WO2003079108A1 - Dispositif d'attenuation et dispositif d'imagerie - Google Patents

Dispositif d'attenuation et dispositif d'imagerie Download PDF

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Publication number
WO2003079108A1
WO2003079108A1 PCT/JP2003/002849 JP0302849W WO03079108A1 WO 2003079108 A1 WO2003079108 A1 WO 2003079108A1 JP 0302849 W JP0302849 W JP 0302849W WO 03079108 A1 WO03079108 A1 WO 03079108A1
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WIPO (PCT)
Prior art keywords
liquid crystal
film
light
control device
cell
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PCT/JP2003/002849
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English (en)
Japanese (ja)
Inventor
Toshiharu Yanagida
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Sony Corporation
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Publication of WO2003079108A1 publication Critical patent/WO2003079108A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133502—Antiglare, refractive index matching layers
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/13725—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on guest-host interaction
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13356—Structural association of cells with optical devices, e.g. polarisers or reflectors characterised by the placement of the optical elements
    • G02F1/133565—Structural association of cells with optical devices, e.g. polarisers or reflectors characterised by the placement of the optical elements inside the LC elements, i.e. between the cell substrates

Definitions

  • the present invention relates to a light control device for adjusting the amount of incident light and emitting the light, and an imaging device using the light control device.
  • a polarizing plate is used for a light control device using a liquid crystal optical element (liquid crystal cell).
  • liquid crystal cell for example, a TN (twisted nematic) liquid crystal cell or a GH (Guest Host) liquid crystal cell is used.
  • This dimmer mainly includes a polarizing plate 1 and a GH cell 2.
  • the GH cell 2 is sealed between two glass substrates (not shown), and has an operating electrode and a liquid crystal alignment film (not shown).
  • liquid crystal molecules 3 and dichroic dye molecules 4 are sealed.
  • the liquid crystal molecule 3 which is the host material, has a positive dielectric constant anisotropy (positive type).
  • the dichroic dye molecule 4 as the guest material has anisotropy in light absorption, and FIGS. 24A to 24B show the positive light absorbing molecules in the longitudinal direction of the molecule.
  • a type (P-type) dye molecule is an example of a type (P-type) dye molecule.
  • FIG. 24A shows the state of GH cell 2 when no voltage is applied.
  • the polarization direction of the polarized light and the molecular long axis direction of the dichroic dye molecule 4 Since they match, the polarized light is easily absorbed by the dichroic dye molecules 4. Therefore, the optical transmittance of the GH cell 2 is low when no voltage is applied as shown in FIG. 24A.
  • FIG. 24B shows a state of the GH cell 2 when a voltage is applied.
  • the liquid crystal molecules 3 are oriented in the direction of the electric field, and accordingly, the direction of the major axis of the dichroic dye molecules 4 is orthogonal to the polarization direction of light. Therefore, the polarized light is transmitted through the dichroic dye molecule 4 without being absorbed. Therefore, the light transmittance of the GH cell 2 is high when the voltage is applied as shown in FIG. 24B.
  • the ratio of the absorbance when no voltage is applied (when light is shielded) and the voltage when voltage is applied (when transparent), that is, the ratio of optical density is about It is 10
  • the dichroic dye molecule 4 a negative (n-type) dye molecule that absorbs light in the direction of the minor axis of the molecule can also be used.
  • the light transmittance is opposite to that of using a positive type dye molecule. Light is hardly absorbed when no voltage is applied, and light is easily absorbed when voltage is applied.
  • an optical density ratio (contrast ratio, dynamic range) determined by the difference in light transmittance between light-shielded and transparent can be achieved. There is an urgent need to ensure a large enough dimming operation and drive with high operation reliability.
  • an object of the present invention is to reduce reflection on the surface of a substrate constituting a liquid crystal optical element and to call visible light when transparent (light having a wavelength of 400 to 700 nm is referred to as visible light). The same applies hereinafter) To improve the performance, image quality, and reliability of dimming devices and imaging devices that use liquid crystal optical elements by increasing the optical density ratio (contrast ratio, dynamic range) of the liquid crystal optical elements by improving the power ratio. It is in. Disclosure of the invention
  • the present invention includes a liquid crystal optical element in which liquid crystal is sealed between opposed substrates, wherein the liquid crystal is a guest-host type liquid crystal using a negative type liquid crystal as a host material,
  • the present invention relates to a light control device in which an antireflection film made of a dielectric film is formed on the inner surface of at least one of the opposed substrates, and a transparent conductive film and a liquid crystal alignment film are sequentially formed thereon.
  • the present invention relates to an imaging device in which the device is arranged in an optical path of an imaging system.
  • the antireflection film is formed on the opposing substrate, reflection of visible light by the liquid crystal optical element can be effectively reduced.
  • FIG. 1A is a schematic cross-sectional view showing the configuration of the GH cell of the prior application
  • FIG. 1B is a schematic cross-sectional view showing the configuration of the GH cell according to the embodiment of the present invention.
  • 2A to 2D are graphs showing the effect of reducing visible light reflectance when an antireflection film made of a dielectric film is optimized on a glass substrate.
  • FIGS. 3A to 3D are graphs showing the effect of reducing visible light reflectance when an antireflection film is formed by optimizing an antireflection film in a configuration in which a transparent electrode and a liquid crystal alignment film are formed to simulate a liquid crystal cell. It is.
  • FIG. 4 is a graph showing an optimum value of the thickness of the A1 2 3 film with respect to the thickness of the liquid crystal alignment film.
  • FIG. 5 is a graph showing a change in reflectance characteristics due to a change in the thickness of the liquid crystal alignment film.
  • FIG. 6 is a graph showing the optimized thicknesses of the antireflection film (II) and the liquid crystal alignment film, and the reflectance characteristics at that time.
  • FIG. 7 is a graph showing the relationship between light transmittance and applied voltage of a light control device using a GH cell according to an embodiment of the present invention.
  • FIG. 8 is a graph showing an optimum value of the thickness of the T i 0 2 (a) / S i ⁇ 2 / ⁇ i 0 2 (b) film with respect to the thickness of the liquid crystal alignment film.
  • FIG. 9 is a graph showing a change in reflectance characteristics due to a change in the thickness of the liquid crystal alignment film.
  • FIG. 10 is a graph showing the optimized thicknesses of the antireflection film (II) and the liquid crystal alignment film, and the reflectance characteristics at that time.
  • FIG. 11 is a schematic diagram showing the operation principle of the light control device according to the embodiment of the present invention.
  • Fig. 12 shows the light transmittance of the dimmer using the GH cell of the prior application.
  • 6 is a graph showing the relationship between the voltage and the applied voltage.
  • FIG. 13 is a graph showing a change in light transmittance and a change in sheet resistance due to a change in ITO film thickness according to the embodiment of the present invention.
  • FIG. 14 is a graph showing the difference in spectral characteristics depending on the ITO film thickness.
  • FIG. 15 is a graph showing the difference in spectral characteristics depending on the thickness of the liquid crystal alignment film on the ITO film.
  • FIG. 16 is a graph showing a relationship between a pretilt angle of liquid crystal molecules and a response time in the liquid crystal optical element of the light control device.
  • FIG. 17 is a graph showing the relationship between the pretilt angle of the liquid crystal molecules in the liquid crystal optical element, the light transmittance, and the dynamic range.
  • FIG. 18 is a schematic plan view of the cell of the liquid crystal optical element.
  • FIGS. 19A to 19B are schematic plan views of the respective substrates.
  • FIG. 20 is a partially enlarged schematic sectional view of the cell of the liquid crystal optical element.
  • FIG. 21 is a schematic side view of the light control device using the liquid crystal element.
  • 22A to 22D are a front view of a mechanical iris of the light control device and a schematic partial enlarged view showing an operation of the mechanical iris near an effective optical path.
  • FIG. 23 is a schematic sectional view of a camera system incorporating the light control device according to the embodiment of the present invention.
  • 24A to 24B are schematic diagrams showing the operation principle of the conventional light control device.
  • the dielectric film the group consisting of M g F 2, S i O 2, A 1 2 0 3, C e F 3, Z r 0 2, T i ⁇ 2, and Z n S It is preferable to form at least one dielectric film of a selected material.
  • At least one of the electrodes of the counter substrate is formed of a transparent conductive film having a thickness of 90 to 120 nm, and the electrode having a thickness of 40 to 90 nm is formed on the transparent conductive film. It is preferable to form a liquid crystal alignment film.
  • the liquid crystal alignment treatment is performed so that the pretilt angle of the liquid crystal molecules (the angle formed by the liquid crystal molecule director with respect to the substrate) is 85 ° to 89 ° (1 ° to 5 ° with respect to the vertical direction). It is better to apply.
  • the guest material of the liquid crystal is preferably a dichroic dye.
  • the polarizing means so as to be able to freely enter and exit the effective optical path of light.
  • Such a liquid crystal element is based on the invention of the prior application disclosed in Japanese Patent Application Laid-Open No. 2001-21069 already filed by the present applicant.
  • a liquid crystal device and a polarizing plate arranged in an optical path of light incident on the liquid crystal device constitute a dimmer, and a guest-host using a negative type liquid crystal as a host material.
  • the ratio of the absorbance that is, the ratio of optical density
  • the contrast ratio of the dimmer is increased. This enables normal dimming operation in a wide range from bright to dark places.
  • a dichroic dye is used as a host material.
  • Positive dye with positive light absorption anisotropy is used as molecule 4.
  • Polarizing plate 1 is arranged on the incident side of GH cell 2 and a rectangular wave driving pulse is applied.
  • the maximum light transmittance when the voltage was increased to 10 V was only about 60%, and the change in light transmittance was gradual.
  • the host material was manufactured by Merck as an example of negative liquid crystal molecules 13 having a negative dielectric anisotropy ( ⁇ ⁇ ).
  • MLC — 666 was used.
  • D5 manufactured by BDH which is a positive dye molecule having a positive light absorption anisotropy ( ⁇ A)
  • ⁇ A positive light absorption anisotropy
  • a GH cell using negative-type liquid crystal molecules By constructing a GH cell using negative-type liquid crystal molecules in this way, the light transmittance (especially when transparent) is increased and the GH cell is imaged.
  • a compact dimmer that can be used with its position fixed in the optical system can be realized.
  • the ratio of the absorbance between when no voltage is applied and when a voltage is applied that is, the ratio of optical density
  • the contrast ratio is further increased, and the dimming operation can be performed more normally from a bright place to a dark place.
  • the host material is a negative type liquid crystal, but the dichroic dye molecules of the guest material may be either positive type or negative type.
  • the negative-type host material, the positive-type or negative-type guest material can be selected from known materials.
  • a blended composition may be used so as to exhibit nematicity in the actual use temperature range.
  • the inventor has diligently studied further improvement of the performance of the light control device, and has a minimum reflectance of visible light when the transparent conductive film and the liquid crystal alignment film are formed on the counter substrate and the liquid crystal is sealed.
  • the anti-reflection film By forming the anti-reflection film on the surface of the substrate, the film material, the film thickness, the layered structure of the film and the like are optimized so that the reflection of visible light when the liquid crystal device is actually manufactured is reduced. It has been found that it can be effectively reduced and the visible light transmittance when transparent can be further improved.
  • the dielectric layer of the selected material from the group consisting of S At least one or more layers are formed on the inner surface of the counter substrate by a vapor deposition method, a sputtering method, or the like, and a transparent conductive film and a liquid crystal alignment film are stacked thereon. At this time, a dielectric film may be formed on the outer surface of the counter substrate as described above.
  • FIG. 1A is a schematic cross-sectional view of an example of a GH cell according to the invention of the prior application (Japanese Patent Application Laid-Open No. 2001-219679).
  • the light passing through this cell from top to bottom is as follows: glass substrate 31a, transparent electrode (transparent conductive film) 32a, liquid crystal alignment film 33a, GH liquid crystal 34, liquid crystal alignment film 33b, transparent
  • the electrode (transparent conductive film) 32 b and the glass substrate 31 b pass through each material in this order, and undergo refraction and reflection at the interface of each material.
  • a spacer 36 is arranged to keep the gap between the opposing substrates constant, and the periphery of the GH liquid crystal cell is sealed with a sealing material 35.
  • FIG. 1B is a schematic cross-sectional view of a GH cell as an example of an embodiment of the present invention, in which an antireflection film made of the above-mentioned dielectric film is formed on all surfaces of a glass substrate. Anti-reflection coating on the outer surface of the substrate (I) 4
  • 1a and 4b are formed on the inner surface of the substrate.
  • FIGs. 2A to 2D show examples of the effect of reducing the visible light reflectance when a dielectric film is formed on the surface of one glass substrate by optimizing the dielectric film.
  • the reflectivity in Figs. 2A to 2D indicates that light enters the glass layer from the air layer and passes once through the interface between the air layer and the glass layer. It is the numerical value of the case.
  • FIGS. 2C to 2D show examples in which a plurality of dielectric films are stacked on the surface of a glass substrate to optimize the reduction in reflectance with a multilayer dielectric film.
  • FIGS. 3A to 3D show the effect of reducing the visible light reflectance by the dielectric film in a state simulating the actual GH cell shown in FIGS. 1A to 1B. It is.
  • ITO Indium Tin Oxide or Tin-doped indium oxide
  • a liquid crystal alignment film composed of a transparent electrode and PI (polyimide) is provided, and the reflectance is measured with the liquid crystal in contact with the liquid crystal alignment film.
  • the reflectivity here is the reflectivity when light that enters the glass layer from the air layer passes through the glass layer, further passes through the transparent electrode and the liquid crystal alignment film, and enters the liquid crystal layer. .
  • the 3 B diagram other surface of the glass substrate i.e., the surfaces corresponding to the outer surface of the liquid crystal cell (hereinafter, abbreviated as outer surface), the same 1 as in the first 2 D view ⁇ 8 2 and Ding i 0
  • outer surface the surfaces corresponding to the outer surface of the liquid crystal cell
  • an antireflection film (I) (see FIG. 1B) consisting of a five-layer film of No. 2 was formed.
  • the reflection from the outer surface in this state can be estimated to be 0.5% or less from Fig. 2D.
  • the reflectivity shown in Figure 3B is much higher, except in the short wavelength region. Therefore, it can be seen that most of the reflection in this state is due to internal reflection. This is particularly noticeable for long wavelength light.
  • FIGS 3C to 3D show that in addition to the anti-reflective coating (I), an anti-reflective coating (II) was added between the inner surface and the transparent electrode to suppress internal reflection, and the reflectance was reduced. This is an example of optimization.
  • Fig. 3D shows the optimization of the reflectivity reduction of a liquid crystal cell with a multilayer dielectric film.
  • the optimized anti-reflection coating (I) By forming the optimized anti-reflection coating (I) on the outer surface of the glass substrate, most of the cell surface reflection was suppressed, which was effective. In addition, by forming an optimized anti-reflection coating (II) on the inner surface of the glass substrate, the effect from the ITO film, ⁇ I film, and liquid crystal (interfacial reflection and scattering), which becomes a problem when cells are actually assembled, is considered. was minimized.
  • the film material, the film thickness, and the laminated structure of the film are optimized so that the visible light reflectance is minimized when the transparent conductive film and the liquid crystal alignment film are formed and the liquid crystal is sealed.
  • the anti-reflection films (I) and ( ⁇ ) are formed on the surface of the glass substrate, it is possible to effectively reduce the visible light reflection when the liquid crystal cell is actually manufactured, and to reduce the visible light transmittance when transparent. Can be improved.
  • the transparent conductive film as at least one electrode of the counter substrate is provided with a thickness of Flat spectral characteristics in the visible range (visible light range of wavelengths from 400 to 700 nm) by forming a wavelength in the range of 90 to 120 nm (transmissivity is very small even if the wavelength of light changes) (A property that does not change) and enable good dimming operation.
  • the transparent conductive film is selected from the group consisting of ITO, FTO (Fluorine-doped tin oxide: tin oxide doped with fluorine), and ATO (Ant imony-doped tin oxide: tin oxide doped with antimony). It is composed of at least one kind.
  • FIG. 13 shows the film thickness dependence of the transmittance of light at a wavelength of 550 nm and the sheet resistance when an ITO film is used as the transparent conductive film.
  • the light transmittance changes while showing a maximum value and a minimum value depending on the thickness of the ITO film. Since the refractive index of the ITO film is about 2.0, the local maximum value appears periodically corresponding to the film thickness pitch of about 1337 nm.
  • the case where the resistivity of the film was 2.0 ⁇ 10 ⁇ Q-cm was shown, but this characteristic changes when the resistivity of the film changes. I do.
  • FIG. 14 shows that the film thickness of the IT film as the transparent conductive film is changed at a value near the film thickness (137 nm) at which the light transmittance shows a maximum value. The figure shows the measurement results of the spectral characteristics in the visible region at the thickness.
  • the change rate ( ⁇ ) of the light transmittance in the visible region shows a preferable value of approximately within 10%. Also, at this time, as is clear from FIG. 13, the light transmittance in the vicinity of the wavelength 550 nm where the visibility is strongest is a high value of about 83% or more.
  • the transparent conductive film in order to ensure a high light transmittance and to have as flat a spectral characteristic as possible in the visible region, it is preferable to form the transparent conductive film with a thickness of 90 to 12 O nm. .
  • FIG. 15 shows the spectral characteristics of a two-layer film when a vertical liquid crystal alignment film is formed with a thickness of 30 to 100 nm on the transparent conductive film formed with a thickness of 100 nm. It is.
  • the vertical liquid crystal alignment film having a thickness of 40 to 90 to 12 O nm is required to be formed on the ITO film having a thickness of 90 to 12 O nm. It is preferably formed to a thickness of about 90 nm.
  • the liquid crystal alignment treatment is performed so that the pretilt angle of the liquid crystal molecules is 85 ° to 89 °.
  • the pretilt angle is an angle formed by a director of liquid crystal molecules with respect to a substrate surface.
  • the transient response time of the GH cell depends on the pretilt angle of the liquid crystal molecules, and the response time when the drive voltage rises (from transparent to light-shielded state) decreases as the pretilt angle decreases. Responds quickly (change rate increases near 87 °).
  • the response time when the drive voltage falls is shorter and faster, as the pretilt angle is larger, contrary to the rise time.
  • FIG. 17 also shows the relationship between the light transmittance of the GH cell and the pretilt angle of the liquid crystal molecules, as well as the value of the dynamic range calculated from the light transmittance in the transparent state and in the light-shielded state.
  • the light transmittance decreases as the pretilt angle decreases (the change in transparency is relatively large).
  • the value of the dynamic range peaks near 87 °, and decreases as the pretilt angle decreases.
  • the difference in the pretilt angle of the liquid crystal molecules depends on the transient response speed, light transmittance, The dynamic
  • the pretilt angle of the liquid crystal molecules of the GH cell is preferably controlled to 85 ° to 89 °.
  • the pretilt angle of the liquid crystal molecules is less than 8 5 0, rising time - although transient response speed of the (transparent shielding state) increases, the light transmittance dynamic range (optical density ratio, Contrast ratio ) Greatly decreases, and the transient response speed at the time of falling (light-shielded ⁇ transparent state) becomes noticeable.
  • the pretilt angle of the liquid crystal molecules exceeds 89 °, the dynamic range of light transmittance (optical density ratio, contrast ratio) can be kept relatively large, and at the time of falling (light-shielding-transparent state). ), The transient response speed at the start-up (transparent-light-shielded state) is significantly reduced.
  • the pretilt angle of the liquid crystal molecules which is an angle formed by the liquid crystal director with respect to the substrate surface, be 85 ° to 89 ° (corresponding to 1 ° to 5 ° when viewed from the normal direction of the substrate).
  • the pretilt angle is more preferably in the range of 86 ° to 88 °, and preferably at or near 87 °.
  • the liquid crystal alignment treatment of the liquid crystal alignment film may be a general rubbing method, and is not limited to this, and may be any vertical alignment treatment that can achieve a predetermined pretilt angle which is preferable in the present invention.
  • Example For example, a photo-alignment method using polarized ultraviolet rays, an oblique deposition method, or the like can be applied.
  • FIG. 18 is a schematic plan view of the GH cell 12.
  • FIG. 20 is a sectional view taken along line XX of FIG.
  • the substrate 31 a shown in FIG. 19A has a rectangular shape, and the transparent conductive film (transparent electrode) 32 a and the alignment film 33 a, and has a transparent electrode lead-out part 21 outside the effective optical path 20.
  • the other substrate 3 lb shown in FIG. 19B has a substantially square shape slightly smaller than the substrate 31 a, a transparent conductive film (transparent electrode) 32 b and an alignment film 33 b,
  • the transparent conductive film (transparent electrode) 32b extends outside the effective optical path 20 and is electrically connected to the transparent electrode lead-out portion 21 provided on the substrate 31a.
  • the substrate 31 a and the substrate 3 lb are sealed by a sealing material 35 at a peripheral portion 24 of the GH cell 12.
  • the transparent conductive film (transparent electrode) 32 b extending from the substrate 31 b and the electrode lead portion 21 of the substrate 31 a are made of carbon outside the sealing material 35. They are connected by a conductive material such as best26.
  • the dimming device 23 composed of the GH cell 12 described above includes, for example, as shown in FIG. 21, a lens front group 15 and a lens rear group 16 composed of a plurality of lenses such as a zoom lens. Placed between.
  • the light transmitted through the front lens group 15 is linearly polarized through the polarizer 11 and then enters the GH cell 12.
  • the light transmitted through the GH cell 12 is collected by the rear lens group 16 and projected as an image on the imaging surface 17.
  • the polarizing plate 11 constituting the dimming device 23 enters the GH cell 12 as previously proposed by the present applicant (Japanese Patent Application No. 11-32 6894). It can be moved in and out of the effective optical path of light. Specifically, by moving the polarizing plate 11 to the position indicated by the imaginary line, the light can be out of the effective optical path.
  • a mechanical iris as shown in FIG. 22A may be used.
  • This mechanical iris is a mechanical diaphragm device generally used for digital still cameras, video cameras, etc., and mainly includes two iris blades 18 and 19 and a polarization plate attached to the iris blade 18. It consists of plates 1 1.
  • the iris blades 18 and 19 can be moved up and down.
  • the iris blades 18 and 19 are relatively moved in the direction indicated by the arrow 28 using a drive motor (not shown).
  • the iris blades 18 and 19 are partially overlapped, and when this overlap increases, the effective iris blades 18 and 19 are located near the center of the iris blades 18 and 19.
  • the opening 22 on the optical path 20 is covered with the polarizing plate 11.
  • FIG. 22B to 22D are partially enlarged views of the mechanical iris near the effective optical path 20.
  • FIG. 22B At the same time as the iris blade 18 moves downward, the iris blade 19 moves upward.
  • the polarizing plate 11 attached to the iris blade 18 also moves out of the effective optical path 20.
  • the polarizing plate 11 moves on the effective optical path 20 and gradually covers the opening 22.
  • the iris blades 18 and 19 overlap each other When it becomes larger, as shown in FIG. 22D, the polarizing plate 11 covers the entire opening 22.
  • the polarizing plate 11 (transmittance, for example, 40% to 50%) can be taken out of the effective optical path 20 of light. .
  • the maximum transmittance of the light control device can be increased to, for example, twice or more.
  • the maximum transmittance of this dimmer is, for example, about twice as large as that of a dimmer including a fixedly installed polarizing plate and a GH cell.
  • the minimum transmittance is the same for both.
  • the polarizer 11 is moved in and out using a mechanical iris practically used in digital still cameras and the like, the light control device can be easily realized. Further, since the GH cell 12 is used, dimming can be performed by absorbing the light by the GH cell 12 itself in addition to the dimming by the polarizing plate 11.
  • the light control device can increase the contrast ratio between light and dark, and can maintain the spatial distribution of the light amount substantially uniform.
  • This dimmer includes a GH cell 12 and a polarizing plate 11 as shown in FIG. And, this GH cell 12 is transparent as described later. Negative liquid crystal molecules 13 (host material) and positive or negative dichroism between two glass substrates (both not shown) with electrodes and alignment films formed on the surface, respectively. A mixture with dye molecule 4 (guest material) is enclosed. FIG. 11 shows a case where the dichroic dye molecule 4 is a positive dye molecule.
  • liquid crystal molecule 13 for example, a negative liquid crystal having negative dielectric anisotropy, Merck MLC — 666, is used.
  • dichroic dye molecule 4 for example, A positive dye D5 manufactured by BDH, which has anisotropy in light absorption, was used. The light absorption axis of the polarizing plate 11 was perpendicular to the light absorption axis when a voltage was applied to the GH cell 12.
  • the dimming device 23 composed of the GH cell 12 includes a front lens group 15 and a rear lens group 16 composed of a plurality of lenses such as a zoom lens. Placed between.
  • the light transmitted through the front lens group 15 is changed into linearly polarized light via the polarizing plate 11 and then enters the GH cell 12.
  • the light transmitted through the GH cell 12 is condensed by the rear lens group 16 and projected on the imaging surface 17 as an image.
  • the polarizing plate 11 constituting the dimmer 23 can be moved in and out of the effective optical path of the light incident on the GH cell 12. Specifically, by moving the polarizing plate 11 to the position indicated by the imaginary line, it can be out of the effective optical path of light.
  • a mechanical iris shown in FIG. 22A may be used as a means for taking the polarizing plate 11 in and out.
  • GH cell 1 and 2 As shown in the cross-sectional view in Fig. 1B, first, for example, on the outer surfaces of glass substrates 31a and 31b each having a thickness of 0.5 mm, a five-layer structure is formed as an anti-reflection film (I).
  • An ITO film having a thickness of 10 O nm is formed thereon as the transparent electrodes 32 a and 32 b by sputtering, and a pattern is formed by etching, and then a vertical liquid crystal alignment film 3 having a thickness of 75 nm is formed.
  • Patterns 3a and 33b were formed by offset printing, respectively.
  • a 1 to 2 0 order sought thickness optimum value of 3 film with a thickness of the liquid crystal alignment film (PI), first, A 1 2 0 3 the thickness of the optimum value of the film for various thickness of the liquid crystal alignment film was calculated, and the results shown in FIG. 4 were obtained.
  • the calculation method was based on the method described in “Lens Design Guide” (Sakae Takano, Photographic Industry Publishing Co., Ltd., 1993, Chapter 9 Optical Thin Film and Chromaticity). Next, for these optimal combinations, the visible light reflectance was experimentally investigated, and the results shown in FIG. 5 were obtained. From Fig.
  • the wavelength region where the reflectance exceeds 3% is minimum when the thickness of the liquid crystal alignment film is around 80 nm, and that the reflectance in the short wavelength region below 500 nm is less than the film thickness. It can be seen that the reflectance becomes minimum when the thickness is around 60 nm, and that the reflectance monotonously increases over the entire wavelength region as the thickness deviates from these values (the thickness is 20 nm, 200 nm). The reflectance at nm is shown in Fig. 4).
  • Fig. 3C Fig. 6 shows the result of optimization by changing only the anti-reflective coating (II), but Fig. 6 shows that the reflectivity is reduced by interlocking the polyimide film thickness in addition to the anti-reflective coating (II). This is the result of further optimization for
  • the surface of the liquid crystal alignment film thus formed was subjected to a rubbing treatment under the conditions set so that the pretilt angle of the liquid crystal molecules was 8 °.
  • a plastic pole (spacer) 36 with a diameter of 3.5 m is evenly sprayed, two glass substrates are aligned and stacked, and then a hot press plate is used to apply appropriate conditions (for example, 15 (0 to 170, 1 to 2 kg Z cm 2 ) Heating while applying pressure to harden the sealing material 35 around the cell and bond the substrates 31 a and 31 b .
  • the GH liquid crystal 34 is injected into the empty cell obtained by cutting the bonded substrate into individual pieces and sealing the GH cell, and the GH cell having the shape shown in FIG. 18 is completed.
  • a square wave drive pulse was applied between the electrodes of this GH cell 12 and the change in average light transmittance (in air) of visible light due to the change in pulse voltage was measured.
  • the maximum transmittance decreased from about 84% to several percent.
  • the light transmittance of about 84% when this is transparent is about 9% higher than the value of about 75% of the example of the invention of the prior application (without anti-reflection coating; the same applies hereinafter) shown by the broken line.
  • the GH cell 12 reached almost the minimum transmittance with a pulse voltage of ⁇ 5 V or more when driven by a 1 kHz rectangular wave pulse.
  • the transient response time of the light transmittance when the drive pulse voltage was changed was able to operate at a high speed of 30 ms or less in both pulse voltage modulation and pulse width modulation.
  • the thickness of the antireflection film and the thickness of the liquid crystal alignment film on the surface of the glass substrate are optimized so that the reflectance is minimized, and thus the GH cell is configured. It is possible to realize a liquid crystal light control device with a flat spectral characteristic in the visible region, which can increase the light transmittance at the time of about 9% higher than that of the prior application and can perform the light control operation at high speed over a wider dynamic range. done.
  • the anti-reflection coating was applied to the outer surfaces of the glass substrates 31 a and 31 b having a thickness of 0.5 mm, respectively.
  • Film (I) as a dielectric multilayer film having a five-layer structure M g F 2 / T i 0 2 ZM g F 2 ZT i 0 2 / M g F 2 (The thickness of each film is 2 1 2 / 16/5 3/23/115 nm).
  • a dielectric multilayer film T i 0 2 (a) / S i 0 2 , T i as a three-layer structure is formed as an anti-reflection film (II).
  • II anti-reflection film
  • 0 2 (b) the thickness of each film is 1/36 Z 20 nm.
  • An ITO film having a thickness of 100 nm is formed thereon as the transparent electrodes 32a and 32b by an ion plating method, and a pattern is formed by etching.
  • the direct liquid crystal alignment films 33a and 33b were each formed by offset printing.
  • the reflectance of visible light was experimentally examined, and the results shown in FIG. 9 were obtained. From Fig. 9, it can be seen that the wavelength region where the reflectivity exceeds 1% is minimum when the thickness of the liquid crystal alignment film is around 70 to 90 nm, and the reflectivity increases as the film thickness deviates from these values. It can be seen that ⁇ monotonically increases over the entire wavelength region (reflectance is shown in Fig. 8 when the film thickness is 10 nm and 200 nm).
  • Fig. 10 shows the optimal Ti 0 2 (a) / SiO 2 / Ti O 2 () and the reflectance at the thickness of the liquid crystal alignment film (about 80 nm). Shown in Fig. 3D shows the result of optimization by changing only the anti-reflective coating (II), but Fig. 10 shows that the polyimide film thickness is linked in addition to the anti-reflective coating (II). This is the result of further optimization for lowering the reflectance.
  • the surface of the liquid crystal alignment film thus formed was subjected to a rubbing treatment under the conditions set so that the pretilt angle of the liquid crystal molecules was 87 °.
  • a plastic ball (spacer) 36 with a diameter of 2.5 m as 24 After uniformly dispersing a plastic ball (spacer) 36 with a diameter of 2.5 m as 24, two glass substrates are aligned and stacked, and then heated under a suitable condition (for example, 15 Heat treatment while applying pressure at 0 to 170 ° C and 1 to 2 kg Z cm 2 ) to cure the sealing material 35 around the cell and bond the substrates 31 a and 31 b. .
  • a suitable condition for example, 15 Heat treatment while applying pressure at 0 to 170 ° C and 1 to 2 kg Z cm 2
  • the GH liquid crystal 34 is injected into the empty cell obtained by cutting the bonded substrate into individual pieces and sealing the GH cell, and the GH cell having the shape shown in FIG. 18 is completed.
  • a square wave drive pulse was applied between the electrodes of this GH cell 12 and the change in average light transmittance (in air) of visible light due to the change in pulse voltage was measured.
  • the maximum transmittance was reduced from about 86% to several% as shown in FIG.
  • the light transmittance of about 86% when this is transparent is about 11% higher than the value of about 75% of the example of the prior invention shown by the broken line. This, A 1 from 2 0 3 Tansomakugata value 8 4% of Example 1 by forming, is improved by about 2% further.
  • the transient response time of the light transmittance when the drive pulse voltage was changed was 15 ms or less in both pulse voltage modulation and pulse width modulation, and the high-speed operation of Example 1 or higher was possible. . This is because the gap between the opposing substrates in the GH cell was about 3.5 m in Example 1 but narrowed to about 2.5 m in Example 2.
  • the ITO film of the transparent electrode is formed by ion plating (activated evaporation), a film having a high carrier density can be formed, and the wiring resistance can be reduced.
  • the configuration and thickness of the antireflection film on the surface of the glass substrate and the thickness of the liquid crystal alignment film were optimized so that the reflectance was minimized, and the GH cell was configured.
  • the light transmittance in the transparent state can be increased by about 11% compared to the invention of the prior application, and the dimming operation can be performed at high speed in a wider dynamic range.
  • a liquid crystal light control device with flat spectral characteristics was realized.
  • FIG. 23 shows an example in which the dimming device 23 according to the above embodiment is incorporated in a CCD (Charge Coupled Device) camera.
  • CCD Charge Coupled Device
  • the third group lens 53 and the fourth group lens (for focusing) 54 corresponding to the group 16 and the CCD package 55 are arranged in this order at appropriate intervals in this order.
  • a dimming device 23 composed of the GH cell 12 and the polarizing plate 11 based on the present invention described above is provided near the third group lens 5 3 to adjust the light amount. (Light stop) on the same optical path.
  • the focus fourth-group lens 54 is arranged so as to be movable between the third-group lens 53 and the CCD package 55 along the optical path by a linear motor 57, and is also provided for zooming.
  • the second lens group 52 is disposed so as to be movable between the first lens group 51 and the dimmer 23 along the optical path.
  • the present invention has been described based on three examples.
  • the present invention is not limited to these examples, and it is needless to say that the sample structure, the materials used, the driving method of the liquid crystal cell, the form of the dimmer, and the like can be appropriately selected without departing from the gist of the invention. No.
  • PWM pulse voltage modulation
  • PWM pulse width modulation
  • the light control device of the present invention can be widely applied to various optical systems, for example, for adjusting the light amount of an electrophotographic copying machine or an optical communication device, in addition to the optical diaphragm of the image pickup device such as the CCD camera described above. It is.
  • the imaging device can be applied to a CMOS (Complementary Metal-Oxide Semiconductor) image sensor and the like.
  • CMOS Complementary Metal-Oxide Semiconductor
  • the light control device of the present invention can be applied to not only an optical filter but also a character and various image display elements for displaying an image.
  • the antireflection film is formed on the opposing substrate, reflection of visible light by the liquid crystal optical element can be effectively reduced.
  • the visible light transmittance in the transparent state can be improved as compared with the case where the positive type liquid crystal is used, and the light transmittance can be further improved by the antireflection film.
  • the optical density ratio of the liquid crystal optical element can be further increased, and the performance, image quality, and reliability of the light control device and the imaging device using the liquid crystal optical element can be improved.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal (AREA)
  • Mathematical Physics (AREA)

Abstract

L'invention concerne un dispositif d'atténuation et un dispositif d'imagerie permettant de réduire la réflexion d'une lumière incidente sur la surface d'un substrat d'un élément optique à cristaux liquides, d'améliorer la transmittance de lumière lorsqu'il est transparent, d'augmenter le rapport de densité optique d'un élément optique à cristaux liquides et d'en améliorer la performance, la qualité d'écran et la fiabilité. L'invention concerne aussi une cellule à cristaux liquides (12), contenant des cristaux liquides GH (34), utilisant des cristaux liquides négatifs en tant que matériau hôte, scellée entre deux contre-substrats (31a), (31b), dans laquelle des films antiréflexion (I) (41a), (41b), et (II) (42a), (42b), constitués de films diélectriques, sont respectivement formés sur les contre-substrats, et des films conducteurs transparents (32a), (32b) et des films d'orientation de cristaux liquides (33a), (33b) sont formés afin de sceller à l'intérieur les cristaux liquides GH (34). En conséquence, il est possible de réduire efficacement la réflexion de lumière visible lors de la production d'un élément à cristaux liquides.
PCT/JP2003/002849 2002-03-20 2003-03-11 Dispositif d'attenuation et dispositif d'imagerie WO2003079108A1 (fr)

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JP2002/77426 2002-03-20
JP2002077426A JP2003279948A (ja) 2002-03-20 2002-03-20 調光装置及び撮像装置

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WO2003079108A1 true WO2003079108A1 (fr) 2003-09-25

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Publication number Priority date Publication date Assignee Title
JP2006259566A (ja) * 2005-03-18 2006-09-28 Hitachi Displays Ltd 表示装置とその製造方法

Citations (8)

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Publication number Priority date Publication date Assignee Title
JPS544156A (en) * 1977-06-13 1979-01-12 Seiko Epson Corp Liquid crystal display device
US4266859A (en) * 1977-10-14 1981-05-12 Citizen Watch Co., Ltd. Liquid crystal display device
JPS62164021A (ja) * 1986-01-14 1987-07-20 Nippon Denso Co Ltd 液晶防眩反射鏡
JPH0398021A (ja) * 1989-09-12 1991-04-23 Toyota Motor Corp 液晶セル
JPH06301020A (ja) * 1993-04-15 1994-10-28 Sharp Corp 表示装置
JP2001100254A (ja) * 1999-09-27 2001-04-13 Kyocera Corp 液晶表示装置
EP1099976A2 (fr) * 1999-11-12 2001-05-16 Sony Corporation Dispositif de modulation spatiale de la lumière et appareil de prise de vue et procédé de commande de leurs temps d'exposition
US6288767B1 (en) * 1996-06-07 2001-09-11 Olympus Optical Company, Ltd Imaging optical system

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS544156A (en) * 1977-06-13 1979-01-12 Seiko Epson Corp Liquid crystal display device
US4266859A (en) * 1977-10-14 1981-05-12 Citizen Watch Co., Ltd. Liquid crystal display device
JPS62164021A (ja) * 1986-01-14 1987-07-20 Nippon Denso Co Ltd 液晶防眩反射鏡
JPH0398021A (ja) * 1989-09-12 1991-04-23 Toyota Motor Corp 液晶セル
JPH06301020A (ja) * 1993-04-15 1994-10-28 Sharp Corp 表示装置
US6288767B1 (en) * 1996-06-07 2001-09-11 Olympus Optical Company, Ltd Imaging optical system
JP2001100254A (ja) * 1999-09-27 2001-04-13 Kyocera Corp 液晶表示装置
EP1099976A2 (fr) * 1999-11-12 2001-05-16 Sony Corporation Dispositif de modulation spatiale de la lumière et appareil de prise de vue et procédé de commande de leurs temps d'exposition

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