JP4556426B2 - Liquid crystal display device and method of manufacturing liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly to a liquid crystal display device having an obliquely deposited alignment film and a manufacturing method thereof.

  In a liquid crystal display device for a projector (so-called liquid crystal projector), a liquid crystal panel used as a light valve has been reduced in size due to miniaturization of wiring. On the other hand, the light intensity of a light source used in a projector is constantly increasing. For this reason, the amount of incident light per unit area for a miniaturized liquid crystal panel has been dramatically increased. Therefore, in such a liquid crystal panel for a liquid crystal projector, a configuration is proposed in which an alignment film (inorganic alignment film) made of an inorganic material such as silicon oxide is used instead of an organic material having poor light resistance. In the formation of an alignment film made of an inorganic material, the rubbing method applied to the formation of an alignment film made of a conventional organic material cannot obtain a sufficient alignment force. The attached vapor deposition method (so-called oblique vapor deposition method) is performed.

  By the way, among the substrates on which the alignment film is formed, there are irregularities due to pixel electrodes and switching elements for driving the pixel electrodes, particularly on the surface of the driving substrate. Moreover, the largest convex part exists in the board | substrate surface by which the columnar spacer for controlling the distance of a liquid-crystal layer is formed. For this reason, in the oblique vapor deposition described above, a portion that is shaded by unevenness with respect to the vapor deposition direction is a portion where the inorganic material is not vapor deposited or is difficult to vapor deposit. And in the part where such vapor deposition unevenness has occurred, there is a problem that the alignment of the liquid crystal is disturbed, and the display characteristics are deteriorated due to the occurrence of light penetration.

  In view of this, a method has been proposed in which an inorganic material is deposited on a shadow portion by performing oblique deposition several times from different azimuth directions of approximately 90 ° (see Patent Document 1 below).

JP 2002-277879 A (refer to paragraph 0024 in particular)

  However, in the oblique deposition from different azimuth directions of approximately 90 ° as described above, the inorganic material is sufficiently deposited in the second oblique deposition on the shadowed portion in the first oblique deposition. However, it is difficult to completely eliminate the influence of the deposited film portion formed by the first oblique deposition in the shaded portion in the second oblique deposition. Accordingly, in the portion that is shaded in the second oblique deposition, the orientation of the liquid crystal molecules is likely to be disturbed by the influence of the first deposited film portion.

  Therefore, the present invention can more reliably prevent liquid crystal molecule alignment defects in the vicinity of the concavo-convex portion of the underlayer of the alignment film, thereby providing a liquid crystal display device with extremely good display characteristics, and this An object of the present invention is to provide a method for manufacturing such a liquid crystal display device.

  In order to achieve such an object, a liquid crystal display device of the present invention includes a pair of substrates opposed to each other with an alignment film provided inside, a liquid crystal layer sandwiched between the pair of substrates, In the liquid crystal display device including the above, at least one of the alignment films has a stacked structure. This laminated structure is composed of a first layer formed by oblique vapor deposition and a second layer formed by oblique vapor deposition from an azimuth angle direction of approximately 180 ° with respect to the first layer.

  The present invention is also a method for manufacturing such a liquid crystal display device. In the formation of the alignment film having the above-described laminated structure, the step of forming the first layer by oblique vapor deposition, and the oblique formation of the first layer are performed. And a step of forming a second layer on the first layer by oblique vapor deposition from an azimuth angle direction of approximately 180 ° with respect to the vapor deposition.

  In the liquid crystal display device having such a configuration, the first layer and the second layer above the first layer are formed by oblique vapor deposition from the azimuth direction forming 180 °. For this reason, the first layer and the second layer have a surface shape in which liquid crystal molecules are aligned at a predetermined pretilt angle in an azimuth angle direction of 180 °. Here, when the underlayer of the alignment film has irregularities, the uneven deposition portion of the second layer which is shaded in the oblique deposition when forming the second layer and is not sufficiently deposited occurs. In such an uneven deposition portion of the second layer, the surface shape of the first layer tends to affect the alignment of the liquid crystal molecules. For this reason, the orientation of the liquid crystal molecules in the uneven deposition portion of the second layer tends to be in the azimuth direction of 180 ° with respect to the orientation of the liquid crystal molecules in the portion where the second layer is sufficiently formed. However, the liquid crystal molecules maintained in the azimuth angle direction of 180 ° with respect to the surrounding orientation direction are in the alignment state of the surrounding liquid crystal molecules as compared with the liquid crystal molecules oriented in other azimuth directions. Easy to align. Such a tendency is particularly noticeable when the alignment film has a configuration in which liquid crystal molecules are aligned at a substantially vertical pretilt angle. For this reason, in the alignment film having the laminated structure as described above, the alignment of the liquid crystal molecules is easily aligned on the entire surface of the second layer (that is, the entire surface of the alignment film) without being affected by the unevenness of the base.

  As described above, according to the liquid crystal display device and the manufacturing method thereof of the present invention, the alignment of the liquid crystal molecules can be easily aligned on the entire surface of the alignment film without being affected by the unevenness of the base. It is possible to improve display characteristics by preventing light leakage due to partial alignment failure.

  Embodiments of the present invention will be described below. Here, first, an embodiment of a manufacturing method of a liquid crystal display device will be described, and then a configuration of the liquid crystal display device obtained by this manufacturing method will be described. Although an embodiment in which the present invention is applied to a liquid crystal panel that is suitably used as a light valve of a projection type liquid crystal display device will be described here, the present invention is limited to application to a projection type liquid crystal display device. However, the present invention can be widely applied to liquid crystal display devices having an alignment film formed by oblique deposition.

  FIG. 1 shows a schematic configuration diagram of a liquid crystal panel which is a main part of the liquid crystal display device formed here. A liquid crystal panel A shown in this figure is a liquid crystal panel to which the present invention is applied, and has a liquid crystal layer 3 sandwiched between a driving substrate 1 and a counter substrate 2. When the liquid crystal panel A having such a configuration is manufactured, first, the pixel electrode and the columnar spacer are formed on the drive substrate 1 side by the following normal procedure.

  That is, the semiconductor layer 5 serving as the active layer of the switching element is formed on the glass substrate 4 in a pattern. At this time, a polycrystalline silicon film is first formed with a thickness of 10 to 100 nm by a CVD method. Thereafter, if necessary, the silicon crystal in the polycrystalline silicon film is once crushed by an ion implantation method, and then recrystallized by annealing at a temperature of 600 to 750 ° C. Next, the semiconductor layer 5 is formed by patterning the polycrystalline silicon film into a predetermined shape.

  Next, a gate insulating film 6 covering the semiconductor layer 5 is formed to a thickness of 10 to 100 nm by means such as thermal oxidation or LPCVD.

  Next, a gate electrode 7 is formed on the semiconductor layer 5 through a gate insulating film 6. In this case, first, a conductive film made of polycrystalline silicon or a metal such as MoSi, WSi, Al, Ta, Mo / Ta, Mo, W, Ti, or Cr is formed, and the conductive film is patterned into a predetermined shape. Thus, the gate electrode 7 is formed. When polycrystalline silicon is used as the gate electrode 7, a step of thermally diffusing impurities such as phosphorus (P) may be performed in order to reduce the resistance.

  After the above, impurity ions are implanted into the semiconductor layer 5 by the ion implantation method or the ion doping method using the gate electrode 7 as a mask to form a source region and a drain region in the semiconductor layer 5, and a thin film transistor ( A switching element made of a thin film transistor (TFT) is formed.

  Subsequently, PSG, NSG or the like is formed to a thickness of 400 to 800 nm by the CVD method to form the first interlayer insulating film 8. Then, first contact holes 9S and 9D communicating with the source region and the drain region of the semiconductor layer 5 are opened in the first interlayer insulating film 8.

  Next, a conductive thin film such as Al is formed to a thickness of 300 to 700 nm by sputtering or the like. This is patterned into a predetermined shape and processed into a source electrode 10S and a drain electrode 10D connected to the source and drain regions of the semiconductor layer 5 through the first contact holes 9S and 9D. Thereafter, PSG or the like is formed to a thickness of 300 to 2000 nm to form the second interlayer insulating film 11 by, for example, atmospheric pressure CVD. If necessary, planarization may be performed by performing a surface treatment of the second interlayer insulating film 11 using a CMP method or the like.

  Next, a second contact hole 12 for establishing electrical connection with the drain electrode 10D is opened in the second interlayer insulating film 11. A light shielding film 13 that also serves as a black mask may be formed thereon if necessary. The light shielding film 13 is formed by depositing Ti, Al, Mo, Cr, W, TiNx, or a silicide of these metals with a thickness of about 50 to 500 nm by a method such as sputtering, and patterning the film into a predetermined shape. By forming. As shown in the figure, when the light shielding film 13 is formed, a third interlayer insulating film 14 covering the light shielding film 13 is formed, and further, the electrical connection with the drain electrode 10D is made through the light shielding film 13. A third contact hole 15 to be taken is formed in the third interlayer insulating film 14.

  Thereafter, the pixel electrode 16 connected to the drain electrode 10 </ b> D is formed on the third interlayer insulating film 14. Here, the pixel electrode 16 is formed by forming a transparent conductive film made of a metal oxide such as ITO with a thickness of about 30 to 300 nm and patterning the transparent conductive film into a predetermined shape. Thereafter, if necessary, annealing at about 200 to 400 ° C. may be performed.

  Next, in order to control the thickness (referred to as cell gap) of the liquid crystal layer 3 sandwiched between the driving substrate 1 and the counter substrate 2 in a systematic manner, the image quality on the driving substrate 1 is not affected. Columnar spacers 17 are formed at desired positions. Here, first, an acrylic photosensitive resin film is applied and formed by spin coating or the like so as to have a thickness of about 2 to 6 μm, and the photosensitive resin film is patterned by a photolithography technique. Then, the columnar spacer 17 is obtained by baking the patterned photosensitive resin film at 150-250 degreeC.

  Up to the above, the steps may be performed in the same manner as in the prior art. The subsequent process, that is, the process of forming the alignment film 18 on the drive substrate 1 that has been performed up to the formation of the pixel electrode 16 and the columnar spacer 17 as described above is a characteristic process of the present invention. Hereinafter, this process will be described with reference to FIGS.

  First, the oblique deposition apparatus shown in FIG. 2 is used to form the alignment film 18. The oblique vapor deposition apparatus includes a vapor deposition source 102 for evaporating a vapor deposition material in a vacuum chamber 101. A mechanism for holding the substrate W at a predetermined distance (not shown) is provided above the vapor deposition source 102. Here, the substrate W is a line connecting the center of the substrate W and the vapor deposition source 2. The angle formed by the normal line L of the deposition surface Wa on the substrate W, that is, the vapor deposition angle θ, is freely maintained, and the substrate W has an azimuth angle direction in which the vapor deposition material G evaporated from the vapor deposition source 102 enters Here, the azimuth angle direction means that the vapor deposition material G irradiated from the predetermined vapor deposition angle θ to the vapor deposition surface Wa of the substrate W is vapor deposition. This is the direction irradiated to the surface Wa.

First, as shown in FIG. 3A, the alignment film is formed on the driving substrate 1 (substrate W) on which the columnar spacers 17 are formed as described above. Then, an inorganic material (vapor deposition material G) is obliquely deposited from a predetermined vapor deposition angle θ1. At this time, an inorganic material is put into the vapor deposition source 102 in the vacuum chamber 101 shown in FIG. Thereafter, the inside of the vacuum chamber 101 is evacuated to a predetermined degree of vacuum, and then the vapor deposition source 102 is heated by an electron beam or the like to evaporate the inorganic material as the vapor deposition material G and obliquely deposit on the surface of the driving substrate 1. Let me. By this first oblique deposition, a first layer 18a formed by oblique deposition of a columnar inorganic material is formed. For example, SiO _x is suitably used as the inorganic material.

  Next, as shown in FIG. 3B, an inorganic material (vapor deposition material G) is obliquely deposited from a predetermined vapor deposition angle θ2 on the drive substrate 1 (substrate W) on which the first layer 18a is formed. . In the second oblique vapor deposition, as shown in FIG. 4, the inorganic material (deposition material G) is applied from the azimuth angle direction which is approximately 180 ° with respect to the azimuth angle direction in the oblique vapor deposition of the first layer 18a. Diagonal evaporation. For this reason, in the oblique deposition apparatus using FIG. 2, the direction of the deposition surface Wa on the substrate W is maintained as it is, and the substrate W is rotated by approximately 180 °, which is the same as the first oblique deposition. The second oblique deposition is performed by the following procedure.

  As a result, as shown in FIG. 3B, the second layer 18b is formed by obliquely depositing the inorganic material from the azimuth angle direction which is approximately 180 ° with respect to the azimuth angle direction in the first oblique deposition. Is deposited. In this case, as the inorganic material (vapor deposition material G), the same material as the first layer 18a may be used, and it is preferable to form the second layer 18b so as to be thicker than the first layer 18a.

  Note that the rotation of the substrate W, that is, the angle formed between the azimuth angle direction in the first oblique deposition and the azimuth direction in the second oblique deposition, that is, approximately 180 ° is about 180 ° ± 20 °. The range is preferably 180 ° ± 3 °. Further, the vapor deposition angle θ1 and the film thickness of the first layer 18a, and the vapor deposition angle θ2 and the film thickness of the second layer 18a are such that the liquid crystal molecules m have a predetermined pretilt angle in the flat portion of the alignment film 18 composed of these laminated films. It is set to be aligned substantially perpendicularly (angle formed by the substrate surface and liquid crystal molecules). However, since the orientation of the liquid crystal molecules m is regulated by the shape of the outermost surface of the alignment film 18, the thickness of the second layer 18b is made thicker in order to make it less susceptible to the surface shape of the first layer 18a serving as the base. It is preferable to do. The vapor deposition angle θ1 when forming the first layer 18a and the vapor deposition angle θ2 when forming the second layer 18b may be the same angle.

  As described above, the alignment film 18 formed by laminating the second layer 18b on the first layer 18a is obtained. Thereby, the manufacturing process on the drive substrate 1 side is completed.

  On the other hand, when the counter substrate 2 shown in FIG. 1 is manufactured, the counter electrode 22 is formed on the glass substrate 21, and the alignment film 23 is formed on the counter electrode 22. The alignment film 23 may be formed by the same procedure as the formation of the alignment film 18 on the drive substrate 1 side described above, or may be formed by one oblique deposition. However, the alignment film 23 is obliquely deposited so that liquid crystal molecules are aligned substantially vertically at a predetermined pretilt angle. In the case where the base surface on which the alignment film 23 is formed, that is, the surface on which the oblique deposition is performed has irregularities, the oblique surface is formed twice as in the formation of the alignment film 18 on the drive substrate 1 side. It is preferable to form the alignment film 23 by side evaporation.

  Then, after the drive substrate 1 and the counter substrate 2 on which the alignment films 18 and 23 are formed as described above, the drive substrate 1 and the counter substrate 2 are arranged to face each other with the alignment films 18 and 23 inside. The liquid crystal layer 3 is filled and sealed between the substrates 1 and 2 to complete the liquid crystal panel A.

  FIG. 5 shows an example of a liquid crystal display device using the liquid crystal panel A manufactured as described above. The liquid crystal display device shown in this figure is a projection-type liquid crystal display device (so-called liquid crystal projector), and a light source 51 that emits light h, and light h emitted from the light source 51 is converted into red (R), green (G), A total reflection mirror 52 and dichroic mirrors 53 and 54 for separating each color of blue (B) are provided. Then, on each optical path of the light divided into three colors by these mirrors 52, 53, 54, a liquid crystal panel A is disposed in a state sandwiched between two orthogonal polarizing plates (not shown), Further, a dichroic prism 55 for synthesizing light transmitted through each liquid crystal panel A is provided. A projection lens 56 is disposed on the optical path of the light synthesized by the dichroic prism 55, and an image is projected from the projection lens 56.

  In the liquid crystal display device obtained as described above, as shown in FIG. 3 (2) in particular, the first layer 18a constituting the alignment film 18 on the drive substrate 1 side in the liquid crystal panel and the second layer on the first layer 18a. The layer 18b is formed by oblique vapor deposition from an azimuth angle direction of 180 °. Therefore, the surface shape of the first layer 18a and the surface shape of the second layer 18b are configured such that liquid crystal molecules are aligned at a predetermined pretilt angle in the azimuth angle direction that is 180 °.

  Here, under the alignment film 18, there are irregularities resulting from the formation of columnar spacers 17, pixel electrodes 16, TFTs that serve as switching elements, and the like. For this reason, in the second layer 18b, there is an uneven deposition portion a which becomes a shadow in oblique vapor deposition when it is formed and is not sufficiently vapor deposited. In such a vapor deposition uneven portion a of the second layer 18b, the surface shape of the first layer 18a tends to affect the alignment of the liquid crystal molecules m. Therefore, normally, the orientation of the liquid crystal molecules m in the vapor deposition unevenness portion a of the second layer 18b is 180 ° with respect to the orientation of the liquid crystal molecules m in the portion where the second layer 18b is sufficiently formed. It tends to be in the angular direction. However, the liquid crystal molecules m maintained in the azimuth direction of 180 ° with respect to the surrounding orientation direction are aligned in the orientation state of the surrounding liquid crystal molecules m as compared with the liquid crystal molecules oriented in other azimuth directions. It is easy to match the condition. In particular, since the alignment film 18 is configured to align the liquid crystal molecules m with a substantially vertical pretilt angle, such a tendency is noticeable. Therefore, in the alignment film 18 having such a laminated structure, the alignment of the liquid crystal molecules m is easily aligned on the entire surface of the second layer 18b (that is, the entire surface of the alignment film 18) without being affected by the unevenness of the base.

  As a result, in the liquid crystal display device having the liquid crystal panel having the above-described configuration obtained as described above, the alignment of the liquid crystal molecules m can be easily aligned over the entire surface of the alignment film 18 without being affected by the unevenness of the base. Therefore, it is possible to prevent light leakage due to partial alignment failure of the liquid crystal molecules m and improve display characteristics.

  In the embodiment described above, a projection type liquid crystal display device using a liquid crystal panel whose alignment film is made of an inorganic material is taken as an example, and the configuration of a liquid crystal panel suitable for this is described. However, the present invention can be applied to, for example, a reflective liquid crystal display device or a transmissive liquid crystal display device in which a panel surface is directly viewed as long as the liquid crystal panel has an alignment film formed by oblique deposition. The same effect can be obtained.

  Further, in the above embodiment, the alignment film 18 on the side of the drive substrate 1 where the unevenness of the underlying layer of the alignment film is particularly large may have a laminated structure, and the alignment film 23 on the counter substrate 2 side may have a similar laminated structure. However, for example, when a columnar spacer is provided on the counter substrate 2 side and there are large irregularities, and there are few irregularities on the drive substrate 1 side, only the alignment film 23 on the counter substrate 2 side may have the above-described laminated structure.

It is an expanded sectional view of the liquid crystal panel which comprises the principal part of a liquid crystal display device. This is an oblique deposition apparatus used for forming an alignment film of a liquid crystal panel. It is sectional process drawing which shows the formation procedure of alignment film. It is a perspective view explaining the azimuth angle direction of oblique vapor deposition in the case of alignment film formation. It is a block diagram of a projection-type liquid crystal display device using a liquid crystal panel.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Driving substrate, 2 ... Counter substrate, 3 ... Liquid crystal layer, 16 ... Pixel electrode, 17 ... Columnar spacer, 18, 23 ... Alignment film, 18a ... 1st layer, 18b ... 2nd layer, TFT ... Switching element, 51 ... light source (optical system), 52 ... total reflection mirror, 53, 54 ... dichroic mirror, A ... liquid crystal panel, m ... liquid crystal molecule

Claims (6)

A pair of substrates opposed to each other with the alignment film provided inside,
And a liquid crystal layer interposed between the pair of substrates,
At least one of the alignment films is a first layer formed by oblique vapor deposition, and is formed by oblique vapor deposition from an azimuthal direction that forms approximately 180 ° with respect to the first layer, and is a film that is more than the first layer. Ri Do a laminated structure of the thickness of the thick second layer,
A liquid crystal display device in which liquid crystal molecules constituting the liquid crystal layer are vertically aligned by the alignment film when no electric field is applied to the liquid crystal layer . Below the alignment film having the laminated structure, switching elements of the pixel electrodes are arranged in a matrix together with the pixel electrodes.
The liquid crystal display device according to claim 1 . A columnar spacer for regulating the distance between the pair of substrates is provided below the alignment film of the laminated structure.
The liquid crystal display device according to claim 1 . The alignment film is made of an inorganic material.
The liquid crystal display device according to claim 1 . An optical system for irradiating light transmitted through the panel is provided on a panel formed by opposingly arranging the pair of substrates.
The liquid crystal display device according to claim 1 . In forming the alignment film on each of the pair of substrates, in the formation of the alignment film on at least one of the substrates,
Forming a first layer by oblique deposition;
Forming a second layer thicker than the first layer on the first layer by oblique vapor deposition from an azimuthal direction that forms approximately 180 ° with respect to the oblique vapor deposition of the first layer; It was carried out,
Thereafter, the pair of substrates are opposed to each other with the alignment film inside, and a liquid crystal layer composed of liquid crystal molecules that are vertically aligned with respect to the substrate when no electric field is applied is sandwiched between the pair of substrates. Production method.

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