JP5602220B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device capable of ensuring a wide viewing angle by applying a specific composite configuration polarizing plate set to a blue phase liquid crystal mode.

  A liquid crystal display (LCD) solves various technical problems in the early stages of development, and is now widely used as a popular image display device. These liquid crystal display devices include a liquid crystal display panel that displays an image and a backlight assembly that provides light to the liquid crystal display panel.

  Examples of the liquid crystal used in the liquid crystal display panel include nematic (NEMATIC) liquid crystal, smectic (SMECTIC) liquid crystal, and cholesteric liquid crystal, and nematic liquid crystal is mainly used. The tilt angle of these nematic liquid crystals is adjusted by an electric field formed between the pixel electrode and the common electrode, and the liquid crystal layer adjusts the light transmittance according to the tilt angle of the nematic liquid crystals. Thereby, the brightness of the liquid crystal display panel is determined by the thickness of the liquid crystal layer, that is, the cell gap of the liquid crystal display panel and the anisotropic refractive index of the liquid crystal.

  In order to overcome the problem of the anisotropic refractive index that induces the dependence of the cell gap and the viewing angle, a liquid crystal display panel having a blue phase liquid crystal has been proposed [US Pat. No. 4,767,149. ]. Since the blue phase liquid crystal has a characteristic that the anisotropic refractive index changes isotropic depending on the magnitude of the applied voltage, the viewing angle and the response speed of the liquid crystal display panel can be improved.

  On the other hand, when implementing the blue phase liquid crystal in normal black, apply the in-plane-switching (IPS) liquid crystal display pixel electrode, common electrode, and composite configuration polarizing plate, which is easy to secure a wide viewing angle. It is common to do this [Republic of Korea No. 2008-67041].

  The in-plane switching-type liquid crystal display device composite configuration polarizing plate is located in both of the liquid crystal cells, includes an isotropic protective film between one liquid crystal cell and the polarizer, and the other liquid crystal cell and the polarizer. Two compensation layers or thickness-oriented films (or three-dimensional retardation films) having different optical characteristics are located between the two.

  However, since two compensation layers having different optical properties are used in the composite configuration polarizing plate, the unit price is higher than that of the conventional liquid crystal display device using other liquid crystal modes, and not only thinning is difficult, The thickness of both liquid crystal cells varies, and there is a high possibility of bending due to changes in temperature and humidity. In particular, a thickness-oriented film has a problem that its cost is very high because a shrinking process in which the shrink film is applied at the time of manufacture is always required.

  Therefore, there is an urgent need for a liquid crystal display device for blue phase liquid crystal that can be realized in a wide viewing angle equal to or greater than that of the in-plane switching type liquid crystal display device, but has a simple structure and low cost, and is easy to mass-produce. It is a fact that has been.

  The present invention is simple and easy in structure and can be mass-produced, and a composite viewing polarizing plate set and the above-described composite polarizing plate set can be applied to easily secure a wide viewing angle particularly among conventional liquid crystal display devices. It is intended to present a blue phase liquid crystal mode liquid crystal display device that can realize a wide viewing angle equal to or greater than that of the in-plane switching liquid crystal display device and is excellent in price competitiveness.

The present invention includes a first composite constituent polarizing plate and a second composite constituent polarizing plate, each of the first composite constituent polarizing plate and the second composite constituent polarizing plate comprising a retardation film, a polarizer and a protective film, 1 The retardation film of a composite polarizing plate has a front retardation value (R0) of 50 to 150 nm, a refractive index ratio (NZ) of −6.0 to −0.1, and a slow axis adjacent thereto. Arranged so as to be parallel to the absorption axis of the polarizer, the retardation film of the second composite configuration polarizing plate has a front retardation value (R0) of 0 to 10 nm and a thickness direction retardation (Rth) of 80 to 310 nm. The composite structure polarizing plate set is a liquid crystal display device including an upper polarizing plate and a lower polarizing plate in a blue phase liquid crystal mode .

  The present invention is a composite configuration polarizing plate set that is advantageous for thinning because of its simple structure, and that can be mass-produced because the manufacturing process is easy. In particular, it is possible to realize a wide viewing angle that is equal to or greater than that of the in-plane switching type liquid crystal display device in which it is easy to ensure a wide viewing angle.

FIG. 1 is a perspective view showing the structure of a liquid crystal display device according to the present invention. FIG. 2 is a schematic diagram for explaining the refractive index of the retardation film according to the present invention. FIG. 3 is a schematic diagram showing the MD direction in the manufacturing process for explaining the stretching direction of the retardation film and the polarizing plate according to the present invention. FIG. 4 is a schematic diagram for explaining the expression by θ and φ in the coordinate system of the present invention. FIG. 5 is a graph showing the full-wavelength wavelength dispersibility of the second retardation film used in Example 1. FIG. 6 is a graph showing the full-wavelength wavelength dispersibility of the first retardation film used in Example 1. FIG. 7 shows the result of simulating the transmittance from all viewing angles of Example 1 according to the present invention. FIG. 8 shows a change in the polarization state of the light emitted in the direction of the inclined surface (θ = 60 °, φ = 45 °) on the Poincare sphere (Poincare Sphere) in Example 1 of the present invention. FIG. 9 shows the result of simulating the transmittance from all viewing angles when the composite polarizing plate set for in-plane switching type liquid crystal display device is applied to the liquid crystal mode of the present invention. FIG. 10 shows the result of simulating the transmittance from all viewing angles of the second embodiment according to the present invention. FIG. 11 shows a change in the polarization state of the light emitted in the direction of the inclined surface (θ = 60 °, φ = 45 °) on the Poincare sphere (Poincare Sphere) in Example 2 of the present invention. FIG. 12 shows the result of simulating the transmittance from all viewing angles of Example 3 according to the present invention. FIG. 13 shows the change in the polarization state of light emitted in the direction of the inclined surface (θ = 60 °, φ = 45 °) on the Poincare sphere (Poincare Sphere) in Example 3 of the present invention. FIG. 14 shows the result of simulating the transmittance from all viewing angles in Example 4 according to the present invention. FIG. 15 shows a change in the polarization state of light emitted in the direction of the inclined surface (θ = 60 °, φ = 45 °) on the Poincare sphere (Poincare Sphere) in Example 4 of the present invention. FIG. 16 shows the result of simulating the transmittance from all viewing angles of the fifth embodiment according to the present invention. FIG. 17 shows the change in the polarization state of the light emitted in the direction of the inclined surface (θ = 60 °, φ = 45 °) on the Poincare sphere (Poincare Sphere) in Example 5 of the present invention. FIG. 18 shows the result of simulating the transmittance from all viewing angles in Example 6 according to the present invention. FIG. 19 shows the change in the polarization state of the light emitted in the direction of the inclined surface (θ = 60 °, φ = 45 °) on the Poincare sphere (Poincare Sphere) in Example 6 of the present invention. FIG. 20 shows the result of simulating the transmittance from all viewing angles of Comparative Example 1 of the present invention. FIG. 21 shows the result of simulating the transmittance from all viewing angles of Comparative Example 2 of the present invention. FIG. 22 shows the result of simulating the transmittance from all viewing angles of Comparative Example 3 of the present invention. FIG. 23 shows the result of simulating the transmittance from all viewing angles of Comparative Example 4 of the present invention. FIG. 24 shows the result of simulating the transmittance from all viewing angles of Comparative Example 5 of the present invention. FIG. 25 is a result of simulating the transmittance from all viewing angles of Comparative Example 6 of the present invention.

  The present invention relates to a composite configuration polarizing plate set including a first composite configuration polarizing plate and a second composite configuration polarizing plate in which retardation films having specific optical characteristics are laminated. Specifically, the first composite constituent polarizing plate and the second composite constituent polarizing plate of the composite constituent polarizing plate set are each composed of a retardation film, a polarizer and a protective film.

  The retardation film of the first composite configuration polarizing plate has a front retardation value (R0) of 50 to 150 nm, a refractive index ratio (NZ) of −6.0 to −0.1, and a second composite configuration polarization. A plate retardation film having a front retardation value (R0) of 0 to 10 nm and a thickness direction retardation (Rth) of 80 to 310 nm is used. At this time, the retardation film of the first composite configuration polarizing plate is arranged so that the slow axis is parallel to the absorption axis of the adjacent polarizer.

  In the present invention, the optical properties of the retardation film are defined by the following formulas 1 to 3 for all wavelengths in the visible light region.

When there is no mention with respect to the wavelength of the light source, the optical characteristic is for light having a wavelength of 589 nm. Here, Nx is the refractive index in the axial direction where the refractive index is maximum in the in-plane direction, Ny is the refractive index in the in-plane direction and perpendicular to Nx, and Nz is the refractive index in the thickness direction. They are shown in FIG. 2 as described below.
[Equation 1]
Rth = [(Nx + Ny) / 2−Nz] × d
(Here, Nx and Ny are in-plane refractive indexes and Nx ≧ Ny, Nz is the refractive index of light vibrating in the thickness direction of the film, and d is the thickness of the film)
[Equation 2]
R0 = (Nx−Ny) × d
(Here, Nx and Ny are in-plane refractive indexes of the retardation film, d indicates the thickness of the film, and Nx ≧ Ny)
[Equation 3]
NZ = (Nx-Nz) / (Nx-Ny) = Rth / R0 + 0.5
(Nx and Ny are in-plane refractive indexes and Nx ≧ Ny, Nz is the refractive index of light vibrating in the thickness direction of the film, and d is the thickness of the film.)

  In the present specification, the Rth is a retardation in the thickness direction, which indicates a difference from the in-plane average refractive index in the thickness direction, and is a reference value that cannot be said to be a substantial retardation, and the R0 Is a front phase difference, which is a substantial phase difference when light passes through the film in the normal direction (vertical direction).

  Moreover, NZ is a refractive index ratio and can classify | categorize the kind of plate of retardation film. The type of retardation film plate is such that no phase difference occurs. When the optical axis, which is the optical path in the film, is in the in-plane direction of the film, the A plate is used. When there are two C-plates and optical axes, they are called biaxial plates.

  Specifically, when NZ = 1, the refractive index satisfies the relationship of Nx> Ny = Nz and is called “POSITIVE A PLATE”, and when 1 <NZ, the refractive index is Nx>. Ny> Nz is satisfied, which is referred to as “NEGATIVE BIAXIAL A PLATE”. When 0 <NZ <1, the refractive index has a relationship of Nx> Nz> Ny, and “Z axis When NZ = 0, the refractive index has a relationship of Nx = Nz> Ny, and is called “Negative A Plate”. When NZ <0, the refractive index is refracted. The refractive index has a relationship of Nz> Nx> Ny and is called “POSITIVE BIAXIAL A PLATE”. When NZ = ∞, the refractive index is Nx = N y> Nz, which is referred to as “Negative C Plate”. When NZ = −∞, the refractive index has a relationship of Nz> Nx = Ny, and “positive C plate ( "POSITIVE C PLATE)".

  However, it is not possible in the actual process to make A and C plates that perfectly match the above theoretical definition. Therefore, in a general process, in the case of the A plate, an approximate range of the refractive index ratio is set, and in the case of the C plate, by setting a predetermined value within the range of the front phase difference, the A plate and the C plate Is divided. The setting of this predetermined value is limited in application to all other materials having different refractive indices depending on the stretching. Therefore, the retardation film included in the first and second composite polarizing plates of the present invention is not the type of plate (polarizing plate) due to refractive index anisotropy, but NZ, RO, Rth, etc., which are optical characteristics of the plate Is shown as a numerical value.

  These retardation films are given a phase difference by stretching. Among them, a film having a refractive index increased in the stretching direction has a “positive (+) refractive index characteristic” and is in the stretching direction. A film having a reduced refractive index has “negative (−) refractive index characteristics”. Retardation films having positive (+) refractive index characteristics include cellulose triacetate (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC ), Polysulfone (PSF) and polymethyl methacrylate (PMMA), and a retardation film having a negative (−) refractive index characteristic is specifically a modified polystyrene ( PS) or modified polycarbonate (PC).

  In addition, the stretching method for imparting optical properties to the retardation film is divided into fixed-end stretching and free-end stretching. Here, the fixed-end stretching is a method of fixing a length other than the stretching direction while stretching the film. The free end stretching is a method of giving a degree of freedom to a direction other than the stretching direction while stretching the film. Generally, when a film is stretched, directions other than the stretching direction shrink, but the Z-axis oriented film requires a specific shrinking process in addition to stretching.

  FIG. 3 shows the direction of the rolled raw material film. The unrolled direction of the rolled film is called the MD (Machine Direction) direction, and the direction perpendicular to this is TD (transverse). Direction: This is referred to as a “Transverse Direction” direction. At this time, in the process, stretching in the MD direction is referred to as free end stretching, and stretching in the TD direction is referred to as fixed end stretching.

  When only the primary process is applied and the types of NZ and plate are arranged by the stretching method, the positive A plate can be produced by stretching a film having a positive (+) refractive index characteristic at the free end, and negative A biaxial A-plate can be produced by stretching a film having a positive (+) refractive index characteristic at a fixed end, and a Z-axis oriented film can have a positive (+) refractive index characteristic or a negative (-) refractive index characteristic. A film having a refractive index characteristic can be manufactured by stretching the free end and then shrinking the fixed end, and the negative A plate can be manufactured by stretching a film having a negative (−) refractive index characteristic by free end stretching. The positive biaxial A-plate can be manufactured by stretching a film having negative (−) refractive index characteristics at a fixed end.

  By applying an additional process other than the above stretching method, the direction of the slow axis (Slow Axis), the phase difference value, and the value of NZ can be controlled. This additional process is generally applied in this field. There is no particular limitation as long as it is a process.

  The composite configuration polarizing plate set according to the present invention includes a first composite configuration polarizing plate and a second composite configuration polarizing plate each including a retardation film, a polarizer, and a protective film.

  The retardation film of the first composite polarizing plate uses a film having a front retardation value (R0) of 50 to 150 nm and a refractive index ratio (NZ) of −6.0 to −0.1. However, the front retardation value (R0) increases under the conditions of the present invention, and the refractive index ratio decreases as the absolute value thereof decreases, so that the dispersibility of the polarization state decreases and can be easily used as the retardation film of the present invention. The front phase difference value (R0) can be used in an appropriate combination depending on the refractive index ratio. If the refractive index ratio (NZ) is less than −6.0, it depends on the wavelength after passing through the liquid crystal display device having the optimum viewing angle effect composed of the first retardation film, the liquid crystal cell, and the second retardation film. Since the dispersibility referred to as the polarization state difference becomes very large, even if compensation for the reference wavelength is performed, compensation for other wavelengths cannot be achieved. Therefore, it is difficult to achieve the effect of the present invention, and the refractive index ratio (NZ) is − If it exceeds 0.1, the slow axis of the retardation film and the MD direction are different, and there is a problem that it is not easy to apply to a roll-to-roll process.

  In addition, it is the minimum for manufacturing a retardation film having a uniform retardation value (within ± 5 nm of the target value) and a retardation angle (± 0.5 °) that are generally applied to current liquid crystal display devices. The phase difference value must be maintained at 40 nm or more, and it is better to maintain the minimum value of the phase difference at 50 nm or more in the actual process.

  Preferably, it is better to use one having a front phase difference value (R0) of 80 to 150 nm and a refractive index ratio (NZ) of −2.0 to −0.1. Is within the range of possible mass production. The front phase difference value (R0) is determined by the refractive index ratio (NZ) value so that it can be compensated by the second phase difference layer. Therefore, the front phase difference (R0) of NZ-2.0 to -0.1 is determined. The range is 80-150 nm. More preferably, it is better to use one having a front retardation value (R0) of 100 to 150 nm and a refractive index ratio (NZ) of −1.0 to −0.1. The TD uniaxial stretching process on the actual process is in an easy range. The front phase difference value (R0) is determined by the refractive index ratio (NZ) value so as to be compensated by the second phase difference layer. Therefore, the front phase difference (R0) of NZ-1.0 to -0.1 is determined. The range is 100-150 nm. At this time, since the TD uniaxial stretching process is simpler than the biaxial stretching, the production cost can be easily reduced.

  Such a retardation film of the first composite configuration polarizing plate is disposed so that the slow axis is parallel to the absorption axis of the adjacent polarizer.

  The retardation film of the second composite constituent polarizing plate is one having a front retardation value (R0) of 0 to 10 nm and a thickness direction retardation (Rth) of 80 to 310 nm. Considering the retardation film of the plate and optical characteristics, use a combination that facilitates securing a wide viewing angle.

  The preferred range of the second retardation layer according to the preferred range of the first retardation layer is that the front retardation value (R0) is 0 to 5 nm, the thickness direction retardation (Rth) is 80 to 200 nm, and the first retardation layer is the first retardation layer. The more preferable range of the second retardation layer due to the more preferable range of the retardation layer is that the front retardation value (R0) is 0 to 3 nm, and the thickness direction retardation (Rth) is preferably maintained at 80 to 140 nm. These ranges are also limited in consideration of the ease of the manufacturing process as well as the optical characteristics like the retardation film of the first composite configuration polarizing plate, and the manufacturing process can be applied by the casting method or the complete biaxial stretching method. Easy.

  Since the retardation film of such a 2nd composite structure polarizing plate does not have a slow axis, it is arrange | positioned irrespective of the absorption axis of an adjacent polarizer especially.

  In general, a retardation film has different retardation values depending on the incident wavelength. Usually, a retardation film having a large retardation value at a short wavelength and a small retardation value at a long wavelength is referred to as a retardation film having positive wavelength dispersion. A film having a small retardation value at a short wavelength and a large retardation value at a long wavelength is referred to as a retardation film having reverse wavelength dispersion. All of the present invention can be used regardless of the dispersibility of the retardation film.

  In the present invention, the dispersibility of the retardation film is represented by a ratio of a retardation value for a light source of 780 nm generally used in this field and a retardation value for a light source of 380 nm. For reference, in the case of a retardation film having perfect reverse wavelength dispersion that can be in the same polarization state for all wavelengths, a value of [R0 (380 nm) / R0 (780 nm)] = 0.4872. Have

  Each of the polarizers of the first and second composite constituent polarizing plates has a polyvinyl alcohol (PVA) layer, which is a polarizer provided with a polarizing function through processes such as stretching and dyeing, and the first composite constituent polarizing plate. Each of the polyvinyl alcohol (PVA) layer and the polyvinyl alcohol (PVA) layer of the second composite configuration polarizing plate is provided with a protective film on the side facing the liquid crystal cell. The first and second composite configuration polarizing plates can be manufactured by a process generally applied in this field. Specifically, a composite roll-to-roll process, a sheet-to-roll process, and the like. A sheet (Sheet to Sheet) process can be applied. It is preferable to apply a roll-to-roll process in consideration of yield and manufacturing process efficiency. In particular, the direction of the absorption axis of the PVA polarizer is always fixed in the MD direction. Therefore, this application is effective.

  In this configuration, the protective film of the first and second composite polarizing plates has no particular limitation on the refractive index in the present invention because the optical characteristics due to the refractive index difference do not affect the viewing angle. As a material for the protective film of the first and second composite polarizing plates, those commonly used in the art can be applied. Specifically, cellulose triacetate (TAC), cycloolefin polymer (COP) ), Cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA) can be used. .

  The present invention also includes a blue composite liquid crystal and a first composite constituent polarizer and a second composite constituent polarizer in which retardation films having specific optical characteristics are disposed on the upper and lower polarizers of the liquid crystal, respectively. The present invention relates to a liquid crystal display device including a composite configuration polarizing plate set. In the liquid crystal display device, the first composite constituent polarizing plate is arranged as the upper polarizing plate, the second composite constituent polarizing plate is arranged as the lower polarizing plate, or the second composite constituent polarizing plate is arranged as the upper polarizing plate. A 1st composite structure polarizing plate can be arrange | positioned as a side polarizing plate. The absorption axis of the first composite constituent polarizing plate is orthogonal to the absorption axis of the second composite constituent polarizing plate.

  The blue phase liquid crystal of the present invention has a refractive index that changes from anisotropy to isotropic depending on whether or not an electric field is applied. These liquid crystals are composed of a cylindrical array in which molecules are twisted and aligned in a three-dimensional spiral shape. Such an alignment structure is called a double twist cylinder (hereinafter referred to as DTC) structure. The blue phase liquid crystal is arranged so as to be twisted further outward from the central axis of the DTC. That is, the blue phase liquid crystal is arranged so as to be twisted along two twist axes that are orthogonal to each other in the DTC, and has directionality in the DTC with reference to the central axis of the DTC.

  Such a blue phase liquid crystal has a first blue phase, a second blue phase, and a third blue phase, and the arrangement structure changes depending on the type of the blue phase in the DTC. The first blue phase is arranged in a body-centered cubic structure with a DTC having a lattice structure, and the second blue phase is arranged in a simple cubic structure with a DTC. Since the DTC is arranged in a lattice structure in the blue phase, disclination occurs at a portion where three adjacent DTCs are in contact. The disclination is an irregularly arranged portion because the liquid crystal does not have a regular directionality, and forms a disclination line.

  The blue phase liquid crystal has an anisotropic refractive index that changes in proportion to the square of the applied voltage depending on the magnitude of the applied voltage. When an electric field is applied to an isotropic polar substance, the optical effect in which the refractive index is proportional to the square of the applied voltage is called the Kerr effect (KERR EFFECT), and the liquid crystal display device uses the Kerr effect of the blue phase liquid crystal to display images. Since it is displayed, the response speed is improved.

  In addition, the refractive index of the blue phase liquid crystal is determined for each region where an electric field is formed. If the region where the electric field is formed is formed uniformly, the display characteristics of the liquid crystal display device can be improved because the luminance is uniform regardless of the cell gap uniformity.

  The liquid crystal display device configured with the optical conditions of the present invention satisfies a compensation relationship in which the maximum transmittance from all viewing angles in the dark state is 0.05% or less, preferably 0.02% or less. The brightest liquid crystal display device currently in mass production has a front luminance of about 10000 nits using the vertical alignment mode (VA Mode), and a brightness of about 10000 nits × cos 60 ° at a viewing angle of 60 ° inclined surface. Yes, 0.05% for this is 2.5 nits. Therefore, the present invention tries to realize the transmittance from all viewing angles equal to or higher than that of the liquid crystal display device to which the vertical alignment mode is applied.

  FIG. 1 is a perspective view showing a basic structure of a liquid crystal display device for a blue phase liquid crystal according to the present invention, which will be described as follows.

  The liquid crystal display device for blue phase liquid crystal according to the present invention includes a second protective film 13, a second polarizer 11, a second retardation film 14, a blue phase liquid crystal cell 30, a first phase from the backlight unit 40 side. The retardation film 24, the first polarizer 21, and the first protective film 23 are laminated in this order. When viewed from the viewing side, the absorption axis 12 of the first polarizer 21 and the absorption axis 22 of the second polarizer 11 are orthogonal to each other, and the slow axis of the first retardation film and the absorption of the first polarizer. The axes are parallel. Specifically, FIG. 1A shows a case where the first composite configuration polarizing plate is arranged as an upper polarizing plate, and the slow axis 25 of the first retardation film 24 and the absorption axis 22 of the first polarizer 21 are as follows. FIG. 1B shows a configuration in which the first composite configuration polarizing plate is arranged as a lower polarizing plate. The slow axis 25 of the first retardation film 24 and the first polarizer 21 are arranged in parallel. The absorption axis 22 is configured in parallel.

  The first composite configuration polarizing plate 20 and the second composite configuration polarizing plate 10 of the present invention are manufactured by applying a roll-to-roll method that is easy to mass-produce. FIG. 3 is a schematic diagram illustrating the MD direction in the roll-to-roll manufacturing process, and the configuration of FIG. 1A will be specifically described below with reference to this.

  The first composite constituent polarizing plate 20 and the second composite constituent polarizing plate 10 are made of a combination of various optical films, and each optical film exists in a rolled state before being bonded to the composite constituent polarizing plate. To do. The direction in which the film is unrolled or wound in the wound state is referred to as the MD (Machine Direction) direction. In the case of the second composite polarizing plate 10, the direction of the second protective film 13 and the second retardation film 14 does not affect the optical performance, so that roll-to-roll production is possible. In the case of the first composite configuration polarizing plate 20, there is no relation to the direction of the first protective film 23, and only the MD direction of the first polarizer 21 and the first retardation film 24 is matched to roll-to-roll. (Roll-to-roll) production is possible.

  Further, when the absorption axis 12 of the second polarizer 11 close to the backlight unit is in the vertical direction, the light passing through the second composite constituent polarizing plate 10 is polarized in the horizontal direction, which is applied with the panel voltage. When the light passes through the liquid crystal cell and becomes bright, the light passes in the vertical direction and passes through the viewing-side first composite polarizing plate 20 whose absorption axis is in the horizontal direction. At this time, a person wearing polarized sunglasses whose absorption axis is in the horizontal direction (the absorption axis of polarized sunglasses is in the horizontal direction) can also recognize light emitted from the liquid crystal display device from the viewing side. If the absorption axis 12 of the second polarizer 11 close to the backlight unit is in the horizontal direction, there arises a problem that an image cannot be seen by a person wearing polarized sunglasses. In addition, in the case of large liquid crystal display devices, special purpose liquid crystal displays such as for advertisements are used in consideration of the fact that the main visual field of human beings is wider in the horizontal direction than in the vertical direction so that the image can be seen well on the viewer side A general liquid crystal display device excluding the device is manufactured in the form of 4: 3 or 16: 9. Therefore, when viewed from the viewing side, the absorption axis of the second polarizer is vertical and the absorption axis of the first polarizer is parallel.

  The effect of the viewing angle compensation of the present invention can be explained through a Poincare sphere. The Poincare sphere is a very useful method for expressing a change in the polarization state at a specific viewing angle. Therefore, the Poincare sphere follows a specific viewing angle in a liquid crystal display device that displays an image using polarized light. The change of the polarization state when the traveling light passes through the respective optical elements inside the liquid crystal display device can be shown. In the present invention, the “specific viewing angle” is the direction of θ = 60 ° and φ = 45 ° in the semicircular coordinate system shown in FIG. 4, and the wavelength at which humans feel the brightest change in the polarization state of light emitted in this direction. The description will be made based on 550 nm. Specifically, when the surface in the φ direction is rotated by θ toward the viewing side around the front φ + 90 ° axis, the change in polarization state with respect to light emitted from the front direction is shown on the Poincare sphere. is there. On the Poincare sphere, right circularly polarized light is shown when the coordinate of the S3 axis indicates positive (+). Here, right circularly polarized light means that when a horizontal polarization component is Ex and a vertical polarization component is Ey, The phase delay (phase delay) of the Ex component of light with respect to the Ey component is greater than 0 and less than half a wavelength.

  Hereinafter, in the above configuration, the effect of realizing the dark state at all viewing angles when no voltage is applied will be described through examples and comparative examples. The present invention will be more readily understood by the following examples, which are provided by way of illustration only and are not intended to limit the scope of protection claimed by the appended claims. Absent.

Example In the following Example 1 to Example 6 and Comparative Example 1 to Comparative Example 6, the wide viewing angle effect was compared through a simulation using TECH WIZ LCD 1D (Sanai System Co., Korea) as an LCD simulation system. .

Example 1
The actual measurement data of each optical film, liquid crystal cell, and backlight according to the present invention was used for TECH WIZ LCD 1D (Sanai System Co., Korea) together with the laminated structure as shown in FIG. The structure of FIG. 1A will be specifically described below.

  From the backlight unit 40 side, the second protective film 13, the second polarizer 11, the second retardation film 14, the blue phase liquid crystal cell 30, the first retardation film 24, the first polarizer 21, the first It is composed of a protective film 23, and the absorption axis 12 of the second polarizer 11 is in the vertical direction when viewed from the viewing side, and the absorption axis 22 of the first polarizer 21 is in the horizontal direction when viewed from the viewing side. The absorption axis 12 of the first polarizer 21 and the absorption axis 22 of the second polarizer 11 are orthogonal to each other, and the slow axis 25 of the first retardation film 24 and the absorption axis 22 of the first polarizer 21 are parallel.

  A liquid crystal cell has a refractive index isotropic property when no electric field is applied, and the refractive index increases in the direction in which the electric field is applied when an electric field is applied. A prototype of such a liquid crystal mode is a blue phase ( Blue Phase) liquid crystal (Samson Electronics, SID2008) was used. When this is applied, the liquid crystal cell manufacturing process is simplified because initial liquid crystal alignment is not required.

  On the other hand, each optical film and backlight used in Example 1 of the present invention has the following optical properties.

First, the first polarizer 11 and the second polarizer 21 are provided with a polarizer function by dyeing stretched PVA with iodine, and the polarization performance of such a polarizer is in the visible light region of 370 to 780 nm. Then, the polarization degree of visibility is 99.9% or more, and the single transmittance of visibility is 41% or more. The visibility polarization degree and the visibility single transmittance are TD (λ) as the transmittance of the transmission axis according to the wavelength, MD (λ) as the transmittance of the absorption axis according to the wavelength, and the visibility defined in JIS Z 8701: 1999. Compensation value
Is defined by the following mathematical formulas 4 to 8. Here, S (λ) is a light source spectrum, and the light source is a C light source.
[Equation 4]
[Equation 5]
[Equation 6]
[Equation 7]
[Equation 8]

  Regarding the optical characteristics generated by the internal refractive index difference depending on the direction of each film, the front retardation value (R0) of the lower second retardation film 14 is 2.0 nm at a wavelength of 589.3 nm, and the thickness direction retardation is A film having a value (Rth) of 90 nm was used, and the upper first retardation film 24 having a front retardation value (R0) of 140 nm and a refractive index ratio (NZ) of −0.11 was used.

  As for the wavelength dispersion of the second retardation film 14, the front phase difference (wavelength, 380 nm) / front phase difference (wavelength, 780 nm) = [R0 (380 nm) / R0 (780 nm)] is 0.862. The wavelength dispersion of the first retardation film 24 is a front phase difference (wavelength, 380 nm) / front phase difference (wavelength, 780 nm) = [R0 (380 nm) / R0 ( 780 nm)] is 1.197, indicating the total wavelength chromatic dispersion as shown in FIG.

  Cellulose triacetate having optical characteristics with a thickness direction retardation value (Rth) of 50 nm with respect to incident light of 589.3 nm as the first protective film 13 and the second protective film 23 outside the first and second polarizers ( TAC) was used. As the backlight unit, backlight measured spectrum data mounted on a Samsung Electronics 46-inch liquid crystal TV PAVV (LTA460HR0) was used.

  FIG. 7 shows the result of simulation of the transmittance of light from all directions after laminating the above optical elements as shown in FIG. The change in the polarization state at a wavelength of 550 nm at the reference viewing angle (θ = 60 °, φ = 45 °) of the present invention is shown in FIG. 8, and the polarization state when passing through the second polarizer 11 on the Poincare sphere (Poincare Sphere). 1, the polarization state when passing through the second retardation film 14, the polarization state when passing through the liquid crystal cell is 2, and the polarization state when passing through the first retardation film 24 is 3.

  FIG. 7 shows the transmittance distribution from all viewing angles when dark (BLACK) is displayed on the screen. The range on the scale is from 0% to 0.05% of the transmittance. The portion where the transmittance exceeds 0.05% is shown in red, and the portion where the transmittance is low is shown in blue. At this time, it was confirmed that the wider the blue range at the center, the wider the viewing angle, and the wide viewing angle can be secured.

  Thus, from FIG. 9 which showed the transmittance | permeability from all the viewing angles when the polarizing plate for liquid crystal display devices in an in-plane switching system (I Plus Pol structure, Toyu Finechem, Korea) is applied to the liquid crystal mode of this invention. It was confirmed that there was an excellent viewing angle compensation effect.

Example 2
Although comprised similarly to the said Example 1, as for the 2nd phase difference film 14 at 589.3 nm, a front phase difference value (R0) is 2.0 nm, and thickness direction phase difference value (Rth) is 300 nm. A first phase difference film 24 having a front phase difference value (R0) of 55 nm and a refractive index ratio (NZ) of −5.9 is used to form a liquid crystal display device for blue phase liquid crystal. Manufactured.

  FIG. 10 shows the transmittance distribution from all viewing angles when dark (BLACK) is displayed on the screen, and the range on the scale is 0% to 0.05%, indicating darkness. When the transmittance exceeds 0.05%, the portion where the transmittance is high is shown in red, and the portion where the transmittance is low is shown in blue. At this time, it was confirmed that the wider the blue range at the center, the wider the viewing angle, and the wide viewing angle can be secured.

  Further, the in-plane switching type liquid crystal display polarizing plate (I Plus Pol configuration, Toyu Finechem, Korea) is equivalent to FIG. 9 showing the transmittance from all viewing angles when applied to the liquid crystal mode of the present invention. It was confirmed that there was a viewing angle compensation effect.

  FIG. 11 shows the optical compensation principle of the second embodiment on the Poincare sphere, and FIG. 8 shows the optical compensation principle of the first embodiment on the Poincare sphere, and two paths on the Poincare sphere. It can be seen that there are an infinite number of paths that can be compensated between. In addition, the optical properties of the first retardation film 24 and the second retardation film 14 are not improved, but the optical properties of the first retardation film 24 are determined optimally by the optical properties of the second retardation film 14. I understand.

Example 3
Although it is comprised similarly to the said Example 1, as shown in FIG.1 (b), the 1st protective film 23, the 1st polarizer 21, the 1st phase difference film 24, the blue phase (blue phase) from the backlight unit 40 side. ) The liquid crystal cell 30, the second retardation film 14, the second polarizer 11, and the second protective film 13 were arranged. The absorption axis 22 of the first polarizer 21 is in the vertical direction when viewed from the viewing side, and the absorption axis 12 of the second polarizer 11 is in the horizontal direction when viewed from the viewing side. The absorption axis 22 of the first polarizer 21 and the absorption axis 12 of the second polarizer 11 are configured to be orthogonal to each other, and the slow axis 25 of the first retardation film 24 and the absorption axis 22 of the first polarizer 21 are parallel to each other. Configured.

  The optical characteristics generated by the internal refractive index difference depending on the direction of each film are a wavelength of 589.3 nm, the second retardation film 14 has a front retardation value (R0) of 2.0 nm, and a thickness direction retardation value (Rth). Is used, and the first retardation film 24 has a front retardation value (R0) of 140 nm and a refractive index ratio (NZ) of −0.11.

  The wavelength dispersion of the second retardation film 14 is 0.862, which is a front retardation (wavelength 380 nm) / front retardation (wavelength 780 nm) = [R0 (380 nm) / R0 (780 nm)], as shown in FIG. The wavelength dispersion of the first retardation film 24 is 1 for front retardation (wavelength 380 nm) / front retardation (wavelength 780 nm) = [R0 (380 nm) / R0 (780 nm)]. .197, indicating the chromatic dispersion of all wavelengths as shown in FIG.

  As a result of laminating the above optical components as shown in FIG. 1B and carrying out transmittance simulations from all viewing angles, results as shown in FIG. 12 were obtained. The change in the polarization state at a wavelength of 550 nm at the reference viewing angle (θ = 60 °, φ = 45 °) of the present invention is shown in FIG. 13, and the polarization state when passing through the first polarizer 21 on the Poincare sphere (Poincare Sphere). 1, the polarization state when passing through the first retardation film 24, the polarization state when passing through the liquid crystal cell is 2, and the polarization state when passing through the second retardation film 14 is 3.

  FIG. 12 shows the transmittance distribution from all viewing angles when dark (BLACK) is displayed on the screen, and the range on the scale is 0% to 0.05%, indicating darkness. When the transmittance exceeds 0.05%, the portion where the transmittance is high is shown in red, and the portion where the transmittance is low is shown in blue. At this time, it was confirmed that the wider the central blue range, the wider the viewing angle, and the wide viewing angle could be secured.

  Thus, from FIG. 9 which showed the transmittance | permeability from all the viewing angles when the polarizing plate for liquid crystal display devices in an in-plane switching system (I Plus Pol structure, Toyu Finechem, Korea) is applied to the liquid crystal mode of this invention. It was also confirmed that the viewing angle compensation effect was excellent.

Example 4
1B, the second retardation film 14 has a front retardation value (R0) of 2.0 nm and a thickness of 589.3 nm. A film having a directional retardation value (Rth) of 300 nm is used, and a first retardation film 24 having a front retardation value (R0) of 55 nm and a refractive index ratio (NZ) of −5.9 is disposed. A liquid crystal display device for a blue phase liquid crystal was manufactured.

  FIG. 14 shows the transmittance distribution from all viewing angles when dark (BLACK) is displayed on the screen, and it was confirmed that a wide viewing angle can be secured. FIG. 15 shows changes in the polarization state at a wavelength of 550 nm at the reference viewing angle (θ = 60 °, φ = 45 °) of the present invention.

Example 5
Although it is comprised similarly to the said Example 1, the 2nd phase difference film 14 is 58 nm, front retardation value (R0) is 2.0 nm, and thickness direction phase difference value (Rth) is 141 nm. A first phase difference film 24 having a front phase difference value (R0) of 99 nm and a refractive index ratio (NZ) of -1.0 is used to manufacture a liquid crystal display device for blue phase liquid crystal. did.

  FIG. 16 shows the transmittance from all viewing angles of the above configuration, and FIG. 17 shows changes in the polarization state at a wavelength of 550 nm at the reference viewing angles (θ = 60 °, φ = 45 °) of the present invention.

Example 6
Although it is comprised similarly to the said Example 1, it is 589.3 nm, the 2nd phase difference film 14 has a front phase difference value (R0) of 2.0 nm, and a thickness direction phase difference value (Rth) is 110 nm. A first phase difference film 24 having a front phase difference value (R0) of 110 nm and a refractive index ratio (NZ) of −0.5 is manufactured to produce a liquid crystal display device for blue phase liquid crystal did.

  The transmittance from all viewing angles of the above configuration is shown in FIG. 18, and FIG. 19 shows changes in the polarization state at a wavelength of 550 nm at the reference viewing angle (θ = 60 °, φ = 45 °) of the present invention. .

Comparative Example 1
Although it is comprised similarly to the said Example 1, the optical characteristic of the 2nd phase difference film 14 and the 1st phase difference film 24 is general TAC (front phase difference value (R0) = 2.0 nm, thickness direction phase difference value ( Rth) = 52 nm) was placed to manufacture a liquid crystal display device for blue phase liquid crystal.

  The results of the transmittance simulation from all viewing angles of the liquid crystal display device are shown in FIG. 20, and since the inclined surface transmittance is high in the dark (BLACK) state as shown in FIG. It could be confirmed.

Comparative Example 2
The first retardation film 14 and the second retardation film 24 are configured in the same manner as in the first embodiment. ) = 1 nm and thickness direction retardation value (Rth) = 2 nm) were arranged to produce a liquid crystal display device for blue phase liquid crystal.

  The results of the transmittance simulation from all the viewing angles of the liquid crystal display device are shown in FIG. 21 and, as shown in FIG. Was confirmed.

Comparative Example 3
Although configured in the same manner as in Example 1, a blue phase liquid crystal display device was manufactured by arranging the slow axis 25 of the first retardation film 24 and the absorption axis 22 of the first polarizer 21 so as to be orthogonal to each other.

  The results of the transmittance simulation from all viewing angles of the liquid crystal display device are shown in FIG. 22. As shown in FIG. 22, the viewing angle is narrow because the inclined surface has high transmittance in the dark state. Was confirmed.

Comparative Example 4
Although it is comprised similarly to the said Example 1, the 2nd phase difference film 14 is 58 nm, front phase difference value (R0) is 2.0 nm, and thickness direction phase difference value (Rth) is 50 nm. A first phase difference film 24 having a front phase difference value (R0) of 55 nm and a refractive index ratio (NZ) of -2.1 is disposed to manufacture a liquid crystal display device for blue phase liquid crystal. did.

  The results of the transmittance simulation from all viewing angles of the liquid crystal display device are shown in FIG. 23. As shown in FIG. 23, the viewing angle is narrow because the inclined surface has a high transmittance in the dark (BLACK) state. Was confirmed.

Comparative Example 5
Although it is comprised similarly to the said Example 1, the 2nd phase difference film 14 is 58 nm, front phase difference value (R0) is 2.0 nm, and thickness direction phase difference value (Rth) is 50 nm. A first phase difference film 24 having a front phase difference value (R0) of 55 nm and a refractive index ratio (NZ) of −8 was used to manufacture a liquid crystal display device for blue phase liquid crystal. .

  The results of the transmittance simulation from all the viewing angles of the liquid crystal display device are shown in FIG. 24. As shown in FIG. 24, the viewing angle is narrow because of the high transmittance on the inclined surface in the dark (BLACK) state. Was confirmed.

Comparative Example 6
Although comprised similarly to the said Example 1, the 2nd phase difference film 14 is 58 nm, front retardation value (R0) is 2.0 nm, and thickness direction phase difference value (Rth) is 350 nm. A first phase difference film 24 having a front phase difference value (R0) of 170 nm and a refractive index ratio (NZ) of −0.3 is manufactured to produce a liquid crystal display device for blue phase liquid crystal did.

  The results of the transmittance simulation from all the viewing angles of the liquid crystal display device are shown in FIG. 25. As shown in FIG. 25, the viewing angle is narrow because the inclined surface has high transmittance in the dark state. Was confirmed.

Industrial applicability

  As described above, the liquid crystal display device for blue phase liquid crystal according to the present invention can provide a wide viewing angle and can be applied to a large-screen liquid crystal display device that requires a high optical level.

Claims (8)

Including a first composite configuration polarizing plate and a second composite configuration polarizing plate,
The first composite constituent polarizing plate and the second composite constituent polarizing plate are each composed of a retardation film, a polarizer and a protective film,
The retardation film of the first composite polarizing plate has a front retardation value (R0) of 50 to 150 nm, a refractive index ratio (NZ) of −6.0 to −0.1, and a slow axis adjacent thereto. Arranged parallel to the absorption axis of the polarizer,
The retardation film of the second composite constituent polarizing plate has a front constituent retardation value (R0) of 0 to 10 nm and a thickness direction retardation (Rth) of 80 to 310 nm. A liquid crystal display device comprising a mode upper polarizing plate and a lower polarizing plate. Blue phase liquid crystal mode liquid crystal display device according to claim 1, characterized in that it consists of an array of cylindrical form blue phase liquid crystal molecules are aligned twisted in a three-dimensional spiral. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device satisfies a compensation relationship in which the transmittance in the black mode is 0.05% or less at an inclination angle (θ = 60 °, φ = 45 °). The retardation film of the first composite polarizing plate has a front retardation value (R0) of 80 to 150 nm and a refractive index ratio (NZ) of −2.0 to −0.1. The liquid crystal display device according to claim 1. The retardation film of the first composite polarizing plate has a front retardation value (R0) of 100 to 150 nm and a refractive index ratio (NZ) of −1.0 to −0.1. The liquid crystal display device according to claim 1. The retardation film of the second composite polarizing plate has a front retardation value (R0) of 0 to 5 nm and a thickness direction retardation (Rth) of 80 to 200 nm. The liquid crystal display device according to any one of the above. The retardation film of the second composite-constituting polarizing plate has a front retardation value (R0) of 0 to 3 nm and a thickness direction retardation (Rth) of 80 to 140 nm. The double liquid crystal display device according to any one of the above. The retardation film and the protective film of the first composite constituent polarizing plate and the second composite constituent polarizing plate are, independently of each other, cellulose triacetate (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate. 4. A product produced from a material selected from the group consisting of (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA). The liquid crystal display device according to any one of the above.