JP2001066595A - Display element and display device - Google Patents

Abstract

(57) [Problem] To provide a display element and a display device capable of performing high-contrast display with high light utilization rate without using a polarizing plate. SOLUTION: In a display element in which liquid crystal is held between substrates having transparent electrodes on at least one substrate, a display element in which a microlens array composed of a diffraction grating is formed on at least one substrate, and Display device used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display element and a display device which use a diffraction grating to control the presence or absence of diffraction due to the response of liquid crystal, and more particularly to a display element and a display device in which the diffraction grating forms a lens.

[0002]

2. Description of the Related Art Liquid crystal elements have been used in various applications such as thermo-optic and electro-optic displays in the past. These displays are still being actively studied because of their low driving voltage and low energy consumption.

As a conventional liquid crystal element, for example, "Applied Physics Letters" (M. Schadt) and W. Helfrich ("Applied Physics Letters") are known.
Letters ") Vol. 18, No. 4 (1971 Feb. 2)
(Published March 15) Pages 127-128
Dependent optical activity
"A Twisted Nematic Liquid Crystal" (“Voltage Dependent O
optical Activity of a Twis
ted Nematic liquid Crysta
l "), the twisted nematic (twis
A liquid crystal using a ted nematic liquid crystal is known. This TN liquid crystal has a problem that crosstalk occurs in time-division driving using a matrix electrode structure with a high pixel density, so that the number of pixels is limited.

In order to solve such a problem, it has been studied to provide an active element for each pixel, and a high-quality display is possible by using a thin film transistor, a thin film diode, and a non-linear element.

[0005] Such a method has an advantage that it can be used with low power because of electric field driving, but it has a problem that a polarizing plate is required and light utilization is low. Further, the response time at the time of voltage off is determined from the interface regulation force on the substrate surface and the physical properties of the liquid crystal, and there is a problem that the response time cannot be improved unless the thickness of the liquid crystal cell is reduced. At this time, if the thickness of the liquid crystal cell is reduced, a problem such as a short circuit occurs, and there is an undesired problem that the stop is reduced.

To solve the above problem, a method using a diffraction grating as shown in US Pat. No. 4,251,137 has been proposed as a method not using a polarizing plate. This means that when the refractive index of the liquid crystal filled in the diffraction grating and the compound forming the diffraction grating match, the diffraction effect does not appear, and diffraction occurs only when there is a difference between the two refractive indices. It can be driven at low voltage and has a short response time.

[0007]

However, in the above conventional example, two diffraction gratings which are orthogonal to each other are required, and there is a problem that the manufacturing cost is increased. Further, in the case where the liquid crystal layer is provided in common and a vertically orthogonal diffraction grating is provided, the orientation of the filled liquid crystal is disturbed, and there is a problem that the refractive index cannot be sufficiently controlled.

The present invention has been made in order to solve such problems of the prior art, and a display with high light utilization and high contrast can be performed without using a polarizing plate. It is an object to provide a display element and a display device.

[0009]

That is, the present invention relates to a display element having a liquid crystal sandwiched between substrates having transparent electrodes on at least one substrate, and a microlens comprising a diffraction grating on at least one substrate. A display element in which an array is formed.

Further, according to the present invention, there is provided a display element which separates light from a light source into three primary colors, forms a microlens array composed of a diffraction grating between substrates having electrodes for the three primary colors, and holds a liquid crystal. Means for applying a voltage to the display element to drive the display element, means for separating the light condensed by the microlenses of the display element, and means for projecting the transmitted light of the three primary colors onto the same screen. It is a display device characterized by the above.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The display element of the present invention is a display element in which liquid crystal is sandwiched between substrates having transparent electrodes on at least one substrate, and a microlens array including a diffraction grating is formed on at least one substrate. Thus, high-contrast display can be performed without using a polarizing plate.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a sectional view showing an example of a display element used in the present invention. In FIG.
1 'can be made of glass, plastic or the like.
Polymer films that can be used as substrates include
Examples include the following, but are not limited thereto.

That is, a low-density polyethylene film,
High-density polyethylene film (Mitsui Toatsu Kagaku Hiblon etc.), polypropylene film (Toray Trefane etc.), polyester film (DuPont Mylar etc.), polyvinyl alcohol film (Nippon Synthetic Chemical Industry Hi-Selon etc.), polyamide film (Toyo Gosei Film Leifan) Etc.), polycarbonate film (Teijin Teijin Panlite etc.), polyimide film (Dupont KAPTON etc.), polyvinyl chloride film (Mitsubishi Hishilex etc.), polytetrafluoroethylene film (Mitsui Fluorochemical Teflon etc.), polyacryl film (Sumitomo Bakelite Sumilite),
Examples include a polystyrene film (Asahi Dow Stylo sheet), a polyvinylidene chloride film (Asahi Dow Saran film), a cellulose film, a polyvinyl fluoride film (Dupont Tedlar) and the like.

[0014] On the substrate is formed an electrode 202, 202 ', to the electrode, ITO, transparent electrodes and Al of SnO ₂ or the like, Au, Ag, Cu, a metal film such as Cr is used. Note that the reflective display element may serve as both an electrode and a reflective layer.

On the substrates 201, 201 'provided with such transparent electrodes 202, 202', for example, silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride Substances, silicon carbide, inorganic insulating substances such as boron nitride, polyvinyl alcohol, polyimide, polyamide imide, polyester imide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal,
An orientation control film formed by using an organic insulating material such as polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, and acrylic resin can be provided.

The orientation control film is obtained by forming a film of the above-mentioned inorganic insulating material or organic insulating material and then rubbing (rubbing) the surface in one direction with velvet, cloth or paper. In another preferred embodiment of the present invention, S
An inorganic insulating material such as iO or SiO _{2 is}
An orientation control film can be obtained by forming a film on 01 ′ by oblique evaporation.

In another embodiment, the above-mentioned inorganic insulating material or organic insulating material is formed on the surfaces of the substrates 201, 201 'made of glass or plastic or on the substrates 201, 201'. Is etched by an oblique etching method, whereby an orientation control effect can be imparted to the surface.

It is preferable that the above-mentioned orientation control film also functions as an insulating film at the same time. For this reason, the thickness of the orientation control film is generally 100 ° to 1 μm, preferably 500 μm.
It can be set in the range of {5000}. This insulating layer also has the advantage of preventing generation of current caused by impurities or the like contained in the display layer 210 in a small amount,
Therefore, even if the operation is repeated, the liquid crystal compound is not deteriorated. In the display element of the present invention, the substrate 201
Alternatively, an alignment control film may be provided on both sides of the surface of the substrate 201 'in contact with the display layer 210.

A micro lens 103 made of a diffraction grating is formed on the electrode 102 or 102 '. FIGS. 5A to 5C are cross-sectional views of the diffraction grating used in the present invention. FIGS. 5A to 5C show a phase modulation type, which does not absorb light, and is therefore preferable because the diffraction efficiency can be made higher than that of an amplitude modulation type diffraction grating using absorption.

The diffraction efficiency is controlled by selecting the filled liquid crystal, the refractive index difference of the diffraction grating, and the thickness of the diffraction grating, and is set so as to reduce the zero-order light. Desirable refractive index difference is 0.01 or more, and less than 0.01 is not preferable because the thickness of the diffraction grating becomes too large. The diffraction grating has a thickness of 0.1 to 20 μm. 0.
If it is less than 1 μm, it is impossible to obtain sufficient diffraction efficiency,
If it exceeds 20 μm, it is difficult to process the element.

The refractive index of the convex portion of the diffraction grating is higher than the ordinary ray refractive index of the liquid crystal used, and is desirably smaller than the extraordinary ray refractive index.

Microlens 20 comprising the diffraction grating
3 and the low-molecular liquid crystal 205 injected into the microlens
Is formed by applying an electric field to the electrodes 202 and 202 ′, whereby the low-molecular liquid crystal 205 is arranged,
The difference between the ordinary ray refractive index and the refractive index of the diffraction grating occurs, and the incident light is collected by functioning as a Fresnel lens.

The collected light passes through an opening 211 provided in the light shielding layer 204 and is displayed. When there is no electric field,
The incident light is not condensed because there is no difference between the refractive index of the liquid crystal and the refractive index of the convex part of the diffraction grating as the average value of the refractive index of the liquid crystal because the orientation is disturbed, or a refractive index difference opposite to that when the voltage is applied occurs. Are blocked by the light shielding layer 204.

It is desirable that the light shielding layer 204 is provided at the focal position of the micro lens. When the active element 208 is used, by using the light-shielding layer and the active element together,
It is desirable because the light use efficiency is improved.

The light shielding layer 204 is provided with an opening 211 through which incident light passes when condensed. The smaller the aperture, the higher the contrast of the display element, but the ratio of outgoing light to incident light is reduced and the light utilization is reduced.

The size of the aperture 211 is 0.1 to 20% of the pixel area. If it is less than 0.1%, the light utilization is too low to make it dark, and if it exceeds 20%, the contrast becomes insufficient. More preferably, it is used at 0.5 to 10%.

Microlens 20 comprising the diffraction grating
2 is formed concentrically as shown in FIG. 2, the period of the diffraction grating is set according to the numerical aperture of the lens, and the period becomes shorter as the outer periphery of the concentric circle.

The period of the diffraction grating is 0.5 to 50 μm
Used in If it is less than 0.5 μm, there is no effect because diffraction itself does not occur, and if it exceeds 50 μm, it becomes difficult to obtain sufficient contrast because the focal length of the microlens becomes too long. More preferably, it is used at 1 to 30 μm.

A method of forming a microlens comprising such a diffraction grating is described in J. Jordan (J.
A. Jordan Jr. ) Et al. (“Applied Optics (Appl. Opt.)”, 9 , 1833 (19)
70)), and creation by photolithography is proposed.

On the other hand, it is also possible to use an electron beam lithography system to produce the optics by using T. Fujita et al. (“Optics Letter (Opt. Lett.)”,
6 , 613 (1981)). The diffraction grating used in the present invention may be formed according to the above-described method, or may be formed by a 2P method or an injection molding method using a mold.

The microlenses 203 formed of a diffraction grating are formed by using an organic substance such as a photoresist, a thermoplastic resin, a thermopolymerizable resin, SiO ₂ , glass, M
An inorganic substance such as gF ₂ is used. Specific photoresists include novolak, acrylate, chlorinated polystyrene, polysiloxane, polyimide, and polyvinyl alcohol, and negative and positive photoresists are used. More specific examples include ODUR series and OEBR series manufactured by Tokyo Ohka Kogyo Co., Ltd.

From the manufacturing process of the display element, the diffraction grating can be an inorganic substance such as SiO ₂ . At this time, it is possible to form a predetermined pattern with a photoresist or the like on a film uniformly formed to a thickness of 0.1 μm to 5 μm and form a diffraction grating by etching.

The thickness of the display layer used is usually from 0.5 to
When the thickness is less than 0.5 μm, the contrast is not sufficient. When the thickness exceeds 100 μm, high-speed driving becomes difficult due to a large driving voltage. More preferably, 1 to 50
A thickness of μm is used. FIG. 3 is a sectional view showing another example of the display element of the present invention.

Next, the structure of the low-molecular liquid crystal and the name of the low-molecular liquid crystal composition to be used are shown below, but are not limited thereto.

[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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[0046]

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The low-molecular liquid crystal and its composition can be used in various combinations. Preferably, it is used as a composition exhibiting a nematic phase.

In the display element of the present invention, when performing display using the effect of heating, a thermal head or a laser beam can be used. As the laser light, He-Ne gas laser, Ar ²⁺ gas laser, N
Gas lasers such as ₂ gas lasers, ruby lasers,
Solid-state lasers such as glass lasers and YAG lasers,
It is desirable to use a semiconductor laser or the like. Also, 60
Semiconductor lasers having a wavelength range of 0 nm to 1600 nm are preferably used. Particularly preferably 600 to 900 nm
Is used. The use of the second and third harmonics of these laser beams makes it possible to shorten the wavelength.

When laser light is used, a light absorbing layer is separately provided, or a laser light absorbing compound is dispersed and dissolved in a display layer. When the display surface is affected by the light absorbing layer or the light absorbing compound, it is preferable that the light absorbing layer or the light absorbing compound does not absorb light in the visible light region.

Examples of the laser light absorbing compound to be added to the display layer include azo compounds, bisazo compounds, trisazo compounds, anthraquinone compounds, naphthoquinone compounds, phthalocyanine compounds, naphthalocyanine compounds, and tetrabenzoporphyrin. Compounds, aminium salt compounds, diimonium salt compounds, metal chelate compounds and the like.

Of the above-mentioned laser light absorbing compounds, compounds for semiconductor lasers have absorption in the near infrared region, are useful as stable light absorbing dyes, and have good compatibility or dispersibility with low molecular liquid crystals. In addition, some have dichroism, and if these dichroic compounds are mixed in a low-molecular liquid crystal, a thermally stable host-guest type memory and display medium can be obtained. . Further, two or more of the above compounds may be contained in the low-molecular liquid crystal.

Further, the above compound may be combined with other near infrared absorbing dyes or dichroic dyes. Representative examples of near infrared absorbing dyes that are suitably combined include cyanine, merocyanine, phthalocyanine, tetrahydrocholine, dioxazine, anthraquinone, triphenodithiazine, xanthene, triphenylmethane, pyrylium, croconium, azulene and triphenylamine. And the like.

The amount of the compound added to the low-molecular liquid crystal is about 0.1 to 20% by weight, preferably about 0.1 to 20%.
0.5 to 10% is good.

Next, FIG. 4 is an explanatory view showing an example of a display device using the display element of the present invention. FIG. 1 shows a full-color projection display device using a schlieren optical system.

In the figure, white light from a light source unit 301 is applied to dichroic mirrors 302, 302 ', 3
02 "is classified into three primary colors of R, G, and B. The separated lights are schlieren optical systems 304, 304 ', and 30.
4 "to the display elements 303, 303 ', 303". At this time, the display element is a display element driving device 307.
Is applied and driven. As the display element, a display element using a simple matrix or a non-linear element is used. More preferably, a TFT having a switch for each pixel is used.
The type is superior in terms of display contrast, response speed, and gradation display.

Here, the non-selected pixels are in a state where non-light can not be condensed on the opening, and shield the incident light, and the selected point transmits the incident light. The transmitted light is converted to a dichroic prism 305
And projected on a screen by the projection lens 306, a good full-color image was obtained.

[0057]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A positive photoresist (TSMR-8) was deposited on a glass substrate having a thickness of 1.1 mm by depositing ITO to a thickness of 500 ° and further depositing an insulating layer (SiO ₂ ) to a thickness of 1000 °.
900, manufactured by Tokyo Ohkasha Co., Ltd., refractive index = 1.64) was applied by a spinner method and prebaked at 90 ° C. to obtain a film having a thickness of 5 μm. The substrate was exposed to Nikon NSR-1505G using a microlens photomask having an outer diameter of 500 μm and a focal length of 1.1 mm, developed with a developing solution (NMD-3, manufactured by Tokyo Ohka Co., Ltd.), and then purified with pure water. After rinsing, a microlens comprising a diffraction grating was obtained.

Post-baked at 120 ° C. for 20 minutes
The substrate was transferred to a 1.1 mm thick glass
TO and 1000mm thick SiO_Two A substrate on which
Epoxy adhesive with glass fiber spacer of μmφ
They were stuck together using an agent. This cell was degassed in vacuum
Low molecular nematic liquid crystal BL006 (manufactured by Merck, n
₀ = 1.530, n_e = 1.816) by capillary method
Entered.

A pinhole plate having a hole diameter of 50 μm was attached to the microlens-side substrate of this cell with the position of the hole and the center of the microlens aligned. When 50 μW white light was incident on the microlens of this display element, the amount of light passing through the pinhole was 0.3 μW. Next, when a voltage of 60 Hz and 30 V was applied to the electrodes on the upper and lower substrates, the amount of light passing therethrough increased to 23 μW. This was favorable with a contrast of 77 and a light utilization of 46%.

Comparative Example 1 A polarizing plate (Nitto Denko Corporation: NPF-1100) was orthogonally bonded to a TN type liquid crystal element (a liquid crystal ZLI2008 manufactured by Merck was injected into a 10 μm cell manufactured by ECH).
When white light of 50 μW was incident simultaneously with Example 5,
The amount of light passing at a voltage of 0 V was 14 μW.

Next, when a voltage of 60 Hz and 20 V was applied to the liquid crystal element, the amount of light passing therethrough was 0.6 μW. This is a low contrast of 23 and a light utilization of 28.
% Was insufficient.

Comparative Example 2 ITO 500２, SiO ₂ on a 1.1 mm thick glass substrate
Negative electron beam resist (OEBR-100, manufactured by Tokyo Ohka Co., Ltd., refractive index =
1.49) was applied by a spinner method and prebaked at 80 ° C. for 10 minutes to obtain a film having a thickness of 1 μm. An electron beam lithography system (manufactured by Elionix Inc., E
Using LS-3300), a pattern similar to the photomask used in Example 1 was drawn. Next, it was developed with an OEBR developer, rinsed with a rinse solution, and post-baked at 130 ° C. to form a microlens comprising a diffraction grating.

This substrate was bonded to a 1.1 mm-thick glass substrate on which 500-mm-thick ITO and 1000-thick SiO ₂ were deposited by using a 5 μmφ glass fiber spacer-containing epoxy resin. After the cell was vacuum degassed, low molecular nematic liquid crystal BL006 (manufactured by Merck & _{Co., n 0 = 1.530, n e} = 1.816) and the injected by capillary method.

A pinhole plate having a hole diameter of 50 μm was attached to the microlens side substrate of this cell with the position of the hole and the center of the microlens aligned. When 50 μW white light was incident on the microlens of this display element, the amount of light passing through the pinhole was 1.4 μW. next,
When a voltage of 60 Hz and 30 V was applied to the upper and lower substrates,
The passing light amount was 2.5 μW. This was insufficient with a contrast of 2 and a light utilization of 5%.

[0066]

As described above, according to the present invention,
By using a display element in which liquid crystal is injected into a microlens array composed of a diffraction grating, a high-contrast display in which a polarizing plate is unnecessary and light utilization is high can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a display element of the present invention.

FIG. 2 is a plan view showing an example of the display element of the present invention.

FIG. 3 is a sectional view showing another example of the display element of the present invention.

FIG. 4 is an explanatory diagram illustrating an example of a display device using the display element of the present invention.

FIG. 5 is a sectional view showing a diffraction grating that can be used in the present invention.

[Explanation of symbols]

 201, 201 'Substrate 202, 202' Electrode 203 Microlens composed of diffraction grating 204 Light shielding layer 205 Low molecular liquid crystal 206 Signal line 207 Insulating film 208 Active element 209 Scanning line 210 Display layer 211 Opening 301 Light source unit 302, 302 ' , 302 "dichroic mirror 303, 303 ', 303" display element 304, 304', 304 "Schlieren optical system 305 dichroic prism 306 projection lens 307 display element driving device 309 optical path length correction lens

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 21/00 G03B 21/00 E (72) Inventor Retsu Shibata 3- 30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Shunichi Onishi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (4)

[Claims] 1. A display element comprising a liquid crystal interposed between substrates having transparent electrodes on at least one substrate, wherein a microlens array comprising a diffraction grating is formed on at least one substrate. Display element. 2. The display device according to claim 5, wherein the refractive index of the substance forming the diffraction grating is between the extraordinary ray refractive index and the ordinary ray refractive index of the liquid crystal. 3. The display device according to claim 5, further comprising a light-shielding portion for separating light condensed by the microlens. 4. A means for separating light from a light source into three primary colors, and projecting the three primary colors to a display element having a liquid crystal sandwiched by a microlens array formed of a diffraction grating between substrates having electrodes. Means for applying and driving a voltage to the display element, means for separating light condensed by the microlenses of the display element, and means for projecting the transmitted light of the three primary colors onto the same screen. Display device.