JP2007047495A - Reflective display device and method for manufacturing reflective display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective display device 5A in a high production yield, the device that reliably keeps electric connection through a contact hole 22e even when the area of the contact hole 22e is reduced and that can achieve bright, fine and high-quality display images. <P>SOLUTION: An insulating layer 18 for protecting elements is formed on a thin film transistor 16. Also, a linked electrode 17 to be in contact with the drain electrode 15 of the thin film transistor 16 through a contact hole 17e formed in an aperture 18h is formed on the insulating layer 18. After the above, a photosensitive film 21 with a fine surface rugged pattern formed is stuck on the insulating layer 18, an aperture 21h is formed in the film, and aluminum is vapor-deposited by sputtering thereon to simultaneously form a reflection electrode 22 having a fine surface rugged pattern and a contact hole 22e. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflective display device suitable for application to an electrophoretic display device, and a method for manufacturing the reflective display device. More specifically, the present invention relates to a predetermined switching element disposed with an element protection layer and a reflective film support layer therebetween. The present invention relates to a technology for electrically connecting the electrode and the reflective film with a shallow minute contact hole.

  A reflective liquid crystal device that reflects natural light and reflected light of room light incident from an image display surface and modulates the light by a liquid crystal element has been put into practical use. Reflective liquid crystal devices are used for portable game machines, communication terminals, and the like in consideration of outdoor use, and achieve low power consumption without depending on a backlight.

  In the reflection type liquid crystal device, a liquid crystal layer as a light modulation layer is arranged between a rear substrate on which switching elements are arranged and a transparent front substrate, and the rear substrate is made to correspond to a liquid crystal cell of each pixel. An infinite number of switching elements are arranged in a lattice pattern, and a reflective electrode for each liquid crystal cell is arranged on each switching element.

  The reflective liquid crystal device disclosed in Patent Document 1 includes a reflective electrode having a minute surface irregular shape. The reflective electrode is formed by laminating a metal thin film on a reflective film support layer having a minute surface irregularity shape, and molding the metal thin film into a reflective electrode for each liquid crystal cell. The reflective electrode also serves as an electrode that modulates the liquid crystal layer, and is electrically connected to a predetermined electrode of the switching element formed on the rear substrate using a contact hole.

  Patent Document 2 discloses an electrophoretic display device in which a light modulation layer (liquid crystal layer) of a transmissive liquid crystal device is replaced with an electrophoretic cell. The electrophoresis cell is filled with a liquid in which light-shielding charged particles are dispersed in an independent space for each display cell, and the charged particles move in the electrophoresis cell according to the applied electric field state. The light shielding property and color tone of the electrophoresis cell change.

  The electrophoretic display device has a higher display contrast and excellent visibility than a liquid crystal display device in which a liquid crystal layer is disposed as a light modulation layer. Further, since the display has a memory property, power consumption can be further reduced. In the electrophoretic display device, a reflective display device that does not rely on a backlight can be formed by disposing a reflective electrode that also serves as an electrode for each display cell on a rear substrate on which switching elements are arranged.

JP 2000-187208 A US Pat. No. 3,612,758

  In the reflective liquid crystal device disclosed in Patent Document 1, an element protective layer of an insulating film is formed on a switching element (TFT: thin film transistor element) formed on a rear substrate, and a predetermined electrode (drain electrode) of the switching element is formed. ) Is opposed to the reflective electrode across the element protective layer and the reflective film support layer, and both are electrically connected by a contact hole penetrating the element protective layer and the reflective film support layer.

  This contact hole forms a cylindrical conductive path by depositing a metal thin film on the inner wall of a deep opening that reaches the drain electrode when a metal thin film is deposited on the reflective film support layer to form a reflective surface. . The deep opening reaching the drain electrode is formed in the reflective film support layer by forming a reflective film support layer on the element protective layer and then positioning the large opening formed in the element protective layer.

  Therefore, the depth of the contact hole is the sum of the thickness of the element protective layer and the thickness of the reflective film support layer. When depositing a metal thin film on the reflective film support layer, the side and bottom surfaces of the opening are formed. It is difficult to achieve both metal thin film growth. When the deposition condition giving priority to the deposition on the side surface of the opening is employed, it is difficult to deposit the metal thin film to every corner of the bottom of the opening of the reflective film support layer. On the other hand, if the deposition condition that prioritizes deposition on the bottom surface of the opening is adopted, line breakage or peeling is likely to occur on the side surface.

  In any case, the electrical connection between the drain electrode and the reflective electrode through the contact hole becomes uncertain, causing pixel defects due to poor connection and reducing the image quality and manufacturing yield of the reflective liquid crystal device.

  However, if the aperture of the reflection film support layer is increased or a large taper is formed in the opening of the reflection film support layer in order to ensure the electrical connection through the contact hole, it occupies the area of the liquid crystal cell. As the proportion of contact holes increases, the effective reflection area of the reflective electrode having a surface irregularity shape decreases, the amount of reflected light decreases, and the quality of reflected light from the reflective electrode also decreases.

  In addition, since an opening having a large aperture is positioned on the inside thereof, a larger opening is formed in the element protection layer, and the possibility that the switching element becomes defective due to impurity diffusion or oxidation through the opening increases.

  Also, if the material and deposition conditions of the metal thin film are changed in a direction that improves the wraparound of the material, it becomes impossible to select materials and deposition conditions that improve the reflective performance of the reflective electrode, and the possibility that the reflective performance of the reflective electrode will deteriorate increases. However, such a change may adversely affect the performance of the liquid crystal cell.

  In addition, in an electrophoretic display device, when a deep contact hole (dent) is formed at the interface of the display cell, charged particles are trapped in the contact hole recess, and the number of charged particles that can freely migrate decreases. The contrast of the display is reduced, and the display switching speed is reduced.

  Therefore, it has been proposed to add a new process for filling the recess in the contact hole. However, the performance of the display cell is reduced by the material filling the recess, and the production yield is reduced and the manufacturing cost is increased due to the addition of a new process. Or cause

  Incidentally, in recent years, there has been a demand for further refinement of the display image of the reflective display device, and the area of the reflective electrode for each display cell is also reduced as the density of the display cell is increased (that is, the area is reduced). There is also a demand for reducing the contact hole area of the reflective electrode. However, when the area of the contact hole is reduced, as described above, the electrical connection failure due to the contact hole increases, which causes the quality of the reflective display device and the manufacturing yield.

  It is an object of the present invention to provide a reflective display device with a high production yield, which can ensure electrical connection through a contact hole even when the area of the contact hole is reduced and can realize a bright, fine and high-quality display image. It is aimed.

  In the reflective display device of the present invention, the switching element formed as a thin film, the insulating element protective layer formed so as to cover the switching element, and the insulating reflective film support disposed so as to cover the element protective layer A reflective display device comprising: a layer; and an electrical connection to a predetermined electrode of the switching element through an opening formed in the element protective layer. A conductive electrode film formed on the reflective film support layer is electrically connected to the connection electrode member through the opening formed in the reflective film support layer. It is what you are doing.

  In the reflective display device of the present invention, since the electrical connection in the depth direction is relayed by the connecting electrode member, the depth of the contact hole formed in the reflective film support layer is equal to or greater than the thickness of the reflective film support layer. In other words, the thickness of the element protection layer is shallower than the contact hole disclosed in Patent Document 1. In addition, the depth of the contact hole formed in the element protective layer cannot be greater than the thickness of the element protective layer, and is shallower than the contact hole disclosed in Patent Document 1 by the thickness of the reflective film support layer.

  Therefore, as the depth becomes shallower, the conductive material wraps around the inner wall and bottom of the opening formed in the reflective film support layer, and the electrical connection from the entrance to the bottom of the contact hole is ensured. .

  Further, since the opening of the reflective film support layer is formed by positioning the connecting electrode member having a larger area than the contact hole of the element protective layer, the contact hole of the reflective film support layer Secure overlay with the connecting electrode member and electrical connection thereby can be ensured.

  In addition, the planar expansion of the connecting electrode member allows the position of the contact hole in the reflective film support layer to be set without being constrained by the position of the predetermined electrode of the switching element, thereby affecting the display function of the display cell. The display function of the display cell can be enhanced by setting a contact hole in the reflective film support layer at a position where the display cell does not exist.

  In addition, since the switching element is completely covered with the element insulating layer and the connecting electrode member before the formation of the reflective film support layer, a predetermined electrode is oxidized or impurities are not formed through the opening of the element insulating layer. Does not spread. Therefore, even if the rear substrate is transported for a long distance or stored for a long time in a state where the connection electrode member is formed, the switching element is unlikely to be defective, and the production yield is not adversely affected.

  In addition, since the electrical connection can be ensured even with a small area contact hole, the effective reflection area is increased by reducing the area ratio of the contact hole to the area of the reflective electrode, and the diffuse reflection performance due to the minute surface irregularities is sufficient. Can be demonstrated.

  In addition, if the contact hole has a small area, it is possible to fill the dent by depositing a conductive reflective film, and even if the dent is left as it is, it does not adversely affect the display performance of the display cell, so the dent is filled. Therefore, it is not necessary to add a new process only for this purpose.

  Hereinafter, reflective display devices 5A to 5D according to an embodiment of the present invention will be described in detail with reference to the drawings. The reflective display devices 5A to 5D of the present embodiment are active matrix type, reflective type, electrophoresis, and display device. However, the present invention may adopt a display cell driving system other than the active matrix type. Reflective display device that modulates external light incident from the image display surface by a light modulation layer and reflects it toward the image display surface by a reflective electrode formed for each display cell, for example, light modulation The present invention can be widely applied to a reflective display device that employs a liquid crystal layer or a shutter element for each pixel as a layer.

  In the following description, the general structure of the display device disclosed in Patent Document 1 and Patent Document 2, the general manufacturing method, for example, the refractive index adjustment layer, the grid arrangement of the display cells and wiring, and the image display including the driver Since the circuit, image signal processing, film formation process, pattern formation process, and the like are different from the spirit of the present invention, some illustrations are omitted and detailed descriptions are omitted to avoid complexity.

<First Embodiment>
FIG. 1 is a cross-sectional view of a display cell of a reflective display device according to a first embodiment which is an embodiment of the present invention. In the reflective display device 5A of the first embodiment, the switching element of the invention is the thin film transistor 16, the element protective layer is the insulating layer 18, the reflective film support layer is the photosensitive film 21, and the opening formed in the element protective layer is the opening 18h. The predetermined electrode corresponds to the drain electrode 15, the opening formed in the reflective film support layer corresponds to the opening 21 h, the connection electrode member corresponds to the connection electrode 17, and the conductive reflection film corresponds to the reflection electrode 22. The present invention is not limited to such combinations by these configurations, and various embodiments can be assembled by any combination selected from these configurations and other alternative configurations.

  As shown in FIG. 1, the reflective display device 5 </ b> A of the first embodiment has an infinite number of display cells 6 </ b> A arranged on a back substrate 10 in a grid pattern. On the rear substrate 10, a common interlayer insulating film 12 is formed, and a thin film transistor (TFT) 16 for each display cell 6 A is formed. A common insulating layer (interlayer insulating layer) 18 is formed to cover the thin film transistor 16. Has been.

  On the insulating layer 18, a photosensitive film 21 having a predetermined fine surface irregularity shape is disposed. The photosensitive film 21 is preferably one that can at least planarize the surface in the formation process. This is because the flattening action of the photosensitive film 21 can offset the unevenness caused by the thin film transistor 16 and its wiring pattern, thereby forming a reflective surface with a uniform surface height. However, a flattening layer (not shown) is separately formed on the insulating layer 18 on which the connection electrode 17 is formed in order to prevent the underlying concave / convex pattern from appearing on the surface of the photosensitive film 21. The photosensitive film 21 may be formed on a flat surface.

  On the photosensitive film 21, a reflective electrode 22 of a metal thin film that also serves as a drive electrode of the display cell 6A is formed for each display cell 6A. The reflective electrode 22 has a surface uneven shape that follows the fine surface uneven shape of the photosensitive film 21, and folds back to the surface substrate 20 side while scattering external light incident from the surface substrate 20 side.

  A planarizing layer 23 is formed on the reflective electrode 22, and an insulating liquid 32 in which charged particles 31 are dispersed is filled in the gap between the planarizing layer 23 and the surface substrate 20. The edge of the outer periphery surrounding the space between the back substrate 10 and the front substrate 20 is sealed with an adhesive seal (not shown).

  Light incident from the surface substrate 20 is scattered or absorbed by the charged particles 31 distributed in the insulating liquid 32 and reaches the reflection electrode 22, and the light reflected by the surface of the reflection electrode 22 is directed forward and further charged. Since the light is scattered or absorbed by the particles 31 and exits from the surface substrate 20, the observer can visually recognize a predetermined reflection intensity that changes according to the distribution of the charged particles 31 in the migration space of the display cell 6 </ b> A through the surface substrate 20. . In this way, an image display is made on the reflective display device 5A according to the distribution of the charged particles 31 controlled in units of pixels (display cells 6A).

  The distribution of the charged particles 31 in the insulating liquid 32 is controlled by a voltage applied between the reflective electrode 22 and the partition wall electrode 25. When the charged particles 31 dispersed in the insulating liquid 32 have a positive polarity, when a positive polarity voltage is applied to the reflecting electrode 22 and a negative polarity voltage is applied to the partition electrode 25, the charged particles 31 are separated from each other. Since the light gathers on the electrode 25 side, the external light incident from the surface substrate 20 reaches the reflective electrode 22 and is reflected at a high rate. Thereby, a bright pixel can be displayed.

  On the other hand, when a negative polarity voltage is applied to the reflective electrode 22 and a positive polarity voltage is applied to the partition wall electrode 25, the charged particles 31 move so as to cover the reflective electrode 22. The display cell 6 </ b> A can display the color of the charged particles 31 by being absorbed by the charged particles 31. For example, if the charged particles 31 are black, the display cell 6A displays black pixels.

  As shown in FIG. 1, a gate line 11 made of an aluminum alloy and molybdenum is formed on a non-alkali glass back substrate 10 and covered with an interlayer insulating layer 12 made of silicon nitride. On the interlayer insulating layer 12, source lines 14 and drain electrodes 15 made of a molybdenum alloy are arranged in a lattice pattern, and a bottom gate type thin film transistor 16 made of amorphous silicon 13 is formed at the intersection of the gate electrode 11 and the source line 14. Is formed. The resolution of the reflective display device 5A is set to be equivalent to 40 μm at the pixel (display cell 6A) pitch.

  An inorganic insulating layer (interlayer insulating layer) 18 made of silicon nitride is formed on the thin film transistor 16 thus formed. The insulating layer 18 functions as a protective film on the thin film transistor 16 and also functions as an electrode protective film in a driver mounting portion set on the edge of the back substrate 10.

  A predetermined resist pattern is formed on the insulating layer 18 by irradiating ultraviolet rays using a photoresist and a predetermined photomask, and then the insulating layer 18 is etched by dry etching. An opening 18h located on the top 15 is formed. The diameter of the opening 18h was φ4 μm. Note that fluorine-based gas was used for etching silicon nitride, and the side surface of the opening 18h was etched so as to have a forward taper.

  On the insulating layer 18, after forming a molybdenum layer having a thickness of 3000 μm (0.3 μm), a predetermined resist pattern is formed by irradiating ultraviolet rays using a photoresist and a predetermined photomask. The connecting electrode 17 was formed by wet-etching the molybdenum layer with a phosphoric acid-based etching solution. The connecting electrode 17 is a conductive thin film pattern formed on the insulating layer 18, and is electrically connected to the drain electrode 15 stably through a contact hole 17 e formed in the opening 18 h of the insulating layer 18.

  On the insulating layer 18 on which the connection electrode 17 is formed, a photosensitive film 21 having a desired uneven structure is attached. The photosensitive film 21 forms a predetermined contour pattern including the opening 21 h positioned in the connection electrode 17 by irradiating ultraviolet rays through a photomask. The photosensitive film 21 used was a negative type, and the film thickness was about 3 μm.

  The opening 21 h formed in the photosensitive film 21 was arranged in a plane so as not to overlap the contact hole 17 e of the insulating layer 18. Since the diameter of the opening 21h is φ8 μm, it is formed in a proportionately larger than that shown in FIG. 1 in consideration of the pitch 40 μm of the display cells 6A.

  The surface of the insulating layer 18 including the connecting electrode 17 has undulations of about 0.1 μm to 1 μm along the wiring pattern of the connecting electrode 17 and the thin film transistor 16, but these undulations are flattened by the photosensitive film 21. The surface shape of the insulating layer 18 including the connection electrode 17 is not reflected on the surface of the photosensitive film 21.

  Thereafter, an aluminum thin film having a film thickness of 1000 mm (0.1 μm) was formed on the photosensitive film 21 having a fine surface irregularity shape at a substrate temperature of 130 ° C. At this time, the contact hole 22e is formed by the aluminum material deposited on the inner wall and bottom of the opening 21h.

  Thereafter, a photoresist is applied on the entire surface, a predetermined resist pattern is formed by irradiating ultraviolet rays using a predetermined photomask, and the aluminum thin film is wet-etched with a phosphoric acid-based etchant, thereby reflecting each display cell 6A. The contour of the electrode 22 was formed. The aluminum thin film having a thickness of 1000 mm had a high specular reflectance of 99% immediately after the vapor deposition.

  The reflective electrode 22 is an electrode patterned according to the pixel shape, and is stably electrically connected to the connecting electrode 17 through the contact hole 22e of the photosensitive film 21, whereby the reflective electrode 22 is connected to the drain electrode 15. Both are in an electrically connected state.

  Thereafter, a low-viscous liquid photosensitive acrylic resin (for example, optmer PC415 manufactured by JSR Corporation) was applied to the entire surface including the reflective electrode 22 to form a planarizing layer 23, and the surface was planarized. By the planarizing layer 23 having a minimum film thickness of 2 μm, the recess (depth of 3 μm) of the contact hole 22 e of the photosensitive film 21 is filled almost flat.

  On the planarizing layer 23, a high-viscosity negative resist (for example, SU8 manufactured by Micro Chemical Co.) is applied and patterned to form the partition walls 24 for each display cell 6A. The partition wall 24 had a height of about 20 μm, a width of 5 μm, and a period of 40 μm.

  Thereafter, black chromium oxide and chromium are continuously vapor-deposited on the entire surface including the partition wall 24 and the planarizing layer 23, a photoresist is applied to the vapor-deposited surface, and a predetermined photomask is used to irradiate ultraviolet rays. A pattern was formed, and then the vapor deposition layer was wet-etched with a nitric acid-based etchant to pattern the partition wall electrode 25 covering the surface of the partition wall 24. The partition wall electrode 25 is insulated from the reflective electrode 22 by the planarizing layer 23, and drives the liquid crystal cell 6A in cooperation with the reflective electrode 22, and is disposed in a grid surrounding the display cell 6A. It also has the function of a black matrix that blocks unnecessary emission light.

  Thereafter, each display cell 6A surrounded by the partition walls 24 is filled with a predetermined amount of a transparent insulating liquid 32 in which charged particles 31 are dispersed at a predetermined concentration, and the surface substrate 20 is brought into close contact with the partition walls 24. Thus, the transparent insulating liquid 32 in which the charged particles 31 are dispersed in each pixel is sealed, and the reflective display device 5A of the first embodiment is manufactured.

  In the reflective display device 5 </ b> A of the first embodiment, the connecting electrode 17 is formed to electrically connect the reflective electrode 22 to the drain electrode 15 of the thin film transistor 16. The drain electrode 15 is electrically connected to the connection electrode 17 through a contact hole 17 e formed in the insulating layer 18 that protects the thin film transistor 16, and the reflective electrode 22 is connected to the connection electrode 17 through a contact hole 22 e formed in the photosensitive film 21. And is electrically connected.

  The contact hole 22e of the photosensitive film 21 and the contact hole 17e of the insulating layer 18 are arranged at different coordinate positions in the plane of the display cell 6A, and the contact hole 22e and the contact hole 17e overlap in a plane. Absent. Therefore, the design of the contact hole 22e is not restricted by the diameter and arrangement of the contact hole 17e, and the design of the contact hole 17e is not restricted by the diameter and arrangement of the contact hole 22e.

  Further, since the connecting electrode 17 is hidden under the reflective electrode 22 and does not affect the display performance of the display cell 6A, the area of the connecting electrode 17 can be designed to be sufficiently wide compared to the diameter of the contact hole 22e. . Accordingly, the design is strong against misalignment of the reflective electrode 22 with respect to the thin film transistor 16, and as a result, defects such as a contact failure between the reflective electrode 22 and the drain electrode 16 can be prevented.

  Further, since the contact hole 17e and the contact hole 22e are set at different coordinate positions in the plane of the display cell 6A, the depth of the contact hole 22e is shallower than the thickness of the photosensitive film 21, and charged particles It is possible to design the depth of the depression by the contact hole 22e formed at the interface of the 31 migration space to be shallow. The standard photosensitive film 21 has a thickness of about 0.5 to 3 μm including a fine surface irregularity shape, which is about the same as the particle size of the charged particles 31, and therefore the contact hole 22 e. Display defects due to the charged particles 31 getting stuck to the surface are unlikely to occur.

  In addition, since the connection electrode 17 is adopted, the depth of the contact hole 17e is not more than the thickness of the insulating layer 18, and the depth of the contact hole 22e is not more than the thickness of the photosensitive film 21. Bonding to the vapor deposition surface was ensured, and there was no contact failure of the contact holes 17e and 22e in all the display cells 6A of the reflective display device 5A in which an infinite number of display cells 6A were arranged. And in the reflective electrode 22, since it was able to select and vapor-deposit the optimal vapor deposition conditions, without restrict | limiting to a film thickness, the display of the high reflectance in the reflection type display apparatus 5A was realizable.

  Further, since the pixel pitch is set to a high resolution of 40 μm, the arrangement density of the thin film transistors 16 is increased, the drain electrode 15 is also reduced, and the diameter of the contact hole 17e of the insulating layer 18 needs to be Φ4 μm. Design in which the diameter of the contact hole 22e of the photosensitive film 21 is smaller than that of the contact hole 17e of the insulating layer 18, as in the connection form of Patent Document 1 in which the contact hole 22e of 21 is arranged so as to overlap the opening 18h of the insulating layer 18. The contact hole 22e of the photosensitive film 21 was able to be set to φ8 μm.

  From this, it was possible to suppress a decrease in manufacturing yield due to high resolution. Since the contact hole 22e of the photosensitive film 21 is disposed at a position that does not overlap with the contact hole 17e of the insulating layer 18, the recess formed by the contact hole 22e of the photosensitive film 21 is filled with only one flattening layer 23. I was able to. As a result, it was possible to suppress display defects caused by charged particles getting stuck in the recesses at the interface of the migration space.

Second Embodiment
FIG. 2 is a cross-sectional view of a display cell of the reflective display device of the second embodiment. The reflective display device 5B of the second embodiment is the same as the reflective display device 5A of the first embodiment in the configuration below the connection electrode 17 and the configuration above the reflective electrode 22 in the display cell 6B. In other words, only the reflective film support layer (photosensitive film 21) having a fine surface uneven shape is different from the reflective display device 5A of the first embodiment. Therefore, in FIG. 2, members common to those in FIG.

  As shown in FIG. 2, as a method of forming a reflective film support layer for forming a predetermined fine surface irregularity shape on the reflective electrode 22, a convex dot is formed by performing exposure and development using a photoresist. There is a method of forming a pattern. In this case as well, it is desirable to form the connecting electrode 17 to relay the electrical connection between the drain electrode 15 and the reflective electrode 22.

  On the rear substrate 10 made of alkali-free glass, after the manufacturing process similar to that of the reflective display device 5A of the first embodiment is performed up to the connection electrode 17, the entire surface of the insulating layer 18 including the connection electrode 17 is exposed to light. A conductive acrylic resin (for example, optmer PC415 manufactured by JSR Corporation) was applied to form an organic insulating layer 21B having a thickness of about 3 μm. The organic insulating layer 21B is applied in a low-viscosity liquid state, and forms a flat surface by canceling unevenness caused by the lower-layer thin film transistor 16 and its wiring pattern.

  Next, the organic insulating layer 21B is irradiated with ultraviolet rays through a photomask to form a pellet-arranged resist pattern, and then heated to melt the pellet-type resist pattern. On the insulating layer 18 formed with a smooth surface with a diameter of about 5 μm with a uniform height and size, a minute surface irregularity shape in which an infinite number of dome-shaped protrusions are arranged is formed.

  In FIG. 2, it appears that the contact hole 22 f is formed so as to overlap the opening 18 h of the insulating layer 18, but actually, the resist pattern is developed and removed in a planar region partially overlapping the opening 18. Coincidentally, the reflective electrode 22 and the connecting electrode 17 merely achieve electrical contact at a position overlapping the opening 18h. A planar region including the opening 18h is a flat reflecting surface covered with an aluminum material.

  Therefore, by changing the removal position of the resist pattern to a position close to the partition wall 24, the resist pattern is left even in the vicinity of the opening 18h to form a mirror-like surface irregularity shape, whereby the reflective display device of the first embodiment. It is also possible to ensure the reflective performance of the reflective electrode 22 equivalent to 5A.

  An aluminum thin film having a thickness of 1000 mm is formed on the organic insulating layer 21B having the minute surface irregularities by the same process as in the first embodiment, and a photoresist is applied on the entire surface, and a predetermined photomask is used. A resist pattern was formed by irradiating ultraviolet rays, and then the aluminum thin film was wet etched with a phosphoric acid-based etchant, thereby forming the reflective electrode 22. The subsequent manufacturing steps were performed in the same manner as in the first embodiment.

  Since the reflective display device 5B of the second embodiment also employs the connection electrode 17, various improvement effects similar to those of the first embodiment described above can be realized.

<Third Embodiment>
FIG. 3 is a cross-sectional view of a display cell of the reflective display device of the third embodiment. The reflective display device 5C of the third embodiment is the same as the reflective display device 5A of the first embodiment in the configuration below the reflective electrode 22 in the display cell 6C. Accordingly, in FIG. 3 as well, members common to those in FIG.

  As shown in FIG. 3, at the interface of the migration space of the charged particles 31 in the display cell 6C, the adsorptive property of the charged particles 31 at the interface is accurately controlled, or an insulating coating layer formed on the reflective electrode 22 From the standpoint of measures against residual electrification stored in (color resist 26), the entire wall surface of the migration space is covered with a resistance film 27 of a low resistance material. The resistance film 27 and the reflective electrode 22 are electrically connected through a contact hole 27 e provided in the color resist 26 disposed on the reflective electrode 22.

  A color resist 26, which is a color filter of R (red), G (green), and B (blue), is patterned on the reflective electrode 22, and color display of one pixel is performed using three display cells 6C. do. The color resist 26 is an example of an insulating coating layer formed on the reflective electrode 22, but the insulating coating layer may include a transparent insulating film that protects the color resist 26.

  The contact hole 27e provided in the color resist 26 and the contact hole 22e of the photosensitive film 21 are preferably arranged at different coordinate positions in the plane of the display cell 6C. This is because the depth of the depression formed by the contact hole 27e in the wall surface of the migration space of the charged particles 31 is made as small as possible.

  On the back substrate 10 made of alkali-free glass, up to the reflective electrode 22 is formed through the same manufacturing process as the reflective display device 5A of the first embodiment, and then a pigment dispersion type photosensitive color is formed on the reflective electrode 22. A resist material was applied and irradiated with ultraviolet rays using a photomask, thereby sequentially forming red, green, and blue resist patterns in stripes penetrating the display cells 6C in a row.

  The photosensitive color resist material of each color is separately applied to each display cell 6C, and an opening 26h is patterned in the color resist 26 disposed on the display cell 6C. The opening 26h is provided at a position that does not overlap with the contact hole 22e of the photosensitive film 21 provided in the lower layer. Thereafter, barrier ribs 24 and barrier rib electrodes 25 were formed on the color resist 26 in the same manner as in Example 1.

  Further, a resistance film 27 was deposited on the entire surface including the partition wall electrode 25. The resistance film 27 connects the partition wall electrode 25 and the reflective electrode 22 in series. The resistance value of the resistance film 27 was defined as a value that can control the potentials of both electrodes independently when different voltages are applied to the partition wall electrode 25 and the reflective electrode 22. As the resistive film 27, diamond-like carbon (volume resistivity 1 × 10 (−8) Ω · cm) was used.

  After that, using the process described in the first embodiment, the transparent insulating liquid 32 in which the charged particles 31 are dispersed is filled and sealed with the surface substrate 20.

  In the reflective display device 5C of the third embodiment, a resistive film 27 is formed at the interface of the migration space, one end of the resistive film 27 is connected to the partition electrode 25, and the other end is electrically connected to the reflective electrode 22. Therefore, the contact hole 27e is provided in the insulating color resist 26 laminated on the reflective electrode 22.

  The position of the contact hole 27e of the color resist 26 is shifted from the contact hole 22e of the photosensitive film 21, so that the depth of the dent created at the interface of the migration space of the charged particles 31 is reduced. . Substantially, the depth of the dent is the thickness of the color resist 26, and display defects caused by the charged particles 31 getting stuck in the dent formed at the interface of the migration space can be suppressed.

  In addition, by adopting the connection electrode 17, the reflection type display device 5C of the third embodiment can realize various improvement effects similar to those of the reflection type display device 5A of the first embodiment.

<Fourth embodiment>
FIG. 4 is a cross-sectional view of a display cell of the reflective display device of the fourth embodiment. In the reflective display device 5D of the fourth embodiment, the configuration above the interlayer insulating layer 12 in the display cell 6D of the active matrix type electrophoretic display device, in other words, the configuration other than the back substrate 10D is the reflective display of the first embodiment. It is the same as the device 5A. Therefore, in FIG. 4 as well, members common to those in FIG.

  As a back substrate on which the thin film transistor 16 is formed, a resin or metal thin plate material having flexibility can be used in addition to a generally used glass substrate. For example, a thin plate material made of metal materials such as SUS, Ti, duralumin, and other alloys, and plastic materials such as PES, PEN, and PET can be employed.

  As shown in FIG. 4, in the reflective display device 5D of the fourth embodiment, a SUS substrate having a plate thickness of 0.2 mm is used as the back substrate 10D, and an insulating layer 40 formed by laminating an inorganic film and an organic film thereon. Formed. A polyimide resin was applied on the back substrate 10D of the SUS substrate and baked in a high-temperature furnace at 380 ° C. for 10 hours. Then, the surface was polished, and SiO 2 having a film thickness of 300 nm was formed on the polished surface. Thereafter, the thin film transistor 16 was formed in the same manner as in the first embodiment, and the subsequent steps were also performed in the same manner to produce an active matrix driven reflective electrophoretic display device.

  In general, by using a SUS plate having a thermal expansion coefficient larger than that of the glass substrate for the back substrate 10D, it is more difficult to obtain pattern alignment accuracy in the stacking process than for the glass substrate. However, in the display cell 6D in the fourth embodiment, the thin film transistor Since the connecting electrode 17 having a large area is disposed between the 16 drain electrodes 15 and the reflective electrode 22, the tolerance of the pattern alignment accuracy is increased. As a result, the drain electrode 15 and the reflective electrode 22 are increased. There was no occurrence of defects in electrical connection between the two. Thereby, even if it used the SUS board | substrate, the reflection type display apparatus 5D which suppressed the display defect was able to be manufactured.

<Correspondence with Invention>
The reflective image display apparatus 5A of the first embodiment includes a thin film transistor 16 formed as a thin film, an insulating insulating layer 18 formed so as to cover the thin film transistor 16, and an insulating photosensitive film disposed so as to cover the insulating layer 18. In the reflective display device 5 </ b> A provided with the photosensitive film 21, it is formed on the insulating layer 18 by being electrically connected to the drain electrode 15 of the thin film transistor 16 through the opening 18 h formed in the insulating layer 18. The connecting electrode 17 reaching the formed opening 21h is provided. The conductive reflective electrode 22 formed on the photosensitive film 21 is electrically connected to the connection electrode 17 through the opening 21 h formed in the photosensitive film 21. In other words, the electrical connection in the depth direction is relayed by the connecting electrode 17. Therefore, the depth of the contact hole 22e formed in the photosensitive film 21 cannot be more than the thickness of the photosensitive film 21, and is shallower by the thickness of the insulating layer 18 than the contact hole shown in Patent Document 1. Further, the depth of the contact hole 17 e formed in the insulating layer 18 cannot be greater than the thickness of the insulating layer 18, and is shallower by the thickness of the photosensitive film 21 than the contact hole disclosed in Patent Document 1.

  Therefore, as the depth becomes shallower, the aluminum particles wrap around the inner wall and the bottom of the opening 21h formed in the photosensitive film 21, and the contact hole can be obtained even if the film forming conditions that give priority to reflectivity are adopted. The electrical connection from the entrance to the bottom of 22e is ensured. In other words, it becomes easy to find the film forming conditions of the reflective electrode 22 having a high reflectance.

  Further, since the opening 21h of the photosensitive film 21 is formed by positioning the connecting electrode 17 having a larger area than the contact hole 17e of the insulating layer 18, even if the positioning accuracy at the time of forming the opening 21h is low, the photosensitive film 21 A reliable overlay between the contact hole 22e and the connecting electrode 17 and an electrical connection thereby can be ensured. In other words, with respect to the miniaturization of the contact holes 17e and 22e due to high definition and the like, the demand for the pattern resolution of the photosensitive film 21 may be about the same as the conventional one, so that the burden on new material design can be reduced.

  Further, since the position of the contact hole 22e of the photosensitive film 21 can be set without being constrained by the position of the drain electrode 15 of the thin film transistor 16 due to the planar expansion of the connecting electrode 17, the display function of the display cell 6A is affected. By setting the contact hole 22e of the photosensitive film 21 at a position that does not affect the display cell 6A, the display function of the display cell 6A can be enhanced.

  Further, since the thin film transistor 16 is completely covered with the insulating layer 18 and the connecting electrode 17 before the formation of the photosensitive film 21, the drain electrode 15 is oxidized or impurities are formed through the opening 18 h of the insulating layer 18. Does not spread. Therefore, even if the back substrate 10 is transported for a long distance or stored for a long time in a state in which the connection electrode 17 is formed, the thin film transistor 16 is unlikely to be defective, and the manufacturing yield is not adversely affected.

  In addition, since the electrical connection can be reliably performed even with the contact holes 22e and 17e having a small area, the effective reflection area is increased by reducing the area ratio of the contact hole 22e to the area of the reflective electrode 22, and the minute surface unevenness shape is used. The diffuse reflection performance can be sufficiently exhibited.

  In addition, if the contact hole has a small area, it is possible to fill the recess by depositing aluminum on the reflective electrode 22, and even if the recess is left as it is, the display performance of the display cell 6 </ b> A is not adversely affected if it is smaller than the charged particles 31. Therefore, it is not necessary to add a new process only for filling the depression.

  As the modulation layer that changes the property and amount of transmitted light according to the electrical signal output to the drain electrode 15 of the thin film transistor 16, instead of an electrophoretic layer in which charged particles 31 are dispersed in an insulating liquid 32, a patent is provided. You may employ | adopt a liquid crystal layer as shown in the literature 1, and another modulation layer.

  In addition, since the opening 18h formed in the insulating layer 18 and the opening 21h formed in the photosensitive film 21 are arranged at positions where they do not overlap, the opening 18h and the opening 21h accidentally overlap with each other to form a deep contact hole. There is no possibility that 22e and 17e are formed. In other words, since the depression due to the contact hole 17e does not overlap with the depression due to the contact hole 22e, the depth of the depression formed at the interface of the migration space of the charged particles 31 can be reduced as compared with the conventional case. Furthermore, since it is not necessary to overlap the contact holes 17e and 22e, it is possible to design an element with a wider alignment margin than before. As a result, the yield can be improved and the compatibility with a process using a flexible substrate that is greatly deformed due to the expansion and contraction of the substrate due to heating as compared with the glass substrate is also improved.

  In addition, since the photosensitive film 21 is formed on the element protection layer with a minute surface uneven shape, the reflective electrode 22 is formed with a minute surface uneven shape to diffuse reflected light, A reflective display device 5A having excellent whiteness, visibility, and viewing angle can be provided.

  And since the reflective electrode 22 is in direct contact with the connection electrode 17 at the bottom of the opening 21h formed in the photosensitive film 21, it does not require another process for forming the contact hole 22e in the opening 21h. The contact hole 22e can be formed simultaneously by forming the aluminum thin film of the reflective electrode 22. In addition, even in the photosensitive film 21 having a thickness increased by dividing the surface uneven shape, reliable electrical contact between the reflective electrode 22 and the drain electrode 15 is ensured by the contact holes 22e and 17e having a small area, and an infinite number of displays. In spite of the reflective display device 5A in which the cells 6A are arranged, it is possible to prevent pixel omission and luminance gradation variation due to poor electrical contact.

  The reflective display device 5D of the fourth embodiment can provide a reflective display device 5D that is lightweight, thin and excellent in impact resistance because the back substrate 10D is a flexible metal substrate.

  In the reflective display device 5C of the third embodiment, a reflective display device in which an insulating liquid 32 in which charged particles 31 are dispersed is arranged in the interval between the back substrate 10 on which the reflective electrodes 22 are formed and the transparent surface substrate 20. 6C, a resistive film 27 made of a conductive material is formed on the color resist 26 disposed on the reflective electrode 22, and the contact hole 27e that electrically connects the resistive film 27 and the reflective electrode 22 has a planar position. A contact hole 22e for supplying an electrical signal from the lower layer to the reflective electrode 22 is disposed. In other words, the insulating color resist 26 formed on the reflective electrode 22 and the resistance film 27 formed so as to cover the color resist 26 and in direct contact with the reflective electrode 22 through the opening 26h formed in the color resist 26. The opening 26h formed in the color resist 26 is arranged at a position that does not overlap the opening 21h formed in the photosensitive film 21. Accordingly, the depression of the contact hole 22e and the contact hole 27e are overlapped to form a deep depression, and the operation, durability, display quality, etc. of the display cell 6C are not adversely affected.

<Background of each embodiment>
Conventionally, in a reflective display device formed on a TFT backplane, as a method for increasing the reflectivity of a reflective plate, there is known a method in which unevenness is provided on the surface of a reflective electrode to provide a light diffusing function for display. It has been. In order to form irregularities on the surface of the reflective electrode, a method is known in which a group of irregularities is formed of an organic material, and a highly reflective electrode material is provided thereon as a reflective electrode. As the reflective electrode (described as a reflector in the literature), the following configuration is known.

  The reflective electrode is formed of a highly reflective conductive material on the concavo-convex structure, and the reflective electrode itself is electrically connected to the drain electrode of the transistor. The concavo-convex structure at this time can be made of, for example, a photoresist material having a convex or concave dot pattern, or a photosensitive film in which a desired concavo-convex structure is formed in advance. Moreover, Al, Al alloy, Ag, Ag alloy etc. can be used suitably as a highly reflective conductive material.

  By the way, in order to electrically connect the reflective electrode and the drain electrode, it is necessary to go through at least a contact hole provided in the protective film of the transistor. That is, the thin film of the reflective electrode is required to have step coverage with respect to the step formed by the contact hole of the protective film. For this reason, the thin film of the reflective electrode needs to have a high reflectivity and sufficient step coverage, but it is generally difficult to find a film formation condition of the reflective electrode that can satisfy both required characteristics. This is because in order to guarantee the step coverage, it is required to increase the thickness of the reflective electrode. On the other hand, as one of the film forming conditions for the reflective electrode having a high reflectivity, vapor deposition that suppresses impurities as much as possible is used. This is because it is important to form a film in a short time. In a general vapor deposition apparatus, shortening the vapor deposition time and increasing the film thickness are contradictory conditions.

  In addition, the reflective electrode is electrically connected to the drain of the thin film transistor via two types of layers, an insulating layer used as an insulating film for protecting the transistor and the photosensitive film layer having the fine surface irregularities described above. Must be connected to an electrode. Conventionally, the contact hole provided in the photosensitive film is disposed so as to overlap with the contact hole provided in the thin film transistor protective insulating layer.

  In such a structure in which two contact holes are stacked, the thin film transistor is protected in order to prevent the reflection electrode from being disconnected (step coverage defect) at the steep step formed by the contact hole of the inorganic insulating layer protecting the thin film transistor. The step portion formed by the insulating layer is covered with an organic film having a concavo-convex group, and the inclination at the step portion formed by the contact hole is made gentle.

  This makes it easier to form a reflective electrode having a high reflectance. However, the contact hole diameter of the thin film transistor protective insulating layer is designed to be larger than the contact hole diameter of the photosensitive film. When such a configuration is used, when there is a demand to reduce the diameter of the contact hole formed in the display pixel for the purpose of achieving high definition and high visibility, the design of the contact hole In addition, a high pattern resolution is required for a layer having a concavo-convex group.

  This is because the photosensitive film layer needs to be designed with a pattern resolution higher than that of the contact hole of the thin film transistor protective insulating layer. For this purpose, a material having a high pattern resolution is required for the photosensitive film, and a higher specification is required for a manufacturing apparatus for manufacturing the material. In other words, the problem is that the manufacturing cost increases as the resolution is increased.

  Further, in a reflective display device using electrophoresis, the contact hole is a local hole existing at the interface of the charged particle migration space. In the reflection type display device using conventional electrophoresis, the contact hole diameter (Φ5 to 20 μm) of the layer having the concavo-convex group is about 1 to 10 times the particle diameter (Φ1 to 10 μm). When the contact hole depth is sufficiently deeper than the particle diameter, the particles are completely trapped in the hole, which causes a problem of deterioration of display quality due to this. Therefore, in a reflective display device using electrophoresis, a design that can reduce the depth of the contact hole is required.

  In order to solve such conflicting problems, the reflective display devices 5A to 5D of the above-described embodiments are the reflective display devices having at least the thin film transistors 16 arranged in a matrix. The drain electrode 15 is electrically connected by the connecting electrode 17.

  According to this, it becomes easy for the reflective electrode 22 to find film forming conditions with high reflectivity. Moreover, since the demand for the pattern resolution of the layer having the concavo-convex group is about the same as the conventional one for high definition, the load on the new material design can be reduced. Further, since the contact holes 22e and 17e do not overlap with each other in the insulating layer 18 that protects the thin film transistor 16 and the photosensitive film 21, the depth of the depression that the contact hole 22e forms at the interface of the migration space of the charged particles 31 is reduced as compared with the conventional case. it can. Furthermore, since it is not necessary to overlap the contact holes 22e and 17e, it is possible to design an element with a wider alignment margin than before. As a result, the compatibility with a process using a flexible substrate, which is largely deformed by the expansion and contraction of the substrate due to heating as compared with the glass substrate, is improved.

It is sectional drawing of the display cell of the reflection type display apparatus of 1st Embodiment which is one Embodiment of this invention. It is sectional drawing of the display cell of the reflection type display apparatus of 2nd Embodiment. It is sectional drawing of the display cell of the reflection type display apparatus of 3rd Embodiment. It is sectional drawing of the display cell of the reflection type display apparatus of 4th Embodiment.

Explanation of symbols

5A, 5B, 5C, 5D Reflective display devices 6A, 6B, 6C, 6D Display cell 10 Back substrate 15 Predetermined electrode (drain electrode)
16 Switching element (TFT: Thin film transistor)
17 Connection electrode member (connection electrode)
18 Element protective layer (insulating layer)
18h Opening (opening) formed in element protection layer
20 Surface substrate 21 Reflective film support layer (photosensitive film)
21h Openings formed in the reflective film support layer 22 Conductive reflective film (reflective electrode)
23 Flattening layer 24 Partition 25 Partition electrode 26 Insulating color filter layer (color resist)
26h Openings formed in the color filter layer 27 Resistive interface layer (resistance film)
31 Charged particles 32 Insulating liquid

Claims (8)

A switching element formed in a thin film;
An insulating element protective layer formed to cover the switching element;
In a reflective display device comprising an insulating reflective film support layer disposed so as to cover the element protective layer,
A connection electrode member is formed on the element protection layer by being electrically connected to a predetermined electrode of the switching element through an opening formed in the element protection layer and reaches the opening formed in the reflection film support layer. ,
A reflective display device, wherein the conductive reflective film formed on the reflective film support layer is electrically connected to the connection electrode member through an opening formed in the reflective film support layer. .   The reflective display device according to claim 1, wherein the opening formed in the element protective layer and the opening formed in the reflective film support layer are arranged at positions that do not overlap. The reflective film support layer is formed on the element protective layer with a minute surface uneven shape,
3. The reflective display device according to claim 1, wherein the reflective film is in direct contact with the connection electrode member at a bottom of an opening formed in the reflective film support layer. The switching element is a thin film transistor element arranged in a grid pattern on a back substrate,
4. The reflection type display device according to claim 1, wherein the predetermined electrode is a drain electrode of the thin film transistor element.   5. The reflective display device according to claim 4, wherein the back substrate is a flexible metal substrate. An insulating color filter layer formed on the reflective film;
A resistive interface layer formed over the color filter layer and in direct contact with the reflective film through an opening formed in the color filter layer;
6. The reflective display device according to claim 1, wherein the opening formed in the color filter layer is disposed at a position that does not overlap with the opening formed in the reflective film support layer. . In a reflective display device in which an insulating liquid in which charged particles are dispersed is arranged in the interval between the back substrate on which the reflective electrode is formed and the transparent surface substrate,
A resistive film of a conductive material is formed on the insulating layer disposed on the reflective electrode;
A reflective display device, wherein a contact hole for electrically connecting the resistive film and the reflective electrode is shifted in plane and a contact hole for supplying an electrical signal from the lower layer to the reflective electrode is disposed. An insulating element protective layer formed so as to cover the switching element formed on the rear substrate, and an insulating reflective film support layer formed on the element protective layer with a minute surface irregularity shape. In a manufacturing method of a reflective display device, wherein a predetermined electrode of the switching element and a conductive reflective film formed on the reflective film support layer are electrically connected to each other through a contact hole having a small area. ,
After forming an opening in the element protective layer, a conductive thin film that directly contacts the predetermined electrode through the opening is formed on the element protective layer, and the thin film is formed into a connecting electrode member having a predetermined planar shape. Contact hole process;
A reflective film support layer step of forming the reflective film support layer on the element protective layer on which the connection electrode member is formed;
And an upper contact hole step of forming on the upper insulating layer a conductive thin film that directly contacts the connection electrode member through the opening after forming the opening in the reflective film support layer. Manufacturing method of type display device.

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