KR20000046921A - Polarization film using cholesteric liquid crystal and liquid crystal display device - Google Patents
Polarization film using cholesteric liquid crystal and liquid crystal display device Download PDFInfo
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- KR20000046921A KR20000046921A KR1019980063649A KR19980063649A KR20000046921A KR 20000046921 A KR20000046921 A KR 20000046921A KR 1019980063649 A KR1019980063649 A KR 1019980063649A KR 19980063649 A KR19980063649 A KR 19980063649A KR 20000046921 A KR20000046921 A KR 20000046921A
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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
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133528—Polarisers
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
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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
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133528—Polarisers
- G02F1/133543—Cholesteric polarisers
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Abstract
Description
본 발명은 콜레스테릭 액정을 이용한 편광필름 및 액정표시장치에 관한 것으로, 특히 위상차 필름을 이용하여 콜레스테릭 액정필름의 시야각에 따른 색변화를 방지하는 방법과 이를 이용한 고휘도 액정표시장치의 제조에 관한 것이다.The present invention relates to a polarizing film and a liquid crystal display device using a cholesteric liquid crystal, and particularly to a method for preventing color change according to the viewing angle of the cholesteric liquid crystal film using a retardation film and to manufacture a high brightness liquid crystal display device using the same. It is about.
콜레스테릭 액정을 이용하면 기존 액정표시장치(LCD)의 단점을 크게 개선시켜 고휘도 액정 표시장치의 구현이 가능하다.By using the cholesteric liquid crystal, a high brightness liquid crystal display device can be realized by greatly improving the disadvantages of the conventional liquid crystal display device (LCD).
상기와 같은 콜레스테릭 액정은 액정의 나선형 구조의 꼬인 방향과 원편광 방향이 일치하고 파장이 액정의 나선피치와 같은 원평광의 빛만을 반사하는 선택반사 특성이 있다.The cholesteric liquid crystal as described above has a selective reflection characteristic in which the twisted direction of the helical structure of the liquid crystal coincides with the circular polarization direction, and the wavelength reflects only light of circular light such as the spiral pitch of the liquid crystal.
또한, 콜레스테릭 액정으로 편광막이나 컬러필터를 제조하면, 선택반사 특성에 의해 반사된 빛을 재활용 할 수 있어 고휘도 액정 표시장치의 구현이 가능하다.In addition, when the polarizing film or the color filter is manufactured using the cholesteric liquid crystal, the light reflected by the selective reflection characteristic may be recycled, thereby enabling the implementation of a high brightness liquid crystal display device.
USP 5506704, USP5691789, 한국 특허출원 97-38643, 98-498, 98-14214에서는 콜레스테릭 액정을 이용하여 액정 표시장치의 광효율을 증가시키는 방법에 대해 기술하고 있다.USP 5506704, USP5691789, Korean Patent Application Nos. 97-38643, 98-498 and 98-14214 describe a method of increasing the light efficiency of a liquid crystal display using cholesteric liquid crystal.
그런데, 콜레스테릭 액정은 시야각에 따라 반사 또는 투과되는 빛의 색이 변하는 특성을 가지고 있다.By the way, the cholesteric liquid crystal has a characteristic that the color of the light reflected or transmitted changes depending on the viewing angle.
피치가 P인 콜레스테릭 액정에 빛이 입사될 때, 입사각(θ)에 따른 빛의 경로차는 P cosθfh 표현되며, Bragg 반사조건에 의해 이 경로차와 일치되는 파장의 빛이 보강간섭되어 강하게 반사된다.When light is incident on the cholesteric liquid crystal having a pitch of P, the path difference of the light according to the incident angle θ is expressed as P cosθfh, and the light of the wavelength consistent with this path difference is reinforced and strongly reflected by the Bragg reflection condition. do.
이는 입사각이 커질수록 경로차가 감소하여 짧은 파장의 빛이 반사된다는 것을 의미한다.This means that as the angle of incidence increases, the path difference decreases and light of short wavelength is reflected.
따라서, 콜레스테릭 액정으로 제조된 편광막이나 컬러필터를 적용하여 액정 표시장치를 제조하면 시야각에 따라 색변화가 발생하게 된다.Therefore, when a liquid crystal display is manufactured by applying a polarizing film or a color filter made of cholesteric liquid crystal, color change occurs according to a viewing angle.
현재 액정 표시장치는 대형화 추세에 있으며, 대형 액정 표시장치에서 광시야각은 필수적으로 요구되고 있다.Currently, liquid crystal displays are becoming larger, and wide viewing angles are indispensable in large liquid crystal displays.
그러므로, 시야각에 따라 색변화가 일어나는 콜레스테릭 액정 편광막이나 컬러필터는 광시야각이 요구되는 액정 표시장치에는 적용이 불가능하다.Therefore, a cholesteric liquid crystal polarizing film or color filter in which color change occurs depending on the viewing angle is not applicable to a liquid crystal display device requiring a wide viewing angle.
본 발명에서는 필름의 굴절율을 조절하는 방법에 의해 원편광을 선편광으로변환시키는 기능외에 시야각에 따른 색변화를 보상하는 기능을 갖는 λ/4 위상차 필름을 제조하고, 이를 이용하여 넓은 시야각 특성이 요구되는 액정 표시장치에 사용가능한 콜레스테릭 액정 편광막과 컬러필터를 제조토록 하는 것을 특징으로 한다.In the present invention, by producing a λ / 4 retardation film having a function of compensating the color change according to the viewing angle in addition to the function of converting the circularly polarized light to linearly polarized light by a method of adjusting the refractive index of the film, by using a wide viewing angle characteristic is required A cholesteric liquid crystal polarizing film and a color filter which can be used in a liquid crystal display are manufactured.
도 1은 콜레스테릭 액정의 시야각에 따른 반사 UV-VIS 스펙트럼1 is a reflection UV-VIS spectrum according to the viewing angle of cholesteric liquid crystal
도 2는 시야각에 따른 Δn'd의 변화도.2 is a change of Δn'd with the viewing angle.
도 3은 본 발명의 액정표시장치의 단면구조도.3 is a cross-sectional structure diagram of a liquid crystal display of the present invention.
<도면의 주요 부분에 대한 부호의 설명><Explanation of symbols for the main parts of the drawings>
1: 램프 2: 반사판1: lamp 2: reflector
3: 도광판 4: 확산판3: light guide plate 4: diffuser plate
5: 콜레스테릭 액정필름 6: 위상차 필름5: cholesteric liquid crystal film 6: retardation film
7: 선평광막 8: 액정셀7: linear light film 8: liquid crystal cell
이하에서 본 발명을 보다 상세히 설명하면 다음과 같다.Hereinafter, the present invention will be described in more detail.
현재 사용되는 액정 표시장치는 선편광을 이용하고 있기 때문에, 콜레스테릭 액정 편광막이나 컬러필터의 경우 원편광을 선편광으로 변환시키는 위상차 필름을 사용해야 하며, 액정 표시장치내에서 장착 위치는 선편광막 바로 아래가 된다.Since the current liquid crystal display uses linear polarization, a cholesteric liquid crystal polarizing film or a color filter should use a retardation film that converts circular polarization into linear polarization. In the liquid crystal display, the mounting position is directly below the linear polarization film. Becomes
콜레스테릭 액정은 나선구조의 규칙성으로 인하여 시야각에 따라 반사 또는 투과되는 빛의 색이 변하는 특성을 가지고 있다.The cholesteric liquid crystal has a characteristic of changing the color of reflected or transmitted light depending on the viewing angle due to the regularity of the spiral structure.
도 1에 이같은 콜레스테릭 액정의 특성이 나타나 있다.Figure 1 shows the characteristics of such a cholesteric liquid crystal.
콜레스테릭 액정을 통과한 원편광의 빛을 선편광의 빛으로 변환시키는 1/4 위상차 필름은 일반적으로 PVA나 PC 등의 광투과율이 높은 고분자 필름을 이축연신하여 제조하며, 연신시 x축 방향 굴절율(nx)가 y축 방향 굴절율(ny)을 조절하여 중심파장을 맞춘다.A quarter-phase retardation film that converts circular polarized light that has passed through cholesteric liquid crystal into linear polarized light is generally manufactured by biaxially stretching a polymer film having a high light transmittance such as PVA or PC. (n x ) adjusts the y-direction refractive index (n y ) to adjust the center wavelength.
이때, 적용되는 수식은 Δnd = λ/4이다.At this time, the formula applied is Δnd = λ / 4.
(여기서 Δn은 필름 표면의 복굴절율, d는 필름의 두께, λ는 파장이다.)(Where Δn is the birefringence of the film surface, d is the thickness of the film, and λ is the wavelength).
따라서, λ/4 위상차 필름을 제조할 때 이축 연신비를 조절하여 원하는 중심파장에 맞추며, 필름 두께 방향의 굴절율(nz)은 고려하지 않는다.Therefore, when manufacturing the lambda / 4 phase difference film to adjust the biaxial stretching ratio to the desired center wavelength, the refractive index (n z ) in the film thickness direction is not considered.
이와 같이 제조된 위상차 필름의 경우, 시야각이 증가하게 되면 경로차 Δn'd값(여기서 Δn'은 필름 두께 표면과 두께 방향의 굴절율(nz)이 포함된 복굴절율을 나타낸다.)이 달라지게 되어 원편광을 선편광으로 변환시키지 못하고, 타원편광으로 변환시키게 된다.In the case of the retardation film manufactured as described above, when the viewing angle is increased, the path difference Δn'd value (where Δn 'represents the birefringence including the film thickness surface and the refractive index n z in the thickness direction) is changed. The circularly polarized light cannot be converted into linearly polarized light, but is converted to elliptical polarized light.
이 타원편광은 선편광막을 통과시 광손실이 발생하므로 콜레스테릭 액정 편광막의 효율을 저하시키고 색변화를 일으키는 원인이 된다.This elliptical polarization causes light loss when passing through the linear polarizing film, thereby lowering the efficiency of the cholesteric liquid crystal polarizing film and causing color change.
이러한 현상을 방지하기 위해서는 Δn'd 값을 유지시키는 것이 중요하며, 이것은 필름 두께 방향의 굴절율(nz)과 관계된다.In order to prevent this phenomenon, it is important to maintain the Δn'd value, which is related to the refractive index n z in the film thickness direction.
그리고, 콜레스테릭 액정이나 네마틱 액정과 같이 이방성을 지닌 물질을 통과한 빛의 굴절방향은 nz에 영향을 받는다.In addition, the direction of refraction of light passing through an anisotropic material such as cholesteric liquid crystal or nematic liquid crystal is affected by n z .
그러므로, 콜레스테릭 액정을 통과한 빛의 시야각에 따른 색변화를 방지하고 Δn'd값을 일정하게 유지하여 위상차 필름의 효율을 높이는 것은 nz수치를 조절하는 방법에 의해 가능하다.Therefore, it is possible to prevent the color change according to the viewing angle of the light passing through the cholesteric liquid crystal and to maintain the Δn'd value to increase the efficiency of the retardation film by a method of adjusting the n z value.
이방성을 지닌 필름의 특성은 다음 식과 같이 두께 방향의 복굴절율과 평면에서의 복굴절율의 비율 Nr로 나타낼 수 있다.The property of the film having anisotropy can be expressed by the ratio N r of the birefringence in the thickness direction and the birefringence in the plane as follows.
Nr= (nx- xz)/(nx- ny)N r = (n x -x z ) / (n x -n y )
도 2에는 Nr값에 따른 Δn'd의 각도별 특성이 나타나 있다.2 shows the angle-specific characteristics of Δn'd according to the N r value.
도면에서 알 수 있듯이, Nr값에 따라 시야각이 증가할수록 Δn'd값이 증가 또는 감소하게 된다.As can be seen from the figure, the Δn'd value increases or decreases as the viewing angle increases according to the N r value.
따라서, Nr값을 조절하면 시야각에 따라 원편광을 선편광으로 변환시키는 파장영역을 조절할 수 있고, 색변화도 보상해 줄 수 있다.Therefore, by adjusting the N r value, the wavelength range for converting the circularly polarized light into linearly polarized light can be adjusted according to the viewing angle, and the color change can be compensated for.
그러므로, 적절한 Nr값을 갖는 λ/4 위상차 필름을 이용하여 콜레스테릭 액정 편광막과 컬러필터를 제조하면 넓은 시야각 특성이 요구되는 대면적 액정 표시장치에 적용이 가능하므로 대면적 고휘도 액정 표시장치를 구현할 수 있다.Therefore, if the cholesteric liquid crystal polarizing film and the color filter are manufactured using the lambda / 4 phase difference film having an appropriate N r value, it can be applied to a large area liquid crystal display device requiring a wide viewing angle characteristic, so a large area high brightness liquid crystal display device Can be implemented.
본 발명은 좌선성 나선구조를 갖는 콜레스테릭 액정을 이용하여 투과되는 빛의 색이 적색, 녹색, 청색을 나타내도록 컬러필터를 제조한다.The present invention uses a cholesteric liquid crystal having a left helical structure to produce a color filter such that the color of light transmitted is red, green, and blue.
여기에 PVA 필름을 이축연신하여 제조한 중심파장이 530㎚이고, Nr값이 0.5인 위상차 필름을 합착하여 콜레스테릭 액정 컬러필터를 제조한다.A cholesteric liquid crystal color filter is prepared by bonding a retardation film having a center wavelength of 530 nm and a N r value of 0.5, prepared by biaxially stretching a PVA film.
그리고, 서로다른 선택반사 파장영역을 갖는 우선성 나선구조의 콜레스테릭 액정 필름들을 적층하여 선택반사 파장영역이 가시광선영역을 포함하는 콜레스테릭 액정 편광막을 제조한다.Then, the cholesteric liquid crystal polarizing film in which the selective reflection wavelength region includes the visible light region is laminated by stacking cholesteric liquid crystal films having a preferential spiral structure having different selective reflection wavelength regions.
제조된 콜레스테릭 액정편광막을 액정 표시장치의 확산판과 아래 선편광막 사이에 삽입하고, 콜레스테릭 액정 컬러필터는 아래쪽 선편광막에 합착함에 의해 장착한다.The prepared cholesteric liquid crystal polarizing film is inserted between the diffuser plate of the liquid crystal display and the lower linear polarizing film, and the cholesteric liquid crystal color filter is attached by bonding to the lower linear polarizing film.
이렇게 제조된 액정 표지장치의 단면구조가 도 3에 나타나 있다.The cross-sectional structure of the liquid crystal label device thus manufactured is shown in FIG. 3.
도 3은 본 발명을 이용하여 제조된 액정표시장치의 단면구조도로써, 여기서 1은 램프이고, 2는 반사판이며, 3은 도광판이고, 4는 확산판이며, 5는 콜레스테릭 액정필름이고, 6은 위상차 필름이며, 7은 선평광막이고, 8은 액정셀을 나타내고 있다.3 is a cross-sectional structure diagram of a liquid crystal display device manufactured using the present invention, wherein 1 is a lamp, 2 is a reflector, 3 is a light guide plate, 4 is a diffuser plate, 5 is a cholesteric liquid crystal film, and 6 Is a retardation film, 7 is a linear light film, and 8 has shown the liquid crystal cell.
콜레스테릭 액정 컬러필터를 사용하는 경우, 투과되는 색이 선명하기 위해서는 나선방향이 반대인 콜레스테릭 액정편광막을 함께 사용해야 하며, 기존의 흡수형 컬러필터와는 달리 반사된 빛을 재활용해야 하므로 선편광막 아래쪽에 위치해야 한다.In the case of using the cholesteric liquid crystal color filter, the cholesteric liquid crystal polarizing film having the opposite helical direction must be used together to make the transmitted color clear, and linearly polarized light because the reflected light must be recycled unlike the conventional absorption type color filter. It should be located just below the membrane.
그림에서 보듯이, 광원에서 나온 비편광(c) 빛이 우선성 나선구조의 콜레스테릭 액정필름을 통과하면 우원편광(b) 빛은 반사되고 좌원편광(c) 빛은 투과한다.As shown in the figure, when the non-polarization (c) light from the light source passes through the cholesteric liquid crystal film of the preferential spiral structure, the right circular polarization (b) light is reflected and the left circular polarization (c) light is transmitted.
투과된 좌원편광 빛은 콜레스테릭 액정 컬러필터에서 투과되지 않은 파장의 빛은 반사되어 반사판에서 편광방향이 바뀌어 재활용 된다.The transmitted left circularly polarized light reflects light of a wavelength not transmitted by the cholesteric liquid crystal color filter and is recycled because the polarization direction is changed in the reflecting plate.
이때 컬러필터를 통과한 빛은 위상차 필름을 거쳐 선편광으로 변환되어 액정셀로 입사하게 된다.At this time, the light passing through the color filter is converted into linearly polarized light through the retardation film is incident to the liquid crystal cell.
이와 같이 콜레스테릭 액정 컬러필터와 편광막을 함께 사용하면 기존의 흡수형 컬러필터와 선편광막을 사용할 때 보다 2.5배 이상 휘도가 증가하며, 좌우 45도 이상까지 색반전이 발생하지 않는다.As such, when the cholesteric liquid crystal color filter and the polarizing film are used together, the luminance is increased by 2.5 times or more than the conventional absorption type color filter and the linear polarizing film, and color reversal does not occur to the left and right 45 degrees or more.
상술한 바와같이 본 발명은, 필름의 굴절율을 조절하는 방법에 의해 원편광을 선편광으로변환시키는 기능외에 시야각에 따른 색변화를 보상하는 기능을 갖는 λ/4 위상차 필름을 제조하고, 이를 이용하여 넓은 시야각 특성이 요구되는 액정 표시장치에 사용가능한 콜레스테릭 액정 편광막과 컬러필터를 제작하는 효과를 제공한다.As described above, the present invention produces a lambda / 4 phase difference film having a function of compensating for the color change according to the viewing angle in addition to the function of converting the circularly polarized light to linearly polarized light by the method of adjusting the refractive index of the film, The present invention provides an effect of manufacturing a cholesteric liquid crystal polarizing film and a color filter which can be used in a liquid crystal display device requiring viewing angle characteristics.
Claims (8)
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| Application Number | Priority Date | Filing Date | Title |
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| KR1019980063649A KR20000046921A (en) | 1998-12-31 | 1998-12-31 | Polarization film using cholesteric liquid crystal and liquid crystal display device |
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| KR1019980063649A KR20000046921A (en) | 1998-12-31 | 1998-12-31 | Polarization film using cholesteric liquid crystal and liquid crystal display device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100443900B1 (en) * | 2001-12-24 | 2004-08-09 | 엘지.필립스 엘시디 주식회사 | liquid crystal display devices and manufacturing method of the same |
| KR100475327B1 (en) * | 2000-08-29 | 2005-03-10 | 엔이씨 엘씨디 테크놀로지스, 엘티디. | Reflection liquid crystal display, method for producing the same, and method for driving the same |
| KR20110120718A (en) * | 2010-04-29 | 2011-11-04 | 엘지디스플레이 주식회사 | Polarizing color filter using surface plasmon and liquid crystal display device having the same |
-
1998
- 1998-12-31 KR KR1019980063649A patent/KR20000046921A/en not_active Application Discontinuation
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100475327B1 (en) * | 2000-08-29 | 2005-03-10 | 엔이씨 엘씨디 테크놀로지스, 엘티디. | Reflection liquid crystal display, method for producing the same, and method for driving the same |
| US6894749B2 (en) | 2000-08-29 | 2005-05-17 | Nec Lcd Technologies, Ltd. | Reflection liquid crystal display |
| US7006180B2 (en) | 2000-08-29 | 2006-02-28 | Nec Corporation | Method for producing a reflection liquid crystal display |
| US7106402B2 (en) | 2000-08-29 | 2006-09-12 | Nec Corporation | Method for driving a reflection liquid crystal display wherein the liquid crystal display having particular cholesteric color filters |
| KR100443900B1 (en) * | 2001-12-24 | 2004-08-09 | 엘지.필립스 엘시디 주식회사 | liquid crystal display devices and manufacturing method of the same |
| KR20110120718A (en) * | 2010-04-29 | 2011-11-04 | 엘지디스플레이 주식회사 | Polarizing color filter using surface plasmon and liquid crystal display device having the same |
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