CN102122104B - Light-deflection apparatus - Google Patents

Abstract

The invention provides a light deflection device, which has: a liquid crystal layer; first and second transparent substrates, which are disposed opposite to each other and sandwich the liquid crystal layer; first and second transparent electrodes, which are respectively formed on the first a side of the liquid crystal layer of one and second transparent substrates and applying a voltage to the liquid crystal layer; and a prism layer formed on the side of the liquid crystal layer of one of the first and second transparent substrates, the liquid crystal layer comprising a The liquid crystal molecules, the refractive index of the liquid crystal layer observed from the normal direction of the first and second transparent substrates is the average value of the ordinary ray refractive index no and the extraordinary ray refractive index ne (2no+ne) in the state of no voltage applied /3, the refractive index of the liquid crystal layer is close to the ordinary ray refractive index no by applying a voltage.

Description

light deflection device

technical field

The present invention relates to a light deflection device that performs light deflection for changing the traveling direction of light.

Background technique

As a light distribution switching technology for vehicle headlights and the like, a technology using a liquid crystal optical element has been proposed.

Japanese Patent Application Laid-Open No. 2006-147377 discloses a technique of deflecting light using a liquid crystal cell in which a prism is formed on the inner surface of one of a pair of substrates. By switching between a state where a voltage is not applied and a state where a voltage is applied, the refractive index of the liquid crystal layer is changed, thereby changing the traveling direction of light. However, in the technique disclosed in Japanese Patent Laid-Open No. 2006-147377, only one of two polarization components whose polarization directions are perpendicular to each other in incident light entering the liquid crystal cell is deflected.

Japanese Patent Application Laid-Open No. 2009-26641 discloses a technique of deflecting both polarized light components using two liquid crystal cells prepared for each polarization direction.

A technique in which a liquid crystal cell deflects both polarized light components of incident light is desired.

In addition, as shown in Japanese Unexamined Patent Application Publication No. 2003-327966, in recent years, as a liquid crystal material, research on a cholesteric blue phase (a cholesteric blue phase) has been carried out, and it has been proposed to stabilize the cholesteric blue phase by polymer stabilization treatment. A technology that expands the temperature range for the appearance of the sterol blue phase.

Contents of the invention

An object of the present invention is to provide a light deflection device that can use a liquid crystal cell to perform light deflection for changing the traveling direction of light to two orthogonally polarized light components of incident light.

Another object of the present invention is to provide a novel light deflecting device.

According to one aspect of the present invention, there is provided a light deflection device, the light deflection device has: a liquid crystal layer; first and second transparent substrates, the first and second transparent substrates are arranged opposite to each other and sandwich the liquid crystal layer; first and second transparent electrodes respectively formed on the liquid crystal layer sides of the first and second transparent substrates and applying a voltage to the liquid crystal layer; and a prism layer, The prism layer is formed on the side of the liquid crystal layer of one of the first and second transparent substrates, and the liquid crystal layer includes liquid crystal molecules with a positive dielectric constant anisotropy. The refractive index of the liquid crystal layer observed by the normal direction of the two transparent substrates is the average value (2no+ne)/3 of the ordinary ray refractive index no and the extraordinary ray refractive index ne under the state of no voltage application, and the voltage is applied to make The refractive index of the liquid crystal layer is close to the ordinary ray refractive index no.

Description of drawings

Fig. 1 is a schematic sectional view in the thickness direction of a light deflecting liquid crystal cell according to a first embodiment of the present invention.

2 is a schematic perspective view of a prism layer and an enlarged view of a cross-sectional shape of a prism.

Fig. 3 is a schematic plan view of a prism layer on a glass substrate.

Fig. 4 is a photograph of the light deflecting liquid crystal cell of the first embodiment with and without voltage applied.

Fig. 5 is a transverse cross-sectional view schematically showing an illumination device of an application example.

FIGS. 6A and 6B are schematic diagrams respectively showing projected images when a voltage is applied and when no voltage is applied in an illumination device using an application example of the light deflection liquid crystal cell of the first embodiment.

Fig. 7 is a schematic sectional view in the thickness direction of a light deflecting liquid crystal cell of a second embodiment.

Fig. 8 is a schematic cross-sectional view in the thickness direction of a light deflecting liquid crystal cell of a third embodiment.

Fig. 9 is a schematic perspective view showing the structure of a blue phase (blue phase I).

10A and 10B are schematic diagrams respectively showing projected images when no voltage is applied and when voltage is applied, respectively, in an illumination device using an application example of the light deflection liquid crystal cell of the third embodiment.

FIG. 11 is a schematic cross-sectional view showing a light deflection device according to a modified example.

Fig. 12 is a schematic sectional view in the thickness direction of a light deflecting liquid crystal cell of a fourth embodiment.

Detailed ways

First, the structure and manufacturing method of the light deflecting liquid crystal cell described in the first embodiment of the present invention will be described.

Fig. 1 is a schematic sectional view in the thickness direction of a light deflecting liquid crystal cell of a first embodiment. A pair of glass substrates formed with transparent electrodes (glass substrate 1 formed with transparent electrodes 2 and glass substrate 11 formed with transparent electrodes 12 ) were prepared. The glass substrates 1 and 11 are alkali-free glass and each have a thickness of 0.7 mmt. The transparent electrodes 2 and 12 are formed of indium tin oxide (ITO) and each have a thickness of 150 nm.

It is preferable that the patterns of the transparent electrodes 2 and 12 are formed in a desired planar shape. The ITO film can be patterned by, for example, wet etching using ferric chloride or a method of removing excess ITO film with a laser.

A prism layer 3 is formed on the transparent electrode 2 of the glass substrate 1 on one side. The prism layer 3 is formed in a shape in which the prisms 3a are arranged on the base layer 3b. The thickness of the base layer 3 b is, for example, about 2 μm to 3 μm.

FIG. 2 is a schematic perspective view of the prism layer 3 and an enlarged view of the cross-sectional shape of the prism 3a. Each prism 3a has a triangular prism shape with an apex angle of 75° and base angles of 15° and 90°, and a plurality of prisms 3a are arranged in a direction (prism width direction) perpendicular to the prism length direction. The height of the prisms 3 a is about 5.2 μm, and the length of the base of the prisms 3 a (prism pitch) is 20 μm.

Preferred materials for the prism layer 3 will be described. On the prism layer 3, a vertical alignment film 4 of polyimide or the like is formed in a later step. In order to form a highly reliable vertical alignment film, heat treatment is preferably performed at a high temperature of about 160° C. to 220° C. (for example, 180° C.). Therefore, it is desired to obtain a prism material whose properties are not easily degraded by high-temperature heat treatment.

The inventors of the present application heat-treated various prism materials at 220° C. for two hours, and evaluated the difference in transmittance in the visible light region before and after the heat treatment. As a result, it was found that although the transmittance of acrylic ultraviolet (UV) curable resin decreased a little on the short-wavelength side, it exhibited the same transmittance as before heat treatment in almost the entire visible wavelength region. The characteristic (transmittance) variation is reduced. In addition, in this specification, "small change in characteristic (transmittance)" refers to a state in which the change in characteristic (transmittance) in the visible light region (wavelength 380nm to 780nm) is within about 2% compared with that before heat treatment.

Acrylic UV-curable resin not only has heat resistance, but also has excellent adhesion to glass, and has the property of being difficult to adhere to metal (good mold release property), so it can be seen that the prism material used as an example is preferred. In addition, epoxy-based resins are also excellent in heat resistance, and can be considered to be used as prism materials. In addition, polyimide can also be used.

FIG. 3 is a schematic plan view of the prism layer 3 on the glass substrate 1 . A method for producing the prism layer 3 will be described. On the transparent electrode 2 of the glass substrate 1, acrylic UV curable resin 3R was dropped, and a mold (overall size: vertical 80 mm x horizontal 80 mm) for forming the shape (type) of the prism layer 3 was placed at a predetermined position thereon, and Pressing is performed in a state where a thick quartz part is placed on the back side of the glass substrate for reinforcement. The dripping amount of the UV curable resin 3R is adjusted so as to match the size of the prism (the range of the prism formation region).

After pressing and leaving for one minute or more to fully expand the UV curable resin, ultraviolet rays are irradiated from the back side of the glass substrate 1 to cure the UV curable resin. The irradiation amount of ultraviolet rays was 20 J/cm ² , and the irradiation amount of ultraviolet rays may be appropriately set so as to cure the resin. In addition, since indium tin oxide (ITO) absorbs ultraviolet rays, if the film thickness of the transparent electrode changes, the amount of ultraviolet irradiation may also change. In addition, minute grooves for exhaust may be formed in the mold for forming the prism. Alternatively, the mold and the substrate may be superimposed in vacuum.

Next, the glass substrate 1 on which the prism layer 3 was formed is cleaned with a cleaning machine. Carried out in sequence: scrubbing with alkaline detergent, pure water washing, blowing, ultraviolet (UV) irradiation, and infrared (IR) drying. The cleaning method is not limited thereto, and high-pressure jet cleaning, plasma cleaning, and the like may be performed.

Return to FIG. 1 to continue the description. A vertical alignment film 13 is formed of polyimide or the like on the transparent electrode 12 of the other glass substrate 11 . Here, SE-4811 manufactured by Nissan Chemical was formed into a thickness of 80 nm by flexographic printing, and fired at 180° C. for 1.5 hours.

Also, on the prism layer 3 of the glass substrate 1, a vertical alignment film 4 is formed of polyimide or the like. Here, SE-4811 manufactured by Nissan Chemical was formed into a thickness of 80 nm by flexographic printing, and fired at 180° C. for 1.5 hours. In addition, the vertical alignment films 4 and 13 can be formed by inkjet, spin coat, slit coat, slit and spin coat, etc. .

Next, a main sealant containing a gap control material in an amount of 2 wt% to 5 wt% is formed on the glass substrate 1 on the prism layer 3 side. The forming method may be screen printing or use of a dispenser. The gap control material is selected so that the thickness of the liquid crystal layer 15 (from the base layer 3b of the prism) including the height of the prism 3a is, for example, 10 μm to 20 μm.

Here, plastic balls produced by Sekisui Chemical Co., Ltd. with a diameter of 30 μm were selected as the gap control material, and added to sealant ES-7500 produced by Mitsui Chemicals at a weight ratio of 4 wt%, thereby obtaining the main sealant 16.

On the other glass substrate 11 , plastic balls produced by Sekisui Chemical Co., Ltd. with a diameter of 17 μm were spread as the gap control material 14 using a dry type gap spreader.

Next, both the glass substrates 1 and 11 are superimposed and heat-treated while a constant pressure is applied by a press machine or the like to harden the main sealant. Here, heat treatment was performed at 150° C. for 3 hours.

The liquid crystal layer 15 is formed by vacuum-injecting liquid crystal into the hollow cell (empty cell) produced in this way. After injecting the liquid crystal, apply a terminal sealant to the injection port to seal it. After sealing, heat treatment was performed at 120° C. for 1 hour to adjust the alignment state of the liquid crystal molecules. In this way, the light deflecting liquid crystal cell of the first embodiment was produced. In addition, the method of forming the liquid crystal layer is not limited to vacuum injection, for example, one drop filling (ODF: One Drop Fill) method may also be used.

In the first embodiment, the liquid crystal adopts the liquid crystal (Δn=0.298) produced by Dainippon Ink Chemical Industry (Dainippon Ink Chemical Industry) whose dielectric constant anisotropy Δε is positive, and the chiral (chiral) produced by Merck is added. ) agent S-811. When the chiral agent is added to the mother liquid crystal at a weight ratio of 9.4 wt%, the chiral pitch is about 1 μm.

By changing the added concentration of the chiral agent, the chiral pitch can be changed. The lower the added concentration of chiral agent, the longer the chiral pitch. Samples with chiral pitches of 1 μm, 2 μm, 3 μm, 5 μm and 9 μm were fabricated.

The liquid crystal cell of the first embodiment exhibits a focal conic state in which the helical axis is parallel to the substrate due to the effect of the vertical alignment film and the chiral agent when no voltage is applied. The degree of light scattering when no voltage is applied varies with the chiral pitch. When the chiral pitch is 1 μm, it shows weak scattering, and when the chiral pitch is above 2 μm, the scattering basically disappears.

The helical axis in the focal conic state is parallel to the substrate, but since it is vertically aligned without alignment treatment, the orientation of the helical axis is random within the substrate plane. Therefore, when no voltage is applied, the refractive index of the liquid crystal layer viewed from the normal direction of the substrate is the average (2no+ne)/3 of the ordinary ray refractive index no and the extraordinary ray refractive index ne of the liquid crystal material used.

Liquid crystal molecules face a certain direction in extremely minute regions, and the molecular alignment direction with respect to the polarization direction is different in each minute region. However, this minute domain is sufficiently small compared to the director level (the level at which the refractive index of light can be determined) of liquid crystal, and the alignment direction of liquid crystal molecules proceeds in a very short period equal to or less than the wavelength of light. Variety. Therefore, in the degree of alignment of the liquid crystal, the alignment directions of the liquid crystal molecules are approximately averaged, and there is no dependence of the refractive index on polarized light.

On the other hand, when a sufficient voltage is applied, almost all of the liquid crystal molecules appear in a homeotropic state standing upright to the substrate vertical direction due to the positive dielectric constant anisotropy, so the observed from the substantially normal direction The refractive index of the liquid crystal layer is the ordinary ray refractive index no and does not depend on polarized light. The vertical state exhibits a transparent appearance.

The ordinary ray refractive index no of the liquid crystal material in the first embodiment is 1.525, and the extraordinary ray refractive index ne is 1.823. Therefore, it can be expected that the refractive index of light traveling along the normal direction of the substrate is 1.624 in the focal conic state of the liquid crystal layer when no voltage is applied, and 1.525 in the homeotropic state of the liquid crystal layer when the voltage is applied, independent of Polarization direction. In addition, the refractive index of the prism material of the example is 1.51.

In the liquid crystal cell of the first embodiment, when no voltage is applied, the refractive index of the liquid crystal layer and the prism layer are different, so the incident light is deflected by the action of the prism. On the other hand, when a voltage is applied, the refractive indices of the liquid crystal layer and the prism layer become substantially equal (equivalent), and incident light travels straight almost unchanged. Also, such an effect does not depend on the polarization direction of the incident light.

Fig. 4 shows side by side the photo (upper side) and the photo (lower side) when no voltage is applied of the light deflection liquid crystal cell (sample with a chiral pitch of 2 μm) of the first embodiment, and shows the transparent Observe the state of the straight line through the light deflection liquid crystal cell.

Inside the framed area is a portion showing the focal conic state when a prism is formed and no voltage is applied (evaluation object portion described below). The upper side of this region is a portion where no prisms are formed, and the lower side of this region is a portion where prisms are formed, but does not exhibit a focal conic state but scatters when no voltage is applied (it is considered that the confinement force of vertical alignment is relatively low. weak part).

When the voltage is applied as shown on the upper side of FIG. 4 , the light is transmitted straight without changing, so the straight line is observed. On the other hand, when no voltage is applied as shown in the lower side of FIG. 4 , the light is distorted at the prism forming portion, and the image is laterally shifted. Although the scattering of the image due to the focal conic state when no voltage is applied can be seen, the scattering is very little.

A lighting device as an application example of a headlight of a vehicle was fabricated by combining the light deflecting liquid crystal cell of the first embodiment and a light source.

Fig. 5 is a lateral cross-sectional view (planar cross-sectional view) schematically showing an illumination device of an application example. The light source 21 adopts a high-intensity (brightness) discharge (HID) lamp. The light emitted from the light source 21 is reflected by the elliptical reflector 22 and condensed on the shade 23 arranged at the focal point of the elliptical reflector 22 . The light rays transmitted through the lampshade 23 are approximately parallelized by the lens 24, and then enter the light deflection liquid crystal cell 25 of the first embodiment. The light exits the lighting device through the light deflecting liquid crystal cell 25 . The voltage applied to the light deflection liquid crystal cell 25 is switched by the control device 26 .

The light deflection liquid crystal cell 25 is arranged so that when viewed from the front of the headlight (relative to the ground), the length direction of the prism is horizontal. Also, the prism side is provided on the light source 21 side (however, even if the prism side is provided on the opposite side to the light source 21, the light deflecting action does not change).

Application examples of lighting devices were fabricated with light deflecting liquid crystal cells with chiral pitches of 1 μm, 2 μm, 3 μm, 5 μm and 9 μm, and the projected images were observed when no voltage was applied and when voltage was applied. First, observation results of a sample with a chiral pitch of 2 μm will be described.

6A and 6B are schematic diagrams schematically showing projected images when a voltage is applied and when no voltage is applied, respectively. As shown in FIG. 6A , when a voltage is applied at a sufficient voltage (for example, 20V), a clear cutoff pattern (equivalent to low-beam) is projected. Light is not scattered in unwanted directions like stray light etc.

As shown in FIG. 6B , when no voltage is applied, the projected image moves upward by about 3° (equivalent to high beam) while maintaining approximately the same size as when the voltage is applied. The brightness of the low beam when the voltage is applied is the same as that of the high beam when the voltage is not applied. All the incident light incident on the light deflection liquid crystal cell is deflected, and the projected image at the time of voltage application does not remain.

In addition, in the light deflection liquid crystal cell of the first embodiment, the deflection angle is about 3°, but the deflection angle can be changed by changing the angle (base angle) of the slope of the prism.

In addition, when the voltage is gradually increased, the projected image does not move continuously from the image when no voltage is applied, but expands slightly up and down in the middle, and at a sufficiently high voltage (above 20V, AC 150Hz) to gradually image clearly with the same size. This is because, since a prism layer is interposed between the transparent electrode on the substrate and the liquid crystal layer, and the thickness of the prism layer varies with different parts, the voltage (divided voltage) actually applied to the liquid crystal layer varies with different parts. , thus forming a distribution of refractive index in the plane.

In addition, by inverting the installation direction of the light deflection liquid crystal cell up and down, it is also possible to relatively achieve a high beam when a voltage is applied, and to achieve a relatively low beam when a voltage is not applied. In addition, from the viewpoint of fail-safe, it is preferable to keep the low beam in a state where no voltage is applied.

On the other hand, from the viewpoint of avoiding the influence of scattering when no voltage is applied and clearly forming a cutoff pattern, it is preferable to form a low beam when a voltage is applied.

Next, the difference in the projection state due to the chiral pitch will be described. When the chiral pitch is 1 μm, weak scattering can be seen in the state where no voltage is applied. By applying a voltage, the projected image moves, the transparency of the liquid crystal cell increases, and the cutoff pattern of the projected image becomes clear.

When the chiral pitch is 3 μm or more, a locally undistorted portion of the projected image can be seen in a state where no voltage is applied. This part is only a very small part when the chiral pitch is 3 μm, but increases when the chiral pitch reaches 5 μm, and the area of the untwisted part becomes larger when the chiral pitch is 9 μm. In these liquid crystal cells, the portion whose image is distorted moves by applying a voltage, while the portion whose image is not distorted does not move even when a voltage is applied.

The longer the chiral pitch, that is, the lower the concentration of the chiral agent, the larger the undistorted portion of the image. The following reasons are presumed for this phenomenon. The longer the chiral pitch, the less the twisting force of the chiral agent on the orientation of the liquid crystal molecules, and the liquid crystal molecules are easy to form vertical alignment even in the state of no voltage applied. That is, it is presumed that the undistorted portion is already in a homeotropic state when no voltage is applied, and the alignment state does not change even when a voltage is applied.

From the viewpoint of good light deflection without voltage application, the chiral pitch is preferably 1 μm and 2 μm, and 3 μm is also feasible, 5 μm shows local defects, and 9 μm is not feasible. It can be said that the chiral pitch The longer the distance, the more difficult it is to deflect light when no voltage is applied. On the other hand, from the viewpoint of scattering in the state where no voltage is applied, weak scattering occurs when the chiral pitch is 1 μm, and scattering almost disappears when the chiral pitch is 2 μm or more. bigger. Therefore, based on these results, it can be said that the chiral pitch is preferably 1 μm or more and less than 5 μm, more preferably 1 μm or more and less than 3 μm.

As described above, a prism layer is provided inside the liquid crystal cell, and the refractive index of the liquid crystal layer is changed by switching between the focal conic state and the homeotropic state with a voltage, thereby functioning as a light deflection cell that changes the traveling direction of light. . By employing the focal conic state and the homeotropic state, light deflection can be performed independent of the polarization direction of incident light incident from the normal direction of the substrate.

In addition, as an application example, a lighting device that deflects light in the vertical direction has been described. However, by changing the direction of the length of the prism, the direction of deflection can be changed. For example, in the case of light deflection in the left and right directions, the light deflection liquid crystal cell can be arranged so that the longitudinal direction of the prism (relative to the ground) is vertical when viewed from the front of the headlight.

The light deflecting liquid crystal cell of the first embodiment (and the second embodiment described later) can be applied to various lighting devices in addition to vehicle headlights. As the light source, in addition to high-intensity discharge lamps, light-emitting diodes (LEDs), field emission (FE) light sources, fluorescent lamps, and the like can also be used.

Next, the light deflection liquid crystal cell of the second embodiment will be described.

Fig. 7 is a schematic sectional view in the thickness direction of a light deflecting liquid crystal cell of a second embodiment. Next, differences from the first embodiment will be described. In the second embodiment, no transparent electrode is formed on the glass substrate 31 on the side of the prism layer 3 , but the prism layer 3 is directly formed on the glass substrate 31 . The prism layer 3 is formed in the same manner as in the first embodiment.

In the second embodiment, the transparent electrode 32 is formed over (the liquid crystal layer side) of the prism layer 3 . First, the glass substrate 31 formed with the prism layer 3 is cleaned in the same manner as in the first embodiment. In order to improve the adhesiveness of the transparent electrode 32 (ITO film), an SiO ₂ film 33 may be formed on the prism layer 3 . The SiO ₂ film 33 is formed to have a thickness of 50 nm by, for example, sputtering (alternating current discharge) at a substrate temperature of 80°C.

Next, an ITO film with a thickness of 100 nm is formed as the transparent electrode 32 on the SiO ₂ film 33 by sputtering (AC discharge), for example, at a substrate temperature of 100° C. An ITO film can be selectively formed on a desired part by masking the excess part with a stainless steel (SUS) mask, a high-temperature heat-resistant tape, or the like. In addition, as a film forming method other than sputtering, vacuum evaporation, ion beam method, chemical vapor deposition (CVD) and the like may be used.

Next, the glass substrate 31 on which the transparent electrode 32 is formed is washed with a washing machine. For example, brush washing with an alkaline detergent, pure water washing, blowing, ultraviolet irradiation, and infrared (IR) drying are performed in this order. The cleaning method is not limited thereto, and high-pressure jet cleaning, plasma cleaning, and the like may be performed.

Next, the vertical alignment film 4 is formed on the transparent electrode 32 using polyimide or the like. For example, SE-4811 manufactured by Nissan Chemical Co., Ltd. was formed into a thickness of 80 nm by flexographic printing, and fired at 180° C. for 1.5 hours. In addition, the method for forming the vertical alignment film 4 may also be inkjet, spin coating, slit coating, slit and spin coating, and the like.

Similar to the first embodiment, a transparent electrode 12 is formed on the opposite glass substrate 11 , and a vertical alignment film 13 is formed on the transparent electrode 12 . Furthermore, similarly to the first embodiment, the two substrates 11, 31 are overlapped to form an empty cell to form the liquid crystal layer 15, thereby producing the light deflection liquid crystal cell of the second embodiment.

The liquid crystal layer 15 is the same as the first embodiment, and the focal conic state and the homeotropic state are switched by voltage. Even the light deflecting liquid crystal cell of the second embodiment in which the prism-side transparent electrode is formed above the prism (the liquid crystal layer side) can perform light deflection similarly to the first embodiment.

In the second embodiment, no prism layer is interposed between the prism-side transparent electrode and the liquid crystal layer. This is considered to reduce the in-plane distribution of the refractive index due to the in-plane distribution of the thickness of the prism layer, and it is expected that the projected image will move without changing its shape when the voltage is continuously changed. In addition, it is expected that the drive voltage required to move the projected image will be reduced.

Next, a third embodiment and a fourth embodiment will be described. In addition, in order to avoid cumbersome marking of reference symbols, in the third embodiment and the fourth embodiment, the components corresponding to the first embodiment and the second embodiment are reused in the first embodiment and the second embodiment The reference symbols used in the description of .

First, the structure and manufacturing method of the light deflection liquid crystal cell of the third embodiment will be described.

Fig. 8 is a schematic cross-sectional view in the thickness direction of a light deflecting liquid crystal cell of a third embodiment. Similar to the first example, a pair of glass substrates (glass substrate 1 formed with transparent electrode 2 and glass substrate 11 formed with transparent electrode 12 ) on which transparent electrodes were formed were prepared. It is preferable that the patterns of the transparent electrodes 2 and 12 are formed in a desired planar shape.

A prism layer 3 is formed on the transparent electrode 2 of the glass substrate 1 on one side. The prism layer 3 is formed in a shape in which the prisms 3a are arranged on the base layer 3b. The thickness of the base layer 3 b is, for example, about 2 μm to 30 μm. Same as the first embodiment (with reference to FIG. 2 ), each prism 3a is a triangular prism with a vertex angle of 75° and a base angle of 15° and 90°, and a plurality of prisms 3a are along the direction perpendicular to the prism length direction ( Prism width direction) arrangement. The height of the prisms 3 a is about 5.2 μm, and the length of the base of the prisms 3 a (prism pitch) is 20 μm. The prism layer 3 can be formed in the same manner as the first embodiment (refer to FIG. 3 ).

In the process mentioned later, the baking of the main sealing agent of a liquid crystal cell is heat-processed, for example at 150 degreeC or more. In addition, in the fourth embodiment, as will be described later, when forming a transparent electrode on the prism layer 3 , heat treatment at 180° C. or higher is performed, for example, to form a transparent electrode with high transparency (low impedance). In addition, (not formed in the third and fourth embodiments), however, when the vertical alignment film is formed on the prism layer 3, the firing of the vertical alignment film requires, for example, heat treatment at 160° C. or higher. Therefore, as the prism material, it is preferable to use a material whose properties are not easily degraded by high-temperature heat treatment, and as in the first embodiment, for example, an acrylic UV-curable resin can be used.

Next, the glass substrate 1 on which the prism layer 3 was formed is washed with a washing machine. Carried out in sequence: scrubbing with alkaline detergent, pure water washing, blowing, ultraviolet irradiation, and infrared (IR) drying. The cleaning method is not limited thereto, and high-pressure jet cleaning, plasma cleaning, and the like may be performed.

Next, the main sealant 16 containing a gap control material in a weight ratio of 2 wt % to 5 wt % is formed on the glass substrate 1 on the side of the prism layer 3 . The forming method may be screen printing or use of a dispenser. The gap control material is selected so that the thickness of the liquid crystal layer 15 (from the base layer 3b of the prism) including the height of the prism 3a is, for example, 10 μm to 20 μm. Here, plastic balls produced by Sekisui Chemical Co., Ltd. with a diameter of 30 μm were selected as the gap control material, and added to sealant ES-7500 produced by Mitsui Chemicals at a weight ratio of 4 wt%, thereby obtaining a primary sealant.

On the other glass substrate 11 , plastic balls produced by Sekisui Chemical Co., Ltd. with a diameter of 17 μm were spread as the gap control material 14 using a dry type gap spreader.

Next, the two glass substrates 1 and 11 are superimposed and heat-treated while a certain pressure is applied by a press machine or the like to harden the main sealant to form an empty box. Here, heat treatment was performed at 150° C. for 3 hours.

In addition, although not formed in the third embodiment, the vertical alignment film 4 may be formed on the prism layer 3 of one substrate 1 , and the vertical alignment film 13 may be formed on the transparent electrode 12 of the other substrate 11 . The vertical alignment film is, for example, formed from polyimide by flexographic printing, and fired at 180° C., for example.

Next, a liquid crystal material is vacuum injected into the cell to form a liquid crystal layer 15 . After the liquid crystal is injected, a terminal sealant is applied to the injection port to seal the liquid crystal cell. In addition, the method of forming the liquid crystal layer is not limited to vacuum injection, for example, one drop filling (ODF, One Drop Fill) method may also be used.

In the third embodiment, as a liquid crystal material for forming the liquid crystal layer 15, a liquid crystal molecule containing a positive dielectric constant anisotropy Δε and exhibiting cholesteric properties when no voltage is applied (within a predetermined temperature range) is used. A liquid crystal material of a blue phase (hereinafter sometimes also referred to as a blue phase). As an example, JC1041-XX (manufactured by Desso, Δn: 0.142), which is a fluorine-containing mixed liquid crystal, and 4-cyano-4'-pentylbiphenyl (5CB) (manufactured by Meiku, Δn: 0.184) were combined to form A mixed liquid crystal was obtained by mixing at a ratio of 1:1, and 5.6% of a chiral agent ZLI-4572 (manufactured by Meiku) was added to the mixed liquid crystal.

In addition, a mixed monomer obtained by mixing a monofunctional material and a bifunctional material was added as a photopolymerizable monomer. Specifically, 2-ethylhexyl acrylate (EHA) (manufactured by Aldrich) was used as a monofunctional material, and RM257 (manufactured by Meik) was used as a bifunctional material, and they were mixed at a molar ratio of 70:30.

In addition, 2,2-dimethoxy-2-phenylacetophenone (DMPDP) was used as a photopolymerization initiator, and it was added in a ratio of 5 mol% with respect to the mixed monomers.

A liquid crystal material for forming the liquid crystal layer 15 was prepared by adding the photopolymerizable mixed monomer to which the photopolymerization initiator was added relative to the mixed liquid crystal to which the chiral agent was added at a ratio of 8 mol%.

When the liquid crystal cell thus formed is heated, it exhibits a blue phase in a narrow temperature range around 60°C. The liquid crystal cell is irradiated with ultraviolet light while maintaining the temperature at which the blue phase appears, to polymerize the photopolymerizable monomer and form a polymer network, thereby stabilizing the polymer in the blue phase.

The ultraviolet irradiation was intermittently repeated 10 times in the irradiation sequence of first irradiating for 1 second and then not irradiating for 10 seconds. Then, after intermittent irradiation, continuous irradiation was performed for 3 minutes. The intensity of ultraviolet rays is 30mW/cm ² (365nm). In addition, the exposure conditions are not limited thereto, and for example, the intensity of ultraviolet rays may be made weaker (only the time required for photopolymerization is increased).

The liquid crystal cell treated with polymer stabilization exhibits a blue phase in a wide temperature range of about -5°C to 60°C. In addition, the temperature range in which the blue phase appears through polymer stabilization treatment may be further expanded by adjusting the liquid crystal material used and its mixing ratio, polymerization conditions, and the like.

As described above, the light deflecting liquid crystal cell of the third embodiment was produced. Next, the operation of the light deflection liquid crystal cell of the third embodiment will be described.

The light deflecting liquid crystal cell of the third embodiment exhibits a blue phase when no voltage is applied. Below, for general descriptions of the blue phase, please refer to the explanatory document on the homepage of the Kikuchi Laboratory (http://kikuchi-lab.cm.kyushu- u.ac.jp/kikuchilab/bluephase.html).

The blue phase is optically isotropic, and three blue phases exist—blue phase I with body-centered cubic symmetry, blue phase II with simple cubic symmetry, and blue phase with isotropic symmetry. Phase III. It shows blue phase I on the lowest temperature side and blue phase III on the highest temperature side. The light deflection liquid crystal cell of the third embodiment adopts the blue phase I.

Fig. 9 is a schematic perspective view showing the structure of the blue phase I (according to the above-mentioned explanatory document). In the state of the blue phase, the liquid crystal molecules near the center form a lattice-like structure in which double twisted columns Cy, which is a collection of all liquid crystal molecules that allow lateral twisting, are stacked orthogonally to each other. body.

Since the blue phase is optically isotropic, the refractive index of the liquid crystal layer observed from the normal direction of the substrate of the light deflection liquid crystal cell of the third embodiment is equal to the ordinary ray refractive index no of the liquid crystal material and the extraordinary ray refractive index ne The average value (2no+ne)/3, the two mutually orthogonal polarized light components of the incident light (light traveling along the normal direction of the substrate) incident to the light deflection liquid crystal cell are equal.

On the other hand, for the light deflecting liquid crystal cell of the third embodiment, when applying a voltage, a voltage is applied in the thickness direction of the liquid crystal layer, and according to the positive dielectric constant anisotropy, the twisted structure of the liquid crystal molecules in the blue phase is eliminated, Almost all liquid crystal molecules stand up vertically to the substrate, showing a homeotropic phase.

In the vertical phase, the refractive index of the liquid crystal layer observed from the normal direction of the substrate becomes the ordinary ray refractive index no, so that the incident rays (lights traveling along the normal direction of the substrate) incident to the light deflection liquid crystal cell are mutually orthogonal The two polarized light components are equal.

The ordinary ray refractive index no of the liquid crystal material in the third embodiment is 1.521, and the extraordinary ray refractive index ne is 1.683. Therefore, it can be estimated that the refractive index of the liquid crystal layer with respect to the incident light incident on the light deflecting liquid crystal cell is about 1.574 in the blue phase when no voltage is applied, and 1.521 in the homeotropic phase when a voltage is applied, regardless of polarization direction. Also, the refractive index of the prism material of the third embodiment is 1.51.

According to the above, when no voltage is applied to the light deflection liquid crystal cell of the third embodiment, the refractive index of the liquid crystal layer and the prism layer are different, so the incident light is deflected by the action of the prism. On the other hand, when a voltage is applied, the liquid crystal layer and the prism layer have the same refractive index, so that the incident light goes straight almost unchanged. Also, such an effect does not depend on the polarization direction of the incident light.

In addition, when the difference between the refractive index of the first member and the refractive index of the second member is within 2% (more preferably within 1%) with respect to the refractive index of the first member or the refractive index of the second member, The refractive indices of the two components are considered to be equal.

In addition, an example in which the refractive index of the liquid crystal layer and the prism layer become equal when a voltage is applied has been described, but the refractive index of the prism layer is not limited to this. If the refractive index of the prism layer changes between the blue phase and the homeotropic phase, the deflection angle by the prism changes, so the traveling direction of light can be changed. For example, the refractive indices of the liquid crystal layer and the prism layer may be made equal when no voltage is applied (although a prism material with a high refractive index is required).

Next, an illumination device as an application example of a headlight of a vehicle in which the light deflection liquid crystal cell of the third embodiment is combined with a light source is fabricated, and an experiment of observing projected images when no voltage is applied and when voltage is applied will be described.

The lighting device of this application example has the same configuration as that of the lighting device of the application example described in the first embodiment (see FIG. 5 ). As the light deflecting liquid crystal cell 25, the light deflecting liquid crystal cell 25 of the third embodiment is used.

The light deflection liquid crystal cell 25 is arranged so that when viewed from the front of the headlight (relative to the ground), the length direction of the prism is horizontal. In addition, the prism side is provided on the light source 21 side (however, even if the prism side is provided on the opposite side to the light source 21, the light deflecting action does not change).

10A and 10B are schematic diagrams respectively schematically showing projected images when no voltage is applied and when voltage is applied. As shown in FIG. 10A, when no voltage is applied, a clear cut-off pattern (equivalent to low beam) is projected. Light is not scattered in unwanted directions like stray light etc.

As shown in FIG. 10B , by applying a voltage, the projected image moves upward continuously while maintaining approximately the same size as when no voltage is applied (corresponding to high beam). The brightness of the low beam when no voltage is applied is the same as that of the high beam when a voltage is applied. All incident light incident on the light deflecting liquid crystal cell is deflected, and no projected image remains when no voltage is applied.

The deflection angle of light saturates at an applied voltage of 90V, and the maximum angle change is 0.9° (the maximum angle change is the traveling direction of the light distorted by the prism when no voltage is applied, and the original state is unchanged when a high voltage is sufficiently applied The difference in the direction of travel of light traveling straight from the ground). The refractive index changes continuously with the magnitude of the applied voltage until the liquid crystal molecules stand up along the normal direction of the substrate (that is, until a sufficiently high voltage is applied so that the light travels straight as it is). The refractive index varies approximately proportional to the square of the electric field intensity. Thus, the deflection angle produced by the applied voltage can vary continuously with the applied voltage until reaching a maximum value indicative of saturation.

In addition, in the light deflection liquid crystal cell of the third embodiment, the prism layer is interposed between the transparent electrode on the prism side substrate and the liquid crystal layer. For this reason, it is considered that a comparatively high driving voltage is required.

In addition, the maximum value of the deflection angle by applying a voltage can be adjusted by changing the angle (base angle) of the slope of the prism.

Further, as in the modified example shown in FIG. 11 , an auxiliary optical system 28 including a prism or the like is disposed on the output side of the light deflection liquid crystal cell 27 to further deflect the outgoing light L emitted from the light deflection liquid crystal cell 27 . In this way, the maximum value of the deflection angle can also be adjusted by using the auxiliary deflection optical system.

When the response speeds of rising up and rising down of the liquid crystal molecules were measured at room temperature, the rising up was about 200 μsec, and the downward rising was about 18 μsec. For example, a faster response can be obtained compared with nematic liquid crystal. In this way, by utilizing the switching between the blue phase and the homeotropic phase, a high-speed liquid crystal element can be obtained.

In addition, by reversing the installation direction of the light deflection liquid crystal cell up and down, it is also possible to relatively achieve high beam when no voltage is applied, and to relatively achieve low beam when voltage is applied. In addition, from the viewpoint of fail-safe, it is preferable to keep the low beam in a state where no voltage is applied.

In addition, as an application example, an illumination device that deflects light in the vertical direction has been described. However, by changing the direction of the length of the prism, the direction of deflection can be changed. For example, in the case of light deflection in the left and right directions, the light deflection liquid crystal cell can be arranged so that the length direction of the prism is vertical when viewed from the front of the headlight (relative to the ground).

As described above, by providing a prism layer inside the liquid crystal cell and switching between the blue phase and the homeotropic phase by voltage, the refractive index of the liquid crystal layer is changed, and it functions as a light deflection liquid crystal cell that changes the traveling direction of light.

By employing the blue phase and the homeotropic phase, light deflection can be performed independently of the polarization direction (ie, with respect to two polarization directions) of incident light incident from the normal direction of the substrate. In addition, high-speed operation can be obtained by utilizing switching between the blue phase and the homeotropic phase.

Next, a light deflection liquid crystal cell of a fourth embodiment will be described.

Fig. 12 is a schematic sectional view in the thickness direction of a light deflecting liquid crystal cell of a fourth embodiment. Next, differences from the third embodiment will be described. In the fourth embodiment, the prism layer 3 is formed on the glass substrate 31 on the side of the prism layer 3 without interposing a transparent electrode. The prism layer 3 can be formed in the same manner as in the third embodiment.

In the fourth embodiment, a transparent electrode 32 is formed over (the liquid crystal layer side) of the prism layer 3 . First, the glass substrate 31 formed with the prism layer 3 is cleaned in the same manner as in the third embodiment. Here, an SiO ₂ film 33 may be formed on the prism layer 3 in order to improve the adhesiveness of the transparent electrode 32 (ITO film). The SiO ₂ film 33 is formed to a thickness of 50 nm by, for example, sputtering (alternating current discharge) at a substrate temperature of 80°C.

Next, an ITO film with a thickness of 100 nm is formed as the transparent electrode 32 on the SiO ₂ film 33 by, for example, sputtering (AC discharge) at a substrate temperature of 100° C. An ITO film can be selectively formed on a desired part by masking the excess part with a stainless steel (SUS) mask, a high-temperature heat-resistant tape, or the like. After the ITO film is formed, firing is performed at, for example, 220° C. for 1 hour in order to improve the transparency and conductivity of the ITO film.

In addition, as a film forming method other than sputtering, vacuum evaporation, ion beam method, chemical vapor deposition (CVD) and the like may be used. In this case, in order to improve the transparency and electroconductivity of an ITO film, baking is performed at 220 degreeC for about 1 hour, for example.

Next, the glass substrate 31 on which the transparent electrode 32 is formed is washed with a washing machine. For example, brush washing with an alkaline detergent, pure water washing, air blowing, ultraviolet irradiation, and infrared (IR) drying are performed in this order. The cleaning method is not limited thereto, and high-pressure jet cleaning, plasma cleaning, and the like may be performed.

A transparent electrode 12 is formed on the opposite glass substrate 11 . The ITO film of the transparent electrode 12 is patterned by removing excess ITO film by laser. Similar to the third embodiment, the two substrates 11, 31 are overlapped to form an empty cell to form the liquid crystal layer 15, thereby producing the light deflection liquid crystal cell of the fourth embodiment. In addition, the alignment film 4 on the transparent electrode 32 and the alignment film 13 on the transparent electrode 12 may be formed as needed.

The liquid crystal layer 15 exhibits a blue phase when no voltage is applied, as in the third embodiment. Further, polymer stabilization of the blue phase was carried out in the same manner as in the third example. In this way, the light deflecting liquid crystal cell of the fourth embodiment was fabricated.

Similar to the third embodiment, the blue phase and the homeotropic phase can be switched by voltage to perform light deflection. In the fourth embodiment, since no prism layer is interposed between the prism-side transparent electrode and the liquid crystal layer, reduction in driving voltage can be expected.

Combining the light deflecting liquid crystal cell of the fourth embodiment with a light source, an application example illuminating device having the structure shown in FIG. 5 was produced, and projected images were observed when no voltage was applied and when voltage was applied. In the fourth embodiment, the deflection angle of light is saturated when a voltage of 19V is applied (the maximum angle change amount is 0.9°). Thus, in the fourth embodiment, by forming the transparent electrode on the prism layer, the drive voltage can be lowered compared with the third embodiment (saturation at 90V).

When the response speeds of rising up and rising down of liquid crystal molecules were measured at room temperature, rising up was about 300 μsec, and rising down was about 16 μsec. Similar to the third embodiment, a high-speed liquid crystal element can be obtained.

In addition, the light deflection liquid crystal cells of the third and fourth embodiments can be applied to various lighting devices in addition to vehicle headlights. As the light source, in addition to high-intensity discharge lamps, light-emitting diodes (LEDs), field emission (FE) light sources, fluorescent lamps, and the like can also be used.

In addition, it is not limited to lighting, and can generally be applied to applications for changing the traveling direction of light. For example, in digital still cameras, projectors, head-up displays (Head Up Displays), three-dimensional displays, etc., it can be applied to devices that change the direction of images entering the camera and images (projected images) of the projector. In addition, since high-speed switching is possible, it is expected to be able to handle video frames (video frame) (double speed).

As described above through the first to fourth embodiments, it is preferable that the liquid crystal layer includes liquid crystal molecules with positive dielectric constant anisotropy, and that the refractive index observed from the normal direction of the substrate is not applied. In the voltage state, it is shown as the average value (2no+ne)/3 of the ordinary ray refractive index no and the extraordinary ray refractive index ne, and (because the dielectric constant anisotropy is positive, so) the refractive index of the liquid crystal layer is approached by applying a voltage Ordinary ray refractive index no, such a liquid crystal layer (by combining with a prism layer) utilizes a liquid crystal cell for light deflection. As the liquid crystal layer, a material that exhibits a focal conic state when no voltage is applied and becomes a homeotropic state by applying a voltage, or a material that exhibits a cholesteric blue phase when no voltage is applied and becomes a homeotropic state by applying a voltage can be used. Material.

Although the present invention was described based on the above examples, the present invention is not limited to these examples. It is obvious to those skilled in the art that various changes, improvements, combinations, etc. can be made, for example.

Claims (10)

1. a light-deflection apparatus, is characterized in that,

This light-deflection apparatus has:

Liquid crystal layer;

First and second transparency carriers, the mutually opposing configuration of described first and second transparency carrier also clamps described liquid crystal layer;

First and second transparency electrodes, described first and second transparency electrodes are formed at the liquid crystal layer side of described first and second transparency carriers respectively and apply voltage to described liquid crystal layer;

Layers of prisms, described layers of prisms is formed at the liquid crystal layer side of a side in described first and second transparency carriers; And

Vertical orientation film, this vertical orientation film is at least formed in described layers of prisms,

It is positive liquid crystal molecule that described liquid crystal layer contains dielectric constant anisotropy, the refractive index of the described liquid crystal layer observed from the normal direction of described first and second transparency carriers is not executing the mean value (2no+ne)/3 for ordinary ray refractive index no and special ray refractive index ne alive state, makes the refractive index of described liquid crystal layer close to described ordinary ray refractive index no by applying voltage.

2. light-deflection apparatus according to claim 1, wherein,

Described liquid crystal layer is added with hand and levies agent, and shows as Focal conic state not executing under alive state.

3. light-deflection apparatus according to claim 2, wherein,

The hand of described liquid crystal layer is levied in the scope of pitch more than 1 μm and less than 5 μm.

4. light-deflection apparatus according to claim 1, wherein,

Described liquid crystal layer to show as the blue phase of courage steroid not executing under alive state.

5. light-deflection apparatus according to claim 4, wherein,

Be formed with macromolecule network in a part for described liquid crystal layer, make described courage steroid indigo plant mutually polymer-stabilized.

6. the light-deflection apparatus according to any one in Claims 1 to 5, wherein,

In described first and second transparency electrodes, the electrode of layers of prisms side is formed at the liquid crystal layer side of described layers of prisms.

7. the light-deflection apparatus according to any one in Claims 1 to 5, wherein,

The material of described layers of prisms is acrylic compounds UV curable resin.

8. the light-deflection apparatus according to any one in Claims 1 to 5, wherein,

Described ordinary ray refractive index no is equal with the refractive index of described layers of prisms.

9. the light-deflection apparatus according to any one in Claims 1 to 5, wherein,

This light-deflection apparatus also has the light source making light incide described liquid crystal layer.

10. the light-deflection apparatus according to any one in Claims 1 to 5, wherein,

This light-deflection apparatus also has the auxiliary deflection optical system of the direct of travel for changing the light penetrated from described layers of prisms.