Method for manufacturing insulating resin layer, substrate for electro-optical devices, method for manufacturing electro-optical device, and electro-optical device

The invention provides a method for manufacturing an insulating layer for electro-optical devices, wherein the insulating layer contains an insulating material used for electro-optical devices and is not deteriorated in display property. The method for manufacturing an insulating layer for electro-optical devices according to the present invention can include an exposure step of performing exposure for a protrusion-forming layer containing a photosensitive resin (insulating material) with an illuminance of 80 mW/cm2 or more. The resin can be decolorized due to the exposure performed with such high illuminance, and therefore an obtained insulating material has a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm.

BACKGROUND OF THE INVENTION

1. Technical Field of Invention

The present invention relates to a method for manufacturing an insulating resin layer, a substrate for electro-optical devices, a method for manufacturing an electro-optical device, and such an electro-optical device. In particular, the present invention relates to a method for manufacturing an insulating layer that is satisfactory in light transmittance.

2. Description of Related Art

The following displays for liquid crystal devices, electroluminescent devices, and the like, can include active matrix displays including thin-film transistors (TFTs) that are thin-film semiconductor elements and are each connected to corresponding pixels such that a plurality of the pixels which are arranged in a matrix are driven for each pixel. In such displays having the above configuration, pixel electrodes are insulated from the TFTs with an interlayer insulating film and driving signals received from the TFTs are transmitted to the pixel electrodes through contact holes. Such an interlayer insulating film principally contain, for example, a photosensitive resin such as an acrylic resin, and liquid crystal panels containing such a photosensitive material are known (see, for example, Japanese Unexamined Patent Application Publication No. 8-211779 and Japanese Unexamined Patent Application Publication No. 9-152625).

SUMMARY OF THE INVENTION

There is a problem in that photosensitive resins are apt to be colored (for example, colored yellow) and particularly deteriorated in transmittance with respect to a colored ray having a low wavelength (for example, a wavelength of about 400 nm) in some cases, whereby display properties are deteriorated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing an insulating resin layer that is an insulating material used for electro-optical devices and is not deteriorated in display property, a substrate, manufactured by the above method, for electro-optical devices, a method for manufacturing an electro-optical device, and an electro-optical device.

In order to achieve the above object, a method for manufacturing an insulating resin layer according to the present invention can include a step of forming a photosensitive resin layer on a substrate, a first exposure step of performing exposure for the obtained photosensitive resin layer, a developing step of developing the photosensitive resin layer subjected to the exposure, and a second exposure step of performing exposure for the developed photosensitive resin layer at a substrate temperature of 100 to 250° C. with an illuminance of 80 mW/cm2or more and an irradiation energy of 5 to 30 J/cm2.

As described above, the insulating resin layer can contain the photosensitive resin and exposure is performed for the photosensitive resin under the above-mentioned conditions, whereby coloration occurring in an obtained insulating layer can be greatly improved. That is, the second exposure is performed with an illuminance of 80 mW/cm2or more, whereby the photosensitive resin is decolorized, and therefore an obtained insulating material has a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm. This is because the application of light having high illuminance promotes the cross-linking reaction of the photosensitive resin and thereby the absorption of visible light is decreased. In the exposure step, when the illuminance is less than 80 mW/cm2, the decolorization is insufficient, and therefore coloration occurs in the obtained insulating material in some cases. In the exposure step of the present invention, when the illuminance is 100 mW/cm2or more, the decolorization can be sufficiently performed.

In the present invention, since the irradiation energy is 5 to 30 J/cm2, heat having reverse effects on the photosensitive resin is hardly generated, and therefore a problem such as the decomposition of the photosensitive resin by heat is hardly caused. When the irradiation energy is less than 5 J/cm2, the decolorization is insufficient in some cases. In contrast, when light having an energy of more than 30 J/cm2is applied, excessive heat is applied to the resin and thereby the decomposition of the resin is caused in some cases. Furthermore, for example, the substrate on which the insulating resin layer is disposed is deformed due to the heat in some cases. In the exposure step of the present invention, the irradiation energy is preferably 10 to 20 J/cm2.

In the present invention, since the exposure is performed at a substrate temperature of 100 to 250° C., the decolorization of the resin is promoted by heating. When the substrate temperature is less than 100° C., the decolorization is not promoted in some cases, and therefore it takes a long time in the exposure step. When the substrate temperature exceeds 250° C., the resin is decomposed in some cases and, for example, the substrate on which the insulating resin layer is disposed is deformed due to the heat. When, for example, the exposure step is performed after the photosensitive resin is formed on the substrate, the substrate temperature is set within the above range. When the temperature is increased by the application of light, the temperature can be controlled within the above range by the use of a predetermined cooling tool, for example, a cooling fan or the like.

The photosensitive resin may contain an acrylic resin as a main component. Since such an acrylic resin has high transmissive properties and insulating properties, this resin is fit for an insulating material for interlayer insulating layers for electro-optical devices.

The second exposure step may be performed using a high-pressure mercury lamp having a luminescence peak at a wavelength of about 365 nm, and the illuminance on the substrate may be 80 mW/cm2or more at a wavelength of 350 to 380 nm. Since such a high-pressure mercury lamp has a luminescence peak in a relatively low wavelength region, the exposure can be performed with high illuminance.

The second exposure step may be performed using a filter for removing rays having a wavelength of less than 300 nm from rays emitted from the high-pressure mercury lamp. When the rays having a wavelength of less than 300 nm are applied, the resin is decomposed in some cases. Therefore, by the use of the filter for removing such rays, the resin can be prevented from being decomposed.

A substrate for electro-optical devices according to the present invention can include an insulating resin layer obtained by the above-mentioned insulating resin layer-manufacturing method. According to this substrate for electro-optical devices, the insulating resin layer has high transmittance with respect to the colored ray as described above and a problem that coloration occurs in a low wavelength region is not caused, and therefore an electro-optical device in which the coloration is hardly caused and the display properties are satisfactory can be provided.

In the substrate for electro-optical devices, the insulating resin layer preferably has a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm. Thereby, an electro-optical device in which the coloration is hardly caused and the display properties are satisfactory can be provided.

In the substrate for electro-optical devices, the insulating resin layer preferably has a thickness of 3 μm or more. According to this configuration, the insulating resin layer has satisfactory insulating properties and functions as a planarizing layer.

A method for manufacturing an electro-optical device according to the present invention includes the steps of manufacturing the insulating resin layer or a step of using the substrate for electro-optical devices. According to this method, the insulating resin layer is transformed into an insulating material that is extremely transparent as described above, and therefore an electro-optical device in which the coloration is hardly caused and the display properties are satisfactory can be provided.

An electro-optical device of the present invention includes an insulating resin layer formed by the manufacturing method or the substrate for electro-optical devices. According to this electro-optical device, a display in which the coloration is hardly caused and the display properties are satisfactory can be obtained.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described with reference to the accompanying drawings. For a liquid crystal display of an electro-optical device according to the present invention, an embodiment is described with reference toFIGS. 1 to 5.

In this embodiment, an example of a liquid crystal transflective display, which is of an active matrix type, is described, wherein the display includes pixel electrodes, disposed on an element substrate, each having a reflective display region and a transmissive display region.

FIG. 1is a plan view showing the liquid crystal display of this embodiment, wherein the display and components thereof are viewed in the direction of a counter substrate.FIG. 2is a sectional view taken along the line H-H′ ofFIG. 1.FIG. 3is a diagram showing an equivalent circuit including various elements and wiring lines of a plurality of pixels, arranged in matrix, placed in an image display region of the electro-optical device (liquid crystal display). In the drawings used in the following description, in order to show layers and members on a recognizable scale, different scales are used depending on the size of the layers and members.

InFIGS. 1 and 2, the liquid crystal display100of this embodiment includes a TFT array substrate10and a counter substrate20joined to each other with a sealing member52disposed therebetween, and also includes liquid crystals50placed in a region, isolated by the sealing member52, in a sealed manner. A periphery-parting portion53including a light-shielding material is disposed in the region surrounded by the sealing member52. In regions outside the sealing member52, a data line-driving circuit201and mount terminals202are arranged along a side of the TFT array substrate10, and scanning line-driving circuits204are each placed along corresponding sides adjacent to this side. A plurality of wiring lines205for connecting the scanning line-driving circuits204each other placed along both sides of an image display region are arranged along the remaining side of the TFT array substrate10. An intersubstrate-conducting member206for electrically connecting the TFT array substrate10to the counter substrate20is placed at least one corner section of the counter substrate20.

However, the data line-driving circuit201and scanning line-driving circuits204are not arranged on the TFT array substrate10. Instead, for example, a TAB (tape automated bonding) substrate on which a driving LSI is mounted may be connected to a group of terminals, arranged on the periphery of the TFT array substrate10, in an electrical, mechanical manner with an isotropic conductive layer disposed therebetween.

In the liquid crystal display100, a retardation film, a polarizing film, or the like is arranged in a predetermined direction depending on the type of the liquid crystals50, that is, an operational mode such as a TN (twisted nematic) mode or an STN (super twisted nematic) mode or a display mode such as a normally white mode or a normally black mode. These components are not shown.

In order to display a color image using the liquid crystal display100, red (R), green (G), and blue (B) color filters and protective layers thereof can each be arranged at corresponding regions of the counter substrate20, wherein the regions each face the corresponding below-mentioned pixel electrodes of the TFT array substrate10.

As shown inFIG. 3, in the image display region of the liquid crystal display100having the above configuration, a plurality of pixels100aare arranged in matrix, TFTs30for switching the pixels are each connected to the corresponding pixels100a, and data lines6afor supplying pixel signals S1, S2, . . . , and Sn are electrically connected to source electrodes of the TFTs30. The pixel signals S1, S2, . . . , and Sn written into the data lines6amay be line-sequentially supplied in this order or may be supplied to each group consisting of a plurality of data lines6aadjacent to each other. Scanning lines3aare each electrically connected to corresponding gate electrodes of the TFTs30such that scanning signals G1, G2, and Gm are line-sequentially applied to the scanning lines3ain this order in a pulse mode with predetermined timing. Reflective electrodes9are each electrically connected to corresponding drain electrodes of the TFTs30such that the TFTs30functioning as switching elements are turned on for a predetermined period, whereby the image signals S1, S2, . . . , and Sn supplied from the data lines6aare written into the pixels with predetermined timing. The image signals S1, S2, . . . , and Sn, transmitted through the reflective electrodes9and then written into the liquid crystals, having a predetermined level are retained between the reflective electrodes9aand a counter electrode21of the counter substrate20, shown inFIG. 2, for a predetermined period.

In order to prevent the retained pixel signals S1, S2, . . . , and Sn from leaking, storage capacitors60are arranged in parallel to liquid crystal capacitors formed between the reflective electrodes9and the counter electrode. For example, voltages applied to the reflective electrodes9are each retained in the corresponding storage capacitors60for a period three orders of magnitude longer than a period for which voltages are applied to the source electrodes. Thereby, the property of retaining charges is enhanced, and thus the liquid crystal display100having high contrast can be achieved. When the storage capacitors60are formed, the storage capacitors60may be each provided between capacitor lines3bfor forming the storage capacitors60, as shown inFIG. 3, or may be each provided between the above-mentioned scanning lines3a.

FIG. 4is a plan view showing one of the pixels on the TFT array substrate of this embodiment.FIG. 5is a sectional view of the pixel taken along the line A-A′ shown inFIG. 4.FIGS. 4 and 5each show a configuration in which a plurality of protrusions containing a photosensitive resin are arranged.

InFIG. 4, the pixel electrodes including the reflective electrodes9and transparent electrodes91are arranged on the TFT array substrate10in matrix. The reflective electrodes9can contain aluminum, silver, or alloy thereof or have a layered structure including a layer containing any one of the above metals and a metal layer containing titanium, titanium nitride, molybdenum, tantalum, or the like. The transparent electrodes91can each include a transparent conductive layer, electrically connected to each reflective electrode9, containing ITO or the like. The reflective electrodes9are each electrically connected to the corresponding TFTs30(seeFIG. 3) for switching the pixels. Each data line6a, scanning line3a, and capacitor line3beach extend along corresponding boundaries, extending lengthwise or widthwise, between regions each having the corresponding pixel electrodes therein. Each TFT30is connected to the data line6aand scanning line3a.

The data line6ais electrically connected to a heavily doped source region1aof the TFT30with each contact hole8, and each reflective electrode9is electrically connected to a heavily doped drain region1dof the TFT30with each contact hole15and drain electrode6b. The scanning line3aextends so as to face a channel-forming region1a′ of the TFT30. Each storage capacitor60(storage capacitor element) has a configuration in which a lower electrode and an upper electrode are stacked. The lower electrode corresponds to an extending portion1fof each semiconductor layer1for forming the TFT30for switching each pixel, the extending portion1fbeing conductive, and the upper electrode corresponds to the capacitor line3bdisposed in the same layer as that in which the scanning line3ais disposed.

In this embodiment, openings9dare each disposed in the corresponding reflective electrodes9and the transparent electrodes91each disposed on the corresponding openings9d. Therefore, in a transmissive display mode, image signals are supplied to the liquid crystals through transparent electrode portions disposed in regions of the openings9d, and light emitted from a backlight (not shown) passes through the openings9dand then liquid crystal layers, thereby displaying an image.

As shown inFIG. 5, which is a sectional view of this reflective region taken along the line A-A′, a base-protecting layer11having a silicon oxide layer (insulating layer) having a thickness of 100 to 500 nm is disposed on a glass substrate10′, functioning as a base of the TFT array substrate10, for transparent TFT array substrates, and the island-shaped semiconductor layers1having a thickness of 30 to 100 nm are disposed on the base-protecting layer11. A gate-insulating layer2that can include a silicon oxide layer having a thickness of about 50 to 150 nm is disposed over the semiconductor layers1, and the scanning lines3ahaving a thickness of 100 to 800 nm are disposed on the gate-insulating layer2and function as gate electrodes. A region of each semiconductor layer1that faces each scanning line3awith the gate-insulating layer2disposed therebetween corresponds to the channel-forming region1a′. Each source region including a lightly doped region1band the heavily doped source region1ais placed on one side of the channel-forming region1a′, and each drain region including another lightly doped region1band the heavily doped drain region1dis placed on the other side. Each heavily doped region1cthat belongs to neither the source region nor the drain region is placed therebetween.

A first interlayer insulating layer4having a silicon oxide layer having a thickness of 300 to 800 nm and a second interlayer insulating layer5(surface-protecting layer) having a silicon nitride layer having a thickness of 100 to 800 nm are disposed over the TFTs30for switching the pixels (the second interlayer insulating layer5(surface-protecting layer) need not be disposed there). The data lines6ahaving a thickness of 100 to 800 nm are disposed on the first interlayer insulating layer4and each electrically connected to the corresponding heavily doped source regions1awith the corresponding contact holes8extending through the first interlayer insulating layer4.

A protrusion-forming layer (interlayer insulating layer)7containing a photosensitive resin (curable resin) of which a main component is an acrylic resin can be disposed on the second interlayer insulating layer5and has a slightly curved surface, which forms a protrusive pattern. The protrusion-forming layer7contains a highly transparent resin and particularly contains a resin having a transmittance of 95% or more with respect to a light ray having a wavelength of 400 nm. That is, the protrusion-forming layer7has a configuration in which coloration that such an acrylic resin is colored yellow is prevented by a predetermined method.

Each reflective electrode9is disposed on the protrusion-forming layer7, wherein the reflective electrode9contains aluminum, silver, or alloy thereof or has a layered structure including a layer containing any one of the above metals and a metal layer containing titanium, titanium nitride, molybdenum, tantalum, or the like. The reflective electrode9has each opening9dpresent in each pixel, and each transparent electrode having a transparent conductive layer containing ITO or the like is disposed on the reflective electrode9and opening9d. Light emitted from the backlight, which is not shown, is allowed to pass through the opening9d, whereby an image can be displayed in a transmissive mode. An alignment layer12comprising a polyimide layer is disposed on the transparent electrode91, and the surface of the alignment layer12is treated by a rubbing process.

The TFTs30preferably have an LDD structure (lightly doped drain structure), as described above, however, the TFTs30may have an offset structure in which impurity ions are not implanted into regions corresponding to the lightly doped regions1b. The TFTs30include self-aligned TFTs having heavily doped source and drain regions formed in a self-aligned manner by implanting such impurity ions in a large amount using the gate electrodes (portions of the scanning lines3a) as masks.

In this embodiment, the TFTs30have a dual gate (double gate) structure having two gate electrodes (the scanning lines3a) placed between each source region and drain region, however, the TFTs30may have a single gate structure having a single gate electrode placed therebetween or a triple or more gate structure having three or more gate electrodes placed therebetween. When a plurality of the gate electrodes are arranged, the same signals are supplied to the gate electrodes. When the TFTs30have the above-mentioned dual gate (double gate) structure or triple or more gate structure, currents can be prevented from leaking at junctions of channels and source or drain regions, whereby the current consumed during downtime can be reduced. Furthermore, when at least one of the gate electrodes has the LDD structure or the offset structure, the current consumed during downtime can be further reduced, thereby obtaining stable switching elements.

On the other hand, in the counter substrate20, light-shielding layers23, called black matrices or black stripes, are placed on regions that are located on the glass substrate20′ of the counter substrate and are located above boundary regions between the reflective electrodes9disposed on the TFT array substrate10, the boundary regions extending lengthwise or widthwise. The counter electrode21having an ITO layer is disposed on the light-shielding layers23. An alignment layer22including a polyimide layer is disposed on the counter electrode21. The liquid crystals50are placed between the TFT array substrate10and counter substrate20in a sealed manner.

A method for manufacturing the liquid crystal display100having the above configuration will now be described in detail with reference toFIGS. 6 to 10.FIGS. 6 to 10are sectional views showing steps of manufacturing the TFT array substrate10of this embodiment.

As shown inFIG. 6(A), after the glass substrate10′ for TFT array substrates cleaned by supersonic washing or the like is prepared, the base-protecting layer11comprising a silicon oxide layer is formed over the glass substrate10′ for TFT array substrates at a substrate temperature of 150 to 450° C. by a plasma CVD process such that the base-protecting layer11has a thickness of 100 to 500 nm. A raw material gas used in this procedure includes a mixed gas containing monosilane and a laughing gas (nitrous oxide), a mixed gas containing TEOS (tetraethoxysilane Si(OC2H5)4) and oxygen, and a mixed gas containing disilane and ammonia.

A semiconductor layer1having an amorphous silicon layer is formed over the resulting glass substrate10′ for TFT array substrates at a substrate temperature of 150 to 450° C. by a plasma CVD process such that the semiconductor layers1has a thickness of 30 to 100 nm. A raw material gas used in this procedure includes, for example, disilane and monosilane. The semiconductor layer1is irradiated with a laser beam, thereby performing laser annealing. As a result, the amorphous semiconductor layer1is once melted, cooled, solidified, and then crystallized.

The semiconductor layer1is etched by a photolithographic process using a resist mask551such that semiconductive layers for forming island-shaped semiconductor layers1(functioning layers) are isolated, as shown inFIG. 6(B).

The gate-insulating layer2having a silicon oxide layer or the like is formed over the resulting glass substrate10′ for TFT array substrates including the semiconductor layers1at a substrate temperature of 350° C. or less by a CVD process such that the gate-insulating layer2has a thickness of 50 to 150 nm. A raw material gas used in this procedure includes, for example, a mixed gas containing TEOS and oxygen. The gate-insulating layer2may comprise a silicon nitride layer instead of the silicon oxide layer.

Impurity ions are implanted into the extending portion1fof each semiconductor layer1using a predetermined resist mask, which is not shown, whereby each lower electrode for forming each storage capacitor60is formed between the capacitor lines3b(seeFIGS. 4 and 5).

As shown inFIG. 6(C), a conductive layer3, having a thickness of 100 to 800 nm, for forming the scanning lines3aand the like is formed over the glass substrate10′ for TFT array substrates by a sputtering process or the like, wherein the conductive layer3comprises a metal layer containing aluminum, tantalum, or molybdenum or an alloy layer containing one of these metals as a main component. A resist mask552is then formed by a photolithographic process.

The conductive layer3is dry-etched using the resist mask, whereby the scanning lines3a(gate electrodes), the capacitor lines3b, and the like are formed, as shown inFIG. 6(D).

Impurity ions (phosphorus ions) are implanted into regions around pixel TFT sections and n-channel TFT sections (not shown) of the driving circuits at a small dose of about 0.1×1013/cm2to 10×1013/cm2using the scanning lines3aand/or the gate electrodes as masks, whereby the lightly doped regions1bare formed such that the lightly doped regions1bare self-aligned with respect to the scanning lines3a. In this configuration, sections which are each located directly below the corresponding scanning lines3aand into which the impurity ions have not been implanted remain as the semiconductor layers1and function as channel-forming regions1a′.

As shown inFIG. 7(A), impurity ions (phosphorus ions) are implanted into the pixel TFT sections at a large dose of about 0.1×1015/cm2to 10×1015/cm2using masks553having a width larger than that of the scanning lines3a(gate electrodes), whereby the heavily doped source regions1a, heavily doped regions1c, and heavily doped drain regions1dare formed.

The impurities are not implanted at a small dose but the impurities (phosphorus ions) may be implanted at a large dose using a resist mask having a line width larger than the width of the gate electrodes instead of the above steps of implanting impurities, whereby source regions and drain regions having an offset structure are formed. The impurities may be implanted at a large dose using the scanning lines3aas masks, whereby source regions and drain regions having a self-aligned structure are formed.

As shown inFIG. 7(B), the first interlayer insulating layer4can include a silicon oxide layer or the like is formed over the scanning lines3aby a CVD process or the like such that the first interlayer insulating layer4has a thickness of 300 to 800 nm. A raw material gas used in this procedure includes, for example, a mixed gas containing TEOS and oxygen. A resist mask554is then formed by a photolithographic process.

As shown inFIG. 7(C), the first interlayer insulating layer4is dry-etched using a resist mask554, whereby contact holes are formed at portions of the first interlayer insulating layer4, the portions corresponding to the source regions and drain regions.

As shown inFIG. 7(D), a metal layer6, having a thickness of 100 to 800 nm, for forming the data lines6a(source electrodes) and the like is formed over the first interlayer insulating layer4by a sputtering process or the like, wherein the metal layer6comprises an aluminum layer, a titanium layer, a titanium nitride layer, a tantalum layer, a molybdenum layer, an alloy layer containing one of these metals as a main component, or a multi-layer film. A resist mask555is then formed by a photolithographic process.

As shown inFIG. 8(A), the metal layer6is dry-etched using the resist mask555, whereby the data lines6aand drain electrodes6bare formed. The metal layer6may be processed by a wet etching method.

As shown inFIG. 8(B), the second interlayer insulating layer5can include a silicon nitride layer or the like is formed over the data lines6aand drain electrodes6bby a CVD process such that the second interlayer insulating layer5has a thickness of 100 to 800 nm. Contact holes15′ to be each electrically connected to the corresponding pixel electrodes are then formed.

As shown inFIG. 8(c), a photosensitive resin7a, such as an acrylic resin, having a thickness of 3.0 μm or more is formed by a spin coating process, the photosensitive resin7abeing of an organic type and transparent. The photosensitive resin7ais then patterned by a photolithographic process, thereby forming the protrusion-forming layer7having a plurality of protrusion patterns7gthereon, as shown inFIG. 9(A).

In this procedure, a photomask having a pattern corresponding to the protrusion patterns7gto be formed is used. When a positive photosensitive resin is used, the photomask has a pattern in which sections corresponding to the protrusion patterns7gare light-proof. When a negative photosensitive resin is used, the photomask has a pattern in which sections corresponding to the protrusion patterns7gare transparent.

As shown inFIG. 9(B), the contact holes15are bored in the protrusion-forming layer7on the contact holes15′ extending through the second interlayer insulating layer5by a photolithographic process such that the contact holes15each extend to the corresponding drain electrodes6b.

Bleach exposure is performed for the protrusion-forming layer7having the contact holes15using a high-pressure mercury lamp. This high-pressure mercury lamp has a luminescence peak at a wavelength of about 365 nm. The exposure is performed with an illuminance of 80 mW/cm2or more at a wavelength of 365 nm. In the exposure, a filter for removing rays having a wavelength of less than 300 nm from emitted rays is used.

Since the exposure is performed using light having such high illuminance, the problem of coloration that is apt to occur in cured resins can be prevented and the transmittance of light having a wavelength of about 400 nm can be enhanced. In the above exposure step, the resin can be effectively decolorized when the irradiation energy is 5 to 30 J. The decolorization can be promoted by performing the exposure at 100 to 250° C.

As shown inFIG. 10(A), after the bleach exposure is performed, a metal layer9ais formed over the protrusion-forming layer7and the contact holes15by a sputtering process or the like, wherein the metal layer9ais reflective and includes a multi-layer film containing aluminum, silver, or alloy thereof and titanium, titanium nitride, molybdenum, tantalum, or the like.

As shown inFIG. 10(B), the metal layer9ais patterned by a photolithographic process and an etching process, whereby the reflective electrodes9each having the corresponding openings9dare formed. The reflective electrodes9formed according to this procedure are each electrically connected to the corresponding drain electrodes6b. Protrusion patterns9ghaving no flat part but a gentle shape are each formed above the corresponding reflective electrodes9using the protrusion patterns7gon the protrusion-forming layer7.

The transparent electrodes91each having a transparent conductive layer containing ITO or the like are formed over the reflective electrodes9and the openings9d. The alignment layer12containing polyimide is formed over the transparent electrodes91. In order to obtain such a layer, a polyimide layer is formed and then treated by a rubbing process. According to the above procedure, the TFT array substrate10is completed.

On the other hand, for the counter substrate20, a substrate body20′ containing glass or the like is prepared. After the light-shielding layers23are formed on regions of the substrate body20′ corresponding to boundaries between the pixels, a transparent conductive material containing ITO or the like is deposited thereon by a sputtering process and then patterned by a photolithographic process, whereby the common electrode21is formed on almost the whole substrate body20′. An application solution for forming alignment layers is applied over the counter electrode21and an obtained layer is treated by a rubbing process, whereby the alignment layer22is obtained. Thereby, the counter substrate20is obtained.

The TFT array substrate10and counter substrate20manufactured according to the above procedures are joined to each other with the sealing member disposed therebetween such that the alignment layer12faces the alignment layer22. The liquid crystals are injected into a space between the substrates by a vacuum injection method or the like, thereby forming the liquid crystal layer50. Finally, a retardation film, a polarizing film, or the like is joined to the outside of a liquid crystal cell obtained according to the above procedure depending on needs, whereby the liquid crystal display100of this embodiment is completed.

In the method for manufacturing the liquid crystal display100of this embodiment, the protrusion-forming layer7, which is an insulating material, is decolorized by the bleach exposure, thereby enhancing the transmittance of light having low wavelength (near a wavelength of 400 nm). Thus, problems such as coloration hardly occur in the liquid crystal display100having the insulating material, that is, the protrusion-forming layer7, formed by this method.

Examples of electronic devices each including the liquid crystal display of the above embodiment will now be described.

FIG. 11is a perspective view showing an example of a mobile phone. InFIG. 11, reference numeral1000represents a mobile phone body and reference numeral1001represents a liquid crystal display section including the above-mentioned liquid crystal display.

FIG. 12is a perspective view showing an example of an electronic device, which is of a wrist watch type. InFIG. 12, reference numeral1100represents a watch body and reference numeral1101represents a liquid crystal display section including the above-mentioned liquid crystal display.

FIG. 13is a perspective view showing an example of a mobile information processor such as a word processor or a personal computer. InFIG. 13, reference numeral1200represents the information processor, reference numeral1202represents an input section such as a keyboard, reference numeral1204represents an information processor body, and reference numeral1206represents a liquid crystal display section including the above-mentioned liquid crystal display.

The electronic devices shown inFIGS. 11 to 13include the liquid crystal display sections each including the liquid crystal display of the embodiment, and therefore bright images can be displayed in a reflective display mode with a wide view angle using the electronic devices including the liquid crystal display sections.

It should be understood that present invention is not limited to the above embodiments and various modifications may be performed within the scope of the present invention. For example, in the above embodiment, an example in which the present invention is used for the active matrix liquid crystal display including TFTs functioning as switching elements is described, however, the present invention can be used for another active matrix liquid crystal display including TFDs functioning as switching elements and a passive matrix liquid crystal display including a pair of substrates each including scanning electrodes and data electrodes. Furthermore, the pixel electrodes of the embodiment have a configuration in which each transparent electrode is disposed on each reflective electrode, however the present invention can be used for a configuration in which the reflective electrode is disposed on the transparent electrode in contrast. Furthermore, in the above embodiment, the transflective liquid crystal display includes the reflective film of the present invention, however, a transmissive liquid crystal display having no reflective film may include the insulating layer for electro-optical devices according to the present invention. In this case, such an insulating material can be used for a planarizing layer disposed on an element substrate.

Particular examples of the present invention will now be described. In the examples below, bleach exposure was performed under different conditions using the high-pressure mercury lamp described in the above-mentioned embodiment.

As shown inFIG. 9(c), the bleach exposure was performed for 60 seconds with an illuminance of 80 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, the substrate temperature was about 100° C. and the irradiation energy was 4.8 J. As a result of the bleach exposure performed under these conditions, an obtained protrusion-forming layer (insulating layer) had a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm.

As shown inFIG. 9(c), the bleach exposure was performed for 300 seconds with an illuminance of 100 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, the substrate temperature was about 120° C. and the irradiation energy was 30 J. As a result of the bleach exposure performed under these conditions, an obtained protrusion-forming layer (insulating layer) had a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm.

As shown inFIG. 9(c), the bleach exposure was performed for 90 seconds with an illuminance of 200 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, the substrate temperature was about 250° C. and the irradiation energy was 18 J. As a result of the bleach exposure performed under these conditions, an obtained protrusion-forming layer (insulating layer) had a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm.

A protrusion-forming layer (insulating layer) having a thickness of 3.0 μm was formed. The bleach exposure was performed for the protrusion-forming layer (insulating layer) under the same conditions as those of Example 3. As a result, the resulting protrusion-forming layer (insulating layer) had a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm. It became clear that the protrusion-forming layer (insulating layer) has satisfactory insulating properties and efficiently functions as a planarizing layer because the thickness is 3.0 Mm, which is relatively large.

As shown inFIG. 9(c), the bleach exposure was performed for 300 seconds with an illuminance of 50 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, the substrate temperature was about 100° C. and the irradiation energy was 15 J. As a result of the bleach exposure performed under these conditions, an obtained protrusion-forming layer (insulating layer) had a transmittance of less than 90% with respect to a colored ray having a wavelength of 400 nm.

As shown inFIG. 9(c), the bleach exposure was performed for 30 seconds with an illuminance of 300 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, the substrate temperature was about 300° C. and the irradiation energy was 9 J. As a result of the bleach exposure performed under these conditions, the decolorization occurred, however, the resin was decomposed in some cases. As a result of the bleach exposure performed under the same conditions as the above except that the substrate was cooled with a cooling fan, the resin was not decomposed in contrast to the above exposure and an obtained protrusion-forming layer (insulating layer) had a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm.

As shown inFIG. 9(c), the bleach exposure was performed for 30 seconds with an illuminance of 80 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, irradiation was performed in such a manner that the substrate temperature was maintained at about 50° C. with a cooling fan and the irradiation energy was 2.4 J. As a result of the bleach exposure performed under these conditions, the decolorization was slightly insufficient due to low temperature. However, when the irradiation time was 300 seconds (in this case, the irradiation energy was 24 J), an obtained protrusion-forming layer (insulating layer) had a transmittance of 95% or more with respect to a colored ray having a wavelength of 400 nm.

As shown inFIG. 9(c), the bleach exposure was performed for 300 seconds with an illuminance of 300 mW/cm2(a wavelength of 365 nm) using the high-pressure mercury lamp. In this exposure, the irradiation energy was 90 J and the substrate temperature was set to about 200° C. As a result of the bleach exposure performed under these conditions, the resin was decolorized, however, the resin was decomposed in some cases because excessive heat was applied to the resin. Furthermore, the substrate was deformed due to such heat in some cases.

From the results of Examples and Comparative Examples described above, it can be seen that the decolorization can be achieved by performing the exposure with an illuminance of 80 mW/cm2or more. Furthermore, the efficiency of the decolorization is improved when the irradiation energy is 5 to 30 J and the substrate temperature is 100 to 250° C.

As described above in detail, according to the present invention, exposure is performed for a photosensitive resin with an illuminance of 80 mW/cm2or more, the resin being used for insulating layers for electro-optical devices, the insulating layers functioning as interlayer insulating layers of such electro-optical devices. Thereby, an obtained protrusion-forming layer is decolorized and has a transmittance of, for example, 95% or more with respect to a colored ray having a wavelength of 400 nm. An electro-optical device including the resulting resin is hardly colored and has satisfactory display properties.