JP5183284B2 - Light guide plate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a light guide plate including a wire grid polarizer and a method for manufacturing the same.

  As a conventional edge-light type backlight, a method of making a wire grid polarizer directly on a light guide plate and aligning the polarization direction with the direction of the polarizer of the liquid crystal panel to improve luminance is proposed in Patent Document 1, for example. Yes. However, there is no description about a method for protecting the wire grid polarizer formed on the outermost surface of the light guide plate.

  About the light guide plate which formed the wire grid in the light emission surface like patent document 1, if another optical member is installed in the surface side, a wire grid will be damaged by rubbing with another optical member, and the performance of a light guide plate will be improved. There is a problem of deterioration.

  On the other hand, Patent Document 2 proposes a method for protecting a wire grid in a means that uses a wire grid polarizer as an optical member of a liquid crystal display device. According to Patent Document 2, after a wire grid polarizer is formed on a transparent first layer, a transparent second layer is bonded to the upper surface to protect the structure.

Japanese Patent Laying-Open No. 2005-259686 JP 2007-033560 A

  However, in the method of Patent Document 2, due to the difference in thermal expansion coefficient between the first layer and the wire grid polarizer and the difference in thermal expansion coefficient due to the difference in material between the second layer and the wire grid polarizer, Compressive / tensile stress due to temperature changes is applied to the top and bottom two locations. In addition, it is necessary to form the second layer after pattern formation. When air confined between the layers repeatedly expands and contracts due to temperature, a problem of peeling occurs. Further, even when air is confined between the first layer and the transparent second layer by the end cutting process, it is conceivable that force due to the contraction and expansion of the air due to temperature change is applied. These stresses are generated every time the power supply of the liquid crystal display is turned on and off, and functional deterioration as a wire grid polarizer can be considered during long-term use.

  The present invention has been made to solve the above-described problems. Regarding a light guide plate using a wire grid polarizer, stress is generated in the light guide plate due to temperature change, and the wire grid polarizer is deteriorated. An object of the present invention is to obtain a light guide plate and a method for manufacturing the same.

The light guide plate according to the present invention comprises a convex portion disposed on the light emitting surface on the base material, a wire grid polarizer disposed in a lower light emission surface the apex of the convex portion excluding the projection portion, the bottom portion of the convex portion And a reflecting mirror formed on the surface .

By providing a convex part on the light output surface of the light guide plate and providing a wire grid polarizer on the light output surface lower than the top of the convex part excluding the convex part, it is possible to prevent damage to the wire grid polarizer due to scratches. is there. Moreover, since the layer which protects by covering a wire grid polarizer like patent document 2 is not used, it suppresses that a stress generate | occur | produces by a temperature change and a wire grid polarizer deteriorates. In addition, since the reflection mirror is formed at the bottom of the convex portion, it is possible to prevent unpolarized light from being emitted.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments and reference embodiments thereof.

< Reference form 1>
(Constitution)
FIG. 1 is a configuration diagram of a backlight using a light guide plate including a wire grid polarizer according to Reference Embodiment 1.

  The backlight 9 has a substantially rectangular light guide plate 3 having a wire grid polarizer 4 on the light output surface, and a prism 8 is formed on the bottom surface of the light guide plate 3. The liquid crystal panel 7 is arranged. In addition, a light source 1 and a reflector 2 that condenses light from the light source 1 are installed in the vicinity of one end surface that is substantially orthogonal to the light emitting surface of the light guide plate 3. In the vicinity of the other end face that is substantially orthogonal to the light exit surface, a λ / 4 phase difference plate 6 and a reflection plate 5 are provided outside thereof.

  Here, regarding the light path, the light from the light source 1 collected by the reflector 2 is introduced into the light guide plate 3 from one end face of the light guide plate 3. The prism 8 formed on the bottom surface of the light guide plate 3 changes the traveling direction of the light, and the light is emitted from the surface on which the wire grid polarizer 4 is arranged to illuminate the liquid crystal panel 7. The wire grid polarizer 4 has a function of reflecting light having an electric field component along the wire and transmitting light having an electric field component orthogonal to the wire. The orientation of the wire grid polarizer 4 is arranged so that the extracted light passes through the polarizer of the liquid crystal panel 7.

  Further, the light reflected by the wire grid polarizer 4 reaches the wire grid polarizer 4 again by the reflector 5 via the λ / 4 retardation plate 6, and thus the λ / 4 retardation plate 6. Is passed through the wire grid polarizer 4 ideally by rotating the direction of the electric field component by 90 °.

  FIG. 2 is a cross-sectional view of the light extraction surface. In the figure, a convex portion 31 that divides the light emitting surface of the light guide plate 3 into blocks is formed, a fine structure 32 is formed on a plane that is one step lower than the convex portion 31, and a wire grid 41 is formed on the side wall of the fine structure 32. It is formed. That is, the light guide plate 3 includes a convex portion 31 installed on the light output surface of the base material of the light guide plate 3 and a wire grid polarizer 4 installed on the light output surface lower than the vertex of the convex portion excluding the convex portion. . One side of the fine structure 32 is substantially vertical, and the other is an inclined surface, and a wire grid 41 is formed on the inclined surface. The interval between the convex portions 31 is 10 to several hundred microns, and the interval between the fine structures 32 is 1 micron or less.

  FIG. 4 is a top view showing an example of one divided block. In the figure, for the sake of simplicity, the block is a square, and the area ratio between the region where the wire grid 41 is formed and the region where the convex portion 31 is formed is shown. Assuming that the length of one side of the block is A and the width of the convex portion 31 is B, for example, when A is 100 microns, B is 5.5 microns or less, and there are 90 regions in the block where the wire grid 41 is formed. % Or more is preferable.

  FIG. 5 is a view of the entire light guide plate 3 as seen from the light extraction surface of the light guide plate 3. By spreading the divided blocks over the entire surface, polarized light can be extracted from an approximately 90% region.

(Manufacturing method)
Next, the light guide plate 3 according to this preferred embodiment, especially for preparation of the light emitting surface will be described.

  The base material of the light guide plate 3 is an acrylic resin, a polyester resin, a polycarbonate resin or the like generally used as a light guide plate material. For this reason, it is possible to form a pattern in a lump by heat molding by stamping such as nanoimprint. By using the embossing method and simultaneously forming the convex portion and the fine structure on the surface of the light emitting surface, a light guide plate having improved scratch resistance can be obtained by a simple and inexpensive method.

  After the convex portion 31 and the fine structure 32 are simultaneously formed as described above, as shown in FIG. 3, sputtering or vapor deposition is performed obliquely to form a thin film of the wire grid 41 on the surface of the fine structure. The material of the wire grid 41 may be a semiconductor material such as silicon or germanium in addition to a metal. Among these, aluminum is optimal in that it has no absorption edge in the visible light region and has a relatively low melting point.

  In FIG. 3, the wire grid material 43 is formed obliquely through the mask 42. By using the mask 42, the wire grid 41 is selectively formed into a thin film in the region of the fine structure, and the wire grid 41 is prevented from being laminated on the outermost surface of the convex portion 31. By doing in this way, it can prevent that a wire grid material peels according to the abrasion when a hand and another optical member hit, and it causes as a fine dust and it causes that an optical function fall is caused.

  As the wire grid polarizer 4, it is most efficient that the periphery of the wire is an air layer having a refractive index of 1, and the effect of being embedded in the fine structure 32 is not so great. By forming the wire grid 41 only on one side of the fine structure 32, one side becomes an air layer, and the function as the wire grid polarizer 4 is not significantly reduced. Therefore, since a reduction in efficiency can be suppressed, there is also an energy saving effect.

(effect)
Thus, by forming the convex part 31 and arranging the wire grid 41 at a position that is one step deeper, it is possible to prevent damage such as peeling of the wire grid 41 due to scratches. Moreover, since the layer which protects by covering a wire grid polarizer is not used, it suppresses that a stress generate | occur | produces by a temperature change and a wire grid polarizer deteriorates. By dividing the region of the wire grid 41 into blocks, even if the wire grid 41 of a certain block is peeled off, it does not spread to the wire grid 41 of other blocks, and the defect region is set to several hundred microns or less. Is possible.

< Reference form 2>
(Constitution)
FIG. 6 is a cross-sectional view of the light extraction surface of the light guide plate according to Reference Embodiment 2 . As illustrated, the wire grid 41 is formed in a convex shape on the surface of the light extraction surface. Moreover, the convex part 31 which divides | segments the light-guide plate surface into a block in the form containing the wire grid 41 is formed.

The other configuration is the same as Reference Embodiment 1, detailed description thereof will be omitted.

(Manufacturing method)
Next, the manufacturing method of the light-emitting surface of the light guide plate 3 according to this embodiment will be described with reference to FIG.

In this reference form, unlike the reference form 1, the wire grid 41 is formed first, and then the convex part 31 is formed using a photo-curing resin.

  First, by a photolithographic method such as UV nanoimprint, a concave groove-like microstructure is formed on the surface of the light emitting surface of the light guide plate 3 with a photocurable resin. Wire grid material is embedded in the surface of the fine structure after the surface treatment with oxygen plasma so that no photocured resin residue remains, and then embedded in the fine structure groove by sputtering or vapor deposition. Form a polarizer. Next, the light curable resin and the wire grid material on the light curable resin are removed by lift-off, and a convex wire grid 41 as shown in the figure is formed on the surface of the light extraction surface.

  Thereafter, the convex portion 31 is formed of a photo-curing resin by a photolithography method.

(effect)
By setting it as the above structures, an air layer can be formed in the side wall of the wire grid 41, and the efficient wire grid polarizer 4 can be formed. In addition, although the wire grid 41 embedded in the convex part 31 almost loses a polarization function, it does not have a bad influence on others.

  Moreover, the convex part 31 formed with a photocurable resin is good also as a square pad or a dot-shaped protrusion. For example, as shown in FIG. 7, it is possible to further widen the effective area of the region where the wire grid 41 is formed by evenly spreading the square pads as the convex portions 31.

<Embodiment 1 >
(Constitution)
8, the light guide plate 3 according to the first implementation, a cross-sectional view of the light extraction surface. In the figure, a convex portion 31 for dividing the light guide plate surface into blocks is formed, a fine structure 32 is formed on a plane that is one step lower than the convex portion 31, and a wire grid 41 is formed on the side wall of the fine structure 32. . One side of the fine structure 32 is substantially vertical, and the other is an inclined surface, and a wire grid 41 is formed on the inclined surface. Further, in the present embodiment, the reflection mirror 44 is provided in a portion where the wire grid is not formed, such as the bottom of the convex portion 31. The convex portion 31 may be formed to have a light shielding property.

The other configuration is the same as Reference Embodiment 1, detailed description thereof will be omitted.

(Manufacturing method)
Next, the manufacturing method of the light-emitting surface of the light guide plate 3 according to the present embodiment will be described.

  After a fine structure is formed on the surface of the light emitting surface of the light guide plate 3 using a technique such as nanoimprinting, vapor deposition is performed without a mask as shown in FIG. 9, and a metal film is also formed on the flat portion. The metal film in the flat portion functions as the reflection mirror described above. Accordingly, the wire grid polarizer 4 is formed on the surface of the fine structure 32 and, at the same time, the reflection mirror 44 is formed in a region excluding the fine structure 32. Then, the convex part 31 is formed in the area | region of the flat part containing the reflective mirror 44 by the photolithographic method, and it becomes a structure shown in FIG. When providing the light-shielding property to the convex part 31, when forming the convex part 31, it forms with a light-shielding material.

(effect)
In the present embodiment, a reflection mirror 44 that reflects light from the inside of the light guide plate 3 to the inner side of the light guide plate (lower side in FIG. 8) is formed in the region excluding the fine structure 32 including the bottom of the convex portion 31. Therefore, it is possible to prevent the unpolarized light from being emitted. The light reflected on the inner side of the light guide plate propagates again in the light guide plate 3, is reflected on the bottom surface side, and is polarized and emitted from the surface on which the wire grid 41 is formed. Therefore, the light incident on the light guide plate 3 is effectively used. Available to:

  Further, when the convex portion 31 is formed of a light-shielding material, external light incident on the light guide plate 3 from the light emitting surface side is prevented from being reflected again by the reflecting mirror such as the bottom of the convex portion 31 to the light emitting surface side. In addition, it is possible to prevent the quality of polarized light from being deteriorated by mixing external light with the polarized light emitted from the light guide plate 3.

<Embodiment 2 >
(Constitution)
The structure of the light guide plate according to the present embodiment will be described. In the reference form 1, as shown in FIG. 5, the plurality of blocks divided by the protrusions 31 are arranged with a constant area and a constant period. However, in this embodiment, the plurality of blocks are irregularly sized. Accordingly, the arrangement of the blocks is also made random.

The other configuration is the same as Reference Embodiment 1, detailed description thereof will be omitted.

(Manufacturing method)
Next, the manufacturing method of the light-emitting surface of the light guide plate 3 according to the present embodiment will be described.

  First, using a technique such as nanoimprinting, the fine structure 32 and the convex portion 31 are simultaneously formed as shown in FIG. At this time, the area of each block divided by the convex portion 31 is set to an irregular size, and the blocks are also arranged to be random. After simultaneously forming the convex portion 31 and the fine structure 32, as shown in FIG. 3, sputtering or vapor deposition is performed obliquely to form a thin film of the wire grid 41 on the surface of the fine structure.

Since other manufacturing methods are the same as those in Reference Embodiment 1, detailed description thereof is omitted here.

(effect)
By arranging the blocks so that the area of each block is not constant and the arrangement of the blocks is also random, the occurrence of moire caused by blocking the surface of the light guide plate 3 when the liquid crystal panel is arranged is suppressed. Is possible.

It is a block diagram of the backlight using the light-guide plate provided with the wire grid polarizer by the reference form 1. FIG. It is sectional drawing of the wire grid polarizer arrangement | positioning surface of the light-guide plate by the reference form 1. FIG. It is sectional drawing which shows the preparation methods of the wire grid by the reference form 1. It is a figure which shows one block of the wire grid polarizer area | region divided | segmented by the reference form 1. FIG. It is a top view of the wire grid polarizer arrangement | positioning surface of the light-guide plate by the reference form 1. FIG. It is sectional drawing of the wire grid polarizer arrangement | positioning surface of the light-guide plate by the reference form 2. FIG. It is a figure which shows one block of the wire grid polarizer area | region of the light-guide plate by the reference form 2. FIG. It is sectional drawing of the wire grid polarizer arrangement | positioning surface of the light-guide plate by Embodiment 1 of this invention. It is sectional drawing which shows the wire grid preparation method by Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Light source, 2 Reflector, 3 Light guide plate, 4 Wire grid polarizer, 5 Reflection plate, 6 (lambda) / 4 phase difference plate, 7 Liquid crystal panel, 8 Prism, 9 Backlight, 31 Convex part, 32 Fine structure, 41 Wire Grid, 42 mask, 43 wire grid material, 44 reflective mirror.

Claims (6)

A convex portion installed on the light exit surface on the substrate;
A wire grid polarizer installed on the light exit surface lower than the top of the convex portion excluding the convex portion;
A reflection mirror formed on the bottom of the convex part ,
Light guide plate. It is a manufacturing method of the light-guide plate of Claim 1, Comprising:
(A) forming a fine structure on the surface of the light emitting surface ;
(B) forming the wire grid polarizer on the surface of the microstructure and simultaneously forming the reflection mirror in a region excluding the microstructure ;
(C) forming the convex portion in a region including the reflection mirror after the formation of the reflection mirror;
A method for manufacturing a light guide plate. The convex portion has a light shielding property ,
The light guide plate according to claim 1 . A method of manufacturing a light guide plate according to 請 Motomeko 3,
(A) forming a fine structure on the surface of the light emitting surface;
(B) forming the wire grid polarizer in the microstructure and simultaneously forming the reflection mirror in a region excluding the microstructure;
(C) forming the light-shielding convex portion in a region including the reflection mirror after the formation of the reflection mirror;
A method for manufacturing a light guide plate . The convex portion divides the surface of the light exit surface into a plurality of blocks;
The light guide plate according to claim 1 or 3 . The plurality of blocks have irregular sizes ;
The light guide plate according to claim 5 .

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