Photography – With exposure objective focusing means – focusing aid – or... – Having viewfinder
Reexamination Certificate
1999-05-19
2001-05-01
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Having viewfinder
C349S084000
Reexamination Certificate
active
06226461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to macromolecular type liquid crystal elements used in a diffusion plate of a camera and the like. More particularly, the present invention relates to a liquid crystal element which can control diffusivity with a low driving voltage.
2. Description of the Related Art
Conventionally, macromolecular liquid crystal elements are incorporated into a structure in which a macromolecular dispersion type liquid crystal is interposed between transparent electrodes, such as indium tin oxide or the like, disposed on the surfaces of two (2) flat transparent plates. The diffusivity in the known macromolecular dispersion type liquid crystal element is regulated by changing between a diffusing state and a transparent state by controlling an alternating voltage or the like applied between the transparent electrodes.
However, when the diffusivity of the prior art macromolecular dispersion type liquid crystal element is increased in the above-described manner, the film thickness of the macromolecular dispersion type liquid crystal layer must be thick. When the film thickness is made thick, the spacing of the transparent electrodes becomes wide, and the driving voltage becomes high.
Moreover, the known macromolecular dispersion type liquid crystal element diffuses light to some degree even when a voltage is applied. Therefore, when the film thickness of the liquid crystal layer is made thick, the optical transmissivity in the transparent state becomes poor, and the contrast between the diffusion state and the transparent state falls off.
Moreover, when the known macromolecular dispersion type liquid crystal element is applied to the diffusion plate of a camera or the like, it becomes difficult to obtain more diffusivity in the diffusion plate because the diffusivity of this element depends on the properties of the macromolecular dispersion type liquid crystal. More specifically, in prior art diffusion plates, because diffused light remains having a diffusion coefficient which is increased to some extent, a so-called “soft focus” image is obtained such that fogginess faintly surrounds a blurred image, even in a region in which the angle from the normal line is rather large.
FIG. 6
is a graph showing the diffusion coefficient of a prior art type of diffusion plate. The prior art diffusion plate includes a plane parallel plate glass, which is unaltered and has no roughness formed on it, used as a glass plate, and both interfaces with the macromolecular dispersion type liquid crystal are flat. In the prior art diffusion plate, as an angle &thgr; from a normal line to the diffusion plate becomes large, the diffusivity of the diffusion plate gradually becomes small, and diffusivity remains to some degree, even in regions in which the angle &thgr; is quite large. Further, in the prior art type of diffusion plate, when an image projected thereon is indistinct, the so-called “soft focus” image is obtained, with fogginess extending widely around a blurred image.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a liquid crystal element which can diversely control the diffusivity.
It is another object of the present invention to provide a liquid crystal element which can easily control diffusivity with a low driving voltage.
It is yet another object of the present invention to provide a liquid crystal element having a sufficiently large contrast between the diffusing state and the transparent state.
It is yet another object of the present invention to provide a liquid crystal element which has a diffusivity suitable for diffusion plate.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a liquid crystal element comprising a macromolecular dispersion type liquid crystal; and transparent plates between which the macromolecular dispersion type liquid crystal is interposed, wherein at least one of the transparent plates has roughness toward the macromolecular dispersion type liquid crystal.
In accordance with embodiments of the present invention, when the refractive index of the liquid crystal comprising the macromolecular dispersion type liquid crystal becomes a value which differs from the refractive index of the macromolecules in a predetermined electric field state, diffusion occurs at the interface of the macromolecules and the liquid crystal. Moreover, dispersion arises corresponding to the configuration of the roughness because of the refractive index of the liquid crystal within the macromolecular dispersion type liquid crystal portions which enter into concave portions of the roughness, even when the value of the refractive index differs because of the changes of a voltage state in the electric field state. Accordingly, the dispersion properties of the liquid crystal element can be diversely regulated.
In accordance with embodiments of the present invention, the refractive index of the transparent plate on which roughness is formed differs from the refractive index of the macromolecules comprising the macromolecular dispersion type liquid crystal. In this case, when the refractive index of the liquid crystal deviates from the refractive index of the macromolecules, the macromolecular dispersion type liquid crystal has diffusion characteristics which are appropriate as a diffusion plate, and can make the diffusion coefficient smaller when the scattering angle of incident light is large.
In accordance with embodiments of the present invention, the refractive index of the transparent plate on which the roughness is formed is approximately equal to the refractive index of the macromolecules comprising the macromolecular dispersion type liquid crystal. In this case, the amplitude of change of the diffusion coefficient becomes large because of the synergistic action of scattering and the diffusion corresponding to the rough configuration in the interface of the macromolecules with the liquid crystal.
Moreover, in accordance with embodiments of the present invention, the macromolecular dispersion type liquid crystal may be a reverse type of macromolecular dispersion type liquid crystal. When the refractive index of the transparent plate on which the roughness is formed differs from the refractive index of the macromolecules comprising the macromolecular dispersion type liquid crystal, the diffusion does not become small and the image surface becomes clear. Therefore, when driving, diffusion arises and focusing becomes possible. Because the non-driving time is normally considerably longer, the electric power consumption of the liquid crystal element can be advantageously reduced. On the other hand, when the refractive index of the transparent plate on which the roughness is formed is approximately equal to the refractive index of the macromolecules comprising the macromolecular dispersion type liquid crystal, the voltage needed to attain a desired diffusion coefficient becomes low, and driving of the liquid crystal element becomes easy.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a method of forming a liquid crystal element, comprising the steps of preparing a first transparent plate; roughening a surface of the first transparent plate; forming a first transparent electrode on the roughened surface of the first transparent plate; preparing a second transparent plate; forming a transparent electrode on one side of the second transparent plate; inserting a spacer between the first and second transparent plates; injecting a mixture of liquid crystal and monomer into a space between the first and second transparent plates; and exposing the mixture of liquid crystal and monomer to ultraviolet radiation to form a network of macromolecules.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a camera, comprising a photographic lens to image a subject; a mirror to change a path of the image i
Homma Itaru
Iwane Toru
Nikon Corporation
Perkey W. B.
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