KR100893831B1 - Reflective polarizing element and the fabrication apparatus thereof - Google Patents

Abstract

The reflective polarizer of the present invention comprises a first refractive body having a prismatic structure surface arrangement;

A unit structure layer comprising a second refractive body that is coated or laminated only on any one of the structural surfaces of the first refractive body is laminated successively, the high refractive index of the second refractive body at a low refractive index of the first refractive body When the non-polarized light is incident, the polarized light is transmitted, and the reflected polarized light is reflected back to internal reflection or total reflection at the prism structure surface and recycled back to the light guide body.

The reflective polarizer having the above configuration exhibits the polarization effect and the light condensing effect at the same time, and can achieve the polarization effect without stacking many unit refractive layers unlike the conventional polarizing film due to the total reflection effect of the inner prism surface.

In addition, there is no stretching process, the continuous production by the forming roll is possible, there is an advantage that the production efficiency is greatly improved.

Polarized light, prism, polarizer, refraction, backlight

Description

Reflective polarizing element and apparatus for manufacturing same

1 is a view showing a general liquid crystal display device.

FIG. 2 is an external perspective view of the reflective polarizer of FIG. 1; FIG.

FIG. 3 is a diagram illustrating a polarization mechanism of unpolarized light in the structural layer of FIG. 2. FIG.

4 is a liquid crystal display showing a polarizing element having a different configuration from that of the polarizing film stack of FIG.

5 is a view showing the polarization mechanism of FIG.

6 is a view showing a reflective polarizer composed of a first prism, a second prism, and a polarization plane modulator.

7 is a view showing a unit structure layer of a reflective polarizer stacked in a prism form in the present invention.

FIG. 8 is a diagram schematically illustrating a second unit structure layer and a polarization mechanism according to the first refraction body of FIG.

FIG. 9 is a diagram illustrating a reflective polarizer of the present invention by repeating the unit structure layers of FIGS. 7 and 8.

10 and 11 are simplified views showing an apparatus for manufacturing the reflective polarizer of the present invention.

[Description of reference numerals for the main parts of the drawings]

1: unpolarized light 2: P polarized light 3: S polarized light

10: liquid crystal display device 11: liquid crystal display module 12: front polarizer

13: rear polarizer 14: liquid crystal layer 15: reflective polarizer

16: polarizing film stack 17: optical structured layer

18: light guide 19: reflector 20: light diffuser

21: light source 22: reflector

41: isotropic layer 42: anisotropic layer

61: first prism 62: second prism 63: polarization plane modulator

70: reflective polarizer 71: first refractive body

72: second refractive body 73: unit structure layer

1-1: Total reflection unpolarized light 1-2: Transmission unpolarized light

2-1: Transmitted P Polarized Light 3-1: Reflected S Polarized Light

100: forming roll 101: startrol 102: finish roll

103: curing device 104: injection device 105: second refractive fluid

106: injection device 107: first refractive fluid

The present invention relates to a reflective polarizer.

The polarizer is a material that converts unpolarized light whose vibration direction is not constant into polarized light that vibrates only in a specific direction.

The polarizer can be broadly divided into a transmissive polarizer and a reflective polarizer. The transmissive polarizer transmits polarized light in a specific vibration direction and absorbs polarized light that is orthogonal thereto. The transmissive polarizer is also referred to as a dichroic polarizer because the transmitted polarized light has a color, and is an iodine polarizer film in which an iodine system is adsorbed on a polyvinyl alcohol film stretched in one direction (stretched and stretched) or stretched There is a dye-based polarizing film obtained by adsorbing a dichroic dye to a polyvinyl alcohol film.

Unlike the transmissive polarizer, the reflective polarizer divides polarized light in a direction orthogonal to the light transmitted from the reflective surface of the polarizer, and reflects the polarized light oscillating in a direction parallel to the reflective surface. The reflective polarizer may be formed by laminating a reflective polarizer using a difference in reflectance between polarization components, a reflective polarizer using circular polarization reflection characteristics at a specific wavelength by cholesteric liquid crystal, and two kinds of polymer films. There is a reflective polarizing element using anisotropy of reflectance by refractive index anisotropy, and an optical element (1/4 wavelength plate) converting circularly polarized light into linearly polarized light when the selective reflection characteristic of cholesteric liquid crystal is used among the polarizing devices. ) Is used as a reflective polarizer.

On the other hand, polarizers used in LCDs require light and unnecessary light when light from the backlight unit (BLU) behind the liquid crystal panel passes through the liquid crystal and passes through the RGB pixels of the color filter. It is the part that plays a role of filtering.

In general, increasing the transmittance of a transmissive (dichroic) polarizing element lowers the degree of polarization, and thus reduces the contrast (contrast ratio) of an image when used in a liquid crystal display device.

Therefore, in the liquid crystal display device in which the contrast ratio is as important as the luminance according to the transmittance, more reflective polarizers are used.

That is, in order to increase the luminance of the light incident on the polarizing plate disposed immediately before the liquid crystal layer is incident to the limited light source, the reflected light other than the transmitted polarized light should be returned to the light guide or the reflecting plate as much as possible and reflected again. It is necessary to change the incident light to polarized light as close as possible to the polarization direction of the polarizing plate again by reflecting polarized light.

Among the polarizing elements, in the case of a reflective polarizing element in which two kinds of polymer films are stacked to use anisotropy of reflectance due to refractive anisotropy, optical isotropic in order to induce polarized light with respect to light having a specific design wavelength (for example, 550 nm). And two types of films each having optical anisotropy and at least 600-800 layers or more are laminated in an extremely thin thickness of 1/2 of the design wavelength and stretched in one direction.

In this case, manufacturing is difficult and the price is expensive.

Unlike the stacked reflective polarizers as described above, two kinds of prism sheets each having optical isotropy and anisotropy are laminated in a direction facing each other. The number of stacks is reduced, but the optical anisotropy is given to any one prism sheet. A separate process (for example, stretching process) was added, and this was not an easy process because the angle of the structural surface of the prism sheet should be maintained at about 90 degrees even after the stretching process.

In the present invention, unlike the conventional reflective polarizers that require such a complex manufacturing process, it is necessary to implement a reflective polarizer in which a prism sheet can be stacked in a continuous manner without requiring an stretching process and greatly reducing the number of stacked layers.

In order to achieve the object of the invention as described above, the present invention has the following main technical configuration.

The present invention is characterized in that the unit structure layer consisting of a first refractive body having a prismatic structure surface arrangement and a second refractive body coated or laminated only on any inclined surface of the structural surface of the first refractive body is laminated successively It is done.

In addition, in order to successively laminate the unit structure layer as described above, the star roll supplying the above-described refraction body or the structural layers of the intermediate step and the forming roll into which the substrate of the refraction body or the structural layer is introduced and molded in the forming roll A manufacturing apparatus based on a finish roll winding the structural layer can be designed.

Of course, in the above manufacturing apparatus, a spraying apparatus for selectively spraying and applying a second refractive body to any inclined surface of the prism-shaped structural surface formed on the forming roll, or a substrate drawn from the forming roll or the start trolley. An injection device for injection coating the refractor is added.

In order to more specifically represent the main technical features of the present invention will be described in more detail below with reference to an example of the present invention included in the drawings.

However, it is to be understood that the components and the coupling structure of the embodiments of the present invention or specific examples described below do not limit the idea inherent in the technical features of the present invention. Reveal it.

1 briefly illustrates a form of the liquid crystal display device 10 currently implemented. In the drawing, the lowermost portion is responsible for light emission and light induction, and the light emitted from the light source 21 is guided to the light guide 18 by the reflector 22, and the bottom of the light guide 18 A light reflecting and diffusing configuration consisting of the reflecting plate 19 and the light diffusing portion 20 may be arranged.

The light emitted through the light guide 18 is incident on the reflective polarizer 15. The reflective polarizer 15 has an extremely thin film having optical properties in different directions and has a stack of tens to hundreds of layers. The polarizing film laminated portion 16 and the optical structured layer 17 for condensing the polarized light while passing through the laminated portion.

Light emitted through the light guide and the reflective polarizer is uniformly incident to the liquid crystal display module 11 almost uniformly with a constant vibration direction, and passes through the rear polarizer 13 of the liquid crystal display module 11 to form a liquid crystal. Incident on layer 14.

In this case, when no voltage is applied to the liquid crystal layer 14, the incident light passes through the twisted optical path of the liquid crystal layer to transmit the front polarizing plate 12 with an optical vibration direction corresponding to the polarization direction of the front polarizing plate 12. will be.

FIG. 2 briefly shows the configuration of the reflective polarizer 15 of FIG. 1 in an external perspective view. The multiple polarizing film stacking portions repeated A, B, A, B ... in the drawing may include hundreds or thousands of layers, and the material of the film may be selected according to the optical performance required for each structural layer.

In general, the laminated layer is stretched in one direction in a laminated state in this case. In this case, the layer B has a constant refractive index and the refractive index is changed depending on the elongation length regardless of the elongation direction 21 and the elongation length. It is laminated | stacked alternately by (A), respectively.

In the figure, layer A exhibits the property that the refractive index is changed by the stretching treatment. For example, the refractive index (1.88) is shown in the stretching direction, while the other refractive index is shown in the transverse direction. On the other hand, layer B exhibits a nominal refractive index (1.64) which is hardly changed by the stretching treatment.

In this case, the laminated layers A, B, A, B ... have a large refractive index difference between layers, and at this time, the P-polarized light 2 transmitted while the non-polarized light is transmitted and reflected in each layer is repeated. It is divided into S-polarized light that is reflected.

FIG. 3 schematically illustrates a polarization mechanism of unpolarized light in the unit A and B stacked layers of FIG. 2. In the drawing, unpolarized light (1 = thick solid line) is incident on the A layer having a high refractive index in the B layer having a small refractive index. Is polarized by P polarized light (2 = thin solid line), which is transmitted light, and S polarized light (3 = thin dotted line), which is reflected light, in a direction orthogonal to the P polarized light (2). Of course, the incident angle of the unpolarized light 1 and the reflected angle of the S polarized light 3 will be the same.

The polarization process cannot be completed in one layer, and some unpolarized light and S polarized light remain in the P-polarized light, which is transmitted light. The remaining components are again incident on the A layer to the B layer, where some unpolarized light is split into P polarized light, which is transmitted light, and S polarized light, which is reflected light.

Since the S-polarized light finally bounced under the B layer in the above process is diffused and re-reflected by the light guide or the reflector to be incident back to the B layer, it may contribute to increase the luminance of the liquid crystal display.

However, since the planar stacked reflective polarizer is difficult to secure a polarization angle, it is necessary to stack a very large number of layers. Preferably, in order to induce constructive interference, a non-polarized wavelength incident on the thickness of the A + B layer is required. You need to adjust it to 1/2 of.

FIG. 4 shows a liquid crystal display device showing a polarizing element having a different configuration from that of the polarizing film stacking portion 17 of FIG. 2.

In the drawing, the prism sheet-like reflective polarizer 40 is located on the rear polarizing plate 13, and is composed of a prism sheet-like isotropic layer 41 made of an isotropic member and a prism sheet-shaped anisotropic layer 42 made of anisotropic member. The anisotropic layer 42 is positioned on the backlight 6 side, and the isotropic layer 41 is positioned on the liquid crystal layer 14 side and stacked on each other.

5 illustrates that the non-polarized light 1 incident on the prism sheet-shaped reflective polarizer 40 of FIG. 4 is orthogonal to the P-polarized light 2 transmitted through the prism boundary surface 43 and the P-polarized light, and is reflected at the boundary surface. The figure which showed S polarized light (3). 4 and 5, a plurality of triangular pyramidal prismatic portions having an isosceles triangle cross-section is stacked so that the prism boundary surface 43, which is an inclined surface, face each other and constitute a geometrical surface.

Meanwhile, the ridge direction of the inclined surface 43 coincides with the transmission axis direction of the rear polarizing plate.

In the prism sheet-shaped reflective polarizer 40, the direction parallel to the ridge line of the prism portion in the anisotropic layer 42 is X direction, perpendicular to the X direction, and parallel to the front and rear surfaces of the reflective polarizer 40 Y direction. In addition, the directions perpendicular to the front and rear surfaces of the reflective polarizer 40 are in the Z direction. When the refractive index in the X direction in the anisotropic layer 42 is NX1, the refractive index in the Y direction is NY1, and the refractive index in the Z direction is NZ1, these relationships are NX1> NY1 = NZ1. When the refractive index in the isotropic layer 41 is NX2, the Y-direction refractive index is NY2, and the Z-direction refractive index is NZ2, these relations are NX2 = NY2 = NZ2.

Based on the above characteristics, the relationship between the relative refractive index between the isotropic layer 41 and the anisotropic layer 42 can be derived that NX1> NX2 (= NY2 = NZ2)> NY1 = NZ1.

In the polarization mechanisms shown in FIGS. 4 and 5, when the non-polarized light 1 is incident toward a larger relative refractive index, the S-polarized light is split and reflected perpendicularly to the P-polarized light 2 and P-polarized light 2 transmitted. Polarized light 3 illustrates the mechanism by which the reflected S-polarized light can be totally reflected at the prism interface and returned to the light guide to be recycled through reflection / diffusion / scattering. However, some S-polarized light may be transmitted without total reflection depending on the angle of incidence after reflection, so a perfect polarization effect is difficult to expect.

FIG. 6 illustrates a reflective polarizer including a first prism 61, a second prism 62, and a polarization plane modulator 63, unlike the polarization structure using one prism boundary plane as shown in FIG. 5.

The polarization splitting part of the reflective polarizing element includes a first refractive prism 61 having a high refractive index and a second prism 62 having a low refractive index. The first prism 61 is an inclined surface 64 inclined such that the incident angle of the unpolarized light 1 is approximately the Brewster angle (polarization angle = θ _b ).

In the drawing, the first prism 61 polarizes and splits the unpolarized light 1. At this time, the polarization plane modulator 63 modulates the phase of the reflected polarized light polarized and divided by the first prism 61.

The polarization dividing portion serves as a dividing portion for dividing the unpolarized light 1 into transmitted light and reflected light in which the polarization plane intersects each other perpendicularly at the boundary surface between the inclined surfaces 64 and 65. Here, the interface between the inclined surfaces 64 and 65 is a boundary for dividing the P-polarized light 2 having a vibrating surface perpendicular to the boundary, that is, a division for dividing the P-polarized light and the S-polarized light with the vibrating surface perpendicular to each other. Is transmitted to and reflects the S-polarized light 3 having an oscillating surface parallel to the interface.

Meanwhile, the reflected light split by the polarization splitter is modulated by the polarization plane modulator 63, and the polarization plane modulator 63 is parallel to the second prism 62 and the unpolarized light 1 having a low refractive index. It is a half-wave plate provided between the surfaces of the first prism 61. The polarization plane modulator 63 serves as a phase modulator for changing the polarization plane of the reflected light reflected from the inclined plane 64 and matching this polarization plane with the polarization plane of the transmitted light, that is, parallel to the inclined plane 64. It modulates the phase of the reflected S-polarized light having an oscillation surface by 1/2 wavelength.

In the polarizing element, the inclined planes of the prisms are inclined such that the incident light of the unpolarized light 1 is generally the Brewster angle θ _b as the incident light source, so that any incident polarized light is incident to the P polarized light 2 by the inclined plane 64. And S polarized light 3. Then, the reflected S-polarized light 3 is converted into P-polarized light by the 1/2 wave plate by the polarization plane modulator 63 parallel to the incident light. As a result, unpolarized light as any polarized light is directed to a non-directional linear polarized light polarized in one direction so that it can be used in a liquid crystal display without optical loss.

However, in the reflective polarizer shown in Fig. 6, when the unpolarized light 1 is incident on the incidence plane, the polarization plane modulator 63 is a half wave plate, sometimes not incident on the inclined plane 64 of the prism. Will be joined. At this time, the reflective polarizer cannot satisfy the function of aligning the light incident on the 1/2 wave plate without being incident on the inclined surface 64 of the prism into linearly polarized light so as to be emitted from the reflective polarizer. For this reason, the problem that the function of a polarizing element falls and the light absorbed in the absorption axis direction of a polarizing element increases.

In order to overcome the above disadvantages, a method of increasing the probability that the unpolarized light 1 is incident on the prism inclined plane 64 can be considered, and a plurality of prisms having the polarization plane modulator 63 can be stacked.

FIG. 7 illustrates a unit structure layer 73 which is an initial configuration step of a reflective polarizer stacked in a prism form in the present invention.

In the drawing, the first refractive body 71 is shaped into a prism shape (a vertex angle of 80 ° to 110 °), on which a second refractive body 72 is formed at any one portion of the prism inclined surface in which the first refractive body is formed in a mountain shape. Only coated or laminated.

Of course, in the unit structure layer 73, the bottom surface of the first refractive body 71 where the first stacking is started may be flat.

It can be seen that the coating or lamination on only one inclined surface at the prism boundary as described above with reference to FIG. 10, which does not vertically inject the second refractive body 72 to be coated on the prism surface, and inclines only one inclined surface. It can be implemented by the method of spraying a minute and then compression molding with a forming roll.

The material of the refractors may be a polymer resin such as acrylic, PEN, etc., light transmittance and refractive index (typically 1.4 to 1.8) is adjustable, it should be a material having a glass transition temperature is not too high.

The refractive index of the first refractive body 71 is preferably about 1.5, and the refractive index of the second refractive body 72 is preferably about 1.75.

If the non-polarized light is incident from the lower side to the upper side in the configuration as described above, the non-polarized light is incident at a high refractive index at a low index of refraction on the inclined surface on which the second refractive index is stacked. Also increases the probability.

FIG. 8 schematically illustrates the second unit structure layer and its polarization mechanism in the state in which the first refractive body 71 is laminated once again in FIG. 7.

In the figure, the unpolarized lights 1, 1-1 and 1-2 are each polarized, totally reflected or transmitted at the prism interface.

In this case, since the second refractive index 72 has a relative refractive index higher than 0.25, polarization splitting through reflection is performed in a range of incident angles wider than the incident angle of unpolarized light incident from the first refractive index 71 to the first refractive index 71. This can happen.

When the non-polarized light 1 is reflected at the prism boundary surface, the polarized light is split into P polarized light 2 transmitted and S polarized light 3 reflected at a 90 ° angle with the P polarized light. Transmitting P-polarized light oscillating in the direction perpendicular to the maximum, and S-polarized light oscillating parallel to the interface is returned and recycled as much as possible. Of course, depending on the incident angle of the non-polarized light, the transmitted P-polarized light 2-1 may return to the light guide body again, and the reflected S-polarized light 3-1 may pass through the upper layer again without returning. As the structure layer is repeatedly transmitted, more P-polarized light is transmitted vertically upwards, and more S-polarized light bounces back down the light guide body and the reflecting surface.

9 is a diagram illustrating the reflective polarizer 70 of the present invention by repeating the unit structure layers of FIGS. 7 and 8.

In the drawing, it is possible to observe the unit structure layer 73 in which the second refraction body 72 in which only one side of the prism interface is laminated on the prism type structure layer of the first refraction body 71 is repeatedly stacked. Due to the effect, the number of the structural layers is much smaller than hundreds to thousands of layers, which are laminated layers of a general polarizing film.

For reference, in the drawing, when the stack thickness of the second refractive body 72 is designed to be 1/2 of the unpolarized wavelength, the polarization modulation using the phase difference (such as the polarization plane modulator 63 in FIG. 6) is performed. Of course you can.

10 and 11 briefly illustrate an apparatus for manufacturing the reflective polarizer 70 of the present invention shown in FIG.

When the substrate layer made of the first refractive body is introduced into the forming roll 100 in the start troll 101 of FIG. 10, the second refractive fluid 105 (second = second) in the injection device 104 inclined at an angle to the upper portion of the forming roll. (Refer to the raw material in the state in which the refractor is fluidized) is sprayed finely and is coated only on one inclined surface on the prism surface of the forming roll 100.

The second refractive fluid may be coated by continuously installing a roll or bar coating portion of a polymer resin (resin) having a viscosity of about 5000 to 10,000 at a temperature of about 25 degrees.

Subsequently, when the base layer of the first refractive body is combined with the forming roll, the unit structure layer 73 as shown in FIG. 7 is formed and wound on the finish roll 102.

At this time, the curing apparatus 103 is properly disposed in the middle of the process to help the first refractive body and the second refractive fluid to be smoothly combined.

In FIG. 11, when the unit structure layer 73, which has undergone the process of FIG. 10, is drawn toward the forming roll 100 from the start roll 101, the first refractive fluid in the injection device 106 disposed on the forming roll. (107 = refers to the raw material in the state in which the first refractive body is fluidized) is micro-sprayed and coated on the entire prism face of the forming roll 100.

Then, when the unit structure layer is combined with the forming roll, as shown in FIG. 8, a structure layer in which the first refractive body 71 is laminated on the unit structure layer is formed and wound on the finish roll 102.

In this case, as in FIG. 10, the curing devices 103 may be properly disposed in the middle of the process to help the unit structure layer and the first refractive fluid to be smoothly combined.

After the process of FIG. 9 is again performed, two unit structure layers may now be stacked. Similarly, repeating the process of FIGS. 9 to 10 may provide a reflective polarizer 70 having a plurality of unit structure layers stacked thereon. .

While the embodiments of the present invention have been described in detail with reference to the drawings, the technical spirit of the present invention is not limited to the above embodiments.

In other words, those skilled in the art to which the present invention pertains, modifications and extended embodiments that are not included in the specification and drawings of the present invention as needed by utilizing the technical spirit contained in the specification and drawings of the present invention. It will be possible to further implement but this is also obviously included in the scope of the technical idea uniquely possessed by the present invention.

As described above, the reflective polarizer of the present invention exhibits a polarization effect and a light condensing effect simultaneously due to the geometric reflective surface peculiar to the prism plane, and is appropriately combined with the total reflectance effect of the inner prism plane and an increase in reflectance due to the difference in interlayer refractive index. Unlike conventional polarizing films, polarizing effects can be achieved without stacking a large number of unit refractive layers.

In addition, unlike the general polarizing laminated film, there is no stretching process, it is possible to continuously produce by the roll has the advantage that the production efficiency is greatly improved.

Claims (8)

And a unit structure layer comprising a first refractive body having a prism-shaped structure surface array and a second refractive body coated or laminated only on any one of the structural surfaces. The method of claim 1, The refractive index of the refractive body is selected from the range of 1.4 ~ 1.8, the refractive index of the second refractive body is reflective polarization element, characterized in that larger than 0.25 by the refractive index of the first refractive body. The method of claim 1, The prism structure surface of the unit structure layer has a reflection angle of 80 ° ~ 110 ° vertex. The method of claim 1, The upper surface of the uppermost structure layer and the lower surface of the lowermost structural layer of the unit structure layer is a reflective polarizing element, characterized in that the plane. A star trol for supplying a first refractive sheet having a prism-shaped structural surface array; A forming roll into which the first refractive sheet is drawn; A spraying apparatus for selectively spraying and applying a second refractive body to any inclined surface of the prism-shaped structural surface formed on the forming roll; And A finish roll for winding a sheet of unit structure layer formed of the second refractive body coated or laminated on only one inclined surface of the first refractive body and the structural surface of the first refractive body formed by the forming roll. Apparatus for manufacturing a polarizing element. A star trol which supplies a unit structure layer sheet made of a first refractive body and a second refractive body which is coated or laminated on only one of the inclined surfaces of the first refractive body and the structural surface of the first refractive body; A forming roll into which the unit structure layer sheet is drawn; An injection apparatus for injecting and applying the first refractive body to the structural surface of the unit structure layer sheet or the forming roll; And And a finish roll for winding a mixed structure layer sheet in which the unit structure layer and the first refractive body formed by the forming roll are stacked. A star trol which supplies a unit structure layer composed of a first refractive body and a second refractive body coated or laminated only on one of the inclined surfaces of the first refractive body and the structural surface of the first refractive body; A forming roll into which the mixed structure layer sheet is inserted; A spraying apparatus for selectively spraying and applying a second refractive body to any inclined surface of the prism-shaped structural surface formed on the forming roll; And A finish roll for winding a multi-layer unit structure layer sheet formed of a second refractive body coated or laminated on only one of the inclined surfaces of the mixed structure layer and the mixed structure layer formed by the forming roll. Apparatus for manufacturing a polarizing element. The method according to any one of claims 5 to 7, Apparatus for manufacturing a reflective polarizing device, characterized in that a curing device is added between the start trol and the finish roll.

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