Patent Application
20080102387
The present invention relates a display panel manufacturing method and a display panel manufacturing apparatus.
Display apparatuses such as a liquid crystal display, a plasma display, an electroluminescence display and a field-emission display can be formed in a plane form, and allows reduction in thickness. These display apparatuses are becoming a mainstream of television sets and the like. Among such display apparatuses, the liquid crystal display have been used more widely than other slim display apparatuses owing to low weight, low power consumption and the like. In addition to the television sets, the liquid crystal panels are used in personal computers, cellular phones, PDAs (Personal Digital Assistances) and the like, and further demand can be expected.
It has been requested to improve performance of the liquid crystal display panels to a further extent. For example, screens of television sets have been increasing, and it is strongly desired to improve brightness and a view angle of displayed images for achieving high-definition images on the large screen.
For improving the display quality, such a liquid crystal display panel has been proposed that a microlens array is arranged at its surface for improving brightness and a view angle. The liquid crystal display panel with the microlens array will now be described in connection with a product for mobile devices such as a cellular phone and a PDA. This kind of mobile device preferably employs a semi-transmissive liquid crystal display panel having both functions of a transmissive liquid crystal display panel that includes a backlight and performs display using light of the backlight, and a reflective liquid crystal display panel that performs display using external light.
The semi-transmissive liquid crystal display panel includes a reflector that is employed for reflecting light and is provided with minute openings, and is configured to reflect the external light by the reflector and to pass the light of the backlight through the openings. The reflector must have large openings for increasing the brightness of the transmissive display performed by the light of the backlight. However, when the openings in the reflector are increased, this results in decrease in area of a reflection surface of the reflector, and thus causes a problem that images displayed by the reflection display become dark. Thus, front brightness lowers.
For overcoming the above problem, such a method has been proposed, e.g., that a microlens is formed in a position corresponding to the openings in the reflector to increase an effective aperture ratio, and thereby the brightness of the transmissive display is proposed without increasing the openings. The arrangement of the microlens corresponding to the openings can improve both the brightness of the transmissive display and the brightness of the reflective display (see, e.g., Japanese Patent Laying-Open No. 2002-62818).
In a method of manufacturing the microlens, a photoresist layer is formed over a surface of a glass substrate, and is patterned with light passing through the openings in the reflector. The resist layer thus patterned is heated to cause thermal deformation so that the resist layer takes a form corresponding to the form of the microlens. Thereafter, dry etching is performed on the glass substrate to provide a microlens array substrate corresponding in form to the resist layer.
In the manufacturing method disclosed in Japanese Patent Laying-Open No. 2002-62818, a microlens stamper corresponding to a pixel pattern is prepared. The microlens stamper is pressed against a transparent insulating substrate carrying ultraviolet curing resin to develop high-refractivity resin. Then, the microlens stamper is released, and the ultraviolet curing resin is cured by irradiation with ultraviolet rays so that hemispheric microlenses are formed.
In the method of manufacturing the microlens disclosed in Japanese Patent Laying-Open No. 2002-62818, a TFT substrate is adhered to an opposite substrate, then a light collecting layer including a photosensitive material is formed at a surface of the opposite substrate other than the adhesion surface, and the light is applied from the side of the TFT substrate. Thereby, portions of the light-collecting layer opposed to the openings in the light shield layer are exposed, and unexposed portions of the collecting layer are removed so that the microlens is formed.
For improving a view angle of the liquid crystal display panel without using a microlens, such a liquid crystal display panel has also been disclosed that includes a plurality of regions exhibiting different orientation states of liquid crystal molecules when a voltage is applied, respectively (e.g., Japanese Patent Laying-Open No. 2004-93846). In this liquid crystal display panel, a light shield is formed in a boundary between the regions of different orientation directions. This light shield can cut off light that may leak when the liquid crystal display panel is viewed obliquely, and display quality can be improved.
Patent Reference 1: Japanese Patent Laying-Open No. 2002-62818 Patent Reference 2: Japanese Patent Laying-Open No. 2004-93846
Problems to Be Solved By The Invention
In the art disclosed in Japanese Patent Laying-Open No. 2002-62818, it is necessary to prepare the microlens stamper so that the form of the lens cannot be determined with sufficient flexibility, and a profound lens effect cannot be achieved. Since the TFT substrate is adhered to the opposite substrate after forming the microlens on the surface of the TFT substrate, variations in alignment may occur to reduce the brightness. For sufficiently achieving the lens effect by the microlens, it is preferable that the substrate bearing the microlens at its surface has a small thickness. However, the substrate must be thick for avoiding restrictions on handling due to bending or the like, and this results in a problem of lowing of the lens effect.
In the manufacturing method disclosed in Japanese Patent Laying-Open No. 2002-62818, ultraviolet is used as the light for exposing the light-collecting layer. Since a color filter absorbs the ultraviolet rays, it is impossible to irradiate the photosensitive material with the ultraviolet rays through the color filter. Therefore, the method disclosed in the reference cannot be used for the liquid crystal display panel provided with the color filter.
In the liquid crystal display panel that has the light shield as disclosed in Japanese Patent Laying-Open No. 2004-93846, the aperture ratio is further smaller than that in the conventional liquid crystal display panel of the semi-transmissive type. Therefore, the front brightness is low. It may be attempted to change the backlight structure for avoiding the lowering of the front brightness. However, it is considerably difficult to increase the front brightness while keeping a large view angle. Therefore, it is effective to arrange the microlens array on the substrate on the same side as the backlight so that the effective aperture ratio may be increased and both the high front brightness and the large view angle may be achieved.
As disclosed in Japanese Patent Laying-Open No. 2002-62818, it is effective in the process of forming the microlens to cure the photosensitive material by passing the light through the openings. In this manufacturing method, the microlens can be formed at a low cost, and further the microlens can be arranged precisely because the microlens is arranged in a self-aligned manner with respect to the openings. Therefore, the microlens can sufficiently offer its light collecting performance, and the liquid crystal display panel capable of display with high brightness can be manufactured. Since the light collected by the microlens disperses at the same angle as the collecting or converging angle after it passed the openings in the reflector, the view angle can be improved.
When the manufacturing method disclosed in Japanese Patent Laying-Open No. 2002-62818 is applied to the liquid crystal display panel having the light shield, the light shield partially cuts off the light curing the photosensitive resin during the processing of forming the microlens array, and the wave surface of the light passed through the opening cannot be uniform. Therefore, a step or a level difference occurs at the lens surface of the microlens thus formed, and impairs lens characteristics. This results in a problem that good brightness and good view angle cannot be obtained.
An object of the invention is to provide a method and an apparatus of manufacturing a display panel that includes a light shield corresponding to each pixel and particularly has good lens characteristics.
According to the invention, a method of manufacturing a display panel including a microlens formed at a surface of a substrate on an arrangement side of a backlight, and a light shield formed corresponding to an inner region of an opening provided for forming a pixel, includes a steps of arranging a photosensitive material on a surface of the substrate on the arrangement side of the backlight, and an exposing step of applying light through the opening from a side opposite to the arrangement side of the backlight, and thereby partially curing the photosensitive material. The exposing step includes a step of performing exposure while shifting an incident angle of the light, and thereby curing the photosensitive material to exhibit a section having a convex form in one direction. The exposing step includes a step of changing at least one of a speed of shifting the incident angle in the one direction and an intensity of the light. This method can manufacture the display panel provided with the microlens of good lens characteristics.
Preferably, according to the invention, the exposing step includes a step of discontinuously changing the exposure. According to this method, it is merely required to change the exposure of the photosensitive resin at discontinuous points, and the control of the exposure of the photosensitive resin can be easy.
Preferably, according to the invention, the exposing step is executed such that the shifting speed at a portion including a top of the convex form is lower than that at a portion including a foot of the convex form. Also, the exposing step is executed such that the intensity of the light at the portion including the top of the convex form is larger than that at the portion including the foot of the convex form. By employing either of these methods, it is possible to form the microlens having a good sectional form while suppressing occurrence of a step.
Preferably, according to the invention, the exposing step is executed to cause discontinuously the change in exposure at each of a discontinuous point 41a and a discontinuous point +θ1b, and the two discontinuous points fall within ranges defined by the following two formulas:
tan−1{((Px−Wx)/2)(T/n)}≦−θ1a≦−tan−1{(P−Wx)/2−(Wx−WA)/2)(T/n)} (1)
tan−1{((Px−Wx)/2−(Wx−WA)/2)(T/n)}≦+θ1b≦tan−1{(Px−Wx)/2)(T/n)} (2)
where Px represents a pitch of the openings in the one direction, Wx indicates a width of the opening in the one direction, WA indicates a width of the light shield in the one direction, T indicates a thickness of the substrate bearing the microlens, n indicates a refractivity of the substrate, +θla and −θ1b are incident angles of the light with respect to a direction perpendicular to a main surface of the substrate in the one direction, and the plus and the minus indicate one and the other sides, respectively. By employing this method, it is possible to suppress effectively the step or level difference that may occur at the microlens.
Preferably, according to the invention, the display panel has the light shield arranged in the position substantially corresponding to a center of the opening and taking an island-like form. By employing this method, the effect of the invention described above can be more remarkable.
According to the invention, an apparatus of manufacturing a display panel including a microlens formed at a surface of a substrate on an arrangement side of a backlight, and a light shield formed corresponding to an inner region of an opening provided for forming a pixel, includes exposing means for exposing a photosensitive material. The exposing means is configured to allow changing of an incident angle of light, and includes at least one of means for changing a shifting speed of the incident angle for the exposure and means for changing an intensity of the light. This structure can provide the manufacturing apparatus for the display panel provided with the microlens that has good lens characteristics.
The invention can provide the method of manufacturing the display panel provided with the microlens having good lens characteristics as well as the apparatus of manufacturing the display panel.
1 liquid crystal display panel, 2 TFT substrate, 3 and 17 microlens, 4 opposite substrate, 5, 5R, 5G and 5B opening, 6 black matrix, 7 color filter, 8 photosensitive resin, 9 liquid crystal layer, 10 light shield layer, 11-14 light shield, 15a cured portion, 15b uncured portion, 20 pixel, 22 exposure quantity distribution (at constant scan speed), 24 exposure quantity distribution (for obtaining an ideal lens form), 25 exposure quantity distribution (in the invention), 26 step, 41, 42, 43a, 43b, 44a, 44b, 45a, 45b, 46a, 46b, 50 and 55 arrow
Referring to
Liquid crystal display panel 1 includes a TFT substrate 2 provided at its surface with TFTs, and an opposite substrate 4. TFT substrate 2 and opposite substrate 4 are adhered together by a seal member (not shown) with their main surfaces opposed to each other. A portion surrounded by TFT substrate 2, opposite substrate 4 and the seal member is filled with liquid crystal. A liquid crystal layer 9 has a thickness of several micrometers.
TFT substrate 2 is provided at its surface with the TFTs (not shown). TFT substrate 2 is also provided with a light shield layer IO, and light shields 11 are formed at portions of light shield layer 10. TFT substrate 2 is provided with pixel electrodes corresponding to red, blue and green picture elements, respectively. Each pixel electrode is connected to the corresponding TFT. TFT substrate 2 is further provided with electric circuitry including a gate bus line, a source bus line and the like for driving the TFTs.
A color filter 7 is arranged on a surface of opposite substrate 4. Openings 5B is formed at color filter 7. Blue filters are arranged in openings 5B, respectively.
In this liquid crystal display panel, backlight is applied from the side of TFT substrate 2 as indicated by arrows 50. Microlenses 3 are formed at one of main surfaces of TFT substrate 2, and particularly at the outer main surface on the same side as the backlight. Microlens 3 has a section of a convex form. Microlens 3 has a curved lens surface. The plurality of microlenses 3 are arranged to form a microlens array.
The openings are repetitively arranged in the order of red, green and blue. Thus, three kinds of picture elements are successively and linearly arranged in each column. In
Microlens 3 extends in the direction of alignment of openings 5R, 5G and 5B. Thus, microlens 3 has a longitudinal direction matching the Y direction in
Referring to
Color filters 7 are arranged in openings 5R, 5G and 5B of color filter 7 to form picture elements, respectively. A black matrix 6 is formed in positions between openings 5R, 5G and 5B. In other words, openings 5R, 5G and 5B are formed in black matrix 6, and each are surrounded by black matrix 6. Black matrix 6 is configured to cut off the light.
As shown in
As shown in
When cured photosensitive resin 8 absorbs the red, green and blue light rays, the brightness of the liquid crystal display panel lowers. Therefore, it is preferable that photosensitive resin 8 does not absorb the light in the wavelength range of a visible light, i.e., between 420 nm and 700 nm. In this embodiment, a negative dry film resist is used as photosensitive resin 8.
Then, an exposing step is executed as shown in
In this embodiment, the light that has the wavelength of about 405 nm and is used for the exposure passes through openings 5B and 5R in color filter 7. In opening 5G, however, the color filter absorbs the light of about 405 nm so that it does not take part in curing. Among the light rays incident on openings 5R, 5G and 5B, therefore, the light rays passed through openings 5R and 5B primarily cure the photosensitive resin to form the microlens in the embodiment.
In the lens direction, as shown in
Referring to
As shown in
The exposing step of partially curing the photosensitive material will now be described in detail. The exposure of the photosensitive resin is performed through the openings.
In the exposing step, the exposure is continuously performed while shifting the incident angle from the incident angle of θ1 indicated by an arrows 43a to the incident angle of +1 indicated by an arrow of 43b. In the invention, the light incident angle is an angle with respect to the direction perpendicular to the main surface of the substrate. In
In this embodiment, the exposure is performed while shifting the incident angle with respect to the lens direction and the lens ridge direction. Referring to, e.g.,
In the exposing step of the embodiment, the shifting speed of the incident angle becomes small during a certain period as illustrated in
Exposure quantity distribution 24 is the distribution for obtaining the ideal lens form, and has a trapezoidal form. When the exposure is performed with the incident angle shifted at a constant speed as illustrated in
In contrast to this, the shifting speed of the incident angle is temporarily lowered, as is done in the exposure method of the embodiment illustrated in
As illustrated in
Also, the microlens array is preferably formed such that a boundary between the neighboring microlenses is in contact with TFT substrate 2. More specifically, it is preferable that, on the external surface of TFT substrate 2, the end of the exposure region related to one microlens and indicated by arrows 43a neither overlaps with nor comes in contact with the end of the exposure region related to the neighboring microlens and indicated by arrow 43b. In this embodiment, it is preferable that the thickness of the microlens becomes zero at a mid-point of black matrix 6 located between the neighboring picture elements, and the neighboring microlenses are in contact with each other at this mid-point.
In
tanθ1=((Px−Wx)/2)/(T/n) (3)
Although not shown, for forming the microlens having a uniform height in the lens ridge direction (Y direction) of the microlens, the incident angle of the light is likewise determined based on θ2 calculated, e.g., from the following formula. In the following formula defining θ2, PY indicates the picture element pitch (pitch of the openings) in the lens ridge direction of the microlens, and WY indicates the picture element width (width of the opening) in the lens ridge direction. Based on the angle obtained from the following formula, the incident angle is shifted from −θ2 to +θ2.
tanθ2=(PY/2)/(T/n) (4)
The microlens having a good lens effect can be formed by employing at least one of the above incident angles of θ1 and θ2.
For example, in this embodiment, pitch Px of the openings in the lens direction is 200 μm, pitch PY of the openings in the lens ridge direction is 200 μm, width Wx of the opening in the lens direction is 84 μm, width WY of the opening in the lens ridge direction is 50 μm, physical thickness T of TFT substrate 2 is 400 μm, and refractivity n of TFT substrate 2 is 1.53. Therefore, the foregoing θ1 and θ2 are as follows:
θ1=tan−1(58/260)=about 13 deg. (5)
θ2=tan−1(100/260)=about 21 deg. (6)
The light passed through the opening forming the picture element may expand due to an influence of diffraction, in which case correction is performed after calculating the above θ1 and θ2.
Description will now be given on the discontinuous point at which a discontinuous change occurs in exposure quantity. In the lens direction (X direction), the shifting speed of the light incident angle increases in the portion including the foot of the convex form of the microlens to be formed, and the shifting speed of the incident angle decreases in the portion including the top of the convex form. In this embodiment, the discontinuous point in shifting speed is defined for changing instantaneously the shifting speed of the incident angle (see
Referring to
−tan−1{((Px−Wx)/2)/(T/n)}≦−θ1a≦−tan−1{((PxWx)/2)−(Wx−WA)/2)/(T/n)} (1)
Likewise, for the positive range of incident angle θ1, it is preferable that incident angle θ1b at the discontinuous point is determined in the following range. An arrow 45b indicates a center line in the width direction of the light passing through opening 5B during the exposure indicated by arrows 43b. When the scanning with the shifted incident angle indicated by arrow 43b ends, arrows 45b indicating the center line in the width direction of the exposure light crosses TFT substrate 2 at a point Q′, and a point R′ shifted inward by only the same width as the foregoing case is set. The shifting speed of the incident angle preferably changes between point R′ (arrows 46b) and point Q′ (arrow 45b):
tan−1{((PxWx)/2)−(Wx−WA)/2)/(T/n)}≦+θ1b≦tan−1{((Px−Wx)/2)/(T/n)} (2)
By setting incident angles −θ1a and +θ1b at the discontinuous points to fall within the ranges of the foregoing two formulas, the steps 26 in exposure quantity distribution 26 that may be caused by light shield 11 can be effectively reduced.
Referring to
As illustrated in
In this embodiment, the shifting speed (scanning speed) of the incident angle at each of the start and end of the exposure is 7.2 deg/sec in the lens direction, and the shifting speed (scanning speed) of the incident angle in the region including the top of the convex section is 6.0 deg/sec.
As illustrated in
According to the invention, as described above, the microlens having a sectional form including the reduced step can be formed by changing the shifting speed of the incident angle at an appropriate point or by changing the light intensity at an appropriate point, even when the display panel has the light shield formed inside the opening arranged for forming the pixel. Further, it is possible to form the microlens having the good light collecting effect and thus having good lens characteristics. Consequently, it is possible to manufacture the liquid crystal display panel that can perform the display with higher brightness. For example, the microlens that was formed by the manufacturing method of the embodiment could increase the brightness on the front side by 1.3 times while keeping the intended characteristics of the view angle.
The apparatus of manufacturing the liquid crystal display panel of the embodiment includes exposing means for performing the exposure of the photosensitive material, and the exposing means is configured to allow shifting of the light incident angle. The exposing means is provided with means for shifting the speed at which the incident angle for the exposure changes. In this embodiment, a reflector or mirror reflects the light emitted from the light source. By driving this mirror, the shifting speed of the light incident angle is changed. This configuration can achieve the exposure method in which the shifting speed of the incident angle changes as described above so that the microlens of the good lens characteristics can be formed.
The apparatus of manufacturing the liquid crystal display panel of the embodiment is configured such that it can change continuously or intermittently the incident angle of the parallel light rays applied from the light source into the opening. Further, it can change continuously or discontinuously the shifting speed of the incident angle.
In the apparatus of manufacturing the liquid crystal display panel in this embodiment, the reflector reflects the light incident from the light source, and a computer controls the movement of the reflector to shift the incident angle with respect to the opening and the shifting speed of the incident angle.
The means for changing the shifting speed of the light incident angle is not restricted to the above form, and may be configured to move the light source itself. Further, it may be configured to move a base carrying the liquid crystal display panel.
In this embodiment, as shown in
In this embodiment, the shifting speed of the incident angle changes. This is not restrictive, and a structure of increasing and/or decreasing the light intensity may be employed. More specifically, the apparatus of manufacturing the liquid crystal display panel may change the light intensity by employing means for changing the light intensity.
Preferably, the points of the above change in exposure are set to fall within the angular ranges defined by the foregoing formulas (1) and (2).
The embodiment has been described in connection with the example in which the light shield is circular in a plane view, and has an island-like form. However, these forms are not restrictive, and the light shield may have any plane form.
In this embodiment, the exposure is performed while moving the exposure target region in the lens ridge direction (Y direction). However, this is not restrictive, and the exposure may be performed while moving the light in the lens direction (X direction).
The embodiment has been described in connection with the method of manufacturing the microlens having a cylindrical form. However, this form is not restrictive, and the invention may be applied to the method of manufacturing the microlens for each of the picture elements or pixels.
As shown in
In this microlens 17, since the Y direction is also the lens direction, the exposure can also be performed for the Y direction similarly to the X direction to form the microlens also having the convex form in the section in the Y direction.
The examples of the embodiment have been described in connection with the liquid crystal display panel having the color filters. However, this form is not restrictive, and present invention can be applied to a monochromatic liquid crystal display panel having pixels. In addition to the semi-transmissive liquid crystal display panel, the invention can be applied to the transmissive type of liquid crystal display panel. The application of the invention can improve the brightness without deteriorate the view angle.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
The invention can be advantageously applied to the display panel.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-362815 | Dec 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/22090 | 12/1/2005 | WO | 00 | 6/15/2007 |
