JP2008032875A - Liquid crystal device and electronic device - Google Patents

Abstract

For example, the image quality of a reflective double-sided display liquid crystal device is improved.
A polarizing film 40f1 converts incident light If0 into linearly polarized light. The retardation film 40f2 converts the linearly polarized light emitted from the polarizing film 40f1 into first circularly polarized light If1, which is right circularly polarized light whose polarization axis rotates rightward along the traveling direction. The first circularly polarized light If1 passes through the liquid crystal layer 50 and reaches the retardation film 40f2 as reflected light Rf2 reflected by the light reflecting film 19f. The polarization axis of the reflected light Rf2 is converted by the refractive index anisotropy of the retardation film 40f2. The polarizing film 40f1 transmits the reflected light Rf1 transmitted through the retardation film 40f2 to the front side as transmitted light Tr. Therefore, the pixel 75f can display an image by the transmitted light Tr.
[Selection] Figure 6

Description

  The present invention relates to a technical field of a liquid crystal device such as a reflective liquid crystal display device capable of double-sided display and an electronic device such as a portable electronic device including such a liquid crystal device.

  As an example of this type of liquid crystal device, a double-sided display type liquid crystal device is known as disclosed in Patent Documents 1 and 2. In such a double-sided display type liquid crystal device, a TFT array substrate on which a TFT (Thin Film Transistor) as a pixel switching element is formed includes a region where a transparent pixel electrode is formed on the substrate surface, and a light reflecting layer. And a region where a transparent pixel electrode is formed. The counter substrate disposed so as to face the TFT array substrate includes a light reflection film partially provided on a surface of the counter substrate facing the TFT array substrate, a pixel electrode provided on the TFT array substrate, Opposite counter electrodes and a color filter layer are provided. In the double-sided display type liquid crystal device disclosed in Patent Documents 1 and 2, the TFT array substrate and the counter substrate are arranged so that the light reflecting films formed on the TFT array substrate and the counter substrate do not overlap each other. Thus, double-sided reflection display using reflected light reflected by each light reflecting film is made possible. More specifically, the double-sided reflection type liquid crystal device disclosed in Patent Documents 1 and 1 displays an image in the display area on the counter substrate side by the reflected light reflected by the light reflecting film formed on the TFT array substrate. At the same time, an image is displayed in the display area on the TFT array substrate side by the reflected light reflected by the light reflecting film formed on the counter substrate.

JP-A-2005-301276 JP 2004-117720 A

  However, in the double-sided display type liquid crystal device disclosed in Patent Documents 1 and 2, the light incident from the upper side of the counter substrate is reflected on the upper side of the counter substrate by the back surface of the light reflecting film disposed on the counter substrate side. . Therefore, the reflected light reflected on the back surface of the light reflecting film formed on the counter substrate is displayed on the image displayed on the upper display area of the counter substrate by the reflected light reflected by the light reflecting film formed on the TFT array substrate. Therefore, it is difficult to improve the quality of the image displayed in the display area on the upper side of the counter substrate. More specifically, when viewed from the upper side of the counter substrate, the back surface side of the light reflecting film formed on the counter substrate is a region where black display is originally performed, but the black display is performed by the reflected light from the back surface. There is a problem that an image cannot be displayed with high contrast because the level is lowered.

  Therefore, the present invention has been made in view of the above-described problems. For example, a double-sided display type liquid crystal device capable of displaying a high-quality image with high contrast, and a portable type including such a liquid crystal device. It is an object to provide an electronic device such as an electronic device.

  In order to solve the above problems, a liquid crystal device according to the present invention includes a first substrate, a second substrate disposed opposite to the first substrate, and a liquid crystal layer sandwiched between the first substrate and the second substrate. A first polarizing plate disposed on the second substrate, a first light reflecting film provided on the first substrate, and a liquid crystal layer side of the second substrate relative to the first polarizing plate. The first light reflecting film and the second light reflecting film are overlapped with the first polarizing plate and are incident on the first polarizing plate from the opposite side of the liquid crystal layer. The first incident light is polarized to the first circularly polarized light and emitted toward the first light reflecting film and the second light reflecting film, and the first circularly polarized light is reflected by the second light reflecting film. The reflected light generated by the absorption is absorbed by the first polarizing plate.

  The liquid crystal device according to the present invention is, for example, a double-sided display type liquid crystal device, the first region is a pixel constituting a front side display region, and the second region is a pixel constituting a rear side display region. . In the liquid crystal device according to the present invention, during the operation, in the first region, for example, liquid crystal interposed between the first pixel electrode which is a transparent electrode such as ITO (Indium Tin Oxide) and the counter electrode is present in the first pixel electrode. It is driven by a driving voltage corresponding to the potential difference between the pixel electrode potential corresponding to the supplied image signal and the counter electrode potential supplied to the counter electrode. Similarly, in the second region, the liquid crystal interposed between the second pixel electrode, which is a transparent electrode such as ITO, and the counter electrode causes the pixel electrode potential corresponding to the image signal supplied to the second pixel electrode and the counter electrode to Driven by a drive voltage corresponding to the potential difference from the supplied counter electrode potential. Thereby, double-sided display in which an image is displayed on each of the front side and the rear side becomes possible.

  The first light reflecting film has a single layer structure or a multilayer structure made of a metal film such as Al, and is provided between the first substrate and the liquid crystal layer in the first region. The second light reflecting film has the same configuration as the first light reflecting film, and is provided between the second substrate and the liquid crystal layer in the second region.

  The first polarizing plate overlaps the first region and the second region, and is disposed on the opposite side of the liquid crystal layer with respect to the second substrate. Here, the opposite side of the liquid crystal layer with respect to the second substrate is, for example, the side having one display surface (front side display surface) of the double-sided display type liquid crystal device, and conversely with the first substrate as a reference. The opposite side of the liquid crystal layer is the side having the other display surface (rear display surface).

  The first polarizing plate converts the first circularly polarized light generated by polarizing the first incident light incident on the first polarizing plate from the opposite side of the second substrate with respect to the first polarizing plate as the first light reflecting film and the first polarizing plate. The light is emitted toward each of the two light reflecting films. The first incident light is, for example, external light that enters the first polarizing plate from the opposite side of the second substrate with reference to the first polarizing plate. The first polarizing plate selectively transmits reflected light generated by the first circularly polarized light reflected by the first light reflecting film to the opposite side of the second substrate in the first region. The first circularly polarized light reaches the first light reflecting film from the first polarizing plate via the liquid crystal layer, and is reflected from the first light reflecting film as reflected light to the first polarizing plate via the liquid crystal layer. The reflected light reaching the first polarizing plate is transmitted through the first polarizing plate to the opposite side of the liquid crystal layer with reference to the second substrate, more specifically, for example, to the front side of the liquid crystal device. An image is displayed in the first region in response to light. That is, the first region is a front-side pixel that is the opposite side of the liquid crystal layer with respect to the second substrate.

  The first polarizing plate absorbs reflected light in which the first circularly polarized light is reflected by the second light reflecting film in the second region. Thereby, in the second region, the reflected light reflected by the second light reflecting film is not emitted to the front side which is the opposite side of the liquid crystal layer with respect to the second substrate. Therefore, the reflected light is emitted only from the first region to the front side, which is the opposite side of the liquid crystal layer with respect to the second substrate.

  On the other hand, the light reflected by the second light reflecting film is emitted on the opposite side of the liquid crystal layer with respect to the first substrate, that is, on the rear side, and an image on the rear side is displayed. Therefore, the liquid crystal device according to the present invention can be applied to a double-sided reflection type liquid crystal display device capable of displaying images on both the front side and the rear side.

  According to the liquid crystal device according to the present invention, light is not emitted from the second region on the opposite side of the liquid crystal layer with respect to the second substrate, for example, on the front side. Since the reflected light from the back surface is not added to the image displayed toward the front side, it is possible to display an image with high contrast on the front side.

  In one aspect of the liquid crystal device according to the present invention, a first pixel electrode provided between the first substrate and the liquid crystal layer and overlapping the first light reflecting film, the first substrate and the liquid crystal layer, Provided between the second substrate and the liquid crystal layer so as to be opposed to the second pixel electrode that overlaps the second light reflecting film and the first pixel electrode and the second pixel electrode. And the reflected light generated when the first circularly polarized light is reflected by the first light reflecting film in a state where a voltage is applied to the liquid crystal layer. May be transmitted.

  According to this aspect, an image can be displayed by the reflected light transmitted through the first polarizing plate.

  In one aspect of the liquid crystal device according to the present invention, the first polarizing plate includes a first polarizing film that converts the first incident light into linearly polarized light, and linearly polarized light emitted from the first polarizing film. You may provide with the 1st phase difference film converted into 1 circularly polarized light.

  According to this aspect, the first incident light can be converted into the first circularly polarized light.

  In this aspect, the first retardation film may be a quarter-wave plate whose retardation value for light having a wavelength of 450 nm is smaller than the retardation value for light having a wavelength of 590 nm.

  According to this aspect, the first incident light can be converted into the first circularly polarized light in the visible light range, that is, in a wide wavelength band where the wavelength of light is 380 nm (blue) to 780 nm (red). More specifically, since the retardation value of the retardation film has wavelength dependency with respect to light, the phase of only long-wavelength light (for example, red light having a wavelength of 780 nm) is ¼. If the retardation film is designed to shift the wavelength, the wavelength shift amount of light having other wavelengths cannot be reduced to ¼ wavelength. Therefore, by adopting a quarter wavelength plate that has a retardation value for light having a wavelength of 450 nm as a first retardation film that is smaller than the retardation value for light having a wavelength of 590 nm, light included in a wide wavelength range. The phase can be shifted by a quarter wavelength. In addition, according to such a first retardation film, reflected light generated by the first circularly polarized light being reflected by the second light reflecting film can be absorbed within the wavelength range of visible light.

  In another aspect of the liquid crystal device according to the present invention, the first retardation film may be configured by combining a quarter wavelength plate and a half wavelength plate.

  According to this aspect, it is possible to absorb only the reflected light reflected by the second light reflecting film and transmit the reflected light reflected by the first light reflecting film.

  In another aspect of the liquid crystal device according to the present invention, a first light source provided on the opposite side of the second substrate may be provided.

  According to this aspect, the light emitted from the first light source enters the first polarizing plate as the first incident light, for example, via the light guide. Accordingly, the liquid crystal device can display an image on the front side, which is the opposite side of the liquid crystal layer, with respect to the second substrate even in a situation where there is no external light (for example, at night and indoors).

  In another aspect of the liquid crystal device according to the present invention, the first light reflecting film and the second light reflecting film are overlapped with each other, and the first substrate is opposite to the liquid crystal layer with respect to the first light reflecting film. The second polarizing plate further includes a second polarizing plate, and second incident light incident on the second polarizing plate from the opposite side of the liquid crystal layer is polarized into second circularly polarized light and the first light reflecting film. The reflected light that is emitted toward the second light reflecting film and is generated when the second circularly polarized light is reflected by the first light reflecting film may be absorbed by the second polarizing plate.

  According to this aspect, it is possible to increase the contrast of an image displayed on the opposite side of the liquid crystal layer, for example, on the rear side with respect to the first substrate. More specifically, in the same manner as the first polarizing plate, the second polarizing plate reflects the reflected light generated by the second circularly polarized light reflected by the second light reflecting film on the liquid crystal layer with reference to the first substrate. The reflected light reflected from the back surface of the first light reflecting film is absorbed so as to be transmitted from the second region toward the rear side, which is the opposite side, and so that the reflected light is not emitted from the first region toward the rear side. That is, in this aspect, the second region is a pixel that displays an image on the rear side. Therefore, according to the second polarizing plate, since the reflected light reflected by the back surface of the first light reflecting film is not emitted to the rear side, it is displayed on the rear side that is the opposite side of the liquid crystal layer with respect to the first substrate. The contrast of the image can be increased, and a high-quality image can be displayed on each of the front side and the rear side.

  In this aspect, the second polarizing plate includes a second polarizing film that converts the second incident light into linearly polarized light, and a second polarizing film that converts the linearly polarized light emitted from the second polarizing film into the second circularly polarized light. And a retardation film.

  According to this aspect, similarly to the first polarizing plate, the second incident light can be converted into the second circularly polarized light.

  In this aspect, the second retardation film may be a quarter-wave plate whose retardation value for light having a wavelength of 450 nm is smaller than the retardation value for light having a wavelength of 590 nm.

  According to this aspect, similarly to the first retardation film, the second retardation film is a quarter wavelength plate whose retardation value for light having a wavelength of 450 nm is smaller than the retardation value for light having a wavelength of 590 nm. By adopting, it is possible to shift the phase by a quarter wavelength with respect to light included in a wide wavelength range. In addition, according to such a second retardation film, the reflected light generated by the second circularly polarized light being reflected by the first light reflecting film can be absorbed within the wavelength range of visible light.

  In another aspect of the liquid crystal device according to the present invention, the second retardation film may be configured by combining a quarter wavelength plate and a half wavelength plate.

  According to this aspect, it is possible to absorb only the reflected light reflected by the first light reflecting film and transmit the reflected light reflected by the second light reflecting film.

  In another aspect of the liquid crystal device according to the present invention, a second light source provided on the opposite side of the first substrate may be provided.

  According to this aspect, the light emitted from the second light source enters the second polarizing plate as the second incident light, for example, via the light guide. Accordingly, the liquid crystal device can display an image on the rear side opposite to the liquid crystal layer with respect to the first substrate even in a situation where there is no external light (for example, at night and indoors).

  In another aspect of the liquid crystal device according to the present invention, a color filter that overlaps the first light reflection film and the second light reflection film may be provided.

  According to this aspect, an image can be displayed by light having a predetermined wavelength.

  In another aspect of the liquid crystal device according to the present invention, a light shielding film provided on the second substrate and covering a region between the first pixel electrode and the second pixel electrode may be provided.

  According to this aspect, a region extending between the first pixel electrode and the second pixel electrode on the first substrate, for example, a region provided with an element such as a pixel switching TFT can be shielded by the light shielding film, and the contrast is high. Image display is possible.

  In another aspect of the liquid crystal device according to the present invention, the second light reflecting film may overlap a part of a region between the first pixel electrode and the second pixel electrode.

  According to this aspect, without providing a light-shielding film separately from the first and second light reflecting films, the first region and the second region can be separated from the opening region, that is, the region excluding the region where light is substantially transmitted. Transmission of light can be reduced, and the contrast of the displayed image can be increased.

  In order to solve the above problems, an electronic device according to the present invention includes the above-described liquid crystal device according to the present invention.

  According to the electronic apparatus according to the present invention, since the electro-optical device according to the present invention described above is included, a cellular phone, an electronic notebook, a word processor, a viewfinder type, or a monitor direct view type capable of high-quality display. Various electronic devices such as a video tape recorder, a workstation, a videophone, a POS terminal, and a touch panel can be realized. In addition, as an electronic apparatus according to the present invention, for example, an electrophoretic device such as electronic paper can be realized.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

  Hereinafter, a liquid crystal device and an electronic apparatus according to the present invention will be described with reference to the drawings.

<1: Liquid crystal device>
<1-1: Overall Configuration of Liquid Crystal Device>
First, an embodiment of a liquid crystal device according to the present invention will be described with reference to FIGS. FIG. 1 is a plan view of the liquid crystal device viewed from the counter substrate side together with each component formed on the TFT array substrate, and FIG. 2 is a plan view of the liquid crystal device viewed from the TFT array substrate side. In the present embodiment, as an example of a liquid crystal device, a TFT active matrix driving type liquid crystal device with a built-in driving circuit is taken as an example. In the following, with the taught liquid crystal layers of the TFT array substrate 10 and the counter substrate 20 as a reference, the image display region 10f side is referred to as a front side, and the image display region 10r side is referred to as a rear side. Moreover, in FIG.1 and FIG.2, illustration of the circularly-polarizing plates 40f and 40r mentioned later is abbreviate | omitted.

  In FIG. 1, in the liquid crystal device 1, a TFT array substrate 10 and a counter substrate 20 are disposed to face each other. A liquid crystal layer is sealed between the TFT array substrate 10 and the counter substrate 20, and the TFT array substrate 10 and the counter substrate 20 are positioned around an image display region 10f that is a pixel region in which a plurality of pixel portions are provided. They are bonded to each other by a sealing material 52 provided in the sealing area. During the operation of the liquid crystal device 1, an image is displayed on the front side through the image display area 10f.

  The sealing material 52 is made of, for example, an ultraviolet curable resin, a thermosetting resin, or the like for bonding the two substrates, and is applied on the TFT array substrate 10 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like. It is. In the sealing material 52, a gap material such as glass fiber or glass beads for dispersing the distance between the TFT array substrate 10 and the counter substrate 20 (inter-substrate gap) to a predetermined value is dispersed.

  A light-shielding frame light-shielding film 53 that defines the frame area of the image display area 10a is provided on the counter substrate 20 side in parallel with the inside of the seal area where the sealing material 52 is disposed. However, part or all of the frame light shielding film 53 may be provided as a built-in light shielding film on the TFT array substrate 10 side. There is a peripheral area located around the image display area 10a. In other words, particularly in the present embodiment, when viewed from the center of the TFT array substrate 10, the distance from the frame light shielding film 53 is defined as the peripheral region.

  A data line driving circuit 101 and an external circuit connection terminal 102 are provided along one side of the TFT array substrate 10 in a region located outside the sealing region in which the sealing material 52 is disposed in the peripheral region. The scanning line driving circuit 104 is provided along two sides adjacent to the one side so as to be covered with the frame light shielding film 53. Further, in order to connect the two scanning line driving circuits 104 provided on both sides of the image display area 10 a in this way, a plurality of the pixel lines are covered along the remaining side of the TFT array substrate 10 and covered with the frame light shielding film 53. Wiring 105 is provided.

  Vertical conductive members 106 functioning as vertical conductive terminals between the two substrates are disposed at the four corners of the counter substrate 20. On the other hand, the TFT array substrate 10 is provided with vertical conduction terminals in a region facing these corner portions. Thus, electrical conduction can be established between the TFT array substrate 10 and the counter substrate 20.

  In FIG. 2, an image display area 10r is provided on the back side of the image display area 10f. Therefore, the liquid crystal device 1 is a double-sided display type liquid crystal device capable of displaying an image on each of the image display areas 10f and 10r on both sides of the device.

<1-2: Configuration of Image Display Area>
Next, a detailed configuration of the image display areas 10f and 10r will be described with reference to FIG. FIG. 3 is an enlarged view showing a part C of the liquid crystal device 1 shown in FIGS. 1 and 2 in an enlarged manner. For convenience of explanation, the pixels 75f and 75r provided on both surfaces of the liquid crystal device 1 are shown on the same plane of the paper.

  In FIG. 3, the pixels 75f and the pixels 75r are alternately arranged for each row. The plurality of pixels 75f is an area through which light subjected to gradation control by the liquid crystal layer for displaying an image on the front side is transmitted, and constitutes an image display area 10f. The plurality of pixels 75r is a region through which light subjected to gradation control by the liquid crystal layer in order to display an image on the rear side is transmitted, and constitutes an image display region 10r.

<1-3: Electrical Connection Configuration of Each Part in Image Display Area>
Next, an electrical connection configuration of each part in the image display areas 10f and 10r will be described with reference to FIG. FIG. 4 is an equivalent circuit of various elements, wirings, and the like in a plurality of pixels 75f and 75r formed in a matrix that constitutes the image display regions 10f and 10r of the liquid crystal device 1, respectively.

  In FIG. 4, a pixel electrode 9 f that is an example of a “first pixel electrode”, a TFT 30 f that is a pixel switching element, and a storage capacitor 70 are formed in a pixel 75 f that forms the image display region 10 f of the liquid crystal device 1. Yes. The data line 6a is electrically connected to the source of the TFT 30f. The scanning line 3f is electrically connected to the gate of the TFT 30f. In the pixel 75r constituting the image display region 10r of the liquid crystal device 1, a pixel electrode 9r which is an example of a “second pixel electrode”, a TFT 30r which is a pixel switching element, and a storage capacitor 70 are formed. The data line 6a is electrically connected to the source of the TFT 30r. The scanning line 3r is electrically connected to the gate of the TFT 30r.

  The TFT 30f is electrically connected to the pixel electrode 9f, and performs switching control of the pixel electrode 9f when the liquid crystal device 1 operates. The image signals S1, S2,..., Sn to be written to the data lines 6a may be supplied line-sequentially in this order, or may be supplied for each group to a plurality of adjacent data lines 6a. May be. Similarly, the TFT 30r is electrically connected to the pixel electrode 9r, and performs switching control of the pixel electrode 9r when the liquid crystal device 1 operates.

  The liquid crystal device 1 applies the scanning signals Gf1, Gf2,..., Gfm, Gr1, Gr2,..., Grm in a line-sequential manner to the scanning lines 3f and 3r in a predetermined timing. It is configured. The pixel electrode 9f is electrically connected to the drain of the TFT 30f. By closing the switch of the TFT 30f, which is a switching element, for a certain period, the image signals S1, S2,. Sn is written at a predetermined timing. A predetermined level of image signals S1, S2,..., Sn written in the liquid crystal as an example of the electro-optical material via the pixel electrode 9f is held for a certain period with the counter electrode formed on the counter substrate. The Similarly, the pixel electrode 9r is electrically connected to the drain of the TFT 30r, and the image signal S1, S2,... Supplied from the data line 6a is closed by closing the switch of the TFT 30r as a switching element for a certain period. ... Sn is written at a predetermined timing. A predetermined level of image signals S1, S2,..., Sn written in the liquid crystal as an example of the electro-optical material via the pixel electrode 9r is held for a certain period with the counter electrode formed on the counter substrate. The Note that a fixed potential is supplied to the storage capacitor 70 via a fixed potential line 71.

  The liquid crystal interposed between the TFT array substrate 10 and the counter substrate 20 modulates light and enables gradation display by changing the orientation and order of the molecular assembly according to the applied voltage level. In the normally white mode, the transmittance for incident light is reduced according to the voltage applied in units of each pixel, and in the normally black mode, the light is incident according to the voltage applied in units of each pixel. The transmittance with respect to light is increased, and light having a contrast corresponding to an image signal is emitted from the liquid crystal device 1 as a whole. In order to prevent the image signal held here from leaking, the storage capacitor 70 is electrically connected in parallel with the liquid crystal capacitor formed between the pixel electrodes 9f and 9r and the counter electrode. The storage capacitor 70 is a capacitive element that functions as a storage capacitor that temporarily holds the potentials of the pixel electrodes 9f and 9r in response to the supply of an image signal. According to the storage capacitor 70, the potential holding characteristics of the pixel electrodes 9f and 9r are improved, and display characteristics such as improvement of contrast and reduction of flicker can be improved.

<1-4: Specific Configuration of Pixel Unit>
Next, a specific configuration of the pixel portion corresponding to each of the pixels 75f and 75r will be described with reference to FIGS. FIG. 5 is a plan view of a pixel portion corresponding to each of the adjacent pixels 75f and 75r, and FIG. 6 is a cross-sectional view taken along the line VI-VI ′ of FIG. FIG. 7 is a cross-sectional view corresponding to FIG. 6 illustrating a comparative example of the liquid crystal device according to the present embodiment. FIG. 8 is a diagram showing the relationship between the retardation value of each of the retardation films 40f2 and 40r2 and the wavelength dependence of light. In FIG. 6, the upper side in the drawing is described as the front side, and the lower side is described as the rear side. However, in the liquid crystal device according to the present invention, the front side and the rear side may be defined oppositely.

  In FIG. 5, the TFT 30f includes a semiconductor layer 33f, a gate electrode 34f, a source electrode 31f, and a drain electrode 32f. The source electrode 31f is electrically connected to the data line 6a, and the drain electrode 32f is electrically connected to the pixel electrode 9f. A first light reflection film 19f made of a metal thin film such as Al is formed on the pixel 75f so as to overlap the pixel electrode 9f. The TFT 30r includes a semiconductor layer 33r, a gate electrode 34r, a source electrode 31r, and a drain electrode 32r. The source electrode 31r is electrically connected to the data line 6a, and the drain electrode 32r is electrically connected to the pixel electrode 9r. A second light reflecting film 19r made of a metal thin film such as Al is formed on the pixel 75r so as to overlap the pixel electrode 9r.

  In FIG. 6, the liquid crystal device 1 includes a TFT array substrate 10, a counter substrate 20, a liquid crystal layer 50, pixel electrodes 9 f and 9 r, a light reflecting film 19 f that is an example of a “first light reflecting film”, and a “second light reflecting film”. ”, A circularly polarizing plate 40 f that is an example of a“ first polarizing plate ”, a circularly polarizing plate 40 r that is an example of a“ second polarizing plate ”, and a color filter 25.

  On the TFT array substrate 10, an alignment film is formed on the pixel electrodes 9f and 9r after the pixel switching TFTs 30f and 30r, wiring lines such as scanning lines and data lines are formed. On the other hand, on the counter substrate 20 (the lower surface of the counter substrate 20 in the drawing), an alignment film is formed on the uppermost layer portion (the lowermost layer in the drawing) in addition to the counter electrode 21. The liquid crystal layer 50 is made of, for example, a liquid crystal in which one or several types of nematic liquid crystals are mixed, and takes a predetermined alignment state between the pair of alignment films. The TFT array substrate 10 is a transparent substrate such as a quartz substrate, a glass substrate, or a silicon substrate. The counter substrate 20 is also a transparent substrate like the TFT array substrate 10. Each of the pixel electrodes 9f and 9r is a transparent electrode having conductivity such as ITO. In the present embodiment, the light reflecting films 19r and 19f may not be provided by sharing a part of the counter electrode 21 facing the pixel electrode 9f or the pixel electrode 9r as the light reflecting film. Each of the first polarizing plate 40f and the second polarizing plate 40r may be provided between the light reflecting film and the substrate.

  Each of the pixel electrodes 9f and 9r is formed in each of the pixels 75f and 75r so as to face the counter electrode 21 with the liquid crystal layer 50 interposed therebetween.

  The circularly polarizing plate 40f overlaps the pixels 75f and 75r, and is disposed on the opposite side of the liquid crystal layer 50 with respect to the counter substrate 20, that is, on the front side. The circularly polarizing plate 40f includes a polarizing film 40f1 that is an example of a “first polarizing film” and a retardation film 40f2 that is an example of a “first retardation film”.

  The circularly polarizing plate 40r overlaps the pixels 75f and 75r, and is disposed on the opposite side of the liquid crystal layer 50 with respect to the TFT array substrate 10, that is, on the rear side. The circularly polarizing plate 40r includes a polarizing film 40r1 that is an example of a “second polarizing film” and a retardation film 40r2 that is an example of a “second retardation film”.

  Next, in FIGS. 6 to 8, during operation of the liquid crystal device 1, incident light incident on the liquid crystal device 1 is transmitted from the liquid crystal device 1 to each image display region by sequentially converting the phase and the like. Each part of the liquid crystal device 1 will be described in detail while explaining the process until the light is transmitted.

  Incident light If0 (external light), which is an example of “first incident light”, enters the circularly polarizing plate 40f from the front side. The circularly polarizing plate 40f emits the first circularly polarized light If1 generated by polarizing the incident light If0 toward the light reflecting films 19f and 19r, and the first circularly polarized light If1 is reflected by the light reflecting film in the pixel 75f. The reflected light Rf2 generated by being reflected by 19f is transmitted to the front side.

  The polarizing film 40f1 converts the incident light If0 into linearly polarized light. The retardation film 40f2 converts the linearly polarized light emitted from the polarizing film 40f1 into first circularly polarized light If1, which is right circularly polarized light whose polarization axis rotates rightward along the traveling direction. The first circularly polarized light If1 passes through the liquid crystal layer 50 and reaches the retardation film 40f2 as reflected light Rf2 reflected by the light reflecting film 19f. The polarization axis of the reflected light Rf2 is converted by the refractive index anisotropy of the retardation film 40f2. The polarizing film 40f1 transmits the reflected light Rf1 transmitted through the retardation film 40f2 to the front side as transmitted light Tr. Therefore, the pixel 75f can display an image by the transmitted light Tr. In addition, only the light having a predetermined wavelength of the reflected light Rf2 reaches the retardation film 40f2 by the color filter 25. Therefore, a color image can be displayed through the image display area 10f composed of a plurality of pixels 75f.

  On the other hand, in the pixel 75r, the reflected light Rf1 generated by reflecting the first circularly polarized light If1 by the light reflecting film 19r is left circularly polarized light whose polarization axis rotates counterclockwise along the traveling direction. Absorbed by 40f.

  As described above, in the image display area 10f displaying an image on the front side, transmitted light whose gradation is controlled according to the image to be displayed is emitted from only the pixel 75f, and in the pixel 75r, the back surface of the light reflecting film 19r is emitted. The reflected light is not emitted to the front side. On the other hand, as shown in FIG. 7, when the circularly polarizing plates 40f and 40r are not provided, the reflected light reflected by the back surface of the light reflecting film 19r is emitted to the front side together with the reflected light Rf2 '. Therefore, an image having high contrast is not displayed.

  Therefore, since the liquid crystal device 1 includes the circularly polarizing plate 40f, the reflected light Rf1 reflected on the back surface of the light reflecting film 19r is not added to the transmitted light Tr as described above. A high quality image with high contrast can be displayed on the front side.

  The retardation film 40f2 is preferably a quarter wavelength plate whose retardation value for light having a wavelength of 450 nm is smaller than the retardation value for light having a wavelength of 590 nm. According to such a retardation film 40f2, the incident light If0 can be converted into the first circularly polarized light If1 within a visible light range, that is, in a wide wavelength band where the wavelength of light is 380 nm (blue) to 780 nm (red). More specifically, as shown in FIG. 8, the retardation value R (λ) of the retardation film has wavelength dependency with respect to the light, so that the long wavelength light (for example, the wavelength is 780 nm). If the retardation film is designed so that the phase of only a certain red light) is shifted by a quarter wavelength, the wavelength shift amount of light having other wavelengths cannot be reduced to a quarter wavelength. Accordingly, as the retardation film 40f2, a retardation plate R having a retardation value R (450) for light having a wavelength of 450 nm is smaller than the retardation value R (590) for light having a wavelength of 590 nm. It is possible to shift the phase by a quarter wavelength with respect to the light included in the wavelength range. In addition, according to such a retardation film, the reflected light Rf1 generated by reflecting the first circularly polarized light If1 by the light reflecting film 19r can be absorbed in a wide wavelength band within the wavelength range of visible light.

  The retardation film 40f may be configured by combining a quarter wavelength plate and a half wavelength plate. According to such a retardation film 40f2, it is possible to absorb only the reflected light Rf1 reflected by the back surface of the light reflecting film 19r and transmit the reflected light Rf2 reflected by the light reflecting film 19f.

  Similarly on the rear side and the front side, the transmitted light Tr is emitted only from the plurality of pixels 75r constituting the image display region 10r, and the reflected light Rr1 is not emitted from the pixel 75f to the rear side. An image having high contrast can be displayed on the rear side through the region 10r.

  More specifically, on the rear side, in the pixel 75r, the reflected light Rr2 generated by reflecting the light obtained by polarizing the second circularly polarized light Ir1 by the light reflecting film 19r is reflected via the circularly polarizing plate 40r. It is emitted as transmitted light Tr to the side. In the pixel 75f, the reflected light Rr1 formed by reflecting the second circularly polarized light Ir1 on the back surface of the light reflecting film 19f is absorbed by the circularly polarizing plate 40r. Thereby, on the rear side, the transmitted light Tr is emitted only from the pixel 75r, and a high-quality image is displayed in the image display region 10r. Note that the polarizing film 40r1 and the retardation film 40r2 may be the same as the polarizing film 40f1 and the retardation film 40f2, respectively.

  As described above, according to the liquid crystal device 1 according to the present embodiment, the double-sided reflection type liquid crystal device capable of displaying an image having high contrast in the respective image display areas on both sides by using external light as a light source. Can provide.

  In the present embodiment, the case where the rows of the pixels 75f and 75r are alternately arranged in plan view is described as an example. However, these pixels constitute an image display area on each of both surfaces of the liquid crystal device. The arrangement is not limited to the arrangement of this embodiment.

<1-5: Modification>
Next, a modification of the liquid crystal device according to the present invention will be described with reference to FIGS. FIG. 9 is a cross-sectional view showing a modification of the liquid crystal device according to the present embodiment, and FIG. 10 is a cross-sectional view showing another modification of the liquid crystal device according to the present embodiment. In FIGS. 9 and 10, the same reference numerals are given to portions common to the liquid crystal device 1 described with reference to FIGS. 1 to 8, and detailed description thereof is omitted.

  In FIG. 9, the liquid crystal device 1 </ b> A includes a light shielding film 45 that covers a region extending between the pixel electrode 9 f and the pixel electrode 9 r on the TFT array substrate 10 and is formed between the liquid crystal layer 50 and the counter substrate 20.

  The light shielding film 45 is formed in the same layer as the light reflecting film 19r and covers each of the TFTs 30r and 30f. According to the light shielding film 45, the region extending between the pixel electrode 9r and the pixel electrode 9f on the TFT array substrate 10, that is, the region where the TFTs 30r and 30f are provided can be shielded from light, and an image display with a high contrast is possible.

  In FIG. 10, the liquid crystal device 1B includes a light reflection film 19r ′ that extends to the pixel 75f and overlaps a part of the light reflection film 19f. According to the light reflecting film 19r ′, the light reflecting films 19f and 19r ′ are not provided with a light-shielding film, but from the respective opening areas of the pixels 75f and 75r, that is, the non-opening areas excluding the areas where light is substantially transmitted. Transmission of light can be reduced, and the contrast of the displayed image can be increased.

  In addition, the liquid crystal device 1B includes a front light 46f that is an example of a “first light source” provided on the front side, and a light guide 47f that guides the light emitted from the front light 46f to the circularly polarizing plate 40f, and the rear side. A front light 46r that is an example of the “second light source” provided and a light guide 47r that guides light emitted from the front light 46r to the circularly polarizing plate 40r are provided. According to the front lights 46f and 46r, images can be displayed on both the front side and the rear side even in a situation where there is no external light, for example, at night and indoors.

<2: Electronic equipment>
Next, an example in which each liquid crystal device described above is applied to a mobile personal computer will be described. FIG. 11 is a perspective view showing the configuration of the personal computer. The personal computer 1200 includes a main body 1204 having a keyboard 1202 and a liquid crystal display unit 1206 to which the above-described liquid crystal device is applied. According to such a personal computer 1200, high-quality images can be displayed on both surfaces of the liquid crystal display unit 1206.

  Further, an example in which the above-described liquid crystal device is applied to a mobile phone will be described. FIG. 12 is a perspective view showing the configuration of this mobile phone. In FIG. 12, a mobile phone 1300 includes a plurality of operation buttons 1302 and a reflective liquid crystal device 1305 to which the above-described liquid crystal device is applied. In the liquid crystal device 1305, a front light is provided on at least one of the front and rear surfaces as necessary, and high-quality image display is possible even in the absence of external light.

  The liquid crystal device according to the present invention includes a television receiver, a viewfinder type or a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, in addition to the electronic devices described above. The present invention can be applied to a word processor, a workstation, a video phone, a POS terminal, a device having a touch panel, and the like.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Equipment is also within the scope of the present invention.

It is the top view which looked at the liquid crystal device concerning this embodiment from the counter substrate side with each component. It is the top view which looked at the liquid crystal device concerning this embodiment from the TFT array substrate side. FIG. 3 is an enlarged view showing a part C of the liquid crystal device 1 shown in FIGS. 1 and 2 in an enlarged manner. 4 is an equivalent circuit of various elements, wirings, and the like in a plurality of pixels formed in a matrix that forms each image display region of the liquid crystal device according to the present embodiment. FIG. 4 is a plan view of a pixel unit corresponding to each of adjacent pixels in the liquid crystal device according to the present embodiment. FIG. 6 is a sectional view taken along line VI-VI ′ of FIG. 5. It is sectional drawing corresponding to FIG. 6 which showed the comparative example of the liquid crystal device which concerns on this embodiment. It is the figure which showed the relationship between the retardation value in a phase difference film, and the wavelength dependence of light. It is sectional drawing which showed the modification of the liquid crystal device which concerns on this embodiment. It is sectional drawing which showed the other modification of the liquid crystal device which concerns on this embodiment. It is a perspective view which shows an example of the electronic device which concerns on this invention. It is a perspective view which shows the other example of the electronic device which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,1A, 1B ... Liquid crystal device, 10 ... TFT array substrate, 19f, 19r ... Light reflection film, 20 ... Opposite substrate, 30f, 30r ... TFT, 40f, 40r ... Circular polarizer

Claims (15)

A first substrate;
A second substrate disposed opposite the first substrate;
A liquid crystal layer sandwiched between the first substrate and the second substrate;
A first polarizing plate disposed on the second substrate;
A first light reflecting film provided on the first substrate;
A second light reflecting film provided on the liquid crystal layer side of the first polarizing plate in the second substrate;
The first light reflection film and the second light reflection film overlap the first polarizing plate,
The first incident light incident on the first polarizing plate from the opposite side of the liquid crystal layer is polarized into first circularly polarized light and emitted toward the first light reflecting film and the second light reflecting film. And
Reflected light generated by reflecting the first circularly polarized light by the second light reflecting film is absorbed by the first polarizing plate. A first pixel electrode provided between the first substrate and the liquid crystal layer and overlapping the first light reflecting film;
A second pixel electrode provided between the first substrate and the liquid crystal layer and overlapping the second light reflecting film;
A counter electrode provided between the second substrate and the liquid crystal layer so as to oppose the first pixel electrode and the second pixel electrode;
The reflected light generated when the first circularly polarized light is reflected by the first light reflection film in a state where a voltage is applied to the liquid crystal layer is transmitted through the first polarizing plate. Item 2. A liquid crystal device according to item 1. The first polarizing plate includes a first polarizing film that converts the first incident light into linearly polarized light, a first retardation film that converts linearly polarized light emitted from the first polarizing film into the first circularly polarized light, and The liquid crystal device according to claim 1, further comprising: 4. The liquid crystal device according to claim 3, wherein the first retardation film is a quarter-wave plate having a retardation value with respect to light having a wavelength of 450 nm that is smaller than a retardation value with respect to light having a wavelength of 590 nm. . The liquid crystal device according to claim 3, wherein the first retardation film is configured by combining a quarter wavelength plate and a half wavelength plate. The liquid crystal device according to claim 1, further comprising a first light source provided on the opposite side of the second substrate. A second polarizing plate that overlaps the first light reflecting film and the second light reflecting film and is disposed on the first substrate on the opposite side of the liquid crystal layer with respect to the first light reflecting film;
Second incident light incident on the second polarizing plate from the opposite side of the liquid crystal layer is polarized into second circularly polarized light and emitted toward the first light reflecting film and the second light reflecting film. And
7. The reflected light generated by reflecting the second circularly polarized light by the first light reflecting film is absorbed by the second polarizing plate. 7. LCD device. The second polarizing plate includes: a second polarizing film that converts the second incident light into linearly polarized light; a second retardation film that converts linearly polarized light emitted from the second polarizing film into the second circularly polarized light; The liquid crystal device according to claim 7, further comprising: The liquid crystal device according to claim 8, wherein the second retardation film is a quarter-wave plate having a retardation value for light having a wavelength of 450 nm that is smaller than a retardation value for light having a wavelength of 590 nm. . The liquid crystal device according to claim 8, wherein the second retardation film is configured by combining a quarter wavelength plate and a half wavelength plate. The liquid crystal device according to claim 6, further comprising a second light source provided on the opposite side of the first substrate. The liquid crystal device according to claim 1, further comprising a color filter that overlaps the first light reflection film and the second light reflection film. 13. The light-shielding film provided on the second substrate and covering a region between the first pixel electrode and the second pixel electrode is provided. 13. Liquid crystal device. The liquid crystal according to any one of claims 2 to 12, wherein the second light reflecting film overlaps a part of a region between the first pixel electrode and the second pixel electrode. apparatus. An electronic apparatus comprising the liquid crystal device according to any one of claims 1 to 14.

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