JP2006323303A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high contrast in a display device provided with a lighting system and reflection LCD. <P>SOLUTION: The lighting system 200 is arranged by being opposed to a reflection electrode 33 of the reflection LCD 300. The lighting system 200 forms an organic EL layer 15 comprising an anode 11, a stripe-like cathode 12 and an organic layer 13. In addition, a shading layer 16 is formed by covering the cathode 12. A distance between centers 13c of an emission region 13a of the organic layer 13 is D1, a distance between the center of the emission region 13a and the surface of the reflection electrode 33 on the vertical direction is D2, and an angle θ made with a beam from the center 13c of the emission region 13a incident on the surface of the reflection electrode 33 and a perpendicular bisector is given by arctan (D1/(2×D2)), on the perpendicular bisector of a line segment connected between the centers of the adjacent emission regions 13a. Then, the angle θ is a prescribed angle without deteriorating a viewing angle dependency of a reflection liquid crystal display device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device including an illumination device and a reflective liquid crystal display device.

  A liquid crystal display device (hereinafter abbreviated as “LCD”) has a feature of being thin and having low power consumption, and is currently widely used as a display device for portable information devices such as computer monitors and mobile phones. LCDs include transmissive LCDs, reflective LCDs, and transflective LCDs. A transmissive LCD uses a transparent electrode as a pixel electrode for applying a voltage to a liquid crystal, and a backlight is placed behind the LCD. By controlling the amount of light transmitted through the backlight, a bright display can be obtained even when the surroundings are dark. it can. However, there is a characteristic that a sufficient contrast cannot be secured in an environment with strong external light such as outdoors in the daytime.

  A reflective LCD uses external light such as sunlight or room light as a light source, and reflects the external light incident on the LCD by a pixel electrode formed of a reflective layer formed on a substrate on the observation surface side, that is, a reflective electrode. . Then, display is performed by controlling the amount of light emitted from the LCD panel of light incident on the liquid crystal and reflected by the reflective electrode for each pixel. Since this reflective LCD uses external light as a light source, there is a problem that display cannot be performed in an environment without external light.

  The transflective LCD has both a transmissive function and a reflective function, and can cope with a bright environment or a dark environment. However, this transflective LCD has a problem that the display efficiency per pixel is poor because it has a transmissive region and a reflective region in one pixel.

  In view of this, it has been considered to enable display even in a dark environment by providing a front light on the reflective LCD. FIG. 5 is a diagram illustrating a display device including a front light and a reflective LCD according to a conventional example. A transparent acrylic plate 110 is disposed facing the display surface of the reflective LCD 100. A plurality of inverted triangular grooves 111 are formed on the surface of the transparent acrylic plate 110 opposite to the surface facing the reflective LCD. A light source 112 is disposed on the side surface of the transparent acrylic plate 110. The light introduced from the light source 112 into the transparent acrylic plate 110 is refracted in the direction of the reflective LCD 100 by the inclined surface of the groove 111 and is incident on the display surface of the reflective LCD 100.

In addition, the following patent documents are mentioned as technical documents relevant to the present application.
JP 2003-255375 A

  However, the light introduced from the light source 112 into the transparent acrylic plate 110 is refracted in the direction of the reflective LCD 100 on the inclined surface of the groove 111 provided in the transparent acrylic plate 110 and is observed in the opposite direction. Since the light 113 is refracted somewhat in the direction in which the viewer 113 is present, the light leaks from the transparent acrylic 110 and enters the eyes of the viewer 113, thereby reducing the contrast of the LCD.

  The present invention has been made in view of the above problems, and is a display device that includes a lighting device and includes a reflective liquid crystal display device that includes a reflective electrode. The lighting device includes a transparent substrate, A light emitting thin body partially disposed on the transparent substrate, the light emitting thin body being disposed with one surface facing the surface of the reflective electrode, and further having the following positional relationship: . That is, the distance between the centers of the adjacent light emitting thin bodies is D1, the distance between the center of the light emitting thin body and the surface of the reflective electrode in the perpendicular direction is D2, and the line segment connecting the centers of the adjacent light emitting thin bodies is D2. On the vertical bisector, θ is the angle formed by the vertical bisector and the light beam from the center of the light emitting thin body incident on the surface of the reflective electrode, and the angle θ is the inverse with the distance D1 and the distance D2 as variables. When given by a tangent function (arctan (D1 / (2 × D2)), the angle θ is a predetermined angle that does not deteriorate the viewing angle dependency of the reflective liquid crystal display device.

  According to the display device of the present invention, display with high contrast can be realized even in a dark environment.

  Next, a display device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a display device including an illumination device and a reflective LCD (liquid crystal display device) according to the present embodiment as viewed from the illumination device side, and FIG. 2 is taken along line XX in FIG. FIG. However, in FIG. 1, only a part of all the components is illustrated.

  As shown in FIGS. 1 and 2, the illuminating device 200 is arranged such that the light irradiation surface faces the display surface of the reflective LCD 300. That is, the illumination device 200 is a light source of the front light of the reflective LCD 300.

  First, the structure of the lighting device 200 will be described. An organic electroluminescence element layer 15 (hereinafter abbreviated as “organic EL element layer 15”) is formed so as to be sandwiched between a first transparent substrate 10 and a second transparent substrate 20 made of a glass substrate or the like. Has been. The organic EL element layer 15 is made of a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), and an anode 11 formed on substantially the entire surface of the first transparent substrate 10. The organic layer 13 is formed on the organic layer 13, and the cathode 12 is formed on the organic layer 13 and patterned in a predetermined shape, for example, in a stripe shape, with a certain pitch.

  Here, the organic layer 13 includes a so-called electron transport layer, a light emitting layer, and a hole transport layer. The cathode 12 is made of, for example, an aluminum layer (Al layer), a laminate composed of a magnesium layer (Mg layer) and a silver layer (Ag layer), or a calcium layer (Ca layer). Further, it is preferable that the thickness of the anode 11 is about 100 nm, the thickness of the cathode 12 is about 500 nm, and the thickness of the organic layer 13 is about 100 nm.

  In the organic EL element layer 15, a region of the organic layer 13 sandwiched between the anode 11 and the cathode 12 becomes a light emitting region 13a. That is, the organic layer 13 immediately below the cathode 12 is a light emitting region 13a, and the organic EL element layer 15 in this region is a light emitting thin body. When the light emitting region 13a is viewed in plan, it has the same predetermined shape as the cathode 12, that is, a stripe shape. The light emitting region 13 a emits omnidirectional light (light that is not linearly polarized light or circularly polarized light) by applying a positive potential to the anode 11 and a negative potential to the cathode 13. The organic layer 13 in other regions does not emit light and becomes a non-light emitting region.

  A light shielding layer 16 is formed so as to cover the cathode 12 patterned in a stripe shape. The light shielding layer 16 is also patterned in the same predetermined shape as the cathode 12, that is, in a stripe shape. Since the light shielding layer 16 is for shielding light emitted upward from the light emitting region 13a, it needs to have a function as a light reflecting layer for reflecting light or a light absorbing layer for absorbing light.

When the light shielding layer 16 functions as a light reflecting layer, it is formed of, for example, chromium (Cr), an aluminum oxide layer (Al ₂ O ₃ layer), or the like. Further, when the light shielding layer 16 functions as a light absorption layer, it is formed of a black pigment layer in which a black pigment is contained in a photoresist material, a black dye layer in which a black dye is contained in a photoresist material, or a chromium oxide layer. . The thickness of the light shielding layer 16 is preferably about 10 nm or less.

  When light is emitted from the light emitting region 13 a of the illumination device 200, light traveling downward (on the side opposite to the observer 113) enters the reflective LCD 300 through the transparent anode 11 and the first transparent substrate 10. In addition, light traveling upward (in the direction of the observer 113) from the light emitting region 13a is reflected or absorbed downward by the cathode 12 and the light shielding layer 16. Therefore, the light from the light emitting region 13a is prevented from entering the eyes of the observer 113 viewing the illumination device 200 from above as much as possible.

  In order to enhance this light shielding effect, the width of the light shielding layer 16 is preferably larger than the width of the patterned cathode 12. Further, as shown in FIG. 3, the distance L1 between the edge of the patterned cathode 12 and the edge of the light shielding layer 16 is the thickness of the light emitting region 13a of the organic layer 13 and the thickness of the patterned cathode 12. In order to further enhance the light shielding effect, it is preferable that the total L2 is equal to or larger than the total L2.

  In the above-described configuration of the present embodiment, the cathode 12 is patterned in a predetermined shape having a constant pitch, for example, a stripe shape, and the anode 11 is not patterned. However, as another example, the cathode 12 and the anode 11 May be replaced. That is, in FIG. 2, the anode 11 may be disposed at the position of the cathode 12, and the cathode 12 may be disposed at the position of the anode 11. In this case, the anode 11 is patterned into the predetermined shape, and the cathode 12 is not patterned.

  As another embodiment different from that, the anode 11 and the cathode 12 are formed on the entire surface without patterning at all, and the three layers of the electron transport layer, the light emitting layer, and the hole transport layer constituting the organic layer 13 are formed. Of these, at least one layer may be patterned into the predetermined shape. In this case, a region formed so that all these three layers overlap each other is a light emitting region, and a region lacking any one of the three layers is a non-light emitting region.

  In addition, when the light emitted from the light emitting region 13a is reflected by a reflective LCD 300 (to be described later) and visually recognized by the viewer 113, the patterned cathode 12 is used to prevent the viewer 113 from feeling uncomfortable. The pitch of the anode 11 or any one of the three layers constituting the organic layer 13 is preferably about 1 mm or less.

  Next, the structure of the reflective LCD 300 will be described. As shown in FIG. 2, a switching thin film transistor 31 (hereinafter abbreviated as “TFT”) is formed in each of a plurality of pixel regions divided into a TFT substrate 30 made of, for example, a glass substrate. The TFT 31 is covered with an interlayer insulating film 32. On the interlayer insulating film 32, a pixel electrode made of a metal material that reflects light such as aluminum (Al), that is, a reflective electrode 33 is formed corresponding to each TFT 31. The reflective electrode 33 is connected to the corresponding drain or source of the TFT 31 through a contact hole CH formed in the interlayer insulating film 32 by a conductive filler (not shown).

  Between adjacent reflective electrodes 33, a predetermined separation region, that is, a slit portion 37S having a predetermined width is provided. The slit portion 37S functions as an alignment control unit for alignment division of the liquid crystal layer 40 described later. Furthermore, an alignment film (not shown) for aligning liquid crystal molecules at a predetermined angle with respect to the TFT substrate 31 is formed so as to cover the reflective electrode 33 and the slit portion 37S.

  A counter substrate 35 made of, for example, a glass substrate is disposed facing the TFT substrate 30 on which the reflective electrode 33 is formed. A common electrode 36 made of, for example, ITO is formed on the surface of the counter substrate 35 (surface facing the TFT substrate 31). On the common electrode 36, a protrusion 37P is formed as an alignment control unit that aligns and divides liquid crystal molecules of a liquid crystal layer 42, which will be described later, in two different predetermined directions. The protrusion 37P is formed by patterning a resist material, for example. Further, an alignment film (not shown) is formed so as to cover the common electrode 36 and the protruding portion 37P.

  On the other hand, on the back surface of the counter substrate 35 (surface facing the observer 113), a λ / 4 wavelength plate 39 (quarter wavelength plate) that generates an optical phase difference of ¼ of the wavelength λ of light. Is arranged. The λ / 4 wavelength plate 39 performs conversion from linearly polarized light to circularly polarized light, or conversion from circularly polarized light to linearly polarized light. Further, the λ / 4 wavelength plate 39 does not cause an optical phase difference of a half of the wavelength λ of the light in order to enable the conversion of the polarization with respect to the light having a broad wavelength. The illustrated λ / 2 wave plate (half wave plate) may be laminated and disposed. On the λ / 4 wavelength plate 39, a light scattering layer 40 made of, for example, a diffusion adhesive layer and a polarizing plate 41 are further laminated in this order. The light scattering layer 40 is for scattering light from the illumination device 200 so that the reflective electrode 33 is uniformly irradiated.

  A liquid crystal layer 42 is sealed between the TFT substrate 30 and the counter substrate 35. The liquid crystal layer 42 includes, for example, liquid crystal molecules (for example, nematic liquid crystal) that have a positive dielectric anisotropy and are spirally aligned so as to have a predetermined optical rotation, and a TN (Twisted Nematic) mode, It drives by MTN (Mixed TN) mode.

  Alternatively, the liquid crystal layer 42 may be driven in a mode other than the above. For example, the liquid crystal layer 42 is composed of vertically aligned liquid crystal molecules (for example, nematic liquid crystal) having a negative dielectric anisotropy, and may be driven in a vertical alignment mode, that is, a VA (Vertically Aligned) mode. Good.

  Next, the coupling relationship between the illumination device 200 and the reflective LCD 300 will be described. As shown in FIGS. 1 and 2, the illumination device 200 is preferably arranged close to the upper side of the reflective LCD 300. However, when an air layer exists between the irradiation device 200 and the reflective LCD 300, the light emitted from the first transparent substrate 10 of the lighting device 200 is reflected when entering the air layer and is reflected on the observer side. There is a risk that the contrast may be lowered.

  Therefore, the light refracting is performed by bonding the irradiation device 200 and the reflective LCD 300 via a resin layer 45 (for example, a UV curable resin layer or a visible light curable resin layer) having the same refractive index as that of the first transparent substrate 10. Is preferably suppressed as much as possible.

  Next, the arrangement relationship between the lighting device 200 and the reflective LCD 300 will be described. As shown in FIGS. 1 and 2, the pitch P <b> 1 of the cathode 12 and the light shielding layer 16 of the lighting device 200 is the same as the pitch P <b> 2 of the reflective electrode 33. In this case, the cathode 12 and the light shielding layer 16 are preferably disposed immediately above the slit portion 37S between the plurality of reflective electrodes 33 that do not contribute to the display of the reflective LCD 300. Accordingly, there is an advantage that most of the light reflected by the reflective electrode 33 is visually recognized by the observer 113 through the gap without being blocked by the light shielding layer 16.

  Further, the pitch P1 between the cathode 12 and the light shielding layer 16 of the lighting device 200 may be smaller than the pitch P2 of the reflective electrode 33, and the ratio of the pitch P1 to the pitch P2, that is, P1 / P2 may be 1 / natural number. If the pitch P1 and the pitch P2 are the same, interference fringes and moire fringes may occur in the display of the reflective LCD 300. By setting the ratio of the pitch P1 and the pitch P2 in this way, The phenomenon can be suppressed.

  Or, conversely, the pitch P1 between the cathode 12 and the light shielding layer 16 of the lighting device 200 may be larger than the pitch P2 of the reflective electrode 33, and the pitch P1 / pitch P2) may be a natural number. This also can suppress the phenomenon such as the interference fringes.

  Furthermore, in this embodiment, the illumination device 200 and the reflective LCD 300 have the following arrangement relationship in addition to the above arrangement relationship. Next, details of the arrangement relationship will be described with reference to the drawings. FIG. 4 is a partially enlarged cross-sectional view of the display device according to the embodiment of the present invention. In FIG. 4, for convenience of explanation, only the light shielding layer 16 of the lighting device 200, the constituent elements of the organic EL element layer 15, the liquid crystal layer 42, the reflective electrode 33 of the reflective LCD 300, and the TFT substrate 31 are illustrated. The illustration of is omitted.

  First, as shown in FIG. 4, in the organic EL element layer 15, the distance between the centers 13c of the adjacent light emitting regions 13a is D1, and the center 13c of the light emitting region 13a and the surface of the reflective electrode 33 in the perpendicular direction thereof Is defined as D2. In addition, on the vertical bisector connecting the centers 13c of the adjacent light emitting regions 13a, the vertical bisector and the light beam from the center 13c of the light emitting region 13a incident on the surface of the reflective electrode 33 Assume that the angle formed is θ, and the angle θ is given by the following equation using an arctangent function with the distance D1 and the distance D2 as variables, that is, arctan (D1, D2).

  At this time, in the present embodiment, as an arrangement relationship between the lighting device 200 and the reflective LCD 300, the angle θ is set to a predetermined angle that does not deteriorate the viewing angle dependency of the reflective LCD 300. That is, the center 13c of the light emitting region 13a of the organic EL element layer 15 and the reflective electrode 33 are arranged with a distance D1 and a distance D2 that can obtain such a predetermined angle θ.

  Here, for example, when the liquid crystal layer 42 is driven in the TN mode, the predetermined angle θ is greater than 0 degree and not more than 20 degrees. For example, when the liquid crystal layer 42 is driven in the vertical alignment mode, the predetermined angle θ is greater than 0 degree and equal to or less than 50 degrees.

  As a method for realizing the above-described angle θ, for example, the cathode 12 (or the layer that determines the light emitting region 13a) of the organic EL element layer 15 is patterned so that the distance D1 satisfying the formula 1 is obtained. In addition, the thickness of at least one layer among the plurality of layers existing between the organic layer 13 and the reflective electrode 33 is adjusted so that the distance D2 satisfying the formula 1 is obtained.

  Next, the operation of the reflective LCD 300 described above will be described. First, the omnidirectional light incident on the reflective LCD 300 from the illumination device 200 becomes linearly polarized light corresponding to the polarization axis of the polarizing plate 41, passes through the λ / 4 wavelength plate 39 through the light scattering layer 40, and is circularly polarized light. It becomes. The circularly polarized light passes through the counter substrate 35 and the common electrode 36 and enters the liquid crystal layer 40.

  At this time, the electric field of the liquid crystal layer 42 changes depending on whether or not a voltage is applied to the reflective electrode 33 and the common electrode 36, and the optical phase difference of the liquid crystal layer 42 changes for each pixel. Then, the circularly polarized light incident on the liquid crystal layer 42 is emitted as circularly polarized light having either the left or right rotation direction due to this optical phase difference and reflection by the reflective electrode. This circularly polarized light is transmitted again through the λ / 4 wavelength plate 39 and is incident on the polarizing plate 41 as linearly polarized light according to the rotation direction. Here, when the polarization axis of the linearly polarized light coincides with the polarization axis of the polarizing plate 41, the linearly polarized light is transmitted through the polarizing plate 41 and becomes white display. It becomes.

  In the above display, light rays from the center 13a of the light emitting region 13a of the organic EL element layer 15 enter the reflective electrode 33 at an angle θ given by the equation (1). Therefore, deterioration of optical characteristics such as contrast due to the angle of light incident on the reflective electrode 33 from the light emitting region 13a, that is, deterioration of viewing angle dependency can be suppressed as much as possible.

  In addition, the liquid crystal layer 42 can be divided by the slits 37S between the plurality of reflective electrodes 33 provided as the alignment control unit and the protrusions 37P of the common electrode 36, and the deterioration of the viewing angle dependency is suppressed as much as possible. be able to.

  Further, according to the illumination device 200 having the above configuration, the light shielding layer 16 prevents light leakage from the light emitting region 13a to the viewer 113 as much as possible, and the contrast on the display of the reflective LCD 300 is higher than that of the conventional example. can do. For example, the contrast at the time of display can be increased as compared with the conventional example even in a dark environment, that is, an environment where external light is insufficient.

  In the reflective LCD 300 of the above embodiment, the protrusion 37P is provided on the common electrode 36 as the alignment control unit, but the present invention is not limited to this. For example, although not shown, the slit portion 37S may be provided in the common electrode 36 instead of the protruding portion 37S. Alternatively, the formation of the protrusion 37P may be omitted.

  Further, the reflective electrode 33 made of a reflective metal material is made of aluminum (Al), but the present invention is not limited to this, and for example, even a laminate of a transparent electrode made of ITO and a reflective film may be used. Good.

  In the lighting device 200 of the above embodiment, the organic EL element layer 15 is formed as a light emitting thin body. However, instead of the organic EL element layer 15, other light emitting thin bodies, for example, inorganic EL element layers are used. May be formed.

  Moreover, although the light shielding layer 16 which covers the cathode 12 was formed in the illuminating device 200 of the said embodiment, formation of the light shielding layer 16 may be abbreviate | omitted. In this case, although the light slightly leaks from the light emitting region 13a to the viewer 113 side, the cathode 12 is also used as a light shielding layer.

It is the top view which looked at the display apparatus which concerns on embodiment of this invention from the illuminating device side. It is sectional drawing which shows the display apparatus which concerns on embodiment of this invention. It is sectional drawing which expands and shows the display apparatus which concerns on embodiment of this invention partially. It is sectional drawing which expands and shows the display apparatus which concerns on embodiment of this invention partially. It is sectional drawing which shows the display apparatus provided with the illuminating device which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st transparent substrate 11 Anode 12 Cathode 13 Organic layer 13a Light emission area 13c Center of light emission area 15 Organic EL element layer 16 Light shielding layer 20 Second transparent substrate 30 TFT substrate 31 Thin film transistor 32 Interlayer insulating film 33 Reflective electrode 35 Counter substrate 36 Common electrode 36 Common electrode 37P Projection part 37S Slit part 39 λ / 4 wavelength plate 40 Light scattering layer 41 Polarizing plate 42 Liquid crystal layer 45 Resin layer
100,300 Reflective LCD 110 Transparent acrylic plate 111 Inverted triangular groove 112 Light source 113 Observer 200 Illuminator CH Contact hole

Claims (9)

A display device including a reflective liquid crystal display device including an illumination device and including a reflective electrode,
The lighting device includes a transparent substrate and a light emitting thin body partially disposed on the transparent substrate, and is disposed with one surface of the light emitting thin body facing the surface of the reflective electrode.
Further, the distance between the centers of the adjacent light emitting thin bodies is D1, the distance between the center of the light emitting thin body and the surface of the reflective electrode in the perpendicular direction is D2, and the distance between the centers of the adjacent light emitting thin bodies is On the perpendicular bisector of the connecting line segment, an angle formed by the perpendicular bisector and a light beam from the center of the light emitting thin body incident on the surface of the reflective electrode is θ, and the angle θ is
θ = arctan (D1 / (2 × D2))
When given in
The display device is characterized in that the angle θ is a predetermined angle that does not deteriorate the viewing angle dependency of the reflective liquid crystal display device. The display device according to claim 1, wherein the display device is driven in a twisted nematic mode, and the angle θ is greater than 0 degree and equal to or less than 20 degrees. The display device according to claim 1, wherein the display device is driven in a vertical alignment mode, and the angle θ is greater than 0 degree and equal to or less than 50 degrees. 4. The display device according to claim 1, wherein the light emitting thin body includes an organic electroluminescence element including an anode and a cathode. The display device according to claim 4, wherein at least one of the anode and the cathode is patterned into a predetermined shape. The display device according to claim 5, wherein the cathode is patterned into the predetermined shape, and the cathode is disposed above the anode. The organic electroluminescence device includes an electron transport layer, a light emitting layer, and a hole transport layer between the anode and the cathode, and at least one of the electron transport layer, the light emitting layer, and the hole transport layer is a predetermined one. The display device according to claim 4, wherein the display device is patterned into a shape. The display device according to claim 5, wherein the predetermined shape is a stripe shape. The display according to any one of claims 1, 2, 3, 4, 5, 6, 7, and 8, wherein a light shielding layer is disposed so as to cover the other surface of the light emitting thin body. apparatus.

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