JP2017067869A - Light control film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light control film that can further reliably block transmitted light compared with a prior art.SOLUTION: A light control film comprises first and second laminates 5D and 5U that sandwiches a liquid crystal layer 8, the first and second laminates formed by providing at least alignment layers 13 and 17 on base materials 6 and 15 made of a transparent film material, and controls the distribution of light to liquid crystal in the liquid crystal layer 8 through the drive of transparent electrodes 11 and 16 provided on the first and second laminates 5D and 5U to control transmitted light. The optical axes of the base materials 6 and 15 of the first and second laminates 5D and 5U are orthogonal to each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light control film that can be used for, for example, an electronic blind that is attached to a window to control the transmission of extraneous light.

  Conventionally, for example, various devices relating to a light control film 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 film uses liquid crystal. The light control film using the liquid crystal is produced by sandwiching a liquid crystal material with a transparent film material on which a transparent electrode is produced, and producing the liquid crystal cell with a linear polarizing plate. As a result, in this light control film, the orientation of the liquid crystal is changed by changing the electric field applied to the liquid crystal, thereby blocking or transmitting the extraneous light, and further changing the amount of transmitted light. To control.

  By the way, in this kind of light control film, it is desired to reduce the transmittance at the time of light shielding so that the transmitted light can be shielded more reliably than in the past.

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

  The present invention has been made in view of such a situation, and an object of the present invention is to make it possible to more reliably block transmitted light with respect to a light control film than in the past.

  The present inventor conducted extensive research to solve the above-mentioned problems, and arranged the transparent film so that the optical axes (slow axis directions) are orthogonal on both sides of the liquid crystal layer. The idea of eliminating the influence and reducing the transmittance at the time of shading was led to the completion of the present invention. Here, the slow axis is the direction in which the refractive index of a material having refractive index anisotropy is maximized.

  Specifically, the present invention provides the following.

(1) A liquid crystal layer is sandwiched between first and second laminates obtained by providing at least an alignment layer on a substrate made of a transparent film material,
Controlling the light distribution of the liquid crystal according to the liquid crystal layer by driving the transparent electrode provided in the first and / or the second laminate to control the transmitted light;
The light control film in which the optical axis of the base material of the said 1st and 2nd laminated body orthogonally crosses.

  According to (1), the phase difference of transmitted light imparted by the substrate of the first or second laminate can be canceled by the phase difference of the substrate of the second or first laminate, This effectively avoids an increase in transmittance due to optical anisotropy of the base material and can reduce the transmittance during light shielding, thereby blocking the transmitted light more reliably than in the past. it can.

(2) In (1),
A light control film comprising an optical functional layer of a linearly polarizing plate on a side surface opposite to the liquid crystal layer of the first and second laminates.

  According to (2), the transmitted light can be more reliably shielded with a more specific configuration than in the prior art.

(3) In (1) or (2),
The transparent film material is
A light control film that is either a polycarbonate film or a COP film.

  According to (3), the transmitted light can be more reliably blocked by the more specific configuration of the base material as compared with the conventional case.

  According to the present invention, with respect to the light control film, it is possible to more reliably block transmitted light as compared with the conventional case.

It is sectional drawing which shows the light control film which concerns on 1st Embodiment of this invention. It is a figure where it uses for description of the detailed structure of the light control film of FIG. It is a figure where it uses for description of the other detailed structure of the light control film of FIG. It is a figure where it uses for description of the comparative example of the light control film of FIG. It is a figure where it uses for description of the other comparative example of the light control film of FIG. It is a flowchart with which it uses for description of the manufacturing process of the light control film of FIG.

[First Embodiment]
[Light control film]
FIG. 1 is a cross-sectional view showing a light control film according to the first embodiment of the present invention. This light control film 1 is used by being attached to an area for light control such as a window glass of a building, a showcase, an indoor transparent partition, etc. with an adhesive layer or the like, and the amount of transmitted light can be reduced by changing the applied voltage. Control.

  This light control film 1 is a film material that controls transmitted light using liquid crystal, and is configured by sandwiching a liquid crystal cell 4 for light control film between linear polarizing plates 2 and 3. Here, the linear polarizing plates 2 and 3 are formed by impregnating polyvinyl alcohol (PVA) with iodine or the like, and then stretched to form an optical functional layer that performs an optical function as a linear polarizing plate. TAC (triacetyl cellulose) The optical functional layer is sandwiched between base materials made of a transparent film material such as the above. The linearly polarizing plates 2 and 3 are arranged in the liquid crystal cell 4 by an adhesive layer made of an ultraviolet curable resin or the like in a crossed Nicol arrangement. The linear polarizing plates 2 and 3 are provided with retardation films 2A and 3A for optical compensation on the liquid crystal cell 4 side, respectively, but the retardation films 2A and 3A may be omitted as necessary.

  The liquid crystal cell 4 controls the polarization plane of transmitted light by an applied voltage to a transparent electrode described later. Thereby, the light control film 1 is comprised so that transmitted light can be controlled and various light control can be aimed at.

[Liquid crystal cell]
The liquid crystal cell 4 is configured by sandwiching a liquid crystal layer 8 between an upper laminate 5U and a lower laminate 5D which are first and second laminates in a film shape. The lower laminate 5D is formed by producing the transparent electrode 11, the spacer 12, and the alignment layer 13 on the base 6 made of a transparent film material. The upper laminate 5U is formed by laminating a transparent electrode 16 and an alignment layer 17 on a base material 15 made of a transparent film material. The liquid crystal cell 4 controls the orientation of the liquid crystal material provided in the liquid crystal layer 8 by the TN (Twisted Nematic) method by driving the transparent electrodes 11 and 16 provided in the upper laminate 5U and the lower laminate 5D. This controls the plane of polarization of the transmitted light.

  In place of the TN method, a driving method such as a VA (Virtual Alignment) method or an IPS (In-Place-Switching) method may be applied. When driving by the IPS method, either the transparent electrode 11 or 16 of the upper laminate 5U or the lower laminate 5D is omitted, and a driving electric field is applied to the liquid crystal material by patterning the other transparent electrode. .

  Although various transparent film materials applicable to this kind of film material can be applied to the base materials 6 and 15, it is desirable to apply a film material having a small optical anisotropy. In this embodiment, although a polycarbonate film is applied to the base materials 6 and 15, a COP (cycloolefin polymer) film or the like may be applied.

  Various electrode materials applied to this kind of film material can be applied to the transparent electrodes 11 and 16, and in this embodiment, the transparent electrodes 11 and 16 are formed of a transparent electrode material made of ITO (Indium Tin Oxide). The spacer 12 is provided to define the thickness of the liquid crystal layer 8, and various resin materials can be widely applied. It is produced by applying a photoresist on 6 and exposing and developing. The spacer 12 may be provided in the upper laminate 5U, or may be provided in both the upper laminate 5U and the lower laminate 5D.

  The alignment layers 13 and 17 are produced by rubbing a polyimide resin layer. The alignment layers 13 and 17 can be applied with various configurations capable of expressing the alignment regulating force with respect to the liquid crystal material related to the liquid crystal layer 8, and may be formed by a so-called photo-alignment layer. You may form and form the fine line-shaped uneven | corrugated shape by a process by a shaping process. The spacer 12 may be provided on the alignment layer 13.

  In addition, although various materials to which the photo-alignment technique can be applied can be applied as the photo-alignment material, in this embodiment, the alignment is not changed by ultraviolet irradiation after the alignment, for example, a light dimerization type. Use materials. The light dimerization 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).

  Various liquid crystal materials applicable to this type of light control film can be widely applied to the liquid crystal layer 8. In the liquid crystal cell 4, a sealing material 19 is disposed so as to surround the liquid crystal layer 8, and the upper stacked body 5 </ b> U and the lower stacked body 5 </ b> D are integrally held by the sealing material 19, thereby preventing leakage of the liquid crystal material. .

[Base material arrangement]
FIG. 2 is a diagram for explaining the arrangement of the base materials 6 and 15 in the light control film 1. As for the light control film 1, the transparent material by the same material and thickness is applied to the base materials 6 and 15, and the base materials 6 and 15 are arrange | positioned so that the optical axis L1 may orthogonally cross. Here, the range perpendicular to the optical axis L1 includes practically sufficient transmittance at the time of light shielding although the angle formed by the two optical axes L1 including the measurement error and the manufacturing error is within 90 ° ± 5 °. From the viewpoint of suppressing the angle, it is preferably within 90 ° ± 2 °, and more preferably within 90 ° ± 1 °. The thickness of the base material varies, and when the same film material is applied to the base materials 6 and 15, the thickness of the base material 6 is ± 10 μm, which is the thickness of the base material 15. From the viewpoint of sufficiently suppressing the thickness of the base material 6, the thickness of the base material 6 is preferably ± 10 μm, and the thickness of the base material 6 is more preferably ± 5 μm. preferable. Thereby, in this light control film 1, in-plane phase difference is equalized by the base materials 6 and 15, and the phase difference given to the transmitted light by the base material 6 is changed by the phase difference given by the base material 15. By canceling, the transmittance at the time of shading (so-called black transmittance) is reduced. Thereby, the light control film 1 shields transmitted light more reliably than before.

  That is, in the configuration in which the linearly polarizing plates 2 and 3 having a crossed Nicol arrangement are arranged on both sides of the liquid crystal cell 4 and the polarization plane of the transmitted light is controlled by the liquid crystal cell 4 as in this embodiment, the transmitted light is controlled. When the base materials 6 and 15 of the cell 4 have optical anisotropy, the incident light of the liquid crystal layer 8 enters the liquid crystal layer 8 by elliptical polarization due to the optical anisotropy of the base materials 6 and 15. . As a result, in a state where no voltage is applied to the transparent electrodes 11 and 16 (when no electric field is applied to the liquid crystal layer 8), transmitted light including the transmission axis direction component of the output side linearly polarizing plate is transmitted from the liquid crystal layer 8. As a result, the transmittance cannot be sufficiently reduced. Thereby, in this kind of light control film, a transparent film material with sufficiently small optical anisotropy is applied to the base materials 6 and 15. Specifically, a polycarbonate film or the like is applied to the base materials 6 and 15, and this polycarbonate film has an extremely small in-plane retardation of about 10 nm.

  However, according to the results of various experiments, even with a transparent film material having such a small optical anisotropy, the transmittance at the time of light shielding increases due to this small in-plane retardation, and this increase in transmittance is observed. It was found that it cannot be ignored.

  However, as in this embodiment, when the base materials 6 and 15 made of a transparent film material having the same material and film thickness are arranged so that the optical axes L1 are orthogonal to each other, the incident-side base material gives the transmitted light. The phase difference thus made can be canceled out by the substrate on the emission side, whereby the transmittance during light shielding can be significantly reduced. Specifically, when a substrate having an in-plane retardation of 10 nm is arranged so that the optical axis is parallel, the transmittance at the time of light shielding is about 2%, whereas the optical axis of this substrate is orthogonal. When arranged in such a manner, the transmittance at the time of light shielding can be reduced to about 0.2%, whereby the transmittance can be reduced to 1/10 as compared with the case of the optical axis parallel arrangement.

  In this embodiment, the light control film 1 has the transmission axes L2 parallel to the linear polarizing plates 3 and 2 laminated on the substrates 6 and 15 with respect to the optical axes L1 of the substrates 6 and 15, respectively. However, the linearly polarizing plates 3 and 2 are arranged in a crossed Nicol arrangement so as to correspond to the alignment direction of the liquid crystal material by the alignment layers 13 and 17. What is necessary is just to be sufficient and can arrange | position in various directions with respect to the optical axis L1 of the base materials 6 and 15. FIG.

〔Experimental result〕
[Example 1]
A polycarbonate film material having a thickness of 100 μm formed by forming hard coat layers on both sides was applied to the base materials 6 and 15, and a light control film was produced according to the configuration of the first embodiment described above. The retardation films 2A and 3A are omitted. The arrangement of the base materials 6 and 15 and the linear polarizing plates 2 and 3 is an arrangement according to the inclination described above with reference to FIG. In Example 1, the transmittance was 0.2% when there was no electric field, and it was confirmed that the transmitted light could be sufficiently shielded when shielded.

[Example 2]
In Example 2, as shown in FIG. 3, the transmission axes L <b> 2 of the linearly polarizing plates 2 and 3 are arranged so as to form an angle of 45 degrees with respect to the optical axis L <b> 1 of the base materials 15 and 6. As a result, in Example 2, the alignment layers 13 and 17 are set to the rubbing direction at an angle of 45 degrees with respect to the optical axis L1 of the base materials 6 and 15. The second embodiment has the same configuration as that of the first embodiment except that the configuration regarding the arrangement of the linearly polarizing plates 2 and 3 is different. Also in Example 2, the transmittance was 0.2% when there was no electric field, and it was confirmed that the transmitted light could be sufficiently shielded when shielded.

[Comparative Example 1]
As shown in FIG. 4, Comparative Example 1 was configured in the same manner as Example 1 except that the optical axes L1 of the base materials 5 and 16 were arranged in parallel. In Comparative Example 1, it was found that the transmittance was 2.0% when no electric field was applied, and the transmittance was high.

[Comparative Example 2]
As shown in FIG. 5, Comparative Example 2 was configured in the same manner as Example 2 except that the optical axes L1 of the base materials 5 and 16 were arranged in parallel. In Comparative Example 2, it was found that the transmittance was 2.0% when no electric field was applied, and the transmittance was high.

〔Manufacturing process〕
FIG. 6 is a flowchart showing the manufacturing process of the light control film. In this manufacturing process, transparent electrodes 11 and 16 are respectively formed on the substrates 6 and 15 by applying a photolithography technique in the electrode manufacturing process SP2. Subsequently, in the spacer preparation step SP3, a photoresist film is prepared on the substrate 6, and then exposed and developed, whereby the spacer 12 is prepared. Subsequently, in the manufacturing step SP4 of the alignment layer, the polyimide resin layer coating solution is formed on the base material 6 formed of the spacer 12 and on the base material 15 formed of the transparent electrode 16. After coating, drying and heat treatment are performed, thereby producing a polyimide film. In addition, the polyimide film is rubbed to produce the alignment layers 13 and 17.

  Subsequently, in the manufacturing process, in the sealing process SP5, a sealant is applied in a frame shape using a dispenser to the substrate 6 formed with the alignment layer 13, and then a predetermined position surrounded by the frame shape. The liquid crystal material according to the liquid crystal layer 8 is dropped using a dispenser. Thereafter, in this manufacturing process, after the base materials 6 and 15 are laminated, the upper laminated body 5U and the lower laminated body 5D are sealed by the sealing material 19 so that the liquid crystal layer 8 is sandwiched by pressing and heating. The light control film 1 is produced by bonding and integrating.

[Other Embodiments]
As mentioned above, although the specific structure suitable for implementation of this invention was explained in full detail, this invention can be variously changed in the range which does not deviate from the meaning of this invention.

  That is, in the above-described embodiment, the case where the liquid crystal material is driven by the TN method has been described. However, the present invention is not limited to this, and can be widely applied to the case where the liquid crystal material is driven by the VA method and the IPS method.

  In the above-described embodiment, the case where the spacer is manufactured using the photoresist has been described. However, the present invention is not limited to this, and a so-called bead spacer may be applied.

DESCRIPTION OF SYMBOLS 1 Light control film 2, 3 Linearly polarizing plate 2A, 3A Phase difference film 4 Liquid crystal cell 5D Lower laminated body 5U Upper laminated body 6, 15 Base material 8 Liquid crystal layer 11, 16 Transparent electrode 12 Spacer 13, 17 Orientation layer 19 Seal Material

Claims (3)

A liquid crystal layer is sandwiched between first and second laminates in which at least an alignment layer is provided on a substrate made of a transparent film material,
Controlling the light distribution of the liquid crystal according to the liquid crystal layer by driving the transparent electrode provided in the first and / or the second laminate to control the transmitted light;
The light control film with which the optical axis of the base material of the said 1st and 2nd laminated body orthogonally crosses. The light control film according to claim 1, further comprising an optical functional layer of a linearly polarizing plate on a side surface opposite to the liquid crystal layer of the first and second laminates. The transparent film material is
The light control film according to claim 1, wherein the light control film is a polycarbonate film or a COP film.

Images