JP2011221115A - Manufacturing method of liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a liquid crystal device including an inorganic alignment film which can reduce a burn-in phenomenon due to current application.SOLUTION: A manufacturing method of a liquid crystal device of this application example includes a pretreatment step (step S2, step S12) for irradiating a surface of at least one of a pair of substrates that faces a liquid crystal layer, with an ultraviolet ray in an atmosphere containing at least oxygen, and an inorganic alignment film formation step (step S3, step S13) for forming an inorganic alignment film on the surface irradiated with the ultraviolet ray. No surface treatment steps other than the pretreatment step are performed before the inorganic alignment film formation step.

Description

  The present invention relates to a method for manufacturing a liquid crystal device.

A liquid crystal device generally has a pair of substrates and a liquid crystal layer sealed between the pair of substrates, and liquid crystal molecules are arranged in a predetermined azimuth direction on the surfaces of the pair of substrates facing the liquid crystal layer. In addition, an alignment film that gives a pretilt angle to the substrate surface is formed.
As the material of such an alignment film, both an organic material and an inorganic material are used. A typical example of the organic material is polyimide, and a typical example of the inorganic material is silicon oxide. It is done. The former performs alignment control by rubbing an organic alignment film formed on a substrate in a predetermined direction (rubbing treatment), for example. The latter performs orientation control by obliquely depositing an inorganic material on a substrate, for example.

In the rubbing treatment for the organic alignment film, the film surface is rubbed with a rubbing member such as cotton or rayon, so that the organic alignment film itself is scraped or the rubbing member is worn, and foreign matter is generated.
Since it adheres to the rubbing-treated film surface and causes orientation failure, it has been proposed to perform cleaning to remove the foreign matter after the rubbing treatment.
For example, in Patent Document 1, single-wafer cleaning is performed after a rubbing-treated substrate is immersed in a solution. Examples of the solution include pure water, a nonionic surfactant, a weak alkaline aqueous solution, a weak acidic aqueous solution, and an organic solvent.

Of course, if an alignment film is not formed on a clean substrate surface, film irregularities such as pinholes will occur, and this will also cause alignment failure, so a method for cleaning the substrate before forming the alignment film is also proposed. Has been.
For example, in Patent Documents 2, 3, and 4, the substrate is subjected to ultrasonic cleaning or shower cleaning with water (pure water), and then irradiated with ultraviolet rays so that not only foreign substances that can be dissolved or dispersed in water, but also ultraviolet irradiation. There has been proposed a method for chemically decomposing and removing organic substances that are hardly soluble in water by the generated ozone.

On the other hand, as a surface treatment for the inorganic alignment film, a method of treating with a higher alcohol (Patent Document 5), a method of cleaning with a cleaning liquid composed of an organic compound solution that is reactively fixed to the inorganic alignment film (Patent Document 6), etc. have been proposed. Yes.
Furthermore, a method of removing an ionic impurity by applying a voltage between a pair of electrodes provided in a cleaning liquid to generate an electric field and immersing a substrate on which an inorganic alignment film is formed between the pair of electrodes. (
Patent Document 7) and supplying ozone water to the formed inorganic alignment film surface to remove foreign substances such as organic substances, and uniformly oxidize Si atoms present on the inorganic alignment film surface by strong oxidizing action of ozone water A method (Patent Document 8) is proposed.

JP-A-6-160855 JP-A-3-254874 JP 2002-196337 A JP 2003-75795 A JP 2000-47211 A JP 2008-83222 A JP 2007-187862 A JP 2008-224923 A

As shown in Patent Document 1 to Patent Document 8, the process of cleaning the substrate before the formation of the alignment film or the process applied to the alignment film after the formation is an important process in the manufacture of the liquid crystal device. There is a problem that the manufacturing process becomes complicated because various cleaning or surface treatments are used in combination in response to contaminants.
In particular, in the case of an inorganic alignment film, since an inorganic material such as silicon oxide is formed so as to grow in a predetermined direction with respect to the substrate surface, the structure of the alignment film is porous as described in Patent Document 6. It is known that Then, unless the ionic impurities on the substrate surface before the inorganic alignment film is formed are properly removed, the ionic impurities diffuse over time in the liquid crystal layer sealed between the pair of substrates. In addition, there is a problem that an electricity storage layer is easily formed on the substrate surface, and a so-called burn-in phenomenon is caused by energization.
In other words, there is a problem that it is necessary to find an appropriate surface treatment method for a substrate related to formation of an inorganic alignment film.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A method for manufacturing a liquid crystal device according to this application example is a method for manufacturing a liquid crystal device having a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates, and at least of the pair of substrates. A pretreatment step of irradiating the surface of one substrate facing the liquid crystal layer with ultraviolet rays in an atmosphere containing at least oxygen; and an inorganic alignment film forming step of forming an inorganic alignment film on the surface irradiated with the ultraviolet rays And a surface treatment step other than the pretreatment step is not performed before the inorganic alignment film forming step.

According to this method, in the pretreatment step, by irradiating the substrate before the formation of the inorganic alignment film with ultraviolet rays, not only decomposing and removing foreign substances composed of organic substances adhered to the substrate surface by ozone generated by the ultraviolet irradiation. The substrate surface can be cleaned by removing ionic impurities. Since the inorganic alignment film is formed on the cleaned substrate surface, initial alignment defects due to defects such as pinholes can be reduced, and the image sticking phenomenon caused by ionic impurities can be reduced. That is, a liquid crystal device having both high reliability and display quality can be manufactured.

Application Example 2 In the method of manufacturing a liquid crystal device according to the application example described above, the method includes a conductive film forming step of forming a conductive film on the one substrate, and the pretreatment step includes the one of the conductive films formed on the one substrate. The surface of the substrate may be irradiated with ultraviolet rays.
According to this method, it is possible to remove the foreign matters and ionic impurities adhering to the formation of the conductive film by irradiating with ultraviolet rays, and to clean the surface on which the inorganic alignment film is formed on at least one of the substrates.

Application Example 3 In the method for manufacturing a liquid crystal device according to the application example described above, a pure water cleaning step of cleaning at least one of the pair of substrates may be provided before the pretreatment step.
According to this method, since at least one of the pair of substrates in the previous stage of the pretreatment process removes some foreign matter and ionic impurities by pure water cleaning and then irradiates ultraviolet rays, at least one of the substrates A high cleanliness is obtained.

Application Example 4 In the method for manufacturing a liquid crystal device according to the application example described above, it is preferable that a switching element is not formed on the one substrate.
According to this method, it is possible to manufacture a liquid crystal device with a high yield by reducing the problems of the switching elements due to ultraviolet irradiation.

Application Example 5 In the method of manufacturing a liquid crystal device according to the application example, the inorganic alignment film forming step includes:
A post-treatment step of forming the inorganic alignment film by obliquely depositing silicon oxide and cleaning at least one of the pair of substrates on which the inorganic alignment film is formed using isopropyl alcohol; Is desirable.
According to this method, the reaction layer is formed on the surface of the inorganic alignment film by reacting the silanol group (—Si—OH) on the surface of the inorganic alignment film with the isopropyl group (—C ₃ H ₇ ) of isopropyl alcohol. . Since this reaction layer can suppress or prevent the reaction activity with the liquid crystal molecules on the surface of the inorganic alignment film, a stable alignment state of the liquid crystal molecules in the liquid crystal layer can be realized.

(A) is a schematic plan view which shows the structure of a liquid crystal device, (b) is a schematic sectional drawing cut | disconnected by the H-H 'line | wire of (a). FIG. 4A is a schematic plan view showing a configuration of a pixel, and FIG. 4B is a schematic cross-sectional view taken along line A-A ′ in FIG. FIG. 3 is a schematic cross-sectional view illustrating an alignment state of liquid crystal molecules in a liquid crystal device. 6 is a flowchart showing a method for manufacturing a liquid crystal device. The schematic plan view which shows a mother board | substrate. The schematic sectional drawing which shows the structure of a vapor deposition apparatus. The graph which shows the result of having surface-analyzed the adhesion state of the foreign material in the board | substrate surface, and the residual state of an ionic impurity. The graph which shows the evaluation result of the burning by electricity supply of a liquid crystal device. The graph which shows the relationship between the electricity supply time of a liquid crystal device, and the shift amount of optimal COM electric potential.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. Note that the drawings to be used are appropriately enlarged or reduced so that the part to be described can be recognized.

In the present embodiment, an active matrix liquid crystal device including a thin film transistor (TFT) as a pixel switching element will be described as an example.
This liquid crystal device can be suitably used as, for example, a light modulation element (liquid crystal light valve) of a projection display device (liquid crystal projector).

<Liquid crystal device>
The liquid crystal device of this embodiment will be described with reference to FIGS. 1A is a schematic plan view showing the configuration of the liquid crystal device, and FIG. 1B is a schematic cross-sectional view taken along the line HH ′ in FIG.
2A is a schematic plan view showing the configuration of the pixel, FIG. 2B is a schematic cross-sectional view taken along line AA ′ in FIG. 2A, and FIG. 3 is an alignment state of liquid crystal molecules in the liquid crystal device. It is a schematic sectional drawing which shows.

As shown in FIGS. 1A and 1B, the liquid crystal device 100 of this embodiment includes an element substrate 10 and a counter substrate 20 as a pair of substrates, and a liquid crystal layer 50 sandwiched between the pair of substrates. Have.
The element substrate 10 is slightly larger than the counter substrate 20, and both substrates are bonded via a seal material 40 arranged in a frame shape, and liquid crystal having negative dielectric anisotropy is sealed in the gap, for example. Layer 50 is configured. For the sealing material 40, for example, an adhesive such as a thermosetting or ultraviolet curable epoxy resin is employed. A spacer (not shown) is mixed in the sealing material 40 to keep the distance between the pair of substrates constant.

On the inner side of the sealing material 40 arranged in a frame shape, a parting portion 21 is provided in the same frame shape. The parting portion 21 is made of, for example, a silicon oxide insulating film doped with boron and has a light shielding property. The inside of the parting portion 21 is a display area E having a plurality of pixels P.

A data line driving circuit 101 is provided between the element substrate 10 and the sealing material 40 along one side. A sampling circuit 103 is provided inside the sealing material 40 along the one side. Furthermore, the sealing material 40 along the other two sides orthogonal to the one side and facing each other.
Is provided with a scanning line driving circuit 102. A plurality of wirings 105 that connect the two scanning line driving circuits 102 are provided inside the sealing material 40 on the other side facing the one side. Wirings connected to the data line driving circuit 101 and the scanning line driving circuit 102 are connected to a plurality of external connection terminals 104 arranged along the one side.
Hereinafter, the direction along the one side will be referred to as the X direction, and the direction along the other two sides orthogonal to the one side and facing each other will be described as the Y direction.

As shown in FIG. 1B, on the surface of the element substrate 10 on the liquid crystal layer 50 side, a light-transmitting pixel electrode 15 provided for each pixel P, a thin film transistor 30 as a switching element, and a signal wiring And the alignment film 18 which covers these is formed.

On the surface of the counter substrate 20 on the liquid crystal layer 50 side, a parting portion 21, a planarization layer 22 formed so as to cover it, a common electrode 23 provided so as to cover the planarization layer 22, Electrode 23
And an alignment film 24 is provided.

As shown in FIG. 1A, the parting part 21 is provided in a frame shape at a position that overlaps the data line driving circuit 101, the scanning line driving circuit 102, and the sampling circuit 103 in a plane.
Thus, the light incident from the counter substrate 20 side is shielded, and the malfunction of the peripheral circuits including these drive circuits due to the light is prevented. Further, unnecessary stray light is shielded from entering the display area E, and high contrast in the display of the display area E is ensured.

The alignment film 18 and the alignment film 24 are inorganic alignment films made of an inorganic material, and are obtained by oblique deposition of SiO _x (silicon oxide) as an inorganic material. Such an alignment film 1
The alignment state of the liquid crystal molecules in the liquid crystal layer 50 sandwiched between 8 and 24 will be described later.

The common electrode 23 provided on the counter substrate 20 is electrically connected to the wiring on the element substrate 10 side by the vertical conduction portions 106 provided at the four corners of the counter substrate 20 as shown in FIG.

As shown in FIG. 2A, the pixel P of the liquid crystal device 100 has a substantially rectangular pixel electrode 15 in a region defined by a scanning line 3a and a data line 6a that intersect (orthogonal) each other. The pixel electrode 15 is made of a transparent conductive film such as ITO (Indium Tin Oxide), for example, and has light transmittance.

The TFT 30 is provided on the scanning line 3a in the vicinity of the intersection of the scanning line 3a and the data line 6a. A semiconductor layer 30a is provided along the scanning line 3a, and a source electrode 30s formed integrally with the data line 6a is provided so as to overlap the source side of the semiconductor layer 30a. A drain electrode 30d is provided so as to overlap the drain side of the semiconductor layer 30a.

The drain electrode 30d extends to the pixel electrode 15 side, and the extended portion is electrically connected to the pixel electrode 15 through the contact hole 15a.

The capacitance line 3b is provided in parallel with the scanning line 3a, and in a region partitioned by the scanning line 3a and the data line 6a, the drain electrode 30d is disposed in a region overlapping the capacitance line 3b in a plan view.
The extending portion 30e is provided.

More specifically, as shown in FIG. 2B, first, scanning lines 3a made of a low-resistance wiring material such as aluminum are formed on the element substrate 10 and capacitance lines 3b parallel to the scanning lines 3a. A gate insulating film 11 made of, for example, silicon oxide is formed so as to cover the scanning line 3a and the capacitor line 3b. Subsequently, the semiconductor layer 30a is located on the gate insulating film 11 so as to overlap the scanning line 3a.
Are formed in islands. A source electrode 30s is formed so as to overlap with the source region of the semiconductor layer 30a, and a drain electrode 30d is also formed so as to overlap with the drain region of the semiconductor layer 30a. The source electrode 30s and the drain electrode 30d are obtained by forming and patterning a low-resistance wiring material, and the data line 6a is patterned together in the process of forming the source electrode 30s and the drain electrode 30d. . Similarly, an extending portion 30e connected to the drain electrode 30d is also formed at a position overlapping the capacitance line 3b.
The storage capacitor 16 is configured by the capacitor line 3b and the extending portion 30e arranged to face each other with the gate insulating film 11 interposed therebetween.
An interlayer insulating film 12 made of, for example, silicon oxide or nitride is formed so as to cover the TFT 30 and the storage capacitor 16, and a contact hole 15a is formed at a position overlapping the drain electrode 30d of the interlayer insulating film 12 in a plane. The By forming and patterning a transparent conductive film so as to cover the interlayer insulating film 12, the pixel electrode 15 electrically connected to the drain electrode 30d through the contact hole 15a is formed.

An alignment film 18 is formed so as to cover the pixel electrode 15. The alignment film 18 is formed by oblique vapor deposition of SiO _x (silicon oxide) as an inorganic material as described above. The planar vapor deposition direction of the oblique vapor deposition is a direction indicated by an arrow in FIG. 2A, has an angle θa with respect to the extending direction of the scanning line 3a, and extends from the upper right to the lower left of the pixel P. ing.
In this case, the angle θa in the vapor deposition direction is approximately 45 degrees. Further, the angle of the vapor deposition direction in the direction perpendicular to the paper surface, that is, the direction perpendicular to the surface of the pixel electrode 15 is about 45 degrees (see FIG. 3).

According to such oblique deposition, as shown in FIG. 2B, a columnar body (column) 18c is formed in which SiO _x crystals as an inorganic material grow in an oblique direction with respect to the substrate surface. The alignment film 18 is made of an aggregate in which such columnar bodies (columns) 18c are erected on the substrate surface.
2 (a) and 2 (b), the configuration on the element substrate 10 side has been described.
Similarly, the alignment film 24 at 0 is formed so as to cover the common electrode 23 using oblique vapor deposition, and the planar vapor deposition direction is 18 with respect to the vapor deposition direction of the angle θa on the element substrate 10.
The direction is 0 degrees.

FIG. 3 is a schematic sectional view showing the formation state of the inorganic alignment film and the alignment state of the liquid crystal molecules in the liquid crystal device. Specifically, it is a cross-sectional view taken along the vapor deposition direction of oblique vapor deposition in FIG.

As shown in FIG. 3, the angle θb of the vapor deposition direction in the alignment films 18 and 24 with respect to the substrate surface facing the liquid crystal layer 50 is about 45 degrees. Also, the angle θ of the column growth direction relative to the substrate surface
c is approximately 70 degrees. Hereinafter, the angle θc is referred to as a column angle θc.

The pretilt angle θp of the liquid crystal molecules LC that are substantially vertically aligned on the surfaces of the alignment films 18 and 24 is approximately 85 degrees. Further, the pretilt direction of the liquid crystal molecules LC viewed from the normal direction of the substrate surface, that is, the azimuth angle direction, is the same as the planar deposition direction of the oblique deposition in the alignment films 18 and 24.

The liquid crystal device 100 includes polarizing elements 41 and 42 disposed on the light incident side and the light exit side of the liquid crystal panel 110, respectively. The polarizing elements 41 and 42 are arranged with respect to the liquid crystal panel 110 so that the absorption axis or transmission axis of each other is orthogonal. More specifically, one absorption axis or transmission axis is arranged in parallel with the scanning line 3a, and the other absorption axis or transmission axis is arranged in parallel with the data line 6a (see FIG. 2A). .
That is, the azimuth direction of the pretilt of the liquid crystal molecules LC intersects the transmission axis or absorption axis of the polarizing elements 41 and 42 at 45 degrees, and a drive voltage is applied between the pixel electrode 15 and the common electrode 23. When the liquid crystal layer 50 is driven, the liquid crystal molecules LC are tilted in the pretilt azimuth direction, so that an optical arrangement is obtained in which high transmittance is obtained.

In addition, the liquid crystal device 100 performs pretreatment for cleaning the surfaces of the element substrate 10 and the counter substrate 20 before the alignment films 18 and 24 are formed, and the alignment film surface after the alignment films 18 and 24 are formed. A post-treatment for surface treatment is performed. This reduces the image sticking phenomenon caused by energization and realizes a stable alignment state of the liquid crystal molecules LC in the liquid crystal layer 50. Details of the pre-processing and post-processing will be described in the following method for manufacturing the liquid crystal device 100.

<Method for manufacturing liquid crystal device>
Next, a method for manufacturing the liquid crystal device 100 of the present embodiment will be described with reference to FIGS. 4 is a flowchart showing a method for manufacturing a liquid crystal device, FIG. 5 is a schematic plan view showing a mother substrate, and FIG. 6 is a schematic cross-sectional view showing the structure of a vapor deposition device.

As shown in FIG. 4, the manufacturing method of the liquid crystal device 100 of the present embodiment includes steps S <b> 1 to S <b> 4 related to the manufacture of the element substrate 10 and step S <b> 11 related to the manufacture of the counter substrate 20.
Step S14, Step S21 of bonding both substrates using the completed element substrate 10 and counter substrate 20, and Step of injecting liquid crystal into the gap between the bonded element substrate 10 and counter substrate 20 for sealing S22.

In addition, the manufacturing method of the liquid crystal device 100 of this embodiment is performed using the wafer-shaped mother board | substrate 10W, as shown in FIG. The mother substrate 10W is the element substrate 1 based on the orientation flat.
The processing on the element substrate 10 side is performed in a state where the plurality of element substrates 10 are arranged in a matrix in the longitudinal direction (X direction) and the lateral direction (Y direction) of 0. A single counter substrate 20 is bonded to each element substrate 10 of the mother substrate 10W one by one.

The counter substrate 20 may be processed in an individual state, or may be processed in a state of being impressed on the mother substrate in the same manner as the element substrate 10, and may be processed before being bonded to the element substrate 10 of the mother substrate 10 </ b> W. It may be separated.

First, from the element substrate 10 side, in the element substrate side thin film forming step of step S1,
Structures (thin films) such as the scanning lines 3 a, the capacitor lines 3 b, the data lines 6 a, the TFTs 30, and the pixel electrodes 15 constituting the pixels P are formed on the element substrate 10. The manufacturing method of these structures can use a well-known manufacturing method, for example, the semiconductor layer 30a in TFT30 is:
It can be formed by patterning a polycrystalline silicon film obtained by forming an amorphous silicon film by using a low pressure CVD method or the like and crystallizing it by heat-treating it at a high temperature. Then, the process proceeds to step S2.

In the pretreatment step of step S2, first, the element substrate 10 is washed with pure water and dried.
As a pure water cleaning method, a method in which the element substrate 10 is immersed in pure water heated to about 40 ° C. to 60 ° C. and ultrasonic waves are applied, and pure water is pressurized and sprayed on the surface of the element substrate 10. You may employ | adopt the method of attaching, or the method of combining these methods.
In the next step S3, the surface on which the inorganic alignment film is formed is irradiated with ultraviolet rays in the atmosphere. The ultraviolet irradiation conditions are, for example, as follows.
Light source: low-pressure mercury lamp, wavelength: 185 nm (10%) + 254 nm (90%)
^{Illuminance; 25mW / cm 2 ~30mW / cm} 2, irradiation time: ozone atmospheric oxygen is excited by irradiation of 5 minutes UV occurs. Foreign matter made of organic matter reacts with ozone by the generated ozone and is discharged as carbon dioxide or water vapor. Further, ionic impurities remaining on the surface can be removed along with the removal of organic matter. If there is a concern about the change in electrical characteristics of the TFT 30 as a switching element due to the irradiation of ultraviolet rays, the irradiation of ultraviolet rays may be canceled. Then, the process proceeds to step S3.

In the inorganic alignment film forming step of step S3, silicon oxide is obliquely deposited to form an alignment film 18 as an inorganic alignment film covering the pixel electrode 15 on the surface of the element substrate 10 (see FIGS. 2 and 3). .

Here, the method of oblique deposition will be described with reference to FIG. The alignment film 18 is formed by the vapor deposition apparatus 300 shown in FIG. That is, the mother substrate 10W is set at a predetermined angle θb (see FIG. 3, approximately 45 degrees) on the substrate disposing portion 307 suspended from the upper portion of the vapor deposition chamber 308, and then the vacuum pump 310 is operated to deposit the mother substrate 10W. The pressure inside the chamber 308 is reduced. Meanwhile, the vapor deposition chamber 308
The evaporation source 302 disposed at the bottom of the substrate is heated by a heating device (not shown), and the evaporation source 3
02 generates silicon oxide vapor. The vapor stream of silicon oxide generated in the vapor deposition source 302 is released through an opening 303 a provided in the vapor circulation part 303, and the mother substrate 10.
Silicon oxide is obliquely deposited on the surface of W. Then, the columnar body 18c of silicon oxide is deposited on the surface of the mother substrate 10W while being aligned at a column angle θc (see FIG. 3, approximately 70 degrees) with respect to the surface of the mother substrate 10W. Is formed. The film thickness of the alignment film 18 is set to about 750 nm. Further, the alignment film 18 is not limited to the oblique vapor deposition method described above, and may be formed by an anisotropic sputtering method or the like. Then, the process proceeds to step S4.

In the post-processing step of step S4, the mother substrate 10W on which the alignment film 18 is formed is washed with isopropyl alcohol. Specific cleaning methods include a method of immersing in isopropyl alcohol and a method of spraying isopropyl alcohol onto the alignment film 18. As a finishing method for uniformly removing the isopropyl alcohol adhering to the alignment film surface, there is a method of exposing the cleaned mother substrate 10W to a vapor bath of isopropyl alcohol.

Next, the counter substrate 20 side will be described. In the counter substrate-side thin film forming step in step S11, a parting portion 21, a planarizing layer 22, and a common electrode 23 are sequentially formed on the surface of the counter substrate 20 on the side facing the liquid crystal layer 50. As a method of forming these structures (thin films), known manufacturing methods can be used. For example, as described above, the parting portion 21 is obtained by doping a silicon oxide film with boron and imparting light shielding properties. After the film is formed by using a method such as plasma CVD, a patterning method is used. Can be mentioned. The film thickness of the parting part 21 is about 3
00 nm. The planarization layer 22 is formed so as to cover the parting portion 21 using an inorganic insulating material such as silicon oxide. The thickness of the planarization layer 22 is approximately 1000 nm. The common electrode 23 is formed by depositing a transparent conductive film such as ITO on the planarizing layer 22 by vapor deposition or sputtering. The common electrode 23 has a thickness of about 100 nm to 150 nm. And step S12
Proceed to

In the pretreatment step of step S12, as in step S2 of the element substrate 10, first, the counter substrate 20 on which the common electrode 23 is formed is subjected to pure water cleaning. Subsequently, the surface on which the common electrode 23 is formed is irradiated with ultraviolet rays. The ultraviolet irradiation condition is the same as that in step S2 of the element substrate 10. Since the counter substrate 20 is not provided with the TFT 30 as a switching element, the parting portion 21 and the common electrode 23 provided on the counter substrate 20 are not deteriorated by the ultraviolet irradiation, so that the ultraviolet irradiation can be safely performed. it can.
Note that the counter substrate-side thin film forming process in step S11 is not complicated with respect to the mother substrate 10W (element substrate 10), and therefore, the counter substrate 20 may be contaminated by being adhered to the counter substrate 20 before the pretreatment process. Is low. Therefore, in the pretreatment process, pure water cleaning can be omitted in consideration of the cleanliness of the counter substrate 20 before the pretreatment process. Then, the process proceeds to step S13.

In the inorganic alignment film forming step of step S13, the vapor deposition apparatus 300 shown in FIG. 6 is used, and the individual counter substrate 20 or the mother substrate on which the counter substrate 20 is imposed is suspended above the vapor deposition chamber 308. The substrate is disposed at a predetermined angle θb (approximately 45 degrees) on the substrate placement portion 307, and silicon oxide is obliquely deposited on the common electrode. Columnar bodies of silicon oxide are deposited while being arranged at a column angle θc (approximately 70 degrees) with respect to the substrate surface, whereby the alignment film 24 is formed. Note that the film thickness of the alignment film 24 is also set to about 750 nm, like the alignment film 18 of the element substrate 10. Further, the alignment film 24 may be formed not only by the above-described oblique vapor deposition method but also by an anisotropic sputtering method or the like. Then, the process proceeds to step S14.

In the post-processing step of step S14, the alignment film 24 is formed in the same manner as in step S4 of the element substrate 10.
The counter substrate 20 on which is formed is cleaned with isopropyl alcohol, and similarly finished using a steam bath.

In the bonding step of step S21, the mother substrate 10W and the counter substrate 20 that have been post-processed in this way (steps S4 and S14) are arranged to face each other at a predetermined position and are bonded via the sealing material 40. . As described above, since the spacer is mixed in the sealing material 40 in advance, the gap between the element substrate 10 and the counter substrate 20 after bonding can be kept constant. Then, the process proceeds to step S22.

In the liquid crystal injection / sealing process in step S22, the bonded mother substrate 10W and counter substrate 20 are placed in a chamber and decompressed. Then, a predetermined amount of liquid crystal is dropped in the vicinity of the inlet provided in the sealing material 40, and the inside of the chamber is returned to atmospheric pressure, whereby the dropped liquid crystal enters the inside from the inlet and is filled. After the liquid crystal is filled, the inlet is sealed using, for example, an ultraviolet curable sealant.

According to such a manufacturing method of the liquid crystal device 100, since the element substrate 10 and the counter substrate 20 are once cleaned with pure water in the pretreatment process (step S2, step S12),
Visible foreign substances and water-soluble ionic impurities attached to the surface are removed. Subsequently, foreign substances made of organic matter are decomposed and removed by ozone generated by irradiation with ultraviolet rays in the atmosphere, and ionic impurities remaining after pure water cleaning are further removed.
Therefore, the inorganic alignment film forming surfaces of the element substrate 10 and the counter substrate 20 are cleaned, and the alignment films 18 and 24 can be formed evenly by oblique deposition. Further, by removing the ionic impurities, the image sticking phenomenon due to energization is improved.

In the post-treatment process (steps S4 and S14), the mother substrate 10W and the counter substrate 20 on which the inorganic alignment film is formed are cleaned with isopropyl alcohol. As a result, the reaction layer is formed on the surface of the inorganic alignment film by reacting the silanol group (—Si—OH) on the surface of the inorganic alignment film with the isopropyl group (—C ₃ H ₇ ) of isopropyl alcohol. Since this reaction layer can suppress or prevent the reaction activity with the liquid crystal molecules LC on the surface of the inorganic alignment film, a stable alignment state of the liquid crystal molecules LC in the liquid crystal layer 50 can be obtained.

In addition, after irradiating an ultraviolet-ray in a pre-processing process (step S2, step S12), during the inorganic alignment film formation process (step S3, step S13), no other surface treatment is implemented at all. Further, in order to enter the next inorganic alignment film forming step while maintaining the cleanliness of the substrate surface, the inorganic alignment film is formed within 48 hours after irradiation with ultraviolet rays.

FIG. 7 is a graph showing the results of surface analysis of the adhesion state of foreign matter and the remaining state of ionic impurities on the substrate surface. In addition, TOF-SIMS (time-of-flight secondary ion mass spectrometry) method was used as the surface analysis method, and the surface on the counter substrate 20 side before forming the inorganic alignment film was analyzed. In addition, FIG. 7 shows a hydrocarbon having 7 carbon atoms (C ₇ H ₇ ⁺ ) and a cyano group (C
The relative amount of N ⁻ ) is shown, and the relative amount of chloride ion (Cl ⁻ ) is shown as a typical ionic impurity. These are expressed by selecting those that exhibit characteristic changes in describing the surface treatment effect of pure water cleaning and ultraviolet irradiation (UV treatment).

As shown in FIG. 7, it can be seen that more hydrocarbon acid and cyano groups are present than chlorine ions on the uncleaned substrate surface. On the other hand, when pure water cleaning is performed on the substrate, it can be seen that hydrocarbon acids and cyano groups, which are water-soluble organic substances, decrease while chlorine ions increase on the contrary.
Although metal ions are generally reduced by cleaning with pure water, it can be seen how difficult it is to remove chlorine ions having a high abundance in comparison with other metal ions in a cleaning environment. On the other hand, it can be seen that the chlorine ions were reduced by further ultraviolet irradiation (UV treatment).
The reason why the relative amount of hydrocarbon acid and cyano group after ultraviolet irradiation (UV treatment) varies after cleaning with pure water is because the average value of the surface analysis results of multiple test samples is used. ,
It is thought that the variation in the analysis method is reflected.
It has been found that the amount of hydrocarbon acid, cyano group, and chlorine ion decreases even when pure water cleaning is not performed and only ultraviolet irradiation (UV treatment) is performed.

FIG. 8 is a graph showing evaluation results of image sticking caused by energization of the liquid crystal device. In the burn-in evaluation method of the liquid crystal device 100 according to the present embodiment, for example, the display in the display area E of the normally black mode liquid crystal device 100 is turned on, that is, energized with all white display. This energization time is taken as the horizontal axis, and the transmittance of all white display after energization is compared with the initial transmittance, and the rate of change is taken as the vertical axis.
As shown in FIG. 8, when only pure water cleaning is performed in the pretreatment process (Δ), the change rate of brightness (transmittance) is increased to about 4% by energization. That is, it is in a state (burn-in state) where the change in brightness can be sufficiently recognized visually. In contrast to this, ultraviolet irradiation (UV
(□), the rate of change in brightness (transmittance) is small regardless of the energization time of 30 minutes, 60 minutes, 120 minutes, and 180 minutes, and the maximum is about 2%. ing. That is, it is difficult to visually recognize the change in brightness.

As a technical matter to support the result of FIG. 8, the common electrode 23 is used in order to perform an optimal white display.
The change of the common potential (COM potential) given to. FIG. 9 is a graph showing the relationship between the energization time of the liquid crystal device and the shift amount of the optimum COM potential.
As shown in FIG. 9, the optimum COM potential shift amount (V) increases until the energization time reaches 10 minutes, and is almost flat at the energization time after that, 20 minutes, 30 minutes, and 40 minutes. It has become. Compared to the case where only pure water cleaning was performed in the pretreatment process (△), further ultraviolet irradiation (U
When (V processing) is performed (□), the value of the shift amount (V) is small.
By cleaning the substrate surface before forming the inorganic alignment film, diffusion of ionic impurities into the liquid crystal layer 50 is reduced, and it becomes difficult to form a power storage layer near the alignment film surface when energized.
The amount of potential shift is reduced. That is, it can be said that the image sticking phenomenon has been reduced.

  Various modifications other than the above embodiment are conceivable. Hereinafter, a modification will be described.

(Modification 1) The configuration of the pixel P in the liquid crystal device 100 is not limited to this. For example,
The pixel electrode 15 is formed using Al (aluminum) having light reflectivity or an alloy thereof,
In order to prevent the surface state of the pixel electrode 15 from changing, an inorganic alignment film may be provided on the protective film after being covered with a transparent protective film. According to this, it is possible to provide the reflective liquid crystal device 100 in which the image sticking phenomenon is reduced.

(Modification 2) The post-processing process (step S4, step S14) in the manufacturing method of the liquid crystal device 100 is not essential. That is, the post-processing step may be omitted.

DESCRIPTION OF SYMBOLS 10 ... Element substrate of a pair of substrates, 18, 24 ... Alignment film as inorganic alignment film, 20 ...
Counter substrate of a pair of substrates, 30... Thin film transistor (T
FT), 50 ... liquid crystal layer, 100 ... liquid crystal device.

Claims (5)

A method of manufacturing a liquid crystal device having a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates,
A pretreatment step of irradiating at least one substrate of the pair of substrates with ultraviolet rays in an atmosphere containing at least oxygen on a surface facing the liquid crystal layer;
An inorganic alignment film forming step of forming an inorganic alignment film on the surface irradiated with the ultraviolet rays,
A method of manufacturing a liquid crystal device, wherein a surface treatment step other than the pretreatment step is not performed before the inorganic alignment film forming step. A conductive film forming step of forming a conductive film on the one substrate;
The method for manufacturing a liquid crystal device according to claim 1, wherein in the pretreatment step, the surface of the one substrate on which the conductive film is formed is irradiated with ultraviolet rays. 3. The method for manufacturing a liquid crystal device according to claim 1, further comprising a pure water cleaning step of cleaning at least one of the pair of substrates before the pretreatment step. 3. The switching element is not formed on the one substrate.
Or a method for producing a liquid crystal device according to 3. The inorganic alignment film forming step forms the inorganic alignment film by obliquely depositing silicon oxide,
5. The method according to claim 1, further comprising a post-processing step of cleaning at least one of the pair of substrates on which the inorganic alignment film is formed with isopropyl alcohol. Liquid crystal device manufacturing method.

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