KR20180111704A - Reflective polarizing film, light source assembly comprising the same, and display comprising the same - Google Patents

Abstract

The present invention relates to a reflective polarization film and, more particularly, to a reflective polarization film, a light source assembly including the same, and a liquid crystal display device including the same, capable of implementing a display which has a wide viewing angle and minimizes a bright line visibility phenomenon and light leakage. The reflective polarization film includes a base layer and a plurality of dispersion bodies which are randomly dispersed inside the base layer and have refractive indexes which are different from the refractive index of the base layer in at least one axial direction.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a reflective polarizing film, a light source assembly including the reflective polarizing film, and a liquid crystal display device including the reflective polarizing film,

The present invention relates to a reflective polarizing film, and more particularly, to a reflective polarizing film having a wide viewing angle and capable of displaying a bright line and minimizing light leakage, a light source assembly including the polarizing film, and a liquid crystal display.

Flat panel display technology is mainly composed of liquid crystal display (LCD), projection display, and plasma display (PDP), which have already secured a market in the TV field. In addition, field emission display (FED) and electroluminescence display (ELD) And it is expected to occupy the field according to each characteristic. Liquid crystal displays are currently being used in a wide range of applications such as notebook computers, personal computer monitors, liquid crystal TVs, automobiles, and aircrafts, accounting for 80% of the flat panel market, and booming demand for LCDs worldwide.

Conventional liquid crystal displays place a liquid crystal and an electrode matrix between a pair of light absorbing optical films. In liquid crystal displays, the liquid crystal portion has an optical state that changes accordingly by moving the liquid crystal portion by an electric field generated by applying a voltage to the two electrodes. This process displays an image by using a polarized light in a specific direction as a 'pixel' containing information. For this reason, liquid crystal displays include a front optical film and a rear optical film that induce polarization.

The optical film used in such a liquid crystal display does not necessarily have a high utilization efficiency of light emitted from the backlight. This is because 50% or more of the light emitted from the backlight is absorbed by the back side optical film (absorption type polarizing film). Therefore, in order to increase the utilization efficiency of the backlight in the liquid crystal display, a reflective polarizer is provided between the optical cavity and the liquid crystal assembly.

 1 is a diagram showing an optical principle of a reflection type polarizer. Specifically, the P polarized light from the optical cavity toward the liquid crystal assembly passes through the reflective polarizer and is transmitted to the liquid crystal assembly. The S polarized light is reflected from the reflective polarizer to the optical cavity, and then the polarization direction of the light By repeating the cycle of being reflected in the randomized state and then being transmitted back to the reflective polarizer, the S polarized light is eventually converted into P polarized light that can pass through the polarizer of the liquid crystal assembly, passes through the reflective polarizer, will be.

In the case of a reflective polarizer exhibiting the above functions, for example, a multilayer reflective polarizer in which a flat optical layer having optical anisotropic refractive index and a flat optical layer having optical isotropic refractive index are alternately laminated, a helical cholesteric liquid crystal A polymer dispersed type reflective polarizer including a discontinuous phase having optical anisotropy or optically isotropic refractive index within a continuous phase having optically isotropic or optical anisotropic refractive index, a polymer dispersed type reflective polarizer including a birefringent And a wire-grid type reflective polarizer.

As an example of the polymer dispersed type reflective polarizer, there has been proposed a reflective polarizer in which a birefringent polymer stretched in the longitudinal direction is arranged in the base layer so that a dispersion capable of achieving the function of the reflection type polarizer is dispersed. 2 is a perspective view of a reflective polarizer 20 including a bar-shaped polymer, in which birefringent polymers 22 stretched in the longitudinal direction are arranged in one direction within the base material layer 21. [ The birefringent interface between the base layer 21 and the birefringent polymer 22 causes a light modulation effect to perform the function of the reflection type polarizer. However, the polymer-dispersed reflective polarizer having such a structure has a problem that the light modulation efficiency is too low because it is difficult to reflect light in the entire wavelength range of visible light. Also, there was a problem that light leakage or bright line appearance was observed due to the spacing space between the rod-shaped polymers. In addition, there still exists a problem of appearance color change caused by the fact that the light transmitted through the reflective polarizer is not uniform in the entire visible light region.

On the other hand, the characteristics that are important characteristics in recent display are the viewing angle, which means that the brightness and the contrast ratio do not change much even if the display is not observed from the front. However, since the conventional reflective polarizer has a function of transmitting / reflecting light in accordance with the polarization and does not have a function of diffusing the light emitted from the reflective polarizer, the viewing angle is not good. It has been common to further provide a diffusing plate on the exit surface of the reflective polarizer. However, in the case of a diffusing sheet or a diffusing plate which is separately provided, there is a problem that the assembly process of the backlight unit is complicated and the production cost is increased. On the other hand, when the diffusibility of the light is increased to improve the viewing angle, there is a problem that the luminance is lowered.

Accordingly, it is urgently required to develop a polymer-dispersed reflective polarizer that can achieve a higher luminance through an improved viewing angle at an appropriate level, while minimizing the problem of color shift, bright line appearance, and color change of appearance.

Korean Patent Publication No. 2014-0021232

Disclosure of the Invention The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a reflective polarizer capable of suppressing bright line appearance, color change of appearance and light leakage, An object of the present invention is to provide a reflective polarizing film which is superior in polarizing characteristics at all wavelengths of visible light and is able to exhibit a further increased luminance as the viewing angle is appropriately adjusted and the light emitted forward is increased.

It is another object of the present invention to provide a backlight unit which can increase the light utilization efficiency, reduce the number of parts, and simplify the assembling process by employing the reflective polarizing film according to the present invention.

It is still another object of the present invention to provide a liquid crystal display device having improved brightness and brilliant line phenomenon by employing the backlight unit according to the present invention.

According to an aspect of the present invention, there is provided a reflective polarizing film that transmits a first polarized light and reflects a second polarized light among incident light, wherein the reflective polarizing film is dispersed randomly in the base layer and the base layer And a plurality of dispersions each having a refractive index different from that of the base layer in at least one axial direction, the plurality of dispersions being oriented in one uniaxial direction and having an average aspect ratio of 1/3 And an average length of the long axis is 0.7 to 1.5 占 퐉.

According to one embodiment of the present invention, the first fiber portion and the second fiber portion may be at least one of different portions of the single-stranded fiber and portions of each of the different fiber strands.

The base layer may have a thickness of 20 to 180 탆.

The reflective polarizing film may further include a skin layer integrally formed on at least one surface of the substrate layer.

The number of dispersions having a major axis length of 0.3 to 5 mu m among the plurality of dispersions may be 90% or more of the total number of dispersions.

In addition, the long axis lengths of the plurality of dispersion bodies may be 60 to 92% in terms of the dispersion factor with respect to the major axis length according to Equation (1).

[Equation 1]

The number of dispersions having a major axis length in the range of 0.3 to 5 占 퐉 among the plurality of dispersions is 90% or more of the total number of the dispersions, and the major axis length of the plurality of dispersions is expressed by the following formula The increased optical properties can be achieved through the 60 to 92% dispersion factor for the length.

In the cumulative number distribution of the long axis lengths of the plurality of dispersions, D ₅₀ may be 0.5 to 0.9 탆, and D ₁₀ may be 0.3 탆 or more.

The ratio of D ₅₀ to D ₁₀ may be 1.6 to 2.4 in the cumulative number distribution of the plurality of dispersoids by the major axis length.

In addition, the average aspect ratio may be 1/10 to 1/3.

In addition, There is provided a light source assembly including a reflective polarizing film according to the present invention.

The present invention also provides a liquid crystal display device including the light source assembly according to the present invention.

The reflective polarizing film of the present invention is excellent in brightness due to the phenomenon of bright line and minimization of light loss due to light leakage and an increase in reflection efficiency of one polarized light and excellent polarizing property at the wavelength of visible light, It can be widely used as a component of a liquid crystal display device such as a light source assembly and can be applied to various windows and various polarizing lighting industries.

1 is a schematic view for explaining the principle of a reflective polarizer,
2 is a perspective view of a conventional polymer-dispersed reflective polarizer including rod-
3 is a perspective view of a reflective polarizing film according to an embodiment of the present invention,
4 is a cross-sectional view of a reflective polarizing film according to an embodiment of the present invention,
FIG. 5 is a cross-sectional view of a dispersion body provided in a reflective polarizing film according to an embodiment of the present invention,
FIG. 6 is a cross-sectional view of a coat-hanger die, which is a kind of flow control unit used in a manufacturing process of a reflective polarizing film according to an embodiment of the present invention,
7 is a side view of Fig. 6,
8 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention,
9 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention,
10 is a schematic view of a manufacturing process of a plate-shaped polymer dispersed reflective polarizer according to a comparative example of the present invention,
11 is an exploded perspective view of a sea-island extrusion / taking-up tool according to a comparative example of the present invention,
12 is a sectional view of a plate-shaped polymer dispersed reflective polarizer according to a comparative example of the present invention, and
13 is a SEM photograph of a base layer of a reflective polarizing film according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification. In addition, the present invention is not limited by the size and shape of one configuration shown in the drawings. For example, the number of dispersions and the respective sizes shown in FIGS. 3 and 4 are only examples for explaining the present invention, and are not shown to exactly match the dispersion aspect ratio, the average length of the major axis, etc. according to the present invention . In addition, the dotted line shown on one side of Fig. 3 does not mean the length of the dispersion inside the base layer, which is not shown, merely explaining the direction of the long axis of the dispersion.

1, a reflective polarizer film 1000 according to an exemplary embodiment of the present invention is randomly dispersed in a base material layer 110 and has a plurality of axially different refractive indices (120). ≪ / RTI >

A birefringence interface may be formed between the base layer 110 and the dispersion 120 contained in the base layer. Specifically, the magnitude of the substantial coincidence or discrepancy of the refractive index along the spatial X, Y and Z axes between the substrate layer 110 and the dispersion 120 affects the degree of scattering of the polarized light along its axis. Generally, the scattering ability changes in proportion to the square of the refractive index mismatch. Thus, the greater the degree of discrepancy in refractive index along a particular axis, the more scattered light rays are polarized along that axis. Conversely, when the inconsistency along a particular axis is small, the polarized light rays along the axis are scattered to a lesser degree. When the refractive index of the base layer substantially coincides with the refractive index of the base layer along an axis, the incident light polarized by the electric field parallel to this axis is not scattered irrespective of the size, shape and density of the portion of the dispersion, Will pass. Also, when the refractive index along the axis is substantially coincident, the light rays pass through the object without being substantially scattered. More specifically, the first polarized light (P wave) is transmitted without being influenced by the birefringent interface formed at the interface between the base layer 110 and the dispersion body 120, while the second polarized light (S wave) ) And the dispersion body 120, the light is modulated by the influence of the birefringent interface. As a result, the P wave is transmitted and the S wave is modulated by light such as scattering and reflection of light, resulting in separation of polarized light.

Therefore, since the base layer 110 and the dispersion 120 form a birefringent interface, a light modulation effect can be generated. Therefore, when the base layer 110 is optically isotropic, the dispersion 120 has birefringence On the other hand, when the base layer 110 is optically birefringent, the dispersion body 120 may have optical isotropy. Specifically, when the refractive index in the x-axis direction of the dispersion body 120 is nX1, the refractive index in the y-axis direction is nY1, the refractive index in the z-axis direction is nZ1, and the refractive indexes of the base layer 110 are nX2, nY2 and nZ2 , an in-plane birefringence between nX1 and nY1 may occur. More preferably, at least one of X, Y and Z axis refractive indices of the base layer 110 and the dispersion body 120 may be different from each other, more preferably, when the extension axis is the X axis, The difference in the refractive indexes for the X axis is 0.05 or less, and the difference in the refractive indexes for the X axis is 0.1 or more. On the other hand, when the difference in the refractive index is 0.05 or less, it is interpreted as matching.

The base layer 110 can be used without limitation in the case of a material of a base layer used in a conventional polymer dispersion type reflective polarizer. Preferably, the base layer 110 is made of polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN) (PS), polymethylmethacrylate (PMMA), polybutylene terephthalate (PBT), poly (ethylene terephthalate), poly (ethylene terephthalate) Polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile blend (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP) For example, polycarbonate (PC) cores This can work.

The dispersion 120 can be used without limitation in the case of a dispersion material used in a polymer dispersion type reflective polarizer, and is preferably polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene (PS), polymethylmethacrylate (PMMA), polybutylene terephthalate (PBT), poly (ethylene terephthalate), poly (ethylene terephthalate) Polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile blend (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP) May be used alone or in combination. For example, PE N < / RTI >

As shown in FIGS. 3 and 4, the plurality of dispersions 121, 122, and 123 dispersed in the base layer 110 may have an average aspect ratio of 1/3 or less and an average length of the major axis of 0.7 to 1.5 占 퐉. As shown in Fig. 5, the aspect ratio is a ratio of the short axis to the long axis (a) in the cross section of each dispersion element dispersed in the cross section of the reflective polarizing film perpendicular to the uniaxial direction with respect to the uniaxial direction in which the reflection polarizing film is stretched b) length ratio (b / a), and the average aspect ratio means the average of these. If the average aspect ratio exceeds 1/3, it may cause defects such as light leakage and bright line appearance, and the luminance The second polarized light, for example, the reflection efficiency of the S polarized light may be lowered, and the desired optical characteristics may not be exhibited. Preferably, the average aspect ratio may be 1/10 to 1/3, and if the average aspect ratio is less than 1/10, there is a fear of remarkably lowering the luminance due to the decrease in straightness of light due to light scattering, rising of haze, and the like.

The average length of the major axis (a) may be 0.7 to 1.5 占 퐉. If the average length of the major axis (a) is less than 0.7 占 퐉, the dispersions (121, 122, 123) The separation distance between the sieves 121, 122, and 123 increases, and the light incident on the back surface of the reflective polarizing film can not be optically modulated and can be transmitted through the upper surface of the reflective polarizing film. In this case, It may not be possible to attain desired optical characteristics such as light emission efficiency may decrease, ultimately, high brightness may not be achieved, and light leakage may occur. If the average length of the long axis (a) is more than 1.5 탆, the number of the dispersing bodies 121, 122 and 123 which can be provided in the substrate layer 110 of a limited thickness can be significantly reduced, It may be difficult to achieve the transmittance of the first polarized light and the reflectance of the second polarized light to a desired level in the wavelength range of visible light, It may not be possible to achieve the optical properties of the level of In addition, as the diffusion polarized light increases, the straightness of the transmitted and reflected light decreases, and there is a fear of lowering the luminance.

According to a preferred embodiment of the present invention, in order to remarkably reduce the light leakage and bright line appearance, to appropriately improve the viewing angle, and to exhibit excellent polarization characteristics in the visible light ray wavelength range region, To 1.5 [mu] m, and the number of dispersion factors with respect to the major axis length according to Equation (1) may be 60 to 92%.

[Equation 1]

The dispersion coefficient (%) with respect to the major axis length according to Equation (1) indicates the degree of spread of each dispersion by the major axis length in a long axis length distribution diagram for a plurality of dispersions. The smaller the number of dispersion factors, Converges to the average length of the long axis, and the longer the length of the long axis of each dispersion means, the wider the spread, without converging to the average length of the long axis. If the dispersion factor of the long axis of the dispersed body included in the reflective polarizing film is less than 60%, there is a possibility that the polarization characteristic in a wavelength band region of the visible light waveband region is lowered. The degraded polarization characteristics in a wavelength range region of the visible light wavelength range ultimately causes a decrease in luminance and a variation in the light transmittance depending on wavelengths, which may cause the appearance to be colored with rainbow light or a certain one color. In addition, the light diffusion property is lowered and it may be difficult to exhibit an excellent viewing angle.

In addition, if the dispersion factor of the long axis length of the dispersion exceeds 92%, the distribution of the long axis length is varied, thereby facilitating the adjustment of the short axis length of each dispersion, thereby achieving the uniformity of the light transmittance But it is difficult to attain the desired optical characteristics such that the linearity of the transmitted and reflected light is reduced due to the increase of the diffused polarized light, have.

On the other hand, the number of dispersions having a major axis length in the range of 0.3 to 5 占 퐉 among the plurality of dispersions is 90% or more of the total number of the dispersions, and the major axis lengths of the plurality of dispersions are the long axis When the number of dispersion factors for the length simultaneously satisfies 60 to 92%, a further improved effect can be achieved in achieving the desired optical properties.

In addition, the number of dispersions having a major axis length in the range of 0.3 to 5 mu m among the plurality of dispersions in the one end face may be 90% or more of the total number of the dispersions. If the number of dispersion bodies having a long axis length within the range of 0.3 to 5 μm is less than 90%, the frequency of occurrence of defects such as decrease in luminance, light leakage, and bright line may be increased. Particularly, if the ratio of the long axis length of less than 0.3 탆 is high, the reflection efficiency of S-polarized light may deteriorate due to the decrease of the reflection efficiency. If the ratio of the dispersing body exceeding the long axis length of 5 탆 is high, And the amount of polarized light that can be reflected or reflected back may be decreased, which may cause a significant decrease in luminance.

On the other hand, in order to more remarkably prevent the phenomenon of visible light and bright line, D ₅₀ is 0.5 to 0.9 탆 and D ₁₀ is 0.3 탆 or more in the cumulative number distribution of the long axis lengths of the plurality of dispersions. The meaning of D _X means that the long axis length of the dispersion corresponding to X% of the total dispersion number when the cumulative number distribution curve for the long axis length is plotted from the shortest long axis length to the longest long axis length based on the long axis length it means. For example, when the total number of dispersions is 10, and the lengths of the dispersion long axes are 0.5, 0.6, 0.6, 0.7, 0.7, 0.7, 0.9, 1.0, 1.1, , D ₂₀ is the long axis length of the dispersion corresponding to 20% of the total 10 dispersions, and D ₅₀ means 0.7 μm, which is the long axis length of the dispersion corresponding to 50% of the total 10 dispersions . If D ₁₀ is less than 0.3 탆, it may be difficult to achieve uniformity of light transmittance for all wavelengths in the visible light region, and the decrease in polarization due to the degradation of polarization characteristics may cause a decrease in luminance. If D ₅₀ exceeds 0.9 탆, the light directivity decreases due to the increase of the diffused polarized light, which may cause a decrease in the overall luminance. Also, if D ₅₀ is less than 0.5 탆, it may be difficult to achieve uniformity of light transmittance by wavelength in the entire visible light region, and the decrease of the polarized light reused due to the degradation of polarization characteristics may cause a decrease in luminance.

In the distribution in the cumulative number distribution by the length of the dispersion long axis, more preferably, the ratio of the dispersion long axis length of D ₅₀ to the dispersion long axis length of D ₁₀ is 1.6 to 2.4. Ten thousand and one D ₁₀ of dispersion major axis length D ₅₀ of the dispersion ratio of the major axis length with respect to (D ₅₀ / D ₁₀₎ of 1.6 is less than when light leakage, bright line visible symptoms significantly, and / or visible light, the light transmittance for each wavelength in the whole area It is difficult to achieve the uniformity of the luminance. Also, when D ₅₀ / D ₁₀ exceeds 2.4, the phenomenon of visible light and bright line becomes remarkable, the quality of appearance color becomes worse, and the linearity of transmitted and reflected light decreases due to an increase of diffusion polarized light. .

The plurality of dispersions (121, 122, 123) may be elongated and / or arranged such that the major axis direction is substantially parallel to one axis direction of the reflective polarizing film, more preferably, in a direction perpendicular to the light emitted from the external light source It is effective that the dispersion body is stretched or arranged in parallel to maximize the light modulation effect.

The plurality of dispersions 121, 122, and 123 may be randomly dispersed in the base layer 110, thereby enhancing the viewing angle characteristics through light diffusion, It may be more advantageous to develop a modulation effect.

The reflective polarizer film 1000 according to an embodiment of the present invention includes a substrate layer 100 including the base layer 110 and the dispersion 120 dispersed in the base layer 110, And a skin layer 211 and 212 provided on at least one side of the base layer 100. [ The skin layers 211 and 212 complement the mechanical strength of the base layer 100. At this time, a separate adhesive layer may be further provided between the base layer 100 and the skin layers 211 and 212. Preferably, the skin layers 211 and 212 are co-extruded together with the base layer 100 without a separate adhesive layer Or may be integrally formed. As a result, deterioration of optical properties due to the adhesive layer can be prevented, and more layers can be added to a limited thickness, so that optical properties can be remarkably improved. Further, unlike the conventional case where the base layer is post-adhered to the unstretched skin layer after stretching, the skin layers 211 and 212 included in one embodiment of the present invention are co-extruded simultaneously with the base layer 100, So that it can be stretched in at least one axial direction. As a result, the surface hardness is improved as compared with the unexposed skin layer, and the scratch resistance is improved and the heat resistance can be improved.

The skin layers 211 and 212 may be materials of a skin layer conventionally used for supporting a reflective polarizing film, and preferably include polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polyethylene (PS), polymethylmethacrylate (PMMA), polybutylene terephthalate (PBT), poly (ethylene terephthalate), poly (ethylene terephthalate) Polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile blend (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP) Can be used alone or in combination, and more preferably It may be the same material as the components of the above-mentioned base material layer 110. The

The thickness of the base layer 110 in the reflective polarizing film 1000 may be 20 to 180 占 퐉, and the thickness of the skin layer may be 50 to 500 占 퐉, but is not limited thereto. The number of total dispersions may be 25,000,000 to 80,000,000 when the thickness of the substrate layer is 120 占 퐉 based on 32 inch, but is not limited thereto.

The reflective polarizing film 1000 described above can be implemented by a manufacturing method described below. However, the present invention is not limited to the production method described below.

First, as the step (1), the base layer component, the dispersion component and the skin layer component are supplied to the extruding portion. The base layer component and the dispersion component may be supplied to the independent extruders, and in this case, the extruder may be composed of two or more. It is also included in the present invention to feed one extruded portion including a separate supply path and a distribution port so that the polymers do not mix. The extruder may be an extruder, which may further include a heating means or the like to convert the supplied polymers in the solid phase into a liquid phase.

The viscosity of the base layer component is designed to be different from that of the dispersion component so that there is a difference in polymer flow so that the dispersion component can be arranged inside the base layer component. Further, the viscosity difference between the base layer component and the dispersion component can be adjusted to a predetermined value or more so that the dispersion component has an appropriate aspect ratio. The following base layer component and the dispersion component pass through the mixing zone and the mesh filter zone, and the dispersion component is randomly arranged in the base layer with a difference in viscosity. At this time, the length change of the long axis of the dispersion can be achieved by changing the viscosity difference.

Then, at least one side of the base layer thus prepared is joined with the skin layer component transferred from the extrusion portion. Preferably, the skin layer component may be laminated on both sides of the substrate layer. When the skin layers are laminated on both sides, the material and the thickness of the skin layer may be the same or different from each other.

Next, the flow control section induces spreading so that the dispersion component contained in the base layer can be randomly arranged. 6 is a cross-sectional view of a coat-hanger die, which is a kind of preferred flow control part applicable to the present invention, and FIG. 7 is a side view of FIG. 6, The size and arrangement of the cross-sectional area of the sieve component can be controlled at random. Specifically, in FIG. 6, since the base layer having the skin layer transferred through the flow path spreads widely from side to side in the coat-hanger die, the dispersion component contained therein also spreads to the left and right.

According to a preferred embodiment of the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising the steps of: cooling and smoothing a reflection polarized film transferred from a flow control unit; And thermally fixing the stretched reflective polarizing film.

First, the step of cooling and smoothing the reflective polarizing film transferred from the flow control unit is performed by employing or appropriately changing the method and conditions used in the production of a general reflective polarizer, solidifying it after cooling, and then smoothening it through a casting roll process or the like .

Thereafter, a step of stretching the reflective polarizing film through the smoothing step is performed. The stretching can be performed through a conventional stretching process of a reflective polarizer, which can cause a difference in refractive index between the base layer component and the dispersion component to cause light modulation phenomenon at the interface, and the spread- The aspect ratio is further reduced through stretching. For this purpose, the uniaxial stretching or biaxial stretching can be preferably performed in the stretching step, and more preferably uniaxial stretching can be performed. In the case of uniaxial stretching, the stretching direction can perform stretching in the longitudinal direction of the dispersion. The stretching ratio may be 3 to 12 times. On the other hand, a method of changing an isotropic material to birefringent is commonly known. For example, in the case of stretching under an appropriate temperature condition, the dispersion polymer molecules can be oriented to exhibit birefringence.

Next, the final reflective polarizing film can be manufactured through a step of heat-setting the stretched reflective polarizing film. The heat setting can be carried out by suitably employing and changing the conditions of the known method, preferably at 180 to 200 ° C for 0.1 to 3 minutes through an IR heater.

Meanwhile, the reflective polarizer film 1000 may further include a structured surface layer on at least one surface thereof. The structured surface layer functions to control the direction of light incident or emitted through the reflective polarizing film (1000). The structured surface layer can be employed without limitation in a known configuration having a structured surface known to have the function of controlling the direction of light. For example, the structured surface layer may have a cross section of a lenticular, a microlens, a prism shape, Lt; / RTI > Or the irregular irregularities generated by the protrusion of the diffusion particles provided in the binder resin. On the other hand, in the case of including the diffusion particles, since the direction of the light can be controlled through the diffusion particles, the unevenness due to the projection of the diffusion particles is not necessarily accompanied.

The structured surface layer may be provided on the upper and / or lower part of the reflective polarizer film 1000 via the skin layers 211 and 212 in the reflective polarizer film 1000 or on the upper part of the substrate layer 100 where the skin layers 211 and 212 are omitted And / or may be provided at a lower portion thereof, which may be integrated with another adhesive layer or may be integrated without an adhesive layer.

The reflective polarizing film satisfying the physical properties according to the present invention can be used in a light source assembly or a liquid crystal display device including the same to improve light efficiency. The light source assembly can be classified as a direct light source assembly in which the lamp is located at the bottom, an edge light source assembly in which the lamp is located at the side, and the like. The reflective polarizing film according to embodiments of the present invention can be applied to any kind of light source assembly . It is also applicable to a back light assembly disposed below the liquid crystal panel or a front light assembly disposed above the liquid crystal panel. Hereinafter, as an example of various applications, a case is described in which a reflective polarizing film is applied to a liquid crystal display including an edge-type light source assembly.

8 is a cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention. The liquid crystal display device 2700 includes a backlight unit 2400 and a liquid crystal panel assembly 2500.

The backlight unit 2400 includes a reflective polarizing film 2111 for modulating the optical characteristics of the emitted light. The other constituents included in the backlight unit and the positional relationship between the other polarizing film and the reflective polarizing film 2111 And is not particularly limited in the present invention.

8, a light source 2410, a light guide plate 2415 for guiding light emitted from the light source 2410, a reflection film 2320 disposed below the light guide plate 2415, And a reflective polarizer 2111 disposed on the upper side of the light guide plate 2415. [

At this time, the light sources 2410 are disposed on both sides of the light guide plate 2415. The light source 2410 may be a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), or an external electro fluorescent lamp (EEFL). In another embodiment, the light source 2410 may be disposed only on one side of the light guide plate 2415. [

The light guide plate 2415 moves the light emitted from the light source 2410 through total internal reflection, and emits the light upward through a scattering pattern or the like formed on the lower surface of the light guide plate 2415. A reflective film 2420 is disposed under the light guide plate 2415 to reflect the light emitted downward from the light guide plate 2415 upward.

A reflective polarizing film 2111 is disposed on the upper side of the light guide plate 2415. Since the reflective polarizing film 2111 has been described in detail above, a duplicate description will be omitted. Other optical sheets may be further disposed above or below the reflective polarizing film 2111. [ For example, an optical film capable of controlling the direction of light such as condensing light or diffusing light, or a phase difference film and / or a protective film for changing the phase of light can be further provided. At this time, the optical film for controlling the direction of the light will be effective when the reflective polarizing film does not have a structured surface layer separately as described above.

The light source 2410, the light guide plate 2415, the reflection film 2420, and the reflection polarizing film 2111 can be received by the bottom chassis 2440.

The liquid crystal panel assembly 2500 includes a first display panel 2511, a second display panel 2512 and a liquid crystal layer (not shown) interposed therebetween. The liquid crystal panel assembly 2500 includes a first display panel 2511 and a second display panel 2512 And a polarizing plate (not shown) attached to the surface of the polarizing plate.

The liquid crystal display device 2700 may further include a top chassis 2600 covering the edges of the liquid crystal panel assembly 2500 and surrounding the sides of the liquid crystal panel assembly 2500 and the backlight unit 2400.

9 is a view illustrating an example of a liquid crystal display device employing a reflective polarizing film according to a preferred embodiment of the present invention. A reflective plate 3280 is inserted on a frame 3270, A cold cathode fluorescent lamp 3290 is placed. An optical film 3320 is disposed on the upper surface of the cold cathode fluorescent lamp 3290 and the optical film 3320 is laminated in order of the diffuser plate 3321, the reflective polarizing film 3322 and the absorbing polarizing film 3323, However, the constitution of the optical film and the order of lamination between the respective constituents may be varied depending on the purpose, and some constituent elements may be omitted or a plurality of them may be provided, and another kind of optics A film may be further provided. On the other hand, the liquid crystal display panel 3310 may be positioned on the upper surface of the optical film 3320 by being inserted into the mold frame 3300.

The light emitted from the cold cathode fluorescent lamp 3290 reaches the diffuser plate 3321 of the optical film 3320. The light transmitted through the diffuser plate 3321 passes through the reflective polarizing film 3322 to cause the light to proceed in a direction perpendicular to the optical film 3320, Specifically, the P wave transmits the reflection polarizer without loss, but in the case of the S wave, light modulation (reflection, scattering, refraction, etc.) occurs and is again reflected by the reflection plate 3280, which is the back surface of the cold cathode fluorescent lamp 3290, The polarized light passes through the reflective polarizing film 3322 again after being randomly changed into a P wave or an S wave. And then reaches the liquid crystal display panel 3310 after passing through the absorption polarizing film 3323. [ Meanwhile, the cold cathode fluorescent lamp 3290 may be replaced with an LED.

In the present invention, the use of the reflective polarizing film has been described mainly with respect to a liquid crystal display, but the present invention is not limited thereto, and can be widely used in flat panel display technologies such as a projection display, a plasma display, a field emission display and an electroluminescence display, , Glass windows, and working lights that require polarized light.

The present invention will now be described more specifically with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

≪ Example 1 >

(PEN) having a refractive index of 1.65 as a dispersion component, and polycyclohexylenedimethylene terephthalate (PEN) having a polymerization ratio of terephthalate, ethyl glycol and cyclohexane dimethanol at a molar ratio of 1: 2 cyclohexylene dimethylene terephthalate (PCTG) having a refractive index of 1.58 including 38% by weight of polycarbonate, 60% by weight of polycarbonate and 2% by weight of a heat stabilizer containing phosphate were charged into the first extruder and the second extruder, respectively. A raw material containing the same components as the base layer component as the skin layer component was added to the third extruding portion.

The extrusion temperature of the base layer component and the dispersion component was adjusted to 245 占 폚, and the flow of the polymer was corrected so that the IV difference of the components was 0.013 as determined by Cap. Rheometer. And the skin layer components were then lined on both sides of the substrate layer component. The spread of polymer was then induced in the coat hanger die of Figs. 6 and 7, which corrected the flow rate and pressure gradient. Specifically, the width of the die inlet was 200 mm, the thickness was 10 mm, the width of the die outlet was 1,260 mm, the thickness was 2.5 mm, and the flow rate was 1.0 m / min. Then, a smoothing process was performed on the cooling and casting rolls and stretched 6 times in the MD direction. Next, thermal fixation was carried out through a heater chamber at 180 캜 for 2 minutes to form a dispersion layer having a cross-sectional structure as shown in Fig. 3, having a base layer thickness of 80 탆 (total thickness including 60 탆 skin layer on both sides) (See Fig. 13). The refractive index of the dispersion components in the manufactured reflective polarizing film _{(n x: 1.88, n y} : 1.58, n z: 1.58) and showed a refractive index of the substrate layer component is 1.58, and the plurality of dispersion under the same conditions as in Table 1 Respectively.

≪ Examples 2 to 10 >

Was prepared in the same manner as in Example 1 except that polyethylene naphthalate and polycarbonate alloy I.V. The retardation polarizing film as shown in Table 1 or Table 2 was prepared by changing the distribution of the dispersion body to the long axis by adjusting the color difference.

≪ Comparative Examples 1 and 2 &

Was prepared in the same manner as in Example 1 except that polyethylene naphthalate and polycarbonate alloy I.V. And the reflection polarizing film as shown in Table 2 below was prepared by changing the distribution of the dispersion body to the long axis by adjusting the color difference.

≪ Comparative Example 3 &

(PEN) having a refractive index of 1.65 as a dispersion component, and polycyclohexylenedimethylene terephthalate (PEN) having a polymerization ratio of terephthalate, ethyl glycol and cyclohexane dimethanol at a molar ratio of 1: 2 cyclohexylene dimethylene terephthalate (PCTG) having a refractive index of 1.58 including 38% by weight of polycarbonate, 60% by weight of polycarbonate and 2% by weight of a heat stabilizer containing phosphate were charged into the first extruder and the second extruder, respectively. A raw material containing the same components as the base layer component as the skin layer component was added to the third extruding portion.

The extrusion temperature of the base layer component and the dispersion component was adjusted to 245 占 폚, and the flow of the polymer was corrected so that the IV difference of the components was 0.003 by Cap. Rheometer. And the skin layer components were then lined on both sides of the substrate layer component. The spread of polymer was then induced in the coat hanger die of Figs. 6 and 7, which corrected the flow rate and pressure gradient. Specifically, the width of the die inlet was 200 mm, the thickness was 10 mm, the width of the die outlet was 1,260 mm, the thickness was 2.5 mm, and the flow rate was 1.0 m / min. Then, a smoothing process was performed on the cooling and casting rolls and stretched 6 times in the MD direction. Next, thermal fixation was carried out through a heater chamber at 180 캜 for 2 minutes to form a dispersion layer having a cross-sectional structure as shown in Fig. 3, having a base layer thickness of 80 탆 (total thickness including 60 탆 skin layer on both sides) (See Fig. 13). (N _x : 1.88, n _y : 1.58, n _z : 1.58) and the refractive index of the base layer component was 1.58 in the prepared reflective polarizing film, and the plurality of dispersions were the same as those shown in Table 2 Respectively.

≪ Comparative Example 4 &

A reflective polarizing film was produced by changing the following. Specifically, PEN having a refractive index of 1.65 as a component of a plate-shaped polymer dispersion (hereinafter referred to as a first component) and PEN having a polymerization ratio of 1: 2 by mole of terephthalate, ethyl glycol, and cyclohexane dimethanol as base components A polycarbonate alloy having a refractive index of 1.58 including 38% by weight of polycyclohexylene dimethylene terephthalate (PCTG), 60% by weight of polycarbonate and 2% by weight of a heat stabilizer containing a phosphate, Components were injected into the first extruding part 220, the second extruding part 221 and the third extruding part 222 of Fig. 10, respectively. The extrusion temperature of the first component and the second component was adjusted to 295 캜 and the Cap flow meter was calibrated through IV adjustment to adjust the polymer flow, and the skin layer was subjected to the extrusion process at a temperature of 280 캜. The first component was transferred to the first pressurizing means (230, Kawasaki gear pump) and the second component was also transferred to the second pressurizing means (231, Kawasaki gear pump). The discharge amounts of the first pressurizing means are respectively 8.9 kg / h and 8.9 kg / h, respectively. Thereafter, a sea-island type mixed flow was produced by using the sea-island type extrusion-porting apparatus as shown in FIG. Specifically, the number of layers of the fourth component distribution plate (T4) in the seawater extrusion opening was 400, the diameter of the retaining hole of the component supply path was 0.17 mm, and the number of the component supply paths was 25,000. The diameter of the discharge port of the sixth corrugated distribution plate was 15 mm x 15 mm. In the three-layered feed block, skin layer components flowed from the third extruded portion through the flow path to form a skin layer on the upper and lower surfaces of the sea-island complex stream (base layer polymer). Spreading was induced in the coat hanger dies of Figs. 6 and 7, in which the base layer polymer formed with the skin layer was adjusted so that the aspect ratio of the sea-island complex flow was 1/30295. Specifically, the width of the die inlet was 200 mm, the thickness was 20 mm, the width of the die outlet was 960 mm, the thickness was 2.4 mm, and the flow rate was 1 m / min. Then, a smoothing process was performed on the cooling and casting rolls and stretched 6 times in the MD direction. As a result, the major axis length of the first component was not changed but the minor axis length was decreased. Thereafter, thermal fixation was carried out through an IR heater at 180 ° C for 2 minutes to prepare a reflective polarizing layer in which the polymer was dispersed as shown in FIG. (N _x : 1.88, n _y : 1.58, n _z : 1.58) and the refractive index of the base component was 1.58, the aspect ratio of the polymer was approximately 1/180000, the number of layers was 400 Layer. The short axis length (thickness direction) was 84 nm, the major axis length was 15.5 mm, and the average optical thickness was 138 nm. The thickness of the base layer of the produced reflective polarizing film was 59 탆, and the total thickness of the skin layer was 170.5 탆.

<Experimental Example 1>

The following properties of the reflective polarizing film prepared through the above Examples and Comparative Examples were evaluated, and the results are shown in Tables 1 and 2.

1. Relative luminance

In order to measure the luminance of the reflective polarizing film, it was performed as follows. A test display in which a panel was assembled on a 32 "edge type backlight unit in which a reflective film, a light guide plate, a diffusion plate, a reflective polarizing film and an absorption type polarizing film were sequentially provided was prepared, And the average brightness was measured.

The relative luminance is a value obtained by calculating the luminance of the other embodiments and the comparative example as a relative percentage value when the luminance of the reflective polarizing film of Example 1 is set to 100. [

2. Relative polarization degree

The polarization degree was measured at? = 550 nm and? = 650 nm using a RETS-100 analysis equipment of OTSKA. When the polarization degree of the reflective polarizing film of Example 1 was set at 100, Percentage values were calculated. The smaller the degree of polarization compared to Example 1, the less the polarization characteristic at the wavelength.

3. Relative Hayes

The haze was measured with a haze meter (NDH 200, NIPPON DENSHOKU), and the haze values of the other embodiments and the comparative example were calculated as a relative percentage value when the haze of the reflective polarizing film of Example 1 was 100. The larger the haze value in comparison with the first embodiment, the more diffusing property of outgoing polarized light is.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 The substrate layer Thickness (㎛) 80 70 70 120 120 70 120 Dispersant Distributed form random random random random random random random Average aspect ratio 1/5 1/4 1/3 1/7 1/9 1 / 3.5 1/8 Dispersant
Long axis Average length 1.03 0.9 0.77 1.17 1.42 0.86 1.36 Number of dispersions (%) having a major axis length of 0.3 to 5 占 퐉 97.9 95.2 92.7 98.6 94.2 96.7 87.5 Dispersion coefficient 70.41 62.29 74.41 70.67 90.51 57.56 93.41 D50 / D10 1.88 1.62 2.73 1.91 2.21 1.62 2.87 D10 0.43 0.45 0.32 0.46 0.38 0.39 0.31 D50 0.81 0.73 0.53 0.88 0.84 0.63 0.89 Relative luminance (%) 100 99.2 99.9 100.5 100.0 92.5 94.2 Opposite brightness (%) 500 nm 100 97.9 98.6 100 99.9 94.1 91.6 650 nm 100 98.5 99.9 100 100 89.8 98.9 Relative haze (%) 100 100 98.5 100.2 101.6 99.9 110.3

Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 The substrate layer Thickness (㎛) 70 70 120 70 120 80 60 Dispersant
Distributed form random random random random random random Random random Average aspect ratio 1 / 3.1 1/3 1 / 10.9 1 / 2.8 1/8 1 / 2.4 1/180000 Dispersant
Long axis Average length 0.72 0.7 1.93 0.64 1.65 0.49 15500 Number of dispersions (%) having a major axis length of 0.3 to 5 占 퐉 96.0 95.4 85.3 92.8 90.1 86.4 0 Dispersion coefficient 54.12 58.88 75.7 56.28 72 46.25 0 D50 / D10 1.56 2.27 2.46 2.23 2.36 3.11 - D10 0.36 0.26 0.62 0.22 0.56 0.18 - D50 0.56 0.59 1.54 0.49 1.32 0.56 - Relative luminance (%) 90.5 92.7 89.5 88.3 87.0 88.5 76.4 Opposite brightness (%) 500 nm 93.0 93.3 86.3 90.1 86.8 92.7 65.2 650 nm 89.6 91.9 90.4 85.5 91.6 86.3 63.5 Relative haze (%) 99.9 99.6 110.5 98.0 113.6 98.9 -

As can be seen from Tables 1 and 2,

In Comparative Examples 1 and 3 in which the average aspect ratio of the dispersoids exceeded 1/3, the brightness was remarkably reduced as compared with the Examples, and the polarization characteristics in the entire visible light region were not uniform. In Comparative Examples 1 and 3, the reduction in luminance can be expected to be caused not only by a decrease in polarization characteristics but also by an increase in light leakage.

In Example 10, in which the aspect ratio was more than 1/10, the brightness was remarkably lowered as compared with Example 5, which was not only deteriorated in terms of polarization characteristics but also caused by an increase in light diffusibility due to a remarkable increase in haze value .

Claims (12)

A reflective polarizing film for transmitting a first polarized light and reflecting a second polarized light among incident light,
Wherein the reflective polarizing film comprises a base layer and a plurality of dispersing bodies randomly dispersed in the base layer and having refractive indices different from each other in at least one axial direction with respect to the base layer,
Wherein the plurality of dispersions at an end face perpendicular to the uniaxial direction have an average aspect ratio of 1/3 or less and an average length of the major axis of 0.7 to 1.5 占 퐉. The method according to claim 1,
Wherein the refractive indexes of the base layer and the dispersion body are 0.05 or less in refractive index in any two axes among three axes orthogonal to each other and the difference in refractive index in the remaining one axial direction is 0.1 or more. The method according to claim 1,
Wherein the base layer has a thickness of 20 to 180 占 퐉. The method according to claim 1,
Wherein the reflective polarizing film further comprises a skin layer integrally formed on at least one surface of the base layer. The method of claim 1, wherein
Wherein the number of dispersion bodies in which the major axis length of the plurality of dispersion bodies is in the range of 0.3 to 5 占 퐉 is 90% or more of the total number of dispersion bodies. The method according to claim 1,
Wherein the plurality of dispersion long axis lengths have a dispersion factor of 60 to 92% with respect to the major axis length according to the following formula (1).
[Equation 1]

The method according to claim 1,
Wherein D ₅₀ is 0.5 to 0.9 탆 and D ₁₀ is 0.3 탆 or more in the cumulative number distribution of the long axis lengths of the plurality of dispersions. 8. The method of claim 7,
Wherein the ratio of the dispersion long axis length of D ₅₀ to the dispersion long axis length of D ₁₀ is 1.6 to 2.4. The method according to claim 1,
Wherein the average aspect ratio is 1/10 to 1/3. The method according to claim 1,
Wherein the number of dispersions having a major axis length in the range of 0.3 to 5 mu m is 90% or more of the total number of the dispersions among the plurality of dispersions, and the major axis lengths of the plurality of dispersions are A reflective polarizing film having a dispersion factor of 60 to 92%.
[Equation 1]

A light source assembly comprising a reflective polarizing film according to any one of the preceding claims. 12. A liquid crystal display comprising the light source assembly according to claim 11.

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