JP2019158955A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing film which transmits one polarized light and reflects another polarized light between a polymer-dispersed liquid crystal film and a display element such as an LCD, so that the display element is in a display state. Provided is a display device that displays without impairing the brightness and whitens the display screen when the display element is in a non-display state. SOLUTION: This is a display device 1 in which a PDLC 4 is arranged on a display surface of an LCD 2, and a polarizing film 3 that transmits P-polarized light and reflects S-polarized light is arranged between the display surface of the LCD 2 and the PDLC 4. , The polarizing surface of the polarizing plate 22b arranged on the display surface of the LCD 2 and the polarizing surface of the polarizing film 3 coincide with each other. When the LCD 2 is in the display state and the PDLC 4 is in the transparent state, P-polarized light is transmitted through the polarizing film 3 and the PDLC 4 and displayed with high brightness. The S-polarized light of the outside light is reflected by the PDLC 4 and the polarizing film 3 to whiten the screen. [Selection diagram] Fig. 1

Description

  The present invention relates to a display device that makes a display screen in a non-display state white.

  For example, a liquid crystal display (LCD: Liquid Crystal Display) such as a liquid crystal television enables a vivid display in the display state, but the screen is dark in the non-display state, which is not preferred in design. . In view of this, it is desired to make the screen white to facilitate matching with the color of the wall in the non-display state.

  As a display element for displaying white, a polymer dispersed liquid crystal (PDLC) is known. When PDLC is superimposed on a display surface such as an LCD, if the PDLC is in a transparent state when the LCD is on (display state), the PDLC has a very high light transmittance, so that it is displayed without impairing the brightness of the LCD. Is possible (see FIG. 6A). On the other hand, when the LCD is in the off state (non-display state) and the PDLC is clouded, there is no incident light from the back side due to the adhesion between the LCD and the PDLC, and only the light that backscatters the light from the display surface. End up. Therefore, the whiteness caused by the white turbidity of the PDLC is greatly reduced, and the black color of the LCD screen remains, so that the desired whiteness cannot be achieved (see FIG. 6B).

  To solve such a problem, it is conceivable to reduce the decrease in whiteness by thickening the liquid crystal layer of the PDLC. In this case, by increasing the thickness of the liquid crystal layer of the PDLC, the backscattering is somewhat improved and the whiteness is improved. However, the backscattering is not sufficiently improved and is driven in proportion to the film thickness. There is a problem that the power consumption increases because the voltage increases (see FIG. 7).

  As technologies combining display elements such as PDLC and LCD, for example, technologies disclosed in Patent Documents 1 to 3 are disclosed. In the technique shown in Patent Document 1, a single-sided transparent electrode substrate is disposed so that transparent electrodes face each other, a (polymer / liquid crystal) composite film is sandwiched between the transparent electrode substrates, a half mirror on the back surface, and a reflector on the back surface Or a color plate is arranged.

  In the technique disclosed in Patent Document 2, polymer dispersed liquid crystal is sealed between an active matrix substrate and a counter electrode glass substrate, and a black substrate is provided behind the polymer dispersed liquid crystal. A color filter is provided on the counter electrode glass substrate. When the voltage applied to each pixel of the polymer dispersed liquid crystal is controlled, when the voltage is applied, the liquid crystal becomes transparent and the black substrate can be seen to display black, and when no voltage is applied, the liquid crystal scatters light and becomes cloudy. The color of the color filter provided thereon is displayed. Furthermore, since a polarizing plate and an alignment film are unnecessary and the light transmittance of the polymer dispersed liquid crystal itself is high, a backlight is unnecessary, and power consumption is greatly reduced.

  In the technique shown in Patent Document 3, a viewing angle limiting device is arranged on the display surface of a reflective TN liquid crystal display device. A transparent electrode facing the inside of the opposing transparent substrate is formed, and a polymer precursor and a liquid crystal are mixed and sealed between them, and the polymer is cured by ultraviolet irradiation, and at the same time the liquid crystal and the polymer are combined. Phase separate. When an AC voltage is applied to the thus formed cell with high light transmittance, the liquid crystal molecules are aligned in the direction of the electric field and become light-scattered due to the difference in refractive index between the liquid crystal and the polymer, resulting in white turbidity. Since this scattering intensity is particularly strong in a specific azimuth angle range, the display content of the liquid crystal display device can be concealed from the surrounding people by setting the azimuth angle range in a predetermined direction.

JP 2004-341379 A Japanese Unexamined Patent Publication No. 07-110468 JP 09-073070 A

  As described above, each of the techniques disclosed in Patent Documents 1 to 3 can solve the problem of reducing the decrease in whiteness due to white turbidity of PDLC and making the screen whiter when a display element such as an LCD is not displayed. It's not technology.

  In particular, when a half mirror as shown in Patent Document 1 is used, half of the light is transmitted by the half mirror and the remaining half of the light is reflected. Therefore, when the display element such as an LCD is not displayed, It is possible to reduce the decrease in whiteness due to the white turbidity of the PDLC and make the screen whiter (see FIG. 8B). However, when a display element such as an LCD is in a display state, the light from the display element is reflected by the half mirror, and even when the PDLC is in a transparent state, the brightness is lowered and the screen becomes dark and visibility is improved. It decreases (see FIG. 8A).

  The present invention provides a polarizing film that transmits one polarized light and reflects the other polarized light between a polymer dispersed liquid crystal film and a display element such as an LCD, so that the display element is in a display state. A display device is provided that displays an image without losing luminance and whitens the display screen when the display element is in a non-display state.

  A display device according to the present invention is a display device in which a polymer-dispersed liquid crystal film is disposed on a display surface of a display means, and one polarized light is provided between the display surface of the display means and the polymer-dispersed liquid crystal film. A polarizing film that transmits and reflects other polarized light is disposed.

  Thus, in the display device according to the present invention, a polarizing film that transmits one polarized light and reflects the other polarized light is disposed between the display surface of the display means and the polymer-dispersed liquid crystal film. When the display means is in a non-display state and the polymer dispersed liquid crystal film is in a cloudy state, other polarized light in the external light from the display surface is reflected by the polarizing film, and the whiteness due to the cloudiness of the polymer dispersed liquid crystal film is reflected. This has the effect of reducing the decline and making the display screen white.

  In the display device according to the present invention, the polarizing surface of the polarizing plate disposed on the display surface of the display means and the polarizing surface of the polarizing film are disposed to coincide with each other.

  As described above, in the display device according to the present invention, the polarizing surface of the polarizing plate disposed on the display surface of the display means and the polarizing surface of the polarizing film are disposed to coincide with each other. When a display unit having a polarizing plate on the display surface is used like a display, the light transmission is not affected when the display unit is in a display state. That is, since the brightness of the display means is not impaired, even if a polarizing film is provided, the visibility is not reduced, and the screen is whitened when the display means is in a non-display state. There is an effect that becomes possible.

  The display device according to the present invention includes a polymer-dispersed liquid crystal film control unit that controls driving of the polymer-dispersed liquid crystal film in a transparent state / white turbid state, and a display control unit that controls on / off driving of the display unit. The polymer-dispersed liquid crystal film control means controls the polymer-dispersed liquid crystal film in a transparent state, and the display control means controls the display means to be turned on, the one polarized light from the display means is When passing through the polarizing film and the polymer-dispersed liquid crystal film, the polymer-dispersed liquid crystal film control means controls the polymer-dispersed liquid crystal film to a cloudy state, and the display control means controls the display means to be off. The other polarized light in the external light from the display surface of the polymer dispersed liquid crystal film is reflected by the polymer dispersed liquid crystal film and the polarizing film. Is shall.

  Thus, in the display device according to the present invention, the polymer-dispersed liquid crystal film control means for controlling the driving of the polymer-dispersed liquid crystal film in the transparent state / white turbid state, and the on / off driving of the display means are controlled. Display control means, and when the polymer-dispersed liquid crystal film control means controls the polymer-dispersed liquid crystal film to a transparent state and the display control means controls the display means to be on, the display means from the display means One polarized light is transmitted through the polarizing film and the polymer-dispersed liquid crystal film, and the polymer-dispersed liquid crystal film control means controls the polymer-dispersed liquid crystal film to a cloudy state, and the display control means turns off the display means. In the case of controlling, the other polarized light in the external light from the display surface of the polymer dispersed liquid crystal film is the polymer dispersed liquid crystal film and the polarized light. Reflected by the film, when the display means is in the display state, it maintains good visibility without impairing the brightness, and when the display means is in the non-display state, the screen is made whiter to improve the design. There is an effect that can be made.

  In the display device according to the present invention, the display means uses liquid crystal, and when the reflector is disposed on the back side of the display and no voltage is applied between the transparent electrodes sandwiching the liquid crystal, the liquid crystal is transmitted. The state is maintained.

  Thus, in the display device according to the present invention, the display means uses liquid crystal, and a reflector is provided on the back side of the display and no voltage is applied between the transparent electrodes sandwiching the liquid crystal. In order to maintain the liquid crystal in the transmissive state, when the display means is in the non-display state, one polarized light in the external light from the display surface passes through the transmissive liquid crystal and is reflected by the reflection plate on the back side of the display. This has the effect of improving the diffusion and making the screen whiter.

  In the display device according to the present invention, the display means uses a liquid crystal, and a reflector is provided on the back side of the display, the backlight is turned off when not displayed, and between the transparent electrodes sandwiching the liquid crystal A voltage is applied to the liquid crystal to make the liquid crystal in a transmissive state.

  Thus, in the display device according to the present invention, the display means uses liquid crystal, and a reflector is provided on the back side of the display, the backlight is turned off when not displayed, and the liquid crystal is In order to make the liquid crystal transmissive by applying a voltage between the transparent electrodes sandwiched, the liquid crystal is applied by applying a voltage between the transparent electrodes sandwiching the liquid crystal when the backlight of the display means is turned off. By making the transmissive state, one polarized light in the external light from the display surface passes through the liquid crystal and is reflected by the reflector on the back side of the display to improve the back diffusion and make the screen whiter. Play.

It is a figure which shows the structure of the display apparatus which concerns on 1st Embodiment. It is a figure which shows the structure of PDLC in the display apparatus which concerns on 1st Embodiment. It is a figure which shows the structure of LCD in the display apparatus which concerns on 1st Embodiment. It is a figure which shows the advancing state of the light in the display apparatus which concerns on 1st Embodiment. It is a figure which shows the structure of the display apparatus which concerns on other embodiment. It is a figure which shows the advancing state of light at the time of attaching PDLC directly to LCD. It is a figure which shows the advancing state of the light when the film thickness of PDLC is enlarged in FIG. It is a figure which shows the advancing state of the light at the time of arrange | positioning a half mirror between LCD and PDLC in FIG.

  Embodiments of the present invention will be described below. Also, the same reference numerals are given to the same elements throughout the present embodiment.

(First embodiment of the present invention)
A display device according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram illustrating a configuration of a display device according to the present embodiment. The display device 1 according to the present embodiment includes a display element (here, a liquid crystal display (hereinafter referred to as LCD 2) as an example), an LCD control unit 20 that controls driving of the LCD 2, and a display surface of the LCD 2. A polarizing film 3 that transmits one polarized light (for example, P-polarized light) and reflects the other polarized light (for example, S-polarized light), and is disposed on the display surface side of the polarizing film 3 to determine whether or not voltage is applied. Accordingly, a polymer-dispersed liquid crystal (hereinafter referred to as PDLC4) that changes state between a transparent state and a cloudy state and a PDLC control unit 40 that controls driving of the PDLC4 are provided.

  Here, the configuration and function of the PDLC 4 will be described in detail. FIG. 2 is a diagram showing the configuration of the PDLC in the display device according to the present embodiment. The PDLC 4 includes a pair of first transparent substrates 41a and 41b that are disposed to face each other, a pair of first transparent electrodes 42a and 42b that are respectively attached to opposing surfaces of the first transparent substrates 41a and 41b, and a first transparent substrate. A first liquid crystal layer 43 stacked in a facing space where the electrodes 42a and 42b face each other, and a PDLC control unit 40 that applies a voltage to the first transparent electrodes 42a and 42b are provided.

  The liquid crystal layer 43 includes a network-like polymer network made of a polymer, and a liquid crystal that is embedded so as to be surrounded by the polymer network and has orientation depending on the presence or absence of an electric field, and is a first transparent layer. In the ON state in which a voltage is applied to the electrodes 42a and 42b (in the case of FIG. 2A), the liquid crystal is aligned in a direction perpendicular to the surfaces of the first transparent substrates 41a and 41b. In order to align with the polymer network, the PDLC 4 becomes transparent and incident light passes through the PDLC 4 as direct light. On the other hand, in the OFF state where no voltage is applied to the first transparent electrodes 42a and 42b (in the case of FIG. 2B), the orientation of the liquid crystal is random, so the polymer network and the liquid crystal A difference occurs in the refractive index, the PDLC 4 becomes cloudy and the incident light is diffused. As described above, the transparency / white turbidity of the PDLC 4 can be controlled by applying a voltage to the first transparent electrodes 42a and 42b and using the presence or absence of an electric field.

  Next, the configuration and functions of the LCD 2 will be described in detail. The LCD 2 has various structures, and an example thereof will be described here. FIG. 3 is a diagram showing a configuration of the LCD in the display device according to the present embodiment. The LCD 2 includes a backlight 21 serving as a light source, a pair of polarizing plates 22a and 22b disposed to face each other, and a pair of second transparent substrates 23a and 23b respectively attached to opposing surfaces of the polarizing plates 22a and 22b. A pair of second transparent electrodes 24a and 24b attached to the opposing surfaces of the second transparent substrates 23a and 23b, and a pair of alignment films 25a and 25b attached to the opposing surfaces of the second transparent electrodes 24a and 24b, respectively. In addition, a voltage is applied to the second liquid crystal layer 26 and the second transparent electrodes 23a and 23b stacked in the facing space where the alignment films 25a and 25b are opposed to each other, and power is supplied to the backlight 21. And an LCD control unit 20.

  The liquid crystal molecules of the second liquid crystal layer 26 are aligned in a predetermined direction by the alignment films 25a and 25b, and the liquid crystal molecules are also twisted by 90 ° when the alignment films 25a and 25b are arranged in a state shifted by 90 °. Arranged in a state. Further, the polarizing plates 22a and 22b are also arranged in a state of being shifted by 90 ° in correspondence with the alignment directions of the alignment films 25a and 25b. In the state where no voltage is applied to the second transparent electrodes 24a and 24b, the liquid crystal molecules are arranged in a spiral shape that is twisted by 90 ° parallel to the second transparent substrates 23a and 23b, and the vibration direction of the light that has passed through the polarizing plate 22a. Changes along the twist of the liquid crystal molecules and passes through the polarizing plate 22b. On the other hand, in a state where no voltage is applied to the second transparent electrodes 24a and 24b, the liquid crystal molecules are aligned perpendicular to the second transparent substrates 23a and 23b, and the liquid crystal molecules do not affect the vibration direction of the light. The light passing through 22a goes straight without changing the vibration direction, and cannot pass through the polarizing plate 22b. As described above, the LCD 2 can pass or block light by the voltage applied to the second transparent electrodes 24a and 24b.

  In addition, as described above, the polarizing plates 22a and 22b are disposed in a state shifted by 90 °, and the voltage is reversed to the normally white mode in which light is transmitted without applying a voltage to the second transparent electrodes 24a and 24b. Although there is a normally black mode in which light is transmitted in the applied state, any mode may be used in the present embodiment.

  Returning to FIG. 1, in the display device 1 according to the present embodiment, the polarizing film 3 is disposed between the PDLC 4 and the LCD 2 described above. The polarizing film 3 transmits P-polarized light and reflects S-polarized light. In addition, although this polarizing film 3 may be the structure which permeate | transmits S polarized light and reflects P polarized light, it is set as the former structure here.

  As the reflective film, a half mirror as shown in Patent Document 1 is well known. This half mirror has a characteristic that it reflects about half of the incident light and transmits the other half regardless of the polarization component. That is, as shown in FIG. 8, when the LCD 2 is in a non-display state and the PDLC 4 is in a cloudy state, the backscattering is as large as about 50% and the screen can be whitened. However, when the LCD 2 is in the display state and the PDLC 4 is in the transparent state, only the P-polarized light is transmitted to the display surface side by the polarizing plates 22a and 22b of the LCD 2, and half light is reflected to the LCD 2 side by the half mirror. . Therefore, even if the PDLC 4 is transparent, the amount of light transmitted to the display surface is reduced to about half, and the luminance is impaired.

  On the other hand, when the polarizing film 3 that transmits the P-polarized light and reflects the S-polarized light shown in FIG. 1 is used, both the polarizing plate 22b and the polarizing film 3 of the LCD 2 have the same polarization plane that transmits the P-polarized light. Therefore, the P-polarized light transmitted through the polarizing plates 22a and 22b of the LCD 2 can be transmitted through the polarizing film 3 with the same amount of light, and the screen can be displayed brightly without loss of luminance. (See FIG. 4A). FIG. 4A shows the progress of light when the LCD 2 is in the display state. Of the light emitted from the LCD 2, S-polarized light (indicated by a colored arrow) is reflected by the polarizing plate 22a and P-polarized ( Only the state (shown by a white arrow) is transmitted to the display surface.

  In addition, when the LCD 2 is in a non-display state and the PDLC 4 is in a cloudy state, S-polarized light corresponding to about half of the external light incident from the display surface is reflected, so that the backscattering is about 50% and half. The screen can be made white as in the case of the mirror (see FIG. 4B). In FIG. 4B, a part of the external light including P-polarized light and S-polarized light is reflected by the PDLC 4, and P-polarized light of the light transmitted through the PDLC 4 is transmitted to the LCD 2, and only the S-polarized light is displayed on the display surface. The state of reflection is shown.

  Next, control of the LCD 2 and the PDLC 4 will be described. As shown in FIG. 1, the display device 1 includes an LCD control unit 20 for controlling the driving of the LCD 2 and a PDLC control unit 40 for controlling the driving of the PDLC 4. Note that the LCD control unit 20 and the PDLC control unit 40 may be an integrated liquid crystal control unit.

  The display device 1 according to the present embodiment displays the LCD 2 with high luminance and makes the screen whiter when not displayed. That is, the LCD control unit 20 and the PDLC control unit 40 control the PDLC 4 to a transparent state when the LCD 2 is in a display state, and control the PDLC 4 to a cloudy state when the LCD 2 is in a non-display state.

  In the former case, as shown in FIG. 4A, the light emitted from the backlight 21 of the LCD 2 passes through the polarizing plates 22a and 22b and the second liquid crystal layer 26, and only the P-polarized light is transmitted. The transmitted P-polarized light passes through the polarizing film 3 and the transparent PDLC 4 as it is, and is transmitted to the display surface of the PDLC 4 while maintaining the brightness of the LCD 2. Therefore, it is possible to display with the brightness of the LCD 2 without being affected by the polarizing film 3 and the PDLC 4.

  On the other hand, in the latter case, as shown in FIG. 4B, since no light is emitted from the backlight 21 of the LCD 2, only external light incident from the display surface affects the appearance of the display surface. Since the PDLC 4 to which external light is directly incident is in a cloudy state, a part of the light is reflected. In addition, P-polarized light out of the external light transmitted through the PDLC 4 passes through the polarizing film 3 as it is and is absorbed by the LCD 2 and disappears. However, the S-polarized light is reflected by the polarizing film 3 and greatly improves backscattering. To do. Therefore, it becomes possible to make the white turbid state of PDLC4 appear whiter.

  As described above, in the display device according to the present embodiment, it is possible to make the screen white when the LCD 2 is in a display state without causing a decrease in visibility and when the LCD 2 is in a non-display state.

  In the display device according to this embodiment, a display that does not use a polarizing plate on the display surface, such as a CRT, can be applied as a display element. In this case, since the light from the display is polarized only to the P-polarized light by the polarizing film 3, the luminance is impaired as compared with the case where the polarizing film 3 is not provided. Since it originally has high brightness, it can be used effectively depending on the usage environment.

(Other embodiments)
The display device according to this embodiment will be described with reference to FIG. The display device according to the present embodiment uses a reflection plate disposed on the display back side of the LCD 2 to make the screen whiter when the LCD 2 is not displayed. FIG. 5 is a diagram illustrating a configuration of the display device according to the present embodiment. The basic configuration is the same as in the case of FIG. 1 in the first embodiment, but the backlight 21 of the LCD 2 incorporates a light source 21a such as an LED or a fluorescent lamp and the light of the light source 21a on the liquid crystal side ( The light guide plate 21b that emits uniform light on the display surface side) and the reflection plate 21c that is disposed on the display back side of the light guide plate 21b to increase the reflection efficiency.

  As described above, the LCD 2 has a normally white mode and a normally black mode. First, in the normally white mode, light is transmitted in a state where no voltage is applied to the second transparent electrodes 23a and 23b, that is, in a state where the power source of the LCD 2 is off (the LCD 2 is not displayed). When the LCD 2 is in a non-display state, the P-polarized light of the external light incident from the display surface is absorbed by the LCD 2 and disappears. However, as shown in FIG. As a result, it is possible to reflect the P-polarized light transmitted through the LCD 2, and it is possible to increase the backscattering and make the display screen whiter.

  On the other hand, in the normally black mode, light is not transmitted in a state where no voltage is applied to the second transparent electrodes 23a and 23b, that is, in a state where the power of the LCD 2 is off (the LCD 2 is not displayed). If the P-polarized light of the external light incident from the display surface does not pass through the LCD 2, the P-polarized light does not reach the reflector 21 c on the display back side of the backlight 21, and the display screen is more in comparison with the normally white mode. The whitening effect is difficult to obtain.

  Therefore, in the normally black mode, the LCD control unit 20 turns off the light source 21a of the backlight 21 and applies a voltage to the second transparent electrodes 24a and 24b, so that P-polarized light from outside light is generated. The light passes through the LCD 2 and is reflected by the reflecting plate 21c on the display back side of the backlight 21 to increase back scattering. By doing so, power for applying a voltage to the second transparent electrodes 24a and 24b is consumed, but the display screen can be made whiter as in the normally white mode.

  As described above, in the display device according to the present embodiment, the P-polarized light from the outside light is reflected by the reflection plate 21c on the display back surface side to improve the back diffusion, and the screen can be made whiter.

1 Display device 2 LCD
3 Polarizing film 4 PDLC
20 LCD controller 21 Backlight 21a Light source 21b Light guide plate 21c Reflector plate 22a, 22b Polarizing plate 23a, 23b Second transparent substrate 24a, 24b Second transparent electrode 25a, 25b Alignment film 26 Second liquid crystal layer 40 PDLC controller 41a, 41b First transparent substrate 42a, 42b First transparent electrode 43 First liquid crystal layer

Claims (5)

A display device in which a polymer-dispersed liquid crystal film is disposed on a display surface of a display means,
A display device, wherein a polarizing film that transmits one polarized light and reflects another polarized light is disposed between a display surface of a display means and a polymer-dispersed liquid crystal film. The display device according to claim 1,
A display device in which a polarizing surface of a polarizing plate disposed on a display surface of a display means and a polarizing surface of the polarizing film are disposed to coincide with each other. The display device according to claim 1 or 2,
A polymer-dispersed liquid crystal film control means for controlling driving of the polymer-dispersed liquid crystal film in a transparent state / cloudy state;
Display control means for controlling on / off driving of the display means,
When the polymer-dispersed liquid crystal film control means controls the polymer-dispersed liquid crystal film in a transparent state and the display control means controls the display means to be on, the one polarized light from the display means is the polarizing film. And transmitted through the polymer-dispersed liquid crystal film,
When the polymer-dispersed liquid crystal film control means controls the polymer-dispersed liquid crystal film to a cloudy state and the display control means controls the display means to be off, external light from the display surface of the polymer-dispersed liquid crystal film A display device in which the other polarized light is reflected by the polymer-dispersed liquid crystal film and the polarizing film. The display device according to any one of claims 1 to 3,
A display device in which the liquid crystal is used as the display means, and a reflection plate is provided on the back side of the display, and the liquid crystal maintains a transmission state when no voltage is applied between the transparent electrodes sandwiching the liquid crystal. The display device according to any one of claims 1 to 3,
The display means uses liquid crystal, a reflector is provided on the back side of the display, the backlight is turned off when not displayed, and a voltage is applied between the transparent electrodes sandwiching the liquid crystal to apply the liquid crystal. Display device in a transparent state.