Reflective liquid crystal display device

The invention is directed to the higher contrast in a liquid crystal display device (LCD) having a lighting portion as a front light. A lighting portion is formed by interposing an organic EL layer between a transparent substrate and a transparent substrate. A light shield layer is formed covering a cathode layer of the organic EL element layer. The lighting portion is disposed above the reflective LCD. The reflective LCD has a polarizing plate, a light scattering layer, an opposing substrate, a common electrode, a liquid crystal layer, and a TFT substrate. When the refractive indexes of seven layers of an anode layer, the transparent substrate, a resin layer, the polarizing plate, the light scattering layer, the opposing substrate, and the common electrode are defined as n(1), n(2), n(3), n(4), n(5), n(6), and n(7) respectively, the relation of 1.33>n(k)/n(k+1)>0.75(k=1−6) holds.

CROSS-REFERENCE OF THE INVENTION

This invention is based on Japanese Patent Applications Nos. 2005-148541, 2005-148545, 2005-199434 and 2005-213453, the contents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a display device having a lighting portion.

2. Description of the Related Art

A liquid crystal display device (hereafter, referred to as a LCD) is thin and consumes low power in its characteristics, and has been broadly used as a monitor of a computer or a monitor of a mobile data terminal such as a cellular phone. There are a transmissive LCD, a reflective LCD, and a semi-transmissive LCD as the LCD. In the transmissive LCD, a transparent electrode is used as a pixel electrode for applying a voltage to a liquid crystal and a back light is set in the rear of the LCD, so that a bright display can be realized by controlling a transmission amount of light of this back light even in the dark. However, in an environment where external light is strong such as out of doors in the daytime, contrast can not be obtained enough.

The reflective LCD uses external light such as sunlight or interior light as a light source, and reflects the external light entering the LCD by a reflective pixel electrode formed of a reflective layer formed on a substrate on a viewer side. The reflective LCD makes a display by controlling an amount of light released from a LCD panel in each of the pixels after the light enters a liquid crystal and is reflected by the reflective pixel electrode. Since this reflective LCD uses external light as a light source, there is a problem that the display can not be made in an environment of no external light.

The semi-transmissive LCD has both the transmissive function and the reflective function, and is applicable to both the bright and dark environments. However, since this semi-transmissive LCD has a transmissive region and a reflective region in a pixel, there is a problem of low display efficiency in each of the pixels.

For solving this, it has been suggested that a front light is provided in the reflective LCD to realize a display even in the dark environment.FIG. 14is a view showing the reflective LCD with the front light. A transparent acrylic plate110is disposed, being opposed to a display surface of a reflective LCD100. A plurality of grooves111shaped in inverted triangles is formed on a surface of this transparent acrylic plate110, which is on the opposite side to the side opposed to the reflective LCD100. Furthermore, a light source112is disposed on a side surface of the transparent acrylic plate110. Light entering the transparent acrylic plate110from the light source112is refracted in a direction to the reflective LCD100by inclined surfaces of the grooves111shaped in inverted triangles, and enters the display surface of the reflective LCD100.

The relating technology is described in the Japanese Patent Application Publication Nos. 5-325586 and 2003-255375.

However, the light entering the transparent acrylic plate110from the light source112is refracted in a direction to a viewer113on the opposite side to the reflective LCD100by a small amount as well as in the direction to the reflective LCD100by the inclined surfaces of the grooves111provided in the transparent acrylic plate110. Therefore, the small amount of light leaks from the transparent acrylic plate110to reach the eyes of the viewer113, causing a problem of degrading the contrast of a LCD display.

SUMMARY OF THE INVENTION

A display device of the invention includes a lighting portion disposed on a liquid crystal display portion, the lighting portion including a light emitting thin body formed on a first substrate and the liquid crystal display portion including a plurality of pixels, a second substrate formed with a reflective pixel electrode receiving light emitted by the light emitting thin body in each of the pixels, a third substrate disposed on and opposed to the second substrate and formed with a common electrode on its front surface, and a liquid crystal layer sealed between the second substrate and the third substrate. When the refractive indexes of two adjacent layers between the light emitting thin body and the liquid crystal layer are defined as n1and n2respectively, the relation of 1.33>n1/n2>0.75 holds.

The display device of the invention can provide a LCD display with enhanced contrast in both the bright and dark environments.

DETAILED DESCRIPTION OF THE INVENTION

A display device of a first embodiment of the invention will be described referring to figures.FIG. 2is a plan view of a reflective LCD300provided with a lighting portion200of this embodiment on the lighting portion200side, andFIG. 1is a cross-sectional view ofFIG. 2along line X-X. In this embodiment, the lighting portion200is disposed above the reflective LCD300, being opposed to a display surface of the LCD300as shown inFIG. 1.

The structure of the lighting portion200will be described first. An organic electroluminescent element layer15(hereafter, abbreviated to an “organic EL element layer15”) is interposed between a transparent substrate10and a transparent substrate20made of a glass substrate or the like. The organic EL element layer15includes an anode layer11made of a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) and formed on substantially the whole surface of the transparent substrate10, an organic layer13formed on this anode layer11, and a cathode layer12formed on the organic layer13and patterned into a grid with a predetermined pitch.

The organic layer13includes a so-called electron transport layer, an emissive layer, and a hole transport layer. The cathode layer12includes, for example, an aluminum layer (Al layer), a layered body of a magnesium layer (Mg layer) and a silver layer (Ag layer), or a calcium layer (Ca layer). It is preferable that the anode layer11is about 100 nm, the cathode layer12is about 500 nm, and the organic layer13is about 100 nm in thickness. An inorganic EL element layer can be used instead of the organic EL element layer15.

In this organic EL element layer15, a region of the organic layer13interposed between the anode layer11and the cathode layer12is an emissive region13a. That is, a region of the organic layer13immediately under the cathode layer12is the emissive region13a. In a plan view of this emissive region13a, this emissive region13ahas the same grid shape as that of the cathode layer12. This emissive region13aemits light by applying a positive potential to the anode layer11and a negative potential to the cathode layer12.

The other region of the organic layer13does not emit light as a non-emissive region. Furthermore, a light shield layer16is formed covering the cathode layer12patterned into a grid. The light shield layer16is also patterned into the same grid shape as that of the cathode layer12. The light shield layer16is provided for shielding light emitted upward from the emissive region13a, and thus need have a function as a light reflection layer for reflecting light or a light absorption layer for absorbing light. The light shield layer16is preferably 10 nm or less in thickness.

The light reflection layer is made of, for example, chromium (Cr), aluminum oxide (Al2O3) or the like. The light absorption layer is made of a black pigment layer made of a photoresist material containing a black pigment, a black dye layer made of a photoresist material containing black dye, a chromium oxide layer, or the like.

Light emitted downward from the emissive region13aenters the reflective LCD300through the transparent anode layer11and the transparent substrate10. Light emitted upward from the emissive region13ais reflected downward or absorbed by the cathode layer12and the light shield layer16. Therefore, light from the emissive region13ais prevented substantially from directly entering the eyes of the viewer113watching the lighting portion200from thereabove.

Although the cathode layer12is patterned into a grid with a predetermined pitch and the anode layer11is not patterned in the described structure, it is possible to change positions of the cathode layer12and the anode layer11. That is, it is possible to place the anode layer11in the position of the cathode layer12and the cathode layer12in the position of the anode layer11inFIG. 1. In this case, the anode layer11is patterned into the predetermined shape and the cathode layer12is not patterned.

Alternatively, the anode layer11and the cathode layer12can be formed on the whole surface without being patterned at all and at least one of the three layers of the electron transport layer, the emissive layer, and the hole transport layer forming the organic layer13can be patterned in the predetermined shape. In this case, a region where all the three layers are formed is the emissive region, and a region where any one of the three layers is missing is the non-emissive region.

It is preferable that the width of the light shield layer16is larger than the width of the patterned cathode layer12(or the anode layer) for enhancing a light shield effect. Furthermore, it is preferable that a length L1between the edge of the patterned cathode layer12(or the anode layer) and the edge of the light shield layer16is equal to or larger than the total thickness L2of the emissive region13aof the organic layer13and the patterned cathode layer12(or the anode) for further enhancing the light shield effect, as shown inFIG. 3.

Furthermore, it is preferable that the pitch (lengths P1and P2inFIG. 2) of the grid of the patterned cathode layer12(or the anode layer11) is 1 mm or less for preventing the viewer113from sensing a discomfort.

Next, the structure of the reflective LCD300to be lighted by the described lighting portion200and the connection of the LCD300with the lighting portion200will be described. A switching thin film transistor31(hereafter, referred to as TFT) is formed on the TFT substrate30made of a glass substrate in each of the pixels. The TFT31is covered with an interlayer insulation film32, and a pixel electrode33made of a reflective material such as aluminum (Al) is formed on the interlayer insulation film32, corresponding to each of the TFTs31. The pixel electrode33is connected to a drain or a source of the corresponding TFT31through a contact hole CH formed in the interlayer insulation film32.

An opposing substrate34made of a glass substrate is disposed, being opposed to the TFT substrate30formed with the pixel electrode33. A common electrode35made of ITO is formed on the front surface of the opposing substrate34. A light scattering layer36made of a diffusion adhesion layer and a polarizing plate37are layered on the back surface of the opposing substrate34in this order. The light scattering layer36scatters light emitted from the lighting portion200to equally irradiate the pixel electrode33with the light. A liquid crystal layer40is sealed between this opposing substrate34and the TFT substrate30.

With the described structure, light emitted from the lighting portion200is polarized in a predetermined direction by the polarizing plate37, passes through the light scattering layer36, the opposing substrate34, and the common electrode35, enters the liquid crystal layer40, and is reflected by the pixel electrode33. The light reflected by the pixel electrode33returns through the same route, and is visually recognized by the viewer113through spaces between the light shield layer16patterned into a grid. At this time, depending on an electric field applied between the pixel electrode33and the common electrode35, light transmittance changes in each of the pixels. This can realize a LCD display since the intensity of light reflected by the pixel electrode33changes in each of the pixels. As described above, since the light shield layer16is provided in the lighting portion200, leakage of light emitted by the emissive region13acan be minimized and thus the contrast of a LCD display can be enhanced.

It is preferable that the lighting portion200is disposed above the reflective LCD300adjacently. If an air layer exists between the lighting portion200and the reflective LCD300, light emitted from the transparent substrate10of the lighting portion200is reflected by an interface between the transparent substrate10and the air layer when entering the air layer and returns to the viewer side, thereby degrading the contrast of a LCD display. Therefore, it is preferable that the lighting portion200and reflective LCD300are attached with a resin layer45(e.g. a UV curable resin layer or a visible light curable resin layer) having the same refractive index as that of the transparent substrate10therebetween in order to minimize light refraction.

Next, descriptions will be given on the structure for preventing reflection of light emitted by the lighting portion200and incident light from outside through the transparent substrate20for further enhancing the contrast of a LCD display. As described above, external light or light from the lighting portion200passes through the anode layer11, the transparent substrate10, the resin layer45, the polarizing plate37, the light scattering layer36, the opposing substrate34, and the common electrode35to enter the liquid crystal layer40. Such light is reflected by interfaces between two adjacent layers (e.g. the interface between the anode layer11and the transparent substrate10, the interface between the transparent substrate10and the resin layer45, and so on) as shown inFIG. 4.

Generally, the more the difference in refractive index between two layers is, the more the reflectance of light at the interface between the two layers is. The refractive indexes of two layers are defined as n1and n2, respectively. Descriptions will be given on a case where light enters from the layer of refractive index n1to the layer of refractive index n2and is reflected by the interface of these layers as shown inFIG. 5.

In this case, the reflectance at the interface between the two layers is expressed by the following formulae 1 and 2.

In these formulae, RPis the reflectance of a polarized light component (P wave) that is polarized in the plane of incidence, and RSis the reflectance of a polarized light component (S wave) that is polarized perpendicularly to the plane of incidence. θ is an incident angle of incident light, and θ′ is the refraction angle of the incident light. Since θ=θ′=°0 for incident light from the front, that is, incident light perpendicular to the interface between two layers, it follows that RP=RS=R. The following formula 3 is obtained by solving the formula 1 for R.

The n1and n2have the relation expressed by the formula 4 or the formula 5 by modifying this formula 3.

When the light reflectance at the interface between the two layers is large, the reflected light is visually recognized by a viewer, thereby degrading the contrast of a LCD display. Therefore, it is necessary to set the reflectance R at the interface between the two adjacent layers for the incident light from the front to 2% or less in the display device of the embodiment, taking the prevention of the degradation of the contrast into account. The refractive index that satisfies this condition can be expressed by the formula 6 from the formula 4 and the formula 5.

That is, it is necessary to set the relation of the refractive indexes of the two adjacent layers as the formula 6 in order to prevent the degradation of the contrast of a LCD display. It is more preferable to set the reflectance R of the incident light from the front to 1% or less in order to further prevent the degradation of the contrast of a LCD display. The relation of the refractive indexes that satisfies this condition can be expressed by the following formula 7.

In this embodiment, when the refractive indexes of the seven layers, i.e., the anode layer11, the transparent substrate10, the resin layer45, the polarizing plate37, the light scattering layer36, the opposing substrate34, and the common electrode35are defined as n(1), n(2), n(3), n(4), n(5), n(6), and n(7) respectively, the relation of the following formula 8 need be satisfied in order to set the reflectance of each of the interfaces between these layers to 2% or less. Furthermore, the relation of the following formula 9 need be satisfied in order to set the reflectance of each of the interfaces between the layers to 1% or less. It is noted that k=1-6 in the formulae 8 and 9.

When there is an omitted layer in these seven layers, the above relation is to be satisfied between the remaining layers. For example, when the transparent substrate10, the resin layer45, and the light scattering layer36are omitted, the relation of the above formula 8 or formula 9 is to be satisfied between the remaining four layers, that is, the anode layer11, the polarizing plate37, the opposing substrate34, and the common electrode35.

Next, the positional relationship between the lighting portion200and the pixels of the reflective LCD300will be described. In the reflective LCD300, a plurality of pixels each having the same size is arrayed at the same pitch in row and column directions.FIG. 1shows a pitch P3of the pixels in the row direction (a pitch of the pixel electrodes33).

Each of the pixels has a TFT31and a pixel electrode33. The pitch of the grid of the cathode layer12and the light shield layer16of the lighting portion200is equal to the pitch of the pixels. That is, a pitch P2of the grid in the row direction is equal to the pitch P3of the pixels in the row direction, and a pitch P1of the grid in the column direction is equal to the pitch of the pixels in the column direction. In this case, it is preferable to dispose the cathode layer12and the light shield layer16of the lighting portion200right above a separating region SR of the pixel electrodes33, which does not contribute to a LCD display. This provides an advantage that most light reflected by the reflective electrodes33is visually recognized by the viewer113through spaces of the grid without being shielded by the light shield layer16.

Alternatively, the pitch of the grid of the cathode layer12and the light shield layer16of the lighting portion200(the pitch in the row and column directions) can be smaller than the pitch of the pixels (the pitch in the row and column directions) and a ratio of the pitch of the grid to the pitch of the pixels (the pitch of the grid/the pitch of the pixels) can be 1/natural number. Although interference fringes or moiré fringes can occur in the LCD display if the pitch of the grid and the pitch of the pixels are equal, this setting can prevent the phenomenon.

Alternatively, the pitch of the grid of the cathode layer12and the light shield layer16of the lighting portion200(the pitch in the row and column directions) can be larger than the pitch of the pixels (the pitch in the row and column directions) and a ratio of the pitch of the grid to the pitch of the pixels (the pitch of the grid/the pitch of the pixels) can be a natural number. This setting can also prevent interference fringes or moiré fringes.

Next, a display device of a second embodiment of the invention will be described referring to figures.FIG. 6is a plan view of a reflective LCD300provided with a lighting portion210on the lighting portion210side, andFIG. 7is a cross-sectional view ofFIG. 6along line Y-Y. In this embodiment, the lighting portion210is disposed above the reflective LCD300, being opposed to a display surface of the LCD300as shown inFIG. 7. Descriptions on the reflective LCD300as an object to be lighted will be omitted since it is the same as that of the first embodiment.

This lighting portion210includes a light guide plate51formed on a transparent substrate50made of a glass substrate or the like and formed in a grid and a light source52supplying light to this light guide plate51instead of the organic EL element layer15, differing from the first embodiment. The other structure is the same as that of the first embodiment.

The light guide plate51is a grid made of transparent resin and having a thickness of 1 μm. The light source52is disposed on the edges of the grid in the row and column directions, and light from the light source52is supplied from the edges into the light guide plate51, and emitted out of the light guide plate51. Thus, the light guide plate51serves as a light source having a grid shape. A light shield layer53is attached to the light guide plate51on the viewer113side. The light guide plate51attached with the light shield layer53can be further covered with a sheet of transparent substrate55.

Light emitted downward from the light guide plate51is emitted to the reflective LCD300through the transparent substrate50. Light emitted upward from the light guide plate51is reflected downward or absorbed by the light shield layer53, and thus light from the light guide plate51is minimized from directly entering the eyes of the viewer113watching the lighting portion210from thereabove.

In the same manner as the first embodiment, the reflectance of incident light at an interface of two adjacent layers is set to 2% or less, or preferably 1% or less in order to prevent degradation of the contrast of a LCD display.

This means to satisfy the above-described formula 8 or preferably the formula 9 when the refractive indexes of the six layers, that is, the transparent substrate50, the resin layer45, the polarizing plate37, the light scattering layer36, the opposing substrate34, and the common electrode35are defined as n(1), n(2), n(3), n(4), n(5), and n(6) respectively. In this case, k=1-5 in the formulae 8 and 9.

When there is an omitted layer in these six layers, the formula 8 or the formula 9 is to be satisfied between the remaining layers. For example, when the transparent substrate50, the resin layer45, and the light scattering layer36are omitted, the relation of the formula 8 or the formula 9 is to be satisfied between the remaining three layers, that is, the polarizing plate37, the opposing substrate34, and the common electrode35.

Although the pixel electrode33is made of a reflective material such as aluminum (Al) in the above-described embodiment, the invention is not limited to this and can be made of a layered body of a transparent electrode made of, for example, ITO and a reflective film. Although the light shield layer16covering the cathode layer12is formed in the lighting portion200in this embodiment, the light shield layer16can be omitted. The cathode layer12functions as the light shield layer in this case although a slight amount of light leaks from the emissive region13ato the viewer113side.

Next, a display device of a third embodiment of the invention will be described referring to figures.FIG. 8is a plan view of a reflective LCD300A provided with a lighting portion200on the lighting portion200side, andFIG. 9is a cross-sectional view ofFIG. 8along line Y-Y The reflective LCD300A of this embodiment is a reflective LCD of a vertical alignment mode, and the reflectance of incident light at an interface of two adjacent layers is set to 2% or less or preferably 1% or less in order to minimize degradation of the contrast of a LCD display in the same manner as the first embodiment. Descriptions on the lighting portion200will be omitted since it is almost the same as that of the first embodiment.

The structure of the reflective LCD300A will be described in different points from the structure of the reflective LCD300of the first embodiment. Separating regions SR, that is, slits37S having a predetermined width are provided between the adjacent pixel electrodes33. These slits37S have a function as alignment control portions for multi-domain alignment of the liquid crystal layer40that will be described below. Furthermore, a vertical alignment film41for vertically aligning liquid crystal molecules relative to the TFT substrate30is formed so as to cover the pixel electrodes33and the slits37S.

An opposing substrate34made of, for example, a glass substrate is disposed, being opposed to the TFT substrate30formed with the pixel electrodes33. A common electrode35made of, for example, ITO is formed on the front surface of the opposing substrate34. Projections37P as alignment control portions for multi-domain alignment of liquid crystal molecules40D of the liquid crystal layer40A in predetermined two different directions, that will be described below, are formed on the common electrode35. The projections37P are formed by patterning a resist material for example. A vertical alignment film42is further formed covering the common electrode35and the projections37P.

A λ/4 wavelength plate39(a quarter wavelength plate) for causing optical retardation of a quarter of a wavelength λ of light is disposed on the back surface of the opposing substrate34. The λ/4 wavelength plate39changes linearly polarized light to circularly polarized light, or changes circularly polarized light to linearly polarized light. It is possible to further laminate a λ/2 wavelength plate (a half wavelength plate) (not shown) causing optical retardation of a half of a wavelength λ of light on this λ/4 wavelength plate39for the polarization change of broadband light. A light scattering layer36made of, for example, a diffusion adhesion layer and a polarizing plate37are further laminated on the λ/4 wavelength plate39in this order. The light scattering layer36is provided for scattering light emitted from the lighting portion200so as to equally irradiate the pixel electrode33with the light.

A liquid crystal layer40A is sealed between the TFT substrate30and the opposing substrate34. The liquid crystal layer40A is made of, for example, liquid crystal molecules40D (e.g. a nematic liquid crystal) having negative dielectric anisotropy and vertically aligned. That is, this reflective LCD300A operates in a vertical alignment mode, that is, a VA mode.

In this embodiment, when the refractive indexes of the nine layers, that is, the anode layer11, the transparent substrate10, the resin layer45, the polarizing plate37, the light scattering layer36, the λ/4 wavelength plate39, the opposing substrate34, the common electrode35, and the vertical alignment film42are defined as n(1), n(2), n(3), n(4), n(5), n(6), n(7), n(8), and n(9) respectively, the relation of the formula 8 need be satisfied in order to set the reflectance at each of the interfaces of these layers to 2% or less. Furthermore, the relation of formula 9 need be satisfied in order to set the reflectance at each of the interfaces of these layers to 1% or less. It is noted that k=1-8 in the formulae 8 and 9.

The connection and the positional relationship between the lighting portion200and the reflective LCD300A are the same as those of the first embodiment.

Next, the operation of the described reflective LCD300A will be described referring to figures.FIGS. 10A and 10Bare cross-sectional views explaining the operation of the display device of this embodiment of the invention, that show the reflective LCD300A only. It is noted that the TFT31and the interlayer insulation film32in the reflective LCD300A are not shown inFIGS. 10A and 10B.FIG. 10Ashows a state where an electric field is not generated in the liquid crystal layer40A, andFIG. 10Bshows a state where an electric field is generated in the liquid crystal layer40A.

As shown inFIG. 10A, when a voltage is not applied to the pixel electrode33and the common electrode35and an electric field is not generated in the liquid crystal layer40A, the liquid crystal molecules40D keeps an initial alignment state, that is, a vertical alignment state by the vertical alignment films41and42. When unpolarized light is emitted from the lighting portion200to the reflective LCD300A, the light enters the polarizing plate37and is changed to linearly polarized light corresponding to its polarization axis. This linearly polarized light is scattered by the light scattering layer36in such directions as to equally irradiate the pixel electrode33with light. This linearly polarized light enters the λ/4 wavelength plate39and is changed to circularly polarized light by its optical retardation, and enters the liquid crystal layer40A through the opposing substrate34and the common electrode35.

At this time, since the liquid crystal molecules40D of the liquid crystal layer40A are vertically aligned, the incident circularly polarized light passes through the liquid crystal layer40A without being changed in its optical retardation and reaches the pixel electrode33. The circularly polarized light reaching the pixel electrode33is reflected toward the common electrode35and changed in its rotatory direction by the pixel electrode33. The circularly polarized light of which the rotatory direction is changed passes through the liquid crystal layer40A without being changed in its optical retardation, and enters the λ/4 wavelength plate39through the common electrode35and the opposing substrate34. This circularly polarized light is changed back to linearly polarized light by the optical retardation of the λ/4 wavelength plate39.

At this time, the linearly polarized light emitted out from this λ/4 wavelength plate39has a polarization axis perpendicular to the polarization axis of the first linearly polarized light by the polarizing plate37, corresponding to the rotatory direction of the circularly polarized light changed when entering. That is, since the polarization axis of this linearly polarized light does not correspond to the polarization axis of the polarizing plate37and is perpendicular thereto, the light does not pass through the polarizing plate37and provides a black display.

On the other hand, when a voltage is applied to the pixel electrode33and the common electrode35and an electric field is generated in the liquid crystal layer40A as shown inFIG. 10B, the liquid crystal molecules40D are aligned in such a direction as to lie nearly perpendicular to the direction of the electric field, that is, nearly horizontally relative to the TFT substrate30and the opposing substrate34by its negative dielectric anisotropy. This alignment state is not completely horizontal, and has predetermined optical retardation that changes circularly polarized light entering the liquid crystal layer40A to linearly polarized light.

When unpolarized light is emitted from the lighting portion200to the reflective LCD300A, the light enters the polarizing plate37, is changed to linearly polarized light corresponding to its polarization axis, is changed to circularly polarized light by passing through the λ/4 wavelength plate39, and enters the liquid crystal layer40A. This circularly polarized light is changed back to linearly polarized light by the predetermined optical retardation of the liquid crystal layer40A, and reaches the pixel electrode33. Then, the linearly polarized light reflected by the pixel electrode33is changed to circularly polarized light again by the predetermined optical retardation of the liquid crystal layer40A, and emitted out from the liquid crystal layer40A. This circularly polarized light enters the λ/4 wavelength plated39and is changed to linearly polarized light. At this time, the circularly polarized light entering the λ/4 wavelength plate39has the same rotatory direction as the direction when entering the liquid crystal layer40A. Therefore, the linearly polarized light emitted out from the λ/4 wavelength plate39has the polarization axis of the same angle as the polarization axis of the linearly polarized light that first passes through the polarizing plate37. Therefore, this linearly polarized light passes through the polarizing plate37and is emitted out on the viewer113side, and provides a white display.

In the display, the slits37S between the plurality of pixel electrodes33and the projections37P of the common electrode35provided as the alignment control portions can realize the wider view angle of the reflective LCD300A when a voltage is applied thereto.

Furthermore, since the liquid crystal layer40A operates in the vertical alignment mode, even if most light from the lighting portion200obliquely enters the display surface of the liquid crystal layer40A, degradation of optical characteristics such as contrast, that is caused by an angle of incident light, can be minimized compared with the other modes.

Although the projections37P as the alignment control portions are provided on the common electrode35in the reflective LCD300of the described embodiment, the invention is not limited to this. For example, slits37S can be provided on the common electrode35instead of the projections37P, as shown inFIG. 11.

Next, a display device of a fourth embodiment of the invention will be described referring to figures.

This embodiment describes a modification of the structure of the lighting portion200of the first and third embodiments. There is no modification to the structure of the reflective LCDs300and300A.

FIG. 12is a cross-sectional view of a lighting portion200A.FIG. 13is a schematic perspective view of the lighting portion200A.FIGS. 12 and 13show one of a plurality of organic EL elements25in the organic EL element layer15.

A step forming layer26is formed on a first transparent substrate61(corresponds to the transparent substrate10of the first embodiment) in a region for forming the organic EL element25as shown inFIG. 12. This step forming layer26is made of transparent resin such as photosensitive acrylic resin. An anode27made of a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) is formed on the step forming layer26.

An organic layer28having an arch-shaped surface is formed, covering the top surface of the anode27and the side surface of the step forming layer26and the anode27. The organic layer28includes a hole transport layer13H, an emissive layer13L, and an electron transport layer13E that are formed on the anode27in this order. The organic layer28can form the arch shape, for example, by forming the hole transport layer13H thicker than the emissive layer13L and the electron transport layer13E. Furthermore, a cathode29made of metal such as aluminum or chromium is formed, covering the organic layer28.

This organic EL element25is sealed in a space CAV between the first transparent substrate61and the second transparent substrate62(corresponding to the transparent substrate20of the first embodiment) with a sealing member63such as UV curable resin therebetween. Furthermore, a desiccant64is disposed in the space CAV on the sealing member63side. Alternatively, it is possible to mix desiccant particles in the sealing member63. It is preferable to seal a dry nitrogen gas in this space CAV. This structure can prevent deterioration of the organic layer28due to moisture.

Alternatively, it is possible to fill the space CAV with resin although not shown. In this case, light reflection by an interface between the first transparent substrate61or the second transparent substrate62and the resin can be minimized by using filling resin having a refractive index near a refractive index of glass. It is also possible that acrylic resin mixed with a desiccant or the like is provided around the organic EL element25in the space CAV, for example.

Furthermore, although the organic EL element25is formed in a half cylinder shape, for example, as shown inFIG. 13, it is preferable that both ends of the cathode29have portions directly formed on the first transparent substrate61in this case. With this structure, the organic layer28can be certainly covered with the cathode29, and moisture can be certainly prevented from infiltrating into the organic layer28.

In the organic EL element25, since the step forming layer26and the anode27are transparent, light emitted downward from the organic layer28on the anode27goes toward the reflective LCD300or300A. On the other hand, light emitted in the other directions from the organic layer28is reflected by the cathode29functioning as a reflection film, being focused on the reflective LCD300or300A. That is, the directivity of light emitted by the organic EL element25is controlled so that the light goes in a vertical direction or almost vertical direction to the reflective LCD300or300A. This reduces light entering the reflective LCD300or300A obliquely relative to its display surface, and thus reduces light emitted out from the reflective LCD300or300A obliquely relative to its display surface. Therefore, the contrast of a display is enhanced, and thus a display quality can be enhanced.

Furthermore, since the step forming layer26is inserted between the anode27and the first transparent substrate61in the lighting portion200A of this embodiment, the relation of the formula 8 need be satisfied in order to set the reflectance at each of the interfaces to 2% or less, and the relation of the formula 9 need be satisfied in order to set the reflectance to 1% or less.

Furthermore, in the first, third, and fourth embodiments, the organic layers13or28can emit a different color of light by using different chemical materials in a dopant for the emissive layer13L. In these embodiments, for example, the organic layer13or28emits light of any one color of R (red), G (green), and B (blue), and a set of the organic layers13or28of the above three colors emits white light. However, wavelengths of R, G, and B colors are not particularly limited, and the wavelengths can lie in a certain range using a specified wavelength as a reference. That is, the wavelengths of R, G, and B can differ from the generally used wavelengths of R, G, and B.