JPH061305B2 - Optical shutter array and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical shutter utilizing an electro-optical effect,
In particular, the present invention relates to an optical shutter array having electrodes with low driving voltage and a method for manufacturing the same.

2. Description of the Related Art In recent years, electro-optical materials such as PLZT that exhibit an electro-optical effect have been developed. Here, the electro-optic effect refers to a phenomenon in which the refractive index of the medium changes due to an applied electric field of direct current or low frequency (compared to high frequency).

A typical example of such an electro-optical material is 9/65 /
PLZT [La9 atom% PbZrO ₃ / Pb consisting of 35 ratios
Transparent ceramics of TiO = 65/35 (molar ratio)] are well known.

An optical shutter uses the PLZT.
The optical shutter has a structure in which a pair of flat electrodes formed at regular intervals on one surface of a plate-shaped PLZT element is installed between a polarizer and an analyzer whose polarization directions are orthogonal to each other. It is possible to control transmission / blocking of light incident from the polarizer side by ON-OFF of the applied voltage.

In such an optical shutter, when the monochromatic light having the intensity I ₀ and the wavelength λ is incident from the polarizer side, the intensity I of the light passing through the analyzer is represented by the following formula (1).

Here, L: thickness of an element having an electro-optical effect through which light passes (= effective optical path length) Δn: birefringence I ₀ : incident light intensity I: outgoing light intensity In equation (1), ΔnL = λ / 2 If birefringence is selected so that I = I ₀ , the intensity I of light passing through the system becomes maximum. At this time, the birefringence Δn can be changed by the magnitude of the electric field applied to the element. For example, if the element is 2
In the case of having the following electro-optical effect, the birefringence Δn changes in proportion to the square of the applied electric field (E), and can be expressed by the following expression (2).

Here, R: electro-optic constant E: electric field strength n: refractive index Therefore, When a rectangular wave voltage of a certain magnitude is applied, the transmitted light intensity I changes from 0 to the maximum value I ₀ .

The voltage V that gives E that satisfies the equation (3) is written as V (1/2) and is called a half-wave voltage. The half-wave voltage is related to the drive voltage of the optical shutter array.

Therefore, when the electric field strength E is increased, the birefringence Δn becomes large and I becomes large. Further, if the effective optical path length L can be increased, the half-wavelength voltage will decrease, and I will increase even with a low drive voltage.

The larger I becomes, the higher the contrast of the emitted light due to ON-OFF of the applied voltage becomes. Therefore, if the effective optical path length can be made longer, the optical shutter array can be driven at a lower voltage.

By the way, the electrode 2 conventionally formed of an electro-optical material such as PLZT is a planar electrode formed by metal vapor deposition or the like as shown in FIG. 3, and when the width of the electrode is W, L becomes large. However, there is a limit to increasing the electrode width W. In particular, in order to increase the density of the optical shutter array and obtain a precise image with good resolution, it is necessary to make one pixel small, and the electrode width W is also required to be as small as 50 μm or sometimes 5 μm. For this reason, in the conventional optical shutter array, it has been performed that E is set to a high value to obtain high I. However, when E is high, energy consumption is large, and there are many problems in designing as a device, and it is said that the relationship of the formula (2) begins to collapse at about 15 to 25 KV / cm or more.

In order to put the PLZT optical shutter array into practical use, it is necessary to reduce the required drive voltage, and V (1/2) in the currently available single shutter is about 280V.
In the optical shutter array, it is desired to set V (1/2) to 80V or less.

For such a planar electrode, a groove-type electrode shown in FIGS. 4 and 5 has been proposed (Japanese Patent Laid-Open No. 58-82221).
44'85 Autumn Biological Society Proceedings, Kurita et al.).

Here, the groove type electrode refers to a structure and electrode in which a conductive material is embedded in a groove formed in a PLZT substrate.

The groove type electrode shown in FIG. 4 is formed by wet etching with a strong acid such as a PLZT substrate HCl by a photolithography technique, and the groove type electrode shown in FIG. 5 is a PLZT substrate.
A groove is formed on a substrate by machining with a dicing saw or the like. By using such a groove-type electrode, the effective optical path length L is increased and the half-wave voltage is lowered.

However, among these groove-type electrodes, those having grooves formed by wet etching have a groove depth D that can be actually produced.
Is about 10 μm even in a deep one, and it is almost impossible to form a groove of 50 μm or more. Therefore, the effective optical path length L cannot be increased further.

Further, as shown in FIG. 5, even when a groove is formed by machining using a dicing saw or the like, metal such as Au is vapor-deposited by sputtering. In the case of a deep groove electrode, the metal film cannot be sufficiently attached to the wall surface in the groove. According to the experimental results which will be described later in Examples, a groove having a width of 40 μm can form an electrode having an effective optical path length of at most about 20 μm in depth. Width 40 μm and depth 50 μm
If it exceeds, the metal cannot be adhered sufficiently and the electrode cannot be formed. For this reason, there is a drawback that the driving power does not decrease sufficiently.

Furthermore, it is difficult to take out the connecting electrode portion from the groove electrode formed by metal vapor deposition or the like by wire bonding or the like, and a countermeasure is desired.

Further, as shown by the dotted lines in FIGS. 3 and 4, the flat electrodes and the electrodes formed by wet etching have electrodes relatively on the surface portion, and therefore a relatively high voltage must be applied. The electric field 4 to the PLZT substrate 1
Is large, and therefore, when the shutter array is formed with one set of electrodes as one pixel, the curved electric field of one pixel leaks to the electrodes of other adjacent pixels. So-called crosstalk occurs, which has the drawback of deteriorating the SN ratio.

<Objects of the Invention> An object of the present invention is to improve such drawbacks, to provide electrodes deep in the substrate, thereby lowering the driving voltage and preventing crosstalk between adjacent electrodes. An array and a method of manufacturing the array are provided.

<Structure of the Invention> A first invention that achieves the above object is to provide a transparent substrate made of an electro-optical material that exhibits an electro-optical effect, and at least two transparent substrates formed on the substrate, which are parallel to the traveling direction of light. An optical shutter array comprising: parallel grooves having a depth of 50 μm or more in a direction; and electrodes formed by filling a conductive resin.

The second invention is to form at least two parallel grooves on a transparent substrate made of an electro-optical material that exhibits an electro-optical effect, fill the grooves with an excess of conductive resin, and then polish the surface. And a method for manufacturing an optical shutter array, which is characterized by performing smoothing.

Here, the groove preferably has a width of 10 to 15 μm. Further, it is preferable to form at least two grooves by mechanical grinding or dry etching.

The present invention is described in detail below with reference to the preferred embodiments shown in the accompanying drawings.

In the optical shutter array of the present invention, as shown in FIG. 1, a substrate 1 is formed of a transparent electro-optical material, and the substrate 1 is formed.
At least two groove electrodes 2 are formed in. The grooves 12 are formed in parallel with the surface of the substrate 1 at equal intervals and have a depth in the direction perpendicular to the surface, and the depth is 50 μm or more and the width is 10 to 50 μm.
It is good to set m. The width of the gold in the groove 12 is preferably more than twice the particle diameter of the particles in the conductive resin for filling the conductive resin described later, but the narrower the width, the smaller the pixel of the optical shutter array (see FIG. 7). 7-1, 7-2) can be reduced.

The groove 12 is filled with the conductive resin 3. Any conductive resin may be used as long as it has good conductivity, but a polyimide resin or an epoxy resin containing Ag, Au, Cu or the like as a filler is preferable.

As the electro-optical material, PLZT [La9 atom%, PbZrO ₃ / PbTiO ₃ = 65/35 having a ratio of 9/65/35 is used.
(Mole ratio)] is most preferable.

Besides this, 7/65/35, 8/65/35, 8/4
PLZT with a ratio of 0/60, 12/40/60, 10/65/35, PBLN with a ratio of 60/2, 70/8, PLZT with a ratio of 10/65/35,
PBL with a ratio of 4/60/40, 8/60/40
N, SBN, LiTaO ₃ , LiNbO ₃ , KH ₂ PO ₄ , KD ₂ PO ₄ , PN
N and KTN can also be used.

In such an electro-optic material, the induced change in refractive index is
Some have a temporary electro-optical effect (Pockels effect) that is proportional to the first power of the electric field and a second electro-optical effect (Kerr effect) that is proportional to the second power of the electric field. Either of them can be used. Those that exhibit the secondary electro-optical effect are preferable.

The manufacturing method of the optical shutter array of the present invention will be described below.

Grooves 12 are formed in the substrate 1 shown in FIG. 2a (see FIG. 2b). The groove 12 may be formed by wet etching the substrate 1 using HCl or the like, but preferably the groove 12 is formed by mechanical processing using a dicing saw or the like, or dry etching processing. Width 10 according to machining
With a thickness of μm to 50 μm, it is easy to process a depth of 50 μm or more. After machining, anneal to remove machining strain (2c
See figure).

As shown in FIG. 2d, the groove 12 is filled with the conductive resin 3. The filling is performed by filling the conductive resin 3 in excess of the volume of the groove 12 in excess.

The conductive resin 3 excessively filled in the groove is cured by heating or the like (see 2e). Next, the surface of the substrate 1 is polished to remove excess conductive resin 3 and the surface is smoothed (see FIG. 2f).

<Operation of the Invention> As shown in FIG. 8, the polarizer 14 on the incident light 19 side of the optical shutter array of the first invention is placed on the exit light 20 side of the analyzer 1.
5 are arranged parallel to each other and facing each other. At this time the polarizer 1
The direction of the polarization plane of No. 4 is the direction shown by the arrow 16, and the direction of the polarization plane of the analyzer 15 is the direction shown by the arrow 17 orthogonal to this.

The parallel light flux, which is the incident light 19, is orthogonally incident on the polarizer 14. This incident light flux is naturally polarized light.

Then, the parallel light flux transmitted through the polarizer 14 becomes
Is converted into linearly polarized light, and its plane of polarization has 16 directions.

Then, the linearly polarized parallel light flux passes through the drive unit 21 of the optical shutter array, but at that time, if no voltage is applied to the electrodes, no change occurs in the polarization state of the transmitted light. Therefore, the transmitted light without changing the polarization state is
When reaching the analyzer 15, the direction of the polarization plane of the analyzer 15 and the polarization direction of the arrived light are orthogonal to each other,
It is blocked by the analyzer 15. That is, it is in a normally closed state.

When voltage is applied to the electrode 2 of the optical shutter array,
An electric field acts on the drive unit 21 to generate an electro-optical effect.

Due to this electro-optical effect, a phase shift occurs between the ordinary ray and the extraordinary ray, and the light transmitted through this portion is generally elliptically polarized light.

Since the elliptically polarized light has a polarization component in the direction indicated by the arrow 17, the light of this polarization component passes through the analyzer 15 and becomes the emitted light 20.

Unlike the example shown in FIG. 8, the polarizer 14 and the analyzer 15 are arranged so that the directions of the polarization planes of the polarizer 14 and the analyzer 15 are the same.
When the electrodes are arranged parallel to each other, the transmitted light is blocked by the analyzer 15 when a voltage is applied to the electrodes of the optical shutter array, and the transmitted light is further transmitted through the analyzer 15 when no voltage is applied to the electrodes. . Such a normally open state can also be used.

In this way, it is possible to control the transmission and blocking of the light of the optical shutter array by turning the applied voltage ON-OFF to the electrodes.

In addition, the intensity of the transmitted light can be controlled by controlling the applied voltage.

In the conventional planar electrode optical shutter array as shown in FIG. 3, the electric field 4 may sneak in and crosstalk may occur between adjacent pixels, but in the optical shutter array of the present invention, the electrodes are inside the substrate. Since a comparatively deep groove reaching to the area is filled with the conductive resin, an electric field is linearly generated even in a deep portion in the substrate, and crosstalk between adjacent pixels is reduced. Furthermore, the deeper the depth of the groove, the longer the effective optical path length,
The optical shutter is driven with a low driving voltage.

In addition, the electrodes formed in the deep groove additionally serve to reinforce the substrate.

This optical shutter array can be used for a printer for hard copy as an example. This is a printer (not shown) equipped with a light-collecting transmitter array, a photoconductor, a phenomenon device, and a transfer charger, which is arranged on the light-emitting side of the optical shutter array, and controls transmission and blocking of light from the optical shutter array. There is one that prints on paper.

<Example> Example 1 PLZT wafer manufactured by Motorola (composition 9/65/3
5, 0.3 mm ^t × 2 inch φ) made by Disco DAD-2H /
Type 6 dicing saw (blade NBC-Z16060,
Dicing was performed using 50.8 mm × 0.035 mm × 40 mm, flange PS4924, rotation speed 30000 rpm, cutting speed 2 mm / sec) to obtain a 10 mm × 10 mm × 0.3 mm PLZT chip.

Next, using the above dicing saw, 30 grooves having a width of 40 μm and a depth of 50 μm and a depth direction perpendicular to the chip surface were formed in parallel at a pitch of 100 μm on the PLZT chip.

This chip is placed in an electric furnace and heated in air at 500 ° C for 5
Strain was removed by heat treatment for a period of time. Next, in the groove of this chip, conductive adhesive Rexbond T-70 manufactured by Muromachi Chemical Co., Ltd.
After overfilling with 0 to overflow the groove, the chip was inserted into an oven and heated at 100 ° C. for 2 hours in air to cure the adhesive.

Further, an excessive adhesive agent on the chip surface was ground using a ML-150 type polishing machine manufactured by Maltaux Co., and the PLZT surface was polished to produce a PLZT shutter array.

When a DC voltage was applied to this shutter array by using a blow bar manufactured by Nippon Micronics Co., Ltd. to operate the shutter array, the half-wave voltage was as shown in Table 1.
FIG. 6 is a graph showing the results of Table 1. The measuring method is as shown in FIG.
Were contacted.

Example 2 An optical shutter array was manufactured in the same manner as in Example 1 except that the vertical groove on the surface of the PLZT chip had a groove depth of 100 μm, and the half-wave voltage was measured in the same manner as in Example 1. The results are shown in Table 1, and the results of Table 1 are shown in a graph in FIG.

Example 3 PLZT substrate similar to that in Example 1 Length 30 mm Width 3000 μ
m × thickness 300 μm, width 20 μm × depth 100 μm
m grooves are formed in parallel at a pitch of 50 μm to form the optical shutter array of the pixels 7-1, 7-2, 7-3, 7-4 shown in FIG. 7, and the optical shutter array drive is performed. A clear image was obtained with little crosstalk.

This is because the PLZT, as shown by the dotted line for the electric field 4 in FIG.
The groove electrode formed perpendicular to the surface has less curvature of the electric field 4 in the substrate and lower drive power than the electrode of the conventional example shown in FIG. This is because there is little penetration of the electric field between the electrodes to the other pixel 7-2, and crosstalk between the adjacent pixels 7-1 and 7-2 can be prevented.

Comparative Example 1 Separately, for comparison, the groove width was 40 μm, the pitch was 100 μm, and the groove depth was 5 μm on the PLZT plate in the same manner as in Example 1.
m, 10μm, 20μm, 50μm, 100μm, metal Cr was sputter-deposited to a thickness of 250Å and Au was sputter-deposited to a thickness of 10000Å. The sputtered film did not adhere sufficiently.

With respect to the groove depths of 5 μm, 10 μm, and 20 μm, the wavelength voltage was measured by applying the same wavelength as in the example. The results are shown in Table 1, and the results in Table 1 are shown in FIG.

From this, it is understood that the groove electrode that can be produced by metal sputter deposition is limited to the case of a shallow groove having a groove depth of less than 50 μm.

On the other hand, the one filled with the conductive resin of the present invention is 50 μm.
A deep electrode as formed is formed even at m or more, and a half-wavelength voltage is extremely low, and the driving voltage is low.

<Effects of the Invention> In the shutter array of the present invention, it is possible to manufacture a groove electrode having a long effective photo furnace length, which is impossible to realize in the related art, because the conductive resin is completely filled in the deep electrode. As a result, the driving voltage is lowered, the electrode shape reduces the curvature of the electric field, and the crosstalk between the electrodes can be prevented. Since the groove surface is smoothed by polishing the above resin, a groove electrode having a long effective optical path length can be easily manufactured unlike the electrode formation conventionally performed by sputtering. Moreover, if the grooves are formed on the substrate by mechanical processing or dry etching, the processing accuracy is good. Further, since the conductive resin is filled, the conductive resin serves as a reinforcing material even when a deep groove electrode is formed in a thin device, the mechanical degree of the device is not lowered, and the electrode can be easily taken out.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an optical shutter array of the present invention. FIG. 2 is a diagram showing a method of manufacturing the optical shutter array of the present invention. FIG. 3 is a diagrammatic sectional view of a conventional planar electrode. FIG. 4 is a diagrammatic sectional view of a groove electrode formed by a conventional etching method. FIG. 5 is a diagrammatic sectional view of a groove electrode formed by conventional metal sputtering deposition. FIG. 6 is a graph showing the relationship between the half-wave voltage and the groove depth. FIG. 7 is a perspective view showing an embodiment of the optical shutter array of the present invention. FIG. 8 is a diagram for explaining the operation of the optical shutter array. DESCRIPTION OF SYMBOLS 1 ... PLZT substrate, 2 ... Electrode, 3 ... Conductive resin, 4 ... Electric field, 6 ... Metal sputter deposition film, 7-1, 7-2, 7-
3, 7-4 ... Pixel, 8 ... Common electrode, 9 ... Individual electrode, 10
... Probe, 11 ... Power supply, 12 ... Groove, D ... Groove depth, W ...
Electrode width, L ... Effective optical path length, 14 ... Polarizer, 15 ... Analyzer, 16, 17 ... Direction of polarization plane, 18 ... Power supply, 19 ... Incident light, 20 ... Outgoing light, 21 ... Driving section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kazuhiro Kawajiri, 798, Miyadai, Kaisei-cho, Ashigarakamigun, Kanagawa Fuji Photo Film Co., Ltd. (56) Reference JP-A-59-104623 (JP, A)

Claims (6)

[Claims] 1. A transparent substrate made of an electro-optical material exhibiting an electro-optical effect, and at least two transparent grooves formed in the substrate and having a depth of 50 μm or more in a direction parallel to the traveling direction of light. An optical shutter array comprising: an electrode filled with a functional resin. 2. The optical shutter array according to claim 1, wherein the groove has a width of 10 to 50 μm. 3. A transparent substrate made of an electro-optical material exhibiting an electro-optical effect, at least two parallel grooves having a depth of 50 μm or more in a direction parallel to a traveling direction of light are formed, and excess grooves are formed in the grooves. The method for manufacturing an optical shutter array, comprising: filling the conductive resin of, and polishing the surface to smooth the surface. 4. The method of manufacturing an optical shutter array according to claim 3, wherein the groove has a width of 10 to 50 μm. 5. The method of manufacturing an optical shutter array according to claim 3, wherein the at least two grooves are formed by mechanical grinding. 6. The method of manufacturing an optical shutter array according to claim 3, wherein the at least two grooves are formed by dry etching.