Liquid crystal display apparatus and electronic apparatus

Disclosed herein is a liquid crystal display apparatus in which a transmission region and a reflection region disposed in parallel. The apparatus includes first and second substrates and a liquid crystal layer disposed between the first and second substrates. The second substrate has at least a counter electrode, an interlayer insulating film and a pixel electrode for forming a fringe field for driving molecules of the liquid crystal. At least one parameter relating to the interlayer insulating film formed on the second substrate is set different between the transmission region side interlayer insulating film and the reflection region side interlayer insulating film so that driving voltages for the transmission and reflection regions are substantially equal to each other.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2006-241355, filed in the Japan Patent Office on Sep. 6, 2006, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a liquid crystal display apparatus and an electronic apparatus wherein, for example, both of reflective type display and transmissive type display are used.

2. Description of the Related Art

A liquid crystal display apparatus is used as a display apparatus for various electronic apparatus making the most of the characteristics of a small thickness and lower power consumption. In particular, a liquid crystal display apparatus is used, for example, as a display apparatus of a notebook type personal computer or a car navigation system or employed in various other electronic apparatus such as a portable digital assistant (PDA), a portable telephone set, a digital camera or a video camera.

Liquid crystal apparatus are roughly divided into two types including a transmissive type and a reflective type. In a liquid crystal display apparatus of the transmissive type, light from an internal light source called backlight is controlled between transmission and interception by a liquid crystal panel to display an image. On the other hand, in a liquid crystal display apparatus of the reflective type, external light such as sunlight is reflected by a reflecting plate or the like and the reflected light is controlled between transmission and interception by a liquid crystal panel to display an image.

In a transmissive type liquid crystal display apparatus, the backlight consumes power by more than 50% the total power consumption of the apparatus, and it is difficult to reduce the power consumption. The transmissive type liquid crystal display apparatus has a problem also in that, where the surroundings are light, the display looks dark and therefore the visibility is low.

On the other hand, in a reflective type liquid crystal display apparatus, since it does not include a backlight, it does not have the problem of high power consumption. However, it has another problem in that, where the surroundings are dark, the visibility is very low.

In order to eliminate the problems of both of transmissive and reflective type display apparatus, a liquid crystal display apparatus of the reflective and transmissive type which implements both of transmissive type display and reflective type display using a single liquid crystal panel has been proposed. The reflective and transmissive type liquid crystal display apparatus makes use of reflection of ambient light for display when the surroundings are light, but makes use of light of a backlight for display when the surroundings are dark.

Incidentally, various liquid crystal display apparatus which make use of IPS (In Plain Switching) or FFS (Fringe Field Switching) have been proposed in order to assure a wide angular field of view. Such liquid crystal display apparatus are disclosed, for example, in Japanese Patent Laid-open Nos. 2002-229032 (hereinafter referred to as Patent Document 1), 2001-42366 (hereinafter referred to as Patent Document 2), 2005-338256 (hereinafter referred to as Patent Document 3), 2005-338264 (hereinafter referred to as Patent Document 4), 2006-71977 (hereinafter referred to as Patent Document 5) and 2005-524115 (hereinafter referred to as Patent Document 6).

SUMMARY OF THE INVENTION

Incidentally, a liquid crystal display apparatus of a transreflective type which can act as an apparatus of both of the transmissive type and the reflective type has many subjects

A representative one of the subjects is to make the driving voltages for liquid crystal in a transmission region and a reflection region equal to each other.

Usually, in ECB liquid crystal or VA liquid crystal which is driven by a voltage generated between an upper electrode and a lower electrode, since the liquid crystal is varied by a vertical voltage, no difference appears in driving voltages for the transmission region and the reflection region.

However, in a reflective type liquid crystal structure of the FFS type or the IPS type, it is known that the following relationship is satisfied:
Vlcd=π·L/D√{square root over ( )}(K/∈lcd)  (1)
where Vlcd is the driving voltage for the liquid crystal, L the interlayer insulating film thickness or line distance, D the liquid crystal thickness (gap), K the viscosity constant of the liquid crystal, and ∈lcd the relative dielectric constant of the liquid crystal.

For example, in the reflective and transmissive type liquid crystal display apparatus disclosed in Patent Document 3 or 4, a multi-gap structure is adopted wherein the gap in the reflection region by a circular polarization method is one half the gap in the transmission region.

Therefore, from the liquid crystal gap D of the expression (1) above, a doubled driving voltage is required. In other words, different driving voltages are required for the transmission region and the reflection region. Therefore, a complicated driving method and complicated circuit design are required.

Further, the liquid crystal display apparatus disclosed in Patent Documents 1 to 6 have the following disadvantages.

The liquid crystal display apparatus disclosed in Patent Documents 1 and 2 adopt a structure that a reflector is provided below a substrate for pixel electrodes and counter electrodes of the FFS structure. Thus, since the liquid crystal display apparatus are not designed for use as a display apparatus of the transmissive type, they cannot be structured for use as a display apparatus of both of the transmissive type and the reflective type.

The liquid crystal display apparatus disclosed in Patent Document 3 is of the transmissive and reflective type which utilizes both of transmission and reflection and uses a built-in phase plate. However, the liquid crystal display apparatus does not include measures for adjusting the driving voltage for the transmissive type and the driving voltage for the reflective type. Therefore, the driving voltage cannot be optimized between transmission and reflection.

The liquid crystal display apparatus disclosed in Patent Document 4 makes the electrode pattern different between the reflection region and the transmission region to generate a phase difference direction of λ/4 to carry out display in the transmission mode and the reflection mode.

However, similarly to the liquid crystal display apparatus described above, the liquid crystal display apparatus of Patent Document 4 does not include measures for adjusting the driving voltages for the reflection and the transmission. Therefore, the driving voltage cannot be optimized for both of transmission and reflection.

The liquid crystal display apparatus disclosed in Patent Documents 5 and 6 are of the transmissive and reflective type which utilizes both of transmission and reflection. However, the liquid crystal display apparatus do not include measures for adjusting the driving voltage between transmission and reflection.

Therefore, it is demanded to provide a liquid crystal display apparatus and an electronic apparatus wherein liquid crystal is driven by a single driving voltage without requiring a complicated driving method or driving circuit.

According to an embodiment of the present invention, there is provided a liquid crystal display apparatus wherein a transmission region and a reflection region are disposed in parallel. The apparatus includes a first substrate, a second substrate, and a liquid crystal layer disposed between the first and second substrates. The second substrate has at least a counter electrode, an interlayer insulating film and a pixel electrode configured to form a fringe field for driving molecules of the liquid crystal. At least one parameter relating to the interlayer insulating film formed on the second substrate is different between the transmission region side interlayer insulating film and the reflection region side interlayer insulating film so that driving voltages for the transmission region and the reflection region are substantially equal to each other.

According to another embodiment of the present invention, there is provided an electronic apparatus includes a liquid crystal display apparatus wherein a transmission region and a reflection region are disposed in parallel. The liquid crystal display apparatus includes a first substrate, a second substrate, and a liquid crystal layer disposed between the first and second substrates. The second substrate has at least a counter electrode, an interlayer insulating film and a pixel electrode configured to form a fringe field for driving molecules of the liquid crystal. At least one parameter relating to the interlayer insulating film formed on the second substrate is different between the transmission region side interlayer insulating film and the reflection region side interlayer insulating film so that driving voltages for the transmission region and the reflection region are substantially equal to each other.

In the liquid crystal display apparatus and the electronic apparatus, the parameter of the interlayer insulating film on the second substrate side such as the film thickness or the relative dielectric constant with which the driving voltages for the transmission region and the reflection region become substantially equal to each other is set so as to be different between the transmission region and the reflection region.

With the liquid crystal display apparatus and the electronic apparatus, a single driving voltage for liquid crystal can be used for the transmission region and the reflection region without using a complicated driving method or driving circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before liquid crystal display apparatus according to preferred embodiments of the present invention are described, a basic configuration and functions of a liquid crystal display apparatus to which the present invention is applied are described in order to facilitate understanding of the present invention.

FIG. 1shows an example of a configuration of a liquid crystal display apparatus to which the present invention is applied.

Referring toFIG. 1, the liquid crystal display apparatus1shown includes an effective pixel region section2, a vertical driving circuit (VDRV)3and a horizontal driving circuit (HDRV)4.

The effective pixel region section2includes a plurality of pixel sections2PXL disposed in a matrix.

Each pixel section2PXL includes a thin film transistor (TFT)21serving as a switching element, a liquid crystal cell LC21having a pixel electrode connected to the drain electrode or the source electrode of the TFT21, and a holding capacitor Cs21having an electrode connected to the drain electrode of the TFT21.

Scanning lines5-1to5-mextend in a pixel array direction along different rows while signal lines6-1to6-nextend in another pixel array direction along different columns of the pixel sections2PXL.

The gate electrodes of the TFTs21of the pixel sections2PXL are connected to the same one of the scanning lines (gate lines)5-1to5-min a unit of a row. Meanwhile, the source electrodes or the drain electrodes of the pixel sections2PXL are connected to the same one of the signal lines6-1to6-nin a unit of a column.

Further, in a general liquid crystal display apparatus, a holding capacitor wiring line Cs is wired independently, and a holding capacitor Cs21is connected between the holding capacitor wiring line Cs and a connection electrode.

For example, a predetermined dc voltage is applied as a common voltage VCOM to the counter electrode of the liquid crystal cell LC21and the other electrode of the holding capacitor Cs21of the pixel section2PXL through a common wiring line7.

Or, a common voltage VCOM whose polarity reverses, for example, after each one horizontal scanning period (1H) is applied to the counter electrode of the liquid crystal cell LC21and the other electrode of the holding capacitor Cs21of each pixel section2PXL.

The scanning lines5-1to5-mare driven by the vertical driving circuit3, and the signal lines6-1to6-nare driven by the horizontal driving circuit4.

The TFT21is a switching element for selecting a pixel to be used for display and supplying a display signal to a display region of the pixel.

The TFT21has, for example, such a bottom gate structure as shown inFIG. 2or such a top gate structure as shown inFIG. 3.

Referring first toFIG. 2, the TFT21A of the bottom gate structure shown includes a gate electrode203formed on a transparent insulating substrate201, which may be a glass substrate, and covered with a gate insulating film202. The gate electrode203is connected to a scanning line (gate line)5such that a scanning signal is inputted from the scanning line5to the gate electrode203so that the TFT21A is turned on or off in response to the scanning signal. The gate electrode is formed by such a method as, for example, sputtering or the like of a metal or an alloy of molybdenum (Mo) or tantalum (Ta).

The TFT21A includes a semiconductor film (channel formation region)204formed on the gate insulating film202and further includes a pair of n+diffused layers205and206formed across the semiconductor film204. An interlayer insulating film207is formed on the semiconductor film204, and another interlayer insulating film208is formed in such a manner as to cover the transparent insulating substrate201, gate insulating film202, n+diffused layers205and206and interlayer insulating film207.

A source electrode210is connected to the n+diffused layer205through a contact hole209aformed in the interlayer insulating film208, and a drain electrode211is connected to the n+diffused layer206through another contact hole209bformed in the interlayer insulating film208.

The source electrode210and the drain electrode211are formed, for example, by patterning aluminum (Al). A signal line6is connected to the source electrode210, and the drain electrode211is connected to the pixel region (pixel electrode) through a connection electrode not shown.

Referring now toFIG. 3, the TFT21B of the top gate structure includes a semiconductor film (channel formation region)222formed on a transparent insulating substrate221which may be a glass substrate. The TFT21B further includes a pair of n+diffused layers223and224formed on the transparent insulating substrate221across the semiconductor film222. Further, a gate insulating film225is formed in such a manner as to cover the semiconductor film222and the n+diffused layers223and224, and a gate electrode226is formed on the gate insulating film225in an opposing relationship to the semiconductor film222. Further, another interlayer insulating film227is formed so as to cover the transparent insulating substrate221, gate insulating film225and gate electrode226.

A source electrode229is connected to the n+diffused layer223through a contact hole228aformed in the interlayer insulating film227and the gate insulating film225. A drain electrode230is connected to the n+diffused layer224through another contact hole228bformed in the interlayer insulating film227and the gate insulating film225.

Referring back toFIG. 1, the vertical driving circuit3receives a vertical start signal VST, a vertical clock VCK and an enable signal ENB and performs processing of scanning in a vertical direction (column direction) for each one-field period to successively select the pixel sections2PXL connected to the scanning lines5-1to5-min a unit of a row.

In particular, when a scanning pulse SP1is applied from the vertical driving circuit3to the scanning line5-1, then the pixels in the columns in the first row are selected, but when another scanning pulse SP2is applied to the scanning line5-2, the pixels in the columns in the second row are selected. Thereafter, scanning pulses SP3, . . . , SPm are successively applied to the scanning lines5-3, . . . ,5-min a similar manner, respectively.

The horizontal driving circuit4receives a horizontal start pulse HST produced by a clock generator not shown for triggering horizontal scanning and horizontal clocks HCK and HCKX of the opposite phases to each other for serving as a reference to horizontal scanning to produce a sampling pulse. Further, the horizontal driving circuit4successively samples image data R (red), G (green) and B (blue) inputted thereto in response to the sampling pulse produced thereby and supplies the sampled data as data signals to be written into the pixel sections2PXL to the signal lines6-1to6-n.

In the liquid crystal display apparatus1described above, the TFT21of the pixel sections2PXL is formed from a transistor of a semiconductor thin film of amorphous silicon (a-Si) or polycrystalline silicon.

In the present embodiment, the liquid crystal display apparatus1having such a configuration as described above is formed as a liquid crystal display apparatus which is configured as an apparatus of the reflective and transmissive type and has a FFS (Fringe Field Switching) structure in order to assure a wide angular field of view.

Further, in the liquid crystal display apparatus1of the present embodiment, the effective pixel region section2has a particular structure described below in order that it can be driven by a single driving voltage for liquid crystal without employing a complicated driving method or driving circuit.

In the following, a particular structure of the liquid crystal display apparatus1is described.

FIG. 4shows a layout of a liquid crystal display apparatus of the reflective and transmissive type according to a first embodiment of the present invention, andFIG. 5shows a cross section of the liquid crystal display apparatus of the reflective and transmissive type.

The liquid crystal display apparatus1A according to the first embodiment includes a liquid crystal layer103including a plurality of liquid crystal molecules and disposed between a first transparent substrate (upper transparent substrate)101and a second transparent substrate (lower transparent substrate)102. In other words, the liquid crystal layer103is held between and by the first transparent substrate101and the second transparent substrate102.

The liquid crystal display apparatus1A has a transmission region A and a reflection region B formed in parallel to each other. The thickness (first liquid crystal thickness: first substrate gap) of the liquid crystal layer103in the transmission region A is set to D1, and the thickness (second liquid crystal thickness: second substrate gap) of the liquid crystal layer103in the reflection region B is set to D2.

In the liquid crystal display apparatus1A, the thicknesses D1and D2are set so as to satisfy a relationship D1>D2as seen inFIG. 5.

The first transparent substrate101and the second transparent substrate102are formed from a transparent insulating substrate of, for example, glass.

The first transparent substrate101has a color filter104formed on a first face101athereof which opposes to the liquid crystal layer103, and an orientation film105is formed on the color filter104. A non-phase difference film106and a phase difference film107are formed in parallel to each other on the orientation film105.

The non-phase difference film106is formed on the transmission region A, and the phase difference film107is formed on the reflection region B. The non-phase difference film106is formed by selective exposure which may be UV exposure after, for example, a phase difference film is formed (applied).

In the transmission region A, transmission light TL passes only once, and no phase difference adjustment is required. Therefore, the non-phase difference film106is disposed.

In contrast, in the reflection region B, incoming light passes once, whereafter reflected light RL of the incoming light passes and gives rise to a light path difference. As a result, there is the necessity to adjust the phase difference. Therefore, the phase difference film107is disposed.

Incidentally, the reflection region B must selectively implement circularly polarized light. Therefore, the reflection region B requires a phase difference plate for establishing a circular polarization mode.

However, it is difficult to selectively mount a phase difference plate in the form of a film for each pixel of the micron order on the outer side of the first transparent substrate101adjacent a light emerging side polarizing plate111if elongation and so forth of the film are taken into consideration.

Therefore, in the present embodiment, the phase difference film107is selectively formed in the liquid crystal cells to form the reflection region B as of the FFS type.

In order to achieve both of the transmission mode and the reflection mode in the FFS structure, it is reasonable to form the phase difference film107in the reflection region B while the transmission region A passes linearly polarized light.

In the present embodiment, the phase difference film107is formed on the first transparent substrate101to form an offset structure.

The built-in phase difference film107applies retardation (circular polarization) of a ½ wavelength to vertically polarized light in the transmission region A.

In addition, the retardation of the liquid crystal layer103in the reflection region B is a ¼ wavelength.

In the reflection region B of the liquid crystal display apparatus1A, light comes in from the polarizing plate111on the upper face of the liquid crystal display apparatus1A and is reflected by the reflecting film121in the liquid crystal panel. Thereafter, the light passes through the light emerging side polarizing plate111on the upper face of the apparatus gain. Consequently, the light can be recognized by an observer.

In the transmission region A of the liquid crystal display apparatus1A, light comes in through a polarizing plate127on the lower face of the liquid crystal display apparatus1A and then passes through the light emerging side polarizing plate111on the upper face of the liquid crystal display apparatus1A so that it is recognized by the observer.

From the difference in light, the phases of the light which is to make dark display from a reflection region B and a transmission region A exhibit a phase difference of a ¼ wavelength. In order to make it possible to apply the same voltage in the reflection region B and the transmission region A, it is necessary to cancel the phase difference of a ¼ wavelength between the reflection region B and the transmission region A. To this end, a phase difference canceling portion (film) for shifting the wavelength of light through the reflection region B by a ¼ wavelength is required.

A flattening film108by which the gap D2of the liquid crystal layer103in the reflection region B can be adjusted is formed on the phase difference film107.

Further, a vertical orientation film (first orientation film)109is formed on the non-phase difference film106, phase difference film107and flattening film108.

Further, the light emerging side polarizing plate111is formed on a second face101bon the light emerging side of the first transparent substrate101with a pressure sensitive adhesive110interposed therebetween.

On a first face102aof the second transparent substrate102which opposes to the liquid crystal layer103, a scanning wiring line112(corresponding to the scanning line (gate line)5ofFIG. 1) which corresponds to the gate electrode of the TFT21is formed on the transmission region A side, and, for example, a VCOM common wiring line113(corresponding to the common wiring line7ofFIG. 1) is formed on the reflection region B side.

It is to be noted that the scanning wiring line112may be formed by forming a film of a metal or an alloy, for example, of molybdenum (Mo) or tantalum (Ta).

An insulating film114which functions as a gate insulating film is formed in such a manner as to cover the scanning wiring line112, VCOM common wiring line113and first face102aof the second transparent substrate102.

An n-type semiconductor layer115is formed in a region of the insulating film114opposing to the scanning wiring line (gate electrode)112. The semiconductor (thin film) layer115includes a source electrode portion (S)1151and a drain electrode portion (D)1152each in the form of a+diffusion layer, and a channel formation region1153.

The semiconductor thin film layer115is formed from a thin film of low temperature polycrystalline silicon obtained, for example, by a CVD method or the like.

A signal wiring line (corresponding to the signal line6ofFIG. 1)116made of, for example, aluminum (Al) is formed on the source electrode portion (S)1151. Meanwhile, a conducting portion (connection electrode)117made of, for example, aluminum in the layer same as that of the signal wiring line116is formed on the drain electrode portion (D)1152.

The TFT21ofFIG. 1is formed from the scanning wiring line (gate electrode)112, semiconductor thin film layer115and so forth. The TFT21has a bottom gate structure.

An interlayer insulating film118is formed on the semiconductor thin film layer115, signal wiring line116, conducting portion117and insulating film114.

Further, a contact hole119is formed in the insulating film114and the interlayer insulating film118on the VCOM common wiring line113such that it extends to the VCOM common wiring line113.

A transparent counter electrode120made of, for example, ITO is formed on the interlayer insulating film118in the transmission region A and the reflection region B, in the contact hole119and on the VCOM common wiring line113in the contact hole119.

Furthermore, the reflecting film121of metal having a high reflection factor is formed on the counter electrode120in the reflection region B. A transparent region side interlayer insulating film (first interlayer insulating film)122is formed on the interlayer insulating film118and the counter electrode120in the TFT regions and the transmission region A, and a reflection region side interlayer insulating film (second interlayer insulating film)123is formed on the reflecting film121in the reflection region B.

While the first interlayer insulating film122and the second interlayer insulating film123are formed parallelly in this manner, the thickness L1of the first interlayer insulating film122and the thickness L2of the second interlayer insulating film123in the transmission region A are different from each other. Here, the thickness L1and the thickness L2have a relationship of L1(t1)>L2(t2).

A contact hole124is formed in the interlayer insulating film118and the first interlayer insulating film122above the conducting portion117formed on the drain electrode portion1152of the semiconductor thin film layer115such that it extends to the conducting portion117.

A transparent pixel electrode125made of, for example, ITO is formed on the first interlayer insulating film122and the second interlayer insulating film123, in the contact hole124and on the conducting portion117in the contact hole124.

Pixel electrode blanked portions1251each in the form of a slit are formed as a fringe pattern on the pixel electrode125as seen inFIGS. 4 and 5.

A horizontal orientation film126having a predetermined rubbing axis is formed on the first interlayer insulating film122, second interlayer insulating film123and pixel electrode125.

Further, the polarizing plate127is formed on a second face102bside of the second transparent substrate102.

In the FFS structure of the liquid crystal display apparatus1A having the configuration described above, electric lines of force generated by the first interlayer insulating film122sandwiched by the pixel electrode125and the counter electrode120in the transmission region A and the second interlayer insulating film123sandwiched by the contact hole124and the counter electrode120in the reflection region B rely upon the film thickness.

As represented by the expression (1), L represents also electric lines of force (electric field strength), and the liquid crystal thickness (D: inter-substrate gap) is designed in order to control the electric lines of force:
Vlcd=n·L/D√{square root over ( )}(K/∈lcd)  (1)
where Vlcd is the driving voltage for the liquid crystal, L the interlayer insulating film thickness or line distance, D the liquid crystal thickness (gap), K the viscosity constant of the liquid crystal, and ∈lcd the relative dielectric constant of the liquid crystal.

If the electric lines of force are intense, then the gap is designed so as to be comparatively great, but if the electric lines of force are weak, then the gap is described so as to be comparatively small.

In such a multi-gap configuration as shown inFIG. 5, since the gap is decided relatively between the transmission region A and the reflection region B, it is necessary to make contrivance so as to adjust the driving voltage using the second transparent substrate102(TFT substrate).

In the present first embodiment, the film thickness L1(t1) of the first interlayer insulating film122is set to twice or more the thickness L2(t2) of the second interlayer insulating film123so that the gap decreased by the reflection region B, that is, ½, is cancelled so that the driving voltages for the transmission region A and the reflection region B may be equal to each other.

It is to be noted that, in the present first embodiment, the first interlayer insulating film122and the second interlayer insulating film123have an equal relative dielectric constant.

FIG. 6illustrates a table of liquid crystal driving voltages and parameters used in the present embodiment.

FIG. 7illustrates a relationship between the interlayer insulation film and the liquid crystal driving voltage in the present embodiment. InFIG. 7, the axis of abscissa indicates the interlayer insulating film L, and the axis of abscissa indicates the liquid crystal driving voltage.

Referring toFIG. 7, a straight line denoted by <1> illustrates a relationship between the interlayer insulating film and the liquid crystal driving voltage where the liquid crystal cell gap (liquid crystal thickness) D is 1 μm. Another straight line denoted by <2> illustrates a relationship between the interlayer insulating film and the liquid crystal driving voltage where the liquid crystal cell gap (liquid crystal thickness) D is 2.25 μm. A further straight line denoted by <3> illustrates a relationship between the interlayer insulating film and the liquid crystal driving voltage where the liquid crystal cell gap (liquid crystal thickness) D is 4.5 μm. A still further straight line denoted by <4> illustrates a relationship between the interlayer insulating film and the liquid crystal driving voltage where the liquid crystal cell gap (liquid crystal thickness) D is 7 μm.

Here, the film thickness of the interlayer insulating film is indicated by L of the expression (1).

It can be recognized from this that, in order to establish liquid crystal display, liquid crystal display required time: τrise+τfall≦33 ms is required. Besides, it is known that, in order to assure the accuracy in fabrication of the liquid crystal cell gap (liquid crystal thickness) from a small to a large liquid crystal cell size, the necessary liquid crystal cell gap D is 1 μm or more.

This gives rise to a limitation (restriction) with regard to the interlayer insulating film L between the thickness L1and the thickness L2as seen inFIG. 7.

In the present embodiment, in order to make the driving voltages for the reflection region B and the transmission region A equal to each other, it is necessary to satisfy the relationship of L2(reflection region)<L1(transmission region).

Further, where a mobile apparatus, a portable telephone set and so forth are taken into consideration, fromFIG. 7, the interlayer insulating film is preferably equal to or greater than 0.15 μm.

In particular, the condition in applications (driving voltage 3 V) to a mobile apparatus and a portable telephone set is 1/7(0.15)<L2/L1<1. In this instance, the interlayer insulating film thickness is not less than 0.15 μm but not more than 1 μm.

The condition in an application (driving voltage 4.5 V) to a mobile apparatus or a notebook PC is ⅕<L2/L1<1. In this instance, the interlayer insulating film thickness is not less than 0.2 μm but not more than 1 μm.

The condition in an application (driving voltage 7.5 V) to a monitor PC is ⅓<L2/L1<1. In this instance, the interlayer insulating film thickness is not less than 0.35 μm but not more than 1 μm.

The condition in an application to a television set is ½<L2/L1<1. In this instance, the interlayer insulating film thickness is more than 0.5 μm but less than 1 μm.

Here, since L1=t1and L2=t2, in order to satisfy the minimum condition described above, it is necessary for the film thickness t1of the first interlayer insulating film122between the pixel electrode125and the counter electrode120in the transmission region A and the film thickness t2of the second interlayer insulating film123between the pixel electrode125and the counter electrode120in the reflection region B to satisfy t1>t2> 1/7×t1or, from the optical condition, t≦½×t1.

It is to be noted that the film thickness t2may be displaced a little from the condition t2=½×t1or may not satisfy the condition t2=½×t1in the optimization of the polarizer, contrast and angular field of view.

The liquid crystal display apparatus1A having such a structure as described above has both of transmission and reflection functions of the FFS type.

Further, since a single driving voltage can be used for both of transmission and reflection, the number of power supply voltages can be reduced and a level shifter circuit in the driving circuit can be configured in a simple circuit configuration.

Further, a complicated pixel layout in transmission and reflection regions of the pixel section can be simplified. Therefore, a pixel layout of a high transmission factor and a high reflection factor can be achieved.

Further, since the driving circuits are handled with a simple power supply, the number of driving circuits can be reduced and the liquid crystal display apparatus can be fabricated at a reduced cost.

FIG. 8shows a liquid crystal display apparatus of the reflective and transmissive type according to a second embodiment of the present invention.

Referring toFIG. 8, the liquid crystal display apparatus1B of the second embodiment is a modification to the liquid crystal display apparatus1A of the first embodiment but is different in the following points. In particular, the liquid crystal display apparatus1B of the second embodiment is different in that the film thickness t1of the first interlayer insulating film122B between the pixel electrode125and the counter electrode120in the transmission region A and the film thickness t2of the second interlayer insulating film123B between the pixel electrode125and the counter electrode120in the reflection region B are set equal to each other so that the first interlayer insulating film122B and the second interlayer insulating film123B may have different relative dielectric constants from each other.

Since, in such a multi-gap structure as shown inFIG. 8, the gap is determined relatively depending upon the transmission region A and the reflection region B, it is necessary to contrive the second transparent substrate102(TFT substrate) to adjust the driving voltages.

In the present second embodiment, the relative dielectric constant ∈1of the first interlayer insulating film122B is set to equal to or less than one half with respect to the relative dielectric constant ∈2of the second interlayer insulating film123B so that the gap reduced to one half in the reflection region is canceled to make the driving voltages for the transmission region A and the reflection region B equal to each other.

This has an effect of strengthening the electric field intensity in the reflection region B so as to actually reduce the constant of L in the expression (1) to one half. It is to be noted that, as described hereinabove, the first interlayer insulating film122B and the second interlayer insulating film123B have an equal film thickness.

Incidentally, as regards the relative dielectric constant of the insulating films of the semiconductors, where the relative dielectric constant ∈1is ∈_SiO2=3.9 and the other relative dielectric constant are ∈2, since ∈_Si3N4=7.5 and ∈_Ta2O2=22 are involved, it is necessary to satisfy ∈1<∈2<6×∈1or ∈2≧2×∈1.

It is to be noted that the relative dielectric constant ∈1may be displaced a little from ∈2=2×∈1or may not satisfy the condition ∈2=2×∈1in the optimization of the polarizer, contrast and angular field of view.

It is to be noted that the interlayer insulating films122B and123B can be formed from an organic film of acrylic polyimide or the like.

The liquid crystal display apparatus1B according to the present second embodiment has both of transmission and reflection functions of the FFS type and the IPS type similarly to the liquid crystal display apparatus1A of the first embodiment described hereinabove.

Further, since a single driving voltage can be used for both of transmission and reflection, the number of power supply voltages can be reduced and a level shifter circuit in the driving circuit can be configured in a simple circuit configuration.

Further, a complicated pixel layout in transmission and reflection regions of the pixel section can be simplified. Therefore, a pixel layout of a high transmission factor and a high reflection factor can be achieved.

Further, since the driving circuits are handled with a simple power supply, the number of driving circuits can be reduced and the liquid crystal display apparatus can be fabricated at a reduced cost.

FIG. 9shows a liquid crystal display apparatus of the reflective and transmissive type according to a third embodiment of the present invention.

Referring toFIG. 9, the liquid crystal display apparatus1C of the third embodiment is a modification to the liquid crystal display apparatus1B of the second embodiment but is different in the following points. In particular, the liquid crystal display apparatus1C of the third embodiment is different in that the liquid crystal layer thickness (gap thickness) D1in the transmission region A is set to equal or more than twice the liquid crystal layer thickness (gap thickness) D2in the reflection region B. Also in this instance, the phase difference film107in the liquid crystal cells disposed in the reflection region B are located on the first transparent substrate101side.

Incidentally, the reflection region B must selectively implement circularly polarized light. Therefore, the reflection region B requires a phase difference plate for establishing a circular polarization mode.

However, it is difficult to selectively mount a phase difference plate in the form of a film for each pixel of the micron order on the outer side of the first transparent substrate101adjacent the light emerging side polarizing plate111if elongation and so forth of the film are taken into consideration.

Therefore, in the present embodiment, the phase difference film107is selectively formed in the liquid crystal cells to form the reflection region B as of the FFS type.

In order to achieve both of the transmission mode and the reflection mode in the FFS structure, it is reasonable to form the phase difference film107in the reflection region B while the transmission region A passes linearly polarized light.

In the present embodiment, the phase difference film107is formed on the first transparent substrate101to form an offset structure.

The built-in phase difference film107applies retardation (circular polarization) of a ½ wavelength to vertically polarized light in the transmission region A.

In addition, the retardation of the liquid crystal layer103in the reflection region B is a ¼ wavelength.

In the reflection region B of the liquid crystal display apparatus1C, light comes in from the polarizing plate111on the upper face of the liquid crystal display apparatus1C and is reflected by the reflecting film121in the liquid crystal panel. Thereafter, the light passes through the polarizing plate111on the upper face of the apparatus gain. Consequently, the light can be recognized by an observer.

In the transmission region A, light comes in through the polarizing plate127on the lower face of the liquid crystal display apparatus1C and then passes through the polarizing plate111on the upper face of the liquid crystal display apparatus1C so that it is recognized by the observer.

From the difference in light, the phases of the light which is to make dark display from a reflection region B and a transmission region A exhibit a phase difference of a ¼ wavelength. In order to make it possible to apply the same voltage in the reflection region B and the transmission region A, it is necessary to cancel the phase difference of a ¼ wavelength between the reflection region B and the transmission region A. To this end, a phase difference canceling portion (film) for shifting the wavelength of light through the reflection region B by a ¼ wavelength is required.

According to the present third embodiment, similar effects to those of the first and second embodiments described hereinabove can be achieved.

FIG. 10shows a liquid crystal display apparatus of the reflective and transmissive type according to a fourth embodiment of the present invention.

Referring toFIG. 10, the liquid crystal display apparatus1D of the fourth embodiment is a modification to the liquid crystal display apparatus1B of the second embodiment but is different in the following points. In particular, the liquid crystal display apparatus1D of the fourth embodiment is different in that the first interlayer insulating film122D in the transmission region A is formed so as to be covered with the second interlayer insulating film123D in the reflection region B and the relative dielectric constant ∈1in the transmission region A and the relative dielectric constant ∈2are made different from each other so as to satisfy ∈1<∈2<6×∈1or ∈2<2×∈1

In this instance, the thickness of the interlayer insulating film in the transmission region A is t1+t2, and the thickness of the interlayer insulating film in the reflection region B is t2. Consequently, the relationship of t1+t2>t2is satisfied.

According to the present fourth embodiment, similar advantages to those of the second embodiment described hereinabove are achieved.

FIG. 11shows a liquid crystal display apparatus of the reflective and transmissive type according to a fifth embodiment of the present invention.

Referring toFIG. 11, the liquid crystal display apparatus1E of the fifth embodiment is a modification to the liquid crystal display apparatus1B of the second embodiment but is different in the following points. In particular, the liquid crystal display apparatus1E of the fifth embodiment is different in that the first interlayer insulating film122E in the transmission region A is formed so as to cover the second interlayer insulating film123E in the reflection region B and the relative dielectric constant ∈1in the transmission region A and the relative dielectric constant ∈2in the reflection region B are made different from each other so as to satisfy the requirement of ∈1<∈2<6×∈1or ∈2≦2×∈1.

In this instance, the thickness of the interlayer insulating film in the transmission region A is t1and the thickness of the interlayer insulating film in the reflection region B is t1+t2. Therefore, the relationship of t1<t1+t2is satisfied.

According to the present fifth embodiment, similar advantages to those of the second embodiment described hereinabove are achieved.

FIG. 12shows a liquid crystal display apparatus of the reflective and transmissive type according to a sixth embodiment of the present invention.

Referring toFIG. 12, the liquid crystal display apparatus1F of the sixth embodiment is a modification to the liquid crystal display apparatus1B of the second embodiment but is different in the following points. In particular, the liquid crystal display apparatus1F of the sixth embodiment is different in that the relative dielectric constant ∈1of the first interlayer insulating film122F is different from the relative dielectric constant ∈2of the second interlayer insulating film123F and besides the first interlayer insulating film122F and the second interlayer insulating film123F have different film thicknesses from each other.

In the present embodiment, in order to make the driving voltages on the transmission region A side and the reflection region B side equal to each other while the first interlayer insulating film122F in the transmission region A and the second interlayer insulating film123F in the reflection region B do not have an equal film thickness, the interlayer insulating film in the transmission region A and the reflection region B have different relative dielectric constants from each other.

In particular, in the liquid crystal display apparatus1F, the first interlayer insulating film122F in the transmission region A and the second interlayer insulating film123F in the reflection region B which have different relative dielectric constants from each other are formed (t1>t2). Thus, in order to make the driving voltage in the transmission region A and the driving voltage in the reflection region B equal to each other, the relative dielectric constant ∈1of the first interlayer insulating film122F in the transmission region A and the relative dielectric constant ∈2of the second interlayer insulating film123F in the reflection region B are made different from each other.

For example, as seen inFIG. 13, the first interlayer insulating film122F is made of SiN and has a relative dielectric constant of 7.5 while the second interlayer insulating film123F is made of SiO2and has another relative dielectric constant of 3.9.

Besides, the film thickness of the first interlayer insulating film122F is 1 μm, and the film thickness of the second interlayer insulating film123F is 0.7 μm.

Consequently, the driving voltage in the transmission region A having the first interlayer insulating film122F is 3.34 V while the driving voltage in the reflection region B having the second interlayer insulating film123F is 3.24 V. Consequently, the driving voltages for transmission and reception can be made substantially equal to each other.

FIGS. 14 and 15show a liquid crystal display apparatus of the reflective and transmissive type according to a seventh embodiment of the present invention.

Referring toFIGS. 14 and 15, the liquid crystal display apparatus1G of the seventh embodiment is a modification to the liquid crystal display apparatus1F of the sixth embodiment but is different in the following points. In particular, the liquid crystal display apparatus1G of the seventh embodiment is different in that the film thickness t2of the second interlayer insulating film123G is set greater than the film thickness t1of the first interlayer insulating film122G to form the gap D2in the reflection region B.

In this instance, the flattening film on the first transparent substrate101side is unnecessary.

In the present seventh embodiment, the film thickness t2of the second interlayer insulating film123G in the reflection region B is set greater than the film thickness t1of the first interlayer insulating film122G in the transmission region A and besides the effective pixel region section2in the reflection region B is used so as to serve also as an offset portion for the multi-gaps in the reflection region B.

In particular, in the present seventh embodiment, in order to make the driving voltages on the transmission region A side and the reflection region B side equal to each other while the first interlayer insulating film122G in the transmission region A and the second interlayer insulating film123G in the reflection region B do not have an equal film thickness, the relative dielectric constant ∈1of the first interlayer insulating film122G in the transmission region A is made different from the relative dielectric constant ∈2of the second interlayer insulating film123G in the reflection region B.

Besides, the effective pixel region section2is formed as an offset portion for obtaining multi-gaps in the reflection region B.

For example, as seen inFIG. 16, the first interlayer insulating film122G is made of SiO2and has a relative dielectric constant of 3.9 while the second interlayer insulating film123G is made of TaO2and has another relative dielectric constant of 22.

Besides, the first interlayer insulating film122G is 0.5 μm, and the second interlayer insulating film123G is 1 μm.

Consequently, the driving voltage in the transmission region A having the first interlayer insulating film122G becomes 3.49 V, and the driving voltage in the reflection region B having the second interlayer insulating film123G becomes 4.39. Consequently, the driving voltages for transmission and reflection can be made substantially equal to each other.

Besides, the liquid crystal layer thickness (substrate gap) D1in the transmission region A can be set to 3 μm, and the gap (substrate gap) D2in the reflection region B can be set to 2 μm. Consequently, an offset portion can be formed from the interlayer insulating film in the reflection region B.

It is to be noted that the present invention can be applied also where the material of the second interlayer insulating film123G in the reflection region B is SIN.

Further, according to the liquid crystal display apparatus1G of the seventh embodiment, the counter electrode overhangs (has an overlapping relationship with) the signal line and the gate line in transmissive and reflective type liquid crystal display as seen inFIG. 14.

In the present seventh embodiment, since the counter electrode120made of ITO or the like is disposed immediately above the signal wiring line116and the scanning wiring line (gate line)112, jumping of a voltage variation from the signal wiring line116and the scanning wiring line (gate line)112into the counter electrode120can be prevented. Consequently, the variation at the signal wiring line116to the pixel electrode125disposed above the counter electrode120and the pixel electrode (ITO)125from the scanning wiring line (gate line)112by jumping in of the voltage variation can be suppressed. As a result, deterioration of the picture quality by flickering by horizontal and vertical crosstalk which appears in the liquid crystal display apparatus can be prevented.

FIGS. 17 and 18show a liquid crystal display apparatus of the reflective and transmissive type according to an eighth embodiment of the present invention.

The liquid crystal display apparatus1H of the eighth embodiment is characterized in that, in transmission liquid crystal display and transmission and reflection liquid crystal display, a counter electrode overhangs (has an overlapping relationship with) a signal line and a gate line.

Referring toFIG. 17, the liquid crystal display apparatus1H of the eighth embodiment is a modification to the liquid crystal display apparatus1A of the first embodiment but is different in the following points. In particular, on the first transparent substrate101side, an orientation film105is formed on the color filter104.

On the other hand, on the second transparent substrate102, the reflecting film121is not formed and no multi-gap structure is provided.

While the liquid crystal display apparatus of the reflective and transmissive type according to the eighth embodiment is shown as of the transmission type inFIGS. 17 and 18, in the present eighth embodiment, the counter electrode120made of ITO or the like is disposed immediately above the signal wiring line116and the scanning wiring line (gate line)112. Therefore, jumping of a voltage variation from the signal wiring line116and the scanning wiring line (gate line)112into the counter electrode120can be prevented. Consequently, the variation at the signal wiring line116to the pixel electrode125disposed above the counter electrode120and the pixel electrode (ITO)125from the scanning wiring line (gate line)112by jumping in of the voltage variation can be suppressed. As a result, deterioration of the picture quality by flickering by horizontal and vertical crosstalk which appears in the liquid crystal display apparatus can be prevented.

FIGS. 19 and 20show a liquid crystal display apparatus of the reflective and transmissive type according to a ninth embodiment of the present invention.

Referring toFIGS. 19 and 20, the liquid crystal display apparatus1I of the ninth embodiment is a modification to the liquid crystal display apparatus1A of the first embodiment but is different in that it is formed not as that of the FFS type but as that of the IPS type.

On the first transparent substrate101side, a flattening film108I is formed on the color filter104, and a non-phase difference film106and a phase difference film107are formed in parallel on the flattening film108I. Further, an orientation film109is formed on the non-phase difference film106and the phase difference film107.

On the second transparent substrate102side, a reflecting film121is formed on the insulating film114in the reflection region B, and a counter electrode120I and a pixel electrode125I are formed in a comb-like shape on the first interlayer insulating film122I and the second interlayer insulating film123I such that they are opposed to each other.

Further, the line distance between the pixel electrode125I and the counter electrode120I is made different between the transmission region A and the reflection region B.

Further, the thickness L1of the first interlayer insulating film122I and the thickness L2of the second interlayer insulating film123I satisfy a relationship of L2≦½×L1.

According to the present ninth embodiment, similar advantages to those of the first to eighth embodiments described hereinabove can be achieved.

In other words, according to the present ninth embodiment of the present invention, a liquid crystal display apparatus can be formed which has both functions of transmission and reception while it is of the IPS type.

Further, since a single driving voltage can be used for both of transmission and reflection, the number of power supply voltages can be reduced and a level shifter circuit in the driving circuit can be configured in a simple circuit configuration.

Further, a complicated pixel layout in transmission and reflection regions of the pixel section can be simplified. Therefore, a pixel layout of a high transmission factor and a high reflection factor can be achieved.

Further, since the driving circuits are handled with a simple power supply, the number of driving circuits can be reduced and the liquid crystal display apparatus can be fabricated at a reduced cost.

Further, an active matrix type display apparatus represented by the active matrix type liquid crystal display apparatus according to the embodiments described above is used as a display apparatus for OA apparatus such as a personal computer or a word processor and a television receiver. Further, the active matrix type display apparatus can be suitably used as a display section for a portable telephone set or a PDA with regard to which miniaturization and compaction particularly of an apparatus body are being proceeded.

FIG. 21shows an outline of a configuration of an electronic apparatus such as, for example, a portable telephone set to which any of the liquid crystal display apparatus according to the embodiments described hereinabove can be applied.

Referring toFIG. 21, the portable telephone set200shown includes a speaker section220, a display section260, an operation section240and a microphone section250disposed in order from above on a front face of an apparatus housing270.

In the portable telephone set200having the configuration just described, for example, a liquid crystal display apparatus is used for the display section260, and any of the active matrix type liquid crystal display apparatus according to the embodiments of the present invention described hereinabove is applied as the liquid crystal display apparatus.

Where the active matrix type liquid crystal display apparatus according to any of the embodiments described hereinabove is used as the display section260in the portable terminal such as the portable telephone set, the dispersion of the output frequency of an oscillator which has some frequency dispersion can be suppressed so as to be within a predetermined certain guaranteed range. Further, a circuit block which is independent and does not rely upon the voltage or the frequency of an interface can be configured and controlled. Therefore, a circuit-integrated type liquid crystal display apparatus compatible with a low voltage and a high frequency of the interface can be implemented.