TWI901487B - Display apparatus - Google Patents

Abstract

A display apparatus including a display panel, an electrically controlled phase retarder and a first polarizer is provided. The display panel has a display surface. The electrically controlled phase retarder is disposed overlapping the display surface of the display panel. The first polarizer is disposed on one side of the electrically controlled phase retarder facing way from the display panel, and has a first absorption axis. An axial direction of the first absorption axis is perpendicular to the display surface.

Description

Display device

The present invention relates to a display technology, and in particular to a display device.

Generally speaking, display devices typically feature a wide viewing angle to allow for shared viewing by multiple people. However, in certain situations or circumstances, such as when browsing private webpages, accessing confidential information, or entering passwords in public, a wide viewing angle can easily expose confidential information to onlookers, potentially leaking it. Currently, most common anti-peeping displays utilize a light control film (LCF) placed in front of the display panel to filter out wide-angle light. Conversely, when anti-peeping is no longer required, the LCF is manually removed from the front of the display panel. In other words, while these LCFs offer an anti-peeping effect, their ease of use still leaves room for improvement.

The present invention provides a display device having an electrically switchable anti-peeping effect.

The display device of the present invention includes a display panel, an electrically controlled phase retarder, and a first polarizer. The display panel has a display surface. The electrically controlled phase retarder is arranged to overlap the display surface of the display panel. The first polarizer is arranged on a side of the electrically controlled phase retarder that faces away from the display panel and has a first absorption axis. The first absorption axis is perpendicular to the display surface.

Based on the above, in one embodiment of the display device of the present invention, by aligning the first absorption axis of the first polarizer perpendicular to the display surface of the display panel, the display device can provide anti-peek display functionality in two mutually perpendicular dimensions. Furthermore, through the operation of an electrically controlled phase retarder, the display device can be electrically switched between sharing mode and anti-peek mode, thereby enhancing the operational convenience of the anti-peek display.

As used herein, "about," "approximately," "substantially," or "substantially" include the stated value and the average within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, taking into account the measurement in question and the particular amount of error associated with the measurement (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or, for example, within ±30%, ±20%, ±15%, ±10%, ±5%. Furthermore, as used herein, "about," "approximately," "substantially," or "substantially" can be used to select an acceptable range of deviation or standard deviation depending on the measured property, cutting property, or other property, and may not apply to all properties without using a single standard deviation.

In the accompanying drawings, the thickness of layers, films, panels, regions, etc., is exaggerated for clarity. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element, or intervening elements may also exist. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements. As used herein, "connected" can refer to physical and/or electrical connections. Furthermore, "electrically connected" can mean the presence of other elements between two elements.

Furthermore, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element, as illustrated in the figures. It will be understood that relative terms are intended to encompass different orientations of a device in addition to the orientations illustrated in the figures. For example, if a device in one of the figures were flipped over, an element described as being on the "lower" side of the other elements would be oriented on the "upper" side of the other elements. Thus, the exemplary term "lower" can encompass both "lower" and "upper" orientations, depending on the particular orientation of the figure. Similarly, if a device in one of the figures were flipped over, an element described as being "below" or "beneath" other elements would be oriented "above" the other elements. Thus, the exemplary terms "above" or "below" can encompass both "above" and "below" orientations.

Exemplary embodiments are described herein with reference to cross-sectional illustrations that are schematic representations of idealized embodiments. Therefore, variations in the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, the embodiments described herein should not be construed as limited to the specific shapes of regions as illustrated herein, but rather include deviations in shape that result, for example, from manufacturing. For example, regions illustrated or described as flat may typically have rough and/or nonlinear features. Furthermore, sharp corners that are illustrated may be rounded. Therefore, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of the regions and are not intended to limit the scope of the claims.

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

Figures 1A and 1B are schematic cross-sectional views of a display device according to the first embodiment of the present invention operating in a sharing mode. Figures 2A and 2B are schematic cross-sectional views of a display device according to the first embodiment of the present invention operating in an anti-peeping mode. Figure 3A is a light output distribution diagram of the display device in Figures 1A and 1B operating in a sharing mode. Figure 3B is a light output distribution diagram of the display device in Figures 2A and 2B operating in an anti-peeping mode. Figure 4 is a distribution diagram of the normalized transmittance versus viewing angle of the display device in Figure 2A operating in an anti-peeping mode along the first anti-peeping axis. Figure 5 is a distribution diagram of the normalized transmittance versus viewing angle of the polarizer in Figures 1A and 1B for P-polarized light.

1A and 1B , a display device 10 includes a display panel 100, an electrically controlled phase retarder 140, and polarizers 121 and 122. In this embodiment, the display panel 100 may be a self-luminous display panel, such as, but not limited to, a micro-light-emitting diode (micro-LED) display panel, a sub-millimeter light-emitting diode (mini-LED) display panel, or an organic light-emitting diode (OLED) display panel.

Polarizers 121, 122, and an electrically controlled phase retarder 140 are disposed on one side of the display surface DS of the display panel 100 and overlap the display surface DS along a stacking direction (e.g., direction Z). The electrically controlled phase retarder 140 is located between the polarizers 121 and 122. In this embodiment, the polarizer 121 is disposed on the side of the electrically controlled phase retarder 140 facing away from the display panel 100, while the polarizer 122 is disposed between the display panel 100 and the electrically controlled phase retarder 140.

The polarizer 121 and the polarizer 122 have an absorption axis AX1 and an absorption axis AX2, respectively. Of particular note, the absorption axis AX1 of the polarizer 121 and the absorption axis AX2 of the polarizer 122 are both perpendicular to the display surface DS of the display panel 100. In other words, the absorption axis AX1 and the absorption axis AX2 are both parallel to the stacking direction of the polarizers 121 and 122. It should be noted that in this embodiment, the display device 10 may have a first anti-seepage axis APX1 and a second anti-seepage axis APX2 that are perpendicular to each other, and both anti-seepage axes are perpendicular to the absorption axis AX1 of the polarizer 121 and the absorption axis AX2 of the polarizer 122.

For example, in this embodiment, the electrically controlled phase retarder 140 includes a substrate 141, a substrate 142, and a liquid crystal layer 145. More specifically, the electrically controlled phase retarder 140 of this embodiment can be an electrically controlled liquid crystal cell. The liquid crystal layer 145 is disposed between the substrates 141 and 142. The materials of the substrates 141 and 142 include, for example, glass, quartz, polyimide (PI), polycarbonate (PC), polymethyl methacrylate (PMMA), or other suitable organic polymer sheets.

It should be understood that, although not shown in the diagram, the electrically controlled phase retarder 140 may also include two alignment layers and two electrode layers, disposed on substrates 141 and 142, respectively. The electric field formed between the two conductive layers is suitable for driving the liquid crystal molecules (not shown) in the liquid crystal layer 145 to rotate, forming an arrangement corresponding to the electric field strength. The arrangement of these liquid crystal molecules in response to different electric field strengths causes different phase delays in passing light, resulting in a change in the light's polarization state. Furthermore, the two alignment layers are configured to align the liquid crystal molecules in the liquid crystal layer 145 in a specific direction or arrangement when not subjected to an electric field.

For example, in this embodiment, when the electrically controlled phase retarder 140 is deactivated, the liquid crystal layer 145 produces a maximum phase delay of half the wavelength of the light passing through it. Therefore, after linearly polarized light passes through the deactivated liquid crystal layer 145, its polarization direction is rotated 90 degrees. Conversely, when the electrically controlled phase retarder 140 is activated, the liquid crystal layer 145 produces no substantial phase delay for the light passing through it. Therefore, after linearly polarized light passes through the activated liquid crystal layer 145, its polarization direction remains unchanged.

However, the present invention is not limited thereto. In other embodiments, the half-wavelength phase delay value of the electronically controlled phase delay device may be generated when the electronically controlled phase delay device is enabled, while no substantial phase delay value is generated when the electronically controlled phase delay device is not enabled.

The following will provide an exemplary description of how the display device 10 operates in the sharing mode and the anti-peek mode.

In this embodiment, the polarization state of light from the display panel 100 after passing through the polarizer 122 varies depending on the angle at which it enters the polarizer 122. For example, light L1 entering the polarizer 122 in the forward direction (i.e., perpendicular to the plane of the polarizer 122) does not form a specific polarization state after passing through the polarizer 122 because the axes of its constituent polarization components are all perpendicular to the absorption axis AX2 of the polarizer 122. In other words, light L1 remains unpolarized after passing through the polarizer 122.

However, light L2 incident at an oblique angle on the polarizer 122 will form a specific polarization state after passing through the polarizer 122. For example, before passing through the polarizer 122, the light L2 may have a linear polarization state P1 and a linear polarization state P2 with mutually perpendicular polarization directions. In this embodiment, the linear polarization state P1 of the light L2 whose plane of incidence is parallel to the first anti-permeability axis APX1 is, for example, an S polarization state, while its linear polarization state P2 is, for example, a P polarization state (as shown in FIG1A ). As the light L2 passes through the polarizer 122, its linear polarization state P1 does not substantially change because its polarization direction is perpendicular to the absorption axis AX2. However, its linear polarization state P2 is absorbed by the polarizer 122 to varying degrees because its polarization direction is not perpendicular to the absorption axis AX2. For example, the greater the angle at which the light L2 is incident on the polarizer 122 , the more its linear polarization state P2 is absorbed when passing through the polarizer 122 .

Similarly, light L3 incident at an oblique angle on the polarizer 122 will form a specific polarization state after passing through the polarizer 122. For example, before passing through the polarizer 122, the light L3 may have a linear polarization state P1 and a linear polarization state P2 with mutually perpendicular polarization directions. In this embodiment, the linear polarization state P2 of the light L3 whose incident plane is parallel to the second anti-perception axis APX2 is, for example, an S polarization state, while the linear polarization state P1 is, for example, a P polarization state (as shown in FIG1B ). As the light L3 passes through the polarizer 122, its linear polarization state P2 does not substantially change because its polarization direction is perpendicular to the absorption axis AX2. However, its linear polarization state P1 is absorbed by the polarizer 122 to varying degrees because its polarization direction is not perpendicular to the absorption axis AX2. For example, the greater the angle at which the light L3 is incident on the polarizer 122 , the more its linear polarization state P1 is absorbed when passing through the polarizer 122 .

Therefore, after light L2 passes through the polarizer 122 obliquely along an incident plane parallel to the first anti-peeping axis APX1, its linear polarization state P1 component remains substantially unchanged, while its linear polarization state P2 component is absorbed by the polarizer 122 to varying degrees depending on the oblique incident angle. After light L3 passes through the polarizer 122 obliquely along an incident plane parallel to the second anti-peeping axis APX2, its linear polarization state P2 component remains substantially unchanged, while its linear polarization state P1 component is absorbed by the polarizer 122 to varying degrees depending on the oblique incident angle. In this embodiment, the transmittance of the polarizer 122 for the linear polarization state P2 of light L2 (i.e., the P polarization state relative to the plane of incidence of light L2) and the linear polarization state P1 of light L3 (i.e., the P polarization state relative to the plane of incidence of light L3) decreases as the viewing angle increases. As shown in Figure 5, for example, at a viewing angle greater than or equal to 45 degrees, the normalized transmittance of the polarizer 122 for the light component of the linear polarization state P2 of light L2 and the light component of the linear polarization state P1 of light L3 can be less than 10%. The normalized transmittance of the polarizer 122 at each viewing angle in Figure 5 is, for example, the percentage of the transmittance at each viewing angle to the transmittance at a viewing angle of 0 degrees.

Referring to Figures 1A and 1B , for example, when the electrically controlled phase retarder 140 is enabled, the liquid crystal layer 145 does not produce a substantial phase retardation for the light passing through it. Therefore, light L1 remains unpolarized after passing through the electrically controlled phase retarder 140, while light L2 remains polarized, such as linear polarization state P1, after passing through the electrically controlled phase retarder 140. Because the axial configuration of the absorption axis AX1 of the polarizer 121 is identical to the axial configuration of the absorption axis AX2 of the polarizer 122, light L1 and light L2 remain unpolarized and polarized, respectively, after passing through the polarizer 121 (as shown in Figure 1A ). Similarly, light L3 remains polarized, such as linear polarization state P2, after passing through the electrically controlled phase retarder 140. Since the axial arrangement of the absorption axis AX1 of the polarizer 121 is the same as the axial arrangement of the absorption axis AX2 of the polarizer 122, the light L3 can maintain its polarization state (as shown in FIG. 1B ) after passing through the polarizer 121. At this time, the display device 10 operates in the sharing mode.

When the electrically controlled phase retarder 140 is deactivated, the liquid crystal layer 145 produces a half-wavelength phase delay for the light passing through it. Therefore, after light L2 passes through the electrically controlled phase retarder 140, its linear polarization state P1 is transformed into linear polarization state P2. Because the polarization direction of linear polarization state P2 is not perpendicular to the absorption axis AX1 of the polarizer 121, light L2 is absorbed by the polarizer 121 (as shown in FIG2A ). Similarly, after light L3 passes through the electrically controlled phase retarder 140, its linear polarization state P2 is transformed into linear polarization state P1. Because the polarization direction of linear polarization state P1 is not perpendicular to the absorption axis AX1 of the polarizer 121, light L3 is absorbed by the polarizer 121 (as shown in FIG2B ). At this time, the display device 10 operates in the anti-peek mode.

Figures 3A and 3B illustrate light distribution diagrams when the display device 10 is operating in sharing mode and anti-peek mode, respectively. Specifically, the horizontal planes along azimuth angles of 0 and 180 degrees in Figures 3A and 3B correspond to the planes of incidence for light ray L2 entering polarizer 122, electrically controlled phase retarder 140, and polarizer 121 in Figures 1A and 1B , while the vertical planes along azimuth angles of 90 and 270 degrees correspond to the planes of incidence for light ray L3 entering polarizer 140, electrically controlled phase retarder 140, and polarizer 121 in Figures 2A and 2B .

As can be seen from Figure 3B, when the display device 10 operates in the anti-peeping mode, it can have an anti-peeping effect in the first anti-peeping axis APX1 (for example, the orientations of 0 degrees and 180 degrees). In the first anti-peeping axis APX1, the transmittance of the display device 10 decreases as the viewing angle relative to the absorption axis AX1 increases. As shown in Figure 4, in this embodiment, the normalized transmittance of the display device 10 at a viewing angle greater than or equal to 45 degrees is less than 10%. In Figure 4, the normalized transmittance of the display device 10 at each viewing angle is, for example, the percentage value of the transmittance at each viewing angle to the transmittance at a viewing angle of 0 degrees. In addition, the display device 10 also has a considerable anti-peeping effect in the second anti-peeping axis APX2 (for example, the orientations of 90 degrees and 270 degrees). That is, the display device 10 of this embodiment has an anti-seepage display function that can be electrically switched on two mutually perpendicular viewing planes.

The following will list some other embodiments to illustrate the present invention in detail, wherein the same components will be marked with the same symbols, and the description of the same technical content will be omitted. For the omitted parts, please refer to the above embodiments and will not be repeated below.

Figure 6 is a schematic cross-sectional view of a display device according to a second embodiment of the present invention. Referring to Figure 6 , the primary difference between display device 11 of this embodiment and display device 10 of Figure 1A lies in the type of display panel. More specifically, in display device 11 of this embodiment, display panel 100A can be a non-self-luminous display panel, such as, but not limited to, a liquid crystal display panel. Therefore, display device 11 also includes a backlight module 50.

In this embodiment, the electrically controlled phase retarder 140, the polarizer 121, and the polarizer 122 can be disposed between the display panel 100A and the backlight module 50. The polarizer 121 is located between the electrically controlled phase retarder 140 and the display panel 100A. The polarizer 122 is located between the electrically controlled phase retarder 140 and the backlight module 50. However, the present invention is not limited to this. In another variant embodiment, the polarizer 123, the polarizer 124, and the display panel 100A can be disposed between the polarizer 122 and the backlight module 50. In particular, if the display panel 100A is disposed between the electrically controlled phase retarder 140 and the backlight module 50, the polarizer 122 can be omitted.

Because the display panel 100A of this embodiment is a liquid crystal display panel, the display device 11 is provided with a polarizer 123 between the display panel 100A and the polarizer 121. A polarizer 124 is also provided on the side of the display panel 100A facing away from the polarizer 121. Of particular note, unlike the polarizers 121 and 122, the absorption axis AX3 of the polarizer 123 and the absorption axis AX4 of the polarizer 124 are both parallel to the display surface DS of the display panel 100A. For example, in this embodiment, the absorption axis AX3 of the polarizer 123 can optionally be perpendicular to the absorption axis AX4 of the polarizer 124, but this is not a limitation. In other embodiments, the directions of the absorption axes of the polarizer 123 and the polarizer 124 can be adjusted according to actual application requirements.

Since the configuration of the polarizer 121, the polarizer 122, and the electrically controlled phase retarder 140 of this embodiment, and thus the electrically controlled anti-peek effect produced thereby, are similar to the polarizer 121, the polarizer 122, and the electrically controlled phase retarder 140 of the display device 10 of FIG. 1A , a detailed description can be found in the relevant paragraphs of the aforementioned embodiment and will not be repeated here.

Figure 7 is a schematic cross-sectional view of a display device according to a third embodiment of the present invention. Referring to Figure 7 , compared to the display device 10 of Figure 1A , the display device 12 of this embodiment may further include a compensation film 160. In this embodiment, the compensation film 160 may be disposed between the polarizer 121 and the electrically controlled phase retarder 140, but is not limited thereto. In other embodiments, the compensation film 160 may also be disposed between the polarizer 122 and the electrically controlled phase retarder 140.

In summary, in a display device according to one embodiment of the present invention, by aligning the first absorption axis of the first polarizer perpendicular to the display surface of the display panel, the display device can provide anti-peek functionality in two mutually perpendicular dimensions. Furthermore, by operating an electrically controlled phase retarder, the display device can be electronically switched between sharing mode and anti-peek mode, further enhancing the operational convenience of the anti-peek display.

10, 11, 12: Display device 50: Backlight module 100, 100A: Display panel 121, 122, 123, 124: Polarizer 140: Electronically controlled phase retarder 141, 142: Substrates 145: Liquid crystal layer 160: Compensation film APX1: First anti-penetration axis APX2: Second anti-penetration axis AX1, AX2, AX3, AX4: Absorption axes DS: Display surface L1, L2, L3: Light P1, P2: Linear polarization states Z: Direction

Figures 1A and 1B are schematic cross-sectional views of a display device according to the first embodiment of the present invention operating in sharing mode. Figures 2A and 2B are schematic cross-sectional views of a display device according to the first embodiment of the present invention operating in anti-peek mode. Figure 3A is a light distribution diagram of the display device in Figures 1A and 1B operating in sharing mode. Figure 3B is a light distribution diagram of the display device in Figures 2A and 2B operating in anti-peek mode. Figure 4 is a graph showing the normalized transmittance versus viewing angle along the first anti-peek axis of the display device in Figure 2A operating in anti-peek mode. Figure 5 is a graph showing the normalized transmittance versus viewing angle of the polarizer in Figures 1A and 1B for P-polarized light. Figure 6 is a schematic cross-sectional view of a display device according to the second embodiment of the present invention. FIG7 is a schematic cross-sectional view of a display device according to a third embodiment of the present invention.

10: Display device

100: Display Panel

121, 122: Polarizer

140: Electronically controlled phase delay device

141, 142: Substrate

145:Liquid crystal layer

APX1: First anti-penetration axis

APX2: Second anti-penetration axis

AX1, AX2: Absorption axis

DS: Display Screen

L1, L2: Light

P1, P2: Linear polarization states

Z: Direction

Claims (9)

A display device includes: a display panel having a display surface; an electrically controlled phase retarder arranged to overlap the display panel; and a first polarizer disposed on a side of the electrically controlled phase retarder facing away from the display panel and having a first absorption axis, wherein the first absorption axis is perpendicular to the display surface. The electrically controlled phase retarder is adapted to adjust the phase retardation value of a light ray from the display panel or the first polarizer, and the maximum phase retardation value of the electrically controlled phase retarder is half the wavelength of the light ray. The display device as described in claim 1 further includes: a second polarizer having a second absorption axis, wherein the electrically controlled phase retarder is located between the first polarizer and the second polarizer, and the axis of the second absorption axis is perpendicular to the display surface. The display device as described in claim 1 further includes: a backlight module, wherein the electrically controlled phase retarder and the first polarizer are located between the display panel and the backlight module. The display device as described in claim 3, wherein the first polarizer is located between the electrically controlled phase retarder and the backlight module. The display device as described in claim 3 further includes: a second polarizer having a second absorption axis, wherein the electrically controlled phase retarder is located between the first polarizer and the second polarizer, and the axis of the second absorption axis is perpendicular to the display surface. The display device as described in claim 5 further includes: a third polarizer, disposed between the display panel and the electrically controlled phase retarder, and having a third absorption axis, wherein the axial direction of the third absorption axis is parallel to the display surface. The display device as described in claim 1 further includes: a compensation film disposed between the electrically controlled phase retarder and the first polarizer. The display device as described in claim 1 has a first anti-seepage axis and a second anti-seepage axis, wherein the first anti-seepage axis and the second anti-seepage axis are perpendicular to the axis of the first absorption axis and perpendicular to each other, the display device has a viewing angle relative to the axis of the first absorption axis along the first anti-seepage axis or the second anti-seepage axis, and the transmittance of the first polarizer decreases as the viewing angle increases. A display device as described in claim 8, wherein the transmittance of the display device decreases as the viewing angle increases, and the transmittance of the display device is less than 10% when the viewing angle is greater than or equal to 45 degrees.