JP2012137620A - Illumination device and light-scattering property controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of adjusting an exiting state of light from the illumination device, the light emitted from a light source, in a range from a direct projection state to a scattered state, and capable of controlling the light, upon radiating light in a direct projection state, to be hardly scattered regardless of an exiting angle of the light from the illumination device.SOLUTION: The illumination device includes a liquid crystal element 3, which comprises a liquid crystal/cured product composite layer containing a liquid crystal and a cured product, held between a pair of transparent substrates with electrodes, and which exhibits a light-transmitting state, a light-scattering state and an intermediate state between the light-transmitting state and the light-scattering state, in accordance with a voltage applied to the element. In the light-transmitting state, even when light from a light source 1 is obliquely incident to the liquid crystal element, the light is hardly scattered. A drive circuit 4 adjusts a voltage to be applied to the liquid crystal/cured product composite layer.

Description

  The present invention relates to an illumination device and a light scattering control device that can electrically control light scattering.

  In general, the brightness, color (color temperature), light output (hereinafter referred to as light scattering property), etc. of lighting fixtures (also called lamps) are selected depending on the environment and conditions in which lighting is used. The

  The brightness of the luminaire is selected depending on the type, size (rating and wattage), number, etc. of the light source to be installed. Moreover, if the lighting fixture provided with a light control device is selected and used, the brightness of light can be adjusted.

  The color (color temperature) of the luminaire can be adjusted, for example, by selecting a light source. If a light bulb is selected, it becomes a reddish color (color temperature) by the incandescent light of the tungsten electrode. In the case of a fluorescent lamp, the color (color temperature) of the lighting fixture can be selected from daylight color, light bulb color, and the like. In addition, since lighting fixtures having a toning function are known in LED (Light Emitting Diode) lighting, when such a lighting fixture is selected and used, the color is changed from daylight to light bulb color. You can also adjust with.

  The scattering property of light emitted from the lighting fixture can be adjusted by using a reflector such as a reflector or a cover of the lighting fixture (for example, a shade). By adjusting how light is emitted (that is, light scattering properties), it is possible to select direct light, scattered light, or the like.

  On the other hand, LED light sources, which have been commercialized in recent years, have a prismatic shape with a side of several hundreds of microns and a high-luminance glare (glare feeling). In order to alleviate this glare, it is essential to cover the material that diffuses light.

  There are examples of lighting fixtures that can adjust the brightness and color tone, but there are few methods for making the light output variable. For a flashlight, etc., a reflector (reflector, reflector) or a lens and a light source that mechanically changes the positional relationship to change the light collecting property. For light scattering, a diffuser (light scattering plate) is attached.・ There are some that can be switched by removal, movement, etc., but there are few that can adjust the light scattering property.

  An attempt to adjust the light scattering property of LED illumination is described in Patent Document 1. In the method described in Patent Document 1, a polymer dispersion type liquid crystal dimming shutter is provided on the light emission side from the light emitting diode, and the light scattering characteristic of the liquid crystal dimming shutter is used to emit strong light from the light emitting diode. It is tempered.

JP 2010-27586 A (paragraph 0008, FIGS. 1 and 2)

  However, in the polymer dispersion type liquid crystal shutter described in Patent Document 1, it is common to use a dispersion of particulate domains composed of liquid crystal in a resin, as shown in FIG. Usually, the light scattering state occurs when no voltage is applied (see FIG. 12).

  The polymer-dispersed liquid crystal shutter described in Patent Document 1 has a refractive index of liquid crystal and surrounding resin viewed from the electric field direction by applying a voltage to control the liquid crystal alignment axis in the dispersed particles in one direction. Are substantially equal, and light incident in a direction that coincides with the direction of the electric field is not reflected at the interface between the liquid crystal and the resin, and is transparent when viewed from the direction of the electric field. However, when the voltage is applied, the refractive indexes of the liquid crystal and the resin do not match when viewed from a direction that does not match the electric field direction, so that light incident in a direction that does not match the electric field direction is reflected and refracted at the interface between the liquid crystal and the resin. Therefore, when the liquid crystal light control shutter is viewed from an oblique direction, it looks like a light scattering state (see FIG. 13). In the polymer-dispersed liquid crystal shutter described above, light incident obliquely on the shutter out of light from a point light source such as an LED is scattered and its directivity cannot be used effectively.

  Further, in the polymer dispersion type liquid crystal shutter described in Patent Document 1, since the phosphor is dispersed in the liquid crystal, this also scatters the light from the light source, and the direct light property of the light source is effectively used. Can not.

  As described above, illumination (LED illumination) using an LED as a light source has a glare feeling (glare feeling) of a point light source when light from the light source directly enters the eyes. For general lighting applications, measures such as providing a cover with an appropriate light scattering material are taken in order to alleviate this glare. However, for example, when it is desired to brightly illuminate the hand where the work is performed, it may be desired to take out strong light directly from the LED.

  If it is possible to adjust the light scattering property with the LED illumination, if you want to increase the contrast of the irradiated object and see a fine thing, you can directly use the light emitted from the LED chip as it is, Or, when watching television, etc., when the strong reflection from the surface to be irradiated is disliked, the light application from the LED chip is scattered and used.

  In other words, in LED lighting, if the light scattering property is variable and can be adjusted arbitrarily, direct light is extracted from the lighting fixture as described above, giving a strong contrast ratio, strong shadow to the object to be illuminated, or scattering light. It can be taken out and softened light can weaken shadows and illuminate a wide area.

  Furthermore, if it is used for an LED light source with a dimming function or a toning function, brightness and color can be controlled in addition to scattering. Note that the light source is not necessarily an LED, but may be a light source having a point-like shape such as a light bulb or an arc sphere, and can be applied to any other lighting device for adjusting the light scattering property.

  Therefore, the present invention can adjust how the light emitted from the light source is emitted from the illumination device between the direct-light state and the scattering state. Further, when the light in the direct-light state is irradiated, the light is emitted from the illumination device. It is an object of the present invention to provide an illumination device and a light scattering control device that are difficult to scatter regardless of the emission angle.

  The lighting device according to the present invention includes at least one light source and a liquid crystal / polymer composite layer sandwiched between a pair of transparent substrates with electrodes, and in a light transmission state and a light scattering state depending on an applied voltage. And a liquid crystal element that takes an intermediate state between a light transmission state and a light scattering state, and is less likely to scatter even when light from a light source is incident from an oblique direction in the transmission state, and a liquid crystal / polymer composite And a drive circuit for adjusting a voltage applied to the layer.

  The liquid crystal element is formed by curing a composition having a total amount of the curable compound of 0.1% by mass or more and 20% by mass or less with respect to the composition containing the liquid crystal and a curable compound soluble in the liquid crystal. It is desirable that

  In addition to the above features, the illumination device according to the present invention may include a reflecting mirror (or a reflective shade) around the light source so that light from the light source is efficiently incident on the liquid crystal element.

  In the lighting device according to the present invention, it is desirable to use an LED or a light source having a light emitting portion volume smaller than that of a fluorescent lamp such as an incandescent bulb or an arc bulb.

  The light scattering control device according to the present invention includes a liquid crystal / polymer composite layer sandwiched between a pair of transparent substrates with electrodes, and a light transmission state, a light scattering state, and a light transmission state according to the applied voltage. The voltage applied to the liquid crystal / polymer composite layer, which takes an intermediate state between the light scattering state and the light scattering state, and is difficult to scatter even when light from the light source is incident in an oblique direction And a drive circuit for adjusting the frequency.

  According to the present invention, the scattering property of light emitted from the light source can be adjusted between the direct-light state and the scattering state. Further, when the light in the direct-light state is irradiated, the light does not depend on the emission angle from the illumination device. Difficult to scatter.

The block diagram which shows embodiment of the illuminating device by this invention. 1 is a schematic cross-sectional view showing a liquid crystal element according to the present invention. Explanatory drawing which illustrates the curable compound which can be used for the liquid crystal element by this invention. Explanatory drawing which shows the transmittance | permeability with respect to the applied voltage (effective value) of the liquid crystal element by this invention. Explanatory drawing which shows the structural example of a schlieren type | system | group optical system measuring device. Explanatory drawing which shows the example of the integrating sphere utilized when measuring total transmittance. Explanatory drawing which shows the state of the light irradiated according to the state of the liquid crystal element by this invention. Explanatory drawing which shows the example of the apparatus which evaluates the incident angle dependence of the transmittance | permeability in a transmissive state. Explanatory drawing which shows the example of the relative transmittance | permeability calculated for every angle. The block diagram which shows the modification of the illuminating device by this invention. Explanatory drawing which shows the state of the light irradiated according to the state of the liquid crystal element by this invention. Explanatory drawing which shows the operation principle at the time of scattering of a general polymer dispersion type liquid crystal element. Explanatory drawing which shows the operation principle at the time of permeation | transmission of a general polymer dispersion type liquid crystal element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a lighting device according to the present invention. An illuminating device 10 illustrated in FIG. 1 includes an LED 1 serving as a light source and a substantially dome-shaped reflecting mirror 2 that reflects light emitted from the LED 1. There is provided a liquid crystal element 3 that can be in a light transmission state and a light scattering state depending on whether or not a voltage is applied to the transparent electrode based on the above signal. A driving circuit 4 is connected to the liquid crystal element 3. Hereinafter, the liquid crystal element 3 and the drive circuit 4 are collectively referred to as a light scattering control device.

  Moreover, in the example shown in FIG. 1, LED1 is arrange | positioned in the center of a substantially dome-shaped reflective mirror. That is, at the same time that the light from the LED 1 is directly incident on the liquid crystal element 2, the light emitted in the direction of the substantially dome-shaped reflector is reflected and incident on the liquid crystal element 2, and can be used effectively as illumination. The LED 1 may be one LED or a plurality of LEDs. Hereinafter, this embodiment demonstrates the case where LED1 is one LED.

  In the liquid crystal element 3, a transparent electrode is formed in a region controlled to a light scattering state. The transparent electrode is driven by the drive circuit 4. Specifically, the drive circuit 4 sets a predetermined potential on the transparent electrode. The drive circuit 4 is realized by a driver or the like that controls the potential of the electrode. Note that the voltage applied by the drive circuit 4 is adjusted according to the situation by a user or the like, for example.

  FIG. 2 is a schematic cross-sectional view showing a configuration example of the liquid crystal element 3 in the lighting device 10. In FIG. 2, transparent electrodes 102 and 107 are provided on opposing surfaces of the pair of substrates 101 and 108. Further, alignment films 103 and 106 are provided on the inner side. A liquid crystal layer 104 containing liquid crystal and having a thickness controlled by a spacer (not shown) is sandwiched between the alignment films 103 and 106. Then, the liquid crystal layer 104 is sealed by the seal layer 105.

  The materials of the substrates 101 and 108 are not particularly limited as long as transparency can be secured. As the substrates 101 and 108, glass substrates or plastic substrates can be used. Further, the shape of the liquid crystal element 3 does not have to be planar, and may be curved.

  Further, as the transparent electrodes 102 and 107 provided on the substrates 101 and 108, a transparent electrode material such as a metal oxide such as ITO (indium oxide-tin oxide) can be used. Hereinafter, the substrates 101 and 108 provided with the transparent electrodes 102 and 107 are referred to as substrates with electrodes.

  The liquid crystal layer 104 capable of taking a light transmission state and a light scattering state is a composition containing a liquid crystal and a curable compound soluble in the liquid crystal (hereinafter, an uncured composition) between a pair of transparent substrates with electrodes. A liquid crystal layer formed by curing a curable compound using means such as heat, ultraviolet rays, or an electron beam. Hereinafter, a liquid crystal composed of a composite of such a liquid crystal and a curable compound is also referred to as a liquid crystal / polymer composite. By using such an uncured composition, the haze value can be kept low when viewed from the oblique direction as well as the front direction when in the transmissive state.

  The liquid crystal used in the liquid crystal / polymer composite may have either positive or negative dielectric anisotropy, but in order to shorten the response time required for switching between the transmission state and the light scattering state, the viscosity of the liquid crystal is low. It is preferable to use a liquid crystal having a negative dielectric anisotropy. A compound that is not curable is used as the liquid crystal. Moreover, the curable compound may have liquid crystallinity.

  In the case where a liquid crystal having a negative dielectric anisotropy is used, in the substrate with electrodes, a treatment is performed so that the pretilt angle of liquid crystal molecules is 60 degrees or more with respect to the substrate surface on the side in contact with the liquid crystal layer 104 When applied, orientation defects can be reduced and transparency is improved, which is preferable. In this case, the rubbing process may not be performed. The pretilt angle is more preferably 70 degrees or more. The pretilt angle is defined as 90 degrees in the direction perpendicular to the substrate surface.

  The liquid crystal constituting the liquid crystal / polymer composite forming the liquid crystal layer 104 can be appropriately selected from known liquid crystals. By using a substrate with an electrode that can control the pretilt angle of the uncured composition by the alignment films 103 and 106, a liquid crystal having a positive dielectric anisotropy and a liquid crystal having a negative dielectric anisotropy can be used. However, a liquid crystal having negative dielectric anisotropy is preferable in terms of higher transparency and response speed. The alignment film can also be rubbed. In order to reduce the driving voltage, it is preferable that the absolute value of dielectric anisotropy is large.

  Further, the curable compound constituting the liquid crystal / polymer composite preferably has transparency. Furthermore, it is preferable that the liquid crystal and the curable compound are separated so that only the liquid crystal responds when a voltage is applied after curing, because the driving voltage can be lowered.

  In the present invention, among the curable compounds that can be dissolved in the liquid crystal, the alignment state of the mixture of the liquid crystal and the curable compound when uncured can be controlled, and high transparency can be maintained when cured. A curable compound is used.

Examples of the curable compound include a compound of formula (1) and a compound of formula (2).
A ¹ —O— (R ¹ ) _m —O—Z—O— (R ² ) _n O—A ² Formula (1)
A ^3- (OR ³ ) _o —O—Z′—O— (R ⁴ O) _p —A ⁴ ... (2)

Here, each of A ¹ , A ² , A ³ , and A ⁴ is independently an acryloyl group, methacryloyl group, glycidyl group, or allyl group that becomes a curing site, and R ¹ , R ² , R ³ , R Each of ⁴ is independently an alkylene group having 2 to 6 carbon atoms, each of Z and Z ′ is independently a divalent mesogenic structure, and each of m, n, o, and p Is independently an integer from 1 to 10. Here, “independently” means that the combination is arbitrary and any combination is possible.

Molecular motion including R ¹ , R ² , R ³ , R ⁴ between the mesogenic structures Z, Z ′ and the cured sites A ¹ , A ² , A ³ , A ^{4 in the} formulas (1) and (2) By introducing a highly functional oxyalkylene structure, the molecular mobility of the cured site can be improved during the curing process during curing, and it can be sufficiently cured in a short time.

The curing sites A ¹ , A ² , A ³ , and A ⁴ in the formulas (1) and (2) may be any functional group as long as they can be photocured or thermally cured. It is preferable that it is an acryloyl group and a methacryloyl group suitable for photocuring.

The carbon number of R ¹ , R ² , R ³ and R ⁴ in formula (1) and formula (2) is preferably 1 to 6 from the viewpoint of molecular mobility, and an ethylene group having 2 carbon atoms and 3 carbon atoms. The propylene group is more preferable.

  Examples of the mesogen structure parts Z and Z ′ in the formulas (1) and (2) include polyphenylene groups in which 1,4-phenylene groups are linked. A part or all of the 1,4-phenylene group may be substituted with a 1,4-cyclohexylene group. In addition, some or all of the hydrogen atoms of the 1,4-phenylene group or the substituted 1,4-cyclohexylene group are substituted with alkyl groups having 1 to 2 carbon atoms, halogen atoms, carboxyl groups, alkoxycarbonyl groups, or the like. It may be substituted with a group.

  As preferable mesogen structure parts Z and Z ′, a biphenylene group in which two 1,4-phenylene groups are linked (hereinafter, a biphenylene group in which two 1,4-phenylene groups are linked is also referred to as a 4,4-biphenylene group). Examples include three linked terphenylene groups, and 1 to 4 of these hydrogen atoms substituted with an alkyl group having 1 to 2 carbon atoms, a fluorine atom, a chlorine atom, or a carboxyl group. Most preferred is a 4,4-biphenylene group having no substituent. All the bonds between 1,4-phenylene groups or 1,4-cyclohexylene groups constituting the mesogenic structure may be single bonds or any of the following bonds.

  M, n, o, and p in Formula (1) and Formula (2) are each independently preferably 1 to 10, and more preferably 1 to 4. This is because if it is too large, the compatibility with the liquid crystal is lowered and the transparency of the electro-optical element after curing is lowered.

  FIG. 3 shows examples of curable compounds that can be used in the present invention. The composition containing a liquid crystal and a curable compound may contain a plurality of curable compounds including the curable compounds represented by the formulas (1) and (2). For example, when the uncured composition contains a plurality of curable compounds having different m, n, o, and p in the formulas (1) and (2), the compatibility with the liquid crystal may be improved. is there.

  The composition containing a liquid crystal and a curable compound may contain a curing catalyst. In the case of photocuring, a photopolymerization initiator generally used for photocurable resins such as benzoin ether, acetophenone, and phosphine oxide can be used. In the case of thermosetting, a curing catalyst such as peroxide, thiol, amine, or acid anhydride can be used depending on the type of curing site, and if necessary, a curing aid such as amines can be added. It can also be used.

  The content of the curing catalyst is preferably 20% by weight or less of the curable compound to be contained, and more preferably 0.1 to 5% by weight when a high molecular weight or high specific resistance of the cured resin is required after curing. .

  The total amount of the curable compound is preferably 0.1 to 20% by mass with respect to the uncured composition. If it is less than 0.1% by mass, the liquid crystal layer cannot be divided into domain structures having an effective shape by the curable compound, and desired transmission-scattering characteristics cannot be obtained. On the other hand, if it exceeds 20% by mass, the haze value in the transmissive state tends to increase as in the case of a general polymer dispersed liquid crystal element. More preferably, the content of the curable compound in the uncured composition is 0.5 to 15% by mass, the scattering intensity in the light scattering state is high, and the voltage value at which transmission-scattering is switched is low. Can do.

  As a processing method for aligning liquid crystal molecules so that the pretilt angle is 60 degrees or more with respect to the substrate surface, there is a method using a vertical alignment agent. As a method using a vertical alignment agent, for example, a method using a surfactant, a method of treating a substrate interface with a silane coupling agent containing an alkyl group or a fluoroalkyl group, or SE1211 or JSR manufactured by Nissan Chemical Industries, Ltd. There is a method using a commercially available vertical alignment agent such as JALS-682-R3 manufactured by the company. In order to create a state in which the liquid crystal molecules are tilted in an arbitrary direction from the vertical alignment state, any known method may be adopted. The vertical alignment agent may be rubbed. Alternatively, a method may be employed in which a slit is provided in the transparent electrodes 101 and 107 or a triangular prism is disposed on the electrodes 101 and 107 so that the voltage is applied obliquely to the substrates 101 and 108. Further, it is not necessary to use means for tilting the liquid crystal molecules in a specific direction.

  The thickness of the liquid crystal layer 104 between the two substrates 101 and 108 can be defined by a spacer or the like. The thickness is preferably 1 to 50 μm, more preferably 3 to 30 μm. If the thickness of the liquid crystal layer 104 is too thin, the contrast is lowered, and if it is too thick, the driving voltage tends to increase, which is not preferable in many cases.

  Any known material can be used as the sealing layer 105 as long as it is a highly transparent resin. If a highly transparent resin is used, the transparency of the liquid crystal element can be enhanced over the entire surface.

  The liquid crystal element 3 manufactured as described above can realize a very fast response speed with a response time between the light transmission state and the light scattering state being shorter than 5 ms. In addition, the viewing angle dependency is better than a transmission scattering mode by a general polymer dispersion type liquid crystal element, and a very good transmission state can be obtained even when viewed from an oblique direction. it can. For example, when the above-mentioned liquid crystal / polymer composite is used, it is possible to make almost no haze even when viewed at an angle of 40 degrees from the vertical.

  As the size of the liquid crystal element 3, any size can be used, including one having a diagonal length of about 1 cm to about 3 m.

  In the lighting device 10, a plurality of liquid crystal elements 3 may be used. Further, in order to increase the impact resistance against the liquid crystal element 3, the upper and lower substrates 101 and 108 may be fixed.

It is preferable to provide an antireflection film or an ultraviolet blocking film on the front and back surfaces of the liquid crystal element 3. For example, by applying AR coating (low reflection coating) made of a dielectric multilayer film such as SiO ₂ or TiO _{2 on} the front and back of the liquid crystal element 3, the reflection of external light on the substrate surface can be reduced, and the contrast Can be further improved.

  In the liquid crystal element 3 described above, when a potential is set in the transparent electrodes 102 and 107, a voltage corresponding to the potential difference is applied to the liquid crystal between the transparent electrodes. FIG. 4 is an explanatory diagram showing the transmittance with respect to the applied voltage (effective value) of the liquid crystal element 3 manufactured as described above.

  The solid line of the graph illustrated in FIG. 4 shows the result of measuring the voltage dependency of the transmittance of the liquid crystal element 3 used in the present invention with a Schlieren optical system having a condensing angle of 5 °. Moreover, the broken line of the graph illustrated in FIG. 4 shows the result of measuring the total transmittance of the liquid crystal element 3 used in the present invention. Here, a method for measuring each transmittance illustrated in FIG. 4 will be described.

  FIG. 5 is an explanatory diagram illustrating a configuration example of a schlieren optical system measuring instrument. The solid line in the graph illustrated in FIG. 4 is a voltage-dependent change in transmittance in a schlieren optical system with a collection angle of 5 °, measured using the measuring device illustrated in FIG.

  Specifically, by calculating the ratio T / T0 between the light intensity T0 when the liquid crystal element (hereinafter, also referred to as a sample) is in the transmissive state and the light intensity T when the liquid crystal element is not in the transmissive state, Measure the degree of scattering. In this measurement, the light intensity measured without putting a sample is T0.

  In the schlieren-type optical system measuring instrument illustrated in FIG. 5, the light emitted from the light source is collimated by Lens 1 and is scattered when the light passes through the sample. Light diffused to a scattering angle of 5 ° (± 2.5 °) or more is blocked by the aperture and does not reach the detector. That is, in this measurement method, light with a scattering angle of 5 ° or more out of the light scattered by the sample does not enter the detector, so that the transmittance decreases when the degree of scattering is large.

  As a result of measuring the transmittance in the transmissive state of the liquid crystal element in the present invention (that is, no voltage application), the reflection at the interface between the air and the glass on the two surfaces of the two glass substrates, the reflection at the interface between the glass and the liquid crystal material, and the liquid crystal material The transmittance was 83% due to the influence of absorption due to the above. From this state, when the voltage value of the liquid crystal element is increased by a rectangular wave with a driving frequency of 200 Hz, light scattering occurs from the applied voltage of 10V, and the scattering characteristics are almost saturated at 40V.

  As described above, the liquid crystal element 3 enters a light scattering state when a predetermined voltage (for example, 60 V) is applied to the liquid crystal layer 104 that can be in a light transmission state and a light scattering state. On the other hand, when no voltage is applied, the light is transmitted. Further, when the applied voltage (effective value) is an intermediate value between 0 V and 60 V (for example, about 18 V to 35 V), the liquid crystal element 3 is in an intermediate state between a light transmission state and a light scattering state ( Intermediate state).

  FIG. 6 is an explanatory diagram showing an example of an integrating sphere used when measuring the total transmittance. The broken line in the graph illustrated in FIG. 4 is the total light transmittance of the liquid crystal element according to the present invention, measured using the measuring device illustrated in FIG.

  In the measuring method using the integrating sphere illustrated in FIG. 6, the measuring window of the integrating sphere for visible light is brought into contact with the light exit surface of the liquid crystal element, and all the light transmitted through the liquid crystal element is guided to the detector, so that the total transmission is achieved. Measure the rate. Here, the total transmittance is defined as a ratio T / T0 between the transmittance T0 when measured without a liquid crystal element and the light intensity T when not in the transmissive state.

  As shown in FIG. 4, in the liquid crystal element 3 according to the present invention, a slight decrease in the total light transmittance is observed due to voltage application, but most of the light incident on the liquid crystal element is emitted to the front surface of the element. Recognize. From the above, as shown in FIG. 4, the liquid crystal element according to the present invention can control the light scattering property by the applied voltage and can increase the total light transmittance.

  In the following description, a case will be described in which a liquid crystal element 3 that enters a light scattering state when a predetermined voltage is applied and enters a light transmission state when no voltage is applied is used. However, as the liquid crystal element 3, an element that enters a light transmission state when a predetermined voltage is applied and enters a light scattering state when no voltage is applied may be used. Further, the timing of applying a voltage to the liquid crystal element 3 (more specifically, the liquid crystal layer 104) and the timing of applying no voltage need not be linked with the timing of turning on the LED 1.

  FIG. 7 is an explanatory diagram showing the state of light irradiated according to the state of the liquid crystal element 3. When the liquid crystal element 3 is in a light transmission state, as illustrated in FIG. 7A, the light emitted from the LED 1 is almost transmitted through the liquid crystal element 3 as it is and is irradiated as strong light that travels straight. On the other hand, when the liquid crystal element 3 is in the light scattering state, as illustrated in FIG. 7B, the light emitted from the LED 1 is scattered by the liquid crystal element 3 and irradiated as light that has been softened.

  Next, a feature that light scattering is small when the liquid crystal element is in a transmissive state will be described. Specifically, light scattering can be reduced even when light from a light source is incident on the liquid crystal element of the present invention at an angle rather than perpendicularly. That is, in the liquid crystal element according to the present invention, even when light from the light source is incident from an oblique direction in the transmissive state, the light is not easily scattered.

  In order to explain that there is little light scattering in the transmissive state, a variable angle measuring device was attached to a spectrophotometric system SolidSpec-3700DUV manufactured by Shimadzu Corporation, and the angle dependence of the transmission characteristics of the liquid crystal element was measured. FIG. 8 is an explanatory diagram illustrating an example of an apparatus that evaluates the incident angle dependency of the transmittance in the transmissive state. The liquid crystal element of the present invention is in a transparent state in which no voltage is applied, and a general polymer dispersion type liquid crystal element is in a transparent state in which a voltage of 200 Hz and 30 V is applied. Arranged. Thereafter, each element was measured by irradiating light with a wavelength of 540 nm.

  Specifically, first, an element in a transmission state is arranged with an angle φ = 0 ° between the normal direction of the element and incident light, and from this state, the element is rotated so as to increase the angle φ, and spectroscopic measurement is performed. It was. Then, relative transmittance T / To was calculated by assuming that the transmittance of the device front (φ = 0 °) at a wavelength of 540 nm was To, and T was the transmittance when the device was rotated to have each angle. FIG. 9 is an explanatory diagram illustrating an example of the relative transmittance calculated for each angle.

  As illustrated in FIG. 9, in the liquid crystal element of the present invention, a high transmittance of about 90% or more is maintained even when the light incident angle φ is tilted to about 60 °, whereas it is general. In such a polymer-dispersed liquid crystal element, a decrease in relative transmittance T / To is observed when the incident angle of light becomes φ = 20 ° or more. Further, when the incident angle is 60 °, the polymer dispersed liquid crystal element has a relative transmittance reduced to about 50% even in the transmissive state. This indicates that even when the polymer-dispersed liquid crystal is in a transmissive state, as the incident angle of light becomes oblique, scattering increases and the transmittance decreases.

  For general polymer dispersion type liquid crystal, when the liquid crystal molecules are aligned in the electric field direction when a voltage is applied, the polymer material is selected so that the refractive index of the liquid crystal matches the refractive index of the surrounding cured product in the electric field direction. Is done. On the other hand, when viewed from the direction perpendicular to the electric field direction, since the polymer material is optically isotropic, the refractive index does not change at all from the voltage application direction, but the voltage is applied and the polymer material is oriented in the electric field direction. Since the liquid crystal molecules have refractive index anisotropy, the liquid crystal molecules exhibit a refractive index different from the electric field direction. Therefore, in the direction different from the electric field direction when a voltage is applied, a difference in refractive index between the polymer material and the liquid crystal material always occurs, and scattering and reflection occur at the interface between the liquid crystal and the polymer, so light is inevitably scattered. The

  On the other hand, the liquid crystal element in the present invention cures the liquid crystal layer by reducing the total amount of the curable compound to 0.1 to 20% by mass, more preferably 0.5 to 15% by mass with respect to the uncured composition. The object can be divided into domain structures having a shape effective for obtaining desired transmission / scattering characteristics, and at the same time, the interface between the liquid crystal and the cured product is reduced. As a result, unlike conventional liquid crystal / polymer composites, the light transmission can be made almost unchanged even when the incident angle of light is changed in the transmission state. Specifically, the liquid crystal element of the present invention can maintain a relative transmittance of at least 90% or more even when the incident angle is 60 °. That is, a general polymer-dispersed liquid crystal element appears cloudy (scatters light) as viewed from an oblique direction even in a transmission state, whereas the liquid crystal element according to the present invention is a light source. Direct light (direct directivity) can be used effectively.

  As described above, by using the light scattering control device according to the present invention, it is possible to adjust the light output from the lighting fixture, in particular, the light scattering property. Specifically, in the polymer dispersed liquid crystal element, it has been difficult to effectively use the direct directivity of the light source. However, by incorporating the light scattering control device of the present invention, from which direction the light scatters. It was possible to adjust in a wide range from almost no state to widely scattered state. Therefore, it is possible to transmit light more clearly from the light source when transmitting light, and to increase the scattering property and to increase the total transmittance when scattering light.

  Next, a modification of this embodiment will be described. FIG. 10 is a block diagram showing a modification of the lighting device according to the present invention. The illuminating device 20 illustrated in FIG. 10 includes a plurality of LEDs 1 as light sources, a substantially U-shaped reflecting mirror 2 that reflects light emitted from the LEDs, and light is provided in front of the opening of the reflecting mirror 2. A liquid crystal element 3 that can be in a transmission state and a light scattering state is provided. A driving circuit 4 is connected to the liquid crystal element 3. In the example shown in FIG. 10, the plurality of LEDs 1 are respectively disposed on the bottom surface of the substantially U-shaped reflecting mirror 2.

  FIG. 10A shows an example of a locus of light rays emitted from the LED 1 when the liquid crystal element is in a light transmission state. A thick arrow extending leftward from the LED 1 indicates light traveling straight from the LED 1, and an arrow indicated by a solid line indicates light other than the straight light emitted from the LED 1. FIG. 10B shows an example of a locus of light rays emitted from the LED 1 when the liquid crystal element is in a light scattering state. The light that has passed through the liquid crystal element is roughly scattered as indicated by a broken line.

  FIG. 11 is an explanatory diagram showing the state of light irradiated according to the state of the liquid crystal element 3. When the liquid crystal element 3 is in a light transmission state, as illustrated in FIG. 11A, light emitted from each of the plurality of LEDs 1 is directly transmitted through the liquid crystal element 3 and irradiated as strong light that travels straight. . On the other hand, when the liquid crystal element 3 is in the light scattering state, as illustrated in FIG. 10B and FIG. 11B, the light emitted from the plurality of LEDs 1 is respectively scattered and moderated by the liquid crystal element 3. Irradiated as light. Furthermore, in this case, since a plurality of lights having a concentric gradation centering on each LED are irradiated, it is possible to further enhance the aesthetics when viewed.

  FIG. 11 illustrates the case where all the light emitted from the plurality of LEDs 1 is scattered by the liquid crystal element 3, but only the light emitted from some LEDs 1 is scattered by the liquid crystal element 3. May be. In this case, in the liquid crystal element 3, a transparent electrode formed as a region controlled to a light scattering state is a range through which light emitted from the LED 1 passes (more specifically, a range through which light emitted from each LED 1 passes. For example).

  In this case, the light emitted from some of the LEDs 1 is always used as light that goes straight, and the light emitted from the other LEDs 1 can be used by changing according to the situation.

  As described above, in this modification, the liquid crystal element 3 is formed with electrodes in a range through which light emitted from the LED 1 passes. Specifically, an electrode is formed for each range through which light emitted from each LED 1 passes. Then, the drive circuit 4 applies a voltage to the liquid crystal layer between the electrodes by setting a potential on the electrodes. Therefore, in addition to the effects of the above-described embodiment, the liquid crystal element 3 can individually control the scattering of light emitted from a plurality of light sources, and thus can enhance the aesthetics when viewed.

  The present invention is preferably applied to an illumination device that can electrically control light scattering.

1 LED
DESCRIPTION OF SYMBOLS 2 Reflector 3 Liquid crystal element 4 Drive circuit 101,108 Glass substrate 102,107 Transparent electrode 103,106 Alignment film 104 Liquid crystal layer 105 Sealing layer

Claims (5)

At least one light source;
The liquid crystal / polymer composite layer is sandwiched between a pair of transparent substrates with electrodes, and is in an intermediate state between a light transmission state, a light scattering state, a light transmission state, and a light scattering state, depending on the applied voltage. A liquid crystal element that is less likely to scatter even when light from the light source is incident from an oblique direction in the transmission state;
And a driving circuit for adjusting a voltage applied to the liquid crystal / polymer composite layer. The liquid crystal element is obtained by curing a composition in which the total amount of the curable compound is 0.1% by mass or more and 20% by mass or less with respect to a composition containing a liquid crystal and a curable compound soluble in the liquid crystal. The lighting device according to claim 1 formed. The illumination device according to claim 1, further comprising a reflecting mirror around the light source. The illuminating device according to any one of claims 1 to 3, wherein the light source is an LED or a light source having a light emitting unit volume smaller than that of a fluorescent lamp. The liquid crystal / polymer composite layer is sandwiched between a pair of transparent substrates with electrodes, and is in an intermediate state between a light transmission state, a light scattering state, a light transmission state, and a light scattering state, depending on the applied voltage. A liquid crystal element that is less likely to scatter even when light from a light source is incident from an oblique direction in the transmission state;
A light scattering control device comprising: a drive circuit that adjusts a voltage applied to the liquid crystal / polymer composite layer.

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