JP2001249348A - Liquid crystal lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal lens, in which the injection efficiency of the liquid crystal and the filling rate of the liquid crystal can be increased. SOLUTION: The liquid crystal lens has optically transparent and almost circular three substrates 1, 2, 3, which are disposed parallel to one another at prescribed intervals. The substrates 1, 2 and the substrates 1, 3 are jointed with each other via annular sealing agents 7, 8, in which a spacer is mixed and which are disposed in the peripheral edge of the side faces of the substrates. Injection grooves 5, 6 for easy injection of the liquid crystal are formed in the peripheral part on the side faces of the substrate 1. The sealing agents 7, 8 have notches corresponding to the part of the injection grooves 5, 6. The injection grooves 5, 6 and the notches form injection passages 21, 31 for injecting the liquid crystal material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to optically transparent,
It is formed by injecting and filling a liquid crystal material between a pair of substrates disposed opposite to each other at a predetermined interval by using an injection path formed between the substrates, and utilizing liquid crystal. The present invention relates to a liquid crystal lens capable of changing a refractive index and a focus and requiring a small size, for example, as used in an endoscope.

[0002]

2. Description of the Related Art As a relatively large optical element utilizing a liquid crystal in which a liquid crystal material is filled between a pair of substrates, for example, P73-77, February, 1993, Electronic Technology.
This is described in "6th Liquid Crystal Device Manufacturing-Cell Process". FIGS. 5A and 5B are a plan view and a longitudinal sectional view, respectively, showing the configuration of the liquid crystal optical element (liquid crystal cell). The liquid crystal cell has a pair of optically transparent substrates 41 and 42 which are arranged to face each other at a predetermined interval. The optimum value of this interval is determined from the characteristics of the liquid crystal material. Typical values are from about 5 μm to about 7 μm. This value is the same for the liquid crystal lens. On the substrates 41 and 42, a transparent electrode and an alignment film are respectively laminated on two surfaces facing each other. 2 above
The periphery of the two surfaces is a spacer (about 5 μm to about 7 μm
Are bonded together via a sealant 43 mixed with a plastic bead having a diameter of 3 mm, and a space for filling a liquid crystal material is formed between the substrates 41 and 42. A part of the sealing agent 43 extends toward the outer edges of the substrates 41 and 42 and forms an injection path 44 for injecting a liquid crystal material. The injection path 44 is sealed after a liquid crystal material is injected and filled in the space.

The injection of the liquid crystal material into the space between the substrates 41 and 42 is performed using a pressure difference as follows. That is,
A liquid crystal cell not filled with a liquid crystal material is set in an airtight container and a vacuum is drawn. Thereafter, the liquid crystal material is introduced into the airtight container, and the pressure in the airtight container is returned to the atmospheric pressure while the injection path 44 is immersed in the liquid crystal material. The pressure difference generated at this time causes the substrate 41,
The liquid crystal material is injected into the space between 42 via the injection path 44.

[0004]

As described above, when the liquid crystal material is injected by utilizing the pressure difference, the liquid crystal injection efficiency (the amount of the liquid crystal material injected with respect to time or pressure) and the liquid crystal filling efficiency are improved. The ratio (the volume actually filled with the liquid crystal material / the volume of the space between the two substrates that is filled with the liquid crystal material, and decreases when the viscosity of the liquid crystal material is high) is:
With a relatively large optical element as described above, it is not so low. However, in a liquid crystal lens, which is a minute optical element, although the substrate spacing is as narrow as about 5 μm to about 7 μm, which is similar to the above-described optical element, the width of the injection path along the substrate is very narrow, and the injection path is cut off. Since the area was very small, the liquid crystal injection efficiency and the liquid crystal filling rate were low.

Accordingly, an object of the present invention is to provide a liquid crystal injection efficiency,
Another object of the present invention is to provide a liquid crystal lens capable of increasing the liquid crystal filling rate.

[0006]

In order to achieve the above object, a liquid crystal lens according to a first aspect of the present invention is optically transparent, and is provided at a predetermined distance from each other.
In a liquid crystal lens formed by injecting and filling a liquid crystal material between a pair of substrates using an injection path formed between the substrates, at least one of the two substrates is provided with the liquid crystal. An injection groove for injecting a material between the two substrates is formed, and the injection groove forms a part of an injection path.

(Function and Effect) Since the injection groove is formed, the liquid crystal injection efficiency and the liquid crystal filling rate can be increased.

In a liquid crystal lens according to a second aspect of the present invention, the peripheral portions of the surfaces of the pair of substrates facing each other are in contact with each other, and this contact is an optical contact.

(Function and Effect) The optical contact is a contact between the surfaces of two optical members having a gap shorter than the wavelength of light so that interference fringes cannot be formed, and is in close contact without an adhesive. By making the contact between the substrates an optical contact, it is possible to eliminate the need for a spacer and to increase the interval accuracy. Also,
Bonding via a sealant can be eliminated, and peeling caused by a difference in linear expansion coefficient between the substrate and the sealant can be prevented.

In the liquid crystal lens according to a third aspect of the present invention, it is preferable that the injection path is sealed after an elastic member having substantially the same cross-sectional shape as that of the injection path is inserted. Features.

(Effect) When the temperature of the external environment changes, the volume change of the liquid crystal material due to the temperature change of the external environment is absorbed by the insertion of the elastic member. Therefore,
Since the deformation of the liquid crystal layer in the optical axis direction can be prevented, the optical characteristics can be kept constant. Further, since it is possible to prevent an excessive stress from being applied to a portion that performs sealing, the sealing can be stabilized. Also,
Since it is possible to prevent the inside of the liquid crystal layer from becoming negative pressure, it is possible to prevent the generation of vacuum bubbles.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, liquid crystal lenses according to first to fourth embodiments of the present invention will be described with reference to FIGS. 1 to 4 in the accompanying drawings. First, referring to FIG.
The liquid crystal lens according to the first embodiment of the present invention will be described.
Here, FIG. 1A is a plan view showing the configuration of the liquid crystal lens of the present embodiment, and FIG.
FIG. 2 is a vertical cross-sectional view taken along line -1B.

The liquid crystal lens is optically transparent, for example,
It has three substrates 1, 2, 3 formed of glass members such as crown glass and flint glass. Substrates 1, 2, 3
Have a substantially disk shape with the same diameter, and the substrates 2 and 3 are positioned on both sides of the substrate 1 so that they are parallel to each other. The central axes of the substrates 1, 2, 3 coincide with each other, and these axes are the optical axis 4 of the liquid crystal lens.
The liquid crystal lens of the present embodiment is symmetric with respect to plane C.

Concave surfaces 12 and 13 are formed on both side surfaces of the substrate 1 in order to obtain a lens effect according to the optical axis 4. Concave surfaces 12 and 13 are symmetric with respect to a plane C orthogonal to the optical axis 4 and bisecting the substrate 1.

A flat edge 12a or 13a is defined on the two corresponding sides of the substrate 1 facing the substrates 2 and 3, respectively, outside the concave surface 12 or 13. Edge 12a,
An injection groove 5 or 6 for injecting a liquid crystal material is formed in a part of each of 13a. Each of the injection grooves 5, 6 is provided between the part of the outer periphery of the corresponding edge 12a or 13a and the part of the outer periphery of the corresponding concave surface 12 or 13,
And has a certain rectangular cross section. Each cross section of the injection grooves 5, 6 has a constant width W and a constant depth D. Further, the injection grooves 5 and 6 are formed in portions outside the effective diameters of the concave surfaces 12 and 13. Effective diameter is concave surface 1
2 is the diameter of the portion of the substrate 1 necessary to obtain the lens effect surrounded by the concave surface 13.

A substantially annular sealant 7 or 8 is disposed concentrically with each of the edges 12a and 13a.
The portions of the sealants 7, 8 corresponding to the injection grooves 5, 6 are notched. A plurality of spacers each having substantially the same size are mixed in the sealants 7 and 8. The spacer is formed into a spherical shape or an irregular shape by, for example, glass or plastic. As the sealants 7 and 8, for example, an epoxy-based thermosetting sealant, an epoxy-based UV-curable sealant, an acrylic-based thermosetting sealant, an acrylic-based UV-curable sealant, or the like is used. A substrate 2 or 3 is placed on each of the sealing agents 7 and 8, and the substrate 1 and the substrates 2 and 3 are maintained at predetermined intervals in parallel with each other. Injection grooves 5, 6 between
Except for a sealed gap. Sealant 7,
The notch 8 and the corresponding injection grooves 5 and 6 form injection paths 21 and 31 that communicate the external space with the gap.

The liquid crystal material is injected by putting a liquid crystal lens in an airtight container, drawing a vacuum, introducing the liquid crystal material into the airtight container, immersing the liquid crystal lens in the liquid crystal material, and then returning to atmospheric pressure. Done. Since the liquid crystal material is drawn into the gap by the negative pressure through the injection paths 21 and 31, the gap is filled with the liquid crystal material to form the liquid crystal layers 9 and 10. As the liquid crystal material, for example, a nematic liquid crystal having a positive dielectric anisotropy is used.

After the liquid crystal material is injected, the injection paths 21 and 31 are:
It is sealed by the sealant 11. As the sealant 11, for example, an epoxy-based thermosetting sealant, an epoxy-based UV-curable sealant, an acrylic-based thermosetting sealant, an acrylic-based UV-curable sealant, or the like is used. .

On the concave surfaces 12 and 13 of the substrate 1 and the flat surfaces 22 and 32 of the substrates 2 and 3 opposed thereto, an undercoat, a transparent electrode electrically connected to a driving circuit, and an alignment film Are stacked in this order. The undercoat is used as a barrier layer of alkali ions eluted from the substrates 1, 2, 3, and for example, a silicon dioxide film is used. The transparent electrode is made of, for example, an optically transparent conductive film such as an indium tin oxide film, an antimony-added tin oxide film, or a zinc oxide film. The alignment film is composed of, for example, an organic alignment film that aligns a liquid crystal material in a specific direction, such as a polyimide alignment film or a polyamide alignment film. The alignment direction of the alignment film on the concave surface 12 and the alignment direction of the alignment film on the concave surface 13 are orthogonal to each other. The alignment direction of the alignment film on the concave surface 12 and the alignment direction of the alignment film on the plane 22 are parallel to each other, and the alignment direction of the alignment film on the concave surface 13 and the alignment direction of the alignment film on the plane 32 are parallel to each other. Are parallel to each other. An antireflection coat is formed on the outer surfaces of the substrates 2 and 3.

Next, the operation principle of the liquid crystal lens will be described. A liquid crystal lens to which an alternating voltage (for example, a voltage whose application direction changes periodically, such as a sine wave; in this case, a rectangular wave is preferably used) is not supplied to the liquid crystal layer 9 and the liquid crystal layer 10. In the state (1), the liquid crystal layer 9 functions as a medium having the ordinary refractive index of the nematic liquid crystal with respect to the polarization component of the light incident from the substrate 2 side in the direction perpendicular to the alignment direction of the alignment film on the plane 22. Layer 10 acts as a medium having an extraordinary refractive index. Conversely, of the incident light, with respect to the polarization component of the component parallel to the orientation direction,
The liquid crystal layer 9 functions as a medium having an extraordinary light refractive index, and the liquid crystal layer 10 functions as a medium having an ordinary light refractive index. When the alternating voltage is supplied to the liquid crystal layer, the liquid crystal layer 9 and the liquid crystal layer 10 function as a medium having an ordinary refractive index regardless of the polarization component of the incident light. Therefore, when the intensity of the electric field changes, the liquid crystal layer 9
The refractive index between the liquid crystal layer 10 and the liquid crystal layer 10 changes, and as a result, the position of the focal point of the liquid crystal lens changes in the direction along the optical axis 4. Since the concave surface 12 and the concave surface 13 which are refraction surfaces are formed close to each other in a substantially symmetric shape with respect to the plane C,
Does not cause double focus.

When a nematic liquid crystal having a negative dielectric anisotropy is used instead of using a nematic liquid crystal having a positive dielectric anisotropy, the opposite phenomenon occurs. That is, the state of the liquid crystal lens of the nematic liquid crystal having the negative dielectric anisotropy supplied with the alternating voltage corresponds to the state of the liquid crystal lens of the nematic liquid crystal having the positive dielectric anisotropy not supplied with the alternating voltage, The state of the liquid crystal lens of the nematic liquid crystal having the negative dielectric anisotropy to which the alternating voltage is not supplied corresponds to the state of the liquid crystal lens of the nematic liquid crystal having the positive dielectric anisotropy to which the alternating voltage is supplied.

In the liquid crystal lens according to the first embodiment of the present invention configured as described above, since the injection grooves 5 and 6 are formed, the openings of the injection paths 21 and 31 are formed. The height (the length in the direction perpendicular to the plane C) is increased to be equal to or larger than the distance between the two substrates 1, 2, 3 facing each other, which is defined by the spacers in the sealants 7, 8. it can.

Therefore, since the cross-sectional area of the injection paths 21 and 31 can be enlarged, the two substrates 1 and 2 of the liquid crystal lens can be formed.
Alternatively, it is possible to increase the liquid crystal injection efficiency and the liquid crystal filling rate through the injection paths 21 and 31 into the gap between 1 and 3. Further, since the injection grooves 5 and 6 can be formed on both side surfaces of the substrate 1 at the same time as the concave surfaces 12 and 13 for obtaining the lens effect, the shape accuracy and the dimensional accuracy can be improved as compared with the case where the concave surfaces 12 and 13 are formed separately. Can be higher.

Next, a liquid crystal lens according to a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 2A is a plan view showing the configuration of the liquid crystal lens of the present embodiment, and FIG. 2B is a longitudinal sectional view taken along line 2B-2B in FIG.

Most of the configuration of the present embodiment is basically the same as most of the configuration of the first embodiment. Note that, in the present embodiment, FIG.
Components that are substantially the same as the components described with reference to (B) are denoted by the same reference numerals as those of the corresponding components of the first embodiment, and detailed descriptions thereof are given. Description is omitted. The configuration of the present embodiment is different from the configuration of the first embodiment in that although the concave surfaces 12 and 13 are formed on both side surfaces of the substrate 1 in the first embodiment, the substrate in the present embodiment is different from that of the first embodiment. 1 has convex surfaces 12 'and 13' formed on both side surfaces. Each of the convex surfaces 12 'and 13' is located on the inner side of the substrate 1 with respect to a virtual plane including each of the edges 12a and 13a. That is, the convex surfaces 12 ′ and 13 ′ do not protrude from this virtual plane in the direction along the optical axis 4. The peripheral portions of the convex surfaces 12 ′ and 13 ′ are
a, 13a, which are depressed compared with the edge portions 12a, 13a.
a is connected via a step. Convex surfaces 12 ', 13'
Is outside the effective diameter of the convex surface.

In the liquid crystal lens according to the second embodiment of the present invention, which is configured as described above, the convex surfaces 12 'and 13' are formed on both sides of the substrate 1 so that When air bubbles are generated in the layer, the air bubbles can accumulate on the periphery of the convex surface (outside the effective diameter of the convex surface), so that optical defects caused by the air bubbles can be prevented.

Next, a liquid crystal lens according to a third embodiment of the present invention will be described with reference to FIG. Here, FIG. 3A is a plan view showing the configuration of the liquid crystal lens of the present embodiment, and FIG. 3B is a longitudinal sectional view taken along line 3B-3B in FIG.

Most of the configuration of the present embodiment is basically the same as most of the configuration of the first embodiment. Note that, in the present embodiment, FIG.
Components that are substantially the same as the components described with reference to (B) are denoted by the same reference numerals as those of the corresponding components of the first embodiment, and detailed descriptions thereof are given. Description is omitted. The difference between the configuration of the present embodiment and the configuration of the first embodiment is that
Although the substrates 2 and 3 are joined via the sealants 7 and 8 in which spacers are mixed, the present embodiment utilizes the fact that the contact between the two opposing substrates is a contact called an optical contact. , Three substrates 1, 2, 3
Are joined.

An optical contact has a gap that is shorter than the wavelength of light such that interference fringes cannot be formed.
Contact between the surfaces of two optical members. Such contact is realized as follows. After polishing the surface (contact surface) with which each optical member comes into contact, activation treatment is performed with an alkaline cleaning solution. Thereafter, the contact surfaces are overlapped with each other in a state where pure water is permeated between the contact surfaces, and heat treatment is performed. By doing so, these two optical members can be brought into close contact with each other without using an adhesive.

The substrate 1 and the substrates 2 and 3 are joined while maintaining an optical contact without using a spacer. The injection paths 21 ′ and 31 ′ include only injection grooves 5 and 6.

In the liquid crystal lens according to the third embodiment of the present invention configured as described above, the substrates 1, 2, and 3 are joined while maintaining the optical contact. The contact of the substrate can be a surface contact.

Therefore, it is possible to eliminate the need for the spacer and to prevent the substrates 1, 2 and 3 from being bent where no spacer is provided when they are joined via the spacer. , 2, and 3 can be increased in accuracy. In addition, sealing agent 7,
8 can be unnecessary, and furthermore, separation caused by a difference in linear expansion coefficient between the substrates 1, 2, 3 and the sealants 7, 8 can be prevented.

Next, a liquid crystal lens according to a fourth embodiment of the present invention will be described with reference to FIG. Here, FIG. 4A is a plan view showing the configuration of the liquid crystal lens of the present embodiment, and FIG. 4B is a longitudinal sectional view taken along line 4B-4B in FIG.

Most of the configuration of the present embodiment is basically the same as most of the configuration of the third embodiment. Note that, in the present embodiment, FIG.
Components that are substantially the same as the components described with reference to (B) are denoted by the same reference numerals as the corresponding components of the third embodiment, and are described in detail. Description is omitted. The configuration of the present embodiment differs from the configuration of the third embodiment in that the injection paths 21 ′ and 31 ′ composed of only the injection grooves 5 and 6 have the same cross-sectional shape as that of the injection channels 21 ′ and 31 ′. After the members 23 and 33 are inserted, they are sealed with the sealant 11.

In the liquid crystal lens according to the fourth embodiment of the present invention configured as described above, the elastic members 23 and 33 are inserted into the injection paths 21 ′ and 31 ′. The elastic members 23 and 33 can absorb the volume change of the liquid crystal material due to the temperature change of the external environment.

Therefore, when the temperature of the external environment changes, the liquid crystal layers 9 and 10 can be prevented from being deformed in the direction of the optical axis 4, so that the optical characteristics of the liquid crystal lens can be precisely maintained constant. Further, since it is possible to prevent an excessive stress from being applied to the sealant 11, it is possible to prevent the sealant 11 from peeling off. In addition, since the inside of the liquid crystal layer can be prevented from becoming negative pressure, generation of vacuum bubbles can be prevented.

In the first to fourth embodiments, the shapes of the outlines of the substrates 1, 2, and 3 as viewed in plan are each circular, but the present invention is not limited to this.
For example, each may be a polygon. In this case, each 3
It may be square, rectangular, pentagonal, or hexagonal. Further, these three contours may be different from each other.

In the first to fourth embodiments, the cross-sectional shape of the injection grooves 5 and 6 is rectangular, but the present invention is not limited to this. It may be U-shaped or V-shaped open to the surface.
Further, the width and depth of the injection grooves 5 and 6 may not be constant, and in this case, the injection grooves 5 and 6 may have a wedge shape that narrows from a part of the outer periphery of the substrate 1 toward the optical axis 4. Further, a plurality of injection grooves 5 and 6 may be provided at each of the edges 12a and 13a, and the widths, depths, and cross-sectional shapes of these grooves may be different from each other.

It should be noted that the present invention is not limited to the above-described four embodiments, and it is needless to say that various modifications and applications can be made without departing from the spirit of the invention.

[0040]

As is clear from the above description,
In the liquid crystal lens according to the present invention, since the injection groove is formed, the liquid crystal injection efficiency and the liquid crystal filling rate can be increased.

[Brief description of the drawings]

FIG. 1A is a plan view showing a configuration of a liquid crystal lens according to a first embodiment; FIG. 1B is a 1B-1B view of FIG.
FIG. 4 is a longitudinal sectional view cut along a line.

FIG. 2A is a plan view illustrating a configuration of a liquid crystal lens according to a second embodiment; FIG. 2B is a plan view of 2B-2B in FIG.
FIG. 4 is a longitudinal sectional view cut along a line.

FIG. 3A is a plan view showing a configuration of a liquid crystal lens according to a third embodiment; FIG. 3B is a plan view showing 3B-3B in FIG.
FIG. 4 is a longitudinal sectional view cut along a line.

FIG. 4A is a plan view showing a configuration of a liquid crystal lens according to a fourth embodiment; FIG. 4B is a view 4A-4B of FIG.
FIG. 4 is a longitudinal sectional view cut along a line.

FIGS. 5A and 5B are a plan view and a longitudinal sectional view, respectively, showing the configuration of a conventional liquid crystal optical element (liquid crystal cell).

[Explanation of symbols]

 1,2,3 substrate 5,6 injection groove 21,21 ', 31,31' injection path 23,33 elastic member

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA42 FA02 FA04 FA10 GA02 HA01 HA03 HA24 KA05 KA26 MA20 2H089 LA28 MA04X MA04Y MA04Z NA25 QA12 SA02 UA09

Claims (3)

[Claims] 1. A liquid crystal material is injected and filled between a pair of substrates which are optically transparent and are opposed to each other with a predetermined space therebetween by using an injection path formed between the substrates. In the liquid crystal lens formed as described above, an injection groove for injecting the liquid crystal material between the two substrates is formed on at least one of the opposing surfaces of the two substrates. A liquid crystal lens characterized by forming a part. 2. The liquid crystal lens according to claim 1, wherein peripheral portions of surfaces of the pair of substrates facing each other are in contact, and the contact is an optical contact. 3. The injection channel is sealed after an elastic member having a cross section substantially the same as the cross section of the injection channel is inserted. Liquid crystal lens.