JP2000171633A - Polarized light converting element and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high transmissivity polarized light converting element for a display which can be used for a large area display and used with <=1 mm thickness by providing a micro lens array, a birefringent film and a liquid crystal retardation plate composed of arrayed parts with and without a retardation plate function. SOLUTION: A polarized light converting element 1 is constructed by incorporating a striped micro lens array 11 to converge incident light, a reflection preventing film 12 to prevent reflection of the incident light and to increase transmitted light quantity, a birefringent film 13 with birefringence and a liquid crystal retardation plate 14 provided with optical rotatory functions and non- optical rotatory functions in stripes. Furthermore, the polarized light converting element 1 has no substrate, supporting the functional films, which is transparent toward visible light. Thereby the thickness of the element as a whole can be made thin, and the incident light can also be converted in polarization with extremely high efficiency and emitted. Furthermore, s-polarized light out of the total incident light can be converted to p-polarized light and emitted with small amount of loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin polarization conversion device having a function of converting incident non-polarized light into linearly polarized light and emitting the same, and further relates to the polarization conversion device and a display device for forming an image using optical rotation. And a display device having a high contrast.

2. Description of the Related Art A conventional liquid crystal projector uses a polarization conversion element having high light use efficiency in order to obtain a bright image. A liquid crystal display utilizing the optical rotation of light uses linearly polarized light of either P-polarized light or S-polarized light, and obtains image contrast by passing or blocking either linearly polarized light. However, in this case, in order to easily obtain linearly polarized light, since an absorption type polarizing plate is used, it is impossible to obtain a transmittance of 50% or more, and only a dark image can be obtained.
On the other hand, in recent years, a method in which S-polarized light is converted to P-polarized light is used, for example, in Japanese Patent Application Laid-Open Nos. 7-218720, 9-145926, and 9-214996.
Has been proposed. Further, liquid crystal projectors have already been put to practical use using these methods.

Further, since a polarizer used as an LCD or an optical element has a different refractive index for P-polarized light or S-polarized light, such as a beam splitter, P-polarized light or S-polarized light is separated, P-polarized light is transmitted, and S-polarized light is reflected. After letting 1 /
It has been proposed to convert to P-polarized light using a two-wave plate and use it. According to this proposal, as a polarization conversion layer,
A structural birefringent film is used in which a high refractive index layer and a low refractive index layer are repeated. By using this structural birefringence film, the device can be made thinner than before because it is manufactured by a thin film method.

[0004]

However, in the above conventional example, Δn (the difference in the refractive index between S and P waves) is about 0.1, and a film thickness of several tens μm is required. The rate was not always sufficient to obtain the intended thin image device. In addition, the microlens and the birefringent layer were provided on one side of the transparent support, and the liquid crystal phase plate was provided on the other side.

The present invention has been made to solve these problems, and can be used for a large-area display such as 100 × 100 mm or more, and can be used with a thickness of 1 mm or less. It is an object to produce a high transmittance polarization conversion element for use. Another object of the present invention is to provide a bright display realizing a high transmittance by using the high-efficiency polarization conversion element and a display using optical rotation in an overlapping manner.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a microlens array for converging incident light, a birefringent film having birefringence comprising an oriented liquid crystal layer, and a stripe formed of a liquid crystal layer. It is characterized by having a wave plate function and a liquid crystal wave plate in which portions having no wave plate function are alternately arranged at a constant pitch. Therefore, the thickness of the entire device can be reduced, and the incident light can be converted into polarized light with very high efficiency and emitted.
Further, the S-polarized light of all incident light can be converted to P-polarized light with very little loss.
It has become possible to convert the light into polarized light and emit it.

[0007] Further, the microlens array can be deformed by plastic. Furthermore, the microlens array has a semi-cylindrical stripe structure, so that it is possible to narrow the incident light linearly and narrowly, and it is possible to emit the P wave of all the incident light with very little loss. .

Further, by providing an antireflection film for preventing reflection of incident light on the microlens array and / or between the microlens array and the birefringent film, reflection of incident light to the element can be prevented. As a result, it is possible to obtain high contrast because light can be effectively used.

Further, as another invention, a microlens array for converging incident light, a birefringent film having birefringence composed of an oriented liquid crystal layer, and a liquid crystal layer having a wavelength plate function and a wavelength plate function in stripes. A polarization conversion element having a liquid crystal wave plate in which no portions are alternately arranged at a constant pitch,
It is characterized in that a reflective display element that forms an image using optical rotation is used in an overlapping manner. Therefore, light use efficiency is improved, and a display device such as a reflective display with high contrast can be obtained.

Further, by using a magnetic garnet thin film as the optical rotation material of the reflection type display element, a much thinner display as a whole can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A microlens array for converging incident light, a birefringent film composed of an oriented liquid crystal layer and a birefringent film, and a portion of the liquid crystal layer which does not have a wavelength plate function and a wavelength plate function in a stripe shape. Liquid crystal wave plates alternately arranged at a constant pitch.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing the basic configuration of the polarization conversion element of the present invention. In the figure, a polarization conversion element 1
A microlens array 11 for reducing incident light, an antireflection film 12 for preventing reflection of incident light and increasing the amount of transmitted light, and a birefringent film 13 having birefringence;
The liquid crystal wave plate 14 is provided with a light-rotating function and a non-light-rotating function in a stripe shape. The polarization conversion element 1 of the present invention having such a configuration can be significantly reduced in thickness because there is no transparent substrate for visible light that supports the functional film.

Next, the operation of the polarization conversion element of the present invention will be described with reference to FIG. So-called natural light is called unpolarized light, and the polarization direction of the light is not constant. This natural light is converged by the microlens array 11 having a convex lens function. The surface of the microlens array 11 and the birefringent film 1
An anti-reflection film 12 is provided on the surface of 3. Linearly polarized light having a polarization plane parallel to the stripe direction of the microlens array 11 is called P-polarized light, and linearly-polarized light at right angles is called S-polarized light. Is separated into This separation angle (α in the figure)
Was about 8 degrees because a film having a columnar structure of obliquely oriented tantalum pentoxide (Ta ₂ O ₅ ) was used, but in the present invention, for example, a film (△ n) horizontally oriented on a substrate surface of a nematic liquid crystal was used. (The refractive index difference between the S and P waves) is as large as about 0.2), so that about half the thickness is sufficient to obtain the same separation angle.

Then, one linearly polarized light of the separated light is expressed by P
When the light is polarized, the P-polarized light goes straight through the birefringent film 13 in FIG. However, as shown in FIG. 1, the S-polarized light separates and further travels in a direction parallel to the P-polarized light on the back surface of the birefringent film 13. On the back surface of the birefringent film 13, there is a liquid crystal layer, which is provided with an optical rotation function in a stripe shape. The optical rotation and non-optical rotation functions are arranged, for example, at equal intervals. Note that the intervals need not always be equal. The S-polarized light that has passed through the birefringent film 13 is
The distances a, b, c, d, and d ′ are determined so as to pass through a liquid crystal wave plate 14 which is a half-wave plate in which liquid crystals are aligned.
Since the S-polarized light that has passed through the liquid crystal wave plate 14 has its polarization plane rotated by 90 degrees, most of the light that has passed through the transparent substrate is P-polarized light. Most of the light incident from the element surface is narrowed down by the microlens array 11 so as to travel in the direction of the non-rotatable liquid crystal layer.

As described above, since the oriented liquid crystal layer is used as the transparent film having high birefringence in the present invention, the birefringence can be further increased and the film thickness can be reduced. Since the alignment liquid crystal layer simply applies a liquid crystal polymer on the substrate (microlens array in the present invention) and performs alignment processing,
It can be manufactured more easily than conventional thin film methods such as the CDV method and the PVD method.

In the present invention, a transparent plastic, for example, acryl or polycarbonate is used for the microlens array 11 of FIG. 1, so that an alignment liquid crystal layer is provided on the opposite side of the microlens, and a liquid crystal phase plate is further provided thereon. It is not necessary to use a substrate as a support separately. Therefore, a thinner polarization conversion element can be obtained.

In the following, each component used in the present invention will be described in detail. In the present invention, a plurality of rows of linear microlenses having a width of several tens to several mm, preferably several tens to 100 μm are used for focusing. Used for Manufacturing methods include, for example, those manufactured by a selective ion exchange method on a multi-component glass substrate, those manufactured by a photothermal method on a liquid crystallized glass substrate, those manufactured by an ion beam etching method on a Si substrate, and press forming optical glass. And many other methods have been reported. In addition, lens materials and processes are also diverse.

In the present invention, it is preferable that a replica prepared from an original plate using a transparent resin as described below is used as it can withstand some deformation. The function required for the microlens is to condense and pass the P-polarized light traveling straight in FIG. 1 to the non-rotational portion of the liquid crystal wave plate, and to collect the S-polarized light to be redirected to the optical rotation portion. is there. It is preferable that the focal point distance is designed so that the above-described function works even for light obliquely incident.

Examples of the transparent resin used for the microlens array 11 of the present invention shown in FIG.
MA, polycarbonate, polypropylene, acrylic resin, styrene resin, ABS resin, polyarylate,
Transparent resins such as polysulfone, polyethersulfone, epoxy resin, poly-4-methylpentene-1, fluorinated polyimide, fluororesin, phenix resin, polyolefin resin, and nylon resin are used. Use of a transparent resin is easy to use because it has advantages such as lightness and flexibility.

Further, the anti-reflection film 12 of the present invention shown in FIG. 1 is formed by a PVD method such as a vacuum evaporation method or a CVD method using the material shown in FIG.

The birefringent film 13 used in the present invention shown in FIG.
FIG. 3 shows a structure of a side chain type liquid crystal polymer as a typical example of FIG.
Shown in The terminal groups are CN, OCH ₃ , OC ₂ H ₅ , OC
₆ H _{13 and the} like are conceivable.

In the liquid crystal wave plate 14 used in the present invention shown in FIG. 1, a part where the plane of polarization of the incident polarized light rotates and a part where the plane of polarization does not rotate coexist. Such a structure can be configured by arranging a liquid crystal material only in a portion that rotates the polarization plane and arranging a general optically isotropic transparent material in other portions. Alternatively, a configuration in which nothing is disposed in a portion that is optically isotropic is also possible, but in this case, unevenness occurs.

When the liquid crystal wave plate is disposed on the whole, it is necessary to partially control the alignment state of the liquid crystal. This is generally performed by a rubbing method, but the width is 10 μm.
It is difficult to rub in a stripe pattern. Rubbing can be performed using a mask having a striped window, but there is a problem that the rubbing strength at the window and the boundary is different from the strength at the center of the window. As a method of forming such a fine rubbing pattern, in addition to the mask rubbing as described above, the applied alignment surface material surface is irradiated with polarized ultraviolet rays, and the portion has an alignment regulating force according to the polarization direction. There is a way to say. For details on this method, see the 22nd Liquid Crystal Symposium
Proceedings of the 1st Liquid Crystal Symposium " 344. In addition, P.S. No. 342 reports that a photosensitive polymer film is irradiated with polarized ultraviolet light to control the alignment state.

In the alignment film irradiated with the polarized ultraviolet light as described above, the liquid crystal molecules are oriented in a certain direction with respect to the irradiated polarization direction. As a method of using the thus arranged liquid crystal wave plate as a polarization conversion element, there are a method of not giving a twisted structure to the liquid crystal alignment and a method of adding a chiral agent to the liquid crystal to give a 90 ° twisted structure. In the former liquid crystal wave plate, since the liquid crystal wave plate is used as a general phase plate, polarized light is incident at an angle of about 45 degrees with respect to the orientation of the liquid crystal, and the retardation of the liquid crystal plate is set to 波長 wavelength.

On the other hand, in a liquid crystal wave plate using a twisted structure, the polarization direction to be incident and the orientation direction of the liquid crystal are parallel or perpendicular. The polarization modulation action of this element is mainly optically rotatory, and can rotate the polarization plane in a relatively wide wavelength range, which is preferable to a general phase plate.

It is known that the alignment of a liquid crystal can be controlled by including or attaching a compound having optical anisotropy such as azobenzene to an alignment film and irradiating the alignment film with polarized light (Japanese Patent Application Laid-Open No. HEI 4 (1994) -104686). -7520 publication). Therefore, patterning in the alignment direction can be performed using this.

As described above, a desired liquid crystal alignment can be obtained. However, when the liquid crystal is a liquid at room temperature, the liquid crystal needs to be sandwiched between two transparent substrates, which is not preferable. Therefore, it is possible to use a polymer as the liquid crystal, obtain a desired alignment at a temperature at which the liquid crystal takes a liquid crystal phase, and then rapidly cool to fix the alignment. In this case, 2
A single substrate is not required and is more preferred.

The polarization conversion device 1 of the present invention shown in FIG.
Needless to say, it can be used as a general optical element, but it can also be applied to a display using optical rotation, such as a liquid crystal display and a display using magnetic rotation. In particular, a display using magnetic rotation may not always provide sufficient optical rotation, and therefore it is preferable to use a bright polarization conversion element having a higher transmittance in the sense of increasing contrast. Further, in a display that does not use a reflection-type backlight, the light use efficiency is low. Therefore, it is preferable to use a brighter polarization conversion element in order to obtain high contrast.

As shown in FIG. 4, a basic structure of a device of the present invention utilizing magnetic rotation is shown in FIG. 4. A dielectric multilayer film formed on a substrate 41 by alternately laminating dielectric materials having a low refractive index and a high refractive index. 43, a transparent magnetic layer 44 provided on the dielectric multilayer film 43, and a dielectric multilayer film 45 having exactly the same configuration as the dielectric multilayer film 43 on the substrate 41. The reflective display is used by providing the reflective film 42 on one side of the dielectric multilayer film sandwiching the transparent magnetic film 44 described above. Since the thickness of the transparent magnetic layer 44 shown in the figure is set to ｎn (n = refractive index of the magnetic material) of the visible light wavelength λ, the Faraday rotation angle may be insufficient in absolute magnitude. . In this case, the dielectric multilayer film 45 / transparent magnetic layer 44 /
By repeating the configuration of the dielectric multilayer film 43 a plurality of times in exactly the same manner, it is possible to obtain a sufficient rotation angle (approximately twice if the configuration is repeated twice). The reason why the polarizer layer 46 is used as shown in FIG. 4 is that in the configuration of the dielectric multilayer film 45 / transparent magnetic layer 44 / dielectric multilayer film 43 / substrate 41,
This is for visualizing a large Faraday rotation angle obtained at a portion magnetized in the transparent magnetic layer as an image. That is, a large Faraday rotation angle is obtained corresponding to the portion magnetized in the transparent magnetic layer, and the light deflection surface does not rotate for the non-magnetized portion. The linearly polarized light is reflected as it is in the non-rotational plane of the deflecting surface, passes through the dielectric multilayer film 45 / transparent magnetic layer 44 / dielectric multilayer film 43 again, and then passes through the polarizer layer 46. However, the linearly polarized light that has first passed through the polarization plane rotation part has a polarization plane of the transparent magnetic layer 44.
After being reflected by the reflection film and rotated again when passing through the transparent magnetic layer 44 to obtain a double rotation angle, the polarizer layer 46 is rotated and cannot pass. According to this principle, contrast can be obtained.

FIG. 2 shows an example of a material used for the dielectric multilayer film. Any of these materials may be appropriately selected, or other materials such as organic substances may be used. The thickness of each multilayer film is preferably about 50 to 200 nm. When the purpose is to increase the magneto-optical effect of a specific wavelength (λ) as in the present invention, the thickness of the dielectric is λ / 4n
(N is the refractive index of the dielectric at λ).

Further, assuming that a stack of low-refractive-index and high-refractive-index dielectrics constitutes one pair, the number of pairs is not limited.
Two to forty layers are preferred for performance and cost. It is preferable that the two dielectric multilayer films in contact with the transparent magnetic layer have exactly the same configuration. However, since the same type of film is used for the type of film directly in contact with the transparent magnetic layer, the order of lamination is reversed.
As the reflective layer 42 in FIG. 4, a mixture of a metal or a metal oxide, a metal nitride, a metal carbide and the like, for example, A
1, Cu, Ag, Au, Pt, Rh, Zr, Cr, T
metals such as a, Mo, Si, Pd, Hf and alloys thereof;
A mixture of these and Zr oxide, Si oxide, Si nitride, Al oxide, or the like can be used. In particular, Al, A
u, Ta, alloys thereof, and alloys of Al, Hf, and Pd are preferable because they can easily form a film. And the film thickness is 10
It is good to make it the range of -300 nm, preferably the range of 50-150 nm. The reflection film is manufactured using various PVD and CVD methods.

Further, the transparent magnetic layer 44 shown in FIG. 4 may be a conventional transparent magnetic material having a magneto-optical effect, but a magnetic material having a large Faraday effect and high transparency, that is, a large figure of merit, may be used. preferable. For example, 50
An ultrafine particle film of a ferromagnetic metal, such as iron, cobalt, or Ni, having particles of nm or less is used. In this case, the film composition other than the ultrafine metal particles is oxygen, carbon, or the like.
Ferromagnetic metals such as iron, cobalt, and Ni exhibit a large magneto-optical effect, but they are not used as they are because of their high light absorption. However, ultrafine particle films have a large figure of merit. Further, an appropriate coercive force can be obtained by controlling the particle diameter. Other oxides such as rare earth iron garnet, cobalt ferrite, Ba ferrite,
Materials with large birefringence, such as FeBO ₃ , FeF ₃ , YFeO ₃ , NdFeO ₃ , MnBi, MnCuBi, Pt
Co and the like. The greatest effect can be obtained when the traveling direction of light and the direction of spin are parallel to each other. Therefore, these materials are preferably films having magnetic anisotropy perpendicular to the film surface. For these transparent magnetic materials, general submersion, vacuum evaporation, PVD such as MBE, CVD, plating and the like are used.

Hereinafter, an embodiment according to the present invention will be described in detail. As a first example, an acrylic resin microlens array was formed from a mold by a molding method. The shape is a kamaboko type. The pitch is 12 μm and the focal length is 1.1
mm. The thickness is 200 μm (a). A 20 μm (b) side-chain type liquid crystal polymer (FIG. 3, n = 6, m = 1, terminal group R is CN) layer is provided on the surface of the acrylic substrate having no lens by spin coating. Was. The transmittance of the film was 94% at a wavelength of 550 nm. The angle formed by the incident S-polarized light and P-polarized light (α in FIG. 1) is about 1
7.2 degrees. The acrylic lens microlens array was provided with a 100 nm-thick MgO antireflection film by using a vacuum evaporation method. The reflectivity of the film dropped by about 3%. After applying polyimide SE7792 manufactured by Nissan Chemical Industries, Ltd. to a thickness (c) of 60 nm by spin coating on a birefringent film manufactured using a side chain type liquid crystal polymer, 180
Bake for 1 hour at ℃ and dried. 40m linearly polarized
W / cm ² , 257 nm deep ultraviolet rays, pitch P = 12
μm (irradiated part d ′ = 6 μm, non-irradiated part d = 6 μm, P =
Irradiation was carried out in a stripe form in 2d). Liquid crystal alignment was observed in the deep ultraviolet irradiation part, and the axis of easy alignment was parallel to the polarization direction. As a result, the polarization rotation angle with respect to the wavelength of 400 to 800 nm was about 90 degrees, and had a function of a wave plate.

Next, a display using magnetic rotation produced as described below was provided on the liquid crystal wave plate side of the polarization conversion element. An aluminum (A1) reflective film having a thickness of 100 nm was provided on a 200 μm-thick surface-polished carbon substrate (manufactured by Nisshinbo Co., Ltd.) by a vacuum evaporation method. The S1 is formed on the A1 film by using the ion plating method.
iO ₂ (low refractive index layer, n = 1.47) at 88.4 nm,
60.5 nm of Ta ₂ O ₅ (high refractive index layer, n = 2.15)
, A total of eight layers were alternately laminated in four layers. Substrate temperature is 3
00 ° C., the oxygen gas pressure in the case of SiO ₂ 1.0 × 10 ^{- 4}
Torr, Ta ₂ O ₅ the case of 1.1 × 10 ^{- 4} Torr
Met. The film formation rate is ₂ nm / S for SiO ₂ ,
In the case of Ta ₂ O ₅ , it was 0.5 nm / sec. In the film thickness distribution of each dielectric multilayer film, the difference between the thickest part and the thinnest part was 3% of the total film thickness. (See Fig. 4)

Further, a Bi-substituted rare earth garnet film (refractive index layer n =
2.1) has an average film thickness of 520/2 × 2.1 = 124 nm
It was prepared so that This 520 nm is an angle at which the magnetic rotation angle of the garnet film shows a peak. The substrate temperature was 400 ° C. Then, a film is placed on this substrate in air,
Heat at 670 ° C. for 3 hours. The composition of the film is Bi ₂ . ₂ D
y ₀ . ₈ Fe ₃ . ₈ Al ₁ . ₂ O ₁₂ . Magneto-optical effect measuring device (K250 manufactured by JASCO Corporation, beam diameter 2 mm
Angle), the half-width of the peak was found to be 19 nm from the wavelength dependence of the Faraday rotation angle measured in (1). Wavelength 520
In nm, the peak value of the rotation angle was 2.0 degrees. VS
The coercive force measured by applying a magnetic field perpendicular to the film surface at M is 5
It was 90 Oersted. Next, on this Bi-substituted rare earth garnet film, using an ion plating method,
A multilayer film of SiO ₂ and Ta ₂ O ₅ was produced in exactly the same manner as above. The film in contact with the Bi-substituted rare earth garnet film is Ta ₂ O ₅ , and the outermost surface is SiO ₂ . From the wavelength dependence of the Faraday rotation angle, at a wavelength of 520 nm, 2.
The rotation angle was about 5 times 0 and 10.5 degrees.

Another two cycles on the dielectric multilayer film,
In the same manner as above, the Bi-substituted rare earth garnet film was provided twice, and the dielectric multilayer film 4 pairs were provided twice. The garnet film has a total of 3 layers, and the 4 pairs of dielectric multilayer films have a total of 4 × 4 pairs, that is, 16 pairs and 32 layers. At a wavelength of 520 nm, the rotation angle was 22.4 degrees, which was about 11 times 2.0 in the case of the single garnet layer.

The display utilizing the above-mentioned magnetic rotation was disposed on the liquid crystal wave plate side of the above-mentioned polarization conversion element with the substrate facing down. In this case, the ratio of return to light incident on the non-magnetized portion of the display and reflected by the reflective film was about 41% (wavelength: 550 nm) with respect to the incident light intensity. Characters were written from above the dielectric multilayer film on the outermost surface with a magnetic pen with a permanent magnet (surface magnetic flux density of 3K gauss). At the part magnetized by the magnetic pen, the plane of polarization of the linearly polarized light that has passed through the above-mentioned polarization conversion element rotates and does not return to the original polarization conversion element, and therefore the characters written with the magnetic pen are displayed in black. Was. The contrast of the image portion was 6.9.

Next, as a second embodiment, the first embodiment is the same as the first embodiment except that the transparent substrate and the polycarbonate as the microlens array used for manufacturing the polarization conversion element were both glass. A polarization conversion element was produced in exactly the same manner as in the example. The polarization conversion element of the first embodiment did not drop or was damaged by some bending. However, when glass was used, it was easily broken.

Next, a comparative example will be described. In the first comparative example, instead of providing the alignment liquid crystal layer and the liquid crystal wave plate using the microlens array of the first embodiment as a substrate,
Using a transparent polycarbonate having a thickness of μm as a substrate, a microlens array was provided on one surface in the same manner as in the first embodiment, and an alignment liquid crystal layer and a liquid crystal wave plate were provided on another surface. In this case, the entire thickness of the polarization conversion element was about 420 μm, which was about 200 μm thicker than in the first embodiment. The transmittance of the polarization conversion element was 76% at a wavelength of 550 nm, which was significantly lower than that of the first embodiment. However, there is a commercially available absorption type film deflector using iodine. Transmittance is 550 wavelength
It was even lower at 42% in the case of nm.

In the second comparative example, a commercially available film wave plate was cut into a thin line and attached to the emission side of the substrate as in the polarization conversion element manufactured in the first embodiment.
The following widths could not be arranged on a straight line.

The third comparative example is the same as the first comparative example except that an antireflection film is provided on the acrylic resin microlens array.
In the same manner as in Example 1, a polarization conversion element was produced. The light transmittance was reduced by about 3% as compared with the first embodiment.

In the fourth comparative example, the display using the magnetic rotatory power produced in the first example was arranged under a commercially available film polarizer. In this case, the ratio of the return light incident on the non-magnetized portion of the display is about 11% with respect to the incident light intensity.
(Wavelength 550 nm) and about 1/4 compared to the first embodiment.
Was low. A portion of the film polarizer was magnetized with a magnetic pen with a permanent magnet. At the portion magnetized by the magnetic pen, the plane of polarization of the linearly polarized light that passed through the polarizer and rotated did not return to the original polarizer, and thus the characters written with the magnetic pen were displayed in black. The contrast of the image portion was 2.3.

The fifth comparative example is a display combined with a polarization conversion element in the same manner as in the first embodiment except that a Ba ferrite thin film is used as the magnetic material of the display using magnetic rotation produced in the first embodiment. Was prepared. Wavelength 520
In nm, the peak value of the polarization plane rotation angle was 8.6 degrees. The coercive force measured by applying a magnetic field perpendicular to the film surface with the VSM was 660 Oersteds. Characters were written from above the outermost dielectric multilayer film with a magnetic pen with a permanent magnet.
The written characters were displayed in black at the parts magnetized by the magnetic pen. The contrast of the image portion was as low as 2.8.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and substitutions can be made within the scope of the claims.

[0045]

As described above, according to the present invention,
A microlens array that converges incident light, a birefringent film composed of an oriented liquid crystal layer and a birefringent film, and portions of the liquid crystal layer that are alternately arranged at a constant pitch in a stripe pattern with no wave plate function and no wave plate function And a liquid crystal wave plate. Therefore, the thickness of the entire device can be reduced, and the incident light can be converted into polarized light with very high efficiency and emitted. Further, it has become possible to convert S-polarized light of all incident light into P-polarized light with very little loss and emit it.

Further, the plastic deformation of the microlens array enabled deformation. Furthermore, the microlens array has a semi-cylindrical stripe structure, so that it is possible to narrow the incident light linearly and narrowly, and it is possible to emit the P wave of all the incident light with very little loss. .

Further, by providing an antireflection film for preventing reflection of incident light on the microlens array and / or between the microlens array and the birefringent film, reflection of incident light to the element can be prevented. As a result, it is possible to obtain high contrast because light can be effectively used.

Further, as another invention, a microlens array for converging incident light, a birefringent film composed of an oriented liquid crystal layer and a birefringent film, and a liquid crystal layer having a wavelength plate function and a wavelength plate function in stripes. A polarization conversion element having a liquid crystal wave plate in which no portions are alternately arranged at a constant pitch,
It is characterized in that a reflective display element that forms an image using optical rotation is used in an overlapping manner. Therefore, light use efficiency is improved, and a display device such as a reflective display with high contrast can be obtained.

Further, by using a magnetic garnet thin film as the optical rotatory material of the reflective display element, it is possible to obtain a much thinner display as a whole.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of a polarization conversion element of the present invention.

FIG. 2 is a diagram showing materials used for a dielectric multilayer film and an antireflection layer.

FIG. 3 is a view showing a structure of a side chain type liquid crystal polymer.

FIG. 4 is a schematic cross-sectional view showing a basic configuration of a device of the present invention using magnetic rotation.

DESCRIPTION OF SYMBOLS 1 Polarization conversion element 11 Microlens array 12 Antireflection layer 13 Birefringent layer 14 Liquid crystal wave plate 40 Reflective display device 41 Substrate 42 Reflective layer 43, 45 Dielectric multilayer film 44 Transparent magnetic layer 46 Polarizer layer

Claims (6)

[Claims] 1. A microlens array for converging incident light, a birefringent film having birefringence composed of an alignment liquid crystal layer, and a portion of the liquid crystal layer having stripe-shaped wave plate functions and portions having no wave plate function alternately. And a liquid crystal wave plate arranged at a constant pitch. 2. The polarization conversion device according to claim 1, wherein the microlens array is made of plastic. 3. The polarization conversion device according to claim 1, wherein the microlens array has a semi-cylindrical stripe structure. 4. The polarization conversion element according to claim 1, wherein an antireflection film for preventing reflection of incident light is provided on the microlens array and / or between the microlens array and the birefringent film. 5. A microlens array for converging incident light, a birefringent film composed of an oriented liquid crystal layer and a birefringent film, and portions of the liquid crystal layer having stripe-shaped wave plate functions and wavelength plate-free functions alternately. A display device, comprising: a polarization conversion element having liquid crystal wave plates arranged at a constant pitch; and a reflective display element for forming an image by utilizing optical rotation. 6. The display device according to claim 5, wherein the optical rotation material of the reflective display element is a magnetic garnet thin film.