JP3721824B2 - Reflective liquid crystal device and electronic apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflective liquid crystal device and an electronic apparatus including the reflective liquid crystal device as a display.
[0002]
[Prior art]
In recent years, an increasing number of electronic devices such as so-called electronic notebooks, mobile phones, and notebook personal computers that can be carried indoors and outdoors. In addition, digital or analog wristwatches having a liquid crystal display portion have been widely spread.
[0003]
As a display unit for displaying various data such as characters and symbols in these electronic devices, a reflective liquid crystal device that does not require a light source such as a backlight and can reduce power consumption is frequently used.
[0004]
There are various liquid crystal display modes that can be used in the reflective liquid crystal device. For example, FIG. 9A shows a case where a twisted nematic (TN) liquid crystal, a super twisted nematic (STN) liquid crystal, or the like is used as the liquid crystal layer and the liquid crystal layer is sandwiched between two polarizers. The liquid crystal 120a is sandwiched between the lower substrate 110a and the upper substrate 110b, the polarizer 100a and the reflector 130a are laminated on the outer surface of the lower substrate 110a, and the polarization is formed on the outer surface of the upper substrate 110b. A child 100b is formed.
[0005]
FIG. 9B shows an example in which an electric field induced birefringence (ECB) liquid crystal, a Heilmeier guest-host (GH) liquid crystal, or the like is used for the liquid crystal layer, and only one polarizer is used only on one substrate side. The liquid crystal 120b is sandwiched between the lower substrate 110a and the upper substrate 110b, the reflection plate 130b is formed on the outer surface of the lower substrate 110a, and the polarizer 100b is formed on the outer surface of the upper substrate 110b. .
[0006]
FIG. 9C shows a configuration that uses a phase transition type (PC type) liquid crystal, a polymer dispersed type liquid crystal (PDLC), or the like and does not require a polarizer. A liquid crystal 120c is sandwiched between the lower substrate 110a and the upper substrate 110b, a reflection plate 130c is formed on the outer surface of the lower substrate 110a, and a polarizer 100b is formed on the outer surface of the upper substrate 110b. .
[0007]
In either case, a reflection plate is formed on the back surface of the normal transmissive cell (outside the lower substrate 110a).
[0008]
[Problems to be solved by the invention]
However, since the above-mentioned liquid crystal device has the reflector disposed on the back surface of the lower substrate, a double image is observed between the liquid crystal display pattern and the shadow on the reflector, and the display quality is remarkably lowered. Further, in order to ensure the brightness of display, it is necessary to increase the reflectance of incident light, and light reflection means such as a reflector is required to further improve the reflectance.
[0009]
On the other hand, in the present situation where digital or analog wristwatches with electronic notebooks, mobile phones, and liquid crystal display units are diversified and overflowing in the market, liquid crystal display of characters and symbols, etc., is being promoted in order to increase the merchantability. The liquid crystal display is required not only to have good visibility but also to have decoration and design that can be differentiated from other products and models.
[0010]
Accordingly, the present invention has been devised to solve the above-described problems, and can improve the reflectance in a reflective liquid crystal device and can add decorativeness and design to a liquid crystal display. The main purpose is to provide new technology.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a reflective liquid crystal device according to the invention is a liquid crystal device in which a liquid crystal is sandwiched between a pair of substrates. The light interference means in which the reflectance of the light on the short wavelength side and the reflectance on the short wavelength side is made higher than the reflectance of the light on the long wavelength side is formed. According to this, since the light reflecting means is formed on the liquid crystal side surface of one of the substrates, the parallax in the display of the liquid crystal device can be eliminated and the display can be brightened to further improve the visibility. Can do.
[0012]
Furthermore, the light interference means is formed on the liquid crystal side surface of the substrate so that the reflectance of the light on the short wavelength side is higher than the reflectance of the light on the long wavelength side. Interference colors can be generated, and for example, the liquid crystal device, like the surface of a soap bubble, becomes iridescent or iridescent depending on the viewing direction, and can add decoration and design to the background of the liquid crystal display .
More specifically, the reflectance of the light interference means gradually decreases as the wavelength increases from the reflectance of the visible blue wavelength to the reflectance of the visible red wavelength. It is possible to employ optical interference means.
[0013]
A metal electrode can be used for the light reflecting means. The size of the apparatus can be reduced by using the metal plate as both the electrode and the light reflecting plate.
[0014]
The light reflecting means can be a metal thin film formed by sputtering. In this case, the metal thin film is preferably a thin film of Al, Cr, Ni, Ta, or Ag. Thereby, the metal reflecting film as the light reflecting means can be easily and inexpensively formed.
[0015]
The optical interference means may be an interference filter. In this case, the interference filter may be a metal oxide film formed by anodizing the vicinity of the surface of the metal thin film. According to this, after forming a Ta metal thin film as a light reflecting means, for example, by sputtering, an interference filter can be easily formed by anodizing the Ta film surface, and forming a thin film by anodizing The film thickness of Ta ₂ O ₅ as the anodic oxide film can be accurately controlled by adjusting the time, so that an interference filter exhibiting a desired interference color can be formed with a high yield.
[0016]
The interference filter can also be formed of a coating film of a predetermined resin such as an acrylic resin by spin coating. In this case, the interference filter can be formed with a simple device configuration.
[0017]
The thickness of the interference filter is preferably 100 to 2000 angstroms. Thereby, interference between incident light and reflected light can be efficiently caused, and various interference colors can be generated in the background of the liquid crystal display.
[0018]
The liquid crystal layer may be a composite layer composed of a polymer and a liquid crystal. Thereby, a liquid crystal device without a polarizer can be provided.
[0019]
In addition, by mounting the reflection type liquid crystal device as a display unit, in an electronic device such as an electronic notebook, a cellular phone, or a liquid crystal display unit, such as a digital or analog wristwatch, the background color of the liquid crystal display can be changed depending on the viewing angle. Since it is possible to exhibit iridescent or iridescent colors as interference colors, it is possible to add new decoration and design.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0021]
FIG. 1 shows a configuration example of a liquid crystal device of the present invention. 1A is a plan view of the liquid crystal device, and FIG. 1B is a cross-sectional view taken along the line HH ′ in FIG. In FIG. 1, the symbol P indicates a liquid crystal panel as a liquid crystal device. In the present liquid crystal device, a substrate 1a and a counter substrate 1b are bonded together with a sealing material 8, and a liquid crystal 10 is sandwiched between these two substrates.
[0022]
A metal thin film 2 as a light reflecting means is formed on the surface of the lower substrate 1a on the liquid crystal 10 side. The metal thin film 2 is formed, for example, by depositing tantalum (Ta) with a thickness of about 1000 angstroms by sputtering.
[0023]
The metal thin film 2 is not limited to the Ta film, and a thin film such as Al, Ni, Cr, Ag, or the like can be appropriately employed.
[0024]
On the metal thin film 2, an interference filter 3 as an optical interference means is formed. The interference filter 3 can be formed of a Ta ₂ O ₅ film having a thickness of about 250 angstroms as a Ta anodic oxide film by, for example, an anodic oxidation method. The anodic oxidation method for forming this Ta ₂ O ₅ film is performed, for example, by immersing in a predetermined electrolyte using the metal thin film 2 on the film forming side as an anode.
[0025]
The interference filter 3 is not limited to the case where the interference filter 3 is formed of the Ta anodic oxide film as described above, and can be formed by applying a resin such as acrylic resin to a thickness of 100 to 2000 angstrom by spin coating.
[0026]
A transparent common electrode 4 made of ITO (Indium-Tin Oxide) or the like formed by sputtering or the like is provided on the interference filter 3, and an alignment film 5 made of polyimide or the like is further formed on the surface of the transparent electrode 4. It is applied by spin coating or the like. For example, the alignment film 5 is subjected to an alignment process by rubbing the surface thereof in a predetermined direction.
[0027]
Further, on the surface of the upper substrate 1b on the liquid crystal 10 side, a segment electrode 6a that represents a symbol such as a numeral or alphabet in combination and a character electrode 6b that itself represents a predetermined character, symbol, figure or the like are formed. . An alignment film 7 made of polyimide or the like is deposited on the surfaces of the segment electrode 6 and the character electrode 6b by spin coating or the like, and an alignment process is performed in the same manner as the alignment film 5. A polarizer 9 is formed on the outer surface of the upper substrate 1b.
[0028]
At this time, the distance between the substrates 1a and 1b is set by a spacer (not shown) so that a gap of about 10 μm is generated between the alignment films 5 and 7, and the liquid crystal panel P is surrounded by the peripheral portion of the liquid crystal panel P. A seal member 8 is provided to prevent leakage.
[0029]
The above is the schematic configuration of the reflective liquid crystal device (liquid crystal panel P) according to the present embodiment, and the operation thereof will be described next.
[0030]
First, a so-called normally white mode state in which a transparent state with a light transmittance of 70% when no voltage is applied between the common electrode 4 and the segment electrode 6a or the character electrode 6b will be described. Needless to say, it can also be implemented in the normally black mode.
[0031]
At this time, since the metal thin film 2 as the light reflecting means is formed on the inner side of the substrate 1a, there is no display parallax, and the visibility can be improved. In addition, since a reflection plate that has been pasted on the back surface of the lower substrate 1a is eliminated, a thin reflective liquid crystal device can be provided.
[0032]
Moreover, in the said transmission state, the reflected light from the metal thin film 2 as a light reflection means will be seen as a background.
[0033]
At this time, due to the action of the interference filter 3 as the light interference means formed on the metal thin film 2, the incident light and the reflected light can interfere with each other to exhibit a specific interference color.
[0034]
The interference light is visually recognized by the viewer as a state in which the color slightly changes in a gradation state expressed as rainbow or iridescent depending on the direction of viewing the liquid crystal panel P.
[0035]
When the state of the interference color is quantitatively expressed, it is expressed as a correlation between the wavelength and the reflectance as shown in FIG. FIG. 2 is a graph showing the wavelength (nm) of interference light on the horizontal axis and the reflectance (%) on the vertical axis.
[0036]
In addition, about the wavelength and reflectance of interference light, about liquid crystal panel P, data were obtained by measuring the reflectance of a normal line direction with an epi-illumination microspectrometer (Hitachi: U-6000).
[0037]
As can be seen from the graph of FIG. 2, the liquid crystal panel P exhibits a characteristic that the reflectance decreases as the wavelength increases due to the action of the interference filter 3.
[0038]
That is, the reflectance on the short wavelength side (the blue side of visible light) is higher than the reflectance on the long wavelength side (the red side of visible light), and as a result, as described above. Depending on the viewing direction, a gradation change such as iridescent or iridescent will be exhibited.
[0039]
Therefore, it is possible to add decorativeness and design to the display part of an electronic device such as a wristwatch or a mobile phone equipped with the liquid crystal panel P, and it is possible to further improve the merchantability.
[0040]
On the other hand, for example, when an AC voltage of 30 Hz and 5 V is applied, only the portion where the common electrode 4 and the segment electrode 6a or the character electrode 6b face each other changes the direction of the liquid crystal 10 to enter a light blocking state. A reflective liquid crystal display having a contrast of 1 can be performed.
[0041]
By changing the material and thickness of the interference filter 3, the correlation between the wavelength and the reflectance shown in FIG. 2 is also changed, so that it is possible to diversify the interference color variations that are visible to the viewer. is there.
[0042]
The present invention is not limited to the above embodiment. For example, with regard to the driving method, the above embodiment has been described with respect to the segment method, but it can also be applied in a matrix method. In that case, the electrodes formed on the substrate 1b side are formed in a matrix, and each scanning line can be selected and driven in a line sequential manner.
[0043]
It is also possible to form the segment-type drive region and the matrix-type drive region described above on the same substrate and combine the respective displays.
[0044]
FIG. 3 is a perspective view of a simple matrix type liquid crystal device. A metal thin film 2, an interference filter 3 and an X-direction electrode 20 are laminated on the surface of the lower substrate 1a, and a Y-direction electrode 30 is formed on the surface of the upper substrate 1b. Further, an alignment film (not shown) is formed on the surfaces of the X-direction electrode 20 and the Y-direction electrode 30.
[0045]
FIG. 4 is a perspective view of an active matrix type liquid crystal device using a thin film transistor (TFT) as a switching element. A metal thin film 2 and an interference filter 3 are laminated on the surface of the lower substrate 1a, and a scanning line 40 and a signal line 30 are formed respectively. Further, a TFT 60 and a pixel electrode 70 are formed for each pixel, and an alignment film (not shown) is formed on the surface of each electrode and the upper substrate surface. Although FIG. 4 shows a configuration in which the scanning lines 40, the signal lines 30, the TFTs 60, and the pixel electrodes 70 are formed on the lower substrate 1a, naturally, a configuration in which these are formed on the upper substrate is also possible.
[0046]
As for the display mode, the above embodiment can use a TN mode including a TN liquid crystal, an STN mode using an STN liquid crystal, and a mode in which a retardation plate is arranged in the STN mode. Further, the present invention can be applied to modes such as a polarizing plate such as a polarizing beam splitter (PBS) such as an ECB liquid crystal or a Heilmeire GH liquid crystal. In the case of a single polarizing plate type, it is desirable that at least one retardation plate is disposed. By arranging a plurality of phase difference plates, viewing angle compensation and color compensation can be performed, so that a liquid crystal device with improved contrast and wide viewing angle characteristics can be obtained.
[0047]
Although the display mode that requires a polarizer has been described above, the present invention can be applied to a mode that does not require a polarizer. In such a mode, a composite layer composed of a polymer and a liquid crystal is used as the liquid crystal layer. In general, it can also be applied to phase transition type guest-host liquid crystal (PC-GH) polymer dispersed liquid crystal (PDLC). A cross-sectional view of the liquid crystal device in this case is shown in FIG. Compared to FIG. 1B, there is no polarizer and the configuration of the liquid crystal layer is different. Of course, the display by the segment method and the display by the matrix method can be applied to these display modes. Further, the segment method and the matrix method can be combined for display.
[0048]
Here, in the case of the PDLC mode, as the composite layer, for example, the polymer precursor is obtained by irradiating ultraviolet rays to a mixture of 4-biphenyl methacrylate and liquid crystal PN-001 at a ratio of 1: 9 as a polymer precursor. Those having a structure dispersed in a shape are used.
[0049]
Furthermore, as shown in FIG. 6, a configuration in which the metal electrode 70, the interference filter 3, and the alignment film 5 are laminated on the surface of the lower substrate 1b is also possible. In this case, the metal electrode 80 also serves as a light reflecting plate. The various display methods and drive methods described above can also be configured as described above.
[0050]
Here, an embodiment of an electronic apparatus using the above-described liquid crystal device according to the present invention will be described with reference to FIGS.
[0051]
FIG. 7 is a perspective view showing a wristwatch type electronic apparatus 1100. Reference numeral 1101 denotes a liquid crystal display unit using the reflective liquid crystal device (liquid crystal panel P) according to this embodiment.
[0052]
As described above, the liquid crystal panel P used in the liquid crystal display unit has the advantage that the background of the liquid crystal display is a rainbow or iridescent color depending on the viewing direction, in addition to the advantages of high reflectivity and brightness. It has the feature of exhibiting changes.
[0053]
Therefore, decoration and design can be added to the wristwatch-type electronic device 1100, and interest can be created for those who hold the electronic device.
[0054]
FIG. 8 is a perspective view showing a mobile phone. Reference numeral 1000 denotes a mobile phone body, and 1001 of the mobile phone body is a liquid crystal display unit using the reflective liquid crystal device (liquid crystal panel P) according to the present embodiment.
[0055]
In this case as well, the liquid crystal panel P used in the liquid crystal display unit has a high reflectance and is easy to see, and the background of the liquid crystal display changes in a gradation state such as iridescent or iridescent depending on the viewing direction. The decorativeness and design can be improved.
[0056]
Since each of the electronic devices is an electronic device driven by a battery, the life of the battery can be extended by using a reflective liquid crystal panel that does not have a light source lamp.
[0057]
The present invention is not limited by the above embodiment, and can be applied to other portable game machines.
[Brief description of the drawings]
FIG. 1A is a plan view and FIG. 1B is a cross-sectional view illustrating a schematic configuration of a reflective liquid crystal device according to an embodiment.
FIG. 2 is a graph showing the correlation between the wavelength and the reflectance of the reflective liquid crystal device according to the embodiment.
FIG. 3 is a perspective view of a direct matrix reflective liquid crystal device according to the present embodiment.
FIG. 4 is a perspective view of an active matrix type reflective liquid crystal device according to the present embodiment.
FIG. 5 is a cross-sectional view of a polymer-dispersed liquid crystal mode reflective liquid crystal device according to the present embodiment.
FIG. 6 is a cross-sectional view showing another schematic configuration of the reflective liquid crystal device according to the embodiment.
FIG. 7 is a perspective view showing a wristwatch type electronic device equipped with a reflective liquid crystal device according to the embodiment.
FIG. 8 is a perspective view showing a mobile phone equipped with the reflective liquid crystal device according to the embodiment.
FIG. 9 is a cross-sectional view showing a schematic configuration of a conventional polymer-dispersed liquid crystal device.
[Explanation of symbols]
1a, 1b Transparent glass substrate 2 Metal thin film (light reflecting means)
3 Interference filter (light interference means)
4 Common electrode (common electrode)
5 Alignment film (orientation means)
6a Segment electrode 6b Character electrode 7 Alignment film (orientation means)
8 Seal member 9 Polarizer 10 Liquid crystal 11 Polymer dispersed liquid crystal 20 Scan electrode 30 Signal electrode 40 Scan line 50 Data line 60 Thin film transistor (TFT)
70 Pixel electrode 80 Metal electrode (light reflecting means)
100a, 100b Polarizers 110a, 110b Transparent glass substrates 120a, 120b, 120c Liquid crystal 130a, 130b, 130c Light reflector 1100 Wristwatch type electronic device 1101 Liquid crystal display unit 1000 Mobile phone 1001 Liquid crystal display unit

Claims (10)

  In a liquid crystal device in which a liquid crystal layer is sandwiched between a pair of substrates, the reflectance of light on the short wavelength side is reflected on the liquid crystal side surface of one of the pair of substrates. A reflection-type liquid crystal device comprising: a light interference means and a light reflection means that are higher than the ratio;   The reflectance of the light of the light interference means is a reflectance that gradually decreases as the wavelength increases from the reflectance of the visible wavelength on the blue side to the reflectance of the visible light on the red side. The reflective liquid crystal device according to claim 1.   3. The reflective liquid crystal device according to claim 1, wherein the light reflecting means is made of a metal thin film that also serves as an electrode.   4. The reflective liquid crystal device according to claim 3, wherein the light reflecting means is made of any one of Al, Cr, Ni, Ta, and Ag formed by sputtering.   5. The reflection type liquid crystal device according to claim 1, wherein the optical interference means is an interference filter.   5. The reflection type liquid crystal device according to claim 1, wherein the light interference means is a metal oxide film formed by anodization in the vicinity of the surface of the metal thin film.   6. The reflective liquid crystal device according to claim 5, wherein the interference filter is an acrylic resin coating film formed on the metal thin film by a spin coating method.   8. The reflection type liquid crystal device according to claim 5, wherein the thickness of the interference filter is 100 to 2000 angstroms.   2. The reflective liquid crystal device according to claim 1, wherein the liquid crystal layer is formed of a composite layer composed of a polymer and a liquid crystal.   An electronic apparatus comprising the reflective liquid crystal device according to claim 1 as a display unit.

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