid crystal display devices using a wide viewing angle mode such as a fringe field have been proposed. One of them is the reflection type of the FFS-HAN (Fringe Field Switching-Hybrid Alignment Nematic) mode in which the lower substrate side is horizontally aligned and the upper substrate is vertically aligned. This mode has the advantage that it can be applied to the process conditions currently used when using it as a reflection type because the transmittance is maximized when the phase delay value (dΔn) of the liquid crystal is larger than that of the normal type in the transmission type. However, the first FFS-HAN reflection mode proposed uses a polarizer, a liquid crystal layer, and a reflection plate, and is dark when used in the normal black mode due to the wavelength dependence of the transmittance of the liquid crystal. There was a difficult problem making).
도 1a는 전압인가전 편광판과 FFS-HAN의 구조를 갖는 액정층만으로 이루어진 반사형의 dΔn에 따른 반사율을 나타낸 그래프이고, 도 1b는 도 1a의 A부분에 대한 확대도로서, 도시한 바와 같이, 전압인가전 편광판과 FFS-HAN의 구조를 갖는 액정층만으로 이루어진 반사형의 dΔn에 따른 반사율에서 볼 수 있듯이 dΔn이 0.29 정도에서 0.01 이라는 최소의 값을 갖는 것을 알 수 있다.따라서, 화이트(white) 상태에서 아무리 큰 반사율을 갖는다고 해도 편광판과 반사판만으로 구성되었을 때가 0.38 이므로 정면 콘트라스트 비가 38 정도 밖에 되지 않는다.FIG. 1A is a graph showing reflectance according to dΔn of a reflection type including only a voltage-applying polarizing plate and a liquid crystal layer having a structure of FFS-HAN, and FIG. 1B is an enlarged view of portion A of FIG. As can be seen from the reflectance according to dΔn of the reflection type consisting of only the voltage-applied polarizing plate and the liquid crystal layer having the structure of FFS-HAN, it can be seen that dΔn has a minimum value of about 0.29 to 0.01. Even if it has a large reflectance in the state, it is 0.38 when only the polarizing plate and the reflecting plate are composed, so that the front contrast ratio is only about 38.
또한, 특정 파장에 대해 액정의 특정 위상값을 갖도록 dΔn을 설계했다고 하더라도, 이 값은 다른 파장에 대해 해당하는 값이 아니므로 파장에 따른 의존성이 발생하게 된다.예를들어, λ/4의 위상차판이라고 해도 실제로 이것이 전파장에 대해 λ/4의 위상차를 나타내는 것은 아니므로, 편광판과 λ/4 위상차판만으로 암흑상태를 만들 경우 특정 파장에는 암흑 상태가 되더라도 다른 파장에 의한 효과 때문에 완전한 암흑이 만들어지지 않는 문제점이 있다.In addition, even if dΔn is designed to have a specific phase value of the liquid crystal for a specific wavelength, this value is not a corresponding value for other wavelengths, so a dependency of wavelength occurs. For example, a phase difference of λ / 4 Even if a plate does not actually represent a phase difference of λ / 4 with respect to a radio wave field, when a dark state is formed only with a polarizing plate and a λ / 4 phase difference plate, even if it is in a dark state at a specific wavelength, full darkness is produced due to the effect of other wavelengths. There is a problem.
이에, 본 발명은 상기한 바와 같은 종래 문제점을 개선하기 위해 안출한 것으로, λ/2 위상차판을 FFS-HAN 모드의 상부기판에 위치시켜서 위상차판과 액정층간의 조합에 의해 기존의 액정층만을 사용한 경우 보다 암흑상태가 향상되도록 한 반사형 액정표시소자를 제공함에 그 목적이 있다.Accordingly, the present invention has been made to solve the above-described problems, and by using a conventional liquid crystal layer by combining the retardation plate and the liquid crystal layer by placing the λ / 2 phase difference plate on the upper substrate of the FFS-HAN mode In this case, an object of the present invention is to provide a reflective liquid crystal display device in which a dark state is improved.
도 1a 는 전압인가전 편광판과 FFS-HAN의 구조를 갖는 액정층만으로 이루어진 반사형 액정표시소자의 dΔn에 따른 반사율을 나타낸 그래프로서,FIG. 1A is a graph showing reflectance according to dΔn of a reflective liquid crystal display device including only a voltage-applied polarizing plate and a liquid crystal layer having a structure of FFS-HAN.
도 1b 는 도 1 a의 A부분에 대한 확대도.FIG. 1B is an enlarged view of portion A of FIG. 1A; FIG.
도 2a 는 편광판과 λ/2 판 그리고 FFS-HAN 모드의 액정층으로 이루어진 전압인가전의 dΔn에 따른 반사율을 나타낸 그래프.FIG. 2A is a graph showing reflectance according to dΔn of voltage application before comprising a polarizing plate, a λ / 2 plate, and a liquid crystal layer in FFS-HAN mode. FIG.
도 2b 는 도 2a 의 A부분에 대한 확대도.FIG. 2B is an enlarged view of portion A of FIG. 2A;
도 3 은 본 발명에 따른 슬릿구조의 FFS전극을 나타낸 단면도.3 is a cross-sectional view showing a slit structure FFS electrode according to the present invention.
도 4 는 본 발명에 따른 박스(Box)구조의 FFS전극을 나타낸 단면도.4 is a cross-sectional view showing an FFS electrode of a box structure according to the present invention.
도 5 는 본 발명에 따른 FFS 전극구조와 러빙방향을 나타낸 도면.5 is a view showing the FFS electrode structure and the rubbing direction according to the present invention.
도 6 은 도 5 의 단면도.6 is a cross-sectional view of FIG. 5;
도 7 은 본 발명에 따른 암흑 상태를 향상시킨 FFS-HAN 구조를 나타낸 도면.7 is a view showing an FFS-HAN structure to improve the dark state according to the present invention.
도 8 은 전파장 암흑상태 반사형 FFS-HAN 모드의 전압인가에 따른 반사율을 나타낸 그래프이다.8 is a graph showing reflectance according to voltage application in a full-field dark state reflection type FFS-HAN mode.
도 9는 본 발명에 따른 다른 실시예를 나타낸 단면도.9 is a sectional view showing another embodiment according to the present invention.
<도면의 주요부분에 대한 부호의 설명><Description of the symbols for the main parts of the drawings>
10 : 유리기판 12 : 상대전극10 glass substrate 12 counter electrode
14 : 절연막 20 : 화소전극14 insulating film 20 pixel electrode
30 : 액정 40 : λ/2 위상차판30 liquid crystal 40 lambda / 2 phase difference plate
50 : 편광판(polarizer) 91: '< ' 자형 슬릿50: polarizer 91: '<' shaped slit
상기와 같은 목적을 달성하기 위하여, 본 발명은, 소정 간격으로 대향 배치된 하부기판 및 상부기판; 상기 하부기판 상에 프린지 필드를 발생시키도록 전극간 간격이 전극 폭 및 셀 갭(cell gap) 보다 작거나 같도록 형성된 상대전극과 화소전극; 상기 하부기판과 상부기판 사이에 개재된 수 개의 액정으로 구성된 액정층; 상기 하부기판과 액정층 사이에 개재되며, 상기 액정층이 양의 유전율 이방성을 갖는 액정들로 구성된 경우는 수평방향에 대해 45∼90°로 수평 배향되고, 음의 유전율 이방성을 갖는 액정들로 구성되는 경우는 수평방향에 대해 0∼45°로 수평 배향된 하부 배향막; 상기 상부기판과 액정층 사이에 개재되며, 하이브리드(hybrid) 배향을 이루도록 수직 배향된 상부 배향막; 및 상기 상부기판의 외측면 상에 차례로 적층된 λ/2 위상차판과 편광판을 포함하며, 상기 상대전극은 반사판의 역할을 겸하는 것을 특징으로 하는 반사형 액정표시소자를 제공한다.In order to achieve the above object, the present invention, the lower substrate and the upper substrate disposed to be disposed at a predetermined interval; A counter electrode and a pixel electrode formed such that an interval between electrodes is smaller than or equal to an electrode width and a cell gap so as to generate a fringe field on the lower substrate; A liquid crystal layer composed of several liquid crystals interposed between the lower substrate and the upper substrate; The liquid crystal layer is interposed between the lower substrate and the liquid crystal layer, and the liquid crystal layer is composed of liquid crystals having negative dielectric anisotropy, horizontally aligned at 45 to 90 ° with respect to the horizontal direction, when the liquid crystal layer is composed of liquid crystals having positive dielectric anisotropy. The lower alignment layer which is horizontally oriented at 0 to 45 ° with respect to the horizontal direction; An upper alignment layer interposed between the upper substrate and the liquid crystal layer and vertically aligned to form a hybrid orientation; And a [lambda] / 2 phase difference plate and a polarizing plate sequentially stacked on the outer surface of the upper substrate, wherein the counter electrode serves as a reflecting plate.
여기서, 상기 편광판의 투과축과 λ/2 위상차판의 축, 그리고, 액정의 위상지연값(dΔn)은 위상 보상이 일어나 암흑상태가 향상되도록 러빙방향에 대해서 각각 75°, 15° 및 0.34의 값을 갖도록 함이 바람직하다.이때, 상기 편광판의 투과축과 λ/2 위상차판의 축은 공정마진을 고려하여 ±5°의 범위를 가지며, 액정의 위상지연값(dΔn)은 ±0.05의 범위를 갖도록 한다.또한, 상기한 본 발명의 반사형 액정표시소자는 상기 편광판과 λ/2 위상차판 사이에 광시야각을 갖도록 위상보상필름이 추가로 삽입된 것을 특징으로 한다.Here, the transmission axis of the polarizing plate, the axis of the λ / 2 retardation plate, and the phase delay value (dΔn) of the liquid crystal have values of 75 °, 15 °, and 0.34 for the rubbing direction, respectively, so that the phase compensation occurs and the dark state is improved. In this case, the transmission axis of the polarizing plate and the axis of the λ / 2 retardation plate have a range of ± 5 ° in consideration of the process margin, and the phase delay value (dΔn) of the liquid crystal has a range of ± 0.05. In addition, the above-described reflective liquid crystal display device of the present invention is characterized in that the phase compensation film is further inserted to have a wide viewing angle between the polarizing plate and the λ / 2 phase difference plate.
(실시예)이하, 첨부된 도면을 참조하여 본 발명의 바람직한 실시예를 상세하게 설명하도록 한다.Embodiments Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
도 2a는 편광판과 λ/2 위상차판 그리고 FFS-HAN 모드의 액정층으로 이루어진 전압인가전의 dΔn에 따른 반사율을 나타낸 그래프이고, 도 2b 는 도 2a 의 A부분에 대한 확대도로서, 도시한 바와 같이, 편광판과 λ/2 위상차판, 그리고, 액정층으로 이루어진 경우 dΔn이 0.34에서 반사율 0.003정도로 화이트 상태에 따라 콘트라스트 비가 100 정도도 가능하다. 이때, 러빙각도를 기준으로 편광판의 투과축은 75°각도를 이루고 있으며, λ/2 위상차판은 그 축이 러빙각도를 기준으로 15°를 이루고 있다.또한, 암흑상태가 우수한 경우는 이 밖에도 러빙각도를 기준으로 편광판 투과축을 85°, λ/2판의 축을 20°로한 경우와 편광판의 투과축을 5°, λ/2판의 축을 25°로 한 경우 등이 있으며, dΔn은 각각 0.32에서 반사율 0.035와 0.0042 정도의 우수한 암흑상태를 나타내고 있다.FIG. 2A is a graph showing reflectance according to dΔn before voltage application including a polarizing plate, a λ / 2 retardation plate, and a liquid crystal layer in FFS-HAN mode, and FIG. 2B is an enlarged view of part A of FIG. 2A. Similarly, in the case of a polarizing plate, a λ / 2 retardation plate, and a liquid crystal layer, a contrast ratio of about 0.33 to about 0.003 may be about 100, depending on the white state. In this case, the transmission axis of the polarizing plate has a 75 ° angle based on the rubbing angle, and the axis of the λ / 2 phase difference plate has a shaft of 15 ° based on the rubbing angle. For example, the transmission axis of the polarizing plate is 85 ° and the axis of the λ / 2 plate is 20 °, and the transmission axis of the polarizing plate is 5 ° and the axis of the λ / 2 plate is 25 °. It shows an excellent dark state of about 0.0042.
도 3 및 도 4는 본 발명에 따른 반사형 액정표시소자에서의 슬릿구조 및 박스(Box)구조의 FFS 전극을 나타낸 단면도이고, 도 5는 본 발명에 따른 반사형 액정표시소자에서의 전극구조와 러빙방향을 설명하기 위한 도면이며, 도 6은 도 5의 단면도이다.도 3 및 도 4에 도시된 바와 같이, 본 발명에 따른 반사형 액정표시소자에서의 FFS 전극, 즉, 상대전극(12)과 화소전극(20)은 슬릿구조 또는 박스구조 모두로 형성 가능하며, 전극간 간격이 전극 폭이나 셀 갭(cell gap) 보다 작거나 같은 구조를 갖도록 설계되어 프린지 필드를 발생시키게 된다. 이때, 상기 상대전극(12)은 반사전극의 역할을 함께 겸하도록 할 수 있으며, 이를 통해, 평행축 문제를 해결하도록 할 수 있다.또한, 이러한 전극 구조를 갖는 하부기판과 이에 대향 배치된 상부기판 사이에 수 개의 액정들로 이루어진 액정층이 개재된 본 발명에 따른 FFS-HAN 모드에 있어서 하부기판과 액정층 사이에 개재되는 하부 배향막은 수평 배향되며, 상부기판과 액정층 사이에 개재되는 상부 배향막은 수직 배향되어 하이브리드(Hybrid) 구조로 액정을 배향시킨다.이때, 도 5에 도시된 바와 같이, 하부 배향막의 러빙각도(α)는 유전율이방성이 양인 액정들로 액정층을 구성한 경우는 수평방향에 대해 45∼90°정도가 되도록, 그리고, 유전율이방성이 음인 액정들로 액정층을 구성하는 경우는 수평방향에 대해 0∼45°정도가 되도록 한다.특히, 본 발명의 반사형 액정표시소자는 편광판과 액정층 사이에, 보다 정확하게는 상부기판과 편광판 사이에 λ/2 위상차판을 배치시키며, 이때, 그 축방향과 액정의 dΔn은 다음과 같은 값을 갖도록 한다.3 and 4 are cross-sectional views illustrating a slit structure and a box structure FFS electrode in the reflective liquid crystal display according to the present invention, and FIG. 5 is an electrode structure in the reflective liquid crystal display according to the present invention. 6 is a cross-sectional view of FIG. 5. As shown in FIGS. 3 and 4, the FFS electrode, that is, the counter electrode 12 of the reflective liquid crystal display device according to the present invention is illustrated. The pixel electrode 20 can be formed of both a slit structure or a box structure, and is designed to have a structure in which an inter-electrode spacing is smaller than or equal to an electrode width or a cell gap to generate a fringe field. In this case, the counter electrode 12 may also serve as a reflective electrode, thereby solving the parallel axis problem. In addition, a lower substrate having such an electrode structure and an upper substrate disposed opposite thereto are provided. In the FFS-HAN mode in which a liquid crystal layer composed of several liquid crystals is interposed therebetween, the lower alignment layer interposed between the lower substrate and the liquid crystal layer is horizontally aligned and the upper alignment layer interposed between the upper substrate and the liquid crystal layer. Is orientated vertically to orient the liquid crystal in a hybrid structure. As shown in FIG. 5, the rubbing angle α of the lower alignment layer is in the horizontal direction when the liquid crystal layer is composed of liquid crystals having positive dielectric anisotropy. When the liquid crystal layer is composed of liquid crystals having negative dielectric anisotropy, it is about 0 to 45 degrees with respect to the horizontal direction. Scanning the liquid crystal display element is more precisely between a polarizing plate and a liquid crystal layer, disposed sikimyeo the λ / 2 phase difference plate between an upper substrate and a polarizer, this time, dΔn in the axial direction and the liquid crystal will have the following values:
(1) 편광판 투과축: 러빙방향에 대하여 75°,(1) Polarizing plate transmission axis: 75 ° with respect to rubbing direction,
λ/2 위상차판의 축: 러빙방향에 대하여 15°, 액정의 dΔn=0.34Axis of the λ / 2 retarder: 15 ° with respect to the rubbing direction, dΔn of the liquid crystal = 0.34
(1) 편광판 투과축: 러빙방향에 대하여 85°,(1) Polarizing plate transmission axis: 85 ° with respect to rubbing direction
λ/2 위상차판의 축: 러빙방향에 대하여 20°, 액정의 dΔn=0.32Axis of the λ / 2 retarder: 20 ° with respect to the rubbing direction, dΔn of the liquid crystal = 0.32
(2) 편광판 투과축: 러빙방향에 대하여 5°,(2) Polarizing plate transmission axis: 5 ° with respect to rubbing direction,
λ/2 위상차판의 축: 러빙방향에 대하여 25°, 액정의 dΔn=0.32axis of the λ / 2 retarder: 25 ° with respect to the rubbing direction, dΔn of the liquid crystal = 0.32
여기서, 상기 편광판 투과축과 λ/2 위상차판의 축은 공정 마진(margin)을 고려하여 목적(target)으로 한 값에 ±5°정도의 마진을 갖도록 하고, 액정의 dΔn역시 셀갭 마진 등을 고려하여 ±0.05의 값을 갖도록 한다.Here, the polarizing plate transmission axis and the axis of the λ / 2 retardation plate have a margin of about 5 ° at a target value in consideration of the process margin, and dΔn of the liquid crystal also considers a cell gap margin. Have a value of ± 0.05.
이렇게 배치된 셀은 전압인가전 위의 조건에 의해 우수한 암흑상태를 갖게 된다.The cells thus arranged have an excellent dark state under the condition of voltage application.
도 7은 본 발명에 따른 암흑 상태를 향상시킨 FFS-HAN 구조를 나타낸 도면이고, 도 8은 전파장 암흑상태 반사형 FFS-HAN 모드의 전압인가에 따른 반사율을 나타낸 그래프이다.전압이 인가되면 액정이 트위스트(twist)되면서 투과율이 발생하게 되는데, 상기한 (1)의 경우에 대하여 그 대략적인 구조가 도 7에 나타나 있고, 전압인가에 따른 정면에서의 반사율이 도 8에 나타나 있다. 도 8의 경우 셀 갭이 4μm, Δn=0.77의 경우로 목적값과는 다소 벗어나 있으나, 일반적으로 dΔn에 의한 화이트상태의 값이 잘 안변한다는 사실을 감안한다면 이 경우 정면에서의 콘트라스트 비는 100:1까지 가능하다.도 7에서, 도면부호 12는 반사판을, 30은 액정층을, 40은 λ/2 위상차판을, 50은 편광판을 각각 나타내며, 각각의 화살표는 러빙방향, 축 방향 및 투과축 방향을 나타낸다. 실시예에서, 편광판(50)의 투과축은 러빙방향에 대해 75°정도를 나타내며, λ/2 위상차판(40)의 축은 러빙방향에 15°정도를 나타낸다.7 is a view showing the FFS-HAN structure to improve the dark state according to the present invention, Figure 8 is a graph showing the reflectance according to the voltage applied to the full-wavelength dark state reflection type FFS-HAN mode. As this twist occurs, the transmittance is generated. The structure of FIG. 1 is shown in FIG. 7, and the reflectance at the front surface according to the application of voltage is shown in FIG. 8. In the case of FIG. 8, the cell gap is 4 μm and Δn = 0.77, which is slightly different from the target value. However, considering the fact that the value of the white state due to dΔn is unstable, in this case, the contrast ratio at the front is 100: In FIG. 7, reference numeral 12 denotes a reflecting plate, 30 denotes a liquid crystal layer, 40 denotes a λ / 2 retardation plate, 50 denotes a polarizing plate, and each arrow indicates a rubbing direction, an axial direction, and a transmission axis. Indicates the direction. In the embodiment, the transmission axis of the polarizing plate 50 represents about 75 ° with respect to the rubbing direction, and the axis of the λ / 2 retardation plate 40 represents about 15 ° with respect to the rubbing direction.
도 9는 본 발명에 따른 다른 실시예를 나타낸 단면도로서, 도시한 바와같이, 더 큰 시야각 특성을 가지기 위하여 편광판(50)과 λ/2 위상차판(40) 사이에 위상보상필름을 추가 삽입시킬 수 있다.또한, 전극 구조는 멀티 도메인(Multi-domain)이 형성되도록 한 화소내를 이분할하여 서로 다른 각도의 '<' 자형 슬릿(91)을 갖는 화소구조로 나눌 수도 있고, 같은 원리로 여러 화소를 서로 다른 각도를 갖도록 화소구조를 형성할 수 있다.9 is a cross-sectional view showing another embodiment according to the present invention, and as shown, a phase compensation film may be additionally inserted between the polarizing plate 50 and the λ / 2 retardation plate 40 to have a larger viewing angle characteristic. In addition, the electrode structure may be divided into a pixel structure having '<' shaped slits 91 having different angles by dividing the pixel into one in which a multi-domain is formed. The pixel structure may be formed to have different angles.
이상에서와 같이, 본 발명에 의하면 기존 FFS 모드의 제작과 거의 동일한 구조로 반사형 액정표시소자의 제작이 가능하며, 특히, 상부기판과 편광판 사이에 λ/2 위상차판을 개재시키는 것을 통해 암흑상태를 향상시킴으로써 우수한 콘트라스트비를 갖는 반사형 액정표시소자의 제작이 가능하다.As described above, according to the present invention, a reflective liquid crystal display device can be manufactured with a structure substantially the same as that of the conventional FFS mode, and in particular, a dark state is provided by interposing a λ / 2 phase difference plate between the upper substrate and the polarizing plate. It is possible to manufacture a reflective liquid crystal display device having an excellent contrast ratio by improving.
또한 하판에 위상차판을 두지 않기 때문에 반사판을 전극으로 사용하면 평행축 문제 해결할 수 있다.In addition, since the retardation plate is not placed on the lower plate, the use of a reflecting plate as an electrode can solve the parallel axis problem.
본 발명 상기한 실시 예에 한정되지 않고, 이하 청구 범위에서 청구하는 본 발명의 요지를 벗어남이 없이 당해 발명이 속하는 분야에서 통상의 지식을 가진자라면 누구든지 다양한 변경 실시가 가능할 것이다.The present invention is not limited to the above embodiments, and various changes can be made by those skilled in the art without departing from the gist of the present invention as claimed in the following claims.
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| JP2000056297A (en) * | 1998-08-07 | 2000-02-25 | Victor Co Of Japan Ltd | Liquid crystal display device |
| JP2000066195A (en) * | 1998-08-24 | 2000-03-03 | Matsushita Electric Ind Co Ltd | Reflection type liquid crystal display device |
| JP2000284127A (en) * | 1998-12-17 | 2000-10-13 | Dainippon Printing Co Ltd | Bidirectional dichroic circular polarization plate and reflection-transmission type liquid crystal display device |
| KR20010096160A (en) * | 2000-04-17 | 2001-11-07 | 구본준, 론 위라하디락사 | transflective liquid crystal display device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000056297A (en) * | 1998-08-07 | 2000-02-25 | Victor Co Of Japan Ltd | Liquid crystal display device |
| JP2000066195A (en) * | 1998-08-24 | 2000-03-03 | Matsushita Electric Ind Co Ltd | Reflection type liquid crystal display device |
| JP2000284127A (en) * | 1998-12-17 | 2000-10-13 | Dainippon Printing Co Ltd | Bidirectional dichroic circular polarization plate and reflection-transmission type liquid crystal display device |
| KR20010096160A (en) * | 2000-04-17 | 2001-11-07 | 구본준, 론 위라하디락사 | transflective liquid crystal display device |
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