WO2017074307A1

WO2017074307A1 - Electrochromic display

Info

Publication number: WO2017074307A1
Application number: PCT/US2015/057482
Authority: WO
Inventors: Polly YUEN; Jack Hui HE
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2015-10-27
Filing date: 2015-10-27
Publication date: 2017-05-04

Abstract

A display that includes an electrochromic film and a layer of display elements such that light passing though the electrochromic film illuminates the layer of display elements. The electrochromic film is transparent when a first voltage is applied to the film.

Description

ELECTROCHROMIC DISPLAY

BACKGROUND

[0001] Displays are used with many types of electronic devices. Some displays use a layer of liquid crystal display elements that are illuminated with a light source. The light source can consume a significant portion of the power used by an electronic device. Thus, optimizing performance of the display, and especially the illumination of the display, may impact the battery life of portable electronic devices that depend on batteries for power.

Battery life is one metric used in assessing the performance of electronic devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various examples of the principles described herein and are a part of the specification. The illustrated examples are exemplary in nature and do not limit the scope of the claims. Like numerals denote like but not necessarily identical elements.

[0003] FIG. 1 shows an example of a device according to the present disclosure.

[0004] FIG. 2 shows an example of a device according to the present disclosure.

[0005] FIG. 3 shows an example of a device according to the present disclosure.

[0006] FIG. 4 shows an example of a flowchart with a method according to the disclosure. DETAILED DESCRIPTION

[0007] Electronic devices consume power in a wide variety of ways.

Displays, used to convey information to users, consume a significant amount of power in devices. The power consumed by the display impacts the battery life for portable devices. Display technologies use a variety of different approaches to form display images. For instance, liquid crystal displays (LCDs) may use a light source to project light through an image forming layer to form an image on a display. A variety of light sources may be used. Light emitting diodes (LEDs) are a popular choice due to their efficiency, response time, lifetime, cost, size, and other factors.

[0008] Electrochromic glass is part of the larger group of materials known as smart glass. Smart glass regulates the passage of light through the material based on some property. For example, electrochromic glass changes based on the application of an electrical potential. Electrochromic glass may be clear under the application of a first potential and translucent and/or opaque under the application of a second potential. Some electrochromic glass materials retain the appearance of the applied potential after the potential has been removed, slowly reverting to the original condition or awaiting the application of a second potential. This may make the glass energy efficient as the charge does not need to be continuously applied to maintain a desired state. Smart glass is used to regulate the light entering buildings and/or vehicles. Smart glass is also used to providing privacy by making transparent partitions temporarily opaque.

[0009] In this specification and the associated claims, the terms electrochromic glass and/or electrochromic film refers to a structure that has a first light interacting property when a first electrical potential is applied and has a second light interacting property when a second electrical potential is applied, the two potentials being different from each other and where one potential may be a zero potential. Electrochromic glasses often include one or more structural layers, while electrochromic films may not have structural layers but are applied to a structural layer to provide the electrochromic properties.

[0010] Glass, as used in this specification and the associated claims, includes not just silicon based materials but any material with similar transparent properties. Examples of such materials include the various silicon and borosilicate glasses, polymers including polymethylmethacrylate (PMMA), polystyrene (PS), polyester, polyurethanes (PU), polycarbonate (PC), etc. and transparent crystalline or amorphous materials including vacuum deposited materials.

[0011] One form of electrochromic film and/or glass utilizes multiple layers of material. Moving through a depth of the electrochromic material, these layers may include 1 ) a structural layer (e.g., glass,

polymethylmethacrylate (PMMA), polyester, or polycarbonate (PC)), 2) an electrode or conductive layer, 3) an ion receipt layer, 4) a permeable layer, 5) an ion source layer, 6) a second electrode layer and 7) a second structural layer. Not all layers are required, for example, in electrochromic films, the structural layer may be eliminated.

[0012] Application of a first potential between the two electrode or conductive layers in the electrochromic materials may induce flow of species from one electrode layer toward the other electrode layer. A wide variety of types of species can be used. Examples of such species include:

vanadium, lithium, molybdenum containing compounds, etc. The species may include a polymer chain that facilitates motion or reorientation. In one example, the polymer chain is a siloxane. In a second example, the polymer chain is a polyol. The species may be a charged ion, for example, lithium. The species may have a dipole or multiple localized potentials, e.g. a zwitterion.

[0013] Another structure of electrochromic material utilizes a different set of layers. These may include 1 ) an optional structural layer, 2) an electrode and/or conductive layer to apply a potential, 3) a layer including material that reorganizes and/or rearranges under the influence of an applied electrical field, and 4) a second electrode and/or conductive layer to serve as a counter electrode.

[0014] When a potential is imposed between the electrode layers, the charged species may reoriented between the electrode layers. In other examples, the changed species may change from a first geometry, structure, and/or complex to second with a different light interaction property. Examples of changes in the species include oxidation state change and ring forming. The species may be a polymer dispersed liquid crystal (PDLC).

[0015] In some applications, the electrochromic layer is made opaque and then an image is projected onto the opaque layer. The opacity allows a clear surface to absorb and retransmit light rather than allowing the light to pass through the film. This may modify the available viewing angle such that the electrochromic layer provides a privacy shield.

[0016] FIG 1 . shows an example of a device according to the present disclosure. The device includes a display (100) with an electrochromic film (1 10), an image forming layer (120), and a light source (130). Ambient light (140) is shown passing through the electrochromic film (1 10) and the image forming layer (120). Light (135) from the light source (130) is shown passing through the image forming layer (120).

[0017] The display (100) could be used with a wide variety of devices including laptops, tablets, phones, viewers, monitors, and/or other electronic devices that use a display to provide information to a user. While the reduced energy consumption is most helpful in devices that use a battery, most devices benefit from decreased power consumption. In some examples, the display is integrated with other portions of the device.

Alternately, the display may be connected to the device on a removable and/or temporary basis.

[0018] The electrochromic film (1 10) may be formed using a variety of different technologies. An electrochromic film (1 10) interacts with light in a first way under a first applied potential and the electrochromic film (1 10) interacts with light in a second way under a second applied potential. The first potential may be a zero potential. In some examples, the applied potential may cause the electrochromic film (1 10) to become transparent, translucent, opaque, frosted, colored, reflective, and/or otherwise modify the passage of light through the electrochromic film (1 10).

[0019] The electrochromic film (1 10) may have a single potential applied across the electrochromic film (1 10) in order to produce a uniform light affecting property behavior. It is also possible to apply a potential across only a portion of the electrochromic film (1 10). For example, the applied potential may be applied in the shape of a logo, design, and/or aesthetic element. One way to accomplish this is by having an electrode with a corresponding shape. In some examples, the side of the electrochromic film with the shaped electrode may also include a second electrode with a second shape. The second shape may include, for example, relatively uniform coverage of the electrochromic film (1 10).

[0020] The electrochromic film (1 10) may include at least two electrodes or conductors. The electrochromic film (1 10) may include a mobile region where molecules are able to rearrange themselves in response to applying potential to the electrodes. The electrochromic effect of the electrochromic film (1 10) may be achieved by modification of orientation, modification of structure, and/or migration of species within the electrochromic film (1 10).

[0021] The image forming layer (120) is a layer made up of display elements. The image forming layer (120) may adjust and/or regulate the color and pattern of light passing through it. The adjustment may include activating pixels of multiple colors that combine to generate a variety of colors. For example, an image forming layer may include blue, red, and green pixels in close proximity that blend so as to be perceived as some other color combination. The image forming layer (120) may lack significant light generation capability. Instead, light is passed through the image forming layer (120) to form the desired image. In one example, the image forming layer (120) is formed from liquid crystal.

[0022] The light source (130) provides light in order to increase the visibility of the image forming layer (120). Many variations of the light source (120) exist. The light source (130) is made of one or more light emitting diodes (LEDs). LEDs are relatively efficient, produce relatively little waste heat, and tend to have good service life. These properties encourage their use in displays (100). In some examples, the light source (130) includes multiple light emitting elements. The light emitting elements may have different voltages applied to the respective light emitting elements, including applying no significant voltage to one or more elements. In some examples, it may be more efficient to apply a uniform voltage across all light emitting elements. In other examples, it may be more efficient to power some light emitting elements and leave others off. Depending on the locations of the light emitting elements, each light emitting element may produce nonuniform illumination of the image forming layer (120). In one example, light passing through the electrochromic film (1 10) is non-uniform and the pattern of illumination of the light emitting elements is selected to reduce the non- uniformity of the light that passes through the image forming layer (120).

[0023] The display (100) also utilizes ambient light (140) from the environment. The ambient light (140) passes through the electrochromic film (1 10) and lights the image forming layer (120). In this specification and the associated claims, ambient light (140) refers to light not provided by the light source (130) or other portions of the display (100). Accordingly, illumination of the image forming layer (120) that is provided by the ambient light (140) does not need to be provided by the light source (130). This reduces the power requirements of the light source (130) which may extend battery life of a device associated with the display (100). Because the amount of light provided to the image forming layer (120) may depend on the ambient lighting conditions, this approach may also reduce the number of light emitting elements of the light source (130) that are required for the display (100) to function over a range of lighting conditions. Alternately, the same number of lighting elements may allow the display (100) to function under a wider variety of ambient lighting conditions.

[0024] FIG. 2 shows an example of a device according to the present disclosure. The device includes a display (100) with an electrochromic film (1 10), an image forming layer (120), and a light source (130). Ambient light (140) is shown passing through the electrochromic film (1 10) and the image forming layer (120). Light (135) from the light source (130) is shown passing through the image forming layer (120). The display may include a sensor (250), an enclosure (260), and a cover (270). These elements may provide additional functionality to the display as described below.

[0025] The display may include a sensor (250). The sensor (250) detects the light impinging on and/or passing through the electrochromic film (1 10). The sensor (250) may include a number of detecting elements capable of detecting the light properties at a variety of locations. The sensor (250) may be mounted on the image forming layer (120) and/or on the electrochromic film (1 10). The sensor (250) may be mounted on a side and not between the electrochromic film (1 10) and image forming layer (120). The sensor (250) may include one or more surfaces to direct light towards the detecting elements. The surface(s) may deflect a fraction of the light while allowing a majority of the light to transmit through the surface. In one example, the sensor is a charge coupled device (CCD). The sensor (250) may use electro-optical, photoelectric, mechano-optical, and/or magneto-optical detection. The sensor (250) may be coupled to the lighting source (130) so as to automatically adjust the amount or distribution of light provided by the light source (130) to the image forming layer (120). The amount and/or distribution of light provided by the light source (120) may also be adjustable by a user accessible control and/or by a processor.

[0026] The display may include an enclosure (260). The enclosure may be made of any suitable material. The enclosure (260) may cover the electrochromic film, in which case it is preferable that the enclosure (260) have a high transmittance. For example, the enclosure (260) may allow a majority of visible light to pass through the enclosure. The enclosure (260) may not cover a portion of the electrochromic film, in which case a wider variety of materials may be used for the enclosure (260). The

electrochromic film (1 10) may be recessed compared to the enclosure (260) in order to protect the electrochromic film (1 10) from damage. [0027] The display may include a cover (270). The cover (270) is between the image forming layer (120) and the user and serves to protect the image forming layer (120) from damage. The cover (270) may also enhance the image coming off the image forming layer. The cover (270) may include sensors, such as touch and/or optical sensors, to provide input to a processor. The cover (270) may be removable or may be fixed relative to the other parts of the display (100).

[0028] FIG. 3 shows an example of a device according to the present disclosure. The device is or includes a display (100) with an electrochromic film (1 10), an image forming layer (120), a light source (130), and a sensor (250). Figure 3 also includes a light guide (380) and a secondary sensor (390).

[0029] The light guide (380) may be between electrochromic film (1 10) and the image forming layer (120). The light guide serves increase the uniformity of light from the electrochromic film (1 10) and from the light source (130) before it is transmitted to the image forming layer (120). The light guide (380) may deflect light so as to collimate the light and/or reduce the amount of scattered light relative to an arc that constitutes the primary viewing angle of the display (100).

[0030] The light guide (380) may be formed from a material with a high refractive index. The light guide (380) may be formed from a transparent material. The light guide (380) may be formed from a polymer. In one example, the light guide (380) is a molded component. The light guide (380) may include reflective features organized around the light emitting elements of the light source (130). The light guide may facilitate direction of light to one or more detectors of the sensor (250) or secondary sensor (390). The light guide (380) may include one or more one-way reflective surfaces to enhance light collection and channeling. In one example, these reflective surfaces are formed by vapor depositing a metal onto a molded polymer substrate. The metal may be Ag, Al, Ni, Sb, alloys that includes these elements, and metal and/or alloys with similar, suitable reflective properties. [0031] The secondary sensor (390) provides additional information of light intensities and/or hues not obtained from the sensor (250). The secondary sensor (390) may measure the ambient light level. The secondary sensor (390) may measure the uniformity of the light on emitted by the image forming layer (120). The secondary sensor may verify the functioning of one or more of the light emitting elements that make up the light source (130). In some examples, the secondary sensor (390) uses a different type of detector than the sensor (250).

[0032] FIG. 4 shows a method (400) with a number of operations.

[0033] Operation 410 includes detecting an amount of light passing through an electrochromic film (1 10) using a sensor (250). The sensor (250) may detect a mean illumination. The sensor (250) may measure the light at multiple points and combine them in some manner. Parts of the sensor (250) may be mounted on the electrochromic film (1 10) and/or the color changing layer (120). The sensor may detect both intensity and hue of light impinging on the electrochromic film (1 10). Alternately, the sensor may detect light that has passed through the electrochromic film (1 10). The sensor (250) may be electrically associated with one or more logic elements that process the sensor outputs to provide commands.

[0034] Operation 420 includes modifying the output of a light source (130) based on the output from the sensor (250). In some examples, the output of the light source (130) includes output from a plurality of light emitting elements. Some light emitting elements may be powered at one voltage level while other light emitting elements are powered at a second voltage level. In one case, the two voltage levels are both non-zero voltage levels. In another case, one of the two voltage levels is a non-emitting voltage level.

[0035] Within the principles described by this specification, a vast number of variations exist. Accordingly, the specification supports and enables a wide variety of geometries.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A electrochromic display, the display comprising:

a first layer comprising an electrochromic film, wherein when a first voltage is applied to the electrochromic film, the electrochromic film is transparent; and

a second layer comprising display elements, the first and second layers positioned such that light passing through the first layer also passes through the second layer.

2. The electrochromic display of claim 1 , further comprising an internal light source to provide light to the second layer.

3. The electrochromic display of claim 1 , wherein light passing through the electrochromic film reduces an amount of light supplied to the second layer by the light source to produce a displayed image of a given visibility.

4. The electrochromic display of claim 1 , wherein when a second voltage is applied to the electrochromic film the electrochromic film displays a symbol.

5. The electrochromic display of claim 1 , wherein when a second voltage is applied to the electrochromic film the electrochromic film is translucent but not transparent.

6. The electrochromic display of claim 1 , further comprising a third layer of touch sensitive material, wherein the second layer is between the first layer and the third layer.

7. The electrochromic display of claim 2, wherein the internal light source is between the first and second layers.

8. The electrochromic display of claim 2, further comprising a light guide located between the first and second layers.

9. The electrochromic display of claim 2, further comprising a sensor to detect light entering the electrochromic film.

10. The electrochromic display of claim 9, wherein the amount of light emitted from the internal light source is regulated based on an output from the sensor.

1 1 . The electrochromic display of claim 9, wherein the internal light source is turned on and off based an output from the sensor.

12. A method of illuminating a display comprising:

detecting with a sensor a level of light passing through an electrochromic film; and

modifying an output of a light source based on an output from the sensor.

13. The method of claim 12, wherein the light passing through the electrochromic film illuminates an image forming layer and light from the light source illuminates the image forming layer.

14. The method of claim 12, further comprising modifying the distribution of light from the light source on an image forming layer to reduce non-uniformity of illumination of the image forming layer.

15. A system for regulating the light level of a display, the system comprising:

a light source;

an electrochromic film on a first side of the light source; and a layer of liquid crystal display (LCD) material on a second side of the light source, where the first and second sides are opposite to each other with respect to the light source.