WO1999023523A1

WO1999023523A1 - A device to adjust light-transmittance

Info

Publication number: WO1999023523A1
Application number: PCT/US1998/022881
Authority: WO
Inventors: Koichi Sano; Yoshifumi Nikaido
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1997-10-31
Filing date: 1998-10-28
Publication date: 1999-05-14
Also published as: JPH11131945A

Abstract

A device to adjust light-transmittance (10) which is capable of adjusting the blockage of light includes a first polarizer (14), a second polarizer (22) having the axis of polarization perpendicular to the polarization axis of the first polarizer and which are arranged with a space between them, a light-transmitting element containing a polymer oriented in a direction different from the polarization axes of the first polarizer and second polarizer, a means to move the light-transmitting element in such a manner that the light-transmitting element can be placed between the first polarizer and second polarizer, or the light-transmitting element can be placed on the side opposite the first polarizer from the second polarizer.

Description

A DEVICE TO ADJUST LIGHT TRANSMITTANCE

Field of the Invention

The present invention relates to a device to adjust light-transmittance capable of adjusting the degree of inhibition of light transmission and further relates to the light adjustment component used.

Background of the Invention

In order to block or control light passing through window panes in buildings, curtains and blinds have been used in the past. Blinds are used for adjusting light through rotation of louvers as well.

However, conventional blinds are capable of adjusting light at the time of light correction only through rotation of louvers, etc., and adjustment of light is made possible through reducing the spaces between the louvers and the brightness inside the room at the time remains constant. The same is true in the case of curtains. It is very inconvenient when adjustment of the light is not possible to prevent a closed-in feeling within the room or lack of privacy.

In an attempt to eliminate the above-mentioned inconvenience, a method for adjustment of light by means of polarizing sheets having different polarization axis in the same plane is disclosed in Japanese Kokai Patent Application No. Hei 5-307112, but the specific form is not disclosed. Thus, it is not possible for those in the field to understand the structure or the method of application.

The present invention provides a device which can adjust a degree of inhibition of light transmission. This is accomplished by varying an arrangement of a first polarizer; a second polarizer; and a light transmitting element, wherein a polarization axis of the second polarizer is perpendicular to a polarization axis of the first polarizer, the second polarizer is spaced from the first polarizer and the light transmitting element contains a polymer oriented in a different direction from the polarization axes of the first polarizer and the second polarizer. By varying the arrangement of the first polarizer, the second polarizer and the light transmitting element, a degree of inhibition of light transmission can be changed.

Summary of the Invention The present invention provides a device to adjust light-transmittance that is capable of adjusting transmittance of light. More particularly, the present invention provides a device to adjust light transmittance by varying the arrangement of a first polarizer, a second polarizer and a light-transmitting element, wherein the polarization axis of the second polarizer is perpendicular to the polarization axis of the first polarizer, the second polarizer is spaced from the first polarizer and the light-transmittance element contains a polymer oriented in a different direction from the polarization axes of the first polarizer and the second polarizer. Upon changing the arrangement of the first polarizer, the second polarizer and the light-transmittance element, the degree of inhibition of light-transmittance can be changed. Furthermore, it is desirable for the orientation axis of the polymer included in the above-mentioned light-transmitting element to be at an angle of 25°-65° to the polarization axis of the first polarizer. In this case, adjustment of light can be efficiently performed at the time of blocking light.

Thus, an adjustment of light-transmittance can be easily accomplished at the time of blocking light by changing the relative positions of the first polarizer and the second polarizer and the light-transmittance element of a device that includes a first polarizer, second polarizer and a light-transmittance element.

Brief Description of the Drawings The present invention will be further described with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional view of one embodiment of a device to adjust light transmittance according to the present invention.

Fig. 2 is a sectional side elevation of a louver for the blind used in the device in Fig. 1. Fig. 3 is a cross-sectional view of an arrangement of a first polarizer, a second polarizer and a light transmitting element for the device, where the device is in a light- transmission prohibited mode.

Fig. 4 is a schematic representation of another embodiment of a device to adjust light transmittance according to the present invention.

Fig. 5 is a schematic representation of still another embodiment of a device to adjust light transmittance according to the present invention.

Fig. 6 is a schematic representation of yet another embodiment of a device to adjust light transmittance according to the present invention.

Detailed Description

In the following, the present invention is explained in further detail with drawings, wherein the same reference numbers indicate the same parts.

Fig. 1 is a cross section that shows a device to adjust light-transmittance according to the present invention. The above-mentioned device to adjust light-transmittance 10 has a structure comprising film-like first polarizer 14 applied to window pane 12 by means of a transparent pressure-sensitive adhesive or double-coated tape (not shown in the figure) and blind 16 suspended from the window frame 15 located at or near the window pane. In this case, the blind includes a film-like second polarizer 22 having a polarization axis perpendicular to the polarization axis of the above-mentioned first polarizer and a film-like light-transmittance element 24 containing a polymer oriented in a direction different from the polarization axes of the above-mentioned first polarizer and second polarizer. The first polarizer and second polarizer used in this case are those commonly used for optical devices, for example, absorption type polarizers or reflection type polarizers. In this case, a reflection type polarizer is especially suitable since the light-transmittance factor is relatively high and the degree of blocking of light can be changed easily. Examples of a suitable reflection type polarizers include Transmax produced by Merck Co., the D-BEF plastic film containing a uniaxially oriented polymer layer produced by 3M Co., and liquid crystals. Furthermore, it is desirable for the thickness of the first polarizer to be in the range of 10-2,000 μm from the standpoint of securing like members of the light- transmittance element.

As shown in Fig. 1, blind 16 is installed maintaining a specified distance by louver 18 that can be mechanically or electrically operated, and which is used for adjustment of light passage and blocking. Fig. 2 is the lateral cross section showing louver 18. In Fig. 2, the louver has a structure consisting of many films formed on a transparent base material 20 made of a resin such as acrylic resin or polycarbonate resin with a thickness in the range of 30-3,000 μm with an acrylic type pressure-sensitive adhesive.

In specific terms, a film-like second polarizer 22 is applied to one surface of transparent base material 20. Furthermore, a light-transmitting element 24 containing a polymer oriented in a direction different from the polarization axes of the first polarizer and the second polarizer, for example, plastic films such as the above-mentioned D-BEF and Transmax, or a liquid crystal, is applied to second polarizer 22. Furthermore, in order to reduce the gloss of the louver 18 which causes reflections and to improve the appearance of the louver surface, a base film with a matte finish or a diffuse transmission type pressure- sensitive adhesive tape (diffuse transmission type film) having a base film made of a nonwoven fabric, woven cloth or paper 26a, 26b, can be further applied to the surface of the light-transmittance element and the other surface of base material 20. For the above- mentioned pressure-sensitive adhesive tape, for example, Scotch (registered Trademark) mending tape, etc. can be mentioned. Furthermore, a paint can be further coated on the above-mentioned tape or a film can be further applied to the tape. Also, an ultraviolet shielding treatment or infrared shielding treatment can be applied to the window pane.

In the device to adjust light-transmittance 10 having the structure described above, it was found that the degree of blockage of light can be varied by changing the relative positions of the first polarizer 14, second polarizer 22 and light-transmittance element 24 even when natural light such as sunlight is blocked by blind 16 through window pane 12. In other words, when the light-transmittance element 24 of the louver is arranged outside the first polarizer and upon rotation of the second polarizer as shown in Fig. 3(a), natural light S is essentially blocked. Furthermore, when the light-transmittance element 24 of louver 18 is arranged between the first polarizer and second polarizer as shown in Fig. 3(b), natural light S is partially transmitted. It was found that blockage of light can be effectively achieved when the orientation of the light-transmittance element is at an angle of 25°-65°, preferably 30°-60°, and ideally 40°-50°, for the first polarizer or the second polarizer. As described above, the light-transmittance at the time of blocking light can be adjusted through rotation of the louver used as a rotational member in the device to adjust light-transmittance. It is possible to prevent the closed-in feeling in rooms and lack of privacy in homes, offices, stores, medical institutions, and halls. Also, the device to adjust light-transmittance can be used effectively for darkrooms used for testing or development of photographs. In this case, working inside the dark room can be improved as the darkness required for tests or development of photographs is provided. Furthermore, the device used to adjust light-transmittance can be used in various modes of transportation such as aiφlanes, trains, and automobiles. In this case, shielding of light is performed at the time of stopping to provide privacy and partial transmission of sunlight during travel can be provided to protect the eyes of passengers, The device to adjust light-transmittance of the present invention is not limited to the first application example shown above. For example, the above-mentioned change can be made possible by louvers 18 that mechanically or electrically rotate around vertical axes as shown in Fig. 4. Furthermore, it is not necessary for the louvers to have a structure consisting of multiple components. For example, a sun visor having a structure the same as that shown for the above-mentioned louver that rotates in the horizontal direction can be installed between the front seat of the automobile and a windshield having the first polarizer.

The device to adjust light-transmittance of the present invention is not limited to the above-mentioned application example or modified example. In the device to adjust light- transmittance shown in the lateral cross section of Fig 6(a) a curtain is used rather than the device to adjust light-transmittance having louvers as shown in Fig. 1. In this example, the ends of light-transmittance sheet 34 are connected to the ends of light-shielding sheet 32 and having a structure the same as the louver of the first application example and forming a continuous strip consisting of blocking sheet 32 and light-transmitting sheet 34. The above-mentioned continuous sheet is placed over two rollers 36a and 36b that rotate. Thus, the above-mentioned continuous sheet and roller structure provide a moveable member capable of changing the relative positions of the first polarizer, second polarizer, and light-transmittance element. Furthermore, the first polarizer 14 is attached to window pane 12 as above. In the above-mentioned structure, when the ring-like member moves through a half- cycle around rollers 36a and 36b by means of the rotation of rollers 36a and 36b as shown in Fig. 6(b), the relative positions between the second polarizer (not shown in the fig.) and the light-transmitting element (not shown in the fig.) on light shielding sheet 32 of the continuous sheet and the first polarizer 14 of the window pane 12 are interchanged. As a result, the degree of blocking of light can be changed. In this case, it is also possible to change the degree of blocking of light through rotation of rollers 36a and 36b alone even when the light shielding sheet has a large surface area. In this case, it is very convenient compared with the above-mentioned blinds whereby the degree of shielding of light is changed through many louvers. Furthermore, when the diameter of the rollers is small, it is possible to reduce the thickness. Furthermore, the continuous sheet is not limited to the above-mentioned example. Instead of the above-mentioned light-transmittance sheet 34, a belt-like first polarizer can be attached and a belt-like light-transmittance element can be used instead of the light-transmittance sheet. In this case also, the relative positions of the first polarizer, second polarizer and light-transmittance element can be changed by the device to adjust the transmission of light. Examples

In the following, the present invention is explained in further detail with examples. Needless to say, the present invention is not limited to these examples.

In this example, a simplified louver that does not include a base material was produced and the effectiveness of the present invention was confirmed. In other words, D- BEF made by 3M Co. was used for the first polarizer, second polarizer and light- transmittance element and Scotch (registered Trademark) mending tape was used for the pressure-sensitive adhesive tape for the diffuse transmission tape. The orientation of the polymer that comprises the light-transmittance element had an angle of 45° with respect to the polarization axis of the first polarizer and the polarization axis of the second polarizer. An evaluation of the above-mentioned louver was made by measuring the luminance at the time of passage of light and the luminance when the light-transmitting element was placed between the first polarizer and second polarizer, and the luminance when the light- transmittance element was arranged outside the first polarizer and the second polarizer. A digital illumination meter produced by Minolta Coφ. was used for measurement of the above-mentioned luminance. The results obtained are shown in Table I.

Table I

As shown in Table I above, an obvious difference in the luminance was observed depending on the presence of the light-transmitting element included between the first polarizer and the second polarizer at the time of shielding light. As a result, it was found that the device to adjust light-transmittance of the present invention is capable of adjusting the blockage of light.

Claims

What is claimed is:

1. A device to adjust light transmittance, comprising a first polarizer; a second polarizer having a polarization axis pe╧åendicular to a polarization axis of the first polarizer, wherein the second polarizer is spaced from the first polarizer; a light transmitting element containing a polymer oriented in a different direction from the polarization axes of the first polarizer and the second polarizer; and, a means to move the light transmitting element such that the light transmitting element can be placed between one of the first polarizer and the second polarizer, or the opposite side of the first polarizer to the second polarizer.

2. A device according to claim 1, wherein an orientation axis of the polymer contained in said light transmitting element has an angle of 25┬░ to 65┬░ to the polarization axis of said first polarizer.