JP2010048907A - Lighting device using voltage control type liquid crystal filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device that uses a voltage control type liquid crystal filter, in which tones are quickly changed and safeness is improved. <P>SOLUTION: The lighting device 10 includes a light source 19 and a voltage control type liquid crystal filter 11. The filter 11 comprises filter substrates 12 each having a transparent substrate 121, a transparent electrode 122 disposed thereon, and an alignment layer 123 further disposed thereon, stacked with the alignment layers 123 opposing to each other, and a liquid crystal 14 mixed with a dye 13 and filling the gap between the alignment layers 123. The filter 11 has a resistance part 15 that releases charges accumulated in the filter 11. Thereby, charges accumulated in the filter 11 are discharged by the resistance part 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illuminating device using a voltage-controlled liquid crystal filter in which liquid crystals containing dichroic dyes having different absorption spectral characteristics are filled between transparent substrates with transparent electrodes and color-adjusted by voltage applied to the transparent electrodes About.

  Conventionally, in an illuminating device including an optical filter and a light source, as an optical filter, a liquid crystal mixed with dichroic dyes having different absorption spectral characteristics according to a wavelength region and a molecular arrangement is provided with a transparent electrode. A device using a liquid crystal cell sandwiched between transparent substrates is known (see, for example, Patent Document 1). FIG. 5 shows the configuration of the optical filter of such an illumination device. The optical filter 50 includes a polarizing filter 51 and at least one liquid crystal cell 52a, 52b. The liquid crystal cells 52a, 52b sandwich a liquid crystal 54 mixed with a dichroic dye 53 (hereinafter referred to as a dye). The transparent substrate 56 with the transparent electrode 55 juxtaposed to each other is provided. The liquid crystal 54 and the dye 53 are aligned according to the drive voltage applied to the transparent electrode 55 from the control circuit 57, and the molecular arrangement of the dye 53 changes. Therefore, the incident light 58 on the optical filter 50 is used as illumination light 59 in which the color temperature is controlled. The liquid crystal cells 52a and 52b are voltage control type liquid crystal filters that are toned and controlled by a drive voltage.

However, unlike the so-called liquid crystal shutters, the liquid crystal cells 52a and 52b as described above are formed by one continuous transparent electrode 55 and have a large size (diagonal length) as one cell, for example, about 125 mm. Therefore, the voltage-controlled liquid crystal cells 52a and 52b have a large capacitor component, and when the drive voltage to be applied is switched, charges remain in the transparent electrode 55, and the switching of toning is delayed. Further, when only the liquid crystal cells 52a and 52b are removed during the operation of the control circuit 57, the state in which charges are charged in the large capacitor components is maintained, which is unsafe.
JP 2004-61828 A

  The present invention solves the above-described problem, and an object of the present invention is to speed up switching of toning and improve safety in an illumination device using a voltage-controlled liquid crystal filter.

  In order to achieve the above object, the invention according to claim 1 provides a substrate for a filter having a transparent substrate, a transparent electrode provided on the transparent substrate, and an alignment film provided on the transparent electrode. A voltage-controlled liquid crystal filter formed by filling a liquid crystal mixed with a dye in a gap between the alignment films, and a light source, and the light from the light source is the voltage-controlled liquid crystal In the lighting device that is toned and controlled by a filter, the voltage-controlled liquid crystal filter includes a resistance unit that discharges charges charged in the filter.

  According to a second aspect of the present invention, in the illumination device according to the first aspect, the resistance portion is disposed between the opposing transparent electrodes.

  According to the first aspect of the present invention, since the charge charged in the voltage-controlled liquid crystal filter is discharged by the resistance portion, the period during which the charge remains is shortened, and the toning switching is accelerated. Moreover, since the electric charge is reliably discharged, safety is improved.

  According to the invention of claim 2, since the resistance portion is disposed between the transparent electrodes, it is possible to easily set a resistance corresponding to the capacitor of the transparent electrode of the voltage controlled liquid crystal filter.

(First embodiment)
A lighting device 10 according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1A shows the lighting device 10 of the present embodiment, and FIG. 1B shows the electrical connection of a voltage-controlled liquid crystal filter 11 (hereinafter referred to as a filter) of the lighting device 10, and FIG. c) shows a cross-sectional configuration of the filter 11. As shown in FIG. 1A, the illumination device 10 includes a filter 11 and a light source 19. The light source 19 is lit with electric power such as alternating current or direct current. The filter 11 is disposed so that light from the light source 19 passes through the filter 11. As shown in FIG. 1B, the filter 11 has a pair of filter substrates 12. As shown in FIG. 1C, the filter substrate 12 includes a transparent substrate 121, a transparent electrode 122 provided on the transparent substrate 121, and an alignment film 123 provided on the transparent electrode 122. In the filter 11, the filter substrate 12 is overlapped so that the alignment films 123 face each other, and the liquid crystal 14 in which the pigment 13 is mixed is filled in the gap between the spacer 16 and the alignment film 123. The filter 11 includes a resistance unit 15 that discharges the electric charge charged in the filter 11.

  The transparent substrate 121 is a substrate made of a light-transmitting insulator or the like, for example, a glass substrate. The transparent electrode 122 is an electrode that generates an electric field that adjusts the alignment of the liquid crystal 14, and for example, indium tin oxide is used. The alignment film 123 is a thin film made of a resin or the like, and an alignment process for aligning the liquid crystal 14 is performed on the surface thereof. The alignment process is, for example, a rubbing process in which a roller-shaped resin fiber is rubbed in one direction on the alignment film 123. The gap between the facing alignment films 123 is set by the outer peripheral spacer 16 together with spacer particles and columns (not shown) dispersed in the gap. The transparent electrode 122 has electrode pins 17a and 17b at its ends, and is connected to the control circuit 18 via the electrode pins 17a and 17b. The control circuit 18 is an electric circuit for controlling the color of the filter 11, and includes a control power source 181 that supplies a drive voltage to the transparent electrode 122 and a switch SW that turns on and off the application of the drive voltage.

  The dye 13 is a dichroic dye having different absorption spectral characteristics depending on the wavelength range and molecular arrangement, has an absorption peak due to a unique molecular structure, and has continuous absorption spectral characteristics from a long wavelength range to a short wavelength range. And the absorption spectral characteristics continuously increase from a short wavelength region to a long wavelength region. The absorption spectral characteristic refers to the light absorption characteristic for each wavelength of each substance. Common dichroic dyes include azo dyes, anthraquinone dyes, and the like. In this embodiment, for example, fluorescent benzothiadiazole dichroic dyes with less fading are used. The liquid crystal 14 may be a nematic liquid crystal, a cholesteric liquid crystal, or a smectic liquid crystal, or may be a ferroelectric liquid crystal that is a kind of smectic liquid crystal.

  The filter 11 equivalently forms a parallel plate capacitor by the transparent electrodes 122 facing each other and the dye 13 and the liquid crystal 14 filled between them. Since the capacitor component (capacitance) of the parallel plate capacitor is substantially proportional to the area of the parallel plate electrode, the capacitor component of the filter 11 increases as the size of one cell increases.

  The resistance portion 15 is a high resistance material connected between the transparent electrodes 122 facing each other. The high resistance material is, for example, a conductive polymer (conductive polymer). FIGS. 2A and 2B show examples of conductive polymers used for the resistance portion 15. FIG. 2A shows a polythiophene derivative, and FIG. 2B shows a “self-doped” polyisothianaphthene derivative (both manufactured by TA Chemical Co., Ltd.). The resistance portion 15 is configured by applying such a conductive polymer to the inner surface of the spacer 16, for example.

  Next, the operation of the illumination device 10 configured as described above will be described with reference to FIGS. 1B and 1C and FIGS. 3A and 3B. FIGS. 1B and 1C show the case where the switch SW is ON, and FIGS. 3A and 3B show the case where the switch SW is OFF. As shown in FIG. 1B, when the switch SW is turned on, a rectangular wave AC driving voltage is applied from the control power source 181 between the electrode pins 17a-17b. As shown in FIG. 1C, an electric field is generated between the opposing transparent electrodes 122 by a driving voltage, and the liquid crystal 14 and the dye 13 having a long and narrow molecular structure are aligned in the direction of the electric field, and the filter substrate 12 is aligned. Stand up vertically. Therefore, light absorption by the dye 13 is reduced, and the light transmittance of the filter 11 is kept high. At this time, the filter 11 is charged with the drive voltage.

  As shown in FIG. 3A, when the switch SW is turned off, the drive voltage is not applied between the electrode pins 17a-17b. As shown in FIG. 3B, the electric charge charged in the filter 11 is discharged by the resistance portion 15, and the electric field between the transparent electrodes 122 facing each other disappears. Therefore, the liquid crystal 14 and the dye 13 having an elongated molecular structure are aligned in parallel to the alignment film 123, and the dye 13 strongly absorbs polarized light that vibrates in the major axis direction. Therefore, for example, the filter 11 including the dye 13 having the absorption spectral characteristic for the long wavelength region increases the color temperature of the transmitted light, while the filter 11 including the dye 13 having the absorption spectral characteristic for the short wavelength region is transmitted. Reduce the color temperature of light. That is, in the lighting device 10, the toning of the filter 11 is switched by the switch SW.

  As described above, in the illumination device 10 according to the present embodiment, when the switch SW of the control circuit 18 is turned from ON to OFF, the charge charged in the filter 11 is discharged by the resistor unit 15, so that the period in which the charge remains is long. Shorter and faster toning switching. Further, when only the filter 11 is removed during the operation of the control circuit 18, the charge charged in the large capacitor component of the filter 11 is surely discharged, so that the charging parts such as the electrode pins 17a and 17b are mistakenly touched. Safety when touched is further improved.

(Second Embodiment)
An illumination device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a cross-sectional configuration of the filter 21 in the illumination device of the present embodiment. In the illumination device of this embodiment, instead of providing the resistor portion 15 in the first embodiment, a conductive polymer dissolved in the liquid crystal 14 is used as the resistor portion 25.

  A conductive polymer is dissolved in the liquid crystal 14 filled between the opposing filter substrates 12. This conductive polymer is a high-resistance material, and connects the opposing transparent electrodes 122 with high resistance, and functions as a resistance portion 25 that discharges the charge charged in the filter 21. The conductive polymer is, for example, a polythiophene derivative or a “self-doped” polyisothianaphthene derivative (see FIGS. 2A and 2B). In addition, although the resistance part 25 is electrically connected with the transparent electrode 122 through the alignment film 123, the alignment film 123 is a thin film and electrical connection is ensured.

  Here, when the capacitor component between the opposing transparent electrodes 122 is C, and the resistance of the resistance portion 25 between the transparent electrodes 122 is R, the capacitor component C is approximately proportional to the area of the transparent electrode 122, and the resistance R is the area. It is approximately inversely proportional. For this reason, if the time constant of the discharge of the charge charged in the transparent electrode 122 is T, T = C × R, so the time constant T is not related to the area of the transparent electrode 122. On the other hand, the resistance R depends on the concentration of the conductive polymer dissolved in the liquid crystal 14. Therefore, the time constant T can be adjusted by increasing or decreasing the concentration of the conductive polymer, and the concentration of the conductive polymer that provides the desired time constant T is applied to the filter 21 regardless of the size of the transparent electrode 122. .

  As described above, in the illumination device according to the present embodiment, since the charge charged in the filter 21 is discharged by the resistance unit 25 as in the first embodiment, the switching of the toning becomes faster, and the filter 21 Safety when touched is improved. Further, since the time constant of the discharge of the charge charged in the transparent electrode 122 is not related to the area of the transparent electrode 122, the resistance corresponding to the capacitor of the transparent electrode 122 of the filter 21 can be easily set.

  In addition, this invention is not restricted to the structure of said embodiment, A various deformation | transformation is possible in the range which does not change the summary of invention. For example, a fixed resistor, a variable resistor, or a semi-fixed resistor may be externally attached between the electrode pins 17a-17b as the resistor unit 15.

(A) is the block diagram of the illuminating device which concerns on the 1st Embodiment of this invention, (b) is the connection figure at the time of the drive voltage application of the voltage control type liquid crystal filter in the illuminating device, (c) is the drive of the filter Sectional drawing at the time of voltage application. (A) (b) is a structural formula of the example of the conductive polymer used for the resistance part of the filter. (A) is a connection diagram when no drive voltage is applied to the filter, and (b) is a cross-sectional view when no drive voltage is applied to the filter. Sectional drawing of the voltage control type liquid crystal filter in the illuminating device which concerns on the 2nd Embodiment of this invention. The block diagram of the illuminating device using the conventional voltage control type liquid crystal filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Illuminating device 11, 21 Voltage control type liquid crystal filter 12 Filter substrate 121 Transparent substrate 122 Transparent electrode 123 Alignment film 13 Dye 14 Liquid crystal 15, 25 Resistor 19 Light source

Claims (2)

A filter substrate having a transparent substrate, a transparent electrode provided on the transparent substrate, and an alignment film provided on the transparent electrode is stacked so that the alignment films face each other. In a lighting device comprising a voltage-controlled liquid crystal filter formed by filling a liquid crystal mixed with a pigment in a gap, and a light source, wherein the light from the light source is toned and controlled by the voltage-controlled liquid crystal filter,
The voltage control type liquid crystal filter is provided with a resistance portion for discharging the electric charge charged in the filter, and the illumination device using the voltage control type liquid crystal filter.   The illumination device using a voltage-controlled liquid crystal filter according to claim 1, wherein the resistance portion is disposed between the opposing transparent electrodes.

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