JPS62238516A - Optical modulator - Google Patents

Abstract

PURPOSE:To easily obtain a grating height of a prescribed quantity, and to satisfactorily display a diffraction effect, by constituting the titled device so that a projecting part and a projecting part, and a recessed part and a recessed part of a diffraction grating part are opposed in parallel to each other and superposed. CONSTITUTION:The titled device is provided with two pieces of substrates 7, 7, a diffraction grating 2 which is placed between these substrates 7, a refractive index variable substance 1 which is packed between grating grooves of this diffraction grating, and a control means for controlling a refractive power of this refractive index variable substance 1. The diffraction grating 2 is constituted of plural diffraction grating parts 20, 21 which have opposed and superposed a projecting part and a projecting part, and a recessed part and a recessed part so that they conform in parallel to each other. In such a way, at the time of executing an optical modulation of a path of light and light-shielding, etc. by utilizing the refractive index variable substance such as a liquid crystal 1, etc. and the diffraction grating 2, height between the projecting and the recessed parts of the diffraction grating 2, and a grating height of about several mum can be secured easily, and also, the adhesion of a transparent electrode 6 and the transparent substrate 7, and the diffraction grating is held satisfactorily, and a drop of a contrast ratio caused by a polarization is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a light modulation device, particularly a diffraction grating and a refractive index 'iT'.
i! i' 1fr t-Ml no ÷
1 Kito i 1, i! krr ΔSei 7T j
Power i nin W /I) Ur! k hill (d
The present invention relates to a light modulation device that produces a desired diffraction phenomenon in incident light by controlling the .

(Prior art) A conventionally well-known light modulation element consists of a pair of polarizing plates arranged so that the polarization directions are perpendicular to each other, and a pair of transparent substrates arranged between the pair of polarizing plates. The device consists of a device in which a liquid crystal is encapsulated with an orientation treatment perpendicular to the substrate surface, and the alignment state of this liquid crystal is switched between a twisted state and a state perpendicular to the substrate surface, thereby modulating the incident light. There is a so-called TN (twisted nematic) type liquid crystal display element that does this. This type of display element has a simple structure and is easy to drive, so it is used in a wide variety of ways. The transmittance during transmission was poor, and it could not be said to be a preferable luminous intensity: A element from the viewpoint of luminous flux utilization efficiency.

In addition, as a similar type of display element using liquid crystal, liquid crystal component -r
- So-called guest host mode 1 used as a special person
There are many liquid crystal devices, but even in this display device, the transmittance when decoloring is about 75% at best due to the presence of dye.

On the other hand, Japanese Patent Publication No. 53-3928 and USP 4,251
, 137, etc., disclose a display element and a variable subtractive color filter element in which a reflective or transmissive phase diffraction grating is combined with a liquid crystal. The elements disclosed in these documents are certainly excellent in luminous flux utilization efficiency, but the element disclosed in Japanese Patent Publication No. 53-3928 merely exhibits a decorative effect, and is not a display element for displaying characters or images. However, it has not been satisfactory as a light modulation element for passing and blocking light beams. In addition, the variable subtractive color filter element disclosed in IJSP 4,251, 1:17 has a diffraction grating made of an isotropic material formed on the surfaces of a pair of opposing substrates so that the alignment directions are orthogonal to each other, and a liquid crystal is placed between the substrates. The alignment state of liquid crystal molecules is filled with ;t,! By controlling the refractive index and changing the difference in refractive index between the material that forms the diffraction grating and the liquid crystal, the spectral transmittance characteristics can be made variable.It has high luminous flux utilization efficiency and high performance as a variable subtractive color filter. have

That is, the difference between the refractive index of the diffraction grating member and the refractive index of the liquid crystal is Δn, the wavelength of the incident light with arbitrary polarization is λ, and the grating base, which is the height between the uneven parts of the diffraction grating, is T. n is the diffraction efficiency of the zero-order transmitted diffracted light in the diffraction grating. Then, approximately Δn −T ηo=%(1◆cO8(2π·λ)) (1). From equation (1), when Δn=0, η. =1゜Δn−T
η when = (34+m)λ (m=0.1, 2, 3°...). =0.

Generally, when the refractive index of a liquid crystal is controlled by an electric field and the incident light is modulated according to equation (1), the lattice group T is used to determine the difference between the ordinary and extraordinary refractive index of the liquid crystal and the difference between the ordinary and extraordinary refractive index of the liquid crystal in order to obtain the desired filter color. If orientation and other factors are taken into consideration, a thickness of approximately several μm is required.

However, in order to secure a predetermined amount of grating groups T, for example, when forming a diffraction grating using photoresist, it is necessary to apply the photoresist in two or three layers to prevent uneven coating due to thick coating. Extra steps are required in diffraction grating manufacture. Furthermore, when using a negative photoresist, which is more durable than a positive photoresist, it becomes very difficult to secure a predetermined amount of lattice groups T depending on exposure conditions, development conditions, etc.

As described above, in the past, it was very difficult to secure a predetermined amount of grating bases for a diffraction grating and obtain good diffracted light, and it was very difficult to perform good optical modulation using a diffraction grating and liquid crystal.

(Problems to be Solved by the Invention) The present invention solves the problem of the height between the concave and convex portions of the diffraction grating when performing light modulation such as passing light or blocking light using a variable refractive index material such as liquid crystal and a diffraction grating. The object of the present invention is to provide a light modulation device that can secure a predetermined amount of so-called grating bases, and that also maintains good adhesion between a transparent electrode or a transparent substrate and a diffraction grating, and prevents a decrease in contrast ratio due to polarized light. .

(Means for solving the problem) A refractive index variable material filled between two substrates, a diffraction grating disposed between the substrates, and the grating grooves of the diffraction grating, and a refractive power of the refractive index variable material. It is constituted by a plurality of diffraction grating sections which are stacked facing each other so that the convex portions and the concave portions coincide with each other in parallel to each other.

Other features of the invention are described in the Examples.

(Example) Fig. 1 is a perspective view of an embodiment of the present invention, Fig. 2 (A),
(B) is an explanatory diagram of the operating principle of FIG. 1.

In the figure, 1 is a liquid crystal, and 2 is a diffraction grating, which has two diffraction grating parts 20 and 21 with approximately equal grating pitches, and each convex part and concave part are aligned parallel to each other. They are stacked facing each other as shown. As a result, a lattice group of approximately several μm is obtained.

In addition, the pattern of the diffraction grating is made by applying photoresist to a spinner.
force such as dipping, roll coating, etc. (A by 'U
After applying 4+ to obtain a uniform flat surface with no uneven coating, it was created by exposure and development.

6 is a pair of transparent electrodes that apply an electric field to the liquid crystal l constituting a part of the liquid crystal control means; 7 is a transparent substrate; 〒→h(:z
nri+117-#1+%Ll-jnc-18#hi! R
atrs+kR? , 1M+-1!1. -r- I'm here. 3 is the incident light, 5.5', and 50 are the outgoing lights.

In the light modulation device shown in FIG. 1, a transparent electrode 6 is placed on a transparent substrate 7.
, and an insulating film 4 is further provided thereon as required. Two transparent diffraction grating sections 20 and 21 are sandwiched between these two insulators 1]Q4. Then, the liquid crystal 1 is filled in the groove portion of the diffraction grating 2 formed by the two diffraction grating portions 20 and 21. The material of the diffraction grating 2 has a refractive index ng
is set to be approximately equal to the ordinary refractive index no of the liquid crystal 1. In the groove portion of the diffraction grating 2, for example, a nematic liquid crystal 1 having a positive dielectric constant anisotropy is homogeneously aligned in the direction of the grating groove. When an electric field is applied between the transparent electrodes J46, which are part of the control means, by a driving device (not shown), the director, which is the direction in which the molecular structure of the liquid crystal is arranged, is homeotropically aligned in the direction of the electric field.

Figures 2 (A) and (11) show the grating member consisting of the liquid crystal 1 and the diffraction grating 2 in the light modulation device of Figure 1, and Figure 2 (A) shows the case where no electric field is applied to the liquid crystal 1. , Figure (b) shows the case where an electric field is applied to the liquid crystal l.

In the same figure (8), the nematic liquid crystal with positive dielectric anisotropy is homogeneously aligned parallel to the groove direction of the diffraction grating 2 (perpendicular to the plane of the paper).

Now, when light 31 polarized in the same direction as the director of the liquid crystal 1 (perpendicular to the plane of the paper) is incident on the light modulator 8, the light 31 that has passed through the grooves of the diffraction grating 2 will be reflected by the abnormality of the liquid crystal 1. Refractive index n. The light that has passed through the convex portion of the diffraction grating 2 has a refractive index ng.

Here, since n g # ne, the grating member consisting of the liquid crystal 1 and the diffraction grating 2 acts as a diffraction grating. Therefore, the large emitted light 31 is diffracted and emitted, and becomes emitted light 5.5'.

On the other hand, when an electric field is applied to liquid crystal 1 in the same figure (B), liquid crystal 1
is homeotropically oriented. Therefore, when light 31 polarized in the same direction as the groove direction of the diffraction grating 2 (perpendicular to the plane of the paper) is incident on the light modulation device 8, the portion of the light 31 that passes through the groove portion of the diffraction grating 2 is the liquid crystal 1. The ordinary refractive index n. The refractive index becomes almost equal to that of the material of the diffraction grating 2. In this case, the grating member consisting of the liquid crystal 1 and the diffraction grating 2 is regarded as an isotropic body, and the incident light 31 passes through without being diffracted and becomes the emitted light 50.

As described above, in this embodiment, by controlling the electric field that applies the light 31 to the liquid crystal 1, light modulation of transmission and non-transmission is performed electrically.

Further, by using the two diffraction grating sections 20 and 21, a predetermined grating height can be easily obtained, thereby achieving a good diffraction effect and performing optical modulation well.

This is the case.

In the example, out of the light 32 that is polarized and incident on the light modulator 8 in a direction perpendicular to the director of the liquid crystal 1 (parallel to the plane of the paper), the light that passes through the grooves of the diffraction grating 2 is the liquid crystal 1. In both cases, the ordinary refractive index n of the liquid crystal l is applied. I feel it.

The refractive index of the member of the diffraction grating is constant n g
= n g, the diffraction grating 2 for the light 32 does not act as a diffraction grating, and the light 32 is transmitted through the liquid crystal l
Before and after the electric field is applied to the light, the light passes through the light modulation device 8 as it is without being diffracted.

(Effects of the Invention) According to the present invention, when performing light modulation using a liquid crystal and a diffraction grating, the diffraction grating is connected to a convex portion of the diffraction grating portion having two concave and convex portions having approximately the same pitch. By configuring the grating in such a way that the concave portions face each other and overlap each other so that they are parallel to each other, it is possible to easily obtain a grating height of about several μm, and the diffraction effect is exhibited well. A light modulation device can be achieved.

Further, according to the present invention, the substrate such as the insulating film and the transparent electrode has a diffraction grating r.
-, and the diffraction grating part is more flexible than the substrate, so when overlapping two diffraction grating parts, the substrate without the diffraction grating and the substrate with the diffraction grating are Easy to adhere to.

Therefore, it is possible to achieve a high-quality optical modulation device that satisfactorily prevents a decrease in contrast due to disordered alignment of liquid crystal between the substrate and the convex portion of the diffraction grating, which has been a problem in the past.

Although this embodiment shows a transmissive light modulation element, it is also possible to provide a reflective element by applying a light reflecting film to one of the substrates, for example. However, in the case of a reflective type, the behavior of diffracted light within the element becomes complicated, so in consideration of the design and application of actual display elements, it is preferable to use a transmissive type light modulation element in the present invention. desirable. In this case, as a matter of course, the diffraction grating, the refractive index variable material, the substrate, etc. are made of members that are transparent to the wavelength used.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 (A),
(B) is an explanatory diagram of the operation of the optical modulation device of FIG. 1. In the figure, 8 is a light modulation device, 1 is a liquid crystal, 2 is a diffraction grating, 20
．． 21 is a diffraction grating portion, 3 is incident light, 4 is an insulating film, 5
．． 5' and 50 are emitted light, 6 is a transparent electrode, and 7 is a transparent substrate. Engraving of drawings (no change in content) Procedural engraving (method) % formula % 16 Indication of incident
Address: 3-30-2 Shimomaruko, Ota-ku, Tokyo
Name (Ion) Canon Co., Ltd. Representative Ka
Ryu 3 Part 4, Agent address: 301 Jiyugaoka, Belheim, 2-17-3 Okusawa, Kaetaya-ku, Tokyo 158 (Telephone: 718-56) Showa 6
June 1, 2015 240 (Despatch [6, Subject of amendment (1) Drawing 7 attached to the application, contents of amendment (1) All drawings attached to application-F will be amended as shown in the attached sheet. (No change in contents. )

Claims (1)

[Claims] Two substrates, a diffraction grating disposed between the substrates, a refractive index variable material filled between the grating grooves of the diffraction grating, and a control means for controlling the refractive power of the refractive index variable material. an optical modulator, characterized in that the diffraction grating is constituted by a plurality of diffraction grating parts stacked facing each other so that the convex parts and the concave parts coincide with each other in parallel. Modulator. (2) The light modulation device according to claim 1, wherein the refractive index variable material is a liquid crystal. (3) The light modulation device according to claim 1, wherein the substrate and the variable refractive index material are transparent to the wavelength used.