Display apparatus and method of driving the same

A display apparatus including a backlight module, first and second electrically-controlled elements, electrically-controlled first and second polarizers, a half-wave plate, and a display panel is provided. An included angle between first and second alignment directions of first and second alignment layers of the first electrically-controlled element is between 75 degrees and 105 degrees. An included angle between third and fourth alignment directions of third and fourth alignment layers of the second electrically-controlled element is between 165 degrees and 195 degrees. The half-wave plate is disposed between the second polarizer and the second electrically-controlled element. The display panel is disposed on the second electrically-controlled element. An included angle between an extending direction of prism structures of each of two optical brightness enhancement films of the backlight module and a viewing angle control direction of the display apparatus is less than 45 degrees. A method of driving the display apparatus is provided.

BACKGROUND

Technical Field

The invention relates to a display apparatus and a method of driving the display apparatus, and particularly relates to a display apparatus having a viewing angle control function and a method of driving the display apparatus.

Description of Related Art

In order to allow multiple viewers to watch a display image at the same time, a display apparatus usually has a wide viewing angle display effect. However, in some situations or occasions, such as browsing private web pages, confidential information, or entering passwords in public, the wide viewing angle display effect is likely to cause the image to be peeped by others, resulting in leakage of confidential information. In order to achieve an anti-peep effect, a general practice is to place a light control film (LCF) in front of a display panel to filter out large-angle light, and set an electrically-controlled diffuser on a light-emitting side of the light control film, such that the display apparatus may be switched between different display modes (such as a wide viewing angle mode and a narrow viewing angle mode).

In order to improve traffic safety, the above-mentioned display apparatus may be designed to have a single-side anti-peep effect. For example: when a vehicle is running, a single-side anti-peep function is turned on, so that the display apparatus does not display images to a driver, but may display the images to a passenger. However, the arrangement of the light control film and the electrically-controlled diffuser not only reduces an overall brightness of the display apparatus, but also increases operating power consumption.

SUMMARY

The invention is directed to a display apparatus with an electrically-controlled viewing angle range, smaller color shift in a narrow viewing angle mode and better anti-peep effect and a method of driving the display apparatus.

Other objects and advantages of the invention may be further illustrated by the technical features broadly embodied and described as follows.

In order to achieve one or a portion of or all of the objects or other objects, an embodiment of the invention provides a display apparatus. The display apparatus includes a backlight module, a first electrically-controlled element, a second electrically-controlled element, a first polarizer, a second polarizer, a half-wave plate, and a display panel. The first electrically-controlled element is disposed on the backlight module and includes a first liquid-crystal layer, a first alignment layer, and a second alignment layer. The first liquid-crystal layer is sandwiched between the first alignment layer and the second alignment layer. An included angle between a first alignment direction of the first alignment layer and a second alignment direction of the second alignment layer is greater than or equal to 75 degrees and less than or equal to 105 degrees. The second electrically-controlled element is disposed on the first electrically-controlled element and includes a second liquid-crystal layer, a third alignment layer, and a fourth alignment layer. The second liquid-crystal layer is sandwiched between the third alignment layer and the fourth alignment layer. An included angle between a third alignment direction of the third alignment layer and a fourth alignment direction of the fourth alignment layer is greater than or equal to 165 degrees and less than or equal to 195 degrees. An included angle between the second alignment direction and the third alignment direction is greater than or equal to 30 degrees and less than or equal to 60 degrees, or greater than or equal to 120 degrees and less than or equal to 150 degrees. The first polarizer is provided between the backlight module and the first electrically-controlled element, and has a first absorption axis parallel or perpendicular to the first alignment direction. The second polarizer is provided between the first electrically-controlled element and the second electrically-controlled element, and has a second absorption axis. An axial direction of the second absorption axis is perpendicular to an axial direction of the first absorption axis. The half-wave plate is provided between the second polarizer and the second electrically-controlled element. The display panel is disposed on the second electrically-controlled element. The backlight module includes a light guide plate, a first optical brightness enhancement film and a second optical brightness enhancement film. The light guide plate has a light incident surface, and a light-emitting surface and a bottom surface connected to the light incident surface and opposite to each other. The first optical brightness enhancement film is disposed on a side of the light-emitting surface of the light guide plate, and has a plurality of first prism structures. An included angle between an extending direction of the first prism structures and a first viewing angle control direction of the display apparatus is less than 45 degrees. The second optical brightness enhancement film is disposed on a side of the first optical brightness enhancement film away from the light guide plate, and has a plurality of second prism structures. An included angle between an extending direction of the second prism structures and the first viewing angle control direction of the display apparatus is less than 45 degrees.

In order to achieve one or a portion of or all of the objects or other objects, an embodiment of the invention provides a display apparatus. The display apparatus includes a backlight module, a first electrically-controlled element, a second electrically-controlled element, a first polarizer, a second polarizer, a half-wave plate, a display panel and a compensation film. The first electrically-controlled element is disposed on the backlight module and includes a first liquid-crystal layer, a first alignment layer, and a second alignment layer. The first liquid-crystal layer is sandwiched between the first alignment layer and the second alignment layer. An included angle between a first alignment direction of the first alignment layer and a second alignment direction of the second alignment layer is greater than or equal to 75 degrees and less than or equal to 105 degrees. The second electrically-controlled element is disposed on the first electrically-controlled element and includes a second liquid-crystal layer, a third alignment layer, and a fourth alignment layer. The second liquid-crystal layer is sandwiched between the third alignment layer and the fourth alignment layer. An included angle between a third alignment direction of the third alignment layer and a fourth alignment direction of the fourth alignment layer is greater than or equal to 165 degrees and less than or equal to 195 degrees. An included angle between the second alignment direction and the third alignment direction is greater than or equal to 30 degrees and less than or equal to 60 degrees, or greater than or equal to 120 degrees and less than or equal to 150 degrees. The first polarizer is provided between the backlight module and the first electrically-controlled element, and has a first absorption axis parallel or perpendicular to the first alignment direction. The second polarizer is provided between the first electrically-controlled element and the second electrically-controlled element, and has a second absorption axis. An axial direction of the second absorption axis is perpendicular to an axial direction of the first absorption axis. The half-wave plate is provided between the second polarizer and the second electrically-controlled element. The display panel is disposed on the second electrically-controlled element. An out-of-plane phase retardation amount of the compensation film is greater than or equal to −400 nm and less than or equal to −50 nm

In order to achieve one or a portion of or all of the objects or other objects, an embodiment of the invention provides a method of driving a display apparatus. The method of driving the display apparatus includes providing the display apparatus, providing a first voltage to a first electrically-controlled element and a second electrically-controlled element of the display apparatus to operate the display apparatus in a wide viewing angle mode, and providing a second voltage and a third voltage to the first electrically-controlled element and the second electrically-controlled element, respectively, to operate the display apparatus in a narrow viewing angle mode. The first voltage is smaller than the second voltage and the third voltage. The display apparatus further includes a backlight module, a first polarizer, a second polarizer, a half-wave plate, and a display panel. The first electrically-controlled element is disposed on the backlight module and includes a first liquid-crystal layer, a first alignment layer, and a second alignment layer. The first liquid-crystal layer is sandwiched between the first alignment layer and the second alignment layer. An included angle between a first alignment direction of the first alignment layer and a second alignment direction of the second alignment layer is between 75 degrees and 105 degrees. The second electrically-controlled element is disposed on the first electrically-controlled element and includes a second liquid-crystal layer, a third alignment layer, and a fourth alignment layer. The second liquid-crystal layer is sandwiched between the third alignment layer and the fourth alignment layer. An included angle between a third alignment direction of the third alignment layer and a fourth alignment direction of the fourth alignment layer is between 165 degrees and 195 degrees. An included angle between the second alignment direction and the third alignment direction is between 30 degrees and 60 degrees, or between 120 degrees and 150 degrees. The first polarizer is provided between the backlight module and the first electrically-controlled element, and has a first absorption axis parallel or perpendicular to the first alignment direction. The second polarizer is provided between the first electrically-controlled element and the second electrically-controlled element, and has a second absorption axis. An axial direction of the second absorption axis is perpendicular to an axial direction of the first absorption axis. The half-wave plate is provided between the second polarizer and the second electrically-controlled element. The display panel is disposed on the second electrically-controlled element.

Based on the above, in the display apparatus of an embodiment of the invention, the electrically-controlled first liquid-crystal layer and second liquid-crystal layer are provided between the backlight module and the display panel. The included angle between the alignment direction on one side of the first liquid-crystal layer and the alignment direction on the other side thereof is between 75 degrees and 105 degrees, and the included angle between the alignment direction on one side of the second liquid-crystal layer and the alignment direction on the other side thereof is between 165 degrees and 195 degrees, wherein the included angle between the alignment direction of the first liquid-crystal layer close to the second liquid-crystal layer and the alignment direction of the second liquid-crystal layer close to the first liquid-crystal layer is between 30 degrees and 60 degrees, or between 120 degrees and 150 degrees, and two opposite sides of the first liquid-crystal layer are provided with two polarizers with absorption axes perpendicular to each other. Through the above configuration, the viewing angle range of the display apparatus in at least one direction may be electrically-controlled and switched to meet different usage situations.

On the other hand, the backlight module is provided with two optical brightness enhancement film, and an included angle between an extending direction of prism structures of each of the two optical brightness enhancement films and a viewing angle control direction of the display apparatus is less than 45 degrees. Accordingly, the anti-peep effect of the display apparatus operated in a narrow viewing angle mode may be improved. A compensation film with an out-of-plane phase retardation amount greater than or equal to −400 nm and less than or equal to −50 nm may also be provided between the first polarizer and the second polarizer to obtain a better anti-peep effect.

DESCRIPTION OF THE EMBODIMENTS

FIG.1is a schematic cross-sectional view of a display apparatus according to the first embodiment of the invention.FIG.2AandFIG.2Bare schematic diagrams showing the arrangement relationship between the alignment direction of the alignment layer, the axial directions of the absorption axes of the polarizers, and the axial direction of the slow axis of the half-wave plate ofFIG.1.FIG.3AandFIG.3Bare transmittance distribution diagrams (viewing angle characteristics) of the display apparatus ofFIG.1operated in different display modes.FIG.4is a luminance-viewing angle curve diagram of the display apparatus ofFIG.1operated in different display modes.FIG.5AtoFIG.5Dare transmittance distribution diagrams of a display apparatus when the first electrically-controlled element ofFIG.1is operated at different voltages.FIG.6is a luminance-viewing angle curve diagram of a display apparatus when the first electrically-controlled element ofFIG.1is operated at different voltages.FIG.7AtoFIG.7Care transmittance distribution diagrams of a display apparatus when the second electrically-controlled element ofFIG.1is operated at different voltages.FIG.7Dis a luminance-viewing angle curve diagram of a display apparatus when the second electrically-controlled element ofFIG.1is operated at different voltages.FIG.8Ais a schematic cross-sectional view of the backlight module ofFIG.1.FIG.8Bis a schematic cross-sectional view of another implementation of the backlight module ofFIG.1.

Referring toFIG.1, a display apparatus10includes a backlight module100, a first electrically-controlled element210, a second electrically-controlled element220, a first polarizer POL1, a second polarizer POL2, a half-wave plate250, and a display panel300. The first electrically-controlled element210is disposed on the backlight module100. The second electrically-controlled element220is disposed on the first electrically-controlled element210, for example, the first electrically-controlled element210is disposed between the second electrically-controlled element220and the backlight module100. The display panel300is disposed on the second electrically-controlled element220, for example, the second electrically-controlled element220is disposed between the first electrically-controlled element210and the display panel300. The first polarizer POL1is disposed between the backlight module100and the first electrically-controlled element210. The second polarizer POL2is disposed between the first electrically-controlled element210and the second electrically-controlled element220. The half-wave plate250is disposed between the second polarizer POL2and the second electrically-controlled element220. Namely, in the embodiment, the first polarizer POL1, the first electrically-controlled element210, the second polarizer POL2, the half-wave plate250, the second electrically-controlled element220, and the display panel300are sequentially disposed on the backlight module100in a direction Z (as shown inFIG.1). The display panel300is, for example, a liquid-crystal display panel, or other suitable non-self-luminous display panels.

In detail, the first electrically-controlled element210includes a first substrate SUB1, a second substrate SUB2, a first electrode layer E1, a second electrode layer E2, a first alignment layer AL1, a second alignment layer AL2, and a first liquid-crystal layer LCL1. The first electrode layer E1and the first alignment layer AL1are provided on a side surface of the first substrate SUB1facing the second substrate SUB2. The second electrode layer E2and the second alignment layer AL2are provided on a side surface of the second substrate SUB2facing the first substrate SUB1. The first liquid-crystal layer LCL1is sandwiched between the first alignment layer AL1and the second alignment layer AL2.

Similarly, the second electrically-controlled element220includes a third substrate SUB3, a fourth substrate SUB4, a third electrode layer E3, a fourth electrode layer E4, a third alignment layer AL3, a fourth alignment layer AL4and a second liquid-crystal layer LCL2. The third electrode layer E3and the third alignment layer AL3are provided on a side surface of the third substrate SUB3facing the fourth substrate SUB4. The fourth electrode layer E4and the fourth alignment layer AL4are provided on a side surface of the fourth substrate SUB4facing the third substrate SUB3. The second liquid-crystal layer LCL2is sandwiched between the third alignment layer AL3and the fourth alignment layer AL4.

Referring toFIG.2AandFIG.2B, an included angle γ1between a first alignment direction AD1of the first alignment layer AL1and a second alignment direction AD2of the second alignment layer AL2is between 75 degrees and 105 degrees. An included angle γ2between a third alignment direction AD3of the third alignment layer AL3and a fourth alignment direction AD4of the fourth alignment layer AL4is between 165 degrees and 195 degrees. An included angle γ3between the second alignment direction AD2and the third alignment direction AD3is between 30 degrees and 60 degrees, or between 120 degrees and 150 degrees. In the embodiment, the included angle γ1between the first alignment direction AD1and the second alignment direction AD2is, for example, 90 degrees, the included angle γ2between the third alignment direction AD3and the fourth alignment direction AD4is, for example, 175 degrees, and the included angle γ3between the second alignment direction AD2and the third alignment direction AD3is, for example, 40 degrees.

Namely, a plurality of liquid-crystal molecules LC1in the first liquid-crystal layer LCL1are arranged in a twist manner along the direction Z (as shown inFIG.1), i.e., the first electrically-controlled element210may be a twisted nematic (TN)-type electrically-controlled liquid-crystal cell. A plurality of liquid-crystal molecules LC2in the second liquid-crystal layer LCL2are generally arranged in parallel with each other (as shown inFIG.1), i.e., the second electrically-controlled element220may be an electrically-controlled birefringence (ECB)-type liquid-crystal cell. Since the first electrically-controlled element210and the second electrically-controlled element220of the embodiment adopt different liquid-crystal driving modes, the color shift of light coming from the backlight module100after passing through these electrically-controlled elements may be effectively suppressed.

In the embodiment, the display apparatus10has a first viewing angle control direction parallel to a direction X (for example, perpendicular to the direction Z). More specifically, a viewing angle range of the display apparatus10along the first viewing angle control direction is electrically adjustable. In the embodiment, the first alignment direction AD1of the first alignment layer AL1is perpendicular to the second alignment direction AD2of the second alignment layer AL2, wherein an included angle α1between the first alignment direction AD1and the direction X is, for example, 135 degrees, and an included angle α2between the second alignment direction AD2and the direction X is, for example, 45 degrees, but the invention is not limited thereto. In another embodiment, the included angle α1may also be 45 degrees, and the included angle α2may also be 135 degrees.

Preferably, in the embodiment, an axial direction of a first absorption axis AX1of the first polarizer POL1may be optionally parallel to the first alignment direction AD1of the first alignment layer AL1, and an axial direction of the second absorption axis AX2of the second polarizer POL2may be optionally parallel to the second alignment direction AD2of the second alignment layer AL2. Namely, the axial direction of the first absorption axis AX1is perpendicular to the axial direction of the second absorption axis AX2, an included angle β1between the first absorption axis AX1and the direction X is 135 degrees, and an included angle β2between the second absorption axis AX2and the direction X is 45 degree. However, the invention is not limited thereto. In other embodiments, the axial direction of the first absorption axis AX1of the first polarizer POL1may be perpendicular to the first alignment direction AD1of the first alignment layer AL1, and the axial direction of the second absorption axis AX2of the second polarizer POL2may be perpendicular to the second alignment direction AD2of the second alignment layer AL2.

In the embodiment, an included angle α3between the third alignment direction AD3of the third alignment layer AL3and the direction X (i.e., the first viewing angle control direction) is, for example, 85 degrees, and an included angle α4between the fourth alignment direction AD4of the fourth alignment layer AL4and the direction X is, for example, −90 degrees. It should be noted that the negative value of the angle here means that the angle is defined based on the direction X and according to an angle magnitude that deviates from the direction X in a clockwise direction; on the contrary, if the angle is positive, it is defined based on the direction X and according to an angle magnitude that deviates from the direction X in a counterclockwise direction.

Moreover, an included angle θ between a slow axis SX of the half-wave plate250and the direction X is between 50 degrees and 80 degrees or between 140 degrees and 170 degrees. In the embodiment, the included angle θ is, for example, 65 degrees. Namely, an axial direction of the slow axis SX of the half-wave plate250of the embodiment is between the second absorption axis AX2of the second polarizer POL2and the third alignment direction AD3of the third alignment layer AL3.

Specifically, when the display apparatus10is operated in a wide viewing angle mode, a first voltage is provided to the first electrically-controlled element210and the second electrically-controlled element220. When the display apparatus10is operated in a narrow viewing angle mode, a second voltage is provided to the first electrically-controlled element210and a third voltage is provided to the second electrically-controlled element220. In particular, the first voltage is lower than the second voltage, and the first voltage is lower than the third voltage. Specifically, the viewing angle range of the wide viewing angle mode is larger than the viewing angle range of the narrow viewing angle mode (for example, in the first viewing angle control direction, the different between the viewing angle range of the wide viewing angle mode and the viewing angle range of the narrow viewing angle mode is greater than 30 degrees), and the viewing angle range is, for example, a viewing angle range corresponding to a brightness greater than a certain threshold brightness (for example, full width at half maximum, FWHM).

In other words, a method of driving the display apparatus10includes providing the first voltage to the first electrically-controlled element210and the second electrically-controlled element220to operate the display apparatus10in the wide viewing angle mode, and respectively providing the second voltage and the third voltage to the first electrically-controlled element210and the second electrically controlled element220to operate the display apparatus10in the narrow viewing angle mode.

For example, in the embodiment, when the voltage between the first electrode layer E1and the second electrode layer E2of the first electrically-controlled element210and the voltage between the third electrode layer E3and the fourth electrode layer E4of the second electrically-controlled element220are both 0 V (i.e., the first voltage), as shown inFIG.3A, the viewing angle ranges of the display apparatus10at different azimuth angles are substantially the same.

When the voltage between the first electrode layer E1and the second electrode layer E2of the first electrically-controlled element210is 1.7 V (i.e., the second voltage), and the voltage between the third electrode layer E3and the fourth electrode layer E4of the second electrically-controlled element220is 3.5 V (i.e., the third voltage), as shown inFIG.3B, the display apparatus10has a narrow viewing angle range in the direction parallel to the direction X, for example, the light emitted to side viewing angle ranges (the left side and the right side of the front view angle direction) may be effectively suppressed. Therefore, the direction parallel to the direction X ofFIG.3Bmay be defined as the first viewing angle control direction of the display apparatus10. It should be noted that the transmittance distribution (viewing angle) of the display apparatus10at this time is asymmetric with respect to the front viewing direction (e.g., the direction Z).

Further, referring toFIG.4at the same time, a curve C1and a curve C2are respectively curves of brightness (or luminance) to viewing angle in the horizontal direction (e.g., parallel to the direction X) when the display apparatus10is operated in the wide viewing angle mode and the narrow viewing angle mode. When the display apparatus10is operated in the narrow viewing angle mode, a narrow viewing angle brightness distribution curve (i.e., the curve C2) thereof clearly shows that the light output in the side viewing angle range above −30 degrees is effectively suppressed, and the viewing angle corresponding to the maximum brightness of the narrow viewing angle brightness distribution curve is deviated from the front viewing angle (i.e., 0 degree) and biased towards a larger viewing angle (as shown inFIG.4, the viewing angle corresponding to the maximum brightness is, for example, 3 degrees).

It should be noted that the above narrow viewing angle brightness distribution curve has a main viewing angle range (for example, the brightness is greater than 60%) covering the front viewing angle. The main viewing angle range has a peak (for example, the maximum brightness), and the peak is moved along the direction X as the applied voltage of the first electrically-controlled element210is changed. In other words, the method of driving the display apparatus10may further includes tuning the applied voltage (i.e., the second voltage) of the first electrically-controlled element210when the display apparatus10is operated in the narrow viewing angle mode.

For example, referring toFIG.1andFIG.5AtoFIG.5D,FIG.5AtoFIG.5Dare respectively transmittance distribution diagrams of the display apparatus10when the applied voltage of the first electrically-controlled element210is 1.6 V, 1.7 V, 1.8 V, and 1.9 V, and the applied voltage of the second electrically-controlled element220is 3.5 V. According to the figures, it is known that the higher the applied voltage of the first electrically-controlled element210is, the more the viewing angle range located on the left side of the front view angle direction is reduced toward the direction X. Referring toFIG.6, a curve C3, a curve C2, a curve C4, and a curve C5respectively show brightness-viewing angle distributions of the display apparatus10along the direction X (or the first viewing angle control direction) ofFIG.5AtoFIG.5Dincluding the front viewing angle when the first electrically-controlled element210is applied with voltages of 1.6 V, 1.7 V, 1.8 V, and 1.9 V. The viewing angle corresponding to the peak of the narrow viewing angle brightness distribution curve is moved along the direction X as the applied voltage (i.e., the second voltage) of the first electrically-controlled element210is increased, i.e., the viewing angle corresponding to the peak may be increased.

It should be noted that when the display apparatus10is used in vehicle, due to design requirements of different vehicle models, the relative position relationship between the display apparatus and the driver may be different. Therefore, by adjusting the applied voltage of the first electrically-controlled element210, the viewing angle control range may be optimized according to the configuration requirements of different vehicle models. In addition, as different drivers have different heights, the angle of viewing the display apparatus10is also different. Therefore, the viewing angle control range may be optimized for drivers of different heights by adjusting the applied voltage of the second electrically-controlled element220. In other words, the method of driving the display apparatus10may further includes tuning the applied voltage (i.e., the third voltage) of the second electrically-controlled element220when the display apparatus10is operated in the narrow viewing angle mode.

For example, referring toFIG.1andFIG.7AtoFIG.7C, whereinFIG.7AtoFIG.7Care respectively transmittance distribution diagrams of the display apparatus10when the second electrically-controlled element220is applied with voltages of 3.1 V, 3.5 V, and 3.9 V, and the first electrically-controlled element210is applied with a voltage of 1.6 V. According to the figures, it is known that when the applied voltage of the second electrically-controlled element220is 3.1 V, a non-viewing area (for example, the brightness is less than 20%) of the display apparatus10within the viewing angle of 50 degrees may be deviated from the front viewing angle direction along a direction Y (for example, the direction Y is perpendicular to the direction X and direction Z), and may be moved toward the opposite direction of the direction Y as the applied voltage is increased. When the applied voltage is 3.9 V, the non-viewing area of the display apparatus10within the viewing angle of 50 degrees may be deviated from the front viewing angle direction along the opposite direction of the direction Y. Namely, by adjusting the applied voltage of the second electrically-controlled element220, the display apparatus10may also have a second viewing angle control direction parallel to the direction Y.

Referring toFIG.7Dat the same time, a curve D1, a curve D2, and a curve D3respectively show brightness-viewing angle distributions (i.e., narrow viewing angle brightness distribution curves) of the display apparatus10along the direction Y (or the second viewing angle control direction) ofFIG.7AtoFIG.7Cincluding a horizontal viewing angle of 35 degrees when the second electrically-controlled element220is applied with voltages of 3.1 V, 3.5 V, and 3.9 V. The viewing angle corresponding to a valley of the narrow viewing angle brightness distribution curve may be moved along the direction Y as the applied voltage (i.e., the third voltage) of the second electrically-controlled element220is increased.

Referring toFIG.8A, for example, the backlight module100may include a light guide plate110, a light source120, a diffuser130, a reflector140, a prism sheet150, and two optical brightness enhancement films161and162. The light guide plate110has a light incident surface110is, and a bottom surface110bsand a light-emitting surface110esconnected to the light incident surface110isand opposite to each other. The light source120is disposed at a side of the light incident surface110isof the light guide plate110. The reflector140is disposed on one side of the bottom surface110bsof the light guide plate110. The diffuser130, the prism sheet150, and the two optical brightness enhancement films161and162are sequentially disposed on one side of the light-emitting surface110esof the light guide plate110, wherein the prism sheet150includes a substrate151and a plurality of prism structures153, and these prism structures153are disposed on a surface of the substrate151facing the light guide plate110. To be specific, the backlight module100of the embodiment may be a light-collecting-type backlight module, but the invention is not limited thereto. In another embodiment, as shown inFIG.8B, the backlight module100A may also adopt a viewing angle control sheet170(for example, 3M LCF) to replace the prism sheet150ofFIG.8A, wherein the viewing angle control sheet170is disposed on one side of the two optical brightness enhancement films161and162away from the light guide plate110. In another embodiment, the backlight module may also be a backlight module commonly used in a vehicle-mounted display apparatus or a general display apparatus, which is not limited by the invention.

Other embodiments are provided below to describe the invention in detail, wherein the same reference numerals denote the same or like components, and descriptions of the same technical contents are omitted. The aforementioned embodiments may be referred for descriptions of the omitted parts, and detailed descriptions thereof are not repeated in the following embodiments.

FIG.9is a schematic cross-sectional view of a display apparatus according to the second embodiment of the invention.FIG.10Ais a schematic diagram illustrating the arrangement relationship between the alignment direction of the alignment layer, the axial directions of the absorption axes of the polarizers, and the axial direction of the slow axis of the half-wave plate ofFIG.9.FIG.10Bis a schematic diagram illustrating another arrangement relationship between the alignment direction of the alignment layer, the axial directions of the absorption axes of the polarizers, and the axial direction of the slow axis of the half-wave plate ofFIG.9.FIG.11AandFIG.11Bare transmittance distribution diagrams of the display apparatus ofFIG.9respectively operated in a wide viewing angle mode and a narrow viewing angle mode.

Referring toFIG.9andFIG.10A, a difference between a display apparatus10A of the embodiment and the display apparatus10ofFIG.1is that the display apparatus10A further includes a third polarizer POL3, a first compensation film271, and a second compensation film272, wherein the third polarizer POL3is disposed between the half-wave plate250and the second electrically-controlled element220, the first compensation film271is disposed between the third polarizer POL3and the second electrically-controlled element220, and the second compensation film272is disposed between the second electrically-controlled element220and the display panel300.

It should be noted that the included angle between the axial direction of a third absorption axis AX3of the third polarizer POL3and the third alignment direction AD3of the third alignment layer AL3is between −15 degrees and 15 degrees or between 75 degrees and 105 degrees. In the embodiment, the third absorption axis AX3is, for example, parallel to the third alignment direction AD3. In another embodiment, as shown inFIG.10B, an included angle β′ between a third absorption axis AX3′ and the third alignment direction AD3may also be 90 degrees. Since the relative arrangement relationship between the first alignment direction, the second alignment direction, the third alignment direction AD3, the fourth alignment direction AD4, the axial direction of the first absorption axis, the axial direction of the second absorption axis AX2and the axial direction of the slow axis SX of the half-wave plate250of the present embodiment is similar to that of the display apparatus10ofFIG.1, detailed description thereof may be deduced by referring to related paragraphs of the aforementioned embodiments, which will not be repeated.

Moreover, the first compensation film271and the second compensation film272are, for example, biaxial compensation films (B-plate) or C-plate compensation films, and the sum of out-of-plane phase retardation amounts (Rth) of the first compensation film271and the second compensation film272is between 200 nm and 1000 nm. For example, in the embodiment, the first compensation film271and the second compensation film272are, for example, biaxial compensation films, and the sum of the out-of-plane phase retardation amounts is, for example, 290 nm.

Referring toFIG.11AandFIG.11Bat the same time, it is particularly noted that, in the display apparatus10A of the embodiment, the anti-peep performance of the display apparatus10A in the first viewing angle control direction may be improved by setting the third polarizer POL3, and the arrangement of the first compensation film271and the second compensation film272may expand the anti-peep range of the display apparatus10A.

FIG.12is a schematic cross-sectional view of a display apparatus according to the third embodiment of the invention.FIG.13is a schematic diagram illustrating the arrangement relationship between the alignment direction of the alignment layer, the axial directions of the absorption axes of the polarizers, and the axial direction of the slow axis of the half-wave plate ofFIG.12.FIG.14AandFIG.14Bare transmittance distribution diagrams of the display apparatus ofFIG.12respectively operated in different display modes.FIG.15is a luminance-viewing angle curve diagram of the display apparatus ofFIG.12and the display apparatus ofFIG.1operated in a narrow viewing angle mode.

Referring toFIG.12andFIG.13, the difference between a display apparatus10B of the embodiment and the display apparatus10ofFIG.1is that the display apparatus10B further includes a third polarizer POL3-A disposed between the half-wave plate250and the second electrically-controlled element220, and the phase retardation amount of the second liquid-crystal layer LCL2of the second electrically-controlled element220is smaller. It should be noted that in the embodiment, an included angle β″ between the axial direction of a third absorption axis AX3″ of the third polarizer POL3-A and the third alignment direction AD3is 10 degrees. Since the configuration of the third alignment direction AD3of the embodiment is the same as that of the third alignment direction AD3of the third alignment layer AL3of the embodiment ofFIG.1, the included angle between the third absorption axis AX3″ and the direction X of the embodiment is 95 degrees. Moreover, different from the half-wave plate250ofFIG.1, an included angle θ″ between a slow axis SX″ of the half-wave plate250A and the direction X of the present embodiment is 70 degrees.

Referring toFIG.14AandFIG.14B, since the third absorption axis AX3″ of the third polarizer POL3-A of the embodiment is neither parallel nor perpendicular to the third alignment direction AD3of the third alignment layer AL3, when the display apparatus10B is operated in the narrow viewing angle mode, the non-viewing area thereof is shifted relative to the non-viewing area of the display apparatus of each of the aforementioned embodiments. For example, when the display apparatus10ofFIG.1is operated in the narrow viewing angle mode, the narrow viewing angle brightness distribution curve C2along the direction X and including the front viewing angle (as shown inFIG.15) shows that the display apparatus10still has a relatively high brightness in a viewing angle range of 55 degrees to 60 degrees, and the emitted light of the viewing angle range may have adverse effects in special usage situations. Therefore, in the present embodiment, when the display apparatus10B is operated in the narrow viewing angle mode, the non-viewing area may be shifted (for example, shifted toward a large viewing angle) through the above configuration of the third polarizer POL3-A, so that the light output of the display apparatus10B in the viewing angle range of 55 degrees to 60 degrees is suppressed (as shown by a curve C6inFIG.15), so as to meet different usage requirements.

Moreover, in the embodiment, by adjusting the phase retardation amount of the second liquid-crystal layer LCL2, the viewing angle range of the non-viewing area of the display apparatus10B may also be adjusted. For example, the range of the non-viewing area of the display apparatus10B is increased as the phase retardation amount of the second liquid-crystal layer LCL2is decreased.

FIG.16is a schematic view of still another implementation of the backlight module ofFIG.1.FIG.17is a schematic top view of a part of film layers of the backlight module ofFIG.16.FIG.18is a normalized luminance-viewing angle curve diagram of the display apparatus when the backlight module ofFIG.1is replaced with the backlight module ofFIG.16.FIG.19is a schematic diagram illustrating the arrangement relationship between the extending directions of the first prism structures of the first optical brightness enhancement film and the second prism structures of the second optical brightness enhancement film. It is particularly noted that a curve diagram inset inFIG.18is a partial enlarged view of a curve C8pand a curve C7p.

Referring toFIG.16andFIG.17, the difference between a backlight module100B and the backlight module100A ofFIG.8Blies in that the backlight module100B of the embodiment is provided without the viewing angle control sheet170. Besides, in the backlight module100B, the optical brightness enhancement film161(i.e., the first optical brightness enhancement film) disposed on a side of the light-emitting surface110esof the light guide plate110may include a substrate161S and a plurality of prism structures161P, and the optical brightness enhancement film162(i.e., the second optical brightness enhancement film) disposed on a side of the optical brightness enhancement film161away from the light guide plate110may includes a substrate162S and a plurality of prism structures162P.

In the embodiment, the prism structures161P of the optical brightness enhancement film161are disposed on a side of the substrate161S away from the light guide plate110, and the prism structures162P of the optical brightness enhancement film162are disposed on a side of the substrate162saway from the light guide plate110. In other words, the prism structures161P of the optical brightness enhancement film161are arranged toward the optical brightness enhancement film162, and the prism structures162P of the optical brightness enhancement film162are arranged away from the optical brightness enhancement film161.

It is particularly noted that, as illustrated inFIG.19, an included angle ϕ1between an extending direction ED1of the prism structures161P of the optical brightness enhancement film161and the first viewing angle control direction (for example, the direction X) is less than 45 degrees, and an included angle ϕ2between an extending direction ED2of the prism structures162P of the optical brightness enhancement film162and the first viewing angle control direction is less than 45 degrees.

For example, as illustrated inFIG.17andFIG.19, in the embodiment, the prism structures161P of the optical brightness enhancement film161may be arranged in the direction Y and extend along the direction X, and the included angle ϕ2between the extending direction ED2of the prism structures162P of the optical brightness enhancement film162and the direction X is, for example, 10 degrees. Namely, the extending direction ED1of the prism structures161P of the optical brightness enhancement film161is parallel to the light incident surface110is(or the direction X) of the light guide plate110, and an included angle A1between the extending direction ED1of the prism structures161P of the optical brightness enhancement film161and the extending direction ED2of the prism structures162P of the optical brightness enhancement film162is 10 degrees, but the invention is not limited thereto.

In other embodiment (not shown), the extending direction of the prism structures of each of two optical brightness enhancement film may not be parallel to the light incident surface of the light guide plate, and the included angle (for example, the included angle A1) between the extending directions of the prism structures of the two optical brightness enhancement films may be greater than or equal to 5 degrees and less than or equal to 40 degrees, preferably, may be greater than or equal to 10 degrees and less than or equal to 20 degrees.

Referring toFIG.16andFIG.18, the curve C8pand the curve C8srespectively illustrate the relationship between the normalized luminance and the viewing angle of the display apparatus operated in the narrow viewing angle mode and the wide viewing angle mode when a backlight module (not illustrated) of a comparative embodiment is provided with only one optical brightness enhancement film and the extending direction of the prism structures thereof are parallel to the light incident surface of the light guide plate. The curve C7pand the curve C7srespectively illustrate the relationship between the normalized luminance and the viewing angle of the display apparatus operated in the narrow viewing angle mode and the wide viewing angle mode when the backlight module100ofFIG.1is replaced with the backlight module100B of present embodiment.

Comparing the curve C7pand the curve C8pof curve diagram inset inFIG.18, it can be known that the luminance of the backlight module with only one optical brightness enhancement film (i.e., the comparative embodiment) at a viewing angle of −60 degrees cannot be effectively supressed. Differently, the luminance of the display apparatus adopting the backlight module100B of the embodiment at the viewing angle of −60 degrees can be suppressed, so as to improve the anti-peep effect of the display apparatus operated in the narrow viewing angle mode.

FIG.20is a schematic cross-sectional view of a display apparatus according to the fourth embodiment of the invention.FIG.21AandFIG.21Bare transmittance-viewing angle curve diagrams of the display apparatus ofFIG.20operated in different display modes.FIG.22AandFIG.22Bare transmittance-viewing angle curve diagrams of the display apparatus operated in different display modes when the first electrically-controlled element ofFIG.20is configured with another maximum phase retardation amount.

Referring toFIG.20, the difference between the display apparatus10C of the embodiment and the display apparatus10ofFIG.1lies in that a compensation film270may be disposed between the first polarizer POL1and the second polarizer POL2of the display apparatus10C, and the out-of-plane phase retardation amount of the compensation film270is greater than or equal to −400 nm and less than or equal to −50 nm (the out-of-plane phase retardation amount of the compensation film270is between −400 nm and −50 nm). The out-of-plane phase retardation amount herein, for example, is defined by [(nx+ny)/2−nz]×d, wherein nx, ny and nz are the refractive indices of the compensation film270along the direction X, the direction Y and the direction Z, respectively, and d is a film thickness of the compensation film270along the direction Z. The compensation film270is, for example, a C-plate compensation film.

When the maximum phase retardation amount (for example, a product of the refractive index difference and thickness) of the first electrically-controlled element210is 0.482 μm, the distribution of transmittance-viewing angle of the display apparatus10C operated in the narrow viewing angle mode is illustrated as the curve C10pofFIG.21A, wherein the out-of-plane phase retardation amount of the compensation film270of the display apparatus10C is, for example, −120 nm. The curve C9pofFIG.21Aillustrates the distribution of transmittance-viewing angle of the display apparatus of the comparative embodiment operated in the narrow viewing angle mode when the out-of-plane phase retardation amount of the compensation film270is 0 nm (i.e., there is no compensation film270).

It can be known fromFIG.21Athat the configuration of the compensation film270may effectively suppress the light emission of the display apparatus in the range of viewing angle from −40 degrees to −80 degrees, so as to further improve the anti-peep effect of the display apparatus10C operated in the narrow viewing angle mode, wherein the out-of-plane phase retardation amount of the compensation film270is greater than or equal to −120 nm and less than or equal to −80 nm. On the other hand. the luminance (as illustrated by the curve C10sofFIG.21B) of the display apparatus10C operated in the wide viewing angle mode at a large viewing angle is lower than the luminance (as illustrated by the curve C9sofFIG.21B) of the display apparatus provided without the compensation film270and operated in the wide viewing angle mode at a large viewing angle.

Referring toFIG.21AandFIG.21B, the luminance of the display apparatus10C near the normal viewing angle will drop significantly (for example, the transmittance will drop from 0.35 to 0.15) when the maximum phase retardation amount of the first electrically-controlled element210is 0.482 μm, and the display apparatus10C is switched from the wide viewing angle mode to the narrow viewing angle mode.

To solve the problem, the maximum phase retardation amount of the first electrically-controlled element210may be greater than or equal to 1 μm and less than or equal to 1.2 μm. Correspondingly, the out-of-plane phase retardation amount of the compensation film270may be greater than or equal to −200 nm and less than or equal to −130 nm.

For example, when the maximum phase retardation amount of the first electrically-controlled element210is 1.08 μm, the distribution of transmittance-viewing angle of the display apparatus10C operated in narrow viewing angle mode is illustrated as the curve C12pofFIG.22A, wherein the out-of-plane phase retardation amount of the compensation film270, for example, is −200 nm. The curve C11pofFIG.22Aillustrates the distribution of transmittance-viewing angle of the display apparatus of comparative embodiment operated in narrow viewing angle mode when the out-of-plane phase retardation amount of the compensation film270is 0 nm (i.e., there is no compensation film270).

It can be known fromFIG.22AandFIG.22B, the drop in luminance of the display apparatus10C near the normal viewing angle is significantly reduced (for example, the transmittance drops from 0.35 to 0.3) when the display apparatus10C is switched from the wide viewing angle mode to the narrow viewing angle mode due to the configuration of compensation film270. On the other hand, the luminance (as illustrated by the curve C12sofFIG.22B) of the display apparatus10C operated in the wide viewing angle mode at a large viewing angle is lower than the luminance (as illustrated by the curve C11sofFIG.22B) of the display apparatus provided without the compensation film270and operated in the wide viewing angle mode at a large viewing angle.

Based on the above, in the display apparatus of an embodiment of the invention, the electrically-controlled first liquid-crystal layer and second liquid-crystal layer are provided between the backlight module and the display panel. The included angle between the alignment direction on one side of the first liquid-crystal layer and the alignment direction on the other side thereof is between 75 degrees and 105 degrees, and the included angle between the alignment direction on one side of the second liquid-crystal layer and the alignment direction on the other side thereof is between 165 degrees and 195 degrees, wherein the included angle between the alignment direction of the first liquid-crystal layer close to the second liquid-crystal layer and the alignment direction of the second liquid-crystal layer close to the first liquid-crystal layer is between 30 degrees and 60 degrees, or between 120 degrees and 150 degrees, and two opposite sides of the first liquid-crystal layer are provided with two polarizers with absorption axes perpendicular to each other. Through the above configuration, the viewing angle range of the display apparatus in at least one direction may be electrically-controlled and switched to meet different usage situations.

On the other hand, the backlight module is provided with two optical brightness enhancement film, and an included angle between an extending direction of prism structures of each of the two optical brightness enhancement films and a viewing angle control direction of the display apparatus is less than 45 degrees. Accordingly, the anti-peep effect of the display apparatus operated in a narrow viewing angle mode may be improved. A compensation film with an out-of-plane phase retardation amount greater than or equal to −400 nm and less than or equal to −50 nm may also be provided between the first polarizer and the second polarizer to obtain a better anti-peep effect.