Patent Application
20070013648
This application claims the benefit of the Japanese Patent Application No. 2005-205409 filed Jul. 14, 2005, which is hereby incorporated by reference.
1. Field
A display element that includes a liquid crystal display panel and a backlight that illuminates the liquid crystal display panel, a method of producing a display element, and an electronic apparatus including a display element are provided.
2. Related Art
Conventionally, in the technical field of liquid crystal display elements, there has been a strong demand to reduce electric power consumption and improve brightness by increasing the pixel area as much as possible. In order to satisfy these demands, a liquid crystal display element produced by applying a thick insulating film on the entire surface of an active matrix substrate and providing reflective pixel electrodes on the insulating film has been put to practical use. In a display element having such a structure in which pixel electrodes are disposed on an insulating film, electric short-circuiting between scanning lines and signal lines disposed on the insulating film at the lower layer and the pixel electrodes at the upper layer can be prevented. Therefore, the pixel electrodes can be provided over a large area in a manner such that the pixel electrode overlaps with the lines. Accordingly, most of the area where switching elements of thin film transistors (TFTs), scanning lines, and signal lines are provided can be used as pixel areas contribute to the display. The aperture ratio can be increased to obtain a bright display.
A liquid crystal display only including reflective pixel electrodes cannot be used in dark places. Therefore, a semi-transmissive liquid crystal display element that is provided with a backlight and that is partially capable of transmissive display is widely used.
In a semi-transmissive liquid crystal display element, one pixel is divided into a light-transmitting display unit and a reflective display unit. For example, to increase the area of the light-reflecting display units, the area of the light-reflecting display units has to be decreased. There is a trade-off between the transmissive display and the reflective display. Thus, if the area of the light-transmitting display units is small, brightness of the liquid crystal display element may be uneven.
To prevent the brightness from being uneven when the semi-transmissive liquid crystal display element is used for transmissive display by using the backlight, a liquid crystal display element including a microlens array interposed between a semi-transmissive TFT liquid crystal display panel and a backlight and a prism sheet disposed on the upper surface of the backlight has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-107505).
The liquid crystal display element according to Japanese Unexamined Patent Application Publication No. 2003-107505 is structured to emit a strongly directional beam of light to the light-transmitting display units by the microlens array interposed between the liquid crystal display panel and the backlight.
However, according to the structure of this liquid crystal display element, focusing is carried out by linking only the positions of one lens among the plurality of lenses included in the microlens array and one light-transmitting display unit of the liquid crystal display panel. Therefore, the light emitted from the backlight and focused by the microlens array is diffused in a narrow angle. Consequently, high brightness and excellent visibility are achieved in the direction of the normal line to the display surface of the liquid crystal display panel, but high brightness is only achieved is a narrow view angle.
The view angle can be widened by providing a diffusion plate on the display surface of the liquid crystal display panel. However, by doing so, diffusion of outside light is increased, causing a reduction in contrast. Moreover, brightness in the viewing direction of the user is decreased because the emitted light is diffused to the outside of the viewing angle of the user. Thus, the effect of focusing the light emitted from the backlight by the microlens array is reduced.
A mobile apparatus, such as a mobile phone, including a liquid crystal display element is often viewed while the user holds the apparatus in hand. Therefore, the viewing angle of the user is limited mainly to the lower half of the normal line to the display surface of the liquid crystal display panel. Thus, even if the brightness of the liquid crystal display element is high within an angular range near the normal line to the display surface, good visibility of the liquid crystal display element viewed by the user cannot be achieved.
For a direct-vision liquid crystal display element used for a mobile apparatus, a polarizing plate is often bonded to the liquid crystal display panel. Since the adhesive used for bonding the polarizing plate to the substrate causes refraction of light, the visibility of the liquid crystal display panel viewed by the user could be reduced even more.
A semi-transmissive liquid crystal display element or a transmissive liquid crystal display element according to an embodiment of the present invention has taken into consideration the above-identified problems, so that light emitted from the backlight is transmitted through the liquid crystal display panel at an optimal angle. In this way, a display apparatus having improved brightness and visibility and reduced electric consumption is provided.
A display element includes a liquid crystal display panel having liquid crystal sealed between first and second substrates. The first and second substrates are disposed opposite to each other. A backlight illuminates the liquid crystal display panel. Electrodes and an alignment film are provided on the liquid crystal layer side of the first substrate and the liquid crystal layer side of the second substrate. Some of the electrodes on the second substrate are light-reflecting pixel electrodes. A light-transiting portion is formed on part of each of the pixel electrodes.
Light-transmitting display units are formed by providing transparent electrodes in the areas where the light-transiting portions are formed. Areas where light-reflecting pixel electrodes are provided function as light-reflecting display units. The backlight is disposed on the second substrate side. Light emitted from the backlight and transmitted through the liquid crystal display panel is emitted from the liquid crystal display panel at a predetermined angle with directionality with respect to the normal line to the light-reflecting display unit or with respect to the display surface of the liquid crystal display panel.
According to the above-described structure, the angle of the light emitted from the liquid crystal display panel can be set to have directionality. Thus, the transmission efficiently of the light emitted from the backlight is improved, increasing brightness and display quality and reducing electrical power consumption.
For the display element according to an embodiment of the present invention, it is desirable that the directionality is oriented toward the viewing direction of the display element.
The angle of the emitted light can be set in accordance with the range of the user's viewing angle. Thus, when the display element is installed in a mobile apparatus, the visibility of the display surface for the user is significantly improved.
It is desirable that the light emitted from the backlight is transmitted through the liquid crystal display panel at an angle within a range of −10° to 30° with respect to the normal line to each of the light-reflecting display units or with respect to the display surface of the liquid crystal display panel.
By setting the transmitted light within the range indicated above, the settings of the display element can be matched with the user's viewing angle.
The display element may be structured so that focusing means are interposed between the liquid crystal display panel and the backlight in a manner such that the positions of the focusing means corresponds to positions of the pixel electrodes, the focal axis of each the focusing means is disposed at an offset position parallel to the normal line to the center of each of the light-transmitting display units, and the light emitted from the backlight is focused by each of the focusing means and is focused at a focal point at the center of each of the light-transmitting display units.
The display element may be structured so that focusing means is interposed between the liquid crystal display panel and the backlight in a manner such that the positions of the focusing means correspond to the positions of the pixel electrodes. The focal axis of the focusing means is disposed at an inclined position with an offset angle with respect to the normal line to the center of each of the light-transmitting display units. The light emitted from the backlight is focused by each of the focusing means and is focused at a focal point at the center of each of the light-transmitting display units.
Light emitted from the backlight can be transmitted through the liquid crystal display panel as light having a predetermined angle with respect to the normal line to each of the light-transmitting display units or the display surface of the liquid crystal display panel. Thus, visibility of the display element viewed by the user is significantly improved.
For the display element the percentage of the area of the light-transmitting display unit to the area of the pixel electrode is desirably within a range of about 5% to 90% and, more desirably, within a range of about 10% to 80%.
By setting the percentage of the area of the light-transmitting display unit to the area of the pixel electrode is within the above range, the brightness of the display element is increased.
For the display element light emitted from the backlight is desirably emitted at an angle within a range of about −20° to 20° and, more desirably, about −10° to 10°, with respect to the normal line of the emission surface of the backlight.
By setting the angle of the emitted light within the above range with respect to the normal line of the emission surface of the backlight, the transmission of the light of the liquid crystal display panel is improved even more.
For the display element the focusing means may be provided on the lower surface of the second substrate of the liquid crystal display panel.
For the display element the focusing means may be a microlens array, a lenticular lens, Fresnel lens, or gradient index lens.
An electronic apparatus including the above-described display element is provided.
When a display element is installed in an electronic apparatus, such as a mobile apparatus, the visibility of the display surface viewed by the user is significantly improved.
A method of producing a display element is provided. The display element includes a liquid crystal display panel having liquid crystal sealed between first and second substrates. The first and second substrates disposed opposite to each other and a backlight that illuminates the liquid crystal display panel. Electrodes and an alignment film are provided on the liquid crystal layer side of the first substrate and the liquid crystal layer side of the second substrate. Some of the electrodes on the second substrate are light-reflecting pixel electrodes. A light-transiting portion is formed on part of each of the pixel electrodes. Light-transmitting display units are formed by providing transparent electrodes in the areas where the light-transiting portions are formed, wherein areas where light-reflecting pixel electrodes are provided function as light-reflecting display units. The backlight is disposed on the second substrate side, wherein a microlens array is interposed between the liquid crystal display panel and the backlight in a manner such that the positions of microlenses of the microlens array correspond to positions of the pixel electrodes. The focal axis of each of the microlenses is disposed at an offset position parallel to the normal line to the center of each of the light-transmitting display units or at an inclined position with an offset angle. The light emitted from the backlight is focused by each of the microlenses and is focused at a focal point at the center of each of the light-transmitting display units.
The method includes producing the microlens array by carrying out mask exposure to a material whose photosensitivity and refraction index change after applying the material to the backlight side surface of the second substrate.
A method of producing a display element that includes a liquid crystal display panel having liquid crystal sealed between first and second substrates. The first and second substrates being disposed opposite to each other. A backlight illuminates the liquid crystal display panel. Electrodes and an alignment film are provided on the liquid crystal layer side of the first substrate and the liquid crystal layer side of the second substrate. Some of the electrodes on the second substrate are light-reflecting pixel electrodes. A light-transiting portion is formed on part of each of the pixel electrodes. Light-transmitting display units are formed by providing transparent electrodes in the areas where the light-transiting portions are formed. Areas where light-reflecting pixel electrodes are provided function as light-reflecting display units. The backlight is disposed on the second substrate side. A microlens array is interposed between the liquid crystal display panel and the backlight in a manner such that the positions of microlenses of the microlens array correspond to positions of the pixel electrodes. The focal axis of each of the microlenses is disposed at an offset position parallel to the normal line to the center of each of the light-transmitting display units or at an inclined position with an offset angle. The light emitted from the backlight is focused by each of the microlenses and is focused at a focal point at the center of each of the light-transmitting display units.
The method includes producing the microlens array by applying transparent resin to the backlight side surface of the second substrate by inkjet application.
A display element is structured so that light emitted from the backlight is transmitting through the liquid crystal display panel with directionality in a predetermined angle with respect to the normal line of each of the light-transmitting display units or the display surface of the liquid crystal display panel.
The angle of the light emitted from the liquid crystal display panel can be set within the viewing angle of the user viewing the display element.
The transmission efficiency of the light emitted from the backlight is increased, increasing brightness and display quality and reducing electrical power consumption. When the display element is installed in a mobile apparatus, the visibility of the display surface for the user is significantly improved.
The display element may be structured so that focusing means is interposed between the liquid crystal display panel and the backlight in a manner such that the positions of the focusing means correspond to positions of the pixel electrodes, the focal axis of each the focusing means is disposed at an offset position parallel to the normal line to the center of each of the light-transmitting display units or at an inclined position with an offset angle with respect to the normal line to the center of each of the light-transmitting display units, and the light emitted from the backlight is focused by each of the focusing means and is focused at a focal point at the center of each of the light-transmitting display units provided in each pixel of the liquid crystal display panel.
Light emitted from the backlight and focused by the focusing means can be transmitted through the liquid crystal display panel at a predetermined angle with respect to the normal line to each of the light-transmitting display units or the display surface of the liquid crystal display panel. Accordingly, the visibility of the display surface for the user is significantly improved.
A display element will be described below with reference to the drawings.
In all drawings referred to in the descriptions below, the thickness and size ratio of each component are changed appropriately to simplify the descriptions.
The display element 1 according to this embodiment is structured so that the light emitted from the backlight 3 is transmitted through the liquid crystal display panel 2 at an angle E with respect to the normal line to each of the transparent electrodes 24 or the display surface 2a of the liquid crystal display panel 2, wherein the angle E is within a range of about −10° to 30° (refer to
As shown in
As shown in
The percentage of the area of the transparent electrodes 24 in the display element 1 to the area of the pixel electrodes 52 is within the range of is about 5% to 90% or, more desirably, about 10% to 80%.
The display element 1 according to this embodiment emits light from the backlight 3 at an average emission angle ψ with respect to the normal line T of an light-emitting surface 3a of the backlight 3, wherein the average emission angle ψ is within the range of about −20° to 20° or, more desirably, about −10° to 10°.
As shown in the schematic views in
As shown in
Each of the TFTs 51 according to this embodiment has an inverse staggered structure. The TFT 51 is constructed by providing the transparent substrate body 5a, which is the main body of the TFTs 51, as the lowest layer, and then stacking a gate electrode 53, a gate insulating film 54, an i-type semiconductor layer 55, a source electrode 56, and a drain electrode 57 in this order. An etching stopper layer 58 is provided on the i-type semiconductor layer 55 and between the source electrode 56 and the drain electrode 57. N-type semiconductor layers 59 are provided between the i-type semiconductor layer 55 and the drain electrode 57 and between the i-type semiconductor layer 55 and the source electrode 56.
The transparent substrate body 5a includes an insulating transparent substrate consisting of glass or synthetic resin. The gate electrode 53 consists of a conductive metal material and is provided as a unit with the scanning lines 5b disposed in the horizontal direction, as shown in
The TFTs 51, structured as described above, and a source insulating film 20A covering the scanning lines 5b and the signal lines 5c are provided on the transparent substrate body 5a.
Inverse staggered type TFTs 51 are provided as switching elements. However, other types of switching elements, such as TFTs having a different laminated structure or thin film diode elements, may be used.
An insulating film 20B consisting of an organic material is stacked on the source insulating film 20A. On this insulating film 20B, the reflective pixel electrodes 52 consisting of a highly reflective metal material, such as aluminum (Al) or silver (Ag), are provided.
The reflective pixel electrodes 52 are provided on the insulating film 20B so that, when viewed from the top, the shape of each of the pixel electrodes 52 is a rectangle slightly smaller than each of the rectangular areas surrounded by the scanning lines 5b and the signal lines 5c. As shown in
The insulating film 20B is an organic insulating film consisting of acryl-based resin, polyimide-based resin, or benzocyclobutene (BCB) polymer. The insulating film 20B is provided to increase the protection of the TFTs 51. The thickness of the insulating film 20B stacked on the transparent substrate body 5a is relatively greater than that of the other layers. The pixel electrodes 52, the TFTs 51, and the various electrical lines are reliably insulated. The insulating film 20B also prevents the generation of a great parasitic capacitance between the pixel electrodes 52.
In the above-described insulating films 20A and 20B, contact holes 21 that reach ends 56a of the source electrodes 56 are formed. Inside each contact hole 21, a connection part 25 consisting of a conductive material is provided so as to electrically connect the pixel electrode 52 and the end 56a of the source electrode 56 provided above and below, respectively, of the contact hole 21. In accordance with the operation of each of the TFTs 51, the connection part 25 can switch the electrical power applied to the pixel electrode 52.
In the insulating film 20B, depressions 22, each having a rectangular shape when viewed from the top, are provided at the central areas of the rectangular areas surrounded by the scanning lines 5b and the signal lines 5c. The depressions 22 are formed so that they penetrate through the insulating film 20B and reach the source insulating film 20A. The planar size of each depression 22 is desirably set so that the horizontal width is a fraction of that of each pixel electrode 52 and the vertical width is about 50% to 60% of that of the pixel electrode 52. The planar area of the depression 22 is desirably about 5% to 90%, or more desirably about 10% to 80%, of the area of the pixel electrode 52.
At the area of the pixel electrode 52 that corresponds to the depression 22, a flat transmissive portion (transmission hole) 23 that matches the shape of the bottom surface of the depression 22 is provided. A transparent (pixel) electrode 24 consisting of a transparent electrode material is provided, so that the bottom surface of the depression 22 at the lower side of the transmissive portion 23 of the pixel electrode 52 is covered.
The reflective pixel electrode 52 is electrically connected to the transparent electrode 24 by the pixel electrode material that extends to cover the inner circumference of the depression 22 and to reach the peripheral area of the transparent electrode 24 at the bottom surface of the depression 22. Thus, the reflective pixel electrode 52 and the transparent electrode 24 are capable of driving the liquid crystal layer by being driven simultaneously by the switching operation of the TFT 51 to apply an electrical field to the liquid crystal layer.
Accordingly, in each pixel area, the area of the depression 22 corresponds to a transmissive portion 30 that transmits light from the outside of the active matrix substrate 5 (i.e., light emitted from the backlight 3). The other area, for example, the non-transmissive portion of the pixel electrode 52 (or the area where the transmissive portion 23 is not provided), corresponds to a reflective display portion 35 that reflects light from the outside of the opposing substrate 6.
Since three reflective pixel electrodes 52 substantially correspond to one pixel area for color display, which is described below, and the bottom areas of the transmissive portions 23 correspond to the light-transmitting area for transmissive display, the area of each transmissive portion 23 is desirably set to about 5% to 90%, or more desirably to about 10% to 80%, of the area of each pixel electrode 52. According to this embodiment, only one transmissive portion 23 is provided for each pixel electrode 52. However, a plurality of transmissive portions may be provided for each pixel electrode 52. In such a case, the area of each transmissive portion is desirably set to about 5% to 90%, or more desirably to about 10% to 80%, of the area of each pixel electrode 52. In such a case, the depressions are formed at positions below the transmissive portions.
As described above, on the transparent substrate body 5a, alignment films 29a and 29b consisting of polyimide are provided on the lower substrate side so as to cover the pixel electrodes 52, the insulating film 20B, the depressions 22. The alignment film 29a is provided on the transmissive portions 30, for example, the bottom of the depressions 22, whereas the alignment film 29b is provided on the pixel electrodes 52.
The alignment films 29a and 29b are rubbed in the direction indicated by arrows R in
A color filter layer 61, a transparent opposing electrode (common electrode) 62 consisting of indium tin oxide (ITO), and an upper substrate side alignment film 63 is provided on a transparent substrate body 6a, which consists of glass or plastic, of the opposing substrate 6 on the side of the liquid crystal layer 8. As shown in
The thickness of the alignment films 63 and 29b is, for example, about 500 to 600 angstroms (0.05 to 0.06 μm).
As shown in
As shown in
A prism sheet 33 including prisms formed of triangular bumps is provided on the front surface 31a side of the light-guiding plate 31. The prism sheet 33 includes a plurality of protruding refraction portions consisting of refracting surfaces 33a and reflecting surfaces 33b provided on the side of the incident surface, for example, the side of the light-guiding plate 31. The prism sheet 33 also includes the flat light-emitting surface 3a provided opposite to the incident surface. Light is emitted from the light-emitting surface 3a toward the liquid crystal display panel 2.
As shown in
If required, a polarizing plate 44 (refer to
By employing the above-described structure, the display element 1 according to this embodiment is capable of collimating the light emitted from the light-emitting surface 3a of the backlight 3.
The light emitted from the backlight 3 can be maintained at a constant angle by setting the two inclination angles θ1 and θ2 of each prism in accordance with the angle α of the light emitted from the surface 31a of the light-guiding plate 31 of the backlight 3 with respect to the normal line T. The inclination angle θ1 is the angle of inclination with respect to the light-emitting surface 3a of the refracting surfaces 33a of the prism sheet 33. The inclination angle θ2 is the angle of inclination with respect to the light-emitting surface 3a of the reflecting surfaces 33b.
The setting conditions of the inclination angles of the prism sheet 33 of backlight 3, as illustrated in
The angles β, γ, ε, and ψ, shown in
β=α−θ1 (2)
γ=sin−1 (sin β/n) (3)
ε=180−2θ2θ1−γ (4)
ψ=sin−1 (n×sin ε) (5)
For the angles represented above, if ψ=ε=0, the inclination angles θ1 and θ2 are represented by Expression 1 below.
θ2=½(180−θ1−sin−1 (sin (α−θ1)/n) (1)
It is desirable to set the inclination angle θ1 to θ1>30° if α=70°, θ1>20° if α=75°, θ1>10° if α=80°, and θ1>0° if α=85° (refer to FIGS. 12 to 15). The range of the inclination angle θ2 is uniquely determined on the basis of α and θ1.
By setting the angles ψ and ε to 0°, setting the inclination angle θ1 within the above-identified range when the angle α is set as above, and uniquely determining the inclination angle θ2, the diffusion angle of the light emitted from the backlight 3 with respect to the normal line T is set within the range of about −20° to about 20°, or more desirably about −10° to about 10°. Thus, the emitted light is substantially collimated, and the use efficiency of the emitted light is increased.
Details on the desirable ranges of the inclination angles θ1 and θ2 will be described in the examples below with reference to data.
The setting conditions of the inclination angles of the reflecting plate 34 disposed on the side of the back surface 31b of the backlight 3 will be described below.
As shown in
θ3=(α−β)/2 (6)
90−α<θ4≦90° (7)
As shown in
According to the structure of the display element 1 according to this embodiment, light emitted from the light source 32 is emitted from the inclined portions 31c of the light-guiding plate 31, reflected at the reflecting plates 34, perpendicularly emitted at and transmitted through the light-guiding plate 31, and emitted from the surface 31a of the light-guiding plate 31.
The inclination angle θ3 is uniquely determined on the basis of the angles α and β. It is desirable to set the inclination angle θ4 within the range of 90°−α≦θ4≦90°.
By setting the inclination angles θ3 and θ4 as indicated above, light emitted from the back side of the backlight 3 is efficiently reflected at the reflecting plate 34 toward the backlight 3. Thus, the light can be emitted from the light-emitting surface 3a of the backlight 3.
By setting the inclination angles θ1 and θ2 on the basis of Expressions 2 to 5, the average emission angle ψ of the light emitted from the light-emitting surface 3a of the backlight 3 with respect to the normal line T can be set appropriately.
The graph illustrated in
The backlight used for the measurement was set, so that the angle α of the light emitted from the light-guiding plate 31 with respect to the normal line T was about 75° and the refraction index n of the prism sheet 33 was about 1.49. The inclination angles θ1 and θ2 of the prisms of the prism sheet 33 of this backlight were set to θ1=50° and θ2=56.8° on the basis of Expression 1, so that a beam of light whose reflection angle ε of the reflecting surfaces 33b with respect to the normal line T and the average emission angle ψ from the light-emitting surface 3a with respect to the normal line T were both set to 0° was emitted from the light-emitting surface 3a.
As shown in the graph illustrated in
In contrast, the brightness at about −25° angle and about 25° angle with respect to the normal line T was about 30 cd/M2. This was smaller than the brightness within the range of −20° to 20°.
According to the brightness-angle distribution graph, for the backlight used in this example, the range in which the highest brightness was achieved was substantially within the range of −20° to 20° or, more desirably −10° to 10°, with respect to the normal line T. Thus, the backlight was capable of emitting well-collimated light beams.
Even when a backlight including a prismatic reflecting plate 34 on the back side of the light-guiding plate 31 is used, well-collimated light beams, similar to that obtained above, are emitted.
According to the display element 1 according to this example, by employing a backlight having the above-described structure, the angle of the light emitted from the backlight was set within the range of about −20° to about 20° or, more desirably about −10° to about 10°. In this way, light emitted from the backlight can be efficiently focused at the microlenses included in the microlens array 4, described below. Thus, the brightness of the display element 1 can be increased.
The microlens array 4 is interposed between the liquid crystal display panel 2 and the backlight 3. The microlens array 4 focuses the light emitted from the backlight 3 and emits the focused light onto the transparent electrodes (light-transmitting display units) 24 of the liquid crystal display panel 2.
As shown in
As shown in
The lens shape of the microlens array 4 is not limited to that shown in
The cross-sectional views in
The microlens array 4 may be an array of convex lenses, as shown in the cross-sectional view of
The microlens array may include a plurality of lenses corresponding to the pixel electrodes 52 shown in
Fresnel lenses or gradient index glass may be used to focus light onto each pixel.
If the microlens array 4 is to be provided on the back side of the substrate body 5a before providing the TFTs 51 on the substrate body 5a, it is desirable to select a material for the microlens array 4 that does not deform during the production and processing of the TFTs 51.
When bonding a polarizing plate on the back side (backlight 3 side) of the substrate body 5a while forming the microlens array 4 on the substrate body 5a, it is desirable to select an adhesive that has a refraction index that is closest to one. In this way, the refraction of the lens is decreased, and the focal length in increased.
After providing gradient index glass at a position corresponding to the pixel electrodes 52 on the back side of the substrate body 5a, the TFTs 51 may be formed on the surface on the opposite side.
When providing the lenses on the back side of the substrate body 5a after forming the TFTs 51 on the substrate body 5a, care must be exercised to prevent the alignment film from being degraded by processing, such as spin coating or wet development.
As shown in
It is desirable to disposed the microlens array 4 in such a manner because, when the microlens array 4 is disposed closely and directly below the transparent electrode 24: 1) a microlens array having great amplitude that is difficult to produce may be required because the focal distance becomes small; 2) a flattening process may be required to be carried out on the microlens array (wherein the thickness of the film to be flattened must be 10 μm or greater); 3) the material used for producing the film to be flattened may be limited to a material that is resistive to heat higher than 200° C. and that has a low refractive index of about 1.3 or smaller; and 4) reliability and yield may be reduced when metal wires and the TFTs 51 are provided on the flattened film.
For the display element 1 according to this embodiment, by employing the microlens array 4 having the above-described structure, light emitted from the backlight 3 can be efficiently focused at the center of each transparent electrode 24 even when the beams of light from the backlight 3 are tilted and emitted to the microlenses of the microlens array 4.
As shown in
For the display element 1 according to this embodiment, by employing the backlight 3 having the above-described structure, the light from the backlight 3 can be emitted as directional light having a diffusion angle within the range of about 20° to about −20°, or more desirably about 10° to about −10°, with respect to the normal line to the light-emitting surface of the backlight 3 (refer to
As shown in
If the angle ψ of the emitted light with respect to the normal line T of the light-emitting surface 3a of the backlight 3 is not within the range of about 10° to about −10°, light may not be efficiently focused at the center of each transparent electrodes 24, causing a reduction in the brightness of the display element 1. To efficiently irradiate the transparent electrodes 24 with the emitted light, the offset amount of the microlenses of the microlens array 4 must be increased, causing an increase in production cost of the display element 1.
For the display element 1 according to this embodiment, by appropriately setting the above-described offset length L, an angle E of the emitted light with respect to the normal line S of each transparent electrode 24 or the normal line U of the display surface 2a while light emitted from the backlight 3 and focused by the microlens array 4 is transmitted through the transparent electrode 24 and emitted from the display surface 2a of the liquid crystal display panel 2 is set within the range of about −10° to about 30°. In this way, the visibility of the display surface (i.e., the display surface of the display element 1) viewed by a user is significantly increased when the display element 1 is used as a display unit of a mobile apparatus (electronic apparatus) 9, such as a mobile phone, on basis of the reason described below.
As shown in
For the display element 1 according to the display element 1, the range of the emission angle E of light with respect to the normal line U of each transparent electrode 24 or the display surface 2a of the liquid crystal display panel 2 is matched with the range of the above-mentioned viewing angle F of the user, for example, a range of about 10° to about 30° (i.e., within a magnitude of 40°). In this way, when the display element 1 is used as the display unit of the mobile apparatus 9, the viewing angle F of the user and the angle of the light emitted from the display surface 2a match. Thus, the user can view the display unit (display element) of the mobile apparatus 9 at an angle that achieves the highest brightness.
In
A method of disposing a microlens array, used for the display element 1 according to this embodiment, onto the surface of a lower polarizing plate provided on the back side of the liquid crystal display panel 2 (i.e., the backlight 3 side) will be described with reference to
When a microlens film is to be directly provide onto the polarizing plate 44 that is bonded to the liquid crystal display panel 2, first, a lens resin material 40 is applied to the polarizing plate 44, as shown in
When the polarizing plate 44 is bonded to the liquid crystal display panel 2 after the microlens film is provided on the polarizing plate 44, the lens resin material 40 is applied to the polarizing plate 44, as shown in
As the lens resin material, it is desirable to use a material whose photosensitivity and refraction index changes, such as polysilane resin.
It is desirable to set the baking temperature according to the process described above to the degradation temperature of the polarizing plate 44 or lower.
When producing the microlens array, a method of producing a microlens film by applying a transparent resin by inkjet application onto the positions where lenses are formed on the polarizing plate may be employed.
When a microlens array is to be interposed between the liquid crystal display panel 2 and the backlight 3, as shown in
When a microlens array is disposed on the upper surface of the backlight 3, as shown in
As described above, for the display element 1 according to this embodiment, the microlens array 4 is interposed between the liquid crystal display panel 2 and the backlight 3 in a manner such that the positions of the microlenses and the positions of the pixel electrodes 52 of the liquid crystal display panel 2 correspond to each other. The lens axis R of each microlens is disposed at a position displaced parallel to the normal line S of the center of the transparent electrode 24 by an offset length L. Light emitted from the backlight 3 is focused at the microlens, wherein the center of the transparent electrode 24 provided in each pixel of the liquid crystal display panel 2 is set as a focal point.
Light emitted from the backlight 3 and focused at the microlenses will have directionality and can be transmitted through the liquid crystal display panel 2 at a predetermined angle with respect to the normal line to the transparent electrodes 24 or the display surface 2a of the liquid crystal display panel 2.
Consequently, the transmission efficiency of the light emitted from the backlight 3 is improved; brightness and display quality are improved; and electric power consumption is reduced. When the display element 1 according to this embodiment is installed in a mobile apparatus, the visibility of the display surface viewed by the user is significantly improved.
A display element according to a second embodiment will be described below with reference to the drawings.
In the description below, the components that are the same as those included in the display element 1 according to the first embodiment will be represented by reference numerals that are the same as those representing the components in the display element 1 according to the first embodiment.
As shown in
As shown in
By setting the offset angle D of the lens axis R of each microlens of the microlens array 41 appropriately with respect to the normal line S, the emission angle of light emitted from a display surface 2a of a liquid crystal display panel 2 with respect to the normal line U of the display surface 2a can be set. In this way, the brightness and the visibility of the display element 11 and the display units of the mobile apparatus 9 including the display element 11 can be improved.
Examples of the display element 11 will be described below.
The liquid crystal display panel 2, such as that shown in
Similar to the example shown in
A semi-transmissive TFT liquid crystal display element having a 30% aperture ratio of the transparent electrodes to the pixel electrodes, a pixel size of 180 μm×60 μm, and a transparent electrode size of 36μ×40 μm was used.
As shown in
Each microlens of the microlens array was disposed at an offset position in a manner such that the lens axis was displaced from the normal line to the center of each transparent electrode by 550×tan ψμm in the upper direction of the display surface of the display element (i.e., left in
The inclination direction of light focused at and transmitted through the transparent electrodes of the liquid crystal display panel by the microlens array was set to a direction opposite to the position of the light source (i.e., right in
A known display element (comparative example) was produced in the same way as described above, except that each microlens of the microlens array was disposed, without offset, on the back side of the TFT substrate body of the semi-transmissive TFT liquid crystal display element by matching the lens axis and the normal line to the center of each transparent electrode and that a prism sheet was not disposed on the light-guiding plate of the backlight.
By using the above-described example and the comparative example, the transmission (%) at each angle with respect to the normal line to the front surface of the display element was measured.
As shown in the graph in
In contrast, for the viewing angle of a known display element, as shown in the graph in
The above-described data clearly shows that the display apparatus is capable of emitting light from the front surface of the display element at an angle matching the viewing angle of the user viewing the display element in a mobile apparatus. This is because the display apparatus according to the embodiments is capable of collimating light emitted from the light-guiding plate of the backlight with a prism sheet, and the collimated light is focused at the center of each transparent electrode and transmitted through the liquid crystal display panel using a microlens array disposed at an offset position, as described above.
It is demonstrated that the display element according to the embodiments of the present invention allows a user to view the display element at highest brightness and visibility.
FIGS. 12 to 15 show data obtained by measuring the relationship between the inclination angles θ1 and θ2 of a prism sheet and the light-emitting angle of a backlight.
If the relationship of a height H where light reaches and a prism height h, as shown in
The relationship between the angles and the size, shown in
d=p×tan θ1/(tan θ1+tan θ2)
H≈(p+d)/tan α
h=d×tan θ2
As shown in FIGS. 12 to 15 and
When H>h, part of the light incident on the prism sheet is not incident on the surface on the θ2 side. Thus, the use efficiency of light is reduced. Therefore, it is desirable to satisfy the condition H<h.
A display element was produced by disposing a microlens array at an offset position and disposing a prism sheet on a light-guiding plate of a backlight according to a similar process as that of the above-described example, except that a transmissive TFT liquid crystal display element was used as a liquid crystal display element.
By carrying out measurements in the same manner as that in the above-described example, a light transmitting characteristic similar to the above-described example was obtained.
A display element was produced by disposing a microlens array at an offset position and disposing a prism sheet on a light-guiding plate of a backlight according to a similar process as that of the above-described example, except that a semi-transmissive super twisted nematic (STN) liquid crystal display element was used as a liquid crystal display element.
By carrying out measurements in the same manner as that in the above-described example, a light transmitting characteristic similar to the above-described example was obtained.
A display element was produced by disposing a microlens array at an offset position according to a similar process as that of the above-described example, except that the microlens array was bonded onto the backlight of the semi-transmissive TFT liquid crystal display element and the liquid crystal display unit and the backlight were aligned and fixed with a chassis.
By carrying out measurements in the same manner as that in the above-described example, a light transmitting characteristic similar to the above-described example was obtained.
A display element was produced by disposing a microlens array at an offset position according to a similar process as that of the above-described example, except that a prism mirror was disposed on the back side of the light-guiding plate of the backlight.
By carrying out measurements in the same manner as that in the above-described example, a light transmitting characteristic similar to the above-described example was obtained.
A display element was produced by disposing focusing means at offset positions according to a similar process as that of the above-described example, except that a lenticular lens or gradient index glass was used as the focusing means.
By carrying out measurements in the same manner as that in the above-described example, the same focusing effect as that of the above-described example, as shown in
A display element was produced through a process including the steps of: applying polysilane resin at a thickness of 20 μm on the backlight side substrate surface of a second substrate of a semi-transmissive TFT liquid crystal display element; carrying out mask exposure by emitting an ultraviolet beam at 6 J/cm2 while aligning the substrate with the liquid crystal layer surface mark; forming minute concave and convex lenses at offset positions with respect to the transparent electrodes; then, baking the substrate at 200° C.; cutting the substrate; and injecting liquid crystal to the substrate.
A display element according to an embodiment of the present invention was produced by using a semi-transmissive STN liquid crystal display element or a transmissive TFT liquid crystal display element as a liquid crystal display element.
By carrying out measurements in the same manner as that in the above-described example, the same focusing effect as that of the above-described example, as shown in
A display element was produced through a process including the steps of: applying polysilane resin at a thickness of 20 μm on the backlight side substrate surface of a second substrate of a semi-transmissive TFT liquid crystal display element; carrying out gray scale mask exposure by emitting an ultraviolet beam at 6 J/cm2 while aligning the substrate with the liquid crystal layer surface mark; forming minute concave and convex lenses at offset positions with respect to the transparent electrodes; then, baking the substrate at 200° C.; cutting the substrate; and injecting liquid crystal to the substrate.
A display element was produced by using a semi-transmissive STN liquid crystal display element or a transmissive TFT liquid crystal display element as a liquid crystal display element.
By carrying out measurements in the same manner as that in the above-described example, the same focusing effect as that of the above-described example, as shown in
A display element was produced through a process including the steps of: applying transparent resin by an inkjet application on the backlight side substrate surface of a second substrate of a semi-transmissive TFT liquid crystal display element while aligning the substrate with the liquid crystal layer surface mark; forming minute concave and convex lenses at offset positions with respect to the transparent electrodes; then, baking the substrate at 200° C.; cutting the substrate; and injecting liquid crystal to the substrate.
A display element was produced by using a semi-transmissive STN liquid crystal display element or a transmissive TFT liquid crystal display element as a liquid crystal display element.
By carrying out measurements in the same manner as that in the above-described example, the same focusing effect as that of the above-described example, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-205409 | Jul 2005 | JP | national |
