FR2682780A1 - LIQUID CRYSTAL DEVICE. - Google Patents

Abstract

A liquid crystal device comprising a pair of transparent substrates (1), transparent conductive films (2) respectively disposed on the inner surfaces of the transparent substrates, and a containment device (4) containing a liquid crystal material (3) in spacings interposed between the transparent conductive films, according to which an average refractive index (na) of the liquid crystal material, a refractive index (nb) of the confinement device, a quantity of total surface (S) [mum- 1] spacings, and a distance (t) [mum] between the transparent conductive films satisfy the following equation: (CF DESSIN DANS BOPI)

Description

BACKGROUND OF THE INVENTION Field of the invention

  The present invention relates to a liquid crystal device comprising

  taking a liquid crystal material, and more particularly a liquid crystal device having a transparent conductive film structure disposed on the inner side surfaces of a pair of transparent substrates respectively, and a confining device interposed to contain the crystal material in the gaps between the previous transparent conductive films,

  which has a function of modulation of the upper light.

Description of the prior art

  In the architectural or automotive application, the entry of solar radiation energy through a window has a large effect on the indoor air conditioning load. energy, it becomes important to provide a light modulation function

by the window.

  As the desired light modulation interval in practical use, it is necessary to choose the optical characteristics at least in a gap between the transparent glass currently used as window pane

  and a heat-absorbing glass for absorbing solar radiation energy.

  the amount of light modulation is preferably in the range of 15% or more in terms of the variable transmittance volume (or

  transmission) of solar radiation energy (hereinafter referred to as "AT").

  Conventionally, as a device having such a light modulation function, an electrochromic device (hereinafter referred to as "ECD") is known. The functions of ECD to control the visibility and the quantity of light transmitted from the energy of solar radiation by absorption of light using a variable material in the optical spectrum due to the electrochemical oxidation-reduction reaction such as tungsten oxide and blue

Prussia.

  However, since the ECD is of the driving current type, when its surface is enlarged, it is remarkably reduced in response time due to a significant drop in voltage and is inevitably

  degraded, for example, due to the electrochemical change of the

  in operation for a long period of time.

  a large-area device having sufficient durability in use

practice.

  To solve the above problem, in place of the previous drive-type type ECD, a drive-voltage type modulation device has been proposed. Japanese Patent Laid-open No. 58-501,631 corresponding No. 443,5047 discloses a nematic curvilinear phase-aligned liquid crystal device (referred to as "NCAP") having a light-modulating function of excellent durability and easy to expand the surface. Similarly, Japanese Patent Laid-Open. Sho 61-502 128 (USP No. 4688900) discloses a liquid crystal device obtained by a method of

  phase separation These devices act on the basis of the following principle.

  The crystal device including tiny droplets of a liquid crystal material dispersed in an inexpensive polymer matrix is milky white without the application of voltage. The reason for this is that the liquid crystals are aligned along the curvilinear surface of a wall. of the polymer, which deforms a light path or causes the reflection and dispersion of the

  light at this interface between the polymer matrix and the liquid crystals.

  By applying a voltage, the liquid crystals in the droplets are aligned parallel to the direction of the electric field. In this case, so that an ordinary refractive index of the liquid crystals no is equal to the index of refraction of the matrix. of np polymer, the normal incident light at the surface of a liquid crystal device passes through the interface of the polymer matrix and each liquid crystal without any reflection thus rendering

  the transparent liquid crystal device.

  The previous liquid crystal device can control visibility; however, since the light incident on the liquid crystal device is often scattered on the opposite side (referred to as "forward") to the incident side in the case of the application of any voltage, the amount of light transmitted from

  the solar radiation energy is little reduced compared to the case of the application of

  voltage, thus obtaining only a few percent of AT.

  To solve the previous problem, it has been proposed a technique

  described in Japanese Patent Laid-open Sho 58-501 631 (USP-

  4435047) that the absorption of light in the case where no voltage is applied is increased by the addition of a pleochroic dye in a liquid crystal material used in the preceding liquid crystal device. Such a device has a large AT. ; however it can not be used in architectural or automotive application exposed to solar radiation for a long time because the pleochroic dye is essentially easy to degrade vis-à-vis

light and heat.

Objects and summary of the invention

  To solve the above problem, the present invention has been

  the object is to provide a liquid crystal device of excellent durability

  slow and easy to expand the surface, and also having a modulation function

  AT light of 15% or more.

  In a preferred embodiment of the present invention, there is provided a liquid crystal device having a structure with interposition of a

  containment device containing the liquid crystal material in

  between the substrates provided by a pair of transparent conductive films,

  according to which an average refractive index of the above liquid crystal material

  na tooth, a refractive index of the confining device nb, a total amount of the specific surface area of the previous spacings per unit volume S Lam-1 l (hereinafter referred to as "total surface area S") and the thickness between a pair

  transparent conductive films t luml (hereinafter referred to as "thickness")

make the following equation (1).

  The liquid crystal material is maintained in the spacings between the confinement device, and according to whether the gaps exist independently or partially or totally integrally, equation (1) is effective hereinafter,

  the previous gap is called "capsule" for convenience.

  | na-nb Ix Sxt> 4.2 (1) Incidentally, the average refractive index na of the preceding liquid crystal material is generally represented by the following equation (2): na = (2 x no + ne) / 3 (2) where no is an ordinary index of the liquid crystal material and is not a

extraordinary index.

  The single figure is a typical view of a liquid crystal device in accordance with the present invention. In this figure, reference 1 indicates a substrate, a transparent conductive film, a liquid crystal material and a

  confinement device Similarly, the total specific surface area S is theoretically

  represented by the following equation (3) using parameters V and D.

S = 6 XV / D (3)

  wherein V indicates a volume ratio of a liquid crystal material per

  in relation to the total volume of the liquid crystal material and the medium (referred to

  after "liquid crystal ratio") and D is a mean diameter of a capsule (hereinafter referred to as "capsule diameter") In this case, even when certain

  capsules are combined, they can be viewed as inde-

  As a result, the previous value D indicates the average diameter

  of a true spherical body having the same volume as that of the independent capsule

  dante. The present inventor has examined the relationship between the parameters of the liquid crystal device and AT and therefore has obtained the following equation (4). Thus, by a suitable combination of a plurality of parameters, it is possible to disperse for the most part the incident light that may be scattered forward on the incident side (hereinafter referred to as "backward"), and thereby reduce the amount of light transmitted when no voltage is applied, thereby significantly increasing the light modulation function. AT = 3.57 x 1 na-nb Ix Sxt (4) When the total specific surface S is constant, by widening the difference between the extraordinary refractive index n o and the ordinary index n o of the liquid crystal material, that is to say a birefringence An = (no no), the index

  mean refraction na is expanded thereby increasing the AT.

  Similarly, when An is constant, expanding the surface area

  S or by thickening the thickness between a pair of conductive films

  t, the AT is increased To enlarge the total surface area S, the capsule diameter D is reduced or the liquid crystal ratio V is increased To obtain a higher AT value, by more than 15%, the parameters of the crystal device liquids may include the right side of equation (4) above to set

  15% or more, that is, to satisfy equation (1).

  Moreover, to satisfy equation (1), the parameters of the device to

  liquid crystal is preferably within the next range.

  The capsule diameter has a large effect on the dispersion of the light entering the liquid crystal device. When the capsule diameter is less than 0.5 μm, the transmittance on the long wavelength side in a region of Visible light is increased, hence the ability to screen visibility by applying no voltage. Similarly, when the capsule diameter exceeds 3 l, the total surface area S is reduced, thus increasing the amount of light transmitted. As a result, the capsule diameter is preferably

  in the range 0.5 to 3 μm, and more preferably 0.8 to 2 μm.

  When the capsule diameter is constant, the total surface area S is enlarged with increasing liquid crystal ratio. Therefore, since the amount of light of the backward dispersion is increased, the transmitted light can be controlled broadly, however. when the liquid crystal ratio becomes much larger (1.0 at most) it is difficult to form the spacing of the confinement device to maintain the material at

  liquid crystal, which reduces the degree of dispersion of incident light, decreases

  Thus, even when the liquid crystal ratio is less than 0.5, it is difficult to make the AT transmittance not less than 15%, even when the birefringence An is made larger. liquid crystal ratio is preferably in the range

from 0.5 to 0.9.

  When the thickness between the substrates provided by the transparent conductive films is narrow, the amounts of capsules and the liquid crystal material held therein are reduced, thereby reducing the total surface area S of the capsules. As a result, the transmittance can be controlled with difficulty ( the transmittance of solar radiation energy) When the thickness between a pair of transparent conductive films is less than 10 μm, it is

  It is difficult to maintain AT transmittance at 15% or more even when bire-

  As the thickness is elongated, the controlled transmittance is increased. However, in proportion to the increase in thickness, the higher tension is required, and therefore a thicker thickness is required.

  In practice, the thickness between a pair of transparent conductive films

  Therefore, the distance between a pair of transparent conductive films is preferably within the range of 10 to 10 μm. The liquid crystal material used in the present invention is not particularly limited but may include a nematic liquid crystal, a cholesteric liquid crystal and a smectic liquid crystal. In particular, the nematic liquid crystal is preferable. application of any voltage, the distortion of the crystal structure of the nematic liquid crystal is due to the alignment at the periphery between the polymer matrix and the liquid crystals, differently from the extremely strong twisting for the cholesteric liquid crystal and

  of the volume effect of a lamellar structure for the smectic liquid crystal.

  Similarly, the containment device for containing the previous liquid crystal material to expand AT without impairing visibility can be selected from inorganic materials and organic materials having an index of refraction nb in accordance with the ordinary index no or with the extraordinary index of the liquid crystal material and maintaining the liquid crystal material in the spacings In particular, a polymer whose refractive index is easy to adjust and whose surface of the device is easy to enlarge is preferable For example the latex disclosed in Japanese Patent Laid-Open No. 60-252,687 is preferable for obtaining the device having excellent substrate adhesivity, excellent optical homogeneity and excellent

excellent physical durability.

  To prepare the device for containing the above liquid crystal material, it is possible to add a certain amount of surfactant. Preferably, the added amount of the surfactant is limited to a minimum amount required to

  stabilize the size of the droplet of the liquid crystal in an emulsion.

  In addition, to prepare the device containing the above liquid crystal material, a crosslinking agent can be added. By adding the above crosslinking agent, it is possible to obtain the liquid crystal device having improved adhesiveness between the device. and the transparent conductive film

  formed on the surface of the substrate, and also the protection against moisture.

  As a substrate provided with the transparent conductive film used in the present invention, a common glass substrate having a tin-indium oxide film (hereinafter referred to as "ITO") or a thin oxide film can be used. (hereinafter referred to as "Sn O 2") on the surface, and also other excellent materials with respect to light transmittance, for example, a

  plastic substrate or a flexible plastic film.

  According to the present invention, a liquid crystal device having a light modulation function of AT equal to% or more can be obtained by suitably combining the parameters of the liquid crystal device, such as the average refractive index. na liquid crystal material, the refractive index nb of the device for maintaining the liquid crystal material, the thickness t, the liquid crystal ratio V, and the capsule diameter D so as to satisfy the following equation ( 5) obtained with reference to equation (1) and

equation (3).

  | na-nb | x (6 x V / D) xtà 24,2 (5) The function mentioned above can be realized by increasing the ratio of the dispersion to the back of the incident light in the application

  No voltage In contrast to the light modulation device con-

  incidental, dispersing the light at the rear without absorbing it, in other words, by reflection of the incident light, the light modulation function is improved. As a result, the material constituting the liquid crystal device is prevented from being degraded by the light and heat that

  accompanies its absorption, thus obtaining excellent durability.

  The liquid crystal device of the present invention is capable of

  to adjust the transmittance sufficiently.

Brief description of the drawings

  The single figure is a typical cross-sectional view of a

  liquid crystal device manufactured in accordance with the present invention.

  Detailed Description of the Preferred Embodiments

  The present invention will be described by embodiments, but

  it is not limited to these embodiments.

  For example, a liquid crystal device of the present invention

  is manufactured in the following manner.

  First, an emulsion as a medium is prepared by

  direct mixing of a liquid crystal material with a water-based latex.

  The emulsion can be prepared by mixing the liquid crystal material with an aqueous phase, and mixing with the latex. During the preparation of the emulsion, a certain amount of surfactant is added to stabilize the droplet size of the liquid crystal material. Similarly, the mixture is executed

  using various types of mixers such as a Ydes mixer or colloid mill.

  In the second place, the emulsion is added with a crosslinking agent, which is stirred slowly. After that, the emulsion in which the crystal material is dispersed.

  liquid is coated on a transparent conductive film of a substrate, which is

  formed at least with the transparent conductive film, at the required thickness using a doctor blade or other means, and is dried. At least the liquid crystal device is obtained by laminating another substrate provided with a transparent conductive film, whose side is positioned on the inside, on the previous dried material. (Work Example 1) A liquid crystal device of the present invention is manufactured in the following manner. The nematic liquid crystal E 49 sold by BDH (average refractive index na = 1.610) is supplemented with the surfactant IGEPAL CO-610 sold by GAF. in an amount of 0.5% by weight, and the whole is added to the Neorez R-967 water-based latex sold by ICI Resin Corp (former name: Polyvinyl Chemical Corp) containing latex particles in an amount of 40% by weight. weight so as to obtain a liquid crystal ratio of 0.62 The mixture is then homogenized at 7000 rpm for 10 min using a homogenizer to thereby obtain an emulsion. Next, the emulsion is supplemented with a crosslinking agent CX. -100 sold by ICI Resin Corp (former name: Polyvinyl Chemical Corp) in an amount of 3% by weight relative to the weight of R-967 while slowly mixing In addition, the refractive index of the containment is the next: Nb = 1.495 This

  The mixture is applied as a coating to a polyethylene terephthalate film.

  ITO (hereinafter referred to as "PET") liner previously formed with the ITO film using a squeegee and then dried The thickness of the coating after drying is about 30 Inm After drying the coating material, the film PET is laminated with another PET film provided by the ITO film in such a manner that the ITO film side is brought into contact with the previous dried material, thereby obtaining a liquid crystal device. liquid crystals thus obtained are shown in Table 1 Using the parameters, the equation of | na nb l x S x t is calculated, giving as results

the value of 4.3.

Table 1

  AT Thickness ratio diameter capsule (min) liquid crystal (nm) Example of 0.251 3.0 0, 62 work 1 Example of 0.143 1.0 0.62 work 2 Example of 0.251 2.3 0.75 work Example of 0.143 2.0 0.62 Work Example 0.143 3.0 0.62 Comparative 1 (Work Example 2) A liquid crystal device having a construction obtained by combining the parameters differently from those of the invention is prepared. example of work 1.

  ZLI-1840 nematic liquid crystal sold by Merck Japan LTD.

  (average refractive index na = 1.543) is added the surfactant IGEPAL CO-

  610 sold by GAF in an amount of 0.5% by weight, and then added to a Neorez R-967 water-based latex sold by ICI Resin Corp. (former name: Polyvinyl Chemical Corp) containing latex particles in an amount of 40%. % by weight in order to obtain a liquid crystal ratio of 0.62. The mixture is then homogenized at 18,000 rpm for 10 min, using a homogenizer to thereby obtain

  Then, the emulsion is supplemented with a CX-crosslinking agent.

  sold by ICI Resin Corp. (former name: Polyvinyl Chemical Corp.) in an amount of 3% by weight of R-967 while slowly mixing

  Furthermore, the refractive index of the containment enclosure is as follows: Nb = 1.484.

  This mixture is applied as a coating to a PET ITO film previously formed with the ITO film using a doctor blade and then is

  The thickness of the coating material after drying is about 20 μm.

  After drying the coating material, the PET film is laminated to another PET film provided by the ITO film in such a way that the side of the ITO film is brought into contact with the previous dried material, thereby obtaining a liquid crystal device The parameters of the liquid crystal device thus obtained are shown in Table 1 similarly to Example 1 Using the parameters, the equation of Na nb lx S xt is calculated, giving as a result

the value of 4.4.

  (Work Example 3) A liquid crystal device having a construction obtained by combining parameters different from those of the examples of

Work 1 and 2.

  The nematic liquid crystal E 49 sold by BDH is supplemented with the surfactant IGEPAL CO-610 sold by GAF in a quantity of 1% by weight, and then added to the Neorez R-967 latex based on water sold by ICI Resin Corp. (former name: Polyvinyl Chemical Corp) containing latex particles in an amount of% by weight so as to obtain a liquid crystal ratio of 0.75. The mixture is then homogenized at 12000 rpm for 10 min using a homogenizer to thereby obtain an emulsion. Then, the emulsion is supplemented with a crosslinking agent CX-100 sold by ICI Resin Corp (former name: Polyvinyl Chemical Corp) in an amount of 3% by weight relative to the weight of R-967 by slowly mixing this mixture. applied as a coating to a PET ITO film previously formed with the ITO film using a doctor blade and then dried The thickness of the coating material after drying is about 20 μm After drying the coating material t, the PET film is laminated with another PET film provided by the ITO film in such a way that the side of the ITO film is brought into contact with the dried material

  previous, to obtain a liquid crystal device.

  The parameters of the liquid crystal device thus obtained are shown in Table 1. Using the parameters, the equation is calculated,

  resulting in the value of 4.5.

  (Work Example 4) A liquid crystal device having a construction obtained by combining the parameters differently from those in the examples of

Work 1, 2 and 3.

  ZLI-1840 nematic liquid crystal sold by Merck Japan LTD.

  is added a surfactant IGEPAL CO-610 sold by GAF in an amount of 0.5% by weight, and then added to a water-based latex Neorez R-967 sold by ICI Resin Corp (former name: Polyvinyl Chemical) Corp) containing latex particles in an amount of 40% by weight so as to obtain a liquid crystal ratio of 0.62. The mixture is then homogenized at 14000 rpm for min using a homogenizer to thereby obtain an emulsion. the emulsion is supplemented with a CX-100 crosslinking agent sold by ICI Resin Corp. (former name Polyvinyl Chemical Corp.) in an amount of 3% by weight based on the weight of R-967 while slowly mixing This mixture is applied as coating on a PET ITO film previously formed with the film of

  ITO using a squeegee and then dried The thickness of the coating material-

  After drying of the material, the PET film is laminated to another PET film supplied with the ITO film so that the side of the ITO film is brought into contact with the previous dried material. ,

  to obtain a liquid crystal device.

  The parameters of the liquid crystal device thus obtained are shown in Table 1 similar to Example 1 Using the parameters,

  the equation l na nb l x S x t is calculated, giving the result of 4.4.

  (Comparative Example 1) For comparison with the liquid crystal device of the

  the present invention, a liquid crystal device having a

  truction contained by suitably combining the parameters described in Japanese Patent Laid-open N sho 60- 252 687 (corresponding to

US Patent No. 4992201.

  ZLI-1840 nematic liquid crystal sold by Merck Japan LTD.

  is added surfactant IGEPAL CO-610 sold by GAF in an amount of 0.5% by weight, and then added to a water-based latex Neorez R-967 sold by ICI Resin Corp. (former name: Polyvinyl Chemical Corp.) containing latex particles in an amount of 40% by weight so as to obtain a liquid crystal ratio of 0.62. The mixture is then homogenized at 7000 rpm for 10 min using a homogenizer to thereby obtain an emulsion. Then, the The emulsion is supplemented with a crosslinking agent CX-100 sold by ICI Resin Corp. (former name: Polyvinyl Chemical Corp.) in an amount of 3% by weight relative to the weight of R-967 while slowly mixing. This mixture is applied as a coating. on an ITO film of a PET previously formed with the ITO film using a doctor blade and is then dried The thickness of the coating material after drying is about 20 μm After drying the material, it is laminated with a other movie of PET supplied with the ITO film so that the side of the ITO film is brought into contact with the previous dried material, thereby obtaining a

liquid crystal device.

  The parameters of the liquid crystal device thus obtained are shown in Table 1 similar to Example 1. Using the parameters, the equation | na nb | x S x t is calculated, giving the result of 1.5.

  (Work Examples 1 to 4 and Comparative Example 1) Each of the liquid crystal devices obtained by Work Examples 1 to 4 and Comparative Example 1 are measured for solar energy transmission in the case of application. d) No voltage (in the OFF state) and the application of a voltage (in the case of operation) according to JIS R 3106 and each AT is calculated on the basis of the measured value The results are shown in Table 2 Moreover, as mentioned above, AT is the variable volume of the solar radiation energy transmittance, and more particularly represents a difference between the solar energy transmittance

  between the off state and the operating state.

  Table 2 | na-nb Ix Sxt AT (% o) Example of work 1 4.3 15.4 Example of work 2 4.4 15.8 Example of work 3 4.5 16.2 Example of work 4 4.4 15.8 Comparative Example 1 1, 5 5.6 From Table 2, it is clear that according to each example of the present invention in which the product of | na nb | and (S xt) constituting the parameters of the liquid crystal device is 4.2 or more, the diameter of the capsule is in the range of 0.5-3 μm, the liquid crystal ratio is in the range of 0.5-0.9, and the thickness is in the range of 10-401 μm, it is possible to obtain the liquid crystal device having a modulation function of

  AT light equal to 15% or more.

  Likewise, the liquid crystal device of the present invention can

  sufficiently control visibility.

  As is clear from the examples, by an appropriate combination

  Given the parameters constituting the liquid crystal device, it is possible to improve the light modulation function of the solar energy transmittance compared to the liquid crystal device obtained in the conventional manner.

Claims (7)

  A liquid crystal device comprising: a pair of transparent substrates, transparent conductive films respectively disposed on the inner surfaces of said transparent substrates, and a containment device containing a liquid crystal material in the gaps interposed between said transparent conductive films, according to which a mean refractive index (na) of said liquid crystal material, a refractive index (nb) of said confining device, a total surface area (S) lum-1 of said spacings, and a distance (t) between said transparent conductive films satisfy the following equation: I na-nb | x Sxt 24,2 2 A liquid crystal device according to claim 1, wherein a mean diameter of each of said spacings in terms of a body   true spherical having the same volume is in the range of 0.5 to 3.0 nm.   A liquid crystal device according to claim 1, wherein a volume ratio of said liquid crystal material to the total volume of said liquid crystal material and said containment device is included in a range of 0.5 to 0.9.   A liquid crystal device according to claim 1, wherein a distance between said transparent conductive films is in the meantime from 10 to 40 μm.   A liquid crystal device according to claim 1, according to   wherein said liquid crystal material comprises a nematic liquid crystal.   A liquid crystal device according to claim 1, according to   said containment device is supplemented with a surfactant.   A liquid crystal device according to claim 1, according to   said containment device is supplemented with a crosslinking agent.   A liquid crystal device according to claim 1, according to   wherein said transparent conductive film comprises a tin oxide.   A liquid crystal device according to claim 1, according to   which said containment device includes a latex.