JP2000193956A - Liquid crystal display device and electronic equipment using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the liquid crystal display device which can make displays entirely on both the surfaces without using two liquid crystal display panels. SOLUTION: This device is equipped with a 1st reflecting polarizer 18 which is arranged on both the sides of one surface of a liquid crystal cell 22, a 2nd reflecting polarizer 42, which is arranged on the other surface side, a 1st absorption type polarizer 14 which is arranged on the external surface side of the 1st reflecting polarizer 18, a 2nd absorption type polarizer 46 which is arranged on the external surface side of the 2nd reflecting polarizer 42, and a light guide plate 52 which is arranged on the most external surface side between the sides of the liquid crystal cell. The 1st reflecting polarizer 18 reflects polarized light having a plane of polarization in a 1st reflection axis direction and transmits polarized light having a plane of polarization in a 1st transmission axis direction different from the 1st reflection axis direction. The 2nd reflecting polarizer 42 reflects polarized light in a 2nd reflection axis direction and transmits polarized light in a 2nd transmission axis direction different from the 2nd reflection axis direction. The 1st absorption type polarizer 14 has an axis of transmission nearly parallel to the 1st axis of transmission and the 2nd absorption type polarizer 46 has an axis of transmission nearly parallel to the 2nd axis of transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device and an electronic apparatus using the same.

[0002]

2. Description of the Related Art Heretofore, there has been a demand for a liquid crystal display device capable of double-sided display, and several structures have been proposed.

[0003] One is to perform two-sided display by arranging two transmissive liquid crystal display panels back to back across a backlight.

Another one is disclosed in Japanese Patent Application Laid-Open No. H10-298291. In one reflection type liquid crystal display panel, a part of the display surface is provided with a reflection plate on one side and the display is performed. For the rest of the surface, a reflector is arranged on the other side. Thus, in one liquid crystal display panel, a part of the display surface can display on one side, and the remaining part of the display surface can display on the other side.

[0005]

However, in a type in which two transmissive liquid crystal display panels are arranged with a backlight interposed therebetween to enable double-sided display, two liquid crystal display panels are prepared. However, there is a problem that the number of parts and the weight are increased, and the outer shape is also increased.

Further, in one reflection type liquid crystal display panel, a part of the display surface is used for display on one side, and the other part is used for display on the other side, so that a double-sided display is performed. In the type that enables the above, there is a problem that the display on the entire surface of the liquid crystal panel cannot be performed on each side.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to perform display over the entire surface of a liquid crystal panel on both sides without the need for two liquid crystal display panels. It is to provide a liquid crystal display device which can perform the above.

[0008]

(1) A liquid crystal display device according to the present invention comprises: a liquid crystal cell formed by enclosing liquid crystal between a pair of substrates each having a transparent electrode provided on an inner surface; It is disposed on one surface side of the cell and reflects polarized light having a polarization plane in a first reflection axis direction, and transmits polarized light having a polarization plane in a first transmission axis direction different from the first reflection axis direction. A first reflection polarizer, disposed on the other surface side of the liquid crystal cell, for reflecting polarized light having a polarization plane in a second reflection axis direction, and in a second transmission axis direction different from the second reflection axis direction; A second reflective polarizer that transmits polarized light having a polarization plane of
A substantially transparent light guide plate that emits light toward the liquid crystal cell is provided on either side of the liquid crystal cell, the outermost surface side.

In the above description, the outer surface refers to a side far from the liquid crystal cell.

According to the present invention, the first reflective polarizer is arranged on one side of the liquid crystal cell, and the second reflective polarizer is arranged on the other side of the liquid crystal cell. Therefore, when the side of the first reflective polarizer is used as a display surface, a reflection type liquid crystal display device using the second reflective polarizer as a reflector is obtained. This is a reflection type liquid crystal display device using one reflection polarizer as a reflection plate.
Thus, according to the present invention, a reflective liquid crystal display device capable of performing double-sided display is obtained. Moreover, since the first and second reflective polarizers can almost reflect polarized light having a polarization plane in a predetermined direction, a bright reflective liquid crystal display device can be obtained.

Further, the liquid crystal display device of the present invention is a liquid crystal display device capable of displaying using light guided through the light guide plate even when there is no external light. Moreover, the light guide plate is
Since it is almost transparent, even when display is performed using light from the light guide plate, the liquid crystal display device can be displayed on any side of the liquid crystal cell as a double-sided display, and does not use light from the light guide plate. It can also be used as a reflective liquid crystal display device.

Further, according to the present invention, a reflection type liquid crystal display device capable of performing double-sided display using one liquid crystal cell is obtained. Therefore, double-sided display is performed using two liquid crystal display panels. Compared to a liquid crystal display device, the number of parts, weight, and thickness can be reduced. In addition, since the liquid crystal display device of the present invention is a reflective liquid crystal display device in which reflective polarizers are arranged on both surfaces over the entire surface of the liquid crystal cell, and they act as a reflector, the liquid crystal display device performs double-sided display over the entire liquid crystal cell. be able to.

(2) More preferably, the liquid crystal display device of the present invention is a first absorption type polarizer disposed on the outer surface side of the first reflective polarizer and having a transmission axis substantially parallel to the first transmission axis. And / or further comprising a second absorption polarizer disposed on the outer surface side of the second reflective polarizer and having a transmission axis substantially parallel to the second transmission axis.

Here, an absorption polarizer is a polarizer that transmits polarized light having a polarization plane in the transmission axis direction and transmits polarized light having a polarization plane in the absorption axis direction different from the transmission axis direction. is there.

According to the liquid crystal display device of the present invention, an absorbing polarizer, ie, a first absorbing polarizer or a second absorbing polarizer, is provided on at least one of the first and second reflective polarizers on the outer surface side. And the transmission axis of the absorbing polarizer is substantially parallel to the adjacent reflective polarizer, ie, the first or second reflective polarizer. Therefore, the absorption type polarizer transmits the polarized light transmitted by the reflection polarizer as it is, and the polarized light that would be reflected by the reflection polarizer without this absorption type polarizer is the absorption type polarizer. Absorb. Therefore, when light having no polarization is directly incident on the reflective polarizer in the absence of the absorption type polarizer, the polarization component which becomes reflected light and causes a decrease in display contrast is converted into the absorption type polarization. Can be absorbed by children. Accordingly, in a display in which the side on which the absorption-type polarizer is arranged is the display surface side, display contrast is improved, and an easy-to-view display without unnecessary reflection can be realized.

(3) More preferably, the liquid crystal display device of the present invention has a scattering layer disposed on at least one of the outer surfaces of the liquid crystal cell.

According to the present invention, the light reflected by the first or second reflective polarizer and returned to the liquid crystal cell side and directed toward the display surface is scattered by the scattering layer. Is not a mirror-like display but a paper-white display that is easy to see.

(4) More preferably, in the liquid crystal display device according to the present invention, the liquid crystal cell is any one of a TN type, an STN type, and a BTN type.

Here, the BTN type liquid crystal cell is a liquid crystal cell using a chiral nematic liquid crystal and having two metastable states, which is disclosed in Japanese Patent Publication No. 1-51818,
And -170888.

According to the present invention, it is possible to form a liquid crystal display device having the above-described functions and effects for various types of liquid crystal cells.

(5) More preferably, in the liquid crystal display device of the present invention, at least one of the outer surface side of the light guide plate and the outermost surface side opposite to the side where the light guide plate is disposed. And a removable light absorbing layer.

According to the present invention, the light absorbing layer is detachably disposed on at least one of the outer surface side of the light guide plate and the outermost surface side opposite to the side where the light guide plate is disposed. Therefore, when the side of the liquid crystal cell where the light absorption layer is not used is used as the display surface side, the light transmitted through the reflective polarizer functioning as a reflector, that is, the first or second reflective polarizer, Absorbed by the absorption layer. Therefore, the amount of light reflected from this region is reduced as compared with the case where there is no light absorption layer, and the contrast can be improved. In addition, since this light absorbing layer is provided detachably, by setting this light absorbing layer on the side opposite to the side used as the display surface, either side of the liquid crystal cell is on the display surface side. In this case, good contrast can be realized.

(6) An electronic apparatus according to the present invention includes any one of the above liquid crystal display devices as display means.

According to the present invention, it is possible to obtain an electronic apparatus having display means having any one of the above-described functions and effects for each of the liquid crystal display devices.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below more specifically with reference to the drawings.

First Embodiment <Structure of Liquid Crystal Display> FIG. 1 is a schematic sectional view showing a liquid crystal display 10 of the present embodiment. As shown in the figure, the liquid crystal display device 10 is formed by disposing the first reflective polarizer 18 on one side of the liquid crystal cell 22 and disposing the second reflective polarizer 42 on the other side of the liquid crystal cell 22. Have been. The outer surface of the first reflective polarizer 18, that is, the liquid crystal cell 22.
The first absorption type polarizer 14 is disposed on the side far from the first. Further, a scattering layer 38 is disposed between the liquid crystal cell 22 and the second reflective polarizer 42. The second absorption polarizer 46 is disposed on the outer surface side of the second reflection polarizer 42, and the light absorption layer 50 is detachably disposed on the outer surface side of the second absorption polarizer 46. Further, on the outer surface side of the first absorption polarizer 14, a substantially transparent light guide plate 52 that emits light toward the liquid crystal cell 22 is disposed. In FIG. 1 and other similar drawings, the liquid crystal display device 10
Are drawn so that there is a gap between the elements constituting the above, but this is for the sake of clarity of illustration, and in fact, the elements are almost in close contact with each other.

The liquid crystal cell 22 is composed of a substrate 24 on which a stripe-shaped transparent electrode 26 is formed on one side and a substrate 32 on which a stripe-shaped transparent electrode 30 is formed on one side, such as a gap material (not shown). The transparent electrodes 26 and 30 of the opposing substrates 24 and 32 are separated from each other by a predetermined distance to form a simple matrix type liquid crystal cell 22 in which the transparent electrodes 26 and 30 oppose each other in a grid pattern. A space between the pair of substrates 24 and 32 is filled with a TN type liquid crystal 28, and opposing peripheral edges of the substrates 24 and 32 are sealed with a sealant 34. In FIG. 1, the pair of substrates 24 and 32 are drawn widely apart, but this is for clarity of illustration, and the pair of substrates 24 and 32 is actually several μm to more than ten They face each other with a narrow gap of μm.

The first and second reflective polarizers 18, 42 are:
It is the same as that disclosed in International Publication (WO 95/17692), and as shown in FIG.
One layer, that is, a layer A and a layer B are alternately stacked and many layers are stacked in the Z-axis direction. First and second
The reflective polarizers 18 and 42 are formed by laminating many layers each having a thickness of less than 1 μm, and have a thin plate shape with a thickness of about 200 μm as a whole.

In the first and second reflective polarizers 18, 42, the refractive index of the layer A in the X-axis direction is Nax, the refractive index in the Y-axis direction is Nay, and the refractive index of the layer B in the X-axis direction is Nb.
Assuming that the refractive indices in the x and Y axis directions are Nby, there is the following relationship between the refractive indices.

Nax ≠ Nay Nbx = Nby Nay = Nby The first and second reflective polarizers 18 thus formed,
Reference numeral 42 transmits linearly polarized light having a polarization plane in the Y-axis direction as it is.

Further, the first and second reflective polarizers 18,
42 is formed so that the thickness Ta of the A layer and the thickness Tb of the B layer in the pair of A layer and B layer adjacent to each other have the following relationship with respect to a predetermined wavelength λ of visible light. Have been.

Ta · Nax + Tb · Nbx = λ / 2 (1) By forming the first and second reflective polarizers 18 and 42 in this way, the reflective polarizers 18 and 4 are viewed from the Z-axis direction.
The linearly polarized light having a wavelength λ and having a plane of polarization in the X-axis direction incident on 2 is reflected as a linearly polarized light having a plane of polarization in the X-axis direction.

Further, a large number of pairs of the layer A and the layer B are formed in various combinations of thicknesses so that the relationship of the formula (1) is satisfied for light of various wavelengths λ in the visible region. I have.
As a result, the reflective polarizers 18 and 42 reflect linearly polarized light having a plane of polarization in the X-axis direction over all wavelengths in the visible region as linearly polarized light having a plane of polarization in the X-axis direction.

Therefore, the first and second reflective polarizers 1
8, 42 reflect linearly polarized light having a plane of polarization in the X-axis direction, that is, the first and second reflection axis directions, as linearly polarized light having a plane of polarization in that direction, in the entire visible region; The linearly polarized light having the polarization plane in the second transmission axis direction is transmitted as the linearly polarized light having the polarization plane in that direction.

First and second absorption polarizers 14, 46
Is an absorption-type polarizer that transmits polarized light having a polarization plane in the transmission axis direction and absorbs polarized light having a polarization plane in the absorption axis direction different from the transmission axis direction. The first and second absorption polarizers are formed using, for example, a halogen substance such as iodine or a dichroic dye such as a dye.

The first absorption polarizer 14 is disposed on the outer surface of the first reflection polarizer 18, that is, farther from the liquid crystal cell 22, and the second absorption polarizer 46 is disposed on the second reflection polarizer 4.
2 is disposed on the outer surface side. In the present embodiment, the transmission axis of the first reflective polarizer 18 and the transmission axis of the first absorption polarizer 14 are substantially parallel, and the second reflective polarizer 42
And the transmission axis of the second absorption polarizer 46 are arranged substantially parallel to each other.

As described above, in the liquid crystal display device 10, the absorption polarizer, that is, the first absorption polarizer 14 or the second absorption polarizer 14 is provided on the outer surface side of the first and second reflection polarizers 18, 42.
Absorptive polarizers 46 are arranged, and their transmission axes are substantially parallel to the adjacent reflective polarizer, ie, the first or second reflective polarizer 18,42. Therefore,
These absorption polarizers transmit the polarized light transmitted by the reflective polarizer as it is, and the polarized light that would be reflected by the reflective polarizer without this absorption polarizer is absorbed by the absorption polarizer. . Therefore, when light having no polarization is directly incident on the reflective polarizer in the absence of the absorption type polarizer, the polarization component which becomes reflected light and causes a decrease in display contrast is converted into the absorption type polarization. Can be absorbed by children. Accordingly, in a display in which the side on which the absorption-type polarizer is arranged is the display surface side, display contrast is improved, and an easy-to-view display without unnecessary reflection can be realized.

The scattering layer 38 is disposed between the liquid crystal cell 22 and the second reflective polarizer 42 and has a function of scattering and diffusing light. Although it is possible to omit the scattering layer 38, in the absence of this, the display corresponding to the portion reflected by the second reflective polarizer 42 is the display giving the impression that the light is reflected by the mirror surface. turn into. Scattering layer 3
8 prevents such a state, and makes the display corresponding to the portion reflected by the second reflective polarizer 42 a display close to paper white. The scattering layer 38 is formed, for example, as a plastic film in which beads are dispersed. Further, the scattering layer 38 may be formed by mixing beads into an adjacent layer, for example, an adhesive layer made of an optical adhesive for adhering the liquid crystal cell 22 and the first or second reflective polarizer 18, 42. .

The scattering layer 38 is formed between the liquid crystal cell 22 and the second
Not only between the reflective polarizer 42 but also between the liquid crystal cell 22 and the first reflective polarizer 42, and between the liquid crystal cell 22 and the second reflective polarizer 4.
2, the first absorption polarizer 14 and the first reflection polarizer 18
, Between the second absorption polarizer 46 and the second reflection polarizer 42, on the outer surface of the first absorption polarizer 14, or on the outer surface of the second absorption polarizer 46. You may make it.

The light guide plate 52 is arranged on the outer side of the first absorption polarizer 14. Note that the light guide plate 52 does not necessarily have to be arranged on the outer surface side of the first absorption polarizer 14, and at least one side of the liquid crystal cell 22 is a component (light absorption) that constitutes the liquid crystal display device 10 described above. (Excluding the layer 50), but may be arranged on the outer surface side. The light guide plate 52 emits the light directed toward the liquid crystal cell 22 when the light guided from, for example, the inside of the frame 67 for fixing the panel or the like from the light source 66 is incident on the end face 57. The light guide plate 52 is formed of, for example, an optically isotropic polyolefin resin or an acrylic resin.

The frame 67 for guiding the light from the light source 66 to the light guide plate 52 is made of an optically isotropic polyolefin resin, polycarbonate resin, acrylic resin, or the like. The light emitted from the light source 66 is guided by the frame 67 to the end face 57 of the light guide plate 52, introduced into the light guide plate 52, and emitted toward the liquid crystal cell 22. Since the light guide plate 52 is formed of a material that hardly absorbs light, light incident from the front side or the back side of the light guide plate 52 is transmitted almost as it is. Further, as the light source 66, an LED (light emitting diode) or the like is used.

Here, the light guide plate 52 will be described in more detail with reference to FIGS. FIG. 3 is a schematic cross-sectional view of the light guide plate 52, and FIG. 4 is a schematic perspective view of the light guide plate 52.

The light guide plate 52 is, as shown in these figures,
It has a flat plate shape made of a transparent resin molded product, and has a large number of projections 54 on one surface (output surface) 53 thereof.
Each of the projections 54 has a columnar shape, and includes a bottom surface 55 substantially parallel to the emission surface 53 and a side surface 56 substantially perpendicular to the emission surface 53. The light guide plate 52 is formed of a material having a refractive index of about 1.4 or more. The light beam incident from the end face 57 of the light guide plate 52, after being incident from the end face 57 as shown schematically by light rays 58 and 59 in FIG. Out only from Therefore, it is possible to effectively illuminate the entire light guide plate 52. In this way, the light guide plate 52 efficiently emits the light incident on the end face 57 from the emission face 53 side, transmits the light incident from the front face to the rear face, and
Light incident from the back side is transmitted to the front side.

The light guide plate 52 has a thickness of about 0.2 mm to 2 mm, preferably about 0.4 mm to 0.8 mm. In the present embodiment, a light guide plate having a thickness of 0.6 mm is used.
The size of the protrusion 54 is such that the wavelength of visible light is approximately 380 nm.
From about 700 nm, it is necessary to have a thickness of about 5 μm or more so that the influence of diffraction does not occur.
Since the size of the projection 54 is small enough to be unnoticeable with the naked eye, the projection 54 is desirably approximately 300 μm or less. Further, in consideration of manufacturing convenience, the size of the protrusion 54 is desirably approximately 10 μm or more and 100 μm or less. Also, protrusion 5
The ratio of the height to the width (diameter) of the light beam in the light guide plate 52 is one to one, assuming that the elevation angle in the plane direction is 45 degrees or less.
In practice, light rays of 20 degrees or less occupy 90% or more, so that sufficient performance is exhibited up to about 1: 2. Therefore, in the present embodiment, the diameter of the projection 54 is 20 μm, the height is 15 μm, and the pitch is 20 μm.

The scattering layer 38 (FIG. 1) has a function of scattering and diffusing light. Although it is possible to omit the scattering layer 38, without this, the display corresponding to the portion reflected by the reflective polarizer 40 becomes a display giving an impression of the light reflected by the mirror surface. Scattering layer 38
Prevents such a state and sets the display corresponding to the portion reflected by the reflective polarizer 40 to a display close to paper white. The scattering layer 38 is formed, for example, as a plastic film in which beads are dispersed. Further, the scattering layer 38 may be formed by mixing beads in adjacent layers, for example, an adhesive layer made of an optical adhesive for adhering the light guide plate 52 and the reflective polarizer 40. In addition, the scattering layer 38
It may be provided between the polarizer 14 and the liquid crystal cell 18 or may be provided on the front surface of the polarizer 14.

The light absorbing layer 50 is detachably disposed on the outer surface of the second absorbing polarizer. Light absorbing layer 5 of liquid crystal cell 22
The first or second reflective polarizer 18, which functions as a reflector when the side where 0 is not used is used as the display surface side,
The light transmitted through the light absorbing layer is absorbed by the light absorbing layer 50. Therefore, the amount of light reflected from this region is reduced as compared with the case where the light absorption layer 50 is not provided, and external light incident on the first or second absorption type polarizers 14 and 46 is reduced. , The contrast is improved. In addition, since the light absorbing layer 50 is detachably provided, the light absorbing layer 50 is attached to a side opposite to a side used as a display surface,
Good contrast can be realized regardless of which side of the liquid crystal cell 22 is used as the display surface side. The light absorption layer 50 is not limited to the outer surface side of the second absorption polarizer, and is provided on at least one side of the liquid crystal cell 22 on the outermost surface of the element constituting the liquid crystal display device 10 described above. It may be removably arranged on the side.

The liquid crystal display device 10 also includes, in addition to the components shown in FIG. 1, an alignment film provided facing the liquid crystal 24, a driving circuit, and the like.

<Operation of Liquid Crystal Display Device as Self-Light Emitting Type> The operation when the liquid crystal display device 10 formed as described above is used as a self light emitting type in a dark environment will be described with reference to FIG. In FIG. 5A, the left half of FIG.
FIG. 5B in the right half shows a switching state in which the liquid crystal cell 22 does not rotate the polarization plane of light passing therethrough. In FIG. 5 and other similar figures, an asterisk symbol indicates light having no polarization, and an arrow symbol indicating both left and right directions indicates polarized light having a polarization plane parallel to the paper surface or polarization separation having an axial direction. An element is shown, and a small black circle symbol in a circle indicates a polarized light having a polarization plane perpendicular to the paper surface or a polarization separation element having an axial direction.

First, the light from the light guide plate 52 enters the switching region where the liquid crystal cell 22 rotates the light by 90 °.
When the light enters from the side of the absorption polarizer 14, that is, FIG.
The case shown in FIG. In this case, in the incident light 64, the polarization component in the direction of the absorption axis 14 </ b> A of the first absorption type polarizer 14 is absorbed by the first absorption type polarizer 14, and the polarized light in the direction of the transmission axis 14 </ b> T of the first absorption type polarizer 14. Only the component passes through the first absorption polarizer 14 and its transmission axis 1
The light is emitted as linearly polarized light 64a having a polarization plane in the direction of 4T. The linearly polarized light 64a passes through the first reflective polarizer 18 having a transmission axis 18T arranged substantially in parallel with the transmission axis 14T of the first absorption polarizer 14, and is rotated by 90 ° when passing through the liquid crystal cell 22. It becomes linearly polarized light 64b. The linearly polarized light 64b is scattered by the scattering layer 38, but enters the reflective polarizer 42 as linearly polarized light 64c with the polarization direction unchanged. The linearly polarized light 64c incident on the reflective polarizer 42 is
Since the plane of polarization is substantially parallel to the reflection axis 42R of the reflective polarizer 42, the light is reflected by the reflective polarizer 42. The reflected linearly polarized light 64d is reflected by the reflection axis 42 of the reflection polarizer 42.
It has a plane of polarization substantially parallel to R, is again scattered by the scattering layer 38, and enters the liquid crystal cell 22 as linearly polarized light 64e whose unchanged plane of polarization. Then, the light is rotated by 90 ° in the liquid crystal cell 22 to become a polarized light 64f having a polarization plane parallel to the transmission axis 18T of the first reflective polarizer 18, which is transmitted through the first reflective polarizer 18 as it is, and further, the first reflective polarizer 18 18T transmission axis
The light passes through the first absorption polarizer 14 having the transmission axis 14T arranged almost in parallel to the display surface.

As described above, when the liquid crystal display device 10 is used as a self-luminous type with the surroundings being dark, the liquid crystal cell 22 is placed in a switching state region where the light is rotated by 90 ° so that the outer surface of the first reflective polarizer can be used. When light from the light guide plate 52 disposed in the first direction enters from the side of the first absorption polarizer 14, most of the light is reflected by the second reflection polarizer 42 and follows a path reverse to the direction of incidence to guide the liquid crystal cell 22. The light is emitted to the light plate 52 side. Therefore, the region in the switching state where the liquid crystal cell 22 rotates the light by 90 ° has a bright white display when viewed from the side where the light guide plate 52 of the liquid crystal cell 22 is disposed, and the liquid crystal cell 2
2 from the side opposite to the side on which the light guide plate 52 is disposed.
The display becomes dark when viewed visually with 0 removed.

Next, the liquid crystal display device 10 is used as a self-luminous type in a situation where the surroundings are dark, and the light 65 from the light guide plate is placed in a switching region where the liquid crystal cell 22 does not rotate light.
Will be described from the side of the first absorption polarizer 14, that is, the case shown in FIG. 5B. In this case, in the incident external light 65, the polarization component of the first absorption polarizer 14 in the direction of the absorption axis 14A is absorbed by the first absorption polarizer 14 and the first absorption polarizer 14 is transmitted in the direction of the transmission axis 14T. The polarized light component passes through the first absorption type polarizer 14 and is emitted from the first absorption type polarizer 14 as linearly polarized light 65a having a polarization plane in the direction of the transmission axis 14T. Its linear polarization 65
a transmits through the first reflective polarizer 18 having a transmission axis 18T substantially parallel to the transmission axis 14T of the first absorption polarizer 14 as it is, passes through the liquid crystal cell 22 without being rotated, and is scattered. The light is scattered through the layer 38, but becomes a linearly polarized light 65b whose polarization plane is not changed, and is transmitted through the second reflective polarizer 42 having a transmission axis 42T substantially parallel to the transmission axis 14T of the first absorption polarizer 14, Then, the light passes through the second absorption polarizer 46 having the transmission axis 46T substantially parallel to the transmission axis 42T of the second reflection polarizer 42, proceeds as it is, and does not return to the incident side.

As described above, when the liquid crystal display device 10 is used as a self-luminous type in a dark state, the liquid crystal cell 22 is placed on the outer surface side of the first reflective polarizer 18 in a switching state where light is not rotated. When light from the disposed light guide plate 52 enters from the side of the first absorption polarizer 14, the first
Except for the components absorbed by the absorption polarizer 18, most of the components pass through the second reflection polarizer 42 and the second absorption polarizer 46 located on the opposite sides, and do not return to the incident side but exit without change. Would. Therefore, the switching region where the liquid crystal cell 22 does not rotate light has a dark display when viewed from the side where the light guide plate 52 of the liquid crystal cell 22 is arranged, and is opposite to the side where the light guide plate 52 of the liquid crystal cell 22 is arranged. When viewed with the light absorbing layer 50 removed from the side, a bright white display is obtained.

As described above, when the liquid crystal display device 10 of the present embodiment is used as a self-luminous type in a dark surrounding, the following display is obtained. That is, the region where the liquid crystal cell 22 rotates the light by 90 ° becomes a bright white display region when viewed from the side of the liquid crystal cell 22 where the light guide plate 52 is disposed, and the side of the liquid crystal cell 22 where the light guide plate 52 is disposed. When viewed from the opposite side, a dark display area is obtained. Further, the area where the liquid crystal cell 22 does not rotate the light by 90 ° becomes a dark display area when viewed from the side of the liquid crystal cell 22 where the light guide plate 52 is arranged, and is different from the side of the liquid crystal cell 22 where the light guide plate 52 is arranged. When viewed from the opposite side, the display area becomes a bright white display area. The liquid crystal display device 10 of the present embodiment can perform such a double-sided display when used as a self-luminous type in a dark state.

The liquid crystal cell 22 can assume an intermediate state between a state in which the light is rotated by 90 ° and a state in which the light is not rotated. At this time, halftone display is performed.

<Operation of Liquid Crystal Display Device as Reflective Type> The liquid crystal display device 10 of the present embodiment formed as described above is used without using light from the light guide plate 52 under bright light. You can also. As described above, the light guide plate 52 can transmit light incident from the front side to the rear side and transmit light incident from the rear side to the front side. Hereinafter, the operation in that case will be described with reference to FIG. In this figure, the left half of FIG.
6A shows a case where the liquid crystal cell 22 is in a switching state in which the polarization plane of the passing light is rotated by 90 °, and FIG. 6B in the right half is a switching state in which the liquid crystal cell 22 does not rotate the polarization plane of the passing light. This shows the case where the state is the state.

First, outside light is applied to the first absorption type polarizer 1 in a switching state where the liquid crystal cell 22 rotates the light by 90 °.
4A, that is, the case shown on the left side of FIG. 6A will be described. In this case, the incident external light 6
0 indicates that after passing through the light guide plate 52 as it is, the polarization component in the direction of the absorption axis 14A of the first absorption polarizer 14 is absorbed by the first absorption polarizer 14, and the transmission axis 14T of the first absorption polarizer 14 Only the polarization component of the first absorption type polarizer 14
And emitted as linearly polarized light 60a having a polarization plane in the direction of the transmission axis 14T. The linearly polarized light 60a is the first
The light passes directly through the first reflective polarizer 18 having a transmission axis 18T disposed substantially parallel to the transmission axis 14T of the absorption polarizer 14, and passes through the liquid crystal cell 22 to become linearly polarized light 60b rotated by 90 °. The linearly polarized light 60b is
, But enters the reflective polarizer 42 as linearly polarized light 60c with the polarization direction unchanged. The linearly polarized light 60c incident on the reflective polarizer 42 is reflected by the reflective polarizer 42 because its polarization plane is substantially parallel to the reflection axis 42R of the reflective polarizer 42. The reflected linearly polarized light 60d has a polarization plane substantially parallel to the reflection axis 42R of the reflection polarizer 42,
Again, the light is scattered by the scattering layer 38 and enters the liquid crystal cell 22 as linearly polarized light 60e whose polarization plane remains unchanged. Then, the light is rotated by 90 ° in the liquid crystal cell 22 to become a polarized light 60 f having a polarization plane parallel to the transmission axis 18 T of the first reflective polarizer 18, transmitted directly through the first reflective polarizer 18, and further transmitted through the first reflective polarizer 18. Through the first absorption polarizer 14 having the transmission axis 14T arranged substantially in parallel with the transmission axis 18T of the light guide plate 5
2 to reach the display surface.

External light is applied to the second absorption type polarizer 4 in a switching state where the liquid crystal cell 22 rotates the light by 90 °.
6, the second absorption polarizer 46 and the second reflection polarizer 42 are arranged symmetrically with the first absorption polarizer 14 and the first reflection polarizer 18 with the liquid crystal cell 22 as a boundary. Although the scattering layer 38 is not symmetrically arranged but only on the side of the second reflective polarizer 42, it does not affect the polarization state, so that the behavior of light incident from the side of the second absorption polarizer 42 6A shows the case where external light is incident from the side of the first absorption polarizer 14 on the switching state region in which the liquid crystal cell 22 rotates the light by 90 °, as shown on the right side of FIG. The behavior becomes almost symmetrical with respect to the cell 22. Therefore, the external light 61 incident on the second absorption polarizer reaches the display surface on the second absorption polarizer 46 side as polarized light 61f parallel to the transmission axis 46T of the second absorption polarizer.

As described above, in the liquid crystal display device 10, most of the external light that has entered the liquid crystal cell 22 when the liquid crystal cell 22 is in the switching state in which the light is rotated by 90 ° is mostly the first or second reflective polarizer. The liquid crystal cell 22 reflects the light from the first and second absorptive polarizers 14 and 46, and reflects the light from the liquid crystal cell 22, because the light is reflected by the light 18 and 42 and exits along the reverse path of the incident light. A region in a switching state of rotating 90 ° has a bright white display.

Next, the external light 62 is applied to the first absorption type polarizer 1 in a switching state where the liquid crystal cell 22 does not rotate the light.
4B, that is, the case shown on the left side of FIG. 6B will be described. In this case, after the incident external light 62 passes through the light guide plate 52 as it is, the polarization component in the direction of the absorption axis 14A of the first absorption polarizer 14 is absorbed by the first absorption polarizer 14, and the first absorption polarizer 14 absorbs. The polarization component of the polarizer 14 in the direction of the transmission axis 14T passes through the first absorption polarizer 14 and exits from the first absorption polarizer 14 as linearly polarized light 62a having a polarization plane in the direction of the transmission axis 14T.
The linearly polarized light 62a passes through the first reflective polarizer 18 having a transmission axis 18T substantially parallel to the transmission axis 14T of the first absorption polarizer 14, and passes through the liquid crystal cell 22 without being rotated. Then, the light is transmitted through the scattering layer 38 and scattered, but becomes a linearly polarized light 62b whose polarization plane does not change, and a transmission axis 42T substantially parallel to the transmission axis 14T of the first absorption polarizer 14.
And the light passes through the second absorption polarizer 46 having a transmission axis 46T substantially parallel to the transmission axis 42T of the second reflection polarizer 42, and proceeds as it is. It does not return to a certain incident side. Although not shown in FIG. 6, as shown in FIG. 1, the second absorption polarizer 4
6, the light absorbing layer 50 is arranged on the outer surface side.
It is possible to surely prevent the light transmitted through the absorption polarizer 46 from being reflected by something and returning to the incident side which is the display surface.

When external light is incident from the side of the second absorption type polarizer 46 to the switching region where the liquid crystal cell 22 does not rotate light, the second absorption type polarizer 46 and the second reflection polarizer 42 are used. Are arranged symmetrically with respect to the first absorption polarizer 14 and the first reflection polarizer 18 with the liquid crystal cell 22 as a boundary, and the scattering layer 38 is not symmetrically arranged but only on the side of the second reflection polarizer 42. However, since the polarization state is not affected, the behavior of the light incident from the side of the second absorption polarizer 42 is such that the liquid crystal cell 22 described above rotates the light as shown on the right side of FIG. A case where external light is incident from the side of the first absorption polarizer 14 on a region in a switching state where the switching is not performed;
The behavior becomes almost symmetrical with respect to the liquid crystal cell 22. Therefore, the external light 63 incident on the second absorption polarizer 46 is polarized light 63b parallel to the transmission axis 14T of the first absorption polarizer 14.
As a result, the light passes through the first absorption polarizer 14 and is emitted as it is, and does not return to the incident side which is the display surface.

As described above, in the liquid crystal display device 10, when the liquid crystal cell 22 is in the switching state in which the light is not rotated, the external light incident on the liquid crystal cell 22 is transmitted to the opposite side to the incident side. Since the light does not return to the incident side, the area where the liquid crystal cell 22 is in a switching state in which the liquid crystal cell 22 does not rotate light is dark even if external light is incident from either side of the first or second absorption polarizers. Display.

If the light absorbing layer 50 is located on the outermost surface side opposite to the light incident side, the liquid crystal cell 22 where the light absorbing layer 50 is not used is used as the display surface side. The light transmitted through the reflective polarizer functioning as a reflective plate, that is, the light transmitted through the first or second reflective polarizer 18 or 42 and the external light incident on the first or second absorption polarizer 14 or 46 are The light is absorbed by the light absorbing layer 50. Therefore, the amount of light reflected from this region and the amount of incident external light are reduced as compared with the case where the light absorption layer 50 is not provided, and the contrast can be improved. Further, by providing the light absorbing layer 50 in a detachable manner, it is possible to easily attach the light absorbing layer 50 to the side opposite to the side used as the display surface. Even when used as a display surface side, good contrast can be realized.

As described above, when the liquid crystal display device 10 of the present embodiment is used as a reflection type under bright external light, the region where the liquid crystal cell 22 rotates light by 90 ° is:
Regardless of which side of the liquid crystal cell 22 is used as the display surface, a bright white display area is obtained. Further, in the liquid crystal display device 10 of the present embodiment, when the liquid crystal display device 10 is used as a reflection type under bright external light, a region where the liquid crystal cell 22 does not rotate light displays either side of the liquid crystal cell. Even when used as a surface, a dark display area results. in this way,
When the liquid crystal display device 10 is used under bright light, a region where the liquid crystal cell rotates light by 90 ° becomes a bright display regardless of which side of the liquid crystal cell is used as a display surface, and the liquid crystal cell emits light. In a region where the optical rotation is not performed, a double-sided display in which a dark display is performed can be performed.

The liquid crystal cell 22 can assume an intermediate state between a state in which the light is rotated by 90 ° and a state in which the light is not rotated. At this time, halftone display is performed.

FIGS. 7 and 8 show display examples when the liquid crystal display device 10 of the present embodiment is formed as a dot matrix display panel. 7A and 7B are display examples in the case where the light absorbing layer 50 is not used. FIG. 7A shows a portion where a number is displayed as a region where the liquid crystal cell 22 does not rotate light and a background where the liquid crystal cell 22 rotates light. 7 shows a display example in the case where a region to be made is set. In this display example, the numeral portion is seen through the back of the panel by the incident light from the back side of the display surface, and the background portion is the first or second reflective polarizer 1.
The light is reflected by 8, 42 and scattered by the scattering layer 38 to form a white display.

FIG. 7 (B) shows the area where the numbers are displayed as the area where the liquid crystal cell 22 rotates the light, and the background is the area where the liquid crystal cell 22 rotates.
Shows a display example in the case where is a region where light is not rotated. In this display example, the display states of the numeral portion and the background portion are opposite to those in the display example shown in FIG.

FIG. 8 is a display example when the light absorbing layer 50 is used. FIG. 8A shows a portion where a numeral is displayed as a region where the liquid crystal cell 22 does not rotate light, and a background is a region where the liquid crystal cell 22 does not rotate.
Shows a display example in the case where is a region where light is rotated. In this display example, the light transmitted through the numeral portion is absorbed by the light absorbing layer 50 to display black. The background portion is reflected by the first or second reflective polarizers 18 and 42 and is scattered by the scattering plate 38 to display white.

FIG. 8 (B) shows a portion where the number is displayed as a region where the liquid crystal cell 22 rotates light, and a background is the liquid crystal cell 22.
Shows a display example in the case where is a region where light is not rotated. In this display example, the display states of the numeral portion and the background portion are opposite to those in the display example shown in FIG.

As described above, by using the light absorbing layer 50, the contrast can be improved. Note that the white display portion in FIGS. 7 and 8 is a mirror display in the case where the scattering layer 38 is not used.

As described above, the liquid crystal display device 10 of the present embodiment is a reflection type liquid crystal display device 10 capable of performing double-sided display using one liquid crystal cell 22, and has two liquid crystal display panels. The number of parts, the weight, and the thickness can be reduced as compared with a liquid crystal display device that performs double-sided display using the same. Moreover, in the liquid crystal display device 10, the reflective polarizers 18 and 42 over the entire surface of the liquid crystal cell 22 are arranged on both sides, and they function as a reflection plate.
Therefore, double-sided display over the entire surface of the liquid crystal cell 22 can be performed.

Further, the first and second reflective polarizers 18,
The light-reflection type liquid crystal display device 42 can almost reflect polarized light having a polarization plane in a predetermined direction.

<Electronic Equipment with Liquid Crystal Display> FIG.
1 is an external view showing a portable computer 96 as an electronic device using the liquid crystal display device 10 of the present embodiment as a display unit. The portable computer 96 includes the liquid crystal display device 1
The input unit 98 is provided with a display unit made of zeros, and can be displayed even when the cover 99 provided with the display unit is closed (not shown). Portable computer 9
Reference numeral 6 includes, in addition to the liquid crystal display device 10, not shown, various circuits such as a display information output source, a display information processing circuit, and a clock generation circuit, and a power supply circuit for supplying power to these circuits. Is done.

The electronic devices into which the liquid crystal display device 10 of the present embodiment is incorporated are not limited to mobile phones, watches, and portable computers, but also mobile phones, notebook computers, electronic organizers, pagers, calculators, and POS terminals. ,
Various electronic devices such as an IC card and a mini-disc player are conceivable.

[Second Embodiment] The second embodiment is different from the first embodiment in that an STN type liquid crystal cell is used as a liquid crystal cell.
A phase difference plate for eliminating coloring accompanying the TN type liquid crystal cell is added; the transmission axes of the first absorption polarizer and the first reflection polarizer; The angles between the transmission axes of the polarizer and the second reflective polarizer are not substantially parallel, and their transmissions in the two switching states of the STN-type liquid crystal cell correspond to the difference in twist angle from the case of the TN-type liquid crystal cell. The difference from the first embodiment is that the angle between the axes is determined. Other points are the same as in the first embodiment, and a description thereof will be omitted. In the drawings, corresponding parts are denoted by the same reference numerals as in the first embodiment.

FIG. 10 shows a liquid crystal display device 70 of this embodiment.
FIG. As shown in this figure, the liquid crystal display device 70 uses a liquid crystal cell 74 using an STN type liquid crystal 72, between the first absorption polarizer 14 and the first reflection polarizer 18, and the second absorption type polarizer 18. Phase difference plates 76 are provided between the polarizer 46 and the second reflective polarizer 42.
The retardation plate 76 can eliminate coloring caused by the STN type liquid crystal cell 74.

Further, in the liquid crystal display device 70 of the present embodiment, as in the case of the first embodiment, the transmission axis of the first absorption polarizer 14 and the transmission axis of the first reflection polarizer 18 are substantially parallel. The transmission axis of the second absorption polarizer 46 and the transmission axis of the second reflection polarizer 42 are substantially parallel. However, the angle between the transmission axis of the first absorption polarizer 14 and the first reflection polarizer 18 and the transmission axis of the second absorption polarizer 46 and the second reflection polarizer 42 is an STN type liquid crystal cell. 74
The angle between the transmission axes is determined according to the difference between the two switching states and the TN type in the twist angle.

The operation of the liquid crystal display device 70 of the present embodiment is the same as that of the first embodiment except that the phase shift associated with the STN type liquid crystal cell 74 is compensated by transmitting through the phase difference plate 76. It is almost the same as the liquid crystal display device 10 of FIG.

The retardation plates 76 and 76 are used to eliminate coloring caused by the use of the STN type liquid crystal cell 74. If the coloring is not a problem, the retardation plates 76 and 76 need to be used. There is no. Therefore, in such a case, a configuration in which at least one of the phase difference plates 76 and 76 is not used may be adopted.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.
Various modifications can be made within the scope of the present invention or within the equivalent scope of the claims.

For example, in each of the above embodiments, the liquid crystal cell is an example of a TN type or STN type simple matrix type liquid crystal cell. However, the liquid crystal cell used in the liquid crystal display device of the present invention is a panel type. If it does not use a switching element itself, it may be a static drive type liquid crystal cell, or an active matrix type using a three-terminal switching element represented by a TFT or a two-terminal switching element represented by a MIM. Liquid crystal cell. Furthermore, the liquid crystal cell may be a BTN type liquid crystal cell in terms of electro-optical characteristics. Note that B
The TN type liquid crystal cell is a liquid crystal cell using a chiral nematic liquid crystal and having two metastable states.
No. 51818, JP-A-10-170888, and the like.

In each of the above embodiments, an example in which the first and second reflective polarizers are of a stacked type has been described.
The first and second reflective polarizers are not limited to this type, but include a combination of a cholesteric liquid crystal layer and a quarter-wave plate (Japanese Patent Application Laid-Open No. 8-271892), and polarized light reflected using Brewster's angle. And separated into transmitted polarized light (SID 92 DIGEST P.427-429), or
A device using a hologram can also be used.

Further, in each of the above-described embodiments, the example in which the liquid crystal display device is formed for monochrome display is shown. A liquid crystal display device can also be used.

In each of the above embodiments, the first
And a liquid crystal display device using the second absorption polarizer, but the liquid crystal display device can perform double-sided display without either or both of the first and second absorption polarizers. Note that when the first or second absorption polarizer is not used on the side serving as the display surface of the liquid crystal cell, the display contrast decreases.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a liquid crystal display device according to a first embodiment.

FIG. 2 is a schematic perspective view showing a structure of first and second reflective polarizers.

FIG. 3 is a schematic sectional view of a light guide plate used in the liquid crystal display device of the first embodiment.

FIG. 4 is a schematic perspective view of a light guide plate used in the liquid crystal display device of the first embodiment.

FIG. 5 is an explanatory diagram showing an operation when the liquid crystal display device of the first embodiment is used as a self-luminous type.

FIG. 6 is an explanatory diagram showing an operation when the liquid crystal display device of the first embodiment is used as a reflection type.

FIGS. 7A and 7B are display examples when the liquid crystal display device of the first embodiment is formed as a dot matrix display panel.

FIGS. 8A and 8B are display examples when the liquid crystal display device of the first embodiment is formed as a dot matrix display panel.

FIG. 9 is an external view showing a portable computer as an electronic apparatus using the liquid crystal display device of the first embodiment.

FIG. 10 is a schematic sectional view illustrating a liquid crystal display device according to a second embodiment.

[Explanation of symbols]

 10, 70 liquid crystal display device 14 first absorption polarizer 18 first reflection polarizer 22, 74 liquid crystal cell 24, 32 substrate 26, 30 transparent electrode 28, 72 liquid crystal 38 scattering layer 42 second reflection polarizer 46 second absorption Type polarizer 50 light absorption layer 52 light guide plate 76 retardation plate 96 portable computer (electronic device)

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Seichi Iino 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko Epson Corporation (reference) 2H091 FA08X FA08Z FA11X FA11Z FA14X FA14Z FA23X FA23Z FD06 FD08 GA13 HA07 HA10 HA12 KA01 LA13 MA10 5G435 AA00 BB12 BB16 CC13 DD13 EE23 EE33 FF03 FF05 FF06 FF08 FF14 GG23 GG26 LL01 LL07

Claims (6)

[Claims] 1. A liquid crystal cell formed by enclosing liquid crystal between a pair of substrates each having a transparent electrode provided on an inner surface thereof; and a liquid crystal cell disposed on one surface of the liquid crystal cell in a first reflection axis direction. A first reflective polarizer that reflects polarized light having a polarization plane of and transmits polarized light having a polarization plane in a first transmission axis direction different from the first reflection axis direction; and the other surface side of the liquid crystal cell. And a second reflective polarizer that reflects polarized light having a polarization plane in the second reflection axis direction and transmits polarized light having a polarization plane in the second transmission axis direction in a direction different from the second reflection axis direction. A liquid crystal display device, comprising: a substantially transparent light guide plate that emits light toward the liquid crystal cell, on either side of the liquid crystal cell, that is, on the outermost surface side. 2. The first absorptive polarizer according to claim 1, wherein the first absorptive polarizer is disposed on the outer surface side of the first reflective polarizer and has a transmission axis substantially parallel to the first transmission axis.
Alternatively, the liquid crystal display device further comprises a second absorption polarizer disposed on an outer surface side of the second reflective polarizer and having a transmission axis substantially parallel to the second transmission axis. 3. The liquid crystal display device according to claim 1, further comprising a scattering layer disposed on at least one of the outer surfaces of the liquid crystal cell. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal cell is one of a TN type, an STN type, and a BTN type. 5. The light guide plate according to claim 1, wherein at least one of an outer surface side of the light guide plate and an outermost surface side opposite to a side on which the light guide plate is arranged, A liquid crystal display device comprising a removable light absorbing layer. 6. An electronic apparatus comprising the liquid crystal display device according to claim 1 as display means.