JP2018106080A - Dimming member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a maximum transmittance in a dimming member and to achieve reduction in drive power.SOLUTION: A dimming member 1 of the present invention includes a first substrate 6 where a first alignment film 13 is disposed, a second substrate 15 where a second alignment film 17 is disposed, a liquid crystal layer 8 comprising a twisted nematic liquid crystal 8a and a dichroic dye 8b disposed between the first substrate 6 and the second substrate 15, and electrodes 11, 16 disposed on at least one of the first substrate 6 and the second substrate 15. At least one of the first alignment film 13 and the second alignment film 17 is a vertical alignment film.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a light control member.

Conventionally, various devices relating to a light control member that is attached to a window to control the transmission of external light have been proposed (Patent Documents 1 and 2). One such light control member uses liquid crystal. The light control member using the liquid crystal sandwiches the liquid crystal between the two transparent substrates on which the transparent electrodes are made, and changes the orientation of the liquid crystal molecules by applying a voltage between the transparent electrodes, thereby increasing the transmittance of the external light. I have control.
One of the light control members using such a liquid crystal is a guest host system. Here, a so-called normally black guest-host-type light control member having a minimum transmittance when no voltage is applied between the transparent electrodes (voltage OFF) allows liquid crystal molecules to be horizontally aligned when the voltage is OFF. It is necessary to be parallel to the direction in which the light control member extends. For this reason, a horizontal alignment film is generally used as the alignment film provided on the surface of the transparent substrate on the liquid crystal layer side.

JP 03-47392 A Japanese Patent Laid-Open No. 08-184273

In recent years, in the light control member, improvement of the maximum transmittance and reduction in driving power have been demanded.
An object of the present invention is to improve the maximum transmittance of the light control member and reduce the driving power.

In order to solve the above problems, the present invention provides the following.
(1) The first base material provided with the first alignment film, the second base material provided with the second alignment film, and the first base material and the second base material, A liquid crystal layer including a twisted nematic liquid crystal and a dichroic dye, and an electrode disposed on at least one of the first base material and the second base material, and the first alignment film and the second alignment film A light control member, at least one of which is a vertical alignment film.

(2) In (1), a normally black type in which the light transmittance of the liquid crystal layer increases as the voltage applied to the electrode increases.

(3) In (1) or (2), when both the first alignment film and the second alignment film are vertical alignment films, the thickness of the liquid crystal layer is d, and the liquid crystal contained in the liquid crystal layer When the chiral pitch is p, d / p is 1.3 or more (1.3 ≦ d / p).

  According to the present invention, it is possible to improve the maximum transmittance of the light control member and reduce the driving power.

It is a typical sectional view showing light control film 1 concerning a 1st embodiment of the present invention. 3 is a schematic cross-sectional view of a light control film 1 in a comparative form in which a horizontal alignment film is used as the first alignment film 13 and the second alignment film 17. FIG. In the light control film 1 of this embodiment, it is the measurement result which measured the relationship between an applied voltage and the transmittance | permeability at the time of applying a voltage to the 1st electrode 11 and the 2nd electrode 16. It is the figure which showed the relationship between a voltage and the transmittance | permeability in five types of light control films 1 which changed d / p. It is a typical sectional view showing light control film 101 as a light control member concerning a 2nd embodiment of the present invention. It is the figure which showed the relationship between a voltage and the transmittance | permeability in four types of light control films 101 which changed d / p in 2nd Embodiment.

(First embodiment)
(Configuration of light control film)
Drawing 1 is a typical sectional view showing light control film 1 as a light control member concerning a 1st embodiment of the present invention. The light control film 1 is used, for example, by adhering it to an area for light control such as a window glass of a building, a showcase, an indoor transparent partition, a sunroof of a vehicle, etc. with an adhesive layer or the like, and changing the voltage. Control the transmitted light.

The light control film 1 sandwiches the liquid crystal layer 8 between the film-like first laminate 5D and the second laminate 5U, and changes the electric field to the liquid crystal layer 8 including the liquid crystal 8a and the dichroic dye 8b. Thus, the light control film 1 is of a guest-host system that controls the transmitted light by changing the alignment direction of the liquid crystal 8a and the dichroic dye 8b.
The first laminate 5D is formed by arranging a first electrode 11, a spacer 12, and a first alignment film 13 on a first base 6 that is a transparent film material.
The second stacked body 5U is formed by arranging the second electrode 16 and the second alignment film 17 on the second base material 15 which is a transparent film material.
By driving the first electrode 11 and the second electrode 16 provided in the second stacked body 5U and the first stacked body 5D, the strength of the electric field in the liquid crystal layer 8 changes.

(Base material)
Various transparent film materials applicable to this kind of film material can be applied to the first base material 6 and the second base material 15. In the present embodiment, a polycarbonate film is applied to the first substrate 6 and the second substrate 15, but a COP (cycloolefin polymer) film, a TAC (triacetylcellulose) film, a PET (polyethylene terephthalate) film, Various transparent film materials such as an acrylic film can be used.

(Transparent electrode)
Various electrode materials applied to this type of film material can be applied to the first electrode 11 and the second electrode 16, and in this embodiment, the first electrode 11 and the second electrode 16 are formed of a transparent electrode material made of ITO (Indium Tin Oxide).

(Spacer)
The spacer 12 is provided to define the thickness of the liquid crystal layer 8 and various resin materials can be widely applied. In this embodiment, the spacer 12 is made of a photoresist, and the first electrode 11 is made. It is produced by applying a photoresist on the substrate 6 and exposing and developing the photoresist.
The spacer 12 may be provided in the second stacked body 5U, or may be provided in both the second stacked body 5U and the first stacked body 5D. The spacer 12 may be a so-called bead spacer.

(Seal material)
In the light control film 1, a sealing material 19 is disposed so as to surround the liquid crystal layer 8, and the second stacked body 5 </ b> U and the first stacked body 5 </ b> D are integrally held by the sealing material 19, and liquid crystal leakage is prevented. .

(Alignment film)
The first alignment film 13 and the second alignment film 17 are produced by rubbing a polyimide resin layer. The first alignment film 13 and the second alignment film 17 can be applied with various configurations capable of expressing the alignment regulating force with respect to the liquid crystal according to the liquid crystal layer 8, and may be made of a so-called photo-alignment film. .
In this case, various materials to which the photo-alignment technique can be applied can be applied as the photo-alignment material. For example, a dimerization-type material in which the alignment does not change by ultraviolet irradiation after alignment is applied. can do. The photodimerization type material is described in “M. Schadt, K. Schmitt, V. Kozinkov and V. Chigrinov: Jpn. J. Appl. Phys., 31, 2155 (1992)”, “M. Schadt, H. Seiberle and A. Schuster: Nature, 381, 212 (1996).
Details of the first alignment film 13 and the second alignment film 17 will be described later.

(Liquid crystal layer)
The liquid crystal layer 8 includes a liquid crystal 8a and a dichroic dye 8b and is driven by a guest-host method.
(liquid crystal)
The liquid crystal 8a is a p (positive) type twisted nematic (TN) liquid crystal. The liquid crystal 8a includes a chiral agent and can adjust the chiral pitch p of the liquid crystal 8a by adjusting the content of the chiral agent. The chiral pitch is a distance when the molecules of the liquid crystal 8a are twisted by one period (360 °).
(Chiral agent)
A chiral agent is a low molecular compound having an optically active site, and induces a helical structure in a nematic liquid crystal. As the chiral agent, for example, S-811, R811, CB-15, MLC6247, MLC6248, R1011, S1011 (all manufactured by Merck) or the like is used.
(Dichroic dye)
A dichroic dye is a dye in which the absorbance in the major axis direction of the molecule is different from the absorbance in the minor axis direction. When the alignment state of the liquid crystal molecules changes due to a change in the voltage applied to the light control film 1, the alignment state of the dichroic dye also changes according to the change in the alignment state of the liquid crystal molecules. As the dichroic dye, for example, LSY-116, LSR-401, LSR-405, LSB-278, LSB-350, LSB-335 (all manufactured by Mitsubishi Kasei Co., Ltd.) and the like are used.

  The light control film 1 of this embodiment is a normally black type. The normally black type is a structure in which the transmittance is minimized when the voltage is not applied to the first electrode 11 and the second electrode 16, and the screen is black (dark state).

Next, the first alignment film 13 and the second alignment film 17 of the present embodiment will be described in detail. First, in order to facilitate the description of the embodiment, a comparative example will be described.
(Comparison form)
FIG. 2 is a schematic cross-sectional view of a light control film 1 ′ in a comparative form in which a horizontal alignment film is used as the first alignment film 13 ′ and the second alignment film 17 ′. In FIG. 2, the illustration of the spacer 12 is omitted.

In order to make the light control film 1 'normally black in the dark state when the voltage is OFF, the liquid crystal 8a' and the dichroic dye 8b 'are placed horizontally (parallel to the extending direction of the light control film 1', the thickness of the liquid crystal layer 8 '). The direction perpendicular to the direction). For this reason, a horizontal alignment film is generally used as the first alignment film 13 ′ and the second alignment film 17 ′ as in the comparative example.
When a horizontal alignment film is used, when no voltage is applied to the first electrode 11 ′ and the second electrode 16 ′, the liquid crystal 8a ′ and the dichroic dye 8b ′ are horizontally aligned in the entire region as shown in the figure. It is twisted and arranged in a horizontal state.

Since the liquid crystal 8a ′ and the dichroic dye 8b ′ are horizontally aligned, the transmittance of the light control film 1 ′ is not applied to the first electrode 11 ′ and the second electrode 16 ′. Minimal, i.e. dark.
When a voltage is applied to the light control film 1 ′, the liquid crystal 8a ′ and the dichroic dye 8b ′ are vertically aligned. If it does so, the transmittance | permeability of light control film 1 'will raise and it will become bright.

  In contrast, the light control film 1 of the present embodiment uses vertical alignment films as the first alignment film 13 and the second alignment film 17. Then, as shown in FIG. 1, the liquid crystal 8 a and the dichroic dye 8 b gradually turn in the vertical direction due to the alignment regulating force as the first alignment film 13 and the second alignment film 17 become closer.

  However, the liquid crystal 8a and the dichroic dye 8b at positions away from the first alignment film 13 and the second alignment film 17 are twisted in a horizontal state as shown in the figure. This is considered to be because when the liquid crystal 8a and the dichroic dye 8b are twisted and arranged, the twisted state in a horizontal state is a more stable state.

FIG. 3 shows measurement results obtained by measuring the relationship between the applied voltage and the transmittance when voltage is applied to the first electrode 11 and the second electrode 16 in the light control film 1 of the present embodiment.
L1 is the light control film 1 of this embodiment, L2 is the light control film 1 'of a comparative form.
As shown in the graph, in the case of the present embodiment L1, the transmittance rises faster when the voltage increases compared to the comparative embodiment L2. That is, the embodiment L1 shows that the transmittance starts to increase from about 8% at a voltage of about 1V, and shows about 34% of the maximum transmittance at a voltage of about 6V.
On the other hand, in the comparative form L2, the transmittance does not increase until the voltage is about 5V, and the transmittance starts to increase from about the voltage 5V, but when the transmittance reaches about 23% at the voltage of about 10V. Even if the increase in transmittance decreases, and then the voltage increases, the increase in transmittance is slight.

As described above, when the p (positive) type twisted nematic liquid crystal is used as the liquid crystal 8a and the first alignment film 13 and the second alignment film 17 are the vertical alignment films as in the present embodiment, the horizontal alignment film is used. The transmittance increases at a lower voltage than the case. That is, since the transmittance rises quickly, the drive voltage can be reduced.
Further, according to the present embodiment, the maximum transmittance is about 34%, while the comparative form is about 25 to 27%. That is, in this embodiment, the transmittance in the bright state can be improved.
Note that the minimum transmittance is about 8% in the embodiment and about 5% in the comparative embodiment.

  In FIG. 4, the thickness of the liquid crystal layer 8 is d, the chiral pitch of the liquid crystal 8a included in the liquid crystal layer 8 is p, and d / p is 0.8, 1.3, 1.7, 2.0, 2 .5 is a result of an experiment showing the relationship between the voltage applied to the first electrode 11 and the second electrode 16 and the transmittance in each of the light control films 1.

When d / p is reduced from 2.3 (the twist angle in the liquid crystal layer having the same thickness is reduced), the transmittance in a state where no voltage is applied to the first electrode 11 and the second electrode 16. It can be seen that (minimum transmittance, transmittance in the darkest) increases.
This is because when the d / p is decreased, the twisting force of the molecules of the liquid crystal 8a is weakened and is easily affected by the vertical alignment film. When the d / p is increased, the twisting force of the molecules of the liquid crystal 8a is increased. This is probably because the film is less affected by the vertical alignment film.
In the light control film of d / p = 0.8, the transmittance does not change even when the voltage applied to the first electrode 11 and the second electrode 16 is changed, and the constant value remains as high as 60%. . That is, the transmittance remained constant and bright. This is because, when d / p = 0.8, the twisting force of the liquid crystal 8a is weak, so that the liquid crystal 8a and the dichroic dye 8b are generally vertically aligned in the thickness direction of the liquid crystal layer 8. Therefore, it is considered that the transmittance did not function as the light control film 1 regardless of voltage application.

  As described above, when the first alignment film 13 and the second alignment film 17 are vertical alignment films as in the present embodiment, d / p is set to 1. from the viewpoint of realizing a sufficient transmittance variation as the light control film 1. 3 or more (1.3 ≦ d / p) is preferable.

(Second Embodiment)
FIG. 5 is a schematic cross-sectional view showing a light control film 101 as a light control member according to the second embodiment of the present invention. The light control film 101 of the second embodiment is different from the first embodiment in that only the first alignment film 113 is a vertical alignment film, and the second alignment film 117 is a horizontal alignment film. Other parts are the same as those in the first embodiment. Description of similar parts is omitted.

  In the light control film 1 of the present embodiment, a vertical alignment film is used as the first alignment film 113, but a horizontal alignment film is used as the second alignment film 117. Then, as shown in FIG. 5, the liquid crystal 108a and the dichroic dye 108b are oriented in the horizontal direction in the most part of the liquid crystal layer 108 from the second alignment film 117 side. However, as it gets closer to the first alignment film 113, the liquid crystal 108 a and the dichroic dye 108 b gradually turn to the vertical direction due to the alignment regulating force of the first alignment film 113.

L3 in FIG. 3 is a measurement result of the second embodiment in which the relationship between the applied voltage and the transmittance is measured when a voltage is applied to the first electrode 111 and the second electrode 116.
As shown in the graph, although not as much as in the first embodiment L1, in the present embodiment L3 as well as the first embodiment L1, the transmittance when the voltage is increased as compared with the comparative embodiment L2. The rise is fast.
That is, the transmittance starts to increase from about 5% at a voltage of about 2.5V, the transmittance reaches 25% at a voltage of about 5V, and then the transmittance continues to increase slightly as the voltage increases, and the transmittance starts from 30%. 31%.

As described above, also in this embodiment, when the p (positive) type twisted nematic liquid crystal is used as the liquid crystal 108a and only one of the first alignment film 113 and the second alignment film 117 is vertical. The transmittance increases at a lower voltage than when a horizontal alignment film is used for the alignment films on both sides. That is, since the transmittance rises quickly, the drive voltage can be reduced.
Further, according to the present embodiment, the maximum transmittance is about 31%, while the comparative form is about 27%. That is, in this embodiment, the transmittance in the bright state can be improved.
The minimum transmittance was about 5% in the embodiment and about 5% in the comparative embodiment, and there was no difference.

  6, as in FIG. 4 of the first embodiment, the thickness of the liquid crystal layer 108 is d, the chiral pitch of the liquid crystal 108 a included in the liquid crystal layer 108 is p, and d / p is 0.8, 1. Four types of light control films 101 of 2, 2.0, and 2.3 were prepared, and the relationship between the voltage applied to the first electrode 111 and the second electrode 116 and the transmittance in each of the light control films 101 was shown. It is the experimental result.

As in the first embodiment, when d / p is reduced from 2.3 (the twist angle in the liquid crystal layer having the same thickness is reduced), a voltage is applied to the first electrode 111 and the second electrode 116. It can be seen that the transmittance (the minimum transmittance, the transmittance at the darkest) in the state of not being increased increases.
The difference from the first embodiment is that the transmittance changes when the voltage applied to the first electrode 111 and the second electrode 116 is changed even at d / p = 0.8.
This is presumably because the vertical alignment film is only one in the second embodiment, and the influence of the vertical alignment film was small even at d / p = 0.8.

  As described above, when one of the first alignment film 113 and the second alignment film 117 is a vertical alignment film as in the present embodiment, not only d / p but also the drive voltage is reduced and the transmittance in the bright state is improved. Such effects can be obtained.

DESCRIPTION OF SYMBOLS 1,101 Light control film 5D 1st laminated body 5U 2nd laminated body 6 1st base material 8,108 Liquid crystal layer 8a Liquid crystal 8b Dichroic dye 11,111 1st electrode 12 Spacer 13,113 1st alignment film 15 1st 2 base material 16,116 2nd electrode 17,117 2nd alignment film 19 Sealing material

Claims (3)

A first substrate provided with a first alignment film;
A second substrate provided with a second alignment film;
A liquid crystal layer comprising a twisted nematic liquid crystal and a dichroic dye disposed between the first substrate and the second substrate;
An electrode disposed on at least one of the first base material and the second base material,
At least one of the first alignment film and the second alignment film is a vertical alignment film;
Light control member. It is a normally black type in which the light transmittance of the liquid crystal layer increases as the voltage applied to the electrode increases.
The light control member according to claim 1. When both the first alignment film and the second alignment film are vertical alignment films,
The d / p is 1.3 or more (1.3 ≦ d / p), where d is the thickness of the liquid crystal layer and p is the chiral pitch of the liquid crystal contained in the liquid crystal layer. The light control member of description.

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