JP2001324615A - Spatial filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome usually recognized difficulties in lamination of crystalline materials with themselves and lamination of two plates having optic axes shifted with each other with a thermosetting adhesive because a coefficient of linear expansion is largely varied by the optic axis and difficulties in arrangement of a dielectric in the vicinity of a photodetector because the photodetector breaks down in this case. SOLUTION: The construction of a spatial filter 3 comprising a pair of birefringent lithium niobate plates stuck to each other with a conductive and sticky adhesive makes the sticking property of the adhesive absorb distortion of the lithium niobate plates under high temperature. This enables the spatial filter 3 to be directly stuck to a casing 2 of a solid-state image pickup element equipped with the photodetector 4 and attains miniaturization of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial filter, and more particularly to a light receiving element (CC) which has been rapidly spreading in recent years.
D) Anti-distortion and / or anti-static at high temperatures of optical filters that remove pseudo-color signals using the birefringence effect of crystals to achieve higher density and higher image quality for on-board 8 mm video and digital still cameras, etc. .

[0002]

2. Description of the Related Art Conventionally, there has been proposed a method of sealing an image sensor using a heat-curable adhesive for a spatial filter. However, it is known that a thermosetting adhesive is difficult to adhere to a housing using a thermosetting adhesive because the dielectric substrate is polarized when cured at a high temperature.

FIG. 5 shows lithium niobate (hereinafter referred to as LN).
FIG. 6 is a diagram showing an example of a conventional space filter using a heat-curable adhesive.
It shows a cross section of the cross section in a high temperature state. FIG. 7 is a graph showing a charged state when a processing temperature stress is applied.

In FIG. 6, reference numeral 16 denotes a first LN forming a spatial filter, 17 denotes a second LN forming a spatial filter, 18 denotes a first thermosetting adhesive, and 19 denotes a second thermosetting adhesive. The adhesive, 11 indicates a light receiving element, and 20 and 21 indicate electric charges indicating a polarization state.

[0005] In the conventional method, curing is performed by heating at 100 ° C to 150 ° C in order to obtain the reliability of the adhesive. When LN is stuck on the light-receiving element at a high temperature, LN is polarized and generates electric charge 20 because it is a dielectric.

The electric charge 21 (-in the figure) on the incident light side is discharged by a holding jig or the like or discharged naturally into the air.
However, since the electric charge 20 (+ in the figure) on the light receiving element side is cured at 100 ° C. or higher, the space containing the second LN 17 and the light receiving element 11 is in a dry state and does not easily discharge.

FIG. 7 is a graph showing data of an example of an actual charging experiment, in which a charged state at 120 ° C. is 200 V. When the jig was removed from the state, the element was destroyed by discharging to the light receiving element 11. An antireflection film or an infrared cut film deposited on LN or quartz is generally an insulator and therefore has a high resistance value and has no discharge effect during drying. For this reason, since this potential continues for a long time even after the jig is removed, the element is destroyed.

[0008]

In recent years, a solid-state imaging device using such a spatial filter has been required to be reduced in size and thickness. LN has a birefringence value of 6.3 of quartz.
Since it can be configured with a thickness of 1 / 6.3 in order to obtain the effect of a spatial filter equivalent to that of quartz, which is twice as large, attention has recently been paid to thinning. At the same time, since the linear expansion coefficients differ greatly depending on the optical axis, it has been difficult to bond crystalline materials together or to bond them with a thermosetting adhesive whose optical axis is shifted. Further, it has been difficult to dispose the dielectric near the light receiving element due to destruction of the light receiving element.

SUMMARY OF THE INVENTION An object of the present invention is to realize high reliability while achieving downsizing of a small and thin spatial filter.

[0010]

In order to solve this problem, a spatial filter according to the present invention comprises at least one or more first crystal plate and second optical glass having birefringence, or at least one or more sheets. A first crystal plate having a birefringence of at least one and a second crystal plate having a birefringence of at least one, wherein the elongation rate is 50% or more at the bonded portion of the filter, It is configured to be directly bonded with a tacky adhesive having a Shore hardness of 60 degrees or less.

An anti-reflection film, a transparent conductive film, a multilayer film containing Ti, or a resin-based conductive material is applied to the side surfaces of the spatial filter simultaneously with the anti-reflection film.

[0012]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, there is provided a first crystal plate and a second optical glass having at least one birefringence, or at least one birefringence. A filter in which a first crystal plate and at least one second crystal plate having birefringence are bonded to each other, and an elongation percentage is 50% or more at a bonded portion of the filter.
By adopting a configuration in which the crystal plate is directly bonded with a tacky adhesive having a Shore hardness of 60 degrees or less, since the crystal plate is a dielectric, the linear expansion coefficient differs depending on the crystal axis. A conventional heat-curable adhesive has a function of generating warpage stress, and a conventional heat-curable adhesive has an effect of being easily polarized at a high temperature, and a tacky adhesive has an effect of reducing stress and reducing the amount of charge.

According to a second aspect of the present invention, the use of a conductive adhesive of 10 ⁺⁸ Ωm or less in the bonding portion has the effect of accelerating the discharge of the substrate surface and preventing the element from being destroyed.

According to a third aspect of the present invention, a filter is provided between a subject and a light receiving element in which pixels of three primary colors are arranged on one plane, and a surface of the filter facing the light receiving element is provided with a filter.
^The configuration in which the antireflection film having the conductor film of ⁺² Ωm or less is formed has an effect that when the dielectric is charged, the electric charge is released to the end face to prevent a voltage breakdown of the light receiving element.

According to a fourth aspect of the present invention, an infrared light cut filter is provided on a surface of the filter facing the light receiving element, and the infrared cut filter has a conductivity of 10 ⁺² Ωm or less due to a film containing Ti. According to the configuration, when the dielectric is discharged, the light receiving element is prevented from being directly discharged, so that a voltage breakdown can be prevented.

According to a fifth aspect of the present invention, since the conductive resin is applied to the end face of the filter, when the dielectric is charged, the electric charge is instantaneously released to the conductive resin, and the electric charge on both surfaces of the dielectric is obtained. Has the effect of preventing the device from being discharged by neutralizing it.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a device using a spatial filter according to the present invention will be described below with reference to FIGS.

FIG. 1 is a top view of a spatial filter according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light-shielding sheet made of a conductive adhesive, and 2 denotes a device using the spatial filter of the present invention. An example of a casing of a solid-state imaging device, 3 is a spatial filter formed of a crystal plate (lithium niobate (LN substrate) or the like), and 4 is a plurality of pixels that separate colors into three primary colors of R, G, and B as incident light. It consists of a light receiving element (CCD) provided on the side.

FIG. 2 is a sectional view taken along the line AA of FIG.
Is a first LN that forms a spatial filter, 6 is a second LN that forms a spatial filter, 7 is a first adhesive that bonds the first and second spatial filters, and 8 is a second adhesive. A second tacky adhesive for bonding the LN and the housing of the solid-state imaging device;
Reference numeral 9 denotes a protection spacer of the solid-state imaging device, 10 denotes a housing of the solid-state imaging device, 11 denotes a light receiving element, 13 denotes a conductive adhesive covering an end face of the LN, and 12 denotes incident light.

The first LN 5 and the second LN 6 are bonded to each other with a tacky adhesive 7 containing 80% or more of a conductive acrylic material, containing a black pigment, and containing no solvent. The central portion of the adhesive is cut in advance by a mold to form a light shielding sheet 1 having light shielding characteristics.

The operation of the solid-state image pickup device constructed as described above will be described below. The incident light 12 is
The light enters the light receiving element 11 through the first LN5 and the second LN6 constituting the spatial filter, and is converted. First
LN5 is an antireflection film (hereinafter referred to as A) having conductive films on both surfaces.
The second LN 6 has an AR coat on one side and an infrared cut filter (hereinafter also referred to as an IR coat) on the other side. At room temperature, an image can be formed on the light receiving element 11 without any particular deformation.

On the other hand, when the solid-state imaging device is placed in a high temperature environment, warpage occurs on the LN substrate. Even in such a high temperature environment, the incident light 12 from the subject passes through a lens (not shown) and then forms a spatial filter with the first LN5 and the second LN5.
Incident on the image sensor 11 through the LN6 of FIG. However, since a crystal having birefringence generally has a different coefficient of linear expansion depending on the crystal axis, at a high temperature, it shows a saddle-shaped warp as shown in FIG.

Even if such a saddle-like warp occurs, the present invention
The first LN5 and the second LN6 forming the bright filter
With an elongation of 50% or more and a Shore hardness of 60 degrees or less
Adhered with adhesive. By the way, linear expansion on LN substrate
Coefficient is 14 × 10 on the largest axis ^-64 × 10 at the minimum axis / ° C^-6
/ ° C., and as shown in FIG.
Indicates warped state, partly compressed, partly stretched
The adhesive 7 has good elongation and adhesiveness
Therefore, the first LN5 and the second LN6 have a small stress.
And the polarization voltage is minimized.

At a high temperature, LN5 and LN6 are polarized as dielectrics, and have electric charge 20 on LN17 facing light receiving element 11 as in the conventional structure of FIG.
When the electric charge 20 accumulated on 17 discharges the light receiving element 11, the light receiving element 11 is destroyed, and the function as a solid-state imaging device is impaired. In the preferred sun of the present invention, a first LN5 and a second LN constituting a spatial filter
Since the surface of the charged substrate is treated with a conductor, the electric charge is discharged from the end surface exposed to the outside air.

According to a preferred embodiment of the present invention in which the end faces of the first LN5 and the second LN6 are joined by the adhesive 13 containing conductive acrylic as a main component, the charges on both surfaces of the LN are neutralized. Will be done.

In FIG. 4, reference numeral 14 denotes data obtained by conducting a discharge experiment in a state where the charged state was exposed to air at a temperature of 25 ° C. and a humidity of 38% without using a conductive film.
Is data of a discharge experiment of the conductive spatial filter of the present invention. As is apparent from the figure, in the spatial filter of the present invention, the accumulated charge disappears in about 10 minutes, and the voltage becomes equal to or lower than the breakdown voltage to the light receiving element 11, so that mass production can be performed without impairing the productivity. It takes several hours to discharge the electric charge. As described above, in the configuration of the present invention, since the time until the potential becomes 0 is extremely short, the reliability of the spatial filter can be improved because there is virtually no charge accumulation.

In the above description, two LNs are used. However, the number of birefringent plates and the number of glasses are not limited. If it is contained, processing can be carried out at room temperature by using a tacky adhesive, and improving the reliability of the CCD will be affected by preventing charging of the dielectric.

When a conductive film cannot be formed,
For example, an equivalent function can be obtained by depositing a TiO ₂ film by metallization or semimetallization (such as a low oxide having a lower valence of oxygen than the stoichiometric composition). In the case of a multilayer film, the absorption becomes intense. Therefore, equivalent performance can be obtained by metallizing or semi-metallizing some of the layers.

As described above, according to the present invention, the spatial filter is not exposed to high temperatures in the processing process, so that the spatial filter can be installed with high reliability. Thinning can be achieved.

[0030]

As described above, according to the present invention, since a heating step is not required at the time of assembly, stress on a spatial filter can be reduced. For example, when the spatial filter of the present invention is applied to a solid-state imaging device, a CCD Thus, a small-sized image sensor directly attached to the device can be obtained.

In addition, according to a preferred embodiment of the present invention, in which both surfaces of the spatial filter are formed of a conductive film, even if the electric charge is erroneously made in normal use, the neutralization of the electric charge eliminates the discharge to the element. For example, the reliability of the solid-state imaging device can be increased.

As described above, according to the spatial filter of the present invention, not only the miniaturization and thinning of the product can be realized at the same time, but also the cost can be reduced by shortening the processing process, and the spatial filter with high reliability can be obtained. In addition, there is an effect that the reliability of a device using the spatial filter of the present invention can be improved.

[Brief description of the drawings]

FIG. 1 is a top view of one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of one embodiment of the present invention.

FIG. 3 is a cross-sectional view of one embodiment of the present invention at a high temperature.

FIG. 4 is a diagram showing the relationship between polarization voltage of lithium niobate and discharge time.

FIG. 5 is a top view of a conventional embodiment.

FIG. 6 is a cross-sectional view taken along a line BB in a high temperature state of FIG. 5;

FIG. 7 is a diagram showing the relationship between the polarization voltage of lithium niobate and the discharge time.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 light-shielding sheet 2 housing of solid-state imaging device 3 spatial filter 4 light-receiving element 5 first lithium niobate constituting spatial filter 6 second lithium niobate constituting spatial filter 7 adhesive 1 Adhesive 8 Adhesive Second Adhesive 9 Housing for Protecting Light-Receiving Element 10 Housing for Solid-State Image Sensor 11 Light-Receiving Element 12 Incident Light from Subject 13 Conductive Adhesive 14 Conventional Discharge Characteristics 15 Discharge Characteristics of the Invention 16 First LN of Conventional Method Constituting Spatial Filter at High Temperature 17 Second LN of Conventional Method Constituting Spatial Filter at High Temperature 18 First Thermosetting Adhesive 19 Second thermosetting adhesive 20 Charge on lithium niobate substrate 21 Charge on lithium niobate substrate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Osamu Doi 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. AA03 BB13 DD02 EE16 EE20

Claims (5)

[Claims] 1. A first material having at least one or more birefringence.
A filter in which any one of the crystal plate and the second optical glass, or at least one or more first crystal plate having birefringence and at least one second crystal plate having birefringence are bonded. And an elongation rate of 50 at the bonded portion of the filter.
%, Characterized by being directly bonded with a tacky adhesive having a Shore hardness of not less than 60 degrees. 2. The spatial filter according to claim 1, wherein a conductive adhesive of 10 ⁺⁸ Ωm or less is used for the bonding portion. 3. A filter is provided between a subject and a light receiving element, and 10 ^{+2 is provided on} a surface of the filter facing the light receiving element.
3. The spatial filter according to claim 1, wherein an anti-reflection film having a conductor film of .OMEGA.m or less is formed. 4. An infrared light cut filter is provided on a surface of the filter facing the light receiving element, wherein the infrared cut filter is
The spatial filter according to any one of claims 1 to 3, having a conductivity of 10 ⁺² Ωm or less by a film containing i. 5. The spatial filter according to claim 1, wherein an end face of the filter is covered with a conductive resin of 10 ⁺² Ωm or less.