JP3389924B2 - Liquid crystal devices and electronic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal device.
More specifically, the present invention relates to a transflective liquid crystal device having both a reflective display mode and a transmissive display mode. The invention also relates to an electronic device equipped with this liquid crystal device.

[0002]

2. Description of the Related Art Since a liquid crystal device is basically a light-receiving type display device, some auxiliary light source is necessary for observing in the dark. Therefore, place a light source on the back of the liquid crystal panel,
A method was devised to switch between reflective display and transmissive display as needed. This is a transflective liquid crystal device.

The structure of a conventional transflective liquid crystal device is shown in FIG.
Will be explained. In FIG. 7, 701 is an upper polarizing plate, 702 is a retardation film, 703 is an upper glass substrate, 704 is a liquid crystal composition, 705 is a lower glass substrate, 7
Reference numeral 06 is a lower polarizing plate, 707 is a semi-transmissive reflection plate, 708 is a light guide plate of a light source, and 709 is a light source. Also 710 and 711
Are strip-shaped transparent electrodes, each of which functions as a scanning line and a signal line. A region where 710 and 711 intersect is a region where a voltage can be applied to the liquid crystal composition, that is, a region where light modulation is possible. The semi-transmissive reflection plate 707 is, for example, a sheet in which pearl pigment beads are dispersed in a resin, and reflects 70% of the amount of incident light and transmits 30% (5% in another type).
There is a function of reflecting 0% and transmitting 50%. Switching between reflective display and transmissive display is performed by turning on / off the light source.

[0004]

However, the above-mentioned conventional transflective liquid crystal device has a problem that the contrast is lowered during transmissive display. This is a region where a voltage cannot be applied to the liquid crystal composition because it is not sandwiched by electrodes, and is not hidden by the light-shielding film, metal wiring, etc. (hereinafter referred to as "dots" as a typical example). It is caused by the light leakage of.

In a normal reflective liquid crystal device, a light-shielding layer is not provided between dots, and the display is normally open (or normally white). In this way, there is an effect that the display between dots is always bright and the display is bright. Further, in reflective display, there is little reduction in contrast due to light leakage between dots. This is because the light passing between the dots is absorbed by the adjacent dark display dot either when the light is incident or when it is reflected. However, since a transmissive liquid crystal device does not have such parallax effect, a light shielding layer is provided between the dots.

Since the conventional transflective liquid crystal device has a design that emphasizes reflective display and has substantially the same structure as the reflective liquid crystal device, the contrast is lowered due to light leakage between dots during transmissive display.

Therefore, the present invention provides a semi-transmissive reflection type liquid crystal device which achieves both bright reflective display and transmissive display with high contrast by making a region between dots a bright display during a reflective display and a dark display during a transmissive display. The purpose is to do.

[0008]

Means for Solving the Problems] The liquid crystal device of the present invention, the inner
The liquid crystal composition is sandwiched between a pair of substrates with transparent electrodes on their surfaces.
And a liquid crystal panel having a plurality of dots arranged in a matrix, a light guide that emits light from a light source toward the liquid crystal panel, and light that is emitted from the light guide toward the liquid crystal panel, And a reflection polarization unit that transmits and reflects light incident on the liquid crystal panel from the opposite side of the light guide body according to a polarization component, and is one of the pair of substrates.
A color filter is provided on one of the substrates, and the plurality of dots are optically modulated by applying a voltage, and both reflective display and transmissive display are possible. becomes the normally black display at the time of display, the area between the plurality of dots, before
The color filter is present and no voltage is applied.

[0009]

Electronic equipment of the present invention is characterized in that the above-mentioned liquid crystal device is mounted as a display device. With this configuration, the electronic device consumes less power than the electronic device equipped with the conventional transmissive liquid crystal device, and also has the semi-transmissive reflection mode having both the conventional reflective display mode and the transmissive display mode. There is an advantage that a bright and easy-to-see display is possible as compared with an electronic device equipped with a liquid crystal device.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings.

Example 1 FIG. 1 is a perspective view of a transflective liquid crystal device according to Example 1. First, the configuration will be described. In FIG. 1, 101 is a polarizing plate, 102 is a retardation film, 103 is an upper glass substrate, 104 is a liquid crystal composition, 105 is a lower glass substrate, 1
Reference numeral 06 is a light scattering plate, 107 is a reflective polarizer used as a reflective polarization means, 108 is a semi-light absorbing plate, 109 is a light guide plate of a light source, and 110 is a light source. Further, both 111 and 112 are strip-shaped transparent electrodes, which serve as a scanning line and a signal line, respectively. A region where 110 and 111 intersect is a region where a voltage can be applied to the liquid crystal composition, that is, a region where light modulation is possible.

Here, 101 and 102, 105 and 106,
Although 106 and 107 are drawn separately from each other, this is for the sake of clarity of the drawing and is actually glued. The upper glass substrate 103 and the lower glass substrate 105 are also widely separated, but this is also for the same reason. Actually, the upper glass substrate 103 and the lower glass substrate 105 are opposed to each other with a narrow gap of several μm to ten and several μm being maintained. There is. Since FIG. 1 shows a part of the transflective liquid crystal device, only a 3 × 3 matrix formed by intersecting three scanning lines 111 and three signal lines 112, that is, only 9 dots is shown. Although not shown, it actually has more dots. In addition to the illustrated components, a liquid crystal alignment film, an insulating film, an anti-glare film,
Elements such as a spacer ball, a liquid crystal driver IC, and a drive circuit are indispensable, but they are omitted because they are not particularly necessary for explaining the present invention.

Next, each component will be described. The polarizing plate 101 has a function of absorbing a predetermined linearly polarized light component and transmitting other polarized light components, and is the same as that normally used in a conventional liquid crystal device. For this, a stretched PVA film adsorbing a dichroic substance such as an iodine complex is often used.

The retardation film 102 is, for example, a uniaxially stretched film of a polycarbonate resin, and in particular STN
It is used to compensate for liquid crystal coloration. In the case of TN liquid crystal, it is often omitted.

The liquid crystal composition 104 is a STN liquid crystal composition twisted at 210 ° to 270 °, but if the display capacity is small, a TN liquid crystal composition twisted at 90 ° may be used.
The twist angle is the direction of the alignment treatment on the upper and lower glass substrates,
It is determined by the amount of chiral agent added to the liquid crystal.

As the light scattering plate 106, an embossed plastic plate or a plastic plate in which beads are dispersed can be used. Also, beads may be mixed in the adhesive layer of 105 and 107 to replace the light scattering plate. The light scattering plate is arranged for the purpose of diffusing the reflected light of the reflective polarizer, which is somewhat close to a mirror surface, but it is possible to display without it. The position is 1
In addition to between 05 and 107, the position of contact with 104, 10
It may be between 2 and 103 or the upper surface of 101.

A birefringent dielectric multilayer film was used as the reflective polarizer 107. The birefringent dielectric multilayer film has a function of reflecting a predetermined linear polarization component and transmitting a polarization component other than the predetermined linear polarization component. For details of such a birefringent dielectric multilayer film, an internationally published international application (International application number: WO97 / 01788)
Alternatively, it is disclosed in Japanese Patent Publication No. 9-506985.
In addition, such a reflective polarizer is available from DBM
It is commercially available as (trade name) and is generally available.

Next, the structure of the reflective polarizer will be described. FIG. 2 is a diagram illustrating a main part of the structure of the reflective polarizer. The reflective polarizer is formed by alternately stacking two types of polymer layers 201 and 202. The two types of polymers are selected from one with a high photoelasticity and another with a low photoelasticity.At that time, the ordinary rays have the same refractive index when they are stretched. Please be careful. For example, PEN (2,6-polyethylene.
Naphthalate) as a small material, coPEN (70
-Naphthalate / 30-terephthalate copolyester). When both films were alternately laminated and stretched about 5 times in the x-axis direction of the Cartesian coordinate system 203 of FIG. 2, the refractive index in the x-axis direction was 1.88 in the PEN layer, coPEN.
It was 1.64 in the layer. The refractive index in the y-axis direction was about 1.64 for both the PEN layer and the coPEN layer.
When light is incident on the laminated film from the normal direction, the light component vibrating in the y-axis direction is transmitted through the film as it is. This is the transmission axis. On the other hand, the component of the light oscillating in the x-axis direction is reflected only when the PEN layer and the coPEN layer satisfy certain conditions. This is the reflection axis. The condition is that the sum of the optical path length of the PEN layer (product of refractive index and film thickness) and the optical path length of the coPEN layer is equal to one half of the wavelength of light. Such PEN layer and coPE
By laminating several tens or more layers, preferably 100 layers or more, each having a thickness of 30 μm, it is possible to reflect almost all of the components of light oscillating in the x-axis direction. The reflective polarizer produced in this way produces a polarization ability only with light of a single designed wavelength. Therefore, by stacking a plurality of reflective polarizers having different design wavelengths with their axes aligned, it is possible to provide a polarizing ability in a wide wavelength range.

This reflective polarizer is at least 30% brighter than the ordinary polarizing plate + aluminum reflector structure. In addition, it is about twice as bright as an ordinary polarizing plate + pearl pigment dispersion type semi-transmissive reflector structure. There are two reasons. One is that the reflectance of metallic aluminum is less than 90% and the reflectance of a semi-transmissive reflector is less than 60%, whereas this reflective polarizer reflects almost 100% of a predetermined linearly polarized light. Another reason is that a normal absorption type polarizing plate uses a halogen substance such as iodine or a dichroic material such as a dye, and its dichroic ratio is not necessarily high.
0% of the light is wasted.

As the reflective polarizer, a liquid crystal polymer exhibiting a cholesteric phase may also be used. This has a function of reflecting a predetermined circularly polarized light component and transmitting a polarized light component other than the predetermined circularly polarized light component. Details of such a reflective polarizer are disclosed in Japanese Patent Application Laid-Open No. 8-271892.

Next, the function of the transflective liquid crystal device of the first embodiment will be described with reference to FIG. In FIG. 3, 30
1 is a polarizing plate, 302 is a retardation film, 303 is an upper glass substrate, 304 is a lower glass substrate, 305 is a reflective polarizer, 306 is a semi-light absorbing plate, 307 is a light source, 308 is in an off state (no voltage is applied). The liquid crystal in) is a liquid crystal in an ON state (voltage applied state).

First, the case where the light source 307 is not turned on, that is, the case of reflective display will be described. Light 31 incident from above
1 and 312 are converted into linearly polarized light by the polarizing plate 301. After that, it is variously modulated by the retardation film and the liquid crystal panel, but when it enters the reflective polarizer 305, it is returned to substantially linearly polarized light. However, in the region 309 in which the liquid crystal panel is in the on state (voltage applied state) and the region 308 in which the liquid crystal panel is off (no voltage applied state), the linearly polarized light beams emitted are orthogonal to each other. Therefore, the linearly polarized light emitted from the region 308 in the off state (state in which no voltage is applied) is reflected,
The axis of the reflective polarizer is arranged in advance so that the linearly polarized light emitted from the region 309 in the on state (voltage applied state) is transmitted. In the off state (state in which no voltage is applied), the linearly polarized light reflected by the reflective polarizer is emitted upward again through the same path as before, resulting in bright display. On the other hand, in the ON state (voltage applied state), the linearly polarized light that has passed through the reflective polarizer is absorbed by the half-light absorber 306, and most of the remaining light is depolarized, so that it can return through the reflective polarizer. Instead, it becomes a dark display. When the liquid crystal panel is in an intermediate state between the ON state (voltage applied state) and the OFF state (voltage not applied state), the both are mixed to provide halftone display. Thus, the reflective display realizes a normally open display.

Next, the case where the light source is turned on, that is, the case of transmissive display will be described. In a situation where transmissive display is performed with a semi-transmissive reflective liquid crystal device, it is considered that the surroundings are sufficiently dark,
The incident light from above can be ignored. The light 321 and 322 emitted by turning on the light source 307 is reflected by the reflective polarizer 305 so that one linearly polarized light is reflected and the remaining linearly polarized light is transmitted. The transmitted linearly polarized light passes through the same path as the reflective display, and displays bright to dark. However, the linearly polarized light reflected by the reflective polarizer in the reflective display and the linearly polarized light transmitted by the reflective polarizer in the transmissive display are not actually the same and are orthogonal to each other. Therefore, the lightness and darkness of the display are reversed in the reflective display and the transmissive display. Thus, in the transparent display, normally closed display is realized. If the display inversion is not preferable, a method of converting the display data so as to invert the display of the liquid crystal panel between the reflective display and the transmissive display is effective.

Now, a region where light modulation is not possible, that is, a region where a voltage cannot be applied to the liquid crystal composition because it is not sandwiched by electrodes, and is not hidden by a light-shielding film or metal wiring (this embodiment). As a typical example, the behaviors of the lights 313 and 323 that have passed through the regions between the dots) are substantially the same as those of the lights 311 and 321 that have passed through the region 308 in which the liquid crystal panel is in the off state (state in which no voltage is applied). That is, a bright display is provided during reflective display and a dark display is provided during transmissive display. Therefore, this non-light-modifiable region contributes to the improvement of the brightness of the reflective display and does not adversely affect the contrast of the transmissive display.

FIG. 4 shows a display example of the transflective liquid crystal device of the first embodiment. The 6 × 12 squares represent dots, the hatched areas represent dark display, and the areas without hatching represent bright display.

FIG. 4A shows an example of reflective display, in which the 6 × 6 dots on the left side are in the dark state in the on state (voltage applied state), and the 6 × 6 dots on the right side are in the off state (voltage). Bright display in no applied state). In the bright display area, the space between the dots is bright, so a brighter display can be performed. Even in the dark display portion, the dots are bright, but in the reflective display, light entering between the dots is highly likely to pass through the adjacent dark display dots at the time of incidence or reflection, so that light leakage is small.

FIG. 4 (b) is similar to FIG. 4 (a).
6x dot is on (voltage applied), 6x on the right
Dot No. 6 remains off (no voltage applied),
This is the display when the light source is turned on. This display is (a)
Brightness is reversed compared to. Then, when the display data is converted so as to compensate for this, the display of FIG. This display is a dark display on the left side and a bright display on the right side as in FIG. 4A, but the area between the dots is dark. Therefore, high contrast can be obtained even in transmissive display.

In this embodiment, a region where light modulation is not possible, that is, a region where a voltage cannot be applied to the liquid crystal composition because it is not sandwiched by electrodes, and which is not hidden by the light shielding film or the metal wiring, I explained it as the area between dots,
As shown in FIG. 4, not only the area between the dots but also the outer peripheral area of the dot group is included.

(Embodiment 2) The semi-transmissive reflection type liquid crystal device described in the above embodiment can also perform color display. An example is shown below.

FIG. 5 is a perspective view of a transflective liquid crystal device according to the second embodiment. First, the configuration will be described. In FIG. 5, 501 is a polarizing plate, 502 is a counter substrate, 503 is a liquid crystal composition, 504 is an element substrate, 505 is a light scattering plate, and 506.
Is a reflective polarizer, 507 is a light guide plate of a light source, 508 is a light absorption plate, 509 is a light source, and a color filter 510 and a counter electrode (scanning line) 511 are provided on the counter substrate 502.
The signal line 512, the pixel electrode 513, and the
A two-terminal type non-linear element 514 is provided. Here 501 and 5
02, 504 and 505, 505 and 506 are drawn apart from each other for the sake of clarity.
Actually, they are glued together. The counter substrate 502 and the element substrate 504 are also widely separated, but for the same reason, there is actually only a gap of several μm to several tens of μm. Further, since FIG. 5 illustrates a part of the liquid crystal device, three scanning lines 511 and three signal lines 512 are provided.
Although a matrix of 3 × 3 formed by intersecting with each other, that is, only 9 dots is shown in the figure, it actually has more dots.

The counter electrode 511 and the pixel electrode 513 are made of ITO.
It is a transparent electrode formed by the above. A region where 511 and 513 intersect is a region where a voltage can be applied to the liquid crystal composition, that is, a region where light modulation is possible. The signal line 512 was formed of metal Ta. The two-terminal type non-linear element uses the insulating film Ta2O5 as a metal T
MIM (Metal-Insulator-Meta sandwiched between a and metal Cr)
l) Structure. The liquid crystal composition 503 is a nematic liquid crystal twisted by 90 degrees, and the polarization axes of the upper and lower polarizing plates are orthogonal to each other. This is a configuration of a general normally white TN mode. Therefore, in the region where light modulation is not possible, a region such as a signal line or a two-terminal type non-linear element that is not shielded by metal is a bright display during reflective display. Further, since a reflective polarizer is used, dark display is performed during transmissive display.

Further, the color filter 510 is composed of three primary colors of additive colors: red (indicated by "R" in the figure), green (indicated by "G" in the figure) and blue (indicated by "B" in the figure). It consisted of three colors, arranged in a mosaic. The same polarizing plate 501, light scattering plate 505, and reflective polarizer 506 as those used in Example 1 were used.

Although the MIM active matrix type liquid crystal device is taken as an example here, the effect of the present invention does not change even if a simple matrix type liquid crystal device is adopted. In that case, connect the signal line to a strip-shaped I like the counter electrode.
It is formed of a transparent electrode such as TO, and the two-terminal type non-linear element and the pixel electrode are not provided. Also, instead of TN mode, 180
The STN mode using a liquid crystal twisted 270 degrees from the degree is adopted. In order to compensate the coloring of the display in STN mode,
A phase difference plate may be provided.

As the light source, a structure different from that of the first embodiment shown in FIG. 1 was adopted. In FIG. 1, the semi-light absorbing plate 108 is arranged on the light guide plate 109 of the light source, but in the second embodiment, the light absorbing plate 508 is arranged under the light guide plate 507. A flat plate of acrylic resin having good transparency was used for the light guide 507, and white paint was printed on the surface thereof. Since the light-scattering body is small in area, the transparency of the light guide body is hardly impaired. With this configuration, the light source becomes substantially black when it is not lit. Even with such a light source, a semi-transmissive reflection type display is possible.

The function of the color transflective liquid crystal device described above is the same as that of the transflective liquid crystal device of the first embodiment described with reference to FIG. In the region where light modulation is not possible, a region such as a signal line or a two-terminal type non-linear element that is not shielded from metal is bright display during reflective display and dark display during transmissive display. Therefore, this non-light-modifiable region contributes to the improvement of the brightness of the reflective display and does not adversely affect the contrast of the transmissive display.

Example 3 Three examples of electronic equipment according to Example 3 will be shown. The transflective liquid crystal device of the present invention is suitable for mobile devices that are used in various environments and require low power consumption.

FIG. 6A shows a mobile phone, which is a main body 601.
A display unit 602 is provided on the upper front part of the. Mobile phones are used in all environments, indoors and outdoors. Moreover, it is necessary for the battery to last for at least 200 hours in the standby state. Therefore, the display device used in the mobile phone is most preferably a semi-transmissive reflection type liquid crystal device capable of mainly performing reflective display with low power consumption and performing transmissive display using auxiliary light as needed. The transflective liquid crystal device of the present invention is brighter and has higher contrast than the conventional transflective liquid crystal device in both reflective display and transmissive display.

FIG. 6B shows a watch, which is a body 603.
A display unit 604 is provided at the center of the. An important aspect in watch applications is fashion. The transflective liquid crystal device of the present invention, by changing the color of the light source,
You can enjoy colorful transmissive displays without compromising the visibility of reflective displays. It is advantageous in design that various color displays can be performed according to the image of the exterior.

FIG. 6C shows a portable information device, which is a main body 6
The display unit 606 is provided on the upper side of 05 and the input unit 607 is provided on the lower side. Since portable information devices often have touch keys on the front surface of the display unit, the display tends to be dark.
Therefore, conventionally, the reflection type liquid crystal device or the transmission type liquid crystal device has been mainly used. However, the former cannot be seen in the darkness,
The latter has a problem that the power consumption is large and the battery life is shortened. The semi-transmissive reflective liquid crystal device of the present invention is also suitable for such an application, and is capable of bright display with low power,
It is also possible to obtain a high quality display in the dark by turning on the light source.

[0041]

As described above, according to the present invention, the reflective polarization means transmits and reflects light according to the polarization component,
Since the liquid crystal device is configured to display normally white during reflective display and normally black during transmissive display, it is possible to provide a semi-transmissive reflective liquid crystal device that achieves both bright reflective display and transmissive display with high contrast. You can

[Brief description of drawings]

FIG. 1 is a perspective view of a transflective liquid crystal device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a main part of a structure of a reflective polarizer used in Examples 1 and 2 of the present invention.

FIG. 3 is a diagram illustrating the function of the transflective liquid crystal device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a display example of a semi-transmissive reflection type liquid crystal device in Embodiment 1 of the present invention. (A) reflective display, (b) transmissive display, (c) transmissive display with display data inverted.

FIG. 5 is a perspective view of a transflective liquid crystal device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing an external appearance of an electronic device according to a third embodiment of the invention. (A) mobile phone, (b) watch,
(C) Portable information device.

FIG. 7 is a perspective view of a conventional transflective liquid crystal device.

[Explanation of symbols]

101 Polarizing plate 102 retardation film 103 upper glass substrate 104 Liquid crystal composition 105 Lower glass substrate 106 light scattering plate 107 reflective polarizer 108 Semi-light absorbing plate 109 Light guide plate for light source 110 light source 111 Transparent electrode (scan line) 112 Transparent electrode (signal line)

Continuation of front page (56) Reference JP-A-6-230362 (JP, A) JP-A-11-153791 (JP, A) JP-A-2001-222005 (JP, A) JP-A-9-506985 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1335 G02F 1/1343 G02B 5/30

Claims (4)

(57) [Claims] 1. A liquid between a pair of substrates having a transparent electrode on the inner surface.
Crystal panel, a liquid crystal panel having a plurality of dots arranged in a matrix, a light guide that emits light from a light source toward the liquid crystal panel, and a light guide from the light guide to the liquid crystal panel One of the pair of substrates , and a reflection polarization unit that transmits and reflects light that is emitted as a light and that is incident on the liquid crystal panel from the opposite side of the light guide body according to a polarization component. To the color filter
Is provided, the multiple dots are optically modulated by the application of electricity, and both reflective display and transmissive display are possible, and normally white display is provided during reflective display and normally black display is provided during transmissive display. , The area between the plurality of dots, the color filter
A liquid crystal device which is present and to which no voltage is applied. 2. The liquid crystal device according to claim 1, wherein a semi-light absorbing plate is provided between the light guide plate and the reflective polarization means. 3. The liquid crystal device according to claim 1 or 2, wherein display data is converted between the reflective display and the transmissive display. 4. An electronic apparatus comprising the liquid crystal device according to claim 1 as a display device.