JPS62194223A - Liquid crystal lens - Google Patents

Abstract

PURPOSE:To for a liquid crystal lens more approximate to a design by selecting an orientation treatment direction according to a lens shape are subjecting the lens to an orientation treatment. CONSTITUTION:The Fresnel face of a Fresnel lens 1 is subjected to a rubbing treatment by rubbing said face in a specified arrow X direction with a brush formed of nylon, cotton, etc. The rubbing treatment is executed with the following results: Many defective parts are generated on the right and left front face side and rear face sides where the peaks or valleys of the Fresnel face in contact with the brush are perpendicular to the rubbing direction of the brush, i.e., arrow X direction and the generation of the defective parts is decreased on the top surface side and bottom surface side when the peaks or valleys of the Fresnel face are horizontal thereto. The Fresnel lens for the liquid crystal cell having the decreased defective parts of the rubbing treatment is thereby cut out if the region long in the vertical direction shown by an alternate long and short dash line 5 is cut out at the time of cutting out the Fresnel lens forming the liquid crystal cell of the liquid crystal from the Fresnel lens 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid crystal lens including a Fresnel lens, and more particularly to a liquid crystal lens having a Fresnel lens in which liquid crystal alignment treatment has been properly performed.

[Prior Art] The idea of making a lens with a variable focal length by utilizing the birefringence phenomenon of liquid crystals has already been proposed in, for example, Japanese Patent Application Laid-Open No. 52-32348, Japanese Patent Application Laid-Open No. 54-99654, and Japanese Patent Publication No. 5G-5.
This can be seen in Publication No. 0339, etc. An example of such a conventional lens using a liquid crystal (hereinafter referred to as a liquid crystal lens) will be explained with reference to the longitudinal cross-sectional view and cross-sectional view of FIGS. 8 and 9.

The liquid crystal lens 20 is constructed by providing transparent conductive layers 23 and 24 on the spherical concave lens 21 and the flat glass 22, respectively, and filling the liquid crystal 26 in the space 1+f7 formed when these are bonded together via the insulating layer 25. There is. An AC voltage from an AC power source 27 is applied between the transparent conductive layers 23 and 24 in a variably adjustable manner. Further, even when this AC voltage is not applied, alignment processing is performed so that the liquid crystal molecules are aligned in a specific direction, and the liquid crystal molecules are homogeneously aligned in the drawing.

When a voltage is applied to this liquid crystal lens 20, the liquid crystal lens 20
The molecules of the liquid crystal 26 in 0 rotate so that the long axis direction of the molecules is aligned with the direction of the electric field (in the case of a liquid crystal with positive dielectric anisotropy). Here, by combining a polarizing plate 28 as shown in FIG. 1O with a liquid crystal lens 20 having a liquid crystal molecule director indicated by an arrow n in FIG. 9, it is possible to allow only extraordinary light to enter the liquid crystal lens 20. If you configure it like this,
As the liquid crystal molecules in the liquid crystal lens 20 are rotated by the electric field, the refractive index of the liquid crystal 26 changes between the refractive index n 2 for extraordinary rays and the refractive index n 2 for ordinary rays, and CO 2 changes. Therefore, if the focal length is C1, the refractive index is n, and the radius of curvature of both surfaces of the lens is 1.2, then the focal length of the lens can be changed by increasing the focal length of the lens.

On the other hand, in FIG. 10, the polarizing plate 28 is rotated 9
When rotated by 0 degrees, only ordinary light enters the liquid crystal lens, but the refractive index of the liquid crystal for ordinary light does not change even when an electric field is applied and remains n.

Therefore, for light having polarization components in all directions, such as natural light and circularly polarized light, the liquid crystal lens acts as a bifocal lens having different focal lengths for the two polarization components.

[Problems to be Solved by the Invention] As seen in the above-mentioned conventional example, the liquid crystal lens 20 is made of a transparent material such as glass or synthetic resin because the liquid crystal is sealed in a lens-shaped space to form the liquid crystal in the lens shape. Liquid crystal cells were formed using spherical lenses made of However, in such a liquid crystal lens, the thickness in the optical axis direction increases, increasing the bulk of the entire liquid crystal lens, and the thickness of the liquid crystal is large at the center including the optical axis of the liquid crystal cell, and thinner at the periphery. However, when the focal length of the liquid crystal lens is changed by changing the AC voltage from the external drive power source, the rotation of the liquid crystal is not uniform across the entire lens, and the responsiveness deteriorates in thick areas of the liquid crystal. also existed.

Therefore, by forming the spherical lens or the like forming the liquid crystal cell with a Fresnel lens, the thickness of the liquid crystal cell can be reduced, and the above-mentioned disadvantages can be improved. However, on the other hand, problems arise such as the occurrence of defective portions in the liquid crystal alignment process.

That is, when attempting to use the electro-optic effect of liquid crystal in a device, alignment treatment on the inner surface of the liquid crystal cell is essential, and this treatment is generally performed by rubbing treatment or oblique vapor deposition.

When performing a rubbing process, if the inner surface of the substrate forming the liquid crystal cell is smooth, the rubbing process can be applied uniformly and there is no problem, but if the surface is uneven like a Fresnel surface, the valleys may be Inevitably, rubbing with a brush cannot be done properly, resulting in areas with poor rubbing. Furthermore, when the liquid crystal alignment process is carried out by the oblique vapor deposition method, shadow areas due to the peaks of the Fresnel surface still occur, and vapor deposition defects in the alignment process occur in the valley areas.

The occurrence of a defective part in the alignment process means that the liquid crystal director cannot control that part, and in the liquid crystal lens, the apparent refractive index is divided into the refractive index n of extraordinary rays and the refractive index n of ordinary rays.

When trying to change the refractive index between the two, the refractive index of that part was different from that of the other parts, and as a result, the liquid crystal lens did not have the optical properties as designed, which caused problems. At the same time, in areas with poor orientation, the direction of the liquid crystal director and the direction of the polarizing plate do not necessarily match, so a polarized light component rotated by 90 degrees with respect to the incident polarized light component is generated, resulting in a so-called bifocal lens, although the light intensity ratio is small. There was a problem with this.

[Means and effects for solving the problem] As described above, when the Fresnel surface of the Fresnel lens forming the liquid crystal cell of the liquid crystal lens is subjected to rubbing treatment and alignment treatment, before the rubbing direction by the brush.

Many misaligned portions occur on the rear surface. Furthermore, in the oblique evaporation method, a portion with poor orientation occurs on a line connecting the evaporation source and the Fresnel lens.

Therefore, in the present invention, the orientation treatment is performed by selecting the orientation treatment direction according to the lens shape so as to reduce the area of the poorly aligned portion occupying the entire liquid crystal lens as much as possible. As a result, the alignment state of the liquid crystal lens is improved, it becomes possible to create a liquid crystal lens that is closer to the designed liquid crystal lens, and the problem of double focus is also alleviated.

[Example] Hereinafter, the liquid crystal Fresnel lens of the present invention will be explained based on the drawings.

A rubbing process is performed by rubbing the Fresnel surface of the Fresnel lens 1, which is formed by injection molding, pressing, cutting, etc., of transparent synthetic resin, etc., in the direction of the arrow X with a brush made of nylon, cotton, etc. It will be done.

By the way, as shown in FIG. 2, since the Fresnel surface of the Fresnel lens 1 has irregularities, the ridges 2 are relatively rubbed by the brush ears 4 and the rubbing process is performed well. , in the valley 3 part, it is inevitably affected by the mountain, resulting in a rubbing defect as shown by the black dot in the figure. When the Fresnel surface of the Fresnel lens 1 is rubbed in the direction of the arrow X, as shown in Fig. 1, the peaks or valleys of the Fresnel surface that come into contact with the brush are in the direction of the arrow X, which is the rubbing direction of the brush. In Figure 1, which is perpendicular to
In FIG. 1, where the peaks or valleys of the Fresnel surface are oriented horizontally, the rubbing process is performed so that fewer defective parts occur on the upper and lower surfaces.

Therefore, from this Fresnel lens 1 to the liquid crystal lens? When cutting out a Fresnel lens to form a liquid crystal cell, if a longitudinally long region shown by the dashed line 5 in FIG. .

Next, a case will be described in which a Fresnel lens is subjected to liquid crystal alignment treatment by an oblique vapor deposition method based on FIGS. 3 and 4.

One Fresnel lens 6 with its Fresnel surface facing downward is placed on a device stand 9 in a pelger of a steaming device.

For example, a vapor deposition source of SiO is placed at a position A diagonally below the angle θ to be aligned on the Fresnel surface of the Fresnel lens 6, and the air in the Pel jar is evaporated after being vacuum-suctioned. In this case, when viewed from position A of the evaporation source, there are shadow areas in the valleys of the Fresnel surface where SiO is not evaporated because they are hidden by the mountains of the Fresnel surface, resulting in poor formation of the SiO alignment film. The portion is formed as shown by the black dot in the figure. Further, as can be seen from FIG. 4, a line connecting the position A of the vapor deposition source and the center O of the Fresnel lens 6 (in this specification, this direction is the orientation process of the oblique thin stone orientation process) is referred to as the j direction; arrow Y On the upper and lower sides of the lens in the figure, which are far from the direction (direction), the peaks or troughs of the Fresnel surface are formed in the deposition direction of the oblique evaporation method, that is, in the Y direction, so there are relatively few shadows. Become.

Therefore, in this case as well, as in Fig. 1 above, many vapor evaporation defects occur on the line connecting the position A of the vapor q source in the direction of the arrow Y and the center O of the Fresnel lens 6, that is, on both the left and right sides of the Fresnel surface in the figure. However, on the upper and lower sides of the Fresnel surface in the figure where the peaks or valleys of the Fresnel surface are 1 deficient with respect to the line connecting the position A of the evaporation source and the center O of the Fresnel lens 6, evaporation occurs; There are fewer

Therefore, in this case as well, the Fresnel lens to be aligned is made large, and the Fresnel lens in the area shown by the dashed line 10 in FIG. By forming the liquid crystal cell of the lens, it is possible to obtain a liquid crystal lens in which the entire surface of the liquid crystal lens is well aligned.

In the example described above, after the Fresnel lens is oriented, the lens is cut out so that the number of poorly oriented parts is reduced as much as possible. The orientation treatment may be performed so that the number of defective portions of the treatment is reduced as much as possible. In this case, for example, as shown in FIG. 5, lenses 11 that have been subjected to alignment treatment such as rubbing or diagonal steaming in the Z direction are placed in four areas a-1, a-2, b-1, and b-2. Divide the area into 5(a-1).

S (a-2), S (b-1) and S (b-
2), 5(a-1)+5(a-2)>5(b-1)+5(b-
2) Use a lens that satisfies -■.

The direction of ±45 degrees and ±135 degrees to the Z direction is a-1 ~
This is the boundary of b-2. As you can see from what I said earlier,
The regions b-1 and b-2 are regions where alignment defects are likely to occur. Therefore, if the desired lens does not have to be circular,
As shown in the figure, if the orientation treatment is performed according to the formula (■), the proportion of the poorly aligned portion in the entire lens will be reduced, compared to the case where the orientation treatment is performed in the direction perpendicular to the Z direction.
Although the lens has the same shape, it is possible to create a lens with optical properties closer to the designed values, and a Fresnel lens for liquid crystal lenses can be made with fewer bifocal problems.

The above has only been described for the case of point symmetry with respect to the Fresnel lens center O. However, the above equation (2) can be applied regardless of the shape of the lens. For example, as shown in Fig. 6, when the desired lens shape center P and the Fresnel lens The above equation (2) is applied in the same way even when the position of the center O is different.

When considering the actual application of liquid crystal lenses to eyeglass lenses,
Eyeglass lenses are often non-circular, and the phenomenon of misaligned centers is a problem that often occurs due to the balance between correction and lens design. Fig. 7 shows a case where the liquid crystal lens of the present invention is applied to a spectacle lens. When the approximate center P of the lens shape of the left lens L coincides with the center 0 of the Fresnel lens, the right lens R corresponds to each other. This shows a case where the center P and 0 are shifted. In either case, the above formula (2) is applied, resulting in a liquid crystal lens with a small proportion of defective portions in the alignment process.

As mentioned above, by forming a liquid crystal lens using a Fresnel lens that has been oriented in a direction according to the lens shape, as expressed by formula As a result, a liquid crystal lens with fewer alignment defects can be obtained.

In the case of a liquid crystal lens, the alignment directions of the substrates on both sides of the liquid crystal are parallel, so the state of poor alignment can be easily observed with a polarizing microscope, and a-1 to b-2
Since the orientation direction of the boundary can be easily determined, it is ±45 degrees based on that axis.

It can be easily determined as ±135 degrees and can be inspected even after production.

[Effects of the Invention] As described above, the Fresnel surface of the Fresnel lens forming the liquid crystal cell of the liquid crystal lens has a large proportion of areas that do not include defective rubbing areas or vapor deposition defects during alignment treatment. In addition, by configuring the liquid crystal lens cells with Fresnel lenses that have undergone alignment treatment according to the lens shape, it is possible to create a liquid crystal lens that exhibits optical characteristics closer to the designed one, and with fewer bifocal problems. It can be done.

[Brief explanation of drawings]

Figures 1 and 2 are a plan view and a cross-sectional view of a Fresnel lens to explain the occurrence of alignment defects caused by rubbing treatment, and Figures 3 and 4 are alignment treatment defects caused by oblique evaporation. A cross-sectional view and a plan view of a Fresnel lens to explain the occurrence of defects, and FIGS. 5 and 6 are diagrams in the case where the Fresnel lens is formed into a desired shape and then subjected to orientation treatment to reduce the number of defective portions. , FIG. 7 is a perspective view of the liquid crystal lens of the present invention applied to eyeglasses, FIGS. 8 and 9 are vertical and cross-sectional views of a conventional liquid crystal lens, and FIG. 10 is a liquid crystal lens. FIG. 1.6 Fresnel lens

Claims (1)

[Claims] In a liquid crystal lens in which the liquid crystal cell is formed by a Fresnel lens, when applying liquid crystal alignment treatment to the lens surface of the Fresnel lens by rubbing treatment or oblique vapor deposition method, from the center of the Fresnel lens in the direction of the alignment treatment. On the other hand, among the four regions divided by lines of ±45 degrees and ±135 degrees, the sum of the areas of the remaining two regions is larger than the sum of the areas of the two diagonally located regions with many defective alignment parts. 1. A liquid crystal lens characterized by using a Fresnel lens that has been subjected to alignment treatment so that the .