JP2007219365A - Method for manufacturing liquid crystal device, liquid crystal device, and electronic apparatus - Google Patents

Abstract

A method for manufacturing a liquid crystal device, a liquid crystal device, and an electronic apparatus including the liquid crystal device, which can prevent defects caused by electrodes and obtain a highly reliable device.
A liquid crystal layer 50, a pair of substrates 10 and 20 sandwiching the liquid crystal layer 50, and a pair of electrodes 9 and 21 disposed on the liquid crystal layer 50 side of the pair of substrates 10 and 20, respectively. It is a manufacturing method of a liquid crystal device. By the atomic layer deposition method, the coating films 41 and 61 are formed on the substrate surface so that at least one of the pair of electrodes 9 and 21 is covered. Then, alignment films 40 and 60 made of an inorganic material are formed on the coating films 41 and 61.
[Selection] Figure 4

Description

  The present invention relates to a method for manufacturing a liquid crystal device, a liquid crystal device, and an electronic apparatus.

  A light modulation means mounted on a projection display device such as a liquid crystal projector or a liquid crystal device used as a direct-view display device mounted on a mobile phone or the like is disposed opposite to each other with a liquid crystal layer interposed therebetween, and a voltage is applied to the liquid crystal layer. It is mainly composed of a pair of substrates each having an electrode for application. In addition, an alignment film that controls the alignment of liquid crystal molecules when no voltage is applied is formed on the liquid crystal layer side of the pair of substrates constituting the liquid crystal device, thereby regulating the alignment state of the liquid crystal molecules when no electric field is applied. It is possible to do.

As such an alignment film, a film made of an alignment polymer such as polyimide is generally used, and the surface thereof is subjected to a rubbing treatment.
However, the alignment film made of the alignment polymer is deteriorated by strong light or heat from a light source, for example, when used as a light modulation means of a liquid crystal projector. When the alignment film deteriorates in this way, the alignment regulating force of the liquid crystal molecules is reduced, the alignment state of the liquid crystal molecules is disturbed, and the display quality of the liquid crystal device is deteriorated. Therefore, in recent years, an inorganic alignment film made of an inorganic material such as silicon oxide (SiO ₂ ) having light resistance and heat resistance has been used. In general, the inorganic alignment film is formed using an oblique vapor deposition method, and thus has a columnar structure inclined in the vapor deposition direction.

  By the way, in general, when a liquid crystal device is driven, a metal element, a metal ion, or the like diffuses from the electrode that applies a voltage to the liquid crystal layer due to heat or the like inside the panel, and becomes an impurity. In particular, since the inorganic alignment film has a columnar structure as described above, there are many gaps, and the impurities pass through the inorganic alignment film and diffuse into the liquid crystal layer. When impurities are diffused in the liquid crystal layer in this way, the liquid crystal layer is deteriorated and the display quality of the liquid crystal device is deteriorated.

Therefore, by forming a vertical vapor deposition film on the electrode by physical vapor deposition and forming an inorganic alignment film formed by oblique vapor deposition on the vertical vapor deposition film, liquid crystal of impurities generated from the electrode by the vertical vapor deposition film. There is a technique for preventing diffusion into a layer (see, for example, Patent Document 1).
JP-A-2005-77901

  However, the vertical alignment film formed by physical vapor deposition does not have a density sufficient to prevent diffusion of impurities generated from the electrodes toward the liquid crystal layer. Therefore, there is a problem that impurities diffuse through the inorganic alignment film (alignment film) into the liquid crystal layer, causing deterioration of the liquid crystal and reducing the reliability of the liquid crystal device. In addition, it may be possible to prevent the diffusion of impurities into the liquid crystal layer by increasing the thickness of the inorganic alignment film. In this case, however, the increase in the thickness of the inorganic alignment film results in inclusion in the inorganic alignment film. The number of carriers (electrons, holes, etc.) increases, and there is a possibility that many carriers are injected into the liquid crystal layer when a voltage is applied, leading to a decrease in the reliability of the liquid crystal device.

  The present invention has been made in view of the above circumstances, and a liquid crystal device manufacturing method, a liquid crystal device, and an electronic apparatus including the liquid crystal device can be obtained by preventing defects caused by electrodes and obtaining a highly reliable one. The purpose is to provide.

  A method of manufacturing a liquid crystal device according to the present invention includes a liquid crystal layer, a pair of substrates that sandwich the liquid crystal layer, and a pair of electrodes that are respectively disposed on the liquid crystal layer side of the pair of substrates. In the manufacturing method, a step of forming a coating film on the substrate surface so as to cover at least one of the pair of electrodes by an atomic layer deposition method, and a step of forming an alignment film made of an inorganic material on the coating film It is characterized by providing.

  According to the method for manufacturing a liquid crystal device of the present invention, since the coating film covering at least one of the electrodes is formed by the atomic layer deposition method, the coating film is highly dense. Since the electrode and the liquid crystal layer are in contact with each other through the coating film, impurities such as metal elements and metal ions generated from the electrode are blocked by the coating film and diffuse to the liquid crystal layer side. Is prevented. Since the coating film has high density, for example, its thickness can be reduced, and the coating film does not lower the transmittance and contrast ratio. In addition, since the diffusion of impurities can be prevented only with a highly dense coating film, the alignment film can be thinned, and carriers (electrons, holes) contained in the alignment film in advance are reduced. The amount of carriers injected into the liquid crystal layer when a voltage is applied to the electrode can be reduced. Further, since the coating film has high density, it can also be employed as an insulating film. In this case, electron injection from the electrode side to the liquid crystal layer side can be suppressed. Furthermore, since the electrode is covered with the coating film, the liquid crystal layer and the electrode are not in direct contact with each other, so that the photocatalytic reaction is prevented from occurring on the electrode, and the liquid crystal layer resulting from the photocatalytic reaction is prevented. Deterioration can be prevented. Therefore, a liquid crystal device with high reliability can be provided by preventing problems caused by the electrodes.

In the method for manufacturing the liquid crystal device, the alignment film is preferably formed by oblique deposition of an inorganic material.
In this way, it is possible to satisfactorily give a pretilt angle to the liquid crystal molecules by the alignment film without performing a rubbing treatment or the like. Further, since the alignment film is made of an inorganic material, the alignment film has heat resistance and light resistance, and a liquid crystal device including the alignment film can be suitably used as a light modulation element of a projector.

In the method for manufacturing the liquid crystal device, the coating film is preferably formed using silicon oxide.
In this way, the adhesion between the coating film and the electrode formed on the substrate can be improved.

  The liquid crystal device of the present invention is a liquid crystal device comprising a liquid crystal layer, a pair of substrates sandwiching the liquid crystal layer, and a pair of electrodes respectively disposed on the liquid crystal layer side of the pair of substrates. At least one of the electrodes is covered with a coating film formed by an atomic deposition method, and an alignment film made of an inorganic material is formed on the coating film.

  According to the liquid crystal device of the present invention, since at least one electrode is covered with a very dense coating film formed by atomic layer deposition, the electrode and the liquid crystal layer are in contact with each other through the coating film. It has become a state. The coating film prevents impurities such as metal elements and metal ions generated from the electrodes from diffusing to the liquid crystal layer side. In addition, since the coating film has high density, the thickness can be reduced. By providing the coating film, the transmittance and contrast ratio of the liquid crystal device are not reduced. In addition, since the diffusion of impurities can be prevented only by the coating film, the alignment film can be thinned, and carriers (electrons, holes) previously contained in the alignment film are reduced. It is possible to reduce the amount of carriers injected into the liquid crystal layer when applying. Further, since the coating film has high density, it can also be employed as an insulating film. In this case, electron injection from the electrode side to the liquid crystal layer side can be suppressed. Furthermore, since the electrode is covered with the coating film, the liquid crystal layer and the electrode are not in direct contact with each other, so that the photocatalytic reaction is prevented from occurring on the electrode, and the liquid crystal layer resulting from the photocatalytic reaction is prevented. Deterioration is prevented. Accordingly, a highly reliable liquid crystal device in which defects due to the electrodes are prevented is obtained.

Moreover, in the said liquid crystal device, it is preferable that the film thickness of the said coating film is 5-50 nm.
According to this, since the film thickness is sufficiently smaller than the wavelength of light (400 nm), light is prevented from being reflected in the coating film, and the transmittance and contrast ratio in the liquid crystal device are not reduced. Moreover, it is possible to reliably prevent the problems caused by impurity diffusion, electron injection, and photocatalytic reaction as described above.

  An electronic apparatus according to the present invention includes the above-described liquid crystal device.

  According to the electronic device of the present invention, the electronic device itself is highly reliable because it includes the liquid crystal device in which the problems due to the diffusion of impurities into the liquid crystal layer, the electron injection, and the photocatalytic reaction are prevented. It will be a thing.

  Next, an embodiment according to the present invention will be described in detail. In each embodiment, description will be made with reference to the drawings. In each drawing, each layer and each member have different scales so that each layer and each member can be recognized on the drawing. is there.

(Schematic configuration of the liquid crystal device)
In the following, an embodiment of the present invention will be described by taking an active matrix type transmissive liquid crystal device of a vertical alignment mode using TFT (Thin-Film Transistor) elements as switching elements based on FIGS. 1 to 5 as an example. The structure of the liquid crystal device will be described.

  FIG. 1 is a diagram showing a liquid crystal device manufactured by the method for manufacturing a liquid crystal device of the present invention. FIG. 1A is a plan configuration diagram of the liquid crystal device, and FIG. 1B is a sectional configuration diagram taken along line H-H ′ in FIG. FIG. 2 is an equivalent circuit diagram of switching elements, signal lines and the like in a plurality of pixels arranged in a matrix constituting the image display area of the liquid crystal device of the present embodiment. FIG. 3 is a plan view showing the structure of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes and the like are formed. FIG. 4 is a cross-sectional view showing the structure of the liquid crystal device of this embodiment, and is a cross-sectional view taken along the line A-A ′ of FIG. 2.

  As shown in FIG. 1A and FIG. 1B, the liquid crystal device 100 according to the present embodiment has a TFT array substrate 10 and a counter substrate 20 attached to each other via a sealing material 52 having a substantially rectangular frame shape in plan view. In addition, the liquid crystal layer 50 is sealed in a region surrounded by the sealing material 52. A peripheral parting line 53 having a rectangular frame shape in plan view is formed along the inner peripheral side of the sealing material 52, and an area inside the peripheral parting part is an image display area 10a. In the area outside the sealing material 52, the data line driving circuit 101 and the external circuit mounting terminal 102 are formed along one side (the lower side in the drawing) of the TFT array substrate 10, and the two sides adjacent to this one side are formed. Scanning line driving circuits 104 and 104 are formed along the lines to constitute peripheral circuits.

  The remaining one side (the upper side in the figure) of the TFT array substrate 10 is provided with a plurality of wirings 105 that connect between the scanning line drive circuits 104 on both sides of the image display region 10a. In addition, an inter-substrate conductive material 106 for providing electrical continuity between the TFT array substrate 10 and the counter substrate 20 is disposed at each corner of the counter substrate 20. The liquid crystal device 100 of the present embodiment is configured as a transmissive liquid crystal device, and modulates light from a light source (not shown) arranged on the TFT array substrate 10 side and emits it as display light from the counter substrate 20 side. It has become.

  As shown in FIG. 1B, a plurality of pixel electrodes 9 are arranged on the inner surface side (liquid crystal layer side) of the TFT array substrate 10, and an alignment film 40 is formed so as to cover these pixel electrodes 9. ing. A peripheral parting 53 and a light shielding film 23 are formed on the inner surface side of the counter substrate 20, and a planar solid counter electrode 21 is formed thereon. An alignment film 60 is formed so as to cover the counter electrode 21.

  The alignment films 40 and 60 provided on the inner surfaces of the TFT array substrate 10 and the counter substrate 20 are formed by oblique deposition of an inorganic material as will be described later. Under 60, a coating film formed by an atomic layer deposition method is formed.

  In the liquid crystal device of the present embodiment, as shown in FIG. 2, a plurality of pixels arranged in a matrix that forms an image display area are a pixel electrode 9 and a switching element for controlling the pixel electrode 9. Each TFT element 30 is formed, and a data line 6 a to which an image signal is supplied is electrically connected to the source of the TFT element 30. Image signals S1, S2,..., Sn to be written to the data line 6a are supplied line-sequentially in this order, or are supplied for each group to a plurality of adjacent data lines 6a.

  In addition, the scanning line 3a is electrically connected to the gate of the TFT element 30, and scanning signals G1, G2,..., Gm are applied to the plurality of scanning lines 3a in a pulse-sequential manner at predetermined timing. The Further, the pixel electrode 9 is electrically connected to the drain of the TFT element 30, and the image signal S1, S2,... Supplied from the data line 6a is turned on by turning on the TFT element 30 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 to the liquid crystal via the pixel electrode 9 is held for a certain period with the common electrode described later. The liquid crystal modulates light by changing the orientation and order of the molecular assembly according to the applied voltage level, thereby enabling gradation display. Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the common electrode.

(Planar structure)
Next, a planar structure of the liquid crystal device 100 of the present embodiment will be described based on FIG.
As shown in FIG. 3, a rectangular pixel electrode 9 made of a transparent conductive material such as indium tin oxide (hereinafter abbreviated as “ITO”) on the TFT array substrate (the outline is indicated by a dotted line portion 9A). Are provided in a matrix, and a data line 6a, a scanning line 3a, and a capacitor line 3b are provided along vertical and horizontal boundaries of the pixel electrode 9, respectively. In the present embodiment, each pixel electrode 9 and the area where the data line 6a, the scanning line 3a, the capacitor line 3b, etc. are arranged so as to surround each pixel electrode 9 are pixels, and are arranged in a matrix. The display can be displayed for each pixel.

  The data line 6a is electrically connected to a source region (described later) through a contact hole 5 in the semiconductor layer 1a made of, for example, a polysilicon film constituting the TFT element 30, and the pixel electrode 9 is connected to the semiconductor layer 1a. Among these, it is electrically connected to a drain region described later via a contact hole 8. In addition, the scanning line 3a is disposed so as to face a channel region (a region with a diagonal line rising to the left in the figure), which will be described later, in the semiconductor layer 1a, and the scanning line 3a serves as a gate electrode at a portion facing the channel region. Function.

The capacitor line 3b is formed from a main line portion extending in a substantially straight line 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 (that is, a second region extending along the data line 6 a when viewed in a plan view) protruding toward the previous stage (upward in the drawing) along the data line 6 a.
In FIG. 3, a plurality of first light shielding films 11 a are provided in a region indicated by a diagonal line rising to the right.

  More specifically, each of the first light shielding films 11a is provided at a position covering the TFT element 30 including the channel region of the semiconductor layer 1a when viewed from the TFT array substrate side, and further, the main line portion of the capacitor line 3b. And a main line portion that extends linearly along the scanning line 3a and a protruding portion that protrudes from the portion intersecting the data line 6a to the rear side adjacent to the data line 6a (that is, downward in the figure). Have. The tip of the downward protruding portion in each stage (pixel row) of the first light shielding film 11a overlaps the tip of the upward protruding portion of the capacitor line 3b in the next stage under the data line 6a. A contact hole 13 for electrically connecting the first light-shielding film 11a and the capacitor line 3b to each other is provided at the overlapping portion. In other words, in the present embodiment, the first light shielding film 11a is electrically connected to the upstream or downstream capacitor line 3b through the contact hole 13.

(Cross-section structure)
Next, a cross-sectional structure of the liquid crystal device of the present embodiment will be described based on FIG. As shown in FIG. 4, in the liquid crystal device of this embodiment, a liquid crystal layer 50 is sandwiched between the TFT array substrate 10 and a counter substrate 20 disposed to face the TFT array substrate 10. The TFT array substrate 10 is mainly composed of a substrate body 10A made of a translucent material such as quartz, a pixel electrode 9 formed on the surface of the liquid crystal layer 50, a TFT element 30, and an alignment film 40. Reference numeral 20 mainly includes a substrate body 20A made of a light-transmitting material such as glass or quartz, a counter electrode 21 formed on the surface of the liquid crystal layer 50, and an alignment film 60.

More specifically, in the TFT array substrate 10, a pixel electrode 9 is provided on the surface of the substrate body 10 </ b> A on the liquid crystal layer 50 side, and for pixel switching for switching control of each pixel electrode 9 at a position adjacent to each pixel electrode 9. A TFT element 30 is provided.
The pixel switching TFT element 30 has an LDD (Lightly Doped Drain) structure, and includes a scanning line 3a, a channel region 1a ′ of the semiconductor layer 1a in which a channel is formed by an electric field from the scanning line 3a, and the scanning line 3a. A gate insulating film 2 that insulates the semiconductor layer 1a, a data line 6a, a low concentration source region 1b and a low concentration drain region 1c of the semiconductor layer 1a, and a high concentration source region 1d and a high concentration drain region 1e of the semiconductor layer 1a. ing.

  Further, a second 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 formed on the substrate main body 10A including the scanning line 3a and the gate insulating film 2. An interlayer insulating film 4 is formed. That is, the data line 6 a is electrically connected to the high concentration source region 1 d through the contact hole 5 that penetrates the second interlayer insulating film 4. Further, on the data line 6a and the second interlayer insulating film 4, a third interlayer insulating film 7 having a contact hole 8 leading to the high concentration drain region 1e is formed. That is, the high concentration drain region 1 e is electrically connected to the pixel electrode 9 through the contact hole 8 that penetrates the second interlayer insulating film 4 and the third interlayer insulating film 7.

  In the present embodiment, the gate insulating film 2 is extended from a position facing the scanning line 3a and used as a dielectric film, the semiconductor film 1a is extended to form the first storage capacitor electrode 1f, and further opposed thereto. The storage capacitor 70 is configured by using a part of the capacitor line 3b to be a second storage capacitor electrode.

  Further, on the surface of the TFT array substrate 10 on the liquid crystal layer 50 side of the substrate main body 10A, the region where the pixel switching TFT elements 30 are formed is transmitted through the TFT array substrate 10, and the lower surface (TFT) of the TFT array substrate 10 is illustrated. Return light reflected by the interface between the array substrate 10 and air and returning to the liquid crystal layer 50 is incident on at least the channel region 1a ′ and the low concentration source / drain regions (LDD regions) 1b and 1c of the semiconductor layer 1a. A first light-shielding film 11a for preventing this is provided. Further, a first interlayer insulation for electrically insulating the semiconductor layer 1a constituting the pixel switching TFT element 30 from the first light shielding film 11a is provided between the first light shielding film 11a and the pixel switching TFT element 30. A film 12 is formed. As shown in FIG. 3, in addition to providing the first light-shielding film 11a on the TFT array substrate 10, the first light-shielding film 11a is electrically connected to the capacitor line 3b at the preceding stage or the subsequent stage through the contact hole 13. Configured to connect to.

  In addition, the inner surface of the TFT array substrate 10 on the liquid crystal layer 50 side covers the pixel electrode 9 and the third interlayer insulating film 7 in the region where the pixel electrode 9 is not formed. An alignment film 40 for controlling the alignment of the liquid crystal molecules is formed.

In the present embodiment, the alignment film 40 has a thickness of 0.02 to 0 using a silicon oxide such as SiO ₂ or SiO, or a metal oxide such as Al ₂ O ₃ , ZnO, MgO, or ITO. .3 μm (preferably 0.02 to 0.08 μm). In the present embodiment, the alignment film 40 is formed by obliquely vapor-depositing a silicon oxide mainly composed of SiO ₂ . For the production of the alignment film 40, a sputtering method such as an ion beam sputtering method or a magnetron sputtering method may be employed.

  As shown in FIG. 5, the alignment film 40 is composed of an infinite number of columnar structures 40a, and a part of the columnar structures 40a is formed with a gap between adjacent columnar structures. . Since these columnar structures 40a are formed by oblique vapor deposition, each of the columnar structures 40a is arranged at a predetermined inclination angle θ with respect to the surface of the substrate body 10A. Thereby, alignment control of the liquid crystal arrange | positioned on the alignment film 40 can be performed now.

A coating film 41 is formed immediately below the alignment film 40, that is, between the pixel electrode 9 and the third interlayer insulating film 7 and the alignment film 40 so as to cover at least the pixel electrode 9. . As described above, the alignment film 40 includes a large number of columnar structures, and has a gap between adjacent columnar structures. On the other hand, the coating film 41 is formed by atomic layer deposition ((Atomic Layer Deposition) method, hereinafter also referred to as “ALD method”) as described later, and SiO _X (where x is 1 or more) It is composed of silicon oxide such as an integer). Note that a material obtained by adding boron, phosphorus, carbon, nitrogen, or the like to the silicon oxide may be used.
The covering film 41 serves to prevent the impurities such as metal elements and metal ions from diffusing from the pixel electrode 9 to the liquid crystal layer 50 side. It is composed of a very dense film having no voids.

  Here, in the conventional liquid crystal device, with the passage of time, metal elements and metal ions generated from the pixel electrode 9 due to heat inside the panel diffuse into the liquid crystal layer and become impurities. Among these impurities, particularly when metal ions diffuse into the liquid crystal layer, the liquid crystal layer is destroyed by the metal ions, resulting in a problem that the display characteristics of the liquid crystal device are deteriorated and reliability is lowered. It was. Further, electrons are injected into the liquid crystal layer from the pixel electrode side, or the liquid crystal layer is deteriorated by a photocatalytic reaction generated on the pixel electrode due to contact between the liquid crystal layer and the pixel electrode made of ITO. The display characteristics and reliability were reduced.

Therefore, if the configuration according to the present embodiment is employed, the pixel electrode 9 and the liquid crystal layer 50 are in contact with each other via the coating film 41, and thus the coating film 41 generates from the pixel electrode 9. This prevents the impurities such as the metal elements and metal ions from diffusing to the liquid crystal layer 50 side.
The coating film 41 is denser and thinner than a film formed by physical vapor deposition. Specifically, in the present embodiment, the coating film 41 has a thickness of 5 to 50 nm. In this way, the diffusion of impurities into the liquid crystal layer 50 is reliably prevented, and the film thickness is sufficiently smaller than the wavelength of light (400 nm), so that light is not reflected by the coating film 41. Thus, the transmittance and the contrast ratio in the liquid crystal device 100 are prevented from being lowered.

Further, as described above, the coating film 41 made of silicon oxide (SiO _X (where x is an integer of 1 or more)) has a high density and can be employed as an insulating film. Electron injection from the electrode 9 side to the liquid crystal layer 50 side can be suppressed. Furthermore, since the pixel electrode 9 is covered with the coating film 41, the liquid crystal layer 50 and the pixel electrode 9 are not in direct contact with each other, so that the photocatalytic reaction is prevented from occurring on the pixel electrode 9, and the photocatalytic reaction is prevented. The liquid crystal layer 50 is prevented from being deteriorated due to the above.

  On the other hand, the counter substrate 20 has a surface facing the liquid crystal layer 50 side of the substrate body 20A and is opposed to the formation region of the data line 6a, the scanning line 3a, and the pixel switching TFT element 30, that is, the opening region of each pixel portion. The second light-shielding film 23 for preventing incident light from entering the channel region 1a ′, the low-concentration source region 1b, and the low-concentration drain region 1c of the semiconductor layer 1a of the pixel switching TFT element 30 in the other regions. Is provided. Further, on the liquid crystal layer 50 side of the substrate body 20A on which the second light shielding film 23 is formed, the counter electrode 21 made of ITO or the like is formed over almost the entire surface.

  An alignment film 60 for controlling the alignment of liquid crystal molecules in the liquid crystal layer 50 when no voltage is applied is formed on the outermost surface of the counter substrate 20 on the liquid crystal layer 50 side. A coating film 61 is formed between the counter electrode 21 and the alignment film 60 to prevent impurities such as metal elements and metal ions from diffusing from the counter electrode 21 toward the liquid crystal layer 50 side. . The alignment film 60 and the coating film 61 have structures equivalent to the alignment film 40 and the coating film 41 of the TFT array substrate 10, respectively.

  In addition, polarizing plates 15 and 25 made of a material obtained by doping polyvinyl alcohol (PVA) with iodine or the like are disposed outside the substrates 10 and 20 (the surface opposite to the liquid crystal layer 50). Each of the polarizing plates 15 and 25 has a function of absorbing linearly polarized light in the absorption axis direction and transmitting linearly polarized light in the transmission axis direction. Further, the polarizing plate 15 on the TFT array substrate 10 side is arranged so that the transmission axis thereof substantially coincides with the alignment regulating direction of the alignment film 40, and the transmission axis of the polarizing plate 25 on the counter substrate 20 side has the alignment film 60. It is arrange | positioned so that it may correspond with the orientation control direction of this.

  As the liquid crystal used in the liquid crystal layer 50, any liquid crystal can be used as long as it can be vertically aligned. For example, a negative dielectric constant in which the minor axis direction of the liquid crystal molecules is more easily polarized than the major axis direction. An anisotropic liquid crystal can be used, and by appropriately combining the surface shape of the alignment films 40 and 60 and the liquid crystal, each liquid crystal molecule in the liquid crystal layer 50 can be transferred to the TFT array substrate 10 (opposing) when no voltage is applied. An alignment film 40 having a predetermined tilt angle with respect to a direction substantially perpendicular to the surface of the substrate 20), specifically, a normal direction of the TFT array substrate 10 (opposing substrate 20) is formed.

  According to the liquid crystal device 100 according to the present embodiment, as described later, the pixel electrode 9 is provided when the liquid crystal device 100 is driven because the coating film 41 having a very high density formed by the atomic layer deposition method is provided. In addition, impurities such as metal elements and metal ions generated from the counter electrode 21 are prevented from diffusing into the liquid crystal layer. Moreover, since the said coating films 41 and 61 function also as an insulating film, the electron injection from the electrodes 9 and 21 side to the liquid crystal layer 50 side can be suppressed. Furthermore, since the liquid crystal layer 50 and the electrodes 9 and 21 are not in direct contact with the coating films 41 and 61, it is possible to prevent deterioration of the liquid crystal layer 50 due to the photocatalytic reaction. Therefore, the liquid crystal device 100 with high reliability is obtained.

(Manufacturing method of liquid crystal device)
Next, a process for manufacturing the liquid crystal device 100 will be described as an embodiment of the method for manufacturing a liquid crystal device of the present invention. In particular, the liquid crystal device of the present embodiment is characterized by the structure including the coating films 41 and 61 covering the pixel electrode 9 and the counter electrode 21 provided below the alignment films 40 and 60 as described above.

The TFT array substrate 10 and the counter substrate 20 forming a pair of substrates are manufactured. Here, a case where the TFT array substrate 10 is manufactured will be described as an example.
First, a first light shielding film 11a, a TFT element 30, an interlayer insulating film (first interlayer insulating film 12, second interlayer insulating film 4, third interlayer insulating film 7) and the like are formed on the surface of the substrate body 10A by a known method. Form. As shown in FIG. 3, a contact hole 8 is formed in the third interlayer insulating film 7, and the pixel electrode 9 made of ITO connected to the TFT element 30 through the contact hole 8 is formed by sputtering or CVD. It forms by using well-known methods, such as a method.

  Thereafter, a coating film 41 is formed on the substrate body 10A so as to cover the pixel electrode 9. As a method of forming the coating film 41, an ALD method (atomic layer deposition method) is used. This ALD method is suitable for forming a very thin film, and enables high-precision film thickness control and composition control. Specifically, when the source gas flows on the surface of the deposition target (pixel electrode 9, third interlayer insulating film 7), the reactive group on the surface of the deposition target reacts with the source gas. In this technique, an adsorption layer is formed, and one atomic layer is formed on the surface of the deposition target. Therefore, a film formed by the ALD method has high density and uniformity, and excellent step coverage.

In the present embodiment, for example, the substrate main body 10A is disposed in a reaction chamber in a nitrogen atmosphere, and an optimal source gas is supplied to the reaction chamber in order to form a monomolecular film made of silicon oxide (SiO ₂ ) on the substrate main body 10A. To supply. By forming the coating film 41 of silicon oxide, it is possible to improve the adhesion with the pixel electrode 9 formed on the substrate body 10A.

Thereafter, the flow of the source gas is stopped, and an inert purge gas for removing all the source gas remaining without being adsorbed on the substrate body 10A from the deposition reaction chamber is supplied. By repeating such steps, the coating film 41 having a desired thickness can be formed.
Through the above steps, the coating film 41 is formed on the front surface of the substrate body 10A so as to cover the pixel electrode 9. In addition, you may form the coating film in which several materials were laminated | stacked by 1 atomic layer by switching source gas for every step.

Since the coating film 41 formed by the ALD method is excellent in step coverage as described above (it is easy to follow), as shown in FIG. 4, the pixel electrode 9 provided in the contact hole 8 is formed. The liquid crystal layer 50 and the pixel electrode 9 are not in direct contact with each other even in the contact hole 8. Therefore, photocatalytic reaction on the pixel electrode 9 can be prevented, and deterioration of the liquid crystal layer 50 due to the photocatalytic reaction can be prevented.
In this way, even the boundary portion between the pixel electrode 9 and the third interlayer insulating film, where the film thickness tends to vary, or the inside of the contact hole 8 is surely covered with the uniform and dense coating film 41. Therefore, the electric field concentration does not occur when the liquid crystal device is driven, and the occurrence of disclination or the like in the liquid crystal layer 50 due to the electric field concentration can be prevented, and the decrease in contrast due to this can be prevented or suppressed. It becomes possible.

Next, with respect to the substrate main body 10A on which the coating film 41 is formed, silicon oxide (SiO, SiO2) is formed from a predetermined direction, that is, a direction that forms a predetermined inclination angle θ with the surface of the substrate main body 10A shown in FIG. _The alignment film 40 having a large number of columnar structures 40a arranged in a specific direction is formed by oblique deposition of an inorganic material such as ₂ ). Note that the pretilt angle of the liquid crystal when no voltage is applied can be controlled by controlling the tilt angle θ when the alignment film 40 is formed.

  Specifically, the inorganic material sublimated from a vapor deposition source (not shown) is continuously incident on the substrate body 10A at a substantially constant incident angle (tilt angle θ). Then, as shown in FIG. 5, the alignment film material is deposited in an oblique column shape on the substrate body 10A, thereby forming a columnar structure 40a of an inorganic material (silicon oxide). The columnar structure 40a is formed innumerably on the surface of the substrate body 10A, whereby the alignment film 40 is formed. Thus, when the columnar structure 40a is formed at a predetermined inclination angle, and thereby the alignment film 40 is formed, in the liquid crystal device 100, the liquid crystal molecules are aligned along the columnar structure 40a. A pretilt angle is given. That is, as described above, the alignment of liquid crystal molecules is regulated in a predetermined direction by the alignment film 40 when a non-selection voltage is applied. In the present embodiment, the alignment film 40 is formed with an evaporation angle (an angle formed between the evaporation direction and the substrate normal L) of 40 to 65 °.

Thus, by forming the alignment film by oblique vapor deposition, it is possible to favorably impart a pretilt angle to the liquid crystal molecules by the alignment film 40 without performing a rubbing process or the like. In addition, since the alignment film 40 is made of an inorganic material and has heat resistance and light resistance, the liquid crystal device 100 including the alignment film 40 is particularly suitable as a light modulation element of a projector, as will be described later. Can be adopted.
As described above, the TFT array substrate 10 on which necessary elements other than the polarizing plate 15 are formed can be manufactured.

  Then, similarly to the process of manufacturing the TFT array substrate 10 described above, the counter electrode 21 made of ITO is formed on the substrate body 20A by a known method, and then the coating film 61 is formed using the ALD method, An alignment film 60 made of an inorganic oblique deposition film having a number of columnar structures is manufactured on the coating film 61. In this way, the counter substrate 20 on which necessary elements other than the polarizing plate 25 are formed can be manufactured. The liquid crystal device 100 can be manufactured by sandwiching the liquid crystal layer 50 between the TFT array substrate 10 and the counter substrate 20 obtained in this manner and bonding the substrates 10 and 20 together through the sealing material 52. .

  In the present embodiment, both the pixel electrode 9 and the counter electrode 21 are covered with the coating films 41 and 61. However, a coating film is provided only on one side of the electrodes 9 and 21, An alignment film may be formed on the coating film. Thereby, at least diffusion of impurities from the electrode covered by the coating film can be prevented, and the reliability of the liquid crystal device can be improved.

  According to the method for manufacturing the liquid crystal device 100 according to the present embodiment, since the coating film 41 is provided between the alignment film 40 and the pixel electrode 9, the pixel electrode 9 and the liquid crystal layer are interposed via the coating film 41. 50 comes into contact. Therefore, impurities such as metal elements and metal ions diffused from the pixel electrode 9 are blocked by the coating film 41 which is a highly dense film, and these impurities can be prevented from diffusing to the liquid crystal layer 50 side. The highly dense coating film formed by the ALD method can be made sufficiently thin as compared with the case where it is formed by the physical vapor deposition method. Thus, the thin coating film 41 does not reduce the transmittance and contrast ratio in the liquid crystal device 100. Further, since diffusion of impurities can be prevented only by the highly dense coating films 41 and 61, the alignment films 40 and 60 can be thinned, and carriers (electrons, holes) previously contained in the alignment films 40 and 60 can be reduced. This reduces the amount of carriers injected into the liquid crystal layer 50 when a voltage is applied to the electrodes 9 and 21, thereby improving the reliability of the liquid crystal device 100. In addition, since the coating films 41 and 61 also function as insulating films, electron injection from the electrodes 9 and 21 side to the liquid crystal layer 50 side can be suppressed. Furthermore, since the liquid crystal layer 50 and the electrodes 9 and 21 are not in direct contact with each other, the deterioration of the liquid crystal layer 50 due to the photocatalytic reaction can be prevented. Therefore, it is possible to provide a highly reliable liquid crystal device 100 in which problems due to the electrodes 9 and 21 are prevented.

(Electronics)
Next, a projector as an embodiment of the electronic apparatus of the invention will be described with reference to FIG. FIG. 6 is a schematic configuration diagram showing a main part of the projector. This projector includes the liquid crystal device 100 according to the above-described embodiment as light modulation means.

  6, 810 is a light source, 813 and 814 are dichroic mirrors, 815, 816 and 817 are reflection mirrors, 818 is an incident lens, 819 is a relay lens, 820 is an exit lens, and 822, 823 and 824 are liquid crystal devices of the present invention. 825 is a cross dichroic prism, and 826 is a projection lens. The light source 810 includes a lamp 811 such as a metal halide and a reflector 812 that reflects the light of the lamp.

  The dichroic mirror 813 transmits red light contained in white light from the light source 810 and reflects blue light and green light. The transmitted red light is reflected by the reflection mirror 817 and is incident on the light modulation means 822 for red light. The green light reflected by the dichroic mirror 813 is reflected by the dichroic mirror 814 and is incident on the light modulating means 823 for green light. Further, the blue light reflected by the dichroic mirror 813 passes through the dichroic mirror 814. For blue light, in order to prevent light loss due to a long optical path, a light guide means 821 including a relay lens system including an incident lens 818, a relay lens 819, and an exit lens 820 is provided. Blue light is incident on the light modulating means 824 for blue light through the light guiding means 821.

  The three color lights modulated by the respective light modulation means 822, 823, and 824 are incident on the cross dichroic prism 825. The cross dichroic prism 825 is formed by bonding four right-angle prisms. A dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in an X shape at the interface. Yes. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the screen 827 by the projection lens 826 which is a projection optical system, and the image is enlarged and displayed.

Since the projector having such a configuration includes the liquid crystal device as a light modulation unit, the liquid crystal layer is prevented from being deteriorated and the display quality is excellent and the reliability is high.
The liquid crystal device of the present invention can also be applied to electronic devices other than projectors. A specific example is a mobile phone. This mobile phone includes the liquid crystal device according to each of the above-described embodiments or modifications thereof in a display unit. Other electronic devices include, for example, IC cards, video cameras, personal computers, head-mounted displays, fax machines with display functions, digital camera finders, portable TVs, DSP devices, PDAs, electronic notebooks, and electronic bulletin boards. And advertising announcement displays.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiment, and includes those in which various modifications are made to the above-described embodiment without departing from the gist of the present invention. For example, in the above-described embodiment, only the vertical alignment mode liquid crystal device has been described. However, the present invention is not limited to this, and the present invention includes an STN (Super Twisted Nematic) mode, a TN (Twisted Nematic) mode, and the like. The alignment state of liquid crystal molecules when no voltage is applied can be applied to any liquid crystal device. Further, in the embodiment, the description has been given by taking a three-plate projection display device (projector) as an example, but the present invention can also be applied to a single-plate projection display device or a direct-view display device.

(A), (b) is a schematic diagram which shows schematic structure of a liquid crystal device. It is an equivalent circuit diagram in a liquid crystal device. It is a top view which shows the structure of a several pixel group. It is sectional drawing which shows the structure of a liquid crystal device. It is a figure which shows schematic structure of an alignment film. It is a schematic block diagram which shows the principal part of a projector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 ... Pixel electrode (electrode), 10 ... TFT array substrate (substrate), 20 ... Counter substrate (substrate), 21 ... Counter electrode (electrode), 40 ... Alignment film, 41 ... Cover film, 50 ... Liquid crystal layer, 60 ... Alignment film 61 ... Coating film 100 ... Liquid crystal device

Claims (6)

In a method for manufacturing a liquid crystal device, comprising: a liquid crystal layer; a pair of substrates sandwiching the liquid crystal layer; and a pair of electrodes respectively disposed on the liquid crystal layer side of the pair of substrates.
Forming a coating film on the surface of the substrate so as to cover at least one of the pair of electrodes by an atomic layer deposition method;
And a step of forming an alignment film made of an inorganic material on the coating film.   The method of manufacturing a liquid crystal device according to claim 1, wherein the alignment film is formed by oblique deposition of an inorganic material.   The method for manufacturing a liquid crystal device according to claim 1, wherein the coating film is formed using silicon oxide. In a liquid crystal device comprising a liquid crystal layer, a pair of substrates sandwiching the liquid crystal layer, and a pair of electrodes respectively disposed on the liquid crystal layer side of the pair of substrates,
At least one of the pair of electrodes is covered with a coating film formed by an atomic deposition method, and an alignment film made of an inorganic material is formed on the coating film.   The liquid crystal device according to claim 4, wherein the coating film has a thickness of 5 to 50 nm. An electronic apparatus comprising the liquid crystal device according to claim 4.

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