JP2011209392A - Liquid crystal display device and projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of eliminating the deviation of a charge generated in a liquid crystal layer by a simpler method, and to provide a projection type display device.SOLUTION: The liquid crystal display device includes an element substrate 11 and a counter substrate 12 holding the liquid crystal layer 13 in between. The element substrate 11 includes a pixel electrode 21 driving a liquid crystal molecule constituting the liquid crystal layer 13, and a first dielectric layer 33 formed on the pixel electrode 21. The counter substrate 12 includes a common electrode 43 driving the liquid crystal molecule constituting the liquid crystal layer 13, and a second dielectric layer 44 formed on the common electrode 43. The density of the first dielectric layer 33 is lower than that of the second dielectric layer 44.

Description

  The present invention relates to a liquid crystal display device and a projection display device.

  Conventionally, liquid crystal display devices have been used as light modulation means of projectors. This liquid crystal display device includes a transmission type that modulates light from a backlight and emits it as transmitted light, and a reflection type that modulates incident light and emits it as reflected light. A reflective liquid crystal display device includes a pair of substrates that sandwich a liquid crystal layer, and one substrate is formed with a reflective electrode that reflects incident light, and the other substrate has incident light incident thereon. A transmissive electrode that transmits light is formed.

  In such a reflective liquid crystal display device, the materials for forming the electrodes provided on each of the pair of substrates are different from each other, and a charge bias may occur in the liquid crystal layer due to a difference in work function of the materials. is there. Then, flicker and image sticking may occur due to the bias of the charge, and the display quality of the liquid crystal display device may be impaired. Thus, for example, it has been proposed to prevent the occurrence of charge bias in the liquid crystal layer by dehydrogenating the density asymmetry of the hydroxyl groups present on the electrodes (see, for example, Patent Documents 1 and 2). .

JP 2008-209692 A JP 2006-349795 A

However, even in the above conventional liquid crystal display device, it is required to eliminate the bias of electric charges generated in the liquid crystal layer by an easier method.
Therefore, an object of the present invention is to provide a liquid crystal display device and a projection display device that can eliminate the unevenness of charge generated in the liquid crystal layer by an easier method.

  The present invention employs the following configuration in order to solve the above problems. That is, the liquid crystal display device according to the present invention is a liquid crystal display device including first and second substrates sandwiching a liquid crystal layer, and the first substrate is a reflective electrode that drives liquid crystal molecules constituting the liquid crystal layer. And a first dielectric layer formed on the reflective electrode, wherein the second substrate has a transmissive electrode for driving liquid crystal molecules constituting the liquid crystal layer, and a first dielectric layer formed on the transmissive electrode. Two dielectric layers, wherein the density of the first dielectric layer is lower than the density of the second dielectric layer.

  In the present invention, the density of the first dielectric layer formed on the reflective electrode is made lower than the density of the second dielectric layer formed on the transmissive electrode, and the density is different between the first and second dielectric layers. Accordingly, the bias of the charge generated in the liquid crystal layer due to the difference in material between the reflective electrode and the transmissive electrode can be suppressed. Therefore, it is possible to eliminate the bias of the charge generated in the liquid crystal layer by an easier method.

In the liquid crystal display device according to the present invention, the first dielectric layer is preferably formed by oblique deposition.
In the present invention, the density of the first dielectric layer can be adjusted more easily by changing the deposition angle of oblique deposition.

In the liquid crystal display device according to the present invention, it is preferable that the first dielectric layer is formed by a sol-gel method.
In the present invention, the density of the first dielectric layer can be more easily adjusted by changing the concentration of the organic additive in the solution.

In the liquid crystal display device according to the present invention, it is preferable that the second dielectric layer is formed by oblique deposition.
In the present invention, the density of the second dielectric layer can be made higher than the density of the first dielectric layer more easily by changing the deposition angle of oblique deposition.

In the liquid crystal display device according to the present invention, it is preferable that the second dielectric layer is formed by a sol-gel method.
In the present invention, the density of the second dielectric layer can be made higher than the density of the first dielectric layer more easily by changing the concentration of the organic additive in the solution.

In the liquid crystal display device according to the present invention, the liquid crystal layer is preferably composed of liquid crystal molecules exhibiting negative dielectric anisotropy.
In the present invention, the liquid crystal layer is composed of liquid crystal molecules driven in a VA (Vertical Alignment) mode, so that a good contrast can be obtained when the liquid crystal display device is viewed from the front.

A projection display device according to the present invention includes the liquid crystal display device described above.
In the present invention, as described above, by making the density of the first dielectric layer lower than the density of the second dielectric layer, it is possible to more easily eliminate the bias of the charge generated in the liquid crystal layer.

1 is a schematic plan view showing a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is an equivalent circuit diagram of FIG. 1. It is sectional drawing which shows a pixel area. It is a schematic block diagram which shows a projection type display apparatus provided with the liquid crystal display device of FIG. It is sectional drawing which shows the liquid crystal display device in the 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, a liquid crystal display device according to a first embodiment of the present invention will be described with reference to the drawings. In each drawing used in the following description, the scale is appropriately changed to make each member a recognizable size.

[Liquid Crystal Display]
The liquid crystal display device 1 according to the present embodiment is a liquid crystal display device used as a light modulation unit in a projector (projection type display device) 100 described later, for example, and as shown in FIG. 1, an element substrate (first substrate) 11 is used. And a counter substrate (second substrate) 12 and a liquid crystal layer 13 sandwiched between the element substrate 11 and the counter substrate 12. Further, in the liquid crystal display device 1, the element substrate 11 and the counter substrate 12 are bonded together by a frame-shaped sealing material 14 provided on the outer peripheral portion of the facing region where the element substrate 11 and the counter substrate 12 face each other. An image display region is formed inside the sealing material in the liquid crystal display device 1.

  In the image display area of the liquid crystal display device 1, a plurality of pixel areas are arranged in a matrix as shown in FIG. In each of the pixel regions, a pixel electrode (reflecting electrode) 21 and a common electrode (transparent electrode) 43 to be described later, and a TFT element 22 for controlling the switching of the pixel electrode 21 are formed. In the image display area, a plurality of data lines 23 and scanning lines 24 are arranged in a grid pattern.

The TFT element 22 has a source connected to the data line 23, a gate connected to the scanning line 24, and a drain connected to the pixel electrode 21.
The data line 23 is configured such that image signals S1 to Sn are supplied to each pixel region from a data line driving circuit (not shown). Further, the scanning line 24 has a configuration in which scanning signals G1 to Gm are supplied to each of the sub-pixel regions from a scanning line driving circuit (not shown). Note that a storage capacitor 25 is provided in parallel with the pixel electrode 21 in order to prevent leakage of the image signals S <b> 1 to Sn written to the pixel electrode 21. Further, the liquid crystal display device 1 is formed with terminals (not shown) for connecting the data line driving circuit and the scanning line driving circuit to the outside of the liquid crystal display device 1.

Next, a detailed configuration of the liquid crystal display device 1 will be described.
As shown in FIG. 3, the element substrate 11 includes a substrate body 31, an element formation layer 32 formed on the inner surface (the liquid crystal layer 13 side) of the substrate body 31, and pixels formed on the element formation layer 32. An electrode 21, a first dielectric layer 33 formed on the pixel electrode 21, and an alignment film 34 formed on the liquid crystal layer 13 side of the first dielectric layer 33 are provided.
The element forming layer 32 has a structure in which an insulating film, a semiconductor film, and a conductor film are appropriately laminated, and constitutes the data line 23, the scanning line 24, and the TFT element 22, and pixel electrodes formed in each of a plurality of pixel regions. 21 can be driven individually.
The pixel electrode 21 is made of a conductive material that also functions as a reflective film, such as Al.

The first dielectric layer 33 is made of, for example, silicon oxide (SiO _x ) or silicon nitride (SiN _x ), and is formed so as to cover the pixel electrode 21 by oblique deposition. Further, the column of silicon oxide constituting the first dielectric layer 33 is inclined, for example, 45 degrees with respect to the normal direction of the substrate surface of the element substrate 11. Therefore, the density of the first dielectric layer 33 is reduced by air entering between the columns as compared with the case where the first dielectric layer 33 is formed by plasma CVD, for example. The density of the first dielectric layer 33 is adjusted by the inclination angle of the column, the deposition rate of the low refractive index layer 35, the deposition pressure, and the like. In general, the density of the first dielectric layer 33 can be lowered by increasing the tilt angle, slowing the deposition rate, and increasing the deposition pressure. Here, the density of the first dielectric layer 33 is 1.9 g / cm ³ .

The first dielectric layer 33 has biaxial optical anisotropy inclined with respect to the normal direction of the substrate surface of the element substrate 11. The slow axis of the first dielectric layer 33 is a direction orthogonal to the column tilt direction or a direction parallel to the column tilt direction, depending on the column tilt direction and density.
The alignment film 34 is made of, for example, SiO ₂ and is formed on the first dielectric layer 33 by oblique vapor deposition.

On the other hand, the counter substrate 12 is formed on the light shielding film 42, a substrate body (base body) 41 made of a translucent material such as glass or quartz, a light shielding film 42 formed on the inner surface of the substrate body 41, and the like. The common electrode 43, a second dielectric layer 44 formed on the common electrode 43, and an alignment film 45 formed on the liquid crystal layer 13 side of the second dielectric layer 44 are provided.
The light shielding film 42 is made of, for example, black resin, and is formed in a region overlapping the edge of the pixel region in plan view on the surface of the substrate body 41, and borders the pixel region.

The common electrode 43 is made of a light-transmitting conductive material such as ITO or IZO. The common electrode 43 is an electrode that is common throughout the plurality of pixel regions.
The second dielectric layer 44 is formed of the same material as the first dielectric layer 33, such as silicon oxide or silicon nitride, and is formed so as to cover the common electrode 43 and the light shielding film 42 by, for example, plasma CVD. Yes. Here, the density of the second dielectric layer 44 is 2.3 g / cm ³ .
Similar to the alignment film 34, the alignment film 45 is made of, for example, SiO ₂ and is formed on the common electrode 43 by oblique vapor deposition.

  The liquid crystal layer 13 is formed of a liquid crystal having negative dielectric anisotropy whose refractive index anisotropy Δn is, for example, 0.1. Here, the alignment films 34 and 45 provided on the element substrate 11 and the counter substrate 12 are formed by oblique vapor deposition, so that liquid crystal molecules can be applied from the normal directions of the element substrate 11 and the counter substrate 12. A pretilt for inclining by a predetermined angle is given. In this embodiment, the azimuth direction of the pretilt between the element substrate 11 and the counter substrate 12 is set to be in an antiparallel (antiparallel) state. Therefore, the twist angle of the liquid crystal molecules is set to approximately 0 degrees in the initial alignment state where no voltage is applied.

  Here, the shift amount of the common potential in each of the case where the density of the first dielectric layer 33 is lower than the density of the second dielectric layer 44 (Example) and the case where the density is equivalent (Comparative Example). Table 1 shows. In the embodiment, the first dielectric layer 33 is formed by oblique vapor deposition so that the density of the first dielectric layer 33 is lower than the density of the second dielectric layer 44. Similarly to the second dielectric layer 44, the dielectric layer 33 is formed by plasma CVD, for example, so that the density of the first dielectric layer 33 is made equal to the density of the second dielectric layer 44.

  As can be seen from Table 1, by adjusting the density of the first dielectric layer 33, the amount of shift of the common potential is reduced, the occurrence of flicker and image sticking is suppressed, and the display quality of the liquid crystal display device 1 is impaired. Is suppressed. Here, since the sign of the shift amount of the common potential is reversed, it can be seen that by adjusting the density of the first dielectric layer 33, the shift amount of the common potential can be set to 0 and occurrence of flicker and image sticking can be suppressed.

[Projection type display device]
The above-described liquid crystal display device 1 is used as light modulation means of a projector 100 as shown in FIG. As shown in FIG. 4, the projector 100 includes a light source 101, dichroic mirrors 102 and 103, a light modulating unit 104 for red light, a light modulating unit 105 for green light, and a blue light including the liquid crystal display device 1 of the present invention. A light modulator 106, a light guide 107, reflection mirrors 110 to 112, a cross dichroic prism 113, and a projection lens 114. The color image light emitted from the projector 100 is projected on the screen 115.

The light source 101 includes a lamp 101a such as a metal halide, and a reflector 101b that reflects light from the lamp 101a.
The dichroic mirror 102 is configured to transmit red light included in white light from the light source 101 and reflect green light and blue light. The dichroic mirror 103 is configured to transmit blue light and reflect green light among green light and blue light reflected by the dichroic mirror 102.

  The light modulation means 104 for red light is configured to receive red light transmitted through the dichroic mirror 102 and modulate the incident red light based on a predetermined image signal. Further, the green light light modulating means 105 is configured to receive the green light reflected by the dichroic mirror 103 and modulate the incident green light based on a predetermined image signal. The blue light light modulating means 106 is configured to receive the blue light transmitted through the dichroic mirror 103 and modulate the incident blue light based on a predetermined image signal.

The light guide unit 107 includes an incident lens 107a, a relay lens 107b, and an output lens 107c, and is provided to prevent light loss due to a long optical path of blue light.
The reflection mirror 110 is configured to reflect the red light transmitted through the dichroic mirror 102 toward the light modulation means 104 for red light. The reflection mirror 111 is configured to reflect the blue light transmitted through the dichroic mirror 103 and the incident lens 107a toward the relay lens 107b. The reflection mirror 112 is configured to reflect the blue light emitted from the relay lens 107b toward the emission lens 107c.

The cross dichroic prism 113 is formed by bonding four right-angle prisms, and a dielectric multilayer film reflecting red light and a dielectric multilayer film reflecting blue light are formed in an X shape at the interface. Has been. These dielectric multilayer films combine light of three colors to form light representing a color image.
The projection lens 114 is configured to enlarge and project the color image synthesized by the cross dichroic prism 113 onto the screen 115.

According to the liquid crystal display device 1 and the projector 100 configured as described above, the density of the first dielectric layer 33 is made lower than the density of the second dielectric layer 44, so that the liquid crystal layer 13 can be formed in an easier way. The bias of the generated charge can be eliminated.
Here, since the first dielectric layer 33 is formed by oblique vapor deposition, the density of the first dielectric layer 33 can be adjusted more easily by changing the vapor deposition angle or the like.

[Second Embodiment]
Hereinafter, a liquid crystal display device according to a second embodiment of the present invention will be described with reference to the drawings. In this embodiment, since the configuration of the counter substrate is different from that of the first embodiment, this point will be mainly described, and the same reference numerals are given to the components described in the above embodiment, and the description thereof will be omitted. To do.

In the counter substrate 201 of the liquid crystal display device 200 in this embodiment, as shown in FIG. 5, the second dielectric layer 202 is formed by oblique deposition.
The inclination angle with respect to the normal direction of the substrate surface of the counter substrate 201 in the column constituting the second dielectric layer 202 is smaller than the inclination angle of the column constituting the first dielectric layer 33. Therefore, the density of the second dielectric layer 202 is higher than the density of the first dielectric layer 33. The retardation amount Δnd, which is the product of the birefringence in the second dielectric layer 202 and the layer thickness of the second dielectric layer 202, is smaller than the retardation amount Δnd of the first dielectric layer 33.

  The liquid crystal display device 200 configured as described above also has the same operations and effects as described above, but the second dielectric layer 202 is formed by oblique vapor deposition, and therefore, by changing the vapor deposition angle or the like, The density of the second dielectric layer 202 can be adjusted more easily.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the first dielectric layer or the second dielectric layer is formed by oblique vapor deposition, but other methods such as a sol-gel method may be used. After forming the dielectric layer by the sol-gel method, an ion beam is formed. You may form by irradiating. Even when the sol-gel method is used, the density of the dielectric layer can be easily changed as in the case of forming the dielectric layer by oblique vapor deposition.
The liquid crystal layer is composed of liquid crystal molecules driven by the VA method. If the liquid crystal display device is configured to form a reflective electrode on the first substrate and a transparent electrode on the second substrate, for example, NT (Twisted A liquid crystal molecule driven by another method, such as a liquid crystal molecule driven by a Nematic method, may be used.
The liquid crystal display device is not limited to a reflective liquid crystal display device, and may be a transflective liquid crystal display device.

  The liquid crystal display device is not limited to a projection type display device such as a projector, and may be used for a direct-view type display device such as a mobile phone. Accordingly, the electronic apparatus including the liquid crystal display device is not limited to a projection display device such as a projector, but is a mobile phone, a PDA (personal digital assistant), a handy terminal, an electronic book, a notebook personal computer, a personal computer, a digital still Various electronic devices such as a camera, a liquid crystal television, a viewfinder type or a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, a workstation, a videophone, and a POS terminal may be used.

1,200 liquid crystal display device, 11 element substrate (first substrate), 12, 201 counter substrate (second substrate), 13 liquid crystal layer, 21 pixel electrode (reflection electrode), 33 first dielectric layer, 43 common electrode ( Transparent electrode), 44, 202 second dielectric layer, 100 projector (projection type display device), 104 light modulation means for red light (liquid crystal display device), 105 light modulation means for green light (liquid crystal display device), 106 blue Light modulation means (liquid crystal display device)

Claims (7)

A liquid crystal display device comprising first and second substrates sandwiching a liquid crystal layer,
The first substrate comprises a reflective electrode for driving liquid crystal molecules constituting the liquid crystal layer, and a first dielectric layer formed on the reflective electrode;
The second substrate comprises a transmissive electrode for driving liquid crystal molecules constituting the liquid crystal layer, and a second dielectric layer formed on the transmissive electrode;
The liquid crystal display device, wherein a density of the first dielectric layer is lower than a density of the second dielectric layer.   The liquid crystal display device according to claim 1, wherein the first dielectric layer is formed by oblique vapor deposition.   The liquid crystal display device according to claim 1, wherein the first dielectric layer is formed by a sol-gel method.   4. The liquid crystal display device according to claim 1, wherein the second dielectric layer is formed by oblique vapor deposition. 5.   The liquid crystal display device according to claim 1, wherein the second dielectric layer is formed by a sol-gel method.   The liquid crystal display device according to claim 2, wherein the liquid crystal layer is composed of liquid crystal molecules exhibiting negative dielectric anisotropy.   A projection display device comprising the liquid crystal display device according to claim 1.

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