JP2003098552A - Method for manufacturing light control device and empty cell for liquid crystal optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a light control device for suppressing variation of a cell gap set before liquid crystal inclusion even after the liquid crystal inclusion while sufficiently securing an optical density ratio (a contrast ratio) of a liquid crystal optical element and an empty cell for the liquid crystal optical element. SOLUTION: A gap d1 of a central part 20 is formed so as to be larger than a gap d2 of a peripheral part 24 in a state of the empty cell 12. A negative liquid crystal with negative dielectric anisotropy is used as a host material 13, i.e., a liquid crystal 34 to be injected. A positive dichroic dye is used as a guest material 4. Therefore, while the liquid crystal is easily filled in the central part, as the liquid crystal is eventually filled in a total region of the gap, the variation of the cell gap is suppressed even after the inclusion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light control device for adjusting and emitting the amount of incident light and an empty cell for a liquid crystal optical element used therein.

[0002]

2. Description of the Related Art Usually, a polarizing plate is used in a light control device using a liquid crystal optical element (liquid crystal cell). For this liquid crystal cell, for example, a TN (Twisted Nematic) type liquid crystal cell or a guest-host (GH (Guest Host)) type liquid crystal cell is used.

FIG. 14 is a schematic diagram showing the operating principle of a conventional light control device. This light control device mainly uses the polarizing plate 1 and the GH.
The GH cell 2 is not shown in the drawing,
It is enclosed between two glass substrates and has a working electrode and a liquid crystal alignment film (the same applies hereinafter). Liquid crystal molecules 3 and dichroic dye molecules 4 are enclosed in the GH cell 2.

The dichroic dye molecule 4 has anisotropy in light absorption, and is, for example, a positive type (p type) that absorbs light in the long axis direction of the molecule.
Type) dye molecule. The liquid crystal molecule 3 is a positive type (positive type) having a positive dielectric anisotropy.

FIG. 14A shows a state of the GH cell 2 when no voltage is applied (no voltage is applied). Incident light 5
Is converted into linearly polarized light by passing through the polarizing plate 1. In FIG. 14A, since the polarization direction matches the molecular long axis direction of the dichroic dye molecule 4, the incident light 5 is absorbed by the dichroic dye molecule 4 and the transmittance of the GH cell 2 is increased. descend.

Then, as shown in FIG. 14B, GH
When a voltage is applied to the cell 2, the molecular major axis direction of the dichroic dye molecule 4 becomes perpendicular to the polarization direction of the linearly polarized light as the liquid crystal molecule 3 faces the electric field direction. Therefore, the incident light 5 is G
It is almost absorbed by H cell 2 and is transmitted.

When a negative type (n-type) dichroic dye molecule that absorbs light in the minor axis direction of the molecule is used, this is the reverse of the case of the positive type dichroic dye molecule 4, and no voltage is applied. Light is not absorbed when applied, and absorbed when voltage is applied.

In the light control device shown in FIG. 14, the ratio of the absorption when the voltage is applied and when the voltage is not applied, that is, the ratio of the optical density is about 10. This has an optical density ratio that is about twice as high as that of a light control device including only the GH cell 2 without using the polarizing plate 1.

[0009]

The present applicant has proposed, in Japanese Patent Application No. 11-322186, a light control device and an image pickup device capable of further improving the optical density ratio. That is, according to Japanese Patent Application No. 11-322186 (hereinafter referred to as prior invention), a liquid crystal device and a polarizing plate arranged in an optical path of light incident on the liquid crystal device constitute a light control device. Then
Furthermore, since a guest-host type liquid crystal having a negative type liquid crystal as a host material is used, the ratio of absorbance (that is, the ratio of optical density) when no voltage is applied (transparent) and when voltage is applied (light-shielded) is improved, The contrast ratio of the light control device is increased, and the light control operation can be normally performed from a bright place to a dark place.

In the guest-host type liquid crystal cell (GH cell) 2 shown in FIG. 14, a positive type liquid crystal having a positive dielectric anisotropy (Δε) is used as the host material 3, and the guest material 4 is of two colors. A positive dye 4 having a positive light absorption anisotropy (ΔA) is used, and the polarizing plate 1 is disposed on the incident side of the GH cell 2. For this GH cell 2, a change in light transmittance when an operating voltage is applied is measured using a rectangular wave as a drive waveform.
As shown in, the average light transmittance of visible light (in air; transmittance when a polarizing plate was added in addition to the liquid crystal cell was referred to (= 100%) with application of an operating voltage: The same)
However, even if the voltage is increased to 10 V, the maximum transmittance is about 60%, and the change in light transmittance is relatively gentle.

This is because, when a positive type host material is used, the interaction of liquid crystal molecules at the interface with the liquid crystal alignment film of the liquid crystal cell is strong when no voltage is applied, and therefore the director of the director is applied even if a voltage is applied. Orientation does not change (or
It is considered that this is because liquid crystal molecules remain (which are difficult to change).

On the other hand, in the prior invention, as shown in FIG. 4, in the guest-host type liquid crystal cell (GH cell) 12, as the host material 13, a negative type having a negative dielectric anisotropy (Δε) is used. Liquid crystal of Merck MLC-66
08 is used as an example, and the guest material 4 is a positive dye having dichroism, D5 manufactured by BDH, Inc. is used as an example, whereby the polarizing plate 11 is arranged on the incident side of the GH cell 12 and a rectangular wave is generated. When a change in light transmittance when an operating voltage is applied as a drive waveform is measured, as shown in FIG. 5, the average light transmittance (in air) of visible light is about 75% with the application of the operating voltage. % To 10% or less, and the change in light transmittance becomes relatively sharp.

This is because when a negative-type host material is used, the interaction of liquid crystal molecules at the interface with the liquid crystal alignment film of the liquid crystal cell is very weak when no voltage is applied, so that light is not applied when no voltage is applied. It is considered that this is because the light is easily transmitted, and the direction of the director of the liquid crystal molecules is easily changed with the application of the voltage.

By thus constructing the GH cell using the negative type host material, the light transmittance (especially when transparent) is improved, and the GH cell is used by fixing the position as it is in the image pickup optical system. A compact dimming device that can be realized can be realized. In this case, by arranging a polarizing plate in the optical path of the incident light to the liquid crystal element, the ratio of the absorbance when no voltage is applied and when the voltage is applied (that is, the optical density ratio) is further improved, and The contrast ratio is further increased, and the dimming operation can be performed more normally from a bright place to a dark place.

[0015]

The present inventor diligently studied to further improve the characteristics of the light control device using such a GH cell. As shown in FIG. 16, when the liquid crystal element is transparent. It was found that the optical density ratio between when the light was shielded was also greatly influenced by the distance (cell gap) between the two glass substrates forming the GH cell.

That is, the larger the cell gap, in other words, the thicker the liquid crystal layer, the larger the difference in light transmittance between the transparent state and the light-shielded state, and the larger the optical density ratio, the more negative the host material. The light transmittance at the time of transparency, which is an advantage of using liquid crystal, is reduced.

Also, as shown in FIG. 17, when the cell gap changes, the response speed of the GH cell as a light control device also changes significantly, and when the cell gap increases and the liquid crystal layer becomes thicker, the response speed decreases. It turns out that it will end up. However, drives a and b represent halftone driving, and drives c and d represent transparent-light-shielding driving.

From the above, when a guest-host type liquid crystal is used to manufacture a light control device, the light transmittance when transparent, the light transmittance when light is blocked, the response time of the liquid crystal element, and the like.
We have found that there is a range of cell gaps to satisfy each of the characteristics that are difficult to achieve at the same time.

That is, in order to realize a practically advantageous light control device using a liquid crystal element, it is necessary to secure a sufficient optical density ratio without lowering the response speed, and the liquid crystal is sealed in the GH cell. Gap between glass substrates (cell gap)
It was found that it is desirable to control the value of 2 μm or more and 4 μm or less.

In other words, if the cell gap is less than 2 μm, the response speed as a light control device is increased, and the light transmittance when transparent is improved, but the light transmittance when shielded is also increased. As a result, it becomes difficult to secure the optical density ratio (contrast ratio). Conversely, the cell gap is 4 μm
If it exceeds, the optical density ratio can be secured large, but the light transmittance at the time of transparency is lowered, and the response speed as the light control device is apt to be deteriorated, and the light transmittance is slightly changed particularly in the halftone. When it is driven, it becomes slow.

However, during further examination, depending on the state of the empty cell before the liquid crystal is filled, FIG.
As shown in FIGS. 18A and 18B, the cell gap before and after the liquid crystal filling is largely varied as shown in FIG. 18B in the central portion 20 forming the effective optical path, and the gap thickness varies within the same cell. It has been confirmed that a defect in which is markedly appears occurs.

As a result of investigating the correlation between the defective sample and the empty cell structure, the dispersion of the cell gap after the liquid crystal filling is particularly large, and as shown in FIG. 19B, a plurality of Newton rings are visually observed under oblique light. 18A and 19A, the gap thickness of the cell central portion 20 is smaller than the gap thickness of the cell peripheral portion 24. We have found that the empty cell before the liquid crystal is filled is concave.

The reason for this is that when liquid crystal is injected into an empty cell as shown in FIG. 18A, the liquid crystal is easily filled in the peripheral portion with a large gap and also in the central portion.
It is considered that this is because the pressure of the liquid crystal filled in the peripheral portion having a large gap changes the small gap in the central portion.

Under these circumstances, in order to realize a highly functional image pickup device by mounting the light control device using the liquid crystal cell as described above, it is determined by the difference in the light transmittance between the transparent state and the light shielding state. Ensure a sufficiently large optical density ratio (contrast ratio),
Moreover, both high response speed and large optical density ratio are compatible,
It is desired to drive at a high transient response speed that is difficult to achieve at the same time.

Therefore, the object of the present invention is to obtain a sufficient optical density ratio (contrast ratio) of the liquid crystal optical element while making use of the features of the above-mentioned prior invention, and between the substrates after the liquid crystal is sealed and before the liquid crystal is sealed. Another object of the present invention is to provide a method for manufacturing a dimming device that suppresses a change in the gap (cell gap) and an empty cell for a liquid crystal optical element.

[0026]

That is, according to the present invention, in manufacturing a light control device composed of a liquid crystal optical element in which liquid crystal is sealed between substrates opposed to each other, a central portion of the substrate among the gaps between the opposed substrates is manufactured. The present invention relates to a method of manufacturing a light control device (hereinafter, referred to as a manufacturing method of the present invention) in which the gap is maintained larger than that in the peripheral portion of the substrate and the liquid crystal is sealed between the opposing substrates in this state. It is a thing.

According to the manufacturing method of the present invention, the gap in the central portion of the substrate is kept larger than that in the peripheral portion of the substrate, and the liquid crystal is sealed between the substrates in this state, so that it is easy to inject the liquid crystal. In this way, the liquid crystal can be filled almost uniformly between the substrates, and as a result, the change (dispersion) in the gap between the substrates before and after the liquid crystal is sealed can be suppressed, and the transmittance and the response speed under the set conditions can be always realized. Can be provided. This effect can be obtained because the liquid crystal is easily filled into the central portion where the gap between the bases is large and the liquid crystal is also filled into the peripheral portion. It is considered that this is because the liquid crystal is injected and the change in the gap between the substrates is reduced.

Further, according to the present invention, there is provided an empty cell for a liquid crystal optical element in which liquid crystal is to be sealed between the substrates facing each other, and the gap at the center of the substrate among the gaps between the opposing substrates is the peripheral portion of the substrate. The present invention relates to an empty cell for a liquid crystal optical element (hereinafter referred to as an empty cell of the present invention) which is held larger than the gap.

According to the empty cell of the present invention, an empty cell which can be effectively used in the manufacturing method of the present invention can be provided.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

In the above-described manufacturing method and empty cell of the present invention, as shown in FIG. 1A, the ratio of the gap d ₁ in the central portion 20 of the base body to the gap d ₂ in the peripheral portion 24 of the base body is set. 1 <d
It is desirable that ₁ / d ₂ ≦ 1.1.

This will be described with reference to FIG. 3 (a graph showing the tendency of variations in the gap ratio and the gap difference after the liquid crystal is filled), and the cell gap ratio (d ₁ / d ₂ ) and the gap after the liquid crystal is filled. The variation (Δd ₁ ) has a tendency like the curve A ₁ shown by the thick line, but a constant fluctuation range shown by the diagonal line A ₂ is seen in this tendency line. Here, description will be given based on the average tendency curve A ₁ .

That is, the cell gap ratio (d ₁ / d ₂ ) is 1.
If it is 0 or less, the gap variation Δd ₁ after the liquid crystal is sealed
Is significantly increased, the gap ratio is 0.92, and Δd ₁ is 0.
Reach 5 μm. However, when the gap ratio exceeds 1.0, the variation Δd ₁ is small and remarkably stable, and the gap ratio is 1.01 to 1.08 (particularly 1.03 or its vicinity).
Thus, the variation Δd ₁ becomes smaller. When the gap ratio exceeds 1.1, the variation Δd ₁ rises again,
When the gap ratio exceeds 1.0, particularly 1.1 or less, the variation Δd ₁ is 0.06 or less and is stable, which is a desirable state. From this fact, the cell gap ratio (d
₁ / d ₂ ) is preferably 1.0 <(d ₁ / d ₂ ) ≦ 1.1,
Further, the range of 1.01 to 1.08 is preferable in order to stably reduce the variation Δd ₁ .

As a result, as shown in FIG.
Central part 2 of base body in GH cell 12 in which liquid crystal 34 is enclosed
It is possible to effectively suppress the variation in the gap between the 0-base peripheral portion 24. That is, as will be apparent from what will be described later, in the empty cell state of FIG. 1A, the gap d ₁ at the cell center is made slightly larger than the gap d ₂ at the cell periphery, and the base is preliminarily set. It is very effective to evenly inject the liquid crystal 34 into the gap by forming the empty cell in a convex shape.

In order to suppress the dispersion of the gap after the liquid crystal is sealed by setting such a gap ratio, it is necessary to dispose a spacer between the opposed bases and hold the gap so that the gap is maintained even after the liquid crystal is injected and after the liquid is filled. It is desirable because it is easy to hold.

In this case, when the spacer is arranged between the opposing transparent substrates on which the transparent electrode and the alignment film are respectively formed, and the peripheral portion is sealed with the sealing material, is the sealing material formed smaller than the spacer? Alternatively, it is preferable to form a mixture containing a harder material from the viewpoint of easily maintaining the holding property of the gap.

Further, the hard material is formed into a ball shape or a fiber shape and sealed with a sealing material containing them, and the distribution density of the spacers dispersed between the substrates is 150 to 150.
It is desirable to control so as to be 500 pieces / mm ² .

As described above, the diameter of the spacer 36 (FIG. 6b) made of, for example, plastic balls dispersed over the entire surface of the cell is larger than the diameter of, for example, glass fiber contained in the sealing material 35 at the periphery of the GH cell 12 shown in FIG. Or a spacer 37 made of a transparent resist formed by printing
If the height of (FIG. 6c) is increased and the substrates 31A and 31B are attached to each other, or if the spacer has the same size as the sealing material 35, the distribution density in the cell is 150 cells / mm.
It is effective to set it to ² or more regardless of the liquid crystal injection method and injection conditions.

However, if there are too many spacers,
It is difficult to eliminate the unevenness of the density when spraying with the general spraying method (even when dry or wet), and when you observe it closely, the light control operation by the liquid crystal molecules may give you a feeling of strangeness (white spots). become. Therefore, it is considered appropriate that the upper limit of the spacer distribution density for producing a liquid crystal cell as a light control element is 500 cells / mm ² or less.

That is, since there are few spacers, the central portion 2
When the gap of 0 is smaller than that of the peripheral portion 24, it is difficult to maintain its shape and the central portion swells when the liquid crystal is injected, and further swells if there is no spacer. Therefore, it is preferable to provide the spacers with an effective distribution density.

Thus, by forming the spacer (36 or 37) in the cell with an effective size and an effective density, the spacer functions as a support material for maintaining the cell gap and expands. By effectively acting as a binder for preventing, the gap thickness can be maintained as designed and the bulge of the cell due to liquid crystal injection can be suppressed.

After the liquid crystal is filled, the gap between the opposing substrates in the effective optical path of the liquid crystal optical element is set to 2 μm.
As described above, controlling to 4 μm or less is as follows.
This is desirable in that the optical density ratio between light transmission and light shielding can be kept high and the response speed can be increased. This can be surely realized by producing an empty cell as shown in FIG.

As the liquid crystal, for example, a negative liquid crystal having a negative dielectric anisotropy (Δε) is used as a host material, and 2
By enclosing a guest-host type liquid crystal containing a chromatic dye (positive type) as a guest material, the light transmittance is improved when a voltage is applied and the optical density ratio is improved when a voltage is not applied and when a voltage is applied. It is desirable in that the contrast ratio can be further increased.
As the negative liquid crystal having a negative dielectric anisotropy (Δε), known materials can be used in addition to the products manufactured by Merck. However, the present invention is not limited to the negative type liquid crystal or the positive type dichroic dye, and the positive type liquid crystal or the negative type dichroic dye may be used.

FIG. 6 shows various cells after the liquid crystal shown in FIG. 1 (b) is filled. That is, FIG. 6A shows an example in which a spacer is not provided, but in this case as well, the gap between the bases according to the present invention is such that the gap d _{1 in the} central portion 20 is larger than the gap d _{2 in the} peripheral portion 24. By being formed larger than the above, as described above, it is possible to easily inject the liquid crystal into the central portion of the base body while injecting the liquid crystal substantially uniformly over the entire area of the substrate, and to reduce the variation in the cell gap before and after the liquid crystal injection. be able to. 6B shows an example in which a spherical spacer 36 is provided, and FIG. 6C shows a columnar spacer 3.
7 is an example in which 7 are provided, all of them are desirable for the reasons described above. That is, d ₁ and d ₂ can be reliably formed by interposing a spacer in the gap (cell gap), and the gap after liquid crystal injection can always be secured at the designed value.

A light control device 2 including the above-mentioned GH cell 12
For example, as shown in FIG. 7, the lens element 3 is arranged between a front lens group 15 and a rear lens group 16 including a plurality of lenses such as a zoom lens. The light that has passed through the front lens group 15 is linearly polarized through the polarizing plate 11, and then the GH cell 1
Incident on 2. The light that has passed through the GH cell 12 is condensed by the rear lens group 16 and is displayed as an image on the imaging surface 17.

Polarizing plate 11 constituting this light control device 23
Can be put in and taken out from the effective optical path of the light incident on the GH cell 12, similarly to the above-mentioned prior invention by the present applicant. Specifically, by moving the polarizing plate 11 to a position indicated by an imaginary line, it is possible to let the light out of the effective optical path. As means for putting in and taking out this polarizing plate 11, FIG.
A mechanical iris as shown in may be used.

This mechanical iris is a mechanical diaphragm device generally used in a digital still camera, a video camera, etc., and mainly comprises two iris blades 18 and 19.
The polarizing plate 11 is attached to the iris blade 18.
The iris blades 18 and 19 can be moved in the vertical direction. The iris blades 18, 19 are relatively moved in the direction indicated by the arrow 27 by using a drive motor (not shown).

As a result, as shown in FIG. 8, the iris blades 18 and 19 are partially overlapped, and when this overlap becomes large, the opening 22 on the effective optical path 20 located near the center of the iris blades 18 and 19 is formed. Is covered with the polarizing plate 11.

FIG. 9 is a partially enlarged view of the mechanical iris near the effective optical path 20. At the same time that the iris blade 18 moves downward, the iris blade 19 moves upward. Along with this, as shown in FIG. 9A, the iris blade 1
The polarizing plate 11 attached to 8 also moves to the outside of the effective optical path 20. On the contrary, by moving the iris blade 18 upward and the iris blade 19 downward, the iris blades 18 and 19 overlap each other. According to this, FIG. 9 (b)
As shown in, the polarizing plate 11 moves to the effective optical path 20,
The opening 22 is gradually covered. When the overlapping of the iris blades 18 and 19 with each other increases, as shown in FIG. 9C,
The polarizing plate 11 covers the entire opening 22.

Next, the dimming operation of the dimming device 23 using this mechanical iris will be described.

As the subject (not shown) becomes brighter, as shown in FIG. 9A, the iris blades 18 and 19 that have been opened in the vertical direction are driven by a motor (not shown) and start overlapping. As a result, the polarizing plate 11 attached to the iris blade 18 starts to enter the effective optical path 20 and covers a part of the opening 22 (FIG. 9B).

At this time, the GH cell 12 is in a state of not absorbing light (note that due to thermal fluctuation, surface reflection, etc.,
There is some absorption by the GH cell 12. ). For this reason,
The light passing through the polarizing plate 11 and the light passing through the opening 22 are
The intensity distributions are almost the same.

Then, the polarizing plate 11 is completely opened 22.
Is covered (FIG. 9C). Furthermore, when the brightness of the subject increases, the voltage to the GH cell 12 is increased,
Light control is performed by absorbing light in the GH cell 12.

On the contrary, when the subject becomes dark,
First, by reducing or not applying the voltage to the GH cell 12, the light absorption effect by the GH cell 12 is eliminated. When the subject becomes darker, drive a motor (not shown) to move the iris blade 18 downward.
Further, the iris blade 19 is moved upward. Thus
The polarizing plate 11 is moved out of the effective optical path 20 (see FIG. 9).
(A)).

As shown in FIGS. 7 to 9, the polarizing plate 11 (transmittance, for example, 40% to 50%) is passed through the effective optical path 2 of light.
Since the light can be emitted from 0, light is not absorbed by the polarizing plate 11. Therefore, the maximum transmittance of the dimmer is, for example, 2
It can be more than doubled. Specifically, when this light control device is compared with a conventional light control device including a fixedly installed polarizing plate and a GH cell, the maximum transmittance is, for example, about twice. The minimum transmittance is the same for both.

Further, since the polarizing plate 11 is put in and out by using the mechanical iris which is put to practical use in a digital still camera or the like, the light control device can be easily realized. Further, since the GH cell 12 is used, in addition to the light control by the polarizing plate 11, the GH cell 12 itself absorbs light, so that the light control can be performed.

In this way, the light control device can increase the contrast ratio of light and dark and can keep the light amount distribution substantially uniform.

[0058]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

Example 1 First, a guest-host type liquid crystal (GH) cell of this example is shown in FIGS. FIG. 1 is a schematic sectional view thereof,
(A) is an empty cell state, (b) is after the liquid crystal is filled, and FIG.
1A and 1B are schematic plan views of FIGS. 1A and 1B, respectively.

This GH cell 12 has transparent electrodes 32A and 32A.
B and the two glass substrates 31A and 31B on which the alignment films 33A and 33B are respectively formed are arranged so as to face each other with the alignment film facing inward, and the cell periphery 24 is sealed by the sealing material 35, and the GH of FIG. An empty cell of cell 12 is formed,
The cell gap between the substrates 31A and 31B, as shown in FIG. 1 (a), is formed towards the cell gap d ₁ of the central portion 20 of the effective optical path is greater than the cell gap d ₂ of the peripheral portion 24.

After the liquid crystal 34 is injected into the empty cell 12 in this state, the liquid crystal injection port 39 is sealed with the end seal material 38 as shown in FIGS. 1 (b) and 2 (b). In this way, in the empty cell state, as shown in FIG.
By forming a gap difference between 0 and the peripheral portion 24, since d _{1 in} the central portion is larger than d _{2 in the} peripheral portion, the liquid crystal 34
Is easily filled in the central portion, and the liquid crystal 34 can be easily filled in the entire gap.

As a result, even after the liquid crystal 34 is filled, the GH cell 1
Deformation due to the pressure at the time of liquid crystal injection is suppressed in the _{No. 2} gap, and as shown in FIG. 3, the ratio of the central gap d ₁ to the peripheral gap d ₂ is (d ₁ / d ₂ ). .0 <(d ₁
/ D ₂ ) ≦ 1.1, the variation of d ₁ Δd
₁ can be suppressed within the allowable limit.

An example of the light control device using the GH cell according to this embodiment is shown in FIG. 4. This light control device comprises a GH cell 12 and a polarizing plate 11 as shown in FIG. And G
In the H cell 12, a mixture of a negative type liquid crystal molecule (host material) 13 and a positive type dichroic dye molecule (guest material) 4 is enclosed as the liquid crystal 34 in the empty cell 12 formed as described above. ing.

As the liquid crystal molecule 13, MLC-6608 manufactured by Merck Co., which is a negative type liquid crystal having a negative dielectric anisotropy, is used as an example, and the dichroic dye molecule 4 is anisotropic in light absorption. D5 manufactured by BDH, which is a positive type dye having properties and absorbing light in the long axis direction of the molecule, was used. The light absorption axis of the polarizing plate 11 was orthogonal to the light absorption axis when a voltage was applied to the GH cell 12.

A light control device 23 including the GH cell 12
Is disposed between the front lens group 15 and the rear lens group 16 including a plurality of lenses such as a zoom lens, as shown in FIG. The light that has passed through the front lens group 15 is linearly polarized through the polarizing plate 11, and then the GH cell 1
Incident on 2. The light that has passed through the GH cell 12 is condensed by the rear lens group 16 and is displayed as an image on the imaging surface 17.

The polarizing plate 11 which constitutes the light control device 23 is the same as the above-mentioned prior invention by the present applicant.
It can be put into and taken out of the effective optical path of the light that enters the GH cell 12. Specifically, by moving the polarizing plate 11 to a position indicated by an imaginary line, it is possible to let the light out of the effective optical path. The mechanical iris shown in FIG. 8 may be used as a means for moving the polarizing plate 11 in and out.

Here, a method of manufacturing the GH cell 12 will be described. A glass substrate 31A on which the above-mentioned transparent electrode patterns 32A and 32B and alignment films 33A and 33B are formed in advance,
A sealing (sealing) material 35 made of a thermosetting epoxy resin containing a glass fiber having a diameter of 3 μm was applied to the periphery of one of the glass substrates of 31B with a predetermined width by a nozzle under the action of compressed air ( 10) After that, spacers 36 made of plastic balls having a diameter of 3.2 μm are evenly dispersed on the other substrate, and the two glass substrates are aligned and stacked, and then heat-pressed under appropriate conditions. By heat treatment while applying pressure (150 to 170 ° C., 1 to ² kg / cm ² as an example), the sealing material in the peripheral portion is cured and the bonding of the substrates is completed (FIG. 6).
(B)).

Thus, the size of the spacer and the pressure
The gap is controlled by the heating conditions. The spacers can be arranged by sticker printing after the rubbing process. The same applies to Example 2 described later. Note that, in FIG. 10, the glass substrate 31 is practically more than the position of the sealing material 35.
It is arranged so that the peripheral edges of A and 31B are located outside (illustrated in a simplified manner in FIG. 6).

The spacers 36 are sprayed from above the substrate by a general method (wet spraying or dry spraying), and the density is approximately 300 to 350 pieces / mm ² , and the spacers 36 are spread over the entire surface of the glass substrate. They were evenly arranged (Fig. 11).

As described above, the bonded substrate is a 3 inch (76.2 mm) ² glass substrate provided with transparent electrodes, alignment films and spacers, and 30 element parts arranged opposite to each other are formed in a matrix. The cell gap of the empty cells obtained by cutting each of the upper and lower substrates with a diamond cutter etc. and singulating (scribing and breaking) was measured with a measuring machine that uses optical interference. , The gap d _{1 at the} center of the cell is about 3.1 μm,
The gap d ₂ around the cell was finished to about 2.9 μm.

The GH cell 12 completed by enclosing (injecting + sealing) the liquid crystal material 34 in such an empty cell is shown in FIG.
As shown in FIG. 7, the gap d ₁ in the cell central portion 20 is somewhat larger than the gap d ₂ in the cell peripheral portion 24, and the state in which the surface distribution of the gap thickness of the empty cell before liquid crystal injection is almost reflected can be maintained. I was able to confirm that

A rectangular wave was input as a drive waveform to the GH cell 12 thus completed by encapsulating the liquid crystal material 34 in such a cell, and the change in light transmittance when an operating voltage was applied was measured (FIG. 4). As shown in FIG. 5, with the application of the operating voltage, the average light transmittance of visible light (in air) was decreased from the maximum transmittance of about 75% to several percent. The GH cell 12 is ± 5 V, although it depends on the liquid crystal cell structure and constituent materials used.
When a pulse voltage of (1 kHz) or higher was applied, the transmittance almost reached the minimum.

Further, as shown in FIG. 5, the high-speed operation was possible in which the response time of the light transmittance when the drive pulse voltage was changed was 30 ms or less.

As a result, also in the present embodiment, a light control device capable of performing a transient response operation at a higher speed while sufficiently securing a difference in optical transmittance (optical density ratio) between when the liquid crystal cell is transparent and when it is shielded. Could be realized.

Example 2 This example is an example in which, in the production of a liquid crystal cell, the diameter of a plastic ball provided between a sealing material and a substrate is changed, and spraying on the substrate is arranged by screen printing.

In the manufacture of the GH cell 12, a glass fiber having a diameter of 2.5 μm is formed around the periphery of one of the pair of glass substrates 31A and 31B on which the transparent electrode patterns 32A and 32B and the alignment films 33A and 33B are formed in advance. Seal made of thermosetting epoxy resin containing
The material 35 is applied in a predetermined width (FIG. 10), the spacers 36 made of plastic balls having a diameter of 2.7 μm are evenly dispersed on the other substrate, and the two glass substrates are aligned and stacked. , Pressure under moderate conditions by hot press plate (150-170 ° C, 1-2 kg / cm ² as an example)
By applying heat treatment while adding, the sealing material 35 in the peripheral portion is cured to complete the liquid crystal cell (FIG. 6).
(B)).

Here, the spacer 36 is scraped out by a squeegee through a screen mask having a predetermined opening and sprayed on the substrate (screen printing).
The density was about 300 pieces / mm ² , and they were arranged almost uniformly on the entire surface of the glass substrate.

The cell gap of an empty cell obtained by dividing the above-mentioned bonded substrates into pieces was measured by a measuring machine utilizing light interference, and the cell gap of the cell central portion 20 was about 2. The cell peripheral portion 24 had a gap of about 2.5 μm. In addition, due to the uniform arrangement of the spacers made of the plastic balls 36 by the screen printing described above, the variation in the cell gap is
It was able to be reduced compared with Example 1.

A liquid crystal material 34 is enclosed in such an empty cell.
GH cell 12 completed by (injection + sealing)
As in Example 1, as shown in FIG.
Up d ₁Is the gap d in the cell peripheral portion 24₂Somewhat larger than
Of the gap thickness of the empty cell before liquid crystal injection.
It was confirmed that the reflected state was maintained.

A liquid crystal material 34 composed of a negative type liquid crystal molecule (host material) 13 and a positive type dichroic dye molecule (guest material) 4 is enclosed in such a cell, and the resulting GH cell 12 is rectangular. Wave was input as a drive waveform and the change in light transmittance when an operating voltage was applied was measured (Fig. 4).
As in Example 1, as shown in FIG. 5, the average light transmittance of visible light (in air) was decreased from the maximum transmittance of about 75% to several% as the operating voltage was applied.

Further, the response time of the light transmittance when the drive pulse voltage was changed was 15 ms or less, and the high speed operation of Example 1 or higher was possible.

As a result of the above, it was possible to realize a light control device capable of performing a transient response operation at a high speed while sufficiently securing a difference (optical density ratio) in light transmittance between when the liquid crystal cell is transparent and when the light is shielded. .

Embodiment 3 FIG. 12 shows a case where the light control device 23 according to the above embodiment is a CCD (Ch
arge coupled device) shows an example incorporated in a camera.

That is, in the CCD camera 50, the first group lens 51 and the second group lens (for zoom) 52 corresponding to the front lens group 15 and the rear lens group 16 are arranged along the optical axis shown by the alternate long and short dash line. The corresponding third group lens 53, fourth group lens (for focus) 54, and CCD package 55 are arranged in this order at appropriate intervals, and the CCD package 55 has an infrared cut filter 55a and an optical low-pass filter system 55b. , CCD image pickup element 55c is housed.

Between the second lens group 52 and the third lens group 53, the G group based on the above-described present invention is provided near the third lens group 53.
A light control device 23 including an H cell 12 and a polarizing plate 11 is mounted on the same optical path for adjusting the light amount (light amount stop). The focusing fourth group lens 54 is arranged so as to be movable between the third group lens 53 and the CCD package 55 along the optical path by the linear motor 57, and the zoom second group lens 52 is located in the optical path. It is arranged so as to be movable between the first group lens 51 and the dimmer 23.

FIG. 13 shows an algorithm of a sequence of light transmittance control by the light control device 23 in this camera system.

According to this embodiment, the second group lenses 52 and 3 are
Since the dimming device 23 according to the present invention is provided between the group lenses 53, the amount of light can be adjusted by applying an electric field as described above, the system can be downsized, and the effective range of the optical path can be substantially achieved. Can be miniaturized. Therefore, CC
It is possible to achieve miniaturization of the D camera. Also,
Since the amount of light can be appropriately controlled by the magnitude of the voltage applied to the patterned electrode, the conventional diffraction phenomenon can be prevented, and a sufficient amount of light can be made incident on the image sensor to eliminate the blurring of the image.

The embodiments and examples of the present invention have been described above, but the above examples can be variously modified based on the technical idea of the present invention.

For example, the cell gap of the above-mentioned liquid crystal element may be changed at least in the range of 2 to 4 μm in the effective optical path, and is preferably set to 2 to 3.5 μm, particularly about 2 to 3 μm. Also, the cell gap around the cell is 2
The thickness may be up to 4 μm, but it is preferable to form it smaller than the central portion.

The ratio (d ₁ / d ₂ ) of the gap d _{1 at the} central portion of the cell to the gap d _{2 at the} peripheral portion may be different from that of the embodiment, and the variation of the gap before and after the liquid crystal injection (Δd ₁ ) Can be further suppressed.

Further, in the present embodiment, an example of using a spherical spacer as the shape of the spacer scattered over the entire GH cell is shown. For example, as shown in FIG. 6C, a columnar spacer 37 is used as a screen. It is also possible to supply and form by a printing method or a lithography method.

Further, the structure and material of the polarizing plate, its driving mechanism and the like can be variously changed. In addition, the drive waveform can be driven by any of a rectangular wave, a trapezoidal wave, and a sine wave, and the inclination of the liquid crystal molecules changes according to the potential difference between the electrodes, and the light transmittance is controlled. Therefore, normally, the transmittance is controlled by this peak value. In the above-mentioned embodiment, the example in which the pulse voltage modulation (PHM) is used for the driving method of the liquid crystal cell is shown, but it can be applied to the case of driving by the pulse width modulation (PWM).

As the GH cell, a GH cell having a two-layer structure or the like can be used in addition to the above-mentioned ones. Polarizing plate 1
The position of No. 1 with respect to the GH cell 12 is between the front lens group 15 and the rear lens group 16. However, the position is not limited to this, and may be any position that is optimal from the setting conditions of the imaging lens. That is, unless an optical element such as a retardation film that changes the polarization state is used, the polarizing plate 11 may be, for example, the imaging surface 17.
It can be placed at any position on the subject side or the image pickup device side, such as between the lens rear group 16 and the like. Furthermore, the polarizing plate 1
1 may be arranged before or after a single lens (single lens) that replaces the front lens group 15 or the rear lens group 16.

The number of iris blades 18 and 19 is not limited to two, and a larger number may be used.
On the contrary, it may be one. Also, the iris blades 18 and 19 are
Although they are stacked by moving in the vertical direction, they may be moved in other directions, or may be narrowed from the periphery toward the center.

Although the polarizing plate 11 is attached to the iris blade 18, it may be attached to the iris blade 19.

As the subject becomes brighter, light is first adjusted by moving the polarizing plate 11 in and out, and then light is absorbed by the GH cell 12. Conversely, light is absorbed by the GH cell 12 first. You may decide to perform light control.
In this case, after the transmittance of the GH cell 12 has decreased to a predetermined value, light adjustment is performed by putting the polarizing plate 11 in and out.

Further, although a mechanical iris is used as a means for moving the polarizing plate 11 in and out of the effective optical path 20, it is not limited to this. For example, by directly installing the film to which the polarizing plate 11 is attached to the drive motor, the polarizing plate 1
1 may be put in and taken out.

Further, in the above example, the polarizing plate 11 is taken in and out from the effective optical path 20, but it is of course possible to fix the position in the effective optical path.

The light control device of the present invention can also be used in combination with other known filter materials (for example, organic electrochromic materials, liquid crystals, electroluminescent materials, etc.).

Further, the light control device of the present invention has the above-mentioned CC.
In addition to the optical diaphragm of an image pickup device such as a D camera, it can be widely applied to various optical systems such as electrophotographic copying machines, optical communication devices, and CMOS image sensors for adjusting the amount of light. Further, the light control device of the present invention can be applied to various image display elements for displaying characters and images, in addition to the optical diaphragm and the filter.

[0101]

In the method for manufacturing a light control device and the empty cell for a liquid crystal optical element of the present invention, the gap in the central portion of the base is kept larger than that in the peripheral portion of the base, and in this state Since the liquid crystal is filled in the liquid crystal, it is easy to fill the liquid crystal almost uniformly between the bases when the liquid crystal is injected. As a result, the change (dispersion) in the gap between the bases before and after the liquid crystal filling is suppressed and the set conditions are set. It is possible to provide a light control device that can always realize the transmittance and the response speed of the light.

[Brief description of drawings]

1A and 1B are schematic cross-sectional views of a liquid crystal cell according to an embodiment of the present invention, in which FIG. 1A is an empty cell state and FIG.

2 is a schematic plan view of FIG. 1, showing a liquid crystal cell according to the embodiment.

FIG. 3 is a graph showing the tendency of variations in the gap ratio (d ₁ / d ₂ ) between the central portion and the peripheral portion of the liquid crystal cell and the gap difference (Δd ₁ ) after the liquid crystal is sealed in the same example.

FIG. 4 is a schematic diagram showing the operating principle of the light control device.

FIG. 5 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.

FIG. 6 is a schematic cross-sectional view of each example of cells of the liquid crystal optical element.

FIG. 7 is a schematic side view of a light control device using the same liquid crystal optical element.

FIG. 8 is a front view of the mechanical iris of the light control device.

FIG. 9 is a schematic partial enlarged view showing the operation of the mechanical iris in the vicinity of the effective optical path of the light control device.

FIG. 10 is a diagram explaining a coating step of the sealing material in the same cell production.

FIG. 11 is a diagram illustrating a spacer spraying step in the same cell production.

FIG. 12 is a schematic cross-sectional view of a camera system incorporating the light control device.

FIG. 13 is an algorithm of light transmittance control in the camera system.

FIG. 14 is a schematic diagram showing an operation principle of a conventional light control device.

FIG. 15 is a graph showing the relationship between the light transmittance of the light control device and the drive applied voltage.

FIG. 16 is a graph showing the relationship between the light transmittance and the liquid crystal cell gap of the light control device (liquid crystal optical element) according to the invention of the prior application.

FIG. 17 is a graph showing the relationship between the response time of the light control device and the liquid crystal cell gap.

FIG. 18 is a schematic cross-sectional view of a liquid crystal cell, in which (a) is an empty cell state and (b) is a state after liquid crystal is filled.

19 is a schematic plan view of FIG. 18, showing a liquid crystal cell.

[Explanation of symbols]

1, 11 ... Polarizing plate, 2, 12 ... GH cell, 3 ... Positive type liquid crystal, 4 ... Positive type dye molecule, 5 ... Incident light, 13 ... Negative type liquid crystal, 15, 16 ... Lens group, 17 ... Imaging surface, 18, 19
... iris blade, 20 ... Effective optical path (intermediate part or central part of cell), 22 ... Opening part, 23 ... Light control device, 24 ... Cell peripheral part, 31A, 31B ... Glass substrate, 32A, 32B ... Transparent (operating) electrode , 33A, 33B ... Alignment film, 34 ... Liquid crystal material, 35, 38 ... Sealing material, 36 ... Spherical spacer, 37 ... Columnar spacer, 39 ... Liquid crystal injection port, 5
0 ... CCD camera, 51 ... 1 group lens, 52 ... 2 group lens, 53 ... 3 group lens, 54 ... 4 group lens, 55 ... CC
D package, 55b ... Optical low pass filter, 55c
... CCD image sensor, A ₁ , A ₂ ... trend curve

Claims (14)

[Claims] 1. When manufacturing a light control device comprising a liquid crystal optical element in which liquid crystal is sealed between substrates facing each other, among the gaps between the facing substrates, the gap at the center of the substrate is the gap at the periphery of the substrate. A method for manufacturing a light control device, in which the liquid crystal is held larger than the above, and the liquid crystal is sealed between the opposed substrates in this state. 2. The adjustment according to claim 1, wherein the ratio of the gap d ₁ at the central portion of the base body to the gap d ₂ at the peripheral portion of the base body is 1 <d ₁ / d ₂ ≦ 1.1. Optical device manufacturing method. 3. The method for manufacturing a light control device according to claim 1, wherein a spacer is arranged between the opposed bases to hold the gap. 4. When the spacer is arranged between opposing transparent substrates on which transparent electrodes and alignment films are respectively formed, and the peripheral portion is sealed with a sealing material, the sealing material is formed smaller than the spacer, Alternatively, the method for manufacturing a light control device according to claim 3, wherein the light control device is formed of a mixture containing a harder material. 5. The method for manufacturing a light control device according to claim 4, wherein the hard material has a ball shape or a fiber shape. 6. The distribution density of the spacer is 150 to 5
The method for manufacturing a light control device according to claim 3, wherein the number is controlled to be 00 / mm ² . 7. After the liquid crystal is filled, the gap between the opposing bases in the effective optical path of the liquid crystal optical element is set to 2 μm.
The method for manufacturing a light control device according to claim 1, wherein the light control device is controlled to be not less than m and not more than 4 μm. 8. The method for manufacturing a light control device according to claim 1, wherein a guest-host type liquid crystal having a negative type liquid crystal as a host material and a dichroic dye as a guest material is enclosed as the liquid crystal. 9. An empty cell for a liquid crystal optical element in which liquid crystal is to be sealed between substrates facing each other, wherein a gap at a central portion of the substrate out of a gap between the opposing substrates is larger than a gap at a peripheral portion of the substrate. An empty cell for liquid crystal optical elements, which is also largely held. 10. The ratio of the gap d ₁ in the central portion of the base body to the gap d ₂ in the peripheral portion of the base body is 1 <d ₁ / d ₂ ≦ 1.1.
The empty cell for a liquid crystal optical element according to claim 9. 11. The empty cell for a liquid crystal optical element according to claim 9, wherein a spacer is arranged between the opposed substrates and the gap is held. 12. The spacer is arranged between opposing transparent substrates on which transparent electrodes and alignment films are respectively formed, and when the peripheral portion is sealed with a sealing material, the sealing material is formed smaller than the spacer. The empty cell for a liquid crystal optical element according to claim 11, which is formed of a mixture containing a harder material. 13. The empty cell for a liquid crystal optical element according to claim 12, wherein the hard material has a ball shape or a fiber shape. 14. The spacer has a distribution density of 150 to 150.
It is controlled to be 500 pieces / mm ² 11.
An empty cell for the liquid crystal optical element described in 1.