KR20100079823A - High-luminance broadband film for lcd - Google Patents

Abstract

PURPOSE: A broadband high luminance film for an LED is provided to keep 80-90% of the polarization value by uniformly reflecting S polarized light. CONSTITUTION: A plurality of birefringence is arranged within material. Luminance is strengthened through the optical interference effect by the selective reflection of the penetration of the p-polarized light and S polarized light. The reflection of S polarized light comes under to the diffuse reflection. In the reflection of S polarized light is uniformly generated in the visible ray entire area. The birefringence suede is perpendicularly arranged about the light source. The polarization value keeps in 80-90% in the visible ray entire area. Thickness of the birefringence suede is 0.3-20 denier. The material has isotropy.

Description

Broadband high brightness film for liquid crystal display {HIGH-LUMINANCE BROADBAND FILM FOR LCD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband high brightness film for liquid crystal display, and more particularly, to a wideband high brightness film for liquid crystal display which enhances luminance through an optical interference effect by transmission of P polarized light and selective reflection of S polarized light. Reflection is diffuse reflection, and the reflection of S-polarized light is generated uniformly in the visible light area, and the polarization degree is maintained at 80 to 90%, which greatly improves the brightness and simultaneously transmits light of any wavelength in the visible light. The present invention relates to a broadband high brightness film for liquid crystal display having an effect.

In information display technology, the display device has occupied the CRT position for more than half a century. However, in the rapidly developing information age, various types of display technologies are required. Among them, flat panel display is expected to become a technology that surpasses CRT in the near future. Already, portable computers, as well as small measuring instruments, have become popular, and existing CRT methods, including various monitors and TVs, are being replaced by flattening.

Flat panel display technology is mainly made up of liquid crystal display (LCD), projection display and plasma display (PDP), which have already secured market in the TV field, and related to field emission display (FED) and electroluminescent display (ELD). With the improvement of technology, it is expected to occupy the field according to each characteristic. LC displays are currently expanding their range of use, including notebooks, personal computer monitors, liquid crystal TVs, automobiles, and airplanes, accounting for about 80% of the flat panel market. have.

Conventional LC displays place liquid crystals and electrode matrices between a pair of light absorbing optical films. In an LC display, the liquid crystal portion has an optical state that is changed accordingly by moving the liquid crystal portion by an electric field generated by applying a voltage to two electrodes. This process displays an image of a 'pixel' carrying information using polarization in a specific direction. For this reason, LC displays include front and back optical films that induce polarization.

The liquid crystal display of such an LC display is not necessarily a high utilization efficiency of light emitted from the backlight. This is because at least 50% of the light emitted from the backlight is absorbed by the rear optical film. Thus, in order to increase the utilization efficiency of backlight light in the liquid crystal display device, a high brightness film for liquid crystal display is provided between the optical cavity and the liquid crystal assembly.

FIG. 1A is a diagram showing the optical principle of a conventional high brightness film for liquid crystal display. Specifically, of the light directed from the optical cavity to the liquid crystal assembly, the P-polarized light is passed through the high-brightness film for the liquid crystal display to the liquid crystal assembly, and the S-polarized light is reflected from the high-brightness film for the liquid crystal display to the optical cavity and then diffused into the optical cavity. The polarization direction of the light is reflected in the randomized state on the reflecting surface, and is then transferred to the LCD display high brightness film. In the end, the S polarization is converted into P polarization that can pass through the polarizer of the liquid crystal assembly, and then passes through the high brightness film for liquid crystal display. After that it is to be delivered to the liquid crystal assembly.

The selective reflection of S-polarized light and the transmission of P-polarized light with respect to the incident light of the high brightness film for liquid crystal display are characterized by the fact that a flat optical layer having anisotropic refractive index and a flat optical layer having an isotropic refractive index are alternately formed in multiple layers (preferably Is achieved by the difference in refractive index between each optical layer in the state of being laminated in tens or more layers, the optical thickness setting of each optical layer and the refractive index change of the optical layer according to the stretching process of the stacked optical layers. That is, the light incident on the high brightness film for liquid crystal display repeats the reflection of S polarization and the transmission of P polarization while passing through each optical layer, and finally, only the P polarization of the incident polarization is transmitted to the liquid crystal assembly. On the other hand, the reflected S-polarized light is reflected in a state in which the polarization state is randomized at the diffuse reflection surface of the optical cavity and is transmitted to the high brightness film for liquid crystal display again. As a result, power loss can be reduced together with the loss of light generated from the light source.

On the other hand, Figure 1b is a graph of the transmittance in the visible light of a conventional laminated high brightness film. Referring to FIG. 1B, it can be seen that the polarization degree exceeds 90% at some wavelengths and the polarization degree is less than 70% at some wavelengths according to the change of wavelength. This means that the polarization degree is changed according to the change of wavelength in visible light, and the degree of increase in luminance at a specific wavelength is changed, resulting in a serious problem of poor visibility. At this time, when the degree of polarization at a particular wavelength is lower than that of other wavelength bands, selective reflection at the wavelength is made less and the light of the wavelength is transmitted through the polarizing film in a non-polarized state, thereby degrading LCD image quality.

Furthermore, the conventional high-brightness film for liquid crystal display is an optical layer between the optical layer that can be optimized for the selective reflection and transmission of the incident polarization by extending the isotropic optical layer and anisotropic optical layer of the plate with different refractive index alternately stacked Since it is manufactured to have thickness and refractive index, the manufacturing process of the high brightness film for liquid crystal displays is complicated. In particular, since each optical layer of the high-brightness film for liquid crystal display has a flat plate structure, the P-polarized light and the S-polarized light must be separated to correspond to the wide range of incident angles of the incident polarization. There is a problem of increasing in number. In addition, due to the structure in which the number of laminated layers of the optical layer is excessively formed, there is a concern that the optical performance is deteriorated due to light loss.

The present invention has been made to solve the above-mentioned problems, an object of the present invention is that the reflection of the S-polarized light is generated uniformly in the visible light region and the polarization degree is maintained at 80 to 90% to significantly improve the brightness and at the same time visible It is to provide a broadband high brightness film for liquid crystal display having the effect of uniformly transmitting light of any wavelength in the light beam.

It is another object of the present invention to provide a broadband high brightness film for liquid crystal display, which is easy to produce and very low in production cost and has an excellent effect of increasing brightness by replacing the conventional laminated luminance enhancing film.

In the broadband high brightness film for liquid crystal display of the present invention for solving the above problems, in the broadband high brightness film for liquid crystal display for enhancing the luminance through the optical interference effect by the transmission of P polarized light and the selective reflection of S polarized light, the S polarized light Is a diffuse reflection, characterized in that the reflection of the S-polarized light occurs uniformly in the visible light region.

The polarization degree of the S-polarized light is maintained at 80 to 90% in the visible light region, and the visible light region is preferably a wavelength of 380 to 780 nm.

The broadband high-brightness film for liquid crystal display includes birefringent islands-in-the-sea yarn in the substrate, preferably, the substrate is isotropic, the island portion of the island-in-the-sea yarn is anisotropic, and the sea portion is isotropic.

The substrate, the island portion and the sea portion are polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS) ), Heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene (ABS), polyurethane (PU) , Polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), Any one or more of urea melanin (UF.MF), unsaturated polyester (UP), silicone (SI), elastomer and cycloolefin polymer can be used.

The refractive index of the substrate and the birefringent island-in-the-sea yarn is preferably a difference in refractive index in two axial directions of 0.03 or less, and a difference in refractive index in one remaining axial direction of 0.05 or more.

The refractive index in the x-axis direction of the substrate is nX ₁ , the refractive index in the y-axis direction is nY ₁ and the refractive index in the z-axis direction is nZ _1, and the refractive indices of the birefringent island-in-the-sea yarns disposed in the substrate are nX ₂ , nY ₂ and nZ _2. When, at least one of the X, Y, Z-axis refractive index of the substrate and the birefringent fibers coincide. Further, preferably the refractive index's if the birefringence ₂ nX> nY nZ ₂ = _2.

When the refractive index in the x-axis direction of the island portion of the island-in-the-sea yarn is nX ₃ , the refractive index in the y-axis direction is nY ₃ and the refractive index in the z-axis direction is nZ _3, and the refractive index of the sea portion is nX ₄ , nY ₄ and nZ _4. At least one of the X, Y, and Z axis refractive indices of the island portion and the sea portion coincides. That is, the refractive index of the island portion is preferably nX ₃ > nY ₃ = nZ ₃ .

The absolute value of the difference in refractive index between nX ₃ and nX ₄ is preferably 0.15 or more, and the absolute value of the difference in refractive index between nY ₃ and nY ₄ , nZ ₃ and nZ ₄ is less than 0.03.

It is also possible that the refractive index of the sea portion of the island-in-the-sea yarn coincides with the refractive index of the substrate. The island-in-the-sea yarn may preferably be woven with a weft yarn and a warp yarn, either one of the weft yarn and the warp yarn is the island-in-the-sea yarn and the other is isotropic fiber.

The weft or warp yarn is preferably formed by gathering 1 to 200 strands of the island-in-the-sea yarn. Preferably, the birefringent island-in-the-sea yarns may be arranged in one direction in the substrate, and further, may be disposed in the substrate perpendicular to the light source.

The island-in-the-sea yarns may have a longitudinal cross section, preferably circular or elliptical, or even a hetero-cross section.

The island-in-the-sea yarn may preferably be extended in the longitudinal direction.

The broadband high brightness film for liquid crystal displays preferably has a structured surface, more preferably the structured surface layer is formed on the surface from which light is emitted.

The structured surface layer may be a prismatic shape with or without a constant pitch between pitches, or the structured surface layer may be a lenticular shape with or without a pitch between pitches.

The birefringent islands or islands may or may not be disposed on the structured surface layer. In the film back layer of the present invention The matte treatment may be performed, and the thickness of the island-in-the-sea yarn may be preferably 0.3 to 20 denier.

The terms used herein are briefly described.

Unless stated otherwise, it means that the film has birefringence. When light is irradiated onto a polymer having different refractive indices depending on the direction, the light incident on the film is refracted by two different directions of light.

Isotropic means that when light passes through an object, the refractive index is constant regardless of the direction.

Anisotropy means that the optical properties of an object vary depending on the direction of light. Anisotropic objects have birefringence and correspond to isotropy.

Light modulation means that the irradiated light is reflected, refracted, scattered, or the intensity of the light, the period of the wave, or the property of the light is changed.

Unlike the conventional laminated high brightness film, the broadband high brightness film for liquid crystal display of the present invention has the reflection of S polarized light uniformly in the visible light region and maintains 80 to 90% of the polarization so that the brightness is dramatically improved and visible at the same time. Light of any wavelength in the light beam has the effect of uniformly transmitting.

In addition, since hundreds of layers are not laminated on one film, the manufacturing process is very easy and the production cost is greatly reduced.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

As described above, the conventional laminated high brightness film can be confirmed that the polarization degree exceeds 90% at some wavelengths and the polarization degree is less than 70% at some wavelengths according to the wavelength change ( FIG. 1B ). This means that the polarization degree is changed according to the change of wavelength in visible light, and the degree of increase in luminance at a specific wavelength is changed, and thus visibility is lowered.

Accordingly, the broadband high-brightness film for liquid crystal display of the present invention is a broadband high-brightness film for liquid crystal display which enhances luminance through the optical interference effect by the transmission of P-polarized light and the selective reflection of S-polarized light, wherein the reflection of the S-polarized light is diffuse reflection It is characterized in that the reflection of S-polarized light occurs uniformly in the visible light region.

More specifically, Figure 2a is a graph of the transmittance in the visible light of the high brightness film of the present invention (see Example 3), through which it can be seen that the polarization degree in the visible light region to maintain 80 to 90%. As a result, the broadband high-brightness film for the liquid crystal display of the present invention is to maintain a constant polarization degree of 80 to 90% in the visible light range so that light can be uniformly transmitted within the wavelength range of all visible light. This improves the visibility of the liquid crystal display and maintains a constant brightness regardless of the size of the wavelength.

Meanwhile, in the conventional broadband high brightness film for liquid crystal display, an isotropic optical layer and an anisotropic optical layer on a flat plate having different refractive indices are alternately stacked and stretched between the optical layers that can be optimized for selective reflection and transmission of incident polarization. Since it is manufactured to have an optical thickness and a refractive index, there is a problem in that the manufacturing process of the high brightness film for liquid crystal display is complicated. In particular, since each optical layer of the high-brightness film for liquid crystal display has a flat plate structure, the P-polarized light and the S-polarized light must be separated to correspond to the wide range of incident angles of the incident polarization. There was a problem of increasing in number. In addition, due to the structure in which the number of laminated layers of the optical layer is excessively formed, there is a problem in that optical performance decreases due to light loss.

Accordingly, in the present invention, the birefringent island-in-the-sea yarn is disposed in the substrate so that the light incident from the light source is reflected at the birefringent interface, which is an interface between the birefringent island-in-the-sea yarn and the isotropic substrate, Light modulation such as scattering and refraction can be generated to dramatically improve luminance.

Specifically, light irradiated from an external light source can be largely divided into S polarization and P polarization. When only a specific polarization is desired, P polarization passes through a broadband high brightness film for liquid crystal display without being affected by a birefringent interface, while S polarization is When the birefringent interface is modulated into randomly shaped wavelengths such as refraction, scattering, and reflection, that is, S-polarized light or P-polarized light, the light is reflected and irradiated back to the broadband high-brightness film for liquid crystal display. Passing through the broadband high brightness film, the S-polarized light is scattered or reflected again. If this process is repeated, the desired P polarization can be obtained. Therefore, when a plurality of polymers having a birefringent interface in the interface with the substrate are arranged in the substrate, the luminance can be improved remarkably.

Furthermore, the inventors of the present invention do not manufacture a laminated type using general birefringent fibers as the polymer having the birefringent interface, and thus, the production cost is low and the production is easy, but the effect of brightness enhancement is insignificant. Instead of high brightness film, it has been found that there is a problem that is difficult to apply to industrial sites.

Accordingly, the present invention solves the conventional problem by using the birefringent islands with a birefringent interface, the use of birefringent islands is significantly more effective in improving the light modulation efficiency and brightness than when using conventional fibers It can be seen that the improvement. More specifically, among the portions constituting the island-in-the-sea yarn, the island portion has birefringence, and the sea portion partitioning the island portion has isotropy. From this structure, not only the interface between the island-in-the-sea yarn and the base material, but also the interface between the plurality of islands and sea portions constituting the inside of the island-in-the-sea yarn are also birefringent interfaces. Therefore, compared with the conventional birefringent fibers, the light modulation effect is significantly increased, and can be applied to actual industrial sites in place of the high brightness film for the laminated liquid crystal display.

Therefore, the use of birefringent island-in-the-sea yarn is superior to the use of ordinary birefringent fibers in terms of luminance enhancement efficiency, and the optical properties of the island portion and sea portion in the birefringent island-in-the-sea yarn also differ, Since the refractive interface is formed, the luminance enhancement efficiency can be significantly improved.

After all, if the conventional islands and islands are to use the remaining island portion as a microfiber by dissolving the sea portion irrespective of birefringence to produce a microfiber, the islands and islands of the present invention, rather than eluting the sea portion It is assumed that the island-in-the-sea yarn itself having different optical properties is used. In the present invention, only the case where the island portion is composed of anisotropy and the sea portion is isotropic is assumed, but the object of the present invention can be achieved in the opposite case.

2B is a schematic diagram of a cross section of a broadband high brightness film for liquid crystal display of the present invention. Specifically, in the broadband high brightness film for liquid crystal display, the island-in-the-sea yarn 210 having birefringence is freely arranged in the substrate 200 having isotropy. At this time, the substrate 200 that can be used is made of a thermoplastic and thermosetting resin that transmits the light wavelength of the desired range. Preferably, the preferred resin that can be used as the substrate 200 may be amorphous or semicrystalline, and may include a homopolymer, a copolymer, or a blend thereof. Specifically poly (carbonate) (PC); Syndiotactic and isotactic poly (styrene) (PS); Alkyl styrenes; Alkyl, aromatic and aliphatic ring containing (meth) acrylates including poly (methylmethacrylate) (PMMA) and PMMA copolymers; Ethoxylated and propoxylated (meth) acrylates; Polyfunctional (meth) acrylates; Acrylated epoxy; Epoxy; And other ethylenically unsaturated substances; Cyclic olefins and cyclic olefin copolymers; Acrylonitrile butadiene styrene (ABS); Styrene acrylonitrile copolymer (SAN); Epoxy; Poly (vinylcyclohexane); PMMA / poly (vinylfluoride) blends; Poly (phenylene oxide) alloys; Styrene block copolymers; Polyimide; Polysulfones; Poly (vinyl chloride); Poly (dimethylsiloxane) (PDMS); Polyurethane; Unsaturated polyesters; Polyethylene; Poly (propylene) (PP); Poly (alkane terephthalates) such as poly (ethylene terephthalate) (PET); Poly (alkane naphthalate) such as poly (ethylene naphthalate) (PEN); Polyamides; Ionomers; Vinyl acetate / polyethylene copolymers; Cellulose acetate; Cellulose acetate butyrate; Fluoropolymers; Poly (styrene) -poly (ethylene) copolymers; PET and PEN copolymers, including polyolefin PET and PEN; And poly (carbonate) / aliphatic PET blends. More preferably, polyethylene naphthalate (PEN), polyethylene naphthalate copolymer (co-PEN) polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styreneacrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea. (UF.MF), unsaturated polyester (UP), silicone (SI), elastomer, cycloolefin polymer (COP, ZEON Japan, JSR) can be used alone or in combination.

Furthermore, additives such as antioxidants, light stabilizers, heat stabilizers, lubricants, dispersants, ultraviolet absorbers, white pigments, and optical brighteners may be contained as long as the above properties are not impaired.

The island-in-the-sea yarn 210 preferably uses a material having optical birefringence and excellent light transmittance, and more preferably, the material having the same material as the base material but having birefringence may be used. On the other hand, as a method of changing the isotropic material into birefringence, it is common to draw under proper temperature conditions to orient the polymer molecules to change into birefringence.

More specifically, polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), copolyethylene terephthalate (co-PET), polycarbonate (PC), polycarbonate (PC) Alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS ), Polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), One or more of phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), silicone (SI), elastomer, and cycloolefin polymer can be selected and used as sea component and island component, respectively. In this case, either sea or island Isotropically, and the other of It consists of anisotropy. More preferably, the island portion is anisotropic and the sea portion is isotropic. For example, the sea portion of the island-in-the-sea yarn may use isotropic co-PEN, the island portion may use birefringent PEN, and the sea portion and the island portion of the island-in-the-sea yarn may use resins that differ only in optical properties.

On the other hand, in an island-in-the-sea yarn having birefringence with an optically isotropic substrate, the magnitude of the substantial coincidence or mismatch of the refractive indices along the X, Y, and Z axes in space affects the degree of scattering of the light polarized along the axis.

In general, the scattering power varies in proportion to the square of the refractive index mismatch. Thus, the greater the degree of mismatch in refractive index along a particular axis, the more strongly scattered light polarized along that axis. Conversely, when the mismatch along a particular axis is small, the light polarized along that axis is scattered to a lesser extent. Depending on the axis, if the refractive index of the substrate substantially coincides with the refractive index of the islands of the islands, incident light polarized by an electric field parallel to these axes passes through the islands without scattering regardless of the size, shape, and density of the portion of the islands of the islands. something to do. Therefore, in the present invention, it is preferable that the refractive index of the base material and the island-in-the-sea yarn is 0.03 or less in the two axial directions, and the difference in the refractive index in the other one axial direction is 0.05 or more. Specifically, the refractive index of the x, y, and z axes is 1.64 as the base material is isotropic, while the refractive index of the y and z axes is 1.64 or the refractive index of the x axis is 1.89. In this case, the P wave passes through the birefringent interface between the substrate and the island-in-the-sea yarn, but the S wave causes light modulation to be reflected, scattered, or refracted, and then converted into an S wave or P wave form, where P wave is a broadband high-brightness liquid crystal display. Re-passing the film, the S wave again causes light modulation.

Furthermore, a birefringent interface is formed inside the birefringent island-in-the-sea yarns, which may cause a light modulation effect. Specifically, the birefringent island-in-the-sea yarn is preferably anisotropic in the island portion, the sea portion may be isotropic, the refractive index in the x-axis direction of the anisotropic islands is nX ₃ , the refractive index in the y-axis direction of the nY ₃ and z-axis direction When the refractive index is nZ ₃ , the refractive index in the x-axis direction of the solution portion is nX ₄ , the refractive index in the y-axis direction is nY ₄ and the refractive index in the z-axis direction is nZ ₄ , the difference between the refractive indices of the nX ₃ and nX ₄ The absolute value is at least 0.05, more preferably at least 0.15. In this case, the absolute value of the difference between the refractive indices of nY ₃ and nY ₄ and / or nZ ₃ and nZ ₄ may be less than 0.03.

More preferably, when the island-in-the-sea yarn is drawn in the x-axis direction, the absolute value of the difference between the refractive indices of nX ₃ and nX ₄ is 0.05 or more, and the absolute value of the difference in the refractive indices of nY ₃ and nY ₄ and nZ ₃ and nZ ₄ . When is less than 0.03, it is advantageous to increase the light modulation efficiency. In this case, nX ₃ > nY ₃ = nZ ₃ .

The island portion may preferably comprise a fiber envelope surrounding the fiber core, the cross-sectional shape of the preferred broadband high brightness film for the liquid crystal display may comprise a plurality of different islands, the filler and the island portion It is also possible for one or more to include a birefringent polymeric material (eg, birefringent cholesteric).

Regarding the shape of the birefringent island-in-the-sea yarn of the present invention, the cross-sectional view of the island-in-the-sea yarn may have any shape depending on the purpose, and may have various cross-sectional shapes of circular, oval, and polygonal shapes. Likewise, in the island-in-the-sea yarns, the cross section of the island portion may have a heterogeneous cross section such as a circle, an ellipse, and a polygon, regardless of the type of shape.

3A to 3I are preferred embodiments as cross sections of the birefringent island-in-the-sea yarn of the present invention. As can be seen in Figures 3a to 3i, the shape, size, number and arrangement of the islands in the present invention can be effectively adjusted according to the purpose of light modulation. 3A is a sectional view of a conventional island-in-the-sea yarn Circular portion 320a is partitioned through sea portion 310a. 3B has a large area of the sea portion 310b, and FIG. 3C has an elliptical shape of the island-in-the-sea yarn. In FIG. 3D, the portion 320d is elliptical and its arrangement is zigzag. In addition, although the cross section of an island-in-the-sea yarn has a rectangular structure, both a polygonal structure and a heteromorphic cross-sectional structure are possible.

As illustrated in FIGS. 3E and 3F, the island portion may be located at the center of the island-in-the-sea yarn or may not be at the center of the island-in-the-sea yarn.

In some embodiments, the parts need not all be the same size. For example, as illustrated in FIGS. 3G and 3H, island-in-the-sea yarns may include island portions 320g and 321g of different cross-sectional sizes. In this particular embodiment, one portion 320g is relatively larger in cross section than the other portion 321g. The portion of the figure may correspond to a group of two or more different sizes, and virtually all of the sizes may be different. Furthermore, it is also possible to add a birefringent and / or isotropic shell 330i to the FIG.

It is preferable that a plurality of island portions are arranged in the island-in-the-sea yarn, and the area ratio of the sea portion and the island portions is preferably 2: 8 to 8: 2. The thickness of the island-in-the-sea yarn is preferably 0.3 to 20 denier, and 500 to 4,000,000 pieces / cm 3 may be disposed in the substrate. In addition, the refractive index of the sea portion may optionally match the refractive index of the substrate of the broadband high brightness film for liquid crystal display.

On the other hand, Figure 4 is a cross-sectional view showing the path of light transmitted through the birefringent islands of the invention, the light transmitted through the birefringent islands in the substrate may be light modulation at the birefringent interface. In this case, the P wave (solid line) is transmitted through the interface between the substrate and the birefringent island-in-the-sea yarn and the birefringence interface between the seam and the seam interface inside the birefringent island-in-the-sea yarn. The modulation of light occurs due to the influence of the birefringence interface between the boundary surface of the island and the sea portion inside the islands of the islands and / or birefringent islands. As a result, a large number of S waves are returned to the light source through light modulation such as reflection, scattering, or refraction, and the returned S waves are reflected and become S waves or P waves, and then pass through the broadband high brightness film for liquid crystal display. As a result, the use of birefringent island-in-the-sea yarn is superior to the use of ordinary birefringent fibers in luminance enhancement efficiency, and when the optical properties of the island portion and the sea portion are different in the birefringent island-in-the-sea yarn, Since the birefringent interface can be formed, the luminance enhancement efficiency can be significantly improved.

On the other hand, it is advantageous that the birefringent island-in-the-sea yarns preferably have a volume of 1% to 90% with respect to 1 cm 3 of the broadband high brightness film for liquid crystal display. If it is less than 1%, the brightness enhancement effect is insignificant, and if it exceeds 90%, the amount of scattering due to the birefringence interface is increased and light loss occurs.

Furthermore, 500 to 4,000,000 birefringent island-in-the-sea yarns of the present invention may be disposed within 1 cm 3 of the broadband high brightness film for liquid crystal display.

The cross-sectional diameter of the islands within the birefringent islands can also have a significant effect on light modulation. When the cross-sectional diameter of each birefringent island-in-the-sea island is smaller than the wavelength of light, the effects of refraction, scattering, and reflection decrease, and light modulation hardly occurs. On the other hand, when the cross-sectional diameter of the island portion is too large, light is specularly reflected from the surface of the island-in-the-sea yarn, and diffusion in other directions is very small. Thus, the cross-sectional diameter of the aligned portion may vary depending on the intended use of the optics. For example, the diameter of the fiber may vary with the wavelength of electromagnetic radiation important for a particular application, and different fiber diameters are required to reflect, scatter or transmit visible, ultraviolet, infrared and microwave radiation.

The broadband high brightness film for liquid crystal display of the present invention may include a surface layer structured according to the purpose. Figure 5a-5f are the incident surface and exit surface of a broadband high brightness film for a liquid crystal display with respect to the light emitted by the light source (500a) in a cross-sectional view of the structured surface of a broadband high brightness film for a liquid crystal display of the present invention, Figure 5a In this case, as shown in FIG. 5B, a birefringent island-in-the-sea yarn 521b positioned (adjacent) on the light source 500b is densely arranged and is a birefringent island far away from the light source 500b. The yarn 520b may be spaced apart.

The structured surface layer may be formed on the surface from which light is emitted. The structured surface layer may be prismatic, lenticular or convex. In detail, in FIG. 5C, the surface on which the light on the wideband high luminance film for the liquid crystal display is emitted may have a curved surface 530c having a convex lens shape. The curved surface 530c may focus or defocus light transmitted through the surface. In addition, as shown in FIG. 5D, the light exit surface may have a prism pattern 530d. In this case, the birefringent island-in-the-sea yarn 520d is not formed in the surface layer 530d structured as shown in FIG. 5D, or the birefringent island-in-the-sea yarn 520e is formed in both the substrate and the surface layer 530e as shown in FIG. 5E, or FIG. It is also possible to form the birefringent island-in-the-sea yarn 520f only in the surface layer 530f structured as in 5f.

In addition, the back layer of the broadband high brightness film for liquid crystal display of the present invention may be provided with scratches by forming irregularities by matte treatment, which is carried out under the condition that it does not cause adverse effects on the effects of the present invention.

On the other hand, the light transmitted through the light source may be both natural light or polarized light. As the birefringent island-in-the-sea yarn of the present invention, various materials exhibiting birefringence can be used, but it is preferable that the birefringent island-in-the-sea yarn is a solid from the viewpoint of orientation, cross-sectional stability, durability, and the like.

6A and 6B , the island-in-the-sea yarn of the present invention may be woven with weft yarns 610a and 600b and warp yarns 600a and 610b, 1 to 200 strands can be gathered to form a weft or warp yarn. One of the weft yarns and the warp yarns is an island-in-the-sea yarn and the other is an isotropic fiber.

The broadband high-brightness film for liquid crystal display of the present invention described above is manufactured through three steps of spinning and stretching the birefringent island-in-the-sea yarn, and then fabricating the fibers or beams in which these fibers are arranged in one direction, and impregnating and fixing the fibers to the substrate. can do.

Spinning, drawing process and fabric or beam manufacturing process of the island-in-the-sea yarns can be carried out by a known method, it is not particularly limited. In the step of impregnating and fixing the fabric or beam to the substrate, a method of polymerizing the precursor of the support medium with light and / or heat after immersing the fabric or beam in monomers and / or oligomers that are precursors of the substrate, A method of removing the solvent after immersing the fabric or the beam in the polymer solution, and impregnating the fine powder with the support medium as the fine powder and then melting the fabric or the beam may be employed.

As another method, the present invention can also be carried out by a melt extrusion method. Specifically, when the shape of the cross section perpendicular to the long axis direction of the birefringent island-in-the-sea yarn dispersed in the substrate is polygonal, the extruder discharge port is divided into a plurality of dies, and the resin constituting the birefringent island-in-the-sea yarn is one spaced apart. The release extrusion method which extrudes from a mold into a polygonal shape and resin which comprises a base material is extruded from the mold in between can be employ | adopted. If the shape of the cross-section perpendicular to the long axis direction of the birefringent island-in-the-sea yarn dispersed in the support is substantially caused, the extruder discharge port is partitioned into a plurality of dies, and the resin constituting the birefringent island-in-the-sea yarn is continuous in the cross section. It is extruded in the shape of a round rod from the back side, and the release extrusion method which resin extrudes from the metal mold | die in between can be employ | adopted. In these cases, the extruder and the detention can be designed such that different types of molten resin are alternately extruded into a predetermined form from the detention of the extruder to form a dispersion arrangement as described above.

On the other hand, it is possible to provide a backlight unit including the above-described broadband high-brightness film for the liquid crystal display of the present invention, and further to provide a liquid crystal display device including the backlight unit.

In conclusion, when the birefringent islands containing the anisotropic island portion disposed in the isotropic sea portion in the broadband high-brightness film for liquid crystal display of the present invention as a birefringent fiber, the birefringence with the optical modulation effect between the substrate and the birefringent islands Since the optical modulation effect between the isotropic seam portion and the anisotropic island portion occurs inside the C Island islands, the light modulation effect of the broadband high brightness film for liquid crystal display is significantly improved.

In particular, when weaving the island-in-the-sea yarn to form a composite fiber, and then woven in a warp, weft form to be placed on a broadband high-brightness film for liquid crystal display, it has a significant light modulation effect than using a conventional birefringent fiber.

Hereinafter, the present invention will be described in detail by Examples and Experimental Examples.

The following Examples and Experimental Examples are only illustrative of the present invention, and the scope of the present invention is not limited to the following Examples and Experimental Examples.

≪ Example 1 >

42 pieces of anisotropic PEN (nx = 1.88, ny = 1.57, nz = 1.57) were placed inside the filler of isotropic Co-PEN (nx = 1.57, ny = 1.57, nz = 1.57). Through such a composition, undrawn yarn 150/24 was prepared and spun under a condition of spinning temperature of 305 ° C. and spinning speed of 1500 M / min, followed by three times stretching to prepare drawn yarn 50/24. In this case, the prepared island-in-the-sea yarn is anisotropic PEN (nx = 1.88, ny = 1.57, nz = 1.57) inside the filler of isotropic Co-PEN (nx = 1.57, ny = 1.57, nz = 1.57), 37 parts were placed. Wind-surfaced 4,200 strands (24 yarns act as a group, so the actual number of fibers is 100,800 strands of 4,200 × 24) side by side in a beam of 762mm width, then the wound beam is matted on the back The polycarbonate (PC) alloy sheet was placed on top of the sheet and laminated with a constant tension. At this time, the refractive index of the PC alloy sheet was 1.57.

Thereafter, a mixed UV curable coating resin of an epoxy acrylate and a urethane acrylate having a refractive index of 1.54 is applied to the point where the fiber is laminated to the PC alloy sheet and the mirror roll, and UV cured over the first and second stages. A fused sheet was prepared in which a birefringent island-in-the-sea yarn was laminated. The coating resin showed a refractive index of 1.54 before UV coating curing but a refractive index of 1.57 after curing. Through this, a broadband high brightness film for liquid crystal display having a thickness of 400 μm was manufactured.

<Example 2>

Except having arranged the number of drawing parts into 217, it carried out similarly to Example 1, and manufactured the broadband high brightness film for liquid crystal displays of 400 micrometers in thickness.

<Example 3>

The liquid crystal display having a thickness of 400 μm was carried out in the same manner as in Example 2, except that 200/96 yarns prepared by four sums (50/24 × 4) of the island-in-the-sea yarns used in Example 2 were used. A broadband high brightness film was prepared.

<Example 4>

In order to simplify the process of incorporating the fiber used in Example 2 into the sheet, as in Example 1, using a beam obtained by winding 4,200 strands side by side in a 762 mm width, at a weft density of 50 / inch Weaving was carried out, and the tissues were plain weave to minimize the weft density. The fabric thus prepared was laminated on the sheet while being cut through the roll on the sheet extrusion die as in Example 1, and then coated and cured to prepare a broadband high brightness film for liquid crystal display having a thickness of 400 μm.

Example 5

In order to improve light utilization efficiency of the broadband high brightness film for liquid crystal display, a structured surface layer was formed on the broadband high brightness film for liquid crystal display of Example 3. In the manufacturing process of the fusion sheet, a broadband high brightness film for liquid crystal display having a thickness of 400 μm was prepared in the same manner as in Example 3, except that a structured surface layer was formed using a prism pattern roll.

Comparative Example 1

In the same manner as in Example 1 except that 150/24 unstretched isotropic fibers composed of Co-PEN (nx = ny = nz = 1.57) were used instead of the birefringent island-in-the-sea yarns, the thickness was 400 μm. A broadband high brightness film for liquid crystal displays was produced.

Comparative Example 2

In the same manner as in Example 1, except that an undrawn yarn of a island-in-the-sea structure (24 island parts) consisting of PET (nx = ny = nz = 1.57) and C0-PEN (nx = ny = nz = 1.57) was used. The broadband high brightness film for liquid crystal displays with a thickness of 400 micrometers was produced.

Comparative Example 3

After polymerizing a PEN resin having an intrinsic viscosity (IV) of 0.53, a yarn of undrawn yarn 150/24 was prepared. At this time, spinning was applied by spinning temperature 305 ℃, spinning speed 1500 M / min. The obtained undrawn yarn was stretched three times at a temperature of 150 ° C. to produce 50/24 drawn yarn. The stretched PEN fibers exhibit birefringence and the refractive indices in each direction are nx = 1.88, ny = 1.57, and nz = 1.57. Instead of the birefringent island-in-the-sea yarn used in Example 1, except that the birefringent PEN fibers were used in the same manner as in Example 1 to prepare a broadband high-bright film for a liquid crystal display having a thickness of 400㎛.

Experimental Example 1

With respect to the broadband high brightness film for liquid crystal display produced through Examples 1 to 5 and Comparative Examples 1 to 3, the following physical properties were evaluated and the results are shown in Table 1 . In addition, the polarization degree and the like of Example 3 were measured and shown in FIG . 2A .

1. Measurement of luminance

In order to measure the luminance of the broadband high brightness film for liquid crystal display manufactured in Examples 1 to 5 and Comparative Examples 1 to 3, a 32 ″ direct type provided with a diffusion plate, two diffusion sheets, and a broadband high brightness film for liquid crystal display After assembling the panel on the backlight unit, the luminance was measured at 9 points using Topcon's BM-7 measuring instrument, and the average value was shown.

2. Permeability Measurement

The transmittance | permeability was measured by the ASTM D1003 method using the permeability analysis equipment [COH300A of NIPPON DENSHOKU, Japan].

3. Polarization measurement

The polarization degree was measured using the polarization degree analyzer (RETS-100, OTSKA Corporation).

4. Water absorption rate

According to ASTM D570, after immersion in water at 23 ° C. for 24 hours, the weight percent change of the sample before and after the treatment was measured.

5. Sheet thickness measurement

Assemble wideband high brightness film for liquid crystal display in 32-inch backlight unit and leave it for 96 hours in a constant temperature and humidity chamber at 60 ° C and 75% condition, then decompose it and visually observe the degree of occurrence of broadband high brightness film for liquid crystal display. Good, (triangle | delta): It divided into normal and x: bad.

6. UV resistance

Using Semyung Baektron's SMDT51H, the output of 130mW UV lamp (365nm) was irradiated for 10 minutes at 10cm height, and the YI (Yellow Index) before and after the treatment was measured by using NIPPON DENSHOKU's SD-5000 analysis equipment. Yellowing degree was evaluated.

As can be seen from Table 1, the broadband high brightness films for liquid crystal displays of Examples 1 to 5 including birefringent island-in-the-sea yarns include the broadband high brightness films for liquid crystal displays of Comparative Examples 1 to 2 and birefringent fibers containing isotropic fibers. Compared with the broadband high brightness film for liquid crystal display of Comparative Example 3, the broadband high brightness film for liquid crystal display including the birefringent island-in-the-sea yarn of the present invention confirmed a remarkable increase in optical properties such as luminance and polarization degree.

The broadband high brightness film for liquid crystal display of the present invention can be widely used in liquid crystal display devices requiring high brightness such as mobile phones and LCDs.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical spirit of the present invention, and such modifications and modifications belong to the appended claims. .

Figure 1a is a schematic diagram illustrating the principle of a conventional brightness enhancement film, Figure 1b is a transmittance graph accordingly.

Figure 2a is a graph of the transmittance of the present invention, Figure 2b is a schematic diagram of a cross section of the cut surface of the luminance-enhanced film according to an embodiment of the present invention.

3A to 3I are exemplary embodiments of a cross-sectional view of a birefringent island-in-the-sea yarn according to the present invention.

4 is a schematic diagram showing a path of light incident on a birefringent island-in-the-sea yarn of the present invention.

5A to 5F are cross- sectional views of the structured surface of the luminance-enhanced film of the present invention.

6A to 6B are layout views of the birefringent islands and islands according to an embodiment of the present invention.

<Short description of the symbols in the drawings>

200: base material 210: birefringent sea island

300, 310b, 310c, 310d, 310e, 410a, 510a, 510b, 530c, 530d, 530e, 310f, 310g, 310h, 310i, 530f: sea section

310a, 320a, 320b, 320c, 320d, 320e, 420a, 520a, 520b, 521b, 520c, 520d, 520e, 320f, 320g, 320g, 320h, 320i, 520f

500a, 500b: light source 330i: outer sheath

600a, 610b: warp yarn 610a, 600b: weft

Claims (27)

A plurality of birefringent island-in-the-sea yarns are disposed in the substrate, and the luminance is enhanced through the optical interference effect of the transmission of P-polarized light and the selective reflection of S-polarized light, the reflection of the S-polarized light is diffuse reflection, and the reflection of S-polarized light is visible light. Broadband high brightness film for liquid crystal display, characterized in that uniformly generated in the entire area. The broadband high brightness film for a liquid crystal display according to claim 1, wherein the birefringent island-in-the-sea yarn is disposed perpendicular to the light source. The broadband high brightness film for liquid crystal display according to claim 1, wherein the polarization degree is maintained at 80 to 90% in the entire visible light region. The thickness of the birefringent island-in-the-sea yarn is 0.3-20 denier, The broadband high brightness film for liquid crystal display according to claim 1. The broadband high brightness film for liquid crystal display according to claim 1, wherein the base material is isotropic. 2. The broadband high brightness for the liquid crystal display according to claim 1, wherein the refractive index difference between the base material and the birefringent island-in-the-sea yarn is 0.03 or less in two axial directions, and the difference in refractive index in the other one axial direction is 0.05 or more. film. The refractive index of the substrate in the x-axis direction is nX ₁ , the refractive index in the y-axis direction is nY ₁ and the refractive index in the z-axis direction is nZ ₁ , and the refractive index of the birefringent island-in-the-sea yarn disposed in the substrate is nX _2. and at least one of X, Y and Z-axis refractive indices of the substrate and the birefringent island-in-the-sea yarn when nY ₂ and nZ ₂ coincide with each other. The broadband high brightness film for liquid crystal display according to claim 7, wherein the birefringent island-in-the-sea yarn has a refractive index of nX ₂ > nY ₂ = nZ ₂ . The broadband high brightness film for liquid crystal display according to claim 1, wherein the island portion of the island-in-the-sea yarn is anisotropic and the sea portion is isotropic. The refractive index of the island portion is nX ₃ , the refractive index of the y-axis direction is nY ₃ and the refractive index of the z-axis direction is nZ _3, and the refractive index of the sea portion is nX ₄ , nY ₄ and when nZ ₄ , At least one of the X, Y, and Z-axis refractive indices of the island portion and the sea portion coincides with the broadband high brightness film for the liquid crystal display. The broadband high brightness film for a liquid crystal display according to claim 9, wherein the refractive index of the island portion is nX ₃ > nY ₃ = nZ ₃ . The broadband high brightness film for liquid crystal display according to claim 9, wherein an absolute value of a difference between refractive indexes of nX ₃ and nX ₄ is 0.15 or more. 10. The broadband high brightness film for liquid crystal display according to claim 9, wherein an absolute value of a difference in refractive index between nY ₃ and nY ₄ and nZ ₃ and nZ ₄ is less than 0.03. The method of claim 1, wherein the substrate is polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS) ), Heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene (ABS), polyurethane (PU) , Polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), Urea. Melanin (UF.MF), unsaturated polyester (UP), silicone (SI), elastomer and cycloolefin polymer, characterized in that any one or more selected from the group consisting of a broadband high brightness film for liquid crystal display. The sea portion of the island-in-the-sea yarn of claim 1 is polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene (ABS), polyurethane ( PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP) ), Urea melanin (UF.MF), unsaturated polyester (UP), silicone (SI), elastomer and cycloolefin polymer, characterized in that any one or more selected from the group consisting of a broadband high brightness film for the liquid crystal display. The island portion of the island-in-the-sea yarn is polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene (ABS), polyurethane ( PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP) ), Urea melanin (UF.MF), unsaturated polyester (UP), silicone (SI), elastomer and cycloolefin polymer, characterized in that any one or more selected from the group consisting of a broadband high brightness film for the liquid crystal display. The broadband high brightness film for a liquid crystal display according to claim 1, wherein the birefringent island-in-the-sea yarn is woven with weft or warp yarns, or is manufactured with weft and warp yarns. 18. The wideband high-brightness film for liquid crystal display according to claim 17, wherein when the birefringent island-in-the-sea yarn is one of weft or warp yarn, the other is isotropic fiber. 18. The broadband high brightness film for liquid crystal display according to claim 17, wherein 1 to 200 strands are formed by the birefringent island-in-the-sea yarns. 2. The broadband high brightness film for liquid crystal display according to claim 1, wherein the longitudinal cross section of the birefringent island-in-the-sea yarn is circular or elliptical. 2. The broadband high brightness film for liquid crystal display according to claim 1, wherein the longitudinal cross section of the birefringent island-in-the-sea yarn is a deformed cross section. The broadband high brightness film for liquid crystal display according to claim 1, wherein the birefringent island-in-the-sea yarn is extended in a longitudinal direction. 2. The broadband high brightness film for liquid crystal display according to claim 1, wherein the broadband high brightness film for liquid crystal display has a structured surface on a surface from which light is emitted. 24. The wideband high brightness film for liquid crystal display according to claim 23, wherein the structured surface has a prism shape with or without a constant pitch between pitches.  24. The wideband high brightness film for liquid crystal display according to claim 23, wherein the structured surface has a lenticular shape with or without a constant pitch between pitches. 24. The wideband high brightness film for liquid crystal display according to claim 23, wherein the birefringent fibers are arranged or not arranged on the structured surface. The back layer of claim 23, wherein the back layer of the high brightness film has a structured surface on the surface from which light is emitted. Broadband high brightness film for the liquid crystal display, characterized in that the matte treatment.

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