Patent Application
20060176410
1. Field of the Invention
The present invention relates to an IC card having a cholesteric liquid crystal display.
2. Description of the Related Art
Conventionally, IC cards with an integrated circuit (IC) such as a memory or a microprocessor built therein and having information storage and processing functions have been widely used. Furthermore, IC cards with a display function for displaying stored data have been used recently.
The IC cards with the display function include an IC card of a thermal writing method where print and deletion are performed by using a thermal coupling material, and an IC card of a magnetic writing method where print and deletion are performed by using a magnetic material.
In such display methods, however, there has been a problem that, when the display is rewritten, it is necessary to insert the IC card into an information recording device having a thermal head or a magnetic head, and hence, it is not suitable for the application to a non-contact type IC card.
To solve that problem, a non-contact information recording and displaying method is disclosed in Japanese Patent Application Laid-open No. 2000-113137, in which the display is rewritten, using radio waves received from an external terminal as a power source, and information is displayed by a liquid crystal display device having a memory property and capable of maintaining the display without consuming the power. As an example of the liquid crystal display device, there is a device using selective reflection of light by the cholesteric liquid crystals.
However, according to the non-contact information recording and displaying method described above, the cholesteric liquid crystal is mentioned only as an example of the liquid crystal display device having the memory property, and there is no mention as to how to use the characteristics of cholesteric liquid crystals effectively in the IC card. That is, a specific method for effectively using the characteristics of the cholesteric liquid crystals is not sufficiently disclosed.
For example, by effectively using the characteristics of the cholesteric liquid crystals, other than the memory property, the convenience of the IC card with the display function can be further improved, for example, the visibility can be improved.
It is an object of the present invention to at least solve the problems in the conventional technology.
According to an aspect of the present invention, an IC card that performs any one of transmission of information to an external device and reception of information from the external device or both, includes an information display unit including a segment type display unit formed of a liquid crystal layer that forms a cholesteric phase, wherein the display unit is capable of selectively reflecting light of a plurality of wavelengths by a voltage pulse converted from an electromagnetic wave received from the external device.
According to another aspect of the present invention, an IC card that performs any one of transmission of information to an external device and reception of information from the external device or both, includes an information display unit in which at least two liquid crystal layers that form a cholesteric phase, which reflect light of a different dominant wavelength in a planar state, are arranged in parallel for each of segments forming an information display pattern, and a voltage is applied to the liquid crystal layers that are arranged in parallel and form the cholesteric phase to change an orientation of liquid crystal molecules in liquid crystals that form the cholesteric phase, so as to transmit or reflect light, thereby displaying predetermined information.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of an IC card and an external device according to the present invention are explained below in detail with reference to the accompanying drawings. An example of a non-contact type IC card that communicates with an external device in a non-contact manner is explained below. However, the present invention is not limited thereto, and can be applied to a contact type IC card that communicates with an external device in a contact manner, and a hybrid type IC card that functions as the contact type and the non-contact type.
A configuration of an IC card system according to a first embodiment is explained below.
The host computer 10 generates data to be transmitted to the IC card 12, and performs data processing and management of data received from the IC card 12. The reader/writer 11 is connected to the host computer 10, and establishes communication with the IC card to transfer data.
The IC card 12 is a card type device having a built-in IC chip, and transfers information between the reader/writer 11 and the IC card 12. The IC card 12 can perform data processing such as operation and storage of the received data.
The IC card 12 according to the present invention is different from the IC cards of the thermal writing method and the magnetic writing method, and can display in color the content of data received from the reader/writer 11, the operation result, and stored data, thereby improving the convenience of the IC card 12. The color display is realized by a plurality of cholesteric liquid crystal layers that reflects light of a different wavelength, respectively. Furthermore, since the liquid crystal display is formed by using the cholesteric liquid crystals, display can be maintained without applying a voltage at all times, thereby reducing the consumption of power.
As shown in
The information display unit 15 displays in color data received from the reader/writer 11, data stored in the storage unit 14, or various types of information such as an error message, by using a plurality of cholesteric liquid crystal layers. The specific method of color display will be explained later in detail.
The controller 16 transmits various control signals to the respective functional units 13 to 15, to control the entire IC card 12. The controller 16 also performs various types of processes such as storage and operation of data. For example, the controller 16 determines whether the received data satisfies a predetermined condition, and requests the information display unit 15 to change the display color of data based on the determination result.
The antenna 20 and the communication control IC 23 correspond to the communication unit 13 shown in
The antenna 20 is a metal wire that emits radio waves to the air or receives radio waves from the air, at a time of communicating with the reader/writer 11. The liquid crystal display 21 displays data and messages in color. The liquid crystal display control IC 22 controls the liquid crystal display 21, to display data and messages in color.
The communication control IC 23 emits radio waves from the antenna 20, to control a transmission process of data to the reader/writer 11. The communication control IC 23 also performs an extraction process of communication data from the radio waves received by the antenna 20.
The card control IC 24 transmits various types of control signals to the liquid crystal display control IC 22 and the communication control IC 23, to control the entire IC card 12. The card control IC 24 has a memory therein for storing various data. The card control IC 24 can perform various types of data processing such as operation and storage of the data, and can store operation results and the like in the memory.
The display principle of the liquid crystal display using the cholesteric liquid crystals is explained below.
In the planar state, a direction of screw axis of a liquid crystal molecule 30 having a helical structure is a direction of electric field generated by electrodes 31 and 32, and light in a particular wavelength band is reflected from the cholesteric liquid crystal layer. When it is assumed that a cycle (pitch) in the helical structure of the liquid crystal molecule 30 is p, a relationship between a wavelength λ having the largest reflectivity and an average refractive index n of the liquid crystals is expressed by λ=p×n, and a relationship between a reflecting wavelength band Δλ and anisotropy Δn in the refractive index of the liquid crystals is expressed by Δλ=p×Δn. The reflecting wavelength band Δλ is widened with an increase of anisotropy Δn in the refractive index of the liquid crystals.
Furthermore, the cholesteric liquid crystals selectively reflect circularly polarized light wound in the same direction as that of distortion of the helical structure. Therefore, since either one of the right-circularly polarized light and the left-circularly polarized light is reflected, and the other is transmitted, the reflectivity becomes 50% theoretically.
In the focal conic state, the direction of screw axis of the liquid crystal molecule 30 having the helical structure is vertical to the direction of electric field generated by the electrodes 31 and 32, and most of the incident light is transmitted.
For example, when figure “3” is displayed, segment 401, segment 403, segment 404, segment 406, and segment 407 are set to the planar state, and segment 402 and segment 405 are set to the focal conic state, and display is performed by controlling reflection and transmission of light.
A method of setting orientation of the liquid crystal molecules in the cholesteric liquid crystals is explained below.
In the solid line 50, a voltage value V1 is a threshold voltage of the voltage pulse at which cholesteric liquid crystals start to shift from the planar state to the focal conic state, and a voltage value V2 and a voltage value V3 indicate a voltage range where the focal conic state is maintained. A value V4 is a voltage value of the voltage pulse at which the cholesteric liquid crystals shift to the complete planar state. Before the cholesteric liquid crystals shift to the planar state, the cholesteric liquid crystals go through a homeotropic state. The homeotropic state stands for a state where the helical structure of the liquid crystal molecules is released, and the major axis of the liquid crystal molecules is directed to the direction of the electric field.
In the dotted line 51, the voltage value V3 is a threshold voltage of the voltage pulse, at which the cholesteric liquid crystals start to shift from the focal conic state to the planar state, and the voltage value V4 is a threshold voltage of the voltage pulse, at which the cholesteric liquid crystals become the complete planar state.
Accordingly, when the state is set from the planar state to the focal conic state, a voltage pulse in a range from the voltage value V2 to the voltage value V3 is provided. When the state is set from the focal conic state to the planar state, a voltage pulse equal to or larger than the voltage value V4 is provided.
When a voltage pulse having a medium size, that is, a voltage pulse in a range from the voltage value V1 to the voltage value V2, and a voltage pulse in a range from the voltage value V3 to the voltage value V4 in the solid line is applied, the orientation of the cholesteric liquid crystals is such that the planar state and the focal conic state are mixed, and the color of the reflected light is a neutral color between a color in the planar state and a color in the focal conic state. The same thing applies to the application of voltage in the range from the voltage value V3 to the voltage value V4 in the dotted line 51.
An application of voltage is performed by using an AC pulse voltage in which the polarity is reversed in positive and negative, and an absolute value of amplitude is the same. This is performed for preventing an ionic substance in the cholesteric liquid crystals is polarized, and the display quality is degraded.
The structure of the liquid crystal display 21 according to the first embodiment is explained below.
As shown in the cross section in
The polymeric films 601 to 603 are transparent film substrates, on the surface of which any one of the ITO electrodes 621 to 625 is formed, and made of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). In the first embodiment, polymeric films 601 to 603 are used as a transparent substrate, however, thin glass substrates can be used instead of the polymeric films 601 to 603.
The separation layer 61 separates the ITO electrodes 621 and 622 and the cholesteric liquid crystal layers 631 and 632. The ITO electrodes 621 to 625 are transparent electrodes that apply voltage to the cholesteric liquid crystal layers 631 to 633. The cholesteric liquid crystal layers 631 to 633 are liquid crystal layers that reflect light of a predetermined wavelength in the planar state, and transmit light in the focal conic state. The photoabsorption layer 64 absorbs light having penetrated the cholesteric liquid crystal layers 631 to 633 and exhibits black color. By the function of the photoabsorption layer 64, the display pattern can be displayed in black, when the cholesteric liquid crystal layers 631 to 633 are in the focal conic state.
The ITO electrodes 621 and 622 are formed in the shape of respective segments 412 and 415, and arranged in parallel on the information display surface. The ITO electrode 623 functions in a set with the ITO electrodes 621 and 622, so as to be able to apply voltage independently to the cholesteric liquid crystal layer 631 corresponding to the segment 412, and the cholesteric liquid crystal layer 632 corresponding to the segment 415.
The cholesteric liquid crystal layers 631, 632, and 633 are applied with a voltage pulse via the ITO electrodes 621 to 625, and change the state between the planar state and the focal conic state. Since the upper cholesteric liquid crystal layers 631 and 632 and the lower cholesteric liquid crystal layer 633 are configured to reflect light having a different wavelength in the planar state, respectively, a color display by a plurality of colors can be realized.
For example, if it is assumed that the reflected light from the cholesteric liquid crystal layers 631 and 632 is red, and the reflected light from the cholesteric liquid crystal layer 633 is blue, when both of the cholesteric liquid crystal layers 631 and 632 and the cholesteric liquid crystal layer 633 are in the planar state, the red light reflected from the cholesteric liquid crystal layers 631 and 632 and the blue light reflected from the cholesteric liquid crystal layer 633 are mixed, thereby generating white display color due to additive mixture of color stimuli. An example of a spectrum of white light obtained by mixing red light and blue light is shown in FIG. 7.
When the cholesteric liquid crystal layers 631 and 632 are in the planar state, and the cholesteric liquid crystal layer 633 is in the focal conic state, the display color becomes red. When the cholesteric liquid crystal layers 631 and 632 are in the focal conic state, and the cholesteric liquid crystal layer 633 is in the planar state, the display color becomes blue. When both the cholesteric liquid crystal layers 631 and 632 and the cholesteric liquid crystal layer 633 are in the focal conic state, the light is absorbed by the photoabsorption layer 64, and the display color becomes black.
The structure is a solid structure in which the ITO electrodes 624 and 625 and the cholesteric liquid crystal layer 633 are common to the respective segments 411 to 417 forming the display pattern. By having these common, a circuit for applying the voltage can be simplified, and the IC card can be produced at a low cost.
In the case of
To increase the contrast of display, it is desired that the dominant wavelength of spectrum of red reflected light reflected by the cholesteric liquid crystal layers 631 and 632 is within a range from 570 to 640 nanometers, and the reflecting band of the reflected light is wide. Furthermore, it is desired that the dominant wavelength of spectrum of blue reflected light reflected by the cholesteric liquid crystal layer 633 is within a range from 450 to 500 nanometers, and the reflecting band of the reflected light is narrow.
A relationship between a bandwidth of the reflecting band of reflected light and contrast of display is explained next.
Thus, by making the reflecting band of the red reflected light wide and the reflecting band of the blue reflected light narrow, the display pattern can be clearly recognized. Furthermore, since the spectral luminous of blue decreases when the area of the blue area is small, the blue color can be made indistinctive on the liquid crystal display of the IC card.
Furthermore, the cholesteric liquid crystal layers 631 and 632 reflecting the red light can be formed of liquid crystal molecules having a helical structure reflecting the right-circularly polarized light and the cholesteric liquid crystal layer 633 reflecting the blue light can be formed of liquid crystal molecules having a helical structure reflecting the left-circularly polarized light. As a result, since right-circularly polarized components and left-circularly polarized components of light in the common wavelength range in the reflecting wavelength band of the cholesteric liquid crystal layers 631 and 632 and the reflecting wavelength band of the cholesteric liquid crystal layer 633 are reflected, a display pattern with high lightness can be obtained. The cholesteric liquid crystal layers 631 and 632 can reflect the left-circularly polarized light, and the cholesteric liquid crystal layer 633 can reflect the right-circularly polarized light.
Alternatively, the cholesteric liquid crystal layers 631 and 632 reflecting the red light can be formed by combining two layers, that is, the cholesteric liquid crystal layer reflecting the right-circularly polarized light and the cholesteric liquid crystal layer reflecting the left-circularly polarized light. The same thing applies to the cholesteric liquid crystal layer 633 reflecting the blue light.
Thus, the liquid crystal display 21 is formed so as to be capable of color display, and the balance is displayed in different colors based on whether a predetermined condition is satisfied, thereby drawing the attention of a user of the IC card 12. While an example of the IC card 12 for displaying the balance of deposit with respect to a bank or the like is shown, the technique can be also applied to the IC card that displays shopping points in a department store or the like.
A manufacturing method of the liquid crystal display according to the first embodiment is explained below. First, the cholesteric liquid crystal layers 631 and 632 are formed so that the dominant wavelength of the red light to be reflected is 480 nanometers, the half breadth of a reflection spectrum is about 70 nanometers, and only the right-circularly polarized light is reflected, by mixing a chiral agent causing a clockwise distortion to the liquid crystal molecules with a nematic liquid crystal material in an appropriate amount.
Furthermore, the cholesteric liquid crystal layer 633 is formed so that the dominant wavelength of the blue light to be reflected is 590 nanometers, the half breadth of the reflection spectrum is about 90 nanometers, and only the left-circularly polarized light is reflected, by mixing a chiral agent causing a counterclockwise distortion to the liquid crystal molecules with the nematic liquid crystal material in an appropriate amount. The thickness of the cholesteric liquid crystal layers 631 to 633 is set to about 5 micrometers, respectively.
The formed cholesteric liquid crystal layers 631 to 633 are clamped, as shown in
When a display was made by the liquid crystal display 21, chromaticity of white was (x, y)=(0.31, 0.33) in the Commission Internationale de I'Eclairage (CIE) color system, and lightness was Y=0.32, exhibiting favorable white. Furthermore, chromaticity of red was (x, y)=(0.57, 0.40), and lightness was Y=0.21, displaying favorable red.
At this time, the voltage applied to the cholesteric liquid crystal layers 631 to 633 was an AC pulse voltage for one cycle, with one cycle being 50 milliseconds. When the cholesteric liquid crystal layers 631 to 633 are set to the planar state, the voltage applied thereto was an AC pulse voltage having an amplitude of ±40 volts, and when the cholesteric liquid crystal layers 631 to 633 are set to the focal conic state, the voltage applied thereto was an AC pulse voltage having an amplitude of ±18 volts.
As explained above, in the first embodiment, the IC card 12 displays a predetermined type of information, by laminating the cholesteric liquid crystal layers 631 and 632 reflecting red light in the planar state and the cholesteric liquid crystal layer 633 reflecting blue light in the planar state, applying a voltage respectively to the laminated cholesteric liquid crystal layers 631 to 633, and changing the orientation of the cholesteric liquid crystals between the planar state and the focal conic state, to transmit or reflect light. As a result, the display color can be changed according to the displayed information, to improve the visibility, and the convenience of the IC card 12 can be further improved.
In the first embodiment, two cholesteric liquid crystal layers are laminated vertically. However, the present invention is not limited thereto, and three or more cholesteric liquid crystal layers can be laminated.
In the first embodiment, the laminated structure of the cholesteric liquid crystals is applied to the IC card with a liquid crystal display. However, the present invention is not limited thereto, and the similar technique can be applied to electronic paper technology for other applications.
In the first embodiment, an example where the cholesteric liquid crystal layers reflecting light having a different wavelength are laminated in two or more layers, to realize color display has been explained. However, at least two cholesteric liquid crystal layers reflecting light having a different wavelength can be laminated for each of the segments forming the display pattern, to -realize color display. In a second embodiment, therefore, an example where color display is realized by arranging at least two cholesteric liquid crystal layers reflecting light having a different wavelength in parallel is explained.
At first, the configuration of the liquid crystal display according to the second embodiment is explained.
In the case of
When one of the two cholesteric liquid crystal layers is set to the planar state, and the other is set to the focal conic state, the color of the display pattern becomes a color of light reflected by the cholesteric liquid crystal layer in the planar state, that is, red or blue. When the two cholesteric liquid crystal layers are in the focal conic state, the color of an underlayer arranged below the cholesteric liquid crystal layer is displayed. If it is assumed that the underlayer is the photoabsorption layer, the display color becomes black.
Thus, by dividing the segments 1401 to 1407 forming the information display pattern into two, respectively, and arranging the two cholesteric liquid crystal layers reflecting light of a different color in parallel, display with four colors of white, red, blue, and black can be realized.
In the case of
The display color becomes black when the photoabsorption layer is arranged below the cholesteric liquid crystal layer, and all the cholesteric liquid crystal layers are in the focal conic state. The cholesteric liquid crystals can display neutral colors between a color in the planar state and a color in the focal conic state by mixing the planar state and the focal conic state. As a result, gradation of display can be increased.
As a method of performing the similar RGB display, a method of laminating three layers of cholesteric liquid crystal layers reflecting red, green, and blue in the planar state can be considered. In this case, however, manufacturing difficulty largely increases with such a limited thickness like the IC card, and the production cost increases. Therefore, the method according to the second embodiment is more suitable. In a color display method using a color filter, the use efficiency of light is poor, and the display becomes darker as compared to the method according to the second embodiment. Furthermore, in a method using reflective liquid crystals, since a liquid crystal device does not have the memory property, it is necessary to supply power at all times.
As shown in
The visual transfer function shown in
The liquid crystal display capable of color display is equipped in the IC card on which the balance of deposit in a bank is displayed, or the IC card on which-shopping points in a department store or the like is displayed. When the balance of deposit or the shopping points satisfies a predetermined condition, display is made with a different color, thereby drawing attention of the user of the IC card, and improving the convenience of the IC card.
In
A manufacturing method of the liquid crystal display shown in
The voltage to be applied to the respective cholesteric liquid crystal layers is an AC pulse voltage with one cycle being 50 milliseconds, and when the cholesteric liquid crystal layers are set to the planar state, the AC pulse voltage has an amplitude of ±40 volts, and when the cholesteric liquid crystal layers are set to the focal conic state, the AC pulse voltage has the amplitude value of ±18 volts.
In the second embodiment, at least two cholesteric liquid crystal layers, respectively, reflecting light of a different wavelength in the planar state are arranged in parallel, for each of the segments 1401 to 1407 or 1411 to 1417 forming the data display pattern, the orientation of the cholesteric liquid crystals are changed by applying a voltage to the cholesteric liquid crystal layers arranged in parallel, so as to transmit or reflect light, thereby displaying predetermined information. Accordingly, the display color can be changed corresponding to the displayed data, to improve the convenience of the IC card. Furthermore, an IC card with a liquid crystal display capable of color display with high lightness can be manufactured at a low cost.
In the second embodiment, the parallel structure of the cholesteric liquid crystals is applied to the IC card with the liquid crystal display, however, the present invention is not limited thereto, and the similar technique can be applied to the electronic paper technology for other applications. Furthermore, the parallel structure explained in the second embodiment can be applied likewise not only to the liquid crystal display using the cholesteric liquid crystals but also to other display methods, like an electrophoretic method and a twist ball method.
An example where at least two cholesteric liquid crystal layers reflecting light of a different wavelength are laminated or arranged in parallel to display single data by color display has been explained in the first and the second embodiments. However, the IC card can be formed such that a plurality of data display is performed simultaneously to further improve the convenience. In a third embodiment, therefore, an example where the IC card displays a plurality of data simultaneously is explained.
The configuration of the IC card system according to the third embodiment is first explained.
As shown in
The IC card 172 according to the present invention can display in color the content of data received from the reader/writer 171, the operation result, and stored data. At this time, different types of data can be displayed in color simultaneously, thereby further improving the convenience of the IC card 172.
As shown in
The information display unit 175 displays in color data received from the reader/writer 171, data stored in the storage unit 174, or a plurality of data such as an error message simultaneously, by using the cholesteric liquid crystal layers. The input receiving unit 176 is an input device such as a button for switching a display mode of data displayed by the information display unit 175 between single data display and plural data display. The input receiving unit 176 has a dedicated input/output channel for controlling the display of the information display unit 175, and can dead data from the storage unit 174 and change over the display, without using the controller 178 that controls the entire IC card. As a result, high-speed data display is realized.
The capacitor 177 is a power unit that accumulates radio energy transmitted from the reader/writer 171 and supplies power to the IC card 172. By accumulating power in the capacitor 177, the IC card 172 can change over the display between the single data display and the plural data display, even when the communication with the reader/writer 171 is not performed. The controller 178 transmits various control signals to the respective functional units 173 to 177, to control the entire IC card 172.
The data display method according to the third embodiment is explained below.
The structure of the liquid crystal display according to the third embodiment is explained next.
As shown in the cross section in
The polymeric films 1911 to 1914 are transparent film substrates, on the surface of which any one of the ITO electrodes 1921 to 19212 is formed. The ITO electrodes 1921 to 19212 are electrodes that apply voltage to the cholesteric liquid crystal layers 1941 to 1948. The separation layers 1931 to 1935 separate the ITO electrodes 1921, 1922, 1924, 1925, 1927, 1928, 19210, and 19211, and the cholesteric liquid crystal layers 1941 to 1948. The cholesteric liquid crystal layers 1941 to 1948 are liquid crystal layers that reflect light of a predetermined wavelength in the planar state, and transmit light in the focal conic state. The photoabsorption layer 195 absorbs light having penetrated the cholesteric liquid crystal layers 1941 to 1948 and exhibits black color.
The cholesteric liquid crystal layers 1941, 1942, 1945, and 1946 are formed so as to reflect light with a wavelength of green in the planar state. Preferably, if the dominant wavelength of the reflected light is in a range from 530 to 570 nanometers inclusive, bright display can be obtained.
The cholesteric liquid crystal layers 1943 and 1944 are formed so as to reflect light with a wavelength of blue in the planar state, and the cholesteric liquid crystal layers 1947 and 1948 are formed so as to reflect light with a wavelength of red in the planar state. If the dominant wavelength of the blue reflected light is in a range from 450 to 490 nanometers inclusive, and the dominant wavelength of the red reflected light is in a range from 610 to 650 nanometers inclusive, when being mixed with the green reflected light, the mixed degree of colors becomes preferable.
By independently applying the voltage to the cholesteric liquid crystal layers 1941 and 1948 and setting respective cholesteric liquid crystal layers to the planar state or the focal conic state, numeric characters can be displayed on the segments 1901 to 1907 and 1908 to 19014 with a different color.
Specifically, when the cholesteric liquid crystal layers 1941 and 1942 and the cholesteric liquid crystal layers 1943 and 1944 are in the planar state, green and blue are mixed and the display color becomes cyan. When the cholesteric liquid crystal layers 1945 and 1946 and the cholesteric liquid crystal layers 1947 and 1948 are in the planar state, green and red are mixed and the display color becomes magenta. Since cyan and magenta are opposite colors, the both displays are clearly distinguished from each other due to the contrast effect of colors to be displayed simultaneously, thereby improving the visibility.
Thus, since the ITO electrodes 1924 and 1925, the ITO electrodes 19210 and 19211, the cholesteric liquid crystal layers 1943 and 1944, and the cholesteric liquid crystal layers 1943 and 1944 have the solid structure, a circuit for switching the orientation of the cholesteric liquid crystals can be simplified, and the IC card can be manufactured at a low cost.
When the cholesteric liquid crystal layers 1941 and 1942 and the cholesteric liquid crystal layer 1949 are in the planar state, among the segments 1901 to 1907 forming the numerical display pattern, segments other than the portion forming a figure are displayed in blue, which is the opposite color of the cholesteric liquid crystal layer 1949. When the cholesteric liquid crystal layers 1945 and 1946 and the cholesteric liquid crystal layer 19410 are in the planar state, among the segments 1908 to 19014 forming the numerical display pattern, segments other than the portion forming a figure are displayed in red, which is the opposite color of the cholesteric liquid crystal layer 19410.
Accordingly, by setting the wavelength band of the blue reflected light and the red reflected light to the wavelength band in a near ultraviolet region and a near infrared region, respectively, corresponding to the opposite ends of the visibility curve shown in
Furthermore, if the cholesteric liquid crystal layers 1941, 1942, 1945, and 1946 reflecting green light are formed by liquid crystal molecules having a helical structure reflecting the right-circularly polarized light, and the cholesteric liquid crystal layers 1943 and 1944 reflecting blue light and the cholesteric liquid crystal layers 1947 and 1948 reflecting red light are formed by liquid crystal molecules having a helical structure reflecting the left-circularly polarized light, the right-circularly polarized components and the left-circularly polarized components of light in the common wavelength range in the reflecting wavelength band of the upper and lower cholesteric liquid crystal layers are reflected. As a result, a display pattern with high lightness can be obtained. The cholesteric liquid crystal layers 1941, 1942, 1945, and 1946 can reflect the left-circularly polarized light, and the cholesteric liquid crystal layers 1943, 1944, 1947, and 1948 can reflect the right-circularly polarized light.
By pressing the display switch button 222, the user of the IC card 220 can switch the display. For example, when the display switch button 222 is pressed once, single data display is performed, and when the display switch button 222 is pressed again, two data display is performed. When the display switch button 222 is pressed again, the display is deleted.
According to the third embodiment, the input receiving unit 176 that receives input of switching request for changing the display from the single data display to simultaneous multiple data display is provided. Upon reception of the input of a display switching request, the information display unit 175 switches the display from the single data display to simultaneous multiple data display. Accordingly, a plurality of data can be immediately confirmed, thereby improving the convenience of the IC card 220.
In the third embodiment, a case that single data display and two data display are switched by pressing the display switch button 222 has been explained. However, the present invention is not limited thereto, and switchover of display can be performed by rotating a rotary dial. By using the rotary dial instead of the display switch button 222, it can be prevented that the display switch button 222 is unexpectedly pressed, and unnecessary display is performed.
In this case, for example, when the rotary dial is rotated once, single data is displayed, when the rotary dial is rotated again, two data is displayed, and when the rotary dial is rotated again, the display is deleted. A circuit for converting the rotation of the job dial to power can be provided, and the generated power is used for display.
In the third embodiment, power is supplied from the reader/writer 171, however, the present invention is not limited thereto, and power can be supplied by wired or wireless communication with another device such as a mobile phone and personal digital assistants (PDA). Furthermore, the IC card 172 can be equipped with a solar battery, and power is supplied from the solar battery. More preferably, if an apparatus that supplies power is provided in each area, so that power can be supplied easily anywhere, the convenience of the IC card 172 is largely improved.
Furthermore, in the third embodiment, the liquid crystal display having two cholesteric liquid crystal layers reflecting light of a different dominant wavelength is used to perform simultaneous display of a plurality of data. However, the present invention is not limited thereto, and when there is only one cholesteric liquid crystal layer, simultaneous display of a plurality of data can be performed with a single color.
In the first, the second, and the third embodiments above, the case that the IC card is equipped with the liquid crystal display using the cholesteric liquid crystals capable of color display has been explained. However, the visibility in a dark place can be improved by equipping a liquid crystal display with a luminous layer that emits light in a dark place and irradiates light to display surfaces of liquid crystals. Therefore, a liquid crystal display further equipped with the luminous layer is explained in a fourth embodiment.
The configuration of the liquid crystal display according to the fourth embodiment is explained first.
The cholesteric liquid crystal portion 230 is a liquid crystal display unit capable of color display as explained in the first to the third embodiments. However, the photoabsorption layer in the liquid crystal display explained in the first to the third embodiments is replaced by the photoabsorption layer 232. The luminous layer 231 is a transparent layer formed of a luminous pigment or a noctilucent material that accumulates energy upon reception of photo irradiation, and emits light for about several tens minutes to several hours. The photoabsorption layer 232 absorbs light and exhibits black.
In
In
In this case, the dominant wavelength of light emitted from the luminous layer 231 is made to match the dominant wavelength of light reflected by the cholesteric liquid crystal portion 230. Furthermore, the wavelength band of light emitted from the luminous layer 231 is made to be wider as much as possible than the wavelength band of light reflected by the cholesteric liquid crystal portion 230. Accordingly, contrast between the display pattern and the portions other than the display pattern can be increased, thereby enabling improvement in visibility.
A liquid crystal display obtained by improving the liquid crystal display equipped with the luminous layer 231 shown in
The cholesteric liquid crystal portion 250 is a liquid crystal display capable of color display as shown in the first to the third embodiments. However, the photoabsorption layer in the liquid crystal display shown in the first to the third embodiments is replaced by the photoabsorption layer 254. The quarter-wave plate 251 is a wave plate that converts plane polarized light to the right-circularly polarized light or the left-circularly polarized light. The polarizing plate 252 converts light to the plane polarized light. The luminous layer 253 is a transparent layer formed of a luminous pigment or a noctilucent material that accumulates energy upon reception of photo irradiation, and emits light for about several tens minutes to several hours. The dominant wavelength of light emitted therefrom substantially matches the dominant wavelength of light reflected by the cholesteric liquid crystal portion 250. The photoabsorption layer 254 absorbs light and exhibits black.
Thus, the polarizing plate 252 and the quarter-wave plate 251 are arranged above the luminous layer 253, so that the light emitted from the luminous layer 253 is converted to the right-circularly polarized light or the left-circularly polarized light, and the cholesteric liquid crystal portion 250 is formed so as to reflect the right-circularly polarized light or the left-circularly polarized light in the planar state. When the cholesteric liquid crystal portion 250 is in the planar state, the light emitted from the luminous layer 253 is reflected by the cholesteric liquid crystal portion 250. Accordingly, the display pattern becomes darker, and portions other than the display pattern become brighter due to the light emitted from the luminous layer 253, thereby further increasing the contrast between the display pattern and other portions, and improving the visibility.
The cholesteric liquid crystal portions 2601 and 2602 are respectively a liquid crystal display unit capable of color display as shown in the first to the third embodiments. However, the photoabsorption layer in the liquid crystal display shown in the first to the third embodiments is replaced by the photoabsorption layer 262. Furthermore, the cholesteric liquid crystal portion 2601 is formed so as to reflect only the right-circularly polarized light, and the cholesteric liquid crystal portion 2602 is formed so as to reflect only the left-circularly polarized light. The luminous layer 261 is a transparent layer formed of a luminous pigment or a noctilucent material that accumulates energy upon reception of photo irradiation, and emits light for about several tens minutes to several hours. The dominant wavelength of light emitted therefrom substantially matches the dominant wavelength of light reflected by the cholesteric liquid crystal portion 250. The photoabsorption layer 262 absorbs light and exhibits black.
Thus, by arranging the cholesteric liquid crystal portions 2601 and 2602 that reflect the right-circularly polarized light and the left-circularly polarized light, in a bright place, right-circularly polarized components and left-circularly polarized components in the light in the common wavelength range in the reflecting wavelength band of the upper and lower cholesteric liquid crystal portions 2601 and 2602 are both reflected, thereby obtaining a clear display pattern.
The cholesteric liquid crystal portion 2601 reflects the right-circularly polarized light and the cholesteric liquid crystal portion 2602 reflects the left-circularly polarized light. However, the cholesteric liquid crystal portion 2601 can reflect the left-circularly polarized light and the cholesteric liquid crystal portion 2602 can reflect the right-circularly polarized light.
In a dark place, a screen factor of light emitted from the luminous layer 261 is largely improved, and the display pattern becomes darker. As a result, contrast between the display pattern and other portions can be increased further, thereby improving the visibility. In this case, different from the configuration of the liquid crystal display shown in
A method by which the IC card is supplied with light energy from the reader/writer is explained next.
According to the fourth embodiment, the luminous layer 261 that accumulates light energy and emits light by using the energy is provided, and the light emitted from the luminous layer 261 is irradiated to the cholesteric liquid crystal portion. Furthermore, the reflecting dominant wavelength of light emitted from the luminous layer 261 is substantially equal to the reflecting dominant wavelength of light reflected from the cholesteric liquid crystal portions 230, 250, 2601, and 2602 in the planar state. As a result, an IC card equipped with a liquid crystal display having high visibility even in a dark place can be realized.
In the fourth embodiment, the luminous layer is provided in the liquid crystal display using the cholesteric liquid crystals. However, the present invention is not limited thereto, and the luminous layer can be provided in other display methods, such as the electrophoretic method and the twist ball method.
In the fourth embodiment, the luminous layer is provided in a liquid crystal display having two cholesteric liquid crystal portions reflecting light of a different dominant wavelength. However, the present invention is not limited thereto, and the luminous layer can be provided when there are three or more cholesteric liquid crystal portions, or when there is only one cholesteric liquid crystal portion.
In the first to the fourth embodiments, to shift the orientation of the liquid crystal molecules in the cholesteric liquid crystal portions to the planar state or to the focal conic state, an AC pulse voltage in which the polarity is reversed in positive and negative and the absolute value of amplitude is the same is used. However, in the liquid crystal display equipped in the IC card, since rewriting frequency of the display pattern is fewer than in the liquid crystal display used for other applications, a voltage waveform different from that of the AC pulse voltage can be used. In the fifth embodiment, therefore, a case that a voltage waveform optimized for an application to the IC card is used to drive the liquid crystal display is explained.
The AC pulse voltage in which the polarity is reversed in positive and negative and the absolute value of amplitude is the same is explained first.
The reason why the pulse width of the AC pulse voltage is set to about 50 milliseconds is that it is necessary to apply a pulse voltage having a pulse width of about 50 milliseconds or more to shift the state to the planar state or to the focal conic state sufficiently, although it depends on the material.
Thus, it is to prevent deterioration due to the ionic substance in the cholesteric liquid crystals being polarized why the AC pulse voltage in which the polarity is reversed in positive and negative and the absolute value of amplitude is the same is applied. However, to apply the AC pulse voltage as shown in
Furthermore, as shown in
The waveform shown in
For example, in a liquid crystal display like a Super Twisted Nematic (STN) display, if it is assumed that display is performed in average for one hour per day with 30 frames per second, the pulse voltage is applied about 40,000,000 times per one pixel in one year. On the other hand, the display rewriting frequency of the IC card is assumed to be about 10,000 times in a whole period during which the IC card is used, and the display is not rewritten at a frequency of 30 frames per second as in the liquid crystal display. Accordingly, even the method of using the DC pulse voltage as shown in
In
In
In
Thus, by alternately changing the polarity of the DC pulse voltage to be applied according to the rewriting frequency, the breakdown voltage margin of the voltage driving circuit can be reduced, and deterioration due to polarization of the cholesteric liquid crystals can be suppressed.
The rewriting frequency is stored in the storage unit included in the IC card, or in the storage unit included in the reader/writer, which communicates with the IC card. When the IC card stores the rewriting frequency, the reader/writer reads the rewriting frequency data from the IC card, and for example, when the rewriting frequency is even, radio wave for controlling such that the display is rewritten by a DC pulse voltage having the positive polarity is emitted. When the rewriting frequency is odd, radio wave for controlling such that the display is rewritten by a DC pulse voltage having the negative polarity is emitted. Thereafter, the IC card increments the rewriting frequency stored in the storage unit by 1.
When the reader/writer stores the rewriting frequency, rewriting frequencies of many and unspecified IC cards are accumulated and stored. In this case, there is the possibility that the DC pulse voltage having the same polarity is applied to the same IC card twice continuously. However, from a long-term point of view, since the probability that the DC pulse voltage having the positive polarity is applied and the probability that the DC pulse voltage having the negative polarity is applied are fifty-fifty, there is no practical problem.
Furthermore, if the method of using the pulse waveform shown in
Thus, by applying the DC pulse voltage having a different polarity in two stages, to reset the cholesteric liquid crystals and form the display pattern, the breakdown voltage margin of the voltage driving circuit can be reduced, and deterioration due to polarization of the cholesteric liquid crystals can be suppressed.
As explained above, in the fifth embodiment, rewriting of display is performed by using a DC pulse voltage, an AC pulse voltage having an interval during which the voltage is not applied at the time of reversing the polarity, or an AC pulse voltage having different amplitude in the positive and negative polarities, using the fact that the rewriting frequency of the display pattern on the liquid crystal display of the IC card is low. As a result, the breakdown voltage margin of the voltage driving circuit can be reduced, and deterioration due to polarization of the cholesteric liquid crystals can be suppressed.
In the fifth embodiment, the liquid crystal display is applied to the IC card, however, the present invention is not limited thereto, and the similar technique can be applied to the electronic paper technology for other applications. Furthermore, the number of cholesteric liquid crystal layers constituting the liquid crystal display can be plural so that display can be made in a plurality of colors as shown in the first or the second embodiment, or can be single.
In the first to the fifth embodiment, when the display is rewritten by shifting the state of the cholesteric liquid crystal layer from the planar state to the focal conic state, or from the focal conic state to the planar state, the display is rewritten by applying a voltage only once. However, since an application of voltage pulse in a plurality of times makes the state transition more complete, voltage can be applied to the cholesteric liquid crystal layer in a plurality of times. In a sixth embodiment, therefore, a case that predetermined display is made by applying a voltage to the cholesteric liquid crystal layer in a plurality of times is explained.
A relationship between voltage and temperature required for shifting the state of the cholesteric liquid crystals is first explained. Generally, in the cholesteric liquid crystals, as the temperature becomes lower, the viscosity increases, and the applied voltage required for shifting the state increases.
As shown in
When the cholesteric liquid crystals are used for the liquid crystal display of the IC card or the like, it is necessary to form a thin cholesteric liquid crystal layer. When the cholesteric liquid crystal layer is thin, a voltage required for changing the state becomes low as a whole, and the voltage margin for shifting to the focal conic state as shown in
When the pulse Width is small, there are problems such as afterimage and a decrease in the display contrast. For example, in
When the state is shifted to the planar state, there can be a case that the applied voltage value is not sufficient to shift the state to the planar state completely. Therefore, when the light is reflected by the cholesteric liquid crystal layer, a part of the light is transmitted by a part of the cholesteric liquid crystals in the focal conic state, and hence, the lightness is not increased, and display contrast can decrease.
This problem can be improved by applying the voltage in a plurality of times.
A dotted line 361 indicates a case that the state of the cholesteric liquid crystal layer is shifted from the planar state to the focal conic state by applying a voltage. In this case, with the first application of voltage, the lightness of reflected light reflected by the cholesteric liquid crystal layer is Y=0.03. With the second application of voltage, the lightness decreases to Y=0.02. Furthermore, the contrast is increased from 10 to 15.
Thus, by increasing the number of voltage application, the lightness can be increased and the contract is further improved in the planar state, or the lightness decreased, and the contract is further improved in the focal conic state.
Initialization of the cholesteric liquid crystal layer when display is made on the liquid crystal display is explained next.
T0 is referred to as reset time, during which the reader/writer resets the influence of previous transmission of power, and during which power is not supplied to the IC card. T1 is referred to as maximum power rise time, which is required for the power to rise up to a value required for the IC card to perform processing. T2 is referred to as data transmission preparation time, which is time required for preparing communication for stabilizing the IC card, during which the reader/writer transmits a signal having a logical level of 1 to the IC card. T3 is referred to as stable logic time, during which the reader/writer transmits the signal having the logical level of 1 to the IC card, and the IC card transmits this signal to the reader/writer. T4 is referred to as maximum ATR transmission time, which is a time zone for the IC card to start transmission of Answer To Reset (ATR) for defining a transfer protocol to the reader/writer. However, the IC card can start the transmission of ATR during the data transmission preparation time at T2.
According to the standard of ISO/IEC 10536, T0 is defined as time equal to or more than 8 milliseconds, T1 as time equal to or less than 0.2 milliseconds, T2 as 8 milliseconds, T3 as 2 milliseconds, and T4 as 30 milliseconds.
Since the time from time T2 when the power of the IC card rises completely till startup of the operating system that controls the processing of the IC card finishes is normally about 100 milliseconds, the AC pulse voltage having a pulse width of 50 milliseconds as explained with reference to
At time T2, the IC card receives a control signal for initializing the display pattern, together with a signal of logical level 1 transmitted from the reader/writer. A voltage is then applied to the cholesteric liquid crystal layer by using a voltage converted from the received radio wave, to initialize the display pattern. After initialization of the display pattern has finished, information transfer is started between the IC card and the reader/writer, and the second application of voltage is performed, to display predetermined data.
The pulse width of the AC pulse voltage to be applied for initialization can be about 50 milliseconds. However, as explained with reference to
According to the method for setting cholesteric liquid crystal layer to the planar state, a voltage for setting the cholesteric liquid crystal layer to the planar state is applied at the timing shown in (d) in
According to the method for making cholesteric liquid crystal layer to the focal conic state, a voltage for setting the cholesteric liquid crystal layer to the focal conic state is applied at the timing shown in (d) in
As explained above, in the sixth embodiment, initialization of the display pattern is started by achieving synchronization with the predetermined signal issued during initialization of communication with the reader/writer. Accordingly, the limited driving time of the IC card can be effectively used to initialize the display pattern.
Furthermore, initialization of the display pattern is executed by applying the voltage for setting the state of the cholesteric liquid crystals to the planar state or the focal conic state, and at the time of displaying the predetermined data, the voltage for setting the cholesteric liquid crystals to the same state as the state at the time of initialization is applied again to the display segments, which maintain the state of the cholesteric liquid crystals set by the initialization. Accordingly, the display contrast can be further increased.
Furthermore, in the sixth embodiment, the IC card with the liquid crystal display using the cholesteric liquid crystals starts initialization of the display pattern by achieving synchronization with the predetermined signal issued during initialization of communication with the reader/writer. However, the present invention is not limited thereto, and similar processing can be performed in other display methods, such as the electrophoretic method and the twist ball method.
The number of the cholesteric liquid crystal layers constituting the liquid crystal display can be plural so that display can be made in a plurality of colors as shown in the first or the second embodiment, or can be single.
In the first to the sixth embodiments, data communication is performed between the IC card and the reader/writer. However, the IC card can be constituted so as to notify the user of the IC card of the completion of communication, when the communication has finished. In a seventh embodiment, therefore, a case that the IC card notifies that the data communication with the reader/writer has finished is explained.
A notification process for notifying the user of completion of data communication by changing the display on the liquid crystal display is explained first.
For example, on the liquid crystal display having upper and lower two cholesteric liquid crystal layers as shown in
When the communication with the reader/writer has finished normally, by maintaining the upper layer in the planar state, and alternately changing the state of the lower layer between the planar state and the homeotropic state, display 390 with cyan, which is a color mixture of green and blue, and display 392 with green can be changed over. Accordingly, the user can be notified immediately and clearly that the communication has normally finished.
When the communication with the reader/writer has not finished normally, by maintaining the lower layer in the focal conic state, and alternately changing the state of the upper layer between the planar state and the homeotropic state, display 394 with green and display 396 for displaying nothing can be changed over. As a result, the user can be notified that the communication has not normally finished immediately and clearly. Particularly, in the case of a non-contact type IC card, when the IC card is away from the reader/writer, communication can be unstable. Therefore, by constituting the liquid crystal display of the IC card as described above, the convenience of the IC card can be further improved.
The IC card determines that an abnormality has occurred when data from the reader/writer is not received for predetermined time. The card control IC that controls the IC card generates an interruption signal, and the liquid crystal display control IC controls so as to perform a flash display as shown in
When the reader/writer supplies driving power to the IC card, as the radio wave for supplying power to the IC card attenuates, the voltage value to be applied to the cholesteric liquid crystal layer in the liquid crystal display decreases.
That is, in the case of
In the case of
When the communication has normally finished, as the AC pulse voltage attenuates, the display of the IC card changes from the flash display to the normal display. Furthermore, when the communication has not finished normally, as the AC pulse voltage attenuates, the display of the IC card changes from the flash display to the non-display state. Therefore, the driving circuit for returning the display state of the IC card to the normal state is not required, thereby enabling reduction in the production cost.
Completion of communication is notified by flashing the liquid crystal display. However, the user can be notified of the completion of communication by generating sound by the IC card.
The vibrating film 410 vibrates to radiate sound, and the vibrator 411 vibrates the vibrating film 410 to generate sound. The polymer films 4121 and 4122 are, respectively, a transparent film substrate on the surface of which an electrode is formed. The cholesteric liquid crystal portion 413 is a liquid crystal display unit as shown in the first to the sixth embodiments. The sealing materials 4141 to 4144 are for fixing the polymer films 4121 and 4122 and the cholesteric liquid crystal portion 413. The wall units 4151 to 4153 are for fixing respective units from the side.
In this case, if the vibrating film 410 itself is formed as a substrate for the cholesteric liquid crystal portion 413, the orientation of the cholesteric liquid crystals changes due to the vibration of the vibrating film 410. Therefore, the polymer films 4121 and 4122 are used as the substrate for the cholesteric liquid crystal portion 413.
When the communication has finished normally, the vibrator 411 vibrates the vibrating film 410 at a high frequency, to generate high pitched sound, and when the communication has not finished normally, the vibrator 411 vibrates the vibrating film 410 at a low frequency, to generate low pitched sound. As a result, the user can be clearly notified whether the communication has finished normally by a different sound.
The IC card then checks whether the communication has finished normally (step S422). When the communication has not finished normally (step S422, No), as explained with reference to
In the flowchart, the user is notified whether the communication has finished normally by the sound or the flash display. However, the sound and the flash display can be used together. Regarding the flash display, the flashing time and display color can be optionally selected so as to enable clear notification to the user. Furthermore, as for the output sound, optional expression such as volume of the sound, high or low pitch, pattern, and rhythm can be selected.
As explained above, according to the seventh embodiment, when transmission of data to the reader/writer or reception of data from the reader/writer has finished, the display is flashed or sound is generated to inform the user of completion of communication. As a result, the user can easily confirm whether the communication with the reader/writer has finished without any problem, thereby improving the convenience of the IC card.
In the seventh embodiment, the IC card with a liquid crystal display using the cholesteric liquid crystals is used. However, the number of the cholesteric liquid crystals constituting the liquid crystal display can be plural so that display can be made in a plurality of colors as shown in the first or the second embodiment, or can be single.
Furthermore, an application of the technique explained in the seventh embodiment is not limited to the liquid crystal display using the cholesteric liquid crystals, and the similar technique can be applied to the liquid crystal display using other display methods such as the electrophoretic method and the twist ball method. Furthermore, the similar technique can be applied to the electronic paper technology for other applications in which liquid crystal display is performed by a simple matrix method or the like.
In the first to the seventh embodiments, the orientation of the liquid crystal molecules in the cholesteric liquid crystal layer is changed, so as to reflect or transmit incident light, thereby displaying predetermined data. However, the liquid crystal display can have a function as a thermometer by using the temperature dependency of the wavelength of reflected light held by the cholesteric liquid crystals. In an eighth embodiment, therefore, a case that the liquid crystal display also functions as the thermometer by using the temperature dependency of the wavelength of reflected light held by the cholesteric liquid crystals is explained.
The temperature dependency of the wavelength of reflected light held by the cholesteric liquid crystals is explained first. As shown in
The cholesteric liquid crystals include two types, that is, the one has a long pitch of the helical structure, and the other has a short pitch, when the temperature becomes high. When the pitch of the helical structure becomes long, the wavelength of reflected light shifts toward a red wavelength range (toward the long wavelength side), and when the pitch of the helical structure becomes short, the wavelength of reflected light shifts toward a blue wavelength range (toward the short wavelength side). That is, by using such a relationship between the color of the reflected light and temperature, the liquid crystal display having the cholesteric liquid crystal layers can be used as the thermometer.
The display state when the liquid crystal display formed of the cholesteric liquid crystals is used as the thermometer is explained next.
This is because as the temperature becomes higher, the wavelength of the reflected light shifts toward the red wavelength range, which is a warm color, and as the temperature becomes lower, the wavelength of the reflected light shifts toward the blue wavelength range, which is a cool color, which matches human feelings. However, even when cholesteric liquid crystals where as the temperature becomes higher, the wavelength of the reflected light shifts to the blue wavelength range side, and as the temperature becomes lower, the wavelength of the reflected light shifts to the red wavelength range side are used, there is no problem in measuring the temperature.
When the cholesteric liquid crystals are used as the thermometer, it is desired to reflect light in a visible radiation range in a wide temperature range. Specifically, the cholesteric liquid crystals are adjusted so that the dominant wavelength of the reflected light is in a range of about 400 to 700 nanometers, in a temperature range from −20° C. to 80° C. Particularly, it is desired that the dominant wavelength of the reflected light be about 400 nanometers at −20° C., and the dominant wavelength of the reflected light be about 700 nanometers at 80° C. Furthermore, if the cholesteric liquid crystals are put in strong direct sunlight, the cholesteric liquid crystals deteriorate due to ultraviolet rays included in the direct sunlight. Therefore, an ultraviolet cut film can be put on the surface of the liquid crystal display.
According to the eighth embodiment, since the temperature dependency of the wavelength of reflected light held by the cholesteric liquid crystals is used, to give the function as the thermometer to the liquid crystal display, multifunctional IC card can be realized.
In the eighth embodiment, the liquid crystal display that displays data has the function as the thermometer, however, the present invention is not limited thereto, and a cholesteric liquid crystal portion that functions as the thermometer can be provided separately from the liquid crystal display that displays data. Furthermore, the number of the cholesteric liquid crystal layer constituting the liquid crystal display can be plural so that display can be made in a plurality of colors as shown in the first or the second embodiment, or can be single.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP03/11307 | Sep 2003 | US |
| Child | 11366737 | Mar 2006 | US |
