JP2004054035A - Liquid crystal display and electronic equipment - Google Patents

Abstract

Provided is a liquid crystal display device that achieves an improvement in luminance while using an EL element as a light source, and an electronic device including the same.
A liquid crystal display device (10) according to the present invention includes a lighting device (40) and a liquid crystal panel (11) provided on the lighting device (40). And a prism sheet 22 provided on the light emitting unit 30, wherein the light emitting unit 30 has a luminance peak in a direction at a wider angle than the normal direction of the light emitting unit 30. And
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device and an electronic device.
[0002]
[Prior art]
Conventionally, as a backlight used in a transmissive or transflective liquid crystal display device, a large one uses a cold cathode tube as a light source and a small one uses an LED (Light Emitting Diode) as a light source. Met.
In recent years, in order to realize power saving of a liquid crystal display device, an illuminating device using an EL (Electro Luminescence) element as a light source instead of the backlight using the cold cathode tube attracts attention. A lighting device using an EL element is not a point light source such as an LED, but is a surface light source, so that uniform lighting is possible and a liquid crystal display device having a uniform display surface luminance can be easily configured. It is being actively performed. FIG. 8 illustrates an example of a liquid crystal display device including a backlight using an EL element as a light source.
[0003]
The liquid crystal display device 100 shown in FIG. 8 includes a liquid crystal panel 110, a backlight 130 disposed on the back side of the liquid crystal panel 110, and a liquid crystal display device 100 disposed between the liquid crystal panel 110 and the backlight 130. And a prism sheet 122 for changing the direction of light emitted from the liquid crystal display device 100 in the front direction.
The liquid crystal panel 110 is a transmissive or transflective liquid crystal panel, and performs transmissive display using light emitted from the backlight 130. The backlight 130 is an EL element formed by sequentially stacking a transparent substrate 141, a transparent anode 142, a hole transport layer 143, a light emitting layer 144, and a cathode 145. The opposite side is the light emitting surface.
The prism sheet 122 is a transparent plate material made of an acrylic resin or the like, and one surface side (upper side in the drawing) is a prism surface 122a in which a prism shape of a side surface triangular wave is formed, and a prism at the top of the prism surface is formed. The vertical angle α is 90 °.
[0004]
The liquid crystal display device 100 having the above configuration introduces the light emitted from the backlight 130 into the prism sheet 122, and when the light propagating in the prism sheet 122 is transmitted to the upper surface thereof, the prism surface 122a of the prism sheet 122 The liquid crystal panel 110 is illuminated by being refracted.
The prism sheet 122 has been conventionally used in combination with a backlight having a light guide plate and a light source disposed on an end face thereof. That is, in a backlight that emits light from a light source through a light guide plate, the intensity of light emitted from the main surface of the light guide plate is slightly oblique from the front because the light source is disposed on the end surface of the light guide plate. Since the direction in which the amount of emitted light is maximized is directed in the normal direction of the light guide plate by the prism sheet, the amount of emitted light in the direction of the user's line of sight is increased, and a substantially bright display is achieved. I was trying to get it.
However, it was found that when such a prism sheet 122 was applied to the backlight 130 having an EL element, the luminance in the normal direction of the liquid crystal display device 100 was lower than when the prism sheet 122 was not provided.
[0005]
[Problems to be solved by the invention]
The present inventor has conducted repeated studies for the purpose of improving luminance in a liquid crystal display device provided with such a lighting device using an EL element, and has completed the present invention. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal display device that realizes an improvement in luminance while using an EL element as a light source, and an electronic apparatus including the same.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, a liquid crystal display device of the present invention is a liquid crystal display device including a lighting device and a liquid crystal panel provided on the lighting device, wherein the lighting device uses an EL element as a light source. A light emitting unit, and a prism sheet disposed on the light emitting unit, wherein the light emitting unit has a luminance peak in a direction of a wider angle than a normal direction of the light emitting unit. I have.
In the liquid crystal display device having such a configuration, of the light emitted from the EL element of the light emitting unit and entering the prism sheet, the intensity of light emitted at a wider angle than the normal direction of the light emitting unit is emitted in the front direction. It is made larger than the light intensity. With such a configuration, the intensity of light that is refracted by the prism sheet and emitted in the front direction of the liquid crystal panel is increased, and the amount of light that can contribute to display is improved, thereby substantially improving display luminance. be able to. In other words, light incident on the prism sheet from the normal direction is reflected on the inner surface side of the convex portion forming the prism surface toward the light emitting unit side and is not transmitted to the upper surface of the prism sheet (the liquid crystal panel side surface). In this configuration, the ratio of light that can be transmitted through the prism sheet is increased, and the luminance of the liquid crystal display device is improved.
[0007]
Next, in the liquid crystal display device according to the present invention, it is preferable that the luminance of the light emitting portion has a minimum value within an angle range of 0 ° or more and 20 ° or less from a normal direction of a light emitting surface of the light emitting portion.
According to the above configuration, it is possible to reduce the light incident at an incident angle within 20 ° from the normal direction, which increases the reflectance by the prism surface of the prism sheet, and prevents reflection by the prism sheet to contribute to display. The amount of light that can be increased can be increased.
[0008]
Next, in the liquid crystal display device according to the present invention, the EL element has an organic film including a light emitting layer and a hole transport layer stacked on one surface side of the light emitting layer. The film thickness may be such that the intensity at the center wavelength of the emitted light in the normal direction of the EL element is reduced.
In the EL device, light is emitted near the interface between the light emitting layer and the hole transport layer, propagates from the light emitting interface to both sides in the organic film thickness direction, and emits light directly from the light emitting surface of the EL element surface. The mixed light with the light that propagates to the opposite side of the surface, is reflected by, for example, a cathode having light reflectivity, and then propagates toward the light emitting surface and is emitted is the emitted light. Therefore, optical interference between the two types of light occurs in the EL element, and the interference state depends on the optical path length of both. In the EL element according to the present configuration, the thickness of the organic film is set so as to have an optical path length in which the two types of light cancel each other out, and the luminance in a direction shifted by a predetermined angle from the normal direction of the EL element. Is to be maximized. With this configuration, the component reflected by the prism sheet can be reduced, and the amount of light transmitted through the prism sheet and contributing to display can be increased.
[0009]
In the liquid crystal display device having the above configuration, it is preferable that the thickness of the organic film is a thickness that gives a minimum value of intensity at a central wavelength of light emitted in a normal direction of the EL element.
As described above, the prism sheet reflects the light incident from the back surface side in the normal direction to the light emitting unit side, so that the light in the prism sheet normal direction is reduced as much as possible, and the prism sheet is inclined from the back surface of the prism sheet. Increasing the component incident in the direction is effective for improving the display luminance. According to this configuration, since the light emitted in the normal direction of the EL element can be minimized, the amount of light reflected by the prism sheet can be reduced, and the display luminance can be increased.
[0010]
Next, in the liquid crystal display device according to the present invention, an optical unit is disposed between the EL element and the prism sheet, and a peak of luminance of emitted light transmitted through the optical unit is caused by the light emitting unit. A configuration that is located at a wider angle than the normal direction can be adopted.
According to such a configuration, before the light emitted from the EL element enters the prism sheet, it is possible to enhance only the light traveling in a predetermined direction by the optical means, so that the light is reflected at an angle that is not reflected by the prism sheet. The display luminance can be improved by increasing the amount of light incident on the prism sheet.
Since the reflection by the prism sheet is maximum for light incident from the normal direction, the peak position of the luminance shifted to the wide-angle side by the optical means is more than 20 ° with respect to the normal direction of the light emitting unit. More preferably, the angle is wide.
Further, the optical unit may be provided outside the light emitting unit or may be built in the light emitting unit. For example, in the case where the EL element constituting the light emitting portion has a configuration in which a transparent anode, a hole transport layer, a light emitting layer, and a cathode are stacked on a transparent substrate, the transparent substrate and the transparent anode are The above optical means can be provided between or on the outer surface side of the transparent substrate.
[0011]
Next, in the liquid crystal display device according to the present invention, it is preferable that the optical unit is a dielectric mirror. According to this configuration, it is possible to easily adjust the direction in which the luminance increases by adjusting the thickness of each layer constituting the dielectric mirror. Therefore, the light emission according to the configuration such as the prism apex angle and the refractive index of the prism sheet can be achieved. It can be a configuration of a part.
[0012]
Next, an electronic apparatus according to the present invention includes the above-described liquid crystal display device according to the present invention. According to such a configuration, it is possible to provide an electronic device including an EL element in the lighting device, low power consumption, and a display unit having high luminance in the front direction of the panel and excellent visibility.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1st Embodiment)
FIG. 1 is a cross-sectional configuration diagram of a liquid crystal display device according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional configuration diagram showing a part of the backlight 30 shown in FIG.
A final product is configured by attaching auxiliary elements such as a liquid crystal driving IC and a support to the liquid crystal display device 10 of this embodiment.
[0014]
The liquid crystal display device 10 of this embodiment has a pair of rectangular substrate units 13 in a plan view that are substantially rectangular in a plan view and that are attached to each other with a cell gap therebetween via an annular sealing material 12. , 14, a liquid crystal layer 15 sandwiched and sandwiched therebetween together with the sealing material 12, a retardation plate 19 and a polarizing plate 16 provided on the upper surface side of one of the substrate units 13 (upper side in FIG. 1). And a liquid crystal panel 11 provided with a retardation plate 26 and a polarizing plate 27 provided on the lower surface side of the other (lower side of FIG. 1) substrate unit 14, and a transparent panel provided below the liquid crystal panel 11. The apparatus mainly includes a plurality of (two in the figure) prism sheets 22 and 22 made of an acrylic resin and the like, and a backlight (light emitting portion) 30. The prism sheets 22 and 22 and the backlight 30 are illuminated. Constitute a 0. The lighting device 40 is arranged such that the light emitting surface 30a of the backlight 20 faces the liquid crystal panel 10 side, that is, the lighting device 40 is disposed below the liquid crystal panel 11 and the liquid crystal panel Illumination light can be emitted toward.
[0015]
Among the substrate units 13 and 14, the substrate unit 13 is a front (upper) substrate unit provided facing the observer, and the substrate unit 14 is provided on the opposite side, in other words, a substrate unit provided on the back side (lower side). It is.
The upper substrate unit 13 includes a light-transmitting substrate 17 made of, for example, a transparent material such as glass, and a retardation plate 19 and a polarizing plate 16 provided sequentially on the front side of the substrate 17 (the upper surface side, the observer side in FIG. 1). A color filter layer 24 and an overcoat layer 21 sequentially formed on the back side of the substrate 17 (in other words, the liquid crystal layer 15 side); and a liquid crystal driving layer formed on the surface of the overcoat layer 21 on the liquid crystal layer 15 side. It has a plurality of striped electrodes 23. The liquid crystal layer 15 is composed of nematic liquid crystal molecules having a twist angle of 240 to 255 degrees.
[0016]
In an actual liquid crystal display device, alignment films are respectively formed on the liquid crystal layer 15 side of the electrode 23 and the liquid crystal layer 15 side of the stripe-shaped electrode 35 on the lower substrate, which will be described later. These alignment films are omitted and description thereof is omitted, and illustration and description of alignment films are also omitted in other embodiments which will be sequentially described below. In the cross-sectional structure of the liquid crystal display device shown in FIG. 1 and each of the following drawings, the thickness of each layer is adjusted to be different from that of the actual liquid crystal display device so that each layer is easy to see in the case shown. . In the present embodiment, each of the driving electrodes 23 on the upper substrate side is formed of a transparent conductive material such as ITO (Indium Tin Oxide: indium tin oxide) in a stripe shape in a plan view. The required number is formed in accordance with the number of pixels.
[0017]
In the present embodiment, the color filter layer 24 is formed by forming a black mask for blocking light and RGB patterns for color display on the inner surface of the upper substrate 17 (in other words, the surface on the liquid crystal layer 15 side). Have been. Further, an overcoat layer 21 is coated as a transparent protective flattening film for protecting the RGB patterns. The black mask is formed by patterning a metal thin film of chromium or the like having a thickness of about 100 to 200 nm by, for example, a sputtering method or a vacuum evaporation method. In each of the above RGB patterns, a red pattern (R), a green pattern (G), and a blue pattern (B) are arranged in a desired pattern shape. For example, a photosensitive resin containing a predetermined coloring material is used. It is formed by various methods such as a pigment dispersion method, various printing methods, an electrodeposition method, a transfer method, and a dyeing method.
[0018]
On the other hand, the lower substrate unit 14 includes a light transmissive substrate 28 made of a transparent material such as glass, and a semi-transmissive substrate sequentially formed on the inner surface side (the upper surface side in FIG. 1, in other words, the liquid crystal layer 15 side) of the substrate 28. The reflective layer 31, the overcoat layer 33, a plurality of stripe-shaped driving electrodes 35 formed on the surface of the overcoat layer 33 on the liquid crystal layer 15 side, and the outer surface side of the substrate 28 (the lower surface side in FIG. In other words, it comprises a retardation plate 26 formed sequentially on the liquid crystal layer 15 side) and a polarizing plate 27. The necessary number of these electrodes 35 is formed in accordance with the display area of the liquid crystal panel 11 and the number of pixels as in the case of the electrode 23 described above.
[0019]
Each of the prism sheets 22 is configured such that one surface side (upper side in the drawing) of a flat plate material made of a transparent acrylic resin or the like is a prism surface 22a, and is formed with periodic irregularities in the shape of a triangular side surface. FIG. 3 is a perspective view of these prism sheets 22, 22, and as shown in FIG. 3, a pair of slope portions 22A, 22B are formed alternately and periodically on the prism surface 22a. The angle (prism vertical angle α) formed by the slope portions 22A and 22B is 90 °. Note that the prism apex angle α of these prism sheets 22, 22 is not limited to 90 °, but may be in the range of 80 ° to 125 °.
These prism sheets 22 are arranged such that the direction in which the ridge line of the convex portion of the upper prism sheet 22 extends and the direction in which the ridge line of the convex portion of the lower prism sheet 22 extends differ by 90 ° in the azimuthal direction. Thus, the light collecting direction is provided so as to match the front direction (normal direction) of the illumination device 40.
[0020]
When light enters from the back side (the opposite side to the liquid crystal panel 11), each prism sheet 22 enters the prism sheet 22 from an oblique direction (an angle range larger than an angle range of approximately ± 20 degrees of the normal direction). The traveling direction of the reflected light can be changed in the front direction of the prism sheet 22, and the light incident perpendicularly to the prism sheet 22 (an angle range of ± 20 degrees in the normal direction) is almost changed by the prism sheet 22. Does not transmit.
[0021]
As shown in FIGS. 1 and 2, the backlight (light emitting unit) 30 includes an EL element unit 50 including a pair of electrodes 42 and 45 facing each other with a light emitting layer 44 interposed therebetween. At least one of the pair of electrodes 42 and 45 located on the light-transmitting substrate 41 side is formed of a light-transmitting electrode such as a transparent conductive film such as ITO, and the other electrode is disposed on one surface. 45 is made of a material used for a conventional metal electrode such as aluminum, silver, a silver alloy, magnesium, or the like, and is made to be able to conduct electricity to the EL element unit 50. The light emitted from the light emitting layer 44 at the time of energization is emitted to the light transmitting substrate 41 side. A hole transport layer 43 for facilitating injection of holes from the electrode 42 is provided between the electrode 42 and the light emitting layer 44 of the EL element portion 50. The light emitting layer 44 and the hole transport layer 45 The organic film of the EL element unit 50 is formed.
[0022]
The hole transport layer 43 includes, for example, a material using a material used for a conventional hole transport layer, such as a triphenylamine derivative, polyvinyl carbazole, or polyethylene dioxythiophene. In addition, as the material used for the hole transport layer 43, one or more kinds can be used.
[0023]
The light-emitting layer 44 can be made of an organic EL material (electroluminescence material) used for a conventional light-emitting layer, and is preferably made of a material that can emit white light.
[0024]
In the backlight 30 according to the present embodiment having the above-described configuration, the thickness of the organic film (the hole transport layer 43 and the light emitting layer 44) of the EL element unit 50 is substantially equal to the emission light in the normal direction of the EL element unit 50. It is said to be a thickness that reduces the strength of. The configuration and operation of the EL element section 50 will be described with reference to FIG. FIG. 4 is an explanatory diagram illustrating a cross-sectional configuration of the EL element unit 50 illustrated in FIG.
[0025]
When the EL element 50 emits light, light is emitted in the vicinity of the interface between the light-emitting layer 43 and the hole transport layer 44 that constitute the organic film, and the high-luminance surface B that emits light most strongly in the in-plane direction of the EL element 50. Is formed, and a luminance distribution is generated in the thickness direction of the EL element portion 50. Here, focusing on the light emitted from the point O on the high luminance surface B, the light L1 traveling from the point O to the electrode 42 side passes through the organic film and the electrode 42 and is located above the EL element portion 50 in the drawing. Emitted to On the other hand, the light L2 traveling from the point O to the electrode 45 side is reflected by the electrode 45, passes through the organic film and the electrode 42, and is emitted upward from the EL element unit 50 in the figure. As described above, the light generated in the EL element unit 50 is emitted from the EL element unit 50 as a mixed light of the lights L1 and L2. As shown in FIG. 4, since the light L1 and the light L2 have different optical path lengths, optical interference occurs between the two. For example, if the light L1 and the light L2 have the same phase when traveling to the electrode 42 side, they will be strengthened by interference, and if they are in the opposite phase, they will cancel each other. In addition, since the hole transport layer 43 and the light emitting layer 44 have a finite thickness, the interference of the lights L1 and L2 differs depending on the direction of light emission from the point O.
[0026]
In such an EL element section 50, the thickness of the organic film is set to a thickness that reduces the luminance of light emitted in the normal direction. That is, the thickness of the organic film is set so that the difference between the phase of the light L1 and the phase of the light L2 in the normal direction of the EL element portion 50 is more than 90 ° and less than 270 °. With this configuration, light emitted from the EL element unit 50 of the present embodiment has low luminance in the normal direction and high luminance of light emitted in an oblique direction. Therefore, the component of the light reflected by the prism sheet 22 can be reduced, and the amount of light traveling in the front direction of the liquid crystal panel 11 can be increased by the refraction of the prism sheet 22.
[0027]
In addition, the direction in which the luminance of the light emitted from the EL element unit 50 is maximum can be adjusted to a desired angle by the thickness of the organic film. In practice, the emission angle at which the maximum luminance is obtained is obtained. Is determined in consideration of the prism apex angle α of the prism sheet 22 and the refractive index of the prism sheet 22 so that the luminance in the front direction of the illumination unit 30 is increased.
[0028]
The thickness of the organic film is set to a thickness at which the light L1 and the light L2 interfere with each other in the normal direction of the EL element portion 50 (that is, a thickness at which the light L1 and the light L2 have opposite phases). Is preferred. With such a film thickness, the component in the normal direction of the EL element unit 50 where the reflectance of the prism sheet 22 is maximized can be suppressed to the minimum light amount, and the light is emitted obliquely from the EL element unit 50. The display brightness can be increased by increasing the amount of light.
[0029]
The liquid crystal display device 10 of the present embodiment can efficiently condense the light emitted from the backlight 30 in the front direction of the liquid crystal panel 11 by providing the illumination device 40 as described above. Since the brightness in the front direction of the panel 11 can be improved, a bright display can be obtained, and the display quality can be improved.
[0030]
Since the liquid crystal display device of the present embodiment is of a transflective type, the backlight 30 is not always turned on, but is turned on by a user or a sensor instruction only when there is almost no ambient light (external light). You can do it. That is, when sufficient ambient light is obtained, the backlight is turned off and the liquid crystal panel 11 is operated as a reflective liquid crystal panel. A layer called a transflective layer 31 is formed on such a transflective liquid crystal panel 11, and the transflective layer 31 is made of a metal material having excellent light reflectivity such as Ag or Al. For example, it can be formed on the substrate 28 shown in FIG. 1 by a vapor deposition method or a sputtering method. The transflective layer 31 is a transflective layer having a thickness capable of passing light emitted from the backlight 30 provided below the liquid crystal panel 11 or a light transmissive layer such as Ag or Al. Any of those widely used in transflective liquid crystal display devices, such as a structure in which a number of fine through holes are formed in a part of the reflective layer having a high light transmittance, can be appropriately adopted. When the transflective layer is made of a material having both light reflectivity and conductivity, the transflective layer can also serve as a drive electrode, and the drive electrode 35 is not separately provided. Is also good.
[0031]
In the present embodiment, the case has been described in which the EL element unit 50 provided in the lighting device 40 includes an EL element that emits white light. However, as the EL element unit 50, an EL element that emits red light, One or more of an EL element that emits green light, an EL element that emits blue light, and an EL element that emits white light may be used. According to such a lighting device 40, depending on the EL element used, or the combination of EL elements used, light of red, green, green, white, or other colors is efficiently emitted, and the luminance in the front direction is improved. Thus, a lighting device is obtained.
[0032]
Note that, in the present embodiment, the illumination device 40 provided with the prism sheets 22 and 22 shown in FIG. 3 has been described, but a prism sheet 52 shown in FIG. 5 is applied instead of the prism sheets 22 and 22 shown in FIG. be able to. The prism sheet 52 shown in the perspective view in FIG. 5 is different from the prism sheet 22 shown in FIG. 3 in the shape of the prism surface. The prism surface 52a of the prism sheet 52 shown in FIG. The protrusions 52b are arranged and formed, and the adjacent protrusions 52b are in contact with each other at their side edges. The prism apex angle in the prism sheet 52 is an angle formed by the adjacent slopes 52A and 52B among the slopes forming the protrusion 52b. The prism apex angle in the prism sheet 52 is preferably in the range of 80 ° to 125 °.
This is because, in the prism sheet 52 having such a configuration, the light condensing function works in directions parallel to the bottom sides 52C and 52D of the projections 52b.
The configuration of the prism sheet according to the present invention is not limited to those shown in FIGS. 3 and 5, and the shape is not limited as long as the prism apex angle is in the range of 80 ° to 125 °. For example, in the case of the one having the prism surface on which the convex portions shown in FIG. 5 are arranged, the shape of the convex portion may be a pentagonal pyramid, a polygonal pyramid having more than that, or a cone.
[0033]
Further, in the liquid crystal display device of the present embodiment, the case where the illumination device is provided in the simple matrix type transflective liquid crystal display device has been described, but such an illumination device may be a two-terminal switching element or a three-terminal switching device. Of course, it may be provided in an active matrix type transflective liquid crystal display device having elements.
Further, in the liquid crystal display device of the present embodiment, the transflective liquid crystal display device including the liquid crystal panel 11 in which one retardation plate 19 is provided between the upper substrate 17 and the polarizing plate 16 is used. Although the example in which the present invention is applied has been described, it goes without saying that the present invention may be applied to a transflective liquid crystal display device provided with a liquid crystal panel provided with a plurality of retardation plates.
Further, in the above embodiment, the example in which the present invention is applied to the transflective liquid crystal display device in which the retardation plate 26 and the polarizing plate 27 are provided on the backlight 30 side of the lower substrate 28 has been described. Of course, the present invention may be applied to a transflective liquid crystal display device in which a retardation plate and a polarizing plate are not provided on the backlight 30 side of the lower substrate 28.
[0034]
(First embodiment)
In this example, as Samples 1 to 4, liquid crystal display devices each including an illuminating device using an EL element as a light source and a liquid crystal panel were manufactured, and the display luminance of each device was evaluated.
As the liquid crystal panel, a transflective passive matrix liquid crystal panel as shown in FIG. 1 was used, which was common to each sample. On the other hand, the configuration of the lighting device was different for each sample as shown below.
(1) Sample 1: The film thicknesses of the hole transport layer and the light emitting layer in the EL element portion of the backlight were optimized so that the peak of the emission luminance was located at a wide angle of 30 ° from the normal direction of the backlight. . Two prism sheets having a prism apex angle of 90 ° and having the shape shown in FIG.
(2) Sample 2: The thicknesses of the hole transport layer and the light emitting layer in the EL element portion of the backlight were optimized so that the peak of the emission luminance was positioned at a wide angle of 30 ° from the normal direction of the backlight. . The backlight was arranged on the back side of the liquid crystal panel without providing a prism sheet.
(3) Sample 3: The backlight had a conventional configuration shown in FIG. 12 in which light was emitted radially from the light emitting surface. Two prism sheets having a prism apex angle of 90 ° and having the shape shown in FIG.
(4) Sample 4: The backlight had the same configuration as that of Sample 3, and had no prism sheet.
[0035]
The results of measuring the display luminance by operating the liquid crystal display devices of Samples 1 to 4 are shown in FIG. Focusing on the luminance in the normal direction of the liquid crystal panel in the graph of FIG. 6, Sample 1 has 242 cd / m2. ² , Sample 2 is 80 cd / m ² 145 cd / m for sample 3 ² , Sample 4 is 148 cd / m ² The brightness in the front direction of the panel where the user is arranged is highest in the sample 1 having the configuration of the present invention in which the emission characteristics of the backlight are optimized and the prism sheet is arranged, and the visibility is excellent. It was confirmed that the property was obtained.
[0036]
Sample 2 has extremely low luminance in the front direction of the liquid crystal panel and has a luminance characteristic similar to that of a backlight having a luminance peak at a position 30 ° wide from the normal direction, and is essential to the present invention. It can be seen that, when the prism sheet having the above configuration is not provided, the effect of the present invention for improving the substantial luminance of the liquid crystal display device and improving the visibility cannot be obtained.
[0037]
Next, Sample 3 and Sample 4 of the conventional configuration have the highest luminance in the front direction of the liquid crystal panel, but the luminance is about 60% of that of Sample 1. Further, when a prism sheet is provided between the backlight and the liquid crystal panel, the luminance in the front direction of the liquid crystal panel is reduced. It was confirmed that a backlight having an EL element portion having a configuration according to the present invention was essential.
[0038]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a diagram illustrating a cross-sectional structure of the liquid crystal display device of the present embodiment. A characteristic point of the liquid crystal display device 90 shown in FIG. 7 is that the liquid crystal display device 90 includes an illumination device 80 having a backlight 60. The liquid crystal panel 11 and the prism sheet 22 are the same as those of the first embodiment shown in FIG. The configuration is similar to that of the first embodiment.
[0039]
In the backlight 60, an EL element portion 70 including a pair of electrodes 62 and 65 opposed to each other with a light emitting layer 64 interposed therebetween is disposed on one surface of the light-transmitting substrate 61. Among them, at least the electrode 62 located on the side of the light-transmitting substrate 61 is a light-transmitting electrode, and the other electrode 65 is a metal electrode and can be energized to the EL element portion 70. The light emitted from the light emitting layer 64 when the portion 70 is energized is emitted to the light transmitting substrate 61 side. A hole transport layer 63 is provided between the electrode 62 and the light-emitting layer 64 of the EL element portion 70 so that holes can be easily injected from the electrode 62. Further, a dielectric mirror (optical means) 68 is provided between the light transmitting substrate 61 and the light transmitting electrode 62.
Note that each layer constituting the EL element unit 70 can be made of the same material as the EL element unit 50 according to the first embodiment, and a detailed description thereof will be omitted in this embodiment. However, the thicknesses of the hole transport layer 63 and the light emitting layer 64 are appropriately adjusted according to the characteristics of the dielectric mirror 68 described later.
[0040]
The backlight 60 according to the present embodiment is configured to emit light in a specific direction by the action of the dielectric mirror 68 provided between the EL element unit 70 and the substrate 61. The dielectric mirror 68 is made of, for example, SiO 2 having a thickness of several tens to several hundreds of nm. ₂ Layer and TiO ₂ A plurality of layers are alternately stacked. In the light incident on such a dielectric mirror 68, only light having a resonance wavelength determined by the layer thickness of the dielectric mirror is enhanced, and light having other wavelengths is suppressed. In addition, a multi-layered SiO ₂ Layer and TiO ₂ When passing through a layer, the optical path length in the dielectric mirror 68 varies depending on the traveling direction of the light, so that the permissible traveling direction differs even for light of the same wavelength. By utilizing such characteristics of the dielectric mirror, only the light traveling at a predetermined angle is enhanced, and the light traveling in other directions is suppressed, so that emission light having an emission luminance peak at a specific angle is obtained. be able to.
Then, in the backlight 60 according to the present embodiment, the peak of the emission luminance is located at a wider angle than the normal direction of the backlight 60. Therefore, it is possible to obtain outgoing light that is not reflected by the prism sheet 22 and that is refracted by the prism sheet 22 and can become light in the front direction of the liquid crystal panel 11, thereby improving the brightness in the front direction of the liquid crystal panel 11. Thus, the substantial luminance of the liquid crystal display device 90 is improved.
[0041]
(Second embodiment)
In this example, a liquid crystal display device having the configuration of the second embodiment was manufactured, and its display luminance was evaluated. As the liquid crystal panel, a panel similar to that of the first embodiment was used, and as the prism sheet, a microprism array in which conical prisms having an apex angle of 110 ° were formed on one surface side was used.
The backlight is made of SiO between the EL element part and the substrate. ₂ / TiO ₂ It was assumed that a dielectric mirror having a multilayer structure was formed. The thickness of each of the layers constituting the dielectric mirror, the hole transport layer of the EL element portion, and the film of the light emitting layer such that the emission luminance peak is positioned at an angle of 40 ° wider than the normal direction of the backlight. The thickness was optimized.
[0042]
When the liquid crystal display device obtained above was operated and the display luminance was measured, 280 cd / m2 in the front direction of the liquid crystal panel. ² Was obtained, and it was confirmed that a liquid crystal display device having high luminance in the front direction of the liquid crystal panel was also obtained with the configuration according to the second embodiment.
[0043]
(Electronics)
An example of an electronic device including the liquid crystal display device of the above embodiment will be described.
FIG. 9A is a perspective view illustrating an example of a mobile phone. In this figure, reference numeral 500 indicates a mobile phone main body, and reference numeral 501 indicates a display unit using the liquid crystal display device of the above embodiment.
[0044]
FIG. 9B is a perspective view illustrating an example of a wristwatch-type electronic device. In this figure, reference numeral 600 indicates a watch main body, and reference numeral 601 indicates a display unit using the liquid crystal display device of the above embodiment.
[0045]
FIG. 9C is a perspective view illustrating an example of a portable information processing device such as a word processor or a personal computer. In this figure, reference numeral 700 denotes an information processing device, reference numeral 702 denotes an input unit such as a keyboard, reference numeral 704 denotes an information processing device main body, and reference numeral 706 denotes a display unit using the liquid crystal display device of the above embodiment.
[0046]
Each of the electronic devices illustrated in FIG. 9 includes the liquid crystal display device according to the above-described embodiment, and is thus an electronic device capable of obtaining high-luminance display in front of a display unit where a user is arranged.
[0047]
【The invention's effect】
As described in detail above, the liquid crystal display device of the present invention is a liquid crystal display device including a lighting device and a liquid crystal panel provided on the lighting device, wherein the lighting device includes an EL element. A light-emitting portion serving as a light source, and a prism sheet disposed on the light-emitting portion, wherein the light-emitting portion has a luminance peak in a direction of a wider angle than the normal direction of the light-emitting portion. Thus, the intensity of light refracted by the prism sheet and emitted in the front direction of the liquid crystal panel can be increased, and the amount of light that can contribute to display can be increased, thereby substantially improving display luminance.
[0048]
Further, according to the present invention, it is possible to provide an electronic device having a display portion with high luminance in the front direction of a user and excellent visibility.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram illustrating a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a sectional configuration diagram showing a backlight 30 shown in FIG. 1;
FIG. 3 is a perspective view of a prism sheet 22 shown in FIG.
FIG. 4 is an explanatory diagram illustrating a cross-sectional configuration of the EL element unit 50 illustrated in FIG. 2;
FIG. 5 is a perspective view showing another example of the prism sheet applicable to the liquid crystal display device according to the present invention.
FIG. 6 is a graph showing a luminance measurement result in the first example of the present invention.
FIG. 7 is a cross-sectional configuration diagram illustrating a liquid crystal display device according to a second embodiment of the present invention.
FIG. 8 is a cross-sectional configuration diagram of a conventional liquid crystal display device.
FIGS. 9A to 9C are perspective configuration diagrams illustrating an example of an electronic apparatus according to the invention.
[Explanation of symbols]
10,90 liquid crystal display device
11 LCD panel
22,52 prism sheet
22a prism surface
30, 60 backlight (light-emitting part)
40,80 lighting equipment
50, 70 EL element
68 Dielectric mirror

Claims (7)

A lighting device, a liquid crystal display device including a liquid crystal panel provided on the lighting device,
The lighting device includes a light-emitting unit having an EL element as a light source, and a prism sheet disposed on the light-emitting unit, and the light-emitting unit extends in a direction wider than a normal direction of the light-emitting unit. A liquid crystal display device having a luminance peak. 2. The liquid crystal display device according to claim 1, wherein the luminance of the light emitting unit has a minimum value within an angle range of 0 ° or more and 20 ° or less from a normal direction of a light emitting surface of the light emitting unit. The EL element has an organic film including a light emitting layer and a hole transport layer stacked on one surface side of the light emitting layer,
3. The liquid crystal display device according to claim 1, wherein the thickness of the organic film is a thickness that reduces intensity at a center wavelength of light emitted in a normal direction of the EL element. 4. 4. The liquid crystal display device according to claim 3, wherein the thickness of the organic film is a thickness that gives a minimum value of intensity at a center wavelength of light emitted in a normal direction of the EL element. 5. Optical means is provided between the EL element and the prism sheet,
5. The liquid crystal display device according to claim 1, wherein a peak of luminance of the emitted light transmitted through the optical unit is located in a direction at a wider angle than a normal direction of the light emitting unit. . 6. The liquid crystal display device according to claim 5, wherein said optical means is a dielectric mirror. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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