JP2003337224A - Polarization beam conversion element, its manufacturing method and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization beam conversion element which can be manufactured in a simple process, whose manufacturing cost can be suppressed and which, even with a large area, is easy to manufacture. <P>SOLUTION: Inclined planes 11a and 11b facing each other with different inclination directions are alternately repeatedly formed on the surface of a transparent substrate 1 or at the middle position in the direction of thickness of the transparent substrate 1, a polarized light separating film 2 is formed on the inclined planes 11a and 11b, and at least a quarter-wave plate 3 and a reflector 4 at a position corresponding to a pair of inclined plates are arranged on the surface of light incident side of the substrate 1. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization beam conversion element for converting non-polarized light or the like into a unidirectional polarization component, a method for manufacturing the same, and a liquid crystal display device.

[0002]

2. Description of the Related Art For example, in a liquid crystal panel display, the light of a backlight is applied to a liquid crystal panel through a polarizing plate, and the transmitted light is turned on / off depending on the alignment state of the liquid crystal depending on the presence or absence of an electric field application. It is displaying. In such a liquid crystal panel, since only light of a specific polarization direction that has passed through the polarizing plate is used, 50% or less of the light of the backlight can be used for display. Therefore, in order to improve the brightness of the display screen, it is indispensable to increase the output of the backlight, resulting in an increase in power consumption. For this reason, for example, a backlight using a light guide plate that efficiently emits light from a light source in the surface direction has been proposed (see, for example, Non-Patent Documents 1 and 2).

Therefore, in order to improve the utilization efficiency of the backlight light, it has been studied to convert the polarized light of the backlight light and utilize most of the light, and a sheet-shaped polarizing element for a liquid crystal panel has been disclosed. (For example, Patent Documents 1 to 3)
reference. ). By using these sheet-shaped polarizing elements, it is possible to convert the non-polarized light from the backlight into linearly polarized light having a specific polarization direction, and as a result, it is possible to dramatically improve the utilization efficiency of the light source, It is expected that low power consumption and high brightness will be achieved.

As a structure of a plate-like polarizing element which is widely used at present, as shown in FIG. 14, a plate is formed by obliquely sandwiching a polarization separation film 102 with glass 101 having a high transparency and a high or low refractive index. And the polarization separation films 102 are arranged at a constant pitch, and according to the pitch of the polarization separation films 102, the ½ wavelength plate 103 is arranged corresponding to every other polarization separation film 102. The formed one is typical. With respect to the plate-shaped polarizing element having such a structure, the light shielding plate 1 in which the slit 104a is arranged corresponding to the arrangement position of the half-wave plate 103
When 04 is provided and light is introduced through this slit 104a, for example, P-polarized wave is transmitted through the polarization separation film 102,
The half-wave plate 103 converts the S-polarized wave. One S
The polarized wave is reflected by the polarization separation film 102, and is derived from the region without the half-wave plate 103 as it is as the S-polarized wave.

In the plate-shaped polarizing element having the above structure, a polarization separation film is formed on the surface of a large number of flat glass plates by a vapor deposition method or a sputtering method, and then these glass plates are superposed and adhered to each other. It is manufactured by cutting (slicing) a glass plate laminated in multiple layers so as to form a predetermined angle (for example, 45 degrees) with respect to the surface, and further mirror-polishing the sliced both surfaces. After this mirror-polishing, half-wave plates are attached to every other position corresponding to the pitch of the polarization separation film.

However, since the plate-shaped polarizing element manufactured through such a process is manufactured through many steps, the manufacturing cost is increased. To illustrate the steps required in the above manufacturing process, for example, glass mirror polishing, cleaning, polarization separation film formation, adhesive application, lamination fixing, adhesive curing temperature heating, jig fixing for diagonal slicing, slicing with a wire saw , Separation and cleaning from jigs, rough polishing on both sides, mirror polishing, and cutting of grindstones for shaping. In addition, according to the above process, it is extremely difficult to manufacture a polarizing element having a large area.

As the structure of the polarizing element for the purpose of polarization separation / conversion, in addition to the example of the laminated member in which the polarization separation film is obliquely provided, a resin molded sheet in which right-angled triangular prisms are arranged in an array There is also a report in which a polarization separation film and a polarization modulator are formed (for example, Patent Document 4).
reference. ). In this example, a polarization separation film is formed on the slope of the triangular prism having the shape of the right triangle, and an optical thin film serving as a polarization modulator is formed on the vertical surface.

However, in order to form the polarization splitting film on the inclined surface of the triangular prism having a right triangle shape and the optical thin film as the polarization modulation portion on the vertical surface, it is necessary to form a uniform film particularly near the groove bottom of the right triangle shape. Is extremely difficult due to the shadow effect on the side wall of the groove, and the yield is reduced when mass production is considered.

Further, there is reported a polarization beam conversion element in which a material having an isotropic refractive index and a material having anisotropy are combined by providing a boundary surface on a triangular cross section (see, for example, Patent Document 5). However, in this case, since the anisotropic refractive index material is used, the cost is increased,
In addition, since it is necessary to align the crystal axes, workability and productivity in the manufacturing process may be reduced, which is disadvantageous in mass production.

[0010]

[Non-Patent Document 1] Akira Hiroe, "New Trend of Injection Molding System", Plastics, November 2001, Supplement, Industrial Research Committee, p12-17

[Non-Patent Document 2] Yoji Oki, "Overview of Latest Backlight Technologies", FLAT PANEL DISPLAY 20
02, Techno Times, p218-223.

[Patent Document 1] JP-A-11-84129

[Patent Document 2] Japanese Patent Laid-Open No. 11-202108

[Patent Document 3] Japanese Patent Laid-Open No. 9-265010

[Patent Document 4] Japanese Patent Laid-Open No. 10-96815

[Patent Document 5] Japanese Unexamined Patent Publication No. 2000-221324

[0011]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned conventional circumstances, can be manufactured by a simple process, can suppress the manufacturing cost, and
It is an object of the present invention to provide a polarized beam conversion element that can be easily manufactured with a large area.

[0012]

In order to achieve the above-mentioned object, the polarized beam conversion element of the first invention is different from each other in the inclination direction at the surface of the transparent substrate or at the intermediate position in the thickness direction thereof. Facing oblique planes are alternately and repeatedly formed. A polarization separation film is formed on the oblique planes, and at least a quarter wavelength plate is provided on the light incident side surface of the transparent substrate, which corresponds to a pair of oblique planes. The reflector is arranged at the position.

The polarized beam conversion element according to the second aspect of the present invention is characterized in that the surface of the transparent substrate or the intermediate position in the thickness direction thereof is
Opposite sloping planes with different inclination directions are alternately and repeatedly formed.The polarization separation film is formed on the sloping planes, and the light guide plate is arranged at the light incident side position of the transparent base material. A reflector, or a quarter wavelength plate and a reflector are arranged.

According to each of the above-described polarized beam conversion elements according to the present invention, as in the conventional polarized beam conversion element described in FIG. 14, conversion to linearly polarized light is performed while maintaining the utilization efficiency of the light source. You can That is, in the above-described polarization beam conversion element according to the first aspect of the present invention, the incident light is incident on the polarization separation film provided on the oblique plane, passing between the reflection plates. The reflector is arranged corresponding to the pair of oblique planes. That is, it is provided on the upper portion of every other inclined plane or on the upper portion of the adjacent inclined planes facing each other.

For example, the case where the polarization separation film is configured to reflect S-polarized light will be described. The incident P-polarized wave is
The light is transmitted through this polarization separation film while maintaining the polarization component, and is emitted to the other surface of the transparent substrate. On the other hand, the S-polarized component is
The light is once reflected by the polarization separation film, passes through the incident side quarter wavelength plate, is reflected by the reflection plate, passes through the quarter wavelength plate again, and is incident on the polarization separation film. At this time, the S-polarized wave passes through the quarter-wave plate twice, so that the phases of the ordinary component and the extraordinary component deviate by half a wavelength, are converted into orthogonal P-polarized light, and enter the polarization separation film again. To be done. The P-polarized wave passes through the polarization separation film and is emitted to the other surface of the transparent base material. In this way, it is possible to obtain a polarization beam conversion element capable of converting linearly polarized light while suppressing a decrease in the amount of light.

On the other hand, in the polarized beam conversion element according to the second aspect of the present invention, the light incident from the light source from the incident side of the transparent substrate can be efficiently converted into the linearly polarized light by the light guide plate. Also in this case, the case where the polarization separation film is configured to reflect the light of the S-polarized component will be described. The P-polarized component of the light incident on the transparent base material from the light guide plate passes through the transparent base material as it is. On the other hand, the S-polarized light component is once reflected by the polarization separation film, passes through the light guide plate, passes through the quarter-wave plate provided behind the light guide plate, is reflected by the reflector plate, and is again divided into quarters. After passing through the wave plate, it is converted into orthogonal P-polarized light, is incident again on the polarization separation film, is transmitted through this polarization separation film, and is emitted to the other surface of the transparent substrate. In this way, it is possible to obtain a polarized beam conversion element with an increased utilization efficiency of light quantity.

The polarized beam conversion element of the present invention can be manufactured by a manufacturing method with simple steps, the manufacturing cost can be suppressed, and a large area can be manufactured. That is, a method of manufacturing a polarization beam conversion element according to the present invention comprises a step of forming a polarization separation film on a slant plane of a first transparent member on which slant planes having different tilt directions and facing each other are formed. A step of arranging a second transparent member on a plane and filling an uncured photocurable resin between the oblique plane and the second transparent member, and a step of interposing the first or second transparent member. A transparent base material is produced by a step of curing the photo-curable resin by light irradiation to flatten the inclined plane, and at least a quarter wavelength plate and a pair of inclined planes are formed on the flattened surface. A reflector is formed at a position corresponding to the upper position.

Further, in another method of manufacturing the polarization beam converting element according to the present invention, the step of forming the polarization separation film on the oblique plane of the first transparent member in which the oblique planes facing each other having different inclination directions are formed. And a step of arranging a second transparent member on the inclined plane and filling the uncured photocurable resin between the inclined plane and the second transparent member, and the first or second transparent member. A transparent base material is produced by a step of curing the photo-curable resin by irradiating light through the plate and flattening the oblique plane. A wave plate and a reflector are arranged, and a light guide plate is arranged between them.

As described above, in the method of manufacturing the polarized beam conversion element according to the present invention, the inclined surfaces facing each other are provided, that is, the groove surface of the transparent member (the glass substrate or the highly transparent organic material substrate) having the inclined grooves facing each other. It can be manufactured by forming a polarization separation film by sputtering, vapor deposition or the like, and filling the inclined groove with a highly transparent material (for example, a highly transparent organic material). Therefore, the polarization beam conversion element according to the present invention is manufactured without using a machining process such as lamination bonding, slicing, flat surface polishing, and mirror surface polishing, and a complicated process is not required, so that the manufacturing cost is significantly increased. Can be suppressed to. Further, it is easy to increase the area. Further, such a polarized beam conversion element of the present invention reduces the shadow effect phenomenon due to the groove slope surface itself when the polarization separation film is formed on the slope surface by the vapor deposition method or the sputtering method by adopting the oblique surface facing each other. It is possible to form a uniform film up to the bottom of the groove, avoid a decrease in yield in the manufacturing process, manufacture with good productivity, and reduce costs. Further, by using this to configure a liquid crystal display device, size reduction and cost reduction can be achieved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a polarization beam conversion element to which the present invention is applied and a method for manufacturing the same will be described in detail with reference to the drawings.

(1) First Embodiment In any of the polarization beam conversion elements to which the present invention described below is applied, a transparent member is used as the material of the transparent base material, and the intermediate position in the thickness direction is set. A case in which a polarized light separation film is formed in FIG. FIG. 1 shows an example of the configuration of a polarized beam conversion element according to the first embodiment of the present invention. The polarization beam conversion element shown in FIG. 1 has a transparent base material 1 on which a polarization separation film 2 is formed as a main constituent element, and a ¼ wavelength plate 3 is provided on one surface (surface on the light incident side) of the transparent base material 1. The reflector 4 and the lens array 5 are formed. In this way, by forming the lens array 5 having the function of the condenser lens in advance, the incident light can be efficiently condensed between the reflection plates 4, and the liquid crystal display device incorporating this polarization beam conversion element. It is possible to achieve simplification and downsizing of the configuration of the optical device such as.

The transparent substrate 1 is made of, for example, a resin having a refractive index of 1.8, has oblique planes 11a and 11b facing each other by forming grooves having a V-shaped cross section, and is made of a transparent material. The transparent member 11 and the inclined plane 1 facing each other
The polarization splitting film 2 is formed on one of the inclined planes 11a of 1a and 11b, and the second transparent member 12 that fills the groove. The polarization separation film 2 is formed at the interface between the first transparent member 11 and the second transparent member 12.

The transparent member 11 is made of, for example, a highly transparent resin such as polymethylmethacrylate, polycarbonate, or Arton, an acrylic UV-curable resin filled with inorganic fine powder such as TiO ₂ or SiO ₂ , and a mixture of silicone resin. Etc., and can be easily molded into a shape having the inclined surfaces 11a and 11b by using a mold or the like. It can also be manufactured by shaving glass with a cutting tool or grindstone.

Inclined surface 11 formed on the transparent member 11
a and 11b are 45 with respect to the substrate surface, that is, the main surface or the back surface of the transparent substrate 1 which is the incident end surface of the incident light.
They are formed with an inclination angle of degrees, and these are alternately and repeatedly formed. Therefore, the cross-sectional shape is, so to speak, sawtooth.

A polarization separation film 2 is formed on the inclined surfaces 11a and 11b. The polarization separation film 2 has a function of transmitting only one of the orthogonal linearly polarized lights and reflecting the other. Is. The polarization separation film 2 is generally composed of
When the reference wavelength of the incident light is λ ₀ , a high refractive index layer H and a low refractive index layer L each having an optical film thickness substantially equal to λ 0/4 are used to form a repeating structure (HL) m of HL (however, , M is an integer of 4 or more), or (0.5HL0.5H) m (m is a power of m times)
It is composed of a multilayer film having a structure shown in. By forming such a polarization separation film 2, it becomes possible to realize sufficient polarization separation characteristics over a wide wavelength range.

As another example of the structure of the polarization separation film,
Basic structure film including an optically transparent high refractive index layer H having a predetermined refractive index with respect to incident light, and an optically transparent low refractive index layer L having a lower refractive index than the high refractive index layer H. H2L
Is a repeating structure of this basic structure film (H2
L) m, (H2L) mH, or 2L (H2L) m
(However, m is an integer of 3 to 7) can be mentioned as a multilayer film. Also in this multilayer film, when the reference wavelength of incident light of 550 nm is λ ₀ , both the high refractive index layer H and the low refractive index layer L are λ ₀ /
By setting the optical film thickness to be almost equal to 4, it functions well as a polarization separation film.

The first transparent member 11 on which the polarization separation film 2 is formed is flattened by the second transparent member 12 so as to fill the groove. For the second transparent member 12, for example, an ultraviolet-curable acrylic transparent resin or a silicone resin mixture is used, and like the first transparent member 11, the same material is used.
Fine powder such as TiO ₂ or SiO ₂ may be dispersed.

On the other hand, the quarter wave plate 3 and the reflection plate 4
Are stacked in this order, and in the direction along the surface of the transparent base material 1, for example, the inclined surface 11 corresponds to one inclined surface.
It is provided on the light incident side surface of the transparent substrate 1 at a position corresponding to a. The pitch is almost the same as that of the inclined surface 11a, and the width thereof is almost the same as the width of the inclined surface 11a projected on the surface of the transparent substrate 1.

Here, as the quarter-wave plate 3, for example, a composite film obtained by laminating films produced by stretching polypropylene or polycarbonate can be used. Other examples of the quarter-wave plate 3 include a stretched film using polyethylene, polyvinyl alcohol, polysulfone, polyarylate, and the like, and a laminated composite film thereof. As the reflection plate 4, a sputtered film of Al or Ag is formed on a polyethylene terephthalate (PET) base, and TiO ₂ is formed on the sputtered film.
It is possible to use a film or the like having an increased reflection film formed of SiO ₂ and SiO ₂ .

Next, the function of the polarized beam conversion element having the above structure will be described. In the polarized beam conversion element, as shown in FIG. 2, the incident light projected from the back side is first transmitted by the lens array 5 to the transparent base material 1.
Is focused on a region where the quarter-wave plate 3 and the reflection plate 4 are not formed. The optical path of the condensed light is shown with dotted lines in FIG.

Of these collected lights, linearly polarized light in one polarization direction (for example, P-polarized wave: shown by a broken line in the figure).
Transmits through the polarization separation film 2 and transmits through the transparent substrate 1 while maintaining the polarization direction (as the P-polarized wave).

The linearly polarized light of the other polarization direction (for example, S-polarized wave: shown by a solid line in the figure) is reflected by the polarization separation film 2 and further reflected by the polarization separation film 2 which is adjacent to the polarization separation film 2.
Heading toward the lens array 5. The S-polarized wave reflected in the direction of the lens array 5 passes through the quarter-wave plate 3 formed on the back surface of the composite plate 1 and is reflected on the surface of the reflection plate 4. Then, it again passes through the quarter-wave plate 3 and is converted into a P-polarized wave. That is, the S-polarized wave is transmitted through the quarter-wave plate 3 twice, and the ordinary light component and the extraordinary light component are out of phase with each other by a half wavelength, and are converted into linearly polarized light (P-polarized light) in the orthogonal direction. To be converted. The converted P polarized wave passes through the polarization separation film 2 and is emitted from the transparent base material 1. In this way, most of the light projected from the rear direction of the lens array 5 is converted into P-polarized waves.

(2) Second Embodiment Next, a second embodiment of the polarization beam conversion element according to the present invention will be described with reference to FIGS. 3 and 4. Figure 3
4 and FIG. 4, parts corresponding to those of FIG. 1 and FIG. In this example, the quarter-wave plate 3 and the reflection plate 4 are arranged so as to straddle a pair of sloping planes 11a and 11b facing each other, in this case, the sawtooth-shaped tops formed by the sloping planes 11a and 11b. The case where it is formed is shown.

Also in this example, as in the example described in the first embodiment, the light reflected by the polarization splitting film 2 is passed through the ½ wavelength plate 3 twice, so that the light is orthogonalized. It can be converted into a polarized light component to be emitted and emitted as light of specific linearly polarized light. That is, as shown in FIG. 4, the incident light projected from the lens array 5 is a region where the quarter wavelength plate 3 and the reflection plate 4 of the transparent substrate 1 are not formed by the lens array 5, in this case. The light is focused on a pair of inclined planes 11b and 11a facing each other. In FIG. 4, in order to facilitate the understanding, only a part of the optical path of the condensed light is shown with dotted lines.

Of these condensed lights, linearly polarized light in one polarization direction (for example, P-polarized wave: shown by a broken line in the figure).
Transmits through the polarization separation film 2 and transmits through the transparent substrate 1 while maintaining the polarization direction (as the P-polarized wave).

Linearly polarized light of the other polarization direction (for example, S-polarized wave: represented by a solid line in the figure) is reflected by the polarization separation film 2 and further reflected by the polarization separation film 2 which is adjacent to and is opposite to the polarization separation film 2.
Heading toward the lens array 5. The S-polarized wave reflected in the direction of the lens array 5 passes through the quarter-wave plate 3 formed on the back surface of the transparent substrate 1 and is reflected on the surface of the reflection plate 4. Then, it again passes through the quarter-wave plate 3 and is converted into a P-polarized wave as in the case of the above-described first embodiment. The converted P polarized wave is transmitted through the polarization separation film 2,
It is ejected from the transparent substrate 1. Thus, also in this example, most of the light projected from the back surface direction of the lens array 5 is converted into P-polarized waves.

As described above, when the quarter-wave plate 3 and the reflecting plate 4 are provided at positions corresponding to adjacent slanting planes, especially when it is necessary to reduce the thickness of the entire polarization beam conversion element. Even if the width is narrowed in order to reduce the height of the inclined plane, the widths of the quarter-wave plate 3 and the reflection plate 4 are doubled as compared with the case of the first embodiment. Since the number to be provided can be reduced to 1/2, the work can be prevented from becoming complicated, the number of manufacturing steps can be reduced, and the productivity can be remarkably improved.

(3) Third Embodiment A third embodiment of the polarization beam conversion element according to the present invention will be described with reference to FIGS. 3 and 4, parts corresponding to those in FIGS. 1 and 2, 3 and 4 are designated by the same reference numerals, and duplicate description will be omitted.
In this example, the reflector 4 is formed so as to straddle a pair of inclined planes 11a and 11b facing each other, in this case, the sawtooth-shaped apex formed by the inclined planes 11a and 11b. The quarter-wave plate 3 is formed on the entire surface of the transparent base material 11 on the light incident side.

Also in this example, similarly to the examples described in the first and second embodiments, the polarization splitting film 2 is used.
The light reflected by is passed through the half-wave plate 3 twice to be converted into orthogonal polarization components, which can be emitted as light of specific linearly polarized light. That is, as shown in FIG. 6, the incident light projected from above the lens array 5 is a region where the reflection plate 4 of the transparent substrate 1 is not formed by this lens array 5, in this case, a pair of obliquely directed toward each other. The light is focused on the planes 11b and 11a. In FIG. 6 as well, only a part of the optical path of the condensed light is shown by stippling. At this time, since the light from the light source is unpolarized, it passes through the quarter-wave plate 3 as it is.

Of the condensed light, linearly polarized light in one polarization direction (for example, P-polarized wave: shown by a broken line in the figure) passes through the polarization separation film 2 and the polarization direction is maintained. The transparent base material 1 is transmitted as it is (as it is as the P-polarized wave).

Linearly polarized light of the other polarization direction (for example, S-polarized wave: represented by a solid line in the figure) is reflected by the polarization separation film 2 and further reflected by the polarization separation film 2 which is adjacent to the polarization separation film 2.
Heading toward the lens array 5. The S-polarized wave reflected in the direction of the lens array 5 passes through the quarter-wave plate 3 formed on the back surface of the transparent substrate 1 and is reflected on the surface of the reflection plate 4. Then, it again passes through the quarter-wave plate 3 and is converted into a P-polarized wave as in the case of the above-described first embodiment. The converted P polarized wave is transmitted through the polarization separation film 2,
It is ejected from the transparent substrate 1. Thus, also in this example, most of the light projected from the back surface direction of the lens array 5 is converted into P-polarized waves.

In the case of the third embodiment described above, it is not necessary to form the quarter-wave plate in a predetermined width, and the quarter-wave plate is accurately aligned to make the transparent substrate. Since it does not need to be formed above, it has advantages that the manufacturing process can be simplified, the number of steps can be reduced, and the productivity can be further improved.

(4) Fourth Embodiment Next, a fourth embodiment of the polarization beam conversion element to which the present invention is applied will be described. FIG. 7 shows a fourth embodiment of the polarized beam conversion element. This polarized light beam conversion element is provided on the light incident side of a transparent base material 21 formed by forming a polarization separation film 22 on an inclined plane provided inside a transparent member.
The lamp light source 23 and the light guide plate 24 are arranged, and the reflection plate 26 or the reflection plate 26 with the quarter-wave plate 25 on the surface is arranged behind it. In FIG. 7, 1 /
The case where the reflection plate 26 with the four-wave plate 25 is provided is shown.

The configurations described in Non-Patent Documents 1 and 2 can be applied to the lamp light source 23 and the light guide plate 24. For example, the light guide plate 24 made of an acrylic plate or the like
The surface facing the transparent substrate 21 is a scattering structure surface 24A (not shown) that scatters light such as a dot structure, while the opposite surface is provided with a prism sheet or the like as a diffusion sheet and a diffusion surface 24B. Thus, the light incident on the light guide plate 24 from the lamp light source 23 formed of a cold cathode ray tube or the like can be efficiently emitted from the diffusion surface 24B. The transparent base material 21 has a structure similar to that of the transparent base material 1 in the first to third embodiments.

FIG. 8 shows how light rays pass in this example. In FIG. 8, the light emitted from the light source 23 and the light guide plate 24 includes S-polarized waves and P-polarized waves. First, of the S-polarized waves, the light emitted toward the transparent base material 21 is After being reflected by the set of polarization separation films 22 and transmitted through the light guide plate 24, it is converted into P-polarized waves by the quarter-wave plate 25 and the reflection plate 26, and the transparent substrate 21 (polarization separation film 22).
Through. Further, of the S-polarized waves, the light emitted in the opposite direction is converted into P-polarized waves by the quarter-wave plate 25 and the reflection plate 26, and passes through the transparent base material 21 (polarization separation film 22). That is, all S polarized waves are converted into P polarized waves and transmitted through the transparent base material 21. Further, when the quarter wave plate 25 is not provided on the surface of the reflection plate 26, the S wave traveling from the light guide plate 24 to the reflection plate 26 is in the light guide plate 24, the surface of the reflection plate 26 and the polarization separation film 22. At this point, the reflection is repeated, and when a phase change of 1/2 wavelength has occurred, the P wave is emitted through the polarization separation film 22.

On the other hand, of the P-polarized waves emitted from the light source 23 via the light guide plate 24, the light emitted toward the transparent base material 21 passes through the polarization separation film 22 as it is and the transparent base material 21. To do. Further, of the P-polarized wave, the light emitted in the opposite direction is converted into the S-polarized wave by the quarter-wave plate 25 and the reflection plate 26 and reflected, but the pair of polarization separation films 22
Is reflected by the 1/4 wavelength plate 25 again through the light guide plate 24.
And to the reflector 26. As a result, the P-polarized wave is returned to the P-polarized wave again, and this time, the P-polarized wave is transmitted through the transparent substrate 21 (polarization separation film 22). Further, when the quarter-wave plate 25 is not provided on the surface of the reflecting plate 26, the P polarized wave emitted from the light guide plate 24 toward the reflecting plate 26 is reflected and reflected by the transparent substrate 21 (polarization separation film 2).
Pass 2).

In this way, most of the light emitted from the lamp light source 23 becomes a P polarized wave and is emitted from the transparent base material 21. Note that the first configuration example and the second
In the embodiment, for example, a 1/2 wavelength plate is added between the transparent base material 1 and the lens array 5 or between the transparent base material 21 and the front light type light guide plate 24, and the emitted light is P-polarized. It is also possible to change from waves to S-polarized waves.

In each of the above-mentioned embodiments, the structure of the transparent substrate having the polarization separation film is characteristic, and it can be manufactured by a simple process. An embodiment of a method of manufacturing a polarized beam conversion element according to the present invention will be described below.

(5) Fifth Embodiment To manufacture a transparent base material having a polarization separation film, first, as shown in FIG. 9, a first transparent member 31 having opposed inclined surfaces repeatedly formed. To prepare. The first transparent member 31 can be easily formed by a method such as injection molding. It is also possible to use an ultraviolet curable resin or the like and cast the resin on a mold having a slope groove to cure the resin by ultraviolet curing.

Next, as shown in FIG. 10, a polarization separation film 32 is formed so as to cover the inclined surface of the first transparent member 31. The polarization separation film can be formed, for example, by alternately stacking high refractive index layers and low refractive index layers. In addition, each layer may be formed by a sputtering method, an evaporation method, or the like.

Next, as shown in FIG. 11, for example, an acrylic transparent substrate 33 is superposed on the inclined surface of the first transparent member 31, and a transparent uncured resin is placed between the acrylic transparent substrate 33 and the first transparent member 31. Fill 34. In this state, ultraviolet rays are radiated through the acrylic transparent substrate 33 to cure the transparent uncured resin with ultraviolet rays to form the second transparent member 35. By removing the acrylic transparent substrate 33, a planarized second transparent member 35 is formed as shown in FIG. As a method for curing the transparent uncured resin, heat curing or the like can be adopted.

After the transparent base material on which the polarization separation film is formed as described above, a quarter wavelength plate or a reflection plate is formed to complete the polarization beam conversion element of the first configuration example. Figure 1
3 shows a state in which the quarter-wave plate 36 and the reflection film 37 are formed. The quarter-wave plate 36 and the reflection film 37 can be easily formed by pasting films prepared in advance. In the case of the examples of the second and third embodiments, it can be manufactured by laminating the film of ½ the number in the case of the first embodiment, and the number of steps can be reduced. . Furthermore, in the example of the third embodiment, since the quarter-wave plate is entirely formed, workability can be further improved and the number of steps can be reduced.

In order to manufacture the polarized beam conversion element described in the fourth embodiment, a light guide plate and a light source are arranged on the back side, and a reflection plate or a reflection plate with a 1/4 wavelength plate is further arranged thereafter. It should be placed on one side.

(6) Sixth Embodiment Next, an example of a liquid crystal display device using the polarized beam conversion element according to the present invention will be described. In this example, the case where the present invention is applied to a projector type liquid crystal display device is shown, but the present invention is not limited to this example and is applied to the case where a polarization beam conversion element is used in other various panel type liquid crystal display devices. It goes without saying that you can do it.

FIG. 14 is a diagram showing a schematic structure of a projector type liquid crystal display device. Reference numeral 51 is a light source, 52 and 53 are integrator lenses, 54 is a polarization beam conversion element having the above-mentioned configuration, 55, 60, 62 and 66 are condenser lenses, and 56, 59, 64 and 66 are total reflection type mirrors. Is. Reference numeral 57 denotes, for example, a dichroic mirror that transmits blue light and reflects green light and red light, and 58 is a dichroic mirror that reflects green light and transmits red light, and separates red, blue, and green light. Each color B, G and R
The liquid crystal plates 61, 63, and 67 corresponding to are arranged at positions facing the incident surface of the cross prism 68, respectively.
69 denotes a projection lens.

The incident / emission mode of each color light in such a configuration will be described. The white light from the light source 51 is efficiently condensed by the integrator lenses 52 and 53, and the P-polarized wave is converted into the S-polarized wave (or the S-polarized wave into the P-polarized wave) by the polarization beam conversion element 54, for example. , S-polarized wave (or P-polarized wave) are taken out, reflected by a mirror 56 via a lens 55, and made incident on a dichroic mirror 57. The blue light passes through the dichroic mirror 57, is reflected by the mirror 59, and enters the liquid crystal plate 61 for blue light via the lens 60. Similarly, green light of the light reflected by the dichroic mirror 57 is reflected by the dichroic mirror 58 and is incident on the liquid crystal plate 63 for green light via the lens 62. The red light transmitted through the dichroic mirror 58 is reflected by the mirrors 64 and 6
5, and further enters the liquid crystal plate 67 for red light through the lens 66. Then, although not shown, an optical modulation signal corresponding to a display signal is inputted from a predetermined modulation circuit to the liquid crystal plates 61, 63 and 67 corresponding to each color to perform optical modulation, and the light is modulated by the cross prism 68, and the projection lens 69 is used. To enlarge and project it on the screen.

As described above, in the liquid crystal display device, by using the polarization beam conversion element to align the polarization directions of the white light, only one of the S polarization wave and the P polarization wave is conventionally used, and the other polarization wave is used. It has been thrown away as heat, so to speak, as described above, by aligning the polarization components of the light from the light source, the utilization efficiency can be significantly increased. Furthermore, as the above-mentioned light source 51,
When the configuration using the light guide plate as described above is used, the liquid crystal display device can be further downsized and thinned.

[0058]

EXAMPLES Specific examples to which the present invention is applied will be described below.

Example 1 A substrate having a sawtooth cross section having a 45-degree inclined plane having an inclination angle of 45 degrees with respect to the bottom surface and extending in a direction orthogonal to the inclination direction of this inclined plane was produced. The substrate was manufactured by injection molding polymethylmethacrylate (PMMA), and this was used as the transparent member A.

Next, a polarization separation film was formed on this inclined plane. This polarization separation film is composed of Y ₂ O ₃ vapor deposition film H and MgF ₂
The vapor-deposited film L was made into one set, and the film was repeatedly formed 16 times to form a total of 32 layers. The film thickness of the Y ₂ O ₃ vapor deposition film H is 78.6.
nm, and the film thickness of the MgF ₂ vapor deposition film L was 99.6 nm.

After the polarized light separating film was formed, an ultraviolet curable acrylic resin was applied and filled from above, and an acrylic transparent substrate was covered from above to spread the acrylic resin. In this state, a transparent uncured resin, which is a UV-curable acrylic resin, was UV-cured and integrated to form a transparent member B.

Further, a film having an optical thickness of ¼ wavelength and a reflection film were bonded to each other at a position corresponding to only one of the inclined planes facing each other at each pitch of the inclined planes via an adhesive layer. The transparent substrate produced in this manner has a P-polarized light in the vicinity of a wavelength of 550 nm, when an antireflection film having an average reflectance of 0.2% is adhered to the surface of the transparent substrate 21 on which light is emitted. While transmitting only the waves, the transmittance of the amount of light was 85%. Further, compared to the conventional polarization beam conversion element, a great simplification of the process has been achieved.

Example 2 The structure of the transparent substrate in the polarized beam conversion element of this example is as follows.
Same as in Example 1 above, except that the transparent member A was replaced with TiO ₂
It was formed from an ultraviolet curable resin in which fine particles were kneaded and filled.

That is, TiO _{2 is} added to a monomer, a polymer and a mixture thereof which can be crosslinked by ultraviolet irradiation or heating.
The fine particles were mixed and dispersed. Specifically, a mixed solvent consisting of 25 wt% of methyl ethyl ketone and 75 wt% of cyclohexanone is prepared, and the photopolymerization initiator (Irgacure 369: Ciba / Specialty / Chemicals) is added to the mixed solvent. 0.3 wt% and a sensitizer (Kayacure RTX: manufactured by Nippon Kayaku Co., Ltd.) 0.1 wt% were dissolved and mixed. Furthermore, 2 wt% of epoxy acrylate (bisphenol A-epichlorohydrin / acrylic acid), 2 wt% of methylolpropane triacrylate, 1 wt% of silicone resin (JCR6122: manufactured by Toray Dow Corning Silicone Co., Ltd.), and 15 wt% of TiO ₂ powder dispersion are mixed. It was mixed. A total amount of 1 kg of material was mixed in a stainless steel closed container for 5 hours, and then, while being dried, 5
A paste-like resin composition was formed while mixing for a period of time to reduce the solvent ratio.

Next, the paste-like resin composition was spread on a metal mold having a groove having 45 ° sloped surfaces facing each other through a PET film by the same method as shown in FIG. Then, after curing at 130 degreeC, ultraviolet curing was further performed. Then, the transparent member A was produced by peeling from the mold.

Since the transparent member A in this case had a refractive index of 1.8, the polarization separation film was made of TiO ₂ and SiO _{2.
It has} a 7-layer structure of ₂ . That is, 1 at 550 nm
TiO ₂ film (thickness 55.9 nm) H having an optical thickness corresponding to / 4 wavelength, and a SiO ₂ film (thickness 188.4 having an optical thickness corresponding to ½ wavelength at 550 nm).
nm) 2L was laminated in the order of H.2L.H.2L.H.2L.H, and a film having a 7-layer structure was formed by a sputtering method.

Then, as in the case of the transparent member A, the transparent member B was formed by filling and coating a resin slurry in which TiO ₂ fine particles were kneaded and dissolved, and then curing the resin slurry by heating and UV irradiation. The polarization beam conversion element produced in this manner has a transmittance of light quantity when measured by bonding an antireflection film having an average reflectance of 0.2% to the surface of the transparent substrate 21 on the light emission side through an adhesive. As a result, it shows 92% around the wavelength of 550 nm, and the process is greatly simplified as compared with the conventional polarization beam separation conversion element.

In the above embodiments, the case where the transparent member A and the transparent member B have a refractive index of 1.49 and 1.8 has been described, but the refractive index is an intermediate value between them, for example, 1. Even in the case of 6 or 1.7, it is possible to realize the above transparent substrate structure in the same manner. For each refractive index, the film configuration of the polarization separation film is (HL) m or (0.5HL0.5H) m based on the target specification of the polarization conversion rate as the polarization beam separation element and the required cost value.
(M means exponentiation of m times), and further (H2L)
m, (H2L) mH, or 2L (H2L) m as a basic type film structure and a derivative film structure derived therefrom, which is a modified film structure. In either case, the polarization separation film has one substrate. Since the three-dimensional block grinding process such as slicing, adhesive bonding, and double-side polishing is not required, it is rich in mass productivity.

Furthermore, in the present invention, since the polarization separation film is formed by sputtering or vapor deposition on the 45 ° oblique planes facing each other, the opening angle of the groove is 90 °, which is the so-called groove wall when forming a sputtering thin film. The shadowing effect is small and it is possible to form a uniform film thickness up to the bottom of the groove. In that sense, it is possible to avoid the adverse effect on the uniformity of the film thickness due to the shadow of the deposition beam due to the triangular groove wall, which is a problem in the case of the inventions described in the respective publications reported as the prior art. Also in this sense, the productivity and yield of the polarized beam conversion element of the present invention are high, and an inexpensive polarized beam conversion element can be supplied.

In each of the above-mentioned embodiments, the case where the transparent member A is formed by the resin material and the resin material filled with the inorganic material has been described, but it is not excluded that the transparent member A is formed by the glass. A method of forming a glass groove having a slope of 45 degrees in a glass viscous state on the glass substrate and a method of processing a groove grindstone and polishing a groove are also possible. Even in that case, although not as much as the groove formation by plastic molding, the whole process can be a simpler and less expensive process than the conventional method. Therefore, by using such a polarized beam conversion element according to the present invention in a liquid crystal panel display, for example, the utilization efficiency of the light source is high, the power consumption is reduced or the brightness is increased, and the cost is reduced. You can also

[0071]

As is apparent from the above description, according to the present invention, it is possible to manufacture by a simple process, the manufacturing cost can be suppressed, and a large area can be easily manufactured. It is possible to provide a polarized beam conversion element and a manufacturing method thereof. In addition, since the shadow effect of vapor deposition or sputtering can be suppressed when forming the polarization separation film, the thickness of the polarization separation film can be made uniform,
A high-performance polarized beam conversion element can be provided.
Therefore, by utilizing this, a liquid crystal display device capable of low power consumption or high brightness can be provided.

In particular, when the ½ wavelength plate and the reflection plate are formed over a pair of adjacent inclined planes, the number of the ½ wavelength plate and the reflection plate can be reduced, and the number of steps can be reduced. Reduction can be achieved and productivity can be improved.

When the half-wave plate is entirely formed, the manufacturing process can be further simplified, the number of steps can be reduced, and the productivity can be improved. Therefore, when applied to a liquid crystal panel display, cost reduction can be achieved.

Further, by arranging the lens array behind the half-wave plate and the reflection plate, the light can be more efficiently condensed between the reflection plates, and the liquid crystal in which the polarization beam conversion element is incorporated. The display device and various other optical devices can be miniaturized.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a polarized beam conversion element.

FIG. 2 is an explanatory diagram schematically showing a conversion mode of incident light in a polarization beam conversion element.

FIG. 3 is a schematic cross-sectional view showing an example of a polarized beam conversion element.

FIG. 4 is an explanatory diagram schematically showing a conversion mode of incident light in a polarization beam conversion element.

FIG. 5 is a schematic sectional view showing an example of a polarized beam conversion element.

FIG. 6 is an explanatory diagram schematically showing a conversion mode of incident light in a polarized beam conversion element.

FIG. 7 is a schematic cross-sectional view showing an example of a polarized beam conversion element.

FIG. 8 is an explanatory diagram schematically showing a conversion mode of incident light in the polarized beam conversion element.

FIG. 9 is a process chart of an example of the method of manufacturing the polarization beam conversion element.

FIG. 10 is a process chart of an example of the method of manufacturing the polarization beam conversion element.

FIG. 11 is a process chart of an example of the method of manufacturing the polarization beam conversion element.

FIG. 12 is a process chart of an example of the method of manufacturing the polarization beam conversion element.

FIG. 13 is a process chart of an example of the method of manufacturing the polarization beam conversion element.

FIG. 14 is a configuration diagram of an example of a liquid crystal display device.

FIG. 15 is a schematic sectional view showing an example of a conventional polarization beam conversion element.

[Explanation of symbols]

1 transparent substrate, 2 polarization separation film, 3 1/4 wavelength plate, 4
Reflector, 5 lens array, 21 transparent substrate, 22
Polarization separation film, 23 light source, 24 light guide plate, 251/4 wavelength plate, 26 reflection plate, 31 first transparent member, 32 polarization separation film, 33 acrylic transparent substrate, 34 transparent uncured resin, 35 second transparent member , 101 glass, 102 polarization separation film, 103 1/2 wavelength plate, 104 light shield plate, 1
04a slit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoji Hasegawa             Miyagi prefecture Tome gun Nakata town Takae Shinida character Kagano boundary             No. 30 Inside Sony Miyagi Co., Ltd. (72) Inventor Shigehisa Okawara             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Yoshihiro Fujimaki             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Kazuhiko Morisawa             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Katakura et al.             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 2H049 BA05 BA06 BA07 BA42 BA43                       BB03 BB63 BC22                 2H091 FA10 FD07 FD10 FD12 HA07

Claims (14)

[Claims] 1. A surface of a transparent substrate or an intermediate position in the thickness direction thereof is alternately and repeatedly formed with inclined planes having different inclination directions, and a polarization separation film is formed on the inclined planes. At the same time, at least a quarter-wave plate and a reflection plate at a position corresponding to the pair of oblique planes are arranged on the light-incident side surface of the transparent base material. 2. The polarized beam conversion element according to claim 1, wherein the quarter-wave plate is provided corresponding to the position where the reflector is arranged. 3. The polarization beam conversion element according to claim 1, wherein the quarter-wave plate and the reflection plate are arranged corresponding to every other oblique plane. 4. The polarization beam conversion element according to claim 1, wherein the quarter-wave plate and the reflection plate are arranged corresponding to two oblique planes that are adjacent to each other and face each other. 5. The polarization beam conversion element according to claim 1, wherein the inclination angle of each of the inclined planes is approximately 45 degrees with respect to the light incident side surface of the transparent base material. 6. The polarization beam conversion element according to claim 1, wherein the quarter-wave plate and the reflection plate are formed so as to overlap each other at the same position. 7. The light-incident side surface of the transparent base material as described above
The polarized beam conversion element according to claim 1, wherein a lens array that collects incident light is provided in a region where the / 4 wavelength plate and the reflection plate are not formed. 8. The polarization beam conversion element according to claim 1, wherein the transparent substrate has a plate shape or a film shape. 9. A step of forming a polarization separation film on the oblique plane of a first transparent member on which oblique planes facing each other having different inclination directions are formed; and a second transparent member on the oblique plane. And a step of filling an uncured photocurable resin between the oblique plane and the second transparent member, and photocuring by irradiating light through the first or second transparent member. A transparent base material is produced by the step of curing the organic resin and flattening the inclined plane, and at least one of the surfaces of the transparent base material is at least 1 /
A method of manufacturing a polarization beam conversion element, characterized in that a four-wave plate and a reflector are formed at positions corresponding to a pair of oblique planes facing each other. 10. A transparent base material is formed on a surface of a transparent substrate or at an intermediate position in a thickness direction thereof, and inclined planes facing each other having different inclination directions are alternately and repeatedly formed, and a polarization separation film is formed on the inclined planes. At the same time, a light guide plate is arranged at a light incident side position of the transparent base material, and a reflection plate, or a quarter wavelength plate and a reflection plate are arranged behind the light guide plate. 11. The polarization beam conversion element according to claim 10, wherein the inclination angle of each of the inclined planes is approximately 45 degrees with respect to the light incident side surface of the transparent substrate. 12. The polarization beam conversion element according to claim 10, wherein the transparent substrate has a plate shape or a film shape. 13. A step of forming a polarization separation film on the oblique plane of a first transparent member on which oblique planes facing each other having different inclination directions are formed, and a second transparent member on the oblique plane. And a step of filling an uncured photocurable resin between the oblique plane and the second transparent member, and photocuring by irradiating light through the first or second transparent member. A transparent base material is produced by the step of curing the organic resin and flattening on the above-mentioned oblique plane, and disposing a reflecting plate, or a 1/4 wavelength plate and a reflecting plate apart from either one of the faces, and between them. A method for manufacturing a polarization beam conversion element, characterized in that a light guide plate is disposed on the substrate. 14. A liquid crystal display device comprising at least a light source, a polarization beam conversion element and a liquid crystal plate, wherein the polarization beam conversion element is a surface of a transparent substrate or an intermediate position in a thickness direction thereof, and a tilt direction. Slant planes facing each other are alternately and repeatedly formed, and a polarization separation film is formed on the slant plane, and at least a quarter wavelength plate and a pair are formed on the light incident side surface of the transparent substrate. 2. A liquid crystal display device, characterized in that a reflection plate is arranged at a position corresponding to the above-mentioned oblique plane.