JP2010164819A - Transparent ceramics substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent ceramics substrate that can form, for the various display device using an optical engine and liquid crystal, a superior video image, wherein definition and contrast ratio of the video image does not degrade due to polarization caused by thermal strain. <P>SOLUTION: The transparent ceramics substrate includes: a transparent ceramics member layer consisting of a transparent ceramics having cubic system; and a resin layer consisting of an adhesive resin and having an optical compensation function for the transparent ceramics member layer. The transparent ceramics member layer and resin layer each has temperature dependency, wherein refractive indice thereof are opposite to each other. The transparent ceramics are spinel, YAG, or MgO. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transparent ceramic substrate mainly used for an optical engine or the like, and more particularly to a transparent ceramic substrate having an optical compensation function.

  Transparent ceramic substrates, especially spinel substrates, have excellent linear transmittance, deflection characteristics, heat dissipation, strength, chemical stability, etc. Since it does not need to be combined and is inexpensive, it is being used for optical engines such as liquid crystal projectors and rear projection television receivers, various display elements using liquid crystals, and the like (Patent Document 1).

  A liquid crystal projector is given as an example of an optical engine using a transparent ceramic substrate that is widely used at present, and the main part thereof will be described with reference to FIG. FIG. 2 is a diagram conceptually showing a configuration of a main part of the optical engine. In the following description, “incident light side” refers to the light source side, and “emitted light side” refers to the prism side. In FIG. 2, R, G, and B are red (R), green (G), and blue (B) incident light respectively transmitted from a light source (not shown). Reference numeral 110 denotes a polarizing film on the incident light side (also referred to as a “polarizing filter” as a function), 121 and 122 denote polarizing films on the outgoing light side, and 210 denotes a transparent ceramic substrate on the incident light side. 221 and 222 are transparent ceramic substrates on the outgoing light side, 300 is a liquid crystal layer, and 500 is a prism.

  In the optical engine shown in FIG. 2, each of R, G, and B has one transparent ceramic substrate (210) on the light source side with respect to the liquid crystal layer 300, and the polarizing film 110 is pasted on the opposite light source side. Yes. In addition, two transparent ceramic substrates (221, 222) are provided on the prism side with respect to the liquid crystal layer 300, and polarizing films 121, 122 are attached to the opposing surface sides thereof.

  In addition, each transparent ceramic substrate performs heat dissipation as well as mechanical protection and support of the polarizing film attached thereto. For this reason, sapphire, quartz, spinel, YAG, etc. with high thermal conductivity are used as the transparent ceramic substrate.

  Next, the operating principle of this optical engine will be described with reference to FIG. (1) of FIG. 3 is a case where light is transmitted without applying a voltage, and (2) is a case where light is not transmitted by applying a voltage. In FIG. 3, 110 is a polarizing filter on the incident light side, 120 is a polarizing filter on the outgoing light side, 300 is a liquid crystal layer, 301 is a liquid crystal molecule, and 610 is a transparent electrode on the incident light side. , 620 is a transparent electrode on the outgoing light side, 690 is an electrode, 691 is a switch, and 700 is a screen. The polarization filter 110 on the incident light side and the polarization filter 120 on the output light side are in a so-called crossed Nicol state (the polarization direction is different by 90 degrees).

  As shown in FIG. 3A, when the switch 691 is opened so that no voltage is applied between the transparent electrode 610 on the incident light side and the transparent electrode 620 on the outgoing light side, the liquid crystal layer between them. The 300 liquid crystal molecules 301 are twisted by 90 degrees and aligned. For this reason, light incident from above and converted into linearly polarized light in the a direction by the polarizing filter 110 on the incident light side is twisted 90 degrees in the liquid crystal layer 300 to be linearly polarized light in the b direction orthogonal to the a direction. The screen 700 becomes brighter after passing through the polarizing filter 120 on the outgoing light side below.

  On the other hand, as shown in (2) of FIG. 3, when the switch 691 is closed and a voltage is applied between the transparent electrode 610 on the incident light side and the transparent electrode 620 on the outgoing light side, The liquid crystal molecules 301 of a certain liquid crystal layer 300 are aligned in the vertical (voltage applied) direction. For this reason, the light incident from above and converted into the linearly polarized light in the a direction by the polarizing filter 110 on the incident light side remains the linearly polarized light in the a direction without being twisted in the liquid crystal layer 300. For this reason, the light does not pass through the polarizing filter 120 on the outgoing light side below, and the screen 700 becomes black. In some optical engines, the relationship between the voltage and the passage of light is reversed (the light passes when a voltage is applied).

JP 2006-273679 A

  In the above, each of the polarization filters on the incident light side and the outgoing light side is used by being attached to a transparent ceramic substrate, respectively, in the case of (2) in FIG. 3, that is, when displaying a black image on the screen, Depending on the positional relationship between each polarizing filter and each bright ceramic substrate, the entire screen may not be black, and light leakage may occur in part.

  This is shown in FIG. In FIG. 4, 110 is a polarizing filter on the incident light side, 120 is a polarizing filter on the outgoing light side, 210 is a transparent ceramic substrate on the incident light side, and 220 is a transparent ceramic substrate on the outgoing light side, Reference numeral 300 denotes a liquid crystal layer, 700 denotes a screen (outgoing light surface), 701 denotes a light leakage portion, and an arrow denotes incident light.

  In FIG. 4 (1), the polarizing filter 120 is attached to the incident light side of the transparent ceramic substrate 220 on the outgoing light side, and the two polarizing filters 110, 120 are formed by the two transparent ceramic substrates 210, 220. Is sandwiched. In this case, the entire surface of the screen 700 is black.

  On the other hand, in (2) of FIG. 4, the polarizing filter 120 is attached to the outgoing light side of the transparent ceramic substrate 220 on the outgoing light side. A transparent ceramic substrate 220 is sandwiched. In this case, the entire surface of the screen 700 is not black, and a light leaking portion 701 is generated in part.

  This light leakage is caused by a birefringence caused by thermal stress (or thermal strain) in the transparent ceramic substrate 220 on the outgoing light side, and further by polarization. A phenomenon that part of the light is cut or, conversely, part of the light that should be completely cut through, so-called light leakage occurs, which may cause image degradation, such as image sharpness and contrast ratio reduction. Become.

  Therefore, for various display devices using an optical engine or liquid crystal, it is possible to form excellent images without lowering the sharpness and contrast ratio due to polarization due to thermal distortion, and at a low cost. It has been desired to develop a transparent ceramic substrate.

  The present invention has been made for the purpose of solving the above-described problems, and by arranging a resin having an optical compensation function for ceramics having cubic crystals, the optical characteristics of the transparent ceramic substrate are improved. It is a thing. The invention of each claim will be described below.

The invention described in claim 1
A transparent ceramic member layer made of transparent ceramics having cubic crystals;
A resin layer made of an adhesive resin and having an optical compensation function for the transparent ceramic member layer;
It is a transparent ceramic substrate characterized by having.

  In the invention of this claim, since the substrate has a two-layer structure of a transparent ceramic member layer and a resin layer having an optical compensation function with respect to the transparent ceramic member layer, the substrate is made of a transparent ceramic material forming the original substrate. It is possible to prevent deterioration of optical characteristics such as generation of polarized light caused by thermal strain generated inside the thin plate, and to suppress the decrease in sharpness and contrast ratio, and to form an excellent image. .

  Here, the transparent ceramics constituting the transparent ceramic member layer is considered to be “cubic” because there is no complicated optical characteristic such as birefringence, so that it is not necessary to align the orientation when assembling. .

  The thickness of the resin layer is selected in consideration of the degree of the optical compensation function of the adhesive resin for the transparent ceramic member layer, the thickness of the transparent ceramic substrate, and the like.

The invention described in claim 2
2. The transparent ceramic substrate according to claim 1, wherein the transparent ceramic member layer and the resin layer have a temperature dependence of refractive indexes that are opposite to each other.

  In the invention of this claim, since the temperature dependence of the refractive index of the transparent ceramic member layer and the resin layer is opposite to each other, it is caused by the thermal strain generated in the transparent ceramic thin plate forming the original substrate. Since the refractive index variation and the generation of polarized light are compensated by the resin layer, the contrast ratio is not lowered, and an excellent image can be formed.

  Here, “temperature dependence of refractive index” refers to the relationship between temperature and a phenomenon in which the refractive index differs depending on the location due to thermal strain or birefringence is generated. As described above, these phenomena affect the polarization of light passing through the transparent ceramic substrate.

The invention according to claim 3
The transparent ceramic substrate according to claim 1, wherein the transparent ceramic is one of spinel, YAG, and MgO.

The transparent ceramic substrate according to the invention of this claim is a spinel (MgO.nAl ₂ O ₃ : n = n) as a material constituting the original substrate that mechanically supports, protects and protects the polarizing filter and radiates heat. 1.050 to 1.200), YAG (3Y ₂ O ₃ .5Al ₂ O ₃ ) or MgO is preferably used. Since these all have good thermal conductivity, they are excellent in heat dissipation, the temperature inside the substrate is easily maintained uniformly, and thermal distortion hardly occurs. Further, it is highly transparent, and there is no complicated characteristic such as a birefringence in a normal state in which no thermal strain is generated. For this reason, a transparent ceramic substrate can be obtained in which a superior image can be obtained with a thickness of about half when compared with a crystal widely used at present.

The invention according to claim 4
4. The transparent ceramic substrate according to claim 1, wherein the adhesive resin is a transparent polyamide. 5.

  In order to bond the polarizing filter to the transparent ceramic substrate, an adhesive made of an adhesive resin is generally used, and it is preferable to use a transparent polyamide as the adhesive. Transparent polyamide not only has temperature dependence of optical properties opposite to transparent ceramics, but also has excellent adhesion and low cost. Therefore, an excellent transparent ceramic substrate can be provided at a low cost.

  In addition, this invention is applicable not only to transparent ceramics but white plate glass.

  According to the present invention, there is provided a transparent ceramic substrate capable of forming an excellent image for various display devices using an optical engine or a liquid crystal without causing a decrease in sharpness and contrast ratio due to polarization due to thermal strain. It becomes possible to provide.

It is a figure which shows notionally the structure of the principal part of the transparent ceramic substrate of embodiment of this invention, and the mode of an effect | action display. It is a figure which shows notionally the structure of the principal part of an optical engine. It is a figure which shows the operating principle of an optical engine. It is a figure which shows a mode that the display of a black image changes with the positional relationship of a board | substrate and a polarizing filter.

  Hereinafter, the present invention will be described based on embodiments. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(First embodiment)
The present embodiment relates to a transparent ceramic substrate on the outgoing light side using spinel for the substrate body of the transparent ceramic substrate and transparent polyamide for the adhesive resin layer.

  A transparent ceramic substrate according to an embodiment of the present invention will be described with reference to FIG. (1) in FIG. 1 shows a cross-sectional shape when the transparent ceramic substrate according to the present embodiment is used as a transparent ceramic substrate on the outgoing light side, and (2) in FIG. 1 shows light incident on the transparent ceramic substrate. A mode that the adhesive resin layer at the time exhibits an effect | action is shown notionally.

  In FIG. 1, reference numeral 220c denotes a transparent ceramic substrate on the outgoing light side made of spinel, 220s denotes a spinel plate material as a substrate body of the transparent ceramic substrate 220c, and 226 denotes an outgoing light side of the transparent ceramic substrate 220c. The reference numeral 120 denotes an adhesive resin layer, and 120 is a polarizing film provided on the outgoing light side. Reference numeral 225 denotes a display indicating the degree of change in optical properties, for example, polarization, caused by thermal strain generated in the spinel plate material 220s, and 227 indicates the thermal strain generated in the adhesive resin layer. This is a display showing the degree of change in optical properties, for example, polarization, which is the cause. The darker the color, the greater the change.

Hereinafter, the production of the transparent ceramic substrate 220c of the present embodiment will be described.
The spinel plate material 220s that forms the substrate body of the transparent ceramic substrate 220c is formed primarily by spinel (MgO.nAl ₂ O ₃ : n = 1.05) powder having a purity of 99.9% or more at a pressure of 196 MPa at 196 MPa. Secondary formed by CIP (cold isostatic pressing) to form a spinel molded body, this spinel molded body is placed in a graphite container and vacuum-sintered at 1500 ° C. to form a spinel sintered body. A polycrystalline spinel crystal having cubic crystals was formed by HIP (hot isostatic pressing) at 1750 ° C. and 200 MPa, and the polycrystalline spinel crystal was cut and polished.

In order to prevent reflection at the boundary surface with the adhesive resin layer, an antireflection layer made of HfO ₂ , Al ₂ O ₃ , TiO ₂ , TaO ₅ , ZnS or the like is provided on the outgoing light side of the transparent ceramic substrate. It is preferable to intervene.

Further, at least one antireflection layer made of HfO ₂ , Al ₂ O ₃ , TiO ₂ , TaO ₅ , ZnS or the like is formed on the incident light side of the transparent ceramic substrate in order to prevent reflection of incident light. Preferably it is.

  Next, as the adhesive resin layer, a transparent polyamide having a thickness of 50 μm was attached. Note that this thickness takes into consideration the difference in temperature dependence of the polarization property between the adhesive resin and the spinel.

  As a polarizing film, a TAC (triacetylcellulose) film layer is formed on both sides as a protective layer, and a resin film having a three-layer structure having a PVA (polyvinyl alcohol) film layer dyed with iodine in the center is uniaxially stretched. A resin film having a thickness of 50 μm in which the PVA film layer was processed to have polarization characteristics (birefringence) was used. This polarizing film was attached to a polycrystalline spinel crystal provided with an adhesive resin layer to produce a transparent ceramic substrate.

  In the transparent ceramic substrate thus manufactured, the rigidity of the adhesive resin is very small compared to the spinel plate material 220s, and the adhesive resin layer 226 is sufficiently thin compared to the spinel plate material 220s. There is a polarizing film on the plate material side of the anti-spinel of the adhesive resin. For this reason, the adhesive resin layer 226 expands and contracts following the spinel plate material 220s and has the same temperature distribution.

  As a result, when the transparent ceramic substrate 220c is used under the conditions as shown in FIG. 4B, the transparent ceramic substrate 220c has a spinel plate 220s as shown in FIG. Along with the temperature distribution generated inside, the change in optical properties due to thermal expansion and thermal strain caused by the temperature distribution, and the distribution of the change, and the thermal expansion of the spinel plate 220s generated inside the adhesive resin layer 226 The change in the optical property and the distribution of the change due to the strain generated by the occurrence occur at the same density at positions opposite to each other.

  As a result, in the entire transparent ceramic substrate 220c, changes in optical properties and distribution of changes caused by thermal strain of the spinel plate 220s and strain of the adhesive resin layer 226 are compensated for each other. That is, in the entire transparent ceramic substrate 220c, the distribution of changes in optical properties at locations such as the central portion and the peripheral portion does not occur. For this reason, even with an optical engine using this transparent ceramic substrate on the outgoing light side and further providing a polarizing film on the outgoing light side of this transparent ceramic substrate, there is no light leakage and an image with excellent sharpness and contrast ratio is formed. It becomes possible.

  Next, the transparent ceramic substrate on the emission side is the same as the first embodiment except that it does not have the transparent ceramic substrate of the first embodiment and the adhesive resin layer that performs the optical compensation function. The presence or absence of color leakage and the image quality when using a transparent ceramic substrate of a comparative example and a current transparent quartz substrate were evaluated.

  As a result, it was confirmed that the transparent ceramic substrate of the first embodiment was clearly superior. This is because the transparent ceramic substrate 220c of the first embodiment has a smaller temperature difference depending on the location in the transparent ceramic substrate than the current transparent quartz substrate. Further, unlike the transparent ceramic substrate of the comparative example, the adhesive resin layer 226 for adhering the polarizing filter has a temperature dependency of the refractive index which is opposite to that of the spinel plate 220s. An optical compensation function is performed for a refractive index abnormality caused by temperature distribution, thermal expansion or thermal strain within 220 s. For this reason, the transparent ceramic substrate of the first embodiment has much less light leakage and a much better contrast ratio than the transparent ceramic substrate and transparent quartz substrate of the comparative example, and an excellent image. It is thought that it was possible to form.

(Second Embodiment)
The present embodiment relates to a transparent ceramic substrate using YAG (3Y ₂ O ₃ .5Al ₂ O ₃ ) as the substrate body of the transparent ceramic substrate, and other configurations such as an adhesive resin layer are the same as those of the first embodiment. It is. Therefore, only the manufacture of the YAG substrate body will be briefly described. However, the thickness of the adhesive resin layer is adjusted (changed) in consideration of the difference in physical properties between spinel and YAG.

  YAG powder having a purity of 99.99% or more was preformed at 1500 kg / cm 2, and the resulting molded body was placed in an alumina container and sintered at 1500 ° C. under vacuum to obtain a YAG polycrystal. The polycrystalline body was processed into a plate material to produce a substrate body of a transparent ceramic substrate. Using this substrate body, a transparent ceramic substrate having the same structure as the transparent ceramic substrate of the first embodiment was manufactured. Even in this case, an excellent image was obtained.

(Third embodiment)
The present embodiment relates to a transparent ceramic substrate using MgO for the substrate body of the transparent ceramic substrate, and other configurations such as an adhesive resin layer are basically the same as those of the first embodiment and the second embodiment. The same. Also in the transparent ceramic substrate of the present embodiment, excellent images were obtained as in the first embodiment and the second embodiment.

110 Incident light side polarizing film (polarizing filter)
120, 121, 122 Output light side polarizing film (polarizing filter)
210 Incoming light side transparent ceramic substrate 220, 221, 222 Outgoing light side transparent ceramic substrate 220 c Outgoing light side transparent ceramic substrate 220 s Spinel plate material 225 Display 226 indicating optical properties generated in the spinel plate material 226 Adhesive resin layer 227 Display 300 showing optical properties generated in adhesive resin layer Liquid crystal layer 301 Liquid crystal molecule 500 Prism 610 Transparent light electrode 620 on incident light side Transparent electrode 690 on output light side Electrode 691 Switch 700 Screen 701 Light leakage location

Claims (4)

A transparent ceramic member layer made of transparent ceramics having cubic crystals;
A resin layer made of an adhesive resin and having an optical compensation function for the transparent ceramic member layer;
A transparent ceramic substrate characterized by comprising:   2. The transparent ceramic substrate according to claim 1, wherein the transparent ceramic member layer and the resin layer have a temperature dependence of refractive indexes that are opposite to each other.   The transparent ceramic substrate according to claim 1, wherein the transparent ceramic is any one of spinel, YAG, or MgO.   The transparent ceramic substrate according to claim 1, wherein the adhesive resin is a transparent polyamide.

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