JP2004192003A - Liquid crystal apparatus, its manufacturing method and projection display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal apparatus and a projection display apparatus in which roughening of an alignment film by light can be suppressed. <P>SOLUTION: In the projection display apparatus by three-plate processing, ITO (indium tin oxide) having ≤2,000 cm<SP>-1</SP>absorbance for light at 410 nm wavelength is used for a pixel electrode 9a formed at a lower layer of an alignment film 16 of a liquid crystal apparatus 961B which modulates at least blue light. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention belongs to the technical field of a liquid crystal device and a projection display device, and particularly to the technical field of a liquid crystal device that suppresses deterioration of an alignment film with respect to light and a projection display device including the liquid crystal device.

  2. Description of the Related Art In a projection display device such as a liquid crystal projector, light emitted from a light source is separated into red, green, and blue, and each color light is modulated by three light valves constituted by a liquid crystal device. Are recombined and are projected on the projection surface in an enlarged manner. As a light valve for a liquid crystal projector or the like, a liquid crystal device of an active matrix driving system generally driven by a thin film transistor (hereinafter, appropriately referred to as a TFT) is used.

  Such a liquid crystal device is configured such that a liquid crystal layer is sandwiched between a TFT array substrate and a counter substrate, and a surface of each substrate on the liquid crystal layer side is formed of indium tin oxide (hereinafter, referred to as a TFT array substrate). A pixel electrode made of ITO) and a counter electrode are arranged on the counter substrate. An alignment film is disposed on the pixel electrode and the counter electrode so as to cover the respective electrodes, and the initial alignment of the liquid crystal is determined by the alignment film. In a liquid crystal device, light emitted from a light source passes through, for example, a counter substrate, a liquid crystal layer, and a TFT array substrate in this order.

  By the way, with the miniaturization of such a projection type display device such as a liquid crystal projector, a liquid crystal device used as a light valve thereof has also been miniaturized, and on the other hand, the intensity of light emitted from a light source has increased. The intensity of each color light passing through is considerably strong.

  In particular, in a liquid crystal device used as a blue light valve, the problem that the alignment film surface of the liquid crystal device becomes rough due to long-time light irradiation, which causes poor alignment of the liquid crystal and deteriorates the display characteristics becomes remarkable. I was

  The present invention has been made in view of the above-described problems, and has as its object to provide a liquid crystal device and a projection display device that can suppress deterioration of an alignment film with respect to light.

The followings were supposed by the inventors as the reason for the occurrence of the above-mentioned roughening of the alignment film surface. That is, in a blue liquid crystal device in which blue light having a part of light in the ultraviolet wavelength region is irradiated, a carrier is generated by ITO absorbing ultraviolet light, and the carrier converts ITO into indium, indium oxide, or the like. Decomposes into oxygen.
It was considered that the surface of the alignment film was roughened by the decomposed indium entering the polyimide film as the alignment film. Furthermore, it was considered that the reaction between oxygen and the polyimide to generate carbon dioxide was also a cause of the roughening of the alignment film surface. Thus, the present inventors have found that by using an ITO electrode having a film quality with a small amount of ultraviolet absorption, it is possible to suppress the decomposition of ITO and prevent the alignment film from being roughened due to In generated by the decomposition. The invention has been made.

In order to solve the above problems, a liquid crystal device of the present invention includes a first substrate and indium tin oxide having a light absorption coefficient of 8000 cm ^-1 or less for light having a wavelength of 410 nm disposed on the first substrate. An electrode, an alignment film made of an organic substance provided over the electrode, a second substrate opposed to the first substrate, and a liquid crystal layer sandwiched in a gap between the first substrate and the second substrate And characterized in that: Further, the light absorption number of the electrode is 2000 cm ^-1 or less.

  According to such a configuration of the present invention, generation of carriers that decompose ITO can be suppressed by limiting the light absorption coefficient of the electrode made of ITO with respect to light in the ultraviolet region. Thereby, there is an effect that it is possible to prevent the alignment film from being roughened due to In which has been conventionally decomposed. This makes it possible to obtain a liquid crystal device having excellent display quality without alignment defects.

In another liquid crystal device of the present invention, a first substrate, an electrode made of indium tin oxide having a specific resistance of 1 × 10 ⁻⁴ Ω · cm or more disposed on the first substrate, An alignment film made of an organic substance, which is provided so as to cover the first substrate, a second substrate facing the first substrate, and a liquid crystal layer sandwiched in a gap between the first substrate and the second substrate. Features. Furthermore, the specific resistance of the electrode is 1 × 10 ⁻⁴ Ω · cm or more.

  According to such a configuration of the present invention, by limiting the specific resistance of the ITO film, the oxygen concentration in the ITO film can be increased to reduce the unbonded In. This has the effect that roughness of the film can be suppressed. This makes it possible to obtain a liquid crystal device having excellent display quality without alignment defects.

In another liquid crystal device of the present invention, the first substrate has a light absorption coefficient of 8000 cm ^-1 or less for light having a wavelength of 410 nm disposed on the first substrate, and a specific resistance of 1 × 10 ^-4 or more. An electrode made of indium-tin-oxide, an alignment film made of an organic material disposed over the electrode, a second substrate opposed to the first substrate, and the first and second substrates. And a liquid crystal layer interposed between the gaps.

  According to such a configuration of the present invention, it is possible to obtain a liquid crystal device excellent in display quality and free from poor alignment as compared with the above-described invention.

  Further, another liquid crystal device according to the present invention includes a first substrate, an electrode made of indium tin oxide disposed on the first substrate, an inorganic film disposed over the electrode, An alignment film made of an organic substance disposed over the inorganic film, a second substrate opposed to the first substrate, and a liquid crystal layer sandwiched in a gap between the first substrate and the second substrate. It is characterized by having. Further, the inorganic film is a nitride film or an oxide film.

  According to such a configuration of the present invention, it is possible to prevent unbonded In in the ITO film from entering the alignment film by interposing the inorganic film between the alignment film and the electrode made of ITO. This has the effect. Thus, the alignment film can be prevented from being roughened by In, and a liquid crystal device having excellent display quality without alignment defects can be obtained. In addition, since there is no particular need to adjust the film quality and the like of ITO, the design range can be expanded. Here, as the inorganic film, an oxide film such as a Nesa film or a silicon oxide film or a nitride film such as a silicon nitride film can be used, and it is necessary that In in the ITO film enter the alignment film through the inorganic film. Anything that can be prevented can be used.

  Further, a polyimide film can be used as an alignment film of each of the above-described liquid crystal devices.

  Further, the liquid crystal device of the present invention includes a first substrate, an electrode made of indium tin oxide disposed on the first substrate, an alignment film made of an organic substance provided over the electrode, and What is claimed is: 1. A liquid crystal device comprising: a second substrate opposed to one substrate; and a liquid crystal layer sandwiched in a gap between the first substrate and the second substrate, wherein an oxygen content of an electrode made of indium tin oxide is provided. Vary in the film thickness direction.

  By doing so, roughness of the alignment film can be suppressed.

  Further, the oxygen content increases as approaching the alignment film.

  By doing so, the higher the oxygen content, the lower the concentration of unbonded indium. Therefore, the closer to the alignment film, the lower the indium concentration. Therefore, it is possible to suppress the alignment film from being roughened by the indium deposition, the deterioration of the alignment characteristics, and the unevenness of the alignment characteristics. In addition, the necessary conductivity of the ITO film is a place where the oxygen concentration is relatively low, and is secured at a cross section away from the alignment film.

  The electrode made of indium tin oxide is formed by changing the oxygen concentration in the argon gas at the time of forming the film by sputtering. The projection display device of the present invention corresponds to a light source, a color separation unit that separates light from the light source into red, blue, and green light, and a color light that modulates the color light separated by the color separation unit. A light modulating means, a color synthesizing means for synthesizing the color lights modulated by the light modulating means, and a projection lens for projecting the light synthesized by the color synthesizing means. At least the blue light modulating means of the means includes the liquid crystal device described above.

  According to such a configuration of the present invention, the above-described liquid crystal device is used as a liquid crystal device that emits blue color light including a wavelength component in the ultraviolet region of 380 nm to 410 nm in addition to the light of the original wavelength. This has the effect of preventing the alignment film from being roughened due to the irradiation of ultraviolet rays, and providing a high-quality and long-life projection display device.

  Specifically, by limiting the light absorption coefficient of the electrode made of ITO at a specific wavelength, generation of carriers that cause decomposition of ITO can be suppressed. Thereby, it is possible to suppress the roughening of the alignment film due to In, which has conventionally been caused by the decomposition of ITO. In addition, by limiting the specific resistance of the electrode made of ITO, the concentration of unbonded In in the ITO film can be reduced, and roughness of the alignment film due to In can be suppressed. Further, by interposing an inorganic film between the ITO and the alignment film, even if ultraviolet light of a wavelength is irradiated on the ITO film, carriers are generated, and the carriers decompose the ITO film to generate In, Due to the presence of the inorganic film, In does not enter the alignment film, so that the alignment film can be prevented from being rough.

  Further, the projection display device of the present invention is a projection display device including a light source, a light modulation unit that modulates light from the light source, and a projection lens that projects light modulated by the light modulation unit, The light modulating means includes the above-described liquid crystal device.

  By adopting such a configuration, even if the light modulating means is irradiated with light containing a wavelength component in the ultraviolet region of 380 nm to 410 nm, the alignment film is prevented from being roughened due to the ultraviolet irradiation, and the display is performed. There is an effect that a high-quality and long-life projection display device can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Configuration and Function of First Embodiment of Liquid Crystal Device)
FIG. 1 is an equivalent circuit of various elements, wiring, and the like in a plurality of pixels formed in a matrix and constituting an image forming area of the liquid crystal device according to the first embodiment of the present invention.
FIG. 2 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, etc. are formed, and FIG. It is. In FIG. 3, the scale of each layer and each member is made different so that each layer and each member have a size recognizable in the drawing.

  In FIG. 1, a plurality of pixels formed in a matrix forming an image display area of the liquid crystal device according to the present embodiment are composed of a plurality of pixel electrodes 9a formed in a matrix and a TFT 30 for controlling the pixel electrodes 9a. The data line 6a to which the image signal is supplied is electrically connected to the source of the TFT 30. 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 to a plurality of adjacent data lines 6a for each group. good. Also, the scanning line 3a is electrically connected to the gate of the TFT 30, and the scanning signals G1, G2,..., Gm are applied to the scanning line 3a in a pulsed manner in this order at a predetermined timing. It is configured. The pixel electrode 9a is electrically connected to the drain of the TFT 30, and by closing the switch of the TFT 30 as a switching element for a certain period, the image signals S1, S2,... Write at a predetermined timing. The image signals S1, S2,..., Sn of a predetermined level written to the liquid crystal via the pixel electrodes 9a are held for a certain period between the counter electrodes (described later) formed on the counter substrate (described later). . The liquid crystal modulates light by changing the orientation and order of the molecular assembly depending on the applied voltage level, thereby enabling gray scale display. In the normally white mode, the incident light cannot pass through the liquid crystal portion according to the applied voltage, and in the normally black mode, the incident light passes through the liquid crystal portion according to the applied voltage. The liquid crystal device emits light having a contrast corresponding to the image signal as a whole. Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is added in parallel with a liquid crystal capacitor formed between the pixel electrode 9a and the counter electrode. For example, the voltage of the pixel electrode 9a is held by the storage capacitor 70 for a time that is three digits longer than the time when the voltage is applied to the data line. Thereby, the holding characteristics are further improved, and a liquid crystal device having a high contrast ratio can be realized. Further, in order to form such a storage capacitor 70, a capacitance line 3b whose resistance is reduced by using a conductive light shielding film is provided.

  In FIG. 2, on a TFT array substrate of a liquid crystal device, a plurality of transparent pixel electrodes 9a (outlined by dotted line portions 9a ') are provided in a matrix, and vertical and horizontal boundaries of the pixel electrodes 9a are provided. , A data line 6a, a scanning line 3a, and a capacitor line 3b are provided. The data line 6a is electrically connected to a later-described source region of the semiconductor layer 1a such as a polysilicon film via the contact hole 5, and the pixel electrode 9a is connected to the later-described semiconductor layer 1a of the semiconductor layer 1a via the contact hole 8. Is electrically connected to the drain region. Further, the scanning line 3a is arranged so as to face a channel region (a hatched region on the right in the figure) of the semiconductor layer 1a, and the scanning line 3a functions as a gate electrode.

  The capacitance line 3b is formed from a main line portion extending substantially linearly along the scanning line 3a (that is, a first region formed along the scanning line 3a in a plan view) and a portion intersecting the data line 6a. And a protruding portion (ie, a second region extending along the data line 6a in a plan view) protruding forward (upward in the figure) along the data line 6a.

  A plurality of first light-shielding films 11a are provided in a region indicated by oblique lines rising to the right in the drawing. More specifically, the first light-shielding film 11a is provided at a position covering the TFT including the channel region of the semiconductor layer 1a in the pixel portion as viewed from the side of the TFT array substrate. A main line portion extending linearly along the scanning line 3a facing the portion, and a protruding portion protruding from a location intersecting with the data line 6a toward an adjacent step side (ie, downward in the drawing) along the data line 6a. Having. The tip of the downward projection in each step (pixel row) of the first light-shielding film 11a overlaps the tip of the upward projection of the capacitor line 3b in the next step below the data line 6a. A contact hole 13 for electrically connecting the first light-shielding film 11a and the capacitance line 3b to each other is provided in the overlapping portion.

  Next, as shown in the cross-sectional view of FIG. 3, the liquid crystal device includes a TFT array substrate 10 that forms an example of one transparent substrate, and a counter substrate that forms an example of the other transparent substrate disposed to face the TFT array substrate 10. 20. The TFT array substrate 10 is made of, for example, a quartz substrate, and the counter substrate 20 is made of, for example, a glass substrate or a quartz substrate. The pixel electrode 9a is provided on the TFT array substrate 10, and an alignment film 16 on which a predetermined alignment process such as a rubbing process is performed is provided above the pixel electrode 9a. The pixel electrode 9a is made of, for example, a transparent conductive thin film such as an ITO film. The orientation film 16 will be described later in detail.

  On the other hand, a counter electrode (common electrode) 21 is provided on the entire surface of the counter substrate 20, and an alignment film 22 on which a predetermined alignment process such as a rubbing process is performed is provided below the counter electrode (common electrode) 21. ing. The counter electrode 21 is made of, for example, a transparent conductive thin film such as an ITO film. The alignment film 22 will be described later in detail.

  As shown in FIG. 3, the TFT array substrate 10 is provided with a pixel switching TFT 30 for controlling the switching of each pixel electrode 9a at a position adjacent to each pixel electrode 9a.

  As shown in FIG. 3, the opposing substrate 20 is further provided with a second light shielding film 23 in a region other than the opening region of each pixel portion. Therefore, the incident light does not enter the channel region 1a 'and the LDD (Lightly Doped Drain) regions 1b and 1c of the semiconductor layer 1a of the pixel switching TFT 30 from the side of the counter substrate 20. Further, the second light-shielding film 23 has functions such as improvement of contrast and prevention of color mixture of coloring materials.

The TFT array substrate 10 and the opposing substrate 20, which are configured as described above and are arranged so that the pixel electrode 9a and the opposing electrode 21 face each other, are surrounded by a sealing material (see FIGS. 5 and 6) described later. The liquid crystal is sealed in the space, and the liquid crystal layer 50 is formed.
The liquid crystal layer 50 assumes a predetermined alignment state by the alignment films 16 and 22 when no electric field is applied from the pixel electrode 9a. The liquid crystal layer 50 is made of, for example, a liquid crystal in which one or several kinds of nematic liquid crystals are mixed. The sealing material is an adhesive made of, for example, a photo-curing resin or a thermosetting resin for bonding the two substrates 10 and 20 around them, and a glass for setting a distance between the two substrates to a predetermined value. Spacers such as fibers or glass beads are mixed.

  As shown in FIG. 3, the first light-shielding films 11a are provided between the TFT array substrate 10 and the pixel switching TFTs 30 at positions facing the pixel switching TFTs 30, respectively. The first light-shielding film 11a is preferably made of a simple metal, an alloy, a metal silicide, or the like containing at least one of Ti, Cr, W, Ta, Mo, and Pb, which are preferably opaque refractory metals. With such a material, the first light-shielding film 11a is not broken or melted by the high-temperature treatment in the step of forming the pixel switching TFT 30 performed after the step of forming the first light-shielding film 11a on the TFT array substrate 10. I can do it. Since the first light-shielding film 11a is formed, it is possible to prevent a situation in which return light or the like from the TFT array substrate 10 enters the channel region 1a 'or the LDD regions 1b and 1c of the pixel switching TFT 30 beforehand. In addition, the characteristics of the pixel switching TFT 30 do not deteriorate due to the generation of the photocurrent.

  Further, a first interlayer insulating film 12 is provided between the first light-shielding film 11a and the plurality of pixel switching TFTs 30. The first interlayer insulating film 12 is provided to electrically insulate the semiconductor layer 1a constituting the pixel switching TFT 30 from the first light shielding film 11a. Further, since the first interlayer insulating film 12 is formed on the entire surface of the TFT array substrate 10, it also has a function as a base film for the pixel switching TFT 30. That is, it has a function of preventing deterioration of the characteristics of the pixel switching TFT 30 due to roughening of the surface of the TFT array substrate 10 during polishing, dirt remaining after cleaning, and the like. The first interlayer insulating film 12 is made of a highly insulating glass such as NSG (non-doped silicate glass), PSG (phosphosilicate glass), BSG (boron silicate glass), BPSG (boron phosphorus silicate glass), or a silicon oxide film. , A silicon nitride film or the like. The first interlayer insulating film 12 can prevent the first light-shielding film 11a from contaminating the pixel switching TFT 30 and the like.

  The gate insulating film 2 extends from a position facing the scanning line 3a and is used as a dielectric film. The semiconductor film 1a extends to form a first storage capacitor electrode 1f. A storage capacitor 70 is formed by partially using the second storage capacitor electrode. More specifically, a high-concentration drain region 1e of the semiconductor layer 1a extends below the data line 6a and the scanning line 3a, and an insulating film is formed on a portion of the capacitance line 3b extending along the data line 6a and the scanning line 3a. The first storage capacitor electrode (semiconductor layer) 1f is disposed so as to be opposed to each other with the first storage capacitor electrode 2 therebetween. In particular, since the insulating film 2 as a dielectric of the storage capacitor 70 is nothing but the gate insulating film 2 of the TFT 30 formed on the polysilicon film by high-temperature oxidation, it can be a thin and high withstand voltage insulating film. The capacitor 70 can be configured as a large-capacity storage capacitor with a relatively small area.

  Further, in the storage capacitor 70, as can be seen from FIGS. 2 and 3, the first light-shielding film 11a is provided on the first storage capacitor electrode 1f on the opposite side of the capacitor line 3b as the second storage capacitor electrode by a first interlayer insulating film. The storage capacitance is further provided by being opposed to the third storage capacitance electrode via the film 12 (see the storage capacitance 70 on the right side of FIG. 3).

In FIG. 3, the pixel switching TFT 30 has an LDD (Lightly Doped Drain) structure, and includes a scanning line 3a and a channel region 1a 'of the semiconductor layer 1a in which a channel is formed by an electric field from the scanning line 3a. A gate insulating film 2 for insulating the scanning line 3a from the semiconductor layer 1a, a data line 6a, a lightly doped source region (source side LDD region) 1b and a lightly doped drain region (drain side LDD region) 1c of the semiconductor layer 1a, semiconductor The layer 1a includes a high-concentration source region 1d and a high-concentration drain region 1e. A corresponding one of the plurality of pixel electrodes 9a is connected to the high-concentration drain region 1e. The source regions 1b and 1d and the drain regions 1c and 1e are formed by doping the semiconductor layer 1a with a predetermined concentration of n-type or p-type dopant depending on whether an n-type or p-type channel is formed. Is formed. An n-type channel TFT has the advantage of a high operating speed, and is often used as a pixel switching TFT 30 that is a pixel switching element.
The data line 6a is formed of a light-shielding thin film such as a metal film of Al or an alloy film of metal silicide. On the scanning line 3a, the gate insulating film 2, and the first interlayer insulating film 12, a contact hole 5 leading to the high concentration source region 1d and a contact hole 8 leading to the high concentration drain region 1e are respectively formed. An interlayer insulating film 4 is formed. Data line 6a is electrically connected to high-concentration source region 1d via contact hole 5 to source region 1b. Further, on the data line 6a and the second interlayer insulating film 4, a third interlayer insulating film 7 having a contact hole 8 to the high-concentration drain region 1e is formed. The pixel electrode 9a is electrically connected to the high-concentration drain region 1e via the contact hole 8 to the high-concentration drain region 1e. The above-mentioned pixel electrode 9a is provided on the upper surface of the third interlayer insulating film 7 configured as described above. The pixel electrode 9a and the high-concentration drain region 1e may be electrically connected to each other by relaying the same Al film as the data line 6a or the same polysilicon film as the scanning line 3b.

  The pixel switching TFT 30 preferably has the LDD structure as described above, but may have an offset structure in which impurity ions are not implanted in the low-concentration source region 1b and the low-concentration drain region 1c, or use the gate electrode 3a as a mask. A self-aligned TFT in which impurity ions are implanted at a high concentration and high-concentration source and drain regions are formed in a self-aligned manner may be used.

  Next, the pixel electrode 9a and the counter electrode 22 will be described in more detail.

The pixel electrodes 9a and the counter electrode 22 described above, both the absorption coefficient of the wavelength of 410nm is 8000 cm ^-1 or less, wherein the 2000 cm ^-1 or less, the specific resistance is 1 × 10 ^-4 Ω · cm or more, here three. An ITO film having a characteristic of 5 × 10 ⁻⁴ Ωcm is used. In the measurement of the absorption coefficient, the extinction coefficient k was obtained from the spectral ellipsometer, and was converted to the absorption coefficient. The chi-square indicating the fitting accuracy at that time was 10 or less. The reason for using the spectral ellipsometer is that if the absorption coefficient is obtained from ordinary transmitted light, interference fringes appear and accurate evaluation cannot be performed.

In the present invention, by using an ITO film having an absorption coefficient of 8000 cm ^-1 or less for light having a wavelength of 410 nm as an electrode used in a liquid crystal device, light having a part of the wavelength region of ultraviolet light can be transmitted for a long time to the liquid crystal device. Irradiation can prevent the occurrence of roughening of the alignment film. Here, FIG. 4 is a graph showing an experimental result of a relationship between a light absorption coefficient and a light resistance lifetime of the ITO film with respect to light having a wavelength of 410 nm. In the light resistance test, a liquid crystal device was exposed at a luminous flux density of 50 lm / mm ² using 120 W-UHP as a light source, and a time until a display defect occurred was measured as a lifetime. As can be seen from FIG. 4, it can be seen that the life becomes longer as the value of the absorption coefficient becomes smaller at the boundary of the absorption coefficient for the wavelength of 410 nm of 8000 cm ⁻¹ . It is considered that the reason why the lifetime is improved is that generation of carriers due to light in the ultraviolet region is suppressed and decomposition of the ITO film by the carriers is suppressed.
Thereby, it is possible to prevent the alignment film from being roughened due to the decomposed In.

An ITO film having an absorption coefficient of 2000 cm ^-1 or less was obtained at a sputtering pressure of 0.4 Pa or less. In this case, it is apparent from FIG. 4 that not only the life is significantly increased, but also the particles during sputtering are reduced (about 約 for a film having an absorption coefficient of 6000 cm ⁻¹ of 0.6 Pa) and etching hardly occurs (0. A special effect of about 1/3) was also obtained for a film having an absorption coefficient of 6000 cm ^-1 of 0.6 Pa.

The specific resistance of the electrodes used for the pixel electrode 9a and the counter electrode 22 is desirably 1 × 10 ⁻⁴ Ω · cm or more and 2 × 10 ⁻² Ω · cm or less. The specific resistance tends to increase as the oxygen concentration of the ITO film increases. If the oxygen concentration in the ITO film is high, the concentration of unbonded In that is not bonded to oxygen can be reduced. Therefore, by setting the specific resistance to 1 × 10 ⁻⁴ Ω · cm or more, the concentration of unbonded In can be reduced. Therefore, it is possible to prevent the unbonded In from entering the alignment film and roughening the alignment film. Can be suppressed. Further, the specific resistance is desirably 2 × 10 ⁻² Ω · cm or less, and the driving voltage can be suppressed low.

  These electrodes are formed by the following manufacturing method.

  In forming the pixel electrodes 9a formed on the TFT array substrate 10, first, the TFT array substrate 10 on which the third interlayer insulating film 7 is formed is prepared. On the other hand, in forming the counter electrode 21 formed on the counter substrate 20, first, the counter substrate 20 on which the second light shielding film 23 is formed is prepared. Both the pixel electrode 9a and the counter electrode 21 are formed under the same sputtering conditions as described later.

  The sputtering is performed by a DC magnetron sputtering apparatus using a target of indium tin oxide. The temperature at the time of sputtering is set to 200 ° C. or higher, here 210 ° C. By setting the temperature to 200 ° C. or higher, the crystallinity of ITO can be improved and the concentration of unbonded In in the formed film can be reduced. That is, since the concentration of unbonded In can be reduced, it is possible to prevent the unbonded In from entering the alignment film and damaging the alignment film. As the sputtering gas, a gas having an oxygen gas amount of 0.6 mol% or more, more preferably 1.1 mol% or more with respect to the argon gas is used. By setting the flow ratio of the oxygen gas higher than the conventional 0.1 mol%, the oxidation rate of the ITO film can be improved and the unbonded In concentration can be reduced. Roughness of the film can be suppressed. Further, the sputtering gas pressure is set to 0.7 Pa or less, more preferably 0.4 Pa or less. With this setting, the mean free path of the sputtered particles becomes longer, and the crystallinity can be improved. The magnetic flux density of the DC magnetron sputtering device is set to 500 gauss or more, whereby the crystallinity of the ITO film can be improved.

Under such sputtering conditions, an ITO film having a film thickness of 120 nm and 83 nm is formed on the opposing substrate 20 and the TFT array substrate 10, respectively. After that, an annealing process is performed in a temperature range of 200 ° C. to 400 ° C. for the purpose of lowering the resistance of the formed ITO film. This annealing process can be performed in any atmosphere such as an N ₂ atmosphere, an H ₂ / Ar atmosphere, or the air. In the annealing treatment, it is preferable to anneal with a gas containing no hydrogen such as N ₂ after forming the ITO film, and then anneal with a gas containing hydrogen. Further, it is preferable to perform annealing at a temperature equal to or lower than 100 ° C. added to the substrate temperature at the time of sputtering.

As described above, the counter electrode 21 made of ITO is formed on the counter substrate 20.
On the other hand, in the TFT array substrate 10, a plurality of pixel electrodes 9a are formed by patterning the formed ITO film into a predetermined shape.

  After the pixel electrode 9a and the counter electrode 21 are formed, alignment films 22, 16 are formed by applying a polyimide on each of the counter substrate 20 and the TFT array substrate 10 and then rubbing the surface. .

(Configuration and Function of Second Embodiment of Liquid Crystal Device)
This embodiment is different only in that the film quality of the pixel electrode 9a and the counter electrode 21 in the above-described first embodiment is different, and other configurations are the same as the first embodiment. explain.

  In the present embodiment, each of the pixel electrode 9a and the counter electrode 21 is formed of ITO, and changes the oxygen content in the film thickness direction, and the oxygen content increases as approaching the alignment films 16 and 22. Has become. Here, the higher the oxygen content is, the lower the unbonded In concentration is. Therefore, the closer the film is to the alignment film, the lower the In concentration is, so that the roughness of the alignment film due to In can be suppressed. In other words, such a layer structure state is a layer structure state in which the higher the oxygen concentration of the ITO film, the higher the resistance. Therefore, the closer to the alignment films 16 and 22, the higher the specific resistance of the electrode.

In the present embodiment, for example, the electrode structure has a two-layer structure having different specific resistances, the specific resistance of the electrode layer in contact with the alignment films 22 and 16 is 3.5 × 10 ⁻⁴ Ωcm, the film thickness is 120 nm, and the other is. The electrode layer had a specific resistance of 2 × 10 ⁻⁴ Ωcmm and a thickness of 83 nm. With such a configuration, it is possible to suppress the roughness of the alignment film due to In while suppressing the resistance of the entire electrode to a low resistance. In this case, the required conductivity of the ITO film is a portion where the oxygen concentration is relatively low, and is secured at a position distant in cross section from the alignment film.

  Such a method of changing the specific resistance value stepwise in the film thickness direction can be performed by changing the sputtering conditions at the time of forming the ITO film. Specifically, for example, the oxygen concentration of the sputtering gas may be changed.

  Further, in the present embodiment, the electrode is formed by laminating electrode layers having different specific resistance values stepwise, but the oxygen concentration of the sputtering gas is gradually increased at the time of film formation, and the oxygen concentration is gradually increased in the layer thickness direction. May be changed, or the sputter argon gas pressure may be reduced to gradually improve the crystallinity in the layer thickness direction.

(Configuration and Function of Third Embodiment of Liquid Crystal Device)
This embodiment is different from the above-described first embodiment in that a protective film is provided between the pixel electrode 9a made of ITO and the alignment film 16, and between the counter electrode 22 made of ITO and the alignment film 16, respectively. The structure is different in that an inorganic film is interposed. Since other configurations are the same as those of the first embodiment, only the differences will be described below.

In the present embodiment, the characteristics of the electrode made of ITO, such as the ultraviolet absorption coefficient, are not particularly limited, and an ITO film formed by a known manufacturing method can be used, and a wide design range can be obtained. As the inorganic film, a silicon nitride film, an oxide film such as a silicon oxide film or a Nesa film can be used, and the unbonded In in the ITO film can be prevented from entering the alignment film through the inorganic film. Is fine. For example, a Nesa film (stannic oxide film) has a higher resistance value than an ITO film, but is excellent in chemical resistance and heat resistance stability. As a film formation method, a film may be formed by sputtering using a target made of stannic oxide after forming the electrode. In this case, the thickness of the stannic oxide film may be set to about 10 to 50 nm. Further, as another oxide film, a SiO ₂ film may be formed by sputtering, CVD, or the like. At this time, the film thickness is, for example, about 30 to 50 nm.

  By thus interposing the inorganic film between the alignment film and the electrode, it is possible to prevent unbonded In in the ITO from entering the alignment film and to prevent the alignment film from being roughened. .

  The electrode structures of the above embodiments may be combined, for example, by limiting the ultraviolet absorption coefficient of ITO, and furthermore, an inorganic film may be interposed between the electrode made of ITO and the alignment film.

(Overall configuration of liquid crystal device)
The overall configuration of each embodiment of the liquid crystal device configured as described above will be described with reference to FIGS. FIG. 5 is a plan view of the TFT array substrate 10 together with the components formed thereon viewed from the counter substrate 20 side. FIG. It is H 'sectional drawing.

  In FIG. 5, a sealing material 52 is provided on the TFT array substrate 10 along the edge thereof, and in parallel with the inside thereof, for example, as a peripheral partition made of the same or different material as the second light shielding film 23. Is provided. In a region outside the sealing material 52, a data line driving circuit 101 and mounting terminals 102 are provided along one side of the TFT array substrate 10, and a scanning line driving circuit 104 extends along two sides adjacent to this one side. It is provided. If the delay of the scanning signal supplied to the scanning line 3a does not matter, it goes without saying that the scanning line driving circuit 104 may be provided on only one side. Further, the data line driving circuits 101 may be arranged on both sides along the side of the screen display area. For example, the odd-numbered data lines 6a supply an image signal from a data line driving circuit disposed along one side of the screen display area, and the even-numbered data lines extend along the opposite side of the screen display area. The image signal may be supplied from a data line driving circuit arranged in a predetermined manner. By driving the data lines 6a in a comb-tooth shape as described above, the area occupied by the data line driving circuit can be expanded, and a complicated circuit can be formed. Further, on the remaining one side of the TFT array substrate 10, a plurality of wirings 105 for connecting between the scanning line driving circuits 104 provided on both sides of the screen display area are provided. A precharge circuit (not shown) may be provided hidden under 53. In at least one of the corners of the opposing substrate 20, a conductive material 106 for establishing electric conduction between the TFT array substrate 10 and the opposing substrate 20 is provided. Then, as shown in FIG. 6, the counter substrate 20 having substantially the same contour as the sealing material 52 shown in FIG. 5 is fixed to the TFT array substrate 10 by the sealing material 52.

  On the TFT array substrate 10 of the liquid crystal device according to the above-described embodiment, an inspection circuit or the like for inspecting the quality, defect, or the like of the liquid crystal device during manufacturing or shipping may be further formed. Further, instead of providing the data line driving circuit 101 and the scanning line driving circuit 104 on the TFT array substrate 10, for example, a driving LSI mounted on a TAB (tape automated bonding substrate) is provided around the TFT array substrate 10. You may make it electrically and mechanically connect via the anisotropic conductive film provided in the part. For example, a TN (twisted nematic) mode, an STN (super TN) mode, and a D-STN (double-side) are provided on the side of the opposite substrate 20 on which the projected light is incident and on the side of the TFT array substrate 10 on which the emitted light is emitted, respectively. A polarizing film, a retardation film, a polarizing means, and the like are arranged in a predetermined direction according to an operation mode such as an STN) mode or a normally white mode / normally black mode.

  Since the liquid crystal device according to the present embodiment is applied to a color liquid crystal projector (projection display device), three liquid crystal devices are used as light valves for RGB, and each panel has an RGB color separation device. The light of each color decomposed via the dichroic mirror is incident as projection light. Therefore, no color filter is provided on the opposing substrate 20. However, an RGB color filter may be formed on the opposing substrate 20 in a predetermined area facing the pixel electrode 9a where the second light-shielding film 23 is not formed, together with the protective film. In this way, the liquid crystal device according to each embodiment can be applied to a color liquid crystal device such as a direct-view or reflection type color liquid crystal television other than the liquid crystal projector. Further, a micro lens may be formed on the counter substrate 20 so as to correspond to one pixel. In this case, a bright liquid crystal device can be realized by improving the efficiency of collecting incident light. Furthermore, a dichroic filter that creates RGB colors using light interference may be formed by depositing many layers of interference layers having different refractive indices on the counter substrate 20. According to the counter substrate with the dichroic filter, a brighter color liquid crystal device can be realized.

  Also, the switching element provided in each pixel has been described as a normal stagger type or coplanar type polysilicon TFT. However, other types of TFTs such as an inverse stagger type TFT and an amorphous silicon TFT are also applicable. The above embodiment is effective.

(Electronics)
As an example of an electronic device using the above-described liquid crystal device, a structure of a projection display device will be described with reference to FIGS. In FIG. 7, a projection display device 1100 is a schematic configuration diagram of an optical system of a projection liquid crystal device in which three liquid crystal devices described above are prepared and used as liquid crystal devices 962R, 962G, and 962B for RGB. The light source device 920 and the uniform illumination optical system 923 described above are adopted as the optical system of the projection display device of this example. The projection display apparatus further includes a color separation optical system 924 as a color separation unit that separates the light beam W emitted from the uniform illumination optical system 923 into red (R), green (G), and blue (B). Three light valves 925R, 925G, and 925B as modulation means for modulating each color light flux R, G, and B, and a color synthesis prism 910 as color synthesis means for recombining the modulated color light flux are synthesized. A projection lens unit 906 is provided as projection means for projecting the light beam onto the surface of the projection surface 100 in an enlarged manner. Further, a light guide system 927 for guiding the blue light flux B to the corresponding light valve 925B is also provided.

  The uniform illumination optical system 923 includes two lens plates 921 and 922 and a reflection mirror 931. The two lens plates 921 and 922 are arranged so as to be orthogonal to each other with the reflection mirror 931 interposed therebetween. Each of the two lens plates 921 and 922 of the uniform illumination optical system 923 includes a plurality of rectangular lenses arranged in a matrix. The light beam emitted from the light source device 920 is divided into a plurality of partial light beams by the rectangular lens of the first lens plate 921. These partial light beams are superimposed near the three light valves 925R, 925G, and 925B by the rectangular lens of the second lens plate 922. Therefore, by using the uniform illumination optical system 923, even when the light source device 920 has a non-uniform illuminance distribution in the cross section of the emitted light beam, the three light valves 925R, 925G, and 925B can emit uniform illumination light. It becomes possible to illuminate.

  Each color separation optical system 924 includes a blue-green reflecting dichroic mirror 941, a green reflecting dichroic mirror 942, and a reflecting mirror 943. First, in the blue-green reflecting dichroic mirror 941, the blue light beam B and the green light beam G included in the light beam W are reflected at right angles, and head toward the green reflecting dichroic mirror 942. The red light beam R passes through the mirror 941, is reflected at a right angle by the rear reflection mirror 943, and is emitted from the emission unit 944 of the red light beam R to the prism unit 910 side.

  Next, in the green reflecting dichroic mirror 942, only the green light flux G among the blue and green light fluxes B and G reflected by the blue-green reflecting dichroic mirror 941 is reflected at a right angle, and the color is emitted from the emission portion 945 of the green light flux G. The light is emitted to the side of the combining optical system. The blue light flux B that has passed through the green reflection dichroic mirror 942 is emitted from the emission section 946 of the blue light flux B to the light guide system 927 side. In this example, the distances from the light emitting portion of the light beam W of the uniform illumination optical element to the light emitting portions 944, 945, 946 of the color light beams in the color separation optical system 924 are set to be substantially equal.

  Condensing lenses 951 and 952 are arranged on the emission sides of the emission sections 944 and 945 of the red and green light fluxes R and G of the color separation optical system 924, respectively. Therefore, the red and green luminous fluxes R and G emitted from the respective emission sections are incident on these condenser lenses 951 and 952 and are parallelized.

  The red and green luminous fluxes R and G thus collimated are incident on the light valves 925R and 925G and modulated, and image information corresponding to each color light is added. That is, the switching of these liquid crystal devices is controlled by a driving unit (not shown) according to image information, whereby each color light passing therethrough is modulated. On the other hand, the blue light flux B is guided to the corresponding light valve 925B via the light guide system 927, where it is similarly modulated according to image information. The light valves 925R, 925G, and 925B of the present example further include an incident-side polarizing unit 960R, 960G, and 960B, an outgoing-side polarizing unit 961R, 961G, and 961B, and liquid crystal devices 962R and 962G disposed therebetween. , 962B.

  The light guide system 927 includes a condenser lens 954 disposed on the exit side of the exit portion 946 of the blue light beam B, an incident side reflection mirror 971, an exit side reflection mirror 972, and an intermediate lens disposed between these reflection mirrors. 973 and a condenser lens 953 disposed on the front side of the light valve 925B. The blue light flux B emitted from the condenser lens 946 is guided to the liquid crystal device 962B via the light guide system 927 and is modulated. The optical path length of each color light beam, that is, the distance from the light emitting portion of the light beam W to each of the liquid crystal devices 962R, 962G, and 962B, is the longest for the blue light beam B, and therefore, the loss of light quantity of the blue light beam is the largest. However, by interposing the light guide system 927, the light amount loss can be suppressed.

  The color light fluxes R, G, and B modulated through the light valves 925R, 925G, and 925B enter the color combining prism 910 and are combined there. The light combined by the color combining prism 910 is enlarged and projected on the surface of the projection surface 100 at a predetermined position via the projection lens unit 906.

  In this example, among the liquid crystal devices 962R, 962G, and 962B, the liquid crystal device of each of the above-described embodiments can be used as a liquid crystal device corresponding to blue color light. In any of the liquid crystal devices according to any of the embodiments, it is possible to suppress occurrence of roughening of the alignment film due to irradiation of blue light.

The blue color light entering the liquid crystal device 962B corresponding to the blue color light contains components having wavelengths in the ultraviolet region of 380 nm to 410 nm in addition to light having the original wavelength.
The ultraviolet rays are absorbed by the ITO electrode to generate carriers in the ITO film, and the carriers decompose the ITO into indium, indium oxide, and oxygen. It is considered that the surface of the alignment film is roughened by the decomposed indium entering the polyimide film as the alignment film.

  When the liquid crystal device of the first embodiment is used, generation of carriers in the ITO film due to ultraviolet absorption can be prevented by specifying the ultraviolet absorption coefficient of the ITO film. As a result, since the ITO film is not decomposed, unbonded In is not generated as a decomposition product, and the alignment film is not roughened. Furthermore, by limiting the specific resistance of the ITO film, it is possible to increase the oxygen concentration in the ITO film and reduce unbonded In, so that it is possible to suppress roughness of the alignment film due to unbonded In. . The limitation of the ultraviolet absorption coefficient and the limitation of the specific resistance of the ITO film can provide the effect of preventing the alignment film from being roughened if either one of the conditions is satisfied. If it does, it goes without saying that the effect is further improved.

  In the case where the liquid crystal device of the second embodiment is used, the amount of unbonded In in the ITO film near the electrode surface on the alignment film side can be reduced while maintaining the electrode at low resistance. Roughness of the alignment film due to unbonded In can be suppressed.

  In the case of using the liquid crystal device of the third embodiment, by interposing an inorganic film between the alignment film and the electrode made of ITO, it is possible to prevent unbonded In in the ITO film from entering the alignment film. It is not necessary to adjust the film quality of the ITO film as in the first and second embodiments.

  As described above, in the present embodiment, it is possible to suppress the roughness of the alignment film surface of the liquid crystal device 962B corresponding to blue color light, extend the life of the alignment film, and realize a projection display device with high display quality.

  In the present embodiment, the liquid crystal device of each of the above embodiments is used as the liquid crystal device 962B corresponding to blue color light, but the liquid crystal device 962R corresponding to red color light and the liquid crystal device 962 corresponding to green color light are used. Needless to say, it can also be used for 962G.

  Further, in a liquid crystal device corresponding to red and green color light, it is not necessary to adjust the ultraviolet absorption coefficient and the specific resistance of the ITO electrode or to interpose an inorganic film between the alignment film and the electrode. A liquid crystal device can be used. In this case, for example, when the manufacturing cost of the liquid crystal device having the configuration of the present invention is high, only the liquid crystal device corresponding to blue may have the structure of the liquid crystal device of the present invention, and the manufacturing cost of the entire projection display device may be reduced. You can also lower it.

5 is an equivalent circuit of various elements, wiring, and the like provided in a plurality of pixels in a matrix forming an image forming area in the liquid crystal device according to the embodiment of the present invention. FIG. 2 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which a data line, a scanning line, a pixel electrode, a light shielding film, and the like are formed in the liquid crystal device according to the embodiment of the present invention. FIG. 3 is a sectional view taken along line A-A ′ of FIG. 2. 5 is a graph showing an experimental result of a relationship between a light absorption coefficient and a light resistance lifetime of an ITO film for light having a wavelength of 410 nm. FIG. 2 is a plan view of a TFT array substrate in an embodiment of a liquid crystal device together with components formed thereon as viewed from a counter substrate side. FIG. 6 is a sectional view taken along line H-H ′ of FIG. 5. FIG. 2 is a configuration diagram of a projection display device that is an example of an electronic device using a liquid crystal device.

Explanation of reference numerals

9a: Pixel electrode 10: TFT array substrate 16: Alignment film 21: Counter electrode 22: Alignment film 20: Counter substrate 50: Liquid crystal layer 100: Projection surface 906: Projection lens unit 910: Color combining prism 920: Light source device 924: Color Separating optical system 925R ... light valve 925G ... light valve 925B ... light valve 962R ... liquid crystal device 962G ... liquid crystal device 962B ... liquid crystal device

Claims (13)

A first substrate;
An electrode made of indium tin oxide and having an optical absorption coefficient of 8000 cm ^-1 or less for light having a wavelength of 410 nm disposed on the first substrate; and an alignment film made of an organic substance provided over the electrode.
A second substrate facing the first substrate,
A liquid crystal device comprising: a liquid crystal layer sandwiched between a gap between the first substrate and the second substrate. A first substrate;
An electrode made of indium tin oxide having a specific resistance of 1 × 10 ⁻⁴ Ω · cm or more, disposed on the first substrate;
An alignment film made of an organic material disposed over the electrode,
A second substrate facing the first substrate,
A liquid crystal device comprising: a liquid crystal layer sandwiched between a gap between the first substrate and the second substrate. A first substrate;
An electrode made of indium tin oxide having a light absorption coefficient of 8000 cm ^-1 or less and a specific resistance of 1 × 10 ^-4 Ω · cm or more for light having a wavelength of 410 nm disposed on the first substrate;
An alignment film made of an organic material disposed over the electrode,
A second substrate facing the first substrate,
A liquid crystal device comprising: a liquid crystal layer sandwiched between a gap between the first substrate and the second substrate. 4. The liquid crystal device according to claim 1, wherein the electrode made of indium tin oxide has a light absorption coefficient of 2000 cm ^-1 or less. The liquid crystal device according to claim 2, wherein the specific resistance of the electrode is 3.5 × 10 ⁻⁴ or more. A first substrate;
An electrode made of indium tin oxide disposed on the first substrate;
An inorganic film disposed over the electrode,
An alignment film made of an organic substance disposed over the electrode and the inorganic film,
A second substrate facing the first substrate,
A liquid crystal device comprising: a liquid crystal layer sandwiched between a gap between the first substrate and the second substrate. The liquid crystal device according to claim 6, wherein the inorganic film is a nitride film or an oxide film. A first substrate;
An electrode made of indium tin oxide disposed on the first substrate;
An alignment film made of an organic material disposed over the electrode,
A second substrate facing the first substrate,
A liquid crystal device having a liquid crystal layer sandwiched in a gap between the first substrate and the second substrate,
A liquid crystal device, wherein the oxygen content of the electrode made of indium tin oxide changes in the thickness direction thereof. 9. The liquid crystal device according to claim 8, wherein the oxygen content increases as approaching the alignment film. The liquid crystal device according to claim 1, wherein the alignment film is formed of a polyimide film. 10. A method for manufacturing a liquid crystal device, comprising: forming an electrode made of indium tin oxide according to claim 8 or 9 while changing an oxygen concentration in an argon gas at the time of sputtering. A light source,
Color separation means for separating the light from the light source into red, blue, and green color light,
Light modulation means corresponding to each color light modulating the color light separated by the color separation means,
Color synthesizing means for synthesizing the color lights modulated by the light modulating means,
And a projection lens that projects the light combined by the color combining unit.
11. A projection display device, wherein at least the blue light modulating means of the light modulating means includes the liquid crystal device according to any one of claims 1 to 10. A light source,
Light modulation means for modulating light from the light source,
A projection display device comprising: a projection lens that projects light modulated by the light modulation unit.
A projection display device, wherein the light modulation unit includes the liquid crystal device according to any one of claims 1 to 10.

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